WorldWideScience

Sample records for safety-catch hydrazine linker

  1. A Fmoc-compatible Method for the Solid-Phase Synthesis of Peptide C-Terminal (alpha)-Thioesters based on the Safety-Catch Hydrazine Linker

    Energy Technology Data Exchange (ETDEWEB)

    Camarero, J A; Hackel, B J; de Yoreo, J J; Mitchell, A R

    2003-11-22

    C-terminal peptide thioesters are key intermediates for the synthesis/semisynthesis of proteins and for the production of cyclic peptides by native chemical ligation. They can be synthetically prepared by solid-phase peptide synthesis (SPPS) methods or biosynthetically by protein splicing techniques. Until recently, the chemical synthesis of C-terminal a-thioester peptides by SPPS was largely restricted to the Boc/Benzyl methodology because of the poor stability of the thioester bond to the basic conditions employed for the deprotection of the N{sup {alpha}}-Fmoc group. In the present work, we describe a new method for the SPPS of C-terminal thioesters by Fmoc/t-Bu chemistry. This method is based on the use of an aryl hydrazide linker, which is totally stable to the Fmoc-SPPS conditions. Once the peptide synthesis has been completed, activation of the linker can be achieved by mild oxidation. This step transforms the hydrazide group into a highly reactive diazene intermediate which can react with different H-AA-SEt to yield the corresponding {alpha}-thioester peptide in good yields. This method has been successfully used for the generation of different thioester peptides, circular peptides and a fully functional SH3 protein domain.

  2. Acylsulfonamide safety-catch linker: promise and limitations for solid–phase oligosaccharide synthesis

    Directory of Open Access Journals (Sweden)

    Jian Yin

    2012-11-01

    Full Text Available Safety-catch linkers are useful for solid-phase oligosaccharide synthesis as they are orthogonal to many common protective groups. A new acylsulfonamide safety-catch linker was designed, synthesized and employed during glycosylations using an automated carbohydrate synthesizer. The analysis of the cleavage products revealed shortcomings for oligosaccharide synthesis.

  3. Library of biphenyl privileged substructures using a safety-catch linker approach

    DEFF Research Database (Denmark)

    Severinsen, Rune; Bourne, Gregory T; Tran, Tran T

    2008-01-01

    A biphenyl privileged structure library containing three attachment points were synthesized using a catechol-based safety-catch linker strategy. The method requires the attachment of a bromo-acid to the linker, followed by a Pd-catalyzed Suzuki cross-coupling reaction. Further derivatization...

  4. Solid-phase oligosaccharide synthesis with tris(alkoxy)benzyl amine (BAL) safety-catch anchoring

    DEFF Research Database (Denmark)

    Tolborg, Jakob Fjord; Jensen, Knud Jørgen

    2000-01-01

    A tris(alkoxy)benzylamine (BAL) handle strategy was developed for safety-catch anchoring of D-glucosamine derivatives in solid-phase synthesis of oligosaccharides; the linkage between the BAL handle and the amine proved stable to conc. TFA and Lewis acids, but after N-acylation the amide could...

  5. The catalysis of hydrazines

    Science.gov (United States)

    Tanatar, S.

    1987-01-01

    Hydrazine sulfate in a hot aqueous solution can be catalyzed in the direction of 3 N2H4 = 4 NH3 + N2. Free hydrazine in a hot aqueous solution dissociates in the presence of platinum in the following direction: 2 N2H4 = 2 NH3 + N2 + H2. In the presence of sodium hydroxide, the catalytic dissociation of hydrazine takes a third direction: 3 N2H4 = 2 NH3 + 2 N3 + 3 H2.

  6. Solid phase synthesis of a functionalized bis-peptide using "safety catch" methodology.

    Science.gov (United States)

    Pfeiffer, Conrad T; Schafmeister, Christian E

    2012-05-15

    In 1962, R.B. Merrifield published the first procedure using solid-phase peptide synthesis as a novel route to efficiently synthesize peptides. This technique quickly proved advantageous over its solution-phase predecessor in both time and labor. Improvements concerning the nature of solid support, the protecting groups employed and the coupling methods employed over the last five decades have only increased the usefulness of Merrifield's original system. Today, use of a Boc-based protection and base/nucleophile cleavable resin strategy or Fmoc-based protection and acidic cleavable resin strategy, pioneered by R.C. Sheppard, are most commonly used for the synthesis of peptides(1). Inspired by Merrifield's solid supported strategy, we have developed a Boc/tert-butyl solid-phase synthesis strategy for the assembly of functionalized bis-peptides(2), which is described herein. The use of solid-phase synthesis compared to solution-phase methodology is not only advantageous in both time and labor as described by Merrifield(1), but also allows greater ease in the synthesis of bis-peptide libraries. The synthesis that we demonstrate here incorporates a final cleavage stage that uses a two-step "safety catch" mechanism to release the functionalized bis-peptide from the resin by diketopiperazine formation. Bis-peptides are rigid, spiro-ladder oligomers of bis-amino acids that are able to position functionality in a predictable and designable way, controlled by the type and stereochemistry of the monomeric units and the connectivity between each monomer. Each bis-amino acid is a stereochemically pure, cyclic scaffold that contains two amino acids (a carboxylic acid with an α-amine)(3,4). Our laboratory is currently investigating the potential of functional bis-peptides across a wide variety of fields including catalysis, protein-protein interactions and nanomaterials.

  7. Shock compression of liquid hydrazine

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, B.O. [Los Alamos National Lab., NM (United States); Chavez, D.J. [Rockwell White Sands Test Facility, Las Cruces, NM (United States)

    1995-01-01

    Liquid hydrazine (N{sub 2}H{sub 4}) is a propellant used by the Air Force and NASA for aerospace propulsion and power systems. Because the propellant modules that contain the hydrazine can be subject to debris impacts during their use, the shock states that can occur in the hydrazine need to be characterized to safely predict its response. Several shock compression experiments have been conducted in an attempt to investigate the detonability of liquid hydrazine; however, the experiments results disagree. Therefore, in this study, we reproduced each experiment numerically to evaluate in detail the shock wave profiles generated in the liquid hydrazine. This paper presents the results of each numerical simulation and compares the results to those obtained in experiment. We also present the methodology of our approach, which includes chemical kinetic experiments, chemical equilibrium calculations, and characterization of the equation of state of liquid hydrazine.

  8. Laboratory Evaluation of a Colorimetric Hydrazine Dosimeter

    Science.gov (United States)

    1990-06-12

    Exposure: Rotating Service I Hydrazine Structure (RSS) II MMH Hypergol Maintenance Personnel MMH Facility (HMF) Fuel Storage Area (FSA) Personnel...The three hydrazines currently being used by the Department of Defense as hypergolic fuels are hydrazine, monomethylhydrazine (MMH), and unsymmetrical...used by Titan missiles, satellites, and aircraft auxiliary-power units. While useful as propellents, the hydrazines impose health hazards to personnel

  9. An Assessment of Hydrazine, Hydrazine Hydrate and Liquid Ammonia as Fuels for Rocket Propulsion

    National Research Council Canada - National Science Library

    Cooper, K. A; Wiseman, L. A

    1949-01-01

    .... More data on the system Hydrazine/water, in which the concentration of water is less than in hydrazine hydrate, are desirable, and other methods of lowering the freezing point of anhydrous hydrazine...

  10. Backbone amide linker strategy

    DEFF Research Database (Denmark)

    Shelton, Anne Pernille Tofteng; Jensen, Knud Jørgen

    2013-01-01

    In the backbone amide linker (BAL) strategy, the peptide is anchored not at the C-terminus but through a backbone amide, which leaves the C-terminal available for various modifications. This is thus a very general strategy for the introduction of C-terminal modifications. The BAL strategy...

  11. Corrosion of metals by hydrazine

    Science.gov (United States)

    Lawton, E. A.; Moran, C. M.; Distefano, S.

    1985-01-01

    The mechanism of corrosion of metals by hydrazine has been studied by means of coupons in sealed ampoules and by electrochemical techniques. The variables considered were temperature, CO2 impurity level, alloy composition and microcrystalline structure. The coupon studies, to date, verify that increasng temperature and the presence of CO2 does increase the corrosion rate as expected. The presence of molybdenum in stainless steels to the 3 percent level is not necessarily deleterious, contrary to published reports. The influence of microcrystalline structure and surface characteristics are more dominant effects. However, with Ti-6Al-4V, two different microcrystalline structures showed no significant differences. Corrosion rates of CRES 304 L in hydrazine have also been measured by several electrochemical techniques such as Tafel plots, polarization resistance and A. C. Impedance. This is the first documented work to show that A. C. Impedance can be used with non-aqueous solvents. Preliminary data correlated satisfactorily with the results of the coupon studies.

  12. COMPLEXES CONTAINING HYDRAZINE AND BENZYL ...

    African Journals Online (AJOL)

    Preferred Customer

    ABSTRACT. The reaction of the polymeric species [{RuCl2(COD)}x] (1 ; x > 2; COD = cyclo-octa-1,5-diene) and hydrazine hydrate in methanol under reflux gave a pale pink solution from which the salt. [Ru(COD)(N2H4)4][BPh4]2.CH3OH (2) was isolated on addition of NaBPh4. Treatment of 2 in refluxing acetone.

  13. Complexes of hydrazine and substituted hydrazines with some oxocations

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.K.; Agarwal, R.K.; Srivastava, M.; Kapur, V.; Sharma, S.; Jain, P.C.

    1982-02-01

    Several new polymeric complexes of general composition MOsub(n)(L)/sub 4/X/sub 2/ (where M = V, Zr and U; n = 1 or 2; X = Cl, Br, I, NO/sub 3/ and NCS and L = N/sub 2/H/sub 4/, PhNHNH/sub 2/ and Me/sub 2/NNH/sub 2/ have been synthesized and characterized by elemental and d.t. analyses and by magnetic measurements, electronic and i.r. spectra. The vanadyl(IV) complexes exhibit subnormal magnetic moments (1.26-1.36BM) possibly because of exchange interaction between vanadium(IV) ions. The thermal stability of hydrazine complexes fall in the order: Cl > Br > NCS > I. The M-N bond strength, as revealed, by ..nu..(M-N), decreases as: Me/sub 2/NNH/sub 2/ > N/sub 2/H/sub 4/ > PhNHNH/sub 2/.

  14. Ionic Liquids to Replace Hydrazine

    Science.gov (United States)

    Koelfgen, Syri; Sims, Joe; Forton, Melissa; Allan, Barry; Rogers, Robin; Shamshina, Julia

    2011-01-01

    A method for developing safe, easy-to-handle propellants has been developed based upon ionic liquids (ILs) or their eutectic mixtures. An IL is a binary combination of a typically organic cation and anion, which generally produces an ionic salt with a melting point below 100 deg C. Many ILs have melting points near, or even below, room temperature (room temperature ionic liquids, RTILs). More importantly, a number of ILs have a positive enthalpy of formation. This means the thermal energy released during decomposition reactions makes energetic ILs ideal for use as propellants. In this specific work, to date, a baseline set of energetic ILs has been identified, synthesized, and characterized. Many of the ILs in this set have excellent performance potential in their own right. In all, ten ILs were characterized for their enthalpy of formation, density, melting point, glass transition point (if applicable), and decomposition temperature. Enthalpy of formation was measured using a microcalorimeter designed specifically to test milligram amounts of energetic materials. Of the ten ILs characterized, five offer higher Isp performance than hydrazine, ranging between 10 and 113 seconds higher than the state-of-the-art propellant. To achieve this level of performance, the energetic cations 4- amino-l,2,4-triazolium and 3-amino-1,2,4-triazolium were paired with various anions in the nitrate, dicyanamide, chloride, and 3-nitro-l,2,4-triazole families. Protonation, alkylation, and butylation synthesis routes were used for creation of the different salts.

  15. Treatment for hydrazine-containing waste water solution

    Science.gov (United States)

    Yade, N.

    1986-01-01

    The treatment for waste solutions containing hydrazine is presented. The invention attempts oxidation and decomposition of hydrazine in waste water in a simple and effective processing. The method adds activated charcoal to waste solutions containing hydrazine while maintaining a pH value higher than 8, and adding iron salts if necessary. Then, the solution is aerated.

  16. Hydrazine in the Ugi Tetrazole Reaction

    NARCIS (Netherlands)

    Patil, Pravin; Zhang, Ji; Kurpiewska, Katarzyna; Kalinowska-Tłuścik, Justyna; Dömling, Alexander

    2016-01-01

    We describe the hitherto unknown use of N-Boc-protected hydrazine in the Ugi tetrazole reaction to access a library of highly substituted 5-(hydrazinomethyl)-1-methyl-1H-tetrazoles. The reaction is very versatile and good to high yielding. A one-pot, two-step procedure is given.

  17. Linker Training Workshops. Final Report.

    Science.gov (United States)

    Thornton, Philip F.

    This report summarizes the efforts made to provide linker training to educational personnel at the local and regional levels in West Virginia. The workshop evaluation follows a review of: (1) the rationale for the National Institute of Education's funding of regionally located Research and Development Exchanges; (2) the workshop planning procedure…

  18. Crystal structure of hydrazine iron(III phosphate, the first transition metal phosphate containing hydrazine

    Directory of Open Access Journals (Sweden)

    Renald David

    2015-12-01

    Full Text Available The title compound, poly[(μ2-hydrazine(μ4-phosphatoiron(III], [Fe(PO4(N2H4]n, was prepared under hydrothermal conditions. Its asymmetric unit contains one FeIII atom located on an inversion centre, one P atom located on a twofold rotation axis, and two O, one N and two H atoms located on general positions. The FeIII atom is bound to four O atoms of symmetry-related PO4 tetrahedra and to two N atoms of two symmetry-related hydrazine ligands, resulting in a slightly distorted FeO4N2 octahedron. The crystal structure consists of a three-dimensional hydrazine/iron phoshate framework whereby each PO4 tetrahedron bridges four FeIII atoms and each hydrazine ligand bridges two FeIII atoms. The H atoms of the hydrazine ligands are also involved in moderate N—H...O hydrogen bonding with phosphate O atoms. The crystal structure is isotypic with the sulfates [Co(SO4(N2H4] and [Mn(SO4(N2H4].

  19. Iodometric microdetermination of hydrazines by amplification reactions.

    Science.gov (United States)

    Gawargious, Y A; Besada, A

    1975-09-01

    Two new, simple, rapid, and accurate iodometric amplification methods are described for the micro and submicro determination of hydrazine. The first depends on oxidation with a chloroform solution of iodine and removal of its excess, oxidation of the resulting iodide with bromine, and iodometric titration of the liberated iodate. The second method is based on oxidation with periodate at pH 8, masking of the excess of periodate with molybdate at pH 3, and iodometric titration of the iodate. The order of amplification involved in the two methods is 6- and 3-fold, respectively. Micro amounts of hydrazine sulphate and dihydrochloride were determined satisfactorily by both methods, the average recoveries being 98.6 and 99.4%.

  20. Acute toxicity of selected hydrazines to the common guppy

    Energy Technology Data Exchange (ETDEWEB)

    Slonim, A.R.

    1977-01-01

    Hydrazine, unsymmetrical dimethylhydrazine (UDMH), Aerozine-50 and monomethylhydrazine were evaluated, respectively, in three or four static bioassays each using hard and soft water. Hydrazine was the most toxic compound and UDMH the least toxic to common guppies. Hydrazine was significantly more toxic in soft water than hard water, whereas UDMH was the opposite. The results of bioassays in which survival times of fish pre-exposed to these compounds were compared to those previously unexposed, along with other observations, indicate that the toxic effects of the hydrazines are cumulative. The effects of chemical differences in these compounds, of water quality characteristics and of other factors on acute toxicity are discussed.

  1. Reaction of Hydrazine Hydrate with Oxalic Acid: Synthesis and ...

    African Journals Online (AJOL)

    NICO

    2013-11-28

    Nov 28, 2013 ... and one hydrazinium ion. KEY WORDS. Hydrazine, oxalic acid, dihydrazinium oxalate, crystal structure. 1. Introduction. Hydrazine, a weaker base than ammonia, is a diacidic base that forms N2H5. + [hydrazinium (+1)] and N2H6. 2+ [hydrazinium (+2)] ionic salts with mineral as well as carboxylic acids.

  2. Auto-ignition of hydrazine by engineering materials

    Science.gov (United States)

    Perkins, J. H.; Riehl, W. A.

    1978-01-01

    Hydrazine, being a monopropellant, can explode and/or detonate in contact with some materials. This has been generally recognized and minimized by testing the compatibility of engineering materials with hydrazine at ambient temperature. Very limited tests have been done at elevated temperatures. To assess the potential hazard of hydrazine leakage into a propulsion compartment (boattail), autoignition characteristics of hydrazine were tested on 18 engineering materials and coatings at temperatures of 120 C to over 330 C. Furthermore, since hydrazine can decompose violently in nitrogen or helium, common purging cannot assure safety. Therefore tests were also made in nitrogen. Detonations occurred on contact with five materials in air. Similar tests in nitrogen did not lead to ignition.

  3. Solid colloids with surface-mobile linkers.

    Science.gov (United States)

    van der Meulen, Stef A J; Helms, Gesa; Dogterom, Marileen

    2015-06-17

    In this report we review the possibilities of using colloids with surface mobile linkers for the study of colloidal self-assembly processes. A promising route to create systems with mobile linkers is the use of lipid (bi-)layers. These lipid layers can be either used in the form of vesicles or as coatings for hard colloids and emulsion droplets. Inside the lipid bilayers molecules can be inserted via membrane anchors. Due to the fluidity of the lipid bilayer, the anchored molecules remain mobile. The use of different lipid mixtures even allows creating Janus-like particles that exhibit directional bonding if linkers are used which have a preference for a certain lipid phase. In nature mobile linkers can be found e.g. as receptors in cells. Therefore, towards the end of the review, we also briefly address the possibility of using colloids with surface mobile linkers as model systems to mimic cell-cell interactions and cell adhesion processes.

  4. Interactions of Hydrazine and of Hydrazine Derivatives with Soil Constituents and with Soils

    Science.gov (United States)

    1984-08-23

    The strong hydrophilic character of the hydrazine had led to more water being adsorbed by this complex than by the monomethylhydraIne complex. Hydroxy...for an extended period before further heating was continued. The thermal derlos ition of hydrazinium zeolite has been shwn to occur by de~rotonation...Mihalyfi Judit. (1980). Thermochemistry of hydroxylammonium and hydrazinium zeolites . J. Chem. Soc. Faraday I. 76, 332. Blaedel, W.J. and R.H. Laessig

  5. Electrocatalytic hydrazine oxidation on quinizarine modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Ardakani, Mohammad Mazloum [Department of Chemistry, Faculty of Science, Yazd University, Yazd (Iran, Islamic Republic of)]. E-mail: mazloum@yazduni.ac.ir; karami, Payam Ebrahimi [Department of Chemistry, Faculty of Science, Yazd University, Yazd (Iran, Islamic Republic of); Rahimi, Parvaneh [Department of Chemistry, Faculty of Science, Yazd University, Yazd (Iran, Islamic Republic of); Zare, Hamid Reza [Department of Chemistry, Faculty of Science, Yazd University, Yazd (Iran, Islamic Republic of); Naeimi, Hossein [Department of Chemistry, Faculty of Science, Kashan University, Kashan (Iran, Islamic Republic of)

    2007-06-10

    The electrocatalytic oxidation of hydrazine has been studied on glassy carbon modified by electrodeposition of quinizarine, using cyclic voltammetry and chronoamperometry techniques. It has been shown that the oxidation of hydrazine to nitrogen occurs at a potential where oxidation is not observed at the bare glassy carbon electrode. The apparent charge transfer rate constant and transfer coefficient for electron transfer between the electrode surface and immobilized quinizarine were calculated as 4.44 s{sup -1} and 0.66, respectively. The heterogenous rate constant for oxidation of hydrazine at the quinizarine modified electrode surface was also determined and found to be about 4.83 x 10{sup 3} M{sup -1} s{sup -1}. The diffusion coefficient of hydrazine was also estimated as 1.1 x 10{sup -6} cm{sup 2} s{sup -1} for the experimental conditions, using chronoamperometry.

  6. Sensitive amperometric determination of hydrazine using a carbon ...

    Indian Academy of Sciences (India)

    4

    compound and can cause different problems for human health such as liver, brain, ... Wide industrial and pharmaceutical applications of hydrazine make it enter to ..... attributed to the cooperative effect of high surface area of nanozeolite L and ...

  7. A Review of Hydrazine Sensors: The State of the Art

    Science.gov (United States)

    Meneghelli, B. J.

    2004-01-01

    Several types of sensors have been developed over the past few years that quantify the vapor concentrations of the hydrazines. These sensor s are able to detect concentrations as low as 10 parts per billion (ppb) up to several parts per million (ppm). The scope of this review wi ll be focused on those sensors that are most current in the marketpla ce as either leak detectors or personnel monitors. Some technical information on the theory of operations of each hydrazine detector will a lso be included. The review will highlight current operations that utilize hydrazine sensors including the Kennedy Space Center (KSC), the United States Air Force (USAF) at Cape Canaveral Air Station (CCAS), USAF F-16 facilities. The orientation of the review will be towards giving users usable practical information on hydrazine sensors.

  8. The effects of aniline impurities on monopropellant hydrazine thruster performance

    Science.gov (United States)

    Holcomb, L.; Mattson, L.; Oshiro, R.

    1976-01-01

    Both a 0.45-N and a 0.9-N thruster representative of the designs being flown on 3-axis stabilized spacecraft were used in testing various grades of hydrazine for the phenomenon of monopropellant hydrazine thruster catalyst bed poisoning. Both designs employed Shell 405 ABSG spontaneous catalyst. It is found that pulse shape distortion can be minimized, if not eliminated, by using aniline-free hydrazine. The mechanisms for both steady-state and pulse-mode performance loss are associated with the formation of a catalyst coke similar to the polycyclic aromatic poisons encountered in the petroleum industry. These poisoning mechanisms are reversible, with high-temperature operation being required to drive off the aniline coke deposits. It is recommended that a purified-grade hydrazine be considered for any mission that imposes operational conditions on a thruster which can result in aniline-induced poisoning of the catalyst bed.

  9. The Effects of Selected Hydrazines Upon Fish and Invertebrates

    Science.gov (United States)

    1980-02-01

    AMRL-TR-79-93 THE EFFECTS OF SELECTED HYDRAZINES UPON FISH AND INVERTEBRATES J. W. FISHER D. S. MYERS M. L. MEYERS FEBRUARY 1980 Approved for public...HYDRAZINES UPON FISH AND INVERTEBRATES 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) 8. CONTRACT OR GRANT NUMBER(s) J. W. Fisher D. S. Myers M. L. Meyers 9...estimations using two freshwater fish, golden shiners and channel catfish, and two invertebrates , amphipods and isopods. The data did not clearly indicate

  10. Bacterial Toxicity and Metabolism of Three Hydrazine Fuels.

    Science.gov (United States)

    1980-09-01

    12). More recently, additional research on hydrazine toxicity to the three- spine sticklebacks produced a 96-hour LC50 at 3 ppm (Reference 13) and a 24...pilot- sized or full-scale development and testing of nitrifica- tion/denitrification schemes. These research efforts yielded data on the effect of...hydrazines to the environment. Be- cause of the size of some of the rail and truck transport containers, the volumes from a spill could easily be large

  11. Mobility Spectrometer Studies on Hydrazine and Ammonia Detection

    Science.gov (United States)

    Niu, William; Eiceman, Gary; Szumlas, Andrew; Lewis, John

    2011-01-01

    An airborne vapor analyzer for detecting sub- to low- parts-per-million (ppm) hydrazine in the presence of higher concentration levels of ammonia has been under development for the Orion program. The detector is based on ambient pressure ionization and ion mobility characterization. The detector encompasses: 1) a membrane inlet to exclude particulate and aerosols from the analyzer inlet; 2) a method to separate hydrazine from ammonia which would otherwise lead to loss of calibration and quantitative accuracy for the hydrazine determination; and 3) response and quantitative determinations for both hydrazine and ammonia. Laboratory studies were made to explore some of these features including mobility measurements mindful of power, size, and weight issues. The study recommended the use of a mobility spectrometer of traditional design with a reagent gas and equipped with an inlet transfer line of bonded phase fused silica tube. The inlet transfer line provided gas phase separation of neutrals of ammonia from hydrazine at 50 C simplifying significantly the ionization chemistry that underlies response in a mobility spectrometer. Performance of the analyzer was acceptable between ranges of 30 to 80 C for both the pre-fractionation column and the drift tube. An inlet comprised of a combined membrane with valve-less injector allowed high speed quantitative determination of ammonia and hydrazine without cross reactivity from common metabolites such as alcohols, esters, and aldehydes. Preliminary test results and some of the design features are discussed.

  12. Liquid fluorine/hydrazine rhenium thruster update

    Science.gov (United States)

    Appel, M. A.; Kaplan, R. B.; Tuffias, R. H.

    1983-01-01

    The status of a fluorine/hydrazine thruster development program is discussed. A solid rhenium metal sea-level thrust chamber was successfully fabricated and tested for a total run duration of 1075 s with 17 starts. Rhenium fabrication methods are discussed. A test program was conducted to evaluate performance and chamber cooling. Acceptable performance was reached and cooling was adequate. A flight-type injector was fabricated that achieved an average extrapolated performance value of 3608 N-s/kg (368 lbf-s/lbm). Altitude thrust chambers were fabricated. One chamber incorporates a rhenium combustor and nozzle with an area ratio of 15:1, and a columbium nozzle extension with area ratios from 15:1 to 60:1. The other chamber was fabricated completely with a carbon/carbon composite. Because of the attributes of rhenium for use in high-temperature applications, a program to provide the materials and processes technology needed to reliably fabricate and/or repair vapor-deposited rhenium parts of relatively large size and complex shape is recommended.

  13. Advances in Hypergolic Propellants: Ignition, Hydrazine, and Hydrogen Peroxide Research

    Directory of Open Access Journals (Sweden)

    Stephen M. Davis

    2014-01-01

    Full Text Available A review of the literature pertaining to hypergolic fuel systems, particularly using hydrazine or its derivatives and hydrogen peroxide, has been conducted. It has been shown that a large effort has been made towards minimizing the risks involved with the use of a toxic propellant such as the hydrazine. Substitution of hydrazines for nontoxic propellant formulations such as the use of high purity hydrogen peroxide with various types of fuels is one of the major areas of study for future hypergolic propellants. A series of criteria for future hypergolic propellants has been recommended, including low toxicity, wide temperature range applicability, short ignition delay, high specific impulse or density specific impulse, and storability at room temperature.

  14. Cracking the enigmatic linker histone code.

    Science.gov (United States)

    Godde, James S; Ura, Kiyoe

    2008-03-01

    Recently, the existence of a 'histone code' has been proposed to explain the link between the covalent chemical modification of histone proteins and the epigenetic regulation of gene activity. Although the role of the four 'core' histones has been extensively studied, little is known about the involvement of the linker histone, histone H1 and its variants, in this code. For many years, few sites of chemical modification had been mapped in linker histones, but this has changed recently with the use of functional proteomic techniques, principally mass spectrometry, to characterize these modifications. The functionality of many of these sites, however, remains to be determined.

  15. Transient inter-cellular polymeric linker.

    Science.gov (United States)

    Ong, Siew-Min; He, Lijuan; Thuy Linh, Nguyen Thi; Tee, Yee-Han; Arooz, Talha; Tang, Guping; Tan, Choon-Hong; Yu, Hanry

    2007-09-01

    Three-dimensional (3D) tissue-engineered constructs with bio-mimicry cell-cell and cell-matrix interactions are useful in regenerative medicine. In cell-dense and matrix-poor tissues of the internal organs, cells support one another via cell-cell interactions, supplemented by small amount of the extra-cellular matrices (ECM) secreted by the cells. Here we connect HepG2 cells directly but transiently with inter-cellular polymeric linker to facilitate cell-cell interaction and aggregation. The linker consists of a non-toxic low molecular-weight polyethyleneimine (PEI) backbone conjugated with multiple hydrazide groups that can aggregate cells within 30 min by reacting with the aldehyde handles on the chemically modified cell-surface glycoproteins. The cells in the cellular aggregates proliferated; and maintained the cortical actin distribution of the 3D cell morphology while non-aggregated cells died over 7 days of suspension culture. The aggregates lost distinguishable cell-cell boundaries within 3 days; and the ECM fibers became visible around cells from day 3 onwards while the inter-cellular polymeric linker disappeared from the cell surfaces over time. The transient inter-cellular polymeric linker can be useful for forming 3D cellular and tissue constructs without bulk biomaterials or extensive network of engineered ECM for various applications.

  16. CU(II): catalyzed hydrazine reduction of ferric nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Karraker, D.G.

    1981-11-01

    A method is described for producing ferrous nitrate solutions by the cupric ion-catalyzed reduction of ferric nitrate with hydrazine. The reaction is complete in about 1.5 hours at 40/sup 0/C. Hydrazoic acid is also produced in substantial quantities as a reaction byproduct.

  17. Reaction of Hydrazine Hydrate with Oxalic Acid: Synthesis and ...

    African Journals Online (AJOL)

    The reaction of oxalic acid with hydrazine hydrate (in appropriate mole ratio) forms the dihydrazinium oxalate under specific experimental condition. The title compound is a molecular salt containing two discrete hydrazinium cations and an oxalate anion. The oxalate anion is perfectly planar and there is a crystallographic ...

  18. Sensitive amperometric determination of hydrazine using a carbon ...

    Indian Academy of Sciences (India)

    Silver-exchanged nanozeolite L (Ag/L) was prepared and mixed with carbon paste to prepare the modified electrode. Cyclic voltammetry studies revealed the ... The unique porous structure of nanozeolite L offers a promising catalyst support candidate for efficient electrochemical sensing of hydrazine. The sensor exhibited ...

  19. Acute toxicity of the vapors of some methylated hydrazine derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, K.H.; Clem, J.H.; Wheelwright, H.J.; Rhinehart, W.E.; Mayes, N.

    1955-01-01

    Methylhydrazine, asym-dimethylhydrazine, and sym-dimethylhydrazine vapors are similar to hydrazine in that they are respiratory irritants an;d convulsants on acute exposure. In addition to causing respiratory distress and convulsions, methylhydrazine vapor was found to produce hemolysis and elevated temperatures in exposed dogs. Methylhydrazine was the most toxic of the vapors tested, and hydrazine the least toxic. The higher volatility of asym-dimethylhydrazine indicates that the hazard of this vapor is similar to methylhydrazine. However, the hemolytic properties of methylhydrazine indicate that this vapor has a greater sublethal hazard. Preliminary data on sym-dimethylhydrazine suggest that this vapor has a toxicity and vapor hazard that is less than methylhydrazine and asym-dimethylhydrazine but greater than hydrazine. The odors of hydrazine, methylhydrazine, and asym-dimethylhydrazine were usually described by human subjects as ammoniacal, fishy, or amine-like. The odor of these vapors appears to offer adequate warning of acute exposure to dangerous aspirations. 16 references, 2 figures, 7 tables.

  20. Sensitive amperometric determination of hydrazine using a carbon ...

    Indian Academy of Sciences (India)

    as platinum [21,22], palladium [23,24], silver [25,26] and gold [27,28] are very active in the anodic oxidation of ..... Ag|AgCl in a stirred 0.1 M NaOH solution. Table 2. Determination of hydrazine in water samples at Ag/L–CPE. Sample. Spiked (μM). Found (μM). RSD (%, n = 3). Recovery (%). Tap water. 100. 96.33. 4.68. 96.33.

  1. Hydrazine Blending and Storage Facility, Interim Response Action

    Science.gov (United States)

    1991-01-07

    increases the rate of ozone oxidation of hydrazine fuel compounds, (2) increasing specie concentration increases the required hydraulic detention ... phthalate 4,6-Dinitro-2-methylphenol 2,4-Dinitrophenol 2,4-DinitrotolueneI I ,2-Diphenylhydrazine bis(2-Ethylhexyl) phthalate Fluoranthene FluoreneI...Nitrosodiphenylamine n-Nitroso-di-n-propylamine di-n-Octyl phthalate Pentachiorophenol Phenanthrene Phenol Pyrene 1 ,2,4-Trichlorobenzene 2,4,5-TrichlorophenolI

  2. Developing a New Sampling And Analysis Method For Hydrazine And Monomethyl Hydrazine: Using a Derivatizing Agent With Solid Phase Microextraction

    Science.gov (United States)

    Allen, John

    2001-01-01

    Solid phase microextraction (SPME) will be used to develop a method for detecting monomethyl hydrazine (MMH) and hydrazine (Hz). A derivatizing agent, pentafluorobenzoyl chloride (PFBCI), is known to react readily with MMH and Hz. The SPME fiber can either be coated with PFBCl and introduced into a gaseous stream containing MMH, or PFBCl and MMH can react first in a syringe barrel and after a short equilibration period a SPME is used to sample the resulting solution. These methods were optimized and compared. Because Hz and MMH can degrade the SPME, letting the reaction occur first gave better results. Only MMH could be detected using either of these methods. Future research will concentrate on constructing calibration curves and determining the detection limit.

  3. Evaluation of consequence due to higher hydrazine content in partitioning stream of PUREX process

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, K. Suresh [Bhabha Atomic Research Centre, Mumbai (India). Special Nuclear Recycle Facility

    2016-07-01

    Hydrazine nitrate is being used as a stabilizer for U(IV) as well as Pu(III) during partitioning of Pu in PUREX process by scavenging the nitrous acid present along with nitric acid. As hydrazine hydrate as well as its salts have been successfully used for scrubbing of degradation products of TBP to aqueous phase, experiments were conducted to evaluate the consequence of hydrazine content during Pu partitioning. It was observed that higher amount of hydrazine nitrate along with uranous nitrate in the partitioning stream of PUREX process leads to build up of DBP in aqueous phase and resulted in precipitation of Pu.

  4. Traceless cross-linker for photocleavable bioconjugation.

    Science.gov (United States)

    Wang, Rong; Yan, Funing; Qiu, Dengli; Jeong, Jae-Sun; Jin, Qiaoling; Kim, Tae-Young; Chen, Liaohai

    2012-04-18

    Photoresponsive bioconjugation empowers the development of novel methods for drug discovery, disease diagnosis, and high-throughput screening, among others. In this paper, we report on the characteristics of a traceless photocleavable cross-linker, di-6-(3-succinimidyl carbonyloxymethyl-4-nitro-phenoxy)-hexanoic acid disulfide diethanol ester (SCNE). The traceless feature and the biocompatibility of this photocleavable cross-linking reagent were corroborated. Consequently, we demonstrated its application in reversible phage particle immobilization that could provide a platform for direct single-phage screening. We also applied it in protein-photoprinting, where SCNE acts as a "photo-eraser" to remove the cross-linked protein molecules at a desired region in a simple, clean, and light-controllable fashion. We further demonstrated the two-tier atomic force microscopic (AFM) method that uses SCNE to carry out two subsequent AFM tasks in situ. The approach allows guided protein delivery and subsequent high-resolution imaging at the same local area, thus opening up the possibility of monitoring protein functions in live cells. The results imply that SCNE is a versatile cross-linker that can be used for a wide range of applications where photocleavage ensures clean and remote-controllable release of biological molecules from a substrate. © 2012 American Chemical Society

  5. Chemosensitive nanocomposite for conductometric detection of hydrazine and NADH

    Energy Technology Data Exchange (ETDEWEB)

    Lange, Ulrich [Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, 93047 Regensburg (Germany); Mirsky, Vladimir M., E-mail: vmirsky@hs-lausitz.d [Department of Nanobiotechnology, Lausitz University of Applied Sciences, 01968 Senftenberg (Germany)

    2011-04-01

    A new chemosensitive material based on palladium nanoparticles and PEDOT-PSS is described. The composite was characterized by transmission electron microscopy, cyclic voltammetry and in situ resistance measurements. The material was applied for conductometric detection of hydrazine and NADH. Upon exposure to these analytes PEDOT is reduced leading to an increase in its conductance. This process is catalyzed by palladium. A model for description of the potential dependence of polymer conductivity was suggested, tested and applied for the development of new calibration procedure of chemiresistors based on electroactive polymers.

  6. An electron spin resonance study of Mn2+ doped calcium hydrazine ...

    Indian Academy of Sciences (India)

    Introduction. The hydrazine carboxylate compounds consisting of the complexes of lid-metals, calcium and magnesium with hydrazine carboxylic acid have attracted recent scientific attention (Ravindranathan and Patil 1985). While they present various types of octahedral coordination, all of them contain pentatomic chelate ...

  7. The potential use of hydrazine as an alternative to peroxidase in a biosensor: comparison between hydrazine and HRP-based glucose sensors.

    Science.gov (United States)

    Rahman, Md Aminur; Won, Mi-Sook; Shim, Yoon-Bo

    2005-08-15

    The potential use of hydrazine sulfate was examined for the catalytic reduction of enzymatically generated H2O2 in a biosensor system. The performance of the hydrazine-based sensor was compared with an HRP-based glucose sensor as a model of a biosensor. Hydrazine and HRP were covalently immobilized onto a conducting polymer layer with glucose oxidase. The direct electron transfer reactions of the immobilized hydrazine and HRP onto the poly-5,2':5,2''-terthiophene-3'-carboxylic acid (poly-TTCA) layer were investigated by using cyclic voltammetric method and the electron transfer rate constants were determined. The glucose oxidase- and hydrazine-immobilized sensor efficiently reduced the enzymatically generated H2O2 at -0.15 V versus Ag/AgCl. The surface of this GOx/hydrazine/poly-TTCA-based glucose sensor was characterized by QCM, SEM, and ESCA. Glucose-sensing properties were studied using cyclic voltammetric and chronoamperometric techniques. Various experimental parameters were optimized according to the amount of hydrazine, pH, the temperature, and the applied potential. A linear calibration plot was obtained in the concentration range between 0.1 and 15.0 mM, and the detection limit was determined to be 40.0+/-7.0 microM. Interferences from other biological compounds were studied. The long-term stability of the GOx/hydrazine sensor was better than that of the one based on a GOx/HRP biosensor. The proposed glucose sensor was successfully applied to human whole blood and urine samples for the detection of glucose.

  8. Impurities within carbon nanotubes govern the electrochemical oxidation of substituted hydrazines.

    Science.gov (United States)

    Stuart, Emma J E; Pumera, Martin

    2011-06-14

    Electrochemistry and electrocatalysis on carbon nanomaterials is at the forefront of research. The presence of carbonaceous and metallic impurities within carbon nanotubes (CNTs) is a persistent problem. Here we show that the electrochemistry of the entire group of hydrazine compounds is governed by impurities within single-walled, double-walled and few-walled CNTs. The oxidation of organic substituted hydrazines at CNTs is driven by nanographitic impurities, in contrast to unsubstituted hydrazine, for which the electrochemistry is driven by metallic impurities within CNTs. This finding is unexpected, as one would assume that a whole group of compounds would be susceptible to "electrocatalysis" by only one type of impurity. This discovery should be taken into account when predicting the susceptibility of whole groups of compounds to electrocatalysis by metallic or nanographitic impurities. Our findings have strong implications on the electrochemical sensing of hydrazines and on the use of hydrazines as fuels for nanomotors. This journal is © the Owner Societies 2011

  9. A rhodol-based fluorescent chemosensor for hydrazine and its application in live cell bioimaging

    Science.gov (United States)

    Tiensomjitr, Khomsan; Noorat, Rattha; Wechakorn, Kanokorn; Prabpai, Samran; Suksen, Kanoknetr; Kanjanasirirat, Phongthon; Pewkliang, Yongyut; Borwornpinyo, Suparerk; Kongsaeree, Palangpon

    2017-10-01

    A rhodol cinnamate fluorescent chemosensor (RC) has been developed for selective detection of hydrazine (N2H4). In aqueous medium, the rhodol-based probe exhibited high selectivity for hydrazine among other molecules. The addition of hydrazine triggered a fluorescence emission with 48-fold enhancement based on hydrazinolysis and a subsequent ring-opening process. The chemical probe also displayed a selective colorimetric response toward N2H4 from colorless solution to pink, readily observed by the naked eye. The detection limit of RC for hydrazine was calculated to be 300 nM (9.6 ppb). RC is membrane permeable and was successfully demonstrated to detect hydrazine in live HepG2 cells by confocal fluorescence microscopy.

