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Sample records for crystallography solid-state nmr

  1. Crystallographic and dynamic aspects of solid-state NMR calibration compounds: towards ab initio NMR crystallography

    DEFF Research Database (Denmark)

    Li, Xiaozhou; Tapmeyer, Lukas; Bolte, Michael

    2016-01-01

    The excellent results of dispersion-corrected density functional theory (DFT-D) calculations for static systems have been well established over the past decade. The introduction of dynamics into DFT-D calculations is a target, especially for the field of molecular NMR crystallography. Four 13C ss...

  2. Fine refinement of solid state structure of racemic form of phospho-tyrosine employing NMR Crystallography approach.

    Science.gov (United States)

    Paluch, Piotr; Pawlak, Tomasz; Oszajca, Marcin; Lasocha, Wieslaw; Potrzebowski, Marek J

    2015-02-01

    We present step by step facets important in NMR Crystallography strategy employing O-phospho-dl-tyrosine as model sample. The significance of three major techniques being components of this approach: solid state NMR (SS NMR), X-ray diffraction of powdered sample (PXRD) and theoretical calculations (Gauge Invariant Projector Augmented Wave; GIPAW) is discussed. Each experimental technique provides different set of structural constraints. From the PXRD measurement the size of the unit cell, space group and roughly refined molecular structure are established. SS NMR provides information about content of crystallographic asymmetric unit, local geometry, molecular motion in the crystal lattice and hydrogen bonding pattern. GIPAW calculations are employed for validation of quality of elucidation and fine refinement of structure. Crystal and molecular structure of O-phospho-dl-tyrosine solved by NMR Crystallography is deposited at Cambridge Crystallographic Data Center under number CCDC 1005924.

  3. A combined solid-state NMR and X-ray crystallography study of the bromide ion environments in triphenylphosphonium bromides.

    Science.gov (United States)

    Burgess, Kevin M N; Korobkov, Ilia; Bryce, David L

    2012-04-27

    Multinuclear ((31)P and (79/81)Br), multifield (9.4, 11.75, and 21.1 T) solid-state nuclear magnetic resonance experiments are performed for seven phosphonium bromides bearing the triphenylphosphonium cation, a molecular scaffold found in many applications in chemistry. This is undertaken to fully characterise their bromine electric field gradient (EFG) tensors, as well as the chemical shift (CS) tensors of both the halogen and the phosphorus nuclei, providing a rare and novel insight into the local electronic environments surrounding them. New crystal structures, obtained from single-crystal X-ray diffraction, are reported for six compounds to aid in the interpretation of the NMR data. Among them is a new structure of BrPPh(4), because the previously reported one was inconsistent with our magnetic resonance data, thereby demonstrating how NMR data of non-standard nuclei can correct or improve X-ray diffraction data. Our results indicate that, despite sizable quadrupolar interactions, (79/81)Br magnetic resonance spectroscopy is a powerful characterisation tool that allows for the differentiation between chemically similar bromine sites, as shown through the range in the characteristic NMR parameters. (35/37)Cl solid-state NMR data, obtained for an analogous phosphonium chloride sample, provide insight into the relationship between unit cell volume, nuclear quadrupolar coupling constants, and Sternheimer antishielding factors. The experimental findings are complemented by gauge-including projector-augmented wave (GIPAW) DFT calculations, which substantiate our experimentally determined strong dependence of the largest component of the bromine CS tensor, δ(11), on the shortest Br-P distance in the crystal structure, a finding that has possible application in the field of NMR crystallography. This trend is explained in terms of Ramsey's theory on paramagnetic shielding. Overall, this work demonstrates how careful NMR studies of underexploited exotic nuclides, such

  4. Fine refinement of solid-state molecular structures of Leu- and Met-enkephalins by NMR crystallography.

    Science.gov (United States)

    Pawlak, Tomasz; Potrzebowski, Marek J

    2014-03-27

    This paper presents a methodology that allows the fine refinement of the crystal and molecular structure for compounds for which the data deposited in the crystallographic bases are of poor quality. Such species belong to the group of samples with molecular disorder. In the Cambridge Crystallographic Data Center (CCDC), there are approximately 22,000 deposited structures with an R-factor over 10. The powerful methodology we present employs crystal data for Leu-enkephalin (two crystallographic forms) with R-factor values of 14.0 and 8.9 and for Met-enkephalin (one form) with an R-factor of 10.5. NMR crystallography was employed in testing the X-ray data and the quality of the structure refinement. The GIPAW (gauge invariant projector augmented wave) method was used to optimize the coordinates of the enkephalins and to compute NMR parameters. As we reveal, this complementary approach makes it possible to generate a reasonable set of new coordinates that better correlate to real samples. This methodology is general and can be employed in the study of each compound possessing magnetically active nuclei.

  5. Solid-state NMR basic principles and practice

    CERN Document Server

    Apperley, David C; Hodgkinson, Paul

    2012-01-01

    Nuclear Magnetic Resonance (NMR) has proved to be a uniquely powerful and versatile tool for analyzing and characterizing chemicals and materials of all kinds. This book focuses on the latest developments and applications for "solid-state" NMR, which has found new uses from archaeology to crystallography to biomaterials and pharmaceutical science research. The book will provide materials engineers, analytical chemists, and physicists, in and out of lab, a survey of the techniques and the essential tools of solid-state NMR, together with a practical guide on applications. In this concise introduction to the growing field of solid-state nuclear magnetic resonance spectroscopy The reader will find: * Basic NMR concepts for solids, including guidance on the spin-1/2 nuclei concept * Coverage of the quantum mechanics aspects of solid state NMR and an introduction to the concept of quadrupolar nuclei * An understanding relaxation, exchange and quantitation in NMR * An analysis and interpretation of NMR data, with e...

  6. Solid-state NMR basic principles and practice

    CERN Document Server

    Apperley, David C; Hodgkinson, Paul

    2014-01-01

    Nuclear Magnetic Resonance (NMR) has proved to be a uniquely powerful and versatile tool for analyzing and characterizing chemicals and materials of all kinds. This book focuses on the latest developments and applications for "solid-state" NMR, which has found new uses from archaeology to crystallography to biomaterials and pharmaceutical science research. The book will provide materials engineers, analytical chemists, and physicists, in and out of lab, a survey of the techniques and the essential tools of solid-state NMR, together with a practical guide on applications. In this concise introduction to the growing field of solid-state nuclear magnetic resonance spectroscopy The reader will find: * Basic NMR concepts for solids, including guidance on the spin-1/2 nuclei concept * Coverage of the quantum mechanics aspects of solid state NMR and an introduction to the concept of quadrupolar nuclei * An understanding relaxation, exchange and quantitation in NMR * An analysis and interpretation of NMR data, with e...

  7. Solid-state NMR and Membrane Proteins

    Science.gov (United States)

    Opella, Stanley J.

    2015-01-01

    The native environment for a membrane protein is a phospholipid bilayer. Because the protein is immobilized on NMR timescales by the interactions within a bilayer membrane, solid-state NMR methods are essential to obtain high-resolution spectra. Approaches have been developed for both unoriented and oriented samples, however, they all rest on the foundation of the most fundamental aspects solid-state NMR, and the chemical shift and homo- and hetero-nuclear dipole-dipole interactions. Solid-state NMR has advanced sufficiently to enable the structures of membrane proteins to be determined under near-native conditions in phospholipid bilayers. PMID:25681966

  8. Solid-state NMR structures of integral membrane proteins.

    Science.gov (United States)

    Patching, Simon G

    2015-01-01

    Solid-state NMR is unique for its ability to obtain three-dimensional structures and to measure atomic-resolution structural and dynamic information for membrane proteins in native lipid bilayers. An increasing number and complexity of integral membrane protein structures have been determined by solid-state NMR using two main methods. Oriented sample solid-state NMR uses macroscopically aligned lipid bilayers to obtain orientational restraints that define secondary structure and global fold of embedded peptides and proteins and their orientation and topology in lipid bilayers. Magic angle spinning (MAS) solid-state NMR uses unoriented rapidly spinning samples to obtain distance and torsion angle restraints that define tertiary structure and helix packing arrangements. Details of all current protein structures are described, highlighting developments in experimental strategy and other technological advancements. Some structures originate from combining solid- and solution-state NMR information and some have used solid-state NMR to refine X-ray crystal structures. Solid-state NMR has also validated the structures of proteins determined in different membrane mimetics by solution-state NMR and X-ray crystallography and is therefore complementary to other structural biology techniques. By continuing efforts in identifying membrane protein targets and developing expression, isotope labelling and sample preparation strategies, probe technology, NMR experiments, calculation and modelling methods and combination with other techniques, it should be feasible to determine the structures of many more membrane proteins of biological and biomedical importance using solid-state NMR. This will provide three-dimensional structures and atomic-resolution structural information for characterising ligand and drug interactions, dynamics and molecular mechanisms of membrane proteins under physiological lipid bilayer conditions.

  9. Scalar operators in solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Boqin

    1991-11-01

    Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.

  10. Oriented solid-state NMR spectrosocpy

    DEFF Research Database (Denmark)

    Bertelsen, Kresten

    This thesis is concerned with driving forward oriented solid-state NMR spectroscopy as a viable technique for studying peptides in membrane bilayers. I will show that structural heterogeneity is an intrinsic part of the peptide/lipid system and that NMR can be used to characterize static...... and dynamic structural features of the peptides and its local surroundings. In fact one need to take into account the dynamical features of the system in order to correctly predict the structure from oriented solid-state NMR spectra.      ...

  11. Solid-state NMR of polymers

    Energy Technology Data Exchange (ETDEWEB)

    Mirau, P

    2001-07-01

    Nuclear magnetic resonance (NMR) spectroscopy has emerged as one of the most important methods for the solid-state characterisation of polymers. The popularity of NMR is due to the fact that many molecular level features can be measured from the NMR spectra, including the polymer chain conformation, the morphology and the dynamics. The spectral features and relaxation times are affected by local interactions, so they provide information about the structure of polymers on a length scale (2-200 A) that is difficult to measure by other methods. In favourable cases, the NMR experiments provide a molecular-level explanation for the transitions observed by differential scanning calorimetry (DSC) and other methods, and the NMR properties can often be related to the bulk properties. Solid-state NMR has long been of interest in polymer science, and the first solid-state NMR studies of polymers were reported approximately a year after the discovery of nuclear resonance in bulk matter. It was reported in this initial study that the proton line width for natural rubber at room temperature is more like that of a mobile liquid than of a solid, but that the resonance broadens near the glass transition temperature (T{sub g}). This was recognised as being related to a change in chain dynamics above and below the T{sub g}. NMR methods developed rapidly after these initial observations, first for polymers in solution and, more recently, for polymers in the solid-state. Solid-state NMR studies of polymers were developed more slowly than their solution-state counterparts because solid-state NMR requires more specialised equipment. Solid-state NMR is now such an important tool that most modern spectrometers are capable of performing these studies. The interest in the NMR of solid polymers is due in part to the fact that most polymers are used in the solid state, and in many cases the NMR properties can be directly related to the macroscopic properties. Polymers have restricted mobility

  12. Solid-state NMR on complex biomolecules: novel methods and applications

    NARCIS (Netherlands)

    Nand, D.

    2011-01-01

    Solid-state NMR (ssNMR) represents a versatile technique in providing atomic-resolution information without the need for crystals or fast molecular motion required for X-ray crystallography and solution-state NMR, respectively. Recent past has witnessed the ability of this technique in providing det

  13. Solid state NMR of biopolymers and synthetic polymers

    Energy Technology Data Exchange (ETDEWEB)

    Jelinski, Lynn W. [Cornell Univ., Geneva, NY (United States)

    1995-12-31

    Solid state NMR has been invaluable in evaluating the structure, phase separation, and dynamics of polymers. Because polymers are generally used in the solid state, solid state NMR is especially powerful because it provides information about the materials in their native state. This review gives a general overview of solid state NMR, concentrating on solid state {sup 13} C and {sup 2} H NMR. It then focuses on two examples: the biopolymer spider silka and the engineering material polyurethane. It illustrates how solid state NMR can provide new information about synthetic and bio-polymers. (author) 11 refs., 5 figs., 3 tabs.

  14. Solid state NMR of sulfa-drugs

    CERN Document Server

    Portieri, A

    2001-01-01

    deducted. Exact positions of the hydrogen has proved to be essential as well in order to improve the calculations. Finally a case study for the REDOR pulse sequence has been carried out. Different attempts to understand the effects influencing this particular experiment have been carried out on 20% and 99% doubly enriched glycine, as well as on a particular sample, doubly enriched BRL55834, but the internuclear distances measured with this technique still displayed some uncertainties that made results not thoroughly reliable. This work has been a study of systems, mostly of sulfa-drugs, showing polymorphic behaviour. Using different means as solid state NMR, X-ray analysis, * and theoretical calculations, we have seen how it is possible to understand results obtained from the different techniques, proving how the study of polymorphic systems needs cooperative advice from the different techniques that are able to detect polymorphic differences. Within the sulfa-drugs I have been mostly concentrating on sulfani...

  15. Lithium Polymer Electrolytes and Solid State NMR

    Science.gov (United States)

    Berkeley, Emily R.

    2004-01-01

    Research is being done at the Glenn Research Center (GRC) developing new kinds of batteries that do not depend on a solution. Currently, batteries use liquid electrolytes containing lithium. Problems with the liquid electrolyte are (1) solvents used can leak out of the battery, so larger, more restrictive, packages have to be made, inhibiting the diversity of application and decreasing the power density; (2) the liquid is incompatible with the lithium metal anode, so alternative, less efficient, anodes are required. The Materials Department at GRC has been working to synthesize polymer electrolytes that can replace the liquid electrolytes. The advantages are that polymer electrolytes do not have the potential to leak so they can be used for a variety of tasks, small or large, including in the space rover or in space suits. The polymers generated by Dr. Mary Ann Meador's group are in the form of rod -coil structures. The rod aspect gives the polymer structural integrity, while the coil makes it flexible. Lithium ions are used in these polymers because of their high mobility. The coils have repeating units of oxygen which stabilize the positive lithium by donating electron density. This aids in the movement of the lithium within the polymer, which contributes to higher conductivity. In addition to conductivity testing, these polymers are characterized using DSC, TGA, FTIR, and solid state NMR. Solid state NMR is used in classifying materials that are not soluble in solvents, such as polymers. The NMR spins the sample at a magic angle (54.7') allowing the significant peaks to emerge. Although solid state NMR is a helpful technique in determining bonding, the process of preparing the sample and tuning it properly are intricate jobs that require patience; especially since each run takes about six hours. The NMR allows for the advancement of polymer synthesis by showing if the expected results were achieved. Using the NMR, in addition to looking at polymers, allows for

  16. Advanced solid-state NMR spectroscopy of natural organic matter

    Science.gov (United States)

    Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially the systematic approach to NOM characterization, and their ...

  17. Solid state NMR study of bone mineral

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y.

    1992-01-01

    In high field (9.4 T) CP MASS (cross polarization magic angle sample spinning) studies, in contrast to the scheme in the literature that infers the presence of minor constituents in spectra, we developed a new scheme to suppress the main part of the spectra to show the minor constituents. In order to perform in vivo solid state NMR studies, a double tuned two port surface coil probe was constructed. This probe is a modified version of the traditional Cross probe, which utilizes two 1/4 wave length 50 ohm transmission line, one with open ended and the other with shorted end, to isolate the high and low frequency circuits. The two resonance frequencies in Cross probe were proton and carbon. Our probe is designed to resonate at the proton and phosphorus frequencies, which are much closer to each other and hence more difficult to be tuned and matched simultaneously. Our approach to solve this problem is that instead of using standard 50 ohm transmission lines, we constructed a low capacity open end coaxial transmission line and low inductance shorted end coaxial transmission line. The Q of the phosphorus channel is high. We developed a short contact time cross polarization technique for non-MASS spectroscopy which reduces the signal of the major component of bone mineral to emphasize the minor component. By applying this technique on intact pork bone samples with our home made surface coil, we observed the wide line component, acid phosphate, for the first time. Hydroxyapatite, brushite and octacalcium are considered in the literature to be the model compounds for bone mineral. Cross polarization dynamics has been studied on hydroxyapatite and brushite, which yielded an NMR value for the distance between proton and phosphorus. One and two dimensional CP MASS spectroscopy of octacalcium phosphate were also studied, which revealed the different cross polarization rates and anisotropic channel shifts of acid phosphate and phosphate ions in octacalcium phosphate.

  18. Perspectives on a Solid State NMR Quantum Computer

    OpenAIRE

    Fel'dman, Edward B.; Lacelle, Serge

    2001-01-01

    A quantum information processing device, based on bulk solid state NMR of the quasi-one dimensional material hydroxyapatite, is proposed following the magnetic resonance force microscopy work of Yamamoto et al (quant-ph/0009122). In a macroscopic sample of hydroxyapatite, our solid state NMR model yields a limit of 10^8 qubits imposed by physics, while development of current technological considerations should allow an upper bound in the range of hundreds to thousands of qubits.

  19. Advanced solid-state NMR spectroscopy of natural organic matter.

    Science.gov (United States)

    Mao, Jingdong; Cao, Xiaoyan; Olk, Dan C; Chu, Wenying; Schmidt-Rohr, Klaus

    2017-05-01

    Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially a systematic approach to NOM characterization, and their applications to the study of NOM. We discuss some basics of how to acquire high-quality and quantitative solid-state (13)C NMR spectra, and address some common technical mistakes that lead to unreliable spectra of NOM. The identification of specific functional groups in NOM, primarily based on (13)C spectral-editing techniques, is described and the theoretical background of some recently-developed spectral-editing techniques is provided. Applications of solid-state NMR to investigating nitrogen (N) in NOM are described, focusing on limitations of the widely used (15)N CP/MAS experiment and the potential of improved advanced NMR techniques for characterizing N forms in NOM. Then techniques used for identifying proximities, heterogeneities and domains are reviewed, and some examples provided. In addition, NMR techniques for studying segmental dynamics in NOM are reviewed. We also briefly discuss applications of solid-state NMR to NOM from various sources, including soil organic matter, aquatic organic matter, organic matter in atmospheric particulate matter, carbonaceous meteoritic organic matter, and fossil fuels. Finally, examples of NMR-based structural models and an outlook are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Solid state NMR studies of gels derived from low molecular mass gelators.

    Science.gov (United States)

    Nonappa; Kolehmainen, E

    2016-07-13

    Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples.

  1. Solid state NMR studies of gels derived from low molecular mass gelators

    Science.gov (United States)

    Kolehmainen, E.

    2016-01-01

    Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples. PMID:27374054

  2. Functional groups identified by solid state 13C NMR spectroscopy

    Science.gov (United States)

    Animal manure is generally high in organic matter intensity so it is well suitable for 13C nuclear magnetic resonance (NMR) analysis. Solid-state 13C NMR techniques used in characterizing organic matter and its components include, but are not limited to, cross-polarization /magic angle spinning (CP...

  3. Perspectives in enzymology of membrane proteins by solid-state NMR.

    Science.gov (United States)

    Ullrich, Sandra J; Glaubitz, Clemens

    2013-09-17

    Membrane proteins catalyze reactions at the cell membrane and facilitate thetransport of molecules or signals across the membrane. Recently researchers have made great progress in understanding the structural biology of membrane proteins, mainly based on X-ray crystallography. In addition, the application of complementary spectroscopic techniques has allowed researchers to develop a functional understanding of these proteins. Solid-state NMR has become an indispensable tool for the structure-function analysis of insoluble proteins and protein complexes. It offers the possibility of investigating membrane proteins directly in their environment, which provides essential information about the intrinsic coupling of protein structure and functional dynamics within the lipid bilayer. However, to date, researchers have hardly explored the enzymology of mem-brane proteins. In this Account, we review the perspectives for investigating membrane-bound enzymes by solid-state NMR. Understanding enzyme mechanisms requires access to kinetic parameters, structural analysis of the catalytic center, knowledge of the 3D structure and methods to follow the structural dynamics of the enzyme during the catalytic cycle. In principle, solid-state NMR can address all of these issues. Researchers can characterize the enzyme kinetics by observing substrate turnover within the membrane or at the membrane interphase in a time-resolved fashion as shown for diacylglycerol kinase. Solid-state NMR has also provided a mechanistic understanding of soluble enzymes including triosephosphate isomerase (TIM) and different metal-binding proteins, which demonstrates a promising perspective also for membrane proteins. The increasing availability of high magnetic fields and the development of new experimental schemes and computational protocols have made it easier to determine 3D structure using solid-state NMR. Dynamic nuclear polarization, a key technique to boost sensitivity of solid-state NMR at low

  4. The development of solid-state NMR of membrane proteins.

    Science.gov (United States)

    Opella, Stanley J

    Most biological functions are carried out in supramolecular assemblies. As a result of their slow reorientation in solution, these assemblies have been resistant to the widely employed solution NMR approaches. The development of solid-state NMR to first of all overcome the correlation time problem and then obtain informative high-resolution spectra of proteins in supramolecular assemblies, such as virus particles and membranes, is described here. High resolution solid-state NMR is deeply intertwined with the history of NMR, and the seminal paper was published in 1948. Although the general principles were understood by the end of the 1950s, it has taken more than fifty years for instrumentation and experimental methods to become equal to the technical problems presented by the biological assemblies of greatest interest. It is now possible to obtain atomic resolution structures of viral coat proteins in virus particles and membrane proteins in phospholipid bilayers by oriented sample solid-state NMR methods. The development of this aspect of the field of solid-state NMR is summarized in this review article.

  5. Yeast-expressed human membrane protein aquaporin-1 yields excellent resolution of solid-state MAS NMR spectra

    Energy Technology Data Exchange (ETDEWEB)

    Emami, Sanaz; Fan Ying; Munro, Rachel; Ladizhansky, Vladimir; Brown, Leonid S., E-mail: lebrown@uoguelph.ca [University of Guelph, Departments of Physics, and Biophysics Interdepartmental Group (Canada)

    2013-02-15

    One of the biggest challenges in solid-state NMR studies of membrane proteins is to obtain a homogeneous natively folded sample giving high spectral resolution sufficient for structural studies. Eukaryotic membrane proteins are especially difficult and expensive targets in this respect. Methylotrophic yeast Pichia pastoris is a reliable producer of eukaryotic membrane proteins for crystallography and a promising economical source of isotopically labeled proteins for NMR. We show that eukaryotic membrane protein human aquaporin 1 can be doubly ({sup 13}C/{sup 15}N) isotopically labeled in this system and functionally reconstituted into phospholipids, giving excellent resolution of solid-state magic angle spinning NMR spectra.

  6. Applications of solid-state NMR to membrane proteins.

    Science.gov (United States)

    Ladizhansky, Vladimir

    2017-07-12

    Membrane proteins mediate flow of molecules, signals, and energy between cells and intracellular compartments. Understanding membrane protein function requires a detailed understanding of the structural and dynamic properties involved. Lipid bilayers provide a native-like environment for structure-function investigations of membrane proteins. In this review we give a general discourse on the recent progress in the field of solid-state NMR of membrane proteins. Solid-state NMR is a variation of NMR spectroscopy that is applicable to molecular systems with restricted mobility, such as high molecular weight proteins and protein complexes, supramolecular assemblies, or membrane proteins in a phospholipid environment. We highlight recent advances in applications of solid-state NMR to membrane proteins, specifically focusing on the recent developments in the field of Dynamic Nuclear Polarization, proton detection, and solid-state NMR applications in situ (in cell membranes). This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Solid state NMR study calcium phosphate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Miquel, J.L.; Facchini, L.; Legrand, A.P. (Laboratoire de Physique Quantique, Paris (France). CNRS, URA421, ESPCI); Rey, C. (CNRS, Toulouse (France). ENSC. Laboratoire de Physico-chimie des Solides); Lemaitre, J. (EPF Lausanne (France). Laboratoire de Technologie des Poudres)

    1990-04-01

    High-resolution {sup 31}P and {sup 1}H NMR spectra at 40 and 121 MHz {sup 31}P and 300 MHz {sup 1}H of synthetic and biological samples of calcium phosphates have been obtained by magic angle spinning (MAS) at spinning speeds up to 6.5 kHz, and high power proton decoupling. The samples include crystalline hydroxyapatite, a deficient hydroxyapatite characterized by a Ca/P atomic ratio of 1.5, a poorly crystallized hydroxyapatite, monetite, brushite, octacalcium phosphate, {beta}-tricalcium phosphate and rabbit femoral bone. The interactions between nuclei in unlike structures and the mobility of acid protons are discussed. (author). 11 refs.; 2 figs.; 1 tab.

  8. Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory

    Science.gov (United States)

    Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

  9. Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory

    Science.gov (United States)

    Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

  10. DFT calculations of quadrupolar solid-state NMR properties: Some examples in solid-state inorganic chemistry.

    Science.gov (United States)

    Cuny, Jerome; Messaoudi, Sabri; Alonzo, Veronique; Furet, Eric; Halet, Jean-François; Le Fur, Eric; Ashbrook, Sharon E; Pickard, Chris J; Gautier, Regis; Le Polles, Laurent

    2008-10-01

    This article presents results of first-principles calculations of quadrupolar parameters measured by solid-state nuclear magnetic measurement (NMR) spectroscopy. Different computational methods based on density functional theory were used to calculate the quadrupolar parameters. Through a series of illustrations from different areas of solid state inorganic chemistry, it is shown how quadrupolar solid-state NMR properties can be tackled by a theoretical approach and can yield structural information.

  11. Structural biology applications of solid state MAS DNP NMR

    Science.gov (United States)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.

  12. Molecular Structure of Humin and Melanoidin via Solid State NMR

    OpenAIRE

    Herzfeld, Judith; Rand, Danielle; Matsuki, Yoh; Daviso, Eugenio; Mak-Jurkauskas, Melody; Mamajanov, Irena

    2011-01-01

    Sugar-derived humins and melanoidins figure significantly in food chemistry, agricultural chemistry, biochemistry and prebiotic chemistry. Despite wide interest and significant experimental attention, the amorphous and insoluble nature of the polymers has made them resistant to conventional structural characterization. Here we make use of solid-state NMR methods, including selective 13C substitution, 1H-dephasing, and double quantum filtration. The spectra, and their interpretation, are simpl...

  13. Investigating albendazole desmotropes by solid-state NMR spectroscopy.

    Science.gov (United States)

    Chattah, Ana K; Zhang, Rongchun; Mroue, Kamal H; Pfund, Laura Y; Longhi, Marcela R; Ramamoorthy, Ayyalusamy; Garnero, Claudia

    2015-03-02

    Characterization of the molecular structure and physicochemical solid-state properties of the solid forms of pharmaceutical compounds is a key requirement for successful commercialization as potential active ingredients in drug products. These properties can ultimately have a critical effect on the solubility and bioavailability of the final drug product. Here, the desmotropy of Albendazole forms I and II was investigated at the atomic level. Ultrafast magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy, together with powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectroscopy, were performed on polycrystalline samples of the two solids in order to fully characterize and distinguish the two forms. High-resolution one-dimensional (1)H, (13)C, and (15)N together with two-dimensional (1)H/(1)H single quantum-single quantum, (1)H/(1)H single quantum-double quantum, and (1)H/(13)C chemical shift correlation solid-state NMR experiments under MAS conditions were extensively used to decipher the intramolecular and intermolecular hydrogen bonding interactions present in both solid forms. These experiments enabled the unequivocal identification of the tautomers of each desmotrope. Our results also revealed that both solid forms may be described as dimeric structures, with different intermolecular hydrogen bonds connecting the tautomers in each dimer.

  14. Solid-State NMR Studies of Chemically Lithiated CFx

    Science.gov (United States)

    Leifer, N. D.; Johnson, V. S.; Ben-Ari, R.; Gan, H.; Lehnes, J. M.; Guo, R.; Lu, W.; Muffoletto, B. C.; Reddy, T.; Stallworth, P. E.; Greenbaum, S. G.

    2010-01-01

    Three types of fluorinated carbon, all in their original form and upon sequential chemical lithiations via n-butyllithium, were investigated by 13C and 19F solid-state NMR methods. The three starting CFx materials [where x = 1 (nominally)] were fiber based, graphite based, and petroleum coke based. The aim of the current study was to identify, at the atomic/molecular structural level, factors that might account for differences in electrochemical performance among the different kinds of CFx. Differences were noted in the covalent F character among the starting compounds and in the details of LiF production among the lithiated samples. PMID:20676233

  15. Monitoring Cocrystal Formation via In Situ Solid-State NMR.

    Science.gov (United States)

    Mandala, Venkata S; Loewus, Sarel J; Mehta, Manish A

    2014-10-02

    A detailed understanding of the mechanism of organic cocrystal formation remains elusive. Techniques that interrogate a reacting system in situ are preferred, though experimentally challenging. We report here the results of a solid-state in situ NMR study of the spontaneous formation of a cocrystal between a pharmaceutical mimic (caffeine) and a coformer (malonic acid). Using (13)C magic angle spinning NMR, we show that the formation of the cocrystal may be tracked in real time. We find no direct evidence for a short-lived, chemical shift-resolved amorphous solid intermediate. However, changes in the line width and line center of the malonic acid methylene resonance, in the course of the reaction, provide subtle clues to the mode of mass transfer that underlies cocrystal formation.

  16. Solid-state NMR characterization of Mowry Formation shales

    Energy Technology Data Exchange (ETDEWEB)

    Miknis, F.P.

    1992-04-01

    Solid-state [sup 13]C and [sup 29]Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS [sup 13]C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of [sup 29]Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The [sup 29]Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

  17. Solid-state NMR characterization of Mowry Formation shales

    Energy Technology Data Exchange (ETDEWEB)

    Miknis, F.P.

    1992-04-01

    Solid-state {sup 13}C and {sup 29}Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS {sup 13}C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of {sup 29}Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The {sup 29}Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

  18. NMR crystallography of enzyme active sites: probing chemically detailed, three-dimensional structure in tryptophan synthase.

    Science.gov (United States)

    Mueller, Leonard J; Dunn, Michael F

    2013-09-17

    NMR crystallography--the synergistic combination of X-ray diffraction, solid-state NMR spectroscopy, and computational chemistry--offers unprecedented insight into three-dimensional, chemically detailed structure. Initially, researchers used NMR crystallography to refine diffraction data from organic and inorganic solids. Now we are applying this technique to explore active sites in biomolecules, where it reveals chemically rich detail concerning the interactions between enzyme site residues and the reacting substrate. Researchers cannot achieve this level of detail from X-ray, NMR,or computational methodologies in isolation. For example, typical X-ray crystal structures (1.5-2.5 Å resolution) of enzyme-bound intermediates identify possible hydrogen-bonding interactions between site residues and substrate but do not directly identify the protonation states. Solid-state NMR can provide chemical shifts for selected atoms of enzyme-substrate complexes, but without a larger structural framework in which to interpret them only empirical correlations with local chemical structure are possible. Ab initio calculations and molecular mechanics can build models for enzymatic processes, but they rely on researcher-specified chemical details. Together, however, X-ray diffraction, solid-state NMR spectroscopy, and computational chemistry can provide consistent and testable models for structure and function of enzyme active sites: X-ray crystallography provides a coarse framework upon which scientists can develop models of the active site using computational chemistry; they can then distinguish these models by comparing calculated NMR chemical shifts with the results of solid-state NMR spectroscopy experiments. Conceptually, each technique is a puzzle piece offering a generous view of the big picture. Only when correctly pieced together, however, can they reveal the big picture at the highest possible resolution. In this Account, we detail our first steps in the development of

  19. Dynamic membrane interactions of antibacterial and antifungal biomolecules, and amyloid peptides, revealed by solid-state NMR spectroscopy.

    Science.gov (United States)

    Naito, Akira; Matsumori, Nobuaki; Ramamoorthy, Ayyalusamy

    2017-06-06

    A variety of biomolecules acting on the cell membrane folds into a biologically active structure in the membrane environment. It is, therefore, important to determine the structures and dynamics of such biomolecules in a membrane environment. While several biophysical techniques are used to obtain low-resolution information, solid-state NMR spectroscopy is one of the most powerful means for determining the structure and dynamics of membrane bound biomolecules such as antibacterial biomolecules and amyloidogenic proteins; unlike X-ray crystallography and solution NMR spectroscopy, applications of solid-state NMR spectroscopy are not limited by non-crystalline, non-soluble nature or molecular size of membrane-associated biomolecules. This review article focuses on the applications of solid-state NMR techniques to study a few selected antibacterial and amyloid peptides. Solid-state NMR studies revealing the membrane inserted bent α-helical structure associated with the hemolytic activity of bee venom melittin and the chemical shift oscillation analysis used to determine the transmembrane structure (with α-helix and 310-helix in the N- and C-termini, respectively) of antibiotic peptide alamethicin are discussed in detail. Oligomerization of an amyloidogenic islet amyloid polypeptide (IAPP, or also known as amylin) resulting from its aggregation in a membrane environment, molecular interactions of the antifungal natural product amphotericin B with ergosterol in lipid bilayers, and the mechanism of lipid raft formation by sphingomyelin studied using solid state NMR methods are also discussed in this review article. This article is part of a Special Issue entitled "Biophysical Exploration of Dynamical Ordering of Biomolecular Systems" edited by Dr. Koichi Kato. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. An extrapolation scheme for solid-state NMR chemical shift calculations

    Science.gov (United States)

    Nakajima, Takahito

    2017-06-01

    Conventional quantum chemical and solid-state physical approaches include several problems to accurately calculate solid-state nuclear magnetic resonance (NMR) properties. We propose a reliable computational scheme for solid-state NMR chemical shifts using an extrapolation scheme that retains the advantages of these approaches but reduces their disadvantages. Our scheme can satisfactorily yield solid-state NMR magnetic shielding constants. The estimated values have only a small dependence on the low-level density functional theory calculation with the extrapolation scheme. Thus, our approach is efficient because the rough calculation can be performed in the extrapolation scheme.

  1. Solid State NMR Characterization of Complex Metal Hydrides systems for Hydrogen Storage Applications

    Directory of Open Access Journals (Sweden)

    Son-Jong Hwang

    2011-12-01

    Full Text Available Solid state NMR is widely applied in studies of solid state chemistries for hydrogen storage reactions. Use of 11B MAS NMR in studies of metal borohydrides (BH4 is mainly focused, revisiting the issue of dodecaborane formation and observation of 11B{1H} Nuclear Overhauser Effect.

  2. Atomic-resolution structure of cytoskeletal bactofilin by solid-state NMR.

    Science.gov (United States)

    Shi, Chaowei; Fricke, Pascal; Lin, Lin; Chevelkov, Veniamin; Wegstroth, Melanie; Giller, Karin; Becker, Stefan; Thanbichler, Martin; Lange, Adam

    2015-12-01

    Bactofilins are a recently discovered class of cytoskeletal proteins of which no atomic-resolution structure has been reported thus far. The bacterial cytoskeleton plays an essential role in a wide range of processes, including morphogenesis, cell division, and motility. Among the cytoskeletal proteins, the bactofilins are bacteria-specific and do not have a eukaryotic counterpart. The bactofilin BacA of the species Caulobacter crescentus is not amenable to study by x-ray crystallography or solution nuclear magnetic resonance (NMR) because of its inherent noncrystallinity and insolubility. We present the atomic structure of BacA calculated from solid-state NMR-derived distance restraints. We show that the core domain of BacA forms a right-handed β helix with six windings and a triangular hydrophobic core. The BacA structure was determined to 1.0 Å precision (heavy-atom root mean square deviation) on the basis of unambiguous restraints derived from four-dimensional (4D) HN-HN and 2D C-C NMR spectra.

  3. 1H NMR spectra dataset and solid-state NMR data of cowpea (Vigna unguiculata)

    DEFF Research Database (Denmark)

    Alves Filho, Elenilson G.; Silva, Lorena M. A.; Teofilo, Elizita M.

    2017-01-01

    In this article the NMR data from chemical shifts, coupling constants, and structures of all the characterized compounds were provided, beyond a complementary PCA evaluation for the corresponding manuscript (E.G. Alves Filho, L.M.A. Silva, E.M. Teofilo, F.H. Larsen, E.S. de Brito, 2017) [3......]. In addition, a complementary assessment from solid-state NMR data was provided. For further chemometric analysis, numerical matrices from the raw 1H NMR data were made available in Microsoft Excel workbook format (.xls)....

  4. (1)H NMR spectra dataset and solid-state NMR data of cowpea (Vigna unguiculata).

    Science.gov (United States)

    Alves Filho, Elenilson G; Silva, Lorena M A; Teofilo, Elizita M; Larsen, Flemming H; de Brito, Edy S

    2017-04-01

    In this article the NMR data from chemical shifts, coupling constants, and structures of all the characterized compounds were provided, beyond a complementary PCA evaluation for the corresponding manuscript (E.G. Alves Filho, L.M.A. Silva, E.M. Teofilo, F.H. Larsen, E.S. de Brito, 2017) [3]. In addition, a complementary assessment from solid-state NMR data was provided. For further chemometric analysis, numerical matrices from the raw (1)H NMR data were made available in Microsoft Excel workbook format (.xls).

  5. Multidimensional solid-state NMR spectroscopy of plant cell walls.

    Science.gov (United States)

    Wang, Tuo; Phyo, Pyae; Hong, Mei

    2016-09-01

    Plant biomass has become an important source of bio-renewable energy in modern society. The molecular structure of plant cell walls is difficult to characterize by most atomic-resolution techniques due to the insoluble and disordered nature of the cell wall. Solid-state NMR (SSNMR) spectroscopy is uniquely suited for studying native hydrated plant cell walls at the molecular level with chemical resolution. Significant progress has been made in the last five years to elucidate the molecular structures and interactions of cellulose and matrix polysaccharides in plant cell walls. These studies have focused on primary cell walls of growing plants in both the dicotyledonous and grass families, as represented by the model plants Arabidopsis thaliana, Brachypodium distachyon, and Zea mays. To date, these SSNMR results have shown that 1) cellulose, hemicellulose, and pectins form a single network in the primary cell wall; 2) in dicot cell walls, the protein expansin targets the hemicellulose-enriched region of the cellulose microfibril for its wall-loosening function; and 3) primary wall cellulose has polymorphic structures that are distinct from the microbial cellulose structures. This article summarizes these key findings, and points out future directions of investigation to advance our fundamental understanding of plant cell wall structure and function.

  6. Applications of high-resolution solid-state NMR spectroscopy in food science.

    Science.gov (United States)

    Bertocchi, Fabio; Paci, Maurizio

    2008-10-22

    The principal applications of high-resolution solid-state NMR spectroscopy, in the field of food science, are reviewed, after a short general introduction, mainly focusing on the potential of these investigations, which are, today, routine tools for resolving technological problems. Selected examples of the applications in the field of food science of high-resolution solid-state NMR spectroscopy both in (13)C and in (1)H NMR particularly illustrative of the results obtainable are reported in some detail.

  7. Arabidopsis thalianafrom Polarization Transfer Solid-State NMR

    Energy Technology Data Exchange (ETDEWEB)

    White, Paul B [Ames Laboratory; Wang, Tuo [Ames Laboratory; Park, Yong Bum [Pennsylvania State University; Cosgrove, Daniel J [Pennsylvania State University; Hong, Mei [Ames Laboratory

    2014-07-23

    Polysaccharide-rich plant cell walls are hydrated under functional conditions, but the molecular interactions between water and polysaccharides in the wall have not been investigated. In this work, we employ polarization transfer solid-state NMR techniques to study the hydration of primary-wall polysaccharides of the model plant, Arabidopsis thaliana. By transferring water 1H polarization to polysaccharides through distance- and mobility-dependent 1H–1H dipolar couplings and detecting it through polysaccharide 13C signals, we obtain information about water proximity to cellulose, hemicellulose, and pectins as well as water mobility. Both intact and partially extracted cell wall samples are studied. Our results show that water–pectin polarization transfer is much faster than water–cellulose polarization transfer in all samples, but the extent of extraction has a profound impact on the water–polysaccharide spin diffusion. Removal of calcium ions and the consequent extraction of homogalacturonan (HG) significantly slowed down spin diffusion, while further extraction of matrix polysaccharides restored the spin diffusion rate. These trends are observed in cell walls with similar water content, thus they reflect inherent differences in the mobility and spatial distribution of water. Combined with quantitative analysis of the polysaccharide contents, our results indicate that calcium ions and HG gelation increase the amount of bound water, which facilitates spin diffusion, while calcium removal disrupts the gel and gives rise to highly dynamic water, which slows down spin diffusion. The recovery of spin diffusion rates after more extensive extraction is attributed to increased water-exposed surface areas of the polysaccharides. Water–pectin spin diffusion precedes water–cellulose spin diffusion, lending support to the single-network model of plant primary walls in which a substantial fraction of the cellulose surface is surrounded by pectins.

  8. Molecular Dynamics and Morphology of High Performance Elastomers and Fibers by Solid State NMR

    Science.gov (United States)

    2016-06-30

    Fibers by Solid-State NMR The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued as an...ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 PBO fiber; environmental degradation; solid-state NMR ...non peer-reviewed journals: Final Report: Molecular Dynamics and Morphology of High-Performance Elastomers and Fibers by Solid-State NMR Report Title

  9. Magic-Angle-Spinning Solid-State NMR of Membrane Proteins

    NARCIS (Netherlands)

    Baker, Lindsay A.; Folkers, Gert E.; Sinnige, Tessa; Houben, Klaartje; Kaplan, M.; van der Cruijsen, Elwin A W; Baldus, Marc

    2015-01-01

    Solid-state NMR spectroscopy (ssNMR) provides increasing possibilities to examine membrane proteins in different molecular settings, ranging from synthetic bilayers to whole cells. This flexibility often enables ssNMR experiments to be directly correlated with membrane protein function. In this

  10. Ageing of Starch Based Systems as observed with FT-IR and Solid State NMR Spectroscopy

    NARCIS (Netherlands)

    Smits, A.L.M.; Ruhnau, F.C.; Vliegenthart, J.F.G.; Soest, van J.J.G.

    1998-01-01

    The retrogradation and physical ageing of model starch systems with respect to their glass transition temperatures Tg have been investigated by Fourier transform infrared spectroscopy and solid state NMR spectroscopy. Diffuse reflectance Fourier transform infrared (DRIFT) spectra demonstrate the com

  11. Ageing of starch based systems as observed with FT-IR and solid state NMR spectroscopy

    NARCIS (Netherlands)

    Vliegenthart, J.F.G.; Smits, A.L.M.; Ruhnau, F.C.; Soest, J.J.G. van

    1998-01-01

    The retrogradation and physical ageing of model starch systems with respect to their glass transition temperatures Tg have been investigated by Fourier transform infrared Spectroscopy and solid state NMR spectroscopy. Diffuse reflectance Fourier transform infrared (DRIFT) spectra demonstrate the com

  12. A Toolbox of Solid-State NMR Experiments for the Characterization of Soft Organic Nanomaterials

    KAUST Repository

    Straasø, Lasse Arnt

    2016-02-02

    Determining how organic molecules self-assemble into a solid material is a challenging and demanding task if a single crystal of the material cannot be produced. Solid-state NMR spectroscopy offers access to such molecular details via an appropriate selection of techniques. This report gives a selected overview of 1D and 2D solid-state NMR techniques for elucidating the structure of soft organic solids. We focus on how the solid-state NMR techniques are designed from the perspective of the different nuclear interactions, using average Hamiltonian theory and product operators. We also introduce recent methods for quantification and reduction of experimental artifacts. Finally, we highlight how the solid-state NMR techniques can be applied to soft organic materials by reviewing recent applications to semicrystalline polymers, π-conjugated polymers, natural silk, and graphene-related materials.

  13. 31P Solid-state NMR based monitoring of permeation of cell penetrating peptides into skin

    Science.gov (United States)

    Desai, Pinaki R.; Cormier, Ashley R.; Shah, Punit P.; Patlolla, Ram R.; Paravastu, Anant K.; Singh, Mandip

    2013-01-01

    The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R8, R11 and YKA) through skin intercellular lipids using 31P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, sections (0–60, 61–120 and 121–180 µm) were collected and analyzed for 31P NMR signal. The concentration dependent shift of 0, 25, 50, 100 and 200 mg/ml of TAT on skin layers, diffusion of TAT, R8, R11 and YKA in the skin and time dependent permeation of R11 was measured on various skin sections using 31P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in 31P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100 mg/ml CPP concentration. R11 and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R11 penetration up to 180 µm within 30 min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, 31P solid-state NMR can be used to track CPP penetration into different skin layers. PMID:23702274

  14. (31)P solid-state NMR based monitoring of permeation of cell penetrating peptides into skin.

    Science.gov (United States)

    Desai, Pinaki R; Cormier, Ashley R; Shah, Punit P; Patlolla, Ram R; Paravastu, Anant K; Singh, Mandip

    2014-02-01

    The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R8, R11, and YKA) through skin intercellular lipids using (31)P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, and sections (0-60, 61-120, and 121-180μm) were collected and analyzed for (31)P NMR signal. The concentration-dependent shift of 0, 25, 50, 100, and 200mg/ml of TAT on skin layers, diffusion of TAT, R8, R11, and YKA in the skin and time dependent permeation of R11 was measured on various skin sections using (31)P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in (31)P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100mg/ml CPP concentration. R11 and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R11 penetration up to 180μm within 30min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, (31)P solid-state NMR can be used to track CPP penetration into different skin layers. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Lithium substitution in strontium chlorapatite studied by solid state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, S.; Sairam, T. N., E-mail: sai@igcar.gov.in; Amarendra, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India); Maji, B. K.; Jena, H. [Chemical Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India)

    2016-05-23

    Strontium Chlorapatites with various amounts of Li substitution (Sr{sub 10-x}Li{sub x}(PO{sub 4}){sub 6}Cl{sub 2-δ}) were prepared by solid state reaction method and characterized by powder XRD and solid state NMR spectroscopy. XRD reveals shortening of lattice parameters upon Li incorporation. The linewidth of {sup 31}P solid state Magic Angle Spinning NMR spectra decreases with increase in Li content within the apatite phase. This study confirms Li uptake within the apatite phase.

  16. Optimized multiple quantum MAS lineshape simulations in solid state NMR

    Science.gov (United States)

    Brouwer, William J.; Davis, Michael C.; Mueller, Karl T.

    2009-10-01

    The majority of nuclei available for study in solid state Nuclear Magnetic Resonance have half-integer spin I>1/2, with corresponding electric quadrupole moment. As such, they may couple with a surrounding electric field gradient. This effect introduces anisotropic line broadening to spectra, arising from distinct chemical species within polycrystalline solids. In Multiple Quantum Magic Angle Spinning (MQMAS) experiments, a second frequency dimension is created, devoid of quadrupolar anisotropy. As a result, the center of gravity of peaks in the high resolution dimension is a function of isotropic second order quadrupole and chemical shift alone. However, for complex materials, these parameters take on a stochastic nature due in turn to structural and chemical disorder. Lineshapes may still overlap in the isotropic dimension, complicating the task of assignment and interpretation. A distributed computational approach is presented here which permits simulation of the two-dimensional MQMAS spectrum, generated by random variates from model distributions of isotropic chemical and quadrupole shifts. Owing to the non-convex nature of the residual sum of squares (RSS) function between experimental and simulated spectra, simulated annealing is used to optimize the simulation parameters. In this manner, local chemical environments for disordered materials may be characterized, and via a re-sampling approach, error estimates for parameters produced. Program summaryProgram title: mqmasOPT Catalogue identifier: AEEC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3650 No. of bytes in distributed program, including test data, etc.: 73 853 Distribution format: tar.gz Programming language: C, OCTAVE Computer: UNIX

  17. Proton-Based Ultrafast Magic Angle Spinning Solid-State NMR Spectroscopy.

    Science.gov (United States)

    Zhang, Rongchun; Mroue, Kamal H; Ramamoorthy, Ayyalusamy

    2017-04-18

    Protons are vastly abundant in a wide range of exciting macromolecules and thus can be a powerful probe to investigate the structure and dynamics at atomic resolution using solid-state NMR (ssNMR) spectroscopy. Unfortunately, the high signal sensitivity, afforded by the high natural-abundance and high gyromagnetic ratio of protons, is greatly compromised by severe line broadening due to the very strong (1)H-(1)H dipolar couplings. As a result, protons are rarely used, in spite of the desperate need for enhancing the sensitivity of ssNMR to study a variety of systems that are not amenable for high resolution investigation using other techniques including X-ray crystallography, cryo-electron microscopy, and solution NMR spectroscopy. Thanks to the remarkable improvement in proton spectral resolution afforded by the significant advances in magic-angle-spinning (MAS) probe technology, (1)H ssNMR spectroscopy has recently attracted considerable attention in the structural and dynamics studies of various molecular systems. However, it still remains a challenge to obtain narrow (1)H spectral lines, especially from proteins, without resorting to deuteration. In this Account, we review recent proton-based ssNMR strategies that have been developed in our laboratory to further improve proton spectral resolution without resorting to chemical deuteration for the purposes of gaining atomistic-level insights into molecular structures of various crystalline solid systems, using small molecules and peptides as illustrative examples. The proton spectral resolution enhancement afforded by the ultrafast MAS frequencies up to 120 kHz is initially discussed, followed by a description of an ensemble of multidimensional NMR pulse sequences, all based on proton detection, that have been developed to obtain in-depth information from dipolar couplings and chemical shift anisotropy (CSA). Simple single channel multidimensional proton NMR experiments could be performed to probe the proximity

  18. Solid-State NMR-Restrained Ensemble Dynamics of a Membrane Protein in Explicit Membranes.

    Science.gov (United States)

    Cheng, Xi; Jo, Sunhwan; Qi, Yifei; Marassi, Francesca M; Im, Wonpil

    2015-04-21

    Solid-state NMR has been used to determine the structures of membrane proteins in native-like lipid bilayer environments. Most structure calculations based on solid-state NMR observables are performed using simulated annealing with restrained molecular dynamics and an energy function, where all nonbonded interactions are represented by a single, purely repulsive term with no contributions from van der Waals attractive, electrostatic, or solvation energy. To our knowledge, this is the first application of an ensemble dynamics technique performed in explicit membranes that uses experimental solid-state NMR observables to obtain the refined structure of a membrane protein together with information about its dynamics and its interactions with lipids. Using the membrane-bound form of the fd coat protein as a model membrane protein and its experimental solid-state NMR data, we performed restrained ensemble dynamics simulations with different ensemble sizes in explicit membranes. For comparison, a molecular dynamics simulation of fd coat protein was also performed without any restraints. The average orientation of each protein helix is similar to a structure determined by traditional single-conformer approaches. However, their variations are limited in the resulting ensemble of structures with one or two replicas, as they are under the strong influence of solid-state NMR restraints. Although highly consistent with all solid-state NMR observables, the ensembles of more than two replicas show larger orientational variations similar to those observed in the molecular dynamics simulation without restraints. In particular, in these explicit membrane simulations, Lys(40), residing at the C-terminal side of the transmembrane helix, is observed to cause local membrane curvature. Therefore, compared to traditional single-conformer approaches in implicit environments, solid-state NMR restrained ensemble simulations in explicit membranes readily characterize not only protein

  19. Solid-state NMR applied to photosynthetic light-harvesting complexes

    NARCIS (Netherlands)

    Pandit, A.; Groot, de H.J.M.

    2012-01-01

    This short review describes how solid-state NMR has provided a mechanistic and electronic picture of pigment–protein and pigment–pigment interactions in photosynthetic antenna complexes. NMR results on purple bacterial antenna complexes show how the packing of the protein and the pigments inside the

  20. Solid-state NMR applied to photosynthetic light-harvesting complexes

    NARCIS (Netherlands)

    Pandit, A.; Groot, de H.J.M.

    2012-01-01

    This short review describes how solid-state NMR has provided a mechanistic and electronic picture of pigment–protein and pigment–pigment interactions in photosynthetic antenna complexes. NMR results on purple bacterial antenna complexes show how the packing of the protein and the pigments inside the

  1. 1020MHz single-channel proton fast magic angle spinning solid-state NMR spectroscopy.

    Science.gov (United States)

    Pandey, Manoj Kumar; Zhang, Rongchun; Hashi, Kenjiro; Ohki, Shinobu; Nishijima, Gen; Matsumoto, Shinji; Noguchi, Takashi; Deguchi, Kenzo; Goto, Atsushi; Shimizu, Tadashi; Maeda, Hideaki; Takahashi, Masato; Yanagisawa, Yoshinori; Yamazaki, Toshio; Iguchi, Seiya; Tanaka, Ryoji; Nemoto, Takahiro; Miyamoto, Tetsuo; Suematsu, Hiroto; Saito, Kazuyoshi; Miki, Takashi; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-12-01

    This study reports a first successful demonstration of a single channel proton 3D and 2D high-throughput ultrafast magic angle spinning (MAS) solid-state NMR techniques in an ultra-high magnetic field (1020MHz) NMR spectrometer comprised of HTS/LTS magnet. High spectral resolution is well demonstrated.

  2. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR

    Science.gov (United States)

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100 K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered.

  3. NMR Crystallography of a Carbanionic Intermediate in Tryptophan Synthase: Chemical Structure, Tautomerization, and Reaction Specificity

    Science.gov (United States)

    2016-01-01

    Carbanionic intermediates play a central role in the catalytic transformations of amino acids performed by pyridoxal-5′-phosphate (PLP)-dependent enzymes. Here, we make use of NMR crystallography—the synergistic combination of solid-state nuclear magnetic resonance, X-ray crystallography, and computational chemistry—to interrogate a carbanionic/quinonoid intermediate analogue in the β-subunit active site of the PLP-requiring enzyme tryptophan synthase. The solid-state NMR chemical shifts of the PLP pyridine ring nitrogen and additional sites, coupled with first-principles computational models, allow a detailed model of protonation states for ionizable groups on the cofactor, substrates, and nearby catalytic residues to be established. Most significantly, we find that a deprotonated pyridine nitrogen on PLP precludes formation of a true quinonoid species and that there is an equilibrium between the phenolic and protonated Schiff base tautomeric forms of this intermediate. Natural bond orbital analysis indicates that the latter builds up negative charge at the substrate Cα and positive charge at C4′ of the cofactor, consistent with its role as the catalytic tautomer. These findings support the hypothesis that the specificity for β-elimination/replacement versus transamination is dictated in part by the protonation states of ionizable groups on PLP and the reacting substrates and underscore the essential role that NMR crystallography can play in characterizing both chemical structure and dynamics within functioning enzyme active sites. PMID:27779384

  4. Solid-state NMR spectroscopic trends for supramolecular assemblies and protein aggregates.

    Science.gov (United States)

    Linser, Rasmus

    2017-08-24

    Solid-state NMR is able to generate structural data on sample preparations that are explicitly non-crystalline. In particular, for amyloid fibril samples, which can comprise significant degrees of sample disorder, solid-state NMR has been used very successfully. But also solid-state NMR studies of other supramolecular assemblies that have resisted assessment by more standard methods are being performed with increasing ease and biological impact, many of which are briefly reviewed here. New technical trends with respect to structure calculation, protein dynamics and smaller sample amounts have reshaped the field of solid-state NMR recently. In particular, proton-detected approaches based on fast Magic-Angle Spinning (MAS) were demonstrated for crystalline systems initially. Currently, such approaches are being expanded to the above-mentioned non-crystalline targets, the characterization of which can now be pursued with sample amounts on the order of a milligram. In this Trends article, I am giving a brief overview about achievements of the last years as well as the directions that the field has been heading into and delineate some satisfactory perspectives for solid-state NMR's future striving. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Toward a structure determination method for biomineral-associated protein using combined solid- state NMR and computational structure prediction.

    Science.gov (United States)

    Masica, David L; Ash, Jason T; Ndao, Moise; Drobny, Gary P; Gray, Jeffrey J

    2010-12-08

    Protein-biomineral interactions are paramount to materials production in biology, including the mineral phase of hard tissue. Unfortunately, the structure of biomineral-associated proteins cannot be determined by X-ray crystallography or solution nuclear magnetic resonance (NMR). Here we report a method for determining the structure of biomineral-associated proteins. The method combines solid-state NMR (ssNMR) and ssNMR-biased computational structure prediction. In addition, the algorithm is able to identify lattice geometries most compatible with ssNMR constraints, representing a quantitative, novel method for investigating crystal-face binding specificity. We use this method to determine most of the structure of human salivary statherin interacting with the mineral phase of tooth enamel. Computation and experiment converge on an ensemble of related structures and identify preferential binding at three crystal surfaces. The work represents a significant advance toward determining structure of biomineral-adsorbed protein using experimentally biased structure prediction. This method is generally applicable to proteins that can be chemically synthesized.

  6. Solid State NMR Studies of Energy Conversion and Storage Materials

    Science.gov (United States)

    Jankuru Hennadige, Sohan Roshel De Silva

    NMR (Nuclear magnetic resonance) spectroscopy is utilized to study energy conversion and storage materials. Different types of NMR techniques including Magic Angle Spinning, Cross-polarization and relaxation measurement experiments were employed. Four different projects are discussed in this dissertation. First, three types of CFx battery materials were investigated. Electrochemical studies have demonstrated different electrochemical performances by one type, delivering superior performance over the other two. 13C and 19F MAS NMR techniques are employed to identify the atomic/molecular structural factors that might account for differences in electrochemical performance among different types. Next as the second project, layered polymer dielectrics were investigated by NMR. Previous studies have shown that thin film capacitors are improved by using alternate layers of two polymers with complementary properties: one with a high breakdown strength and one with high dielectric constant as opposed to monolithic layers. 13C to 1H cross-polarization techniques were used to investigate any inter-layer properties that may cause the increase in the dielectric strength. The third project was to study two types of thermoelectric materials. These samples were made of heavily doped phosphorous and boron in silicon by two different methods: ball-milled and annealed. These samples were investigated by NMR to determine the degree of disorder and obtain insight into the doping efficiency. The last ongoing project is on a lithium-ion battery system. The nature of passivating layers or the solid electrolyte interphase (SEI) formed on the electrodes surface is important because of the direct correlation between the SEI and the battery life time/durability. Multinuclear (7Li, 19F, 31P) techniques are employed to identify the composition of the SEI formation of both positive and negative electrodes.

  7. (13)C and (15)N solid-state NMR studies on albendazole and cyclodextrin albendazole complexes.

    Science.gov (United States)

    Ferreira, M João G; García, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

    2015-06-05

    (13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:β-cyclodextrin, ABZ:methyl-β-cyclodextrin, ABZ:hydroxypropyl-β-cyclodextrin and ABZ:citrate-β-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes.

  8. Solid state NMR: The essential technology for helical membrane protein structural characterization.

    Science.gov (United States)

    Cross, Timothy A; Ekanayake, Vindana; Paulino, Joana; Wright, Anna

    2014-02-01

    NMR spectroscopy of helical membrane proteins has been very challenging on multiple fronts. The expression and purification of these proteins while maintaining functionality has consumed countless graduate student hours. Sample preparations have depended on whether solution or solid-state NMR spectroscopy was to be performed - neither have been easy. In recent years it has become increasingly apparent that membrane mimic environments influence the structural result. Indeed, in these recent years we have rediscovered that Nobel laureate, Christian Anfinsen, did not say that protein structure was exclusively dictated by the amino acid sequence, but rather by the sequence in a given environment (Anfinsen, 1973) [106]. The environment matters, molecular interactions with the membrane environment are significant and many examples of distorted, non-native membrane protein structures have recently been documented in the literature. However, solid-state NMR structures of helical membrane proteins in proteoliposomes and bilayers are proving to be native structures that permit a high resolution characterization of their functional states. Indeed, solid-state NMR is uniquely able to characterize helical membrane protein structures in lipid environments without detergents. Recent progress in expression, purification, reconstitution, sample preparation and in the solid-state NMR spectroscopy of both oriented samples and magic angle spinning samples has demonstrated that helical membrane protein structures can be achieved in a timely fashion. Indeed, this is a spectacular opportunity for the NMR community to have a major impact on biomedical research through the solid-state NMR spectroscopy of these proteins. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. What Can Solid State NMR Contribute To Our Understanding of Protein Folding?

    Science.gov (United States)

    Hu, Kan-Nian; Tycko, Robert

    2010-01-01

    Complete understanding of the folding process that connects a structurally disordered state of a protein to an ordered, biochemically functional state requires detailed characterization of intermediate structural states with high resolution and site specificity. While the intrinsically inhomogeneous and dynamic nature of unfolded and partially folded states limits the efficacy of traditional x-ray diffraction and solution NMR in structural studies, solid state NMR methods applied to frozen solutions can circumvent the complications due to molecular motions and conformational exchange encountered in unfolded and partially folded states. Moreover, solid state NMR methods can provide both qualitative and quantitative structural information at the site-specific level, even in the presence of structural inhomogeneity. This article reviews relevant solid state NMR methods and their initial applications to protein folding studies. Using either chemical denaturation to prepare unfolded states at equilibrium or a rapid freezing apparatus to trap non-equilibrium, transient structural states on a sub-millisecond time scale, recent results demonstrate that solid state NMR can contribute essential information about folding processes that is not available from more familiar biophysical methods. PMID:20542371

  10. In situ solid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach.

    Science.gov (United States)

    Zhang, Weiping; Xu, Shutao; Han, Xiuwen; Bao, Xinhe

    2012-01-07

    In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references).

  11. Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy, a new approach to study humic material?

    Science.gov (United States)

    Knicker, Heike; Lange, Sascha; van Rossum, Barth; Oschkinat, Hartmut

    2016-04-01

    Compared to solution NMR spectroscopy, solid-state NMR spectra suffer from broad resonance lines and low resolution. This could be overcome by the use of 2-dimenstional solid-state NMR pulse sequences. Until recently, this approach has been unfeasible as a routine tool in soil chemistry, mainly because of the low NMR sensitivity of the respective samples. A possibility to circumvent those sensitivity problems represents high-field Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy (Barnes et al., 2008), allowing considerable signal enhancements (Akbey et al., 2010). This is achieved by a microwave-driven transfer of polarization from a paramagnetic center to nuclear spins. Application of DNP to MAS spectra of biological systems (frozen solutions) showed enhancements of the factor 40 to 50 (Hall et al., 1997). Enhancements of this magnitude, thus may enable the use of at least some of the 2D solid-state NMR techniques that are presently already applied for pure proteins but are difficult to apply to soil peptides in their complex matrix. After adjusting the required acquisition parameters to the system "soil organic matter", lower but still promising enhancement factors were achieved. Additional optimization was performed and allowed the acquisition of 2D 13C and 15N solid-state NMR spectra of humified 13C and 15N enriched plant residues. Within the present contribution, the first solid-state DNP NMR spectra of humic material are presented. Those data demonstrate the great potential of this approach which certainly opens new doors for a better understanding of biochemical processes in soils, sediments and water. Akbey, Ü., Franks, W.T., Linden, A., Lange, S., Griffin, R.G., van Rossum, B.-J., Oschkinat, H., 2010. Dynamic nuclear polarization of deuterated proteins. Angewandte Chemie International Edition 49, 7803-7806. Barnes, A.B., De Paëpe, G., van der Wel, P.C.A., Hu, K.N., Joo, C.G., Bajaj, V.S., Mak-Jurkauskas, M.L., Sirigiri, J.R., Herzfeld, J

  12. Genetic algorithms and solid state NMR pulse sequences

    CERN Document Server

    Bechmann, Matthias; Sebald, Angelika

    2013-01-01

    The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C7 dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is found to be robust over a wide range of parameters, requires only minimal a priori knowledge of the spin system for experimental implementations with buildup rates being solely determined by the magnitude of the dipolar coupling interaction, but is found to be less broadbanded than the original C7 pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.

  13. Concepts and Methods of Solid-State NMR Spectroscopy Applied to Biomembranes.

    Science.gov (United States)

    Molugu, Trivikram R; Lee, Soohyun; Brown, Michael F

    2017-09-14

    Concepts of solid-state NMR spectroscopy and applications to fluid membranes are reviewed in this paper. Membrane lipids with (2)H-labeled acyl chains or polar head groups are studied using (2)H NMR to yield knowledge of their atomistic structures in relation to equilibrium properties. This review demonstrates the principles and applications of solid-state NMR by unifying dipolar and quadrupolar interactions and highlights the unique features offered by solid-state (2)H NMR with experimental illustrations. For randomly oriented multilamellar lipids or aligned membranes, solid-state (2)H NMR enables direct measurement of residual quadrupolar couplings (RQCs) due to individual C-(2)H-labeled segments. The distribution of RQC values gives nearly complete profiles of the segmental order parameters SCD((i)) as a function of acyl segment position (i). Alternatively, one can measure residual dipolar couplings (RDCs) for natural abundance lipid samples to obtain segmental SCH order parameters. A theoretical mean-torque model provides acyl-packing profiles representing the cumulative chain extension along the normal to the aqueous interface. Equilibrium structural properties of fluid bilayers and various thermodynamic quantities can then be calculated, which describe the interactions with cholesterol, detergents, peptides, and integral membrane proteins and formation of lipid rafts. One can also obtain direct information for membrane-bound peptides or proteins by measuring RDCs using magic-angle spinning (MAS) in combination with dipolar recoupling methods. Solid-state NMR methods have been extensively applied to characterize model membranes and membrane-bound peptides and proteins, giving unique information on their conformations, orientations, and interactions in the natural liquid-crystalline state.

  14. High-Resolution Solid-State NMR Spectroscopy: Characterization of Polymorphism in Cimetidine, a Pharmaceutical Compound

    Science.gov (United States)

    Pacilio, Julia E.; Tokarski, John T.; Quiñones, Rosalynn; Iuliucci, Robbie J.

    2014-01-01

    High-resolution solid-state NMR (SSNMR) spectroscopy has many advantages as a tool to characterize solid-phase material that finds applications in polymer chemistry, nanotechnology, materials science, biomolecular structure determination, and others, including the pharmaceutical industry. The technology associated with achieving high resolution…

  15. High-Resolution Solid-State NMR Spectroscopy: Characterization of Polymorphism in Cimetidine, a Pharmaceutical Compound

    Science.gov (United States)

    Pacilio, Julia E.; Tokarski, John T.; Quiñones, Rosalynn; Iuliucci, Robbie J.

    2014-01-01

    High-resolution solid-state NMR (SSNMR) spectroscopy has many advantages as a tool to characterize solid-phase material that finds applications in polymer chemistry, nanotechnology, materials science, biomolecular structure determination, and others, including the pharmaceutical industry. The technology associated with achieving high resolution…

  16. Solid-state NMR and ESR studies of activated carbons produced from pecan shells

    Science.gov (United States)

    Activated carbon from pecan shells has shown promise as an adsorbent in water treatment and sugar refining. However, the chemistry of the material is complex and not fully understood. We report here the application of solid state NMR and ESR to study the chemical structure, mobility, and pore volu...

  17. Investigation of Rhodopsin Dynamics in its Signaling State by Solid-State Deuterium NMR Spectroscopy

    Science.gov (United States)

    Struts, Andrey V.; Chawla, Udeep; Perera, Suchithranga M.D.C.; Brown, Michael F.

    2017-01-01

    Site-directed deuterium NMR spectroscopy is a valuable tool to study the structural dynamics of biomolecules in cases where solution NMR is inapplicable. Solid-state 2H NMR spectral studies of aligned membrane samples of rhodopsin with selectively labeled retinal provide information on structural changes of the chromophore in different protein states. In addition, solid-state 2H NMR relaxation time measurements allow one to study the dynamics of the ligand during the transition from the inactive to the active state. Here we describe the methodological aspects of solid-state 2H NMR spectroscopy for functional studies of rhodopsin, with an emphasis on the dynamics of the retinal cofactor. We provide complete protocols for the preparation of NMR samples of rhodopsin with 11-cis-retinal selectively deuterated at the methyl groups in aligned membranes. In addition, we review optimized conditions for trapping the rhodopsin photointermediates; and lastly we address the challenging problem of trapping the signaling state of rhodopsin in aligned membrane films. PMID:25697522

  18. Studies of Molecular Dynamics by Solid State Deuterium NMR Spectroscopy

    Science.gov (United States)

    Zhao, Baiyi

    The rotational dynamics of molecules in a number of solid systems were followed by variable temperature deuterium (^2H), nuclear magnetic resonance (NMR) spectroscopy via changes in the spectral lineshapes and spin-lattice relaxation times (T _1). First the pure solid trimethylamine-borane adduct, (CH_3)_3NBH_3, was studied. For a methyl deuterated sample, T _1 measurements yielded two T_1 minima, 6.9 ms and 4.3 ms corresponding to the slowing of methyl and trimethyl rotation, respectively, with decreasing temperature. Activation energies for methyl and trimethyl rotation, obtained from fitting the T _1 curve as a function of temperature, were 32.8 and 15.0 kJ/mol, respectively; simulations of the spectral lineshapes gave 26.6 and 18.9 kT/mol, respectively. Fitting of the ^2H T_1 curve for the borane deuterated sample gave a BH _3 rotation activation energy of 14.1 kT/mol and a ^2H quadrupolar coupling constant, chi, of 101 kHz. The activation energy for BH_3 rotation obtained from the spectral lineshape simulations gave 12.6 kT/mol. A series of deuterated organic chalcogen cations: (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, were ion exchanged into the cavities of sodium Mordenite LZ-M5 and the dynamics of these guests within the hydrated zeolite were followed by ^2H NMR. All three undergo isotropic motion above about -80 to -90^circC. Below this temperature two superimposed ^2H powder spectra appear; the broad lineshape is consistent with only methyl rotation in a hindered, coordinated site, and the other narrow lineshape is due to both methyl and trimethyl rotation in a less hindered, uncoordinated site. As the temperature is lowered the population of the lower energy coordinated site increases. Relative peak areas yield adsorption enthalpies of 6.7, 7.8 and 10.0 kJ/mol for (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, respectively. The series of methyl deuterated ammonium and phosphonium cations: (CH_3)NH_3^+ , (CH_3)_2NH^+ , (CH_3)_3NH^+ and (CH_3)_4P^+ , were

  19. Solid-state (17)O NMR study of 2-acylbenzoic acids and warfarin.

    Science.gov (United States)

    Kong, Xianqi; Dai, Yizhe; Wu, Gang

    We report synthesis and solid-state (17)O NMR characterization of four site-specifically (17)O-labeled 2-acylbenzoic acids (2-RC(O)C6H4COOH) where R=H and CH3): 2-[3-(17)O]formylbenzoic acid, 2-[1,2-(17)O2]formylbenzoic acid, 2-[3-(17)O]acetylbenzoic acid, and 2-[1,2,3-(17)O3]acetylbenzoic acid. In the solid state, both 2-formyl- and 2-acetyl-benzoic acids exist as the cyclic phthalide form each containing a five-membered lactone ring and a cyclic hemiacetal/hemiketal group. Static and magic-angle-spinning (17)O NMR spectra were recorded at 14.1 and 21.1T for these compounds, from which the (17)O chemical shift and nuclear quadrupolar coupling tensors were determined for each oxygen site. These results represent the first time that (17)O NMR tensors are fully characterized for lactone, cyclic hemiacetal, and cyclic hemiketal functional groups. We also report solid-state (17)O NMR data for the cyclic hemiketal group an anticoagulant drug, warfarin. Experimental (17)O NMR tensors in these compounds were compared with computational results obtained with a periodic DFT code BAND. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. 113Cd solid-state NMR for probing the coordination sphere in metal-organic frameworks.