  10. Enhanced dehydrogenation of hydrazine bisborane for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Li, Leigang [Department of Materials Science, Fudan University, Shanghai 200433 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Tan, Yingbin; Tang, Ziwei; Xia, Guanglin; Yuan, Feng [Department of Materials Science, Fudan University, Shanghai 200433 (China); Li, Qian, E-mail: shuliqian@shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Yu, Xuebin, E-mail: yuxuebin@fudan.edu.cn [Department of Materials Science, Fudan University, Shanghai 200433 (China)

    2014-02-14

    NiCl{sub 2} and CoCl{sub 2} were adopted to enhance the dehydrogenation of hydrazine bisborane (HBB), respectively, of which NiCl{sub 2} showed better performance. By adding 2.0 mol. % NiCl{sub 2}, the dehydrogenation property of HBB was significantly improved, for example, the impurity of NH{sub 3} during the dehydrogenation of HBB was totally suppressed with more than 13.0 wt. % of pure hydrogen evolved. By Kissinger method, the apparent activation energies of the first step for HBB and Ni-doped HBB were calculated to be 143.2 and 60.7 kJ mol{sup −1}, respectively. DSC result showed that the addition of NiCl{sub 2} did not change the enthalpy change of HBB dehydrogenation. Based on theoretical analysis and literature review, the improved dehydrogenation property of HBB was potentially ascribed to the solid state interaction of Ni{sup 2+} with the electronegative N in the NH{sub 2} group of HBB. - Highlights: • NiCl{sub 2} enhanced dehydrogenation of hydrazine bisborane (HBB) was reported. • By adding NiCl{sub 2}, the desorption rate and the hydrogen purity were improved. • A possible explanation was proposed to understand NiCl{sub 2} enhanced desorption of HBB.

  11. Structural Mechanisms of Nucleosome Recognition by Linker Histones.

    Science.gov (United States)

    Zhou, Bing-Rui; Jiang, Jiansheng; Feng, Hanqiao; Ghirlando, Rodolfo; Xiao, T Sam; Bai, Yawen

    2015-08-20

    Linker histones bind to the nucleosome and regulate the structure of chromatin and gene expression. Despite more than three decades of effort, the structural basis of nucleosome recognition by linker histones remains elusive. Here, we report the crystal structure of the globular domain of chicken linker histone H5 in complex with the nucleosome at 3.5 Å resolution, which is validated using nuclear magnetic resonance spectroscopy. The globular domain sits on the dyad of the nucleosome and interacts with both DNA linkers. Our structure integrates results from mutation analyses and previous cross-linking and fluorescence recovery after photobleach experiments, and it helps resolve the long debate on structural mechanisms of nucleosome recognition by linker histones. The on-dyad binding mode of the H5 globular domain is different from the recently reported off-dyad binding mode of Drosophila linker histone H1. We demonstrate that linker histones with different binding modes could fold chromatin to form distinct higher-order structures. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Analysis of hydrazine in smokeless tobacco products by gas chromatography-mass spectrometry.

    Science.gov (United States)

    McAdam, Kevin; Kimpton, Harriet; Essen, Sofia; Davis, Peter; Vas, Carl; Wright, Christopher; Porter, Andrew; Rodu, Brad

    2015-01-01

    Due to the lower health risks associated with the use of certain categories of smokeless tobacco products (STPs) such as Swedish snus, there is interest in the comparative levels of toxic chemical constituents in different types of STPs. A method has been developed and validated for the analysis of hydrazine in STPs. Seventy four commercial STPs from the US and Sweden, representing 80-90% of the 2010 market share for all the major STP categories in these two countries, as well as three reference STPs, were analysed for hydrazine. Aqueous extracts of the STPs were treated with excess pentafluorobenzaldehyde (PFB), which reacted with hydrazine in solution to form decafluorobenzaldehyde azine (DFBA). DFBA was partitioned into hexane and then quantified by gas chromatography-mass spectrometry (GC-MS). The method was validated using five different types of STP, was linear in the range 8-170 ng/mL, and had limits of quantification (LOQ) from 26-53 ng of hydrazine per g of STP (as sold). The method was applied to the analysis of 74 contemporary STPs commercially available in the United States and Sweden, none of which were found to contain hydrazine above the LOQ or LOD. Trace levels of compounds showing chromatographic and mass spectral features consistent with hydrazine were identified at very low levels (sub-limit of detection, tobacco. Our results show that hydrazine is not a prevalent constituent of STPs, and when present is not quantifiable using currently available analytical methodology.

  13. Photolabile linker for the synthesis of hydroxamic acids

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention relates to a photolabile hydroxamate linker based on the o - nitroveratryl group and its application for multistep solid-phase synthesis and controlled photolytic release of hydroxamic acids. The invention provides a method for producing a solid support comprising...... a hydroxylamine - functionalized photolabile linker, and the so produced hydroxylamine - functionalized photolabile solid support. The invention further provides a method for synthesizing a one-bead-one compound library of hydroxamic acid derivatives on a photolabile linker, as well as a method for screening...... a library of hydroxamic acid derivatives....

  14. Crystallization of Galectin-8 Linker Reveals Intricate Relationship between the N-terminal Tail and the Linker

    Directory of Open Access Journals (Sweden)

    Yunlong Si

    2016-12-01

    Full Text Available Galectin-8 (Gal-8 plays a significant role in normal immunological function as well as in cancer. This lectin contains two carbohydrate recognition domains (CRD connected by a peptide linker. The N-terminal CRD determines ligand binding specificity, whereas the linker has been proposed to regulate overall Gal-8 function, including multimerization and biological activity. Here, we crystallized the Gal-8 N-terminal CRD with the peptide linker using a crystallization condition that contains Ni2+. The Ni2+ ion was found to be complexed between two CRDs via crystal packing contacts. The coordination between Ni2+ and Asp25 plays an indirect role in determining the structure of β-strand F0 and in influencing the linker conformation which could not be defined due to its dynamic nature. The linker was also shortened in situ and crystallized under a different condition, leading to a higher resolution structure refined to 1.08 Å. This crystal structure allowed definition of a short portion of the linker interacting with the Gal-8 N-terminal tail via ionic interactions and hydrogen bonds. Observation of two Gal-8 N-terminal CRD structures implies that the N-terminal tail and the linker may influence each other’s conformation. In addition, under specific crystallization conditions, glycerol could replace lactose and was observed at the carbohydrate binding site. However, glycerol did not show inhibition activity in hemagglutination assay.

  15. Anodic oxidation of hydrazine at carbon nanotube powder microelectrode and its detection.

    Science.gov (United States)

    Zhao, Yuan-Di; Zhang, Wei-De; Chen, Hong; Luo, Qing-Ming

    2002-09-12

    Carbon nanotube powder microelectrodes (CNTPMEs) were used to study the anodic oxidation of hydrazine at Carbon nanotube (CNT)-the novel carbon material. It was found that the electrochemical behaviours were greatly improved at CNTs, indicating that the anodic oxidation could be catalyzed at CNTs. The kinetics parameters of this process were calculated, the heterogeneous electron transfer rate constant k was 0.0019 cm s(-1), (1-alpha)n(alpha) was 0.22. The CNTPMEs were also found with high sensitivity for hydrazine detection, could be used as hydrazine sensors.

  16. Nanocatalysts for Hydrogen Generation from Ammonia Borane and Hydrazine Borane

    Directory of Open Access Journals (Sweden)

    Zhang-Hui Lu

    2014-01-01

    Full Text Available Ammonia borane (denoted as AB, NH3BH3 and hydrazine borane (denoted as HB, N2H4BH3, having hydrogen content as high as 19.6 wt% and 15.4 wt%, respectively, have been considered as promising hydrogen storage materials. Particularly, the AB and HB hydrolytic dehydrogenation system can ideally release 7.8 wt% and 12.2 wt% hydrogen of the starting materials, respectively, showing their high potential for chemical hydrogen storage. A variety of nanocatalysts have been prepared for catalytic dehydrogenation from aqueous or methanolic solution of AB and HB. In this review, we survey the research progresses in nanocatalysts for hydrogen generation from the hydrolysis or methanolysis of NH3BH3 and N2H4BH3.

  17. Determination of hydrazines by chip electrophoresis with contactless conductivity detection.

    Science.gov (United States)

    Kumar, Ashwini; Burns, Jacob; Hoffmann, Werner; Demattio, Horst; Malik, Ashok Kumar; Matysik, Frank-Michael

    2011-04-01

    In this report, a new approach for the fast determination of hydrazine compounds (hy) in complex matrices is presented. The experimental protocol is based on poly(methylmethacrylate) (PMMA) microchip separations with contactless conductivity detection using a compact portable device, which integrates all separation and detection components. Three hy (hydrozine (Hy), methylhydrazine (MH), and 1,1-dimethylhydrazine (UDMH)) were separated within river water, interferences were eliminated by implementing ultrasound-assisted headspace single-drop microextraction of hy under strongly alkaline conditions, using an aqueous drop of His/MES buffer as the extractant phase. The incorporation of this miniaturized sample preparation step led to improved limits of detection for Hy, MH, and UDMH of 6.5, 15.3, and 11.4 ng/mL, respectively. The overall protocol demonstrates a promising approach for interfacing chip electrophoresis with real-world applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Highly durable direct hydrazine hydrate anion exchange membrane fuel cell

    Science.gov (United States)

    Sakamoto, Tomokazu; Serov, Alexey; Masuda, Teruyuki; Kamakura, Masaki; Yoshimoto, Koji; Omata, Takuya; Kishi, Hirofumi; Yamaguchi, Susumu; Hori, Akihiro; Horiuchi, Yousuke; Terada, Tomoaki; Artyushkova, Kateryna; Atanassov, Plamen; Tanaka, Hirohisa

    2018-01-01

    The factors influenced on degradation of direct hydrazine hydrate fuel cells (DHFCs) under operation conditions are analyzed by in situ soft X-ray radiography. A durability of DHFCs is significantly improved by multi-step reaction DHFCs (MSR-DHFCs) approach designed to decrease the crossover of liquid fuel. An open circuit voltage (OCV) as well as cell voltage at 5 mA cm-2 of MSR-DHFC construct with commercial anion exchange membrane (AEM) maintained for over of 3500 h at 60 °C. Furthermore, the commercial proton exchange membrane (PEM) is integrated into AEM of MSR-DHFCs resulting in stable power output of MSR-DHFCs for over than 2800 h at 80 °C.

  19. Linker-mediated assembly of gold nanoparticles into multimeric motifs

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, Mateusz; Cieplak, Marek [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland); Szymczak, Piotr [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ulica Hoza 69, 00-681 Warsaw (Poland); Thompson, Damien, E-mail: mc@ifpan.edu.pl [Tyndall National Institute, Lee Maltings, University College Cork, Cork (Ireland)

    2011-11-04

    We present a theoretical description of linker-mediated self-assembly of gold nanoparticles (Au-NP). Using mesoscale simulations with a coarse-grained model for the Au NPs and dirhenium-based linker molecules, we investigate the conditions under which large clusters can grow and construct a phase diagram that identifies favorable growth conditions in terms of floating and bound linker concentrations. The findings can be considered as generic, as we expect other NP-linker systems to behave in a qualitatively similar way. In particular, we also discuss the case of antibody-functionalised Au NPs connected by the C-reactive proteins (CRPs). We extract some general rules for NP linking that may aid the production of size- and shape-specific NP clusters for technology applications.

  20. Photocleavable linker for the patterning of bioactive molecules.

    Science.gov (United States)

    Wegner, Seraphine V; Sentürk, Oya I; Spatz, Joachim P

    2015-12-16

    Herein, we report the use of a versatile photocleavable nitrobenzyl linker to micropattern a wide variety of bioactive molecules and photorelease them on demand. On one end, the linker has an NHS group that can be coupled with any amine, such as peptides, proteins or amine-linkers, and on the other end an alkyne for convenient attachment to materials with an azide functional group. This linker was conjugated with NTA-amine or the cell adhesion peptide cRGD to enable straightforward patterning of His6-tagged proteins or cells, respectively, on PEGylated glass surfaces. This approach provides a practical way to control the presentation of a wide variety of bioactive molecules with high spatial and temporal resolution. The extent of photocleavage can also be controlled to tune the biomolecule density and degree of cell attachment to the surface.

  1. Novel mixing method for cross linker introduction into droplet emulsions

    CSIR Research Space (South Africa)

    Land, KJ

    2013-10-01

    Full Text Available the introduction of cross linker after droplet formation, together with the utilisation of topological microfluidic channel structures, allowing for the novel manufacture of particles. Flow over these structures has been simulated in order to choose the most...

  2. The SNAP-25 Linker as an Adaptation Toward Fast Exocytosis

    Science.gov (United States)

    Nagy, Gábor; Milosevic, Ira; Mohrmann, Ralf; Wiederhold, Katrin; Walter, Alexander M.

    2008-01-01

    The assembly of four soluble N-ethylmaleimide-sensitive factor attachment protein receptor domains into a complex is essential for membrane fusion. In most cases, the four SNARE-domains are encoded by separate membrane-targeted proteins. However, in the exocytotic pathway, two SNARE-domains are present in one protein, connected by a flexible linker. The significance of this arrangement is unknown. We characterized the role of the linker in SNAP-25, a neuronal SNARE, by using overexpression techniques in synaptosomal-associated protein of 25 kDa (SNAP-25) null mouse chromaffin cells and fast electrophysiological techniques. We confirm that the palmitoylated linker-cysteines are important for membrane association. A SNAP-25 mutant without cysteines supported exocytosis, but the fusion rate was slowed down and the fusion pore duration prolonged. Using chimeric proteins between SNAP-25 and its ubiquitous homologue SNAP-23, we show that the cysteine-containing part of the linkers is interchangeable. However, a stretch of 10 hydrophobic and charged amino acids in the C-terminal half of the SNAP-25 linker is required for fast exocytosis and in its absence the calcium dependence of exocytosis is shifted toward higher concentrations. The SNAP-25 linker therefore might have evolved as an adaptation toward calcium triggering and a high rate of execution of the fusion process, those features that distinguish exocytosis from other membrane fusion pathways. PMID:18579690

  3. Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Feller, David [Department; Bross, David H. [Chemical; Ruscic, Branko [Chemical; Computation

    2017-08-02

    In order to address the accuracy of the long-standing experimental enthalpy of formation of gas-phase hydrazine, fully confirmed in earlier versions of Active Thermochemical Tables (ATcT), the provenance of that value is re-examined in light of new high-end calculations of the Feller-Peterson-Dixon (FPD) variety. An overly optimistic determination of the vaporization enthalpy of hydrazine, which created an unrealistically strong connection between the gas phase thermochemistry and the calorimetric results defining the thermochemistry of liquid hydrazine was identified as the probable culprit. The new enthalpy of formation of gas-phase hydrazine, based on balancing all available knowledge, was determined to be 111.57 ± 0.47 kJ/mol at 0 K (97.41 kJ/mol at 298.15 K). Close agreement was found between the ATcT (even excluding the latest theoretical result) and FPD enthalpies.

  4. Contamination Assessment Report, Site 1-7, Hydrazine Blending and Storage Facility. Version 3.2

    Science.gov (United States)

    1988-09-01

    OSC Organosulfur compounds HYD Hydrazines (by GC) ONC Nitlroeamines (by GC) GC/US WC/iis verification 0I Sampling Intervo I Analysis 21 36 ~(feet) l...for organosulfur compounds (OSC) to assess the tentatively identified benzothiazole and for semivolatile organics to assess the extent of other...pesticides (OCP) 6 Organosulfur compounds (OSC) 12 Dibromochloropropane (DBCP) 2 Hydrazines (BYD) 50 Nitrosamines (ONC) 50 ICP metals 26 Arsenic (As) 11

  5. Steady State Analysis of Hydrazine Catalytic Thrusters for Different Types of Catalysts

    Science.gov (United States)

    1976-01-15

    AD-A023 231 STEADY STATE ANALYSIS OF HYDRAZINE CATALYTIC THRUSTERS FOR DIFFERENT TYPES OF CATALYSTS Antonio Crespo Instituto Nacional de Tecnica... ANALYSIS OF HYDRAZINE CATALYTIC -1 Jan 1975-30 June 1975 THRUSTERS FOR -DIFFERENT TYPES OF CATALYSTS 6. PERFORMING ORG. ftZPORT NU~n ER...ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK- AREA A WORK UNIT NUMBERS .INSTITUTO NACIONAL DE TECRICA AERO) ESPACIAL (INTA) 681308 PASEOPINTOR ROSALES

  6. Photoelectrochemical generation of hydrogen and electricity from hydrazine hydrate using BiVO4 electrodes.

    Science.gov (United States)

    Pilli, Satyananda Kishore; Summers, Kodi; Chidambaram, Dev

    2015-06-07

    This study demonstrates solar driven oxidation of hydrazine hydrate and the simultaneous production of hydrogen and electricity in photoelectrochemical cells and photofuel cells, respectively, using a visible light active molybdenum doped BiVO4 photoelectrode. The developed photoelectrodes exhibited tremendous efficiency towards anodic oxidation of hydrous hydrazine with continuous and stable hydrogen evolution at the Pt cathode under benign pH and zero bias conditions. Significantly, the photofuel cell containing hydrazine hydrate fuel has generated electricity with a high open circuit potential of 0.8 V. The presence of bicarbonate ions in the electrolyte has played a significant role in enhancing the kinetics of photoelectrochemical oxidation of hydrazine and improved the hydrogen and electricity generation efficiency thus avoiding the integration of an oxidation electrocatalyst. In addition, molybdenum doped BiVO4 as a possible photoelectrochemical hydrazine sensor has been investigated and the electrode photocurrent was found to be linearly dependent on the concentration of the hydrazine hydrate in the range of 20-90 mM with a correlation coefficient of 0.9936.

  7. Hydrazine selective dual signaling chemodosimetric probe in physiological conditions and its application in live cells

    Energy Technology Data Exchange (ETDEWEB)

    Nandi, Sandip; Sahana, Animesh; Mandal, Sandip [Department of Chemistry, The University of Burdwan, Burdwan, 713104 West Bengal (India); Sengupta, Archya; Chatterjee, Ansuman [Department of Zoology, Visva Bharati University, Santiniketan, West Bengal (India); Safin, Damir A., E-mail: damir.a.safin@gmail.com [Institute of Condensed Matter and Nanosciences, Molecules, Solids and Reactivity (IMCN/MOST), Université catholique de Louvain, Place L. Pasteur 1, 1348 Louvain-la-Neuve (Belgium); Babashkina, Maria G.; Tumanov, Nikolay A.; Filinchuk, Yaroslav [Institute of Condensed Matter and Nanosciences, Molecules, Solids and Reactivity (IMCN/MOST), Université catholique de Louvain, Place L. Pasteur 1, 1348 Louvain-la-Neuve (Belgium); Das, Debasis, E-mail: ddas100in@yahoo.com [Department of Chemistry, The University of Burdwan, Burdwan, 713104 West Bengal (India)

    2015-09-17

    A rhodamine–cyanobenzene conjugate, (E)-4-((2-(3′,6′-bis(diethylamino)-3-oxospiro[isoindoline-1,9′-xanthene] -2-yl)ethylimino)methyl)benzonitrile (1), which structure has been elucidated by single crystal X-ray diffraction, was synthesized for selective fluorescent “turn-on” and colorimetric recognition of hydrazine at physiological pH 7.4. It was established that 1 detects hydrazine up to 58 nM. The probe is useful for the detection of intracellular hydrazine in the human breast cancer cells MCF-7 using a fluorescence microscope. Spirolactam ring opening of 1, followed by its hydrolysis, was established as a probable mechanism for the selective sensing of hydrazine. - Highlights: • A selective rhodamine–cyanobenzene conjugate is synthesized. • The conjugate is a selective dual signaling chemodosimetric probe towards hydrazine. • Spirolactam ring opening of the probe, followed by its hydrolysis, is the sensing mechanism. • The probe detects hydrazine in the human breast cancer cells MCF-7 imaging.

  8. Preparation of hydrazine functionalized polymer brushes hybrid magnetic nanoparticles for highly specific enrichment of glycopeptides.

    Science.gov (United States)

    Huang, Guang; Sun, Zhen; Qin, Hongqiang; Zhao, Liang; Xiong, Zhichao; Peng, Xiaojun; Ou, Junjie; Zou, Hanfa

    2014-05-07

    Hydrazide chemistry is a powerful technique in glycopeptides enrichment. However, the low density of the monolayer hydrazine groups on the conventional hydrazine-functionalized magnetic nanoparticles limits the efficiency of glycopeptides enrichment. Herein, a novel magnetic nanoparticle grafted with poly(glycidyl methacrylate) (GMA) brushes was fabricated via reversible addition-fragmentation chain transfer (RAFT) polymerization, and a large amount of hydrazine groups were further introduced to the GMA brushes by ring-opening the epoxy groups with hydrazine hydrate. The resulting magnetic nanoparticles (denoted as Fe3O4@SiO2@GMA-NHNH2) demonstrated the high specificity of capturing glycopeptides from a tryptic digest of the sample comprising a standard non-glycosylated protein bovine serum albumin (BSA) and four standard glycoproteins with a weight ratio of 50 : 1, and the detection limit was as low as 130 fmol. In the analysis of a real complex biological sample, the tryptic digest of hepatocellular carcinoma, 179 glycosites were identified by the Fe3O4@SiO2@GMA-NHNH2 nanoparticles, surpassing that of 68 glycosites by Fe3O4@SiO2-single-NHNH2 (with monolayer hydrazine groups on the surface). It can be expected that the magnetic nanoparticles modified with hydrazine functionalized polymer brushes via RAFT technique will improve the specificity and the binding capacity of glycopeptides from complex samples, and show great potential in the analysis of protein glycosylation in biological samples.

  9. Sonochemical decomposition of hydrazine in water: effects of coal ash and pH on the decomposition and adsorption behavior.

    Science.gov (United States)

    Nakui, Hiroyuki; Okitsu, Kenji; Maeda, Yasuaki; Nishimura, Rokurou

    2009-07-01

    Sonochemical decomposition of hydrazine in aqueous suspension of coal ash particles was investigated in the different pH solutions. It was clearly found that the initial rate of hydrazine decomposition and adsorption is strongly dependent on the amount of coal ash and pH. At pH1, the amount of the hydrazine adsorption on coal ash was very small and hydrazine was mainly decomposed by ultrasonic irradiation. At pH4, hydrazine was mainly adsorbed on coal ash and not decomposed by ultrasonic irradiation. At pH8, the sonochemical decomposition and the adsorption on coal ash proceeded simultaneously. These results were due to the interactions between the degree of the protonation of hydrazine, the electric charge of coal ash and the amount of OH radicals formed in the sonolysis of water.

  10. Multidisciplinary Design Optimization and Analysis of Hydrazine Monopropellant Propulsion System

    Directory of Open Access Journals (Sweden)

    Amirhossein Adami

    2015-01-01

    Full Text Available Monopropellant propulsion systems are widely used especially for low cost attitude control or orbit correction (orbit maintenance. To optimize the total propulsion system, subsystems should be optimized. Chemical decomposition, aerothermodynamics, and structure disciplines demand different optimum condition such as tank pressure, catalyst bed length and diameter, catalyst bed pressure, and nozzle geometry. Subsystem conflicts can be solved by multidisciplinary design optimization (MDO technique with simultaneous optimization of all subsystems with respect to any criteria and limitations. In this paper, monopropellant propulsion system design algorithm is presented and the results of the proposed algorithm are validated. Then, multidisciplinary design optimization of hydrazine propulsion system is proposed. The goal of optimization can be selected as minimizing the total mass (including propellant, minimizing the propellant mass (maximizing the Isp, or minimizing the dry mass. Minimum total mass, minimum propellant mass, and minimum dry mass are derived using MDO technique. It is shown that minimum total mass, minimum dry mass, and minimum propellant mass take place in different conditions. The optimum parameters include bed-loading, inlet pressure, mass flow, nozzle geometry, catalyst bed length and diameter, propellant tank mass, specific impulse (Isp, and feeding mass which are derived using genetic algorithm (GA.

  11. Synthesis and structural studies of Cp{sup *} rhodium and Cp{sup *} iridium complexes of picolinic hydrazine ligand

    Energy Technology Data Exchange (ETDEWEB)

    Palepu, Narasinga Rao; Kollipara, Mohan Rao [Centre for Advanced Studies in Chemistry, North-Eastern Hill University, Shillong (India); Kaminsky Werner [Dept. of Chemistry, University of Washington, Seattle (United States)

    2017-01-15

    A series of Cp{sup *}Rh and Cp{sup *}Ir complexes of picolinic hydrazine ligand are synthesized and characterized. Picolinic hydrazine has yielded only dinuclear complexes in the case of rhodium metal whereas both mono and dinuclear complexes with iridium metal. Iridium complexes are formed as quaternary salts by the migration of the N–H proton onto the adjacent amine group of the hydrazine after binding to the metal. Picolinic hydrazine acts as nitrogen and oxygen donor ligand in the form of bi and tetradentate bonding modes.

  12. Immune Response Modulation of Conjugated Agonists with Changing Linker Length.

    Science.gov (United States)

    Ryu, Keun Ah; Slowinska, Katarzyna; Moore, Troy; Esser-Kahn, Aaron

    2016-12-16

    We report immune response modulation with linked Toll-like receptor (TLR) agonists. Conjugating two agonists of synergistic TLRs induce an increase in immune activity compared to equal molarity of soluble agonists. Additionally, varying the distance between the agonists by changing the linker length alters the level of macrophage NF-κB activity as well as primary bone marrow derived dendritic cell IL-6 production. This modulation is effected by the size of the agonists and the pairing of the stimulated TLRs. The sensitivity of linker-length-dependent immune activity of conjugated agonists provides the potential for developing application specific therapeutics.

  13. Hydrazine-mediated construction of nanocrystal self-assembly materials.

    Science.gov (United States)

    Zhou, Ding; Liu, Min; Lin, Min; Bu, Xinyuan; Luo, Xintao; Zhang, Hao; Yang, Bai

    2014-10-28

    Self-assembly is the basic feature of supramolecular chemistry, which permits to integrate and enhance the functionalities of nano-objects. However, the conversion of self-assembled structures to practical materials is still laborious. In this work, on the basis of studying one-pot synthesis, spontaneous assembly, and in situ polymerization of aqueous semiconductor nanocrystals (NCs), NC self-assembly materials are produced and applied to design high performance white light-emitting diode (WLED). In producing self-assembly materials, the additive hydrazine (N2H4) is curial, which acts as the promoter to achieve room-temperature synthesis of aqueous NCs by favoring a reaction-controlled growth, as the polyelectrolyte to weaken inter-NC electrostatic repulsion and therewith facilitate the one-dimensional self-assembly, and in particular as the bifunctional monomers to polymerize with mercapto carboxylic acid-modified NCs via in situ amidation reaction. This strategy is versatile for mercapto carboxylic acid-modified aqueous NCs, for example CdS, CdSe, CdTe, CdSe(x)Te(1-x), and Cd(y)Hg(1-y)Te. Because of the multisite modification with carboxyl, the NCs act as macromonomers, thus producing cross-linked self-assembly materials with excellent thermal, solvent, and photostability. The assembled NCs preserve strong luminescence and avoid unpredictable fluorescent resonance energy transfer, the main problem in design WLED from multiple NC components. These advantages allow the fabrication of NC-based WLED with high color rendering index (86), high luminous efficacy (41 lm/W), and controllable color temperature.

  14. Adjustable hydrazine modulation of single-wall carbon nanotube network field effect transistors from p-type to n-type

    Science.gov (United States)

    Dai, Ruixuan; Xie, Dan; Xu, Jianlong; Sun, Yilin; Sun, MengXing; Zhang, Cheng; Li, Xian

    2016-11-01

    Single-wall carbon nanotube (SWCNT) network field effect transistors (FETs), which show decent p-type electronic properties, have been fabricated. The use of hydrazine as an aqueous solution and a strong n-type dopant for the SWCNTs is demonstrated in this paper. The electrical properties are obviously tuned by hydrazine treatment at different concentrations on the surface of the SWCNT network FETs. The transport behavior of SWCNTs can be modulated from p-type to n-type, demonstrating the controllable and adjustable doping effect of hydrazine. With a higher concentration of hydrazine, more electrons can be transferred from the hydrazine molecules to the SWCNT network films, thus resulting in a change of threshold voltage, carrier mobility and on-current. By cleaning the device, the hydrazine doping effects vanish, which indicates that the doping effects of hydrazine are reversible. Through x-ray photoelectron spectroscopy (XPS) characterization, the doping effects of hydrazine have also been studied.

  15. Arrays of TiO2 Nanowires as Photoelectrochemical Sensors for Hydrazine Detection

    Directory of Open Access Journals (Sweden)

    Michael Ongaro

    2015-05-01

    Full Text Available Electrodes based on arrays of TiO2 nanowires were prepared by template sol-gel synthesis with the goal of developing a hydrazine photoelectrochemical sensor. Experimental conditions were chosen so that the gelation reaction occurred inside the nanopores of track-etched polycarbonate membranes, with consequent filling with TiO2 nanowires. Different procedures for the removal of the template were examined, in order to obtain arrays of self-standing TiO2 nanowires. The nanowire arrays were bound to fluorine doped tin oxide substrates to produce handy photoelectrodes. The photocurrent recorded with the photoelectrodes in the presence of hydrazine showed significant dependence on the pollutant concentration. The development of a photoelectrochemical sensor for hydrazine detection in water samples, based on this principle, is presented.

  16. Development of partitioning process: back-extraction of actinoid and lanthanoid with hydrazine carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Masayuki; Morita, Yasuji; Kubota, Masumitsu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Tatsugae, Ryozo; Takada, Kiyoshi

    1999-05-01

    In the present study the back extraction of actinoid, lanthanoid, Y, Zr, and Mo from DIDPA [Diisodecylphosphoric Acid] and HDEHP [Di(2-ethylhexylphosphoric) Acid] was investigated by using hydrazine carbonate solution. Hydrazine carbonate is a salt-free reagent and easy to decompose. If it is possible to apply this reagent to the 4-group partitioning process, more sophisticated process would be constructed, because of the reduction of secondary wastes. All the elements other than Y could be back-extracted from HDEHP and all the elements other than Y and Mo could be back-extracted from DIDPA by hydrazine carbonate. It was found that the nature of alcohol which was added to avoid emulsification affects on the distribution ratio more than the added amount. (author)

  17. A biochemical and NMR spectroscopic study of hydrazine in the isolated rat hepatocyte

    Energy Technology Data Exchange (ETDEWEB)

    Ghatineh, S.; Morgan, W.; Timbrell, J.A. (London School of Pharmacy (United Kingdom). Dept. of Toxicology); Preece, N.E. (Hunterian Inst., Royal Coll. of Surgeons, London (United Kingdom). Dept. of Biophysics)

    1992-11-01

    Using isolated rat hepatocytes the biochemical effects of hydrazine have been investigated using both conventional assay techniques and high resolution proton NMR. High resolution proton NMR revealed that hydrazine caused a significant increase in alanine and lactate levels in the incubation buffer, whereas levels of [beta]-hydroxybutyrate were decreased. NMR also detected metabolites of hydrazine notably acetylhydrazine and a cyclised hydrazone formed with [alpha]-ketoglutarate. Changes were detected in NADH and NADPH, ATP, succinate dehydrogenase (SDH) and total non-protein sulphydryl groups (TNPSH). However, the changes in pyridine nucleotides occurred at higher concentrations than those affecting succinate dehydrogenase and ATP. Similarly, the depletion of TNPSH occurred at a higher concentration and with a different time course to that seen with ATP depletion and inhibition of succinate dehydrogenase. (orig.).

  18. Concentric-electrode organic electrochemical transistors: case study for selective hydrazine sensing

    Science.gov (United States)

    Pecqueur, S.; Lenfant, S.; Guérin, D.; Alibart, F.; Vuillaume, D.

    2017-12-01

    We report on hydrazine-sensing organic electrochemical transistors (OECTs) with a design consisting in concentric annular electrodes. The design engineering of these OECTs was motivated by the great potential of using OECT sensing arrays in fields such as bioelectronics. In this work, PEDOT:PSS-based OECTs have been studied as aqueous sensors, specifically sensitive to the lethal hydrazine molecule. These amperometric sensors have many relevant features for the development of hydrazine sensors, such as a sensitivity down to 10-5 M of hydrazine in water, an order of magnitude higher selectivity for hydrazine than for 9 other water soluble common analytes, the capability to recover entirely its base signal after water flushing and a very low voltage operation. The specificity for hydrazine to be sensed by our OECTs is caused by its catalytic oxidation at the gate electrode and enables increasing the output current modulation of the devices. This has permitted the device-geometry study of the whole series of 80 micrometric OECT devices with sub-20-nm PEDOT:PSS layers, channel lengths down to 1 μm and a specific device geometry of coplanar and concentric electrodes. The numerous geometries unravel new aspects of the OECT mechanisms governing the electrochemical sensing behaviours of the device, more particularly the effect of the contacts which are inherent at the micro-scale. By lowering the device cross-talking, micrometric gate-integrated radial OECTs shall contribute to the diminishing of the readout invasiveness and therefore promotes further the development of OECT biosensors.

  19. Concentric-Electrode Organic Electrochemical Transistors: Case Study for Selective Hydrazine Sensing

    Directory of Open Access Journals (Sweden)

    Sébastien Pecqueur

    2017-03-01

    Full Text Available We report on hydrazine-sensing organic electrochemical transistors (OECTs with a design consisting of concentric annular electrodes. The design engineering of these OECTs was motivated by the great potential of using OECT sensing arrays in fields such as bioelectronics. In this work, poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate (PEDOT:PSS-based OECTs have been studied as aqueous sensors that are specifically sensitive to the lethal hydrazine molecule. These amperometric sensors have many relevant features for the development of hydrazine sensors, such as a sensitivity down to 10−5 M of hydrazine in water, an order of magnitude higher selectivity for hydrazine than for nine other water-soluble common analytes, the capability to entirely recover its base signal after water flushing, and a very low operation voltage. The specificity for hydrazine to be sensed by our OECTs is caused by its catalytic oxidation at the gate electrode, and enables an increase in the output current modulation of the devices. This has permitted the device-geometry study of the whole series of 80 micrometric OECT devices with sub-20-nm PEDOT:PSS layers, channel lengths down to 1 µm, and a specific device geometry of coplanar and concentric electrodes. The numerous geometries unravel new aspects of the OECT mechanisms governing the electrochemical sensing behaviours of the device—more particularly the effect of the contacts which are inherent at the micro-scale. By lowering the device cross-talk, micrometric gate-integrated radial OECTs shall contribute to the diminishing of the readout invasiveness and therefore further promote the development of OECT biosensors.

  20. Carbon dioxide laser absorption spectra and low ppb photoacoustic detection of hydrazine fuels.

    Science.gov (United States)

    Loper, G L; Calloway, A R; Stamps, M A; Gelbwachs, J A

    1980-08-15

    Absorption cross-section data are reported for the toxic rocket fuels hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine (UDMH), as well as for their selected air oxidation products dimethylamine, trimethylamine, and methanol at up to seventy-eight CO(2) laser wavelengths each. These data are important for the assessment of the capability of CO(2) laser-based spectroscopic techniques for monitoring low levels of hydrazine-fuel vapors in the ambient air. Interference-free detection sensitivities of <30 ppb have been demonstrated for UDMH using a laboratory photoacoustic detection system.

  1. Synthesis, characterization and antioxidant study of N,N’-bis(2-chlorobenzamidothiocarbonyl)hydrazine

    Energy Technology Data Exchange (ETDEWEB)

    Firdausiah, Syadza; Hasbullah, Siti Aishah; Yamin, Bohari M. [School of Chemical Science and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

    2015-09-25

    N,N’-bis(2-chlorobenzamidothiocarbonyl)hydrazine was synthesized from 2-chlorobenzoylisothiocyanate and hydrazine in acetone. The compound was characterized by infrared, {sup 1}H and {sup 13}C NMR, and UV-Vis spectroscopies. X-ray crystallography study showed the molecule adopt trans configuration at both N-N and C-N bonds. The compound showed high antioxidant activity, EC{sub 50} of 374.89 µM, compared to ascorbic acid (EC{sub 50} of 561.36 µM)

  2. Highly sensitive hydrazine chemical sensor fabricated by modified electrode of vertically aligned zinc oxide nanorods.

    Science.gov (United States)

    Ameen, Sadia; Akhtar, M Shaheer; Shin, Hyung Shik

    2012-10-15

    A highly sensitive, reliable and reproducible hydrazine chemical sensor was fabricated using vertically aligned ZnO nanorods (NRs) electrode. The low temperature hydrothermal process was adopted to synthesize the vertically aligned ZnO NRs on fluorine doped tin oxide (FTO) glass. The morphological characterizations revealed the vertical arrangement of highly dense ZnO NRs on FTO substrates. The ultraviolet diffused reflectance spectroscopy (UV-DRS) of aligned ZnO NRs electrode obtained the band gap of ~3.29eV which was close to that of bulk ZnO nanomaterials. The synthesized aligned ZnO NRs electrode was directly used to elucidate the chemical sensing performance towards the detection of hydrazine by simple current-voltage (I-V) characteristics. The aligned ZnO NRs electrode based hydrazine chemical sensor presented a significantly high sensitivity of ~4.42446×10(-5) A mM(-1) cm(-2) and the detection limit of ~515.7 μM with a correlation coefficient (R) of ~0.73297 and a short response time (10s). The electrochemical analysis of vertically aligned ZnO NRs electrode in the presence of hydrazine showed the increased current with high height of anodic peak which confirmed the involvement of high electron transfer process via high electrocatalytic activity of the electrode. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Heterobifunctional Dyes: Highly Fluorescent Linkers Based on Cyanine Dyes

    OpenAIRE

    Wycisk, Virginia; Achazi, Katharina; Hirsch, Ole; Kuehne, Christian; Dernedde, Jens; Haag, Rainer; Licha, Kai

    2017-01-01

    Abstract Herein, we present a new synthetic route to cyanine?based heterobifunctional dyes and their application as fluorescent linkers between polymers and biomolecules. The synthesized compounds, designed in the visible spectral range, are equipped with two different reactive groups for highly selective conjugation under physiological conditions. By applying indolenine precursors with functionalized benzenes, we achieved water?soluble asymmetric cyanine dyes bearing maleimido and N?hydroxys...

  4. Polyimide Aerogels Using Triisocyanate as Cross-linker.

    Science.gov (United States)

    Nguyen, Baochau N; Meador, Mary Ann B; Scheiman, Daniel; McCorkle, Linda

    2017-08-16

    A family of polyimide (PI)-based aerogels is produced using Desmodur N3300A, an inexpensive triisocyanate, as the cross-linker. The aerogels are prepared by cross-linking amine end-capped polyimide oligomers with the triisocyanate. The polyimide oligomers are formulated using 2,2'-dimethylbenzidine, 4,4'-oxydianiline, or mixtures of both diamines, combined with 3,3',4,4'-biphenyltetracarboxylic dianhydride, and are chemically imidized at room temperature. Depending on the backbone chemistry, chain length, and polymer concentration, density of the aerogels ranged from 0.06 to 0.14 g/cm(3) and Brunauer-Emmett-Teller surface areas ranged from 350 to 600 m(2)/g. Compressive moduli of these aerogels were as high as 225 MPa, which are comparable to, or higher than, those previously reported prepared with similar backbone structures but with other cross-linkers. Because of their lower cost and commercial availability as cross-linker, the aerogels may have further potential as insulation for building and construction, clothing, sporting goods, and automotive applications, although lower-temperature stability may limit their use in some aerospace applications.

  5. Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor.

    Science.gov (United States)

    Heydari, Hamid; Gholivand, Mohammad B; Abdolmaleki, Abbas

    2016-09-01

    In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS-MWCNTs composite sensor (CuNS-MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50-800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. Copyright © 2016. Published by Elsevier B.V.

  6. Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor

    Energy Technology Data Exchange (ETDEWEB)

    Heydari, Hamid [Faculty of Sciences, Razi University, Kermanshah (Iran, Islamic Republic of); Gholivand, Mohammad B., E-mail: mbgholivand@razi.ac.ir [Faculty of Sciences, Razi University, Kermanshah (Iran, Islamic Republic of); Abdolmaleki, Abbas [Department of Chemistry, Malek Ashtar University of Technology, Tehran (Iran, Islamic Republic of)

    2016-09-01

    In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS–MWCNTs composite sensor (CuNS–MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800 μM with a low detection limit of 70 nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50–800 μM with the detection limit of 4.3 μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. - Highlights: • The Copper nanostructures (CuNS) were prepared by cyclic voltammetry deposition. • The CuNS-MWCNT/PGE sensor shows high activity toward hydrazine (N{sub 2}H{sub 4}). • The proposed sensor exhibits a wide linear range (0.1 to 800 μM), low detection limit (70 nM), high sensitivity and stability for hydrazine.

  7. Nucleosome assembly protein-1 is a linker histone chaperone in Xenopus eggs.

    Science.gov (United States)

    Shintomi, Keishi; Iwabuchi, Mari; Saeki, Hideaki; Ura, Kiyoe; Kishimoto, Takeo; Ohsumi, Keita

    2005-06-07

    In eukaryotic cells, genomic DNA is primarily packaged into nucleosomes through sequential ordered binding of the core and linker histone proteins. The acidic proteins termed histone chaperones are known to bind to core histones to neutralize their positive charges, thereby facilitating their proper deposition onto DNA to assemble the core of nucleosomes. For linker histones, however, little has been known about the regulatory mechanism for deposition of linker histones onto the linker DNA. Here we report that, in Xenopus eggs, the linker histone is associated with the Xenopus homologue of nucleosome assembly protein-1 (NAP-1), which is known to be a chaperone for the core histones H2A and H2B in Drosophila and mammalian cells [Ito, T., Bulger, M., Kobayashi, R. & Kadonaga, J. T. (1996) Mol. Cell Biol. 16, 3112-3124; Chang, L., Loranger, S. S., Mizzen, C., Ernst, S. G., Allis, C. D. & Annunziato, A. T. (1997) Biochemistry 36, 469-480]. We show that NAP-1 acts as the chaperone for the linker histone in both sperm chromatin remodeling into nucleosomes and linker histone binding to nucleosome core dimers. In the presence of NAP-1, the linker histone is properly deposited onto linker DNA at physiological ionic strength, without formation of nonspecific aggregates. These results strongly suggest that NAP-1 functions as a chaperone for the linker histone in Xenopus eggs.

  8. Nucleosomes, Linker DNA, and Linker Histone form a Unique Structural Motif that Directs the Higher-Order Folding and Compaction of Chromatin

    Science.gov (United States)

    Bednar, Jan; Horowitz, Rachel A.; Grigoryev, Sergei A.; Carruthers, Lenny M.; Hansen, Jeffrey C.; Koster, Abraham J.; Woodcock, Christopher L.

    1998-11-01

    The compaction level of arrays of nucleosomes may be understood in terms of the balance between the self-repulsion of DNA (principally linker DNA) and countering factors including the ionic strength and composition of the medium, the highly basic N termini of the core histones, and linker histones. However, the structural principles that come into play during the transition from a loose chain of nucleosomes to a compact 30-nm chromatin fiber have been difficult to establish, and the arrangement of nucleosomes and linker DNA in condensed chromatin fibers has never been fully resolved. Based on images of the solution conformation of native chromatin and fully defined chromatin arrays obtained by electron cryomicroscopy, we report a linker histone-dependent architectural motif beyond the level of the nucleosome core particle that takes the form of a stem-like organization of the entering and exiting linker DNA segments. DNA completes ≈ 1.7 turns on the histone octamer in the presence and absence of linker histone. When linker histone is present, the two linker DNA segments become juxtaposed ≈ 8 nm from the nucleosome center and remain apposed for 3-5 nm before diverging. We propose that this stem motif directs the arrangement of nucleosomes and linker DNA within the chromatin fiber, establishing a unique three-dimensional zigzag folding pattern that is conserved during compaction. Such an arrangement with peripherally arranged nucleosomes and internal linker DNA segments is fully consistent with observations in intact nuclei and also allows dramatic changes in compaction level to occur without a concomitant change in topology.

  9. (E)-1,1,4,4-Tetramethyl-2-tetrazene (TMTZ): A Prospective Alternative to Hydrazines in Rocket Propulsion.

    Science.gov (United States)

    Dhenain, Anne; Darwich, Chaza; Sabaté, Carlos Miró; Le, Duc-Minh; Bougrine, Anne-Julie; Delalu, Henri; Lacôte, Emmanuel; Payen, Léa; Guitton, Jérôme; Labarthe, Emilie; Jacob, Guy

    2017-07-21

    1,1,4,4-Tetramethyl-2-tetrazene (TMTZ) is considered as a prospective replacement for toxic hydrazines used in liquid rocket propulsion. The heat of formation of TMTZ was computed and measured, giving values well above those of the hydrazines commonly used in propulsion. This led to a predicted maximum I sp of 337 s for TMTZ/N 2 O 4 mixtures, which is a value comparable to that of monomethylhydrazine. We found that TMTZ has a vapor pressure well below that of liquid hydrazines, and it is far less toxic. Finally, an improved synthesis is proposed, which is compatible with existing industrial production facilities after minor changes. TMTZ is thus an attractive liquid propellant candidate, with a performance comparable to hydrazines but a lower vapor pressure and toxicity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Secondary chemistry of steam generator. Influence of hydrazine on corrosion potential. Optimisation of shutdown conditions and return to nominal conditions

    Energy Technology Data Exchange (ETDEWEB)

    Foucault, M.; Long, A.; Combrade, P. [Framatome-ANP, Paris (France); Rodet, I.; Bouchacourt, M. [EdF-SEPTEN, Lyon (France)

    2002-07-01

    The oxygen and hydrazine contents of the secondary environment have a great importance in the build-up and the modification of the oxide layer formed on carbon steel or LAS surfaces of the secondary side of the SG. These modifications may have an important influence on general release, deposits in tube support plates. A program has been carried out to evaluate the influence of hydrazine on the structure and the composition of the oxide layer formed on carbon steel in different environmental conditions: nominal conditions, hot shutdown transient with high or low hydrazine concentration and come back to nominal conditions after a hot shut down. In order to reach the aim of this program, a special device has been built on with the following main characteristics: temperature up to 320 C, secondary environment with control of hydrazine and oxygen content, water-flow velocity up to 1 m/s, measurement of electrochemical potential on Carbon Steel samples. (authors)

  11. Reactivity Studies of 2,6-Bis-(1,2,3-triazolyl)purine Nucleosides with Hydrazines and Amino Acids

    OpenAIRE

    Laķis, E; Novosjolova, I; Bizdēna, Ē; Turks, M

    2014-01-01

    Reactions of 2,6-bis-(1,2,3-triazolyl)purine nucleosides with nucleophiles is efficient route to C(6)-derivatization of purine base. To extend the field of application of the method, we studied reactivity of bis-(1,2,3-triazolyl)purine derivatives toward hydrazines and amino acids and obtained nucleosides substituted at C(6) with hydrazine and amino acid moieties.

  12. Formation of raspberry like cobalt particles with hydrazine reduction in a polyol route

    Science.gov (United States)

    Khe, Cheng Seong; Aziz, Azizan; Lockman, Zainovia; Rajalingam, Sokkalingam; Merican, Zulkifli; Vasant, Pandian

    2016-11-01

    This work describes the effect of hydrazine hydrate on the formation of the raspberry-like morphology of the cobalt nanomaterials in a polyol route. In the synthesis, the molar ratio of N2H4 to Co2+was varied from 2.5 to 10. At the beginning with low molar ratio, spherical microspheres were formed. When the molar ratio was increased to 5 and above, final morphology of the cobalt nanomaterials became raspberry-like. This might be attributed to the absorption of the hydrazine complex of cobalt nanoparticles at certain facets during their growth stage and later self-assembled into the raspberry shaped microparticles. The plausible formation mechanism were proposed.

  13. Towards Safer Rocket Fuels: Hypergolic Imidazolylidene-Borane Compounds as Replacements for Hydrazine Derivatives.

    Science.gov (United States)

    Huang, Shi; Qi, Xiujuan; Liu, Tianlin; Wang, Kangcai; Zhang, Wenquan; Li, Jianlin; Zhang, Qinghua

    2016-07-11

    Currently, toxic and volatile hydrazine derivatives are still the main fuel choices for liquid bipropellants, especially in some traditional rocket propulsion systems. Therefore, the search for safer hypergolic fuels as replacements for hydrazine derivatives has been one of the most challenging tasks. In this study, six imidazolylidene-borane compounds with zwitterionic structure have been synthesized and characterized, and their hypergolic reactivity has been studied. As expected, these compounds exhibited fast spontaneous combustion upon contact with white fuming nitric acid (WFNA). Among them, compound 5 showed excellent integrated properties including wide liquid operating range (-70-160 °C), superior loading density (0.99 g cm(-3) ), ultrafast ignition delay times with WFNA (15 ms), and high specific impulse (303.5 s), suggesting promising application potential as safer hypergolic fuels in liquid bipropellant formulations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Specific distribution of the Saccharomyces cerevisiae linker histone homolog HHO1p in the chromatin

    OpenAIRE

    Freidkin, Ilya; Katcoff, Don J.

    2001-01-01

    In virtually all eukaryotic organisms, linker DNA between nucleosomes is associated with a histone termed linker histone or histone H1. In Saccharomyces cerevisiae, HHO1 encodes a putative linker histone with very significant homology to histone H1. The encoded protein is expressed in the nucleus, but has not been shown to affect global chromatin structure, nor has its deletion shown any detectable phenotype. In vitro chromatin assembly experiments with recombinant HHO1p have shown that it is...

  15. Anode catalysts for direct hydrazine fuel cells: from laboratory test to an electric vehicle.

    Science.gov (United States)

    Serov, Alexey; Padilla, Monica; Roy, Aaron J; Atanassov, Plamen; Sakamoto, Tomokazu; Asazawa, Koichiro; Tanaka, Hirohisa

    2014-09-22

    Novel highly active electrocatalysts for hydrazine hydrate fuel cell application were developed, synthesized and integrated into an operation vehicle prototype. The materials show in both rotating disc electrode (RDE) and membrane electrode assembly (MEA) tests the world highest activity with peak current density of 16,000 A g(-1) (RDE) and 450 mW cm(-2) operated in air (MEA). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. (E)-1-Benzyl-idene-2,2-diphenyl-hydrazine.

    Science.gov (United States)

    Mendoza, Angel; Meléndrez-Luevano, Ruth; Cabrera-Vivas, Blanca M; Lozano-Márquez, Claudia D; Carranza, Vladimir

    2012-02-01

    The asymmetric unit of the title compound, C(19)H(16)N(2), contains two independent mol-ecules, both of which show an E configuration with respect to the C=N bond. The dihedral angles between the phenyl rings bonded to the hydrazine group are 81.00 (10) and 88.34 (8)° in the two mol-ecules. Inter-molecular C-H⋯π inter-actions are observed in the crystal structure.

  17. Reactivity of 4-tert-Butyldimethylsiloxy-1,2,3,6-tetrahydropyridines with Hydrazines

    Directory of Open Access Journals (Sweden)

    Manuel Medarde

    2006-11-01

    Full Text Available The reactivity of 6-(nitrophenyl or trimethoxyphenyl-4-tert-butyldimethyl- siloxy-1,2,3,6-tetrahydropyridine derivatives with hydrazines under acid conditions is described. The structure of the products isolated − hydrazones, pyrazolines or pyridazinones − depended on the conditions used. In addition, a systematic study of the reaction outcomes was carried out by introducing variations on the substituents of the tetrahydropyridine ring.

  18. Preparation of Peptide p-Nitroanilides using an Aryl Hydrazine Solid Support

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Y; Welsh, K; Mitchell, A R; Camarero, J A

    2004-08-05

    Peptide p-nitroanilides are useful compounds for studying protease activity, however the poor nucleophilicity of p-nitroaniline makes their preparation difficult. We describe a new efficient approach for the Fmoc-based synthesis of peptide p-nitroanilides using an aryl hydrazine resin. Mild oxidation of the peptide hydrazide resin yields a highly reactive acyl diazene, which efficiently reacts with weak nucleophiles. We have prepared several peptide p-nitroanilides, including substrates for the Lethal Factor protease from B. anthracis.

  19. Nanostructured SnO2 encapsulated guar-gum hybrid nanocomposites for electrocatalytic determination of hydrazine.

    Science.gov (United States)

    Malik, Priya; Srivastava, Manish; Verma, Ranjana; Kumar, Manish; Kumar, D; Singh, Jay

    2016-01-01

    The present article deals with synthesis of sol-gel derived tin dioxide (SnO2) nanoparticles encapsulated in to guar gum (GG) biopolymer as the organic-inorganic hybrid materials for the determination of hydrazine. The organic-inorganic hybrid combines the perfunctory strength offered by the inorganic SnO2 nanoparticles with flexible binding sites provided by the organic biopolymer (GG) solution by the ultrasonication. The phase identification, crystalline size, surface morphology and optical properties of prepared SnO2 and SnO2-GG nanocomposites has been investigated through FT-IR, XRD, SEM, AFM, TEM, UV-Vis, and PL techniques. The colloidal solution of SnO2 and GG is electrophoretically deposited (EPD) onto the indium tin-oxide (ITO) glass substrate and studied for the electrooxidation of hydrazine. Under the optimized experimental conditions, the linearity between the current response and the hydrazine concentration has been obtained in the range of 2-22 mM, with a low detection limit of 2.76 mM and a high sensitivity of 5.72 μA cm(-2). Based on the linear increase in amperometric current, a sensitive hydrazine electrochemical sensor is constructed. The proposed SnO2-GG/ITO electrode shows a good response time (35s), reproducibility, and long-term stability. The obtained results suggest that SnO2-GG nanocomposites electrode provides a favorable sensing platform for the electrochemical studies. In addition, the cyclic voltammetry (CV) studies are used to evaluate the kinetic parameters. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Hydrazine Blending and Storage Facility, Interim Response Action Implementation. Final Safety Plan

    Science.gov (United States)

    1989-08-30

    gestion . EFFECTS OF ACUTE EXPOSURE Corr. To eyes. sKin. mucous memo. Tem. 0liniress. o’czzness, rausea. CNS cezr. :amage to liver, lungs, kicneysolocC ard... Humana Hospital 1501 S. Potomac 695-2600 12.6.3 Emergency Telephone Call Protocol Give: Name Telephone Number Address Location, if different than address...07 25 SCALEA ARMY CENTER L)AURORA 2.NVER APRESBYTERIANHOSPITAL C ~ ~ HUMANA [ HOSPITALPTL SHO CCor AOr HYDRAZINE BLENDING AND STORAGE FACILITY

  1. Tunable CO 2 Adsorbents by Mixed-Linker Synthesis and Postsynthetic Modification of Zeolitic Imidazolate Frameworks

    KAUST Repository

    Thompson, Joshua A.

    2013-04-25

    The incorporation of accessible amine functionality in zeolitic imidazolate frameworks (ZIFs) is used to improve the adsorption selectivity for CO 2/CH4 gas separation applications. Two synthetic approaches are described in this work to introduce functionality into the ZIF: (i) mixed-linker ZIF synthesis with 2-aminobenzimidazole as a substitution linker and (ii) postsynthetic modification of a mixed-linker ZIF with ethylenediamine. Using 2-aminobenzimidazole, a linker with a primary amine functional group, substitution of the ZIF-8 linker during synthesis allows for control over the adsorption properties while maintaining the ZIF-8 structure with up to nearly 50% substitution in the mixed-linker ZIF framework, producing a material with tunable pore size and amine functionality. Alternatively, postsynthetic modification of a mixed-linker ZIF containing an aldehyde functional group produces a ZIF material with a primary amine without detrimental loss of micropore volume by controlling the amount of functional group sites for modification. Both approaches using mixed-linker ZIFs yield new materials that show improvement in adsorption selectivity for the CO 2/CH4 gas pair over ZIF-8 and commercially available adsorbents as well as an increase in the heat of adsorption for CO2 without significant changes to the crystal structure. These results indicate that tuning the surface properties of ZIFs by either mixed-linker synthesis and/or postsynthetic modification may generate new materials with improved gas separation properties, thereby providing a new method for tailoring metal-organic frameworks. © 2013 American Chemical Society.

  2. Balancing BMP Signaling through Integrated Inputs into the Smad1 Linker

    National Research Council Canada - National Science Library

    Sapkota, Gopal; Alarcón, Claudio; Spagnoli, Francesca M; Brivanlou, Ali H; Massagué, Joan

    2007-01-01

    .... BMP receptors signal through C-terminal phosphorylation and nuclear translocation of the transcription factor Smad1, whereas MAPKs catalyze inhibitory phosphorylation in the Smad1 linker region...

  3. Tuning the structure and function of metal-organic frameworks via linker design.

    Science.gov (United States)

    Lu, Weigang; Wei, Zhangwen; Gu, Zhi-Yuan; Liu, Tian-Fu; Park, Jinhee; Park, Jihye; Tian, Jian; Zhang, Muwei; Zhang, Qiang; Gentle, Thomas; Bosch, Mathieu; Zhou, Hong-Cai

    2014-08-21

    Metal-organic frameworks (MOFs) are constructed from metal ions/clusters coordinated by organic linkers (or bridging-ligands). The hallmark of MOFs is their permanent porosity, which is frequently found in MOFs constructed from metal-clusters. These clusters are often formed in situ, whereas the linkers are generally pre-formed. The geometry and connectivity of a linker dictate the structure of the resulting MOF. Adjustments of linker geometry, length, ratio, and functional-group can tune the size, shape, and internal surface property of a MOF for a targeted application. In this critical review, we highlight advances in MOF synthesis focusing on linker design. Examples of building MOFs to reach unique properties, such as unprecedented surface area, pore aperture, molecular recognition, stability, and catalysis, through linker design are described. Further search for application-oriented MOFs through judicious selection of metal clusters and organic linkers is desirable. In this review, linkers are categorized as ditopic (Section 1), tritopic (Section 2), tetratopic (Section 3), hexatopic (Section 4), octatopic (Section 5), mixed (Section 6), desymmetrized (Section 7), metallo (Section 8), and N-heterocyclic linkers (Section 9).

  4. Germline-specific H1 variants: the "sexy" linker histones.

    Science.gov (United States)

    Pérez-Montero, Salvador; Carbonell, Albert; Azorín, Fernando

    2016-03-01

    The eukaryotic genome is packed into chromatin, a nucleoprotein complex mainly formed by the interaction of DNA with the abundant basic histone proteins. The fundamental structural and functional subunit of chromatin is the nucleosome core particle, which is composed by 146 bp of DNA wrapped around an octameric protein complex formed by two copies of each core histone H2A, H2B, H3, and H4. In addition, although not an intrinsic component of the nucleosome core particle, linker histone H1 directly interacts with it in a monomeric form. Histone H1 binds nucleosomes near the exit/entry sites of linker DNA, determines nucleosome repeat length and stabilizes higher-order organization of nucleosomes into the ∼30 nm chromatin fiber. In comparison to core histones, histone H1 is less well conserved through evolution. Furthermore, histone H1 composition in metazoans is generally complex with most species containing multiple variants that play redundant as well as specific functions. In this regard, a characteristic feature is the presence of specific H1 variants that replace somatic H1s in the germline and during early embryogenesis. In this review, we summarize our current knowledge about their structural and functional properties.

  5. Electrochemical behavior of rhodium acetamidate immobilized on a carbon paste electrode: a hydrazine sensor

    Directory of Open Access Journals (Sweden)

    Gil Eric de S.

    2000-01-01

    Full Text Available The electrochemical behavior of rhodium acetamidate immobilized in carbon paste electrode and the consequences for sensor construction were evaluated. The electrode showed good stability and redox properties. Two reversible redox couples with midpoint potentials between 0.15 and 0.55 V vs SCE were observed. However, peak resolution in voltammetric studies was very dependent on the supporting electrolyte. The correlation between coordinating power of the electrolyte and peak potential suggests that the electrolyte can coordinate through the axial position of the complexes. Furthermore, the axial position may be also the catalytic site, as a catalytical response was observed for hydrazine oxidation. A good linear response range for hydrazine was fit by the equation i = 23.13 (± 0.34 c , where i = current in mA and c = concentration in mol dm-3 in the range of 10-5 up to 10-2 mol dm-3. The low applied potential (<300 mV indicates a good device for hydrazine sensor, minimizing interference problems. The short response time (~1 s may be useful in flow injection analysis. Furthermore, this system was very stable presenting good repeatability even after 30 measurements with a variance of 0.5 %.

  6. Redox Response of Reduced Graphene Oxide-Modified Glassy Carbon Electrodes to Hydrogen Peroxide and Hydrazine

    Directory of Open Access Journals (Sweden)

    Jun-ichi Anzai

    2013-05-01

    Full Text Available The surface of a glassy carbon (GC electrode was modified with reduced graphene oxide (rGO to evaluate the electrochemical response of the modified GC electrodes to hydrogen peroxide (H2O2 and hydrazine. The electrode potential of the GC electrode was repeatedly scanned from −1.5 to 0.6 V in an aqueous dispersion of graphene oxide (GO to deposit rGO on the surface of the GC electrode. The surface morphology of the modified GC electrode was characterized by scanning electron microscopy (SEM and atomic force microscopy (AFM. SEM and AFM observations revealed that aggregated rGO was deposited on the GC electrode, forming a rather rough surface. The rGO-modified electrodes exhibited significantly higher responses in redox reactions of H2O2 as compared with the response of an unmodified GC electrode. In addition, the electrocatalytic activity of the rGO-modified electrode to hydrazine oxidation was also higher than that of the unmodified GC electrode. The response of the rGO-modified electrode was rationalized based on the higher catalytic activity of rGO to the redox reactions of H2O2 and hydrazine. The results suggest that rGO-modified electrodes are useful for constructing electrochemical sensors.

  7. Hydrazide and hydrazine reagents as reactive matrices for MALDI-MS to detect gaseous aldehydes.

    Science.gov (United States)

    Shigeri, Yasushi; Ikeda, Shinya; Yasuda, Akikazu; Ando, Masanori; Sato, Hiroaki; Kinumi, Tomoya

    2014-08-01

    The reagents 19 hydrazide and 14 hydrazine were examined to function as reactive matrices for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to detect gaseous aldehydes. Among them, two hydrazide (2-hydroxybenzohydrazide and 3-hydroxy-2-naphthoic acid hydrazide) and two hydrazine reagents [2-hydrazinoquinoline and 2,4-dinitrophenylhydrazine (DNPH)] were found to react efficiently with carbonyl groups of gaseous aldehydes (formaldehyde, acetaldehyde and propionaldehyde); these are the main factors for sick building syndrome and operate as reactive matrices for MALDI-MS. Results from accurate mass measurements by JMS-S3000 Spiral-TOF suggested that protonated ion peaks corresponding to [M + H](+) from the resulting derivatives were observed in all cases with the gaseous aldehydes in an incubation, time-dependent manner. The two hydrazide and two hydrazine reagents all possessed absorbances at 337 nm (wavelength of MALDI nitrogen laser), with, significant electrical conductivity of the matrix crystal and functional groups, such as hydroxy group and amino group, being important for desorption/ionization efficiency in MALDI-MS. To our knowledge, this is the first report that gaseous molecules could be derivatized and detected directly in a single step by MALDI-MS using novel reactive matrices that were derivatizing agents with the ability to enhance desorption/ionization efficiency. Copyright © 2014 John Wiley & Sons, Ltd.

  8. Cellulase linkers are optimized based on domain type and function: insights from sequence analysis, biophysical measurements, and molecular simulation.

    Directory of Open Access Journals (Sweden)

    Deanne W Sammond

    Full Text Available Cellulase enzymes deconstruct cellulose to glucose, and are often comprised of glycosylated linkers connecting glycoside hydrolases (GHs to carbohydrate-binding modules (CBMs. Although linker modifications can alter cellulase activity, the functional role of linkers beyond domain connectivity remains unknown. Here we investigate cellulase linkers connecting GH Family 6 or 7 catalytic domains to Family 1 or 2 CBMs, from both bacterial and eukaryotic cellulases to identify conserved characteristics potentially related to function. Sequence analysis suggests that the linker lengths between structured domains are optimized based on the GH domain and CBM type, such that linker length may be important for activity. Longer linkers are observed in eukaryotic GH Family 6 cellulases compared to GH Family 7 cellulases. Bacterial GH Family 6 cellulases are found with structured domains in either N to C terminal order, and similar linker lengths suggest there is no effect of domain order on length. O-glycosylation is uniformly distributed across linkers, suggesting that glycans are required along entire linker lengths for proteolysis protection and, as suggested by simulation, for extension. Sequence comparisons show that proline content for bacterial linkers is more than double that observed in eukaryotic linkers, but with fewer putative O-glycan sites, suggesting alternative methods for extension. Conversely, near linker termini where linkers connect to structured domains, O-glycosylation sites are observed less frequently, whereas glycines are more prevalent, suggesting the need for flexibility to achieve proper domain orientations. Putative N-glycosylation sites are quite rare in cellulase linkers, while an N-P motif, which strongly disfavors the attachment of N-glycans, is commonly observed. These results suggest that linkers exhibit features that are likely tailored for optimal function, despite possessing low sequence identity. This study suggests

  9. Dependence of the Linker Histone and Chromatin Condensation on the Nucleosome Environment.

    Science.gov (United States)

    Perišić, Ognjen; Schlick, Tamar

    2017-08-24

    The linker histone (LH), an auxiliary protein that can bind to chromatin and interact with the linker DNA to form stem motifs, is a key element of chromatin compaction. By affecting the chromatin condensation level, it also plays an active role in gene expression. However, the presence and variable concentration of LH in chromatin fibers with different DNA linker lengths indicate that its folding and condensation are highly adaptable and dependent on the immediate nucleosome environment. Recent experimental studies revealed that the behavior of LH in mononucleosomes markedly differs from that in small nucleosome arrays, but the associated mechanism is unknown. Here we report a structural analysis of the behavior of LH in mononucleosomes and oligonucleosomes (2-6 nucleosomes) using mesoscale chromatin simulations. We show that the adapted stem configuration heavily depends on the strength of electrostatic interactions between LH and its parental DNA linkers, and that those interactions tend to be asymmetric in small oligonucleosome systems. Namely, LH in oligonucleosomes dominantly interacts with one DNA linker only, as opposed to mononucleosomes where LH has similar interactions with both linkers and forms a highly stable nucleosome stem. Although we show that the LH condensation depends sensitively on the electrostatic interactions with entering and exiting DNA linkers, other interactions, especially by nonparental cores and nonparental linkers, modulate the structural condensation by softening LH and thus making oligonucleosomes more flexible, in comparison to to mono- and dinucleosomes. We also find that the overall LH/chromatin interactions sensitively depend on the linker length because the linker length determines the maximal nucleosome stem length. For mononucleosomes with DNA linkers shorter than LH, LH condenses fully, while for DNA linkers comparable or longer than LH, the LH extension in mononucleosomes strongly follows the length of DNA linkers

  10. Electroless plating of Ni–B film as a binder-free highly efficient electrocatalyst for hydrazine oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Xiao-Ping; Dai, Hong-Bin, E-mail: mshbdai@scut.edu.cn; Wu, Lin-Song; Wang, Ping, E-mail: mspwang@scut.edu.cn

    2017-07-01

    Graphical abstract: A Ni–B film was grown on Ni foam to form a binder-free highly efficient electrocatalyst for hydrazine oxidation in alkaline medium. The newly-developed Ni–B/Ni foam electrocatalyst may promote the practical application of hydrazine as a viable energy carrier for fuel cells. - Highlights: • A Ni–B film grown on Ni foam electrocatalyst is prepared by the electrless plating. • The Ni–B film shows high activity and stability for N{sub 2}H{sub 4} electrooxidation reaction. • The improved catalytic property is ascribed to B-tuned electronic structure of Ni. • The resultant catalyst may promote application of N{sub 2}H{sub 4} as a viable energy carrier. - Abstract: Hydrazine is a promising energy carrier for fuel cells owing to its combined advantages of high theoretical cell voltage, high-power density, and no greenhouse gas emission. By using an electroless plating process, we have prepared a robust Ni–B film grown on Ni foam that is highly effective for hydrazine electrooxidation in alkaline media. The effects of reaction temperature, concentrations of hydrous hydrazine and sodium hydroxide in the fuel solution on performance of hydrazine electrooxidation reaction are investigated. The mechanistic reason for the property advantage of as-prepared Ni–B/Ni foam catalyst over the relevant catalysts is discussed based on careful kinetics studies and characterization. The facile synthesis of Ni-based catalyst with high activity and good stability is of clear significance for the development of hydrous hydrazine as a viable energy carrier.

  11. A New Methodology for Incorporating Chiral Linkers into Stapled Peptides.

    Science.gov (United States)

    Serrano, Juan C; Sipthorp, James; Xu, Wenshu; Itzhaki, Laura S; Ley, Steven V

    2017-06-19

    Stapled peptides have arisen as a new class of chemical probe and potential therapeutic agents for modulating protein-protein interactions. Here, we report the first two-component i,i+7 stapling methodology that makes use of two orthogonal, on-resin stapling reactions to incorporate linkers bearing a chiral centre into a p53-derived stapled peptide. Post-stapling modifications to the chain were performed on-resin and enabled rapid access to various peptide derivatives from a single staple. The stapled peptides have increased helicity, protease stability and in vitro binding affinities to MDM2 compared to the equivalent unstapled peptide. This approach can be used to generate a library of diverse stapled peptides with different properties starting from a single stapled peptide, with scope for much greater functional diversity than that provided by existing stapling methodologies. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  12. Linker-determined drug release mechanism of free camptothecin from self-assembling drug amphiphiles.

    Science.gov (United States)

    Cheetham, Andrew G; Ou, Yu-Chuan; Zhang, Pengcheng; Cui, Honggang

    2014-06-07

    We report here that the release mechanism of free camptothecin from self-assembling drug amphiphiles can be regulated by use of different linker groups. Our results highlight the significance of the linker group of drug amphiphiles on the drug release efficiency and their consequent in vitro efficacy.

  13. A traceless photocleavable linker for the automated glycan assembly of carbohydrates with free reducing ends.

    Science.gov (United States)

    Wilsdorf, M; Schmidt, D; Bartetzko, M P; Dallabernardina, P; Schuhmacher, F; Seeberger, P H; Pfrengle, F

    2016-08-09

    We report a traceless photocleavable linker for the automated glycan assembly of carbohydrates with free reducing ends. The reductive-labile functionality in the linker tolerates all commonly used reagents and protocols for automated glycan assembly, as demonstrated with the successful preparation of nine plant cell wall-related oligosaccharides, and is cleaved by hydrogenolysis.

  14. Dipolar cross-linkers for PDMS networks with enhanced dielectric permittivity and low dielectric loss

    DEFF Research Database (Denmark)

    Bahrt, Frederikke; Daugaard, Anders Egede; Hvilsted, Søren

    2013-01-01

    -(4-((4-nitrophenyl)diazenyl)phenoxy)-prop-1-yn-1-ylium, with a synthesized silicone compatible azide-functional cross-linker by click chemistry. The thermal, mechanical and electromechanical properties were investigated for PDMS films with 0 to 3.6 wt% of dipole-cross-linker. The relative dielectric permittivity...

  15. Description of a cellulose-binding domain and a linker sequence from Aspergillus fungi

    NARCIS (Netherlands)

    Quentin, M; Ebbelaar, M; Derksen, J; Mariani, C; van der Valk, H

    A family I cellulose-binding domain (CBD) and a serine- and threonine-rich linker peptide were cloned from the fungi Aspergillus japonicus and Aspergillus aculeatus. A glutathione S-transferase (GST) fusion protein comprising GST and a peptide linker with the CBD fused to its C-terminus, was

  16. Linker Installation: Engineering Pore Environment with Precisely Placed Functionalities in Zirconium MOFs.

    Science.gov (United States)

    Yuan, Shuai; Chen, Ying-Pin; Qin, Jun-Sheng; Lu, Weigang; Zou, Lanfang; Zhang, Qiang; Wang, Xuan; Sun, Xing; Zhou, Hong-Cai

    2016-07-20

    Precise placement of multiple functional groups in a highly ordered metal-organic framework (MOF) platform allows the tailoring of the pore environment, which is required for advanced applications. To realize this, we present a comprehensive study on the linker installation method, in which a stable MOF with coordinatively unsaturated Zr6 clusters was employed and linkers bearing different functional groups were postsynthetically installed. A Zr-MOF with inherent missing linker sites, namely, PCN-700, was initially constructed under kinetic control. Twelve linkers with different substituents were then designed to study their effect on MOF formation kinetics and therefore resulting MOF structures. Guided by the geometrical analysis, linkers with different lengths were installed into a parent PCN-700, giving rise to 11 new MOFs and each bearing up to three different functional groups in predefined positions. Systematic variation of the pore volume and decoration of pore environment were realized by linker installation, which resulted in synergistic effects including an enhancement of H2 adsorption capacities of up to 57%. In addition, a size-selective catalytic system for aerobic alcohol oxidation reaction is built in PCN-700 through linker installation, which shows high activity and tunable size selectivity. Altogether, these results exemplify the capability of the linker installation method in the pore environment engineering of stable MOFs with multiple functional groups, giving an unparalleled level of control.

  17. Hemidesmosomal linker proteins regulate cell motility, invasion and tumorigenicity in oral squamous cell carcinoma derived cells.

    Science.gov (United States)

    Chaudhari, Pratik Rajeev; Charles, Silvania Emlit; D'Souza, Zinia Charlotte; Vaidya, Milind Murlidhar

    2017-11-15

    BPAG1e and Plectin are hemidesmosomal linker proteins which anchor intermediate filament proteins to the cell surface through β4 integrin. Recent reports indicate that these proteins play a role in various cellular processes apart from their known anchoring function. However, the available literature is inconsistent. Further, the previous study from our laboratory suggested that Keratin8/18 pair promotes cell motility and tumor progression by deregulating β4 integrin signaling in oral squamous cell carcinoma (OSCC) derived cells. Based on these findings, we hypothesized that linker proteins may have a role in neoplastic progression of OSCC. Downregulation of hemidesmosomal linker proteins in OSCC derived cells resulted in reduced cell migration accompanied by alterations in actin organization. Further, decreased MMP9 activity led to reduced cell invasion in linker proteins knockdown cells. Moreover, loss of these proteins resulted in reduced tumorigenic potential. SWATH analysis demonstrated upregulation of N-Myc downstream regulated gene 1 (NDRG1) in linker proteins downregulated cells as compared to vector control cells. Further, the defects in phenotype upon linker proteins ablation were rescued upon loss of NDRG1 in linker proteins knockdown background. These data together indicate that hemidesmosomal linker proteins regulate cell motility, invasion and tumorigenicity possibly through NDRG1 in OSCC derived cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Novel silicone compatible cross-linkers for controlled functionalization of PDMS networks

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    2013-01-01

    Polydimethylsiloxane (PDMS) elastomers are excellent materials for dielectric electroactive polymers (DEAPs) due to their high efficiency and fast response. PDMS suffers, however, from low dielectric permittivity and high voltages are therefore required when the material is used for DEAP actuators....... In order to improve the dielectric properties of PDMS a novel system is developed where push-pull dipoles are grafted to a new silicone compatible cross-linker. The grafted cross-linkers are prepared by reaction of two different push-pull dipole alkynes as well as a fluorescent alkyne with the new azide......-functional cross-linker by click chemistry. The dipole cross-linkers are used to prepare PDMS elastomers of various chains lengths providing different network densities. The functionalized cross-linkers are incorporated successfully into the networks and are well distributed as determined by the fluorescent...

  19. Versatile Platform for the Synthesis of Orthogonally Cleavable Heteromultifunctional Cross-Linkers.

    Science.gov (United States)

    Sorkin, Michelle R; Walker, Joshua A; Brown, Joseph S; Alabi, Christopher A

    2017-04-19

    Cleavable and heteromultifunctional cross-linkers have proven critical in a wide range of biological applications. Traditional approaches for synthesizing these linkers suffer from various synthetic and functional limitations. In this work, an efficient sequence-defined synthetic methodology, developed for the assembly of oligothioetheramides, was used to address many of these limitations. Four heterotrifunctional cross-linkers with up to two orthogonal internal cleavage sites were synthesized. These linkers were conjugated to a pair of fluorophores that undergo Förster resonance energy transfer (FRET) and a model protein-human transferrin. Orthogonal bond cleavage was validated by mass spectrometry, fluorescent gel electrophoresis, and confocal microscopy. These studies demonstrate the versatility and biological utility of oligothioetheramides as a new class of multifunctional chemical cross-linkers and biologically relevant fluorescent probes.

  20. Construction of hierarchically porous metal-organic frameworks through linker labilization

    Science.gov (United States)

    Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; Li, Jialuo; Huang, Lan; Feng, Liang; Wang, Xuan; Bosch, Mathieu; Alsalme, Ali; Cagin, Tahir; Zhou, Hong-Cai

    2017-05-01

    A major goal of metal-organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.