    Science.gov (United States)

    Kuttatheyil, Anusree Viswanath; Handke, Marcel; Bergmann, Jens; Lässig, Daniel; Lincke, Jörg; Haase, Jürgen; Bertmer, Marko; Krautscheid, Harald

    2015-01-12

    Spectroscopic techniques are a powerful tool for structure determination, especially if single-crystal material is unavailable. (113)Cd solid-state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical-shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by (113)Cd solid-state NMR is reported. The results obtained demonstrate that (113)Cd NMR is a very sensitive tool to characterize the cadmium environment, also in non-single-crystal materials. Furthermore, this method allows the observation of guest-induced phase transitions supporting understanding of the structural flexibility of coordination frameworks.

  1. Solid-state NMR in macromolecular systems: insights on how molecular entities move.

    Science.gov (United States)

    Hansen, Michael Ryan; Graf, Robert; Spiess, Hans Wolfgang

    2013-09-17

    The function of synthetic and natural macromolecularsystems critically depends on the packing and dynamics of the individual components of a given system. Not only can solid-state NMR provide structural information with atomic resolution, but it can also provide a way to characterize the amplitude and time scales of motions over broad ranges of length and time. These movements include molecular dynamics, rotational and translational motions of the building blocks, and also the motion of the functional species themselves, such as protons or ions. This Account examines solid-state NMR methods for correlating dynamics and function in a variety of chemical systems. In the early days, scientists thought that the rotationalmotions reflected the geometry of the moving entities. They described these phenomena as jumps about well-defined axes, such as phenyl flips, even in amorphous polymers. Later, they realized that conformational transitions in macromolecules happen in a much more complex way. Because the individual entities do not rotate around well-defined axes, they require much less space. Only recently researchers have appreciated the relative importance of large angle fluctuations of polymers over rotational jumps. Researchers have long considered that cooperative motions might be at work, yet only recently they have clearly detected these motions by NMR in macromolecular and supramolecular systems. In correlations of dynamics and function, local motions do not always provide the mechanism of long-range transport. This idea holds true in ion conduction but also applies to chain transport in polymer melts and semicrystalline polymers. Similar chain motions and ion transport likewise occur in functional biopolymers, systems where solid-state NMR studies are also performed. In polymer science, researchers have appreciated the unique information on molecular dynamics available from advanced solid-state NMR at times, where their colleagues in the biomacromolecular

  2. Solid-state NMR spectra of lipid-anchored proteins under magic angle spinning.

    Science.gov (United States)

    Nomura, Kaoru; Harada, Erisa; Sugase, Kenji; Shimamoto, Keiko

    2014-03-01

    Solid-state NMR is a promising tool for elucidating membrane-related biological phenomena. We achieved the measurement of high-resolution solid-state NMR spectra for a lipid-anchored protein embedded in lipid bilayers under magic angle spinning (MAS). To date, solid-state NMR measurements of lipid-anchored proteins have not been accomplished due to the difficulty in supplying sufficient amount of stable isotope labeled samples in the overexpression of lipid-anchored proteins requiring complex posttranslational modification. We designed a pseudo lipid-anchored protein in which the protein component was expressed in E. coli and attached to a chemically synthesized lipid-anchor mimic. Using two types of membranes, liposomes and bicelles, we demonstrated different types of insertion procedures for lipid-anchored protein into membranes. In the liposome sample, we were able to observe the cross-polarization and the (13)C-(13)C chemical shift correlation spectra under MAS, indicating that the liposome sample can be used to analyze molecular interactions using dipolar-based NMR experiments. In contrast, the bicelle sample showed sufficient quality of spectra through scalar-based experiments. The relaxation times and protein-membrane interaction were capable of being analyzed in the bicelle sample. These results demonstrated the applicability of two types of sample system to elucidate the roles of lipid-anchors in regulating diverse biological phenomena.

  3. Quantification of protein secondary structure by (13)C solid-state NMR.

    Science.gov (United States)

    Andrade, Fabiana Diuk; Forato, Lucimara Aparecida; Bernardes Filho, Rubens; Colnago, Luiz Alberto

    2016-05-01

    High-resolution (13)C solid-state NMR stands out as one of the most promising techniques to solve the structure of insoluble proteins featuring biological and technological importance. The simplest nuclear magnetic resonance (NMR) spectroscopy method to quantify the secondary structure of proteins uses the areas of carbonyl and alpha carbon peaks. The quantification obtained by fitting procedures depends on the assignment of the peaks to the structure, type of line shape, number of peaks to be used, and other parameters that are set by the operator. In this paper, we demonstrate that the analysis of (13)C NMR spectra by a pattern recognition method-based on the singular value decomposition (SVD) regression, which does not depend on the operator-shows higher correlation coefficients for α-helix and β-sheet (0.96 and 0.91, respectively) than Fourier transform infrared spectroscopy (FTIR) method. Therefore, the use of (13)C solid-state NMR spectra and SVD is a simple and reliable method for quantifying the secondary structures of insoluble proteins in solid-state.

  4. Interactions of protein side chains with RNA defined with REDOR solid state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Huang Wei; Varani, Gabriele; Drobny, Gary P., E-mail: drobny@chem.washington.edu [University of Washington, Department of Chemistry (United States)

    2011-11-15

    Formation of the complex between human immunodeficiency virus type-1 Tat protein and the transactivation response region (TAR) RNA is vital for transcriptional elongation, yet the structure of the Tat-TAR complex remains to be established. The NMR structures of free TAR, and TAR bound to Tat-derived peptides have been obtained by solution NMR, but only a small number of intermolecular NOEs could be identified unambiguously, preventing the determination of a complete structure. Here we show that a combination of multiple solid state NMR REDOR experiments can be used to obtain multiple distance constraints from {sup 15}N to {sup 13}C spins within the backbone and side chain guanidinium groups of arginine in a Tat-derived peptide, using {sup 19}F spins incorporated into the base of U23 in TAR and {sup 31}P spins in the P22 and P23 phosphate groups. Distances between the side chain of Arg52 and the base and phosphodiester backbone near U23 measured by REDOR NMR are comparable to distances observed in solution NMR-derived structural models, indicating that interactions of TAR RNA with key amino acid side chains in Tat are the same in the amorphous solid state as in solution. This method is generally applicable to other protein-RNA complexes where crystallization or solution NMR has failed to provide high resolution structural information.

  5. Solid-state NMR, electrophysiology and molecular dynamics characterization of human VDAC2

    Energy Technology Data Exchange (ETDEWEB)

    Gattin, Zrinka; Schneider, Robert; Laukat, Yvonne; Giller, Karin [Max Planck Institute for Biophysical Chemistry (Germany); Maier, Elke [Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Lehrstuhl für Biotechnologie (Germany); Zweckstetter, Markus; Griesinger, Christian [Max Planck Institute for Biophysical Chemistry (Germany); Benz, Roland [Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Lehrstuhl für Biotechnologie (Germany); Becker, Stefan; Lange, Adam, E-mail: alange@fmp-berlin.de [Max Planck Institute for Biophysical Chemistry (Germany)

    2015-04-15

    The voltage-dependent anion channel (VDAC) is the most abundant protein of the outer mitochondrial membrane and constitutes the major pathway for the transport of ADP, ATP, and other metabolites. In this multidisciplinary study we combined solid-state NMR, electrophysiology, and molecular dynamics simulations, to study the structure of the human VDAC isoform 2 in a lipid bilayer environment. We find that the structure of hVDAC2 is similar to the structure of hVDAC1, in line with recent investigations on zfVDAC2. However, hVDAC2 appears to exhibit an increased conformational heterogeneity compared to hVDAC1 which is reflected in broader solid-state NMR spectra and less defined electrophysiological profiles.

  6. Automated solid-state NMR resonance assignment of protein microcrystals and amyloids

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Elena [Goethe University Frankfurt am Main, Center for Biomolecular Magnetic Resonance, Institute of Biophysical Chemistry (Germany); Gath, Julia [ETH Zurich, Physical Chemistry (Switzerland); Habenstein, Birgit [UMR 5086 CNRS/Universite de Lyon 1, Institut de Biologie et Chimie des Proteines (France); Ravotti, Francesco; Szekely, Kathrin; Huber, Matthias [ETH Zurich, Physical Chemistry (Switzerland); Buchner, Lena [Goethe University Frankfurt am Main, Center for Biomolecular Magnetic Resonance, Institute of Biophysical Chemistry (Germany); Boeckmann, Anja, E-mail: a.bockmann@ibcp.fr [UMR 5086 CNRS/Universite de Lyon 1, Institut de Biologie et Chimie des Proteines (France); Meier, Beat H., E-mail: beme@ethz.ch [ETH Zurich, Physical Chemistry (Switzerland); Guentert, Peter, E-mail: guentert@em.uni-frankfurt.de [Goethe University Frankfurt am Main, Center for Biomolecular Magnetic Resonance, Institute of Biophysical Chemistry (Germany)

    2013-07-15

    Solid-state NMR is an emerging structure determination technique for crystalline and non-crystalline protein assemblies, e.g., amyloids. Resonance assignment constitutes the first and often very time-consuming step to a structure. We present ssFLYA, a generally applicable algorithm for automatic assignment of protein solid-state NMR spectra. Application to microcrystals of ubiquitin and the Ure2 prion C-terminal domain, as well as amyloids of HET-s(218-289) and {alpha}-synuclein yielded 88-97 % correctness for the backbone and side-chain assignments that are classified as self-consistent by the algorithm, and 77-90 % correctness if also assignments classified as tentative by the algorithm are included.

  7. Analysis of Structural Variability in Pharmaceutical Excipients Using Solid-State NMR Spectroscopy

    OpenAIRE

    Sperger, Diana M.; Munson, Eric Jon

    2011-01-01

    Polysaccharide-based excipients comprise the majority of most solid dosage forms and can vary dramatically in terms of structural and functionally related properties. Analytical methods for characterizing these important formulation components are crucial. Solid-state NMR spectroscopy (SSNMR) can provide a wealth of information on these materials while offering the advantages of non-destructive sample preparation and selectivity. The overall objective of this work is to identify SSNMR paramet...

  8. 13C high resolution solid state NMR spectra of Chinese coals

    Institute of Scientific and Technical Information of China (English)

    陈德玉; 胡建治; 叶朝辉

    1997-01-01

    Several typical exinites in China including alginite, cultinite, suberinite and bituminite are analysed by means of 13C high solution solid state CP MAS TOSS NMR spectra to determine their chemical structures and hydrocarbon potential. Thermal simulation solid products (TSSP) of hydrogen-rich coals arc studied to discuss the generation and expulsion mechanism of coal-generating hydrocarbon. The preliminary results are quite encouraging, containing useful information about genesis of coal-generating oil and gases.

  9. Practical considerations over spectral quality in solid state NMR spectroscopy of soluble proteins

    Energy Technology Data Exchange (ETDEWEB)

    Fragai, Marco; Luchinat, Claudio, E-mail: claudioluchinat@cerm.unifi.it; Parigi, Giacomo; Ravera, Enrico [University of Florence, Center for Magnetic Resonance (CERM) (Italy)

    2013-10-15

    Great theoretical and methodological advances are pushing the limits of resolution and sensitivity in solid state NMR (SSNMR). However, sample preparation remains a critical issue for the success of an experiment. The factors affecting spectral quality in SSNMR samples are discussed, examining cases encountered in the literature and presenting new experimental data. A discussion on resolution and sensitivity in sedimented solutes is framed in this context.

  10. LARGE SCALE PRODUCTION, PURIFICATION, AND 65CU SOLID STATE NMR OF AZURIN

    Energy Technology Data Exchange (ETDEWEB)

    Gao, A.; Heck, R.W.

    2008-01-01

    This paper details a way to produce azurin with an effi ciency over 10 times greater than previously described and demonstrates the fi rst solid state nuclear magnetic resonance spectrum of 65Cu(I) in a metalloprotein. A synthetic gene for azurin based upon the DNA sequence from Pseudomonas aeruginosa including the periplasmic targeting sequence was subcloned into a T7 overexpression vector to create the plasmid pGS-azurin, which was transformed into BL21 (DE3) competent cells. The leader sequence on the expressed protein causes it to be exported to the periplasmic space of Escherichia coli. Bacteria grown in a fermentation unit were induced to overexpress the azurin, which was subsequently purifi ed through an endosmotic shock procedure followed by high performance liquid chromatography (HPLC). 1,500 mg of azurin were purifi ed per liter of culture. 65Cu(II) was added to apo-azurin and then reduced. The 65Cu metal cofactor in azurin was observed with solid state nuclear magnetic resonance (NMR) to determine any structural variations that accompanied copper reduction. This is the fi rst solid state NMR spectra of a copper(I) metalloprotein. Analysis of the NMR spectra is being used to complement hypotheses set forth by x-ray diffraction and computational calculations of electron transfer mechanisms in azurin.

  11. Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs

    Directory of Open Access Journals (Sweden)

    Stefan Kaskel

    2012-11-01

    Full Text Available Nuclear Magnetic Resonance (NMR spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of the structure, dynamics and flexibility of these materials, as well as for the characterization of host–guest interactions with adsorbed species such as xenon, carbon dioxide, water, and many others. The present review introduces and highlights recent developments in this rapidly growing field.

  12. New methods and applications in solid-state NMR spectroscopy of quadrupolar nuclei.

    Science.gov (United States)

    Ashbrook, Sharon E; Sneddon, Scott

    2014-11-05

    Solid-state nuclear magnetic resonance (NMR) spectroscopy has long been established as offering unique atomic-scale and element-specific insight into the structure, disorder, and dynamics of materials. NMR spectra of quadrupolar nuclei (I > (1)/2) are often perceived as being challenging to acquire and to interpret because of the presence of anisotropic broadening arising from the interaction of the electric field gradient and the nuclear electric quadrupole moment, which broadens the spectral lines, often over several megahertz. Despite the vast amount of information contained in the spectral line shapes, the problems with sensitivity and resolution have, until very recently, limited the application of NMR spectroscopy of quadrupolar nuclei in the solid state. In this Perspective, we provide a brief overview of the quadrupolar interaction, describe some of the basic experimental approaches used for acquiring high-resolution NMR spectra, and discuss the information that these spectra can provide. We then describe some interesting recent examples to showcase some of the more exciting and challenging new applications of NMR spectra of quadrupolar nuclei in the fields of energy materials, microporous materials, Earth sciences, and biomaterials. Finally, we consider the possible directions that this highly informative technique may take in the future.

  13. Solid-state NMR (31)P paramagnetic relaxation enhancement membrane protein immersion depth measurements.

    Science.gov (United States)

    Maltsev, Sergey; Hudson, Stephen M; Sahu, Indra D; Liu, Lishan; Lorigan, Gary A

    2014-04-24

    Paramagnetic relaxation enhancement (PRE) is a widely used approach for measuring long-range distance constraints in biomolecular solution NMR spectroscopy. In this paper, we show that (31)P PRE solid-state NMR spectroscopy can be utilized to determine the immersion depth of spin-labeled membrane peptides and proteins. Changes in the (31)P NMR PRE times coupled with modeling studies can be used to describe the spin-label position/amino acid within the lipid bilayer and the corresponding helical tilt. This method provides valuable insight on protein-lipid interactions and membrane protein structural topology. Solid-state (31)P NMR data on the 23 amino acid α-helical nicotinic acetylcholine receptor nAChR M2δ transmembrane domain model peptide followed predicted behavior of (31)P PRE rates of the phospholipid headgroup as the spin-label moves from the membrane surface toward the center of the membrane. Residue 11 showed the smallest changes in (31)P PRE (center of the membrane), while residue 22 shows the largest (31)P PRE change (near the membrane surface), when compared to the diamagnetic control M2δ sample. This PRE SS-NMR technique can be used as a molecular ruler to measure membrane immersion depth.

  14. Ultra fast magic angle spinning solid - state NMR spectroscopy of intact bone.

    Science.gov (United States)

    Singh, Chandan; Rai, Ratan Kumar; Kayastha, Arvind M; Sinha, Neeraj

    2016-02-01

    Ultra fast magic angle spinning (MAS) has been a potent method to significantly average out homogeneous/inhomogeneous line broadening in solid-state nuclear magnetic resonance (ssNMR) spectroscopy. It has given a new direction to ssNMR spectroscopy with its different applications. We present here the first and foremost application of ultra fast MAS (~60 kHz) for ssNMR spectroscopy of intact bone. This methodology helps to comprehend and elucidate the organic content in the intact bone matrix with resolution and sensitivity enhancement. At this MAS speed, amino protons from organic part of intact bone start to appear in (1) H NMR spectra. The experimental protocol of ultra-high speed MAS for intact bone has been entailed with an additional insight achieved at 60 kHz.

  15. Efficient cellular solid-state NMR of membrane proteins by targeted protein labeling

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Lindsay A. [University of Oxford, Oxford Particle Imaging Centre, The Wellcome Trust Centre for Human Genetics, Division of Structural Biology, Nuffield Department of Medicine (United Kingdom); Daniëls, Mark; Cruijsen, Elwin A. W. van der; Folkers, Gert E.; Baldus, Marc, E-mail: m.baldus@uu.nl [Utrecht University, NMR Spectroscopy, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands)

    2015-06-15

    Solid-state NMR spectroscopy (ssNMR) has made significant progress towards the study of membrane proteins in their native cellular membranes. However, reduced spectroscopic sensitivity and high background signal levels can complicate these experiments. Here, we describe a method for ssNMR to specifically label a single protein by repressing endogenous protein expression with rifampicin. Our results demonstrate that treatment of E. coli with rifampicin during induction of recombinant membrane protein expression reduces background signals for different expression levels and improves sensitivity in cellular membrane samples. Further, the method reduces the amount of time and resources needed to produce membrane protein samples, enabling new strategies for studying challenging membrane proteins by ssNMR.

  16. Proton detection of MAS solid-state NMR spectra of half-integer quadrupolar nuclei.

    Science.gov (United States)

    Venkatesh, Amrit; Hanrahan, Michael P; Rossini, Aaron J

    Fast magic angle spinning (MAS) and proton detection has found widespread application to enhance the sensitivity of solid-state NMR experiments with spin-1/2 nuclei such as (13)C, (15)N and (29)Si, however, this approach is not yet routinely applied to half-integer quadrupolar nuclei. Here we have investigated the feasibility of using fast MAS and proton detection to enhance the sensitivity of solid-state NMR experiments with half-integer quadrupolar nuclei. The previously described dipolar hetero-nuclear multiple quantum correlation (D-HMQC) and dipolar refocused insensitive nuclei enhanced by polarization transfer (D-RINEPT) pulse sequences were used for proton detection of half-integer quadrupolar nuclei. Quantitative comparisons of signal-to-noise ratios and the sensitivity of proton detected D-HMQC and D-RINEPT and direct detection spin echo and quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) solid-state NMR spectra, demonstrate that one dimensional proton detected experiments can provide sensitivity similar to or exceeding that obtainable with direct detection QCPMG experiments. 2D D-HMQC and D-RINEPT experiments provide less sensitivity than QCPMG experiments but proton detected 2D hetero-nuclear correlation solid-state NMR spectra of half-integer nuclei can still be acquired in about the same time as a 1D spin echo spectrum. Notably, the rarely used D-RINEPT pulse sequence is found to provide similar, or better sensitivity than D-HMQC in some cases. Proton detected D-RINEPT benefits from the short longitudinal relaxation times (T1) normally associated with half-integer quadrupolar nuclei, it can be combined with existing signal enhancement methods for quadrupolar nuclei, and t1-noise in the indirect dimension can easily be removed by pre-saturation of the (1)H nuclei. The rapid acquisition of proton detected 2D HETCOR solid-state NMR spectra of a range of half-integer quadrupolar nuclei such as (17)O, (27)Al, (35)Cl and (71)Ga is demonstrated. Copyright

  17. Solid-state 17O NMR of pharmaceutical compounds: salicylic acid and aspirin.

    Science.gov (United States)

    Kong, Xianqi; Shan, Melissa; Terskikh, Victor; Hung, Ivan; Gan, Zhehong; Wu, Gang

    2013-08-22

    We report solid-state NMR characterization of the (17)O quadrupole coupling (QC) and chemical shift (CS) tensors in five site-specifically (17)O-labeled samples of salicylic acid and o-acetylsalicylic acid (Aspirin). High-quality (17)O NMR spectra were obtained for these important pharmaceutical compounds under both static and magic angle spinning (MAS) conditions at two magnetic fields, 14.0 and 21.1 T. A total of 14 (17)O QC and CS tensors were experimentally determined for the seven oxygen sites in salicylic acid and Aspirin. Although both salicylic acid and Aspirin form hydrogen bonded cyclic dimers in the solid state, we found that the potential curves for the concerted double proton transfer in these two compounds are significantly different. In particular, while the double-well potential curve in Aspirin is nearly symmetrical, it is highly asymmetrical in salicylic acid. This difference results in quite different temperature dependencies in (17)O MAS spectra of the two compounds. A careful analysis of variable-temperature (17)O MAS NMR spectra of Aspirin allowed us to obtain the energy asymmetry (ΔE) of the double-well potential, ΔE = 3.0 ± 0.5 kJ/mol. We were also able to determine a lower limit of ΔE for salicylic acid, ΔE > 10 kJ/mol. These asymmetrical features in potential energy curves were confirmed by plane-wave DFT computations, which yielded ΔE = 3.7 and 17.8 kJ/mol for Aspirin and salicylic acid, respectively. To complement the solid-state (17)O NMR data, we also obtained solid-state (1)H and (13)C NMR spectra for salicylic acid and Aspirin. Using experimental NMR parameters obtained for all magnetic nuclei present in salicylic acid and Aspirin, we found that plane-wave DFT computations can produce highly accurate NMR parameters in well-defined crystalline organic compounds.

  18. 1H to 13C Energy Transfer in Solid State NMR Spectroscopy of Natural Organic Systems

    Science.gov (United States)

    Berns, Anne E.; Conte, Pellegrino

    2010-05-01

    Cross polarization (CP) magic angle spinning (MAS) 13C-NMR spectroscopy is a solid state NMR technique widely used to study chemical composition of organic materials with low or no solubility in the common deuterated solvents used to run liquid state NMR experiments. Based on the magnetization transfer from abundant nuclei (with spin of 1 -2) having a high gyromagnetic ratio (γ), such as protons, to the less abundant 13C nuclei with low γ values, 13C-CPMAS NMR spectroscopy is often applied in environmental chemistry to obtain quantitative information on the chemical composition of natural organic matter (NOM) (Conte et al., 2004), although its quantitative assessment is still matter of heavy debates. Many authors (Baldock et al., 1997; Conte et al., 1997, 2002; Dria et al., 2002; Kiem et al., 2000; Kögel-Knabner, 2000; Preston, 2001), reported that the application of appropriate instrument setup as well as the use of special pulse sequences and correct spectra elaboration may provide signal intensities that are directly proportional to the amount of nuclei creating a NMR signal. However, many other papers dealt with the quantitative unsuitability of 13C-CPMAS NMR spectroscopy. Among those, Mao et al. (2000), Smernik and Oades (2000 a,b), and Preston (2001) reported that cross-polarized NMR techniques may fail in a complete excitation of the 13C nuclei. In fact, the amount of observable carbons via 13C-CPMAS NMR spectroscopy appeared, in many cases, lower than that measured by a direct observation of the 13C nuclei. As a consequence, cross-polarized NMR techniques may provide spectra where signal distribution may not be representative of the quantitative distribution of the different natural organic matter components. Cross-polarization is obtained after application of an initial 90° x pulse on protons and a further spin lock pulse (along the y axis) having a fixed length (contact time) for both nuclei (1H and 13C) once the Hartmann-Hahn condition is matched

  19. Application and Reliability of Solid-State NMR in Environmental Sciences

    Science.gov (United States)

    Knicker, Heike

    2010-05-01

    For the characterization of soil organic matter, a suite of analytical approaches are available. Chemical degradative methods involve an extraction scheme with which the soluble part of the mixture is isolated and analyzed by colorimetrical or chromatographic means. Macromolecular structures can be subjected to thermolytic or combined thermochemolytic degradation. Because secondary reactions (rearrangement, cracking, hydrogenation and polymerization) in a heterogeneous mixture cannot be excluded, it is obvious that conclusions regarding the original structure in the macromolecular phase have to be drawn with caution. A powerful alternative represents solid-state nuclear magnetic resonance (NMR) spectroscopy, allowing the examination of the bulk sample without major pre-treatment In environmental sciences, this technique mostly involves the isotope 13C to study the chemical composition of organic matter in soils, sediments or compost to study the temporal development of humic material or chemical alterations due to variation in environmental parameters. Due to its low sensibility solid-state 15N NMR studies on such samples are only found occasionally. The emphasis of solid-state NMR spectroscopy is not only to determine the gross chemical composition of the material under study via a chemical shift assignment but also a quantitative correlation between the different signal intensities and the relative contribution of the respective C or N types to the total organic C or N content. However, despite increasing popularity, this approach is still viewed as mysterious techniques, in particular with respect to quantification. Accordingly, the purpose of this review is to give a short overview on the possibilities and limitations of this technique in environmental science and in particular for the study of soil organic matter. In general, solid-state 13C NMR spectra of soil organic matter are obtained with the cross polarization magic angle spinning (CPMAS) technique. This

  20. Intercalation complex of proflavine with DNA: Structure and dynamics by solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Pei; Juang, Chilong; Harbison, G.S. (State Univ. of New York, Stony Brook (USA))

    1990-07-06

    The structure of the complex formed between the intercalating agent proflavine and fibrous native DNA was studied by one- and two-dimensional high-resolution solid-state nuclear magnetic resonance (NMR). Carbon-13-labeled proflavine was used to show that the drug is stacked with the aromatic ring plane perpendicular to the fiber axis and that it is essentially immobile. Natural abundance carbon-13 NMR of the DNA itself shows that proflavine binding does not change the puckering of the deoxyribose ring. However, phosphorus-31 NMR spectra show profound changes in the orientation of the phosphodiester grouping on proflavine binding, with some of the phosphodiesters tilting almost parallel to the helix axis, and a second set almost perpendicular. The first group to the phosphodiesters probably spans the intercalation sites, whereas the tilting of the second set likely compensates for the unwinding of the DNA by the intercalator.

  1. New in situ solid-state NMR strategies for exploring materials formation and adsorption processes: prospects in heterogenous catalysis

    OpenAIRE

    Harris, Kenneth David Maclean

    2016-01-01

    Solid-state NMR spectroscopy is a powerful technique for studying structural and dynamic properties of solids and has considerable potential to be exploited for in situ studies of chemical processes. However, adapting solid-state NMR techniques and instrumentation for in situ applications are often associated with technical challenges, and for this reason, the opportunities remain underexploited. This paper highlights two experimental strategies that we have developed in recent years for in s...

  2. In situ solid-state NMR spectroscopy of protein in heterogeneous membranes: the baseplate antenna complex of Chlorobaculum tepidum.

    Science.gov (United States)

    Kulminskaya, Natalia V; Pedersen, Marie Ø; Bjerring, Morten; Underhaug, Jarl; Miller, Mette; Frigaard, Niels-Ulrik; Nielsen, Jakob T; Nielsen, Niels Chr

    2012-07-01

    A clever combination: an in situ solid-state NMR analysis of CsmA proteins in the heterogeneous environment of the photoreceptor of Chlorobaculum tepidum is reported. Using different combinations of 2D and 3D solid-state NMR spectra, 90 % of the CsmA resonances are assigned and provide on the basis of chemical shift data information about the structure and conformation of CsmA in the CsmA-bacteriochlorophyll a complex.

  3. Computer-intensive simulation of solid-state NMR experiments using SIMPSON

    Science.gov (United States)

    Tošner, Zdeněk; Andersen, Rasmus; Stevensson, Baltzar; Edén, Mattias; Nielsen, Niels Chr.; Vosegaard, Thomas

    2014-09-01

    Conducting large-scale solid-state NMR simulations requires fast computer software potentially in combination with efficient computational resources to complete within a reasonable time frame. Such simulations may involve large spin systems, multiple-parameter fitting of experimental spectra, or multiple-pulse experiment design using parameter scan, non-linear optimization, or optimal control procedures. To efficiently accommodate such simulations, we here present an improved version of the widely distributed open-source SIMPSON NMR simulation software package adapted to contemporary high performance hardware setups. The software is optimized for fast performance on standard stand-alone computers, multi-core processors, and large clusters of identical nodes. We describe the novel features for fast computation including internal matrix manipulations, propagator setups and acquisition strategies. For efficient calculation of powder averages, we implemented interpolation method of Alderman, Solum, and Grant, as well as recently introduced fast Wigner transform interpolation technique. The potential of the optimal control toolbox is greatly enhanced by higher precision gradients in combination with the efficient optimization algorithm known as limited memory Broyden-Fletcher-Goldfarb-Shanno. In addition, advanced parallelization can be used in all types of calculations, providing significant time reductions. SIMPSON is thus reflecting current knowledge in the field of numerical simulations of solid-state NMR experiments. The efficiency and novel features are demonstrated on the representative simulations.

  4. Motion-adapted pulse sequences for oriented sample (OS) solid-state NMR of biopolymers.

    Science.gov (United States)

    Lu, George J; Opella, Stanley J

    2013-08-28

    One of the main applications of solid-state NMR is to study the structure and dynamics of biopolymers, such as membrane proteins, under physiological conditions where the polypeptides undergo global motions as they do in biological membranes. The effects of NMR radiofrequency irradiations on nuclear spins are strongly influenced by these motions. For example, we previously showed that the MSHOT-Pi4 pulse sequence yields spectra with resonance line widths about half of those observed using the conventional pulse sequence when applied to membrane proteins undergoing rapid uniaxial rotational diffusion in phospholipid bilayers. In contrast, the line widths were not changed in microcrystalline samples where the molecules did not undergo global motions. Here, we demonstrate experimentally and describe analytically how some Hamiltonian terms are susceptible to sample motions, and it is their removal through the critical π/2 Z-rotational symmetry that confers the "motion adapted" property to the MSHOT-Pi4 pulse sequence. This leads to the design of separated local field pulse sequence "Motion-adapted SAMPI4" and is generalized to an approach for the design of decoupling sequences whose performance is superior in the presence of molecular motions. It works by cancelling the spin interaction by explicitly averaging the reduced Wigner matrix to zero, rather than utilizing the 2π nutation to average spin interactions. This approach is applicable to both stationary and magic angle spinning solid-state NMR experiments.

  5. Sensitivity and resolution enhancement in solid-state NMR spectroscopy of bicelles

    Science.gov (United States)

    Dvinskikh, Sergey V.; Yamamoto, Kazutoshi; Dürr, Ulrich H. N.; Ramamoorthy, Ayyalusamy

    2007-02-01

    Magnetically aligned bicelles are becoming attractive model membranes to investigate the structure, dynamics, geometry, and interaction of membrane-associated peptides and proteins using solution- and solid-state NMR experiments. Recent studies have shown that bicelles are more suitable than mechanically aligned bilayers for multidimensional solid-state NMR experiments. In this work, we describe experimental aspects of the natural abundance 13C and 14N NMR spectroscopy of DMPC/DHPC bicelles. In particular, approaches to enhance the sensitivity and resolution and to quantify radio-frequency heating effects are presented. Sensitivity of 13C detection using single pulse excitation, conventional cross-polarization (CP), ramp-CP, and NOE techniques are compared. Our results suggest that the proton decoupling efficiency of the FLOPSY pulse sequence is better than that of continuous wave decoupling, TPPM, SPINAL, and WALTZ sequences. A simple method of monitoring the water proton chemical shift is demonstrated for the measurement of sample temperature and calibration of the radio-frequency-induced heating in the sample. The possibility of using 14N experiments on bicelles is also discussed.

  6. Motion-adapted pulse sequences for oriented sample (OS) solid-state NMR of biopolymers

    Science.gov (United States)

    Lu, George J.; Opella, Stanley J.

    2013-01-01

    One of the main applications of solid-state NMR is to study the structure and dynamics of biopolymers, such as membrane proteins, under physiological conditions where the polypeptides undergo global motions as they do in biological membranes. The effects of NMR radiofrequency irradiations on nuclear spins are strongly influenced by these motions. For example, we previously showed that the MSHOT-Pi4 pulse sequence yields spectra with resonance line widths about half of those observed using the conventional pulse sequence when applied to membrane proteins undergoing rapid uniaxial rotational diffusion in phospholipid bilayers. In contrast, the line widths were not changed in microcrystalline samples where the molecules did not undergo global motions. Here, we demonstrate experimentally and describe analytically how some Hamiltonian terms are susceptible to sample motions, and it is their removal through the critical π/2 Z-rotational symmetry that confers the “motion adapted” property to the MSHOT-Pi4 pulse sequence. This leads to the design of separated local field pulse sequence “Motion-adapted SAMPI4” and is generalized to an approach for the design of decoupling sequences whose performance is superior in the presence of molecular motions. It works by cancelling the spin interaction by explicitly averaging the reduced Wigner matrix to zero, rather than utilizing the 2π nutation to average spin interactions. This approach is applicable to both stationary and magic angle spinning solid-state NMR experiments. PMID:24006989

  7. Computer-intensive simulation of solid-state NMR experiments using SIMPSON.

    Science.gov (United States)

    Tošner, Zdeněk; Andersen, Rasmus; Stevensson, Baltzar; Edén, Mattias; Nielsen, Niels Chr; Vosegaard, Thomas

    2014-09-01

    Conducting large-scale solid-state NMR simulations requires fast computer software potentially in combination with efficient computational resources to complete within a reasonable time frame. Such simulations may involve large spin systems, multiple-parameter fitting of experimental spectra, or multiple-pulse experiment design using parameter scan, non-linear optimization, or optimal control procedures. To efficiently accommodate such simulations, we here present an improved version of the widely distributed open-source SIMPSON NMR simulation software package adapted to contemporary high performance hardware setups. The software is optimized for fast performance on standard stand-alone computers, multi-core processors, and large clusters of identical nodes. We describe the novel features for fast computation including internal matrix manipulations, propagator setups and acquisition strategies. For efficient calculation of powder averages, we implemented interpolation method of Alderman, Solum, and Grant, as well as recently introduced fast Wigner transform interpolation technique. The potential of the optimal control toolbox is greatly enhanced by higher precision gradients in combination with the efficient optimization algorithm known as limited memory Broyden-Fletcher-Goldfarb-Shanno. In addition, advanced parallelization can be used in all types of calculations, providing significant time reductions. SIMPSON is thus reflecting current knowledge in the field of numerical simulations of solid-state NMR experiments. The efficiency and novel features are demonstrated on the representative simulations.

  8. Solid-state NMR paramagnetic relaxation enhancement immersion depth studies in phospholipid bilayers

    KAUST Repository

    Chu, Shidong

    2010-11-01

    A new approach for determining the membrane immersion depth of a spin-labeled probe has been developed using paramagnetic relaxation enhancement (PRE) in solid-state NMR spectroscopy. A DOXYL spin label was placed at different sites of 1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine (PSPC) phospholipid bilayers as paramagnetic moieties and the resulting enhancements of the longitudinal relaxation (T1) times of 31P nuclei on the surface of the bilayers were measured by a standard inversion recovery pulse sequence. The 31P NMR spin-lattice relaxation times decrease steadily as the DOXYL spin label moves closer to the surface as well as the concentration of the spin-labeled lipids increase. The enhanced relaxation vs. the position and concentration of spin-labels indicate that PRE induced by the DOXYL spin label are significant to determine longer distances over the whole range of the membrane depths. When these data were combined with estimated correlation times τc, the r-6-weighted, time-averaged distances between the spin-labels and the 31P nuclei on the membrane surface were estimated. The application of using this solid-state NMR PRE approach coupled with site-directed spin labeling (SDSL) may be a powerful method for measuring membrane protein immersion depth. © 2010 Elsevier Inc. All rights reserved.

  9. Crystal structure and tautomerism of Pigment Yellow 138 determined by X-ray powder diffraction and solid-state NMR

    DEFF Research Database (Denmark)

    Gumbert, Silke D.; Körbitzer, Meike; Alig, Edith;

    2016-01-01

    The crystal structure of C.I. Pigment Yellow 138 was determined from X-ray powder diffraction data using real-space methods with subsequent Rietveld refinements. The tautomeric state was investigated by solid-state 1D and 2D multinuclear NMR experiments. In the crystals, the compound exhibits...... the NH-tautomer with a hydrogen atom situated at the nitrogen of the quinoline moiety. Direct evidence of the presence of the NH-tautomer is provided by 1H–14N HMQC solid-state NMR at very fast MAS. Solid-state dispersion-corrected density functional theory calculations with BLYP-D3 confirm...

  10. Solid-state (19)F-NMR of peptides in native membranes.

    Science.gov (United States)

    Koch, Katja; Afonin, Sergii; Ieronimo, Marco; Berditsch, Marina; Ulrich, Anne S

    2012-01-01

    To understand how membrane-active peptides (MAPs) function in vivo, it is essential to obtain structural information about them in their membrane-bound state. Most biophysical approaches rely on the use of bilayers prepared from synthetic phospholipids, i.e. artificial model membranes. A particularly successful structural method is solid-state NMR, which makes use of macroscopically oriented lipid bilayers to study selectively isotope-labelled peptides. Native biomembranes, however, have a far more complex lipid composition and a significant non-lipidic content (protein and carbohydrate). Model membranes, therefore, are not really adequate to address questions concerning for example the selectivity of these membranolytic peptides against prokaryotic vs eukaryotic cells, their varying activities against different bacterial strains, or other related biological issues.Here, we discuss a solid-state (19)F-NMR approach that has been developed for structural studies of MAPs in lipid bilayers, and how this can be translated to measurements in native biomembranes. We review the essentials of the methodology and discuss key objectives in the practice of (19)F-labelling of peptides. Furthermore, the preparation of macroscopically oriented biomembranes on solid supports is discussed in the context of other membrane models. Two native biomembrane systems are presented as examples: human erythrocyte ghosts as representatives of eukaryotic cell membranes, and protoplasts from Micrococcus luteus as membranes from Gram-positive bacteria. Based on our latest experimental experience with the antimicrobial peptide gramicidin S, the benefits and some implicit drawbacks of using such supported native membranes in solid-state (19)F-NMR analysis are discussed.

  11. 6-Aminopenicillanic acid revisited: A combined solid state NMR and in silico refinement

    Science.gov (United States)

    Aguiar, Daniel Lima Marques de; San Gil, Rosane Aguiar da Silva; Alencastro, Ricardo Bicca de; Souza, Eugenio Furtado de; Borré, Leandro Bandeira; Vaiss, Viviane da Silva; Leitão, Alexandre Amaral

    2016-09-01

    13C/15N (experimental and ab initio) solid-state NMR was used to achieve an affordable way to improve hydrogen refinement of 6-aminopenicillanic acid (6-APA) structure. The lattice effect on the isotropic chemical shifts was probed by using two different magnetic shielding calculations: isolated molecules and periodic crystal structure. The electron density difference maps of optimized and non-optimized structures were calculated in order to investigate the interactions inside the 6-APA unit cell. The 13C and 15N chemical shifts assignments were unambiguously stablished. In addition, some of the literature 13C resonances ambiguities could be properly solved.

  12. Effects of sample preparation conditions on biomolecular solid-state NMR lineshapes

    Energy Technology Data Exchange (ETDEWEB)

    Jakeman, David L.; Mitchell, Dan J.; Shuttleworth, Wendy A.; Evans, Jeremy N.S. [Washington State University, Department of Biochemistry and Biophysics (United States)

    1998-10-15

    Sample preparation conditions with the 46 kDa enzyme complex of 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase, shikimate-3-phosphate (S3P) and glyphosate (GLP) have been examined in an attempt to reduce linewidths in solid-state NMR spectra. The linewidths of {sup 13}P resonances associated with enzyme bound S3P and GLP in the lyophilized ternary complex have been reduced to 150 {+-} 12 Hz and 125 {+-} 7 Hz respectively, by a variety of methods involving additives and freezing techniques.

  13. Solid-State NMR Studies of HIV-1 Capsid Protein Assemblies

    OpenAIRE

    HAN, YUN; Ahn, Jinwoo; Concel, Jason; Byeon, In-Ja L.; Gronenborn, Angela M.; YANG, Jun; Polenova, Tatyana

    2010-01-01

    In mature HIV-1 virions, a 26.6 kDa CA protein is assembled into a characteristic cone shaped core (capsid) that encloses the RNA viral genome. The assembled capsid structure is best described by a fullerene cone model that is made up from a hexameric lattice containing a variable number of CA pentamers, thus allowing for closure of tubular or conical structures. In this report, we present a solid-state NMR analysis of the wild type HIV-1 CA protein, prepared as conical and spherical assembli...

  14. Solid-state NMR of the Yersinia pestis outer membrane protein Ail in lipid bilayer nanodiscs sedimented by ultracentrifugation

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Yi; Fujimoto, L. Miya; Yao, Yong; Marassi, Francesca M., E-mail: fmarassi@sbmri.org [Sanford-Burnham Medical Research Institute (United States)

    2015-04-15

    Solid-state NMR studies of sedimented soluble proteins has been developed recently as an attractive approach for overcoming the size limitations of solution NMR spectroscopy while bypassing the need for sample crystallization or precipitation (Bertini et al. Proc Natl Acad Sci USA 108(26):10396–10399, 2011). Inspired by the potential benefits of this method, we have investigated the ability to sediment lipid bilayer nanodiscs reconstituted with a membrane protein. In this study, we show that nanodiscs containing the outer membrane protein Ail from Yersinia pestis can be sedimented for solid-state NMR structural studies, without the need for precipitation or lyophilization. Optimized preparations of Ail in phospholipid nanodiscs support both the structure and the fibronectin binding activity of the protein. The same sample can be used for solution NMR, solid-state NMR and activity assays, facilitating structure–activity correlation experiments across a wide range of timescales.

  15. Coordination-Site Exchange and Solid-State *O1*O3C NMR Studies of Bis(oxalato)dioxovanadate(V) Ion

    DEFF Research Database (Denmark)

    Schaumburg, Kjeld; Lee, Man-Ho

    1992-01-01

    Coordination-site exchange, *O1*O3 C NMR, solid state *O1*O3C NMR, Bis(oxalato)dioxovanadate(V) ion......Coordination-site exchange, *O1*O3 C NMR, solid state *O1*O3C NMR, Bis(oxalato)dioxovanadate(V) ion...

  16. Prediction of recrystallization behavior of troglitazone/polyvinylpyrrolidone solid dispersion by solid-state NMR.

    Science.gov (United States)

    Ito, Atsutoshi; Watanabe, Tomoyuki; Yada, Shuichi; Hamaura, Takeshi; Nakagami, Hiroaki; Higashi, Kenjirou; Moribe, Kunikazu; Yamamoto, Keiji

    2010-01-04

    The purpose of this study was to elaborate the relationship between the (13)C CP/MAS NMR spectra and the recrystallization behavior during the storage of troglitazone solid dispersions. The solid dispersions were prepared by either the solvent method or by co-grinding. The recrystallization behavior under storage conditions at 40 degrees C/94% RH was evaluated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. Solid dispersions prepared by the solvent method or by prolonged grinding brought about inhibition of the nucleation and the nuclei growth at the same time. No differences in the PXRD profiles were found in the samples prepared by the co-grinding and solvent methods, however, (13)C CP/MAS NMR showed significant differences in the spectra. The correlation coefficients using partial least square regression analysis between the PXRD profiles and the apparent nuclei-growth constant or induction period to nucleation were 0.1305 or 0.6350, respectively. In contrast, those between the (13)C CP/MAS NMR spectra and the constant or the period were 0.9916 or 0.9838, respectively. The (13)C CP/MAS NMR spectra had good correlation with the recrystallization kinetic parameters evaluated by the KJMA equation. Consequently, solid-state NMR was judged to be a useful tool for the prediction of the recrystallization behavior of solid dispersions.

  17. Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy

    Science.gov (United States)

    Ferro, Monica; Pastori, Nadia; Punta, Carlo; Melone, Lucio; Panzeri, Walter; Rossi, Barbara; Trotta, Francesco

    2017-01-01

    Two different formulations of cyclodextrin nanosponges (CDNS), obtained by polycondensation of β-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn), were treated with aqueous solutions of ibuprofen sodium salt (IbuNa) affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. 1H fast MAS NMR and 13C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH) after freeze-drying. 13C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system. However, the 13C NMR spectra collected under variable contact time cross-polarization (VCT-CP) conditions showed that the polymeric scaffold CDNS changed significantly its dynamic regime on passing from the empty CDNS to the drug-loaded CDNS, thus showing that the drug encapsulation can be seen as the formation of a real supramolecular aggregate rather than a conglomerate of two solid components. Finally, the structural features obtained from the different solid-state NMR approaches reported matched the information from powder X-ray diffraction profiles. PMID:28228859

  18. STUDIES ON THE CHEMICAL STRUCTURES OF ACTIVATED CARBON FIBERS BY SOLID STATE NMR

    Institute of Scientific and Technical Information of China (English)

    FURuowen; HuangWenqiang; 等

    1999-01-01

    The solid state C13-NMR spectra of different ACFs from various precursor fibers were recorded in this paper,The effects of activation conditions on chemical structures of ACFs,as well as the changes of chemical structures during carbonization and redox reaction were inverstigated by NMR technique,At same time,the soild state P31-NMR spectra of ACFS are studied.The C13-NMR spectra of ACFs can be divided into six bands that are assigned to methyl and methylene groups,hydroxyl and ether groups.acetal (or methylenedioxy) carbon,graphite-like aromatic carbon structure,phenol,and quinone groups,respectively.Only phosphorous pentoxide exists on ACFs and CFs.Moreover,most of them are stuck over the crystal face but not at the edge of graphite-like micro-crystal.The carbonization and activation conditions affect the C13-NMR spectra of ACFs.The experimental rsults indicate that the redox reaction of ACFs with oxidants greatly consumes C-H group.

  19. STRUCTURAL STUDIES OF BIOMATERIALS USING DOUBLE-QUANTUM SOLID-STATE NMR SPECTROSCOPY

    Energy Technology Data Exchange (ETDEWEB)

    Drobny, Gary P.; Long, J. R.; Karlsson, T.; Shaw, Wendy J.; Popham, Jennifer M.; Oyler, N.; Bower, Paula M.; Stringer, J.; Gregory, D.; Mehta, M.; Stayton, Patrick S.

    2004-10-31

    Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-stateNMR(ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.

  20. Reorientation phenomena in imidazolium methyl sulfonate as probed by advanced solid-state NMR.

    Science.gov (United States)

    Goward, Gillian R; Saalwächter, Kay; Fischbach, Ingrid; Spiess, Hans Wolfgang

    2003-01-01

    Evidence for reorientation of imidazolium rings in imidazolium methylsulfonate is demonstrated using solid-state NMR. This material is a model system for exciting new proton-conducting materials based on imidazole. Two advanced NMR methods, including 1H-13C and 1H-15N recoupled polarization transfer with dipolar sideband pattern analysis and analysis of the coalescence of 13C lineshapes are used to characterize the ring reorientation. The process is found to occur at temperatures well below the melting point of the salt, between 240 and 380 K, and is described by a single activation energy, of 38+/-5 kJ/mol. This material is considered as a model system for quantifying the ring reorientation process, which is often proposed to be the rate-limiting step in proton transport in imidazole-based proton conducting materials.

  1. Solid state 31NMR studies of the conversion of amorphous tricalcium phosphate to apatitic tricalcium phosphate.

    Science.gov (United States)

    Roberts, J E; Heughebaert, M; Heughebaert, J C; Bonar, L C; Glimcher, M J; Griffin, R G

    1991-12-01

    The hydrolytic conversion of a solid amorphous calcium phosphate of empirical formula Ca9 (PO4)6 to a poorly crystalline apatitic phase, under conditions where Ca2+ and PO4(3-) were conserved, was studied by means of solid-state magic-angle sample spinning 31P-NMR (nuclear magnetic resonance). Results showed a gradual decrease in hydrated amorphous calcium phosphate and the formation of two new PO4(3-)-containing components: an apatitic component similar to poorly crystalline hydroxyapatite and a protonated PO4(3-), probably HPO4(2-) in a dicalcium phosphate dihydrate (DCPD) brushite-like configuration. This latter component resembles the brushite-like HPO4(2-) component previously observed by 31P-NMR in apatitic calcium phosphates of biological origin. Results were consistent with previous studies by Heughebaert and Montel [18] of the kinetics of the conversion of amorphous calcium phosphate to hydroxyapatite under the same conditions.

  2. A high-resolution solid-state NMR approach for the structural studies of bicelles.

    Science.gov (United States)

    Dvinskikh, Sergey; Dürr, Ulrich; Yamamoto, Kazutoshi; Ramamoorthy, Ayyalusamy

    2006-05-17

    Bicelles are increasingly being used as membrane mimicking systems in NMR experiments to investigate the structure of membrane proteins. In this study, we demonstrate the effectiveness of a 2D solid-state NMR approach that can be used to measure the structural constraints, such as heteronuclear dipolar couplings between 1H, 13C, and 31P nuclei, in bicelles without the need for isotopic enrichment. This method does not require a high radio frequency power unlike the presently used rotating-frame separated-local-field (SLF) techniques, such as PISEMA. In addition, multiple dipolar couplings can be measured accurately, and the presence of a strong dipolar coupling does not suppress the weak couplings. High-resolution spectra obtained from magnetically aligned DMPC:DHPC bicelles even in the presence of peptides suggest that this approach will be useful in understanding lipid-protein interactions that play a vital role in shaping up the function of membrane proteins.

  3. Structural studies of proteins by paramagnetic solid-state NMR spectroscopy

    Science.gov (United States)

    Jaroniec, Christopher P.

    2015-04-01

    Paramagnetism-based nuclear pseudocontact shifts and spin relaxation enhancements contain a wealth of information in solid-state NMR spectra about electron-nucleus distances on the ∼20 Å length scale, far beyond that normally probed through measurements of nuclear dipolar couplings. Such data are especially vital in the context of structural studies of proteins and other biological molecules that suffer from a sparse number of experimentally-accessible atomic distances constraining their three-dimensional fold or intermolecular interactions. This perspective provides a brief overview of the recent developments and applications of paramagnetic magic-angle spinning NMR to biological systems, with primary focus on the investigations of metalloproteins and natively diamagnetic proteins modified with covalent paramagnetic tags.

  4. A High Resolution Solid State NMR Approach for the Structural Studies of Bicelles

    Science.gov (United States)

    Dvinskikh, Sergey; Dürr, Ulrich; Yamamoto, Kazutoshi; Ramamoorthy, Ayyalusamy

    2008-01-01

    Bicelles are increasingly being used as membrane mimicking systems in NMR experiments to investigate the structure of membrane proteins. In this study, we demonstrate the effectiveness of a 2D solid-state NMR approach that can be used to measure the structural constraints such as heteronuclear dipolar couplings between 1H, 13C and 31P nuclei in bicelles without the need for isotopic enrichment. This method does not require a high radio frequency power unlike the presently used rotating-frame separated-local-field (SLF) techniques like PISEMA. In addition, multiple dipolar couplings can be measured accurately and the presence of a strong dipolar coupling does not suppress the weak couplings. High resolution spectra obtained from magnetically aligned DMPC:DHPC bicelles even in the presence of peptides suggest that this approach will be useful in understanding lipid-protein interactions that play a vital role in shaping up the function of membrane proteins. PMID:16683791

  5. Structural studies of proteins by paramagnetic solid-state NMR spectroscopy

    Science.gov (United States)

    Jaroniec, Christopher P.

    2015-01-01

    Paramagnetism-based nuclear pseudocontact shifts and spin relaxation enhancements contain a wealth of information in solid-state NMR spectra about electron-nucleus distances on the ~20 Å length scale, far beyond that normally probed through measurements of nuclear dipolar couplings. Such data are especially vital in the context of structural studies of proteins and other biological molecules that suffer from a sparse number of experimentally-accessible atomic distances constraining their three-dimensional fold or intermolecular interactions. This perspective provides a brief overview of the recent developments and applications of paramagnetic magic-angle spinning NMR to biological systems, with primary focus on the investigations of metalloproteins and natively diamagnetic proteins modified with covalent paramagnetic tags. PMID:25797004

  6. Solid state NMR investigation of silica aerogel supported Fischer-Tropsch catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zhiru; Dunn, Brian C.; Turpin, Gregory C.; Eyring, Edward M.; Ernst, Richard D.; Pugmire, Ronald J. [Department of Chemistry, University of Utah, Salt Lake City, UT 84112 (United States)

    2007-01-15

    The Fischer-Tropsch (F-T) catalyst is the critical component for the F-T synthesis of a variety of hydrocarbons from syngas. Fischer-Tropsch cobalt, iron and ruthenium catalysts supported on silica aerogel have been prepared using a combination of sol-gel chemistry and vapor phase deposition methods. Solid state NMR spectroscopy, a very powerful technique for analyzing the structure and dynamics of various materials, was employed in the study of these F-T catalyst systems. The silica aerogel supported F-T catalysts have been investigated using both solid state {sup 29}Si and {sup 13}C NMR methods. The silica aerogel's tetrahedral sub-unit structure and the influence of the loaded metal compounds have been observed. Three types of Si(O{sub 1/2}){sub 4} tetrahedral unit structure (Q{sub 2}, Q{sub 3} and Q{sub 4}) are clearly resolved in the silica aerogel samples. The calcining process and the loading of metal compounds produce line broadening in the {sup 29}Si spectra sufficient to prevent clear resolution of the three distinct Q{sub n} spectral lines, but the broadened spectra indicate that the three Q sub-unit structures are still present. The ferrocene and ruthenocene molecules used in the vapor phase deposition method exhibit a rapid exchange within the silica aerogel support similar to what one would expect in the gas or liquid state. (author)

  7. Structure and dynamics of cationic membrane peptides and proteins: Insights from solid-state NMR

    Science.gov (United States)

    Hong, Mei; Su, Yongchao

    2011-01-01

    Many membrane peptides and protein domains contain functionally important cationic Arg and Lys residues, whose insertion into the hydrophobic interior of the lipid bilayer encounters significant energy barriers. To understand how these cationic molecules overcome the free energy barrier to insert into the lipid membrane, we have used solid-state NMR spectroscopy to determine the membrane-bound topology of these peptides. A versatile array of solid-state NMR experiments now readily yields the conformation, dynamics, orientation, depth of insertion, and site-specific protein–lipid interactions of these molecules. We summarize key findings of several Arg-rich membrane peptides, including β-sheet antimicrobial peptides, unstructured cell-penetrating peptides, and the voltage-sensing helix of voltage-gated potassium channels. Our results indicate the central role of guanidinium-phosphate and guanidinium-water interactions in dictating the structural topology of these cationic molecules in the lipid membrane, which in turn account for the mechanisms of this functionally diverse class of membrane peptides. PMID:21344534

  8. A combination of novel solid-state NMR methods and related software to study molecular assemblies and biomolecules

    NARCIS (Netherlands)

    Gradmann, S.H.E.

    2013-01-01

    Solid-state Nuclear Magnetic Resonance (ssNMR) is a versatile spectroscopic method that can be applied to various samples relevant in life and material science and provides atomic insight into molecular structure, dynamics and assembly. The present thesis describes the diversity and utility of ssNMR

  9. An explanation for the high stability of polycarboxythiophenes in photovoltaic devices—A solid-state NMR dipolar recoupling study

    DEFF Research Database (Denmark)

    Bierring, M.; Nielsen, J.S.; Siu, Ana

    2008-01-01

    observed in photovoltaic devices employing polythiophene substituted with carboxylic-acid moieties under oxygen free conditions. H-1 and C-13 solid-state NMR, IR, and ESR spectroscopy of unmodified and isotopically labeled polythiophenes were studied. Distances between the isotopically labeled carboxylic...... acid carbon atoms were measured by C-13 solid-state magic-angle-spinning (MAS) NMR using symmetry-based double-quantum (2Q) dipolar recoupling. This revealed the presence of C-13-C-13 distances of 3.85 angstrom, which correspond to the C-C distance in hydrogen-bonded carboxylic acid dimers. In spite...... of the presence of carboxylic groups in the polymer as demonstrated by C-13 CP/MAS NMR and IR spectroscopy, the absence of carboxylic protons in solid state H-1 NMR spectra indicate that they are mobile. We link the extraordinary stability of this system to the rigid nature, cross-linking through a hydrogen...

  10. Solid-state and unilateral NMR study of deterioration of a Dead Sea Scroll fragment.

    Science.gov (United States)

    Masic, A; Chierotti, M R; Gobetto, R; Martra, G; Rabin, I; Coluccia, S

    2012-02-01

    Unilateral and solid-state nuclear magnetic resonance (NMR) analyses were performed on a parchment fragment of the Dead Sea Scroll (DSS). The analyzed sample belongs to the collection of non-inscribed and nontreated fragments of known archaeological provenance from the John Rylands University Library in Manchester. Therefore, it can be considered as original DSS material free from any contamination related to the post-discovery period. Considering the paramount significance of the DSS, noninvasive approaches and portable in situ nondestructive methods are of fundamental importance for the determination of composition, structure, and chemical-physical properties of the materials under study. NMR studies reveal low amounts of water content associated with very short proton relaxation times, T(1), indicating a high level of deterioration of collagen molecules within scroll fragments. In addition, (13)C cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy shows characteristic peaks of lipids whose presence we attribute to the production technology that did not involve liming. Extraction with chloroform led to the reduction of both lipid and protein signals in the (13)C CPMAS spectrum indicating probable involvement of lipids in parchment degradation processes. NMR absorption and relaxation measurements provide nondestructive, discriminative, and sensitive tools for studying the deterioration effects on the organization and properties of water and collagen within ancient manuscripts.

  11. Development of solid-state NMR techniques for the characterisation of pharmaceutical compounds

    Science.gov (United States)

    Tatton, Andrew S.

    Structural characterisation in the solid state is an important step in understanding the physical and chemical properties of a material. Solid-state NMR techniques applied to solid delivery forms are presented as an alternative to more established structural characterisation methods. The effect of homonuclear decoupling upon heteronuclear couplings is investigated using a combination of experimental and density-matrix simulation results acquired from a 13C-1H spinecho pulse sequence, modulated by scalar couplings. It is found that third-order cross terms under MAS and homonuclear decoupling contribute to strong dephasing effects in the NMR signal. Density-matrix simulations allow access to parameters currently unattainable in experiment, and demonstrate that higher homonuclear decoupling rf nutation frequencies reduce the magnitude of third-order cross terms. 15N-1H spinecho experiments were applied to pharmaceutically relevant samples to differentiate between the number of directly attached protons. Using this method, proton transfer in an acid-base reaction is proven in pharmaceutical salts. The indirect detection of 14N lineshapes via protons obtained using 2D 14N-1H HMQC experiments is presented, where coherence transfer is achieved via heteronuclear through-space dipolar couplings. The importance of fast MAS frequencies is demonstrated, and it is found that increasing the recoupling duration reveals longer range NH proximities. The 2D 14N-1H HMQC method is used to demonstrate the presence of specific hydrogen bonding interactions, and thus aid in identifying molecular association in a cocrystal and an amorphous dispersion. In addition, hydrogen bonding motifs were identified by observing the changes in the 14N quadrupolar parameters between individual molecular components relative to the respective solid delivery form. First-principles calculations of NMR chemical shifts and quadrupolar parameters using the GIPAW method were combined with 14N-1H experimental

  12. Applications of Solid State NMR to the Study of Molecular Structure

    Science.gov (United States)

    Curtis, Ronald Dean

    This thesis illustrates several applications of dilute spin I = 1over2 solid state nmr spectroscopy to the study of molecular structure in systems of chemical interest. Specifically, the compounds studied include benzylideneaniline and several related imines, the first stable iminophosphenium cation containing a N,P triple bond and several tetracyclines. The first two applications describe the use of dipolar-chemical shift nmr of "isolated" spin-pairs to fully characterize chemical shift tensors. For example, the carbon and nitrogen shift tensors of the C=N linkage of the Schiff base benzylideneaniline have been completely specified. The most shielded principal component of both carbon and nitrogen shift tensors is approximately perpendicular to the imine fragment. For the imine carbon, the intermediate component of the shift tensor is directed approximately along the C=N bond whereas the corresponding component of the nitrogen shift tensor is oriented along the direction of the nitrogen lone pair. Examination of the nitrogen chemical shift parameters for several related imines suggests that variations in the least shielded principal component are mainly responsible for changes in the nitrogen shieldings in the imine system. For the N,P moiety of the iminophosphenium cation, the most shielded principal component of both nitrogen and phosphorus tensors is oriented along the N,P bond axis. Comparison of both shift tensors with those of related compounds suggests that the electronic environment surrounding the N,P moiety is similar to other systems containing a formal triple bond. The final application section demonstrates the utility of high-resolution ^{13} C and ^{15}N cp/mas nmr for studying the molecular structure of solid tetracycline antibiotics. Comparison of ^{15} C chemical shifts in the solid state to those determined in (CD_3)_2SO solutions indicates for the first time that the structural integrity of the A ring of the tetracyclines is maintained in

  13. Modern solid-state NMR on functional polymers; Moderne Festkoerper-NMR an Funktionspolymeren

    Energy Technology Data Exchange (ETDEWEB)

    Wang, M.

    2004-07-01

    In this thesis the microscopic structures of natural caoutchouc, on silicic acid plugged polydimethylsiloxane (PDMS), and polyamide-clay-nanocomposite are studied. For natural caoutchouc it is shown how the network density can be characterized by the study of the dipole-dipole couplings between protons and carbon by means of the heteronuclear double-quantum NMR method and further double-resonance experiments. In PDMS homo- and heteronuclear multi-quantum NMR, spin-diffusion, relaxometry, and double-resonance experiments are used for the study of the dependence of the molecular motion on external influences. Finally the structural change of polyamides by addition of clay particles is studied.

  14. Atomic substitutions in synthetic apatite; Insights from solid-state NMR spectroscopy

    Science.gov (United States)

    Vaughn, John S.

    Apatite, Ca5(PO4)3X (where X = F, Cl, or OH), is a unique mineral group capable of atomic substitutions for cations and anions of varied size and charge. Accommodation of differing substituents requires some kind of structural adaptation, e.g. new atomic positions, vacancies, or coupled substitutions. These structural adaptations often give rise to important physicochemical properties relevant to a range of scientific disciplines. Examples include volatile trapping during apatite crystallization, substitution for large radionuclides for long-term storage of nuclear fission waste, substitution for fluoride to improve acid resistivity in dental enamel composed dominantly of hydroxylapatite, and the development of novel biomaterials with enhanced biocompatibility. Despite the importance and ubiquity of atomic substitutions in apatite materials, many of the mechanisms by which these reactions occur are poorly understood. Presence of substituents at dilute concentration and occupancy of disordered atomic positions hinder detection by bulk characterization methods such as X-ray diffraction (XRD) and infrared (IR) spectroscopy. Solid-state nuclear magnetic resonance (NMR) spectroscopy is an isotope-specific structural characterization technique that does not require ordered atomic arrangements, and is therefore well suited to investigate atomic substitutions and structural adaptations in apatite. In the present work, solid-state NMR is utilized to investigate structural adaptations in three different types of apatite materials; a series of near-binary F, Cl apatite, carbonate-hydroxylapatite compositions prepared under various synthesis conditions, and a heat-treated hydroxylapatite enriched in 17O. The results indicate that hydroxyl groups in low-H, near binary F,Cl apatite facilitate solid-solution between F and Cl via column reversals, which result in average hexagonal symmetry despite very dilute OH concentration ( 2 mol percent). In addition, 19F NMR spectra indicate

  15. Application of Solid-State NMR Relaxometry for Characterization and Formulation Optimization of Grinding-Induced Drug Nanoparticle.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

    2016-03-07

    The formation mechanism of drug nanoparticles was investigated using solid-state nuclear magnetic resonance (NMR) techniques for the efficient discovery of an optimized nanoparticle formulation. The cogrinding of nifedipine (NIF) with polymers, including hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) was performed to prepare the NIF nanoparticle formulations. Then, solid-state NMR relaxometry was used for the nanometer-order characterization of NIF in the polymer matrix. Solid-state NMR measurements revealed that the crystal size of NIF was reduced to several tens of nanometers with amorphization of NIF by cogrinding with HPMC and SDS for 100 min. Similarly, the size of the NIF crystal was reduced to less than 90 nm in the 40 min ground mixture of NIF/PVP/SDS. Furthermore, 100 min grinding of NIF/PVP/SDS induced amorphization of almost all the NIF crystals followed by nanosizing. The hydrogen bond between NIF and PVP led to the efficient amorphization of NIF in the NIF/PVP/SDS system compared with NIF/HPMC/SDS system. The efficient nanosizing of the NIF crystal in the solid state, revealed by the solid-state NMR relaxation time measurements, enabled the formation of large amounts of NIF nanoparticles in water followed by the polymer dissolution. In contrast, excess amorphization of the NIF crystals failed to efficiently prepare the NIF nanoparticles. The solid-state characterization of the crystalline NIF revealed good correlation with the NIF nanoparticles formation during aqueous dispersion. Furthermore, the solid-state NMR measurements including relaxometry successfully elucidated the nanometer-order dispersion state of NIF in polymer matrix, leading to the discovery of optimized conditions for the preparation of suitable drug nanoparticles.

  16. Action of the multifunctional peptide BP100 on native biomembranes examined by solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Misiewicz, Julia [Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry (Germany); Afonin, Sergii; Grage, Stephan L.; Berg, Jonas van den; Strandberg, Erik; Wadhwani, Parvesh [Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2) (Germany); Ulrich, Anne S., E-mail: anne.ulrich@kit.edu [Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry (Germany)

    2015-04-15

    Membrane composition is a key factor that regulates the destructive activity of antimicrobial peptides and the non-leaky permeation of cell penetrating peptides in vivo. Hence, the choice of model membrane is a crucial aspect in NMR studies and should reflect the biological situation as closely as possible. Here, we explore the structure and dynamics of the short multifunctional peptide BP100 using a multinuclear solid-state NMR approach. The membrane alignment and mobility of this 11 amino acid peptide was studied in various synthetic lipid bilayers with different net charge, fluidity, and thickness, as well as in native biomembranes harvested from prokaryotic and eukaryotic cells. {sup 19}F-NMR provided the high sensitivity and lack of natural abundance background that are necessary to observe a labelled peptide even in protoplast membranes from Micrococcus luteus and in erythrocyte ghosts. Six selectively {sup 19}F-labeled BP100 analogues gave remarkably similar spectra in all of the macroscopically oriented membrane systems, which were studied under quasi-native conditions of ambient temperature and full hydration. This similarity suggests that BP100 has the same surface-bound helical structure and high mobility in the different biomembranes and model membranes alike, independent of charge, thickness or cholesterol content of the system. {sup 31}P-NMR spectra of the phospholipid components did not indicate any bilayer perturbation, so the formation of toroidal wormholes or micellarization can be excluded as a mechanism of its antimicrobial or cell penetrating action. However, {sup 2}H-NMR analysis of the acyl chain order parameter profiles showed that BP100 leads to considerable membrane thinning and thereby local destabilization.

  17. Molecular structure of crude beeswax studied by solid-state 13C NMR.

    Science.gov (United States)

    Kameda, Tsunenori

    2004-01-01

    13C solid-state NMR experiments were performed to investigate the structure of beeswax in the native state (crude beeswax) for the first time. From quantitative direct polarization 13C MAS NMR spectrum, it was found that the fraction of internal-chain methylene (int-(CH2)) component compared to other components of crude beeswax was over 95%. The line shape of the int-(CH2) carbon resonance region was comprehensively analyzed in terms of NMR chemical shift. The 13C broad peak component covering from 31 to 35 ppm corresponds to int-(CH2) carbons with trans conformation in crystalline domains, whereas the sharp signal at 30.3 ppm corresponds to gauche conformation in the non-crystalline domain. From peak deconvolution of the aliphatic region, it was found that over 85% of the int-(CH2) has a crystal structure and several kinds of molecular packing for int-(CH2), at least three, exist in the crystalline domain.

  18. Solid-state NMR applied to photosynthetic light-harvesting complexes.

    Science.gov (United States)

    Pandit, Anjali; de Groot, Huub J M

    2012-03-01

    This short review describes how solid-state NMR has provided a mechanistic and electronic picture of pigment-protein and pigment-pigment interactions in photosynthetic antenna complexes. NMR results on purple bacterial antenna complexes show how the packing of the protein and the pigments inside the light-harvesting oligomers induces mutual conformational stress. The protein scaffold produces deformation and electrostatic polarization of the BChl macrocycles and leads to a partial electronic charge transfer between the BChls and their coordinating histidines, which can tune the light-harvesting function. In chlorosome antennae assemblies, the NMR template structure reveals how the chromophores can direct their self-assembly into higher macrostructures which, in turn, tune the light-harvesting properties of the individual molecules by controlling their disorder, structural deformation, and electronic polarization without the need for a protein scaffold. These results pave the way for addressing the next challenge, which is to resolve the functional conformational dynamics of the lhc antennae of oxygenic species that allows them to switch between light-emitting and light-energy dissipating states.

  19. Solid state NMR investigation of a novel Li ion ceramic electrolyte. Li doped BPO sub 4

    CERN Document Server

    Dodd, A J

    2002-01-01

    Over the last decade lithium ion conducting batteries have emerged as the leading technology in battery materials. Their performance, however, is limited to applications below around 50 deg C by the liquid nature of the electrolytes used. In the quest for a solid state electrolyte for use in high temperature applications the nano-crystalline ceramic lithium doped boron phosphate material was developed. Solid state nuclear magnetic resonance (NMR) has been employed to investigate some of the fundamental properties of this material including ionic mobility, defect structure, sample purity and ionic distribution. The findings of this work show that when synthesised at a reaction temperature above 600 deg C the loss of boron from the structure results in the incorporation of vacancy sites about which the Li ions gather in small clusters. Multiple-pulse multiple-quantum spin counting techniques are employed in an effort to count the number of quadrupolar sup 7 Li nuclei interacting in a cluster though it is ultima...