  1. Construction of hierarchically porous metal–organic frameworks through linker labilization

    Science.gov (United States)

    Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; Li, Jialuo; Huang, Lan; Feng, Liang; Wang, Xuan; Bosch, Mathieu; Alsalme, Ali; Cagin, Tahir; Zhou, Hong-Cai

    2017-01-01

    A major goal of metal–organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis. PMID:28541301

  2. An Improved Calibration Method for Hydrazine Monitors for the United States Air Force

    Energy Technology Data Exchange (ETDEWEB)

    Korsah, K

    2003-07-07

    This report documents the results of Phase 1 of the ''Air Force Hydrazine Detector Characterization and Calibration Project''. A method for calibrating model MDA 7100 hydrazine detectors in the United States Air Force (AF) inventory has been developed. The calibration system consists of a Kintek 491 reference gas generation system, a humidifier/mixer system which combines the dry reference hydrazine gas with humidified diluent or carrier gas to generate the required humidified reference for calibrations, and a gas sampling interface. The Kintek reference gas generation system itself is periodically calibrated using an ORNL-constructed coulometric titration system to verify the hydrazine concentration of the sample atmosphere in the interface module. The Kintek reference gas is then used to calibrate the hydrazine monitors. Thus, coulometric titration is only used to periodically assess the performance of the Kintek reference gas generation system, and is not required for hydrazine monitor calibrations. One advantage of using coulometric titration for verifying the concentration of the reference gas is that it is a primary standard (if used for simple solutions), thereby guaranteeing, in principle, that measurements will be traceable to SI units (i.e., to the mole). The effect of humidity of the reference gas was characterized by using the results of concentrations determined by coulometric titration to develop a humidity correction graph for the Kintek 491 reference gas generation system. Using this calibration method, calibration uncertainty has been reduced by 50% compared to the current method used to calibrate hydrazine monitors in the Air Force inventory and calibration time has also been reduced by more than 20%. Significant findings from studies documented in this report are the following: (1) The Kintek 491 reference gas generation system (generator, humidifier and interface module) can be used to calibrate hydrazine detectors. (2) The

  3. Spectrophotometric determination of pico-molar level of hydrazine by using Alizarin red in water and urine samples

    Science.gov (United States)

    Arulraj, Abraham Daniel; Vijayan, Muthunanthevar; Vasantha, Vairathevar Sivasamy

    2015-09-01

    In this paper, very simple and rapid sensor has been developed for the spectrophotometric determination of pico-molar level of hydrazine using Alizarin red. There was a decrease of optical intensity of the probe in the presence of hydrazine. The LOD is calculated from the linear graph between 5-100 pM as 0.66 pM of hydrazine which is well below the risk level proposed by Agency for Toxic Substance and Disease Registry. The probe selectivity for the detection of hydrazine was tested in the presence of commonly encountered metal ions and anions. The calibration curves showed good linearity for working ranges from 5-100 pM and 0.5-40 mM respectively, with R2 = 0.9911 and 0.9744, indicate the validity of the Beer-Lambert law. The binding constant and the free energy change values are determined by the Benesi-Hildebrand method. Determination of hydrazine in environmental water and human urine samples are successfully performed by the proposed method with the recovery of 100%.

  4. Thionine-Bromate as a New Reaction System for Kinetic Spectrophotometric Determination of Hydrazine in Cooling Tower Water Samples

    Directory of Open Access Journals (Sweden)

    Masoud Reza Shishehbore

    2013-01-01

    Full Text Available A simple, selective, and inexpensive kinetic method was developed for the determination of hydrazine based on its inhibitory effect on the thionine-bromate system in sulfuric acid media. The reaction was monitored spectrophotometrically at 601 nm by a fixed time method. The effect of different parameters such as concentration of reactants, ionic strength, temperature, and time on the rate of reaction was investigated, and the optimum conditions were obtained. Under optimum conditions, the calibration curve was linear in the concentration range from 0.8–23.0 μg mL−1 of hydrazine, and the detection limit of the method was 0.22 μg mL−1. The relative standard deviation for five replicate determinations of 1.0 μg mL−1 of hydrazine was 0.74%. The potential of interfering effect of foreign species on the hydrazine determination was studied. The proposed method was successfully applied for the determination of hydrazine in different water samples.

  5. Bisquaternary pyridinium oximes: Comparison of in-vitro reactivation potency of compounds bearing aliphatic linkers and heteroaromatic linkers for paraoxon-inhibited electric eel and recombinant human acetylcholinesterase

    Science.gov (United States)

    Bharate, Sandip B.; Guo, Lilu; Reeves, Tony E.; Cerasoli, Douglas M.; Thompson, Charles M.

    2009-01-01

    Oxime reactivators are the drugs of choice for the post-treatment of OP (organophosphorus) intoxication and used widely for mechanistic and kinetic studies of OP-inhibited cholinesterases. The purpose of the present study was to evaluate new oxime compounds to reactivate acetylcholinesterase (AChE) inhibited by the OP paraoxon. Several new bisquaternary pyridinium oximes with heterocyclic linkers along with some known bisquaternary pyridinium oximes bearing aliphatic linkers were synthesized and evaluated for their in vitro reactivation potency against paraoxon-inhibited electric eel acetylcholinesterase (EeAChE) and recombinant human acetylcholinesterase (rHuAChE). Results herein indicate that most of the compounds are better reactivators of EeAChE than of rHuAChE. The reactivation potency of two different classes of compounds with varying linker chains was compared and observed that the structure of the connecting chain is an important factor for the activity of the reactivators. At a higher concentration (10−3 M), compounds bearing aliphatic linker showed better reactivation than compounds with heterocyclic linkers. Interestingly, oximes with a heterocyclic linker inhibited AChE at higher concentration (10−3 M), whereas their ability to reactivate was increased at lower concentrations (10−4 M and 10−5 M). Compounds bearing either a thiophene linker 26, 46 or a furan linker 31 showed 59%, 49% and 52% reactivation of EeAChE, respectively, at 10−5 M. These compounds showed 14%, 6% and 15% reactivation of rHuAChE at 10−4 M. Amongst newly synthesized analogs with heterocyclic linkers (26–35 and 45–46), compound 31, bearing furan linker chain, was found to be the most effective reactivator with a kr 0.042 min−1, which is better than obidoxime (3) for paraoxon-inhibited EeAChE. Compound 31 showed a kr 0.0041 min−1 that is near equal to pralidoxime (1) for paraoxon-inhibited rHuAChE. PMID:20005727

  6. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Guy [Univ. of California, San Diego, CA (United States)

    2012-06-29

    The efficient and selective preparation of organic molecules is critical for mankind. For the future, it is of paramount importance to find catalysts able to transform abundant and cheap feedstocks into useful compounds. Acyclic and heterocyclic nitrogen-containing derivatives are common components of naturally occurring compounds, agrochemicals, cosmetics, and pharmaceuticals; they are also useful intermediates in a number of industrial processes. One of the most widely used synthetic strategies, allowing the formation of an N-C bond, is the addition of an N-H bond across a carbon-carbon multiple bond, the so-called hydroamination reaction. This chemical transformation fulfills the principle of “green chemistry” since it ideally occurs with 100% atom economy. Various catalysts have been found to promote this reaction, although many limitations remain; one of the most prominent is the lack of methods that permit the use of NH3 and NH2NH2 as the amine partners. In fact, ammonia and hydrazine have rarely succumbed to homogeneous catalytic transformations. Considering the low cost and abundance of ammonia (136 million metric tons produced in 2011) and hydrazine, catalysts able to improve the reactivity and selectivity of the NH3- and NH2NH2-hydroamination reaction, and more broadly speaking the functionalization of these chemicals, are highly desirable. In the last funded period, we discovered the first homogeneous catalysts able to promote the hydroamination of alkynes and allenes with ammonia and the parent hydrazine. The key feature of our catalytic systems is that the formation of catalytically inactive Werner complexes is reversible, in marked contrast to most of the known ammonia and hydrazine transition metal complexes. This is due to the peculiar electronic properties of our neutral ancillary ligands, especially their strong donating capabilities. However, our catalysts currently require

  7. Characterization of Anammox Hydrazine Dehydrogenase, a Key N2-producing Enzyme in the Global Nitrogen Cycle.

    Science.gov (United States)

    Maalcke, Wouter J; Reimann, Joachim; de Vries, Simon; Butt, Julea N; Dietl, Andreas; Kip, Nardy; Mersdorf, Ulrike; Barends, Thomas R M; Jetten, Mike S M; Keltjens, Jan T; Kartal, Boran

    2016-08-12

    Anaerobic ammonium-oxidizing (anammox) bacteria derive their energy for growth from the oxidation of ammonium with nitrite as the electron acceptor. N2, the end product of this metabolism, is produced from the oxidation of the intermediate, hydrazine (N2H4). Previously, we identified N2-producing hydrazine dehydrogenase (KsHDH) from the anammox organism Kuenenia stuttgartiensis as the gene product of kustc0694 and determined some of its catalytic properties. In the genome of K. stuttgartiensis, kustc0694 is one of 10 paralogs related to octaheme hydroxylamine (NH2OH) oxidoreductase (HAO). Here, we characterized KsHDH as a covalently cross-linked homotrimeric octaheme protein as found for HAO and HAO-related hydroxylamine-oxidizing enzyme kustc1061 from K. stuttgartiensis Interestingly, the HDH trimers formed octamers in solution, each octamer harboring an amazing 192 c-type heme moieties. Whereas HAO and kustc1061 are capable of hydrazine oxidation as well, KsHDH was highly specific for this activity. To understand this specificity, we performed detailed amino acid sequence analyses and investigated the catalytic and spectroscopic (electronic absorbance, EPR) properties of KsHDH in comparison with the well defined HAO and kustc1061. We conclude that HDH specificity is most likely derived from structural changes around the catalytic heme 4 (P460) and of the electron-wiring circuit comprising seven His/His-ligated c-type hemes in each subunit. These nuances make HDH a globally prominent N2-producing enzyme, next to nitrous oxide (N2O) reductase from denitrifying microorganisms. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Synthesis of the row of new functional derivatives of 7-arylalkyl-8-hydrazine theophyllines

    Directory of Open Access Journals (Sweden)

    Dmytro Korobko

    2016-03-01

    Full Text Available Hydrazine functional derivatives are widely used in medical practice as remedies applied for pharmacotherapy of depression, infection diseases, hypertension, diabetes, etc. It is worth mentioning that among obtained 7-R-8-hydrazine derivatives of 1,3-dimethylxantine promising substances have been identified. Due to the fact that literature sources display only results of occasional studies of the reactions between 7-R-8-hydrazine theophyllines and mono- or dicarbonyle substances, the use of other keto reagents for xanthine bicycle at 8th position functionalization will allow to explore synthetic potential of the last one, and with high probability may lead to obtaining original biologically active substances.Aim. To study types of reaction between 8-hydrazinyl-1,3-dimethyl-7-aryl alkyl-1H-purine-2,6(3H,7H-diones and a number of carbonyl containing reagents.Methods. A nucleophilic addition reaction followed by dehydration or ethanol splitting was used, as well as the complex of the modern analysis methods to confirm the structure and individuality of the synthesized substances.Results. Different directions of 8-hydrazinyl-1,3,-dimethyl-7(fenetyl-, 3-phenylpropyl-, 3-phenylalyl-1H-purine-2,6(3H,7H-diones chemical transformations in reactions with the appropriate carbonyl containing compounds have been studied experimentally. The structure of synthesized substances was confirmed by chromatography/mass and 1H NMR spectroscopy.Conclusion. The group of 7-arylalkyl-8-(3,5-R,R1-pyrazole-1-yltheophyllines, consisting of two functionally substituted bioactive heterocycles, has been synthesized by reaction between initial substances and selected mono- and dicarbonyl compounds

  9. Green Propellant Demonstration with Hydrazine Catalyst of F-16 Emergency Power Unit

    Science.gov (United States)

    Robinson, Joel W.; Brechbill, Shawn

    2015-01-01

    Some space vehicle and aircraft Auxiliary Power Units (APUs) use hydrazine propellant for generating power. Hydrazine is a toxic, hazardous fuel which requires special safety equipment and processes for handling and loading. In recent years, there has been development of two green propellants that could enable their use in APU's: the Swedish LMP-103S and the Air Force Research Laboratory (AFRL) AF-M315E. While there has been work on development of these propellants for thruster applications (Prisma and Green Propulsion Infusion Mission, respectively), there has been less focus on the application to power units. Beginning in 2012, an effort was started by the Marshall Space Flight Center (MSFC) on the APU application. The MSFC plan was to demonstrate green propellants with residual Space Shuttle hardware. The principal investigator was able to acquire a Solid Rocket Booster gas generator and an Orbiter APU. Since these test assets were limited in number, an Air Force equivalent asset was identified: the F-16 Emergency Power Unit (EPU). In June 2013, two EPU's were acquired from retired aircraft located at Davis Monthan Air Force Base. A gas generator from one of these EPU's was taken out of an assembly and configured for testing with a version of the USAF propellant with a higher water content (AF-M315EM) to reduce decomposition temperatures. Testing in November 2014 has shown that this green propellant is reactive with the Hydrazine catalyst (Shell 405) generating 300 psi of pressure with the existing F-16 EPU configuration. This paper will highlight the results of MSFC testing in collaboration with AFRL.

  10. Thermal design of the IUE hydrazine auxiliary propulsion system. [International Ultraviolet Explorer

    Science.gov (United States)

    Skladany, J. T.; Kelly, W. H.

    1977-01-01

    The International Ultraviolet Explorer is a large astronomical observatory scheduled to be placed in a three-axis stabilized synchronous orbit in the fourth quarter of 1977. The Hydrazine Auxiliary Propulsion System (HAPS) must perform a number of spacecraft maneuvers to achieve a successful mission. This paper describes the thermal design which accomplishes temperature control between 5 and 65 C for all orbital conditions by utilizing multilayer insulation and commandable component heaters. A primary design criteria was the minimization of spacecraft power by the selective use of the solar environment. The thermal design was carefully assessed and verified in both spacecraft thermal balance and subsystem solar simulation testing.

  11. Hydrogen generation from decomposition of hydrous hydrazine over Ni-Ir/CeO2 catalyst

    OpenAIRE

    Dai, Hongbin; Zhong, Yujie; Wang, Ping

    2017-01-01

    The synthesis of highly active and selective catalysts is the central issue in the development of hydrous hydrazine (N2H4·H2O) as a viable hydrogen carrier. Herein, we report the synthesis of bimetallic Ni-Ir nanocatalyts supported on CeO2 using a one-pot coprecipitation method. A combination of XRD, HRTEM and XPS analyses indicate that the Ni-Ir/CeO2 catalyst is composed of tiny Ni-Ir alloy nanoparticles with an average size of around 4 nm and crystalline CeO2 matrix. The Ni-Ir/CeO2 catalyst...

  12. Using Hydrazine to Link Ferrocene with Re(CO)3: A Modular Approach.

    Science.gov (United States)

    Chanawanno, Kullapa; Rhoda, Hannah M; Hasheminasab, Abed; Crandall, Laura A; King, Alexander J; Herrick, Richard S; Nemykin, Victor N; Ziegler, Christopher J

    2016-09-01

    Acetyl ferrocene and diacetyl ferrocene both readily react with an excess of hydrazine to afford the corresponding hydrazone compounds. These compounds can then be linked to Re(CO)3 via a metal-mediated Schiff base reaction, resulting in a series of ferrocene-Re(CO)3 conjugates with different stoichiometries. Conjugates with 1:1, 1:2, and 2:1 ferrocene: Re(CO)3 ratios can be produced via this "modular" type synthesis approach. Several examples of these conjugates were structurally characterized, and their spectroscopic, electrochemical, and spectroelectrochemical behaviors were investigated. The electronic structures of these compounds were also probed using DFT and TDDFT calculations.

  13. Studies on the Mechanism of Action of Hydrazine-Induced Methylation of DNA Guanne

    Science.gov (United States)

    1984-10-03

    addition, 1 out of 3 animals died after single administration of disulfiram, semicarbazide, or sodium formate alone (Groups 3, 9, and 12). The high mortality ...Formaldehyde Acetaldehyde Treatment (nmol/g liver) (nmol/g liver) Control (MeOH expt ) 82 tr MeOH, 1 mL/kg 80 tr 2 mL/kg 80 tr 4 mL/kg 95, 81 tr 6 mL...Hamsters Given Ethanol and Hydrazine in Two Experiments Aldehydes (nmol/g liver) Formaldehyde Acetaldehyde Treatment Expt 1" Expt 2** Expt 1* Expt 2

  14. Application of methyl orange oxidation in the presence of hydrazine to kinetic determination of periodate ion

    OpenAIRE

    Danilina, E.; Ibragimova, Yu

    2014-01-01

    It is possible to apply the induction period of Landolt reaction of methyl orange with potassium bromate in the presence of hydrazine to determination of periodate ion. Optimal conditions are: 0.030 M HCl, 10 mg/mL methyl orange, 1.6·10 -4 M KBrO 3, 3·10-5 M N 2H 4. Calibration curve is linear (0.06-0.9) mg/mL periodate ion range, reproducibility error is 2.6%, relative error is 4.6%.

  15. Back-extraction of tri- and tetravalent actinides from di(2-ethylhexyl)phosphoric acid (HDEHP) with hydrazine carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, M.; Morita, Y.; Kubota, M. [Japan Atomic Energy Research Inst., Dept. of Materials Science, Tokai-mura, Ibaraki (Japan); Tatsugae, R. [Ishikawajima Harima Heavy Industry Co. Ltd., Isogo-ku, Yokohama (Japan)

    1999-07-01

    Back-extraction of tri- and tetravalent actinides from di(2-ethylhexyl)phosphoric acid (HDEHP) was studied using hydrazine carbonate as back-extractant. In experiments using 0.5 M HDEHP-0.2 M TBP n-dodecane solution, Am(III), Eu(III), Pu(IV) and Np(IV) were back-extracted, and the distribution ratios were decreased with an increase of hydrazine carbonate concentration. The back-extraction equilibria were confirmed by slope analysis in consideration of neutralization between HDEHP and hydrazine carbonate, which occurred quantitatively during the back-extraction. In particular, oxidation of Np(IV) to Np(V) during the back-extraction was observed by measuring absorption spectra. The hydrazinium ion acts as an oxidation reagent in the back-extraction of NP(IV). (orig.)

  16. Effect of the linkers between the zinc fingers in zinc finger protein 809 on gene silencing and nuclear localization

    Energy Technology Data Exchange (ETDEWEB)

    Ichida, Yu, E-mail: ichida-y@ncchd.go.jp; Utsunomiya, Yuko; Onodera, Masafumi

    2016-03-18

    Zinc finger protein 809 (ZFP809) belongs to the Kruppel-associated box-containing zinc finger protein (KRAB-ZFP) family and functions in repressing the expression of Moloney murine leukemia virus (MoMLV). ZFP809 binds to the primer-binding site (PBS)located downstream of the MoMLV-long terminal repeat (LTR) and induces epigenetic modifications at integration sites, such as repressive histone modifications and de novo DNA methylation. KRAB-ZFPs contain consensus TGEKP linkers between C2H2 zinc fingers. The phosphorylation of threonine residues within linkers leads to the inactivation of zinc finger binding to target sequences. ZFP809 also contains consensus linkers between zinc fingers. However, the function of ZFP809 linkers remains unknown. In the present study, we constructed ZFP809 proteins containing mutated linkers and examined their ability to silence transgene expression driven by MLV, binding ability to MLV PBS, and cellular localization. The results of the present study revealed that the linkers affected the ability of ZFP809 to silence transgene expression. Furthermore, this effect could be partly attributed to changes in the localization of ZFP809 proteins containing mutated linkers. Further characterization of ZFP809 linkers is required for understanding the functions and features of KRAB-ZFP-containing linkers. - Highlights: • ZFP809 has three consensus linkers between the zinc fingers. • Linkers are required for ZFP809 to silence transgene expression driven by MLV-LTR. • Linkers affect the precise nuclear localization of ZFP809.

  17. Quantitative Conjugated Payload Measurement Using Enzymatic Release of Antibody-Drug Conjugate with Cleavable Linker.

    Science.gov (United States)

    Rago, Brian; Tumey, L Nathan; Wei, Cong; Barletta, Frank; Clark, Tracey; Hansel, Steven; Han, Xiaogang

    2017-02-15

    As antibody-drug conjugate (ADC) design is evolving with novel payload, linker, and conjugation chemistry, the need for sensitive and precise quantitative measurement of conjugated payload to support pharmacokinetics (PK) is in high demand. Compared to ADCs containing noncleavable linkers, a strategy specific to linkers which are liable to pH, chemical reduction, or enzymatic cleavage has gained popularity in recent years. One bioanalytical approach to take advantage of this type of linker design is the development of a PK assay measuring released conjugated payload. For the ADC utilizing a dipeptide ValCit linker studied in this report, the release of payload PF-06380101 was achieved with high efficiency using a purified cathepsin B enzyme. The subsequent liquid chromatography mass spectrometry (LC/MS) quantitation leads to the PK profile of the conjugated payload. For this particular linker using a maleimide-based conjugation chemistry, one potential route of payload loss would result in an albumin adduct of the linker-payload. While this adduct's formation has been previously reported, here, for the first time, we have shown that payload from a source other than ADC contributes only up to 4% of total conjugated payload while it accounts for approximately 35% of payload lost from the ADC at 48 h after dosing to rats.

  18. Creating Hierarchical Pores by Controlled Linker Thermolysis in Multivariate Metal-Organic Frameworks

    KAUST Repository

    Feng, Liang

    2018-01-18

    Sufficient pore size, appropriate stability and hierarchical porosity are three prerequisites for open frameworks designed for drug delivery, enzyme immobilization and catalysis involving large molecules. Herein, we report a powerful and general strate-gy, linker thermolysis, to construct ultra-stable hierarchically porous metal−organic frameworks (HP-MOFs) with tunable pore size distribution. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous MOF crystal via thermolysis. The crystallinity and stability of HP-MOFs remain after thermolabile linkers are selectively removed from multivariate metal-organic frameworks (MTV-MOFs) through a decarboxyla-tion process. A domain-based linker spatial distribution was found to be critical for creating hierarchical pores inside MTV-MOFs. Furthermore, linker thermolysis promotes the formation of ultra-small metal oxide (MO) nanoparticles immobilized in an open framework that exhibits high catalytic activity for Lewis acid catalyzed reactions. Most importantly, this work pro-vides fresh insights into the connection between linker apportionment and vacancy distribution, which may shed light on prob-ing the disordered linker apportionment in multivariate systems, a long-standing challenge in the study of MTV-MOFs.

  19. Linker histone partial phosphorylation: effects on secondary structure and chromatin condensation

    Science.gov (United States)

    Lopez, Rita; Sarg, Bettina; Lindner, Herbert; Bartolomé, Salvador; Ponte, Inma; Suau, Pedro; Roque, Alicia

    2015-01-01

    Linker histones are involved in chromatin higher-order structure and gene regulation. We have successfully achieved partial phosphorylation of linker histones in chicken erythrocyte soluble chromatin with CDK2, as indicated by HPCE, MALDI-TOF and Tandem MS. We have studied the effects of linker histone partial phosphorylation on secondary structure and chromatin condensation. Infrared spectroscopy analysis showed a gradual increase of β-structure in the phosphorylated samples, concomitant to a decrease in α-helix/turns, with increasing linker histone phosphorylation. This conformational change could act as the first step in the phosphorylation-induced effects on chromatin condensation. A decrease of the sedimentation rate through sucrose gradients of the phosphorylated samples was observed, indicating a global relaxation of the 30-nm fiber following linker histone phosphorylation. Analysis of specific genes, combining nuclease digestion and qPCR, showed that phosphorylated samples were more accessible than unphosphorylated samples, suggesting local chromatin relaxation. Chromatin aggregation was induced by MgCl2 and analyzed by dynamic light scattering (DLS). Phosphorylated chromatin had lower percentages in volume of aggregated molecules and the aggregates had smaller hydrodynamic diameter than unphosphorylated chromatin, indicating that linker histone phosphorylation impaired chromatin aggregation. These findings provide new insights into the effects of linker histone phosphorylation in chromatin condensation. PMID:25870416

  20. Where Did the Linker-Payload Go? A Quantitative Investigation on the Destination of the Released Linker-Payload from an Antibody-Drug Conjugate with a Maleimide Linker in Plasma.

    Science.gov (United States)

    Wei, Cong; Zhang, Guodong; Clark, Tracey; Barletta, Frank; Tumey, L Nathan; Rago, Brian; Hansel, Steven; Han, Xiaogang

    2016-05-03

    The reactive thiol of cysteine is often used for coupling maleimide-containing linker-payloads to antibodies resulting in the generation of antibody drug conjugates (ADCs). Currently, a numbers of ADCs in drug development are made by coupling a linker-payload to native or engineered cysteine residues on the antibody. An ADC conjugated via hinge-cysteines to an auristatin payload was used as a model in this study to understand the impact of the maleimide linkers on ADC stability. The payload was conjugated to trastuzumab by a protease-cleavable linker, maleimido-caproyl-valine-citruline-p-amino-benzyloxy carbonyl (mcVC-PABC). In plasma stability assays, when the ADC (Trastuzumab-mcVC-PABC-Auristatin-0101) was incubated with plasma over a 144-h time-course, a discrepancy was observed between the measured released free payload concentration and the measured loss of drug-to-antibody ratio (DAR), as measured by liquid chromatography-mass spectrometry (LC-MS). We found that an enzymatic release of payload from ADC-depleted human plasma at 144 h was able to account for almost 100% of the DAR loss. Intact protein mass analysis showed that at the 144 h time point, the mass of the major protein in ADC-depleted human plasma had an additional 1347 Da over the native albumin extracted from human plasma, exactly matching the mass of the linker-payload. In addition, protein gel electrophoresis showed that there was only one enriched protein in the 144 h ADC-depleted and antipayload immunoprecipitated plasma sample, as compared to the 0 h plasma immunoprecipitated sample, and the mass of this enriched protein was slightly heavier than the mass of serum albumin. Furthermore, the albumin adduct was also identified in 96 h and 168 h postdose in vivo cynomolgus monkey plasma. These results strongly suggest that the majority of the deconjugated mc-VC-PABC-auristatin ultimately is transferred to serum albumin, forming a long-lived albumin-linker-payload adduct. To our knowledge, this is

  1. Glycosylated linkers in multimodular lignocellulose-degrading enzymes dynamically bind to cellulose

    Science.gov (United States)

    Payne, Christina M.; Resch, Michael G.; Chen, Liqun; Crowley, Michael F.; Himmel, Michael E.; Taylor, Larry E.; Sandgren, Mats; Ståhlberg, Jerry; Stals, Ingeborg; Tan, Zhongping; Beckham, Gregg T.

    2013-01-01

    Plant cell-wall polysaccharides represent a vast source of food in nature. To depolymerize polysaccharides to soluble sugars, many organisms use multifunctional enzyme mixtures consisting of glycoside hydrolases, lytic polysaccharide mono-oxygenases, polysaccharide lyases, and carbohydrate esterases, as well as accessory, redox-active enzymes for lignin depolymerization. Many of these enzymes that degrade lignocellulose are multimodular with carbohydrate-binding modules (CBMs) and catalytic domains connected by flexible, glycosylated linkers. These linkers have long been thought to simply serve as a tether between structured domains or to act in an inchworm-like fashion during catalytic action. To examine linker function, we performed molecular dynamics (MD) simulations of the Trichoderma reesei Family 6 and Family 7 cellobiohydrolases (TrCel6A and TrCel7A, respectively) bound to cellulose. During these simulations, the glycosylated linkers bind directly to cellulose, suggesting a previously unknown role in enzyme action. The prediction from the MD simulations was examined experimentally by measuring the binding affinity of the Cel7A CBM and the natively glycosylated Cel7A CBM-linker. On crystalline cellulose, the glycosylated linker enhances the binding affinity over the CBM alone by an order of magnitude. The MD simulations before and after binding of the linker also suggest that the bound linker may affect enzyme action due to significant damping in the enzyme fluctuations. Together, these results suggest that glycosylated linkers in carbohydrate-active enzymes, which are intrinsically disordered proteins in solution, aid in dynamic binding during the enzymatic deconstruction of plant cell walls. PMID:23959893

  2. Liquid-Phase Heat-Release Rates of the Systems Hydrazine-Nitric Acid and Unsymmetrical Dimethylhydrazine-Nitric Acid

    Science.gov (United States)

    Somogyi, Dezso; Feiler, Charles E.

    1960-01-01

    The initial rates of heat release produced by the reactions of hydrazine and unsymmetrical dimethylhydrazine with nitric acid were determined in a bomb calorimeter under conditions of forced mixing. Fuel-oxidant weight ratio and injection velocity were varied. The rate of heat release apparently depended on the interfacial area between the propellants. Above a narrow range of injection velocities representing a critical amount of interfacial area, the rates reached a maximum and were almost constant with injection velocity. The maximum rate for hydrazine was about 70 percent greater than that for unsymmetrical dimethylhydrazine. The total heat released did not vary with mixture ratio over the range studied.

  3. A Traceless Aryl-Triazene Linker for DNA-Directed Chemistry

    DEFF Research Database (Denmark)

    Hejesen, Christian; Pedersen, Lars Kolster; Gothelf, Kurt Vesterager

    2013-01-01

    DNA-directed synthesis of encoded combinatorial libraries of small organic compounds most often involves transfer of organic building blocks from one DNA strand to another. This requires cleavable linkers to enable cleavage of the link to the original DNA strand from which the building block...... is transferred. Relatively few cleavable linkers are available for DNA-directed synthesis and most often they leave an amino group at the organic molecule. Here we have extended the application of 10 aryltriazenes as traceless linkers for DNA-directed synthesis. After reaction of one building block...

  4. Syntabulin, a motor protein linker, controls dorsal determination.

    Science.gov (United States)

    Nojima, Hideaki; Rothhämel, Sophie; Shimizu, Takashi; Kim, Cheol-Hee; Yonemura, Shigenobu; Marlow, Florence L; Hibi, Masahiko

    2010-03-01

    In amphibian and teleost embryos, the dorsal determinants (DDs) are believed to be initially localized to the vegetal pole and then transported to the prospective dorsal side of the embryo along a microtubule array. The DDs are known to activate the canonical Wnt pathway and thereby promote the expression of genes that induce the dorsal organizer. Here, by identifying the locus of the maternal-effect ventralized mutant tokkaebi, we show that Syntabulin, a linker of the kinesin I motor protein, is essential for dorsal determination in zebrafish. We found that syntabulin mRNA is transported to the vegetal pole during oogenesis through the Bucky ball (Buc)-mediated Balbiani body-dependent pathway, which is necessary for establishment of animal-vegetal (AV) oocyte polarity. We demonstrate that Syntabulin is translocated from the vegetal pole in a microtubule-dependent manner. Our findings suggest that Syntabulin regulates the microtubule-dependent transport of the DDs, and provide evidence for the link between AV and dorsoventral axis formation.

  5. Mobile linkers on DNA-coated colloids: valency without patches.

    Science.gov (United States)

    Angioletti-Uberti, Stefano; Varilly, Patrick; Mognetti, Bortolo M; Frenkel, Daan

    2014-09-19

    Colloids coated with single-stranded DNA (ssDNA) can bind selectively to other colloids coated with complementary ssDNA. The fact that DNA-coated colloids (DNACCs) can bind to specific partners opens the prospect of making colloidal "molecules." However, in order to design DNACC-based molecules, we must be able to control the valency of the colloids, i.e., the number of partners to which a given DNACC can bind. One obvious, but not very simple approach is to decorate the colloidal surface with patches of single-stranded DNA that selectively bind those on other colloids. Here we propose a design principle that exploits many-body effects to control the valency of otherwise isotropic colloids. Using a combination of theory and simulation, we show that we can tune the valency of colloids coated with mobile ssDNA, simply by tuning the nonspecific repulsion between the particles. Our simulations show that the resulting effective interactions lead to low-valency colloids self-assembling in peculiar open structures, very different from those observed in DNACCs with immobile DNA linkers.

  6. Synthesis and characterizations of ferrite nanomaterials for phenyl hydrazine chemical sensor applications.

    Science.gov (United States)

    Al-Heniti, S H; Umar, Ahmad; Zaki, H M; Dar, G N; Al-Ghamdi, A A; Kim, S H

    2014-05-01

    This paper presents the synthesis, characterization and phenyl hydrazine chemical sensing applications of Cd0.5Mg0.5Fe2O4 ferrite nanoparticles. The nanoparticles were synthesized by facile and simple co-precipitation method and characterized in detail in terms of their morphological, structural, compositional and electrical properties. The detailed characterization studies revealed that the prepared nanoparticles are grown in high density, possessing Cd0.5Mg0.5Fe2O4 composition and exhibiting spinel cubic structure. Moreover, the prepared Cd0.5Mg0.5Fe2O4 ferrite nanoparticles were used as efficient electron mediators for the fabrication of high-sensitive, robust, reliable and reproducible phenyl hydrazine chemical sensor by simple I-V technique. The fabricated chemical sensor exhibits a highsensitivity of 7.01 microA mM(-1) cm(-2) with an experimental detection limit of 3.125 mM in a short response time of -10.0 s. This work demonstrates that Cd0.5Mg0.5Fe2O4 ferrite nanoparticles can efficiently be utilized for the fabrication of highly sensitive and reliable chemical sensors.

  7. Meiotic changes in Vicia faba L. subsequent to treatments of hydrazine hydrate and maleic hydrazide

    Directory of Open Access Journals (Sweden)

    Shaheen Husain

    2013-01-01

    Full Text Available Assessing the impact of mutagens for creating variations in crops like faba bean (Vicia faba L. is an important criterion in the contemporary world where food insecurity and malnutrition is alarming at the doors of various nations. Impact of two chemical mutagens viz. hydrazine hydrate (HZ and maleic hydrazide (MH on the two varieties (NDF-1 and HB-405 of Vicia faba were analysed in terms of meiotic behavior and pollen sterility. Since there are not enough data about the effect of these mutagens on the chromosomal behaviors of Vicia faba, this study presents the role of hydrazine hydrate and maleic hydrazide as well as various types of chromosomal aberrations in crop improvement. The lower concentration of mutagens showed less pollen sterility compared to the higher concentrations. Manipulation of plant structural component to induce desirable alternations provides valuable material for the breeders and could be used favorably for increasing mutation rate and obtaining a desirable spectrum of mutation in faba beans based on preliminary studies of cell division.

  8. Iridium-decorated multiwall carbon nanotubes and its catalytic activity with Shell 405 in hydrazine decomposition

    Science.gov (United States)

    Prasad, V.; Vasanthkumar, M. S.

    2015-10-01

    Iridium-functionalized multiwalled carbon nanotubes (Ir-MWNT) are the future catalyst support material for hydrazine fuel decomposition. The present work demonstrates decoration of iridium particle on iron-encapsulated multiwalled carbon nanotubes (MWNT) by wet impregnation method in the absence of any stabilizer. Electron microscopy studies reveal the coated iridium particle size in the range of 5-10 nm. Elemental analysis by energy dispersive X-ray diffraction confirms 21 wt% of Ir coated over MWNT. X-ray photoelectron spectroscopy (XPS) shows 4f5/2 and 4f7/2 lines of iridium and confirms the metallic nature. The catalytic activity of Ir-MWNT/Shell 405 combination is performed in 1 N hydrazine micro-thrusters. The thruster performance shows increase in chamber pressure and decrease in chamber temperature when compared to Shell 405 alone. This enhanced performance is due to high thermal conducting nature of MWNTs and the presence of Ir active sites over MWNTs.

  9. Sol-gel process preparation and evaluation of the analytical performances of an hydrazine specific chemical sensor; Preparation par procede sol-gel et evaluation des performances analytiques d`un capteur chimique specifique de l`hydrazine

    Energy Technology Data Exchange (ETDEWEB)

    Gojon, C

    1996-12-01

    The realisation of optical fibers active chemical collector to analyze hydrazine in line, in the spent fuel reprocessing process is the subject of this work. The p.dimethyl-amino-benzaldehyde has been chosen as reagent for its chemical and optical properties. 186 refs.

  10. Investigation of the direct and indirect electrochemical oxidation of hydrazine in nitric acid medium on platinum; Etude de l`oxydation electrochimique directe et indirecte de l`hydrazine en milieu acide nitrique sur platine

    Energy Technology Data Exchange (ETDEWEB)

    Cames, B

    1997-12-31

    In nuclear fuel processing by the PUREX process, the purification of plutonium in nitric acid medium requires the oxidation of Pu(III) to Pu(IV), and of hydrazinium nitrate to nitrogen. The study helped to characterize the electrochemical behavior of the oxidation of hydrazinium nitrate and the reduction of nitric acid to nitrous acid, a compound which can chemically oxidize hydrazinium nitrate and Pu(III). Electro-analytical studies on polycrystalline platinum showed that hydrazine is oxidized in two potential zones, which depend on the surface texture of the platinum anode. Electrolysis in separate compartments, carried out in medium-acid media (2 and 4 mo/l) in the potential zone where these processes take place, showed that, at 0.9 V/ECS, the hydrazine oxidation reactions involved are: a four-electron process (75 %) with nitrogen formation and a one-electron process (25 %) with formation of nitrogen and ammonium ion. By contrast, electrolysis carried out at 0.65 V/ECS (with reactivation of the electrode at - 0.2 V/ECS to remove the poison from the platinum) allowed the selective oxidation of hydrazine to nitrogen by the four-electron reaction. Nitric acid can only be reduced to nitrous acid in the absence of hydrazine. For medium-acid media ({<=} 6 mol/l), this reaction takes place at potentials below - 0.2 V/ECS. However, the production rate of nitrous acid (partial order 0 with respect to nitric acid) is very low compared with the values obtained for strongly-acid media (6 to 10 mol/l) at the potential of - 0.1 V/ECS. Note that, in concentrated nitric medium, the selectivity of the reduction reaction is 47 to 85 % for nitrous acid, depending on the nitric acid concentration (6 to 10 mol/l) and the potential imposed (- 0.1 {<=} E {<=} 0.6 V/ECS). A kinetic study helped to determine the hydrazine oxidation rates as a function of the operating conditions. In all cases, the reaction rate is of partial order 0 with respect to hydrazine. These studies accordingly

  11. LRRC45 is a centrosome linker component required for centrosome cohesion

    National Research Council Canada - National Science Library

    He, Runsheng; Huang, Ning; Bao, Yitian; Zhou, Haining; Teng, Junlin; Chen, Jianguo

    2013-01-01

    During interphase, centrosomes are connected by a proteinaceous linker between the proximal ends of the centrioles, which is important for the centrosomes to function as a single microtubule-organizing center...

  12. High-Flux Zeolitic Imidazolate Framework Membranes for Propylene/Propane Separation by Postsynthetic Linker Exchange.