  20. Characterisation of hydrogen bonding networks in RNAs via magic angle spinning solid state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Riedel, Kerstin; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai [Institut fuer Molekulare Biotechnologie, Abteilung Molekulare Biophysik/NMR-Spektroskopie (Germany)], E-mail: raman@imb-jena.de

    2005-04-15

    It is demonstrated that the spatial proximity of {sup 1}H nuclei in hydrogen bonded base-pairs in RNAs can be conveniently mapped via magic angle spinning solid state NMR experiments involving proton spin diffusion driven chemical shift correlation of low gamma nuclei such as the imino and amino nitrogens of nucleic acid bases. As different canonical and non-canonical base-pairing schemes encountered in nucleic acids are characterised by topologically different networks of proton dipolar couplings, different base-pairing schemes lead to characteristic cross-peak intensity patterns in such correlation spectra. The method was employed in a study of a 100 kDa RNA composed of 97 CUG repeats, or (CUG){sub 97} that has been implicated in the neuromuscular disease myotonic dystrophy. {sup 15}N-{sup 15}N chemical shift correlation studies confirm the presence of Watson-Crick GC base pairs in (CUG){sub 97}.

  1. Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR

    Science.gov (United States)

    Simmons, Thomas J.; Mortimer, Jenny C.; Bernardinelli, Oigres D.; Pöppler, Ann-Christin; Brown, Steven P.; Deazevedo, Eduardo R.; Dupree, Ray; Dupree, Paul

    2016-12-01

    Exploitation of plant lignocellulosic biomass is hampered by our ignorance of the molecular basis for its properties such as strength and digestibility. Xylan, the most prevalent non-cellulosic polysaccharide, binds to cellulose microfibrils. The nature of this interaction remains unclear, despite its importance. Here we show that the majority of xylan, which forms a threefold helical screw in solution, flattens into a twofold helical screw ribbon to bind intimately to cellulose microfibrils in the cell wall. 13C solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, supported by in silico predictions of chemical shifts, shows both two- and threefold screw xylan conformations are present in fresh Arabidopsis stems. The twofold screw xylan is spatially close to cellulose, and has similar rigidity to the cellulose microfibrils, but reverts to the threefold screw conformation in the cellulose-deficient irx3 mutant. The discovery that induced polysaccharide conformation underlies cell wall assembly provides new principles to understand biomass properties.

  2. A solid-state NMR method to determine domain sizes in multi-component polymer formulations

    Science.gov (United States)

    Schlagnitweit, Judith; Tang, Mingxue; Baias, Maria; Richardson, Sara; Schantz, Staffan; Emsley, Lyndon

    2015-12-01

    Polymer domain sizes are related to many of the physical properties of polymers. Here we present a solid-state NMR experiment that is capable of measuring domain sizes in multi-component mixtures. The method combines selective excitation of carbon magnetization to isolate a specific component with proton spin diffusion to report on domain size. We demonstrate the method in the context of controlled release formulations, which represents one of today's challenges in pharmaceutical science. We show that we can measure domain sizes of interest in the different components of industrial pharmaceutical formulations at natural isotopic abundance containing various (modified) cellulose derivatives, such as microcrystalline cellulose matrixes that are film-coated with a mixture of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC).

  3. A Solid State NMR Investigation of Recent Marine Siliceous Sponge Spicules

    Directory of Open Access Journals (Sweden)

    Sylvie Masse

    2016-03-01

    Full Text Available The composition of four recent siliceous marine sponge spicules was studied and compared. In particular, multinuclear (29Si, 13C, 31P solid state nuclear magnetic resonance (NMR allowed the characterization of both the mineral and organic constituents in a non-destructive manner. The silica network condensation was similar for all samples. The organic matter showed a similar pattern but varied in abundance as a function of the sponge group (Hexactinellida or Demospongiae and sampling conditions (living or dead organisms. This indicates that the striking morphological differences observed at the macroscale for the various samples do not lead to significant fingerprints in the spectroscopic signatures of the mineral and organic constituents.

  4. Monitoring the evolution of crystallization processes by in-situ solid-state NMR spectroscopy.

    Science.gov (United States)

    Harris, Kenneth D M; Hughes, Colan E; Williams, P Andrew

    2015-02-01

    Crystallization processes play a crucial role in many aspects of biological and physical sciences. Progress in deepening our fundamental understanding of such processes relies, to a large extent, on the development and application of new experimental strategies that allow direct in-situ monitoring of the process. In this paper, we give an overview of an in-situ solid-state NMR strategy that we have developed in recent years for monitoring the time-evolution of different polymorphic forms (or other solid forms) that arise as the function of time during crystallization from solution. The background to the strategy is described and several examples of the application of the technique are highlighted, focusing on both the evolution of different polymorphs during crystallization and the discovery of new polymorphs.

  5. Molecular dynamics of neutral polymer bonding agent (NPBA) as revealed by solid-state NMR spectroscopy.

    Science.gov (United States)

    Hu, Wei; Su, Yongchao; Zhou, Lei; Pang, Aimin; Cai, Rulin; Ma, Xingang; Li, Shenhui

    2014-01-22

    Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg). In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions.

  6. Sine-squared shifted pulses for recoupling interactions in solid-state NMR.

    Science.gov (United States)

    Jain, Mukul G; Rajalakshmi, G; Equbal, Asif; Mote, Kaustubh R; Agarwal, Vipin; Madhu, P K

    2017-06-28

    Rotational-Echo DOuble-Resonance (REDOR) is a versatile experiment for measuring internuclear distance between two heteronuclear spins in solid-state NMR. At slow to intermediate magic-angle spinning (MAS) frequencies, the measurement of distances between strongly coupled spins is challenging due to rapid dephasing of magnetisation. This problem can be remedied by employing the pulse-shifted version of REDOR known as Shifted-REDOR (S-REDOR) that scales down the recoupled dipolar coupling. In this study, we propose a new variant of the REDOR sequence where the positions of the π pulses are determined by a sine-squared function. This new variant has scaling properties similar to S-REDOR. We use theory, numerical simulations, and experiments to compare the dipolar recoupling efficiencies and the experimental robustness of the three REDOR schemes. The proposed variant has advantages in terms of radiofrequency field requirements at fast MAS frequencies.

  7. A solid state NMR investigation of char forming processes in polymer degradation

    CERN Document Server

    Dick, C M

    2002-01-01

    A detailed knowledge of the condensed phase chemistry occurring in polymers exposed to elevated temperatures is crucial to understanding the behaviour of polymers exposed to fire. This is particularly true when trying to reduce polymer flammability by means of promoting char-forming reactions. Until recently, however, structural information on highly crosslinked chars and their precursors has been difficult to obtain, and as a consequence many degradation workers have merely labelled degradation residues as 'intractable'. However, the application of solid state NMR techniques developed in our laboratories for the structural characterisation of coals has provided a considerable insight into the structure and chemistry of polymer chars formed under both oxidative and non-oxidative conditions. A series of polymers including poly(vinyl chloride), poly(vinyl acetate), polyurethanes, polychloropene, cis and trans polyisoprene have been studied. These polymers have been used to describe the application of quantitati...

  8. Combining oximes with azides to create a novel 1-D [NaCo(III)(2)] system: synthesis, structure and solid-state NMR.

    Science.gov (United States)

    Pathmalingam, Thushan; Habib, Fatemah; Widdifield, Cory M; Loiseau, Francis; Burchell, Tara J; Gorelsky, Serge I; Beauchemin, André M; Bryce, David L; Murugesu, Muralee

    2010-02-14

    The synthesis and structure of a novel complex with the formula [NaCo(III)(2)(dmo)(2)(mu-N(3))(3)(N(3))(2)](infinity), , are reported. Complex was synthesized from the reaction of 1-(dimethylamino)propan-2-one oxime (Hdmo), CoCl(2).6H(2)O, and NaN(3) in MeOH. It crystallizes in the monoclinic space group C2/c. The molecular structure consists of one Na(I) and two Co(III) ions bridged by two oxime ligands, two end-to-end azide and three end-on azide anions. The units are linked, forming a 1-D chain. This complex was characterized by UV-Vis spectroscopy where the data confirm the presence of low-spin Co(III) ions. Solid-state (23)Na NMR experiments indicate the presence of one magnetically unique site in the repeating unit, that sample purity in the bulk powdered form is high, and that it possesses microcrystalline order. Solid-state (59)Co NMR experiments at ultra-high field (B(0) = 21.1 T) are in agreement with the structure obtained through X-ray crystallography where the Co(III) ions are coordinated to five nitrogen atoms as well as an oxygen atom.

  9. Highly efficient F-19 heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation

    DEFF Research Database (Denmark)

    Equbal, Asif; Basse, Kristoffer; Nielsen, Niels Christian

    2016-01-01

    We present heteronuclear F-19 refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle- spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent C-13-F-19 dipolar coupling interactions while simultaneously suppress......We present heteronuclear F-19 refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle- spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent C-13-F-19 dipolar coupling interactions while simultaneously...

  10. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR

    Science.gov (United States)

    Vacchi, Isabella A.; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-01

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by

  11. In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.

    Science.gov (United States)

    Blanc, Frédéric; Leskes, Michal; Grey, Clare P

    2013-09-17

    Electrochemical cells, in the form of batteries (or supercapacitors) and fuel cells, are efficient devices for energy storage and conversion. These devices show considerable promise for use in portable and static devices to power electronics and various modes of transport and to produce and store electricity both locally and on the grid. For example, high power and energy density lithium-ion batteries are being developed for use in hybrid electric vehicles where they improve the efficiency of fuel use and help to reduce greenhouse gas emissions. To gain insight into the chemical reactions involving the multiple components (electrodes, electrolytes, interfaces) in the electrochemical cells and to determine how cells operate and how they fail, researchers ideally should employ techniques that allow real-time characterization of the behavior of the cells under operating conditions. This Account reviews the recent use of in situ solid-state NMR spectroscopy, a technique that probes local structure and dynamics, to study these devices. In situ NMR studies of lithium-ion batteries are performed on the entire battery, by using a coin cell design, a flat sealed plastic bag, or a cylindrical cell. The battery is placed inside the NMR coil, leads are connected to a potentiostat, and the NMR spectra are recorded as a function of state of charge. (7)Li is used for many of these experiments because of its high sensitivity, straightforward spectral interpretation, and relevance to these devices. For example, (7)Li spectroscopy was used to detect intermediates formed during electrochemical cycling such as LixC and LiySiz species in batteries with carbon and silicon anodes, respectively. It was also used to observe and quantify the formation and growth of metallic lithium microstructures, which can cause short circuits and battery failure. This approach can be utilized to identify conditions that promote dendrite formation and whether different electrolytes and additives can help

  12. Solid state NMR method development and studies of biological and biomimetic nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yanyan [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    This thesis describes application and development of advanced solid-state nuclear magnetic resonance techniques for complex materials, in particular organic-inorganic nanocomposites and thermoelectric tellurides. The apatite-collagen interface, essential for understanding the biomineralization process in bone and engineering the interface for controlled bio-mimetic synthesis and optimized mechanical properties, is buried within the nanocomposite of bone. We used multinuclear solid-state NMR to study the composition and structure of the interface. Citrate has been identified as the main organic molecule strongly bound to the apatite surface with a density of 1/(2 nm)2, covering 1/6 of the total surface area in bovine bone. Citrate provides more carboxylate groups, one of the key functional groups found to affect apatite nucleation and growth, than all the non-collagenous proteins all together in bone; thus we propose that citrate stabilizes apatite crystals at a very small thickness of ~3 nm (4 unit cells) to increase bone fracture tolerance. The hypothesis has been confirmed in vitro by adding citrate in the bio-mimetic synthesis of polymerhydroxyapatite nanocomposites. The results have shown that the size of hydroxyapatite nanocrystals decreases as increasing citrate concentration. With citrate concentrations comparable to that in body fluids, similar-sized nanocrystals as in bone have been produced. Besides the dimensions of the apatite crystals, the composition of bone also affects its biofunctional and macroscopic mechanical properties; therefore, our team also extended its effort to enhance the inorganic portion in our bio-mimetic synthesis from originally 15 wt% to current 50 wt% compared to 65 wt% in bovine bone, by using Lysine-Leucine hydroxyapatite nucleating diblock co-polypeptide, which forms a gel at very low concentration. In this thesis, various advanced solid state NMR techniques have been employed to characterize nanocomposites

  13. Structural investigation of aluminium doped ZnO nanoparticles by solid-state NMR spectroscopy.

    Science.gov (United States)

    Avadhut, Yamini S; Weber, Johannes; Hammarberg, Elin; Feldmann, Claus; Schmedt auf der Günne, Jörn

    2012-09-07

    The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ((27)Al, (13)C, (1)H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T(1)-measurements, (27)Al-MQMAS, (27)Al-(1)H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related (27)Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated (27)Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out.

  14. SIMPSON: a general simulation program for solid-state NMR spectroscopy.

    Science.gov (United States)

    Bak, M; Rasmussen, J T; Nielsen, N C

    2000-12-01

    A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tcl scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basically, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple 1D experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

  15. Investigations of adsorption sites on oxide surfaces using solid-state NMR and TPD-IGC

    Science.gov (United States)

    Golombeck, Rebecca A.

    The number and chemical identity of reactive sites on surfaces of glass affects the processing, reliability, and lifetime of a number of important commercial products. Surface site densities, distributions, and structural identities are closely tied to the formation and processing of the glass surface, and exert a direct influence on strength and coating performance. The surface of a glass sample may vary markedly from the composition and chemistry of the bulk glass. We are taking a physicochemical approach to understanding adsorption sites on pristine multicomponent glass fibers surfaces, directly addressing the effect of processing on surface reactivity. This project aimed to understand the energy distributions of surface adsorption sites, the chemical/structural identity of those sites, and the relationship of these glasses to glass composition, thermal history, and in future work, surface coatings. We have studied the bulk and surface structure as well as the surface reactivity of the glass fibers with solid-state nuclear magnetic resonance (NMR) spectroscopy, inverse gas chromatography (IGC), and computational chemistry methods. These methods, solid-state NMR and IGC, typically require high surface area materials; however, by using probe molecules for NMR experiments or packing a column at high density for IGC measurements, lower surface area materials, such as glass fibers, can be investigated. The glasses used within this study were chosen as representative specimens of fibers with potentially different reactive sites on their surfaces. The two glass compositions were centered around a nominal E-glass, which contains very little alkali cations and mainly alkaline earth cations, and wool glass, which contains an abundance of alkali cations. The concentration of boron was varied from 0 to 8 mole % in both fiber compositions. Fibers were drawn from each composition at a variety of temperatures and draw speeds to provide a range of glass samples with varying

  16. Solid-state NMR reveals differential carbohydrate utilization in diapausing Culex pipiens

    Science.gov (United States)

    Chang, James; Singh, Jugeshwar; Kim, Sungshil; Hockaday, William C.; Sim, Cheolho; Kim, Sung Joon

    2016-11-01

    Culex pipiens is the mosquito that vectors West Nile Virus and other human-pathogenic flavivruses in North America. In response to shortened day length and lower temperatures, female Cx. pipiense prepares for the diapause by actively feeding on carbohydrates to increase the biosynthesis of glycogen and lipid to store energy for overwintering. The effect of feeding different carbohydrates on glycogen and lipid biosynthesis in diapausing mosquitoes was investigated in vivo using 13C solid-state NMR. Diapause-destined adult females and nondiapausing counterparts after adult eclosion were fed with three different carbohydrate sources for 7 days: 1) 10% sucrose, 2) 10% D-[13C6]glucose, and 3) 1% D-[13C6]glucose co-provisioned with 10% sucrose. NMR measurements show that sucrose and glucose are metabolized differently in diapausing mosquitoes. Mosquitoes fed on sucrose primarily accumulate glycogen with increased branching structures, but less of lipids. In contrast, mosquitoes fed exclusively on glucose show accumulation of both glycogen and lipid with increased aliphatic chain length. Glucose is exclusively metabolized for the biosynthesis of triacylglyceride when mosquitoes were co-fed with sucrose. Our findings provide novel insights into the insect carbohydrate metabolism that governs glycogen and lipid biosynthesis during diapause, which is fundamental for the insect survival during inimical environments.

  17. Solid-state NMR characterization of tri-ethyleneglycol grafted polyisocyanopeptides.

    Science.gov (United States)

    Zinkevich, T; Venderbosch, B; Jaspers, M; Kouwer, P H J; Rowan, A E; van Eck, E R H; Kentgens, A P M

    2016-04-01

    In aqueous media, ethylene glycol substituted polyisocyanopeptides (PICPs) change their state (undergo a sol-to-gel transition) as a response to temperature. This makes them promising materials for various biomedical applications, for instance, for controlled drug release and non-damaging wound dressing. To utilize PICP in biomedical applications, understanding of the origin of the gelation process is needed, but this is experimentally difficult because of the notoriously low gelator concentration in combination with the slow polymer dynamics in the sample. This paper describes a detailed characterization of the dried state of PICPs by solid-state NMR measurements. Both the (13) C and the (1) H NMR resonances were assigned using a combination of 1D cross-polarization magic angle spinning, 2D (13) C-(1) H heteronuclear correlation spectra and (1) H-(1) H single quantum-double quantum experiments. In addition, the chemical groups involved in dipolar interaction with each other were used to discuss the dynamics and spatial conformation of the polymer. In contrast to other PICP polymers, two resonances for the backbone carbon are observed, which are present in equal amounts. The possible origin of these resonances is discussed in the last section of this work. The data obtained during the current studies will be further used in elucidating mechanisms of the bundling and gelation. A comprehensive picture will make it possible to tailor polymer properties to meet specific needs in different applications. Copyright © 2015 John Wiley & Sons, Ltd.

  18. Phosphorus speciation in calcite speleothems determined from solid-state NMR spectroscopy

    Science.gov (United States)

    Mason, Harris E.; Frisia, Silvia; Tang, Yuanzhi; Reeder, Richard J.; Phillips, Brian L.

    2007-02-01

    Variations in speleothem P concentration show cyclic patterns that have important implications for high resolution palaeoclimate and palaeoenvironmental reconstructions. However, little is known about the speciation of P in calcite speleothems. Here we employ solid-state 31P and 1H magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopic techniques as a non-destructive method for analyzing the distribution of P in speleothems. The 31P MAS NMR results show three peaks indicating the presence of three primary types of phosphate species in samples from the Grotta di Ernesto (northeastern Italy): a broad peak at a chemical shift δP-31 = 3.1 to 3.7 ppm from individual phosphate ions incorporated within calcite, a narrow set of peaks near δP-31 = - 0.9 ppm from crystalline monetite and a narrow peak at δP-31 = 2.9 ppm from an unidentified crystalline phosphate phase. Essentially identical results were obtained for a synthetic calcite/phosphate coprecipitate. Spectra collected for a sample from Grotte de Clamouse (southern France) show only a broad peak near 3.5 ppm suggesting a possible limit for phosphate incorporation into the calcite structure. These data suggest that P in this system can interact to form calcium phosphate surface precipitates during infiltration events and are subsequently enclosed during calcite growth.

  19. Probing Silica-Biomolecule Interactions by Solid-State NMR and Molecular Dynamics Simulations.

    Science.gov (United States)

    Brückner, Stephan Ingmar; Donets, Sergii; Dianat, Arezoo; Bobeth, Manfred; Gutiérrez, Rafael; Cuniberti, Gianaurelio; Brunner, Eike

    2016-11-08

    Understanding the molecular interactions between inorganic phases such as silica and organic material is fundamental for chromatographic applications, for tailoring silica-enzyme interactions, and for elucidating the mechanisms of biomineralization. The formation, structure, and properties of the organic/inorganic interface is crucial in this context. Here, we investigate the interaction of selectively (13)C-labeled choline with (29)Si-labeled monosilicic acid/silica at the molecular level. Silica/choline nanocomposites were analyzed by solid-state NMR spectroscopy in combination with extended molecular dynamics (MD) simulations to understand the silica/organic interface. Cross-polarization magic angle spinning (CP MAS)-based NMR experiments like (1)H-(13)C CP-REDOR (rotational-echo double resonance), (1)H-(13)C HETCOR (heteronuclear correlation), and (1)H-(29)Si-(1)H double CP are employed to determine spatial parameters. The measurement of (29)Si-(13)C internuclear distances for selectively (13)C-labeled choline provides an experimental parameter that allows the direct verification of MD simulations. Atomistic modeling using classical MD methodologies is performed using the INTERFACE force field. The modeling results are in excellent agreement with the experimental data and reveal the relevant molecular conformations as well as the nature and interplay of the interactions between the choline cation and the silica surface. Electrostatic interactions and hydrogen bonding are both important and depend strongly on the hydration level as well as the charge state of the silica surface.

  20. Oriented bilayers of a proteolipid complex, Annexin V phospholipids, for solid state NMR analyses

    Science.gov (United States)

    Saurel, O.; Demange, P.; Milon, A.

    1998-02-01

    We were able to obtain oriented bilayers in the presence of annexin V (35 kDa) and to measure structural and dynamic parameters. NMR results obtained so far show that annexin does not affect the structure of the membrane but modifies the dynamics of the phospholipids (T2e decrease). Our new method to prepare oriented biological samples, based on the preparation of small unilamellar proteolipid vesicles in biological buffers, should be suitable for any membrane protein phospholipid complex and for solid state NMR or neutron diffraction experiments. La préparation de petites vésicules protéo-lipidiques dans un tampon physiologique, nous a permis d'obtenir des bicouches orientées en présence d'annexine V (35 kDa) et de mesurer les paramètres structuraux et dynamiques de ce complexe protéolipidique. Les résultats obtenus par RMN du solide montrent que l'annexine n'affecte pas la structure en bicouche de la membrane mais modifie la dynamique des phospholipides (diminution du temps de relaxation T2e). Cette nouvelle méthode de préparation d'échantillons orientés peut être applicable à tout complexe protéine-phospholipides pour des études par RMN à l'état solide ou par diffraction des neutrons.

  1. Comparison among Magnus/Floquet/Fer expansion schemes in solid-state NMR

    Science.gov (United States)

    Takegoshi, K.; Miyazawa, Norihiro; Sharma, Kshama; Madhu, P. K.

    2015-04-01

    We here revisit expansion schemes used in nuclear magnetic resonance (NMR) for the calculation of effective Hamiltonians and propagators, namely, Magnus, Floquet, and Fer expansions. While all the expansion schemes are powerful methods there are subtle differences among them. To understand the differences, we performed explicit calculation for heteronuclear dipolar decoupling, cross-polarization, and rotary-resonance experiments in solid-state NMR. As the propagator from the Fer expansion takes the form of a product of sub-propagators, it enables us to appreciate effects of time-evolution under Hamiltonians with different orders separately. While 0th-order average Hamiltonian is the same for the three expansion schemes with the three cases examined, there is a case that the 2nd-order term for the Magnus/Floquet expansion is different from that obtained with the Fer expansion. The difference arises due to the separation of the 0th-order term in the Fer expansion. The separation enables us to appreciate time-evolution under the 0th-order average Hamiltonian, however, for that purpose, we use a so-called left-running Fer expansion. Comparison between the left-running Fer expansion and the Magnus expansion indicates that the sign of the odd orders in Magnus may better be reversed if one would like to consider its effect in order.

  2. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR.

    Science.gov (United States)

    Vacchi, Isabella A; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-14

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.

  3. Thin-film solid-state proton NMR measurements using a synthetic mica substrate: Polymer blends

    Science.gov (United States)

    VanderHart, David L.; Prabhu, Vivek M.; Lavery, Kristopher A.; Dennis, Cindi L.; Rao, Ashwin B.; Lin, Eric K.

    2009-11-01

    Solid-state proton nuclear magnetic resonance (NMR) measurements are performed successfully on polymer blend thin films through the use of synthetic mica as a substrate. When used as a substrate, synthetic fluorophlogopite mica with its proton-free, diamagnetic character, allows for adequate measurement sensitivity while minimally perturbing the proton thin-film spectra, especially relative to more commonly available natural micas. Specifically, we use multiple-pulse techniques in the presence of magic-angle spinning to measure the degree of mixing in two different polymer blend thin films, polystyrene/poly(xylylene ether) and poly(1-methyladamantyl methacrylate) (PMAdMA)/triphenylsulfonium perfluorobutanesulfonate (TPS-PFBS), spin-coated onto mica substrates. Our earlier studies had focused on bulk systems where NMR signals are stronger, but may not be representative of thin films of the same systems that are relevant to many applications such as photoresist formulations in the electronics industry. The superiority of synthetic over natural paramagnetic mica is demonstrated by the maintenance of resolution and spinning sideband intensities (relative to bulk samples) for the synthetic mica samples. In contrast, degraded resolution and large spinning sidebands are shown to typify spectra of the natural mica samples. This approach can be applied to many other proton measurements of solid thin films, thereby greatly extending the types of systems to be investigated. Magnetic susceptibility measurements are also reported for all micas used.

  4. Comparison among Magnus/Floquet/Fer expansion schemes in solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Takegoshi, K., E-mail: takeyan@kuchem.kyoto-u.ac.jp; Miyazawa, Norihiro [Division of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto (Japan); Sharma, Kshama [TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500 075 (India); Madhu, P. K. [TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500 075 (India); Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India)

    2015-04-07

    We here revisit expansion schemes used in nuclear magnetic resonance (NMR) for the calculation of effective Hamiltonians and propagators, namely, Magnus, Floquet, and Fer expansions. While all the expansion schemes are powerful methods there are subtle differences among them. To understand the differences, we performed explicit calculation for heteronuclear dipolar decoupling, cross-polarization, and rotary-resonance experiments in solid-state NMR. As the propagator from the Fer expansion takes the form of a product of sub-propagators, it enables us to appreciate effects of time-evolution under Hamiltonians with different orders separately. While 0th-order average Hamiltonian is the same for the three expansion schemes with the three cases examined, there is a case that the 2nd-order term for the Magnus/Floquet expansion is different from that obtained with the Fer expansion. The difference arises due to the separation of the 0th-order term in the Fer expansion. The separation enables us to appreciate time-evolution under the 0th-order average Hamiltonian, however, for that purpose, we use a so-called left-running Fer expansion. Comparison between the left-running Fer expansion and the Magnus expansion indicates that the sign of the odd orders in Magnus may better be reversed if one would like to consider its effect in order.

  5. Hexameric Capsules Studied by Magic Angle Spinning Solid-State NMR Spectroscopy: Identifying Solvent Molecules in Pyrogallol[4]arene Capsules.

    Science.gov (United States)

    Avram, Liat; Goldbourt, Amir; Cohen, Yoram

    2016-01-18

    Powders of pyrogallol[4]arene hexamers were produced by evaporation from organic solvents and were studied, for the first time, by magic angle spinning solid-state NMR (MAS ssNMR). Evaporation selectively removed non-encapsulated solvent molecules leaving stable hexameric capsules encapsulating solvent molecules. After exposure of the powder to solvent vapors, (1)H/(13)C heteronuclear correlation MAS ssNMR experiments were used to assign the signals of the external and encapsulated solvent molecules. The formed capsules were stable for months and the process of solvent encapsulation was reversible. According to the ssNMR experiments, the encapsulated solvent molecules occupy different sites and those sites differ in their mobility. The presented approach paves the way for studying guest exchange, guest affinity, and gas storage in hexamers of this type in the solid state.

  6. Low-power broadband solid-state MAS NMR of 14N

    Science.gov (United States)

    Pell, Andrew J.; Sanders, Kevin J.; Wegner, Sebastian; Pintacuda, Guido; Grey, Clare P.

    2017-05-01

    We propose two broadband pulse schemes for 14N solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) that achieves (i) complete population inversion and (ii) efficient excitation of the double-quantum spectrum using low-power single-sideband-selective pulses. We give a comprehensive theoretical description of both schemes using a common framework that is based on the jolting-frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983)]. This formalism is used to determine for the first time that we can obtain complete population inversion of 14N under low-power conditions, which we do here using single-sideband-selective adiabatic pulses. It is then used to predict that double-quantum coherences can be excited using low-power single-sideband-selective pulses. We then proceed to design a new experimental scheme for double-quantum excitation. The final double-quantum excitation pulse scheme is easily incorporated into other NMR experiments, as demonstrated here for double quantum-single quantum 14N correlation spectroscopy, and 1H-14N dipolar heteronuclear multiple-quantum correlation experiments. These pulses and irradiation schemes are evaluated numerically using simulations on single crystals and full powders, as well as experimentally on ammonium oxalate ((NH4)2C2O4) at moderate MAS and glycine at ultra-fast MAS. The performance of these new NMR methods is found to be very high, with population inversion efficiencies of 100% and double-quantum excitation efficiencies of 30%-50%, which are hitherto unprecedented for the low radiofrequency field amplitudes, up to the spinning frequency, that are used here.

  7. β-Sheet core of tau paired helical filaments revealed by solid-state NMR.

    Science.gov (United States)

    Daebel, Venita; Chinnathambi, Subashchandrabose; Biernat, Jacek; Schwalbe, Martin; Habenstein, Birgit; Loquet, Antoine; Akoury, Elias; Tepper, Katharina; Müller, Henrik; Baldus, Marc; Griesinger, Christian; Zweckstetter, Markus; Mandelkow, Eckhard; Vijayan, Vinesh; Lange, Adam

    2012-08-29

    One of the hallmarks of Alzheimer's disease is the self-assembly of the microtubule-associated protein tau into fibers termed "paired helical filaments" (PHFs). However, the structural basis of PHF assembly at atomic detail is largely unknown. Here, we applied solid-state nuclear magnetic resonance (ssNMR) spectroscopy to investigate in vitro assembled PHFs from a truncated three-repeat tau isoform (K19) that represents the core of PHFs. We found that the rigid core of the fibrils is formed by amino acids V306 to S324, only 18 out of 99 residues, and comprises three β-strands connected by two short kinks. The first β-strand is formed by the well-studied hexapeptide motif VQIVYK that is known to self-aggregate in a steric zipper arrangement. Results on mixed [(15)N:(13)C]-labeled K19 fibrils show that β-strands are stacked in a parallel, in-register manner. Disulfide bridges formed between C322 residues of different molecules lead to a disturbance of the β-sheet structure, and polymorphism in ssNMR spectra is observed. In particular, residues K321-S324 exhibit two sets of resonances. Experiments on K19 C322A PHFs further confirm the influence of disulfide bond formation on the core structure. Our structural data are supported by H/D exchange NMR measurements on K19 as well as a truncated four-repeat isoform of tau (K18). Site-directed mutagenesis studies show that single-point mutations within the three different β-strands result in a significant loss of PHF aggregation efficiency, highlighting the importance of the β-structure-rich regions for tau aggregation.

  8. Rapid acquisition of 14N solid-state NMR spectra with broadband cross polarization.

    Science.gov (United States)

    Harris, Kristopher J; Veinberg, Stanislav L; Mireault, Christopher R; Lupulescu, Adonis; Frydman, Lucio; Schurko, Robert W

    2013-11-25

    Nitrogen is an element of utmost importance in chemistry, biology and materials science. Of its two NMR-active isotopes, (14)N and (15)N, solid-state NMR (SSNMR) experiments are rarely conducted upon the former, due to its low gyromagnetic ratio (γ) and broad powder patterns arising from first-order quadrupolar interactions. In this work, we propose a methodology for the rapid acquisition of high quality (14)N SSNMR spectra that is easy to implement, and can be used for a variety of nitrogen-containing systems. We demonstrate that it is possible to dramatically enhance (14)N NMR signals in spectra of stationary, polycrystalline samples (i.e., amino acids and active pharmaceutical ingredients) by means of broadband cross polarization (CP) from abundant nuclei (e.g., (1)H). The BRoadband Adiabatic INversion Cross-Polarization (BRAIN-CP) pulse sequence is combined with other elements for efficient acquisition of ultra-wideline SSNMR spectra, including Wideband Uniform-Rate Smooth-Truncation (WURST) pulses for broadband refocusing, Carr-Purcell Meiboom-Gill (CPMG) echo trains for T2-driven S/N enhancement, and frequency-stepped acquisitions. The feasibility of utilizing the BRAIN-CP/WURST-CPMG sequence is tested for (14)N, with special consideration given to (i) spin-locking integer spin nuclei and maintaining adiabatic polarization transfer, and (ii) the effects of broadband polarization transfer on the overlapping satellite transition patterns. The BRAIN-CP experiments are shown to provide increases in signal-to-noise ranging from four to ten times and reductions of experimental times from one to two orders of magnitude compared to analogous experiments where (14)N nuclei are directly excited. Furthermore, patterns acquired with this method are generally more uniform than those acquired with direct excitation methods. We also discuss the proposed method and its potential for probing a variety of chemically distinct nitrogen environments.

  9. Kinetic analysis of protein aggregation monitored by real-time 2D solid-state NMR spectroscopy

    NARCIS (Netherlands)

    Etzkorn, M.; Böckmann, A.; Baldus, M.

    2011-01-01

    It is shown that real-time 2D solid-state NMR can be used to obtain kinetic and structural information about the process of protein aggregation. In addition to the incorporation of kinetic information involving intermediate states, this approach can offer atom-specific resolution for all detectable

  10. Characterization of phosphate sequestration by a lanthanum modified bentonite clay: A solid-state NMR, EXAFS and PXRD study

    DEFF Research Database (Denmark)

    Dithmer, Line; Lipton, Andrew S; Reitzel, Kasper;

    2015-01-01

    Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of 31P and 139La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy...

  11. Characterization of phosphate sequestration by a lanthanum modified bentonite clay: A solid-state NMR, EXAFS and PXRD study

    DEFF Research Database (Denmark)

    Dithmer, Line; Lipton, Andrew S; Reitzel, Kasper

    2015-01-01

    Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of 31P and 139La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy...... formed upon Pi sequestration is in close proximity to the clay matrix....

  12. Interaction between dry starch and plasticisers glycerol or ethylene glycol, measured by differential scanning calorimetry and solid state NMR spectroscopy

    NARCIS (Netherlands)

    Smits, A.L.M.; Kruiskamp, P.H.; Soest, van J.J.G.; Vliegenthart, J.F.G.

    2003-01-01

    The interaction of crystalline amylose and of crystalline and amorphous amylopectin with the plasticisers glycerol or ethylene glycol in the absence of water was studied, by using differential scanning calorimetry (DSC) and solid state nuclear magnetic resonance (NMR) spectroscopy. Upon heating

  13. Structural analysis of a melaminium polyphosphate from X-ray powder diffraction and solid-state NMR data

    NARCIS (Netherlands)

    Brodski, V.; Peschar, R.; Schenk, H.; Brinkmann, A.; Bloemberg, T.G.; Eck, E.R.H. van; Kentgens, A.P.M.

    2005-01-01

    The crystal structure of the environmentally friendly flame retardant melaminium polyphosphate (MPoly) (2,4,6-triamino-1,3,5-triazinium-PO3)(n) was determined by a direct-space global optimization technique from X-ray powder diffraction data. Solid-state NMR was used to corroborate the proposed

  14. Variable-temperature 13C solid-state NMR study of the molecular structure of honeybee wax and silk.

    Science.gov (United States)

    Kameda, Tsunenori; Tamada, Yasushi

    2009-01-01

    To elucidate the native-state crystal structure of beeswax from the Japanese bee, Apis cerana japonica, we determined the relationship between temperature and the 13C solid-state nuclear magnetic resonance (NMR) chemical shift of methylene carbon of beeswax, with comparison to n-alkanes and polyethylene in the orthorhombic, monoclinic, or triclinic crystal form. Variable-temperature 13C solid-state NMR observations of n-alkanes and polyethylene revealed that the chemical shifts of methylene carbon in the orthorhombic crystal form increased linearly with increasing temperature, that of the triclinic form decreased, and that of the monoclinic form was unaltered. These relations were compared with results of variable-temperature 13C solid-state NMR observation of beeswax. Results clarified that the two crystal forms comprising the beeswax in the native state are orthorhombic and monoclinic. The variable-temperature 13C solid-state NMR observations were also applied to interpret the differential scanning calorimetry (DSC) curve of beeswax. They were used to clarify the structural changes of beeswax for widely various temperatures. For beeswax secreted by the Japanese bee, the transition from the orthorhombic form to the rotator phase occurred at 36 degrees C, that is from the crystalline to the intermediate state at 45 degrees C. Moreover, the variable-temperature 13C solid-state NMR spectrum of honeybee silk in the native state was observed. Results demonstrated that the secondary structures of honeybee silk proteins in the native state comprised coexisting alpha-helix and beta-sheet conformations and that the amount of alpha-helices was greater. The alpha-helix content of honeybee silk was compared with that of hornet silk produced by Vespa larvae.

  15. Helical Conformation in the CA-SP1 Junction of the Immature HIV-1 Lattice Determined from Solid-State NMR of Virus-like Particles.

    Science.gov (United States)

    Bayro, Marvin J; Ganser-Pornillos, Barbie K; Zadrozny, Kaneil K; Yeager, Mark; Tycko, Robert

    2016-09-21

    Maturation of HIV-1 requires disassembly of the Gag polyprotein lattice, which lines the viral membrane in the immature state, and subsequent assembly of the mature capsid protein lattice, which encloses viral RNA in the mature state. Metastability of the immature lattice has been proposed to depend on the existence of a structurally ordered, α-helical segment spanning the junction between capsid (CA) and spacer peptide 1 (SP1) subunits of Gag, a segment that is dynamically disordered in the mature capsid lattice. We report solid state nuclear magnetic resonance (ssNMR) measurements on the immature lattice in noncrystalline, spherical virus-like particles (VLPs) derived from Gag. The ssNMR data provide definitive evidence for this critical α-helical segment in the VLPs. Differences in ssNMR chemical shifts and signal intensities between immature and mature lattice assemblies also support a major rearrangement of intermolecular interactions in the maturation process, consistent with recent models from electron cryomicroscopy and X-ray crystallography.

  16. Dispersion of Silicate in Tricalcium Phosphate Elucidated by Solid-State NMR

    Energy Technology Data Exchange (ETDEWEB)

    Rewal, A.; Wei, X.; Akinc, M.; Schmidt-Rohr, K.

    2008-03-12

    The dispersion of silicate in tricalcium phosphate, a resorbable bioceramics for bone replacement, has been investigated by various solid-state nuclear magnetic resonance (NMR) methods. In samples prepared with 5 and 10 mol% of both {sup 29}SiO{sub 2} and ZnO, three types of silicate have been detected: (i) SiO{sub 4}{sup 4-} (Q{sub 0} sites) with long longitudinal (T{sub 1,Si}) relaxation times ({approx} 10,000 s), which substitute for {approx}1% of PO{sub 4}{sup 3-}; (ii) silicate nanoinclusions containing Q{sub 2}, Q{sub 1}, and Q{sub 0} sites with T{sub 1,Si} 100 s, which account for most of the silicon; and (iii) crystalline Q{sub 4} (SiO{sub 2}) with long T{sub 1,Si}. Sensitivity was enhanced >100-fold by {sup 29}Si enrichment and refocused detection. The inclusions in both samples have a diameter of {approx}8 nm, as proved by {sup 29}Si{l_brace}{sup 31}P{r_brace} REDOR dephasing on a 30-ms time scale, which was simulated using a multispin approach specifically suited for nanoparticles. {sup 29}Si CODEX NMR with 30-s {sup 29}Si spin diffusion confirms that an inclusion contains >10 Si (consistent with the REDOR result of >100 Si per inclusion). Overlapping signals of silicate Q{sub 2}, Q{sub 1}, and Q{sub 0} sites were spectrally edited based on their J-couplings, using double-quantum filtering. The large inhomogeneous broadening of the Q{sub 2}, Q{sub 1}, and Q{sub 0} {sup 29}Si subspectra indicates that the nanoinclusions are amorphous.

  17. High-Resolution NMR of Quadrupolar Nuclei in the Solid State

    Energy Technology Data Exchange (ETDEWEB)

    Gann, Sheryl Lee

    1995-11-30

    This dissertation describes recent developments in solid state nuclear magnetic resonance (NMR), for the most part involving the use of dynamic-angle spinning (DAS) NMR to study quadrupolar nuclei. Chapter 1 introduces some of the basic concepts and theory that will be referred to in later chapters, such as the density operator, product operators, rotations, coherence transfer pathways, phase cycling, and the various nuclear spin interactions, including the quadrupolar interaction. Chapter 2 describes the theory behind motional averaging experiments, including DAS, which is a technique where a sample is spun sequentially about two axis oriented at different angles with respect to the external magnetic field such that the chemical shift and quadrupolar anisotropy are averaged to zero. Work done on various rubidium-87 salts is presented as a demonstration of DAS. Chapter 3 explains how to remove sidebands from DAS and magic-angle spinning (MAS) experiments, which result from the time-dependence of the Hamiltonian under sample spinning conditions, using rotor-synchronized {pi}-pulses. Data from these experiments, known as DAH-180 and MAH-180, respectively, are presented for both rubidium and lead salts. In addition, the applicability of this technique to double rotation (DOR) experiments is discussed. Chapter 4 concerns the addition of cross-polarization to DAS (CPDAS). The theory behind spin locking and cross polarizing quadrupolar nuclei is explained and a method of avoiding the resulting problems by performing cross polarization at 0{sup o} (parallel) with respect to the magnetic field is presented. Experimental results are shown for a sodium-23 compound, sodium pyruvate, and for oxygen-17 labeled L-akmine. In Chapter 5, a method for broadening the Hartmann-Hahn matching condition under MAS, called variable effective field cross-polarization (VEFCI?), is presented, along with experimental work on adamantane and polycarbonate.

  18. Calcination products of gibbsite studied by X-ray diffraction, XPS and solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Malki, A. [Laboratoire des structures, propriétés et interactions inter atomiques (LASPI2A), Faculté des sciences et technologies, Université Abbes Laghrour, Khenchela 40000 (Algeria); Mekhalif, Z.; Detriche, S.; Fonder, G. [Laboratoire de Chimie et Electrochimie des Surfaces, Facultés Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61, B-5000 Namur (Belgium); Boumaza, A., E-mail: charif_boumaza@yahoo.com [Laboratoire des structures, propriétés et interactions inter atomiques (LASPI2A), Faculté des sciences et technologies, Université Abbes Laghrour, Khenchela 40000 (Algeria); Djelloul, A. [Laboratoire des structures, propriétés et interactions inter atomiques (LASPI2A), Faculté des sciences et technologies, Université Abbes Laghrour, Khenchela 40000 (Algeria)

    2014-07-01

    The changes caused by heat treatment of gibbsite powder at 300–1473 K were studied using the X-ray diffraction (XRD), X-ray photoemission (XPS) spectra and {sup 27}Al magic angle spinning nuclear magnetic resonance spectroscopy ({sup 27}Al MAS NMR). XRD analysis indicates that the transformation sequence involves the formation of κ-Al{sub 2}O{sub 3} as an intermediate phase between χ- and α-Al{sub 2}O{sub 3}. The crystallite size of χ-Al{sub 2}O{sub 3} is as small as 10 nm. XPS analysis indicates that the ratio of aluminium atoms to oxygen atoms in χ-Al{sub 2}O{sub 3} and κ-Al{sub 2}O{sub 3} increases, whereas the expected ratio is observed in α-Al{sub 2}O{sub 3}. The percentage of AlO{sub 4} units in the transition aluminas follows the same behaviour as the ratio of Al/O. - Graphical abstract: The percentage of AlO{sub 4} units in transition aluminas follows the same behaviour as the ratio of Al/O. - Highlights: • Calcination products of gibbsite studied by XRD, XPS and solid-state NMR. • The crystallite size of χ-Al{sub 2}O{sub 3} is as small as 10 nm. • The Al/O atomic ratio determined by XPS is larger than 2/3 in χ-Al{sub 2}O{sub 3} and κ-Al{sub 2}O{sub 3}. • The percentage of AlO{sub 4} in the aluminas follows the same behaviour as the Al/O atomic ratio.

  19. Applications of solid-state Nuclear Magnetic Resonance (NMR) in studies of Portland cements-based materials

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Andersen, Morten Daugaard; Jakobsen, Hans Jørgen

    2007-01-01

    Solid-state NMR spectroscopy represents an important research tool in the characterization of a range of structural properties for cement-based materials. Different approaches of the technique can be used to obtain information on hydration kinetics, mobile and bound water, porosity, and local...... atomic structures. After a short introduction to these NMR techniques, it is exemplified how magic-angle spinning (MAS) NMR can provide quantitative and structural information about specific phases in anhydrous and hydrated Portland cements with main emphasis on the incorporation of Al3+ ions...

  20. Solid state field-cycling NMR relaxometry: instrumental improvements and new applications.

    Science.gov (United States)

    Fujara, Franz; Kruk, Danuta; Privalov, Alexei F

    2014-10-01

    The paper reviews recent progress in field cycling (FC) NMR instrumentation and its application to solid state physics. Special emphasis is put on our own work during the last 15years on instrumentation, theory and applications. As far as instrumentation is concerned we report on our development of two types of electronical FC relaxometers, a mechanical FC relaxometer and a combination of FC and one-dimensional microimaging. Progress has been achieved with respect to several parameters such as the accessible field and temperature range as well as the incorporation of sample spinning. Since an appropriate analysis of FC data requires a careful consideration of relaxation theory, we include a theory section discussing the most relevant aspects of relaxation in solids which are related to residual dipolar and quadrupolar interactions. The most important limitations of relaxation theory are also discussed. With improved instrumentation and with the help of relaxation theory we get access to interesting new applications such as ionic motion in solid electrolytes, structure determination in molecular crystals, ultraslow polymer dynamics and rotational resonance phenomena.

  1. Analysis of structural variability in pharmaceutical excipients using solid-state NMR spectroscopy.

    Science.gov (United States)

    Sperger, Diana M; Munson, Eric Jon

    2011-09-01

    Polysaccharide-based excipients comprise the majority of most solid dosage forms and can vary dramatically in terms of structural and functionally related properties. Analytical methods for characterizing these important formulation components are crucial. Solid-state NMR spectroscopy (SSNMR) can provide a wealth of information on these materials while offering the advantages of non-destructive sample preparation and selectivity. The overall objective of this work is to identify SSNMR parameters that can be used to detect differences among these excipients. Excipients were obtained from a wide range of suppliers and analyzed as received; (13)C SSNMR spectra were acquired using a Chemagnetics CMX-300 spectrometer operating at approximately 75 MHz. The resolution of SSNMR signals of many excipients allows for positive identification of the major form present. Alginic acid and sodium alginate can be differentiated based on carbonyl peak position. Analysis of relative peak intensities provides insight into the purity of a carrageenan sample compared to known standards. The SSNMR spectrum of starch can be used to identify the source and to quantitate the amorphous and crystalline content. Relaxation values and peak areas of starch derivatives can be related to the degree of hydrolysis, providing an alternative method for determining dextrose equivalent. Differences in peak intensities and relaxation time values of HPMC samples can be correlated to the amount of methoxy subsituent groups. Important characteristics of excipients such as form identification, structural differences, crystalline and amorphous content, and water content variations can be detected using SSNMR spectroscopy.

  2. Indirect detection of infinite-speed MAS solid-state NMR spectra

    Science.gov (United States)

    Perras, Frédéric A.; Venkatesh, Amrit; Hanrahan, Michael P.; Goh, Tian Wei; Huang, Wenyu; Rossini, Aaron J.; Pruski, Marek

    2017-03-01

    Heavy spin-1/2 nuclides are known to possess very large chemical shift anisotropies that can challenge even the most advanced magic-angle-spinning (MAS) techniques. Wide manifolds of overlapping spinning sidebands and insufficient excitation bandwidths often obfuscate meaningful spectral information and force the use of static, low-resolution solid-state (SS)NMR methods for the characterization of materials. To address these issues, we have merged fast-magic-angle-turning (MAT) and dipolar heteronuclear multiple-quantum coherence (D-HMQC) experiments to obtain D-HMQC-MAT pulse sequences which enable the rapid acquisition of 2D SSNMR spectra that correlate isotropic 1H chemical shifts to the indirectly detected isotropic "infinite-MAS" spectra of heavy spin-1/2 nuclides. For these nuclides, the combination of fast MAS and 1H detection provides a high sensitivity, which rivals the DNP-enhanced ultra-wideline SSNMR. The new pulse sequences were used to determine the Pt coordination environments in a complex mixture of decomposition products of transplatin and in a metal-organic framework with Pt ions coordinated to the linker ligands.

  3. Application Of Density Matrix Methods To Quadrupolar Spins In Solid State Nmr And Nqr

    CERN Document Server

    Ageev, S Z

    1997-01-01

    Spin dynamics in solid state NMR and NQR are studied using spin density matrix theory. First, the response of spin 7/2 subject to the first order quadrupolar interaction, excited by one and two pulse sequences is examined. Specific pulse sequences with appropriate phase cycling designed for detection of MQ coherences developed during the first pulse are calculated analytically. The results are applied to the determination of quadrupolar parameters and true chemical shifts utilizing a 1D nutation experiment. Solomon echoes under soft pulse excitation are also considered for spin 7/2. Second, analytical solutions of off-resonance nutation line intensities for spin 3/2 are presented. The first order quadrupolar interaction is retained during the pulse. The third case puts forward a new theory of composite pulses in NQR. Shaped pulses are also considered. The calculation is valid for a non-zero asymmetry parameter and arbitrary orientation of the rf field. The results are generalized for half integer spins of mag...

  4. Structure and backbone dynamics of a microcrystalline metalloprotein by solid-state NMR.

    Science.gov (United States)

    Knight, Michael J; Pell, Andrew J; Bertini, Ivano; Felli, Isabella C; Gonnelli, Leonardo; Pierattelli, Roberta; Herrmann, Torsten; Emsley, Lyndon; Pintacuda, Guido

    2012-07-10

    We introduce a new approach to improve structural and dynamical determination of large metalloproteins using solid-state nuclear magnetic resonance (NMR) with (1)H detection under ultrafast magic angle spinning (MAS). The approach is based on the rapid and sensitive acquisition of an extensive set of (15)N and (13)C nuclear relaxation rates. The system on which we demonstrate these methods is the enzyme Cu, Zn superoxide dismutase (SOD), which coordinates a Cu ion available either in Cu(+) (diamagnetic) or Cu(2+) (paramagnetic) form. Paramagnetic relaxation enhancements are obtained from the difference in rates measured in the two forms and are employed as structural constraints for the determination of the protein structure. When added to (1)H-(1)H distance restraints, they are shown to yield a twofold improvement of the precision of the structure. Site-specific order parameters and timescales of motion are obtained by a gaussian axial fluctuation (GAF) analysis of the relaxation rates of the diamagnetic molecule, and interpreted in relation to backbone structure and metal binding. Timescales for motion are found to be in the range of the overall correlation time in solution, where internal motions characterized here would not be observable.

  5. Molecular Dynamics of Neutral Polymer Bonding Agent (NPBA as Revealed by Solid-State NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Wei Hu

    2014-01-01

    Full Text Available Neutral polymer bonding agent (NPBA is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR. The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg. In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions.

  6. Hydration properties and phosphorous speciation in native, gelatinized and enzymatically modified potato starch analyzed by solid-state MAS NMR

    DEFF Research Database (Denmark)

    Larsen, Flemming H.; Kasprzak, Miroslaw Marek; Lærke, Helle Nygaard

    2013-01-01

    Hydration of granular, gelatinized and molecularly modified states of potato starch in terms of molecular mobility were analyzed by 13C and 31P solid-state MAS NMR. Gelatinization (GEL) tremendously reduced the immobile fraction compared to native (NA) starch granules. This effect was enhanced...... by enzyme-assisted catalytic branching with branching enzyme (BE) or combined BE and β-amylase (BB) catalyzed exo-hydrolysis. Carbons of the glycosidic α-1,6 linkages required high hydration rates before adopting uniform chemical shifts indicating solid-state disorder and poor water accessibility...

  7. Solid state NMR and pair distribution function studies of silicon electrodes for lithium-ion batteries

    Science.gov (United States)

    Key, Baris

    observed in the in situ NMR experiments; this mechanism results in self-discharge, and potentially capacity loss. The rate of this self-discharge process is much slower when CMC (carboxymethylcellulose) is used as the binder. Previous work has shown that the electrochemical performance of nanoparticulate crystalline silicon is different from the bulk. The lithiation and delithiation mechanisms of nano-Si for lithium ion batteries are studied by using ex-situ solid state MAS NMR and PDF analysis. The main differences vs. bulk lithiation and delithiation are identified by characterizing the amorphous phases formed.

  8. Solid-state (13)C CP MAS NMR spectroscopy of mushrooms gives directly the ratio between proteins and polysaccharides.

    Science.gov (United States)

    Pizzoferrato, L; Manzi, P; Bertocchi, F; Fanelli, C; Rotilio, G; Paci, M

    2000-11-01

    The solid-state (13)C CP MAS NMR technique has the potential of monitoring the chemical composition in the solid state of an intact food sample. This property has been utilized to study mushrooms of different species (Pleurotus ostreatus, Pleurotus eryngii, Pleurotus pulmunarius, and Lentinula edodes), already characterized by chemical analyses for protein and dietary fiber components. Solid-state (13)C CP MAS NMR spectroscopy reveals a large difference in the ratio between the glucidic and the proteic resonances probably depending on the mushroom species. An accurate inspection by model compounds and suitable mixtures of proteins and saccharides gives a methodology to interpret these experimental data. A good correlation (R(2) = 0.93; R(2) = 0.81) has been obtained by comparing the NMR data with the results of the chemical analyses. The results suggest the possibility to perform a taxonomic study and/or a nutritional study on the basis of the ratio between protein and polysaccharide levels determined by NMR or chemical methodologies.

  9. Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.

    Science.gov (United States)

    Perić, Berislav; Gautier, Régis; Pickard, Chris J; Bosiočić, Marko; Grbić, Mihael S; Požek, Miroslav

    2014-01-01

    Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined δiso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and δ33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (δ11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements.

  10. On The Potential of Dynamic Nuclear Polarization Enhanced Diamonds in Solid-State and Dissolution (13) C NMR Spectroscopy.

    Science.gov (United States)

    Bretschneider, Christian O; Akbey, Ümit; Aussenac, Fabien; Olsen, Greg L; Feintuch, Akiva; Oschkinat, Hartmut; Frydman, Lucio

    2016-09-01

    Dynamic nuclear polarization (DNP) is a versatile option to improve the sensitivity of NMR and MRI. This versatility has elicited interest for overcoming potential limitations of these techniques, including the achievement of solid-state polarization enhancement at ambient conditions, and the maximization of (13) C signal lifetimes for performing in vivo MRI scans. This study explores whether diamond's (13) C behavior in nano- and micro-particles could be used to achieve these ends. The characteristics of diamond's DNP enhancement were analyzed for different magnetic fields, grain sizes, and sample environments ranging from cryogenic to ambient temperatures, in both solution and solid-state experiments. It was found that (13) C NMR signals could be boosted by orders of magnitude in either low- or room-temperature solid-state DNP experiments by utilizing naturally occurring paramagnetic P1 substitutional nitrogen defects. We attribute this behavior to the unusually long electronic/nuclear spin-lattice relaxation times characteristic of diamond, coupled with a time-independent cross-effect-like polarization transfer mechanism facilitated by a matching of the nitrogen-related hyperfine coupling and the (13) C Zeeman splitting. The efficiency of this solid-state polarization process, however, is harder to exploit in dissolution DNP-enhanced MRI contexts. The prospects for utilizing polarized diamond approaching nanoscale dimensions for both solid and solution applications are briefly discussed.

  11. {sup 13}C solid-state NMR analysis of heterogeneous structure of beeswax in native state

    Energy Technology Data Exchange (ETDEWEB)

    Kameda, Tsunenori [National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8634 (Japan)

    2005-12-21

    I investigated the molecular structure of natural wax from Japanese bees (Apis cerana japonica) in its native state (neither purified nor recrystallized) by {sup 13}C and {sup 1}H solid-state NMR. Two strong {sup 13}C peaks at 32.9 and 34.0 ppm were attributed to signals from internal-chain methylene carbons [int-(CH{sub 2})] in two types of crystal form. The peak at 32.9 ppm was assigned to an orthorhombic crystal form, and that at 34.0 ppm was assigned to a triclinic or monoclinic form. In both crystalline regions, bi-exponential decay of {sup 13}C spin-lattice relaxation [T{sub 1}(C)] for the crystalline peaks due to chain diffusion was observed. {sup 1}H spin-lattice relaxation [T{sub 1}(H)] values for protons of the CH{sub 3} group and for int-(CH{sub 2}) in the crystalline and amorphous regions were identical; this was interpreted as being due to averaging of the T{sub 1}(H) relaxation rates via spin diffusion. In contrast, although the T{sub 1{sub {rho}}}(H) decay curves for protons of the CH{sub 3} group and for int-(CH{sub 2}) in the amorphous and orthorhombic forms were almost identical, those of the triclinic or monoclinic forms were different. This unhomogeneous character of T{sub 1{sub {rho}}}(H) was interpreted as resulting from differences in the molecular composition of each crystal form. Moreover, two components with long and short {sup 1}H spin-spin relaxation [T{sub 2}(H)] values, arising from the mobile and rigid phases, respectively, were observed at above about -30 deg. C.

  12. 13C solid-state NMR analysis of heterogeneous structure of beeswax in native state

    Science.gov (United States)

    Kameda, Tsunenori

    2005-12-01

    I investigated the molecular structure of natural wax from Japanese bees (Apis cerana japonica) in its native state (neither purified nor recrystallized) by 13C and 1H solid-state NMR. Two strong 13C peaks at 32.9 and 34.0 ppm were attributed to signals from internal-chain methylene carbons [int-(CH2)] in two types of crystal form. The peak at 32.9 ppm was assigned to an orthorhombic crystal form, and that at 34.0 ppm was assigned to a triclinic or monoclinic form. In both crystalline regions, bi-exponential decay of 13C spin-lattice relaxation [T1(C)] for the crystalline peaks due to chain diffusion was observed. 1H spin-lattice relaxation [T1(H)] values for protons of the CH3 group and for int-(CH2) in the crystalline and amorphous regions were identical; this was interpreted as being due to averaging of the T1(H) relaxation rates via spin diffusion. In contrast, although the T_{{1}_{\\rho}}(H) decay curves for protons of the CH3 group and for int-(CH2) in the amorphous and orthorhombic forms were almost identical, those of the triclinic or monoclinic forms were different. This unhomogeneous character of T_{{1}_{\\rho}}(H) was interpreted as resulting from differences in the molecular composition of each crystal form. Moreover, two components with long and short 1H spin-spin relaxation [T2(H)] values, arising from the mobile and rigid phases, respectively, were observed at above about -30 °C.

  13. Rheological and solid-state NMR assessments of copovidone/clotrimazole model solid dispersions.

    Science.gov (United States)

    Yang, Fengyuan; Su, Yongchao; Zhu, Lei; Brown, Chad D; Rosen, Lawrence A; Rosenberg, Kenneth J

    2016-03-16

    This study aims to assess several model solid dispersions by using dynamic oscillatory rheology, solid-state NMR and other solid phase characterization techniques, and correlate their viscoelastic responses with processing methods and microstructures. A model active pharmaceutical ingredient (API), clotrimazole, was compounded with copovidone to form solid dispersions via various techniques with different mixing capabilities. Physicochemical characterizations of the resulting solid dispersions demonstrated that simple physical mixing led to a poorly mixed blend manifested by existence of large API crystalline content and heterogeneous distribution. Cryogenic milling significantly improved mixing of two components as a result of reduced particle size and increased contact surface area, but produced limited amorphous content. In contrast, hot melt extrusion (HME) processing resulted in a homogenous amorphous solid dispersion because of its inherent mixing efficiency. Storage modulus and viscosities versus frequency of different solid dispersions indicated that the incorporation of API into the polymer matrix resulted in a plasticizing effect which reduced the viscosity. The crystalline/aggregated forms of API also exhibited more elastic response than its amorphous/dispersed counterpart. Temperature ramps of the physical mixture with high API concentration captured a critical temperature, at which a bump was observed in damping factor. This bump was attributed to the dissolution of crystalline API into the polymer. In addition, heating-cooling cycles of various solid dispersions suggested that cryomilling and HME processing could form a homogeneous solid dispersion at low API content, whereas high drug concentration led to a relatively unstable dispersion due to supersaturation of API in the polymer.

  14. Probing Membrane Protein Structure Using Water Polarization Transfer Solid-State NMR

    Science.gov (United States)

    Williams, Jonathan K.; Hong, Mei

    2014-01-01

    Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected 1H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane peptide of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins. PMID:25228502

  15. Solid-state 13C NMR and molecular modeling studies of acetyl aleuritolic acid obtained from Croton cajucara Benth

    Science.gov (United States)

    da Silva San Gil, Rosane Aguiar; Albuquerque, Magaly Girão; de Alencastro, Ricardo Bicca; da Cunha Pinto, Angelo; do Espírito Santo Gomes, Fabiano; de Castro Dantas, Tereza Neuma; Maciel, Maria Aparecida Medeiros

    2008-08-01

    Solid-state 13C nuclear magnetic resonance ( 13C NMR) with magic-angle spinning (MAS) and with cross-polarization and magic-angle spinning (CP/MAS) spectra, and differential scanning calorimetry (DSC) techniques were used to obtain structural data from a sample of acetyl aleuritolic acid (AAA) extracted from the stem bark of Croton cajucara Benth. (Euphorbiaceae) and recrystallized from acetone. Since solid-state 13C NMR results suggested the presence of more than one molecule in the unitary cell for the AAA, DSC analysis and molecular modeling calculations were used to access this possibility. The absence of phase transition peaks in the DSC spectra and the dimeric models of AAA simulated using the semi-empirical PM3 method are in agreement with that proposal.

  16. High-resolution solid-state NMR spectroscopy of protons with homonuclear dipolar decoupling schemes under magic-angle spinning.

    Science.gov (United States)

    Madhu, P K

    2009-02-01

    High-resolution NMR spectroscopy of (1)H spins in the solid state is normally rendered difficult due to the strong homonuclear (1)H-(1)H dipolar couplings. Even under very high-speed magic-angle spinning (MAS) at ca. 60-70kHz, these couplings are not completely removed. An appropriate radiofrequency pulse scheme is required to average out the homonuclear dipolar interactions in combination with MAS to get high-resolution (1)H NMR spectrum in solid state. Several schemes have been introduced in the recent past with a variety of applications also envisaged. Development of some of these schemes has been made possible with a clear understanding of the underlying spin physics based on bimodal Floquet theory. The utility of these high-resolution pulse schemes in combination with MAS has been demonstrated for spinning speeds of 10-65kHz in a range of (1)H Larmor frequencies from 300 to 800MHz.

  17. The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

    Directory of Open Access Journals (Sweden)

    Gary E. Maciel

    2012-12-01

    Full Text Available The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline” silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of 1H, 29Si and 2H magic-angle-spinning (MAS NMR results and quantum mechanical 29Si chemical shift calculations, silicon atoms on the surface of “as-received” np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a (Si–O–3Si–H > (b (Si–O–3SiOH > (c (HO–nSi(Sim(–OSi4−m−n ≈ (d (Si–O–2Si(HOH > (e (Si–O–2Si(–OH2 > (f (Si–O–4Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O2 gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–3Si–H, as well as (Si–O–3SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of 1H and 2H MAS experiments provide evidence for a substantial population of silanol (Si–OH moieties, some of which are not readily H-exchangeable, along with the dominant Si–H sites, on the surface of “as-received” np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T2 relaxation parameter simultaneously with background suppression.

  18. Structural Investigations of Portland Cement Components, Hydration, and Effects of Admixtures by Solid-State NMR Spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen Bengaard; Andersen, Morten D.; Jakobsen, Hans Jørgen

    2006-01-01

    Solid-state, magic-angle spinning (MAS) NMR spectroscopy represents a valuable tool for structural investigations on the nanoscale of the most important phases in anhydrous and hydrated Portland cements and of various admixtures. This is primarily due to the fact that the method reflects the first...... in the cement phases. The role of flouride ions is of special interest for mineralized Portland cements and it demonstrated that the location of these anions in anhydrous and hydrated Portland cements can be clarified using 19F MAS or 29Si{19F} CP/MAS NMR despite these cements contain only about 0.2 wt...

  19. Lipid Dynamics Studied by Calculation of 31P Solid-State NMR Spectra Using Ensembles from Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Hansen, Sara Krogh; Vestergaard, Mikkel; Thøgersen, Lea;

    2014-01-01

    We present a method to calculate 31P solid-state NMR spectra based on the dynamic input from extended molecular dynamics (MD) simulations. The dynamic information confered by MD simulations is much more comprehensive than the information provided by traditional NMR dynamics models based on......, for example, order parameters. Therefore, valuable insight into the dynamics of biomolecules may be achieved by the present method. We have applied this method to study the dynamics of lipid bilayers containing the antimicrobial peptide alamethicin, and we show that the calculated 31P spectra obtained...

  20. Structural Dynamics and Conformational Equilibria of SERCA Regulatory Proteins in Membranes by Solid-State NMR Restrained Simulations

    Science.gov (United States)

    De Simone, Alfonso; Mote, Kaustubh R.; Veglia, Gianluigi

    2014-01-01

    Solid-state NMR spectroscopy is emerging as a powerful approach to determine structure, topology, and conformational dynamics of membrane proteins at the atomic level. Conformational dynamics are often inferred and quantified from the motional averaging of the NMR parameters. However, the nature of these motions is difficult to envision based only on spectroscopic data. Here, we utilized restrained molecular dynamics simulations to probe the structural dynamics, topology and conformational transitions of regulatory membrane proteins of the calcium ATPase SERCA, namely sarcolipin and phospholamban, in explicit lipid bilayers. Specifically, we employed oriented solid-state NMR data, such as dipolar couplings and chemical shift anisotropy measured in lipid bicelles, to refine the conformational ensemble of these proteins in lipid membranes. The samplings accurately reproduced the orientations of transmembrane helices and showed a significant degree of convergence with all of the NMR parameters. Unlike the unrestrained simulations, the resulting sarcolipin structures are in agreement with distances and angles for hydrogen bonds in ideal helices. In the case of phospholamban, the restrained ensemble sampled the conformational interconversion between T (helical) and R (unfolded) states for the cytoplasmic region that could not be observed using standard structural refinements with the same experimental data set. This study underscores the importance of implementing NMR data in molecular dynamics protocols to better describe the conformational landscapes of membrane proteins embedded in realistic lipid membranes. PMID:24940774

  1. Molecular characterization and quantification using state of the art solid-state adiabatic TOBSY NMR in burn trauma.

    Science.gov (United States)

    Righi, Valeria; Andronesi, Ovidiu; Mintzopoulos, Dionyssios; Tzika, A Aria

    2009-12-01

    We describe a novel solid-state nuclear magnetic resonance (NMR) method that maximizes the advantages of high-resolution magic-angle-spinning (HRMAS), relative conventional liquid-state NMR approaches, when applied to intact biopsies of skeletal muscle specimens collected from burn trauma patients. This novel method, termed optimized adiabatic TOtal through Bond correlation SpectroscopY (TOBSY) solid-state NMR pulse sequence for two-dimensional (2D) 1H-1H homonuclear scalar-coupling longitudinal isotropic mixing, was demonstrated to provide a 40-60% improvement in signal-to-noise ratio (SNR) relative to its liquid-state analogue TOCSY (TOtal Correlation SpectroscopY). Using 1- and 2-dimensional HRMAS NMR experiments, we identified several metabolites in burned tissues. Quantification of metabolites in burned tissues showed increased levels of lipid compounds, intracellular metabolites (e.g., taurine and phosphocreatine) and substantially decreased water-soluble metabolites (e.g., glutathione, carnosine, glucose, glutamine/glutamate and alanine). These findings demonstrate that HRMAS NMR Spectroscopy using TOBSY is a feasible technique that reveals new insights into the pathophysiology of burn trauma. Moreover, this method has applications that facilitate the development of novel therapeutic strategies.

  2. Solid state (47,49)Ti, (87)Sr and (137)Ba NMR characterisation of mixed barium/strontium titanate perovskites.

    Science.gov (United States)

    Gervais, Christel; Veautier, Delphine; Smith, Mark E; Babonneau, Florence; Belleville, Philippe; Sanchez, Clément

    2004-01-01

    Solid state (47,49)Ti, (137)Ba, (87)Sr NMR spectra have been recorded on BaxSrl-xTiO3 (0 strontium) in the coordination second sphere of the probed titanium site: substitution of strontium by barium induces the broadening of the peaks, due to quadrupolar effects, while the isotropic chemical shift increases. (137)Ba NMR spectra exhibit a distribution of the quadrupolar interaction, that could be tentatively quantified, CQ increasing with the amount of strontium. Preliminary results were also obtained on (87)Sr NMR showing behaviour comparable to (137)Ba NMR, i.e. a broadening of the peaks due to an increasing quadrupolar interaction with the amount of barium distorting the environment of the strontium sites.

  3. Powder-XRD and (14) N magic angle-spinning solid-state NMR spectroscopy of some metal nitrides.

    Science.gov (United States)

    Kempgens, Pierre; Britton, Jonathan

    2016-05-01

    Some metal nitrides (TiN, ZrN, InN, GaN, Ca3 N2 , Mg3 N2 , and Ge3 N4 ) have been studied by powder X-ray diffraction (XRD) and (14) N magic angle-spinning (MAS) solid-state NMR spectroscopy. For Ca3 N2 , Mg3 N2 , and Ge3 N4 , no (14) N NMR signal was observed. Low speed (νr  = 2 kHz for TiN, ZrN, and GaN; νr  = 1 kHz for InN) and 'high speed' (νr  = 15 kHz for TiN; νr  = 5 kHz for ZrN; νr  = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder-XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their (14) N MAS solid-state NMR spectrum matches perfectly well with the number of nitrogen-containing phases identified by powder-XRD. The (14) N MAS solid-state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Qcc 's arising from structural defects in the compounds studied.