    Science.gov (United States)

    Lee, Moon Joo; Kwon, Hyuk Taek; Jeong, Hae-Kwon

    2018-01-02

    While zeolitic imidazolate framework, ZIF-8, membranes show impressive propylene/propane separation, their throughput needs to be greatly improved for practical applications. A method is described that drastically reduces the effective thickness of ZIF-8 membranes, thereby substantially improving their propylene permeance (that is, flux). The new strategy is based on a controlled single-crystal to single-crystal linker exchange of 2-methylimidazole in ZIF-8 membrane grains with 2-imidazolecarboxaldehyde (ZIF-90 linker), thereby enlarging the effective aperture size of ZIF-8. The linker-exchanged ZIF-8 membranes showed a drastic increase in propylene permeance by about four times, with a negligible loss in propylene/propane separation factor when compared to as-prepared membranes. The linker-exchange effect depends on the membrane synthesis method. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Tethering metal ions to photocatalyst particulate surfaces by bifunctional molecular linkers for efficient hydrogen evolution

    KAUST Repository

    Yu, Weili

    2014-08-19

    A simple and versatile method for the preparation of photocatalyst particulates modified with effective cocatalysts is presented; the method involves the sequential soaking of photocatalyst particulates in solutions containing bifunctional organic linkers and metal ions. The modification of the particulate surfaces is a universal and reproducible method because the molecular linkers utilize strong covalent bonds, which in turn result in modified monolayer with a small but controlled quantity of metals. The photocatalysis results indicated that the CdS with likely photochemically reduced Pd and Ni, which were initially immobilized via ethanedithiol (EDT) as a linker, were highly efficient for photocatalytic hydrogen evolution from Na2S-Na2SO3-containing aqueous solutions. The method developed in this study opens a new synthesis route for the preparation of effective photocatalysts with various combinations of bifunctional linkers, metals, and photocatalyst particulate materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Replacement of the human topoisomerase linker domain with the plasmodial counterpart renders the enzyme camptothecin resistant

    DEFF Research Database (Denmark)

    Arnò, Barbara; D'Annessa, Ilda; Tesauro, Cinzia

    2013-01-01

    a conformational space much larger than the corresponding domain in the human enzyme. The large linker conformational variability is then linked to important functional properties such as an increased religation rate and a low drug reactivity, demonstrating that the linker domain has a crucial role......A human/plasmodial hybrid enzyme, generated by swapping the human topoisomerase IB linker domain with the corresponding domain of the Plasmodium falciparum enzyme, has been produced and characterized. The hybrid enzyme displays a relaxation activity comparable to the human enzyme......, but it is characterized by a much faster religation rate. The hybrid enzyme is also camptothecin resistant. A 3D structure of the hybrid enzyme has been built and its structural-dynamical properties have been analyzed by molecular dynamics simulation. The analysis indicates that the swapped plasmodial linker samples...

  15. Structural analysis of the S4-S5 linker of the human KCNQ1 potassium channel.

    Science.gov (United States)

    Gayen, Shovanlal; Li, Qingxin; Kang, CongBao

    2015-01-02

    KCNQ1 plays important roles in the cardiac action potential and consists of an N-terminal domain, a voltage-sensor domain, a pore domain and a C-terminal domain. KCNQ1 is a voltage-gated potassium channel and its channel activity is regulated by membrane potentials. The linker between transmembrane helices 4 and 5 (S4-S5 linker) is important for transferring the conformational changes from the voltage-sensor domain to the pore domain. In this study, the structure of the S4-S5 linker of KCNQ1 was investigated by solution NMR, circular dichroism and fluorescence spectroscopic studies. The S4-S5 linker adopted a helical structure in detergent micelles. The W248 may interact with the cell membrane. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Composite materials with metal oxide attached to lead chalcogenide nanocrystal quantum dots with linkers

    Science.gov (United States)

    Fuke, Nobuhiro; Koposov, Alexey Y; Sykora, Milan; Hoch, Laura

    2014-12-16

    Composite materials useful for devices such as photoelectrochemical solar cells include a substrate, a metal oxide film on the substrate, nanocrystalline quantum dots (NQDs) of lead sulfide, lead selenide, and lead telluride, and linkers that attach the NQDs to the metal oxide film. Suitable linkers preserve the 1s absorption peak of the NQDs. A suitable linker has a general structure A-B-C where A is a chemical group adapted for binding to a MO.sub.x and C is a chemical group adapted for binding to a NQD and B is a divalent, rigid, or semi-rigid organic spacer moiety. Other linkers that preserve the 1s absorption peak may also be used.

  17. Identification of novel post-translational modifications in linker histones from chicken erythrocytes.

    Science.gov (United States)

    Sarg, Bettina; Lopez, Rita; Lindner, Herbert; Ponte, Inma; Suau, Pedro; Roque, Alicia

    2015-01-15

    Chicken erythrocyte nuclei were digested with micrococcal nuclease and fractionated by centrifugation in low-salt buffer into soluble and insoluble fractions. Post-translational modifications of the purified linker histones of both fractions were analyzed by LC-ESI-MS/MS. All six histone H1 subtypes (H1.01, H1.02, H1.03, H1.10, H1.1L and H1.1R) and histone H5 were identified. Mass spectrometry analysis enabled the identification of a wide range of PTMs, including N(α)-terminal acetylation, acetylation, formylation, phosphorylation and oxidation. A total of nine new modifications in chicken linker histones were mapped, most of them located in the N-terminal and globular domains. Relative quantification of the modified peptides showed that linker histone PTMs were differentially distributed among both chromatin fractions, suggesting their relevance in the regulation of chromatin structure. The analysis of our results combined with previously reported data for chicken and some mammalian species showed that most of the modified positions were conserved throughout evolution, highlighting their importance in specific linker histone functions and epigenetics. Post-translational modifications of linker histones could have a role in the regulation of gene expression through the modulation of chromatin higher-order structure and chromatin remodeling. Finding new PTMs in linker histones is the first step to elucidate their role in the histone code. In this manuscript we report nine new post-translational modifications of the linker histones from chicken erythrocytes, one in H5 and eight in the H1 subtypes. Chromatin fractionated by centrifugation in low-salt buffer resulted in two fractions with different contents and compositions of linker histones and enriched in specific core histone PTMs. Of particular interest is the fact that linker histone PTMs were differentially distributed in both chromatin fractions, suggesting specific functions. Future studies are needed to

  18. Novel Concepts of MS-Cleavable Cross-linkers for Improved Peptide Structure Analysis

    Science.gov (United States)

    Hage, Christoph; Falvo, Francesco; Schäfer, Mathias; Sinz, Andrea

    2017-10-01

    The chemical cross-linking/mass spectrometry (MS) approach is gaining increasing importance as an alternative method for studying protein conformation and for deciphering protein interaction networks. This study is part of our ongoing efforts to develop innovative cross-linking principles for a facile and efficient assignment of cross-linked products. We evaluate two homobifunctional, amine-reactive, and MS-cleavable cross-linkers regarding their potential for automated analysis of cross-linked products. We introduce the bromine phenylurea (BrPU) linker that possesses a unique structure yielding a distinctive fragmentation pattern on collisional activation. Moreover, BrPU delivers the characteristic bromine isotope pattern and mass defect for all cross-linker-decorated fragments. We compare the fragmentation behavior of the BrPU linker with that of our previously described MS-cleavable TEMPO-Bz linker (which consists of a 2,2,6,6-tetramethylpiperidine-1-oxy moiety connected to a benzyl group) that was developed to perform free-radical-initiated peptide sequencing. Comparative collisional activation experiments (collision-induced dissociation and higher-energy collision-induced dissociation) with both cross-linkers were conducted in negative electrospray ionization mode with an Orbitrap Fusion mass spectrometer using five model peptides. As hypothesized in a previous study, the presence of a cross-linked N-terminal aspartic acid residue seems to be the prerequisite for the loss of an intact peptide from the cross-linked products. As the BrPU linker combines a characteristic mass shift with an isotope signature, it presents a more favorable combination for automated assignment of cross-linked products compared with the TEMPO-Bz linker. [Figure not available: see fulltext.

  19. Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

    Directory of Open Access Journals (Sweden)

    Mayeul Collot

    2013-01-01

    Full Text Available Automated oligosaccharide assembly requires suitable linkers to connect the first monosaccharide to a solid support. A new hydrogenolysis-labile linker that is stable under both acidic and basic conditions was designed, synthesized and coupled to different resins. Glycosylation and cleavage efficiencies on these functionalized solid supports were investigated, and restrictions for the choice of solid support for oligosaccharide synthesis were found.

  20. Monte Carlo analysis of neck linker extension in kinesin molecular motors.

    Directory of Open Access Journals (Sweden)

    Matthew L Kutys

    2010-11-01

    Full Text Available Kinesin stepping is thought to involve both concerted conformational changes and diffusive movement, but the relative roles played by these two processes are not clear. The neck linker docking model is widely accepted in the field, but the remainder of the step--diffusion of the tethered head to the next binding site--is often assumed to occur rapidly with little mechanical resistance. Here, we investigate the effect of tethering by the neck linker on the diffusive movement of the kinesin head, and focus on the predicted behavior of motors with naturally or artificially extended neck linker domains. The kinesin chemomechanical cycle was modeled using a discrete-state Markov chain to describe chemical transitions. Brownian dynamics were used to model the tethered diffusion of the free head, incorporating resistive forces from the neck linker and a position-dependent microtubule binding rate. The Brownian dynamics and chemomechanical cycle were coupled to model processive runs consisting of many 8 nm steps. Three mechanical models of the neck linker were investigated: Constant Stiffness (a simple spring, Increasing Stiffness (analogous to a Worm-Like Chain, and Reflecting (negligible stiffness up to a limiting contour length. Motor velocities and run lengths from simulated paths were compared to experimental results from Kinesin-1 and a mutant containing an extended neck linker domain. When tethered by an increasingly stiff spring, the head is predicted to spend an unrealistically short amount of time within the binding zone, and extending the neck is predicted to increase both the velocity and processivity, contrary to experiments. These results suggest that the Worm-Like Chain is not an adequate model for the flexible neck linker domain. The model can be reconciled with experimental data if the neck linker is either much more compliant or much stiffer than generally assumed, or if weak kinesin-microtubule interactions stabilize the diffusing

  1. Homoaromatics as intermediates in the substitution reactions of 1,2,4,5-tetrazines with ammonia and hydrazine

    NARCIS (Netherlands)

    Counotte-Potman, A.

    1981-01-01

    This thesis describes some nucleophilic substitution reactions between the red 1,2,4,5-tetrazines and hydrazine-hydrate or ammonia. Special attention was paid to the occurrence of the S N (ANRORC) mechanism in these substitution reactions.

  2. Adsorption of hydrazine on the perfect and defective copper (111) surface: A dispersion-corrected DFT study

    NARCIS (Netherlands)

    Tafreshi, Saeedeh S.; Roldan, Alberto; Dzade, Nelson Y.|info:eu-repo/dai/nl/41249311X; de Leeuw, Nora H.|info:eu-repo/dai/nl/376421061

    We have investigated the adsorption of hydrazine (N2H4) on perfect and defect-containing copper (111) surfaces by first-principles calculations. The long-range interactions are included in the geometry optimization through the application of the generalised gradient approximation with dispersion

  3. Biogenesis of the T1-S1 linker of voltage-gated K+ channels.

    Science.gov (United States)

    Tu, LiWei; Wang, Jing; Deutsch, Carol

    2007-07-10

    In the model derived from the crystal structure of Kv1.2, a six-transmembrane voltage-gated potassium channel, the linker between a cytosolic tetramerization domain, T1, and the first transmembrane segment, S1, is projected radially outward from the channel's central axis. This T1-S1 linker was modeled as two polyglycine helices to accommodate the residues between T1 and S1 [Long et al. (2005) Science 309, 897-903]; however, the structure of this linker is not known. Here, we investigate whether a compact secondary structure of the T1-S1 linker exists at an early stage of Kv channel biogenesis. We have used a mass-tagging accessibility assay to report the biogenesis of secondary structure for three consecutive regions of Kv1.3, a highly homologous isoform of Kv1.2. The three regions include the T1-S1 linker and its two flanking regions, alpha5 of the T1 domain and S1. Both alpha5 and S1 manifest compact structures (helical) inside the ribosomal exit tunnel, whereas the T1-S1 linker does not. Moreover, the location of the peptide in the tunnel influences compaction.

  4. Highly tunable molecular sieving and adsorption properties of mixed-linker zeolitic imidazolate frameworks.

    Science.gov (United States)

    Eum, Kiwon; Jayachandrababu, Krishna C; Rashidi, Fereshteh; Zhang, Ke; Leisen, Johannes; Graham, Samuel; Lively, Ryan P; Chance, Ronald R; Sholl, David S; Jones, Christopher W; Nair, Sankar

    2015-04-01

    Nanoporous zeolitic imidazolate frameworks (ZIFs) form structural topologies equivalent to zeolites. ZIFs containing only one type of imidazole linker show separation capability for limited molecular pairs. We show that the effective pore size, hydrophilicity, and organophilicity of ZIFs can be continuously and drastically tuned using mixed-linker ZIFs containing two types of linkers, allowing their use as a more general molecular separation platform. We illustrate this remarkable behavior by adsorption and diffusion measurements of hydrocarbons, alcohols, and water in mixed-linker ZIF-8(x)-90(100-x) materials with a large range of crystal sizes (338 nm to 120 μm), using volumetric, gravimetric, and PFG-NMR methods. NMR, powder FT-Raman, and micro-Raman spectroscopy unambiguously confirm the mixed-linker nature of individual ZIF crystals. Variation of the mixed-linker composition parameter (x) allows continuous control of n-butane, i-butane, butanol, and isobutanol diffusivities over 2-3 orders of magnitude and control of water and alcohol adsorption especially at low activities.

  5. Heterocycles 27. Microwave assisted synthesis and antitumour activity of novel phenothiazinyl-thiazolyl-hydrazine derivatives.

    Science.gov (United States)

    Ignat, Adriana; Lovasz, Tamas; Vasilescu, Mihai; Fischer-Fodor, Eva; Tatomir, Corina Bianca; Cristea, Castelia; Silaghi-Dumitrescu, Luminiţa; Zaharia, Valentin

    2012-07-01

    A series of new phenothiazinyl-thiazolyl-hydrazine derivatives were synthesized by Hantzsch cyclization of 1-(10-ethyl-10H-phenothiazin-3-yl)-methylidene-thiosemicarbazide with α-halocarbonyl derivatives. Comparison between classical and microwave assisted synthesis emphasizes the great advantages induced by microwaves irradiation which afforded high reaction yields in much shorter reaction time. Structural assignments were based on spectroscopic methods (high resolution NMR, FTIR, MS). The new compounds were tested in vitro for their antiproliferative activity against tumor cell lines using spectrometric methods. Most of the compounds exhibit cytotoxicity against hepatic and colon tumor cells in a dose-dependent mode and a relationship between the structure and their biological activity was observed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Locally hydrazine doped WSe2 p-n junction toward high-performance photodetectors

    Science.gov (United States)

    Sun, Mengxing; Xie, Dan; Sun, Yilin; Li, Weiwei; Ren, Tianling

    2018-01-01

    Two dimensional (2D) materials have shown great potential in the photodetection and other optoelectronic applications. Exploiting 2D materials to form p-n junctions enables effective generation and separation of carriers excited by light, thus creating high-performance optoelectronic devices. This paper demonstrates a lateral WSe2 p-n junction through a locally hydrazine doping method. Good current-rectifying characteristics, including a high rectification ratio of ∼103, have been observed; this indicates that a high-quality p-n junction has been formed by chemical doping. Under light illumination, the device shows improved photoresponse capabilities with a responsivity of 30 mA W‑1, a detectivity of 6.18 × 108 Jones, photocurrent/dark current ratio of 103 and a response time of 2 ms. These results suggest an effective way to get a p-n junction and reveal the application potential of the device for next generation photodetectors.

  7. Cubic Copper Hexacyanoferrates Nanoparticles: Facile Template-Free Deposition and Electrocatalytic Sensing Towards Hydrazine

    Directory of Open Access Journals (Sweden)

    Xingxing Wang

    2011-01-01

    Full Text Available Cubic copper hexacyanoferrate (CuHCF nanoparticles prepared via electrolytic deposition are presented with their morphology and crystalline structure characterized with SEM and XRD. The advantage of this methodology is that it allows the fabrication of uniform cubic nanoparticles with permeable structures onto the desired underlying electrode substrate. It was observed that the CuHCF film acts as a permeable membrane for cations such as K+, Na+, Li+, and NH4+ with a selection order of K+> Li+>NH4+> Na+. Furthermore, the analytical utility of these cubic-like CuHCF morphologies supported on a glassy carbon electrode was evaluated towards the electrochemical oxidation of hydrazine which was found to exhibit a linear response over the range 66 M to 17 mM with a detection limit corresponding to 16.5 M.

  8. Improved carrier mobility of chemical vapor deposition-graphene by counter-doping with hydrazine hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhiying; Zhang, Yanhui; Zhang, Haoran; Sui, Yanping; Zhang, Yaqian; Ge, Xiaoming; Yu, Guanghui, E-mail: ghyu@mail.sim.ac.cn; Xie, Xiaoming; Li, Xiaoliang [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Jin, Zhi; Liu, Xinyu [Microwave Devices and Integrated Circuits Department, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

    2015-03-02

    We developed a counter-doping method to tune the electronic properties of chemical vapor deposition (CVD)-grown graphene by varying the concentration and time of graphene exposure to hydrazine hydrate (N{sub 2}H{sub 4}·H{sub 2}O). The shift of G and 2D peaks of Raman spectroscopy is analyzed as a function of N{sub 2}H{sub 4}·H{sub 2}O concentration. The result revealed that N{sub 2}H{sub 4}·H{sub 2}O realized n-type doping on CVD grown graphene. X-ray photoelectron spectroscopy measurement proved the existence of nitrogen, which indicated the adsorption of N{sub 2}H{sub 4} on the surface of graphene. After counter-doping, carrier mobility, which was measured by Hall measurements, increased three fold.

  9. Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition

    DEFF Research Database (Denmark)

    Ryuzaki, Sou; Meyer, Jakob Abild Stengaard; Petersen, Søren Vermehren

    2014-01-01

    Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially...... increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp3carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics...... with a conductivity of 267.2-537.5S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective...

  10. Identification of putative domain linkers by a neural network – application to a large sequence database

    Directory of Open Access Journals (Sweden)

    Kuroda Yutaka

    2006-06-01

    Full Text Available Background The reliable dissection of large proteins into structural domains represents an important issue for structural genomics/proteomics projects. To provide a practical approach to this issue, we tested the ability of neural network to identify domain linkers from the SWISSPROT database (101602 sequences. Results Our search detected 3009 putative domain linkers adjacent to or overlapping with domains, as defined by sequence similarity to either Protein Data Bank (PDB or Conserved Domain Database (CDD sequences. Among these putative linkers, 75% were "correctly" located within 20 residues of a domain terminus, and the remaining 25% were found in the middle of a domain, and probably represented failed predictions. Moreover, our neural network predicted 5124 putative domain linkers in structurally un-annotated regions without sequence similarity to PDB or CDD sequences, which suggest to the possible existence of novel structural domains. As a comparison, we performed the same analysis by identifying low-complexity regions (LCR, which are known to encode unstructured polypeptide segments, and observed that the fraction of LCRs that correlate with domain termini is similar to that of domain linkers. However, domain linkers and LCRs appeared to identify different types of domain boundary regions, as only 32% of the putative domain linkers overlapped with LCRs. Conclusion Overall, our study indicates that the two methods detect independent and complementary regions, and that the combination of these methods can substantially improve the sensitivity of the domain boundary prediction. This finding should enable the identification of novel structural domains, yielding new targets for large scale protein analyses.

  11. Spectroscopic study of the light-harvesting protein C-phycocyanin associated with colorless linker peptides

    Energy Technology Data Exchange (ETDEWEB)

    Pizarro, Shelly Ann [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The phycobilisome (PBS) light-harvesting antenna is composed of chromophore-containing biliproteins and 'colorless' linker peptides and is structurally designed to support unidirectional transfer of excitation energy from the periphery of the PBS to its core. The linker peptides have a unique role in this transfer process by modulating the spectral properties of the associated biliprotein. There is only one three-dimensional structure of a biliprotein/linker complex available to date (APC/LC7.8) and the mechanism of interaction between these two proteins remains unknown. This study brings together a detailed spectroscopic characterization of C-Phycocyanin (PC)-linker complexes (isolated from Synechococcus sp. PCC 7002) with proteomic analysis of the linker amino acid sequences to produce a model for biliprotein/linker interaction. The amino acid sequences of the rod linkers [LR8.9, LR32.3 and LRC28.5] were examined to identify evolutionarily conserved regions important to either the structure or function of this protein family. Although there is not one common homologous site among all the linkers, there are strong trends across each separate subset (LC, LR and LRC) and the N-terminal segments of both LR32.3 and LRC28.5 display multiple regions of similarity with other linkers. Predictions of the secondary structure of LR32.3 and LRC28.5, and comparison to the crystal structure of LC7.8, further narrowed the candidates for interaction sites with the PC chromophores. Measurements of the absorption, fluorescence, CD and excitation anisotropy of PC trimer, PC/LR32.3, and PC/LRC28.5, document the spectroscopic effect of each linker peptide on the PC chromophores at a series of temperatures (298 to 77 K

  12. Nanostructured SnO{sub 2} encapsulated guar-gum hybrid nanocomposites for electrocatalytic determination of hydrazine

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Priya [Department of Applied Chemistry & Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Srivastava, Manish [Department of Physics & Astrophysics, University of Delhi, Delhi 110007 (India); Verma, Ranjana [Solar Energy Material Laboratory, Department of Energy, Tezpur University, Tezpur, Assam 784 028 (India); Kumar, Manish [Department of Applied Chemistry & Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Kumar, D., E-mail: dkumar@dce.ac.in [Department of Applied Chemistry & Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Singh, Jay, E-mail: jay_singh143@yahoo.co.in [Department of Applied Chemistry & Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India)

    2016-01-01

    The present article deals with synthesis of sol–gel derived tin dioxide (SnO{sub 2}) nanoparticles encapsulated in to guar gum (GG) biopolymer as the organic–inorganic hybrid materials for the determination of hydrazine. The organic–inorganic hybrid combines the perfunctory strength offered by the inorganic SnO{sub 2} nanoparticles with flexible binding sites provided by the organic biopolymer (GG) solution by the ultrasonication. The phase identification, crystalline size, surface morphology and optical properties of prepared SnO{sub 2} and SnO{sub 2}-GG nanocomposites has been investigated through FT-IR, XRD, SEM, AFM, TEM, UV–Vis, and PL techniques. The colloidal solution of SnO{sub 2} and GG is electrophoretically deposited (EPD) onto the indium tin-oxide (ITO) glass substrate and studied for the electrooxidation of hydrazine. Under the optimized experimental conditions, the linearity between the current response and the hydrazine concentration has been obtained in the range of 2–22 mM, with a low detection limit of 2.76 mM and a high sensitivity of 5.72 μA cm{sup −2}. Based on the linear increase in amperometric current, a sensitive hydrazine electrochemical sensor is constructed. The proposed SnO{sub 2}-GG/ITO electrode shows a good response time (35 s), reproducibility, and long-term stability. The obtained results suggest that SnO{sub 2}-GG nanocomposites electrode provides a favorable sensing platform for the electrochemical studies. In addition, the cyclic voltammetry (CV) studies are used to evaluate the kinetic parameters. - Graphical abstract: Synthesis of sol–gel derived tin dioxide (SnO{sub 2}) nanoparticles grafted in to gaur gum (GG) organic–inorganic hybrid nanocomposite for determination of hydrazine (HZ). Under optimized experimental conditions, SnO{sub 2}-GG/ITO electrode shows, linearity 2–22 mM, and detection limit 2.769 mM with high sensitivity of 5.72 μA cm{sup −2}. The results clearly suggest that SnO{sub 2}-GG

  13. Electrochemical Detection of Hydrazine and 4-Nitrophenol Based on Layer-by-Layer Assembled Multilayer Films of Reduced Graphene Oxide/Gold Nanoparticles

    National Research Council Canada - National Science Library

    Shuohan Huang; Yueshan Zhou; Yan Gao; Lei Xu; Huijun Jiang

    2015-01-01

    ...) and polyamidoamine (PAMAM) dendrimer protected gold nanoparticles (AuNPs), a novel electrochemical sensing platform for sensitive detection of 4-nitrophenol and hydrazine was fabricated via electrostatic layer-by-layer (LBL...

  14. Top-down synthesis of versatile polyaspartamide linkers for single-step protein conjugation to materials.

    Science.gov (United States)

    Cha, Chaenyung; Jeong, Jae Hyun; Tang, Xin; Zill, Andrew T; Prakash, Y S; Zimmerman, Steven C; Saif, Taher A; Kong, Hyunjoon

    2011-12-21

    Materials used in various biological applications are often modified with proteins to regulate biomolecular and cellular adhesion. Conventional strategies of protein conjugation accompany monovalent bifunctional protein linkers, which present several limitations in molecular synthesis and protein conjugation. Herein, we present a new strategy of preparing multivalent polyaspartamide linkers in a simple top-down manner, and also demonstrate that the resulting polymer linkers allow us to readily conjugate proteins to both organic and inorganic materials. The top-down synthesis of polyaspartamide linkers was performed by partially opening succinimidyl ring moieties of polysuccinimide (PSI) with the controlled number of nucleophiles reactive to photo-cross-linked hydrogel or gold-coated inorganic materials: (1) Poly(2-hydroxyethyl-co-2-methacryloxyethyl aspartamide) (PHMAA) presenting methacrylate was used to micropattern fibronectin or collagen on a hydrogel in order to regulate cell adhesion and growth area on a micrometer scale. (2) Poly(2-hydroxyethyl-co-2-mercaptoethyl aspartamide) (PHMCA) presenting thiol functional groups was used to link fibronectin to a gold-coated silicon microelectromechanical probe designed to measure cell traction force. Overall, these multivalent polyaspartamide protein linkers will greatly assist efforts to analyze and regulate the cellular adhesion to and phenotypic activities of a wide array of substrates and devices.

  15. Global mitotic phosphorylation of C2H2 zinc finger protein linker peptides.

    Science.gov (United States)

    Rizkallah, Raed; Alexander, Karen E; Hurt, Myra M

    2011-10-01

    Cessation of transcriptional activity is a hallmark of cell division. Many biochemical pathways have been shown and proposed over the past few decades to explain the silence of this phase. In particular, many individual transcription factors have been shown to be inactivated by phosphorylation. In this report, we show the simultaneous phosphorylation and mitotic redistribution of a whole class of modified transcription factors. C(2)H(2) zinc finger proteins (ZFPs) represent the largest group of gene expression regulators in the human genome. Despite their diversity, C(2)H(2) ZFPs display striking conservation of small linker peptides joining their adjacent zinc finger modules. These linkers are critical for DNA binding activity. It has been proposed that conserved phosphorylation of these linker peptides could be a common mechanism for the inactivation of the DNA binding activity of C(2)H(2) ZFPs, during mitosis. Using a novel antibody, raised against the phosphorylated form of the most conserved linker peptide sequence, we are able to visualize the massive and simultaneous mitotic phosphorylation of hundreds of these proteins. We show that this wave of phosphorylation is tightly synchronized, starting in mid-prophase right after DNA condensation and before the breakdown of the nuclear envelope. This global phosphorylation is completely reversed in telophase. In addition, the exclusion of the phospho-linker signal from condensed DNA clearly demonstrates a common mechanism for the mitotic inactivation of C(2)H(2) ZFPs. © 2011 Landes Bioscience

  16. A quantitative investigation of linker histone interactions with nucleosomes and chromatin

    Science.gov (United States)

    White, Alison E.; Hieb, Aaron R.; Luger, Karolin

    2016-01-01

    Linker histones such as H1 are abundant basic proteins that bind tightly to nucleosomes, thereby acting as key organizers of chromatin structure. The molecular details of linker histone interactions with the nucleosome, and in particular the contributions of linker DNA and of the basic C-terminal tail of H1, are controversial. Here we combine rigorous solution-state binding assays with native gel electrophoresis and Atomic Force Microscopy, to quantify the interaction of H1 with chromatin. We find that H1 binds nucleosomes and nucleosomal arrays with very tight affinity by recognizing a specific DNA geometry minimally consisting of a solitary nucleosome with a single ~18 base pair DNA linker arm. The association of H1 alters the conformation of trinucleosomes so that only one H1 can bind to the two available linker DNA regions. Neither incorporation of the histone variant H2A.Z, nor the presence of neighboring nucleosomes affects H1 affinity. Our data provide a comprehensive thermodynamic framework for this ubiquitous chromatin architectural protein. PMID:26750377

  17. A High-Throughput Small Molecule Screen for C. elegans Linker Cell Death Inhibitors.

    Science.gov (United States)

    Schwendeman, Andrew R; Shaham, Shai

    2016-01-01

    Programmed cell death is a ubiquitous process in metazoan development. Apoptosis, one cell death form, has been studied extensively. However, mutations inactivating key mammalian apoptosis regulators do not block most developmental cell culling, suggesting that other cell death pathways are likely important. Recent work in the nematode Caenorhabditis elegans identified a non-apoptotic cell death form mediating the demise of the male-specific linker cell. This cell death process (LCD, linker cell-type death) is morphologically conserved, and its molecular effectors also mediate axon degeneration in mammals and Drosophila. To develop reagents to manipulate LCD, we established a simple high-throughput screening protocol for interrogating the effects of small molecules on C. elegans linker cell death in vivo. From 23,797 compounds assayed, 11 reproducibly block linker cell death onset. Of these, five induce animal lethality, and six promote a reversible developmental delay. These results provide proof-of principle validation of our screening protocol, demonstrate that developmental progression is required for linker cell death, and suggest that larger scale screens may identify LCD-specific small-molecule regulators that target the LCD execution machinery.

  18. Linker length and flexibility induces new cellobiohydrolase activity of PoCel6A from Penicillium oxalicum.

    Science.gov (United States)

    Gao, Le; Wang, Lushan; Jiang, Xukai; Qu, Yinbo

    2015-06-01

    In a previous study, a novel cellobiohydrolase, PoCel6A, with new enzymatic activity against p-nitrophenyl-β-D-cellobioside (pNPC), was purified from Penicillium oxalicum. The cellulose-binding module and catalytic domain of PoCel6A showed a high degree of sequence similarity with other fungal Cel6As. However, PoCel6A had 11 more amino acids in the linker region than other Cel6As. To evaluate the relationship between the longer linker of PoCel6A and its enzymatic activity, 11 amino acids were deleted from the linker region of PoCel6A. The shortened PoCel6A linker nullified the enzymatic activity against pNPC but dramatically increased the enzyme's capacity for crystalline cellulose degradation. The shortened linker segment appeared to have no effect on the secondary structural conformation of PoCel6A. Another variant (PoCel6A-6pro) with six consecutive proline residues in the interdomain linker had a higher rigid linker, and no enzymatic activity was observed against soluble and insoluble substrate. The flexibility of the linker had an important function in the formation of active cellulase. The length and flexibility of the linker is clearly able to modify the function of PoCel6A and induce new characteristics of Cel6A. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. A linker peptide with high affinity towards silica-containing materials.

    Science.gov (United States)

    Sunna, Anwar; Chi, Fei; Bergquist, Peter L

    2013-06-25

    A peptide sequence with affinity to silica-containing materials was fused to a truncated form of Streptococcus strain G148 Protein G. The resulting recombinant Linker-Protein G (LPG) was produced in Escherichia coli and purified to apparent homogeneity. It displayed high affinity towards two natural clinoptilolite zeolites. The LPG also displayed high binding affinity towards commercial-grade synthetic zeolite, silica and silica-containing materials. A commercial sample of the truncated Protein G and a basic protein, both without the linker, did not bind to natural or synthetic zeolites or silica. We conclude that the zeolite-binding affinity is mediated by the linker peptide sequence. As a consequence, these data may imply that the binding affinity is directed to the SiO2 component rather than to the atomic orientation on the zeolite crystal surface as previously assumed. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. A histone-mimicking interdomain linker in a multidomain protein modulates multivalent histone binding.

    Science.gov (United States)

    Kostrhon, Sebastian; Kontaxis, Georg; Kaufmann, Tanja; Schirghuber, Erika; Kubicek, Stefan; Konrat, Robert; Slade, Dea

    2017-10-27

    N-terminal histone tails are subject to many posttranslational modifications that are recognized by and interact with designated reader domains in histone-binding proteins. BROMO domain adjacent to zinc finger 2B (BAZ2B) is a multidomain histone-binding protein that contains two histone reader modules, a plant homeodomain (PHD) and a bromodomain (BRD), linked by a largely disordered linker. Although previous studies have reported specificity of the PHD domain for the unmodified N terminus of histone H3 and of the BRD domain for H3 acetylated at Lys14 (H3K14ac), the exact mode of H3 binding by BAZ2B and its regulation are underexplored. Here, using isothermal titration calorimetry and NMR spectroscopy, we report that acidic residues in the BAZ2B PHD domain are essential for H3 binding and that BAZ2B PHD-BRD establishes a polyvalent interaction with H3K14ac. Furthermore, we provide evidence that the disordered interdomain linker modulates the histone-binding affinity by interacting with the PHD domain. In particular, lysine-rich stretches in the linker, which resemble the positively charged N terminus of histone H3, reduce the binding affinity of the PHD finger toward the histone substrate. Phosphorylation, acetylation, or poly(ADP-ribosyl)ation of the linker residues may therefore act as a cellular mechanism to transiently tune BAZ2B histone-binding affinity. Our findings further support the concept of interdomain linkers serving a dual role in substrate binding by appropriately positioning the adjacent domains and by electrostatically modulating substrate binding. Moreover, inhibition of histone binding by a histone-mimicking interdomain linker represents another example of regulation of protein-protein interactions by intramolecular mimicry. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  1. Linker length affects expression and bioactivity of the onconase fusion protein in Pichia pastoris.

    Science.gov (United States)

    Yang, G G; Xu, X Y; Ding, Y; Cui, Q Q; Wang, Z; Zhang, Q Y; Shi, S H; Lv, Z Y; Wang, X Y; Zhang, J H; Zhang, R G; Xu, C S

    2015-12-29

    The aim of this study was to analyze the effect of linker length on the expression and biological activity of recombinant protein onconase (ONC) in fusion with human serum albumin (HSA) in Pichia pastoris. Four flexible linkers with different lengths namely Linker L0, L1: (GGGGS)1, L2: (GGGGS)2, and L3:(GGGGS)3 were inserted into the fusion gene and referred to as HSA-n-ONC, where N = 0, 5, 10, or 15. The sequence of the fusion gene HSA-ONC was designed based on the GC content and codon bias in P. pastoris; the signal peptide of albumin was used as the secretion signal. Gene sequences coding for the fusion protein with different linkers were inserted into pPICZα-A to form recombinant plasmids pPICZα-A/HSA-n-ONC, which were then transformed into P. pastoris X-33 for protein expression. Ideal conditions for expression of the fusion proteins were optimized at a small scale, using shake flasks before proceeding to mass production in 10-L fermenters. The recombinant fusion proteins were purified by aqueous two-phase extraction coupled with DEAE anion exchange chromatography, and their cytotoxic effect on the tumor cell was evaluated by the sulforhodamine B assay. The results showed that the expressed amount of fusion proteins had no significant relationship with the length of different linkers and rHSA-0-ONC had no cytotoxic effect on the tumor cells. While rHSA-5-ONC and rHSA-10-ONC had a weak cytotoxic effect, rHSA-15-ONC could kill various tumor cells in vitro. In summary, the biological activity of the fusion protein gradually improved with increasing length of the linker.

  2. Mechanistic aspects of hydrazine-induced Pt colloid instability and monitoring aggregation kinetics with nanoparticle impact electroanalysis.

    Science.gov (United States)

    Robinson, D A; Duay, J; Kondajji, A M; Stevenson, K J

    2016-12-12

    Here we investigate the mechanistic aspects of Pt nanoparticle (NP) aggregation in solutions typically used for detecting NP/electrode impacts by electrocatalytic amplification (ECA). We previously proposed a general mechanism for Pt colloid destabilization that involved the participation of both the hydrazine redox probe and the pH buffer species as coagulants. Herein the Pt NP coagulation and aggregation mechanisms were further investigated with microscopic kinetic NP concentration monitoring and zeta potential measurements using nanoparticle tracking analysis (NTA), as well as open circuit potential experiments with a citrate-treated polycrystalline Pt surface to assess electrical double layer potential. After considering the combined results of these experiments we propose that the colloidal stability of citrate-capped platinum nanoparticles involves much more than the typical physicochemical interactions predicted by DLVO theory. A structure based on intermolecular H-bonding in the citrate capping layer is the most plausible explanation for the exceptional stability of large Pt NPs in high ionic strength buffers. Thus, the mechanism of Pt NP aggregation includes specific reactive contributions from hydrazine. The catalytic decomposition of hydrazine, in particular, is thought to occur to some extent at the citrate-coated Pt surface while the citrate remains adsorbed. Evolved gases such as ammonia and possible surface bound intermediates from Pt-catalyzed decomposition of hydrazine may disrupt the stability of the citrate layer, causing colloidal instability and thus promoting Pt NP coagulation. In the closing section, we demonstrate nanoparticle impact electroanalysis by ECA detection as a method to quantify Pt NP concentration with adequate time resolution for monitoring the kinetics of Pt NP coagulation.

  3. N'-[5-(4-Nitro-phen-yl)furan-2-yl-methyl-idene]-N,N-diphenyl-hydrazine.

    Science.gov (United States)

    Mendoza, Angel; Cabrera-Vivas, Blanca M; Meléndrez-Luevano, Ruth; Pacheco-Álvarez, Teresa; Carranza, Vladimir

    2010-07-17

    The title compound, C(23)H(17)N(3)O(3), has an E configuration with respect to the C=N bond. The dihedral angle between the two phenyl rings bonded to the hydrazine group is 86.45 (13)°. The furan ring makes dihedral angles of 3.4 (2) and 7.06 (13)°, respectively, with the methyl-idenehydrazine C=N-N plane and the benzene ring.

  4. Thermodynamically Modeled Non-equilibrium Structure of Combustion Products and Decomposition of Hydrazine-based Liquid Propellants

    OpenAIRE

    A. A. Dorofeev; D. M. Yagodnikov

    2016-01-01

    The paper studies the emerging hallmarks and the characteristics of a two-parameter chemical non-equilibrium structure of the combustion products of liquid propellants as applied to the low-thrust liquid propellant engines (LT LPE) operating in the aircraft control system. The study is based on hydrazine and nitrogen tetroxide products. The paper also analyses the catalytic and thermal decomposition of these substances in terms of inter-conditionality of the working process components in the ...

  5. A flexible protein linker improves the function of epitope-tagged proteins in Saccharomyces cerevisiae.

    Science.gov (United States)

    Sabourin, Michelle; Tuzon, Creighton T; Fisher, Timothy S; Zakian, Virginia A

    2007-01-01

    Epitope tagging permits the detection of proteins when protein-specific antibodies are not available. However, the epitope tag can reduce the function of the tagged protein. Here we describe a cassette that can be used to introduce an eight amino acid flexible linker between multiple Myc epitopes and the open reading frame of a given gene. We show that inserting the linker improves the in vivo ability of the telomerase subunits Est2p and Est1p to maintain telomere length. The methods used here are generally applicable to improve the function of tagged proteins in both Saccharomyces cerevisiae and Schizosaccharomyces pombe. Copyright (c) 2007 John Wiley & Sons, Ltd.

  6. Synthesis and properties of cholesteryl-modified triple-helix forming oligonucleotides containing a triglycyl linker.

    Science.gov (United States)

    Vu, H; Hill, T S; Jayaraman, K

    1994-01-01

    In order to enhance the nuclear uptake of triple-helix forming oligonucleotides (TFOs), a triglycylcholesterol group was attached to the 3' end. The peptide unit was introduced as a "labile" linker with the aim of releasing the oligonucleotide from the endosomes by the action of peptidases after crossing the cell membrane. Cholesteryl-CPG (8) and -TentaGel (9) supports containing 2-[N-(glycylglycylglycyl)amino]propane-1,3-diol (GAP-3) linker were prepared and used for automated oligonucleotide synthesis. The synthesis, characterization, and stability of these compounds are described.