  4. Single-crystal X-ray diffraction and NMR crystallography of a 1:1 cocrystal of dithianon and pyrimethanil.

    Science.gov (United States)

    Pöppler, Ann Christin; Corlett, Emily K; Pearce, Harriet; Seymour, Mark P; Reid, Matthew; Montgomery, Mark G; Brown, Steven P

    2017-03-01

    A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile-4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectra are presented together with GIPAW (gauge-including projector augmented wave) calculations of NMR chemical shieldings. Specifically, experimental (1)H and (13)C chemical shifts are determined from two-dimensional (1)H-(13)C MAS NMR correlation spectra recorded with short and longer contact times so as to probe one-bond C-H connectivities and longer-range C...H proximities, whereas H...H proximities are identified in a (1)H double-quantum (DQ) MAS NMR spectrum. The performing of separate GIPAW calculations for the full periodic crystal structure and for isolated molecules allows the determination of the change in chemical shift upon going from an isolated molecule to the full crystal structure. For the (1)H NMR chemical shifts, changes of 3.6 and 2.0 ppm correspond to intermolecular N-H...O and C-H...O hydrogen bonding, while changes of -2.7 and -1.5 ppm are due to ring current effects associated with C-H...π interactions. Even though there is a close intermolecular S...O distance of 3.10 Å, it is of note that the molecule-to-crystal chemical shifts for the involved sulfur or oxygen nuclei are small.

  5. Tannin Fingerprinting in Vegetable Tanned Leather by Solid State NMR Spectroscopy and Comparison with Leathers Tanned by Other Processes

    Directory of Open Access Journals (Sweden)

    Jan H. van der Westhuizen

    2011-01-01

    Full Text Available Solid state 13C-NMR spectra of pure tannin powders from four different sources – mimosa, quebracho, chestnut and tara – are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan.  Groups of signals indicative of the source, and type (condensed vs. hydrolyzable of tannin used in the manufacture are well resolved in the spectra of the finished leathers.  These fingerprints are compared with those arising from leathers tanned with other common tanning agents.  Paramagnetic chromium (III tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III structures. Aluminium (III and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The 27Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance.

  6. Tannin fingerprinting in vegetable tanned leather by solid state NMR spectroscopy and comparison with leathers tanned by other processes.

    Science.gov (United States)

    Romer, Frederik H; Underwood, Andrew P; Senekal, Nadine D; Bonnet, Susan L; Duer, Melinda J; Reid, David G; van der Westhuizen, Jan H

    2011-01-28

    Solid state ¹³C-NMR spectra of pure tannin powders from four different sources--mimosa, quebracho, chestnut and tara--are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan. Groups of signals indicative of the source, and type (condensed vs. hydrolyzable) of tannin used in the manufacture are well resolved in the spectra of the finished leathers. These fingerprints are compared with those arising from leathers tanned with other common tanning agents. Paramagnetic chromium (III) tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III) structures. Aluminium (III) and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The ²⁷Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance.

  7. High-resolution membrane protein structure by joint calculations with solid-state NMR and X-ray experimental data

    Energy Technology Data Exchange (ETDEWEB)

    Tang Ming; Sperling, Lindsay J.; Berthold, Deborah A. [University of Illinois at Urbana-Champaign, Department of Chemistry (United States); Schwieters, Charles D. [National Institutes of Health, Division of Computational Bioscience, Center for Information Technology (United States); Nesbitt, Anna E.; Nieuwkoop, Andrew J.; Gennis, Robert B.; Rienstra, Chad M., E-mail: rienstra@scs.illinois.edu [University of Illinois at Urbana-Champaign, Department of Chemistry (United States)

    2011-11-15

    X-ray diffraction and nuclear magnetic resonance spectroscopy (NMR) are the staple methods for revealing atomic structures of proteins. Since crystals of biomolecular assemblies and membrane proteins often diffract weakly and such large systems encroach upon the molecular tumbling limit of solution NMR, new methods are essential to extend structures of such systems to high resolution. Here we present a method that incorporates solid-state NMR restraints alongside of X-ray reflections to the conventional model building and refinement steps of structure calculations. Using the 3.7 A crystal structure of the integral membrane protein complex DsbB-DsbA as a test case yielded a significantly improved backbone precision of 0.92 A in the transmembrane region, a 58% enhancement from using X-ray reflections alone. Furthermore, addition of solid-state NMR restraints greatly improved the overall quality of the structure by promoting 22% of DsbB transmembrane residues into the most favored regions of Ramachandran space in comparison to the crystal structure. This method is widely applicable to any protein system where X-ray data are available, and is particularly useful for the study of weakly diffracting crystals.

  8. Applications of Solid-State NMR Spectroscopy for the Study of Lipid Membranes with Polyphilic Guest (MacroMolecules

    Directory of Open Access Journals (Sweden)

    Ruth Bärenwald

    2016-12-01

    Full Text Available The incorporation of polymers or smaller complex molecules into lipid membranes allows for property modifications or the introduction of new functional elements. The corresponding molecular-scale details, such as changes in dynamics or features of potential supramolecular structures, can be studied by a variety of solid-state NMR techniques. Here, we review various approaches to characterizing the structure and dynamics of the guest molecules as well as the lipid phase structure and dynamics by different high-resolution magic-angle spinning proton and 13C NMR experiments as well as static 31P NMR experiments. Special emphasis is placed upon the incorporation of novel synthetic polyphilic molecules such as shape-persistent T- and X-shaped molecules as well as di- and tri-block copolymers. Most of the systems studied feature dynamic heterogeneities, for instance those arising from the coexistence of different phases; possibilities for a quantitative assessment are of particular concern.

  9. Predicting Molecular Crystal Properties from First Principles: Finite-Temperature Thermochemistry to NMR Crystallography.

    Science.gov (United States)

    Beran, Gregory J O; Hartman, Joshua D; Heit, Yonaton N

    2016-11-15

    errors in the enthalpy and entropy cancel somewhat. Second, because solid state nuclear magnetic resonance (NMR) plays an increasingly important role in molecular crystal studies, this Account discusses how fragment methods can be used to achieve higher-accuracy chemical shifts in molecular crystals. Whereas widely used plane wave density functional theory models are largely restricted to generalized gradient approximation (GGA) functionals like PBE in practice, fragment methods allow the routine use of hybrid density functionals with only modest increases in computational cost. In extensive molecular crystal benchmarks, hybrid functionals like PBE0 predict chemical shifts with 20-30% higher accuracy than GGAs, particularly for (1)H, (13)C, and (15)N nuclei. Due to their higher sensitivity to polarization effects, (17)O chemical shifts prove slightly harder to predict with fragment methods. Nevertheless, the fragment model results are still competitive with those from GIPAW. The improved accuracy achievable with fragment approaches and hybrid density functionals increases discrimination between different potential assignments of individual shifts or crystal structures, which is critical in NMR crystallography applications. This higher accuracy and greater discrimination are highlighted in application to the solid state NMR of different acetaminophen and testosterone crystal forms.

  10. Crystal structure, magnetism, {sup 89}Y solid state NMR, and {sup 121}Sb Moessbauer spectroscopic investigations of YIrSb

    Energy Technology Data Exchange (ETDEWEB)

    Benndorf, Christopher [Institut fuer Physikalische Chemie, Universitaet Muenster (Germany); Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Heletta, Lukas; Block, Theresa; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Universitaet Muenster (Germany); Institute of Physics in Sao Carlos, University of Sao Paulo, Sao Carlos (Brazil)

    2017-02-15

    The ternary antimonide YIrSb was synthesized from the binary precursor YIr and elemental antimony by a diffusion controlled solid-state reaction. Single crystals were obtained by a flux technique with elemental bismuth as an inert solvent. The YIrSb structure (TiNiSi type, space group Pnma) was refined from single-crystal X-ray diffractometer data: a = 711.06(9), b = 447.74(5), c = 784.20(8) pm, wR{sub 2} = 0.0455, 535 F{sup 2} values, 20 variables. {sup 89}Y solid state MAS NMR and {sup 121}Sb Moessbauer spectra show single resonance lines in agreement with single-crystal X-ray data. YIrSb is a Pauli paramagnet. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. The dynamics of the G protein-coupled neuropeptide Y2 receptor in monounsaturated membranes investigated by solid-state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Lars; Kahr, Julian; Schmidt, Peter; Krug, Ulrike; Scheidt, Holger A.; Huster, Daniel, E-mail: daniel.huster@medizin.uni-leipzig.de [University of Leipzig, Institute of Medical Physics and Biophysics (Germany)

    2015-04-15

    In contrast to the static snapshots provided by protein crystallography, G protein-coupled receptors constitute a group of proteins with highly dynamic properties, which are required in the receptors’ function as signaling molecule. Here, the human neuropeptide Y2 receptor was reconstituted into a model membrane composed of monounsaturated phospholipids and solid-state NMR was used to characterize its dynamics. Qualitative static {sup 15}N NMR spectra and quantitative determination of {sup 1}H–{sup 13}C order parameters through measurement of the {sup 1}H–{sup 13}C dipolar couplings of the CH, CH{sub 2} and CH{sub 3} groups revealed axially symmetric motions of the whole molecule in the membrane and molecular fluctuations of varying amplitude from all molecular segments. The molecular order parameters (S{sub backbone} = 0.59–0.67, S{sub CH2} = 0.41–0.51 and S{sub CH3} = 0.22) obtained in directly polarized {sup 13}C NMR experiments demonstrate that the Y2 receptor is highly mobile in the native-like membrane. Interestingly, according to these results the receptor was found to be slightly more rigid in the membranes formed by the monounsaturated phospholipids than by saturated phospholipids as investigated previously. This could be caused by an increased chain length of the monounsaturated lipids, which may result in a higher helical content of the receptor. Furthermore, the incorporation of cholesterol, phosphatidylethanolamine, or negatively charged phosphatidylserine into the membrane did not have a significant influence on the molecular mobility of the Y2 receptor.

  12. Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments.

    Science.gov (United States)

    Wang, Jing; Zhang, Zhengfeng; Zhao, Weijing; Wang, Liying; Yang, Jun

    2016-05-09

    The MAS solid-state NMR has been a powerful technique for studying membrane proteins within the native-like lipid bilayer environment. In general, RF irradiation in MAS NMR experiments can heat and potentially destroy expensive membrane protein samples. However, under practical MAS NMR experimental conditions, detailed characterization of RF heating effect of lipid bilayer samples is still lacking. Herein, using (1) H chemical shift of water for temperature calibration, we systematically study the dependence of RF heating on hydration levels and salt concentrations of three lipids in MAS NMR experiments. Under practical (1) H decoupling conditions used in biological MAS NMR experiments, three lipids show different dependence of RF heating on hydration levels as well as salt concentrations, which are closely associated with the properties of lipids. The maximum temperature elevation of about 10 °C is similar for the three lipids containing 200% hydration, which is much lower than that in static solid-state NMR experiments. The RF heating due to salt is observed to be less than that due to hydration, with a maximum temperature elevation of less than 4 °C in the hydrated samples containing 120 mmol l(-1) of salt. Upon RF irradiation, the temperature gradient across the sample is observed to be greatly increased up to 20 °C, as demonstrated by the remarkable broadening of (1) H signal of water. Based on detailed characterization of RF heating effect, we demonstrate that RF heating and temperature gradient can be significantly reduced by decreasing the hydration levels of lipid bilayer samples from 200% to 30%. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Unraveling the complexity of protein backbone dynamics with combined (13)C and (15)N solid-state NMR relaxation measurements.

    Science.gov (United States)

    Lamley, Jonathan M; Lougher, Matthew J; Sass, Hans Juergen; Rogowski, Marco; Grzesiek, Stephan; Lewandowski, Józef R

    2015-09-14

    Typically, protein dynamics involve a complex hierarchy of motions occurring on different time scales between conformations separated by a range of different energy barriers. NMR relaxation can in principle provide a site-specific picture of both the time scales and amplitudes of these motions, but independent relaxation rates sensitive to fluctuations in different time scale ranges are required to obtain a faithful representation of the underlying dynamic complexity. This is especially pertinent for relaxation measurements in the solid state, which report on dynamics in a broader window of time scales by more than 3 orders of magnitudes compared to solution NMR relaxation. To aid in unraveling the intricacies of biomolecular dynamics we introduce (13)C spin-lattice relaxation in the rotating frame (R1ρ) as a probe of backbone nanosecond-microsecond motions in proteins in the solid state. We present measurements of (13)C'R1ρ rates in fully protonated crystalline protein GB1 at 600 and 850 MHz (1)H Larmor frequencies and compare them to (13)C'R1, (15)N R1 and R1ρ measured under the same conditions. The addition of carbon relaxation data to the model free analysis of nitrogen relaxation data leads to greatly improved characterization of time scales of protein backbone motions, minimizing the occurrence of fitting artifacts that may be present when (15)N data is used alone. We also discuss how internal motions characterized by different time scales contribute to (15)N and (13)C relaxation rates in the solid state and solution state, leading to fundamental differences between them, as well as phenomena such as underestimation of picosecond-range motions in the solid state and nanosecond-range motions in solution.

  14. Cellular solid-state NMR on large prokaryotic and eukaryotic membrane protein complexes

    NARCIS (Netherlands)

    Kaplan, M.

    2015-01-01

    Unraveling the structure and dynamics of biomolecules is pivotal to understand their function. Hitherto, structural biology has been dependent on data obtained under in-vitro circumstances thereby neglecting the influence of the natural environment. Here, we developed a solid-state Nuclear Magnetic

  15. Cellular solid-state NMR on large prokaryotic and eukaryotic membrane protein complexes

    NARCIS (Netherlands)

    Kaplan, M.

    2015-01-01

    Unraveling the structure and dynamics of biomolecules is pivotal to understand their function. Hitherto, structural biology has been dependent on data obtained under in-vitro circumstances thereby neglecting the influence of the natural environment. Here, we developed a solid-state Nuclear Magnetic

  16. Structural investigation of bistrifluron using x-ray crystallography, NMR spectroscopy, and molecular modeling

    CERN Document Server

    Moon, J K; Rhee, S K; Kim, G B; Yun, H S; Chung, B J; Lee, S S; Lim, Y H

    2002-01-01

    A new insecticide, bistrifluron acts as an inhibitor of insect development and interferes with the cuticle formation of insects. Since it shows low acute oral and dermal toxicities, it can be one of potent insecticides. Based on X-ray crystallography, NMR spectroscopy and molecular modeling, the structural studies of bistrifluron have been carried out.

  17. Bottom-up and top-down solid-state NMR approaches for bacterial biofilm matrix composition

    Science.gov (United States)

    Cegelski, Lynette

    2015-04-01

    The genomics and proteomics revolutions have been enormously successful in providing crucial "parts lists" for biological systems. Yet, formidable challenges exist in generating complete descriptions of how the parts function and assemble into macromolecular complexes and whole-cell assemblies. Bacterial biofilms are complex multicellular bacterial communities protected by a slime-like extracellular matrix that confers protection to environmental stress and enhances resistance to antibiotics and host defenses. As a non-crystalline, insoluble, heterogeneous assembly, the biofilm extracellular matrix poses a challenge to compositional analysis by conventional methods. In this perspective, bottom-up and top-down solid-state NMR approaches are described for defining chemical composition in complex macrosystems. The "sum-of-the-parts" bottom-up approach was introduced to examine the amyloid-integrated biofilms formed by Escherichia coli and permitted the first determination of the composition of the intact extracellular matrix from a bacterial biofilm. An alternative top-down approach was developed to define composition in Vibrio cholerae biofilms and relied on an extensive panel of NMR measurements to tease out specific carbon pools from a single sample of the intact extracellular matrix. These two approaches are widely applicable to other heterogeneous assemblies. For bacterial biofilms, quantitative parameters of matrix composition are needed to understand how biofilms are assembled, to improve the development of biofilm inhibitors, and to dissect inhibitor modes of action. Solid-state NMR approaches will also be invaluable in obtaining parameters of matrix architecture.

  18. Protein secondary structure of Green Lynx spider dragline silk investigated by solid-state NMR and X-ray diffraction.

    Science.gov (United States)

    Xu, Dian; Shi, Xiangyan; Thompson, Forrest; Weber, Warner S; Mou, Qiushi; Yarger, Jeffery L

    2015-11-01

    In this study, the secondary structure of the major ampullate silk from Peucetia viridans (Green Lynx) spiders is characterized by X-ray diffraction and solid-state NMR spectroscopy. From X-ray diffraction measurement, β-sheet nanocrystallites were observed and found to be highly oriented along the fiber axis, with an orientational order, fc≈0.98. The size of the nanocrystallites was determined to be on average 2.5nm×3.3nm×3.8nm. Besides a prominent nanocrystalline region, a partially oriented amorphous region was also observed with an fa≈0.89. Two-dimensional (13)C-(13)C through-space and through-bond solid-state NMR experiments were employed to elucidate structure details of P. viridans silk proteins. It reveals that β-sheet nanocrystallites constitutes 40.0±1.2% of the protein and are dominated by alanine-rich repetitive motifs. Furthermore, based upon the NMR data, 18±1% of alanine, 60±2% glycine and 54±2% serine are incorporated into helical conformations. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Cation ion specifically induces a conformational change in trans-dehydroandrosterone - a solid-state NMR study.

    Science.gov (United States)

    Wang, Darong; Chen, Meiman; Chein, Rong-Jie; Ching, Wei-Min; Hung, Chen-Hsiung; Tzou, Der-Lii M

    2015-04-01

    In this work, we demonstrated that calcium (Ca(+2)) is able to induce a conformational change in trans-dehydroandrosterone (DHEA). To this respect, solid-state NMR spectroscopy was applied to a series of DHEA molecules that were incubated with Ca(+2) under different concentrations. The high-resolution (13)C NMR spectra of the DHEA/Ca(+2) mixtures exhibited two distinct sets of signals; one was attributed to DHEA in the free form, and the second set was due to the DHEA/Ca(+2) complex. Based on chemical shift isotropy and anisotropy analyses, we postulated that Ca(+2) might have associated with the oxygen attached to C17 via a lone-pair of electrons, which induced a conformational change in DHEA. Apart from Ca(+2), we also incubated DHEA with magnesium (Mg(+2)) to determine whether Mg(+2) was able to interact with DHEA in a similar manner to Ca(+2). We found that Mg(+2) was able to induce a conformational change in DHEA deviated from that of Ca(+2). These solid-state NMR observations indicate that DHEA is able to interact with cations, such as Mg(+2) and Ca(+2), with specificity.

  20. Structural Investigations of Portland Cement Components, Hydration, and Effects of Admixtures by Solid-State NMR Spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen Bengaard; Andersen, Morten D.; Jakobsen, Hans Jørgen

    2006-01-01

    Solid-state, magic-angle spinning (MAS) NMR spectroscopy represents a valuable tool for structural investigations on the nanoscale of the most important phases in anhydrous and hydrated Portland cements and of various admixtures. This is primarily due to the fact that the method reflects the firs.......% flourine. Finally, the detection and quantification of strätlingite (2CaO·Al2O3·SiO2·8H2O) in Portland cement mixtures containing metakaolin will be demonstrated....

  1. Proton clouds to measure long-range contacts between nonexchangeable side chain protons in solid-state NMR.

    Science.gov (United States)

    Sinnige, Tessa; Daniëls, Mark; Baldus, Marc; Weingarth, Markus

    2014-03-26

    We show that selective labeling of proteins with protonated amino acids embedded in a perdeuterated matrix, dubbed 'proton clouds', provides general access to long-range contacts between nonexchangeable side chain protons in proton-detected solid-state NMR, which is important to study protein tertiary structure. Proton-cloud labeling significantly improves spectral resolution by simultaneously reducing proton line width and spectral crowding despite a high local proton density in clouds. The approach is amenable to almost all canonical amino acids. Our method is demonstrated on ubiquitin and the β-barrel membrane protein BamA.

  2. Molecular-level secondary structure, polymorphism, and dynamics of full-length -synuclein fibrils studied by solid-state NMR

    Science.gov (United States)

    Heise, Henrike; Hoyer, Wolfgang; Becker, Stefan; Andronesi, Ovidiu C.; Riedel, Dietmar; Baldus, Marc

    2005-11-01

    The 140-residue protein -synuclein (AS) is able to form amyloid fibrils and as such is the main component of protein inclusions involved in Parkinson's disease. We have investigated the structure and dynamics of full-length AS fibrils by high-resolution solid-state NMR spectroscopy. Homonuclear and heteronuclear 2D and 3D spectra of fibrils grown from uniformly 13C/15N-labeled AS and AS reverse-labeled for two of the most abundant amino acids, K and V, were analyzed. 13C and 15N signals exhibited linewidths of HR ALIGN=LEFT WIDTH=50% NOSHADE SIZE=1>

  3. On the structure of amorphous calcium carbonate--a detailed study by solid-state NMR spectroscopy.

    Science.gov (United States)

    Nebel, Holger; Neumann, Markus; Mayer, Christian; Epple, Matthias

    2008-09-01

    The calcium carbonate phases calcite, aragonite, vaterite, monohydrocalcite (calcium carbonate monohydrate), and ikaite (calcium carbonate hexahydrate) were studied by solid-state NMR spectroscopy ( (1)H and (13)C). Further model compounds were sodium hydrogencarbonate, potassium hydrogencarbonate, and calcium hydroxide. With the help of these data, the structure of synthetically prepared additive-free amorphous calcium carbonate (ACC) was analyzed. ACC contains molecular water (as H 2O), a small amount of mobile hydroxide, and no hydrogencarbonate. This supports the concept of ACC as a transient precursor in the formation of calcium carbonate biominerals.

  4. Nano-mole scale sequential signal assignment by 1 H-detected protein solid-state NMR

    KAUST Repository

    Wang, Songlin

    2015-01-01

    We present a 3D 1H-detected solid-state NMR (SSNMR) approach for main-chain signal assignments of 10-100 nmol of fully protonated proteins using ultra-fast magic-angle spinning (MAS) at ∼80 kHz by a novel spectral-editing method, which permits drastic spectral simplification. The approach offers ∼110 fold time saving over a traditional 3D 13C-detected SSNMR approach. This journal is © The Royal Society of Chemistry 2015.

  5. Hydration properties and phosphorous speciation in native, gelatinized and enzymatically modified potato starch analyzed by solid-state MAS NMR

    DEFF Research Database (Denmark)

    Larsen, Flemming H.; Kasprzak, Miroslaw Marek; Lærke, Helle Nygaard

    2013-01-01

    Hydration of granular, gelatinized and molecularly modified states of potato starch in terms of molecular mobility were analyzed by 13C and 31P solid-state MAS NMR. Gelatinization (GEL) tremendously reduced the immobile fraction compared to native (NA) starch granules. This effect was enhanced....... Comparative analysis of wheat and waxy maize starches demonstrated that starches were similar upon gelatinization independent of botanical origin and that the torsion angles of the glycosidic linkages were averages of the crystalline A and B type structures. In starch suspension phosphorous in immobile...

  6. Refocused continuous-wave decoupling: A new approach to heteronuclear dipolar decoupling in solid-state NMR spectroscopy

    DEFF Research Database (Denmark)

    Vinther, Joachim Møllesøe; Nielsen, Anders B.; Bjerring, Morten

    2012-01-01

    A novel strategy for heteronuclear dipolar decoupling in magic-angle spinning solid-state NMR spectroscopy is presented, which eliminates residual static high-order terms in the effective Hamiltonian originating from interactions between oscillating dipolar and anisotropic shielding tensors...... rCW decoupling sequences are presented and their performance is compared to state-of-the-art decoupling methods. The rCW decoupling sequences benefit from extreme broadbandedness, tolerance towards rf inhomogeneity, and improved potential for decoupling at relatively low average rf field strengths...

  7. Preparation of Uniformly 13C,15N-Labeled Recombinant Human Amylin for Solid-State NMR Investigation

    DEFF Research Database (Denmark)

    Kosicka, Iga; Kristensen, Torsten; Bjerring, Morten

    2014-01-01

    of amyloidogenic proteins in large amounts remains challenging due to their aggregation potential, toxicity for cells and difficult purification. In this work, we report a method for the production of large amounts of uniformly labeled 13C,15N-human amylin, being one of the most amyloidogenic peptides known...... crystal ordering, solid-state NMR forms the most suited method to determine the structures of the fibrils with atomic resolution. To exploit this potential, large amounts of isotopic-labeled protein need to be obtained through recombinant protein expression. However, expression and purification...

  8. Can the conformation of flexible hydroxyl groups be constrained by simple NMR crystallography approaches? The case of the quercetin solid forms.

    Science.gov (United States)

    Filip, Xenia; Filip, Claudiu

    2015-02-01

    Hydrogen atoms in systems with many flexible hydroxyl side-groups are difficult to be exactly located from experimental X-Ray diffraction and/or solid-state NMR data, thus often leading to wrong conclusions with respect to the hydrogen bonding network established in crystal lattice. A simple computational method is proposed in the present work to tackle this problem, which may be readily incorporated in conventional NMR crystallography protocols. The method is based on ranking all possible conformations of the flexible hydroxyls according to their lattice energy in crystalline environments. Its effectiveness is investigated on two distinct solid forms of quercetin, for which only two out of the five hydroxyl side-groups can be well constrained from experimental/theoretical data. For this purpose, first-principle quantum-mechanical computations were combined with calculations at the molecular mechanics (MM) level of theory, and previous ss-NMR and X-Ray diffraction data. To assess accuracy in ranking the identified conformers, tests have been performed first on quercetin dihydrate, for which an X-Ray single-crystal structure is available. The possibility of applying this method in a real NMR crystallography context has been investigated finally on anhydrous quercetin, for which only powder X-Ray crystal structure has been reported so far.

  9. Probing the interaction of U(vi) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy.

    Science.gov (United States)

    Uribe, Eva C; Mason, Harris E; Shusterman, Jennifer A; Bruchet, Anthony; Nitsche, Heino

    2016-06-21

    The fundamental interaction of U(vi) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U(vi) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse (31)P NMR on U(vi) contacted samples revealed that U(vi) only interacts with a fraction of the ligands present on the surface. At pH 4 the U(vi) extraction capacity of the material is limited to 27-37% of the theoretical capacity, based on ligand loading. We combined single pulse (31)P NMR on U(vi)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U(vi) binds to deprotonated phosphonate and/or silanol sites. We use (31)P-(31)P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U(vi)-complexed and non-complexed ligand environments. These measurements reveal that U(vi) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.

  10. αB-Crystallin. A Hybrid Solid-State/Solution-State NMR Investigation Reveals Structural Aspects of the Heterogeneous Oligomer

    Energy Technology Data Exchange (ETDEWEB)

    Jehle, Stefan [Freie Univ., Berlin (Germany); Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); van Rossum, Barth [Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Stout, Joseph R. [Univ. of Washington, Seattle, WA (United States); Noguchi, Satoshi M. [Univ. of Washington, Seattle, WA (United States); Falber, Katja [Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Rehbein, Kristina [Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Oschkinat, Hartmut [Freie Univ., Berlin (Germany); Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Klevit, Rachel E. [Univ. of Washington, Seattle, WA (United States); Rajagopal, Ponni [Univ. of Washington, Seattle, WA (United States)

    2008-11-14

    Atomic-level structural information on αB-Crystallin (αB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an ~580-kDa human αB assembled from 175-residue 20-kDa subunits. An ~100-residue α-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different α- crystallin domain constructs isolated from αB. In vitro, the chaperone-like activities of full-length αB and the isolated α-crystallin domain are identical. Chemical shifts of the backbone and Cβ resonances have been obtained for residues 64–162 (α-crystallin domain plus part of the C-terminus) in αB and the isolated α-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six β-strands in the α-crystallin domain. A majority of residues in the α-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the α-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within αB. Evidence for a novel dimerization motif in the human α-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) 1H–15N heteronuclear single quantum coherence spectra as a function of pH. The isolated α-crystallin domain undergoes a dimer–monomer transition over the pH range 7.5–6.8. This steep pHdependent switch may be important for αB to function optimally (e.g., to preserve the filament integrity

  11. Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy

    Science.gov (United States)

    Nusair, Nisreen A.; Tiburu, Elvis K.; Dave, Paresh C.; Lorigan, Gary A.

    2004-06-01

    This is the first time 2H solid-state NMR spectroscopy and spin-labeled EPR spectroscopy have been utilized to probe the structural orientation and dynamics of a stearic acid incorporated into magnetically aligned phospholipid bilayers or bicelles. The data gleaned from the two different techniques provide a more complete description of the bilayer membrane system. Both methods provided similar qualitative information on the phospholipid bilayer, high order, and low motion for the hydrocarbon segment close to the carboxyl groups of the stearic acid and less order and more rapid motion at the end towards the terminal methyl groups. However, the segmental order parameters differed markedly due to the different orientations that the nitroxide and C-D bond axes transform with the various stearic acid acyl chain conformations, and because of the difference in dynamic sensitivity between NMR and EPR over the timescales examined. 5-, 7-, 12-, and 16-doxylstearic acids spin-labels were used in the EPR experiments and stearic acid-d 35 was used in the solid-state NMR experiments. The influence of the addition of cholesterol and the variation of temperature on the fatty acid hydrocarbon chain ordering in the DMPC/DHPC phospholipid bilayers was also studied. Cholesterol increased the degree of ordering of the hydrocarbon chains. Conversely, as the temperature of the magnetically aligned phospholipid bilayers increased, the order parameters decreased due to the higher random motion of the acyl chain of the stearic acid. The results indicate that magnetically aligned phospholipid bilayers are an excellent model membrane system and can be used for both NMR and EPR studies.

  12. Identification of double four-ring units in germanosilicate ITQ-13 zeolite by solid-state NMR spectroscopy.

    Science.gov (United States)

    Liu, Xiaolong; Chu, Yueying; Wang, Qiang; Wang, Weiyu; Wang, Chao; Xu, Jun; Deng, Feng

    2017-05-17

    Well-crystallized Ge-free and Ge-ITQ-13 were successfully obtained by solid state synthesis method. The Ge/Si ratio and the water content that are the two important factors in the synthesis of germanosilicate zeolites were explored for the formation of ITQ-13. The effect of the mineralizing agents (NH4F and NH4Cl) on the ITQ-13 synthesis was investigated as well. The obtained pure silica ITQ-13 and Ge-ITQ-13 were characterized by one- and two-dimensional solid- state NMR techniques. One-dimensional (1D) (19)F MAS, (1)H→(29)Si CP/MAS and (19)F→(29)Si CP/MAS NMR spectroscopy evidenced the formation of pure Si-D4R (double four ring) and Ge-D4R units, with the latter being generated by substitution of Si atom from the former units. The detailed configurations of the Ge-D4R units in ITQ-13 was revealed by two-dimensional (2D) (29)Si{(19)F} HETCOR NMR spectroscopy. With the help of theoretical calculations on the (19)F and (29)Si NMR chemical shifts, six types of D4R units were determined. The formation of the specific D4R unit confirms the structural directing roles of Ge atom and F ions in the formation of the D4R units in zeolite framework. The identification of the SiOSi bonds in the D4R units that connects the layers of ITQ-13 framework provided rationale for the high stability of the ITQ-13 in the degermanation treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. (31)P Solid-State NMR study of the chemical setting process of a dual-paste injectable brushite cements.

    Science.gov (United States)

    Legrand, A P; Sfihi, H; Lequeux, N; Lemaître, J

    2009-10-01

    The composition and evolution of a brushite-type calcium phosphate cement was investigated by Solid-State NMR and X-ray during the setting process. The cement is obtained by mixing beta-tricalcium phosphate [Ca(3)(PO(4))(2), beta-TCP] and monocalcium phosphate monohydrate [Ca(H(2)PO(4))(2).H(2)O, MCPM] in presence of water, with formation of dicalcium phosphate dihydrate or brushite [CaHPO(2).2H(2)O, DCPD]. Analysis of the initial beta-TCP paste has shown the presence of beta-calcium pyrophosphate [Ca(2)P(2)O(7), beta-CPy] and that of the initial MCPM a mixture of MCPM and dicalcium phosphate [CaHPO(4), DCP]. Follow-up of the chemical composition by (31)P Solid-State NMR enables to show that the chemical setting process appeared to reach an end after 20 min. The constant composition observed at the end of the process was similarly determined.

  14. Study of cross - relaxation and molecular dynamics in the solid 3-(trifluoromethyl) benzoic acid by solid state NMR off - resonance.

    Science.gov (United States)

    Woźniak-Braszak, Aneta

    2017-02-01

    Molecular dynamics of the solid 3-(trifluoromethyl) benzoic acid containing proton (1)H and fluorine (19)F nuclei was explored by the solid-state NMR off - resonance technique. Contrary to the previous experiments the proton nuclei system I relaxed in the off - resonance effective field B→e while fluorine nuclei system S was saturated for short time in comparison to the relaxation time T1I. New cross - relaxation solid - state NMR off - resonance experiments were conducted on a homebuilt pulse spectrometer operating at the on-resonance frequency of 30.2MHz, at the off - resonance frequency varied between 30.2 and 30.6MHz for protons and at the frequency of 28.411MHz for fluorines, respectively. Based on the experimental data the dispersions of the proton off - resonance spin - lattice relaxation rate ρρ(I), the fluorine off - resonance spin - lattice relaxation rate ρρ(S) and the cross - relaxation rate σρ in the rotating frame were determined. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Combining (27)Al Solid-State NMR and First-Principles Simulations To Explore Crystal Structure in Disordered Aluminum Oxynitride.

    Science.gov (United States)

    Tu, Bingtian; Liu, Xin; Wang, Hao; Wang, Weimin; Zhai, Pengcheng; Fu, Zhengyi

    2016-12-19

    The nuclear magnetic resonance (NMR) technique gives insight into the local information in a crystal structure, while Rietveld refinement of powder X-ray diffraction (PXRD) sketches out the framework of a crystal lattice. In this work, first-principles calculations were combined with the solid-state NMR technique and Rietveld refinement to explore the crystal structure of a disordered aluminum oxynitride (γ-alon). The theoretical NMR parameters (chemical shift, δiso, quadrupolar coupling constants, CQ, and asymmetry parameter, η) of Al22.5O28.5N3.5, predicted by the gauge-including projector augmented wave (GIPAW) algorithm, were used to facilitate the analytical investigation of the (27)Al magic-angle spinning (MAS) NMR spectra of the as-prepared sample, whose formula was confirmed to be Al2.811O3.565N0.435 by quantitative analysis. The experimental δiso, CQ, and η of (27)Al showed a small discrepancy compared with theoretical models. The ratio of aluminum located at the 8a to 16d sites was calculated to be 0.531 from the relative integration of peaks in the (27)Al NMR spectra. The occupancies of aluminum at the 8a and 16d positions were determined through NMR investigations to be 0.9755 and 0.9178, respectively, and were used in the Rietveld refinement to obtain the lattice parameter and anion parameter of Al2.811O3.565N0.435. The results from (27)Al NMR investigations and PXRD structural refinement complemented each other. This work provides a powerful and accessible strategy to precisely understand the crystal structure of novel oxynitride materials with multiple disorder.

  16. Quantitation of recombinant protein in whole cells and cell extracts via solid-state NMR spectroscopy.

    Science.gov (United States)

    Vogel, Erica P; Weliky, David P

    2013-06-25

    Recombinant proteins (RPs) are commonly expressed in bacteria followed by solubilization and chromatography. Purified RP yield can be diminished by losses at any step with very different changes in methods that can improve the yield. Time and labor can therefore be saved by first identifying the specific reason for the low yield. This study describes a new solid-state nuclear magnetic resonance approach to RP quantitation in whole cells or cell extracts without solubilization or purification. The method is straightforward and inexpensive and requires only ∼50 mL culture and a low-field spectrometer.

  17. Regenerated silk fibers: Structural studies and solid state NMR techniques for efficient multiple distance determinations in proteins

    Science.gov (United States)

    Liivak, Oskar

    2000-09-01

    Material Science is the science of understanding the relationship between the molecular level structure of a material and its macroscopic properties. Such research requires both the ability to determine molecular structure and the ability to control and modify the molecular structure. The present research into silks, especially the dragline silk from the spider Nephila clavipes , is occurring at a time when these two criteria are beginning to be met for proteins like spider silk. Genetic engineering has evolved to the point where material scientists have full control over the primary sequence of amino acids that comprise proteins. In addition, solid state nuclear magnetic resonance (NMR) techniques exist which allow us to probe molecular structure. This work applies solid state NMR to the study of the structure of silk fibers. In particular, we focus on techniques of fiber regeneration from solution. The purpose is not only to develop the techniques by which genetically engineered fibers could be spun into fibers for mass production but also as a tool into fundamental silk research. Results on these regenerated fibers show a correlation between the fraction of the silk's alanine residues which are in the β-sheet conformation and the ultimate tensile strength of the fibers. In addition, in a clever mating of the fiber regeneration technique and the solid state NMR distance measurement experiment, rotational echo double resonance (REDOR), we investigate the supramolecular topology of the alanine β-sheet crystals. Even though the REDOR technique has failings for the complicated ISn spin systems found in the silk samples, a qualitative analysis does indicate that the β-sheet crystals are intermolecular. Finally, we investigate a new class of REDOR-like experiments which are designed to overcome the failings of REDOR in ISn spin systems. Experimental data is shown to validate these ideas. An alternate pulse sequence is also introduced and verified with experimental

  18. Synthesis and solid-state NMR characterization of cubic mesoporous silica SBA-1 functionalized with sulfonic acid groups.

    Science.gov (United States)

    Tsai, Hui-Hsu Gavin; Chiu, Po-Jui; Jheng, Guang-Liang; Ting, Chun-Chiang; Pan, Yu-Chi; Kao, Hsien-Ming

    2011-07-01

    Well-ordered cubic mesoporous silicas SBA-1 functionalized with sulfonic acid groups have been synthesized through in situ oxidation of mercaptopropyl groups with H(2)O(2) via co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) templated by cetyltriethylammonium bromide (CTEABr) under strong acidic conditions. Various synthesis parameters such as the amounts of H(2)O(2) and MPTMS on the structural ordering of the resultant materials were systematically investigated. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), multinuclear solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, (29)Si{(1)H} 2D HETCOR (heteronuclear correlation) NMR spectroscopy, thermogravimetric analysis (TGA), and nitrogen sorption measurements. By using (13)C CPMAS NMR technique, the status of the incorporated thiol groups and their transformation to sulfonic acid groups can be monitored and, as an extension, to define the optimum conditions to be used for the oxidation reaction to be quantitative. In particular, (29)Si{(1)H} 2D HETCOR NMR revealed that the protons in sulfonic acid groups are in close proximity to the silanol Q(3) species, but not close enough to form a hydrogen bond.

  19. Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the Balkan peninsula

    Directory of Open Access Journals (Sweden)

    ANDREAS GEORGAKOPOULOS

    2003-09-01

    Full Text Available The cross-polarized magic-angle-spinning NMR (CPMAS-NMR technique was used in this work to assess the carbon distribution in coals of different rank (peat, lignite, xylite, sub-bituminous coal from important deposits in Greece and Bulgaria. The technique is assumed to be only semiquantitative, due to a number of interferences, such as spinning side bands (SSB in the spectra, paramagnetic species in the samples, and low or remote protonation of aromatic carbons. The Bulgarian sub-bituminous coal shows the greatest amounts of aromatic structures. The lignite sample from the Drama basin, Northern Greece, is relatively unaltered and largely unweathered, and shows the greatest amounts of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from endemic areas in Serbia and Montenegro and Bosnia, taken from published papers, show significantly more intense resonances for methoxyl, phenolic, and polysaccharide moieties compared to the Drama lignite NMR spectrum. Xylite reveals high contents of carbohydrates.

  20. Quantitative analysis of backbone motion in proteins using MAS solid-state NMR spectroscopy.

    Science.gov (United States)

    Chevelkov, Veniamin; Fink, Uwe; Reif, Bernd

    2009-09-01

    We present a comprehensive analysis of protein dynamics for a micro-crystallin protein in the solid-state. Experimental data include (15)N T (1) relaxation times measured at two different magnetic fields as well as (1)H-(15)N dipole, (15)N CSA cross correlated relaxation rates which are sensitive to the spectral density function J(0) and are thus a measure of T (2) in the solid-state. In addition, global order parameters are included from a (1)H,(15)N dipolar recoupling experiment. The data are analyzed within the framework of the extended model-free Clore-Lipari-Szabo theory. We find slow motional correlation times in the range of 5 and 150 ns. Assuming a wobbling in a cone motion, the amplitude of motion of the respective amide moiety is on the order of 10 degrees for the half-opening angle of the cone in most of the cases. The experiments are demonstrated using a perdeuterated sample of the chicken alpha-spectrin SH3 domain.

  1. Solid-state Hadamard NMR spectroscopy: simultaneous measurements of multiple selective homonuclear scalar couplings.

    Science.gov (United States)

    Kakita, Veera Mohana Rao; Kupče, Eriks; Bharatam, Jagadeesh

    2015-02-01

    Unambiguous measurement of homonuclear scalar couplings (J) in multi-spin scalar network systems is not straightforward. Further, the direct measurement of J-couplings is obscured in solid-state samples due to the dipolar and chemical shift anisotropy (CSA)-dominated line broadening, even under the magic angle spinning (MAS). We present a new multiple frequency selective spin-echo method based on Hadamard matrix encoding, for simultaneous measurement of multiple homonuclear scalar couplings (J) in the solid-state. In contrast to the Hadamard encoded selective excitation schemes known for the solution-state, herein the selectivity is achieved during refocusing period. The Hadamard encoded refocusing scheme concurrently allows to create the spin-spin commutation property between number of spin-pairs of choice in uniformly labelled molecules, which, therefore avoids (1) the repetition of the double selective refocusing experiments for each spin-pair and (2) the synthesis of expensive selective labelled molecules. The experimental scheme is exemplified for determining (1)JCC and (3)JCC values in (13)C6l-Histidine.HCl molecule, which are found to be in excellent agreement with those measured in conventional double frequency selective refocusing mode as well as in the solution-state. This method can be simply extended to 2D/3D pulse schemes and be applied to small bio-molecular solids.

  2. Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

    Science.gov (United States)

    Sarkar, Gautam

    Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of

  3. Rapid measurement of pseudocontact shifts in metalloproteins by proton-detected solid-state NMR spectroscopy.

    Science.gov (United States)

    Knight, Michael J; Felli, Isabella C; Pierattelli, Roberta; Bertini, Ivano; Emsley, Lyndon; Herrmann, Torsten; Pintacuda, Guido

    2012-09-12

    Pseudocontact shifts (PCSs) arise in paramagnetic systems in which the susceptibility tensor is anisotropic. PCSs depend upon the distance from the paramagnetic center and the position relative to the susceptibility tensor, and they can be used as structural restraints in protein structure determination. We show that the use of (1)H-detected solid-state correlations provides facile and rapid detection and assignment of site-specific PCSs, including resolved (1)H PCSs, in a large metalloprotein, Co(2+)-substituted superoxide dismutase (Co(2+)-SOD). With only 3 mg of sample and a small set of experiments, several hundred PCSs were measured and assigned, and these PCSs were subsequently used in combination with (1)H-(1)H distance and dihedral angle restraints to determine the protein backbone geometry with a precision paralleling those of state-of-the-art liquid-state determinations of diamagnetic proteins, including a well-defined active site.

  4. Solid-state NMR studies of bacteriorhodopsin and the purple membrane

    CERN Document Server

    Mason, A J

    2001-01-01

    proteins. This technique may prove particularly useful when studying large proteins that are difficult to orient where the MAS lineshapes will remain relatively unaffected in comparison with current static NMR methods. Finally the MAOSS method was extended to the study of the lipid components of the purple membrane and the feasibility of determining structural constraints from phospholipid headgroups was assessed. The potential of using sup 3 sup 1 P NMR to observe qualitative protein-lipid interactions in both the purple membrane and reconstituted membranes containing bovine rhodopsin was also demonstrated. Following the demonstration of a new MAS NMR method for resolving orientational constraints in uni-axially oriented biological membranes (Glaubitz and Watts, 1998), experiments were performed to realise the potential of the new method on large, oriented membrane proteins. Using bacteriorhodopsin in the purple membrane as a paradigm for large membrane proteins, the protein was specifically labelled with de...

  5. New in situ solid-state NMR techniques for probing the evolution of crystallization processes: pre-nucleation, nucleation and growth.

    Science.gov (United States)

    Hughes, Colan E; Williams, P Andrew; Keast, Victoria L; Charalampopoulos, Vasileios G; Edwards-Gau, Gregory R; Harris, Kenneth D M

    2015-01-01

    The application of in situ techniques for investigating crystallization processes promises to yield significant new insights into fundamental aspects of crystallization science. With this motivation, we recently developed a new in situ solid-state NMR technique that exploits the ability of NMR to selectively detect the solid phase in heterogeneous solid-liquid systems (of the type that exist during crystallization from solution), with the liquid phase "invisible" to the measurement. As a consequence, the technique allows the first solid particles produced during crystallization to be observed and identified, and allows the evolution of different solid phases (e.g., polymorphs) present during the crystallization process to be monitored as a function of time. This in situ solid-state NMR strategy has been demonstrated to be a powerful approach for establishing the sequence of solid phases produced during crystallization and for the discovery of new polymorphs. The most recent advance of the in situ NMR methodology has been the development of a strategy (named "CLASSIC NMR") that allows both solid-state NMR and liquid-state NMR spectra to be measured (essentially simultaneously) during the crystallization process, yielding information on the complementary changes that occur in both the solid and liquid phases as a function of time. In this article, we present new results that highlight the application of our in situ NMR techniques to successfully unravel different aspects of crystallization processes, focusing on: (i) the application of a CLASSIC NMR approach to monitor competitive inclusion processes in solid urea inclusion compounds, (ii) exploiting liquid-state NMR to gain insights into co-crystal formation between benzoic acid and pentafluorobenzoic acid, and (iii) applications of in situ solid-state NMR for the discovery of new solid forms of trimethylphosphine oxide and L-phenylalanine. Finally, the article discusses a number of important fundamental issues

  6. Which kind of aromatic structures are produced during biomass charring? New insights provided by modern solid-state NMR spectroscopy

    Science.gov (United States)

    Knicker, Heike; Paneque-Carmona, Marina; Velasco-Molina, Marta; de la Rosa, José Maria; León-Ovelar, Laura Regina; Fernandez-Boy, Elena

    2017-04-01

    Intense research on biochar and charcoal of the last years has revealed that depending on the production conditions, the chemical and physical characteristics of their aromatic network can greatly vary. Since such variations are determining the behavior and stability of charred material in soils, a better understanding of the structural changes occurring during their heating and the impact of those changes on their function is needed. One method to characterize pyrogenic organic matter (PyOM) represents solid-state 13C NMR spectroscopy applying the cross polarization (CP) magic angle spinning technique (MAS). A drawback of this technique is that the quantification of NMR spectra of samples with highly condensed and proton-depleted structures is assumed to be bias. Typical samples with such attributes are charcoals produced at temperatures above 700°C under pyrolytic conditions. Commonly their high condensation degree leads to graphenic structures that are not only reducing the CP efficiency but create also a conductive lattice which acts as a shield and prevents the entering of the excitation pulse into the sample during the NMR experiments. Since the latter can damage the NMR probe and in the most cases the obtained NMR spectra show only one broad signal assignable to aromatic C, this technique is rarely applied for characterizing high temperature chars or soot. As a consequence, a more detailed knowledge of the nature of the aromatic ring systems is still missing. The latter is also true for the aromatic domains of PyOM produced at lower temperatures, since older NMR instruments operating at low magnetic fields deliver solid-state 13C NMR spectra with low resolution which turns a more detailed analysis of the aromatic chemical shift region into a challenging task. In order to overcome this disadvantages, modern NMR spectroscopy offers not only instruments with greatly improved resolution but also special pulse sequences for NMR experiments which allow a more

  7. Distinguishing bicontinuous lipid cubic phases from isotropic membrane morphologies using (31)P solid-state NMR spectroscopy.

    Science.gov (United States)

    Yang, Yu; Yao, Hongwei; Hong, Mei

    2015-04-16

    Nonlamellar lipid membranes are frequently induced by proteins that fuse, bend, and cut membranes. Understanding the mechanism of action of these proteins requires the elucidation of the membrane morphologies that they induce. While hexagonal phases and lamellar phases are readily identified by their characteristic solid-state NMR line shapes, bicontinuous lipid cubic phases are more difficult to discern, since the static NMR spectra of cubic-phase lipids consist of an isotropic (31)P or (2)H peak, indistinguishable from the spectra of isotropic membrane morphologies such as micelles and small vesicles. To date, small-angle X-ray scattering is the only method to identify bicontinuous lipid cubic phases. To explore unique NMR signatures of lipid cubic phases, we first describe the orientation distribution of lipid molecules in cubic phases and simulate the static (31)P chemical shift line shapes of oriented cubic-phase membranes in the limit of slow lateral diffusion. We then show that (31)P T2 relaxation times differ significantly between isotropic micelles and cubic-phase membranes: the latter exhibit 2 orders of magnitude shorter T2 relaxation times. These differences are explained by the different time scales of lipid lateral diffusion on the cubic-phase surface versus the time scales of micelle tumbling. Using this relaxation NMR approach, we investigated a DOPE membrane containing the transmembrane domain (TMD) of a viral fusion protein. The static (31)P spectrum of DOPE shows an isotropic peak, whose T2 relaxation times correspond to that of a cubic phase. Thus, the viral fusion protein TMD induces negative Gaussian curvature, which is an intrinsic characteristic of cubic phases, to the DOPE membrane. This curvature induction has important implications to the mechanism of virus-cell fusion. This study establishes a simple NMR diagnostic probe of lipid cubic phases, which is expected to be useful for studying many protein-induced membrane remodeling phenomena

  8. Acceleration of natural-abundance solid-state MAS NMR measurements on bone by paramagnetic relaxation from gadolinium-DTPA

    Science.gov (United States)

    Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2014-07-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans.

  9. Probing the nanostructure, interfacial interaction, and dynamics of chitosan-based nanoparticles by multiscale solid-state NMR.

    Science.gov (United States)

    Wang, Fenfen; Zhang, Rongchun; Wu, Qiang; Chen, Tiehong; Sun, Pingchuan; Shi, An-Chang

    2014-12-10

    Chitosan-based nanoparticles (NPs) are widely used in drug and gene delivery, therapy, and medical imaging, but a molecular-level understanding of the internal morphology and nanostructure size, interface, and dynamics, which is critical for building fundamental knowledge for the precise design and efficient biological application of the NPs, remains a great challenge. Therefore, the availability of a multiscale (0.1-100 nm) and nondestructive analytical technique for examining such NPs is of great importance for nanotechnology. Herein, we present a new multiscale solid-state NMR approach to achieve this goal for the investigation of chitosan-poly(N-3-acrylamidophenylboronic acid) NPs. First, a recently developed (13)C multiple cross-polarization magic-angle spinning (MAS) method enabled fast quantitative determination of the NPs' composition and detection of conformational changes in chitosan. Then, using an improved (1)H spin-diffusion method with (13)C detection and theoretical simulations, the internal morphology and nanostructure size were quantitatively determined. The interfacial coordinated interaction between chitosan and phenylboronic acid was revealed by one-dimensional MAS and two-dimensional (2D) triple-quantum MAS (11)B NMR. Finally, dynamic-editing (13)C MAS and 2D (13)C-(1)H wide-line separation experiments provided details regarding the componential dynamics of the NPs in the solid and swollen states. On the basis of these NMR results, a model of the unique nanostructure, interfacial interaction, and componential dynamics of the NPs was proposed.

  10. Investigating miscibility and molecular mobility of nifedipine-PVP amorphous solid dispersions using solid-state NMR spectroscopy.

    Science.gov (United States)

    Yuan, Xiaoda; Sperger, Diana; Munson, Eric J

    2014-01-06

    Solid-state NMR (SSNMR) (1)H T1 and T1ρ relaxation times were used to evaluate the miscibility of amorphous solid dispersions of nifedipine (NIF) and polyvinylpyrrolidone (PVP) prepared by three different methods: melt quenching in the typical lab setting, spray drying and melt quenching in the NMR rotor while spinning. Of the five compositions prepared by melt quenching in the lab setting, the 95:5 and 90:10 NIF:PVP (w:w) amorphous solid dispersions were not miscible while 75:25, 60:40, and 50:50 NIF:PVP dispersions were miscible by the (1)H T1ρ measurements. The domain size of the miscible systems was estimated to be less than 4.5 nm. Amorphous solid dispersions with composition of 90:10 NIF:PVP prepared by spray drying and melt quenching in the NMR rotor showed miscibility by (1)H T1ρ values. Variable-temperature SSNMR (1)H T1ρ relaxation measurements revealed a change in relaxation time at approximately 20 °C below Tg, suggesting increased molecular mobility above that temperature.

  11. Probing the assembly and dynamics of graphene-inspired molecular wires by solid-state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Michael Ryan; Graf, Robert; Sebastiani, Daniel; Spiess, Hans-Wolfgang [Max Planck Institute for Polymer Research, Mainz (Germany)

    2010-07-01

    Molecular wires based on polycyclic aromatic hydrocarbons (PAHs) are a promising class of materials for future applications in nano-scale electronic devices. Critical for the performance of such wires are their molecular assembly, which on the NMR length and time scales translates into the local packing arrangement, molecular dynamics, and pitch angle(s) between successive molecules. Here, we show that solid-state NMR in combination with MD and ab-initio calculations can provide unique information with respect to these structural features. To illustrate this we examine two perylene tetracarboxydiimides (PDIs) with different side chains attached and a larger triangular-shaped PAH. Specifically, we measure 1H chemical shifts using fast MAS and their spatial connectivities through 2D 1H-1H DQ-SQ correlation spectra and probe the molecular dynamics via 1H-13C heteronuclear dipolar couplings. To support the experimental findings we have performed CPMD-NMR calculations to reveal the effects of packing on the 1H chemical shifts for the PDIs, including an estimate of the line broadening due to local disorder. This provides a series of finger prints for different pitch angles between neighboring molecules, that are closely related to the electronic conduction properties of the supramolecular stacks.

  12. Probing molecular dynamics of metal borohydrides on the surface of mesoporous scaffolds by multinuclear high resolution solid state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Son-Jong, E-mail: Sonjong@cheme.caltech.edu [Division of Chemistry and Chemical Eng., California Institute of Technology, Pasadena, CA 91125 (United States); Lee, Hyun-Sook [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); To, Magnus [Division of Chemistry and Chemical Eng., California Institute of Technology, Pasadena, CA 91125 (United States); Lee, Young-Su; Cho, Young Whan [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Choi, Hyungkeun; Kim, Chul [Department of Chemistry, Hannam University, Daejeon 305-811 (Korea, Republic of)

    2015-10-05

    Graphical abstract: In situ variable temperature multinuclear solid state NMR allows to probe surface wetting, diffusivity, and confinement of metal borohydrides into nanopores. - Abstract: Understanding of surface interactions between borohydride molecules and the surfaces of porous supports have gained growing attention for successful development of nano-confinement engineering. By use of in situ variable temperature (VT) magic angle spinning (MAS) NMR, molecular mobility changes of LiBH{sub 4} crystalline solid has been investigated in the presence of silica based and carbonaceous surfaces. Spin–spin J-coupling of {sup 1}H–{sup 11}B in LiBH{sub 4} was monitored in series of VT NMR spectra to probe translational mobility of LiBH{sub 4} that appeared to be greatly enhanced upon surface contact. Such enhanced diffusivity was found to be effective in the formation of solid solution and co-confinement with other metal borohydrides. Co-confinement of LiBH{sub 4}–Ca(BH{sub 4}){sub 2} mixture was demonstrated at temperature as low as 100 °C, much lower than the reported bulk eutectic melting temperature. The discovery adds a novel property of LiBH{sub 4} that has been proven to be highly versatile in many energy related applications.

  13. Unlocking the molecular structure of fungal melanin using 13C biosynthetic labeling and solid-state NMR.

    Science.gov (United States)

    Tian, Shiying; Garcia-Rivera, Javier; Yan, Bin; Casadevall, Arturo; Stark, Ruth E

    2003-07-15

    Melanins are enigmatic pigments found in all biological kingdoms that are associated with a variety of functions, including microbial virulence. Despite being ubiquitous in nature, melanin pigments have long resisted atomic-level structural examination because of their insolubility and amorphous organization. Cryptococcus neoformans is a human pathogenic fungus that melanizes only when provided with exogenous substrate, thus offering a unique system for exploring questions related to melanin structure at the molecular level. We have exploited the requirement for exogenous substrate in melanin synthesis as well as the capabilities of high-resolution solid-state nuclear magnetic resonance (NMR) to establish the predominantly aliphatic composition of l-dopa melanin and to introduce (13)C labels that permit the identification of proximal carbons in the developing biopolymer. By swelling solid melanin samples in organic solvents and using two-dimensional heteronuclear NMR in conjunction with magic-angle spinning, we have identified chemical bonding patterns typical of alkane, alkene, alcohol, ketone, ester, and indole functional groups. These findings demonstrate the feasibility of a novel approach to determining the structure of melanin using metabolic labeling and NMR spectroscopy.

  14. Solid state NMR, MRI and Sir Peter Mansfield: (1) from broad lines to narrow and back again; and (2) a highly tenuous link to landmine detection.

    Science.gov (United States)

    Garroway, A N

    1999-12-01

    The contributions of Sir Peter Mansfield to MRI are rooted in solid state NMR. I summarize some of the important contributions of Sir Peter to that field, provide a glimpse of the state of the art in multiple-pulse line-narrowing in the early 1970s, and indicate how the earliest MRI efforts at Nottingham flowed from solid state NMR. These line-narrowing methods, providing control over the Hamiltonian governing the dynamics of nuclear spins, continue to evolve and to find new uses. I indicate how some methods and ideas from solid state NMR of the 1970s are at present applied to the detection of explosives in landmines by nuclear quadrupole resonance (NQR).

  15. Mobility and relaxation determinations of lithium in lithium aluminate ceramics using solid-state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, F.F.; Peterson, E.S. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Stebbins, J.F. [Stanford Univ., CA (United States)] [and others

    1995-02-01

    Lithium aluminate is one of the materials being considered for fusion reactor blankets. When preparing the ceramic, it is important to be able to monitor the microstructures since it is a controlling factor in the rate of tritium release from the blanket. Nuclear magnetic resonance spectroscopy (NMR) has been shown to be a useful tool for the nondestructive analysis of ceramics. Studies detailed in this paper include spectral acquisition, assignment, spin-lattice relaxation time measurements, temperature effects, their correlation to structure, and material purity. The ceramic of interest was lithium aluminate, LiAl{sub 5}O{sub 8}. This material was studied by observation of the NMR active nuclei {sup 6}Li, {sup 7}Li, and {sup 27}Al. For these nuclei, spin-lattice relaxation times (T{sub 1}) were measured and were found to vary considerably, correlating to the presence of paramagnetic impurities within the crystalline lattice. Previous research has shown that the coordination about the aluminum nucleus can be determined using {sup 27}Al NMR spectroscopy. Aluminum-27 NMR spectroscopy was successfully applied, and it provided valuable insight into composition of the ceramic. 20 refs., 4 figs., 3 tabs.

  16. Solid-state 31P NMR spectroscopy of bacteriophage M13 and tobacco mosaic virus.

    NARCIS (Netherlands)

    Magusin, P.C.M.M.

    1995-01-01

    In this thesis, the results of various 31P NMR experiments observed for intact virus particles of bacteriophage M13 and Tobacco Mosaic Virus (TMV), are presented. To explain the results in a consistent way, models are developed and tested. 31

  17. 2D 31P solid state NMR spectroscopy, electronic structure and thermochemistry of PbP7

    Science.gov (United States)

    Benndorf, Christopher; Hohmann, Andrea; Schmidt, Peer; Eckert, Hellmut; Johrendt, Dirk; Schäfer, Konrad; Pöttgen, Rainer

    2016-03-01

    Phase pure polycrystalline PbP7 was prepared from the elements via a lead flux. Crystalline pieces with edge-lengths up to 1 mm were obtained. The assignment of the previously published 31P solid state NMR spectrum to the seven distinct crystallographic sites was accomplished by radio-frequency driven dipolar recoupling (RFDR) experiments. As commonly found in other solid polyphosphides there is no obvious correlation between the 31P chemical shift and structural parameters. PbP7 decomposes incongruently under release of phosphorus forming liquid lead as remainder. The thermal decomposition starts at T>550 K with a vapor pressure almost similar to that of red phosphorus. Electronic structure calculations reveal PbP7 as a semiconductor according to the Zintl description and clearly shows the stereo-active Pb-6s2 lone pairs in the electron localization function ELF.

  18. Synthesis, solid-state NMR characterization, and application for hydrogenation reactions of a novel Wilkinson's-type immobilized catalyst.

    Science.gov (United States)

    Abdulhussain, Safaa; Breitzke, Hergen; Ratajczyk, Tomasz; Grünberg, Anna; Srour, Mohamad; Arnaut, Danjela; Weidler, Heiko; Kunz, Ulrike; Kleebe, Hans Joachim; Bommerich, Ute; Bernarding, Johannes; Gutmann, Torsten; Buntkowsky, Gerd

    2014-01-20

    Silica nanoparticles (SiNPs) were chosen as a solid support material for the immobilization of a new Wilkinson's-type catalyst. In a first step, polymer molecules (poly(triphenylphosphine)ethylene (PTPPE); 4-diphenylphosphine styrene as monomer) were grafted onto the silica nanoparticles by surface-initiated photoinferter-mediated polymerization (SI-PIMP). The catalyst was then created by binding rhodium (Rh) to the polymer side chains, with RhCl3⋅x H2O as a precursor. The triphenylphosphine units and rhodium as Rh(I) provide an environment to form Wilkinson's catalyst-like structures. Employing multinuclear ((31)P, (29)Si, and (13)C) solid-state NMR spectroscopy (SSNMR), the structure of the catalyst bound to the polymer and the intermediates of the grafting reaction have been characterized. Finally, first applications of this catalyst in hydrogenation reactions employing para-enriched hydrogen gas (PHIP experiments) and an assessment of its leaching properties are presented.

  19. {sup 13}C solid-state n.m.r. spectroscopy of fossil sporopollenins: variation in composition independent of diagenesis

    Energy Technology Data Exchange (ETDEWEB)

    Hemsley, A.R.; Barrie, P.J.; Scott, A.C. [University of London, Egham (United Kingdom). Royal Holloway, Dept. of Biology and Geology

    1995-07-01

    {sup 13}C solid-state nuclear magnetic resonance of sporopollenin from extant and extinct lycopods and gymnosperms shows that this material differs in composition between these major groups. The relative amounts of unsaturated carbon species are lower in the gymnsopersms than in the lycopods in both the modern and fossil material. This suggests that the proportion of unsaturated carbon species present in the fossils is related to that of the original material. Since the fossil material used in this study was obtained from single rock samples, this largely eliminates the possibility that the observed differences in n.m.r. characteristics in fossil spore exines from different species can be attributed to different diagenetic histories. 16 refs., 2 figs.

  20. Principles of spin-echo modulation by J-couplings in magic-angle-spinning solid-state NMR.

    Science.gov (United States)

    Duma, Luminita; Lai, Wai Cheu; Carravetta, Marina; Emsley, Lyndon; Brown, Steven P; Levitt, Malcolm H

    2004-06-21

    In magic-angle-spinning solid-state NMR, the homonuclear J-couplings between pairs of spin-1/2 nuclei may be determined by studying the modulation of the spin echo induced by a pi-pulse, as a function of the echo duration. We present the theory of J-induced spin-echo modulation in magic-angle-spinning solids, and derive a set of modulation regimes which apply under different experimental conditions. In most cases, the dominant spin-echo modulation frequency is exactly equal to the J-coupling. Somewhat surprisingly, the chemical shift anisotropies and dipole-dipole couplings tend to stabilise--rather than abscure--the J-modulation. The theoretical conclusions are supported by numerical simulations and experimental results obtained for three representative samples containing 13C spin pairs.

  1. An efficient method and device for transfer of semisolid materials into solid-state NMR spectroscopy rotors.

    Science.gov (United States)

    Hisao, Grant S; Harland, Michael A; Brown, Robert A; Berthold, Deborah A; Wilson, Thomas E; Rienstra, Chad M

    2016-04-01

    The study of mass-limited biological samples by magic angle spinning (MAS) solid-state NMR spectroscopy critically relies upon the high-yield transfer of material from a biological preparation into the MAS rotor. This issue is particularly important for maintaining biological activity and hydration of semi-solid samples such as membrane proteins in lipid bilayers, pharmaceutical formulations, microcrystalline proteins and protein fibrils. Here we present protocols and designs for rotor-packing devices specifically suited for packing hydrated samples into Pencil-style 1.6 mm, 3.2 mm standard, and 3.2 mm limited speed MAS rotors. The devices are modular and therefore readily adaptable to other rotor and/or ultracentrifugation tube geometries.

  2. Solid state 13C NMR and FT-IR spectroscopy of the cocoon silk of two common spiders

    Science.gov (United States)

    Bramanti, Emilia; Catalano, Donata; Forte, Claudia; Giovanneschi, Mario; Masetti, Massimo; Veracini, Carlo Alberto

    2005-11-01

    The structure of the silk from cocoons of two common spiders, Araneus diadematus (family Araneidae) and Achaearanea tepidariorum (family Theridiidae) was investigated by means of 13C solid state NMR and FT-IR spectroscopies. The combined use of these two techniques allowed us to highlight differences in the two samples. The cocoon silk of Achaearanea tepidariorum is essentially constituted by helical and β-sheet structures, whereas that of Araneus diadematus shows a more complex structure, containing also β-strands and β-turns. Moreover, the former silk is essentially crystalline while the latter contains more mobile domains. The structural differences of the two cocoon silks are ascribed to the different habitat of the two species.

  3. Characterizing the secondary protein structure of black widow dragline silk using solid-state NMR and X-ray diffraction.

    Science.gov (United States)

    Jenkins, Janelle E; Sampath, Sujatha; Butler, Emily; Kim, Jihyun; Henning, Robert W; Holland, Gregory P; Yarger, Jeffery L

    2013-10-14

    This study provides a detailed secondary structural characterization of major ampullate dragline silk from Latrodectus hesperus (black widow) spiders. X-ray diffraction results show that the structure of black widow major ampullate silk fibers is comprised of stacked β-sheet nanocrystallites oriented parallel to the fiber axis and an amorphous region with oriented (anisotropic) and isotropic components. The combination of two-dimensional (2D) (13)C-(13)C through-space and through-bond solid-state NMR experiments provide chemical shifts that are used to determine detailed information about the amino acid motif secondary structure in black widow spider dragline silk. Individual amino acids are incorporated into different repetitive motifs that make up the majority of this protein-based biopolymer. From the solid-state NMR measurements, we assign distinct secondary conformations to each repetitive amino acid motif and, hence, to the amino acids that make up the motifs. Specifically, alanine is incorporated in β-sheet (poly(Alan) and poly(Gly-Ala)), 3(1)-helix (poly(Gly-Gly-Xaa), and α-helix (poly(Gln-Gln-Ala-Tyr)) components. Glycine is determined to be in β-sheet (poly(Gly-Ala)) and 3(1)-helical (poly(Gly-Gly-X(aa))) regions, while serine is present in β-sheet (poly(Gly-Ala-Ser)), 3(1)-helix (poly(Gly-Gly-Ser)), and β-turn (poly(Gly-Pro-Ser)) structures. These various motif-specific secondary structural elements are quantitatively correlated to the primary amino acid sequence of major ampullate spidroin 1 and 2 (MaSp1 and MaSp2) and are shown to form a self-consistent model for black widow dragline silk.

  4. An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism

    Directory of Open Access Journals (Sweden)

    Carla I. Nieto

    2014-07-01

    Full Text Available This paper reports the 1H, 13C and 15N NMR experimental study of five benzimidazoles in solution and in the solid state (13C and 15N CPMAS NMR as well as the theoretically calculated (GIAO/DFT chemical shifts. We have assigned unambiguously the "tautomeric positions" (C3a/C7a, C4/C7 and C5/C6 of NH-benzimidazoles that, in some solvents and in the solid state, appear different (blocked tautomerism. In the case of 1H-benzimidazole itself we have measured the prototropic rate in HMPA-d18.

  5. Solid state {sup 13}C NMR analysis of Brazilian cretaceous ambers

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Ricardo; Azevedo, Debora A., E-mail: ricardopereira@iq.ufrj.b, E-mail: debora@iq.ufrj.b [Universidade Federal do Rio de Janeiro (IQ/UFRJ), Rio de Janeiro, RJ (Brazil). Inst. de Quimica. Lab. de Geoquimica Organica Molecular e Ambiental; San Gil, Rosane A.S. [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica. Lab. de RMN de Solidos; Carvalho, Ismar S. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Geociencias. Dept. de Geologia; Fernandes, Antonio Carlos S. [Museu Nacional (MN/UFRJ), RJ (Brazil). Dept. de Geologia e Paleontologia

    2011-07-01

    {sup 13}C cross polarization with magic angle spinning nuclear magnetic resonance ({sup 13}C CPMAS NMR) spectra have been obtained for the first time to three Cretaceous amber samples from South America. The samples were dated to Lower Cretaceous and collected in sediments from the Amazonas, Araripe and Reconcavo basins, Brazil. All samples have very similar spectra, consistent with a common paleobotanical source. Some aspects of the spectra suggest a relationship between Brazilian ambers and Araucariaceae family, such as intense resonances at 38-39 ppm. All samples are constituted by polylabdane structure associated to Class Ib resins, constituted by polymers of labdanoid diterpenes. Finally, information concerning some structural changes during maturation, such as isomerization of {Delta}{sup 8(17)} and {Delta}{sup 12(13)} unsaturations, were obtained by {sup 13}C NMR analyses. The results concerning botanical affinities are in accordance with previous results obtained by gas chromatography-mass spectrometry (GC-MS). (author)

  6. Characterization of pyrogenic organic matter by 2-dimenstional HETeronucleus CORelation solid-state 13C NMR (HETCOR) spectroscopy

    Science.gov (United States)

    Knicker, Heike

    2016-04-01

    During the last years, increasing evidences are provided that the common view of charcoal as a polyaromatic network is too much simplified. Experiments with model compounds indicated that it represents a heterogeneous mixture of thermally altered biomacromolecules with N, O and likely also S substitutions as common features. If produced from a N-rich feedstock, the so called black nitrogen (BN) has to be considered as an integral part of the aromatic charcoal network. In order to study this network one-dimensional (1D) solid-state nuclear magnetic resonance (NMR) spectroscopy is often applied. However, this technique suffers from broad resonance lines and low resolution. Applying 2D techniques can help but until recently, this was unfeasible for natural organic matter (NOM) due to sensitivity problems and the high complexity of the material. On the other hand, during the last decade, the development of stronger magnetic field instruments and advanced pulse sequences has put them into reach for NOM research. Although 2D NMR spectroscopy has many different applications, all pulse sequences are based on the introduction of a preparation time during which the magnetization of a spin system is adjusted into a state appropriate to whatever properties are to be detected in the indirect dimension. Then, the spins are allowed to evolve with the given conditions and after their additional manipulation during a mixing period the modulated magnetization is detected. Assembling several 1D spectra with incrementing evolution time creates a data set which is two-dimensional in time (t1, t2). Fourier transformation of both dimensions leads to a 2D contour plot correlating the interactions detected in the indirect dimension t1 with the signals detected in the direct dimension t2. The so called solid-state heteronuclear correlation (HETCOR) NMR spectroscopy represents a 2D technique allows the determination which protons are interacting with which carbons. In the present work this

  7. Selective measurements of long-range homonuclear J-couplings in solid-state NMR.

    Science.gov (United States)

    Thureau, Pierre; Mollica, Giulia; Ziarelli, Fabio; Viel, Stéphane

    2013-06-01

    We demonstrate here that the principle of frequency-selective spin-echoes can be extended to the measurements of long-range homonuclear scalar J-couplings in the solid-state. Singly or doubly frequency-selective pulses were used to generate either a J-modulated experiment (S) or a reference experiment (S0). The combination of these two distinct experiments provides experimental data that, in favorable cases, are insensitive to incoherent relaxation effects, and which can be used to estimate long-range homonuclear J-couplings in multiple spin-systems. The concept is illustrated in the case of a uniformly (13)C and (15)N labeled sample of L-histidine, where the absolute value of homonuclear J-couplings between two spins separated by one, two or three covalent bonds are measured. Moreover, we show that a (2)J((15)N-C-(15)N) coupling as small as 0.9 Hz can be precisely measured with the method presented here.

  8. A unified heteronuclear decoupling strategy for magic-angle-spinning solid-state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Equbal, Asif; Bjerring, Morten; Nielsen, Niels Chr., E-mail: madhu@tifr.res.in, E-mail: ncn@inano.au.dk [Center for Insoluble Protein Structures, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C (Denmark); Madhu, P. K., E-mail: madhu@tifr.res.in, E-mail: ncn@inano.au.dk [Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005 (India); TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500075 (India)

    2015-05-14

    A unified strategy of two-pulse based heteronuclear decoupling for solid-state magic-angle spinning nuclear magnetic resonance is presented. The analysis presented here shows that different decoupling sequences like two-pulse phase-modulation (TPPM), X-inverse-X (XiX), and finite pulse refocused continuous wave (rCW{sup A}) are basically specific solutions of a more generalized decoupling scheme which incorporates the concept of time-modulation along with phase-modulation. A plethora of other good decoupling conditions apart from the standard, TPPM, XiX, and rCW{sup A} decoupling conditions are available from the unified decoupling approach. The importance of combined time- and phase-modulation in order to achieve the best decoupling conditions is delineated. The consequences of different indirect dipolar interactions arising from cross terms comprising of heteronuclear and homonuclear dipolar coupling terms and also those between heteronuclear dipolar coupling and chemical-shift anisotropy terms are presented in order to unfold the effects of anisotropic interactions under different decoupling conditions. Extensive numerical simulation results are corroborated with experiments on standard amino acids.

  9. Membrane proteins in their native habitat as seen by solid-state NMR spectroscopy

    Science.gov (United States)

    Brown, Leonid S; Ladizhansky, Vladimir

    2015-01-01

    Membrane proteins play many critical roles in cells, mediating flow of material and information across cell membranes. They have evolved to perform these functions in the environment of a cell membrane, whose physicochemical properties are often different from those of common cell membrane mimetics used for structure determination. As a result, membrane proteins are difficult to study by traditional methods of structural biology, and they are significantly underrepresented in the protein structure databank. Solid-state Nuclear Magnetic Resonance (SSNMR) has long been considered as an attractive alternative because it allows for studies of membrane proteins in both native-like membranes composed of synthetic lipids and in cell membranes. Over the past decade, SSNMR has been rapidly developing into a major structural method, and a growing number of membrane protein structures obtained by this technique highlights its potential. Here we discuss membrane protein sample requirements, review recent progress in SSNMR methodologies, and describe recent advances in characterizing membrane proteins in the environment of a cellular membrane. PMID:25973959

  10. Protein fold determined by paramagnetic magic-angle spinning solid-state NMR spectroscopy

    Science.gov (United States)

    Sengupta, Ishita; Nadaud, Philippe S.; Helmus, Jonathan J.; Schwieters, Charles D.; Jaroniec, Christopher P.

    2012-01-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state nuclear magnetic resonance. However, the paucity of >5 Å distance restraints, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogs of the protein of interest containing covalently-attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu2+ mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone 15N PREs corresponding to ~10-20 Å distances were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å. PMID:22522262

  11. Solid-state NMR analysis of a complex crystalline phase of ronacaleret hydrochloride.

    Science.gov (United States)

    Vogt, Frederick G; Williams, Glenn R; Strohmeier, Mark; Johnson, Matthew N; Copley, Royston C B

    2014-08-28

    A crystalline phase of the pharmaceutical compound ronacaleret hydrochloride is studied by solid-state nuclear magnetic resonance (SSNMR) spectroscopy and single-crystal X-ray diffraction. The crystal structure is determined to contain two independent cationic molecules and chloride anions in the asymmetric unit, which combine with the covalent structure of the molecule to yield complex SSNMR spectra. Experimental approaches based on dipolar correlation, chemical shift tensor analysis, and quadrupolar interaction analysis are employed to obtain detailed information about this phase. Density functional theory (DFT) calculations are used to predict chemical shielding and electric field gradient (EFG) parameters for comparison with experiment. (1)H SSNMR experiments performed at 16.4 T using magic-angle spinning (MAS) and homonuclear dipolar decoupling provide information about hydrogen bonding and molecular connectivity that can be related to the crystal structure. (19)F and (13)C assignments for the Z' = 2 structure are obtained using DFT calculations, (19)F homonuclear dipolar correlation, and (13)C-(19)F heteronuclear dipolar correlation experiments. (35)Cl MAS experiments at 16.4 T observe two chlorine sites that are assigned using calculated chemical shielding and EFG parameters. SSNMR dipolar correlation experiments are used to extract (1)H-(13)C, (1)H-(15)N, (1)H-(19)F, (13)C-(19)F, and (1)H-(35)Cl through-space connectivity information for many positions of interest. The results allow for the evaluation of the performance of a suite of SSNMR experiments and computational approaches as applied to a complex but typical pharmaceutical solid phase.

  12. Preparation of highly and generally enriched mammalian tissues for solid state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Veronica Wai Ching; Reid, David G.; Chow, Wing Ying; Rajan, Rakesh [University of Cambridge, Department of Chemistry (United Kingdom); Green, Maggie [University of Cambridge, Central Biomedical Resources, School of Clinical Medicine (United Kingdom); Brooks, Roger A. [University of Cambridge, Department of Trauma and Orthopaedic Surgery, Addenbrooke’s Hospital (United Kingdom); Duer, Melinda J., E-mail: mjd13@cam.ac.uk [University of Cambridge, Department of Chemistry (United Kingdom)

    2015-10-15

    An appreciable level of isotope labelling is essential for future NMR structure elucidation of mammalian biomaterials, which are either poorly expressed, or unexpressable, using micro-organisms. We present a detailed protocol for high level {sup 13}C enrichment even in slow turnover murine biomaterials (fur keratin), using a customized diet supplemented with commercial labelled algal hydrolysate and formulated as a gel to minimize wastage, which female mice consumed during pregnancy and lactation. This procedure produced approximately eightfold higher fur keratin labelling in pups, exposed in utero and throughout life to label, than in adults exposed for the same period, showing both the effectiveness, and necessity, of this approach.

  13. Investigating lanthanide dopant distributions in Yttrium Aluminum Garnet (YAG) using solid state paramagnetic NMR.

    Science.gov (United States)

    McCarty, Ryan J; Stebbins, Jonathan F

    2016-10-01

    This paper demonstrates the approach of using paramagnetic effects observed in NMR spectra to investigate the distribution of lanthanide dopant cations in YAG (yttrium aluminum garnet, Y3Al5O12) optical materials, as a complimentary technique to optical spectroscopy and other standard methods of characterization. We investigate the effects of Ce(3+), Nd(3+), Yb(3+), Tm(3+), and Tm(3+)-Cr(3+) on (27)Al and (89)Y NMR spectra. We note shifted resonances for both AlO4 and AlO6 sites. In some cases, multiple shifted peaks are observable, and some of these can be empirically assigned to dopant cations in known configurations to the observed nuclides. In many cases, AlO6 peaks shifted by more than one magnetic neighbor can be detected. In general, we observe that the measured intensities of shifted resonances, when spinning sidebands are included, are consistent with predictions from models with dopant cations that are randomly distributed throughout the lattice. In at least one set of (27)Al spectra, we identify two sub-peaks possibly resulting from two paramagnetic cations with magnetically coupled spin states neighboring the observed nucleus. We identify systematic changes in the spectra related to known parameters describing the magnetic effects of lanthanide cations, such as larger shift distances when the expectation value of electron spins is greater. We lastly comment on the promise of this technique in future analyses of laser and other crystalline oxide materials. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Intermolecular alignment in Y145Stop human prion protein amyloid fibrils probed by solid-state NMR spectroscopy.

    Science.gov (United States)

    Helmus, Jonathan J; Surewicz, Krystyna; Apostol, Marcin I; Surewicz, Witold K; Jaroniec, Christopher P

    2011-09-07

    The Y145Stop mutant of human prion protein, huPrP23-144, has been linked to PrP cerebral amyloid angiopathy, an inherited amyloid disease, and also serves as a valuable in vitro model for investigating the molecular basis of amyloid strains. Prior studies of huPrP23-144 amyloid by magic-angle-spinning (MAS) solid-state NMR spectroscopy revealed a compact β-rich amyloid core region near the C-terminus and an unstructured N-terminal domain. Here, with the focus on understanding the higher-order architecture of huPrP23-144 fibrils, we probed the intermolecular alignment of β-strands within the amyloid core using MAS NMR techniques and fibrils formed from equimolar mixtures of (15)N-labeled protein and (13)C-huPrP23-144 prepared with [1,3-(13)C(2)] or [2-(13)C]glycerol. Numerous intermolecular correlations involving backbone atoms observed in 2D (15)N-(13)C spectra unequivocally suggest an overall parallel in-register alignment of the β-sheet core. Additional experiments that report on intermolecular (15)N-(13)CO and (15)N-(13)Cα dipolar couplings yielded an estimated strand spacing that is within ∼10% of the distances of 4.7-4.8 Å typical for parallel β-sheets.

  15. DNP-enhanced ultrawideline (207)Pb solid-state NMR spectroscopy: an application to cultural heritage science.

    Science.gov (United States)

    Kobayashi, Takeshi; Perras, Frédéric A; Murphy, Anna; Yao, Yao; Catalano, Jaclyn; Centeno, Silvia A; Dybowski, Cecil; Zumbulyadis, Nicholas; Pruski, Marek

    2017-03-14

    Dynamic nuclear polarization (DNP) is used to enhance the (ultra)wideline (207)Pb solid-state NMR spectra of lead compounds of relevance in the preservation of cultural heritage objects. The DNP SSNMR experiments enabled, for the first time, the detection of the basic lead carbonate phase of the lead white pigment by (207)Pb SSNMR spectroscopy. Variable-temperature experiments revealed that the short T'2 relaxation time of the basic lead carbonate phase hinders the acquisition of the NMR signal at room temperature. We additionally observe that the DNP enhancement is twice as large for lead palmitate (a lead soap, which is a degradation product implicated in the visible deterioration of lead-based oil paintings), than it is for the basic lead carbonate. This enhancement has allowed us to detect the formation of a lead soap in an aged paint film by (207)Pb SSNMR spectroscopy; which may aid in the detection of deterioration products in smaller samples removed from works of art.

  16. sup 3 sup 1 P high resolution solid state NMR studies of phosphoorganic compounds of biological interest

    CERN Document Server

    Potrzebowski, M J; Kazmierski, S

    2001-01-01

    In this review several applications of sup 3 sup 1 P high resolution solid state NMR spectroscopy in structural studies of bioorganic samples is recorded. The problem of pseudopolymorphism of bis[6-O,6'-O-(1,2:3,4diisopropylidene-alpha-D-galactopyranosyl) phosphothionyl] disulfide (1) and application of sup 3 sup 1 P C/MAS experiment to investigate of this phenomenon is discussed. The influence of weak C-H--S intermolecular contacts on molecular packing of 1,6-anhydro-2-O-tosyl-4-S- (5,5-dimethyl-2-thioxa-1,3,2-dioxaphosphophorinan-2-= yl)-beta-D-glucopyranose (2) and S sub P , R sub P diastereomers of deoxyxylothymidyl-3'-O-acetylthymidyl (3',5')-O-(2-cyanoethyl) phosphorothioate (3) and their implication on sup 3 sup 1 P NMR spectra is shown. The final part of review describes the recent progress in structural studies of O-phosphorylated amino acids (serine, threonine, tyrosine), relationship between molecular structure and sup 3 sup 1 P chemical shift parameters delta sub i sub i and influence of hydrogen ...

  17. Direct assessment of substrate binding to the Neurotransmitter:Sodium Symporter LeuT by solid state NMR

    Science.gov (United States)

    Erlendsson, Simon; Gotfryd, Kamil; Larsen, Flemming Hofmann; Mortensen, Jonas Sigurd; Geiger, Michel-Andreas; van Rossum, Barth-Jan; Oschkinat, Hartmut; Gether, Ulrik; Teilum, Kaare; Loland, Claus J

    2017-01-01

    The Neurotransmitter:Sodium Symporters (NSSs) represent an important class of proteins mediating sodium-dependent uptake of neurotransmitters from the extracellular space. The substrate binding stoichiometry of the bacterial NSS protein, LeuT, and thus the principal transport mechanism, has been heavily debated. Here we used solid state NMR to specifically characterize the bound leucine ligand and probe the number of binding sites in LeuT. We were able to produce high-quality NMR spectra of substrate bound to microcrystalline LeuT samples and identify one set of sodium-dependent substrate-specific chemical shifts. Furthermore, our data show that the binding site mutants F253A and L400S, which probe the major S1 binding site and the proposed S2 binding site, respectively, retain sodium-dependent substrate binding in the S1 site similar to the wild-type protein. We conclude that under our experimental conditions there is only one detectable leucine molecule bound to LeuT. DOI: http://dx.doi.org/10.7554/eLife.19314.001 PMID:28117663

  18. Direct observation of cell wall structure in living plant tissues by solid-state C NMR spectroscopy.

    Science.gov (United States)

    Jarvis, M C; Apperley, D C

    1990-01-01

    Solid-state (13)C nuclear magnetic resonance (NMR) spectra of the following intact plant tissues were recorded by the crosspolarization magic-angle spinning technique: celery (Apium graveolens L.) collenchyma; carob bean (Ceratonia siliqua L.), fenugreek (Trigonella foenum-graecum L.), and nasturtium (Tropaeolum majus L.) endosperm; and lupin (Lupinus polyphyllus Lindl.) seed cotyledons. All these tissues had thickened cell walls which allowed them to withstand the centrifugal forces of magic angle spinning and which, except in the case of lupin seeds, dominated the NMR spectra. The celery collenchyma cell walls gave spectra typical of dicot primary cell walls. The carob bean and fenugreek seed spectra were dominated by resonances from galactomannans, which showed little sign of crystalline order. Resonances from beta(1,4')-d galactan were visible in the lupin seed spectrum, but there was much interference from protein. The nasturtium seed spectrum was largely derived from a xyloglucan, in which the conformation of the glucan core chain appeared to be intermediate between the solution form and solid forms of cellulose.

  19. Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR

    Science.gov (United States)

    Basse, Kristoffer; Shankar, Ravi; Bjerring, Morten; Vosegaard, Thomas; Nielsen, Niels Chr.; Nielsen, Anders B.

    2016-09-01

    We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization (RESPIRATIONCP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the RESPIRATIONCP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous 15N → 13CO and 15N → 13Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability.

  20. Solvation and hydrogen bonding in alanine- and glycine-containing dipeptides probed using solution- and solid-state NMR spectroscopy.

    Science.gov (United States)

    Bhate, Manasi P; Woodard, Jaie C; Mehta, Manish A

    2009-07-15

    The NMR chemical shift is a sensitive reporter of peptide secondary structure and its solvation environment, and it is potentially rich with information about both backbone dihedral angles and hydrogen bonding. We report results from solution- and solid-state (13)C and (15)N NMR studies of four zwitterionic model dipeptides, L-alanyl-L-alanine, L-alanyl-glycine, glycyl-L-alanine, and glycyl-glycine, in which we attempt to isolate structural and environmental contributions to the chemical shift. We have mapped hydrogen-bonding patterns in the crystalline states of these dipeptides using the published crystal structures and correlated them with (13)C and (15)N magic angle spinning chemical shift data. To aid in the interpretation of the solvated chemical shifts, we performed ab initio quantum chemical calculations to determine the low-energy conformers and their chemical shifts. Assuming low energy barriers to interconversion between thermally accessible conformers, we compare the Boltzmann-averaged chemical shifts with the experimentally determined solvated-state shifts. The results allow us to correlate the observed differences in chemical shifts between the crystalline and solvated states to changes in conformation and hydrogen bonding that occur upon solvation.

  1. Probing physical and chemical changes in cortical bone due to osteoporosis and type 2 diabetes by solid-state NMR

    Science.gov (United States)

    Zhou, Donghua; Taylor, Amanda; Rendina, Beth; Smith, Brenda; Department of Physics Collaboration; Department of Nutritional Sciences Collaboration

    2013-03-01

    Approximately 1.5 million fractures occur each year in the U.S. due to osteoporosis, which is characterized by decreased bone mineral density and deterioration of bone micro-architecture. On the other hand, type 2 diabetes also significantly increases fracture risks, despite having a normal or even higher bone mineral density. Solid-state NMR has been applied to bone tissues from normal and disease-inflicted mouse models to study structural and chemical dynamics as the disease progresses. Proton relaxation experiments were performed to measure water populations in the bone matrix and pores. Collagen-bound water has strong influence on bone resilience, while water content in the pores reveals amount and size of pores from micro- to millimeter range. Other biochemical and atomic-scale structural alterations in the mineral and organic phases and their interface were investigated by proton, phosphorus, and carbon NMR spectroscopy. Experiments were designed to individually detect different types of phosphorus environments: near the mineral surface, similar to hydroxyapatite, and deficient of hydrogens due to substitution of the hydroxyl group by other ions. A new method was also developed for accurate quantification of each phosphorus species. The authors appreciate financial support for this project from the College of Human Sciences and the College of Arts and Sciences, Oklahoma State University.

  2. Direct assessment of substrate binding to the Neurotransmitter:Sodium Symporter LeuT by solid state NMR.

    Science.gov (United States)

    Erlendsson, Simon; Gotfryd, Kamil; Larsen, Flemming Hofmann; Mortensen, Jonas Sigurd; Geiger, Michel-Andreas; van Rossum, Barth-Jan; Oschkinat, Hartmut; Gether, Ulrik; Teilum, Kaare; Loland, Claus J

    2017-01-24

    The Neurotransmitter:Sodium Symporters (NSSs) represent an important class of proteins mediating sodium-dependent uptake of neurotransmitters from the extracellular space. The substrate binding stoichiometry of the bacterial NSS protein, LeuT, and thus the principal transport mechanism, has been heavily debated. Here we used solid state NMR to specifically characterize the bound leucine ligand and probe the number of binding sites in LeuT. We were able to produce high-quality NMR spectra of substrate bound to microcrystalline LeuT samples and identify one set of sodium-dependent substrate-specific chemical shifts. Furthermore, our data show that the binding site mutants F253A and L400S, which probe the major S1 binding site and the proposed S2 binding site, respectively, retain sodium-dependent substrate binding in the S1 site similar to the wild-type protein. We conclude that under our experimental conditions there is only one detectable leucine molecule bound to LeuT.

  3. Study of ion diffusional motion in ionic liquid-based polymer electrolytes by simultaneous solid state NMR and DTA.

    Science.gov (United States)

    Rajput, Dushyant Singh; Yamada, Koji; Sekhon, S S

    2013-02-28

    Polymer electrolytes containing ionic liquid (IL), 2-methyl-1,3-dipropylimidazolium dihydrogenphosphate (MDPImH2PO4) have been studied by (1)H solid state NMR and differential thermal analysis (DTA) simultaneously by using a specially designed probe. To the best of our knowledge, this is the first report of its kind for IL based polymer electrolytes. The variation of NMR line width with temperature for the IL and polymer electrolytes shows line narrowing at the glass transition and melting temperature. The onset of long-range ion diffusional motion also takes place at these temperatures and is accompanied by a sudden increase in ionic conductivity value by 2-3 orders of magnitude. The presence of amorphous and crystalline phases in IL-based polymer electrolytes has been observed from X-ray diffraction (XRD) studies, and the amorphous phase is the high conducting phase in these polymer electrolytes. The IL-based polymer electrolytes have been observed to be thermally stable up to 200 °C. The results obtained from ion transport studies have also been supported by Fourier transform infrared (FTIR), XRD, and cyclic voltammetry (CV) studies.

  4. Variability of cork from Portuguese Quercus suber studied by solid-state (13)C-NMR and FTIR spectroscopies.

    Science.gov (United States)

    Lopes, M H; Barros, A S; Pascoal Neto, C; Rutledge, D; Delgadillo, I; Gil, A M

    2001-01-01

    A new approach is presented for the study of the variability of Portuguese reproduction cork using solid-state (13)C-NMR spectroscopy and photoacoustic (PAS) FTIR (FTIR-PAS) spectroscopy combined with chemometrics. Cork samples were collected from 12 different geographical sites, and their (13)C-cross-polarization with magic angle spinning (CP/MAS) and FTIR spectra were registered. A large spectral variability among the cork samples was detected by principal component analysis and found to relate to the suberin and carbohydrate contents. This variability was independent of the sample geographical origin but significantly dependent on the cork quality, thus enabling the distinction of cork samples according to the latter property. The suberin content of the cork samples was predicted using multivariate regression models based on the (13)C-NMR and FTIR spectra of the samples as reported previously. Finally, the relationship between the variability of the (13)C-CP/MAS spectra with that of the FTIR-PAS spectra was studied by outer product analysis. This type of multivariate analysis enabled a clear correlation to be established between the peaks assigned to suberin and carbohydrate in the FTIR spectrum and those appearing in the (13)C-CP/MAS spectra.

  5. Using solid-state NMR to monitor the molecular consequences of Cryptococcus neoformans melanization with different catecholamine precursors.

    Science.gov (United States)

    Chatterjee, Subhasish; Prados-Rosales, Rafael; Frases, Susana; Itin, Boris; Casadevall, Arturo; Stark, Ruth E

    2012-08-07

    Melanins are a class of natural pigments associated with a wide range of biological functions, including microbial virulence, energy transduction, and protection against solar radiation. Because of their insolubility and structural heterogeneity, solid-state nuclear magnetic resonance (NMR) spectroscopy provides an unprecedented means to define the molecular architecture of these enigmatic pigments. The requirement of obligatory catecholamines for melanization of the pathogenic fungus Cryptococcus neoformans also offers unique opportunities for investigating melanin development. In the current study, pigments produced with L-dopa, methyl-L-dopa, epinephrine, and norepinephrine precursors are compared structurally using (13)C and (1)H magic-angle spinning (MAS) NMR. Striking structural differences were observed for both aromatic and aliphatic molecular constituents of the mature fungal pigment assemblies, thus making it possible to redefine the molecular prerequisites for formation of the aromatic domains of insoluble indole-based biopolymers, to rationalize their distinctive physical characteristics, and to delineate the role of cellular constituents in assembly of the melanized macromolecules with polysaccharides and fatty acyl chain-containing moieties. By achieving an augmented understanding of the mechanisms of C. neoformans melanin biosynthesis and cellular assembly, such studies can guide future drug discovery efforts related to melanin-associated virulence, resistance to tumor therapy, and production of melanin mimetics under cell-free conditions.

  6. Quantitative analysis of Bordeaux red wine precipitates by solid-state NMR: Role of tartrates and polyphenols.

    Science.gov (United States)

    Prakash, Shipra; Iturmendi, Nerea; Grelard, Axelle; Moine, Virginie; Dufourc, Erick

    2016-05-15

    Stability of wines is of great importance in oenology matters. Quantitative estimation of dark red precipitates formed in Merlot and Cabernet Sauvignon wine from Bordeaux region for vintages 2012 and 2013 was performed during the oak barrel ageing process. Precipitates were obtained by placing wine at -4°C or 4°C for 2-6 days and monitored by periodic sampling during a one-year period. Spectroscopic identification of the main families of components present in the precipitate powder was performed with (13)C solid-state CPMAS NMR and 1D and 2D solution NMR of partially water re-solubilized precipitates. The study revealed that the amount of precipitate obtained is dependent on vintage, temperature and grape variety. Major components identified include potassium bitartrate, polyphenols, polysaccharides, organic acids and free amino acids. No evidence was found for the presence of proteins. The influence of main compounds found in the precipitates is discussed in relation to wine stability.

  7. Molecular Insights into Covalently Stained Carious Dentine Using Solid-State NMR and ToF-SIMS.

    Science.gov (United States)

    Almhöjd, Ulrica S; Lingström, Peter; Nilsson, Åke; Norén, Jörgen G; Siljeström, Sandra; Östlund, Åsa; Bernin, Diana

    2017-01-01

    Dyes currently used to stain carious dentine have a limited capacity to discriminate normal dentine from carious dentine, which may result in overexcavation. Consequently, finding a selective dye is still a challenge. However, there is evidence that hydrazine-based dyes, via covalent bonds to functional groups, bind specifically to carious dentine. The aim of this study was to investigate the possible formation of covalent bonds between carious dentine and 15N2-hydrazine and the hydrazine-based dye, 15N2-labelled Lucifer Yellow, respectively. Powdered dentine from extracted carious and normal teeth was exposed to the dyes, and the staining reactions were analysed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), solid-state 13C-labelled nuclear magnetic resonance (NMR) and 15N-NMR spectroscopy. The results showed that 15N2-hydrazine and 15N2-labelled Lucifer Yellow both bind to carious dentine but not to normal dentine. It can thus be concluded that hydrazine-based dyes can be used to stain carious dentine and leave normal dentine unstained. © 2017 S. Karger AG, Basel.

  8. Mechanistic insight into formation and changes of nanoparticles in MgF2 sols evidenced by liquid and solid state NMR.

    Science.gov (United States)

    Karg, M; Scholz, G; König, R; Kemnitz, E

    2012-02-28

    The fluorolytic sol-gel reaction of magnesium methoxide with HF in methanol was studied by (19)F, (1)H and (13)C liquid and solid state NMR. In (19)F NMR five different species were identified, three of which belong to magnesium fluoride nanoparticles, i.e. NMR gave access to local structures of solid particles in suspensions. The long-term evolution of (19)F signals was followed and along with (19)F MAS NMR experiments of sols rotating at 13 kHz mechanistic insights into the ageing processes were obtained.

  9. Investigation of Ti-doped NaAlH4 by solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, R; Majzoub, E; Herberg, J

    2003-11-24

    In recent years, the development of Ti-doped NaAlH{sub 4} as a hydrogen storage material has gained attention because of its large weight percentage of hydrogen ({approx}5%) compared to traditional interstitial hydrides. The addition of transition-metal dopants, in the form of Ti-halides, such as TiCl{sub 3}, dramatically improves the kinetics of the absorption and desorption of hydrogen from NaAlH{sub 4}. However, the role that Ti plays in enhancing the absorption and desorption of H{sub 2} is still unknown. In the present study, {sup 27}Al, {sup 23}Na, and {sup 1}H MAS (Magic Angle Spinning) NMR (Nuclear Magnetic Resonance) has been performed to understand the titanium speciation in Ti-doped NaAlH{sub 4}. All experiments were performed on a sample of crushed single crystals exposed to Ti during growth, a sample of solvent-mixed 4TiCl{sub 3} + 112NaAlH{sub 4}, a reacted sample of solvent-mixed TiCl{sub 3} + {sup 3}NaAlH{sub 4} with THF, and a reacted sample of ball-milled TiCl3 + 3NaAlH{sub 4}. The {sup 27}Al MAS NMR has shown differences in compound formation between solvent-mixed TiCl{sub 3} + 3NaAlH{sub 4} with THF and the mechanically ball-milled TiCl{sub 3} + 3NaAlH{sub 4}. {sup 27}Al MAS NMR of the mechanically ball-milled mixture of fully-reacted TiCl{sub 3} + 3NaAlH{sub 4} showed spectral signatures of TiAl{sub 3} while, the solvent-mixed 4TiCl{sub 3} + 112NaAlH{sub 4}, which is totally reacted, does not show the presences of TiAl{sub 3}, but shows the existence of Al{sub 2}O{sub 3}.

  10. Solid-state NMR characterization of pyrene-cuticular matter interactions.

    Science.gov (United States)

    Sachleben, Joseph R; Chefetz, Benny; Deshmukh, Ashish; Hatcher, Patrick G

    2004-08-15

    One- and two-dimensional nuclear magnetic resonance (NMR) experiments were performed on Agave americana cutan and tomato cutin to examine the interactions between a hydrophobic pollutant, pyrene, and cuticular material. Variable-temperature NMR experiments show that cutan, an acid- and base-resistant cuticular biopolymer, undergoes the characteristic melting behavior of "polyethylene-like" crystallites, while the tomato cutin does not. The melting point of A. americana cutan was found to be approximately 360 K, which is consistent with the thickness of the polyethylene crystallites of 30-40 methylene units. Sorption models predict that the sorption behavior of hydrophobic pollutants should depend on the phase of the cuticular material. 13C NMR experiments on labeled pyrene were performed. The 13C T1 of pyrene decreases significantly from that of crystalline pyrene upon sorption to both tomato fruit cutin and A. americana cutan, indicating that the pyrene is mobile upon sorption. Magic angle spinning experiments at low spinning frequencies (2-4 kHz) provided the chemical shift anisotropy (CSA) parameters delta, the anisotropy, and eta, the asymmetry parameter, for crystalline and sorbed pyrene. For crystalline pyrene, two types of crystallographically distinctive pyrenes were observed. The first had delta = -97.4+/-0.5 ppm and eta = 0.934+/-0.006, while the second had delta = -98.1+/-0.5 ppm and eta = 0.823+/-0.008. After sorption to cutan, these CSA parameters were found to be delta = -78.9+/-5.3 ppm and eta < 0.70 independent of the length of time since completion of the sorption procedure. In tomato cutin, the CSA parameters were found to be dependent upon the time since completion of the sorption procedure. One and one-half months after sorption, delta was found to have a value of -30.4 ppm < delta < 0.0 ppm and eta was undeterminable, while after 22 months these values become delta = -80.0 +/-3.3 ppm and eta< 0.42. These changes in the CSA parameters

  11. Mechanism of Solid-State Thermolysis of Ammonia Boraine: 15N NMR Study Using Fast Magic-Angle Spinning and Dynamic Nuclear Polarization

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Takeshi [Ames Laboratory; Gupta, Shalabh [Ames Laboratory; Caporini, Marc A [Bruker BioSpin Corporation; Pecharsky, Vitalij K [Ames Laboratory; Pruski, Marek [Ames Laboratory

    2014-08-28

    The solid-state thermolysis of ammonia borane (NH3BH3, AB) was explored using state-of-the-art 15N solid-state NMR spectroscopy, including 2D indirectly detected 1H{15N} heteronuclear correlation and dynamic nuclear polarization (DNP)-enhanced 15N{1H} cross-polarization experiments as well as 11B NMR. The complementary use of 15N and 11B NMR experiments, supported by density functional theory calculations of the chemical shift tensors, provided insights into the dehydrogenation mechanism of AB—insights that have not been available by 11B NMR alone. Specifically, highly branched polyaminoborane derivatives were shown to form from AB via oligomerization in the “head-to-tail” manner, which then transform directly into hexagonal boron nitride analog through the dehydrocyclization reaction, bypassing the formation of polyiminoborane.

  12. Sensitivity-enhanced solid-state NMR detection of expansin's target in plant cell walls

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tuo [Iowa State Univ., Ames, IA (United States); Park, Yong Bum [Pennsylvania State Univ., State College, PA (United States); Caporini, Marc A. [Bruker Biospin Corporation, Billerica, MA (United States); Rosay, Melanie [Bruker Biospin Corporation, Billerica, MA (United States); Zhong, Linghao [Pennsylvania State Univ., State College, PA (United States); Cosgrove, Daniel J. [Pennsylvania State Univ., State College, PA (United States); Hong, Mei [Iowa State Univ., Ames, IA (United States)

    2013-08-29

    Structure determination of protein binding to noncrystalline macromolecular assemblies such as plant cell walls (CWs) poses a significant structural biology challenge. CWs are loosened during growth by expansin proteins, which weaken the noncovalent network formed by cellulose, hemicellulose, and pectins, but the CW target of expansins has remained elusive because of the minute amount of the protein required for activity and the complex nature of the CW. Using solid-state NMR spectroscopy, combined with sensitivity-enhancing dynamic nuclear polarization (DNP) and differential isotopic labeling of expansin and polysaccharides, we have now determined the functional binding target of expansin in the Arabidopsis thaliana CW. By transferring the electron polarization of a biradical dopant to the nuclei, DNP allowed selective detection of 13C spin diffusion from trace concentrations of 13C, 15N-labeled expansin in the CW to nearby polysaccharides. From the spin diffusion data of wild-type and mutant expansins, we conclude that to loosen the CW, expansin binds highly specific cellulose domains enriched in xyloglucan, whereas more abundant binding to pectins is unrelated to activity. Molecular dynamics simulations indicate short 13C-13C distances of 4–6 Å between a hydrophobic surface of the cellulose microfibril and an aromatic motif on the expansin surface, consistent with the observed NMR signals. DNP-enhanced 2D 13C correlation spectra further reveal that the expansin-bound cellulose has altered conformation and is enriched in xyloglucan, thus providing unique insight into the mechanism of CW loosening. DNP-enhanced NMR provides a powerful, generalizable approach for investigating protein binding to complex macromolecular targets.

  13. Solid state 13C NMR studies of methane dehydroaromatization reaction on Mo/HZSM-5 and W/HZSM-5 catalysts.

    Science.gov (United States)

    Yang, Jun; Ma, Ding; Deng, Feng; Luo, Qing; Zhang, Mingjin; Bao, Xinhe; Ye, Chaohui

    2002-12-21

    Methane dehydroaromatization on Mo/HZSM-5 and W/HZSM-5 catalysts was studied by solid state 13C NMR spectroscopy, both variation of the state of transition metal component and products such as ethane, benzene, ethene adsorbed on or in zeolite were observed after high temperature (900-1000 K) reaction.

  14. High-resolution solid-state {sup 13}C and {sup 15}N NMR spectroscopy of pyrazole and 3,5-dimethylpyrazole adsorbed on alumina and silica

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar-Parrilla, F.; Limbach, H.H. [Ciudad Universitaria, Madrid (Spain); Claramunt, R.M. [Instituto de Quimica Medica, Madrid (Spain)] [and others

    1994-09-01

    Using pyrazole and 3,5-dimethylpyrazole mixtures with alumina and silica, high-resolution solid state {sup 13}C and {sup 15}N CPMAS NMR was performed to compare the spectra. The NH-N proton tautomers resulting depend strongly on the environment. 70 refs., 8 figs., 4 tabs.

  15. Exploration of structure and function in biomolecules through solid-state NMR and computational methods

    Science.gov (United States)

    Heider, Elizabeth M.

    Solid-State Nuclear Magnetic Resonance (SSNMR) spectroscopy and quantum mechanical calculations are powerful analysis tools. Leveraged independently, each method yields important nuclear and molecular information. Used in concert, SSNMR and computational techniques provide complementary data about the structure of solids. These methods are particularly useful in characterizing the structures of microcrystalline organic compounds and revealing mechanisms of biological activity. Such applications may possess special relevance in analysis of pharmaceutical products; 90% of all pharmaceuticals are marketed as solids and bioactivity is strongly linked with molecular conformation. Accordingly, this dissertation employs both SSNMR and quantum mechanical computation to study three bioactive molecules: citrinin, two forms of Atrasentan (Abt-627), and paclitaxel (Taxol RTM). First, a computational study is utilized to determine the mechanism for unusual antioxidant activity in citrinin. Here, molecular geometries and bond dissociation enthalpies (BDE) of the citrinin O--H groups are calculated from first principles (ab initio). The total molecular Hamiltonian is determined by approximating the individual contributors to energy including electronic energy and contributions from modes of molecular vibration. This study of citrinin clearly identifies specific reaction sites in the active form, establishing the central role of intramolecular hydrogen bonding in this activity. Notably, it is discovered that citrinin itself is not the active species. Instead, a pair of hydrated Michael addition products of citrinin act as radical scavengers via O--H bond dissociation. Next, two separate compounds of the anticancer drug Abt-627 (form I and form II) are examined via SSNMR. The three principal values of the 13C diagonalized chemical shift tensor are acquired through the high resolution 2D experiment, FIREMAT. Isotropic chemical shift assignments are made utilizing both dipolar

  16. Determination of structural topology of a membrane protein in lipid bilayers using polarization optimized experiments (POE) for static and MAS solid state NMR spectroscopy.

    Science.gov (United States)

    Mote, Kaustubh R; Gopinath, T; Veglia, Gianluigi

    2013-10-01

    The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments, for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ~0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional oriented solid-state NMR and magic angle spinning solid-state NMR.

  17. Determination of structural topology of a membrane protein in lipid bilayers using polarization optimized experiments (POE) for static and MAS solid state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mote, Kaustubh R. [University of Minnesota, Department of Chemistry (United States); Gopinath, T. [University of Minnesota, Department of Biochemistry, Molecular Biology and Biophysics (United States); Veglia, Gianluigi, E-mail: vegli001@umn.edu [University of Minnesota, Department of Chemistry (United States)

    2013-10-15

    The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments, for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD {approx}0.44 A, a tilt angle of 24 Degree-Sign {+-} 1 Degree-Sign , and an azimuthal angle of 55 Degree-Sign {+-} 6 Degree-Sign . This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional oriented solid-state NMR and magic angle spinning solid-state NMR.

  18. Solid-state (13)C NMR and synchrotron SAXS/WAXS studies of uniaxially-oriented polyethylene.

    Science.gov (United States)

    Afeworki, Mobae; Brant, Pat; Lustiger, Arnold; Norman, Alexander

    2015-11-01

    We report solid-state (13)C NMR and synchrotron wide-and small-angle X-ray scattering experiments (WAXS, SAXS) on metallocene linear low density polyethylene films (e.g., Exceed™ 1018 mLLDPE; nominally 1MI, 0.918 density ethylene-hexene metallocene copolymer) as a function of uniaxial draw ratio, λ. Combined, these experiments provide an unambiguous, quantitative molecular view of the orientation of both the crystalline and amorphous phases in the samples as a function of draw. Together with previously reported differential scanning calorimetry (DSC), gas transport measurements, transmission electron microscopy (TEM), optical birefringence, small angle X-ray scattering (SAXS) as well as other characterization techniques, this study of the state of orientation in both phases provides insight concerning the development of unusually high barrier properties of the most oriented samples (λ=10). In this work, static (non-spinning) solid-state NMR measurements indicate that in the drawn Exceed(TM) films both the crystalline and amorphous regions are highly oriented. In particular, chemical shift data show the amorphous phase is comprised increasingly of so-called "taut tie chains" (or tie chains under any state of tautness) in the mLLDPE with increasing draw ratio - the resonance lines associated with the amorphous phase shift to where the crystalline peaks are observed. In the sample with highest total draw (λ=10), virtually all of the chains in the non-crystalline region have responded and aligned in the machine (draw) direction. Both monoclinic and orthorhombic crystalline peaks are observed in high-resolution, solid-state magic-angle spinning (MAS) NMR measurements of the oriented PE films. The orientation is comparable to that obtained for ultra-high molecular weight HDPE fibers described as "ultra-oriented" in the literature. Furthermore, the presence of a monoclinic peak in cold-drawn samples suggests that there is an appreciable internal stress associated

  19. Solid-state NMR Study of Ion Adsorption and Charge Storage in Graphene Film Supercapacitor Electrodes

    Science.gov (United States)

    Li, Kecheng; Bo, Zheng; Yan, Jianhua; Cen, Kefa

    2016-12-01

    Graphene film has been demonstrated as promising active materials for electric double layer capacitors (EDLCs), mainly due to its excellent mechanical flexibility and freestanding morphology. In this work, the distribution and variation pattern of electrolyte ions in graphene-film based EDLC electrodes are investigated with a 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. For neutral graphene films soaked with different amounts of electrolytes (1 M TEABF4/ACN), weakly and strongly adsorbed anions are identified based on the resonances at different 11B chemical shifts. Unlike other porous carbonaceous materials, the strongly adsorbed anions are found as the major electrolyte anions components in graphene films. Further measurements on the ion population upon charging are carried out with applying different charging voltages on the graphene films. Results indicate that the charging process of graphene-film based EDLCs can be divided into two distinct charge storage stages (i.e., ejection of co-ions and adsorption of counter-ions) for different voltages. The as-obtained results will be useful for the design and fabrication of high performance graphene-film based EDLCs.

  20. Solid state 1H NMR studies of cell wall materials of potatoes

    Science.gov (United States)

    Tang, Huiru; Belton, Peter S.; Ng, Annie; Waldron, Keith W.; Ryden, Peter

    1999-04-01

    Cell wall materials from potatoes ( Solanum tuberosum) prepared by two different methods have been studied using NMR proton relaxation times. Spin lattice relaxation in both the rotating and laboratory frames as well as transverse relaxation have been measured over a range of temperatures and hydration levels. It was observed that the sample prepared using a DMSO extraction showed anomalous behaviour of spin lattice relaxation in the laboratory frame probably due to residual solvent in the sample. Spin lattice relaxation in the laboratory frame is the result of hydroxymethyl rotation and another unidentified high frequency motion. In the rotating frame relaxation is adequately explained by hydroxymethyl rotation alone. In neither experiment is methyl group rotation observed, calculation suggests that this is due to the low density of methyl groups in the sample. Non-freezing water in potato cell walls, α-cellulose and pectin was found about 0.2, 0.04 and 0.18 g per gram dry matter, indicating preferable hydration of pectin compared to cellulose. The effects of hydration are most noticeable in the measurements that reflect low frequency motions, particularly transverse relaxation, where both second moments and the relative intensity of signals arising from immobile material are reduced by hydration.

  1. On the exactness of effective Floquet Hamiltonians employed in solid-state NMR spectroscopy

    Science.gov (United States)

    Garg, Rajat; Ramachandran, Ramesh

    2017-05-01

    Development of theoretical models based on analytic theory has remained an active pursuit in molecular spectroscopy for its utility both in the design of experiments as well as in the interpretation of spectroscopic data. In particular, the role of "Effective Hamiltonians" in the evolution of theoretical frameworks is well known across all forms of spectroscopy. Nevertheless, a constant revalidation of the approximations employed in the theoretical frameworks is necessitated by the constant improvements on the experimental front in addition to the complexity posed by the systems under study. Here in this article, we confine our discussion to the derivation of effective Floquet Hamiltonians based on the contact transformation procedure. While the importance of the effective Floquet Hamiltonians in the qualitative description of NMR experiments has been realized in simpler cases, its extension in quantifying spectral data deserves a cautious approach. With this objective, the validity of the approximations employed in the derivation of the effective Floquet Hamiltonians is re-examined through a comparison with exact numerical methods under differing experimental conditions. The limitations arising from the existing analytic methods are outlined along with remedial measures for improving the accuracy of the derived effective Floquet Hamiltonians.

  2. Solid state NMR and bioequivalence comparison of the pharmacokinetic parameters of two formulations of clindamycin

    KAUST Repository

    Al-Talla, Zeyad

    2011-01-01

    Objective: The purpose of this study was to compare the pharmacokinetic parameters and determine the bioequivalence of a generic formulation of clindamycin that is sold in the local markets in the Middle East (Clindox® 150 mg capsule; test) with a reference formulation (Dalacin C® 150 mg capsule) in healthy adult male volunteers. Methods: A single-dose, open-label, 2-period crossover study was conducted. Healthy male volunteers were randomly assigned to oral administration of a single treatment of the reference and test formulations. The same groups were given the alternate formulation. After dosing, serial blood samples were withdrawn for a period of 24 h. Serum harvested from the blood samples was analyzed for clindamycin by high performance liquid chromatography (HPLC) with ultraviolet detection. Pharmacokinetic parameters, including AUC0-∞, AUC 0-t, Cmax, Ke, tmax and t 1/2 were determined from the serum concentrations for both formulations (test and reference). The products were tested for bioequivalence after log-transformation of the data. Results: 24 healthy adult male volunteers from Jordan (mean [SD] age, 28.8 (7.7) years (range 19-45 years); height, 175.8 (10.6) cm (range 159.0-192.0 cm); weight, 75.6 (11.0) kg (range 58-101 kg); and body mass index, 24.4 (1.8) kg/m2 (range 21.3-28 kg/m2)) were enrolled in and completed the study. The 13C NMR spectra for both Dalacin C® and Clindox® showed 18 distinct lines associated with the 18 different carbon atoms. Conclusion: The statistical comparison suggested that Clindox® capsules are bioequivalent to Dalacin C® capsules. The 13C CPMAS results confirmed that the two drugs exhibit typical clindamycin spectra. ©2011 Dustri-Verlag Dr. K. Feistle.

  3. Dynamics of Hydrophobic Core Phenylalanine Residues Probed by Solid-State Deuteron NMR

    Energy Technology Data Exchange (ETDEWEB)

    Vugmeyster, Liliya; Ostrovsky, Dmitry; Villafranca, Toni; Sharp, Janelle; Xu, Wei; Lipton, Andrew S.; Hoatson, Gina; Vold, Robert L.

    2015-11-03

    We conducted a detailed investigation of the dynamics of two phenylalanine side chains in the hydrophobic core of the villin headpiece subdomain protein (HP36) in the hydrated powder state over the 298–80 K temperature range. We utilized static deuteron NMR measurements of longitudinal relaxation and line shapes supplemented with computational modeling. The temperature dependence of the relaxation times reveals the presence of two main mechanisms that can be attributed to the ring-flips, dominating at high temperatures, and small-angle fluctuations, dominating at low temperatures. The relaxation is non- exponential at all temperatures with the extent of non-exponentiality increasing from higher to lower temperatures. This behavior suggests a distribution of conformers with unique values of activation energies. The central values of the activation energies for the ring-flipping motions are among the smallest reported for aromatic residues in peptides and proteins and point to a very mobile hydrophobic core. The analysis of the widths of the distributions, in combination with the earlier results on the dynamics of flanking methyl groups (Vugmeyster et al., J. Phys. Chem. 2013, 117, 6129–6137), suggests that the hydrophobic core undergoes concerted fluctuations. There is a pronounced effect of dehydration on the ring-flipping motions, which shifts the distribution toward more rigid conformers. The cross-over temperature between the regions of dominance of the small-angle fluctuations and ring-flips shifts from 195 K in the hydrated protein to 278 K in the dry one. This result points to the role of solvent in the onset of the concerted fluctuations of the core and highlights aromatic residues as markers of the protein dynamical transitions.

  4. An efficient 2D (11)B-(11)B solid-state NMR spectroscopy strategy for monitoring covalent self-assembly of boronic acid-derived compounds: the transformation and unique architecture of bortezomib molecules in the solid state.

    Science.gov (United States)

    Brus, J; Czernek, J; Urbanova, M; Kobera, L; Jegorov, A

    2016-12-21

    The difficulty in the prediction of the complicated solid-state structure of boronic acid derivatives, resulting from the complex pathway of reversible covalent interactions, represents a significant obstacle to the development of a new generation of advanced supramolecular systems such as covalent organic frameworks of efficient anticancer drugs. In this contribution, various 2D (11)B-(11)B solid-state NMR correlation techniques supported by DFT calculations were explored to formulate a reliable tool for monitoring the covalent assembly of boronic acid residues in the solid state. This way, the self-condensation of bortezomib molecules was investigated, different local constitutions of boroxine motifs were unveiled, and the previously unreported boroxine structures of bortezomib polymorphs exhibiting secondary coordination were discovered and described in detail. The recorded (11)B NMR parameters responded sensitively to subtle changes in the local geometries, which were reliably interpreted and directly visualized by the DFT calculations. A uniform 2.6 Å distance in bortezomib (11)B-(11)B spin pairs was conclusively identified by the through-space (11)B-(11)B double-quantum (DQ) coherence build-up curves, whereas distinct 2D (11)B-(11)B DQ correlation patterns revealed unique boroxine structures existing in the crystalline as well as amorphous state. The boroxine rings were found to be internally stabilized through the transformation of the trigonal boron sites toward tetrahedral geometry, as the secondary five-membered rings were formed. This way, the nature of bortezomib polymorphism is disclosed, and an efficient strategy for exploring the assembly of boronic acid derivatives in the solid state, for which no crystallographic data are available, is thus demonstrated.

  5. Significance of symmetry in the nuclear spin Hamiltonian for efficient heteronuclear dipolar decoupling in solid-state NMR: A Floquet description of supercycled rCW schemes

    Science.gov (United States)

    Equbal, Asif; Shankar, Ravi; Leskes, Michal; Vega, Shimon; Nielsen, Niels Chr.; Madhu, P. K.

    2017-03-01

    Symmetry plays an important role in the retention or annihilation of a desired interaction Hamiltonian in NMR experiments. Here, we explore the role of symmetry in the radio-frequency interaction frame Hamiltonian of the refocused-continuous-wave (rCW) pulse scheme that leads to efficient 1H heteronuclear decoupling in solid-state NMR. It is demonstrated that anti-periodic symmetry of single-spin operators (Ix, Iy, Iz) in the interaction frame can lead to complete annihilation of the 1H-1H homonuclear dipolar coupling effects that induce line broadening in solid-state NMR experiments. This symmetry also plays a critical role in cancelling or minimizing the effect of 1H chemical-shift anisotropy in the effective Hamiltonian. An analytical description based on Floquet theory is presented here along with experimental evidences to understand the decoupling efficiency of supercycled (concatenated) rCW scheme.

  6. Structural Basis for Asymmetric Conductance of the Influenza M2 Proton Channel Investigated by Solid-State NMR Spectroscopy.

    Science.gov (United States)

    Mandala, Venkata S; Liao, Shu-Yu; Kwon, Byungsu; Hong, Mei

    2017-07-07

    The influenza M2 protein forms an acid-activated proton channel that is essential for virus replication. The transmembrane H37 selects for protons under low external pH while W41 ensures proton conduction only from the N terminus to the C terminus and prevents reverse current under low internal pH. Here, we address the molecular basis for this asymmetric conduction by investigating the structure and dynamics of a mutant channel, W41F, which permits reverse current under low internal pH. Solid-state NMR experiments show that W41F M2 retains the pH-dependent α-helical conformations and tetrameric structure of the wild-type (WT) channel but has significantly altered protonation and tautomeric equilibria at H37. At high pH, the H37 structure is shifted toward the π tautomer and less cationic tetrads, consistent with faster forward deprotonation to the C terminus. At low pH, the mutant channel contains more cationic tetrads than the WT channel, consistent with faster reverse protonation from the C terminus. (15)N NMR spectra allow the extraction of four H37 pKas and show that the pKas are more clustered in the mutant channel compared to WT M2. Moreover, binding of the antiviral drug, amantadine, at the N-terminal pore at low pH did not convert all histidines to the neutral state, as seen in WT M2, but left half of all histidines cationic, unambiguously demonstrating C-terminal protonation of H37 in the mutant. These results indicate that asymmetric conduction in WT M2 is due to W41 inhibition of C-terminal acid activation by H37. When Trp is replaced by Phe, protons can be transferred to H37 bidirectionally with distinct rate constants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Revisiting spin-lattice relaxation time measurements for dilute spins in high-resolution solid-state NMR spectroscopy

    Science.gov (United States)

    Fu, Riqiang; Li, Jun; Cui, Jingyu; Peng, Xinhua

    2016-07-01

    Numerous nuclear magnetic resonance (NMR) measurements of spin-lattice relaxation times (T1S) for dilute spins such as 13C have led to investigations of the motional dynamics of individual functional groups in solid materials. In this work, we revisit the Solomon equations and analyze how the heteronuclear cross relaxation between the dilute S (e.g. 13C) and abundant I (e.g. 1H) spins affects the measured T1S values in solid-state NMR in the absence of 1H saturation during the recovery time. It is found theoretically that at the beginning of the S spin magnetization recovery, the existence of non-equilibrium I magnetization introduces the heteronuclear cross relaxation effect onto the recovery of the S spin magnetization and confirmed experimentally that such a heteronuclear cross relaxation effect results in the recovery overshoot phenomena for the dilute spins when T1S is on the same order of T1H, leading to inaccurate measurements of the T1S values. Even when T1S is ten times larger than T1H, the heteronuclear cross relaxation effect on the measured T1S values is still noticeable. Furthermore, this cross relaxation effect on recovery trajectory of the S spins can be manipulated and even suppressed by preparing the initial I and S magnetization, so as to obtain the accurate T1S values. A sample of natural abundance L-isoleucine powder has been used to demonstrate the T1S measurements and their corresponding measured T1C values under various experimental conditions.

  8. Exploring the salt–cocrystal continuum with solid-state NMR using natural-abundance samples: implications for crystal engineering

    Directory of Open Access Journals (Sweden)

    Lalit Rajput

    2017-07-01

    Full Text Available There has been significant recent interest in differentiating multicomponent solid forms, such as salts and cocrystals, and, where appropriate, in determining the position of the proton in the X—H...A—Y X−...H—A+—Y continuum in these systems, owing to the direct relationship of this property to the clinical, regulatory and legal requirements for an active pharmaceutical ingredient (API. In the present study, solid forms of simple cocrystals/salts were investigated by high-field (700 MHz solid-state NMR (ssNMR using samples with naturally abundant 15N nuclei. Four model compounds in a series of prototypical salt/cocrystal/continuum systems exhibiting {PyN...H—O—}/{PyN+—H...O−} hydrogen bonds (Py is pyridine were selected and prepared. The crystal structures were determined at both low and room temperature using X-ray diffraction. The H-atom positions were determined by measuring the 15N—1H distances through 15N-1H dipolar interactions using two-dimensional inversely proton-detected cross polarization with variable contact-time (invCP-VC 1H→15N→1H experiments at ultrafast (νR ≥ 60–70 kHz magic angle spinning (MAS frequency. It is observed that this method is sensitive enough to determine the proton position even in a continuum where an ambiguity of terminology for the solid form often arises. This work, while carried out on simple systems, has implications in the pharmaceutical industry where the salt/cocrystal/continuum condition of APIs is considered seriously.

  9. Operando Solid-State NMR Observation of Solvent-Mediated Adsorption-Reaction of Carbohydrates in Zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Long; Alamillo, Ricardo; Elliott, William A.; Andersen, Amity; Hoyt, David W.; Walter, Eric D.; Han, Kee Sung; Washton, Nancy M.; Rioux, Robert M.; Dumesic, James A.; Scott, Susannah L.

    2017-03-31

    In the liquid-phase catalytic processing of molecules using heterogeneous catalysts - an important strategy for obtaining renewable chemicals from biomass - many of the key reactions occur at solid-liquid interfaces. In particular, glucose isomerization occurs when the glucose is adsorbed in the micropores of a zeolite catalyst. Since solvent molecules are coadsorbed, the catalytic activity depends strongly and often nonmonotonically on the solvent composition. For glucose isomerization catalyzed by NaX and NaY zeolites, there is an initial steep decline when water is mixed with a small amount of the organic cosolvent γ-valerolactone (GVL), followed by a dramatic and surprising recovery as the GVL content in the mixed solvent increases. Here we elucidate the origin of this complex solvent effect using operando solid-state NMR spectroscopy. The glucopyranose tautomers immobilized in the zeolite pores were observed and their transformations into fructose and mannose followed in real time. The microheterogeneity of the solvent system, manifested by a nonmonotonic trend in the mixing enthalpy, influences the mobility and adsorption behavior of the carbohydrates, water, and GVL, which were studied using pulsed-field gradient (PFG) NMR diffusivity measurements. At low GVL concentrations, glucose is depleted in the zeolite pores relative to the solution phase and changes in the local structure of coadsorbed water serve to further suppress the isomerization rate. At higher GVL concentrations, this lower intrinsic reactivity is largely compensated by strong glucose partitioning into the pores, resulting in dramatic (up to 32×) enhancements in the local sugar concentration at the solid-liquid interface.

  10. Exploring the salt-cocrystal continuum with solid-state NMR using natural-abundance samples: implications for crystal engineering.

    Science.gov (United States)

    Rajput, Lalit; Banik, Manas; Yarava, Jayasubba Reddy; Joseph, Sumy; Pandey, Manoj Kumar; Nishiyama, Yusuke; Desiraju, Gautam R

    2017-07-01

    There has been significant recent interest in differentiating multicomponent solid forms, such as salts and cocrystals, and, where appropriate, in determining the position of the proton in the X-H⋯A-YX(-)⋯H-A(+)-Y continuum in these systems, owing to the direct relationship of this property to the clinical, regulatory and legal requirements for an active pharmaceutical ingredient (API). In the present study, solid forms of simple cocrystals/salts were investigated by high-field (700 MHz) solid-state NMR (ssNMR) using samples with naturally abundant (15)N nuclei. Four model compounds in a series of prototypical salt/cocrystal/continuum systems exhibiting {PyN⋯H-O-}/{PyN(+)-H⋯O(-)} hydrogen bonds (Py is pyridine) were selected and prepared. The crystal structures were determined at both low and room temperature using X-ray diffraction. The H-atom positions were determined by measuring the (15)N-(1)H distances through (15)N-(1)H dipolar interactions using two-dimensional inversely proton-detected cross polarization with variable contact-time (invCP-VC) (1)H→(15)N→(1)H experiments at ultrafast (νR ≥ 60-70 kHz) magic angle spinning (MAS) frequency. It is observed that this method is sensitive enough to determine the proton position even in a continuum where an ambiguity of terminology for the solid form often arises. This work, while carried out on simple systems, has implications in the pharmaceutical industry where the salt/cocrystal/continuum condition of APIs is considered seriously.

  11. Solid-state and solution /sup 13/C NMR in the conformational analysis of methadone-hydrochloride and related narcotic analgesics

    Energy Technology Data Exchange (ETDEWEB)

    Sumner, S.C.J.

    1986-01-01

    Solid state and solution /sup 13/C NMR have been used to study the conformations of the racemic mixtures and single enantiomers of methadone hydrochloride, alpha and beta methadol hydrochloride, and alpha and beta acetylmethadol hydrochloride. The NMR spectra acquired for the compounds as solids, and in polar and nonpolar solvents are compared, in order to determine the conformation of the molecules in solution. To determine the reliability of assigning solution conformations by comparing solution and solid state chemical shift data, three bond coupling constants measured in solution are compared with those calculated from X-ray data. The conformations of the racemic mixture and plus enantiomer of methadone hydrochloride have been shown to be very similar in the solid state, where minor differences in conformation can be seen by comparing NMR spectra obtained for the solids. Also shown is that the molecules of methadone hydrochloride have conformations in polar and in nonpolar solvents which are very similar to the conformation of the molecules in the solid state.

  12. Synthesis, Isotopic Enrichment, and Solid-State NMR Characterization of Zeolites Derived from the Assembly, Disassembly, Organization, Reassembly Process.

    Science.gov (United States)

    Bignami, Giulia P M; Dawson, Daniel M; Seymour, Valerie R; Wheatley, Paul S; Morris, Russell E; Ashbrook, Sharon E

    2017-04-12

    The great utility and importance of zeolites in fields as diverse as industrial catalysis and medicine has driven considerable interest in the ability to target new framework types with novel properties and applications. The recently introduced and unconventional assembly, disassembly, organization, reassembly (ADOR) method represents one exciting new approach to obtain solids with targeted structures by selectively disassembling preprepared hydrolytically unstable frameworks and then reassembling the resulting products to form materials with new topologies. However, the hydrolytic mechanisms underlying such a powerful synthetic method are not understood in detail, requiring further investigation of the kinetic behavior and the outcome of reactions under differing conditions. In this work, we report the optimized ADOR synthesis, and subsequent solid-state characterization, of (17)O- and doubly (17)O- and (29)Si-enriched UTL-derived zeolites, by synthesis of (29)Si-enriched starting Ge-UTL frameworks and incorporation of (17)O from (17)O-enriched water during hydrolysis. (17)O and (29)Si NMR experiments are able to demonstrate that the hydrolysis and rearrangement process occurs over a much longer time scale than seen by diffraction. The observation of unexpectedly high levels of (17)O in the bulk zeolitic layers, rather than being confined only to the interlayer spacing, reveals a much more extensive hydrolytic rearrangement than previously thought. This work sheds new light on the role played by water in the ADOR process and provides insight into the detailed mechanism of the structural changes involved.

  13. Advanced solid-state NMR techniques for characterization of membrane protein structure and dynamics: application to Anabaena Sensory Rhodopsin.

    Science.gov (United States)

    Ward, Meaghan E; Brown, Leonid S; Ladizhansky, Vladimir

    2015-04-01

    Studies of the structure, dynamics, and function of membrane proteins (MPs) have long been considered one of the main applications of solid-state NMR (SSNMR). Advances in instrumentation, and the plethora of new SSNMR methodologies developed over the past decade have resulted in a number of high-resolution structures and structural models of both bitopic and polytopic α-helical MPs. The necessity to retain lipids in the sample, the high proportion of one type of secondary structure, differential dynamics, and the possibility of local disorder in the loop regions all create challenges for structure determination. In this Perspective article we describe our recent efforts directed at determining the structure and functional dynamics of Anabaena Sensory Rhodopsin, a heptahelical transmembrane (7TM) protein. We review some of the established and emerging methods which can be utilized for SSNMR-based structure determination, with a particular focus on those used for ASR, a bacterial protein which shares its 7TM architecture with G-protein coupled receptors.

  14. 13C and 15N spectral editing inside histidine imidazole ring through solid-state NMR spectroscopy.

    Science.gov (United States)

    Li, Shenhui; Zhou, Lei; Su, Yongchao; Han, Bin; Deng, Feng

    2013-01-01

    Histidine usually exists in three different forms (including biprotonated species, neutral τ and π tautomers) at physiological pH in biological systems. The different protonation and tautomerization states of histidine can be characteristically determined by (13)C and (15)N chemical shifts of imidazole ring. In this work, solid-state NMR techniques were developed for spectral editing of (13)C and (15)N sites in histidine imidazole ring, which provides a benchmark to distinguish the existing forms of histidine. The selections of (13)Cγ, (13)Cδ2, (15)Nδ1, and (15)Nε2 sites were successfully achieved based on one-bond homo- and hetero-nuclear dipole interactions. Moreover, it was demonstrated that (1)H, (13)C, and (15) chemical shifts were roughly linearly correlated with the corresponding atomic charge in histidine imidazole ring by theoretical calculations. Accordingly, the (1)H, (13)C and (15)N chemical shifts variation in different protonation and tautomerization states could be ascribed to the atomic charge change due to proton transfer in biological process.

  15. Characterization of phosphate sequestration by a lanthanum modified bentonite clay: A solid- state NMR, EXAFS and PXRD study

    Energy Technology Data Exchange (ETDEWEB)

    Dithmer, Line; Lipton, Andrew S.; Reitzel, Kasper; Warner, Terence E.; Lundberg, Daniel; Nielsen, Ulla Gro

    2015-04-07

    Phosphate (P) sequestration by a lanthanum (La) exchanged bentonite (a clay mineral), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of 31P and 139La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EX-AFS) and powder X-ray diffraction (PXRD) in combination with sorption studies. 31P SSNMR show that all phosphate is immobilized as rhabdophane, LaPO4·xH2O, which is further supported by 139La SSNMR and EXAFS; whereas PXRD results are ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies show that, at humic acids (HA) concentrations above ca. 250 μM the binding capacity is only 50 % of the theoretical value or even less. No other lanthanum or phosphate phases are detected by SSNMR and EXAFS indicating the effect of HA is kinetic. Moreover, 31P SSNMR shows that rhabdophane formed upon P sequestration is in close proximity to the clay matrix.

  16. Investigation of drug-excipient interactions in lapatinib amorphous solid dispersions using solid-state NMR spectroscopy.

    Science.gov (United States)

    Song, Yang; Yang, Xinghao; Chen, Xin; Nie, Haichen; Byrn, Stephen; Lubach, Joseph W

    2015-03-02

    This study investigated the presence of specific drug-excipient interactions in amorphous solid dispersions of lapatinib (LB) and four commonly used pharmaceutical polymers, including Soluplus, polyvinylpyrrolidone vinyl acetate (PVPVA), hydroxypropylmethylcellulose acetate succinate (HPMCAS), and hydroxypropylmethylcellulose phthalate (HPMCP). Based on predicted pKa differences, LB was hypothesized to exhibit a specific ionic interaction with HPMCP, and possibly with HPMCAS, while Soluplus and PVPVA were studied as controls without ionizable functionality. Thermal studies showed a single glass transition (Tg) for each dispersion, in close agreement with predicted values for Soluplus, PVPVA, and HPMCAS systems. However, the Tg values of LB-HPMCP solid dispersions were markedly higher than predicted values, indicating a strong intermolecular interaction between LB and HPMCP. (15)N solid-state NMR provided direct spectroscopic evidence for protonation of LB (i.e., salt formation) within the HPMCP solid dispersions. (1)H T1 and (1)H T1ρ relaxation studies of the dispersions supported the ionic interaction hypothesis, and indicated multiple phases in the cases of excess drug or polymer. In addition, the dissolution and stability behavior of each system was examined. Both acidic polymers, HPMCAS and HPMCP, effectively inhibited the crystallization of LB on accelerated stability, likely owing to beneficial strong intermolecular hydrogen and/or specific ionic bonds with the acidic polymers. Soluplus and PVPVA showed poor physical properties on stability and subsequently poor crystallization inhibition.

  17. Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements.

    Science.gov (United States)

    Pham, Tran N; Watson, Simon A; Edwards, Andrew J; Chavda, Manisha; Clawson, Jacalyn S; Strohmeier, Mark; Vogt, Frederick G

    2010-10-04

    Solid-state NMR (SSNMR) can provide detailed structural information about amorphous solid dispersions of pharmaceutical small molecules. In this study, the ability of SSNMR experiments based on dipolar correlation, spin diffusion, and relaxation measurements to characterize the structure of solid dispersions is explored. Observation of spin diffusion effects using the 2D (1)H-(13)C cross-polarization heteronuclear correlation (CP-HETCOR) experiment is shown to be a useful probe of association between the amorphous drug and polymer that is capable of directly proving glass solution formation. Dispersions of acetaminophen and indomethacin in different polymers are examined using this approach, as well as (1)H double-quantum correlation experiments to probe additional structural features. (1)H-(19)F CP-HETCOR serves a similar role for fluorinated drug molecules such as diflunisal in dispersions, providing a rapid means to prove the formation of a glass solution. Phase separation is detected using (13)C, (19)F, and (23)Na-detected (1)H T(1) experiments in crystalline and amorphous solid dispersions that contain small domains. (1)H T(1) measurements of amorphous nanosuspensions of trehalose and dextran illustrate the ability of SSNMR to detect domain size effects in dispersions that are not glass solutions via spin diffusion effects. Two previously unreported amorphous solid dispersions involving up to three components and containing voriconazole and telithromycin are analyzed using these experiments to demonstrate the general applicability of the approach.

  18. Accurate determination of order parameters from 1H,15N dipolar couplings in MAS solid-state NMR experiments.

    Science.gov (United States)

    Chevelkov, Veniamin; Fink, Uwe; Reif, Bernd

    2009-10-01

    A reliable site-specific estimate of the individual N-H bond lengths in the protein backbone is the fundamental basis of any relaxation experiment in solution and in the solid-state NMR. The N-H bond length can in principle be influenced by hydrogen bonding, which would result in an increased N-H distance. At the same time, dynamics in the backbone induces a reduction of the experimental dipolar coupling due to motional averaging. We present a 3D dipolar recoupling experiment in which the (1)H,(15)N dipolar coupling is reintroduced in the indirect dimension using phase-inverted CP to eliminate effects from rf inhomogeneity. We find no variation of the N-H dipolar coupling as a function of hydrogen bonding. Instead, variations in the (1)H,(15)N dipolar coupling seem to be due to dynamics of the protein backbone. This is supported by the observed correlation between the H(N)-N dipolar coupling and the amide proton chemical shift. The experiment is demonstrated for a perdeuterated sample of the alpha-spectrin SH3 domain. Perdeuteration is a prerequisite to achieve high accuracy. The average error in the analysis of the H-N dipolar couplings is on the order of +/-370 Hz (+/-0.012 A) and can be as small as 150 Hz, corresponding to a variation of the bond length of +/-0.005 A.

  19. A structural model for Alzheimer's β-amyloid fibrils based on experimental constraints from solid state NMR

    Science.gov (United States)

    Petkova, Aneta T.; Ishii, Yoshitaka; Balbach, John J.; Antzutkin, Oleg N.; Leapman, Richard D.; Delaglio, Frank; Tycko, Robert

    2002-01-01

    We present a structural model for amyloid fibrils formed by the 40-residue β-amyloid peptide associated with Alzheimer's disease (Aβ1–40), based on a set of experimental constraints from solid state NMR spectroscopy. The model additionally incorporates the cross-β structural motif established by x-ray fiber diffraction and satisfies constraints on Aβ1–40 fibril dimensions and mass-per-length determined from electron microscopy. Approximately the first 10 residues of Aβ1–40 are structurally disordered in the fibrils. Residues 12–24 and 30–40 adopt β-strand conformations and form parallel β-sheets through intermolecular hydrogen bonding. Residues 25–29 contain a bend of the peptide backbone that brings the two β-sheets in contact through sidechain-sidechain interactions. A single cross-β unit is then a double-layered β-sheet structure with a hydrophobic core and one hydrophobic face. The only charged sidechains in the core are those of D23 and K28, which form salt bridges. Fibrils with minimum mass-per-length and diameter consist of two cross-β units with their hydrophobic faces juxtaposed. PMID:12481027

  20. Advanced solid-state NMR techniques for characterization of membrane protein structure and dynamics: Application to Anabaena Sensory Rhodopsin

    Science.gov (United States)

    Ward, Meaghan E.; Brown, Leonid S.; Ladizhansky, Vladimir

    2015-04-01

    Studies of the structure, dynamics, and function of membrane proteins (MPs) have long been considered one of the main applications of solid-state NMR (SSNMR). Advances in instrumentation, and the plethora of new SSNMR methodologies developed over the past decade have resulted in a number of high-resolution structures and structural models of both bitopic and polytopic α-helical MPs. The necessity to retain lipids in the sample, the high proportion of one type of secondary structure, differential dynamics, and the possibility of local disorder in the loop regions all create challenges for structure determination. In this Perspective article we describe our recent efforts directed at determining the structure and functional dynamics of Anabaena Sensory Rhodopsin, a heptahelical transmembrane (7TM) protein. We review some of the established and emerging methods which can be utilized for SSNMR-based structure determination, with a particular focus on those used for ASR, a bacterial protein which shares its 7TM architecture with G-protein coupled receptors.