  7. A New Achiral Linker Reagent for the Incorporation of Multiple Amino Groups Into Oligonucleotides

    DEFF Research Database (Denmark)

    1997-01-01

    The present invention relates to a new functionalized achiral linker reagent for incorporating multiple primary amino groups or reporter groups into oligonucleotides following the phosphoramidite methodology. It is possible to substitute any ribodeoxynucleotide, deoxynucleotide, or nucleotide......-oxyl-2,2,5,5-tetramethylpyrrolidine), TEMPO (N-oxyl-2,2,6,6-tetramethylpiperidine), dinitrophenyl, texas red, tetramethyl rhodamine, 7-nitrobenzo-2-oxa-1-diazole (NBD), or pyrene. The present invention also relates to a solid phase support, e.g. a Controlled Pore Glass (CPG), immobilized linker reagent...

  8. Noble metal-free hydrazine fuel cell catalysts: EPOC effect in competing chemical and electrochemical reaction pathways.

    Science.gov (United States)

    Sanabria-Chinchilla, Jean; Asazawa, Koichiro; Sakamoto, Tomokazu; Yamada, Koji; Tanaka, Hirohisa; Strasser, Peter

    2011-04-13

    We report the discovery of a highly active Ni-Co alloy electrocatalyst for the oxidation of hydrazine (N(2)H(4)) and provide evidence for competing electrochemical (faradaic) and chemical (nonfaradaic) reaction pathways. The electrochemical conversion of hydrazine on catalytic surfaces in fuel cells is of great scientific and technological interest, because it offers multiple redox states, complex reaction pathways, and significantly more favorable energy and power densities compared to hydrogen fuel. Structure-reactivity relations of a Ni(60)Co(40) alloy electrocatalyst are presented with a 6-fold increase in catalytic N(2)H(4) oxidation activity over today's benchmark catalysts. We further study the mechanistic pathways of the catalytic N(2)H(4) conversion as function of the applied electrode potential using differentially pumped electrochemical mass spectrometry (DEMS). At positive overpotentials, N(2)H(4) is electrooxidized into nitrogen consuming hydroxide ions, which is the fuel cell-relevant faradaic reaction pathway. In parallel, N(2)H(4) decomposes chemically into molecular nitrogen and hydrogen over a broad range of electrode potentials. The electroless chemical decomposition rate was controlled by the electrode potential, suggesting a rare example of a liquid-phase electrochemical promotion effect of a chemical catalytic reaction ("EPOC"). The coexisting electrocatalytic (faradaic) and heterogeneous catalytic (electroless, nonfaradaic) reaction pathways have important implications for the efficiency of hydrazine fuel cells. © 2011 American Chemical Society

  9. Silver nanoparticles sensitized C60(Ag@C60) as efficient electrocatalysts for hydrazine oxidation: Implication for hydrogen generation reaction

    Science.gov (United States)

    Narwade, Shankar S.; Mulik, Balaji B.; Mali, Shivsharan M.; Sathe, Bhaskar R.

    2017-02-01

    Herein, we report the synthesis of silver nanoparticles (Ag NPs; 10 ± 0.5 nm) sensitized Fullerene (C60; 15 ±2 nm) nanocatalysts (Ag@C60) for the first time showing efficient electroatalytic activity for the oxidation of hydrazine demonstrating activity comparable to that of Pt in acidic, neutral and basic media. The performance is comparable with the best available electrocatalytic system and plays a vital role in the overall hydrogen generation reactions from hydrazine as a one of the fuel cell reaction. The materials are synthesized by a simple and scalable synthetic route involving acid functionalization of C60 followed by chemical reduction of Ag+ ions in ethylene glycol at high temperature. The distributation of Silver nanoparticles (Ag NPs) (morphological information) on C60, bonding, its crystal structure, along with activity towards hydrazine oxidation (electrocatalytic) is studied using TEM, XRD, UV-vis, XPS, FTIR and electrochemical (cyclic voltammetry) studies, respectively. The observed efficient electrocatalytic activity of the as-synthesized electrode is attributed to the co-operative response and associated structural defects due to their oxidative functionalization along with thier cooperative functioning at nanodimensions.

  10. Liquid Exfoliated Graphene as Dopant for Improving the Thermoelectric Power Factor of Conductive PEDOT:PSS Nanofilm with Hydrazine Treatment.

    Science.gov (United States)

    Xiong, Jinhua; Jiang, Fengxing; Shi, Hui; Xu, Jingkun; Liu, Congcong; Zhou, Weiqiang; Jiang, Qinglin; Zhu, Zhengyou; Hu, Yongjing

    2015-07-15

    Here, we fabricated a highly conductive poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) ( PSS) nanofilm via vacuum filtration with enhanced thermoelectric power factor by doping of liquid exfoliated graphene (GE) and hydrazine treatment. The effect of GE exfoliated in dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) on the electrical conductivity and thermopower of PSS was investigated. Although electrical conductivity decreased with increasing GE, thermoelectric power factors of PSS nanofilms were improved with 3 wt % GE in DMF (38.6 μW m(-1) K(-2)) and in NMP (28.0 μW m(-1) K(-2)) compared to pure PSS (11.5 μW m(-1) K(-2)). The mechanism of improvement was proposed to be the removal of PSS and the good interaction between PEDOT and GE. With hydrazine treatment, 3 wt % GE-doped PSS nanofilm (PG3) showed a further enhanced power factor of 53.3 μW m(-1) K(-2) (∼5 times higher than that of pristine PSS nanofilm). The effects of hydrazine containing concentration, treatment time, and temperature on the electrical conductivity and Seebeck coefficient of PG3 were investigated systematically. An estimated thermoelectric figure of merit (ZT) is 0.05 with the optimized power factor at room temperature.

  11. Synthesis, characterization, thermal behavior and antimicrobial activity of 3-methyl benzoate complexes of transition metal with hydrazine

    Directory of Open Access Journals (Sweden)

    S. Mohanapriya

    2016-08-01

    Full Text Available Reaction of the ligands, 3-methyl benzoic acid (mbH and hydrazine with transition metal ions form the complexes of formulae, [M(N2H42(mb2].H2O where M = Co(II and Zn(II at pH = 5-6, [M(N2H4n(mb2].xH2O where M = Ni(II, n = 2, x = 0 at pH = 5 and M = Cd, n = 1, x = 1 at pH = 6. The same acid also forms metal carboxylates with zinc and copper of formula, [Zn(mb2H2O].H2O at pH = 6 and [Cu(mb2].H2O at pH = 5, respectively. The IR spectra of the complexes show that hydrazine is present as bridging bidentate ligand and the carboxylic acid as monodentate bridging carboxylate anion. The electronic spectra, magnetic moments and ESR spectral data suggest the coordination number. Thermal studies show that cobalt, zinc and nickel complexes containing hydrazine, and carboxylates of copper, zinc on their thermal decomposition form the corresponding metal oxides in nano size in the temperature range 755-815 °C. The antibacterial and antifungal activity show that both activities of the complexes are higher than that of the acid and among the complexes, cadmium compound shows more antimicrobial activity towards bacteria and fungi.

  12. Derivatization Ion Chromatography for the Determination of Monoethanolamine in Presence of Hydrazine in PHWR Steam-Water Circuits

    Directory of Open Access Journals (Sweden)

    Ayushi D.

    2011-01-01

    Full Text Available A simple, rapid and accurate method for the determination of monoethanolamine (MEA in PHWR steam-water circuits has been developed. MEA is added in the feed water to provide protection against corrosion while hydrazine is added to scavenge dissolved oxygen. The quantitative determination of MEA in presence of hydrazine was accomplished using derivatization ion chromatography with conductometric detection in nonsuppressed mode. A Metrosep cation 1-2 analytical column and a Metrosep cartridge were used for cation separation. A mixture of 4 mM tartaric acid, 20% acetone and 0.05 mM HNO3 was used as eluent. Acetone in the mobile phase leads to the formation of different derivatives with MEA and hydrazine. The interferences due Na+ and NH4 + were eliminated by adopting a simple pretreatment procedure employing OnGuard-H cartridge. The limit of detection limit of MEA was 0.1 μg mL−1 and the relative standard deviation was 2% for the overall method. The recovery of MEA added was in the range 95%–102%. The method was applied to the determination of MEA in steam generator water samples.

  13. Highly stable hydrazine chemical sensor based on vertically-aligned ZnO nanorods grown on electrode.

    Science.gov (United States)

    Ahmad, Rafiq; Tripathy, Nirmalya; Ahn, Min-Sang; Hahn, Yoon-Bong

    2017-05-15

    Herein, we report a binder-free, stable, and high-performance hydrazine chemical sensor based on vertically aligned zinc oxide nanorods (ZnO NRs), grown on silver (Ag) electrode via low-temperature solution route. The morphological characterizations showed that the NRs were grown vertically in high density and possess good crystallinity. The as-fabricated hydrazine chemical sensors showed an excellent sensitivity of 105.5 μAμM-1cm-2, a linear range up to 98.6μM, and low detection limit of 0.005μM. It also showed better long-term stability, good reproducibility and selectivity. Furthermore, the fabricated electrodes were evaluated for hydrazine detection in water samples. We found the approach of directly growing nanostructures as a key factor for enhanced sensing performance of our electrodes, which effectively transfers electron from ZnO NRs to conductive Ag electrode. Thus it holds future prospective applications as binder-free, cost-effective, and stable sensing devices fabrication. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Enzyme-free electrochemical immunosensor based on methylene blue and the electro-oxidation of hydrazine on Pt nanoparticles.

    Science.gov (United States)

    Dutta, Gorachand; Nagarajan, Sureshbabu; Lapidus, Lisa J; Lillehoj, Peter B

    2017-06-15

    Enzyme-free electrochemical sensors enable rapid, high sensitivity measurements without the limitations associated with enzyme reporters. However, the performance of non-enzymatic electrochemical sensors tends to suffer from slow electrode kinetics and poor signal stability. We report a new enzyme-free electrochemical immunosensor based on a unique competitive detection scheme using methylene blue (MB), hydrazine and platinum nanoparticles (Pt NPs). This scheme is coupled with a robust immunosandwich format employing a MB-labelled detection antibody as a non-enzymatic reporter. In the presence of the target antigen, surface-immobilized MB consumes interfacial hydrazine thereby diminishing the electro-oxidation of hydrazine on Pt NPs. Thus, the concentration of the antigen is directly proportional to the reduction in the electrochemical signal. For proof-of-concept, this sensor was used to detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2), an important malaria biomarker, in unadulterated human saliva samples. Chronocoulometric measurements showed that this platform exhibits pM-range sensitivity, high specificity and good reproducibility, making it well suited for many biosensing applications including noninvasive diagnostic testing. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. A photolabile linker for the solid-phase synthesis of 4-substituted NH-1,2,3-triazoles

    DEFF Research Database (Denmark)

    Qvortrup, Katrine; Nielsen, Thomas Eiland

    2011-01-01

    A novel photolabile linker for solid-phase synthesis is presented. The linker displays an azido handle for copper-catalyzed azide–alkyne cycloaddition reactions with a variety of alkynes, remains intact under typical solid-phase reaction conditions, and enables a mild photolytic release of 4...

  16. General Approach for Introduction of Various Chemical Labels in Specific RNA Locations Based on Insertion of Amino Linkers

    Directory of Open Access Journals (Sweden)

    Dmitri Graifer

    2013-11-01

    Full Text Available Introduction of reporter groups at designed RNA sites is a widely accepted approach to gain information about the molecular environment of RNAs in their complexes with other biopolymers formed during various cellular processes. A general approach to obtain RNAs bearing diverse reporter groups at designed locations is based on site-specific insertion of groups containing primary aliphatic amine functions (amino linkers with their subsequent selective derivatization by appropriate chemicals. This article is a brief review on methods for site-specific introduction of amino linkers in different RNAs. These methods comprise: (i incorporation of a nucleoside carrying an amino-linker or a function that can be substituted with it into oligoribonucleotides in the course of their chemical synthesis; (ii assembly of amino linker-containing RNAs from short synthetic fragments via their ligation; (iii synthesis of amino linker-modified RNAs using T7 RNA polymerase; (iv insertion of amino linkers into unmodified RNAs at functional groups of a certain type such as the 5'-phosphates and N7 of guanosine residues and (v introduction of an amino linker into long highly structured RNAs exploiting an approach based on sequence-specific modification of nucleic acids. Particular reporter groups used for derivatization of amino linker-containing RNAs together with types of RNA derivatives obtained and fields of their application are presented.

  17. Novel cross-linkers for PDMS networks for controlled and well distributed grafting of functionalities by click chemistry

    DEFF Research Database (Denmark)

    Bahrt, Frederikke; Dimitrov, Ivaylo; Daugaard, Anders Egede

    2013-01-01

    An azide-containing, trifunctional vinyl cross-linker for silicone networks has been synthesized. The cross-linker has through Cu(i) catalyzed 1,3-cycloaddition been reacted with six different alkyne-containing chemical groups which each possess a particular functionality. The functional cross-li...

  18. Clicking Hydrazine and Aldehyde: The Way to Labeling of Viruses with Quantum Dots.

    Science.gov (United States)

    Hong, Zheng-Yuan; Lv, Cheng; Liu, An-An; Liu, Shu-Lin; Sun, En-Ze; Zhang, Zhi-Ling; Lei, Ai-Wen; Pang, Dai-Wen

    2015-12-22

    Real-time tracking of fluorophore-tagged viruses in living cells can help uncover virus infection mechanisms. Certainly, the indispensable prerequisite for virus-tracking is to label viruses with some bright and photostable beacons such as quantum dots (QDs) via an appropriate labeling strategy. Herein, we devise a convenient hydrazine-aldehyde based strategy to label viruses with QDs through the conjugation of 4-formylbenzoate (4FB) modified QDs to 6-hydrazinonicotinate acetone hydrazone (HyNic) modified viruses under mild conditions. On the basis of this strategy, viruses can be successfully labeled with QDs with high selectivity, stable conjugation, good reproducibility, high labeling efficiency of 92-93% and maximum retention of both fluorescence properties of QDs and infectivity of viruses, which is very meaningful to tracking and statistical analysis of virus infection processes. By further comparing with the most widely used labeling strategy based on the Biotin-SA system, this new strategy has advantages of both high labeling efficiency and good retention of virus infectivity, thus offering a promising alternative for virus-labeling. Moreover, due to the ubiquitous presence of exposed amino groups on the surface of various viruses, this selective, efficient, reproducible and biofriendly strategy should have good universality for labeling both enveloped and nonenveloped viruses.

  19. Conformational effects on hydrazine and OH coadsorption on Ni(111): A first-principles investigation

    Science.gov (United States)

    Agusta, Mohammad Kemal; Purwoko, Prasetiyo Hadi; Saputro, Adhitya Gandaryus; Fathurrahman, Fadjar; Dipojono, Hermawan K.; Diño, Wilson Agerico

    2017-10-01

    Using first-principles Density Functional Theory calculations, we investigated coadsorption of hydrazine (N2H4) and OH on Ni(111) surface. Two types of N2H4 conformations: anti and cis-conformer, with coadsorbed OH on several high symmetry sites on Ni(111) surface were studied. We found that coadsorption with cis-conformer N2H4 significantly modifies OH site preferences while such modification is less profound for coadsorption with anti-conformer N2H4. On the other way around, the cis-confomer N2H4 coadsorption becomes more stable due to the pressence of OH. We identified the electrostatic attractive dipole interaction between the coadsorbed species as the underlying mechanism for the stabilization. This electrostatic interaction is particularly strong for cis-conformer N2H4 due to its large dipole moment. We also found Nsbnd H bond elongation for cis-conformer N2H4 coadsorption with OH due to the interaction between accumulated charge in OH with the H atom of N2H4. Therefore, it can be inferred that coadsorption with OH promotes the dehydrogenation reaction of N2H4 via stabilization of cis-confomer N2H4.

  20. Hydrogen generation from decomposition of hydrous hydrazine over Ni-Ir/CeO2 catalyst

    Directory of Open Access Journals (Sweden)

    Hongbin Dai

    2017-02-01

    Full Text Available The synthesis of highly active and selective catalysts is the central issue in the development of hydrous hydrazine (N2H4·H2O as a viable hydrogen carrier. Herein, we report the synthesis of bimetallic Ni-Ir nanocatalyts supported on CeO2 using a one-pot coprecipitation method. A combination of XRD, HRTEM and XPS analyses indicate that the Ni-Ir/CeO2 catalyst is composed of tiny Ni-Ir alloy nanoparticles with an average size of around 4 nm and crystalline CeO2 matrix. The Ni-Ir/CeO2 catalyst exhibits high catalytic activity and excellent selectivity towards hydrogen generation from N2H4·H2O at mild temperatures. Furthermore, in contrast to previously reported Ni-Pt catalysts, the Ni-Ir/CeO2 catalyst shows an alleviated requirement on alkali promoter to achieve its optimal catalytic performance.

  1. Review on effects of hydrazine hydrate and L-ascorbic acid on electrical conductivity of graphene

    Science.gov (United States)

    Zainuddin, Mohammad Fiqri; Him, Nik Raikhan Nik; Othman, Nur Hidayati; So'aib, Mohamad Sufian; Abdullah, Wan Fazlida Hanim

    2017-12-01

    Graphene is a 2D carbon-based materials that comprises one atom-thick planar sheets of sp2-bonded carbon atoms making it as the thinnest compound in the world. Its application in electronics devices has been widely investigated because of the high electron density on monochrome graphene sheets. Graphene can be synthesized using top down approach, which involves oxidation of graphite to GO using Staudenmaier or Hummer's methods and subsequently reducing the GO to graphene. The. At the current state of graphene research, the controlled, large scale synthesis of high quality graphene is still remains a challenge. All the methods and raw materials used for graphene synthesis have their advantages and disadvantages. Thus, the purpose of this study is to review the effects of reducing agents particularly, hydrazine hydrate (HH) and L-ascorbic acid (L-AA) on the electrical conductivity of graphene. The review was carried out by comparing characteristic properties of graphene after the reduction process using several equipment such as FTIR, XRD and four-point probe for conductivity.

  2. Hierarchical nano-on-micro copper with enhanced catalytic activity towards electro-oxidation of hydrazine

    Science.gov (United States)

    Yan, Xiaodong; Liu, Yuan; Scheel, Kyle R.; Li, Yong; Yu, Yunhua; Yang, Xiaoping; Peng, Zhonghua

    2018-01-01

    The electrochemical properties of catalyst materials are highly dependent on the materials structure and architecture. Herein, nano-on-micro Cu electrodes are fabricated by growing Cu microcrystals on Ni foam substrate, followed by introducing Cu nanocrystals onto the surface of the Cu microcrystals. The introduction of Cu nanocrystals onto the surface of Cu microcrystals is shown to dramatically increase the electrochemically active surface area and thus significantly enhances the catalytic activity of the catalyst electrode towards electro-oxidation of hydrazine. The onset potential (-1.04 V vs. Ag/AgCl) of the nano-on-micro Cu electrode is lower than those of the reported Cu-based catalysts under similar testing conditions, and a current density of 16 mA·cm-2, which is 2 times that of the microsized Cu electrode, is achieved at a potential of -0.95 V vs. Ag/AgCl. Moreover, the nano-on-micro Cu electrode demonstrates good long-term stability.

  3. Investigation of a catalytic gas generator for the Space Shuttle APU. [hydrazine Auxiliary Propulsion Unit

    Science.gov (United States)

    Emmons, D. L.; Huxtable, D. D.; Blevins, D. R.

    1974-01-01

    An investigation was conducted to establish the capability of a monopropellant hydrazine catalytic gas generator to meet the requirements specified for the Space Shuttle APU. Detailed analytical and experimental studies were conducted on potential problem areas including long-term nitriding effects on materials, design variables affecting catalyst life, vehicle vibration effects, and catalyst oxidation/contamination. A full-scale gas generator, designed to operate at a chamber pressure of 750 psia and a flow rate of 0.36 lbm/sec, was fabricated and subjected to three separate life test series. The objective of the first test series was to demonstrate the capability of the gas generator to successfully complete 20 simulated Space Shuttle missions in steady-state operation. The gas generator was then refurbished and subjected to a second series of tests to demonstrate the pulse-mode capability of the gas generator during 20 simulated missions. The third series of tests was conducted with a refurbished reactor to further demonstrate pulse-mode capability with a modified catalyst bed.

  4. Data from computational analysis of the peptide linkers in the MocR bacterial transcriptional regulators

    Directory of Open Access Journals (Sweden)

    Sebastiana Angelaccio

    2016-12-01

    Interpretation and discussion of reported data refer to the article “Structural properties of the linkers connecting the N- and C- terminal domains in the MocR bacterial transcriptional regulators” (T. Milano, S. Angelaccio, A. Tramonti, M. L. Di Salvo, R. Contestabile, S. Pascarella, 2016 [1].

  5. Antibody drug conjugates: design and selection of linker, payload and conjugation chemistry.

    Science.gov (United States)

    McCombs, Jessica R; Owen, Shawn C

    2015-03-01

    Antibody drug conjugates (ADCs) have emerged as an important pharmaceutical class of drugs designed to harness the specificity of antibodies with the potency of small molecule therapeutics. The three main components of ADCs are the antibody, the linker, and the payload; the majority of early work focused intensely on improving the functionality of these pieces. Recently, considerable attention has been focused on developing methods to control the site and number of linker/drug conjugated to the antibody, with the aim of producing more homogenous ADCs. In this article, we review popular conjugation methods and highlight recent approaches including "click" conjugation and enzymatic ligation. We discuss current linker technology, contrasting the characteristics of cleavable and non-cleavable linkers, and summarize the essential properties of ADC payload, centering on chemotherapeutics. In addition, we report on the progress in characterizing to determine physicochemical properties and on advances in purifying to obtain homogenous products. Establishing a set of selection and analytical criteria will facilitate the translation of novel ADCs and ensure the production of effective biosimilars.

  6. School Improvement Efforts via Linkers and Linkage Systems. A Paper Presented to the Dissemination Community.

    Science.gov (United States)

    Haugerud, Al, Ed.

    Compiled from papers written by project linkers after they spent two and one-half years working with schools, this report describes the Northwest Reading Consortium, a program linking schools in Washington, Idaho, Alaska, and Oregon with research and development (R&D) resources for improving reading instruction. The function of the linking…

  7. Folic acid-functionalized fluorescent gold nanoclusters with polymers as linkers for cancer cell imaging.

    Science.gov (United States)

    Qiao, Juan; Mu, Xiaoyu; Qi, Li; Deng, Jingjing; Mao, Lanqun

    2013-09-21

    A novel nano-conjugate containing ultrasmall water-soluble AuNCs protected by ovalbumin as the fluorescent part, folic acid as the targeting ligand and a homopolymer N-acryloxysuccinimide as the linker has been investigated. Moreover, specific staining of HeLa cells by the nano-conjugate has been demonstrated.

  8. frameworks bearing1,3-bis(4-pyridyl)propane and inorganic linkers

    Indian Academy of Sciences (India)

    up like mushrooms, some of which exhibit certain con- formational effects such as breathing effects.11–18 As is well known, one of the key factors for the construc- tion of MOFs is the design and selection of appropriate linkers which link the metal ions or secondary build- ing units into the targeted MOFs. Most of the recent.

  9. Novel pH-Sensitive Cationic Lipids with Linear Ortho Ester Linkers for Gene Delivery

    Science.gov (United States)

    Chen, Haigang; Zhang, Huizhen; Thor, Der; Rahimian, Roshanak; Guo, Xin

    2012-01-01

    In an effort to develop pH-sensitive lipoplexes for efficient gene delivery, we report three novel cationic lipids containing a linear ortho ester linker that conjugates either the headgroup (Type I) or one hydrocarbon chain (Type II) with the rest of the lipid molecule. The cationic lipids carry either an iodide or a chloride counterion. Compared to our previously reported cyclic ortho ester linker, the linear ortho ester linker facilitated the construction of cationic liposomes and lipoplexes with different helper lipids. The chloride counterion not only facilitated the hydration of the lipid films during liposome construction, but also enhanced the hydrolysis of the ortho ester linker in the lipoplexes. After incubation at endosomal pH 5.5, the Type I lipoplexes aggregated and destabilized the endosome-mimicking model liposomes, but not the Type II lipoplexes. The helper lipids (DOPE or cholesterol) of the lipoplexes enhanced the pH-sensitivity of the Type I lipoplexes. In CV-1 cells (monkey kidney fibroblast), the Type I ortho ester-based lipoplexes, especially those with the chloride counterion, significantly improved the gene transfection efficiency, in some cases by more than 100 fold, compared to their pH-insensitive counterparts consisting of DOTAP. The gene transfection efficiency of the ortho ester-based lipoplexes was well correlated with their rate of aggregation and membrane destabilization in response to the endosomal pH 5.5. PMID:22480493

  10. The linker pivot in Ci-VSP: the key to unlock catalysis.

    Science.gov (United States)

    Hobiger, Kirstin; Utesch, Tillmann; Mroginski, Maria Andrea; Seebohm, Guiscard; Friedrich, Thomas

    2013-01-01

    In the voltage-sensitive phosphatase Ci-VSP, conformational changes in the transmembrane voltage sensor domain (VSD) are transduced to the intracellular catalytic domain (CD) leading to its dephosphorylation activity against membrane-embedded phosphoinositides. The linker between both domains is proposed to be crucial for the VSD-CD coupling. With a combined approach of electrophysiological measurements on Xenopus oocytes and molecular dynamics simulations of a Ci-VSP model embedded in a lipid bilayer, we analyzed how conformational changes in the linker mediate the interaction between the CD and the activated VSD. In this way, we identified specific residues in the linker that interact with well-defined amino acids in one of the three loops forming the active site of the protein, named TI loop. With our results, we shed light into the early steps of the coupling process between the VSD and the CD, which are based on fine-tuned electrostatic and hydrophobic interactions between the linker, the membrane and the CD.

  11. The linker pivot in Ci-VSP: the key to unlock catalysis.

    Directory of Open Access Journals (Sweden)

    Kirstin Hobiger

    Full Text Available In the voltage-sensitive phosphatase Ci-VSP, conformational changes in the transmembrane voltage sensor domain (VSD are transduced to the intracellular catalytic domain (CD leading to its dephosphorylation activity against membrane-embedded phosphoinositides. The linker between both domains is proposed to be crucial for the VSD-CD coupling. With a combined approach of electrophysiological measurements on Xenopus oocytes and molecular dynamics simulations of a Ci-VSP model embedded in a lipid bilayer, we analyzed how conformational changes in the linker mediate the interaction between the CD and the activated VSD. In this way, we identified specific residues in the linker that interact with well-defined amino acids in one of the three loops forming the active site of the protein, named TI loop. With our results, we shed light into the early steps of the coupling process between the VSD and the CD, which are based on fine-tuned electrostatic and hydrophobic interactions between the linker, the membrane and the CD.

  12. The Role of Intracellular Linkers in Gating and Desensitization of Human Pentameric Ligand-Gated Ion Channels

    Science.gov (United States)

    Papke, David

    2014-01-01

    It has recently been proposed that post-translational modification of not only the M3–M4 linker but also the M1–M2 linker of pentameric ligand-gated ion channels modulates function in vivo. To estimate the involvement of the M1–M2 linker in gating and desensitization, we engineered a series of mutations to this linker of the human adult-muscle acetylcholine receptor (AChR), the α3β4 AChR and the homomeric α1 glycine receptor (GlyR). All tested M1–M2 linker mutations had little effect on the kinetics of deactivation or desensitization compared with the effects of mutations to the M2 α-helix or the extracellular M2–M3 linker. However, when the effects of mutations were assessed with 50 Hz trains of ∼1 ms pulses of saturating neurotransmitter, some mutations led to much more, and others to much less, peak-current depression than observed for the wild-type channels, suggesting that these mutations could affect the fidelity of fast synaptic transmission. Nevertheless, no mutation to this linker could mimic the irreversible loss of responsiveness reported to result from the oxidation of the M1–M2 linker cysteines of the α3 AChR subunit. We also replaced the M3–M4 linker of the α1 GlyR with much shorter peptides and found that none of these extensive changes affects channel deactivation strongly or reduces the marked variability in desensitization kinetics that characterizes the wild-type channel. However, we found that these large mutations to the M3–M4 linker can have pronounced effects on desensitization kinetics, supporting the notion that its post-translational modification could indeed modulate α1 GlyR behavior. PMID:24849357

  13. SH2-catalytic domain linker heterogeneity influences allosteric coupling across the SFK family.

    Science.gov (United States)

    Register, A C; Leonard, Stephen E; Maly, Dustin J

    2014-11-11

    Src-family kinases (SFKs) make up a family of nine homologous multidomain tyrosine kinases whose misregulation is responsible for human disease (cancer, diabetes, inflammation, etc.). Despite overall sequence homology and identical domain architecture, differences in SH3 and SH2 regulatory domain accessibility and ability to allosterically autoinhibit the ATP-binding site have been observed for the prototypical SFKs Src and Hck. Biochemical and structural studies indicate that the SH2-catalytic domain (SH2-CD) linker, the intramolecular binding epitope for SFK SH3 domains, is responsible for allosterically coupling SH3 domain engagement to autoinhibition of the ATP-binding site through the conformation of the αC helix. As a relatively unconserved region between SFK family members, SH2-CD linker sequence variability across the SFK family is likely a source of nonredundant cellular functions between individual SFKs via its effect on the availability of SH3 and SH2 domains for intermolecular interactions and post-translational modification. Using a combination of SFKs engineered with enhanced or weakened regulatory domain intramolecular interactions and conformation-selective inhibitors that report αC helix conformation, this study explores how SH2-CD sequence heterogeneity affects allosteric coupling across the SFK family by examining Lyn, Fyn1, and Fyn2. Analyses of Fyn1 and Fyn2, isoforms that are identical but for a 50-residue sequence spanning the SH2-CD linker, demonstrate that SH2-CD linker sequence differences can have profound effects on allosteric coupling between otherwise identical kinases. Most notably, a dampened allosteric connection between the SH3 domain and αC helix leads to greater autoinhibitory phosphorylation by Csk, illustrating the complex effects of SH2-CD linker sequence on cellular function.

  14. Arsenic metalation of seaweed Fucus vesiculosus metallothionein: the importance of the interdomain linker in metallothionein.

    Science.gov (United States)

    Ngu, Thanh T; Lee, Janice A; Rushton, Moira K; Stillman, Martin J

    2009-09-22

    The presence of metallothionein in seaweed Fucus vesiculosus has been suggested as the protecting agent against toxic metals in the contaminated waters it can grow in. We report the first kinetic pathway data for A3+ binding to an algal metallothionein, F. vesiculosus metallothionein (rfMT). The time and temperature dependence of the relative concentrations of apo-rfMT and the five As-containing species have been determined following mixing of As3+ and apo-rfMT using electrospray ionization mass spectrometry (ESI MS). Kinetic analysis of the detailed time-resolved mass spectral data for As3+ metalation allows the simulation of the metalation reactions showing the consumption of apo-rfMT, the formation and consumption of As1- to As4-rfMT, and subsequent, final formation of As5-rfMT. The kinetic model proposed here provides a stepwise analysis of the metalation reaction showing time-resolved occupancy of the Cys7 and the Cys9 domain. The rate constants (M(-1) s(-1)) calculated from the fits for the 7-cysteine gamma domain are k1gamma, 19.8, and k2gamma, 1.4, and for the 9-cysteine beta domain are k1beta, 16.3, k2beta, 9.1, and k3beta, 2.2. The activation energies and Arrhenius factors for each of the reaction steps are also reported. rfMT has a long 14 residue linker, which as we show from analysis of the ESI MS data, allows each of its two domains to bind As3+ independently of each other. The analysis provides for the first time an explanation of the differing metal-binding properties of two-domain MTs with linkers of varying lengths, suggesting further comparison between plant (with long linkers) and mammalian (with short linkers) metallothioneins will shed light on the role of the interdomain linker.

  15. Polyglycine hydrolases secreted by Pleosporineae fungi that target the linker region of plant class IV chitinases.

    Science.gov (United States)

    Naumann, Todd A; Wicklow, Donald T; Price, Neil P J

    2014-06-01

    Cmps (chitinase-modifying proteins) are fungal proteases that truncate plant class IV chitinases by cleaving near their N-termini. We previously described Fv-cmp, a fungalysin protease that cleaves a conserved glycine-cysteine bond within the hevein domain. In the present paper we describe a new type of cmp, polyglycine hydrolases, as proteases that selectively cleave glycine-glycine peptide bonds within the polyglycine linker of plant class IV chitinases. Polyglycine hydrolases were purified from Cochliobolus carbonum (syn. Bipolaris zeicola; Bz-cmp) and Epicoccum sorghi (syn. Phoma sorghina; Es-cmp) and were shown to cleave three different maize class IV chitinase substrates. The proteolytic cleavage sites were assessed by SDS/PAGE and MALDI-TOF-MS and indicated the cleavage of multiple peptide bonds within the polyglycine linker regions. Site-directed mutagenesis was used to produce mutants of maize ChitB chitinase in which two serine residues in its linker were systematically modified to glycine. Serine to glycine changes in the ChitB linker resulted in higher susceptibility to truncation by Bz-cmp and altered substrate specificity for Bz-cmp and Es-cmp, such that different glycine-glycine peptide bonds were cleaved. Removal of the hevein domain led to loss of Es-cmp activity, indicating that interactions outside of the active site are important for recognition. Our findings demonstrate that plant class IV chitinases with polyglycine linkers are targeted for truncation by selective polyglycine hydrolases that are secreted by plant pathogenic fungi. This novel proteolysis of polyglycine motifs is previously unreported, but the specificity is similar to that of bacterial lysostaphin proteases, which cleave pentaglycine cross-links from peptidoglycan.

  16. Biodistribution of the chimeric monoclonal antibody U36 radioiodinated with a closo-dodecaborate-containing linker. Comparison with other radioiodination methods.

    NARCIS (Netherlands)

    Nestor, M; Persson, M; Cheng, J.; Tolmachev, V; Dongen, van G.A.M.S.; Anniko, M; Kairemo, K

    2003-01-01

    We have evaluated the applicability of the [(4-isothiocyanatobenzylammonio)undecahydro-closo-dodecaborate (1-)] (DABI) linker molecule for antibody radiohalogenation and compared it to radiohalogenation using the linker N-succinimidyl 4-iodobenzoate (PIB) and to direct radiohalogenation using

  17. Synthesis, thermo-analytical and IR spectral studies of hydrazinated mixed metal carboxylates: A single source precursor to nanosize mixed metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Gawas, U.B. [Department of Chemistry, Goa University, Taleigao Plateau, Goa 403 206 (India); Verenkar, V.M.S., E-mail: vmsv@rediffmail.com [Department of Chemistry, Goa University, Taleigao Plateau, Goa 403 206 (India)

    2013-03-20

    Highlights: ► The hydrazinated nickel manganese zinc ferrous fumarate precursors were synthesized. ► The chemical and thermo-analytical studies confirm the formation of precursors. ► The TG/DTA studies of precursors show three-step decomposition to nanosize ferrites. ► The XRD studies indicate the formation of Ni{sub 0.5−x}Mn{sub x}Zn{sub 0.5}Fe{sub 2}O{sub 4} (x = 0.0–0.5) ferrites. ► The Scherrer crystallite size was 19–28 nm while TEM shows particle size of 12–50 nm. - Abstract: A series of hydrazinated mixed nickel manganese zinc ferrous hydrazine fumarate complexes were synthesized from aqueous mixed metal chloride solutions and sodium fumarate-hydrazine hydrate mixture. The detailed characterization was carried out by chemical analysis, infrared spectroscopy and isothermal mass loss studies. The hydrazine ligand in these complexes shows bidentate bridging nature while fumarate anion exhibit monodentate behavior. These complexes act as single source precursors for nanosize ferrites. Thermal decomposition of these precursors was studied upto 800 °C in static air using simultaneous TG/DTA. The thermal decomposition study indicates 3-step decomposition of these precursors into nanosize mixed metal oxides. The nanosize mixed metal oxides were then characterized by X-ray diffraction, transmission electron microscopy and infrared spectral studies.

  18. Mechanistic insight into the hydrazine decomposition on Rh(111): effect of reaction intermediate on catalytic activity.

    Science.gov (United States)

    Deng, Zhigang; Lu, Xiaoqing; Wen, Zengqiang; Wei, Shuxian; Liu, Yunjie; Fu, Dianling; Zhao, Lianming; Guo, Wenyue

    2013-10-14

    Periodic density functional theory (DFT) calculations have been performed to systematically investigate the effect of reaction intermediate on catalytic activity for hydrazine (N2H4) decomposition on Rh(111). Reaction mechanisms via intramolecular and NH2-assisted N2H4 decompositions are comparatively analyzed, including adsorption configuration, reaction energy and barrier of elementary step, and reaction network. Our results show that the most favorable N2H4 decomposition pathway starts with the initial N-N bond scission to the NH2 intermediate, followed by stepwise H stripping from adsorbed N2Hx (x = 1-4) species, and finally forms the N2 and NH3 products. Comparatively, the stepwise intramolecular dehydrogenation via N2H4→ N2H3→ N2H2→ N2H → N2, and N2H4→ NH2→ NH → N with or without NH2 promotion effect, are unfavorable due to higher energy barriers encountered. Energy barrier analysis, reaction rate constants, and electronic structures are used to identify the crucial competitive route. The promotion effect of the NH2 intermediate is structurally reflected in the weakening of the N-H bond and strengthening of the N-N bond in N2Hx in the coadsorption system; it results intrinsically from the less structural deformation of the adsorbate, and weakening of the interaction between dehydrogenated fragment and departing H in transition state. Our results highlight the crucial effect of reaction intermediate on catalytic activity and provide a theoretical approach to analyze the effect.

  19. Hydrazine-enhanced NO conversion in a pulsed corona discharge plasma (PCDP reactor: Behaviors and mechanism

    Directory of Open Access Journals (Sweden)

    Liu Hong

    2016-09-01

    Full Text Available The NO conversion efficiency in a pulsed corona discharge plasma (PCDP reactor in the presence of a new additive, hydrazine hydrate (N2H4·H2O, was studied, and the reaction mechanism was analyzed. The NO conversion efficiency reached 62.5%, and the NO conversion Energy Yield (EY reached 20.9 gNO/kWh, which is higher than that obtained using water or ammonia additives under the same conditions. The predominant elementary reactions and radicals, as well as the mechanism by which the additive enhanced the NO conversion process, were determined by comparing experimental data with theoretical simulation results and by performing a sensitivity analysis. After the addition of N2H4·H2O, the N2H4 reacts with radicals generated in the PCDP reactor to form a large quantity of strongly reducing species with NH2 as the predominant component, which can directly reduce NO to N2 and effectively prevent the generation of N2O. Compared with the traditional PCDP-based De-NOx process in which nitric acid is generated by oxidation with an additional neutralization step required, this new PCDP-based De-NOx process with N2H4·H2O addition is superior because NO is mostly reduced to N2. The study provides a basis for the application of N2H4·H2O as a synergist to improve NO abatement in a PCDP reactor.

  20. Development of Bioorthogonally Degradable Linkers and Polymers Using alpha-Azidoethers

    Science.gov (United States)

    Rajagopalan, Chandrasekhar Ramasubramanian

    Degradable polymers have gained a lot of attention in recent years for applications in biotechnology and medicine. External control over polymer degradation can be obtained by incorporating functional groups that cleave in the presence of triggers that would normally be absent in biological environments, i.e. are bioorthogonal. This thesis explores the use of chemically cleavable alpha-azidoethers as a new method to obtain external control over the degradation behavior of polymers. My first goal is to illustrate the potential of alpha-azidoethers toward developing cleavable linkers. We have studied the relationship between alpha-azidoether structure and hydrolytic stability, to prepare linkers that withstand background hydrolytic cleavage until they are exposed to the cleaving trigger. The cleavage kinetics of the alpha-azidoether functional group was quantified. In addition to the conventionally used tris(2-carboxyethyl)phosphine (TCEP), dihydrolipoic acid (DHLA), a previously unexplored, biocompatible reducing agent, was also evaluated as a cleaving trigger. Based on these results, we have proposed design rules for utilizing alpha-azidoethers as cleavable linkers in applications that require bioorthogonal control over linker cleavage. Secondly, the alpha-azidoether cleavable linker chemistry was implemented into the development of polymeric materials. Two different types of polymers were developed. Polyamides incorporating alpha-azidoethers along the backbone were synthesized, and their physical properties and chemically triggered degradation behavior were characterized. The degradation timescale of these polymers can be tuned simply by manipulating the concentration of the externally applied chemical trigger. The alpha-azidoether functional group was then utilized to develop a unique triggered-release polymeric adhesive for potential applications in dental adhesive formulations. A methacrylamide-phosphonate adhesive monomer incorporating an alpha

  1. Thermodynamically Modeled Non-equilibrium Structure of Combustion Products and Decomposition of Hydrazine-based Liquid Propellants

    Directory of Open Access Journals (Sweden)

    A. A. Dorofeev

    2016-01-01

    Full Text Available The paper studies the emerging hallmarks and the characteristics of a two-parameter chemical non-equilibrium structure of the combustion products of liquid propellants as applied to the low-thrust liquid propellant engines (LT LPE operating in the aircraft control system. The study is based on hydrazine and nitrogen tetroxide products. The paper also analyses the catalytic and thermal decomposition of these substances in terms of inter-conditionality of the working process components in the combustion chamber and liquid pre-burner. The paper offers a technique to simulate these types of non-equilibrium as applied both to the a priori estimate and to the parametric optimization of LT LPE performance. It presents the possible equations of chemical dissociation reactions of hydrazine under various conditions, which determine a chemical disequilibrium of the process, and gives the examples to specify the source files for the software systems "Astra 4.rs" or "Terra".The technique is implemented and tested on the basis of the software systems "Astra4.rs" and "Terra" in calculating the structure and properties of the liquid propellant combustion products, which include hydrazine, combustion products, ammonia, and products of their catalytic thermal decomposition. The paper provides numerical values of the upper and lower concentration limits of the non-equilibrium of a generated propellant, which correspond to the equilibrium ratio of concentrations between ammonia and products of its decomposition, as well as meet the absence of ammonia pyrolysis. For possible conditions of the non-equilibrium work process the values of void specific impulse are calculated.

  2. cis-Apa: a practical linker for the microwave-assisted preparation of cyclic pseudopeptides via RCM cyclative cleavage.

    Science.gov (United States)

    Baron, Alice; Verdié, Pascal; Martinez, Jean; Lamaty, Frédéric

    2011-02-04

    A new linker cis-5-aminopent-3-enoic acid (cis-Apa) was prepared for the synthesis of cyclic pseudopeptides by cyclization-cleavage by using ring-closing methatesis (RCM). We developed a new synthetic pathway for the preparation of the cis-Apa linker that was tested in the cyclization-cleavage process of different RGD peptide sequences. Different macrocyclic peptidomimetics were prepared by using this integrated microwave-assisted method, showing that the readily available cis-Apa amino acid is well adapted as a linker in the cyclization-cleavage process.

  3. Density functional theory calculations of the hydrazine decomposition mechanism on the planar and stepped Cu(111) surfaces.

    Science.gov (United States)

    Tafreshi, Saeedeh S; Roldan, Alberto; de Leeuw, Nora H

    2015-09-07

    We have investigated the adsorption of hydrazine (N2H4) and its reactivity on terraces and steps of Cu(111) surfaces by first-principles calculations in order to gain insight into the hydrazine decomposition mechanism. We have investigated different possibilities for the N-N and N-H bond cleavage for any intermediate states by analysing the reaction and barrier energies of each elementary step. We have found that hydrazine dehydrogenation via N-H bond scission is neither energetically nor kinetically favourable on the flat and stepped surfaces, but hydrazine prefers to form NH2via N-N bond decoupling on the Cu(111) with an activation energy below 1 eV. The NH2 molecule reacts fairly easily with co-adsorbed NH2 to form NH3 as well as with N2Hx (x = 1-4) by abstracting hydrogen to produce NH3 and N2 molecules on both the flat and stepped surfaces. We also found that all intermediates except NNH prefer N-N bond breaking as the most likely dissociation pathway, where the amide and imide intermediates produced can be hydrogenated to form NH3 in the presence of hydrogen. NNH is the only intermediate, which prefers to dissociate via a highly exothermic N-H bond breaking process to produce an N2 molecule after overcoming a small barrier energy. We also studied the production of H2 by recombination of hydrogen ad-atoms which, considering the activation energies, is particularly favoured under conditions of moderate temperatures. Our results agree well with experiments suggesting that N2H4 adsorbs dissociatively on copper above ∼300 K leading to N2, NH3 and H2. In general, the lower coordination of the steps is found to lead to higher reactivity than on the flat Cu(111) surface. Furthermore, the calculations show that the influence of step edge atoms is very different for the intra- and intermolecular dehydrogenation mechanisms. They also increase the barrier of N-N decoupling of all the existing species in the reaction.

  4. An Overview of Demise Calculations, Conceptual Design Studies, and Hydrazine Compatibility Testing for the GPM Core Spacecraft Propellant Tank

    Science.gov (United States)

    Estes, Robert H.; Moore, N. R.

    2007-01-01

    NASA's Global Precipitation Measurement (GPM) mission is an ongoing Goddard Space Flight Center (GSFC) project whose basic objective is to improve global precipitation measurements. It has been decided that the GPM spacecraft is to be a "design for demise" spacecraft. This requirement resulted in the need for a propellant tank that would also demise or ablate to an appropriate degree upon re-entry. This paper will describe GSFC-performed spacecraft and tankage demise analyses, vendor conceptual design studies, and vendor performed hydrazine compatibility and wettability tests performed on 6061 and 2219 aluminum alloys.

  5. Engineering Cel7A carbohydrate binding module and linker for reduced lignin inhibition.

    Science.gov (United States)

    Strobel, Kathryn L; Pfeiffer, Katherine A; Blanch, Harvey W; Clark, Douglas S

    2016-06-01

    Non-productive binding of cellulases to lignin inhibits enzymatic hydrolysis of biomass, increasing enzyme requirements and the cost of biofuels. This study used site-directed mutagenesis of the Trichoderma Cel7A carbohydrate binding module (CBM) and linker to investigate the mechanisms of adsorption to lignin and engineer a cellulase with increased binding specificity for cellulose. CBM mutations that added hydrophobic or positively charged residues decreased the specificity for cellulose, while mutations that added negatively charged residues increased the specificity. Linker mutations that altered predicted glycosylation patterns selectively impacted lignin affinity. Beneficial mutations were combined to generate a mutant with 2.5-fold less lignin affinity while fully retaining cellulose affinity. This mutant was uninhibited by added lignin during hydrolysis of Avicel and generated 40% more glucose than the wild-type enzyme from dilute acid-pretreated Miscanthus. Biotechnol. Bioeng. 2016;113: 1369-1374. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  6. A Facile N-Mercaptoethoxyglycinamide (MEGA) Linker Approach to Peptide Thioesterification and Cyclization.

    Science.gov (United States)

    Shelton, Patrick M M; Weller, Caroline E; Chatterjee, Champak

    2017-03-22

    The C-terminal electrophilic activation of peptides by α-thioesterification requires strongly acidic conditions or complex chemical manipulations, which ultimately limit functional group compatibility and broad utility. Herein, we report a readily accessible N-mercaptoethoxyglycinamide (MEGA) solid-phase linker for the facile synthesis of latent peptide α-thioesters. Incubating peptide-MEGA sequences with 2-mercaptoethanesulfonic acid at mildly acidic pH yielded α-thioesters that were directly used in NCL without purification. The MEGA linker yielded robust access to thioesters ranging in length from 4 to 35 amino acids, and greatly simplified the synthesis of cyclic peptides. Finally, the high utility of MEGA was demonstrated by the one-pot synthesis of a functional analog of the Sunflower Trypsin Inhibitor 1.

  7. Gold Nanoparticle Assemblies on Surfaces: Reactivity Tuning through Capping-Layer and Cross-Linker Design.

    Science.gov (United States)

    Shankar, Sreejith; Orbach, Meital; Kaminker, Revital; Lahav, Michal; van der Boom, Milko E

    2016-01-26

    The immobilization of metal nanoparticles (NPs) with molecular control over their organization is challenging. Herein, we report the formation of molecularly cross-linked AuNP assemblies using a layer-by-layer approach. We observed four types of assemblies: 1) small aggregates of individual AuNPs, 2) large aggregates of individual AuNPs, 3) networks of fused AuNPs, and 4) gold islands. Interestingly, these assemblies with the different cross-linkers and capping layers represent different stages in the complete fusion of AuNPs to afford islands of continuous gold. We demonstrate that the stability toward fusion of the nanoparticles of the on-surface structures can be controlled by the reactivity of the cross-linkers and the hydrophilicity/hydrophobicity of the nanoparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Intrinsically disordered linkers determine the interplay between phase separation and gelation in multivalent proteins.

    Science.gov (United States)

    Harmon, Tyler S; Holehouse, Alex S; Rosen, Michael K; Pappu, Rohit V

    2017-11-01

    Phase transitions of linear multivalent proteins control the reversible formation of many intracellular membraneless bodies. Specific non-covalent crosslinks involving domains/motifs lead to system-spanning networks referred to as gels. Gelation transitions can occur with or without phase separation. In gelation driven by phase separation multivalent proteins and their ligands condense into dense droplets, and gels form within droplets. System spanning networks can also form without a condensation or demixing of proteins into droplets. Gelation driven by phase separation requires lower protein concentrations, and seems to be the biologically preferred mechanism for forming membraneless bodies. Here, we use coarse-grained computer simulations and the theory of associative polymers to uncover the physical properties of intrinsically disordered linkers that determine the extent to which gelation of linear multivalent proteins is driven by phase separation. Our findings are relevant for understanding how sequence-encoded information in disordered linkers influences phase transitions of multivalent proteins.

  9. Structural and dynamic properties of linker histone H1 binding to DNA

    CERN Document Server

    Dootz, Rolf; Pfohl, Thomas

    2010-01-01

    Found in all eukaryotic cells, linker histones H1 are known to bind to and rearrange nucleosomal linker DNA. In vitro, the fundamental nature of H1/DNA interactions has attracted wide interest among research communities - for biologists from a chromatin organization deciphering point of view, and for physicists from the study of polyelectrolyte interactions point of view. Hence, H1/DNA binding processes, structural and dynamical information about these self-assemblies is of broad importance. Targeting a quantitative understanding of H1 induced DNA compaction mechanisms our strategy is based on using small angle X-ray microdiffraction in combination with microfluidics. The usage of microfluidic hydrodynamic focusing devices facilitate a microscale control of these self-assembly processes. In addition, the method enables time-resolved access to structure formation in situ, in particular to transient intermediate states. The observed time dependent structure evolution shows that the interaction of H1 with DNA ca...

  10. A short cross-linker activates human P-glycoprotein missing a catalytic carboxylate.

    Science.gov (United States)

    Loo, Tip W; Clarke, David M

    2017-12-01

    P-glycoprotein (P-gp) is an ATP-dependent drug pump that protects us from toxic agents and confers multidrug resistance. It has a tweezer-like structure with each arm consisting of a transmembrane domain (TMD) and a nucleotide-binding domain (NBD). Drug substrates bind to sites within the TMDs to activate ATPase activity by promoting a tweezer-like closing of the gap between the NBDs. The catalytic carboxylates may be critical for NBD movements because the E556Q(NBD1) or E1201Q(NBD2) mutation inhibited drug-stimulated ATPase activity. If the catalytic carboxylates were components of the mechanism to bring the NBDs together, then we predicted that insertion of a flexible cross-linker between the arms would increase ATPase activity of the mutants. We found that cross-linking (between L175C(TMD1) and N820C(TMD2)) with a short flexible cross-linker (7.8Å maximum) restored high levels of drug-stimulated ATPase activity of the E556Q or E1201Q mutants. Cross-linking with a longer cross-linker (22Å maximum) however, did not restore activity. Cross-linking could not rescue all ATPase deficient mutants. For example, cross-linking L175C/N820C with short or long cross-linkers did not activate the H-loop mutants H587A or H1232A or the Walker A K433M or K1076M mutants. The results suggest that the E556 and E1201 catalytic carboxylates are part of a spring-like mechanism that is required to facilitate movements between the open and closed conformations of P-gp during ATP hydrolysis. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. P-Link: A method for generating multicomponent cytochrome P450 fusions with variable linker length

    DEFF Research Database (Denmark)

    Belsare, Ketaki D.; Ruff, Anna Joelle; Martinez, Ronny

    2014-01-01

    -LinK),. which was validated by fusing P450(cin) monooxygenase (CinA) to the flavodoxin shuttle protein (CinC). CinC was fused to the C terminus of CinA through a series of 16 amino acid linkers of different lengths in a single experiment employing 3 PCR amplifications. Screening for 2-beta-hydroxy-1,8-cineole...

  12. Assessing the bio-compatibility of a click DNA backbone linker

    OpenAIRE

    Sanzone, A Pia

    2013-01-01

    Click chemistry has the potential to be employed for the assembly of large DNA fragments, by purely chemical methods. However to enable this, the bio-compatibility of the resulting click-linked DNA must be examined. Click DNA linkers were incorporated into a plasmid within the gene encoding for an ampicillin resistance marker. The plasmid was transformed into E. coli and resulting colonies found to survive on LB agar plates supplemented with ampicillin. This indicated that the click DNA linke...

  13. Expression of a linker histone-like gene in the primordial germ cells in zebrafish

    OpenAIRE

    Müller, Katja; Thisse, Christine; Thisse, Bernard; Raz, Erez

    2002-01-01

    Similar to many other organisms, specification of primordial germ cells (PGCs) in zebraftsh occurs during early development and depends on inheritance of 'germ plasm' determinants. Following their specification, the PGCs exhibit characteristic transcriptional profile and cell behaviour. Here we describe the cloning, expression pattern and sub-cellular localization of the zebrafish H I type linker histone, HIM, which is specifically expressed in the PGCs in the second phase of their developmen...

  14. Construction of hierarchically porous metal?organic frameworks through linker labilization

    OpenAIRE

    Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; Li, Jialuo; Huang, Lan; Feng, Liang; Wang, Xuan; Bosch, Mathieu; Alsalme, Ali; Cagin, Tahir; Zhou, Hong-Cai

    2017-01-01

    A major goal of metal?organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro...

  15. Studies on Metal-Organic Frameworks of Cu(II) with Isophthalate Linkers for Hydrogen Storage

    OpenAIRE

    Yan, Yong; Yang, Sihai; Blake, Alexander J.; Schröder, Martin

    2014-01-01

    Hydrogen (H2) is a promising alternative energy carrier due to its environmental benefits, high energy density and its abundance. However, development of a practical storage system to enable the “Hydrogen Economy” remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers, and show promise for H2 storage due to their high surface area and tuneable properties. We summarize our ...

  16. Design of an in vivo cleavable disulfide linker in recombinant fusion proteins.

    Science.gov (United States)

    Chen, Xiaoying; Bai, Yun; Zaro, Jennica L; Shen, Wei-Chiang

    2010-07-01

    In order to achieve optimal biological activity and desired pharmacokinetic profiles, a dithiocyclopeptide linker was designed for in vivo release of protein domains from a recombinant fusion protein. This novel in vivo cleavable disulfide linker, based on a dithiocyclopeptide containing a thrombin-sensitive sequence and an intramolecular disulfide bond, was inserted between transferrin and granulocyte colony-stimulating factor (G-CSF) recombinant fusion protein domains. After expression of the fusion protein, G-C-T, from HEK293 cells, thrombin treatment in vitro generated a fusion protein linked via a reversible disulfide bond that was quickly cleaved in vivo, separating the protein domains. After release from the fusion protein, free G-CSF exhibited an improved biological activity in a cell proliferation assay. Although reversible disulfide bonds are commonly used in protein chemical conjugation methods, to our knowledge this report is the first example of the construction of a recombinant fusion protein with a disulfide linkage for the release of the functional domain. This linker design can be adapted to diverse recombinant fusion proteins in which in vivo separation of protein domains is required to achieve an improved therapeutic effect and a desirable pharmacokinetic profile and biodistribution of the functional domain.

  17. A linker strategy for trans-FRET assay to determine activation intermediate of NEDDylation cascade.

    Science.gov (United States)

    Malik-Chaudhry, Harbani Kaur; Saavedra, Amanda; Liao, Jiayu

    2014-07-01

    Förster resonance energy transfer (FRET) technology has been widely used in biological and biomedical research and is a valuable tool for elucidating molecular interactions in vitro and in vivo. Quantitative FRET analysis is a powerful method for determining biochemical parameters and molecular distances at nanometer levels. Recently, we reported theoretical developments and experimental procedures for determining the dissociation constant, Kd and enzymatic kinetics parameters, Kcat and KM, of protein interactions with the engineered FRET pair, CyPet and YPet. The strong FRET signal from this pair made these developments possible. However, the direct link of fluorescent proteins with proteins of interests may interfere with the folding of some fusion proteins. Here, we report a new protein engineering strategy for improving FRET signals by adding a linker between the fluorescent protein and the targeted protein. This improvement allowed us to follow the covalent conjugation of NEDD8 to its E2 ligase in the presence of E1 and ATP, which was difficult to determine without linker. Three linkers, LAEAAAKEAA, TSGSPGLQEFGT, and LAAALAAA, which are alpha helix or random coil, all significantly improved the FRET signals. Our results show a general methodology for improving trans-FRET signals to effectively determine biochemical reaction intermediates. © 2014 Wiley Periodicals, Inc.

  18. Efficient Naphthalenediimide-Based Hole Semiconducting Polymer with Vinylene Linkers between Donor and Acceptor Units

    KAUST Repository

    Zhang, Lei

    2016-11-04

    We demonstrate a new method to reverse the polarity and charge transport behavior of naphthalenediimide (NDI)-based copolymers by inserting a vinylene linker between the donor and acceptor units. The vinylene linkers minimize the intrinsic steric congestion between the NDI and thiophene moieties to prompt backbone planarity. The polymers with vinylene linkers exhibit electron n-channel transport characteristics under vacuum, similar to the benchmark polymer, P(NDI2OD-T2). To our surprise, when the polymers are measured in air, the dominant carrier type switches from n- to p-type and yield hole mobilities up to 0.45 cm(2) s(-1) with hole to electron mobility ratio of three (mu(h)/mu(e), similar to 3), which indicates that the hole density in the active layer can be significantly increased by exposure to air. This increase is consistent with the intrinsic more delocalized nature of the highest occupied molecular orbital of the charged vinylene polymer, as estimated by density functional theory (DFT) calculations, which facilitates hole transport within the polymer chains. This is the first demonstration of an efficient NDI-based hole semiconducting polymer, which will enable new developments in all-polymer solar cells, complementary circuits, and dopable polymers for use in thermoelectrics.

  19. The linker histone plays a dual role during gametogenesis in Saccharomyces cerevisiae.

    Science.gov (United States)

    Bryant, Jessica M; Govin, Jérôme; Zhang, Liye; Donahue, Greg; Pugh, B Franklin; Berger, Shelley L

    2012-07-01

    The differentiation of gametes involves dramatic changes to chromatin, affecting transcription, meiosis, and cell morphology. Sporulation in Saccharomyces cerevisiae shares many chromatin features with spermatogenesis, including a 10-fold compaction of the nucleus. To identify new proteins involved in spore nuclear organization, we purified chromatin from mature spores and discovered a significant enrichment of the linker histone (Hho1). The function of Hho1 has proven to be elusive during vegetative growth, but here we demonstrate its requirement for efficient sporulation and full compaction of the spore genome. Hho1 chromatin immunoprecipitation followed by sequencing (ChIP-seq) revealed increased genome-wide binding in mature spores and provides novel in vivo evidence of the linker histone binding to nucleosomal linker DNA. We also link Hho1 function to the transcription factor Ume6, the master repressor of early meiotic genes. Hho1 and Ume6 are depleted during meiosis, and analysis of published ChIP-chip data obtained during vegetative growth reveals a high binding correlation of both proteins at promoters of early meiotic genes. Moreover, Ume6 promotes binding of Hho1 to meiotic gene promoters. Thus, Hho1 may play a dual role during sporulation: Hho1 and Ume6 depletion facilitates the onset of meiosis via activation of Ume6-repressed early meiotic genes, whereas Hho1 enrichment in mature spores contributes to spore genome compaction.

  20. Bifunctional bridging linker-assisted synthesis and characterization of TiO{sub 2}/Au nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Žunič, Vojka, E-mail: vojka.zunic@ijs.si, E-mail: vojka13@gmail.com; Kurtjak, Mario; Suvorov, Danilo [Jožef Stefan Institute, Advanced Materials Department (Slovenia)

    2016-11-15

    Using a simple organic bifunctional bridging linker, titanium dioxide (TiO{sub 2}) nanoparticles were coupled with the Au nanoparticles to form TiO{sub 2}/Au nanocomposites with a variety of Au loadings. This organic bifunctional linker, meso-2,3-dimercaptosuccinic acid, contains two types of functional groups: (i) the carboxyl group, which enables binding to the TiO{sub 2}, and (ii) the thiol group, which enables binding to the Au. In addition, the organic bifunctional linker acts as a stabilizing agent to prevent the agglomeration and growth of the Au particles, resulting in the formation of highly dispersed Au nanoparticles. To form the TiO{sub 2}/Au nanocomposites in a simple way, we deliberately applied a synthetic method that simultaneously ensures: (i) the capping of the Au nanoparticles and (ii) the binding of different amounts of Au to the TiO{sub 2}. The TiO{sub 2}/Au nanocomposites formed with this method show enhanced UV and Vis photocatalytic activities when compared to the pure TiO{sub 2} nanopowders.Graphical Abstract.

  1. Linker engineering for fusion protein construction: Improvement and characterization of a GLP-1 fusion protein.

    Science.gov (United States)

    Kong, Yuelin; Tong, Yue; Gao, Mingming; Chen, Chen; Gao, Xiangdong; Yao, Wenbing

    2016-01-01

    Protein engineering has been successfully applied in protein drug discovery. Using this technology, we previously have constructed a fusion protein by linking the globular domain of adiponectin to the C-terminus of a glucagon-like peptide-1 (GLP-1) analog. Herein, to further improve its bioactivity, we reconstructed this fusion protein by introducing linker peptides of different length and flexibility. The reconstructed fusion proteins were overexpressed in Escherichia coli and purified using nickel affinity chromatography. Their agonist activity towards receptors of GLP-1 and adiponectin were assessed in vitro by using luciferase assay and AMP-activated protein kinase (AMPK) immunoblotting, respectively. The effects of the selected fusion protein on glucose and lipid metabolism were evaluated in mice. The fusion protein reconstructed using a linker peptide of AMGPSSGAPGGGGS showed high potency in activating GLP-1 receptor and triggering AMPK phosphorylation via activating the adiponectin receptor. Remarkably, the optimized fusion protein was highly effective in lowering blood glucose and lipids in mice. Collectively, these findings demonstrate that the bioactivity of this GLP-1 fusion protein can be significantly promoted by linker engineering, and indicate that the optimized GLP-1 fusion protein is a promising lead structure for anti-diabetic drug discovery. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Solid-Phase Synthesis of Triostin A Using a Symmetrical Bis(diphenylmethyl) Linker System.

    Science.gov (United States)

    Sable, Ganesh A; Lim, Dongyeol

    2015-08-07

    Triostin A is a symmetric bicyclic depsipeptide with very potent antitumoral activity because of its bisintercalation into DNA. In this study, we report a new synthetic strategy that exploits a structural symmetry of triostin A. First, we prepared a novel symmetric linker molecule that is labile under mildly acidic conditions and suitable for a solid-phase synthesis procedure. Two Cys units were attached to a linker-resin conjugate via their free thiol groups, and double deprotection and double coupling reactions were then applied to synthesize linear tetradepsipeptides. Subsequently, the key biscyclization of the tetradepsipeptides was performed on the resin, and the resulting cyclic octapeptide was detached from the linker-resin conjugate to give a peptide with two free thiols. Finally, triostin A was obtained by oxidizing the free thiols in solution to produce a disulfide. The yield was improved through exploration of two different solid-phase synthetic approaches under similar strategy. Mainly, this strategy was developed to enable the ease and rapid preparation of libraries of symmetric bicyclic depsipeptides. It also addresses several synthetic problems with our synthesis, including diketopiperazine (DKP) formation, poor cyclization yields and preparation of noncommercial N-methyl amino acids in good yields.

  3. Structural and functional insights into an archaeal L-asparaginase obtained through the linker-less assembly of constituent domains.

    Science.gov (United States)

    Tomar, Rachana; Sharma, Pankaj; Srivastava, Ankit; Bansal, Saurabh; Kundu, Bishwajit

    2014-12-01

    Covalent linkers bridging the domains of multidomain proteins are considered to be crucial for assembly and function. In this report, an exception in which the linker of a two-domain dimeric L-asparaginase from Pyrococcus furiosus (PfA) was found to be dispensable is presented. Domains of this enzyme assembled without the linker into a conjoined tetrameric form that exhibited higher activity than the parent enzyme. The global shape and quaternary structure of the conjoined PfA were also similar to the wild-type PfA, as observed by their solution scattering profiles and X-ray crystallographic data. Comparison of the crystal structures of substrate-bound and unbound enzymes revealed an altogether new active-site composition and mechanism of action. Thus, conjoined PfA is presented as a unique enzyme obtained through noncovalent, linker-less assembly of constituent domains that is stable enough to function efficiently at elevated temperatures.

  4. New PCR primers targeting hydrazine synthase and cytochrome c biogenesis proteins in anammox bacteria.

    Science.gov (United States)

    Zhou, Zhichao; Chen, Jing; Meng, Han; Dvornyk, Volodymyr; Gu, Ji-Dong

    2017-02-01

    PCR primers targeting genes encoding the two proteins of anammox bacteria, hydrazine synthase and cytochrome c biogenesis protein, were designed and tested in this study. Three different ecotypes of samples, namely ocean sediments, coastal wetland sediments, and wastewater treatment plant (WWTP) samples, were used to assess the primer efficiency and the community structures of anammox bacteria retrieved by 16S ribosomal RNA (rRNA) and the functional genes. Abundances of hzsB gene of anammox bacteria in South China Sea (SCS) samples were significantly correlated with 16S rRNA gene by qPCR method. And hzsB and hzsC gene primer pair hzsB364f-hzsB640r and hzsC745f-hzsC862r in combination with anammox bacterial 16S rRNA gene primers were recommended for quantifying anammox bacteria. Congruent with 16S rRNA gene-based community study, functional gene hzsB could also delineate the coastal-ocean distributing pattern, and seawater depth was positively associated with the diversity and abundance of anammox bacteria from shallow- to deep-sea. Both hzsC and ccsA genes could differentiate marine samples between deep and shallow groups of the Scalindua sp. clades. As for WWTP samples, non-Scalindua anammox bacteria reflected by hzsB, hzsC, ccsA, and ccsB gene-based libraries showed a similar distribution pattern with that by 16S rRNA gene. NH4+ and NH4+/Σ(NO3- + NO2-) positively correlated with anammox bacteria gene diversity, but organic matter contents correlated negatively with anammox bacteria gene diversity in SCS. Salinity was positively associated with diversity indices of hzsC and ccsB gene-harboring anammox bacteria communities and could potentially differentiate the distribution patterns between shallow- and deep-sea sediment samples. SCS surface sediments harbored considerably diverse community of Scalindua. A new Mai Po clade representing coastal estuary wetland anammox bacteria group based on 16S rRNA gene phylogeny is proposed. Existence of anammox bacteria within

  5. A first-principles study on adsorption behaviors of pristine and Li-decorated graphene sheets toward hydrazine molecules

    Science.gov (United States)

    Zeng, Huadong; Cheng, Xinlu; Wang, Wei

    2018-03-01

    The adsorption behaviors and properties of hydrazine (N2H4) molecules on pristine and Li-decorated graphene sheets were investigated by means of first-principles based on density functional theory. We systematically analyzed the optimal geometry, average binding energy, charge transfer, charge density difference and density of states of N2H4 molecules adsorbed on pristine and Li-decorated graphene sheets. It is found that the interaction between single N2H4 molecule and pristine graphene is weak physisorption with the low binding energy of -0.026 eV, suggesting that the pristine graphene sheet is insensitive to the presence of N2H4 molecule. However, it is markedly enhanced after lithium decoration with the high binding energy of -1.004 eV, verifying that the Li-decorated graphene sheet is significantly sensitive to detect N2H4 molecule. Meanwhile, the effects of the concentrations of N2H4 molecules on two different substrates were studied detailedly. For pristine graphene substrate, the average binding energy augments apparently with increasing the number of N2H4 molecules, which is mainly attributed to the van der Waals interactions and hydrogen bonds among N2H4 clusters. Li-decorated graphene sheet has still a strong affinity to N2H4 molecules despite the corresponding average binding energy emerges a contrary tendency. Overall, Li-decorated graphene sheet could be considered as a potential gas sensor in field of hydrazine molecules.

  6. Gram-scale synthesis of silica nanotubes with controlled aspect ratios by templating of nickel-hydrazine complex nanorods.

    Science.gov (United States)

    Gao, Chuanbo; Lu, Zhenda; Yin, Yadong

    2011-10-04

    We have developed a robust method for the synthesis of silica nanotubes with controlled aspect ratios on a large scale by templating against rod-like nanocrystals. Crystalline nanorods of a nickel-hydrazine complex are first formed in reverse micelles by surfactant capping on side facets, and subsequent silica coating and selective etching give rise to silica nanotubes of high uniformity and yield. The length of the silica nanotubes is tunable in the range 37-340 nm and can reach as long as micrometers. Control of the length is conveniently achieved by tuning the hydrazine/nickel ratio, which affects the growth kinetics of the nanocrystal templates. The inner diameter of the silica nanotubes can be adjusted in the range 10-20 nm by choosing different surfactants. This method is unique in utilizing reverse micelles as discrete nanoscale reactors for the growth of nanocrystals, allowing for precise control of the features of the nanotubes and opening up new opportunities in the synthesis of novel anisotropic nanomaterials, construction of nanodevices, and potential drug delivery applications. © 2011 American Chemical Society

  7. Impact of Linker Length and Composition on Fragment Binding and Cell Permeation: Story of a Bisbenzimidazole Dye Fragment.

    Science.gov (United States)

    Ranjan, Nihar; Kellish, Patrick; King, Ada; Arya, Dev P

    2017-12-12

    Small molecules that modulate biological functions are targets of modern day drug discovery efforts. In a common platform fragment-based drug discovery, two fragments that bind to adjacent sites on a target are identified and are then linked together using different linkers to identify the linkage for optimum activity. What are not known from these studies are the effects these linkers, which typically contain C, H, and O atoms, have on the properties of the individual fragment. Herein, we investigate such effects in a bisbenzimidazole fragment whose derivatives have a wide range of therapeutic applications in nucleic acid recognition, sensing, and photodynamic therapy and as cellular probes. We report a dramatic effect of linker length and composition of alkynyl (clickable) Hoechst 33258 derivatives in target binding and cell uptake. We show that the binding of Hoechst 33258-modeled bisbenzimidazoles (1-9) that contain linkers of varying lengths (3-21 atoms) display length- and composition-dependent variation in B-DNA stabilization using a variety of spectroscopic methods. For a dodecamer DNA duplex, the thermal stabilization varied from 0.3 to 9.0 °C as the linker length increased from 3 to 21 atoms, respectively. Compounds with linker lengths of ≤11 atoms (such as compounds 1 and 5) are localized in the nucleus, while compounds with long linkers (such as compounds 8 and 9) are distributed in the extranuclear space, as well, with possible interactions with extranuclear targets. These findings provide insights into future drug design by revealing how linkers can influence the biophysical and cellular properties of individual drug fragments.

  8. Mixed-linker zeolitic imidazolate framework mixed-matrix membranes for aggressive CO2 separation from natural gas

    KAUST Repository

    Thompson, Joshua A.

    2014-07-01

    Zeolitic imidazolate framework (ZIF) materials are a promising subclass of metal-organic frameworks (MOF) for gas separations. However, due to the deleterious effects of gate-opening phenomena associated with organic linker rotation near the limiting pore apertures of ZIFs, there have been few demonstrations of improved gas separation properties over pure polymer membranes when utilizing ZIF materials in composite membranes for CO2-based gas separations. Here, we report a study of composite ZIF/polymer membranes, containing mixed-linker ZIF materials with ZIF-8 crystal topologies but composed of different organic linker compositions. Characterization of the mixed-linker ZIFs shows that the mixed linker approach offers control over the porosity and pore size distribution of the materials, as determined from nitrogen physisorption and Horváth-Kawazoe analysis. Single gas permeation measurements on mixed-matrix membranes reveal that inclusion of mixed-linker ZIFs yields membranes with better ideal CO2/CH4 selectivity than membranes containing ZIF-8. This improvement is shown to likely occur from enhancement in the diffusion selectivity of the membranes associated with controlling the pore size distribution of the ZIF filler. Mixed-gas permeation experiments show that membranes with mixed-linker ZIFs display an effective plasticization resistance that is not typical of the pure polymeric matrix. Overall, we demonstrate that mixed-linker ZIFs can improve the gas separation properties in composite membranes and may be applicable to aggressive CO2 concentrations in natural gas feeds. © 2013 Elsevier Inc. All rights reserved.

  9. Improvement of a puromycin-linker to extend the selection target varieties in cDNA display method.

    Science.gov (United States)

    Ueno, Shingo; Kimura, Shinnosuke; Ichiki, Takanori; Nemoto, Naoto

    2012-12-31

    cDNA display using a puromycin-linker to covalently bridge a protein and its coding cDNA is a stable and efficient in vitro protein selection method. The optimal design of the often-used puromycin-linker is vital for effective selection. In this report, an improved puromycin-linker containing deoxyinosine bases as cleavage sites, which are recognized by endonuclease V, was introduced to extend the variety of the selection targets to molecules such as RNA. The introduction of this linker enables efficient in vitro protein selection without contamination from RNase T1, which is used for the conventional linker containing ribonucleotide G bases. In addition, mRNA-protein fusion efficiency was found to not depend on the length of the flexible poly (ethylene glycol) (PEG) region of the linker. These findings will allow practical and easy-to-use in vitro protein selection by cDNA display. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Hydrogen physisorption on metal-organic framework linkers and metalated linkers: a computational study of the factors that control binding strength.

    Science.gov (United States)

    Tsivion, Ehud; Long, Jeffrey R; Head-Gordon, Martin

    2014-12-24

    In order for hydrogen gas to be used as a fuel, it must be stored in sufficient quantity on board the vehicle. Efforts are being made to increase the hydrogen storage capabilities of metal-organic frameworks (MOFs) by introducing unsaturated metal sites into their linking element(s), as hydrogen adsorption centers. In order to devise successful hydrogen storage strategies there is a need for a fundamental understanding of the weak and elusive hydrogen physisorption interaction. Here we report our findings from the investigation of the weak intermolecular interactions of adsorbed hydrogen molecules on MOF-linkers by using cluster models. Since physical interactions such as dispersion and polarization have a major contribution to attraction energy, our approach is to analyze the adsorption interaction using energy decomposition analysis (EDA) that distinguishes the contribution of the physical interactions from the charge-transfer (CT) "chemical" interaction. Surprisingly, it is found that CT from the adsorbent to the σ*(H2) orbital is present in all studied complexes and can contribute up to approximately -2 kJ/mol to the interaction. When metal ions are present, donation from the σ(H2) → metal Rydberg-like orbital, along with the adsorbent → σ*(H2) contribution, can contribute from -2 to -10 kJ/mol, depending on the coordination mode. To reach a sufficient adsorption enthalpy for practical usage, the hydrogen molecule must be substantially polarized. Ultimately, the ability of the metalated linker to polarize the hydrogen molecule is highly dependent on the geometry of the metal ion coordination site where a strong electrostatic dipole or quadrupole moment is required.

  11. Photoconversion of 4-nitrophenol in the presence of hydrazine with AgNPs-TiO{sub 2} nanoparticles prepared by the sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Hernández-Gordillo, Agileo, E-mail: agileo12@hotmail.com [División de Materiales Avanzados, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055 Col. Lomas 4a. sección, C.P. 78216 San Luis Potosí, SLP, México (Mexico); CIIEMAD, Instituto Politécnico Nacional, Calle 30 de Junio de 1520 s/n, Barrio la Laguna Ticomán, C.P. 07340, Del. Gustavo A. Madero, DF, México (Mexico); Arroyo, Missael [División de Materiales Avanzados, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055 Col. Lomas 4a. sección, C.P. 78216 San Luis Potosí, SLP, México (Mexico); Zanella, R. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, A.P. 70-186, Delegación Coyoacán, C.P. 04510 México, DF, México (Mexico); and others

    2014-03-01

    Graphical abstract: - Highlights: • AgNPs are well dispersed on TiO{sub 2} semiconductor surface. • TiO{sub 2} with 1.5 wt% of Ag{sup 0} is the most photoactive for the 4-nitrophenol conversion. • High conversion of 4-nitrofenol to 4-aminophenol was achieved with hydrazine. • Enhanced photoactivity of Ag-TiO{sub 2} is associated with the ability to oxidize hydrazine. - Abstract: The photocatalytic properties of functionalized TiO{sub 2} with silver nanoparticles (AgNPs) for the conversion of 4-nitrophenol to 4-aminophenol in the presence of hydrazine were investigated. The TiO{sub 2} semiconductor synthesized by the sol–gel method was functionalized with AgNPs at different loadings, and their structural and optical properties were characterized by several techniques. The functionalized TiO{sub 2} with 1.5 wt% AgNPs presented the highest photocatalytic activity for the conversion of 4-nitrophenol with appropriate hydrazine concentrations (0.5 M). The photoefficiency enhancement under UV light irradiation was attributed to the electron transfer from the TiO{sub 2} semiconductor surface to the adsorbed acceptor reactant (4-nitrophenol) through the deposited AgNPs.

  12. A QSAR/QSTR Study on the Environmental Health Impact by the Rocket Fuel 1,1-Dimethyl Hydrazine and its Transformation Products.