  1. Solid-State Selective 13C Excitation and Spin Diffusion NMR to Resolve Spatial Dimensions in Plant Cell Walls

    Energy Technology Data Exchange (ETDEWEB)

    Foston, M.; Katahira, R.; Gjersing, E.; Davis, M. F.; Ragauskas, A. J.

    2012-02-15

    The average spatial dimensions between major biopolymers within the plant cell wall can be resolved using a solid-state NMR technique referred to as a {sup 13}C cross-polarization (CP) SELDOM (selectively by destruction of magnetization) with a mixing time delay for spin diffusion. Selective excitation of specific aromatic lignin carbons indicates that lignin is in close proximity to hemicellulose followed by amorphous and finally crystalline cellulose. {sup 13}C spin diffusion time constants (T{sub SD}) were extracted using a two-site spin diffusion theory developed for {sup 13}C nuclei under magic angle spinning (MAS) conditions. These time constants were then used to calculate an average lower-limit spin diffusion length between chemical groups within the plant cell wall. The results on untreated {sup 13}C enriched corn stover stem reveal that the lignin carbons are, on average, located at distances {approx}0.7-2.0 nm from the carbons in hemicellulose and cellulose, whereas the pretreated material had larger separations.

  2. Refocused continuous-wave decoupling: A new approach to heteronuclear dipolar decoupling in solid-state NMR spectroscopy

    Science.gov (United States)

    Vinther, Joachim M.; Nielsen, Anders B.; Bjerring, Morten; van Eck, Ernst R. H.; Kentgens, Arno P. M.; Khaneja, Navin; Nielsen, Niels Chr.

    2012-12-01

    A novel strategy for heteronuclear dipolar decoupling in magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy is presented, which eliminates residual static high-order terms in the effective Hamiltonian originating from interactions between oscillating dipolar and anisotropic shielding tensors. The method, called refocused continuous-wave (rCW) decoupling, is systematically established by interleaving continuous wave decoupling with appropriately inserted rotor-synchronized high-power π refocusing pulses of alternating phases. The effect of the refocusing pulses in eliminating residual effects from dipolar coupling in heteronuclear spin systems is rationalized by effective Hamiltonian calculations to third order. In some variants the π pulse refocusing is supplemented by insertion of rotor-synchronized π/2 purging pulses to further reduce the residual dipolar coupling effects. Five different rCW decoupling sequences are presented and their performance is compared to state-of-the-art decoupling methods. The rCW decoupling sequences benefit from extreme broadbandedness, tolerance towards rf inhomogeneity, and improved potential for decoupling at relatively low average rf field strengths. In numerical simulations, the rCW schemes clearly reveal superior characteristics relative to the best decoupling schemes presented so far, which we to some extent also are capable of demonstrating experimentally. A major advantage of the rCW decoupling methods is that they are easy to set up and optimize experimentally.

  3. Highly efficient (19)F heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation.

    Science.gov (United States)

    Equbal, Asif; Basse, Kristoffer; Nielsen, Niels Chr

    2016-12-07

    We present heteronuclear (19)F refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle-spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent (13)C-(19)F dipolar coupling interactions while simultaneously suppressing strong anisotropic chemical shift as well as homonuclear (19)F-(19)F dipolar coupling effects as typically present in perfluorated compounds. In an extensive numerical and experimental analysis using a rigid, organic solid as a model compound, it becomes evident that the supercycled rCW schemes markedly improve the decoupling efficiency, leading to substantial enhancements in resolution and sensitivity when compared to previous state-of-the-art methods. Furthermore, considerable gains in robustness toward rf mismatch as well as offset in the radio-frequency carrier frequency are observed, all of which clearly render the new rCW schemes the methods of choice for (19)F decoupling in rigid, fluorinated compounds - which is further supported by a Floquet-based theoretical analysis.

  4. Grasping hydrogen adsorption and dynamics in metal-organic frameworks using (2)H solid-state NMR.

    Science.gov (United States)

    Lucier, Bryan E G; Zhang, Yue; Lee, Kelly J; Lu, Yuanjun; Huang, Yining

    2016-06-18

    Record greenhouse gas emissions have spurred the search for clean energy sources such as hydrogen (H2) fuel cells. Metal-organic frameworks (MOFs) are promising H2 adsorption and storage media, but knowledge of H2 dynamics and adsorption strengths in these materials is lacking. Variable-temperature (VT) (2)H solid-state NMR (SSNMR) experiments targeting (2)H2 gas (i.e., D2) shed light on D2 adsorption and dynamics within six representative MOFs: UiO-66, M-MOF-74 (M = Zn, Mg, Ni), and α-M3(COOH)6 (M = Mg, Zn). D2 binding is relatively strong in Mg-MOF-74, Ni-MOF-74, α-Mg3(COOH)6, and α-Zn3(COOH)6, giving rise to broad (2)H SSNMR powder patterns. In contrast, D2 adsorption is weaker in UiO-66 and Zn-MOF-74, as evidenced by the narrow (2)H resonances that correspond to rapid reorientation of the D2 molecules. Employing (2)H SSNMR experiments in this fashion holds great promise for the correlation of MOF structural features and functional groups/metal centers to H2 dynamics and host-guest interactions.

  5. Static solid-state (14)N NMR and computational studies of nitrogen EFG tensors in some crystalline amino acids.

    Science.gov (United States)

    O'Dell, Luke A; Schurko, Robert W

    2009-08-28

    The recently reported direct enhancement of integer spin magnetization (DEISM) methodology for signal enhancement in solid-state NMR of integer spins has been used to obtain static (14)N powder patterns from alpha-glycine, L-leucine and L-proline in relatively short experimental times at 9.4 T, allowing accurate determination of the quadrupolar parameters. Proton decoupling and deuteration of the nitrogen sites were used to reduce the (1)H-(14)N dipolar contribution to the transverse relaxation time allowing more echoes to be acquired per scan. In addition, ab initio calculations using molecular clusters (Gaussian 03) and the full crystal lattice (CASTEP) have been employed to confirm these results, to obtain the orientation of the electric field gradient (EFG) tensors in the molecular frame, and also to correctly assign the two sets of parameters for L-leucine. The (14)N EFG tensor is shown to be highly sensitive to the surrounding environment, particularly to nearby hydrogen bonding.

  6. Integrating solid-state NMR and computational modeling to investigate the structure and dynamics of membrane-associated ghrelin.

    Directory of Open Access Journals (Sweden)

    Gerrit Vortmeier

    Full Text Available The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide's secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide's positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8-17 form an α-helix, while residues 21-23 and 26-27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane.

  7. A solid state NMR study of layered double hydroxides intercalated with para-amino salicylate, a tuberculosis drug

    DEFF Research Database (Denmark)

    Jensen, Nicholai Daugaard; Bjerring, Morten; Nielsen, Ulla Gro

    2016-01-01

    Para-amino salicylate (PAS), a tubercolosis drug, was intercalated in three different layered double hydroxides (MgAl, ZnAl, and CaAl-LDH) and the samples were studied by multi-nuclear (1H, 13C, and 27Al) solid state NMR (SSNMR) spectroscopy in combination with powder X-ray diffraction (PXRD......), elemental analysis and IR-spectroscopy to gain insight into the bulk and atomic level structure of these LDHs especially with a view to the purity of the LDH-PAS materials and the concentration of impurities. The intercalations of PAS in MgAl-, ZnAl-, and CaAl-LDH's were confirmed by 13C SSNMR and PXRD...... showed that the M(II):Al ratio was higher than predicted from the bulk metal composition of MgAl-PAS and ZnAl-PAS. Moreover, the first high-resolution 1H SSNMR spectra of a CaAl LDH is reported and assigned using 1H single and double quantum experiments in combination with 27Al{1H} HETCOR....

  8. Solid-State (13)C NMR Delineates the Architectural Design of Biopolymers in Native and Genetically Altered Tomato Fruit Cuticles.

    Science.gov (United States)

    Chatterjee, Subhasish; Matas, Antonio J; Isaacson, Tal; Kehlet, Cindie; Rose, Jocelyn K C; Stark, Ruth E

    2016-01-11

    Plant cuticles on outer fruit and leaf surfaces are natural macromolecular composites of waxes and polyesters that ensure mechanical integrity and mitigate environmental challenges. They also provide renewable raw materials for cosmetics, packaging, and coatings. To delineate the structural framework and flexibility underlying the versatile functions of cutin biopolymers associated with polysaccharide-rich cell-wall matrices, solid-state NMR spectra and spin relaxation times were measured in a tomato fruit model system, including different developmental stages and surface phenotypes. The hydrophilic-hydrophobic balance of the cutin ensures compatibility with the underlying polysaccharide cell walls; the hydroxy fatty acid structures of outer epidermal cutin also support deposition of hydrophobic waxes and aromatic moieties while promoting the formation of cell-wall cross-links that rigidify and strengthen the cuticle composite during fruit development. Fruit cutin-deficient tomato mutants with compromised microbial resistance exhibit less efficient local and collective biopolymer motions, stiffening their cuticular surfaces and increasing their susceptibility to fracture.

  9. Detection of low-level PTFE contamination: An application of solid-state NMR to structure elucidation in the pharmaceutical industry.

    Science.gov (United States)

    Pham, Tran N; Day, Caroline J; Edwards, Andrew J; Wood, Helen R; Lynch, Ian R; Watson, Simon A; Bretonnet, Anne-Sophie Z; Vogt, Frederick G

    2011-01-25

    We report a novel use of solid-state ¹⁹F nuclear magnetic resonance to detect and quantify polytetrafluoroethylene contamination from laboratory equipment, which due to low quantity (up to 1% w/w) and insolubility remained undetected by standard analytical techniques. Solid-state ¹⁹F NMR is shown to be highly sensitive to such fluoropolymers (detection limit 0.02% w/w), and is demonstrated as a useful analytical tool for structure elucidation of unknown solid materials.

  10. Sensitivity and Resolution Enhanced Solid-State NMR for Paramagnetic Systems and Biomolecules under Very Fast Magic Angle Spinning

    KAUST Repository

    Parthasarathy, Sudhakar

    2013-09-17

    Recent research in fast magic angle spinning (MAS) methods has drastically improved the resolution and sensitivity of NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarize recent and ongoing developments in this area by presenting (13)C and (1)H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of at least 20 kHz allows us to overcome major difficulties in (1)H and (13)C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (∼ms/scan) with short (1)H T1 values, we can perform (1)H SSNMR microanalysis of paramagnetic systems on the microgram scale with greatly improved sensitivity over that observed for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ∼40 kHz can enhance the sensitivity and resolution of (13)C biomolecular SSNMR measurements. Low-power (1)H decoupling schemes under VFMAS offer excellent spectral resolution for (13)C SSNMR by nominal (1)H RF irradiation at ∼10 kHz. By combining the VFMAS approach with enhanced (1)H T1 relaxation by paramagnetic doping, we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments with (13)C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine (13)C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary (13)C SSNMR data of Aβ amyloid fibrils and GB1 microcrystals acquired at (1)H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and ultrahigh fields could allow for routine multidimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the

  11. Sensitivity and Resolution Enhanced Solid-state NMR for Paramagnetic Systems and Biomolecules under Very Fast Magic Angle Spinning

    Science.gov (United States)

    PARTHASARATHY, SUDHAKAR; NISHIYAMA, YUSUKE; ISHII, YOSHITAKA

    2013-01-01

    CONSPECTUS Recent research in fast magic angle spinning (MAS) methods has drastically improved in the resolution and sensitivity for NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarizes recent and ongoing developments in this area by presenting 13C and 1H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of 20 kHz allows us to overcome major difficulties in 1H and 13C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (~ms/scan) using short 1H T1 values we can perform 1H SSNMR micro-analysis of paramagnetic systems in the μg scale with greatly improved sensitivity over that for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ~40 kHz can enhance the sensitivity and resolution of 13C biomolecular SSNMR measurements. Low-power 1H decoupling schemes under VFMAS offer excellent spectral resolution for 13C SSNMR by nominal 1H RF irradiation at ~10 kHz. By combining the VFMAS approach and enhanced 1H T1 relaxation by paramagnetic doping we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments for 13C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine 13C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary 13C SSNMR data of Aβ amyloid fibrils and GB1 microcrystals acquired at 1H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and the ultra-high fields could allow for routine multi-dimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the prospects for studying bimolecules using 13

  12. Solid state theory

    CERN Document Server

    Harrison, Walter A

    2011-01-01

    ""A well-written text . . . should find a wide readership, especially among graduate students."" - Dr. J. I. Pankove, RCA.The field of solid state theory, including crystallography, semi-conductor physics, and various applications in chemistry and electrical engineering, is highly relevant to many areas of modern science and industry. Professor Harrison's well-known text offers an excellent one-year graduate course in this active and important area of research. While presenting a broad overview of the fundamental concepts and methods of solid state physics, including the basic quantum theory o

  13. Genotype evaluation of cowpea seeds (Vigna unguiculata) using (1)H qNMR combined with exploratory tools and solid-state NMR.

    Science.gov (United States)

    Alves Filho, Elenilson G; Silva, Lorena M A; Teofilo, Elizita M; Larsen, Flemming H; de Brito, Edy S

    2017-01-01

    The ultimate aim of this study was to apply a non-targeted chemometric analysis (principal component analysis and hierarchical clustering analysis using the heat map approach) of NMR data to investigate the variability of organic compounds in nine genotype cowpea seeds, without any complex pre-treatment. In general, both exploratory tools show that Tvu 233, CE-584, and Setentão genotypes presented higher amount mainly of raffinose and Tvu 382 presented the highest content of choline and least content of raffinose. The evaluation of the aromatic region showed the Setentão genotype with highest content of niacin/vitamin B3 whereas Tvu 382 with lowest amount. To investigate rigid and mobile components in the seeds cotyledon, (13)C CP and SP/MAS solid-state NMR experiments were performed. The cotyledon of the cowpea comprised a rigid part consisting of starch as well as a soft portion made of starch, fatty acids, and protein. The variable contact time experiment suggests the presence of lipid-amylose complexes.

  14. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations, Part I: Chemical shifts assignment.

    Science.gov (United States)

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika Agnieszka; Szeleszczuk, Łukasz; Wawer, Iwona

    2016-04-15

    Solid-state NMR is an excellent and useful method for analyzing solid-state forms of drugs. In the (13)C CP/MAS NMR spectra of the solid dosage forms many of the signals originate from the excipients and should be distinguished from those of active pharmaceutical ingredient (API). In this work the most common pharmaceutical excipients used in the solid drug formulations: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. Their (13)C CP/MAS NMR spectra were recorded and the signals were assigned, employing the results (R(2): 0.948-0.998) of GIPAW calculations and theoretical chemical shifts. The (13)C ssNMR spectra for some of the studied excipients have not been published before while for the other signals in the spectra they were not properly assigned or the assignments were not correct. The results summarize and complement the data on the (13)C ssNMR analysis of the most common pharmaceutical excipients and are essential for further NMR studies of API-excipient interactions in the pharmaceutical formulations.

  15. Water-polysaccharide interactions in the primary cell wall of Arabidopsis thaliana from polarization transfer solid-state NMR.

    Science.gov (United States)

    White, Paul B; Wang, Tuo; Park, Yong Bum; Cosgrove, Daniel J; Hong, Mei

    2014-07-23

    Polysaccharide-rich plant cell walls are hydrated under functional conditions, but the molecular interactions between water and polysaccharides in the wall have not been investigated. In this work, we employ polarization transfer solid-state NMR techniques to study the hydration of primary-wall polysaccharides of the model plant, Arabidopsis thaliana. By transferring water (1)H polarization to polysaccharides through distance- and mobility-dependent (1)H-(1)H dipolar couplings and detecting it through polysaccharide (13)C signals, we obtain information about water proximity to cellulose, hemicellulose, and pectins as well as water mobility. Both intact and partially extracted cell wall samples are studied. Our results show that water-pectin polarization transfer is much faster than water-cellulose polarization transfer in all samples, but the extent of extraction has a profound impact on the water-polysaccharide spin diffusion. Removal of calcium ions and the consequent extraction of homogalacturonan (HG) significantly slowed down spin diffusion, while further extraction of matrix polysaccharides restored the spin diffusion rate. These trends are observed in cell walls with similar water content, thus they reflect inherent differences in the mobility and spatial distribution of water. Combined with quantitative analysis of the polysaccharide contents, our results indicate that calcium ions and HG gelation increase the amount of bound water, which facilitates spin diffusion, while calcium removal disrupts the gel and gives rise to highly dynamic water, which slows down spin diffusion. The recovery of spin diffusion rates after more extensive extraction is attributed to increased water-exposed surface areas of the polysaccharides. Water-pectin spin diffusion precedes water-cellulose spin diffusion, lending support to the single-network model of plant primary walls in which a substantial fraction of the cellulose surface is surrounded by pectins.

  16. Direct Speciation of Phosphorus in Alum-Amended Poultry Litter: Solid-State 31P NMR Investigation

    Energy Technology Data Exchange (ETDEWEB)

    Hunger, Stefan; Cho, Herman M.; Sims, James T.; Sparks, Donald L.

    2004-02-01

    Amending poultry litter (PL) with aluminum sulfate (alum) has proven to be effective in reducing water-soluble phosphorus (P) in the litter and in runoff from fields that have received PL applications; it has therefore been suggested as a best management practice. Although its effectiveness has been demonstrated on a macroscopic scale in the field, little is known about P speciation in either alumamended or unamended litter. This knowledge is important for the evaluation of the long-term stability and bioavailability of P, which is a necessary prerequisite for the assessment of the sustainability of intensive poultry operations. Both solid state MAS and CP-MAS {sup 31}P NMR as well as {sup 31}P({sup 27}Al) TRAPDOR were used to investigate P speciation in alumamended and unamended PL. The results indicate the presence of a complex mixture of organic and inorganic orthophosphate phases. A calcium phosphate phase, probably a surface precipitate on calcium carbonate, could be identified in both unamended and alum-amended PL, as well as physically bound HPO{sub 4}{sup 2-}. Phosphate associated with Al was found in the alum-amended PL, most probably a mixture of a poorly ordered wavellite and phosphate surface complexes on aluminum hydroxide that had been formed by the hydrolysis of alum. However, a complex mixture of organic and inorganic phosphate species could not be resolved. Phosphate associated with Al comprised on average 40{+-}14% of the total P in alum-amended PL, whereas calcium phosphate phases comprised on average 7{+-}4% in the alum-amended PL and 14{+-}5% in the unamended PL.

  17. Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time 13C CP-MAS solid-state NMR characterization

    Science.gov (United States)

    Mallard, Isabelle; Baudelet, Davy; Castiglione, Franca; Ferro, Monica; Panzeri, Walter; Ragg, Enzio

    2015-01-01

    Summary The polymerization of partially methylated β-cyclodextrin (CRYSMEB) with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3) of imprinted polymers were obtained and characterized by solid-state 13C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS) conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: T CH (the CP time constant) and T 1ρ (the proton spin-lattice relaxation time in the rotating frame). The results and the analysis presented in the paper pointed out that T CH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T 1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of T CH and T 1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices. PMID:26877800

  18. Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time 13C CP-MAS solid-state NMR characterization

    Directory of Open Access Journals (Sweden)

    Isabelle Mallard

    2015-12-01

    Full Text Available The polymerization of partially methylated β-cyclodextrin (CRYSMEB with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3 of imprinted polymers were obtained and characterized by solid-state 13C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: TCH (the CP time constant and T1ρ (the proton spin-lattice relaxation time in the rotating frame. The results and the analysis presented in the paper pointed out that TCH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of TCH and T1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices.

  19. Solid-state NMR Reveals the Carbon-based Molecular Architecture of Cryptococcus neoformans Fungal Eumelanins in the Cell Wall.

    Science.gov (United States)

    Chatterjee, Subhasish; Prados-Rosales, Rafael; Itin, Boris; Casadevall, Arturo; Stark, Ruth E

    2015-05-29

    Melanin pigments protect against both ionizing radiation and free radicals and have potential soil remediation capabilities. Eumelanins produced by pathogenic Cryptococcus neoformans fungi are virulence factors that render the fungal cells resistant to host defenses and certain antifungal drugs. Because of their insoluble and amorphous characteristics, neither the pigment bonding framework nor the cellular interactions underlying melanization of C. neoformans have yielded to comprehensive molecular-scale investigation. This study used the C. neoformans requirement of exogenous obligatory catecholamine precursors for melanization to produce isotopically enriched pigment "ghosts" and applied 2D (13)C-(13)C correlation solid-state NMR to reveal the carbon-based architecture of intact natural eumelanin assemblies in fungal cells. We demonstrated that the aliphatic moieties of solid C. neoformans melanin ghosts include cell-wall components derived from polysaccharides and/or chitin that are associated proximally with lipid membrane constituents. Prior to development of the mature aromatic fungal pigment, these aliphatic moieties form a chemically resistant framework that could serve as the scaffold for melanin synthesis. The indole-based core aromatic moieties show interconnections that are consistent with proposed melanin structures consisting of stacked planar assemblies, which are associated spatially with the aliphatic scaffold. The pyrrole aromatic carbons of the pigments bind covalently to the aliphatic framework via glycoside or glyceride functional groups. These findings establish that the structure of the pigment assembly changes with time and provide the first biophysical information on the mechanism by which melanin is assembled in the fungal cell wall, offering vital insights that can advance the design of bioinspired conductive nanomaterials and novel therapeutics.

  20. Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

    Science.gov (United States)

    Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

    1996-01-01

    The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

  1. Local environment and composition of magnesium gallium layered double hydroxides determined from solid-state 1H and 71Ga NMR spectroscopy

    DEFF Research Database (Denmark)

    Boisen Staal, Line; Lipton, Andrew S.; Zorin, Vadim

    2014-01-01

    Ordering of gallium(III) in a series of magnesium gallium (MgGa) layered double hydroxides (LDHs), [Mg1−xGax(OH)2(NO3)x·yH2O] was investigated using solid-state 1H and 71Ga NMR spectroscopy as well as powder X-ray diffraction. Three different proton environments from Mg3single bondOH, Mg2Gasingle...

  2. From discrete molecule, to polymer, to MOF: mapping the coordination chemistry of Cd(II) using (113)Cd solid-state NMR.

    Science.gov (United States)

    Frost, Jamie M; Kobera, Libor; Pialat, Amélie; Zhang, Yixin; Southern, Scott A; Gabidullin, Bulat; Bryce, David L; Murugesu, Muralee

    2016-08-23

    Studies of three related Cd(II) systems (a discrete [Cd(II)2] unit, a one-dimensional [Cd(II)2]n coordination polymer and a Cd(II)-based MOF) all derived from the ligand 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine, reveal an exceptionally rare example of (113)Cd-(113)Cd J coupling in the polymer that is detectable by solid-state NMR ((2)JCd-Cd = ∼65 Hz).

  3. The potential for the indirect crystal structure verification of methyl glycosides based on acetates' parent structures: GIPAW and solid-state NMR approaches

    Science.gov (United States)

    Szeleszczuk, Łukasz; Gubica, Tomasz; Zimniak, Andrzej; Pisklak, Dariusz M.; Dąbrowska, Kinga; Cyrański, Michał K.; Kańska, Marianna

    2017-10-01

    A convenient method for the indirect crystal structure verification of methyl glycosides was demonstrated. Single-crystal X-ray diffraction structures for methyl glycoside acetates were deacetylated and subsequently subjected to DFT calculations under periodic boundary conditions. Solid-state NMR spectroscopy served as a guide for calculations. A high level of accuracy of the modelled crystal structures of methyl glycosides was confirmed by comparison with published results of neutron diffraction study using RMSD method.

  4. Correlations between (51)V solid-state NMR parameters and chemical structure of vanadium (V) complexes as models for related metalloproteins and catalysts.

    Science.gov (United States)

    Fenn, Annika; Wächtler, Maria; Gutmann, Torsten; Breitzke, Hergen; Buchholz, Axel; Lippold, Ines; Plass, Winfried; Buntkowsky, Gerd

    2009-12-01

    The parameters describing the quadrupolar and CSA interactions of 51V solid-state MAS NMR investigations of model complexes mimicking vanadoenzymes as well as vanadium containing catalysts and enzyme complexes are interpreted with respect to the chemical structure. The interpretation is based on the data of 15 vanadium complexes including two new complexes with previously unpublished data and 13 complexes with data previously published by us. Correlations between the chemical structure and the 51V solid-state NMR data of this class of compounds have been established. Especially for the isotropic chemical shift delta(iso) and the chemical shift anisotropy delta(sigma), correlations with specific structural features like the coordination number of the vanadium atom, the number of coordinating nitrogens, the number of oxygen atoms and the chemical surrounding of the complex could be established for these compounds. Moreover, quantitative correlations between the solid-state NMR parameters and specific bond angles and bond lengths have been obtained. Our results can be of particular interest for future investigations concerning the structure and the mode of action of related vanadoenzymes and vanadate protein assemblies, including the use of vanadate adducts as transition state analogs for phosphate metabolizing systems.

  5. Solid-state NMR analysis of a peptide (Gly-Pro-Gly-Gly-Ala)6-Gly derived from a flagelliform silk sequence of Nephila clavipes.

    Science.gov (United States)

    Ohgo, Kosuke; Kawase, Taiji; Ashida, Jun; Asakura, Tetsuo

    2006-04-01

    Solid-state NMR is especially useful when the structures of peptides and proteins should be analyzed by taking into account the structural distribution, that is, the distribution of the torsion angle of the individual residue. In this study, two-dimensional spin-diffusion solid-state NMR spectra of 13C-double-labeled model peptides (GPGGA)6G of flagelliform silk were observed for studying the local structure in the solid state. The spin-diffusion NMR spectra calculated by assuming the torsion angles of the beta-spiral structure exclusively could not reproduce the observed spectra. In contrast, the spectra calculated by taking into account the statistical distribution of the torsion angles of the individual central residues in the sequences Ala-Gly-Pro, Gly-Pro-Gly, Pro-Gly-Gly, Gly-Gly-Ala, and Gly-Ala-Gly from PDB data could reproduce the observed spectra well. This indicates that the statistical distribution of the torsion angles should be considered for the structural model of (GPGGA)6G similar to the case of the model peptide of elastin.

  6. 15N and 1H Solid-State NMR Investigation of a Canonical Low-Barrier Hydrogen-Bond Compound: 1,8-bis(dimethylamino) naphthalene

    OpenAIRE

    White, Paul B.; Hong, Mei

    2015-01-01

    Strong or low-barrier hydrogen bonds have been often proposed in proteins to explain enzyme catalysis and proton transfer reactions. So far 1H chemical shifts and scalar couplings have been used as the main NMR spectroscopic signatures for strong H-bonds. In this work, we report simultaneous measurements of 15N and 1H chemical shifts and N-H bond lengths by solid-state NMR in 15N-labeled 1,8-bis(dimethylamino) naphthalene (DMAN), which contains a well known strong NHN H-bond. We complexed DMA...

  7. Characteristics and degradation of carbon and phosphorus from aquatic macrophytes in lakes: Insights from solid-state {sup 13}C NMR and solution {sup 31}P NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shasha [College of Water Sciences, Beijing Normal University, Beijing 100875 (China); State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012 (China); Zhu, Yuanrong, E-mail: zhuyuanrong07@mails.ucas.ac.cn [State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012 (China); Meng, Wei, E-mail: mengwei@craes.org.cn [State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012 (China); He, Zhongqi [USDA-ARS Southern Regional Research Center, 1100 Robert E Lee Blvd, New Orleans, LA 70124 (United States); Feng, Weiying [College of Water Sciences, Beijing Normal University, Beijing 100875 (China); State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012 (China); Zhang, Chen [State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012 (China); Giesy, John P. [State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012 (China); Department of Biomedical and Veterinary Biosciences and Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan (Canada)

    2016-02-01

    Water extractable organic matter (WEOM) derived from macrophytes plays an important role in biogeochemical cycling of nutrients, including carbon (C), nitrogen (N) and phosphorus (P) in lakes. However, reports of their composition and degradation in natural waters are scarce. Therefore, compositions and degradation of WEOM derived from six aquatic macrophytes species of Tai Lake, China, were investigated by use of solid-state {sup 13}C NMR and solution {sup 31}P NMR spectroscopy. Carbohydrates were the predominant constituents of WEOM fractions, followed by carboxylic acid. Orthophosphate (ortho-P) was the dominant form of P (78.7% of total dissolved P) in the water extracts, followed by monoester P (mono-P) (20.6%) and little diester P (0.65%). The proportion of mono-P in total P species increased with the percentage of O-alkyl and O–C–O increasing in the WEOM, which is likely due to degradation and dissolution of biological membranes and RNA from aquatic plants. Whereas the proportion of mono-P decreased with alkyl-C, NCH/OCH{sub 3} and COO/N–C=O increasing, which may be owing to the insoluble compounds including C functional groups of alkyl-C, NCH/OCH{sub 3} and COO/N–C=O, such as aliphatic biopolymers, lignin and peptides. Based on the results of this study and information in the literature about water column and sediment, we propose that WEOM, dominated by polysaccharides, are the most labile and bioavailable component in debris of macrophytes. Additionally, these WEOMs would also be a potential source for bioavailable organic P (e.g., RNA, DNA and phytate) for lakes. - Highlights: • WEOM derived from aquatic macrophytes was characterized. • C and P in WEOM were characterized by solid {sup 13}C NMR and solution {sup 31}P NMR. • Degradation and transformation of macrophyte-derived C and P were investigated. • Macrophyte-derived WEOM are important source for bioavailable nutrients in lakes.

  8. Characteristics and degradation of carbon and phosphorus from aquatic macrophytes in lakes: Insights from solid-state 13C NMR and solution 31P NMR spectroscopy

    Science.gov (United States)

    LIU, S. S.; Zhu, Y.; Meng, W.; Wu, F.

    2016-12-01

    Water extractable organic matter (WEOM) derived from macrophytes plays an important role in biogeochemical cycling of nutrients, including carbon (C), nitrogen (N) and phosphorus (P) in lakes. However, reports of their composition and degradation in natural waters are scarce. Therefore, compositions and degradation of WEOM derived from six aquatic macrophytes species of Tai Lake, China, were investigated by use of solid-state 13C NMR and solution 31P NMR spectroscopy. Carbohydrates were the predominant constituents of WEOM fractions, followed by carboxylic acid. Orthophosphate (ortho-P) was the dominant form of P (78.7% of total dissolved P) in the water extracts, followed by monoester P (mono-P) (20.6%) and little diester P (0.65%). The proportion of mono-P in total P species increased with the percentage of O-alkyl and O-C-O increasing in the WEOM, which is likely due to degradation and dissolution of biological membranes and RNA from aquatic plants. Whereas the proportion of mono-P decreased with alkyl-C, NCH/OCH3 and COO/N-C=O increasing, which may be owing to the insoluble compounds including C functional groups of alkyl-C, NCH/OCH3 and COO/N-C=O, such as aliphatic biopolymers, lignin and peptides. Based on the results of this study and information in the literature about water column and sediment, we propose that WEOM, dominated by polysaccharides, are the most labile and bioavailable component in debris of macrophytes. Additionally, these WEOMs would also be a potential source for bioavailable organic P (e.g., RNA, DNA and phytate) for lakes.

  9. Extensive de novo solid-state NMR assignments of the 33 kDa C-terminal domain of the Ure2 prion

    Energy Technology Data Exchange (ETDEWEB)

    Habenstein, Birgit [UMR 5086 CNRS/Universite de Lyon 1, Institut de Biologie et Chimie des Proteines (France); Wasmer, Christian [Harvard Medical School (United States); Bousset, Luc; Sourigues, Yannick [UPR 3082 CNRS, Laboratoire d' Enzymologie et Biochimie Structurales (France); Schuetz, Anne [ETH Zurich, Physical Chemistry (Switzerland); Loquet, Antoine [Max Planck Institute for Biophysical Chemistry (Germany); Meier, Beat H., E-mail: beme@ethz.ch [ETH Zurich, Physical Chemistry (Switzerland); Melki, Ronald, E-mail: melki@lebs.cnrs-gif.fr [UPR 3082 CNRS, Laboratoire d' Enzymologie et Biochimie Structurales (France); Boeckmann, Anja, E-mail: a.bockmann@ibcp.fr [UMR 5086 CNRS/Universite de Lyon 1, Institut de Biologie et Chimie des Proteines (France)

    2011-11-15

    We present the de novo resonance assignments for the crystalline 33 kDa C-terminal domain of the Ure2 prion using an optimized set of five 3D solid-state NMR spectra. We obtained, using a single uniformly {sup 13}C, {sup 15}N labeled protein sample, sequential chemical-shift information for 74% of the N, C{alpha}, C{beta} triples, and for 80% of further side-chain resonances for these spin systems. We describe the procedures and protocols devised, and discuss possibilities and limitations of the assignment of this largest protein assigned today by solid-state NMR, and for which no solution-state NMR shifts were available. A comparison of the NMR chemical shifts with crystallographic data reveals that regions with high crystallographic B-factors are particularly difficult to assign. While the secondary structure elements derived from the chemical shift data correspond mainly to those present in the X-ray crystal structure, we detect an additional helical element and structural variability in the protein crystal, most probably originating from the different molecules in the asymmetric unit, with the observation of doubled resonances in several parts, including entire stretches, of the protein. Our results provide the point of departure towards an atomic-resolution structural analysis of the C-terminal Ure2p domain in the context of the full-length prion fibrils.

  10. Solid-State 13C NMR Spectroscopy Applied to the Study of Carbon Blacks and Carbon Deposits Obtained by Plasma Pyrolysis of Natural Gas

    Directory of Open Access Journals (Sweden)

    Jair C. C. Freitas

    2016-01-01

    Full Text Available Solid-state 13C nuclear magnetic resonance (NMR spectroscopy was used in this work to analyze the physical and chemical properties of plasma blacks and carbon deposits produced by thermal cracking of natural gas using different types of plasma reactors. In a typical configuration with a double-chamber reactor, N2 or Ar was injected as plasma working gas in the first chamber and natural gas was injected in the second chamber, inside the arc column. The solid residue was collected at different points throughout the plasma apparatus and analyzed by 13C solid-state NMR spectroscopy, using either cross polarization (CP or direct polarization (DP, combined with magic angle spinning (MAS. The 13C CP/MAS NMR spectra of a number of plasma blacks produced in the N2 plasma reactor showed two resonance bands, broadly identified as associated with aromatic and aliphatic groups, with indication of the presence of oxygen- and nitrogen-containing groups in the aliphatic region of the spectrum. In contrast to DP experiments, only a small fraction of 13C nuclei in the plasma blacks are effectively cross-polarized from nearby 1H nuclei and are thus observed in spectra recorded with CP. 13C NMR spectra are thus useful to distinguish between different types of carbon species in plasma blacks and allow a selective study of groups spatially close to hydrogen in the material.

  11. Solid-state 51V MAS NMR spectroscopy determines component concentration and crystal phase in co-crystallised mixtures of vanadium complexes

    DEFF Research Database (Denmark)

    Nielsen, Ulla Gro; Hazell, Alan Charles; Skibsted, Jørgen Bengaard

    2010-01-01

    resonances are sensitive to intermolecular interactions specific to each crystal phase. The solid-state V-51 MAS NMR spectroscopic data show that the different phases do not co-precipitate but the concentration of the solute (which can be either 1 or 2) can vary. Thus co-crystallised mixtures of 1 and 2 can...... be classed as a molecular mixture capable of forming continuous solid solutions....... for the vanadium atoms of the two complexes mean that V-51 solution state and MAS NMR spectroscopy can be used to determine the concentration of 1 and 2 in bulk samples. Significantly, however, V-51 MAS NMR spectroscopy also reports on the identity of the crystal phase. This is possible because the isotropic V-51...

  12. Solid-state NMR spectroscopic investigation at thermal waste products from embedded flame retardants and polymers; Festkoerper-NMR-Untersuchungen an thermischen Abbauprodukten von flammgeschuetzten Polymeren

    Energy Technology Data Exchange (ETDEWEB)

    Fichera, M.A.

    2008-07-01

    The author of the contribution under consideration describes the structural characterisation of embedded flame retardants and polymers. Analysis includes determination of the phase contents as well as description of their mutual interactions as a function of their thermal history in different atmospheres (air and nitrogen). Solid-state NMR spectroscopy enables structural information about the amorphous state of the decomposed products, determination of the thermal and thermo-oxidative conversion in different amorphous and crystalline structures, and predictions about the short-range order of the observed nuclei. In this context measurements of single pulse, rotor-synchronised spin echo (SP) and cross polarisation (CP) experiments, as well as REDOR (rotational echo double resonance) and TRAPDOR- (transfer of population in double resonance) have been conducted. Additionally, {sup 1}B SP and {sup 31}P RSE experiments have been used to study quantitatively the borate and both phosphorus and phosphate contents in the solid residues. Particular emphasis was put on quantifying crystalline and non-crystalline phosphate phases. The first system consists o a combination of the flame retardants red phosphorus and magnesium hydroxide in high impact polystyrene (HIPS). From the results of extensive NMR experiments it was deduced that most of inserted red phosphorus remains in amorphous phosphates phases (ortho, pyro, and chain/ring phosphates) besides some crystalline phosphate phases. Decomposition characteristics such as temperature and the availability of oxygen (N{sub 2} atmosphere/air) show a significant influence on the decomposition process and the formation of phosphate phases (crystalline/amorphous). By comparing the results of the annealing processes to the results of the cone calorimeter measurements an anaerobic decomposition way was confirmed. In a second system, thermal reactions between the two flame retardants bisphenol A bis diphenyl phosphate and zinc borate

  13. NMR doesn't lie or how solid-state NMR spectroscopy contributed to a better understanding of the nature and function of soil organic matter (Philippe Duchaufour Medal Lecture)

    Science.gov (United States)

    Knicker, Heike

    2016-04-01

    "Nuclear magnetic resonance (NMR) does not lie". More than anything else, this statement of a former colleague and friend has shaped my relation to solid-state NMR spectroscopy. Indeed, if this technique leads to results which contradict the expectations, it is because i) some parts of the instrument are broken, ii) maladjustment of the acquisition parameters or iii) wrong preparation or confusion of samples. However, it may be even simpler, namely that the expectations were wrong. Of course, for researchers, the latter is the most interesting possibility since it forces to reassess accepted views and to search for new explanations. As my major analytical tool, NMR spectroscopy has confronted me with this challenge often enough to turn this issue into the main subject of my talk and to share with the audience how it formed my understanding of function and nature of soil organic matter (SOM). Already shortly after its introduction into soil science in the 1980's, the data obtained with solid-state 13C NMR spectroscopy opened the stage for ongoing discussions, since they showed that in humified SOM aromatic carbon is considerably less important than previously thought. This finding had major implications regarding the understanding of the origin of SOM and the mechanisms by which it is formed. Certainly, the discrepancy between the new results and previous paradigms contributed to mistrust in the reliability of solid-state NMR techniques. The respective discussion has survived up to our days, although already in the 1980's and 1990's fundamental studies could demonstrate that quantitative solid-state NMR data can be obtained if i) correct acquisition parameters are chosen, ii) the impact of paramagnetic compounds is reduced and iii) the presence of soot in soils can be excluded. On the other hand, this mistrust led to a detailed analysis of the impact of paramagnetics on the NMR behavior of C groups which then improved our understanding of the role of carbohydrates

  14. A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples

    Science.gov (United States)

    Grant, Christopher V.; Yang, Yuan; Glibowicka, Mira; Wu, Chin H.; Park, Sang Ho; Deber, Charles M.; Opella, Stanley J.

    2009-11-01

    The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the 1H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B 1 field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the 1H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.

  15. A chelate-stabilized ruthenium(sigma-pyrrolato) complex: resolving ambiguities in nuclearity and coordination geometry through 1H PGSE and 31P solid-state NMR studies.

    Science.gov (United States)

    Foucault, Heather M; Bryce, David L; Fogg, Deryn E

    2006-12-11

    Reaction of RuCl2(PPh3)3 with LiNN' (NN' = 2-[(2,6-diisopropylphenyl)imino]pyrrolide) affords a single product, with the empirical formula RuCl[(2,6-iPr2C6H3)N=CHC4H3N](PPh3)2. We identify this species as a sigma-pyrrolato complex, [Ru(NN')(PPh3)2]2(mu-Cl)2 (3b), rather than mononuclear RuCl(NN')(PPh3)2 (3a), on the basis of detailed 1D and 2D NMR characterization in solution and in the solid state. Retention of the chelating, sigma-bound iminopyrrolato unit within 3b, despite the presence of labile (dative) chloride and PPh3 donors, indicates that the chelate effect is sufficient to inhibit sigma --> pi isomerization of 3b to a piano-stool, pi-pyrrolato structure. 2D COSY, SECSY, and J-resolved solid-state 31P NMR experiments confirm that the PPh3 ligands on each metal center are magnetically and crystallographically inequivalent, and 31P CP/MAS NMR experiments reveal the largest 99Ru-31P spin-spin coupling constant (1J(99Ru,31P) = 244 +/- 20 Hz) yet measured. Finally, 31P dipolar-chemical shift spectroscopy is applied to determine benchmark phosphorus chemical shift tensors for phosphine ligands in hexacoordinate ruthenium complexes.

  16. Hydrido-ruthenium cluster complexes as models for reactive surface hydrogen species of ruthenium nanoparticles. Solid-state 2H NMR and quantum chemical calculations.

    Science.gov (United States)

    Gutmann, Torsten; Walaszek, Bernadeta; Yeping, Xu; Wächtler, Maria; del Rosal, Iker; Grünberg, Anna; Poteau, Romuald; Axet, Rosa; Lavigne, Guy; Chaudret, Bruno; Limbach, Hans-Heinrich; Buntkowsky, Gerd

    2010-08-25

    The (2)H quadrupolar interaction is a sensitive tool for the characterization of deuterium-metal binding states. In the present study, experimental solid-state (2)H MAS NMR techniques are used in the investigations of two ruthenium clusters, D(4)Ru(4)(CO)(12) (1) and D(2)Ru(6)(CO)(18) (2), which serve as model compounds for typical two-fold, three-fold, and octahedral coordination sites on metal surfaces. By line-shape analysis of the (2)H MAS NMR measurements of sample 1, a quadrupolar coupling constant of 67 +/- 1 kHz, an asymmetry parameter of 0.67 +/- 0.1, and an isotropic chemical shift of -17.4 ppm are obtained. In addition to the neutral complex, sample 2 includes two ionic clusters, identified as anionic [DRu(6)(CO)(18)](-) (2(-)) and cationic [D(3)Ru(6)(CO)(18)](+) (2(+)). By virtue of the very weak quadrupolar interaction (Quantum chemical DFT calculations at different model structures for these ruthenium clusters were arranged in order to help in the interpretation of the experimental results. It is shown that the (2)H nuclear quadrupolar interaction is a sensitive tool for distinguishing the binding state of the deuterons to the transition metal. Combining the data from the polynuclear complexes with the data from mononuclear complexes, a molecular ruler for quadrupolar interactions is created. This ruler now permits the solid-state NMR spectroscopic characterization of deuterium adsorbed on the surfaces of catalytically active metal nanoparticles.

  17. Distribution and mobility of phosphates and sodium ions in cheese by solid-state 31P and double-quantum filtered 23Na NMR spectroscopy.

    Science.gov (United States)

    Gobet, Mallory; Rondeau-Mouro, Corinne; Buchin, Solange; Le Quéré, Jean-Luc; Guichard, Elisabeth; Foucat, Loïc; Moreau, Céline

    2010-04-01

    The feasibility of solid-state magic angle spinning (MAS) (31)P nuclear magnetic resonance (NMR) spectroscopy and (23)Na NMR spectroscopy to investigate both phosphates and Na(+) ions distribution in semi-hard cheeses in a non-destructive way was studied. Two semi-hard cheeses of known composition were made with two different salt contents. (31)P Single-pulse excitation and cross-polarization MAS experiments allowed, for the first time, the identification and quantification of soluble and insoluble phosphates in the cheeses. The presence of a relatively 'mobile' fraction of colloidal phosphates was evidenced. The detection by (23)Na single-quantum NMR experiments of all the sodium ions in the cheeses was validated. The presence of a fraction of 'bound' sodium ions was evidenced by (23)Na double-quantum filtered NMR experiments. We demonstrated that NMR is a suitable tool to investigate both phosphates and Na(+) ions distributions in cheeses. The impact of the sodium content on the various phosphorus forms distribution was discussed and results demonstrated that NMR would be an important tool for the cheese industry for the processes controls.

  18. Determining hydrogen-bond interactions in spider silk with 1H-13C HETCOR fast MAS solid-state NMR and DFT proton chemical shift calculations.

    Science.gov (United States)

    Holland, Gregory P; Mou, Qiushi; Yarger, Jeffery L

    2013-07-28

    Two-dimensional (2D) (1)H-(13)C heteronuclear correlation (HETCOR) solid-state NMR spectra collected with fast magic angle spinning (MAS) are used in conjunction with density functional theory (DFT) proton chemical shift calculations to determine the hydrogen-bonding strength for ordered β-sheet and disordered 310-helical structures in spider dragline silk. The hydrogen-bond strength is determined to be identical for both structures in spider silk with a 1.83-1.84 Å NH···OC hydrogen-bond distance.

  19. A 1H, 13C and 15N NMR study in solution and in the solid state of six N-substituted pyrazoles and indazoles.

    Science.gov (United States)

    Claramunt, Rosa M; Santa María, M Dolores; Sanz, Dionisia; Alkorta, Ibon; Elguero, José

    2006-05-01

    Three N-substituted pyrazoles and three N-substituted indazoles [1-(4-nitrophenyl)-3,5-dimethylpyrazole (1), 1-(2,4-dinitrophenyl)-3,5-dimethylpyrazole (2), 1-tosyl-pyrazole (3), 1-p-chlorobenzoylindazole (4), 1-tosylinda-zole (5) and 2-(2-hydroxy-2-phenylethyl)-indazole (6)] have been studied by NMR spectroscopy in solution (1H, 13C, 15N) and in the solid state (13C, 15N). The chemical shifts have been compared with GIAO/DFT calculated absolute shieldings. Some discrepancies have been analyzed.

  20. Extra-framework aluminium species in hydrated faujasite zeolite as investigated by two-dimensional solid-state NMR spectroscopy and theoretical calculations.

    Science.gov (United States)

    Li, Shenhui; Zheng, Anmin; Su, Yongchao; Fang, Hanjun; Shen, Wanling; Yu, Zhiwu; Chen, Lei; Deng, Feng

    2010-04-21

    Extra-framework aluminium (EFAL) species in hydrated dealuminated HY zeolite were thoroughly investigated by various two-dimensional solid-state NMR techniques as well as density functional theoretical calculations. (27)Al MQ MAS NMR experiments demonstrated that five-coordinated and four-coordinated extra-framework aluminium subsequently disappeared with the increase of water loading, and the quadrupole interaction of each aluminium species decreased gradually during the hydration process. (1)H double quantum MAS NMR revealed that the EFAL species in the hydrated zeolite consisted of three components: a hydroxyl AlOH group, and two types of water molecule (rigid and mobile water). (1)H-(27)Al LG-CP HETCOR experiments indicated that both the extra-framework and the framework Al atoms were in close proximity to the rigid water in the fully rehydrated zeolite. The experimental results were further confirmed by DFT theoretical calculations. Moreover, theoretical calculation results further demonstrated that the EFAL species in the hydrated zeolite consisted of the three components and the calculated (1)H NMR chemical shift for each component agreed well with our NMR observations. It is the rigid water that connects the extra-framework aluminium with the four-coordinated framework aluminium through strong hydrogen bonds.

  1. Solid-state NMR studies of Al-doped and Al{sub 2}O{sub 3}-coated LiCoO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Youngil; Kim, Dongmin; Lee, Hyeyeoun [Dongbu Advanced Research Inst., Daejeon (Korea). Chemical Analysis Team; Woo, Ae Ja [Ewha Womans Univ., Seoul (Korea); Han, Kyoo Seung [Chungnam National Univ., Daejeon (Korea). Dept. of Fine Chemicals Engineering and Chemistry; Ryu, D. [Electronics and Telecommunications Research Inst., Daejeon (Korea); Sohn, Daewon [Hanyang Univ., Seoul (Korea). Dept. of Chemistry

    2004-11-30

    As a cathode material for commercial lithium rechargeable battery, Al-doped and Al{sub 2}O{sub 3}-coated LiCoO{sub 2} were structurally characterized and compared by using solid-state {sup 7}Li and {sup 27}Al magic angle spinning (MAS) NMR. The structural states of lithium and aluminum in those samples were successfully identified by calculation of NMR spectra. {sup 7}Li MAS NMR spectra of samples had shown similar features having more than three lithium sites, which were determined as quadrupole coupling constant with the same asymmetric parameter ({eta} = 0.1); C{sub Q} = 1.10 MHz for octahedral site, and C{sub Q} 2.97 MHz and C{sub Q} = 3.83 MHz for shoulders. {sup 27}Al MAS NMR spectra of samples, however, showed significant difference in two observed aluminum sites. In the simulation of NMR spectrum for Al{sub 2}O{sub 3}-coated LiCoO{sub 2}, the values of C{sub Q} and {eta} were obtained; 4.45 MHz and {eta} = 0.86 for tetrahedral site and 4.31 MHz and {eta} = 0.81 for octahedral.

  2. Insight into the conformational stability of membrane-embedded BamA using a combined solution and solid-state NMR approach

    Energy Technology Data Exchange (ETDEWEB)

    Sinnige, Tessa; Houben, Klaartje [Utrecht University, NMR Spectroscopy, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Pritisanac, Iva [Physical and Theoretical Chemistry Laboratory (United Kingdom); Renault, Marie [Institute of Pharmacology and Structural Biology (France); Boelens, Rolf; Baldus, Marc, E-mail: m.baldus@uu.nl [Utrecht University, NMR Spectroscopy, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands)

    2015-04-15

    The β-barrel assembly machinery (BAM) is involved in folding and insertion of outer membrane proteins in Gram-negative bacteria, a process that is still poorly understood. With its 790 residues, BamA presents a challenge to current NMR methods. We utilized a “divide and conquer” approach in which we first obtained resonance assignments for BamA’s periplasmic POTRA domains 4 and 5 by solution NMR. Comparison of these assignments to solid-state NMR (ssNMR) data obtained on two BamA constructs including the transmembrane domain and one or two soluble POTRA domains suggested that the fold of POTRA domain 5 critically depends on the interface with POTRA 4. Using specific labeling schemes we furthermore obtained ssNMR resonance assignments for residues in the extracellular loop 6 that is known to be crucial for BamA-mediated substrate folding and insertion. Taken together, our data provide novel insights into the conformational stability of membrane-embedded, non-crystalline BamA.

  3. 1H and 23Na MAS NMR spectroscopy of cationic species in CO2 selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    Science.gov (United States)

    Arévalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernández-Maldonado, Arturo J.

    2012-07-01

    The location of extraframework cations in Sr2+ and Ba2+ ion-exchanged SAPO-34 was estimated by means of 1H and 23Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO2 adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium.

  4. Solid-State NMR and DFT Studies on the Formation of Well-Defined Silica-Supported Tantallaaziridines: From Synthesis to Catalytic Application

    KAUST Repository

    Hamzaoui, Bilel

    2016-01-27

    Single-site, well-defined, silica-supported tantallaaziridine intermediates [≡Si-O-Ta(η2-NRCH2)(NMe2)2] [R=Me (2), Ph (3)] were prepared from silica-supported tetrakis(dimethylamido)tantalum [≡Si-O-Ta(NMe2)4] (1) and fully characterized by FTIR spectroscopy, elemental analysis, and 1H,13C HETCOR and DQ TQ solid-state (SS) NMR spectroscopy. The formation mechanism, by β-H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C-H activation of the dimethylamide ligand is favored for R=Ph. The results from catalytic testing in the hydroaminoalkylation of alkenes were consistent with the N-alkyl aryl amine substrates being more efficient than N-dialkyl amines. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Structural features of a bituminous coal and their changes during low-temperature oxidation and loss of volatiles investigated by advanced solid-state NMR spectroscopy

    Science.gov (United States)

    Mao, J.-D.; Schimmelmann, A.; Mastalerz, Maria; Hatcher, P.G.; Li, Y.

    2010-01-01

    Quantitative and advanced 13C solid-state NMR techniques were employed to investigate (i) the chemical structure of a high volatile bituminous coal, as well as (ii) chemical structural changes of this coal after evacuation of adsorbed gases, (iii) during oxidative air exposure at room temperature, and (iv) after oxidative heating in air at 75 ??C. The solid-state NMR techniques employed in this study included quantitative direct polarization/magic angle spinning (DP/MAS) at a high spinning speed of 14 kHz, cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CH, CH2, and CHn selection, 13C chemical shift anisotropy (CSA) filtering, two-dimensional (2D) 1H-13C heteronuclear correlation NMR (HETCOR), and 2D HETCOR with 1H spin diffusion. With spectral editing techniques, we identified methyl CCH 3, rigid and mobile methylene CCH2C, methine CCH, quaternary Cq, aromatic CH, aromatic carbons bonded to alkyls, small-sized condensed aromatic moieties, and aromatic C-O groups. With direct polarization combined with spectral-editing techniques, we quantified 11 different types of functional groups. 1H-13C 2D HETCOR NMR experiments indicated spatial proximity of aromatic and alkyl moieties in cross-linked structures. The proton spin diffusion experiments indicated that the magnetization was not equilibrated at a 1H spin diffusion time of 5 ms. Therefore, the heterogeneity in spatial distribution of different functional groups should be above 2 nm. Recoupled C-H long-range dipolar dephasing showed that the fraction of large charcoal-like clusters of polycondensed aromatic rings was relatively small. The exposure of this coal to atmospheric oxygen at room temperature for 6 months did not result in obvious chemical structural changes of the coal, whereas heating at 75 ??C in air for 10 days led to oxidation of coal and generated some COO groups. Evacuation removed most volatiles and caused a significant reduction in aliphatic signals in its DP

  6. A multinuclear solid-state NMR study of alkali metal ions in tetraphenylborate salts, M[BPh4] (M = Na, K, Rb and Cs): what is the NMR signature of cation-pi interactions?

    Science.gov (United States)

    Wu, Gang; Terskikh, Victor

    2008-10-16

    We report a multinuclear solid-state ( (23)Na, (39)K, (87)Rb, (133)Cs) NMR study of tetraphenylborate salts, M[BPh 4] (M = Na, K, Rb, Cs). These compounds are isostructural in the solid state with the alkali metal ion surrounded by four phenyl groups resulting in strong cation-pi interactions. From analyses of solid-state NMR spectra obtained under stationary and magic-angle spinning (MAS) conditions at 11.75 and 21.15 T, we have obtained the quadrupole coupling constants, C Q, and the chemical shift tensor parameters for the alkali metal ions in these compounds. We found that the observed quadrupole coupling constant for M (+) in M[BPh 4] is determined by a combination of nuclear quadrupole moment, Sternheimer antishielding factor, and unit cell dimensions. On the basis of a comparison between computed paramagnetic and diamagnetic contributions to the total chemical shielding values for commonly found cation-ligand interactions, we conclude that cation-pi interactions give rise to significantly lower paramagnetic shielding contributions than other cation-ligand interactions. As a result, highly negative chemical shifts are expected to be the NMR signature for cations interacting exclusively with pi systems.

  7. Chemical and nanometer-scale structure of kerogen and its change during thermal maturation investigated by advanced solid-state 13C NMR spectroscopy

    Science.gov (United States)

    Mao, J.; Fang, X.; Lan, Y.; Schimmelmann, A.; Mastalerz, Maria; Xu, L.; Schmidt-Rohr, K.

    2010-01-01

    We have used advanced and quantitative solid-state nuclear magnetic resonance (NMR) techniques to investigate structural changes in a series of type II kerogen samples from the New Albany Shale across a range of maturity (vitrinite reflectance R0 from 0.29% to 1.27%). Specific functional groups such as CH3, CH2, alkyl CH, aromatic CH, aromatic C-O, and other nonprotonated aromatics, as well as "oil prone" and "gas prone" carbons, have been quantified by 13C NMR; atomic H/C and O/C ratios calculated from the NMR data agree with elemental analysis. Relationships between NMR structural parameters and vitrinite reflectance, a proxy for thermal maturity, were evaluated. The aromatic cluster size is probed in terms of the fraction of aromatic carbons that are protonated (???30%) and the average distance of aromatic C from the nearest protons in long-range H-C dephasing, both of which do not increase much with maturation, in spite of a great increase in aromaticity. The aromatic clusters in the most mature sample consist of ???30 carbons, and of ???20 carbons in the least mature samples. Proof of many links between alkyl chains and aromatic rings is provided by short-range and long-range 1H-13C correlation NMR. The alkyl segments provide most H in the samples; even at a carbon aromaticity of 83%, the fraction of aromatic H is only 38%. While aromaticity increases with thermal maturity, most other NMR structural parameters, including the aromatic C-O fractions, decrease. Aromaticity is confirmed as an excellent NMR structural parameter for assessing thermal maturity. In this series of samples, thermal maturation mostly increases aromaticity by reducing the length of the alkyl chains attached to the aromatic cores, not by pronounced growth of the size of the fused aromatic ring clusters. ?? 2010 Elsevier Ltd. All rights reserved.

  8. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations Part II: CP kinetics and relaxation analysis.

    Science.gov (United States)

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika; Szeleszczuk, Łukasz; Wawer, Iwona

    2016-04-15

    Excipients used in the solid drug formulations differ in their NMR relaxation and (13)C cross-polarization (CP) kinetics parameters. Therefore, experimental parameters like contact time of cross-polarization and repetition time have a major impact on the registered solid state NMR spectra and in consequence on the results of the NMR analysis. In this work the CP kinetics and relaxation of the most common pharmaceutical excipients: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. The studied excipients differ significantly in their optimum repetition time (from 5 s to 1200 s) and T(1ρ)(I) parameters (from 2 ms to 73 ms). The practical use of those differences in the excipients composition analysis was demonstrated on the example of commercially available tablets containing indapamide as an API. The information presented in this article will help to choose the correct acquisition parameters and also will save the time and effort needed for their optimization in the NMR analysis of the solid drug formulations.

  9. Probing lipid-cholesterol interactions in DOPC/eSM/Chol and DOPC/DPPC/Chol model lipid rafts with DSC and (13)C solid-state NMR.

    Science.gov (United States)

    Fritzsching, Keith J; Kim, Jihyun; Holland, Gregory P

    2013-08-01

    The interaction between cholesterol (Chol) and phospholipids in bilayers was investigated for the ternary model lipid rafts, DOPC/eSM/Chol and DOPC/DPPC/Chol, with differential scanning calorimetry (DSC) and (13)C cross polarization magic angle spinning (CP-MAS) solid-state NMR. The enthalpy and transition temperature (Tm) of the Lα liquid crystalline phase transition from DSC was used to probe the thermodynamics of the different lipids in the two systems as a function of Chol content. The main chain (13)C (CH2)n resonance is resolved in the (13)C CP-MAS NMR spectra for the unsaturated (DOPC) and saturated (eSM or DPPC) chain lipid in the ternary lipid raft mixtures. The (13)C chemical shift of this resonance can be used to detect differences in chain ordering and overall interactions with Chol for the different lipid constituents in the ternary systems. The combination of DSC and (13)C CP-MAS NMR results indicate that there is a preferential interaction between SM and Chol below Tm for the DOPC/eSM/Chol system when the Chol content is ≤20mol%. In contrast, no preferential interaction between Chol and DPPC is observed in the DOPC/DPPC/Chol system above or below Tm. Finally, (13)C CP-MAS NMR resolves two Chol environments in the DOPC/eSM/Chol system below Tm at Chol contents >20mol% while, a single Chol environment is observed for DOPC/DPPC/Chol at all compositions.

  10. Multiple acquisitions via sequential transfer of orphan spin polarization (MAeSTOSO): How far can we push residual spin polarization in solid-state NMR?

    Science.gov (United States)

    Gopinath, T.; Veglia, Gianluigi

    2016-06-01

    Conventional multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) experiments detect the signal arising from the decay of a single coherence transfer pathway (FID), resulting in one spectrum per acquisition time. Recently, we introduced two new strategies, namely DUMAS (DUal acquisition Magic Angle Spinning) and MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), that enable the simultaneous acquisitions of multidimensional ssNMR experiments using multiple coherence transfer pathways. Here, we combined the main elements of DUMAS and MEIOSIS to harness both orphan spin operators and residual polarization and increase the number of simultaneous acquisitions. We show that it is possible to acquire up to eight two-dimensional experiments using four acquisition periods per each scan. This new suite of pulse sequences, called MAeSTOSO for Multiple Acquisitions via Sequential Transfer of Orphan Spin pOlarization, relies on residual polarization of both 13C and 15N pathways and combines low- and high-sensitivity experiments into a single pulse sequence using one receiver and commercial ssNMR probes. The acquisition of multiple experiments does not affect the sensitivity of the main experiment; rather it recovers the lost coherences that are discarded, resulting in a significant gain in experimental time. Both merits and limitations of this approach are discussed.

  11. High-resolution solid-state 13C NMR spectroscopy of the paramagnetic metal-organic frameworks, STAM-1 and HKUST-1.

    Science.gov (United States)

    Dawson, Daniel M; Jamieson, Lauren E; Mohideen, M Infas H; McKinlay, Alistair C; Smellie, Iain A; Cadou, Romain; Keddie, Neil S; Morris, Russell E; Ashbrook, Sharon E

    2013-01-21

    Solid-state (13)C magic-angle spinning (MAS) NMR spectroscopy is used to investigate the structure of the Cu(II)-based metal-organic frameworks (MOFs), HKUST-1 and STAM-1, and the structural changes occurring within these MOFs upon activation (dehydration). NMR spectroscopy is an attractive technique for the investigation of these materials, owing to its high sensitivity to local structure, without any requirement for longer-range order. However, interactions between nuclei and unpaired electrons in paramagnetic systems (e.g., Cu(II)-based MOFs) pose a considerable challenge, not only for spectral acquisition, but also in the assignment and interpretation of the spectral resonances. Here, we exploit the rapid T(1) relaxation of these materials to obtain (13)C NMR spectra using a spin-echo pulse sequence at natural abundance levels, and employ frequency-stepped acquisition to ensure uniform excitation of resonances over a wide frequency range. We then utilise selective (13)C isotopic labelling of the organic linker molecules to enable an unambiguous assignment of NMR spectra of both MOFs for the first time. We show that the monomethylated linker can be recovered from STAM-1 intact, demonstrating not only the interesting use of this MOF as a protecting group, but also the ability (for both STAM-1 and HKUST-1) to recover isotopically-enriched linkers, thereby reducing significantly the overall cost of the approach.

  12. A solid-state NMR and DFT study of compositional modulations in AlxGa1-xAs

    NARCIS (Netherlands)

    Knijn, Paulus J.; Bentum, P. Jan M. van; Eck, Ernst R.H. van; Fang, Changming; Grimminck, Dennis L.A.G.; Groot, Robert A. de; Havenith, Remco W.A.; Marsman, Martijn; Meerts, W. Leo; Wijs, Gilles A. de; Kentgens, Arno P.M.

    2010-01-01

    We have conducted 75As and 69Ga Nuclear Magnetic Resonance (NMR) experiments to investigate order/disorder in AlxGa1-xAs lift-off films with x ~ 0.297 and 0.489. We were able to identify all possible As(AlnGa4-n) sites with n = 0–4 coordinations in 75As NMR spectra using spin-echo experiments at 18.

  13. Investigating the interaction between peptides of the amphipathic helix of Hcf106 and the phospholipid bilayer by solid-state NMR spectroscopy

    Science.gov (United States)

    Zhang, Lei; Liu, Lishan; Maltsev, Sergey; Lorigan, Gary A.; Dabney-Smith, Carole

    2013-01-01

    The chloroplast twin arginine translocation (cpTat) system transports highly folded precursor proteins into the thylakoid lumen using the protonmotive force as its only energy source. Hcf106, as one of the core components of the cpTat system, is part of the precursor receptor complex and functions in the initial precursor-binding step. Hcf106 is predicted to contain a single amino terminal transmembrane domain followed by a Pro-Gly hinge, a predicted amphipathic α-helix (APH), and a loosely structured carboxy terminus. Hcf106 has been shown biochemically to insert spontaneously into thylakoid membranes. To better understand the membrane active capabilities of Hcf106, we used solid-state NMR spectroscopy to investigate those properties of the APH. In this study, synthesized peptides of the predicted Hcf106 APH (amino acids 28–65) were incorporated at increasing mol% into 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) and POPC/MGDG (monogalactosyldiacylglycerol; mole ratio 85:15) multilamellar vesicles (MLVs) to probe the peptide-lipid interaction. Solid-state 31P NMR and 2H NMR spectroscopic experiments revealed that the peptide perturbs the headgroup and the acyl chain regions of phospholipids as indicated by changes in spectral lineshape, chemical shift anisotropy (CSA) line width, and 2H order SCD parameters. In addition, the comparison between POPC MLVs and POPC/MGDG MLVs indicated that the lipid bilayer composition affected peptide perturbation of the lipids, and such perturbation appeared to be more intense in a system more closely mimicking a thylakoid membrane. PMID:24144541

  14. Adsorption-desorption induced structural changes of Cu-MOF evidenced by solid state NMR and EPR spectroscopy.

    Science.gov (United States)

    Jiang, Yijiao; Huang, Jun; Kasumaj, Besnik; Jeschke, Gunnar; Hunger, Michael; Mallat, Tamas; Baiker, Alfons

    2009-02-18

    Adsorption-desorption induced structural changes of Cu(bpy)(H(2)O)(2)(BF(4)),(bpy) (bpy = 4,4'-bipyridine) [Cu-MOF] have been evidenced by combined NMR and EPR spectroscopy. Upon adsorption of probe molecules even at a few mbar, EPR spectra show that they are activated to form complexes at Cu(II) sites, which results in a change of the Cu-MOF's structure as indicated by a high-field shift of the (11)B MAS NMR. After desorption, both EPR and (11)B MAS NMR spectra evidenced that the structure of the Cu-MOF reversibly shifted to the original state. This observation indicates that MOFs can undergo structural changes during processes where adsorption-desorption steps are involved such as gas storage, separation, and catalysis.

  15. Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Miknis, F.P.; Jiao, Z.S.; Zhao, Hanqing; Surdam, R.C.

    1998-12-31

    This Western Research Institute (WRI) jointly sponsored research (JSR) project augmented and complemented research conducted by the University of Wyoming Institute For Energy Research for the Gas Research Institute. The project, {open_quotes}A New Innovative Exploitation Strategy for Gas Accumulations Within Pressure Compartments,{close_quotes} was a continuation of a project funded by the GRI Pressure Compartmentalization Program that began in 1990. That project, {open_quotes}Analysis of Pressure Chambers and Seals in the Powder River Basin, Wyoming and Montana,{close_quotes} characterized a new class of hydrocarbon traps, the discovery of which can provide an impetus to revitalize the domestic petroleum industry. In support of the UW Institute For Energy Research`s program on pressure compartmentalization, solid-state {sup 13}C NMR measurements were made on sets of shales and coals from different Laramide basins in North America. NMR measurements were made on samples taken from different formations and depths of burial in the Alberta, Bighorn, Denver, San Juan, Washakie, and Wind River basins. The carbon aromaticity determined by NMR was shown to increase with depth of burial and increased maturation. In general, the NMR data were in agreement with other maturational indicators, such as vitrinite reflectance, illite/smectite ratio, and production indices. NMR measurements were also obtained on residues from hydrous pyrolysis experiments on Almond and Lance Formation coals from the Washakie Basin. These data were used in conjunction with mass and elemental balance data to obtain information about the extent of carbon aromatization that occurs during artificial maturation. The data indicated that 41 and 50% of the original aliphatic carbon in the Almond and Lance coals, respectively, aromatized during hydrous pyrolysis.

  16. High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy

    Science.gov (United States)

    Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G.

    2014-09-01

    We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4 Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation.

  17. Specific binding of a naturally occurring amyloidogenic fragment of Streptococcus mutans adhesin P1 to intact P1 on the cell surface characterized by solid state NMR spectroscopy.

    Science.gov (United States)

    Tang, Wenxing; Bhatt, Avni; Smith, Adam N; Crowley, Paula J; Brady, L Jeannine; Long, Joanna R

    2016-02-01

    The P1 adhesin (aka Antigen I/II or PAc) of the cariogenic bacterium Streptococcus mutans is a cell surface-localized protein involved in sucrose-independent adhesion and colonization of the tooth surface. The immunoreactive and adhesive properties of S. mutans suggest an unusual functional quaternary ultrastructure comprised of intact P1 covalently attached to the cell wall and interacting with non-covalently associated proteolytic fragments thereof, particularly the ~57-kDa C-terminal fragment C123 previously identified as Antigen II. S. mutans is capable of amyloid formation when grown in a biofilm and P1 is among its amyloidogenic proteins. The C123 fragment of P1 readily forms amyloid fibers in vitro suggesting it may play a role in the formation of functional amyloid during biofilm development. Using wild-type and P1-deficient strains of S. mutans, we demonstrate that solid state NMR (ssNMR) spectroscopy can be used to (1) globally characterize cell walls isolated from a Gram-positive bacterium and (2) characterize the specific binding of heterologously expressed, isotopically-enriched C123 to cell wall-anchored P1. Our results lay the groundwork for future high-resolution characterization of the C123/P1 ultrastructure and subsequent steps in biofilm formation via ssNMR spectroscopy, and they support an emerging model of S. mutans colonization whereby quaternary P1-C123 interactions confer adhesive properties important to binding to immobilized human salivary agglutinin.

  18. Fast magic-angle sample spinning solid-state NMR at 60-100kHz for natural abundance samples.

    Science.gov (United States)

    Nishiyama, Yusuke

    2016-09-01

    In spite of tremendous progress made in pulse sequence designs and sophisticated hardware developments, methods to improve sensitivity and resolution in solid-state NMR (ssNMR) are still emerging. The rate at which sample is spun at magic angle determines the extent to which sensitivity and resolution of NMR spectra are improved. To this end, the prime objective of this article is to give a comprehensive theoretical and experimental framework of fast magic angle spinning (MAS) technique. The engineering design of fast MAS rotors based on spinning rate, sample volume, and sensitivity is presented in detail. Besides, the benefits of fast MAS citing the recent progress in methodology, especially for natural abundance samples are also highlighted. The effect of the MAS rate on (1)H resolution, which is a key to the success of the (1)H inverse detection methods, is described by a simple mathematical factor named as the homogeneity factor k. A comparison between various (1)H inverse detection methods is also presented. Moreover, methods to reduce the number of spinning sidebands (SSBs) for the systems with huge anisotropies in combination with (1)H inverse detection at fast MAS are discussed.

  19. Unexpected solvent impact in the crystallinity of praziquantel/poly(vinylpyrrolidone) formulations. A solubility, DSC and solid-state NMR study.

    Science.gov (United States)

    Costa, Emanuel D; Priotti, Josefina; Orlandi, Silvina; Leonardi, Darío; Lamas, María C; Nunes, Teresa G; Diogo, Hermínio P; Salomon, Claudio J; Ferreira, M João

    2016-09-25

    The saturation solubility of PVP:PZQ physical mixtures (PMs) and solid dispersions (SDs) prepared from ethanol (E/E) or ethanol/water (E/W) by the solvent evaporation method at 1:1, 2:1 and 3:1 ratio (w/w) was determined. The presence of PVP improves the solubility of PZQ (0.31±0.01mg/mL). A maximum of 1.29±0.03mg/mL of PZQ in solution was achieved for the 3:1 SD (E/E). The amount of PZQ in solution depends on the amount of polymer and on the preparation method. Solid-state NMR (ssNMR) and DSC were used to understand this behavior. Results show that PMs are a mixture of crystalline PZQ with the polymer, while SDs show different degrees of drug amorphization depending on the solvent used. For E/W SDs, PZQ exists in amorphous and crystalline states, with no clear correlation between the amount of crystalline PZQ and the amount of PVP. For E/E SDs, formulations with a higher percentage of PZQ are amorphous with the components miscible in domains larger than 3nm ((1)H ssNMR relaxation measurements). Albeit its higher saturation solubility, the 3:1 E/E PVP:PZQ sample has a significant crystalline content, probably due to the water introduced by the polymer. High PVP content and small crystal size account for this result.

  20. Membrane topologies of the PGLa antimicrobial peptide and a transmembrane anchor sequence by Dynamic Nuclear Polarization/solid-state NMR spectroscopy.

    Science.gov (United States)

    Salnikov, Evgeniy Sergeevich; Aisenbrey, Christopher; Aussenac, Fabien; Ouari, Olivier; Sarrouj, Hiba; Reiter, Christian; Tordo, Paul; Engelke, Frank; Bechinger, Burkhard

    2016-02-15

    Dynamic Nuclear Polarization (DNP) has been introduced to overcome the sensitivity limitations of nuclear magnetic resonance (NMR) spectroscopy also of supported lipid bilayers. When investigated by solid-state NMR techniques the approach typically involves doping the samples with biradicals and their investigation at cryo-temperatures. Here we investigated the effects of temperature and membrane hydration on the topology of amphipathic and hydrophobic membrane polypeptides. Although the antimicrobial PGLa peptide in dimyristoyl phospholipids is particularly sensitive to topological alterations, the DNP conditions represent well its membrane alignment also found in bacterial lipids at ambient temperature. With a novel membrane-anchored biradical and purpose-built hardware a 17-fold enhancement in NMR signal intensity is obtained by DNP which is one of the best obtained for a truly static matrix-free system. Furthermore, a membrane anchor sequence encompassing 19 hydrophobic amino acid residues was investigated. Although at cryotemperatures the transmembrane domain adjusts it membrane tilt angle by about 10 degrees, the temperature dependence of two-dimensional separated field spectra show that freezing the motions can have beneficial effects for the structural analysis of this sequence.

  1. CF3 Rotation in 3-(Trifluoromethyl)phenanthrene: Solid State 19F and 1H NMR relaxation and Bloch-Wangsness-Redfield theory.

    Science.gov (United States)

    Beckmann, Peter A; Rosenberg, Jessie; Nordstrom, Kerstin; Mallory, Clelia W; Mallory, Frank B

    2006-03-23

    We have observed and modeled the 1H and 19F solid-state nuclear spin relaxation process in polycrystalline 3-(trifluoromethyl)phenanthrene. The relaxation rates for the two spin species were observed from 85 to 300 K at the low NMR frequencies of omega/2pi = 22.5 and 53.0 MHz where CF3 rotation, characterized by a mean time tau between hops, is the only motion on the NMR time scale. All motional time scales (omegatau 1) are observed. The 1H spins are immobile on the NMR time scale but are coupled to the 19F spins via the unlike-spin dipole-dipole interaction. The temperature dependence of the observed relaxation rates (the relaxation is biexponential) shows considerable structure and a thorough analysis of Bloch-Wangsness-Redfield theory for this coupled spin system is provided. The activation energy for CF3 rotation is 11.5 +/- 0.7 kJ/mol, in excellent agreement with the calculation in a 13-molecule cluster provided in the companion paper where the crystal structure is reported and detailed ab initio electronic structure calculations are performed [Wang, X.; Mallory F. B.; Mallory, C. W; Beckmann, P. A.; Rheingold, A. L.; Francl, M. M J. Phys. Chem. A 2006, 110, 3954].

  2. A novel solid-state NMR method for the investigation of trivalent lanthanide sorption on amorphous silica at low surface loadings.

    Science.gov (United States)

    Mason, H E; Begg, J D; Maxwell, R S; Kersting, A B; Zavarin, M

    2016-07-13

    The modelling of radionuclide transport in the subsurface depends on a comprehensive understanding of their interactions with mineral surfaces. Spectroscopic techniques provide important insight into these processes directly, but at high concentrations are sometimes hindered by safety concerns and limited solubilities of many radionuclides, especially the actinides. Here we use Eu(iii) as a surrogate for trivalent actinide species, and study Eu(iii) sorption on the silica surface at pH 5 where sorption is fairly limited. We have applied a novel, surface selective solid-state nuclear magnetic resonance (NMR) technique to provide information about Eu binding at the silica surface at estimated surface loadings ranging from 0.1 to 3 nmol m(-2) (<0.1% surface loading). The NMR results show that inner sphere Eu(iii) complexes are evenly distributed across the silica surface at all concentrations, but that at the highest surface loadings there are indications that precipitates may form. These results illustrate that this NMR technique may be applied in solubility-limited systems to differentiate between adsorption and precipitation to better understand the interactions of radionuclides at solid surfaces.

  3. β-Sheet Nanocrystalline Domains Formed from Phosphorylated Serine-Rich Motifs in Caddisfly Larval Silk: A Solid State NMR and XRD Study

    Science.gov (United States)

    Addison, J. Bennett; Ashton, Nicholas N.; Weber, Warner S.; Stewart, Russell J.; Holland, Gregory P.; Yarger, Jeffery L.

    2013-01-01

    Adhesive silks spun by aquatic caddisfly (order Trichoptera) larvae are used to build both intricate protective shelters and food harvesting nets underwater. In this study, we use 13C and 31P solid-state Nuclear Magnetic Resonance (NMR) and Wide Angle X-ray Diffraction (WAXD) as tools to elucidate molecular protein structure of caddisfly larval silk from the species Hesperophylax consimilis. Caddisfly larval silk is a fibroin protein based biopolymer containing mostly repetitive amino acid motifs. NMR and X-ray results provide strong supporting evidence for a structural model in which phosphorylated serine repeats (pSX)4 complex with divalent cations Ca2+ and Mg2+ to form rigid nanocrystalline β-sheet structures in caddisfly silk. 13C NMR data suggests that both phosphorylated serine and neighboring valine residues exist in a β-sheet secondary structure conformation while glycine and leucine residues common in GGX repeats likely reside in random coil conformations. Additionally, 31P chemical shift anisotropy (CSA) analysis indicates that the phosphates on phosphoserine residues are doubly ionized, and are charge-stabilized by divalent cations. Positively charged arginine side chains also likely play a role in charge stabilization. Finally, WAXD results finds that the silk is at least 7–8% crystalline, with β-sheet inter-plane spacings of 3.7 and 4.5 Å. PMID:23452243

  4. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves.

    Science.gov (United States)

    Thurber, Kent R; Tycko, Robert

    2014-05-14

    We report solid state (13)C and (1)H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, (1)H and cross-polarized (13)C NMR signals from (15)N,(13)C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

  5. Solid state structure by X-ray and 13C CP/MAS NMR of new 5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarins

    Science.gov (United States)

    Ostrowska, Kinga; Maciejewska, Dorota; Dobrzycki, Łukasz; Socha, Pawel

    2016-05-01

    5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarin (1) and 6-acetyl-5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarin (2), structurally related, were synthesized using both conventional and microwave-assisted approach. An impact of acetyl groups on the molecular structure of coumarin derivatives has been examined. Crystals of 2 were investigated using single crystal and powder X-ray diffraction techniques. Compound 2 crystallizes forming two polymorphs (denoted as 2_1 and 2_2), both belonging to P21/c space group. Both polymorphs are comparably stable and can be formed simultaneously during crystallization process. The solid state structure was also analysed using the fully resolved 13C CP/MAS NMR. The double signals with the intensity ratio of about 1:1 which were observed in the 13C CP/MAS NMR spectrum of compound 1 must arise due to the presence of two conformers of 1. In contrast, NMR spectrum recorded for powder mixture of two polymorphs of compound 2 displays no signal splitting. This is related to structural similarities of molecules in both polymorphs.

  6. Specific binding of a naturally occurring amyloidogenic fragment of Streptococcus mutans adhesin P1 to intact P1 on the cell surface characterized by solid state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Wenxing; Bhatt, Avni [University of Florida, Department of Biochemistry and Molecular Biology, College of Medicine (United States); Smith, Adam N. [University of Florida, Department of Chemistry, College of Liberal Arts and Sciences (United States); Crowley, Paula J.; Brady, L. Jeannine, E-mail: jbrady@dental.ufl.edu [University of Florida, Department of Oral Biology, College of Dentistry (United States); Long, Joanna R., E-mail: jrlong@ufl.edu [University of Florida, Department of Biochemistry and Molecular Biology, College of Medicine (United States)

    2016-02-15

    The P1 adhesin (aka Antigen I/II or PAc) of the cariogenic bacterium Streptococcus mutans is a cell surface-localized protein involved in sucrose-independent adhesion and colonization of the tooth surface. The immunoreactive and adhesive properties of S. mutans suggest an unusual functional quaternary ultrastructure comprised of intact P1 covalently attached to the cell wall and interacting with non-covalently associated proteolytic fragments thereof, particularly the ∼57-kDa C-terminal fragment C123 previously identified as Antigen II. S. mutans is capable of amyloid formation when grown in a biofilm and P1 is among its amyloidogenic proteins. The C123 fragment of P1 readily forms amyloid fibers in vitro suggesting it may play a role in the formation of functional amyloid during biofilm development. Using wild-type and P1-deficient strains of S. mutans, we demonstrate that solid state NMR (ssNMR) spectroscopy can be used to (1) globally characterize cell walls isolated from a Gram-positive bacterium and (2) characterize the specific binding of heterologously expressed, isotopically-enriched C123 to cell wall-anchored P1. Our results lay the groundwork for future high-resolution characterization of the C123/P1 ultrastructure and subsequent steps in biofilm formation via ssNMR spectroscopy, and they support an emerging model of S. mutans colonization whereby quaternary P1-C123 interactions confer adhesive properties important to binding to immobilized human salivary agglutinin.

  7. Solid-state {sup 27}Al and {sup 29}Si NMR investigations on Si-substituted hydrogarnets

    Energy Technology Data Exchange (ETDEWEB)

    Rivas Mercury, J.M. [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain); Pena, P. [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain)]. E-mail: ppena@icv.csic.es; Aza, A.H. de [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain); Turrillas, X. [Instituto de Ciencias de la Construccion Eduardo Torroja, CSIC, Serrano Galvache, 4, 28033 Madrid (Spain); Sobrados, I. [Instituto de Ciencia de Materiales, CSIC, Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco-Madrid (Spain); Sanz, J. [Instituto de Ciencia de Materiales, CSIC, Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco-Madrid (Spain)

    2007-02-15

    Partially deuterated Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-x}(OH){sub 4x} hydrates prepared by a reaction in the presence of D{sub 2}O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by {sup 29}Si and {sup 27}Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The {sup 29}Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-x}(OH){sub 4x} was followed by {sup 27}Al NMR spectroscopy: Si:OH ratios were determined quantitatively from octahedral Al signals ascribed to Al(OH){sub 6} and Al(OSi)(OH){sub 5} environments. The NMR data obtained were consistent with the concentrations of the Al and Si species deduced from transmission electron microscopy energy-dispersive spectrometry and Rietveld analysis of both X-ray and neutron diffraction data.

  8. Insight into the Supramolecular Architecture of Intact Diatom Biosilica from DNP-Supported Solid-State NMR Spectroscopy

    NARCIS (Netherlands)

    Jantschke, Anne; Koers, Eline; Mance, Deni; Weingarth, Markus; Brunner, Eike; Baldus, Marc

    2015-01-01

    Diatom biosilica is an inorganic/organic hybrid with interesting properties. The molecular architecture of the organic material at the atomic and nanometer scale has so far remained unknown, in particular for intact biosilica. A DNP-supported ssNMR approach assisted by microscopy, MS, and MD

  9. Insight into the Supramolecular Architecture of Intact Diatom Biosilica from DNP-Supported Solid-State NMR Spectroscopy

    NARCIS (Netherlands)

    Jantschke, Anne; Koers, Eline; Mance, Deni; Weingarth, Markus; Brunner, Eike; Baldus, Marc

    2015-01-01

    Diatom biosilica is an inorganic/organic hybrid with interesting properties. The molecular architecture of the organic material at the atomic and nanometer scale has so far remained unknown, in particular for intact biosilica. A DNP-supported ssNMR approach assisted by microscopy, MS, and MD simulat

  10. Elucidating connectivity and metal-binding structures of unlabeled paramagnetic complexes by 13C and 1H solid-state NMR under fast magic angle spinning.

    Science.gov (United States)

    Wickramasinghe, Nalinda P; Shaibat, Medhat A; Ishii, Yoshitaka

    2007-08-23

    Characterizing paramagnetic complexes in solids is an essential step toward understanding their molecular functions. However, methodologies to characterize chemical and electronic structures of paramagnetic systems at the molecular level have been notably limited, particularly for noncrystalline solids. We present an approach to obtain connectivities of chemical groups and metal-binding structures for unlabeled paramagnetic complexes by 13C and 1H high-resolution solid-state NMR (SSNMR) using very fast magic angle spinning (VFMAS, spinning speed >or=20 kHz). It is experimentally shown for unlabeled Cu(II)(Ala-Thr) that 2D 13C/1H correlation SSNMR under VFMAS provides the connectivity of chemical groups and assignments for the characterization of unlabeled paramagnetic systems in solids. We demonstrate that on the basis of the assignments provided by the VFMAS approach multiple 13C-metal distances can be simultaneously elucidated by a combination of measurements of 13C anisotropic hyperfine shifts and 13C T1 relaxation due to hyperfine interactions for this peptide-Cu(II) complex. It is also shown that an analysis of 1H anisotropic hyperfine shifts allows for the determination of electron-spin states in Fe(III)-chloroprotoporphyin-IX in solid states.

  11. Solid-state {sup 17}O magic-angle and dynamic-angle spinning NMR study of the SiO{sub 2} polymorph coesite

    Energy Technology Data Exchange (ETDEWEB)

    Grandinetti, P.J. [Ohio State Univ., Columbus, OH (United States); Baltisberger, J.H. [Berea College, KY (United States); Farnan, I.; Stebbins, J.F. [Stanford Univ., CA (United States); Werner, U.; Pines, A. [Lawrence Berkeley Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States)

    1995-08-10

    Five distinctly resolved {sup 17}O solid-state NMR resonances in room temperature coesite, an SiO{sub 2} polymorph, have been observed and assigned using dynamic angle spinning (DAS) at 11.7 T along with magic angle spinning (MAS) spectra at 9.4 and 11.7 T. The {sup 17}O quadrupolar parameters for each of the five oxygen environments in coesite are correlated with the Si-O-Si bridging bond angles determined by diffraction experiments. The sign of e{sup 2}-qQ/h along with the orientation of the electric field gradient for oxygen in the Si-O-Si linkage were determined from a Townes-Dailey analysis of the data. 41 refs., 7 figs., 5 tabs.

  12. Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy

    Science.gov (United States)

    Park, Sang Ho; Yang, Chen; Opella, Stanley J.; Mueller, Leonard J.

    2013-12-01

    Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H-15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600 MHz under 50 kHz magic angle spinning using ∼0.5 mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H-15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra.

  13. Specific 13C labeling of leucine, valine and isoleucine methyl groups for unambiguous detection of long-range restraints in protein solid-state NMR studies.

    Science.gov (United States)

    Fasshuber, Hannes Klaus; Demers, Jean-Philippe; Chevelkov, Veniamin; Giller, Karin; Becker, Stefan; Lange, Adam

    2015-03-01

    Here we present an isotopic labeling strategy to easily obtain unambiguous long-range distance restraints in protein solid-state NMR studies. The method is based on the inclusion of two biosynthetic precursors in the bacterial growth medium, α-ketoisovalerate and α-ketobutyrate, leading to the production of leucine, valine and isoleucine residues that are exclusively (13)C labeled on methyl groups. The resulting spectral simplification facilitates the collection of distance restraints, the verification of carbon chemical shift assignments and the measurement of methyl group dynamics. This approach is demonstrated on the type-three secretion system needle of Shigella flexneri, where 49 methyl-methyl and methyl-nitrogen distance restraints including 10 unambiguous long-range distance restraints could be collected. By combining this labeling scheme with ultra-fast MAS and proton detection, the assignment of methyl proton chemical shifts was achieved.

  14. Relative merits of rCW(A) and XiX heteronuclear spin decoupling in solid-state magic-angle-spinning NMR spectroscopy: A bimodal Floquet analysis.

    Science.gov (United States)

    Equbal, Asif; Leskes, Michal; Nielsen, Niels Chr; Madhu, P K; Vega, Shimon

    2016-02-01

    We present a bimodal Floquet analysis of the recently introduced refocused continuous wave (rCW) solid-state NMR heteronuclear dipolar decoupling method and compare it with the similar looking X-inverse X (XiX) scheme. The description is formulated in the rf interaction frame and is valid for both finite and ideal π pulse rCW irradiation that forms the refocusing element in the rCW scheme. The effective heteronuclear dipolar coupling Hamiltonian up to first order is described. The analysis delineates the difference between the two sequences to different orders of their Hamiltonians for both diagonal and off-diagonal parts. All the resonance conditions observed in experiments and simulations have been characterised and their influence on residual line broadening is highlighted. The theoretical comparison substantiates the numerical simulations and experimental results to a large extent.

  15. A novel Zn(4)O-based triazolyl benzoate MOF: synthesis, crystal structure, adsorption properties and solid state 13C NMR investigations.

    Science.gov (United States)

    Lincke, Jörg; Lässig, Daniel; Stein, Karolin; Moellmer, Jens; Kuttatheyil, Anusree Viswanath; Reichenbach, Christian; Moeller, Andreas; Staudt, Reiner; Kalies, Grit; Bertmer, Marko; Krautscheid, Harald

    2012-01-21

    The newly synthesized Zn(4)O-based MOF (3)(∞)[Zn(4)(μ(4)-O){(Metrz-pba)(2)mPh}(3)]·8 DMF (1·8 DMF) of rare tungsten carbide (acs) topology exhibits a porosity of 43% and remarkably high thermal stability up to 430 °C. Single crystal X-ray structure analyses could be performed using as-synthesized as well as desolvated crystals. Besides the solvothermal synthesis of single crystals a scalable synthesis of microcrystalline material of the MOF is reported. Combined TG-MS and solid state NMR measurements reveal the presence of mobile DMF molecules in the pore system of the framework. Adsorption measurements confirm that the pore structure is fully accessible for nitrogen molecules at 77 K. The adsorptive pore volume of 0.41 cm(3) g(-1) correlates well with the pore volume of 0.43 cm(3) g(-1) estimated from the single crystal structure.

  16. Atomic-Level Structure Characterization of Biomass Pre- and Post-Lignin Treatment by Dynamic Nuclear Polarization-Enhanced Solid-State NMR.

    Science.gov (United States)

    Perras, Frédéric A; Luo, Hao; Zhang, Ximing; Mosier, Nathan S; Pruski, Marek; Abu-Omar, Mahdi M

    2017-01-26

    Lignocellulosic biomass is a promising sustainable feedstock for the production of biofuels, biomaterials, and biospecialty chemicals. However, efficient utilization of biomass has been limited by our poor understanding of its molecular structure. Here, we report a dynamic nuclear polarization (DNP)-enhanced solid-state (SS)NMR study of the molecular structure of biomass, both pre- and postcatalytic treatment. This technique enables the measurement of 2D homonuclear (13)C-(13)C correlation SSNMR spectra under natural abundance, yielding, for the first time, an atomic-level picture of the structure of raw and catalytically treated biomass samples. We foresee that further such experiments could be used to determine structure-function relationships and facilitate the development of more efficient, and chemically targeted, biomass-conversion technologies.

  17. Specific 13C labeling of leucine, valine and isoleucine methyl groups for unambiguous detection of long-range restraints in protein solid-state NMR studies

    Science.gov (United States)

    Fasshuber, Hannes Klaus; Demers, Jean-Philippe; Chevelkov, Veniamin; Giller, Karin; Becker, Stefan; Lange, Adam

    2015-03-01

    Here we present an isotopic labeling strategy to easily obtain unambiguous long-range distance restraints in protein solid-state NMR studies. The method is based on the inclusion of two biosynthetic precursors in the bacterial growth medium, α-ketoisovalerate and α-ketobutyrate, leading to the production of leucine, valine and isoleucine residues that are exclusively 13C labeled on methyl groups. The resulting spectral simplification facilitates the collection of distance restraints, the verification of carbon chemical shift assignments and the measurement of methyl group dynamics. This approach is demonstrated on the type-three secretion system needle of Shigella flexneri, where 49 methyl-methyl and methyl-nitrogen distance restraints including 10 unambiguous long-range distance restraints could be collected. By combining this labeling scheme with ultra-fast MAS and proton detection, the assignment of methyl proton chemical shifts was achieved.

  18. Comprehensive MS and Solid-State NMR Metabolomic Profiling Reveals Molecular Variations in Native Periderms from Four Solanum tuberosum Potato Cultivars.

    Science.gov (United States)

    Huang, Wenlin; Serra, Olga; Dastmalchi, Keyvan; Jin, Liqing; Yang, Lijia; Stark, Ruth E

    2017-03-15

    The potato (Solanum tuberosum L.) ranks third in worldwide consumption among food crops. Whereas disposal of potato peels poses significant challenges for the food industry, secondary metabolites in these tissues are also bioactive and essential to crop development. The diverse primary and secondary metabolites reported in whole tubers and wound-healing tissues prompted a comprehensive profiling study of native periderms from four cultivars with distinctive skin morphologies and commercial food uses. Polar and nonpolar soluble metabolites were extracted concurrently, analyzed chromatographically, and characterized with mass spectrometry; the corresponding solid interfacial polymeric residue was examined by solid-state (13)C NMR. In total, 112 secondary metabolites were found in the phellem tissues; multivariate analysis identified 10 polar and 30 nonpolar potential biomarkers that distinguish a single cultivar among Norkotah Russet, Atlantic, Chipeta, and Yukon Gold cultivars which have contrasting russeting features. Compositional trends are interpreted in the context of periderm protective function.

  19. Analysis of the mechanical properties and characterization by solid state 13C NMR of recycled EVA copolymer/silica composites

    Directory of Open Access Journals (Sweden)

    Giovanni Chaves Stael

    2005-09-01

    Full Text Available The incorporation of micrometer sized silica particles on poly (ethylene-co-vinyl acetate - EVA - residues from the footwear industry was evaluated. The effects of the processing parameters - temperature and mixing ratio - on the mechanical behavior of molded plates of neat recycled EVA and EVA/silica composites were also investigated. The mechanical properties measured by the tensile test, the fractographic analysis by scanning electron microscopy (SEM, and the 13C Nuclear Magnetic Resonance (NMR showed a reduced EVA to silica compatibility. Therefore, incorporation of untreated silica to recycled EVA copolymer produced a slight decrease on the mechanical performance of EVA/silica composites in respect to neat EVA copolymer. The NMR analysis also shows that the crosslinking process on recycled EVA may be occurring at the carbonyl group.

  20. Solid-state NMR studies of a diverged microsomal amino-proximate delta12 desaturase peptide reveal causes of stability in bilayer: tyrosine anchoring and arginine snorkeling.

    Science.gov (United States)

    Gibbons, William J; Karp, Ethan S; Cellar, Nick A; Minto, Robert E; Lorigan, Gary A

    2006-02-15

    This study reports the solid-state NMR spectroscopic characterization of the amino-proximate transmembrane domain (TM-A) of a diverged microsomal delta12-desaturase (CREP-1) in a phospholipid bilayer. A series of TM-A peptides were synthesized with 2H-labeled side chains (Ala-53, -56, and -63, Leu-62, Val-50), and their dynamic properties were studied in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) bilayers at various temperatures. At 6 mol % peptide to lipid, 31P NMR spectra indicated that the peptides did not significantly disrupt the phospholipid bilayer in the L(alpha) phase. The 2H NMR spectra from Ala-53 and Ala-56 samples revealed broad Pake patterns with quadrupolar splittings of 16.9 kHz and 13.3 kHz, respectively, indicating restricted motion confined within the hydrocarbon core of the phospholipid bilayer. Conversely, the deuterated Ala-63 sample revealed a peak centered at 0 kHz with a linewidth of 1.9 kHz, indicating increased side-chain motion and solvent exposure relative to the spectra of the other Ala residues. Val-50 and Leu-62 showed Pake patterns, with quadrupolar splittings of 3.5 kHz and 3.7 kHz, respectively, intermediate to Ala-53/Ala-56 and Ala-63. This indicates partial motional averaging and supports a model with the Val and Leu residues embedded inside the lipid bilayer. Solid-state NMR spectroscopy performed on the 2H-labeled Ala-56 TM-A peptide incorporated into magnetically aligned phospholipid bilayers indicated that the peptide is tilted 8 degrees with respect to the membrane normal of the lipid bilayer. Snorkeling and anchoring interactions of Arg-44 and Tyr-60, respectively, with the polar region or polar hydrophobic interface of the lipid bilayer are suggested as control elements for insertional depth and orientation of the helix in the lipid matrix. Thus, this study defines the location of key residues in TM-A with respect to the lipid bilayer, describes the conformation of TM-A in a biomembrane mimic, presents a

  1. Proton detection for signal enhancement in solid-state NMR experiments on mobile species in membrane proteins

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Meaghan E.; Ritz, Emily [University of Guelph, Department of Physics (Canada); Ahmed, Mumdooh A. M. [Suez University, The Department of Physics, Faculty of Science (Egypt); Bamm, Vladimir V.; Harauz, George [University of Guelph, Biophysics Interdepartmental Group (Canada); Brown, Leonid S.; Ladizhansky, Vladimir, E-mail: vladizha@uoguelph.ca [University of Guelph, Department of Physics (Canada)

    2015-12-15

    Direct proton detection is becoming an increasingly popular method for enhancing sensitivity in solid-state nuclear magnetic resonance spectroscopy. Generally, these experiments require extensive deuteration of the protein, fast magic angle spinning (MAS), or a combination of both. Here, we implement direct proton detection to selectively observe the mobile entities in fully-protonated membrane proteins at moderate MAS frequencies. We demonstrate this method on two proteins that exhibit different motional regimes. Myelin basic protein is an intrinsically-disordered, peripherally membrane-associated protein that is highly flexible, whereas Anabaena sensory rhodopsin is composed of seven rigid transmembrane α-helices connected by mobile loop regions. In both cases, we observe narrow proton linewidths and, on average, a 10× increase in sensitivity in 2D insensitive nuclear enhancement of polarization transfer-based HSQC experiments when proton detection is compared to carbon detection. We further show that our proton-detected experiments can be easily extended to three dimensions and used to build complete amino acid systems, including sidechain protons, and obtain inter-residue correlations. Additionally, we detect signals which do not correspond to amino acids, but rather to lipids and/or carbohydrates which interact strongly with membrane proteins.

  2. The local physical structure of amorphous hydrogenated boron carbide: insights from magic angle spinning solid-state NMR spectroscopy.

    Science.gov (United States)

    Paquette, Michelle M; Li, Wenjing; Sky Driver, M; Karki, Sudarshan; Caruso, A N; Oyler, Nathan A

    2011-11-01

    Magic angle spinning solid-state nuclear magnetic resonance spectroscopy techniques are applied to the elucidation of the local physical structure of an intermediate product in the plasma-enhanced chemical vapour deposition of thin-film amorphous hydrogenated boron carbide (B(x)C:H(y)) from an orthocarborane precursor. Experimental chemical shifts are compared with theoretical shift predictions from ab initio calculations of model molecular compounds to assign atomic chemical environments, while Lee-Goldburg cross-polarization and heteronuclear recoupling experiments are used to confirm atomic connectivities. A model for the B(x)C:H(y) intermediate is proposed wherein the solid is dominated by predominantly hydrogenated carborane icosahedra that are lightly cross-linked via nonhydrogenated intraicosahedral B atoms, either directly through B-B bonds or through extraicosahedral hydrocarbon chains. While there is no clear evidence for extraicosahedral B aside from boron oxides, ∼40% of the C is found to exist as extraicosahedral hydrocarbon species that are intimately bound within the icosahedral network rather than in segregated phases.

  3. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems

    Science.gov (United States)

    Baranowski, M.; Woźniak-Braszak, A.; Jurga, K.

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2 MHz and 28.411 MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins 1H are polarized in the magnetic field B0 while fluorine spins 19F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

  4. NATURAL CYCLOPENTANOID CYANOHYDRIN GLYCOSIDES .13. STRUCTURE DETERMINATION OF NATURAL EPOXYCYCLOPENTANES BY X-RAY CRYSTALLOGRAPHY AND NMR-SPECTROSCOPY

    DEFF Research Database (Denmark)

    Olafsdottir, E. S.; Sorensen, A. M.; Cornett, Claus;

    1991-01-01

    nonannellated cyclopentane derivatives. The new glucosides were shown, by NMR spectroscopy (including NOE measurements), X-ray crystallography, and enzymatic hydrolysis to the corresponding cyanohydrins, to be (1R,2R,3R,4R)- and (1S,2S,3S,4S)-1-(beta-D-glucopyranosyloxy)-2,3-epoxy-4-hydroxycyclopenta ne-1...... side as the three oxygen substituents. In addition to the glucosides, two amides, (1S,2S,3R,4R)-2,3-epoxy-1,4-dihydroxycyclopentane-1-carboxamide and (1S,4R)-1,4-dihydroxy-2-cyclopentene-1-carboxamide, were isolated from P. suberosa and characterized; the amides are probably artefacts...

  5. Investigating sorption on iron-oxyhydroxide soil minerals by solid-state NMR spectroscopy: a 6Li MAS NMR study of adsorption and absorption on goethite

    DEFF Research Database (Denmark)

    Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia;

    2005-01-01

    High-resolution 2H MAS NMR spectra can be obtained for nanocrystalline particles of goethite (alpha-FeOOH, particle size approximately 4-10 nm) at room temperature, facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, th...

  6. The Target of β-Expansin EXPB1 in Maize Cell Walls from Binding and Solid-State NMR Studies.

    Science.gov (United States)

    Wang, Tuo; Chen, Yuning; Tabuchi, Akira; Cosgrove, Daniel J; Hong, Mei

    2016-12-01

    The wall-loosening actions of β-expansins are known primarily from studies of EXPB1 extracted from maize (Zea mays) pollen. EXPB1 selectively loosens cell walls (CWs) of grasses, but its specific binding target is unknown. We characterized EXPB1 binding to sequentially extracted maize CWs, finding that the protein primarily binds glucuronoarabinoxylan (GAX), the major matrix polysaccharide in grass CWs. This binding is strongly reduced by salts, indicating that it is predominantly electrostatic in nature. For direct molecular evidence of EXPB1 binding, we conducted solid-state nuclear magnetic resonance experiments using paramagnetic relaxation enhancement (PRE), which is sensitive to distances between unpaired electrons and nuclei. By mixing (13)C-enriched maize CWs with EXPB1 functionalized with a Mn(2+) tag, we measured Mn(2+)-induced PRE Strong (1)H and (13)C PREs were observed for the carboxyls of GAX, followed by more moderate PREs for carboxyl groups in homogalacturonan and rhamnogalacturonan-I, indicating that EXPB1 preferentially binds GAX In contrast, no PRE was observed for cellulose, indicating very weak interaction of EXPB1 with cellulose. Dynamics experiments show that EXPB1 changes GAX mobility in a complex manner: the rigid fraction of GAX became more rigid upon EXPB1 binding while the dynamic fraction became more mobile. Combining these data with previous results, we propose that EXPB1 loosens grass CWs by disrupting noncovalent junctions between highly substituted GAX and GAX of low substitution, which binds cellulose. This study provides molecular evidence of β-expansin's target in grass CWs and demonstrates a new strategy for investigating ligand binding for proteins that are difficult to express heterologously.

  7. Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments

    Science.gov (United States)

    Hatcher, P.G.; VanderHart, D.L.; Earl, W.L.

    1980-01-01

    13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra. ?? 1980.

  8. Fast and simple acquisition of solid-state 14N NMR spectra with signal enhancement via population transfer.

    Science.gov (United States)

    O'Dell, Luke A; Schurko, Robert W

    2009-05-20

    A new approach for the acquisition of static, wideline (14)N NMR powder patterns is outlined. The method involves the use of frequency-swept pulses which serve two simultaneous functions: (1) broad-band excitation of magnetization and (2) signal enhancement via population transfer. The signal enhancement mechanism is described using numerical simulations and confirmed experimentally. This approach, which we call DEISM (Direct Enhancement of Integer Spin Magnetization), allows high-quality (14)N spectra to be acquired at intermediate field strengths in an uncomplicated way and in a fraction of the time required for previously reported methods.

  9. Multiple-quantum magic-angle spinning: high-resolution solid state NMR spectroscopy of half-integer quadrupolar nuclei

    CERN Document Server

    Goldbourt, A

    2002-01-01

    Experimental and theoretical aspects of the multiple-quantum magic-angle spinning experiment (MQMAS) are discussed in this review. The significance of this experiment, introduced by Frydman and Harwood, is in its ability to provide high-resolution NMR spectra of half-integer quadrupolar nuclei (I /geq 3/2). This technique has proved to be useful in various systems ranging from inorganic materials to biological samples. This review addresses the development of various pulse schemes aimed at improving the signal-to-noise ratio and anisotropic lineshapes. Representative spectra are shown to underscore the importance and applications of the MQMAS experiment. Refs. 97 (author)

  10. Solid-state NMR and short-range order in crystalline oxides and silicates: a new tool in paramagnetic resonances.

    Science.gov (United States)

    Stebbins, Jonathan F; McCarty, Ryan J; Palke, Aaron C

    2017-03-01

    Most applications of high-resolution NMR to questions of short-range order/disorder in inorganic materials have been made in systems where ions with unpaired electron spins are of negligible concentration, with structural information extracted primarily from chemical shifts, quadrupolar coupling parameters, and nuclear dipolar couplings. In some cases, however, the often-large additional resonance shifts caused by interactions between unpaired electron and nuclear spins can provide unique new structural information in materials with contents of paramagnetic cations ranging from hundreds of ppm to several per cent and even higher. In this brief review we focus on recent work on silicate, phosphate, and oxide materials with relatively low concentrations of paramagnetic ions, where spectral resolution can remain high enough to distinguish interactions between NMR-observed nuclides and one or more magnetic neighbors in different bonding configurations in the first, second, and even farther cation shells. We illustrate the types of information available, some of the limitations of this approach, and the great prospects for future experimental and theoretical work in this field. We give examples for the effects of paramagnetic transition metal, lanthanide, and actinide cation substitutions in simple oxides, pyrochlore, zircon, monazite, olivine, garnet, pyrochlores, and olivine structures.

  11. Development of Solid State NMR Methods for the Structural Characterization of Membrane Proteins: Applications to Understand Multiple Sclerosis

    Energy Technology Data Exchange (ETDEWEB)

    Cosman, M; Tran, A T; Ulloa, J; Maxwell, R S

    2003-03-04

    Multiple sclerosis (MS) is a relapsing-remitting disorder of the central nervous system that results in the loss of the myelin sheaths insulating nerve fibers (axons). Strong evidence suggests that MS is an autoimmune disease mediated by T-cell and antibody responses against myelin antigens. Myelin oligodendrocyte glycoprotein (MOG) is a 26 kD to 28 kD an integral membrane protein of the central nervous system implicated as a target for autoaggressive antibodies in MS. To date, the conformation of MOG in association with the myelin membrane is unknown and the exact nature of the interactions between this protein and disease-inducing immune responses have not been determined. Since membrane associated proteins are typically characterized by decreased correlation times, solution state NMR methodologies are often impracticable. Membrane proteins are also often difficult to crystallize for X-ray diffraction studies, Consequently, there is an urgent need to develop new structure characterization tools for this important class of biomolecules. The research described here overviews the initial stages of our effort to develop an integrated, NMR based approach to structural studies of MOG over the many structural domains it is postulated to posses. The structural knowledge gained about this important MS antigen in its native environment will contribute significantly to our understanding of its function in vivo. This project will also aid in the development of therapeutics to inhibit the antigedantibody interaction and thus prevent demyelination in MS patients.

  12. A 13C solid-state NMR study of the structure and the dynamics of the polymorphs of sulphanilamide

    Science.gov (United States)

    Frydman, Lucio; Olivieri, Alejandro C.; Diaz, Luis E.; Frydman, Benjamin; Schmidt, Asher; Vega, Shimon

    The 13C CPMAS NMR spectra of four crystalline forms of p-aminobenzenesulphonamide (sulphanilamide) were recorded at room temperature. Three of these forms (α, β, and γ) showed doublings in the resonances of the carbon atoms ortho to the amino group, but only a single signal was obtained from those ortho to the asymmetric sulphonamide group. A variabletemperature study allowed the interconversion of the α and β forms to the γ form to be monitored. Changes were also observed in the spectrum of the γ form as the temperature was increased, and were ascribed to the presence of 180° flips of the phenyl rings about their para axis. This interpretation was confirmed by analysis of the broadenings introduced by the assumed motion on the centreband and sidebands in the 13C CPMAS NMR spectrum of the exchanging nuclei. Variable-temperature spectra of the γ form were simulated in order to obtain information about the geometry, the rates and the activation parameters involved in the process. These calculations were in good agreement with the experimental data. The possible relevance that the observed doublings and ring motion may have for the mode of action of sulphonamides is also discussed.

  13. Proton-detected solid-state NMR spectroscopy of fully protonated proteins at slow to moderate magic-angle spinning frequencies.

    Science.gov (United States)

    Mote, Kaustubh R; Madhu, Perunthiruthy K

    2015-12-01

    (1)H-detection offers a substitute to the sensitivity-starved experiments often used to characterize biomolecular samples using magic-angle spinning solid-state NMR spectroscopy (MAS-ssNMR). To mitigate the effects of the strong (1)H-(1)H dipolar coupled network that would otherwise severely broaden resonances, high MAS frequencies (>40kHz) are often employed. Here, we have explored the alternative of stroboscopic (1)H-detection at moderate MAS frequencies of 5-30kHz using windowed version of supercycled-phase-modulated Lee-Goldburg homonuclear decoupling. We show that improved resolution in the (1)H dimension, comparable to that obtainable at high spinning frequencies of 40-60kHz without homonuclear decoupling, can be obtained in these experiments for fully protonated proteins. Along with detailed analysis of the performance of the method on the standard tri-peptide f-MLF, experiments on micro-crystalline GB1 and amyloid-β aggregates are used to demonstrate the applicability of these pulse-sequences to challenging biomolecular systems. With only two parameters to optimize, broadbanded performance of the homonuclear decoupling sequence, linear dependence of the chemical-shift scaling factor on resonance offset and a straightforward implementation under experimental conditions currently used for many biomolecular studies (viz. spinning frequencies and radio-frequency amplitudes), we expect these experiments to complement the current (13)C-detection based methods in assignments and characterization through chemical-shift mapping.

  14. Determining the effects of lipophilic drugs on membrane structure by solid-state NMR spectroscopy: the case of the antioxidant curcumin.

    Science.gov (United States)

    Barry, Jeffrey; Fritz, Michelle; Brender, Jeffrey R; Smith, Pieter E S; Lee, Dong-Kuk; Ramamoorthy, Ayyalusamy

    2009-04-01

    Curcumin is the active ingredient of turmeric powder, a natural spice used for generations in traditional medicines. Curcumin's broad spectrum of antioxidant, anticarcinogenic, antimutagenic, and anti-inflammatory properties makes it particularly interesting for the development of pharmaceutical compounds. Because of curcumin's various effects on the function of numerous unrelated membrane proteins, it has been suggested that it affects the properties of the bilayer itself. However, a detailed atomic-level study of the interaction of curcumin with membranes has not been attempted. A combination of solid-state NMR and differential scanning calorimetry experiments shows curcumin has a strong effect on membrane structure at low concentrations. Curcumin inserts deep into the membrane in a transbilayer orientation, anchored by hydrogen bonding to the phosphate group of lipids in a manner analogous to cholesterol. Like cholesterol, curcumin induces segmental ordering in the membrane. Analysis of the concentration dependence of the order parameter profile derived from NMR results suggests curcumin forms higher order oligomeric structures in the membrane that span and likely thin the bilayer. Curcumin promotes the formation of the highly curved inverted hexagonal phase, which may influence exocytotic and membrane fusion processes within the cell. The experiments outlined here show promise for understanding the action of other drugs such as capsaicin in which drug-induced alterations of membrane structure have strong pharmacological effects.

  15. A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission.

    Science.gov (United States)

    Pike, Kevin J; Kemp, Thomas F; Takahashi, Hiroki; Day, Robert; Howes, Andrew P; Kryukov, Eugeny V; MacDonald, James F; Collis, Alana E C; Bolton, David R; Wylde, Richard J; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M; Newton, Mark E; Dupree, Ray; Smith, Mark E

    2012-02-01

    A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE(13) fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz (1)H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE(16) second-harmonic mode of the gyrotron) for DNP at 14.1T (600 MHz (1)H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ~1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz (1)H and double channel HX mode for 284 MHz (1)H, with MAS sample temperatures ≥85 K. Initial data at 6.7 T and ~1 W pulsed microwave power are presented with (13)C enhancements of 60 for a frozen urea solution ((1)H-(13)C CP), 16 for bacteriorhodopsin in purple membrane ((1)H-(13)C CP) and 22 for (15)N in a frozen glycine solution ((1)H-(15)N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design.

  16. Grid-free powder averages: on the applications of the Fokker-Planck equation to solid state NMR

    CERN Document Server

    Edwards, Luke J; Nevzorov, A A; Concistre, M; Pileio, G; Kuprov, Ilya

    2013-01-01

    We demonstrate that Fokker-Planck equations in which spatial coordinates are treated on the same conceptual level as spin coordinates yield a convenient formalism for treating magic angle spinning NMR experiments. In particular, time dependence disappears from the background Hamiltonian (sample spinning is treated as an interaction), spherical quadrature grids are avoided completely (coordinate distributions are a part of the formalism) and relaxation theory with any linear diffusion operator is easily adopted from the Stochastic Liouville Equation theory. The proposed formalism contains Floquet theory as a special case. The elimination of the spherical averaging grid comes at the cost of increased matrix dimensions, but we show that this can be mitigated by the use of state space restriction and tensor train techniques. It is also demonstrated that low correlation order basis sets apparently give accurate answers in powder-averaged MAS simulations, meaning that polynomially scaling simulation algorithms do e...

  17. The high-temperature modification of ScRuSi - Structure, 29Si and 45Sc solid state NMR spectroscopy

    Science.gov (United States)

    Hoffmann, Rolf-Dieter; Rodewald, Ute Ch.; Haverkamp, Sandra; Benndorf, Christopher; Eckert, Hellmut; Heying, Birgit; Pöttgen, Rainer

    2017-10-01

    A polycrystalline sample of the TiNiSi type low-temperature (LT) modification of ScRuSi was synthesized by arc-melting. Longer annealing in a sealed silica tube (6 weeks at 1270 K) followed by quenching led to the high-temperature (HT) phase. HT-ScRuSi adopts the ZrNiAl structure type: P 6 bar 2 m , a = 688.27(9), c = 336.72(5) pm, wR2 = 0.0861, 260 F2 values, 14 variables. The striking structural building units are regular, tricapped trigonal prisms Si1@Ru3Sc6 and Si2@Ru6Sc3. Both polymorphs have been characterized by 29Si and 45Sc MAS-NMR spectroscopy. The local scandium environments in the two polymorphs are easily distinguished by their electric field gradient tensor values, in agreement with theoretically calculated values.

  18. Insight into the Supramolecular Architecture of Intact Diatom Biosilica from DNP-Supported Solid-State NMR Spectroscopy.

    Science.gov (United States)

    Jantschke, Anne; Koers, Eline; Mance, Deni; Weingarth, Markus; Brunner, Eike; Baldus, Marc

    2015-12-01

    Diatom biosilica is an inorganic/organic hybrid with interesting properties. The molecular architecture of the organic material at the atomic and nanometer scale has so far remained unknown, in particular for intact biosilica. A DNP-supported ssNMR approach assisted by microscopy, MS, and MD simulations was applied to study the structural organization of intact biosilica. For the first time, the secondary structure elements of tightly biosilica-associated native proteins in diatom biosilica were characterized in situ. Our data suggest that these proteins are rich in a limited set of amino acids and adopt a mixture of random-coil and β-strand conformations. Furthermore, biosilica-associated long-chain polyamines and carbohydrates were characterized, thereby leading to a model for the supramolecular organization of intact biosilica.

  19. Mechanism of Phenol Alkylation in Zeolite H-BEA Using In Situ Solid-State NMR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Zhenchao [Institute; Shi, Hui [Institute; Wan, Chuan [Institute; Hu, Mary Y. [Institute; Liu, Yuanshuai [Department; Mei, Donghai [Institute; Camaioni, Donald M. [Institute; Hu, Jian Zhi [Institute; Lercher, Johannes A. [Institute; Department

    2017-06-27

    Alkylation of phenolic compounds in the liquid phase is of fundamental and practical importance to the conversion of biomass-derived feedstocks into fuels and chemicals. In this work, the reaction mechanism for phenol alkylation with cyclohexanol and cyclohexene has been investigated on a commercial HBEA zeolite by in situ 13C MAS NMR, using decalin as the solvent. From the variable temperature 13C MAS NMR measurements of phenol and cyclohexanol adsorption on HBEA from decalin solutions, it is shown that the two molecules have similar adsorption strength in the HBEA pore. Phenol alkylation with cyclohexanol, however, becomes significantly measurable only after cyclohexanol is largely converted to cyclohexene via dehydration. This is in contrast to the initially rapid alkylation of phenol when using cyclohexene as the co-reactant. 13C isotope scrambling results demonstrate that the electrophile, presumably cyclohexyl carbenium ion, is directly formed in a protonation step when cyclohexene is the co-reactant, but requires re-adsorption of the alcohol dehydration product, cyclohexene, when cyclohexanol dimer is the dominant surface species (e.g., at 0.5 M cyclohexanol concentration) that is unable to generate carbenium ion. At the initial reaction stage of phenol-cyclohexanol alkylation on HBEA, the presence of the cyclohexanol dimer species hinders the adsorption of cyclohexene at the Brønsted acid site and the subsequent activation of the more potent electrophile (carbenium ion). Isotope scrambling data also show that intramolecular rearrangement of cyclohexyl phenyl ether, the O-alkylation product, does not significantly contribute to the formation of C-alkylation products.

  20. Spin-transfer pathways in paramagnetic lithium transition-metal phosphates from combined broadband isotropic solid-state MAS NMR spectroscopy and DFT calculations.

    Science.gov (United States)

    Clément, Raphaële J; Pell, Andrew J; Middlemiss, Derek S; Strobridge, Fiona C; Miller, Joel K; Whittingham, M Stanley; Emsley, Lyndon; Grey, Clare P; Pintacuda, Guido

    2012-10-17

    Substituted lithium transition-metal (TM) phosphate LiFe(x)Mn(1-x)PO(4) materials with olivine-type structures are among the most promising next generation lithium ion battery cathodes. However, a complete atomic-level description of the structure of such phases is not yet available. Here, a combined experimental and theoretical approach to the detailed assignment of the (31)P NMR spectra of the LiFe(x)Mn(1-x)PO(4) (x = 0, 0.25, 0.5, 0.75, 1) pure and mixed TM phosphates is developed and applied. Key to the present work is the development of a new NMR experiment enabling the characterization of complex paramagnetic materials via the complete separation of the individual isotropic chemical shifts, along with solid-state hybrid DFT calculations providing the separate hyperfine contributions of all distinct Mn-O-P and Fe-O-P bond pathways. The NMR experiment, referred to as aMAT, makes use of short high-powered adiabatic pulses (SHAPs), which can achieve 100% inversion over a range of isotropic shifts on the order of 1 MHz and with anisotropies greater than 100 kHz. In addition to complete spectral assignments of the mixed phases, the present study provides a detailed insight into the differences in electronic structure driving the variations in hyperfine parameters across the range of materials. A simple model delimiting the effects of distortions due to Mn/Fe substitution is also proposed and applied. The combined approach has clear future applications to TM-bearing battery cathode phases in particular and for the understanding of complex paramagnetic phases in general.

  1. Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy.

    Science.gov (United States)

    Allan, Phoebe K; Griffin, John M; Darwiche, Ali; Borkiewicz, Olaf J; Wiaderek, Kamila M; Chapman, Karena W; Morris, Andrew J; Chupas, Peter J; Monconduit, Laure; Grey, Clare P

    2016-02-24

    Operando pair distribution function (PDF) analysis and ex situ (23)Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from (23)Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na(3-x)Sb (x ≈ 0.4-0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na(1.7)Sb, a highly amorphous structure featuring some Sb-Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na(3-x)Sb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na(1.7)Sb, then a-Na(3-x)Sb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na(3-x)Sb without the formation of a-Na(1.7)Sb. a-Na(3-x)Sb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature (23)Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.

  2. A study of transition-metal organometallic complexes combining 35Cl solid-state NMR spectroscopy and 35Cl NQR spectroscopy and first-principles DFT calculations.

    Science.gov (United States)

    Johnston, Karen E; O'Keefe, Christopher A; Gauvin, Régis M; Trébosc, Julien; Delevoye, Laurent; Amoureux, Jean-Paul; Popoff, Nicolas; Taoufik, Mostafa; Oudatchin, Konstantin; Schurko, Robert W

    2013-09-09

    A series of transition-metal organometallic complexes with commonly occurring metal-chlorine bonding motifs were characterized using (35)Cl solid-state NMR (SSNMR) spectroscopy, (35)Cl nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static (35)Cl ultra-wideline NMR spectra were acquired in a piecewise manner at standard (9.4 T) and high (21.1 T) magnetic field strengths using the WURST-QCPMG pulse sequence. The (35)Cl electric field gradient (EFG) and chemical shielding (CS) tensor parameters were readily extracted from analytical simulations of the spectra; in particular, the quadrupolar parameters are shown to be very sensitive to structural differences, and can easily differentiate between chlorine atoms in bridging and terminal bonding environments. (35)Cl NQR spectra were acquired for many of the complexes, which aided in resolving structurally similar, yet crystallographically distinct and magnetically inequivalent chlorine sites, and with the interpretation and assignment of (35)Cl SSNMR spectra. (35)Cl EFG tensors obtained from first-principles DFT calculations are consistently in good agreement with experiment, highlighting the importance of using a combined approach of theoretical and experimental methods for structural characterization. Finally, a preliminary example of a (35)Cl SSNMR spectrum of a transition-metal species (TiCl4) diluted and supported on non-porous silica is presented. The combination of (35)Cl SSNMR and (35)Cl NQR spectroscopy and DFT calculations is shown to be a promising and simple methodology for the characterization of all manner of chlorine-containing transition-metal complexes, in pure, impure bulk and supported forms.

  3. Conformational Plasticity of the Cell-Penetrating Peptide SAP As Revealed by Solid-State (19)F-NMR and Circular Dichroism Spectroscopies.

    Science.gov (United States)

    Afonin, Sergii; Kubyshkin, Vladimir; Mykhailiuk, Pavel K; Komarov, Igor V; Ulrich, Anne S

    2017-07-13

    The cell-penetrating peptide SAP, which was designed as an amphipathic poly-l-proline helix II (PPII), was suggested to self-assemble into regular fibrils that are relevant for its internalization. Herein we have analyzed the structure of SAP in the membrane-bound state by solid-state (19)F-NMR, which revealed other structural states, in addition to the expected surface-aligned PPII. Trifluoromethyl-bicyclopentyl-glycine (CF3-Bpg) and two rigid isomers of trifluoromethyl-4,5-methanoprolines (CF3-MePro) were used as labels for (19)F-NMR analysis. The equilibria between different conformations of SAP were studied and were found to be shifted by the substituents at Pro-11. Synchrotron-CD results suggested that substituting Pro-11 by CF3-MePro governed the coil-to-PPII equilibrium in solution and in the presence of a lipid bilayer. Using CD and (19)F-NMR, we examined the slow kinetics of the association of SAP with membranes and the dependence of the SAP conformational dynamics on the lipid composition. The peptide did not bind to lipids in the solid ordered phase and aggregated only in the liquid ordered "raft"-like bilayers. Self-association could not be detected in solution or in the presence of liquid disordered membranes. Surface-bound amphipathic SAP in a nonaggregated state was structured as a mixture of nonideal extended conformations reflecting the equilibrium already present in solution, i.e., before binding to the membrane.

  4. Structural investigation of α-LaZr2F11 by coupling X-ray powder diffraction, 19F solid state NMR and DFT calculations

    Science.gov (United States)

    Martineau, Charlotte; Legein, Christophe; Body, Monique; Péron, Olivier; Boulard, Brigitte; Fayon, Franck

    2013-03-01

    α-LaZr2F11 has been synthesized by solid state reaction. Its crystal structure has been refined from X-ray powder diffraction data (space group no. 72 Ibam, a=7.785(1) Å, b=10.086(1) Å and c=11.102(1) Å). α-LaZr2F11 contains one La, one Zr and four F inequivalent crystallographic sites. F3 and F4 are shared between one ZrF73- polyhedron and one LaF85- polyhedron, while F1 and F2 bridge two ZrF73- polyhedra. 19F 1D MAS NMR spectra of α-LaZr2F11 are in agreement with the proposed structural model. Assignment of the 19F resonances to the corresponding crystallographic sites has been performed on the basis of both their relative intensities and their correlation patterns in a 19F 2D dipolar-based double-quantum recoupling MAS NMR spectrum. DFT calculations of the 19F chemical shielding tensors have been performed using the GIPAW method implemented in the NMR-CASTEP code, for the experimental structure and two PBE-DFT geometry optimized structures of α-LaZr2F11 (atomic position optimization and full geometry optimization with rescaling of the unit cell volume to the experimental value). Computations were done with and without using a modified La pseudopotential allowing the treatment of the 4f localized empty orbitals of La3+. A relatively nice agreement between the experimental 19F isotropic and anisotropic chemical shifts and the values calculated for the proposed structural model is obtained.

  5. Determination of the torsion angles of alanine and glycine residues of model compounds of spider silk (AGG){sub 10} using solid-state NMR methods

    Energy Technology Data Exchange (ETDEWEB)

    Ashida, Jun; Ohgo, Kosuke; Komatsu, Kohei; Kubota, Ayumi; Asakura, Tetsuo [Tokyo University of Agriculture and Technology, Department of Biotechnology (Japan)], E-mail: asakura@cc.tuat.ac.jp

    2003-02-15

    Spiders synthesize several kinds of silk fibers. In the primary structure of spider silk, one of the major ampullate (dragline, frame) silks, spidroin 1, and flagelliform silk (core fibers of adhesive spiral), there are common repeated X-Gly-Gly (X = Ala, Leu, Pro, Tyr, Glu, and Arg) sequences, which are considered to be related to the elastic character of these fibers. In this paper, two dimensional spin diffusion solid-state NMR under off magic angle spinning (OMAS), {sup 13}C chemical shift contour plots, and Rotational Echo DOuble Resonance (REDOR) were applied to determine the torsion angles of one Ala and two kinds of Gly residues in the Ala-Gly-Gly sequence of {sup 13}C=O isotope-labeled (Ala-Gly-Gly){sub 10}. The torsion angles were determined to be ({phi}, {psi}) = (-90 deg., 150 deg.) within an experimental error of {+-}10 deg. for each residue. This conformation is characterized as 3{sub 1} helix which is in agreement with the structure proposed from the X-ray powder diffraction pattern of poly(Ala-Gly-Gly). The 3{sub 1} helix of (Ala-Gly-Gly){sub 10} does not change by formic acid treatment although (Ala-Gly){sub 15} easily changes from the silk I conformation (the structure of Bombyx mori silk fibroin before spinning in the solid state) to silk II conformation (the structure of the silk fiber after spinning) by such treatment. Thus, the 3{sub 1} helix conformation of (Ala-Gly-Gly){sub 10} is considered very stable. Furthermore, the torsion angles of the 16th Leu residue of (Leu-Gly-Gly){sub 10} were also determined as ({phi}, {psi}) = (-90 deg., 150 deg.) and this peptide is also considered to take 3{sub 1} helix conformation.

  6. Synthetic routes to a nanoscale inorganic cluster [Ga13(μ3-OH)6(μ2-OH)18(H2O)](NO3)15 evaluated by solid-state 71Ga NMR

    Science.gov (United States)

    Hammann, Blake A.; Marsh, David A.; Ma, Zayd L.; Wood, Suzannah R.; Eric West, Michael; Johnson, Darren W.; Hayes, Sophia E.

    2016-10-01

    Solid-state 71Ga NMR was used to characterize a series of [Ga13(μ3-OH)6(μ2-OH)18(H2O)](NO3)15 "Ga13" molecular clusters synthesized by multiple methods. These molecular clusters are precursors to thin film electronics and may be employed in energy applications. The synthetic routes provide varying levels of impurities in the solid phase, and these impurities often elude traditional characterization techniques such as powder X-ray diffraction and Raman spectroscopy. Solid-state NMR can provide a window into the gallium species even in amorphous phases. This information is vital in order to prevent the impurities from causing defect sites in the corresponding thin films upon gelation and condensation (polymerization) of the Ga13 clusters. This work demonstrates the resolving power of solid-state NMR to evaluate structure and synthetic quality in the solid state, and the application of high-field NMR to study quadrupolar species, such as 71Ga.

  7. Cation size effects in mixed-ion metaphosphate glasses: structural characterization by multinuclear solid state NMR spectroscopy.

    Science.gov (United States)

    Schneider, J; Tsuchida, J; Eckert, H

    2013-09-14

    Metaphosphate glasses with two monovalent species A(1-x)B(x)PO3 (0 ≤x≤ 1) show mixed-ion effects (MIE) in the dc conductivities and glass transition temperatures, which are strongly dependent on the cation size mismatch between the two mobile species. In the present contribution, mixed-ion metaphosphate glasses based on the cation combinations Cs-Li, Rb-Li, and Cs-Ag, exhibiting particularly large size mismatches, are analyzed by (31)P, (87)Rb, (109)Ag and (133)Cs NMR to determine possible correlations between this mismatch and some of the structural properties critical to the development of the MIE: the local environments around the mobile species and their spatial distribution relative to each other. The results are compared with those obtained in the Na-Ag metaphosphate series, which serves as a reference system, with minimized cation mismatch MIE. The local coordination environments of the Ag(+), Rb(+) and Cs(+) ions follow analogous compositional trends as previously observed in Na-based mixed-ion metaphosphate glasses: for a given cation species A, the average A-O distance shows an expansion/compression when this cation is replaced by a second species B with smaller/bigger ionic radius, respectively. This compositional differentiation of the structural sites for the mobile species may contribute to the MIE. Concerning the relative spatial distribution of the mobile ions, results from (7)Li-(133)Cs (SEDOR) experiments indicate a random mixture of Cs and Li in Cs-Li metaphosphate glasses. While this result is in agreement with one of the fundamental hypotheses of the models proposed to describe the MIE, it is at variance with the observation of various partial cation segregation phenomena observed in Na-based mixed alkali glasses. This result suggests that cation size mismatch is not the decisive parameter in determining segregation or non-statistical mixing of cations in the glass. In the Cs-Ag and Na-Ag glasses, (109)Ag spin-echo NMR reveals a progressive

  8. Short-Range Order of Mesomorphic Phase of a Semi-crystalline Polymer by Solid-State NMR: Isotactic Polypropylene

    Science.gov (United States)

    Yuan, Shichen; Miyoshi, Toshikazu

    2015-03-01

    Mesophase is intermediate phase between crystalline and melt state. Characterization of short-range structures of disordered mesomorphic phase without long-range order is challenging issue in polymer characterization. The short range order was considered same as α or β i PP, or neither. In this work, a new strategy using 13C-13C through space interactions as well as molecular dynamics based on chemical shift anisotropy (CSA) re-orientation is proposed for evaluating short-range order of mesophase of isotactic-polypropylene (iPP). 13C-13C double quantum (DQ) build up curves of 13C 15 percent CH3 selectively labeled iPP and spin dynamics simulations elucidate that local packing structures in mesophase is very close to that in β phase. Moreover, exchange NMR proves that the crystalline chains perform large amplitude motions in all α, β, and mesophase. The correlation time of overall dynamics of stems in mesophase follows the same Arrhenius line with that of β phase but is largely deviated from the Arrhenius line of the α phase. Through the obtained results, it is concluded that short-range order in mesophase is exceedingly close or same to those in β phase. This work was financially supported by the National Science Foundation (Grant No. DMR-1105829) and by UA startup funds.

  9. Solid-state 13C and 1H spin diffusion NMR analyses of the microfibril structure for bacterial cellulose.

    Science.gov (United States)

    Masuda, Kenji; Adachi, Masayuki; Hirai, Asako; Yamamoto, Hiroyuki; Kaji, Hironori; Horii, Fumitaka

    2003-06-01

    To obtain further information about the cause for the rather large splitting of the C4 resonance line into the downfield (C4D) and upfield (C4U) lines in CP/MAS 13C NMR spectra for native cellulose, 13C and 1H spin diffusion measurements have been conducted by using different types of bacterial cellulose samples. In 13C spin diffusion measurements, the C4D resonance line is selectively inverted by the Dante pi pulse sequence and the 13C spin diffusion is allowed to proceed from the C4D carbons to other carbons including the C4U carbons with use of the 13C4-enriched bacterial cellulose sample. The analysis based on the simple spin diffusion theory for the process experimentally observed reveals that the C4U carbons may be located at distances less than about 1 nm from the C4D carbons. In 1H spin diffusion measurements, poly(vinyl alcohol) (PVA) films in which ribbon assemblies of bacterial cellulose are dispersed are employed and the 1H spin diffusion process is examined from the water-swollen PVA continuous phase to the dispersed ribbon assemblies by the 13C detection through the 1H-13C CP technique. As a result, it is found that the C4D and C4U carbons are almost equally subjected to the 1H spin diffusion from the PVA phase, indicating that the C4U carbons are not localized in some limited area, e.g. in the surfacial region, but are distributed in the whole area in the microfibrils. These experimental results suggest that the C4U carbons may exist as structural defects probably due to conformational irregularity associated with disordered hydrogen bonding of the CH(2)OH groups in the microfibrils.

  10. Studies of the Active Sites for Methane Dehydroaromatization Using Ultrahigh-Field Solid-State Mo95 NMR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Peden, Charles HF; Zheng, Heng; Ma, Ding; Bao, Xinhe

    2009-01-26

    Abstract It is found that the spin-lattice relaxation time, T1, corresponding to the surface exchanged molybdenum species in Mo/HZSM-5 catalysts is short, i.e., less than about 100ms at 21.1 T while the value of T1 for the crystallite MoO3 molecules is longer, i.e., about 30 s. Such a difference, more than two orders in magnitude, is utilized to differentiate the exchanged Mo species from the agglomerate MoO3 in Mo/HZSM-5 catalyst. An approximately linear correlation between the amount of exchanged species and the aromatics formation rate is obtained. This result significantly strengthens our prior conclusion that the exchanged Mo species are the active centers for the methane dehydroaromatization reaction on Mo/HZSM-5 catalysts (J. Am. Chem. Soc. 2008, 130, 3722-3723). Our results also suggest that one exchanged Mo atom anchors on two ion exchange sites and the exchanged Mo species on catalysts are possibly monomeric. Analyzing the linshapes obtained from both the 95Mo MAS and the static spectra indicates that the exchanged sites are heterogeneous, resulting in a significantly broadened MAS spectrum and essentially a featureless but nearly symmetric static lineshape for the exchanged Mo species. Furthermore, for crystallite MoO3 powder sample, the parameters related to the electric-field-gradient (EFG) tensor, the chemical shift anisotropy (CSA) and the three Euler angles required to align the CSA principal axis system with the quadrupolar principal axis system are determined by analyzing both the 95Mo MAS and the static spectra obtained at ultra-high field of 21.1 T. The new results obtained from this study on crystallite MoO3 powders should help to clarify some of the contradictions in prior literature reports from other groups. Key words: 95Mo NMR, MAS, relaxation, surface exchanged species, HZSM-5, electric-field-gradient (EFG), chemical shift anisotropy (CSA), active centers.

  11. Metal Carbonation of Forsterite in Supercritical CO2 and H2O Using Solid State 29Si, 13C NMR Spectroscop

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ja Hun; Hu, Jian Z.; Hoyt, David W.; Sears, Jesse A.; Wang, Chong M.; Rosso, Kevin M.; Felmy, Andrew R.

    2010-03-11

    Ex situ solid state NMR was used for the first time to study fundamental mineral carbonation processes and reaction extent relevant to geologic carbon sequestration (GCS) using a model silicate mineral forsterite (Mg2SiO4)+supercriticalCO2 with and without H2O. Run conditions were 80 C and 96 atm. 29Si NMR clearly shows that in the absence of CO2, the role of H2O is to hydrolyze surface Mg-O-Si bonds to produce dissolved Mg2+, and mono- and oligomeric hydroxylated silica species. Surface hydrolysis products contain only Q0 (Si(OH)4) and Q1(Si(OH)3OSi) species. An equilibrium between Q0, Q1 and Mg2+ with a saturated concentration equivalent to less than 3.2% of the Mg2SiO4 conversion is obtained at a reaction time of up to 7 days. Using scCO2 without H2O, no reaction is observed within 7 days. Using both scCO2 and H2O, the surface reaction products for silica are mainly Q3 (SiOH(OSi)3) species accompanied by a lesser amount of Q2 (Si(OH)2(OSi)2) and Q4 (Si(OSi)4). However, no Q0 and Q1 were detected, indicating the carbonic acid formation/deprotonation and magnesite (MgCO3) precipitation reactions are faster than the forsterite hydrolysis process. Thus it can be concluded that the Mg2SiO4 hydrolysis process is the rate limiting step of the overall mineral carbonation process. 29Si NMR combined with XRD, TEM, SAED and EDX further reveal that the reaction is a surface reaction with the Mg2SiO4 crystallite in the core and with condensed Q2-Q4 species forming amorphous surface layers. 13C MAS NMR identified a possible reaction intermediate as (MgCO3)4-Mg(OH)2-5H2O. However, at long reaction times only crystallite magnesite MgCO3 products are observed.

  12. Towards an integrative structural biology approach: combining Cryo-TEM, X-ray crystallography, and NMR.

    Science.gov (United States)

    Lengyel, Jeffrey; Hnath, Eric; Storms, Marc; Wohlfarth, Thomas

    2014-09-01

    Cryo-transmission electron microscopy (Cryo-TEM) and particularly single particle analysis is rapidly becoming the premier method for determining the three-dimensional structure of protein complexes, and viruses. In the last several years there have been dramatic technological improvements in Cryo-TEM, such as advancements in automation and use of improved detectors, as well as improved image processing techniques. While Cryo-TEM was once thought of as a low resolution structural technique, the method is currently capable of generating nearly atomic resolution structures on a routine basis. Moreover, the combination of Cryo-TEM and other methods such as X-ray crystallography, nuclear magnetic resonance spectroscopy, and molecular dynamics modeling are allowing researchers to address scientific questions previously thought intractable. Future technological developments are widely believed to further enhance the method and it is not inconceivable that Cryo-TEM could become as routine as X-ray crystallography for protein structure determination.

  13. Probing the role of the ceramide acyl chain length and sphingosine unsaturation in model skin barrier lipid mixtures by (2)H solid-state NMR spectroscopy.

    Science.gov (United States)

    Stahlberg, Sören; Školová, Barbora; Madhu, Perunthiruthy K; Vogel, Alexander; Vávrová, Kateřina; Huster, Daniel

    2015-05-05

    We investigated equimolar mixtures of ceramides with lignoceric acid and cholesterol as models for the human stratum corneum by differential scanning calorimetry and (2)H solid-state NMR spectroscopy. Our reference system consisted of lignoceroyl sphingosine (Cer[NS24]), which represents one of the ceramides in the human stratum corneum. Furthermore, the effect of ceramide acyl chain truncation to 16 carbons as in Cer[NS16] and the loss of the C4 trans double bond as in dihydroceramide Cer[NDS24] were studied. Fully relaxed (2)H NMR spectra were acquired for each deuterated component of each mixture separately, allowing the quantitative determination of the individual lipid phases. At skin temperature, the reference system containing Cer[NS24] is characterized by large portions of each component of the mixture in a crystalline phase, which largely restricts the permeability of the skin lipid barrier. The loss of the C4 trans double bond in Cer[NDS24] leads to the replacement of more than 25% of the crystalline phase by an isotropic phase of the dihydroceramide that shows the importance of dihydroceramide desaturation in the formation of the skin lipid barrier. The truncated Cer[NS16] is mostly found in the gel phase at skin temperature, which may explain its negative effect on the transepidermal water loss in atopic dermatitis patients. These significant alterations in the phase behavior of all lipids are further reflected at elevated temperatures. The molecular insights of our study may help us to understand the importance of the structural parameters of ceramides in healthy and compromised skin barriers.

  14. Monitoring and understanding the paraelectric-ferroelectric phase transition in the metal-organic framework [NH4 ][M(HCOO)3 ] by solid-state NMR spectroscopy.

    Science.gov (United States)

    Xu, Jun; Lucier, Bryan E G; Sinelnikov, Regina; Terskikh, Victor V; Staroverov, Viktor N; Huang, Yining

    2015-10-01

    The paraelectric-ferroelectric phase transition in two isostructural metal-organic frameworks (MOFs) [NH4 ][M(HCOO)3 ] (M=Mg, Zn) was investigated by in situ variable-temperature (25) Mg, (67) Zn, (14) N, and (13) C solid-state NMR (SSNMR) spectroscopy. With decreasing temperature, a disorder-order transition of NH4 (+) cations causes a change in dielectric properties. It is thought that [NH4 ][Mg(HCOO)3 ] exhibits a higher transition temperature than [NH4 ][Zn(HCOO)3 ] due to stronger hydrogen-bonding interactions between NH4 (+) ions and framework oxygen atoms. (25) Mg and (67) Zn NMR parameters are very sensitive to temperature-induced changes in structure, dynamics, and dielectric behavior; stark spectral differences across the paraelectric-ferroelectric phase transition are intimately related to subtle changes in the local environment of the metal center. Although (25) Mg and (67) Zn are challenging nuclei for SSNMR experiments, the highly spherically symmetric metal-atom environments in [NH4 ][M(HCOO)3 ] give rise to relatively narrow spectra that can be acquired in 30-60 min at a low magnetic field of 9.4 T. Complementary (14) N and (13) C SSNMR experiments were performed to probe the role of NH4 (+) -framework hydrogen bonding in the paraelectric-ferroelectric phase transition. This multinuclear SSNMR approach yields new physical insights into the [NH4 ][M(HCOO)3 ] system and shows great potential for molecular-level studies on electric phenomena in a wide variety of MOFs.

  15. Multidimensional solid-state NMR studies of the structure and dynamics of pectic polysaccharides in uniformly 13C-labeled Arabidopsis primary cell walls

    Energy Technology Data Exchange (ETDEWEB)

    Dick-Perez, Marilu; Wang, Tuo; Salazar, Andre; Zabotina, Olga A.; Hong, Mei

    2012-07-08

    Plant cell wall (CW) polysaccharides are responsible for the mechanical strength and growth of plant cells; however, the high-resolution structure and dynamics of the CW polysaccharides are still poorly understood because of the insoluble nature of these molecules. Here, we use 2D and 3D magic-angle-spinning (MAS) solid-state NMR (SSNMR) to investigate the structural role of pectins in the plant CW. Intact and partially depectinated primary CWs of Arabidopsis thaliana were uniformly labeled with 13C and their NMR spectra were compared. Recent 13C resonance assignment of the major polysaccharides in Arabidopsis thaliana CWs allowed us to determine the effects of depectination on the intermolecular packing and dynamics of the remaining wall polysaccharides. 2D and 3D correlation spectra show the suppression of pectin signals, confirming partial pectin removal by chelating agents and sodium carbonate. Importantly, higher cross peaks are observed in 2D and 3D 13C spectra of the depectinated CW, suggesting higher rigidity and denser packing of the remaining wall polysaccharides compared with the intact CW. 13C spin–lattice relaxation times and 1H rotating-frame spin–lattice relaxation times indicate that the polysaccharides are more rigid on both the nanosecond and microsecond timescales in the depectinated CW. Taken together, these results indicate that pectic polysaccharides are highly dynamic and endow the polysaccharide network of the primary CW with mobility and flexibility, which may be important for pectin functions. This study demonstrates the capability of multidimensional SSNMR to determine the intermolecular interactions and dynamic structures of complex plant materials under near-native conditions. Copyright © 2012 John Wiley & Sons, Ltd.

  16. A Solid-State 11B NMR and Computational Study of Boron Electric Field Gradient and Chemical Shift Tensors in Boronic Acids and Boronic Esters

    Science.gov (United States)

    2010-01-01

    The results of a solid-state 11B NMR study of a series of 10 boronic acids and boronic esters with aromatic substituents are reported. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron nucleus. Data collected at 21.1 T clearly show the effects of chemical shift anisotropy (CSA), with tensor spans (Ω) on the order of 10−40 ppm. Signal enhancements of up to 2.95 were achieved with a DFS-modified QCPMG pulse sequence. To understand the relationship between the measured tensors and the local structure better, calculations of the 11B EFG and magnetic shielding tensors for these compounds were conducted. The best agreement was found between experimental results and those obtained from GGA revPBE DFT calculations. A positive correlation was found between Ω and the dihedral angle (ϕCCBO), which describes the orientation of the boronic acid/ester functional group relative to an aromatic system bound to boron. The small boron CSA is discussed in terms of paramagnetic shielding contributions as well as diamagnetic shielding contributions. Although there is a region of overlap, both Ω and the 11B quadrupolar coupling constants tend to be larger for boronic acids than for the esters. We conclude that the span is generally the most characteristic boron NMR parameter of the molecular and electronic environment for boronic acids and esters, and show that the values result from a delicate interplay of several competing factors, including hydrogen bonding, the value of ϕCCBO, and the electron-donating or withdrawing substituents bound to the aromatic ring. PMID:20337440

  17. Early diagenesis of mangrove leaves in a tropical estuary: Bulk chemical characterization using solid-state 13C NMR and elemental analyses

    Science.gov (United States)

    Benner, R.; Hatcher, P.G.; Hedges, J.I.

    1990-01-01

    Changes in the chemical composition of mangrove (Rhizophora mangle) leaves during decomposition in tropical estuarine waters were characterized using solid-state 13C nuclear magnetic resonance (NMR) and elemental (CHNO) analysis. Carbohydrates were the most abundant components of the leaves accounting for about 50 wt% of senescent tissues. Tannins were estimated to account for about 20 wt% of leaf tissues, and lipid components, cutin, and possibly other aliphatic biopolymers in leaf cuticles accounted for about 15 wt%. Carbohydrates were generally less resistant to decomposition than the other constituents and decreased in relative concentration during decomposition. Tannins were of intermediate resistance to decomposition and remained in fairly constant proportion during decomposition. Paraffinic components were very resistant to decomposition and increased in relative concentration as decomposition progressed. Lignin was a minor component of all leaf tissues. Standard methods for the colorimetric determination of tannins (Folin-Dennis reagent) and the gravimetric determination of lignin (Klason lignin) were highly inaccurate when applied to mangrove leaves. The N content of the leaves was particularly dynamic with values ranging from 1.27 wt% in green leaves to 0.65 wt% in senescent yellow leaves attached to trees. During decomposition in the water the N content initially decreased to 0.51 wt% due to leaching, but values steadily increased thereafter to 1.07 wt% in the most degraded leaf samples. The absolute mass of N in the leaves increased during decomposition indicating that N immobilization was occurring as decomposition progressed. ?? 1990.

  18. Thermal aging of interfacial polymer chains in ethylene-propylene-diene terpolymer/aluminum hydroxide composites: solid-state NMR study.

    Science.gov (United States)

    Gabrielle, Brice; Lorthioir, Cédric; Lauprêtre, Françoise

    2011-11-01

    The possible influence of micrometric-size filler particles on the thermo-oxidative degradation behavior of the polymer chains at polymer/filler interfaces is still an open question. In this study, a cross-linked ethylene-propylene-diene (EPDM) terpolymer filled by aluminum trihydrate (ATH) particles is investigated using (1)H solid-state NMR. The time evolution of the EPDM network microstructure under thermal aging at 80 °C is monitored as a function of the exposure time and compared to that of an unfilled EPDM network displaying a similar initial structure. While nearly no variations of the topology are observed on the neat EPDM network over 5 days at 80 °C, a significant amount of chain scission phenomena are evidenced in EPDM/ATH. A specific surface effect induced by ATH on the thermodegradative properties of the polymer chains located in their vicinity is thus pointed out. Close to the filler particles, a higher amount of chain scissions are detected, and the characteristic length scale related to these interfacial regions displaying a significant thermo-oxidation process is determined as a function of the aging time.

  19. Protein structural studies by paramagnetic solid-state NMR spectroscopy aided by a compact cyclen-type Cu(II) binding tag

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, Ishita; Gao, Min; Arachchige, Rajith J.; Nadaud, Philippe S. [The Ohio State University, Department of Chemistry and Biochemistry (United States); Cunningham, Timothy F.; Saxena, Sunil [University of Pittsburgh, Department of Chemistry (United States); Schwieters, Charles D. [National Institutes of Health, Center for Information Technology (United States); Jaroniec, Christopher P., E-mail: jaroniec@chemistry.ohio-state.edu [The Ohio State University, Department of Chemistry and Biochemistry (United States)

    2015-01-15

    Paramagnetic relaxation enhancements (PREs) are a rich source of structural information in protein solid-state NMR spectroscopy. Here we demonstrate that PRE measurements in natively diamagnetic proteins are facilitated by a thiol-reactive compact, cyclen-based, high-affinity Cu{sup 2+} binding tag, 1-[2-(pyridin-2-yldisulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (TETAC), that overcomes the key shortcomings associated with the use of larger, more flexible metal-binding tags. Using the TETAC–Cu{sup 2+} K28C mutant of B1 immunoglobulin-binding domain of protein G as a model, we find that amino acid residues located within ∼10 Å of the Cu{sup 2+} center experience considerable transverse PREs leading to severely attenuated resonances in 2D {sup 15}N–{sup 13}C correlation spectra. For more distant residues, electron–nucleus distances are accessible via quantitative measurements of longitudinal PREs, and we demonstrate such measurements for {sup 15}N–Cu{sup 2+} distances up to ∼20 Å.

  20. Improved transfer efficiencies in radio-frequency-driven recoupling solid-state NMR by adiabatic sweep through the dipolar recoupling condition.

    Science.gov (United States)

    Straasø, Lasse A; Shankar, Ravi; Tan, Kong Ooi; Hellwagner, Johannes; Meier, Beat H; Hansen, Michael Ryan; Nielsen, Niels Chr; Vosegaard, Thomas; Ernst, Matthias; Nielsen, Anders B

    2016-07-21

    The homonuclear radio-frequency driven recoupling (RFDR) experiment is commonly used in solid-state NMR spectroscopy to gain insight into the structure of biological samples due to its ease of implementation, stability towards fluctuations/missetting of radio-frequency (rf) field strength, and in general low rf requirements. A theoretical operator-based Floquet description is presented to appreciate the effect of having a temporal displacement of the π-pulses in the RFDR experiment. From this description, we demonstrate improved transfer efficiency for the RFDR experiment by generating an adiabatic passage through the zero-quantum recoupling condition. We have compared the performances of RFDR and the improved sequence to mediate efficient (13)CO to (13)Cα polarization transfer for uniformly (13)C,(15)N-labeled glycine and for the fibril forming peptide SNNFGAILSS (one-letter amino acid codes) uniformly (13)C,(15)N-labeled at the FGAIL residues. Using numerically optimized sweeps, we get experimental gains of approximately 20% for glycine where numerical simulations predict an improvement of 25% relative to the standard implementation. For the fibril forming peptide, using the same sweep parameters as found for glycine, we have gains in the order of 10%-20% depending on the spectral regions of interest.

  1. Ammonia-Containing Species Formed in Cu-Chabazite As Per In Situ EPR, Solid-State NMR, and DFT Calculations.

    Science.gov (United States)

    Moreno-González, Marta; Hueso, Beatriz; Boronat, Mercedes; Blasco, Teresa; Corma, Avelino

    2015-03-19

    Nowadays, the most attractive technology for the elimination of nitric oxides from the exhaust gas of diesel vehicles is the selective catalytic reduction with ammonia (NH3-SCR-NOx) using Cu zeolite with the chabazite structure as the catalyst. Isolated copper species are the active sites, but the reaction intermediates and the overall reaction mechanism are still under debate. Here, we study the interaction of ammonia with zeolite Cu-SSZ-13 (CHA topology) with a uniform distribution of Cu(2+) sites prepared in one pot and a conventional Cu-ZSM-5 (MFI topology) for comparison. In situ EPR and solid-state NMR spectroscopies combined with DFT calculations have allowed the identification of NH4(+), [Cu(NH3)5](2+), [Cu(Of)2(NH3)2](2+), [Cu(Of)3NH3](2+), [Cu(NH3)2](+), and [CuOf(NH3)](+) (Of being framework oxygen) under different conditions. The results demonstrate that ammonia is able to reduce Cu(2+) to Cu(+) and provide new information on the species formed in Cu-SSZ-13, which have important implications for the elucidation of the SCR reaction mechanism.

  2. Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N-Donor SBA15 Surface Ligands: A Solid-State NMR and DFT Study

    KAUST Repository

    Bendjeriou-Sedjerari, Anissa

    2016-08-11

    Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(CtBu)(CH(2)tBu)(3) with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(SiOH)(SiNH2)], leads to [(SiNH2-)(SiO-)W(CHtBu)(CH(2)tBu)(2)] and [(SiNH2-)(SiO-)W(=CHtBu)(2)(CH(2)tBu). Variable temperature, H-1-H-1 2D double-quantum, H-1-C-13 HETCOR, and HETCOR with spin diffusion solid-state NMR spectroscopy demonstrate tautomerization between the alkyl alkylidyne and the bis(alkylidene) on the SBA15 surface. Such equilibrium is possible through the coordination of W to the surface [(Si-OH)(Si-NH2)] groups, which act as a [N,O] pincer ligand. DFT calculations provide a rationalization for the surface-complex tautomerization and support the experimental results. This direct observation of such a process shows the strong similarity between molecular mechanisms in homogeneous and heterogeneous catalysis. In propane metathesis (at 150 degrees C), the tungsten bis(carbene) tautomer is favorable, with a turnover number (TON) of 262. It is the highest TON among all the tungsten alkyl-supported catalysts.

  3. In situ solid-state NMR and XRD studies of the ADOR process and the unusual structure of zeolite IPC-6

    Science.gov (United States)

    Morris, Samuel A.; Bignami, Giulia P. M.; Tian, Yuyang; Navarro, Marta; Firth, Daniel S.; Čejka, Jiří; Wheatley, Paul S.; Dawson, Daniel M.; Slawinski, Wojciech A.; Wragg, David S.; Morris, Russell E.; Ashbrook, Sharon E.

    2017-10-01

    The assembly-disassembly-organization-reassembly (ADOR) mechanism is a recent method for preparing inorganic framework materials and, in particular, zeolites. This flexible approach has enabled the synthesis of isoreticular families of zeolites with unprecedented continuous control over porosity, and the design and preparation of materials that would have been difficult—or even impossible—to obtain using traditional hydrothermal techniques. Applying the ADOR process to a parent zeolite with the UTL framework topology, for example, has led to six previously unknown zeolites (named IPC-n, where n = 2, 4, 6, 7, 9 and 10). To realize the full potential of the ADOR method, however, a further understanding of the complex mechanism at play is needed. Here, we probe the disassembly, organization and reassembly steps of the ADOR process through a combination of in situ solid-state NMR spectroscopy and powder X-ray diffraction experiments. We further use the insight gained to explain the formation of the unusual structure of zeolite IPC-6.

  4. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning.

    Science.gov (United States)

    Sharma, Kshama; Madhu, P K; Agarwal, Vipin

    2016-09-01

    The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1=n·νr). Recently, two schemes, namely, PISSARRO and rCW(ApA), have been shown to be less affected by the problem of MAS and RF interference, specifically at the n=2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n=1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power (1)H irradiation of ca.195kHz.

  5. A suite of pulse sequences based on multiple sequential acquisitions at one and two radiofrequency channels for solid-state magic-angle spinning NMR studies of proteins.

    Science.gov (United States)

    Sharma, Kshama; Madhu, Perunthiruthy K; Mote, Kaustubh R

    2016-08-01

    One of the fundamental challenges in the application of solid-state NMR is its limited sensitivity, yet a majority of experiments do not make efficient use of the limited polarization available. The loss in polarization in a single acquisition experiment is mandated by the need to select out a single coherence pathway. In contrast, sequential acquisition strategies can encode more than one pathway in the same experiment or recover unused polarization to supplement a standard experiment. In this article, we present pulse sequences that implement sequential acquisition strategies on one and two radiofrequency channels with a combination of proton and carbon detection to record multiple experiments under magic-angle spinning. We show that complementary 2D experiments such as [Formula: see text] and [Formula: see text] or DARR and [Formula: see text], and 3D experiments such as [Formula: see text] and [Formula: see text], or [Formula: see text] and [Formula: see text]  can be combined in a single experiment to ensure time savings of at least 40 %. These experiments can be done under fast or slow-moderate magic-angle spinning frequencies aided by windowed [Formula: see text] acquisition and homonulcear decoupling. The pulse sequence suite is further expanded by including pathways that allow the recovery of residual polarization, the so-called 'afterglow' pathways, to encode a number of pulse sequences to aid in assignments and chemical-shift mapping.

  6. Revealing protein structures in solid-phase peptide synthesis by 13C solid-state NMR: evidence of excessive misfolding for Alzheimer's β.

    Science.gov (United States)

    Wang, Songlin; Ishii, Yoshitaka

    2012-02-15

    Solid-phase peptide synthesis (SPPS) is a widely used technique in biology and chemistry. However, the synthesis yield in SPPS often drops drastically for longer amino acid sequences, presumably because of the occurrence of incomplete coupling reactions. The underlying cause for this problem is hypothesized to be a sequence-dependent propensity to form secondary structures through protein aggregation. However, few methods are available to study the site-specific structure of proteins or long peptides that are anchored to the solid support used in SPPS. This study presents a novel solid-state NMR (SSNMR) approach to examine protein structure in the course of SPPS. As a useful benchmark, we describe the site-specific SSNMR structural characterization of the 40-residue Alzheimer's β-amyloid (Aβ) peptide during SPPS. Our 2D (13)C/(13)C correlation SSNMR data on Aβ(1-40) bound to a resin support demonstrated that Aβ underwent excessive misfolding into a highly ordered β-strand structure across the entire amino acid sequence during SPPS. This approach is likely to be applicable to a wide range of peptides/proteins bound to the solid support that are synthesized through SPPS.

  7. Investigation of Phase Mixing in Amorphous Solid Dispersions of AMG 517 in HPMC-AS Using DSC, Solid-State NMR, and Solution Calorimetry.

    Science.gov (United States)

    Calahan, Julie L; Azali, Stephanie C; Munson, Eric J; Nagapudi, Karthik

    2015-11-02

    Intimate phase mixing between the drug and the polymer is considered a prerequisite to achieve good physical stability for amorphous solid dispersions. In this article, spray dried amorphous dispersions (ASDs) of AMG 517 and HPMC-as were studied by differential scanning calorimetry (DSC), solid-state NMR (SSNMR), and solution calorimetry. DSC analysis showed a weakly asymmetric (ΔTg ≈ 13.5) system with a single glass transition for blends of different compositions indicating phase mixing. The Tg-composition data was modeled using the BKCV equation to accommodate the observed negative deviation from ideality. Proton spin-lattice relaxation times in the laboratory and rotating frames ((1)H T1 and T1ρ), as measured by SSNMR, were consistent with the observation that the components of the dispersion were in intimate contact over a 10-20 nm length scale. Based on the heat of mixing calculated from solution calorimetry and the entropy of mixing calculated from the Flory-Huggins theory, the free energy of mixing was calculated. The free energy of mixing was found to be positive for all ASDs, indicating that the drug and polymer are thermodynamically predisposed to phase separation at 25 °C. This suggests that miscibility measured by DSC and SSNMR is achieved kinetically as the result of intimate mixing between drug and polymer during the spray drying process. This kinetic phase mixing is responsible for the physical stability of the ASD.

  8. STUDY OF THE MOLECULAR MOTION AND COMPATIBILITY IN AB-CROSSLINKED POLYMER BASED ON POLYURETHANE AND POLYSTYRENE-co-ACRYLIC ACID BY SOLID STATE HIGH RESOLUTION NMR

    Institute of Scientific and Technical Information of China (English)

    JIA Mingchun; SHEN Lianfang; QIAN Baogong; ZHANG Baozhen; YAO Shuren

    1994-01-01

    The 13C T1s of -CH3 side group in PPU/P(St-co-AA), AB-crosslinked polymers (i. e.ABCP) was studied by using high resolution solid state NMR. The rotation motion of -CH3 side group in PPU was analyzed by means of the average spectral density functions of internal rotation. The results showed that the rotation of the -CH3 side group is related closely to the compatibility between the two components. The compatibility was studied by analyzing the proton spin-lattice relaxation in rotating frame, spin-spin relaxation and spin-diffusion. The results showed that the hydrogen bonds between the components play a major role in determining the compatibility. Through spin diffusion studying, the soft phase domain size was calculated. By studying proton spin-spin relaxation, the content of each component in each phase and that of each phase in the samples can be obtained. The result shows that the content of interphase is related closely to the compatibility.

  9. Interaction of Alamethicin with Ether-Linked Phospholipid Bilayers: Oriented Circular Dichroism, 31P Solid-State NMR, and Differential Scanning Calorimetry Studies

    Science.gov (United States)

    Dave, Paresh C.; Billington, Emma; Pan, Yeang-Ling; Straus, Suzana K.

    2005-01-01

    The arrangement of the antimicrobial peptide alamethicin was studied by oriented circular dichroism, 31P solid-state NMR, and differential scanning calorimetry in ether-linked phospholipid bilayers composed of 1,2-O-dihexadecyl-sn-glycero-3-phosphocholine (DHPC). The measurements were performed as a function of alamethicin concentration relative to the lipid concentration, and results were compared to those reported in the literature for ester-linked phospholipid bilayers. At ambient temperature, alamethicin incorporates into the hydrophobic core of DHPC bilayers but results in more lipid disorder than observed for ester-linked 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) lipid bilayers. This orientational disorder appears to depend on lipid properties such as bilayer thickness. Moreover, the results suggest that alamethicin inserts into the hydrophobic core of the bilayers (at high peptide concentration) for both ether- and ester-linked lipids but using a different mechanism, namely toroidal for DHPC and barrel-stave for POPC. PMID:16055546

  10. A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance.

    Science.gov (United States)

    Tan, Kong Ooi; Agarwal, Vipin; Meier, Beat H; Ernst, Matthias

    2016-09-01

    We present a generalized theoretical framework that allows the approximate but rapid analysis of residual couplings of arbitrary decoupling sequences in solid-state NMR under magic-angle spinning conditions. It is a generalization of the tri-modal Floquet analysis of TPPM decoupling [Scholz et al., J. Chem. Phys. 130, 114510 (2009)] where three characteristic frequencies are used to describe the pulse sequence. Such an approach can be used to describe arbitrary periodic decoupling sequences that differ only in the magnitude of the Fourier coefficients of the interaction-frame transformation. It allows a ∼100 times faster calculation of second-order residual couplings as a function of pulse sequence parameters than full spin-dynamics simulations. By comparing the theoretical calculations with full numerical simulations, we show the potential of the new approach to examine the performance of decoupling sequences. We exemplify the usefulness of this framework by analyzing the performance of commonly used high-power decoupling sequences and low-power decoupling sequences such as amplitude-modulated XiX (AM-XiX) and its super-cycled variant SC-AM-XiX. In addition, the effect of chemical-shift offset is examined for both high- and low-power decoupling sequences. The results show that the cross-terms between the dipolar couplings are the main contributions to the line broadening when offset is present. We also show that the SC-AM-XIX shows a better offset compensation.

  11. Understanding API-polymer proximities in amorphous stabilized composite drug products using fluorine-carbon 2D HETCOR solid-state NMR.

    Science.gov (United States)

    Abraham, Anuji; Crull, George

    2014-10-06

    A simple and robust method for obtaining fluorine-carbon proximities was established using a (19)F-(13)C heteronuclear correlation (HETCOR) two-dimensional (2D) solid-state nuclear magnetic resonance (ssNMR) experiment under magic-angle spinning (MAS). The method was applied to study a crystalline active pharmaceutical ingredient (API), avagacestat, containing two types of fluorine atoms and its API-polymer composite drug product. These results provide insight into the molecular structure, aid with assigning the carbon resonances, and probe API-polymer proximities in amorphous spray dried dispersions (SDD). This method has an advantage over the commonly used (1)H-(13)C HETCOR because of the large chemical shift dispersion in the fluorine dimension. In the present study, fluorine-carbon distances up to 8 Å were probed, giving insight into the API structure, crystal packing, and assignments. Most importantly, the study demonstrates a method for probing an intimate molecular level contact between an amorphous API and a polymer in an SDD, giving insights into molecular association and understanding of the role of the polymer in API stability (such as recrystallization, degradation, etc.) in such novel composite drug products.

  12. Structure and disorder in iron-bearing sodium silicate glasses and melts: High-resolution 29Si and 17O solid-state NMR study

    Science.gov (United States)

    Kim, H.; Lee, S.

    2012-12-01

    Understanding of the effect of iron content on the structure (Si coordination environment and the degree of polymerization) of iron-bearing silicate melts and glasses is essential for studying their macroscopic properties and diverse geological processes in Earth's interior. Although the recent advances in high-resolution solid-state NMR techniques provide detailed structural information of a diverse iron-free oxide glasses with varying composition (e.g., Lee, P. Natl. Acad. Sci. USA., 2011, 108, 6847; Lee and Sung, Chem. Geol., 2008, 256, 326; Park and Lee, Geochim. Cosmochim. Acta, 2012, 80, 125; Lee et al., Phys. Rev., 103, 095501, 2009), their application to iron-bearing silicate glasses has a limited usefulness in resolving atomic configurations due to the effect of paramagnetic cation (i.e., Fe) on the NMR spectra. Here, we report the first ^{29}Si and ^{17}O NMR spectra for sodium-iron silicate glasses with varying iron content (Na_{2}O-Fe_{2}O_{3}-SiO_{2} glasses, up to 34.60 wt% Fe_{2}O_{3}), revealing previously unknown details of iron-induced changes in structure and disorder. While signal intensity decreases and peak width increases exponentially with increasing iron content [=Fe_{2}O_{3}/(Na_{2}O+Fe_{2}O_{3})], ^{29}Si MAS NMR spectra for sodium-iron silicate glasses present the slight peak shift and an asymmetrical peak broadening toward higher Q^{n} species with increasing iron content. This result implies an increase in the degree of polymerization with increasing iron content. Additionally, ^{29}Si spin-relaxation time (T_{1}) for the glasses decreases with increasing of iron content by several orders of magnitude. ^{17}O 3QMAS NMR spectra for the glasses show well-resolved non-bridging oxygen (NBO, Na-O-Si) and bridging oxygen (BO, Si-O-Si) even at relatively high iron content, providing the first direct experimental estimation of the degree of polymerization. In sodium-iron silicate glasses, the fraction of NBO decreases with increasing iron

  13. Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy

    Science.gov (United States)

    2016-01-01

    Operando pair distribution function (PDF) analysis and ex situ 23Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from 23Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na3–xSb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na1.7Sb, a highly amorphous structure featuring some Sb–Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3–xSb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na1.7Sb, then a-Na3–xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na3–xSb without the formation of a-Na1.7Sb. a-Na3–xSb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature 23Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes. PMID:26824406

  14. Periodic ab initio calculation of nuclear quadrupole parameters as an assignment tool in solid-state NMR spectroscopy: applications to 23Na NMR spectra of crystalline materials.

    Science.gov (United States)

    Johnson, Clive; Moore, Elaine A; Mortimer, Michael

    2005-05-01

    Periodic ab initio HF calculations using the CRYSTAL code have been used to calculate (23)Na NMR quadrupole parameters for a wide range of crystalline sodium compounds including Na(3)OCl. An approach is developed that can be used routinely as an alternative to point-charge modelling schemes for the assignment of distinct lines in (23)Na NMR spectra to specific crystallographic sodium sites. The calculations are based on standard 3-21 G and 6-21 G molecular basis sets and in each case the same modified basis set for sodium is used for all compounds. The general approach is extendable to other quadrupolar nuclei. For the 3-21 G calculations a 1:1 linear correlation between experimental and calculated values of C(Q)((23)Na) is obtained. The 6-21 G calculations, including the addition of d-polarisation functions, give better accuracy in the calculation of eta((23)Na). The sensitivity of eta((23)Na) to hydrogen atom location is shown to be useful in testing the reported hydrogen-bonded structure of Na(2)HPO(4).

  15. (13)C and (19)F solid-state NMR and X-ray crystallographic study of halogen-bonded frameworks featuring nitrogen-containing heterocycles.

    Science.gov (United States)

    Szell, Patrick M J; Gabriel, Shaina A; Gill, Russell D D; Wan, Shirley Y H; Gabidullin, Bulat; Bryce, David L

    2017-03-01

    Halogen bonding is a noncovalent interaction between the electrophilic region of a halogen (σ-hole) and an electron donor. We report a crystallographic and structural analysis of halogen-bonded compounds by applying a combined X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (SSNMR) approach. Single-crystal XRD was first used to characterize the halogen-bonded cocrystals formed between two fluorinated halogen-bond donors (1,4-diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene) and several nitrogen-containing heterocycles (acridine, 1,10-phenanthroline, 2,3,5,6-tetramethylpyrazine, and hexamethylenetetramine). New structures are reported for the following three cocrystals, all in the P21/c space group: acridine-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C13H9N, 1,10-phenanthroline-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C12H8N2, and 2,3,5,6-tetramethylpyrazine-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C8H12N2. (13)C and (19)F solid-state magic-angle spinning (MAS) NMR is shown to be a convenient method to characterize the structural features of the halogen-bond donor and acceptor, with chemical shifts attributable to cocrystal formation observed in the spectra of both nuclides. Cross polarization (CP) from (19)F to (13)C results in improved spectral sensitivity in characterizing the perfluorinated halogen-bond donor when compared to conventional (1)H CP. Gauge-including projector-augmented wave density functional theory (GIPAW DFT) calculations of magnetic shielding constants, along with optimization of the XRD structures, provide a final set of structures in best agreement with the experimental (13)C and (19)F chemical shifts. Data for carbons bonded to iodine remain outliers due to well-known relativistic effects.

  16. Solid state structural analysis of new pentamidine analogs designed as chemotherapeutics that target DNA by X-ray diffraction and 13C, 15N CP/MAS NMR methods

    Science.gov (United States)

    Żabiński, Jerzy; Maciejewska, Dorota; Wolska, Irena

    2010-12-01

    The paper presents the solid-state analysis of the crystalline form of 1,5- bis[(4-cyanophenyl)- N-methylamino]pentane ( 1) and polycrystalline powder sample of 1,5- bis[(4-amidinophenyl)- N-methylamino]pentane dihydrochloride ( 2). The methods used are X-ray diffraction technique and 13C, 15N CP/MAS NMR spectroscopy in an attempt to detect the effects of possible polymorphism. Both methods indicate that only single conformers exist in the solid-state for 1 and 2. 1,5- Bis[(4-cyanophenyl)- N-methylamino]pentane 1, crystallizes in the orthorhombic space group P2 12 12. The asymmetric unit contains one half of the ordered molecule. Only weak intermolecular interactions were found in solid-state, in which methyl groups are engaged.

  17. Solid-state structures of (R sub 3 P) sub 2 PtX sub 2 complexes as determined by a combination of sup 13 C( sup 1 H) and sup 31 P( sup 1 H) NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rahn, J.A.; Nelson, J.H. (Univ. of Nevada, Reno (USA)); Baltusis, L. (Varian Instrument Div., Palo Alto, CA (USA))

    1990-02-21

    Cross-polarization, combined with magic-angle spinning, has been employed to obtain high-resolution solid-state {sup 13}C and {sup 31}P NMR spectra of a series of 31 (R{sub 3}P){sub 2}PtX{sub 2} complexes. These data together with spectra obtained in solution were used to compare the solid-state structures with those in solution. It was found that most of these complexes, which have regular square-planar structures in solution, are distorted in the solid state. The extent of the solid-state distortion is a function of the bulk of the coordinated ligands and increases as the ligand size increases. The solid-state distortions appear to result from intramolecular steric effects for cis-(R{sub 3}P){sub 2}PtX{sub 2} and probably from intermolecular crystal packing forces for trans-(R{sub 3}P){sub 2}PtX{sub 2}. 37 refs., 6 figs., 3 tabs.

  18. Litter decomposition over broad spatial and long time scales investigated by advanced solid-state NMR: insight into effects of climate, litter quality, and time

    Science.gov (United States)

    Mao, J.; Chen, N.; Harmon, M. E.; Li, Y.; Cao, X.; Chappell, M.

    2012-12-01

    Advanced 13C solid-state NMR techniques were employed to study the chemical structural changes of litter decomposition across broad spatial and long time scales. The fresh and decomposed litter samples of four species (Acer saccharum (ACSA), Drypetes glauca (DRGL), Pinus resinosa (PIRE), and Thuja plicata (THPL)) incubated for up to 10 years at four sites under different climatic conditions (from Arctic to tropical forest) were examined. Decomposition generally led to an enrichment of cutin and surface wax materials, and a depletion of carbohydrates causing overall composition to become more similar compared with original litters. However, the changes of main constituents in the four litters were inconsistent with the four litters following different pathways of decomposition at the same site. As decomposition proceeded, waxy materials decreased at the early stage and then gradually increased in PIRE; DRGL showed a significant depletion of lignin and tannin while the changes of lignin and tannin were relative small and inconsistent for ACSA and THPL. In addition, the NCH groups, which could be associated with either fungal cell wall chitin or bacterial wall petidoglycan, were enriched in all litters except THPL. Contrary to the classic lignin-enrichment hypothesis, DRGL with low-quality C substrate had the highest degree of composition changes. Furthermore, some samples had more "advanced" compositional changes in the intermediate stage of decomposition than in the highly-decomposed stage. This pattern might be attributed to the formation of new cross-linking structures, that rendered substrates more complex and difficult for enzymes to attack. Finally, litter quality overrode climate and time factors as a control of long-term changes of chemical composition.

  19. Solid-state NMR spectroscopy of a membrane protein in biphenyl phospholipid bicelles with the bilayer normal parallel to the magnetic field

    Science.gov (United States)

    Park, Sang Ho; Loudet, Cécile; Marassi, Francesca M.; Dufourc, Erick J.; Opella, Stanley J.

    2008-07-01

    Bicelles composed of the long-chain biphenyl phospholipid TBBPC (1-tetradecanoyl-2-(4-(4-biphenyl)butanoyl)-sn-glycero-3-PC) and the short-chain phospholipid DHPC align with their bilayer normals parallel to the direction of the magnetic field. In contrast, in typical bicelles the long-chain phospholipid is DMPC or DPPC, and the bilayers align with their normals perpendicular to the field. Samples of the membrane-bound form of the major coat protein of Pf1 bacteriophage in TBBPC bicelles are stable for several months, align magnetically over a wide range of temperatures, and yield well-resolved solid-state NMR spectra similar to those obtained from samples aligned mechanically on glass plates or in DMPC bicelle samples "flipped" with lanthanide ions so that their bilayer normals are parallel to the field. The order parameter of the TBBPC bicelle sample decreases from approximately 0.9 to 0.8 upon increasing the temperature from 20 °C to 60 °C. Since the frequency spans of the chemical shift and dipolar coupling interactions are twice as large as those obtained from proteins in DMPC bicelles without lanthanide ions, TBBPC bicelles provide an opportunity for structural studies with higher spectral resolution of the metal-binding membrane proteins without the risk of chemical or spectroscopic interference from the added lanthanide ions. In addition, the large temperature range of these samples is advantageous for the studies of membrane proteins that are unstable at elevated temperatures and for experiments requiring measurements as a function of temperature.

  20. In situ microscopic studies on the structures and phase behaviors of SF/PEG films using solid-state NMR and Raman imaging.

    Science.gov (United States)

    Chen, Congheng; Yao, Ting; Tu, Sidong; Xu, Weijie; Han, Yi; Zhou, Ping

    2016-06-28

    In order to overcome the drawbacks of silk fibroin (SF)-based materials, SF has been blended with some polymers. Before using the blend material, understanding of the structures and phase behaviors of the blend is thought to be essential. In this study, solid-state (13)C CP-MAS NMR and Raman imaging techniques were used to study the structures and phase behaviors of blends of SF with polyethylene glycol (PEG) at a molecular weight that varied from 2 to 20 kDa and a blend ratio of SF/PEG from 95/5 to 70/30 (w/w%) at the molecular and microscopic levels. It is found that the conformational transition of SF to the β-sheet increased as the PEG content increased, while the amount of the formed β-sheet conformers was decreased as the PEG molecular weight increased for a given content. It is also observed that SF was incompatible with PEG to some extent. The phase separation into "sea" and "island" domains took place in the SF/PEG blend films. SF was dominantly present in the "sea" domain, while PEG in the "island" domains. The conformation of SF in the interface between SF and PEG was changed to the β-sheet, while that in the protein-rich domain remained in the random coil and/or helix conformation. These observations suggest that the specifically expected materials, for example, the silk-based microspheres or scaffold materials can be manufactured by controlling the molecular weight and content of PEG in the blend system.

  1. Probing local structures of siliceous zeolite frameworks by solid-state NMR and first-principles calculations of 29Si-O-29Si scalar couplings.

    Science.gov (United States)

    Cadars, Sylvian; Brouwer, Darren H; Chmelka, Bradley F

    2009-03-21

    Subtle structural details of siliceous zeolites are probed by using two-bond scalar (J) coupling constants to characterize covalently bonded 29Si-O-29Si site pairs and local framework order. Solid-state two-dimensional (2D) 29Si{29Si} NMR measurements and first-principles calculations of 2J(29Si-O-29Si) couplings shed insights on both the local structures of siliceous zeolites Sigma-2 and ZSM-12, as well as the sensitivity of J couplings for detailed characterization analyses. DFT calculations on a model linear silicate dimer show that 2J(Si-O-Si) couplings have complicated multiple angular dependencies that make semi-empirical treatments impractical, but which are amenable to cluster approaches for accurate J-coupling calculations in zeolites. DFT calculations of 2J(29Si-O-29Si) couplings of the siliceous zeolite Sigma-2, whose framework structure is known to high accuracy from single-crystal X-ray diffraction studies, yield excellent agreement between calculated and experimentally measured 2J(Si-O-Si) couplings. For the siliceous zeolite ZSM-12, calculated 2J(29Si-O-29Si) couplings based on less-certain powder X-ray diffraction analyses deviate significantly from experimental values, while a refined structure based on 29Si chemical-shift-tensor analyses shows substantially improved agreement. 29Si J-coupling interactions can be used as sensitive probes of local structures of zeolitic frameworks and offer new opportunities for refining and solving complicated structures, in combination with complementary scattering, modeling, and other nuclear spin interactions.

  2. Characterization of the spherical intermediates and fibril formation of hCT in HEPES solution using solid-state 13C-NMR and transmission electron microscopy.

    Science.gov (United States)

    Itoh-Watanabe, Hikari; Kamihira-Ishijima, Miya; Kawamura, Izuru; Kondoh, Masashi; Nakakoshi, Masamichi; Sato, Michio; Naito, Akira

    2013-10-21

    Human calcitonin (hCT) is a 32-amino acid peptide hormone that contains an intrachain disulfide bridge between Cys1 and Cys7 and a proline amide at the C-terminus. hCT tends to associate to form a fibril precipitate of the same type as amyloid fibrils, and hence has been studied as a model of amyloid fibril formation. The fibrillation process in N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid (HEPES) solution was examined using transmission electron microscopy. The rate of hCT fibrillation in HEPES solution was much lower than in phosphate buffer and acetic acid solution. Spherical intermediate aggregates (nuclei) were observed during the early stage of fibril formation. Short proto-fibrils appeared on the surface of the spherical intermediates. Subsequently, the spherical intermediates transformed directly into long proto-fibrils, which then elongated into mature hCT fibrils. The fibrillation process was also examined using solid-state (13)C-NMR spectroscopy, which indicated that the fibril structure was a β-sheet in the central region and a mixture of random coils and β-sheets at the C-terminus. The kinetics of fibril formation was examined in terms of a two-step autocatalytic reaction mechanism. The first-step nucleation rate (k1) was lower in HEPES solution than in phosphate buffer and acetic acid solution because the half-life of the intermediates is significantly longer in HEPES solution. In contrast, the second-step fibril elongation rate (k2) was similar in HEPES solution and acidic solutions. Specific interaction of HEPES molecules with hCT may stabilize the spherical intermediates and consequently inhibit the fibril elongation process of hCT.

  3. Evaluation of natural rubber from IAC series clones by solid state {sup 13}C NMR; Avaliacao da borracha natural de clones da serie IAC por {sup 13}C RMN no estado solido

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Maria A.; Moreno, Rogerio M.B.; Goncalves, Paulo S. [Instituto Agronomico de Campinas, SP (Brazil). Centro de Cafe e Plantas Tropicais. Programa Seringueira]. E-mails: paulog@iac.sp.gov.br; mariaalice@cnpdia.embrapa.br; Forato, Lucimara A.; Colnago, Luiz A.; Mattoso, Luiz H.C. [EMBRAPA Instrumentacao Agropecuaria, Sao Carlos, SP (Brazil)]. E-mail: colnago@cnpdia.embrapa.br; forato@cnpdia.embrapa.br; rogerio@cnpdia.embrapa.br; mattoso@cnpdia.embrapa.br; Job, Aldo E. [Universidade Estadual Paulista (UNESP), Presidente Prudente, SP (Brazil). Departamento de Fisica, Quimica e Biologia

    2005-07-01

    Agronomic Institute (IAC) and EMBRAPA Agricultural Instrumentation (EMBRAPA/CNPDIA) have been studied Hevea species in order to increase the production of the natural rubber and to develop new clones more appropriated to Brazil's soil and climate. Structural characterization of natural rubber [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. - Arg.] from new clones of the IAC series (IAC 300, 301, 302, 303, 35, 40, and 56) and from RRIM 600 clone has been studied by high-resolution solid-state {sup 13}C NMR and by single pulse technique. The results have shown that the application of solid-state {sup 13}C NMR using the single pulse technique is a powerful tool to study natural rubber. The spectra obtained through this technique confirmed that natural rubber from all clones studied are cis-1,4-polyisoprene (author) form.(author)

  4. Crowding, molecular volume and plasticity: An assessment involving crystallography, NMR and simulations

    Indian Academy of Sciences (India)

    M Selvaraj; Rais Ahmad; Umesh Varshney; M Vijayan

    2012-12-01

    The discrepancy between the X-ray and NMR structures of Mycobacterium tuberculosis peptidyl-tRNA hydrolase in relation to the functionally important plasticity of the molecule led to molecular dynamics simulations. The X-ray and the NMR studies along with the simulations indicated an inverse correlation between crowding and molecular volume. A detailed comparison of proteins for which X-ray and the NMR structures appears to confirm this correlation. In consonance with the reported results of the investigations in cellular compartments and aqueous solution, the comparison indicates that the crowding results in compaction of the molecule as well as change in its shape, which could specifically involve regions of the molecule important in function. Crowding could thus influence the action of proteins through modulation of the functionally important plasticity of the molecule.

  5. Dynamic Evolution in PVPh/PEO Blend Studied by Solid-State NMR%PVPh/PEO共混物动力学演化过程的NMR研究

    Institute of Scientific and Technical Information of China (English)

    彭永进; 孙平川; 李宝会

    2016-01-01

    聚合物共混物中链段的慢取向运动与其玻璃化转变行为和宏观力学性质密切关联,而基于化学位移各向异性重聚的13C CODEX(centerband-only detection of exchange)固体核磁共振(SSNMR)技术能够有效表征共混物中链段的慢取向运动。该文利用13C CODEX NMR技术详细研究了相容性聚合物共混物聚乙烯基苯酚/聚氧乙烯(PVPh/PEO)中的刚性组分 PVPh 在较宽温度范围内的慢取向运动特性与玻璃化转变过程的关联。研究表明,在玻璃化转变起始温度以下,PVPh主链的分子运动被冻结,而侧基存在b-松弛的慢取向运动;在玻璃化转变起始温度附近,PVPh主链具有明显的慢取向运动,而且主链和侧基是一种协同的分子运动。该文利用 NMR 技术揭示了共混物中的玻璃化转变起止温度分别对应于高分子主链慢取向运动CODEX信号的开始和极大值处的温度。%The13C centerband-only-detection-of-exchange (CODEX) variable-temperature solid-state NMR (SSNMR) technique was used to investigate the evolution of segmental dynamics in poly (vinyl phenol) (PVPh)/ poly (ethylene oxide) (PEO) polymer blend within a wide range of temperatures. It was found that the glass transition began with the emergence of remarkable slow motions of the PVPh backbone segments, and ended when the CODEX signal intensity of segmental slow motion reached maximum. The SSNMR results revealed, at molecular level, that the onset and endpoint of conventional calorimetric glass transition are closely associated with the evolution of slow motions in this polymer blend.

  6. Acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR and Ab initio model calculations.

    Science.gov (United States)

    Dos, Alexandra; Schimming, Volkmar; Tosoni, Sergio; Limbach, Hans-Heinrich

    2008-12-11

    The interactions of the 15N-labeled amino groups of dry solid poly-L-lysine (PLL) with various halogen and oxygen acids HX and the relation to the secondary structure have been studied using solid-state 15N and 13C CPMAS NMR spectroscopy (CP = cross polarization and MAS = magic angle spinning). For comparison, 15N NMR spectra of an aqueous solution of PLL were measured as a function of pH. In order to understand the effects of protonation and hydration on the 15N chemical shifts of the amino groups, DFT and chemical shielding calculations were performed on isolated methylamine-acid complexes and on periodic halide clusters of the type (CH3NH3(+)X(-))n. The combined experimental and computational results reveal low-field shifts of the amino nitrogens upon interaction with the oxygen acids HX = HF, H2SO4, CH3COOH, (CH3)2POOH, H3PO4, HNO3, and internal carbamic acid formed by reaction of the amino groups with gaseous CO2. Evidence is obtained that only hydrogen-bonded species of the type (Lys-NH2***H-X)n are formed in the absence of water. 15N chemical shifts are maximum when H is located in the hydrogen bond center and then decrease again upon full protonation, as found for aqueous solution at low pH. By contrast, halogen acids interact in a different way. They form internal salts of the type (Lys-NH3(+)X(-))n via the interaction of many acid-base pairs. This salt formation is possible only in the beta-sheet conformation. By contrast, the formation of hydrogen-bonded complexes can occur both in beta-sheet domains as well as in alpha-helical domains. The 15N chemical shifts of the protonated ammonium groups increase when the size of the interacting halogen anions is increased from chloride to iodide and when the number of the interacting anions is increased. Thus, the observed high-field 15N shift of ammonium groups upon hydration is the consequence of replacing interacting halogen atoms by oxygen atoms.

  7. Solid-state (79/81)Br NMR and gauge-including projector-augmented wave study of structure, symmetry, and hydration state in alkaline earth metal bromides.

    Science.gov (United States)

    Widdifield, Cory M; Bryce, David L

    2010-02-11

    Bromine-79/81 solid-state NMR (SSNMR) spectroscopy is established as a tool to characterize the local structure and symmetry about bromide ions in inorganic systems. Benchmark experimental (79/81)Br SSNMR data are acquired for CaBr(2), SrBr(2), BaBr(2), MgBr(2).6H(2)O, SrBr(2).6H(2)O, BaBr(2).2H(2)O, and CaBr(2).xH(2)O using the Solomon echo and/or QCPMG pulse sequences in magnetic fields of 11.75 and 21.1 T. Analytical line-shape analysis provides (79/81)Br electric field gradient (EFG) tensor parameters (including (79)Br quadrupolar coupling constants, C(Q)((79)Br), of up to 75.1(5) MHz in CaBr(2)), chemical shift tensor parameters (including the largest reported anisotropy), and the relative orientation of the tensor principal axis systems. These data are interpreted in terms of structure and symmetry. Our results indicate that ionic bromide systems should be generally accessible to characterization by (79/81)Br SSNMR despite sizable quadrupolar interactions. The resolving capabilities of (79/81)Br SSNMR spectroscopy are illustrated, using samples which possess up to four magnetically inequivalent sites, and through a rare example of (79)Br magic-angle spinning NMR for a Br in a noncubic lattice. Bromine-79/81 SSNMR spectroscopy is demonstrated to be sensitive to the presence of hydrates (i.e., pseudopolymorphism), via drastic changes in C(Q) and delta(iso). The changes are diagnostic to an extent that the composition of the mixture CaBr(2).xH(2)O is determined for the first time. This technique should therefore be applicable to characterize other unknown mixtures or polymorphs. Important instances where (79)Br nuclear quadrupole resonance data were found to be deficient are noted and corrected. GIPAW DFT computations are shown to be generally in very good agreement with the experimental (79/81)Br SSNMR observations. Finally, it is demonstrated that the origin of the EFG at the Br nuclei cannot be described quantitatively using a point charge model, even after

  8. Synthesis and structure elucidation of a series of pyranochromene chalcones and flavanones using 1D and 2D NMR spectroscopy and X-ray crystallography.

    Science.gov (United States)

    Pawar, Sunayna S; Koorbanally, Neil A

    2014-06-01

    A series of novel pyranochromene chalcones and corresponding flavanones were synthesized. This is the first report on the confirmation of the absolute configuration of chromene-based flavanones using X-ray crystallography. These compounds were characterized by 2D NMR spectroscopy, and their assignments are reported herein. The 3D structure of the chalcone 3b and flavanone 4g was determined by X-ray crystallography, and the structure of the flavanone was confirmed to be in the S configuration at C-2.

  9. Structure determination of uniformly {sup 13}C, {sup 15}N labeled protein using qualitative distance restraints from MAS solid-state {sup 13}C-NMR observed paramagnetic relaxation enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Tamaki, Hajime [Hokkaido University, Graduate School of Life Science (Japan); Egawa, Ayako [Osaka University, Institute for Protein Research (Japan); Kido, Kouki [Hokkaido University, Graduate School of Life Science (Japan); Kameda, Tomoshi [National Institute of Advanced Industrial Science and Technology, Biotechnology Research Institute for Drug Discovery (Japan); Kamiya, Masakatsu; Kikukawa, Takashi; Aizawa, Tomoyasu [Hokkaido University, Faculty of Advanced Life Science (Japan); Fujiwara, Toshimichi [Osaka University, Institute for Protein Research (Japan); Demura, Makoto, E-mail: demura@sci.hokudai.ac.jp [Hokkaido University, Faculty of Advanced Life Science (Japan)

    2016-01-15

    Magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is a powerful method for structure determination of insoluble biomolecules. However, structure determination by MAS solid-state NMR remains challenging because it is difficult to obtain a sufficient amount of distance restraints owing to spectral complexity. Collection of distance restraints from paramagnetic relaxation enhancement (PRE) is a promising approach to alleviate this barrier. However, the precision of distance restraints provided by PRE is limited in solid-state NMR because of incomplete averaged interactions and intermolecular PREs. In this report, the backbone structure of the B1 domain of streptococcal protein G (GB1) has been successfully determined by combining the CS-Rosetta protocol and qualitative PRE restraints. The derived structure has a Cα RMSD of 1.49 Å relative to the X-ray structure. It is noteworthy that our protocol can determine the correct structure from only three cysteine-EDTA-Mn{sup 2+} mutants because this number of PRE sites is insufficient when using a conventional structure calculation method based on restrained molecular dynamics and simulated annealing. This study shows that qualitative PRE restraints can be employed effectively for protein structure determination from a limited conformational sampling space using a protein fragment library.

  10. Hydrogen Bonding Interactions in Amorphous Indomethacin and Its Amorphous Solid Dispersions with Poly(vinylpyrrolidone) and Poly(vinylpyrrolidone-co-vinyl acetate) Studied Using (13)C Solid-State NMR.

    Science.gov (United States)

    Yuan, Xiaoda; Xiang, Tian-Xiang; Anderson, Bradley D; Munson, Eric J

    2015-12-07

    Hydrogen bonding interactions in amorphous indomethacin and amorphous solid dispersions of indomethacin with poly(vinylpyrrolidone), or PVP, and poly(vinylpyrrolidone-co-vinyl acetate), or PVP/VA, were investigated quantitatively using solid-state NMR spectroscopy. Indomethacin that was (13)C isotopically labeled at the carboxylic acid carbon was used to selectively analyze the carbonyl region of the spectrum. Deconvolution of the carboxylic acid carbon peak revealed that 59% of amorphous indomethacin molecules were hydrogen bonded through carboxylic acid cyclic dimers, 15% were in disordered carboxylic acid chains, 19% were hydrogen bonded through carboxylic acid and amide interactions, and the remaining 7% were free of hydrogen bonds. The standard dimerization enthalpy and entropy of amorphous indomethacin were estimated to be -38 kJ/mol and -91 J/(mol · K), respectively, using polystyrene as the "solvent". Polymers such as PVP and PVP/VA disrupted indomethacin self-interactions and formed hydrogen bonds with the drug. The carboxylic acid dimers were almost completely disrupted with 50% (wt) of PVP or PVP/VA. The fraction of disordered carboxylic acid chains also decreased as the polymer content increased. The solid-state NMR results were compared with molecular dynamics (MD) simulations from the literature. The present work highlights the potential of (13)C solid-state NMR to detect and quantify various hydrogen bonded species in amorphous solid dispersions as well as to serve as an experimental validation of MD simulations.

  11. Characterization of polysulfone and polysulfone/vanillin microcapsules by 1H NMR spectroscopy, solid-state 13C CP/MAS-NMR spectroscopy, and N2 adsorption-desorption analyses.

    Science.gov (United States)

    Peña, Brisa; de Ménorval, Louis-Charles; Garcia-Valls, Ricard; Gumí, Tània

    2011-11-01

    Textile detergent and softener industries have incorporated perfume microencapsulation technology to improve their products. Perfume encapsulation allows perfume protection until use and provides a long-lasting fragrance release. But, certain industrial microcapsules show low encapsulation capacity and low material stability. Polysulfone capsules have been already proposed to solve these drawbacks. Among them, PSf/Vanillin capsules were considered as a desirable system. They present both good material stability and high encapsulation capacity. However, several factors such as the final location of the perfume in the polymeric matrix, the aggregation state that it has in the capsule and its interaction with the capsule components have not been studied yet. These factors can provide vast information about the capsule performance and its improvement. With the aim to characterize these parameters, the physical and chemical properties of PSf/Vanillin capsules have been investigated by nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and N(2) adsorption-desorption measurements. AFM micrograph and N(2) isotherms confirm that the presence of vanillin modify the physical structure of PSf/Vanillin microcapsules as it is trapped in the capsule porosity. NMR results show that vanillin is present in solid state in PSf/Vanillin microcapsules.

  12. Spectral editing at ultra-fast magic-angle-spinning in solid-state NMR: facilitating protein sequential signal assignment by HIGHLIGHT approach.

    Science.gov (United States)

    Wang, Songlin; Matsuda, Isamu; Long, Fei; Ishii, Yoshitaka

    2016-02-01

    This study demonstrates a novel spectral editing technique for protein solid-state NMR (SSNMR) to simplify the spectrum drastically and to reduce the ambiguity for protein main-chain signal assignments in fast magic-angle-spinning (MAS) conditions at a wide frequency range of 40-80 kHz. The approach termed HIGHLIGHT (Wang et al., in Chem Comm 51:15055-15058, 2015) combines the reverse (13)C, (15)N-isotope labeling strategy and selective signal quenching using the frequency-selective REDOR pulse sequence under fast MAS. The scheme allows one to selectively observe the signals of "highlighted" labeled amino-acid residues that precede or follow unlabeled residues through selectively quenching (13)CO or (15)N signals for a pair of consecutively labeled residues by recoupling (13)CO-(15)N dipolar couplings. Our numerical simulation results showed that the scheme yielded only ~15% loss of signals for the highlighted residues while quenching as much as ~90% of signals for non-highlighted residues. For lysine-reverse-labeled micro-crystalline GB1 protein, the 2D (15)N/(13)Cα correlation and 2D (13)Cα/(13)CO correlation SSNMR spectra by the HIGHLIGHT approach yielded signals only for six residues following and preceding the unlabeled lysine residues, respectively. The experimental dephasing curves agreed reasonably well with the corresponding simulation results for highlighted and quenched residues at spinning speeds of 40 and 60 kHz. The compatibility of the HIGHLIGHT approach with fast MAS allows for sensitivity enhancement by paramagnetic assisted data collection (PACC) and (1)H detection. We also discuss how the HIGHLIGHT approach facilitates signal assignments using (13)C-detected 3D SSNMR by demonstrating full sequential assignments of lysine-reverse-labeled micro-crystalline GB1 protein (~300 nmol), for which data collection required only 11 h. The HIGHLIGHT approach offers valuable means of signal assignments especially for larger proteins through reducing the

  13. Metal Carbonation of Forsterite in Wet Supercritical CO2: The Role of H2O Studied by Solid State C-13 and Si-29 NMR Spectroscopy

    Science.gov (United States)

    Hu, J.; Kwak, J.; Turcu, R. V.; Rosso, K. M.; Ilton, E. S.; Wang, C.; Sears, J. A.; Felmy, A. R.; Hoyt, D. W.

    2010-12-01

    Selected as a model mineral carbonation system for geological carbon sequestration in mafic host rocks, chemical mechanisms of forsterite carbonation in supercritical CO2 containing water varied from dry to well above saturation, including at saturation, were investigated by a combination of solid state NMR (C-13 SP-, CP-MAS, Si-29 SP-, CP-MAS), XRD, TEM and XPS. Run conditions were 80 degrees (C) and 75 bars. Major findings are as follows. At high water contents where a bulk aqueous solution coexisted with water-saturated scCO2, forsterite was converted into magnesite and a separate Mg-free amorphous SiO2 reaction product characterized by highly polymerized oligomeric Q4, and to a lesser extent by Q3 silica species. As the amount of added water was reduced, hydrated intermediate reaction products that did not evolve to magnesite could be identified until at zero water no reaction intermediates or magnesite carbonation products were observed. The intermediate reaction products identified were a complex mixture of partially hydrated/hydroxylated magnesium carbonate species and a variety of surface silica species with low polymerization extent. The intermediates were mainly in an amorphous state, forming a thin layer on the surface. Formation of these intermediate species consumes water by hydrolysis of Mg-O-Si linkages at the forsterite surface as well as by incorporation of water in the lattice. If insufficient water is available, the reaction is found not to proceed far enough to form magnesite and amorphous SiO2. Water in excess of this limit appears necessary for the intermediates to evolve to anhydrous magnesite, a process that is expected to liberate water for continued reaction. Hence, for a given fluid/forsterite ratio there appears to be a water threshold (i.e., the formation of H2O film with sufficient thickness estimated to be between 3.2 and 18.4 nm) above which a significant portion of the water is recycled in an apparent quasi-catalytic role for the

  14. Spectral editing at ultra-fast magic-angle-spinning in solid-state NMR: facilitating protein sequential signal assignment by HIGHLIGHT approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Songlin; Matsuda, Isamu; Long, Fei; Ishii, Yoshitaka, E-mail: yishii@uic.edu [University of Illinois at Chicago, Department of Chemistry (United States)

    2016-02-15

    This study demonstrates a novel spectral editing technique for protein solid-state NMR (SSNMR) to simplify the spectrum drastically and to reduce the ambiguity for protein main-chain signal assignments in fast magic-angle-spinning (MAS) conditions at a wide frequency range of 40–80 kHz. The approach termed HIGHLIGHT (Wang et al., in Chem Comm 51:15055–15058, 2015) combines the reverse {sup 13}C, {sup 15}N-isotope labeling strategy and selective signal quenching using the frequency-selective REDOR pulse sequence under fast MAS. The scheme allows one to selectively observe the signals of “highlighted” labeled amino-acid residues that precede or follow unlabeled residues through selectively quenching {sup 13}CO or {sup 15}N signals for a pair of consecutively labeled residues by recoupling {sup 13}CO–{sup 15}N dipolar couplings. Our numerical simulation results showed that the scheme yielded only ∼15 % loss of signals for the highlighted residues while quenching as much as ∼90 % of signals for non-highlighted residues. For lysine-reverse-labeled micro-crystalline GB1 protein, the 2D {sup 15}N/{sup 13}C{sub α} correlation and 2D {sup 13}C{sub α}/{sup 13}CO correlation SSNMR spectra by the HIGHLIGHT approach yielded signals only for six residues following and preceding the unlabeled lysine residues, respectively. The experimental dephasing curves agreed reasonably well with the corresponding simulation results for highlighted and quenched residues at spinning speeds of 40 and 60 kHz. The compatibility of the HIGHLIGHT approach with fast MAS allows for sensitivity enhancement by paramagnetic assisted data collection (PACC) and {sup 1}H detection. We also discuss how the HIGHLIGHT approach facilitates signal assignments using {sup 13}C-detected 3D SSNMR by demonstrating full sequential assignments of lysine-reverse-labeled micro-crystalline GB1 protein (∼300 nmol), for which data collection required only 11 h. The HIGHLIGHT approach offers valuable

  15. The application of tailor-made force fields and molecular dynamics for NMR crystallography: a case study of free base cocaine

    DEFF Research Database (Denmark)

    Li, Xiaozhou; Neumann, Marcus A.; van de Streek, Jacco

    2017-01-01

    Motional averaging has been proven to be significant in predicting the chemical shifts in ab initio solid-state NMR calculations, and the applicability of motional averaging with molecular dynamics has been shown to depend on the accuracy of the molecular mechanical force field. The performance...... cocaine is used as an example. The results reveal that, even though the TMFF outperforms the COMPASS force field for representing the energies and conformations of predicted structures, it does not give significant improvement in the accuracy of NMR calculations. Further studies should direct more...

  16. Hydrogen Atomic Positions of O-H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with ¹H-NMR Chemical Shifts and X-ray Diffraction Methods.

    Science.gov (United States)

    Siskos, Michael G; Choudhary, M Iqbal; Gerothanassis, Ioannis P

    2017-03-07

    The exact knowledge of hydrogen atomic positions of O-H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i) density functional theory (DFT) calculations after a structure has been determined by X-ray from single crystals or from powders; (ii) ¹H-NMR chemical shifts as constraints in DFT calculations, and (iii) use of root-mean-square deviation between experimentally determined and DFT calculated ¹H-NMR chemical shifts considering the great sensitivity of ¹H-NMR shielding to hydrogen bonding properties.

  17. Solid-state 13C NMR study of banana liquid crystals - 3: Alkyl-tail-group packing environments of an acute-angle bent-core molecule in the hexagonal columnar and cubic phases

    Science.gov (United States)

    Kurosu, Hiromichi; Endo, Yumi; Kimura, Saori; Hashimoto, Tomoko; Harada, Motoi; Lee, Eun-Woo; Sone, Masato; Watanabe, Junji; Kang, Sungmin

    2016-02-01

    Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed on the hexagonal columnar and cubic phases of an acute-angle banana-shaped molecule, N(1,7)-S30. In the hexagonal columnar phase, three peaks appear at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that the two alkyl tails have different packing structures, and one of the tails has two different conformations within a single molecule. Combined cross-polarization/magic-angle spinning and pulse saturation transfer/magic-angle spinning measurements show that one of the alkyl chains is located inside and the other is located outside the columnar structure. In the cubic phase, pulse saturation transfer/magic-angle spinning measurement shows that only one peak appears at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that both of the alkyl chains are located outside the cubic structure.

  18. Applications of Advanced Solid-State NMR Techniques in Studying the Structure and Dynamics of Polymers%先进固体 NMR 技术研究高分子结构与动力学

    Institute of Scientific and Technical Information of China (English)

    张荣纯; 孙平川

    2012-01-01

    With the advances in NMR theories and spectrometer hardware technology, NMR is playing an increasingly important role in studying multi-scale structure and dynamics of polymers. In this paper, the newest developments in solid-state 1H and 13C NMR techniques and their applications in the studies of polymer structures and dynamics were reviewed. High-resolution solid-state 1H NMR techniques, such as multiple-pulse and fast magic angle spinning (MAS) , have made it possible to determine the chemical structures of polymers and to detect the intra- and inter-polymer interactions effectively. Taking advantages of through-bond (/ coupling) and through-space (dipolar coupling) interactions, two dimensional heteronuclear correlation NMR experiments now can be used to resolve the microstructures of complex polymer chains. The recoupling techniques allow dipolar interactions and chemical shift anisotropy to be observed under MAS conditions, thus enabling simultaneous detection of high-resolution 1H or 13C signals and quasi-static anisotropic interactions. The domain sizes and interphase thickness in multiphase polymers and miscibility in polymer blends can now be determined effectively using the dipolar filter techniques. In the dynamics studies, it is now possible to obtain information on local fast motions of a single bond and super-slow chain dynamics by efficient suppression of spin-diffusion among protons and recoupling of chemical shift anisotropy. In summary, the advanced solid-state NMR techniques have enabled detailed studies on polymer microstructure, phase separation and dynamic behavior at different time and length scales, and on the relationship between the microstructure and macroscopic properties of polymers.%随着固体NMR理论和谱仪硬件技术的不断发展,近年来固体NMR技术在高分子多尺度结构与动力学研究领域中正发挥着越来越重要的作用.多脉冲及高速魔角旋转(MAS)等质子高分辨技术的发展使得

  19. 固体核磁共振在膦酸基质子交换膜中的应用%Solid state NMR and its application in phosphonic acid proton exchange membranes

    Institute of Scientific and Technical Information of China (English)

    项婧娈; 沈春晖; 孔更金

    2015-01-01

    综述了固体核磁共振(NMR)技术的特点及其在燃料电池用膦酸基质子交换膜分析研究中的应用,重点介绍了运用 1H、31P、29Si固体NMR以及 1H、31P变温固体NMR技术表征膦酸基质子交换膜的化学结构、氢键网络和质子传导机理等方面的研究进展.该综述表明固体NMR技术是一种研究膦酸基质子交换膜中氢键网络以及局部质子移动性的有效手段,并能进一步探索其质子传导的机理,为固体NMR技术在其他类型质子交换膜研究中的应用给予借鉴,为质子交换膜结构的表征提供一种新的方法.%In this paper,the characteristics of solid state NMR and its application in the analysis of phosphonic acid proton exchange membranes (PEM) are described briefly. The research progress of1H、31P、29Si solid state NMR and1H、31P variable temperature solid state NMR in terms of the characterization of chemical structure,hydrogen bonding network and proton conduction mechanism of phosphonic acid PEM are introduced. All these applications indicate that solid state NMR is an effective technique for the study of hydrogen bonding network and the local proton mobility of PEM,thereby it can be used to explore the mechanism of proton conduction. Also,it can give reference to the research of other kinds of proton exchange membranes by providing a new method for characterization.

  20. The stoichiometry of synthetic alunite as a function of hydrothermal aging investigated by solid-state NMR spectroscopy, powder X-ray diffraction and infrared spectroscopy

    DEFF Research Database (Denmark)

    Grube, Elisabeth; Nielsen, Ulla Gro

    2015-01-01

    The stoichiometry of a series of synthetic alunite (nominally KAl3(SO4)2(OH)6) samples prepared by hydrothermal methods as a function of reaction time (1 – 31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic...

  1. The stoichiometry of synthetic alunite as a function of hydrothermal aging investigated by solid-state NMR spectroscopy, powder X-ray diffraction and infrared spectroscopy

    DEFF Research Database (Denmark)

    Grube, Elisabeth; Nielsen, Ulla Gro

    2015-01-01

    The stoichiometry of a series of synthetic alunite (nominally KAl3(SO4)2(OH)6) samples prepared by hydrothermal methods as a function of reaction time (1 – 31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic...

  2. Applications of Floquet-Magnus expansion, average Hamiltonian theory and Fer expansion to study interactions in solid state NMR when irradiated with the magic-echo sequence.

    Science.gov (United States)

    Mananga, Eugene Stephane

    2013-01-01

    This work presents the possibility of applying the Floquet-Magnus expansion and the Fer expansion approaches to the most useful interactions known in solid-state nuclear magnetic resonance using the magic-echo scheme. The results of the effective Hamiltonians of these theories and average Hamiltonian theory are presented.

  3. Protein dynamics at Eph receptor-ligand interfaces as revealed by crystallography, NMR and MD simulations

    Directory of Open Access Journals (Sweden)

    Qin Haina

    2012-01-01

    Full Text Available Abstract Background The role of dynamics in protein functions including signal transduction is just starting to be deciphered. Eph receptors with 16 members divided into A- and B- subclasses are respectively activated by 9 A- and B-ephrin ligands. EphA4 is the only receptor capable of binding to all 9 ephrins and small molecules with overlapped interfaces. Results We first determined the structures of the EphA4 ligand binding domain (LBD in two crystals of P1 space group. Noticeably, 8 EphA4 molecules were found in one asymmetric unit and consequently from two crystals we obtained 16 structures, which show significant conformational variations over the functionally critical A-C, D-E, G-H and J-K loops. The 16 new structures, together with previous 9 ones, can be categorized into two groups: closed and open forms which resemble the uncomplexed and complexed structures of the EphA4 LBD respectively. To assess whether the conformational diversity over the loops primarily results from the intrinsic dynamics, we initiated 30-ns molecular dynamics (MD simulations for both closed and open forms. The results indicate that the loops do have much higher intrinsic dynamics, which is further unravelled by NMR H/D exchange experiments. During simulations, the open form has the RMS deviations slightly larger than those of the closed one, suggesting the open form may be less stable in the absence of external contacts. Furthermore, no obvious exchange between two forms is observed within 30 ns, implying that they are dynamically separated. Conclusions Ou