    Science.gov (United States)

    Carlsen, Lars; Kenessov, Bulat N; Batyrbekova, Svetlana Ye

    2008-07-18

    QSAR/QSTR modelling constitutes an attractive approach to preliminary assessment of the impact on environmental health by a primary pollutant and the suite of transformation products that may be persistent in and toxic to the environment. The present paper studies the impact on environmental health by residuals of the rocket fuel 1,1-dimethyl hydrazine (heptyl) and its transformation products. The transformation products, comprising a variety of nitrogen containing compounds are suggested all to possess a significant migration potential. In all cases the compounds were found being rapidly biodegradable. However, unexpected low microbial activity may cause significant changes. None of the studied compounds appear to be bioaccumulating.Apart from substances with an intact hydrazine structure or hydrazone structure the transformation products in general display rather low environmental toxicities. Thus, it is concluded that apparently further attention should be given to tri- and tetramethyl hydrazine and 1-formyl 2,2-dimethyl hydrazine as well as to the hydrazones of formaldehyde and acetaldehyde as these five compounds may contribute to the overall environmental toxicity of residual rocket fuel and its transformation products.

  13. Expression and identification of the ADF-linker-3-1E gene of Eimeria acervulina of chicken.

    Science.gov (United States)

    Yuelan, Zhao; Yiwei, Liu; Liyuan, Liu; Yue, Zhao; Wenbo, Cao; Yongzhan, Bao; Jianhua, Qin

    2016-04-01

    Coccidiosis is a widely distributed disease with higher mortality and morbidity, which is caused by several species of protozoan parasites belonging to the genus Eimeria and recognized as a serious challenge for the poultry industry. This research was conducted to construct the recombinant plasmid pET32a(+)-ADF-linker-3-1E of Eimeria acervulina (E. acervulina) of the chicken and test the bioactivity of the ADF-linker-3-1E protein. The ADF-linker-3-1E gene of E. acervulina of the chicken was cloned by splicing by overlap extension by the polymerase chain reaction (SOE-PCR) and then inserted into the pET32a(+) to construct the recombinant plasmid pET32a(+)-ADF-linker-3-1E. The recombinant plasmid was transformed into Escherichia coli Rosetta (DE3) competent cells and then induced by IPTG (0.6 mmol/L). The expressed product in the culture medium was identified by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The bioactivity of the ADF-linker-3-1E protein was tested by Western blotting. The result showed that the amplified ADF-linker-3-1E gene was about 1346 bp. The PCR amplification with the recombinant plasmid pET-32a(+)-ADF-linker-3-1E as a template resulted in a special band of 1346 bp. The digested products resulted in two fragments of 1346 bp target fragment and 5.9 kb pET-32a(+)-vector fragment. The results indicated that the ADF-linker3-1E gene was successfully inserted into the pET-32a(+)-vector. The expressed products in the culture medium resulted in a single band of approximately 54.8 kDa by SDS-PAGE. Western blotting analysis indicated that the recombinant protein could be reacted specifically with His-Tag(2A8) Mouse mAb. This study indicated that the ADF-linker-3-1E protein with good bioactivity was successfully obtained, which laid a foundation for the exploitation of the nuclear vaccine by using the ADF-linker-3-1E protein.

  14. A Novel MS-Cleavable Azo Cross-Linker for Peptide Structure Analysis by Free Radical Initiated Peptide Sequencing (FRIPS)

    Science.gov (United States)

    Iacobucci, Claudio; Hage, Christoph; Schäfer, Mathias; Sinz, Andrea

    2017-10-01

    The chemical cross-linking/mass spectrometry (MS) approach is a growing research field in structural proteomics that allows gaining insights into protein conformations. It relies on creating distance constraints between cross-linked amino acid side chains that can further be used to derive protein structures. Currently, the most urgent task for designing novel cross-linking principles is an unambiguous and automated assignment of the created cross-linked products. Here, we introduce the homobifunctional, amine-reactive, and water soluble cross-linker azobisimidoester (ABI) as a prototype of a novel class of cross-linkers. The ABI-linker possesses an innovative modular scaffold combining the benefits of collisional activation lability with open shell chemistry. This MS-cleavable cross-linker can be efficiently operated via free radical initiated peptide sequencing (FRIPS) in positive ionization mode. Our proof-of-principle study challenges the gas phase behavior of the ABI-linker for the three amino acids, lysine, leucine, and isoleucine, as well as the model peptide thymopentin. The isomeric amino acids leucine and isoleucine could be discriminated by their characteristic side chain fragments. Collisional activation experiments were conducted via positive electrospray ionization (ESI) on two Orbitrap mass spectrometers. The ABI-mediated formation of odd electron product ions in MS/MS and MS3 experiments was evaluated and compared with a previously described azo-based cross-linker. All cross-linked products were amenable to automated analysis by the MeroX software, underlining the future potential of the ABI-linker for structural proteomics studies. [Figure not available: see fulltext.

  15. The tumor suppressor proteins ASPP1 and ASPP2 interact with C-Nap1 and regulate centrosome linker reassembly.

    Science.gov (United States)

    Zhang, Yuanyuan; Wang, Yuqi; Wei, Youheng; Ma, Jian; Peng, Jingtao; Wumaier, Reziya; Shen, Suqin; Zhang, Pingzhao; Yu, Long

    2015-03-13

    Centrosome linker tethers interphase centrosomes together allowing them to function as a single microtubule organization center. The centrosome linker is disrupted at the onset of mitosis to ensure timely centrosome disjunction and bipolar spindle formation and is reassembled at the end of mitosis. While the mechanism controlling centrosome linker disassembly at early mitosis has been well explored, little is known about how the linker is subsequently reassembled before mitotic exit. Here we report that ASPP1 and ASPP2, two members of the apoptosis stimulating proteins of p53 (ASPP) family, are involved in centrosome linker reassembly. We showed that ASPP1/2 interacted with centrosome linker protein C-Nap1. Co-depletion of ASPP1 and ASPP2 inhibited re-association of C-Nap1 with centrosome at the end of mitosis. Moreover, ASPP1/2 facilitated the interaction between C-Nap1 and PP1α, and this interaction was significantly reduced by co-depletion of ASPP1/2. ASPP1/2 antagonized the NEK2A-mediated C-Nap1 Ser2417/2421 phosphorylation in a PP1-dependent manner. Co-depletion of ASPP1 and ASPP2 inhibited dephosphorylation of C-Nap1 (Ser2417/2421) at the end of mitosis. Based on these findings, we propose that ASPP1/2 act as PP1-targeting subunits to facilitate C-Nap1 dephosphorylation and centrosome linker reassembly at the end of mitosis. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Reaction of Oxidized Polysialic Acid and a Diaminooxy Linker: Characterization and Process Optimization Using Nuclear Magnetic Resonance Spectroscopy.

    Science.gov (United States)

    Ray, G Joseph; Siekmann, Jürgen; Scheinecker, Richard; Zhang, Zhenqing; Gerasimov, Mikhail V; Szabo, Christina M; Kosma, Paul

    2016-09-21

    Native polysialic acid (natPSA) is a high-molecular-weight glycan composed of repeat units of α-(2 → 8) linked N-acetylneuraminic acid (Neu5Ac). Mild periodate oxidation of PSA selectively targets the end sialic acid ring containing three adjacent alcohols generating a putative aldehyde, which can be used, after attachment of a linker molecule, for terminal attachment of PSA to protein. Previously, we showed that the oxidized PSA (oxoPSA) contained a hemiacetal at the oxidation site and can react with a linker containing an aminooxy group in a conjugation reaction to form a stable oxime linkage. Thus, reagents containing an aminooxy group may be prepared for conjugation of PSA to the carbohydrate moiety of therapeutic proteins, thereby increasing their half-life. These aminooxy-PSA reagents can selectively react with aldehyde groups generated by mild NaIO4 oxidation of glycans on the surface of the target protein. To comprehend the conjugation, unoxidized tetrasialic acid and Neu5Ac were reacted in model reactions with a diaminooxy linker to define the nuclear magnetic resonance (NMR) chemical shifts. Based on these data, we were able to show that, in the case of PSA, the reaction with the linker occurs not only at the expected oxidized end to form an aldoxime but also at the end distal to the oxidation to form a ketoxime. We determined that, in aged solutions, both oxoPSA and PSA aldoxime were hydrolyzed. PSA aldoxime was also shown to disproportionate to form a dimer (PSA-linker-PSA), which then could react further with the released linker at one of its PSA termini. Furthermore, NMR was used to monitor the effects of deliberate process changes so that conditions could be optimized for attachment of linker at the desired end of the PSA chain, which led to a well-defined product.

  17. Dynamics of Linker Residues Modulate the Nucleic Acid Binding Properties of the HIV-1 Nucleocapsid Protein Zinc Fingers

    Science.gov (United States)

    Zargarian, Loussiné; Tisné, Carine; Barraud, Pierre; Xu, Xiaoqian; Morellet, Nelly; René, Brigitte; Mély, Yves; Fossé, Philippe; Mauffret, Olivier

    2014-01-01

    The HIV-1 nucleocapsid protein (NC) is a small basic protein containing two zinc fingers (ZF) separated by a short linker. It is involved in several steps of the replication cycle and acts as a nucleic acid chaperone protein in facilitating nucleic acid strand transfers occurring during reverse transcription. Recent analysis of three-dimensional structures of NC-nucleic acids complexes established a new property: the unpaired guanines targeted by NC are more often inserted in the C-terminal zinc finger (ZF2) than in the N-terminal zinc finger (ZF1). Although previous NMR dynamic studies were performed with NC, the dynamic behavior of the linker residues connecting the two ZF domains remains unclear. This prompted us to investigate the dynamic behavior of the linker residues. Here, we collected 15N NMR relaxation data and used for the first time data at several fields to probe the protein dynamics. The analysis at two fields allows us to detect a slow motion occurring between the two domains around a hinge located in the linker at the G35 position. However, the amplitude of motion appears limited in our conditions. In addition, we showed that the neighboring linker residues R29, A30, P31, R32, K33 displayed restricted motion and numerous contacts with residues of ZF1. Our results are fully consistent with a model in which the ZF1-linker contacts prevent the ZF1 domain to interact with unpaired guanines, whereas the ZF2 domain is more accessible and competent to interact with unpaired guanines. In contrast, ZF1 with its large hydrophobic plateau is able to destabilize the double-stranded regions adjacent to the guanines bound by ZF2. The linker residues and the internal dynamics of NC regulate therefore the different functions of the two zinc fingers that are required for an optimal chaperone activity. PMID:25029439

  18. Synthesis, structures, and magnetic properties of metal-coordination polymers with benzenepentacarboxylate linkers.

    Science.gov (United States)

    Wang, Xin-Yi; Sevov, Slavi C

    2008-02-04

    Three hybrid organic-inorganic coordination polymers with benzenepentacarboxylate (BPCA) linkers, [Co3(C6H(COO)5)(OH)(H2O)3] (1-Co), [Zn3(C6H(COO)5)(OH)(H2O)3] (2-Zn), and [Co5(C6H(COO)5)2(H2O)12].(H2O)12 (3-Co), were synthesized hydrothermally and were characterized structurally and magnetically. 1-Co and 2-Zn are isostructural [C2/c; Z=8; 1-Co, a=19.5350(6) A, b=10.4494(4) A, and c=13.2353(5) A, beta=97.2768(8) degrees; 2-Zn, a=19.5418(9) A, b=10.3220(10) A, and c=13.4660(10) A, beta=98.455(10) degrees] with three-dimensional structures that contain [M6] secondary building units bridged by BPCA ligands. A different cobalt-based compound, 3-Co, forms at lower pH and lower reaction temperature. Its structure [P21/c; Z=2; a=12.6162(2) A, b=11.3768(2) A, and c=15.3401(3) A, beta=91.539(1) degrees] is a more loosely packed framework with free (noncoordinated) carboxylic groups pointing at water-filled cavities in the framework. The magnetic phase diagram of 1-Co established through detailed magnetic measurements shows a metamagnetic transition below TN=3.8 K. The less-packed compound 3-Co, on the other hand, remains paramagnetic above 1.9 K. The three compounds are the first examples of coordination polymers with benzenepentacarboxylate linkers and fill the gap of coordination polymers involving benzenepolycarboxylate linkers of the general type C6H6-n(COOH)n, where n=2-6.

  19. A push-pull organic dye with a quinoidal thiophene linker: Photophysical properties and solvent effects

    Science.gov (United States)

    Climent, Clàudia; Carreras, Abel; Alemany, Pere; Casanova, David

    2016-10-01

    In the present work we perform a computational study of the properties of a push-pull organic dye with a quinoidal thiophene unit as the conjugated linker between the electron donor and acceptor groups. We investigate the photophysical properties of the dye related to its potential use as a molecular sensitizer in dye-sensitized solar cells. We rationalize the solvation effects on the absorption band of the dye in protic and aprotic solvents, identifying the interaction of alcohol solvents with the amine in the donor group as the source for the blue shift of the absorption band with respect to aprotic solvents.

  20. Solid-phase synthesis of polyfunctional polylysine dendrons using aldehyde linkers

    DEFF Research Database (Denmark)

    Svenssen, Daniel K.; Mirsharghi, Sahar; Boas, Ulrik

    2014-01-01

    A straightforward method for the solid-phase synthesis of C-terminally modified polylysine dendrons has been developed by applying bisalkoxybenzaldehyde and trisalkoxybenzaldehyde linkers. The method has been used for the synthesis of polylysine dendrons with a variety of C-terminal ‘tail groups......’ such as alkyl, propargyl, and dansyl to give dendrons in high crude purity. Furthermore, the method was successful for the synthesis of dendrons with multiple N-terminal pentapeptide groups together with C-terminal alkyl and propargyl tail groups. Finally, the method was shown to be well-suited for automated...

  1. SEVA Linkers: A Versatile and Automatable DNA Backbone Exchange Standard for Synthetic Biology

    DEFF Research Database (Denmark)

    Kim, Se Hyeuk; Cavaleiro, Mafalda; Rennig, Maja

    2016-01-01

    DNA vectors serve to maintain and select recombinant DNA in cell factories, and as design complexity increases, there is a greater need for well-characterized parts and methods for their assembly. Standards in synthetic biology are top priority, but standardizing molecular cloning contrasts...... flexibility, and different researchers prefer and master different molecular technologies. Here, we describe a new, highly versatile and automatable standard “SEVA linkers” for vector exchange. SEVA linkers enable backbone swapping with 20 combinations of classical enzymatic restriction/ligation, Gibson...... to the synthetic biology community....

  2. Nanomolar concentrations determination of hydrazine by a modified carbon paste electrode incorporating TiO2nanoparticles

    Science.gov (United States)

    Mazloum-Ardakani, Mohammad; Taleat, Zahra; Beitollahi, Hadi; Naeimi, Hossein

    2011-04-01

    In the present paper, the use of a carbon paste electrode modified by quinizarine (QZ) and TiO2nanoparticles prepared by a simple and rapid method was described. The heterogeneous electron-transfer properties of quinizarine coupled to TiO2nanoparticles at a carbon paste electrode was investigated using cyclic voltammetry and chronoamperometry in aqueous buffer solutions. The modified electrode showed excellent character for the electrocatalytic oxidization of hydrazine (HZ). Differential pulse voltammetric peak currents of HZ increased linearly with their concentrations at the range of 0.5 µM to 1900.0 µM and the detection limit (2σ) was determined to be 77 nM. Finally, this method was used for the determination of HZ in water samples, using a standard addition method.

  3. A highly selective long-wavelength fluorescent probe for hydrazine and its application in living cell imaging

    Science.gov (United States)

    Hao, Yuanqiang; Zhang, Yintang; Ruan, Kehong; Meng, Fanteng; Li, Ting; Guan, Jinsheng; Du, Lulu; Qu, Peng; Xu, Maotian

    2017-09-01

    A highly selective long-wavelength turn-on fluorescent probe has been developed for the detection of N2H4. The probe was prepared by conjugation the tricyanofuran-based D-π-A system with a recognizing moiety of acetyl group. In the presence of N2H4, the probe can be effectively hydrazinolysized and produce a turn-on fluorescent emission at 610 nm as well as a large red-shift in the absorption spectrum corresponding to a color change from yellow to blue. The sensing mechanism was confirmed by HPLC, MS, UV-vis, emission spectroscopic and theoretical calculation studies. The probe displayed high selectivity and sensitivity for N2H4 with a LOD (limit of detection) of 0.16 μM. Moreover, the probe was successfully utilized for the detection of hydrazine in living cells.

  4. Characterization of cobalt oxide nanocatalysts prepared by microemulsion with different surfactants, reduction by hydrazine and mechanochemical method

    Energy Technology Data Exchange (ETDEWEB)

    Morsy, Salwa M.I. [Applied Surfactanst Laboratory (Egypt); Egyptian Petroleum Research Institute, Nasr City, Cairo (Egypt); Shaban, Seham Ali, E-mail: sehamshaban@yahoo.co [Applied Catalysts Laboratory (Egypt); Egyptian Petroleum Research Institute, Nasr City, Cairo (Egypt); Ibrahim, Amal M. [Nano and Composite Material Department (Egypt); Mubarak City for Scientific Research and Technology Applications, Borg El Arab City, Alexandria (Egypt); Selim, Mohamed M. [Surface Chemistry and Catalysis Laboratory, National Research Center, Doky, Cairo (Egypt)

    2009-11-03

    Cobalt oxide (Co{sub 3}O{sub 4}) nanoparticles were prepared by different techniques (i) by microemulsion with different surfactants, (ii) by reduction as nanometal with hydrazine hydrates and (iii) by thermal treatment of precursor obtained from mechanochemical reaction of Co(NO{sub 3}).H{sub 2}O with NH{sub 4}HCO{sub 3}. The products were calcined at 400 deg. C to give crystalline Co{sub 3}O{sub 4}. The obtained different samples of Co{sub 3}O{sub 4} were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) from which the particle size was calculated. The results revealed that all samples obtained from different methods were nanosized particles.

  5. A Pyridine-Based Ligand with Two Hydrazine Functions for Lanthanide Chelation: Remarkable Kinetic Inertness for a Linear, Bishydrated Complex.

    Science.gov (United States)

    Bonnet, Célia S; Laine, Sophie; Buron, Frédéric; Tircsó, Gyula; Pallier, Agnès; Helm, Lothar; Suzenet, Franck; Tóth, Éva

    2015-06-15

    To study the influence of hydrazine functions in the ligand skeleton, we designed the heptadentate HYD ligand (2,2',2″,2‴-(2,2'-(pyridine-2,6-diyl)bis(2-methylhydrazine-2,1,1-triyl)) tetraacetic acid) and compared the thermodynamic, kinetic, and relaxation properties of its Ln(3+) complexes to those of the parent pyridine (Py) analogues without hydrazine (Py = 2,6-pyridinebis(methanamine)-N,N,N',N'-tetraacetic acid). The protonation constants of HYD were determined by pH-potentiometric measurements, and assigned by a combination of UV-visible and NMR spectroscopies. The protonation sequence is rather unusual and illustrates that small structural changes can strongly influence ligand basicity. The first protonation step occurs on the pyridine nitrogen in the basic region, followed by two hydrazine nitrogens and the carboxylate groups at acidic pH. Contrary to Py, HYD self-aggregates through a pH-dependent process (from pH ca. 4). Thermodynamic stability constants have been obtained by pH-potentiometry and UV-visible spectrophotometry for various Ln(3+) and physiological cations (Zn(2+), Ca(2+), Cu(2+)). LnHYD stability constants show the same trend as those of LnDTPA complexes along the Ln(3+) series, with log K = 18.33 for Gd(3+), comparable to the Py analogue. CuHYD has a particularly high stability (log K > 19) preventing its determination from pH-potentiometric measurements. The stability constant of CuPy was also revisited and found to be underestimated in previous studies, highlighting that UV-visible spectrophotometry is often indispensable to obtain reliable stability constants for Cu(2+) chelates. The dissociation of GdL, assessed by studying the Cu(2+)-exchange reaction, occurs mainly via an acid-catalyzed process, with limited contribution from direct Cu(2+) attack. The kinetic inertness of GdHYD is remarkable for a linear bishydrated chelate; the 25-fold increase in the dissociation half-life with respect to the monohydrated commercial contrast agent

  6. Incorporation of alpha-Ketoglutaric Acid as a Fixed Bed Scrubber Media for the Neutralization of Hydrazine Family Hypergolic Fuels

    Science.gov (United States)

    DeVor, R. W.; Santiago-Maldonado, E.; Parkerson, J. K.

    2010-01-01

    A candidate scrubber media, alpha-ketoglutaric acid (aKGA) adsorbed onto a silica-based substrate was examined as a potential alternative to the hydrazine-family hypergolic fuel neutralization techniques currently utilized at NASA/Kennedy Space Center (KSC). Helvenson et. al. has indicated that aKGA will react with hydrazines to produce non-hazardous, possibly biodegradable products. Furthermore, the authors have previously tested and demonstrated the use of aKGA aqueous solutions as a replacement neutralizing agent for citric acid, which is currently used as a scrubbing agent in liquid scrubbers at KSC. Specific properties examined include reaction efficiency, the loading capacity of aKGA onto various silica substrates, and the comparison of aKGA media performance to that of the citric acid vapor scrubber systems at KSC and a commercial vapor scrubber media. Preliminary investigations showed hydrophobic aerogel particles to be an ideal substrate for the deposition of the aKGA. Current studies have shown that the laboratory produced aKGA-Aerogel absorbent media are more efficient and cost effective than a commercially available fixed bed scrubber media, although much less cost effective than liquid-based citric acid scrubbers (although possibly safer and less labor intensive). A comparison of all three alternative scrubber technologies (liquid aKGA, solid-phase aKGA, and commercially available sorbent materials) is given considering both hypergolic neutralization capabilities and relative costs (as compared to the current citric acid scrubbing technology in use at NASA/KSC).

  7. Immobilized iron oxide nanoparticles as stable and reusable catalysts for hydrazine-mediated nitro reductions in continuous flow.

    Science.gov (United States)

    Moghaddam, Mojtaba Mirhosseini; Pieber, Bartholomäus; Glasnov, Toma; Kappe, C Oliver

    2014-11-01

    An experimentally easy to perform method for the generation of alumina-supported Fe3O4 nanoparticles [(6±1) nm size, 0.67 wt %]and the use of this material in hydrazine-mediated heterogeneously catalyzed reductions of nitroarenes to anilines under batch and continuous-flow conditions is presented. The bench-stable, reusable nano-Fe3O4@Al2O3 catalyst can selectively reduce functionalized nitroarenes at 1 mol % catalyst loading by using a 20 mol % excess of hydrazine hydrate in an elevated temperature regime (150 °C, reaction time 2-6 min in batch). For continuous-flow processing, the catalyst material is packed into dedicated cartridges and used in a commercially available high-temperature/-pressure flow device. In continuous mode, reaction times can be reduced to less than 1 min at 150 °C (30 bar back pressure) in a highly intensified process. The nano-Fe3O4@Al2O3 catalyst demonstrated stable reduction of nitrobenzene (0.5 M in MeOH) for more than 10 h on stream at a productivity of 30 mmol h(-1) (0.72 mol per day). Importantly, virtually no leaching of the catalytically active material could be observed by inductively coupled plasma MS monitoring. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Accurate distance determination of nucleic acids via Förster resonance energy transfer: implications of dye linker length and rigidity.

    Science.gov (United States)

    Sindbert, Simon; Kalinin, Stanislav; Nguyen, Hien; Kienzler, Andrea; Clima, Lilia; Bannwarth, Willi; Appel, Bettina; Müller, Sabine; Seidel, Claus A M

    2011-03-02

    In Förster resonance energy transfer (FRET) experiments, the donor (D) and acceptor (A) fluorophores are usually attached to the macromolecule of interest via long flexible linkers of up to 15 Å in length. This causes significant uncertainties in quantitative distance measurements and prevents experiments with short distances between the attachment points of the dyes due to possible dye-dye interactions. We present two approaches to overcome the above problems as demonstrated by FRET measurements for a series of dsDNA and dsRNA internally labeled with Alexa488 and Cy5 as D and A dye, respectively. First, we characterize the influence of linker length and flexibility on FRET for different dye linker types (long, intermediate, short) by analyzing fluorescence lifetime and anisotropy decays. For long linkers, we describe a straightforward procedure that allows for very high accuracy of FRET-based structure determination through proper consideration of the position distribution of the dye and of linker dynamics. The position distribution can be quickly calculated with geometric accessible volume (AV) simulations, provided that the local structure of RNA or DNA in the proximity of the dye is known and that the dye diffuses freely in the sterically allowed space. The AV approach provides results similar to molecular dynamics simulations (MD) and is fully consistent with experimental FRET data. In a benchmark study for ds A-RNA, an rmsd value of 1.3 Å is achieved. Considering the case of undefined dye environments or very short DA distances, we introduce short linkers with a propargyl or alkenyl unit for internal labeling of nucleic acids to minimize position uncertainties. Studies by ensemble time correlated single photon counting and single-molecule detection show that the nature of the linker strongly affects the radius of the dye's accessible volume (6-16 Å). For short propargyl linkers, heterogeneous dye environments are observed on the millisecond time scale. A

  9. Multivalent Polyaspartamide Cross-Linker for Engineering Cell-Responsive Hydrogels with Degradation Behavior and Tunable Physical Properties.

    Science.gov (United States)

    Jang, Jinhyeong; Cha, Chaenyung

    2018-01-30

    Hydrogels possess favorable physical properties ideally suited for various biotechnology applications. To tailor to specific needs, a number of modification strategies have been employed to tune their properties. Herein, a multifunctional polymeric cross-linker based on polyaspartamide is developed, which allows for the facile adjustment of the type and number of reactive functional groups to fit different reaction schemes and control the physical properties of the hydrogels. The amine-based nucleophiles containing desired functional groups are reacted with polysuccinimide to synthesize polyaspartamide cross-linkers. The cross-linking density and the concurrent change in mechanical properties of the resulting hydrogels are controlled in a wide range only with the degree of substitution. This multivalency of the polyaspartamide linkers also induced the degradation of hydrogels by the unreacted functional groups on polyaspartamide involved in the hydrolysis. Furthermore, the polyaspartamide cross-linker conjugated with cell-recognition molecules via the same conjugation mechanism (i.e., nucleophilic substitution) render the hydrogels cell-responsive without the need of additional processing steps. This versatility of polyaspartamide-based cross-linker is expected to provide an efficient and versatile route to engineer hydrogels with controllable properties for biomedical applications.

  10. Preferential domain orientation of HMGB2 determined by the weak intramolecular interactions mediated by the interdomain linker

    Science.gov (United States)

    Uewaki, Jun-ichi; Kamikubo, Hironari; Kurita, Jun-ichi; Hiroguchi, Noriteru; Moriuchi, Hiroshi; Yoshida, Michiteru; Kataoka, Mikio; Utsunomiya-Tate, Naoko; Tate, Shin-ichi

    2013-06-01

    High mobility group box protein 2 (HMGB2) contains homologous tandem HMG box DNA-binding domains, boxes A and B. These two boxes are linked by a short basic linker having a sequence characteristic of an intrinsically disordered element. The combined use of NMR and small angle X-ray scattering (SAXS) showed that the two boxes assume a preferred orientation to make their DNA binding surface in opposite directions, although the linker does not keep any specific conformation. A series of site directed mutations to the residues in the linker showed that a network of CH-π interactions connects the N-terminal part of the linker to box A. The mutants having impaired intramolecular CH-π interactions changed the interdomain dynamics and their dynamic averaged orientation relative to the wild-type. This work demonstrates that the apparently unstructured linker plays a role in defining the preferential domain orientation through the intramolecular CH-π interactions, even though the interactions are weak and transient.

  11. Modulating Therapeutic Activity and Toxicity of Pyrrolobenzodiazepine Antibody-Drug Conjugates with Self-Immolative Disulfide Linkers.

    Science.gov (United States)

    Pillow, Thomas H; Schutten, Melissa; Yu, Shang-Fan; Ohri, Rachana; Sadowsky, Jack; Poon, Kirsten Achilles; Solis, Willy; Zhong, Fiona; Del Rosario, Geoffrey; Go, Mary Ann T; Lau, Jeffrey; Yee, Sharon; He, Jintang; Liu, Luna; Ng, Carl; Xu, Keyang; Leipold, Douglas D; Kamath, Amrita V; Zhang, Donglu; Masterson, Luke; Gregson, Stephen J; Howard, Philip W; Fang, Fan; Chen, Jinhua; Gunzner-Toste, Janet; Kozak, Katherine K; Spencer, Susan; Polakis, Paul; Polson, Andrew G; Flygare, John A; Junutula, Jagath R

    2017-05-01

    A novel disulfide linker was designed to enable a direct connection between cytotoxic pyrrolobenzodiazepine (PBD) drugs and the cysteine on a targeting antibody for use in antibody-drug conjugates (ADCs). ADCs composed of a cysteine-engineered antibody were armed with a PBD using a self-immolative disulfide linker. Both the chemical linker and the antibody site were optimized for this new bioconjugation strategy to provide a highly stable and efficacious ADC. This novel disulfide ADC was compared with a conjugate containing the same PBD drug, but attached to the antibody via a peptide linker. Both ADCs had similar efficacy in mice bearing human tumor xenografts. Safety studies in rats revealed that the disulfide-linked ADC had a higher MTD than the peptide-linked ADC. Overall, these data suggest that the novel self-immolative disulfide linker represents a valuable way to construct ADCs with equivalent efficacy and improved safety. Mol Cancer Ther; 16(5); 871-8. ©2017 AACR . ©2017 American Association for Cancer Research.

  12. Fine tuning of spatial arrangement of enzymes in a PCNA-mediated multienzyme complex using a rigid poly-L-proline linker.

    Directory of Open Access Journals (Sweden)

    Tomoaki Haga

    Full Text Available Inspired by natural multienzyme complexes, many types of artificial multienzyme complexes have recently been constructed. We previously constructed a self-assembled complex of a bacterial cytochrome P450 and its ferredoxin and ferredoxin reductase partners using heterotrimerization of proliferating cell nuclear antigen (PCNA from Sulfolobus solfataricus. In this study, we inserted different peptide linkers between ferredoxin and the PCNA subunit, and examined the effect on activity of the self-assembled multienzyme complex. Although the activity was affected by the lengths of both the rigid poly-L-proline-rich linkers and the flexible Gly4-Ser repeating linkers, the poly-L-proline-rich linkers provided the greatest activity enhancement. The optimized poly-L-proline-rich linker enhanced the activity 1.9-fold compared with the GGGGSLVPRGSGGGGS linker used in the previously reported complex, while the Gly4-Ser repeating linkers, (G4Sn (n = 1-6, did not yield higher activity than the maximum activity by the optimized poly-L-proline linker. Both the rigidity/flexibility and length of the peptide linker were found to be important for enhancing the overall activity of the multienzyme complex.

  13. A structured interdomain linker directs self-polymerization of human uromodulin.

    Science.gov (United States)

    Bokhove, Marcel; Nishimura, Kaoru; Brunati, Martina; Han, Ling; de Sanctis, Daniele; Rampoldi, Luca; Jovine, Luca

    2016-02-09

    Uromodulin (UMOD)/Tamm-Horsfall protein, the most abundant human urinary protein, plays a key role in chronic kidney diseases and is a promising therapeutic target for hypertension. Via its bipartite zona pellucida module (ZP-N/ZP-C), UMOD forms extracellular filaments that regulate kidney electrolyte balance and innate immunity, as well as protect against renal stones. Moreover, salt-dependent aggregation of UMOD filaments in the urine generates a soluble molecular net that captures uropathogenic bacteria and facilitates their clearance. Despite the functional importance of its homopolymers, no structural information is available on UMOD and how it self-assembles into filaments. Here, we report the crystal structures of polymerization regions of human UMOD and mouse ZP2, an essential sperm receptor protein that is structurally related to UMOD but forms heteropolymers. The structure of UMOD reveals that an extensive hydrophobic interface mediates ZP-N domain homodimerization. This arrangement is required for filament formation and is directed by an ordered ZP-N/ZP-C linker that is not observed in ZP2 but is conserved in the sequence of deafness/Crohn's disease-associated homopolymeric glycoproteins α-tectorin (TECTA) and glycoprotein 2 (GP2). Our data provide an example of how interdomain linker plasticity can modulate the function of structurally similar multidomain proteins. Moreover, the architecture of UMOD rationalizes numerous pathogenic mutations in both UMOD and TECTA genes.

  14. Linker structure-activity relationships in fluorodeoxyglucose chlorambucil conjugates for tumor-targeted chemotherapy.

    Science.gov (United States)

    El Hilali, Mostafa; Reux, Bastien; Debiton, Eric; Leal, Fernand; Galmier, Marie-Josephe; Vivier, Magali; Chezal, Jean-Michel; Miot-Noirault, Elisabeth; Coudert, Pascal; Weber, Valérie

    2017-10-15

    Nitrogen mustards, such as chlorambucil (CLB), can cause adverse side-effects due to ubiquitous distribution in non-target organs. To minimize this toxicity, strategies of tumor-targeting drug delivery have been developed, where a cytotoxic warhead is linked to a tumor-cell-specific small ligand. Malignant cells exhibit marked glucose avidity and an accelerated metabolism by aerobic glycolysis, known as the Warburg effect, and recognized as a hallmark of cancer. A targeting approach exploiting the Warburg effect by conjugation of CLB to 2-fluoro-2-deoxyglucose (FDG) was previously reported and identified two peracetylated glucoconjugates 2 and 3 with promising antitumor activities in vivo. These results prompted us to investigate the importance of the spacer in this tumor-targeting glucose-based conjugates. Here we report the chemical synthesis and an in vitro cytotoxicity evaluation, using a 5-member panel of human tumor cell lines and human fibroblasts, of 16 new CLB glucoconjugates in which the alkylating drug is attached to the C-1 position of FDG via different linkages. We studied the structure-activity relationships in the linker, and evidenced the positive impact of an aromatic linker on in vitro cytotoxicity: compound 51 proved to be the most active FDG-CLB glucoside, characterized by a bis-aromatic spacer tethered to CLB through an amide function. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Structural Basis for Activation of ZAP-70 by Phosphorylation of the SH2-Kinase Linker

    Science.gov (United States)

    Yan, Qingrong; Barros, Tiago; Visperas, Patrick R.; Deindl, Sebastian; Kadlecek, Theresa A.; Weiss, Arthur

    2013-01-01

    Serial activation of the tyrosine kinases Lck and ZAP-70 initiates signaling downstream of the T cell receptor. We previously reported the structure of an autoinhibited ZAP-70 variant in which two regulatory tyrosine residues (315 and 319) in the SH2-kinase linker were replaced by phenylalanine. We now present a crystal structure of ZAP-70 in which Tyr 315 and Tyr 319 are not mutated, leading to the recognition of a five-residue sequence register error in the SH2-kinase linker of the original crystallographic model. The revised model identifies distinct roles for these two tyrosines. As seen in a recently reported structure of the related tyrosine kinase Syk, Tyr 315 of ZAP-70 is part of a hydrophobic interface between the regulatory apparatus and the kinase domain, and the integrity of this interface would be lost upon engagement of doubly phosphorylated peptides by the SH2 domains. Tyr 319 is not necessarily dislodged by SH2 engagement, which activates ZAP-70 only ∼5-fold in vitro. In contrast, phosphorylation by Lck activates ZAP-70 ∼100-fold. This difference is due to the ability of Tyr 319 to suppress ZAP-70 activity even when the SH2 domains are dislodged from the kinase domain, providing stringent control of ZAP-70 activity downstream of Lck. PMID:23530057

  16. A minimal phycobilisome: fusion and chromophorylation of the truncated core-membrane linker and phycocyanin.

    Science.gov (United States)

    Tang, Kun; Zeng, Xiao-Li; Yang, Yi; Wang, Zhi-Bin; Wu, Xian-Jun; Zhou, Ming; Noy, Dror; Scheer, Hugo; Zhao, Kai-Hong

    2012-07-01

    Phycobilisomes, the light-harvesting antennas in cyanobacteria and red algae, consist of an allophycocyanin core that is attached to the membrane via a core-membrane linker, and rods comprised of phycocyanin and often also phycoerythrin or phycoerythrocyanin. Phycobiliproteins show excellent energy transfer among the chromophores that renders them biomarkers with large Stokes-shifts absorbing over most of the visible spectrum and into the near infrared. Their application is limited, however, due to covalent binding of the chromophores and by solubility problems. We report construction of a water-soluble minimal chromophore-binding unit of the red-absorbing and fluorescing core-membrane linker. This was fused to minimal chromophore-binding units of phycocyanin. After double chromophorylation with phycocyanobilin, in E. coli, the fused phycobiliproteins absorbed light in the range of 610-660nm, and fluoresced at ~670nm, similar to phycobilisomes devoid of phycoerythr(ocyan)in. The fused phycobiliprotein could also be doubly chromophorylated with phycoerythrobilin, resulting in a chromoprotein absorbing around 540-575nm, and fluorescing at ~585nm. The broad absorptions and the large Stokes shifts render these chromoproteins candidates for imaging; they may also be helpful in studying phycobilisome assembly. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Effective experimental validation of miRNA targets using an improved linker reporter assay.

    Science.gov (United States)

    Choi, Cheolwon; Han, James; Thao Tran, Nguyen Thi; Yoon, Seulgi; Kim, Goeun; Song, Sujung; Kim, Youngjo; Ryu, Seongho

    2017-01-30

    miRNAs are small, non-coding RNAs that play critical roles in various cellular processes. Although there are several algorithms that can predict the potential candidate genes that are regulated by a miRNA, these algorithms require further experimental validation in order to demonstrate genuine targets of miRNAs. Moreover, most algorithms predict hundreds to thousands of putative target genes for each miRNA, and it is difficult to validate all candidates using the whole 3'-untranslated region (UTR) reporter assay. We report a fast, simple and efficient experimental approach to screening miRNA candidate targets using a 3'-UTR linker assay. Critically, the linker has only a short miRNA regulatory element sequence of approximately 22 base pairs in length and can provide a benefit for screening strong miRNA candidates for further validation using the whole 3'-UTR sequence. Our technique will provide a simplified platform for the high-throughput screening of miRNA target gene validation.

  18. Hybrid Zeolitic Imidazolate Frameworks: Controlling Framework Porosity and Functionality by Mixed-Linker Synthesis

    KAUST Repository

    Thompson, Joshua A.

    2012-05-22

    Zeolitic imidazolate frameworks (ZIFs) are a subclass of nanoporous metal-organic frameworks (MOFs) that exhibit zeolite-like structural topologies and have interesting molecular recognition properties, such as molecular sieving and gate-opening effects associated with their pore apertures. The synthesis and characterization of hybrid ZIFs with mixed linkers in the framework are described in this work, producing materials with properties distinctly different from the parent frameworks (ZIF-8, ZIF-90, and ZIF-7). NMR spectroscopy is used to assess the relative amounts of the different linkers included in the frameworks, whereas nitrogen physisorption shows the evolution of the effective pore size distribution in materials resulting from the framework hybridization. X-ray diffraction shows these hybrid materials to be crystalline. In the case of ZIF-8-90 hybrids, the cubic space group of the parent frameworks is continuously maintained, whereas in the case of the ZIF-7-8 hybrids there is a transition from a cubic to a rhombohedral space group. Nitrogen physisorption data reveal that the hybrid materials exhibit substantial changes in gate-opening phenomena, either occurring at continuously tunable partial pressures of nitrogen (ZIF-8-90 hybrids) or loss of gate-opening effects to yield more rigid frameworks (ZIF-7-8 hybrids). With this synthetic approach, significant alterations in MOF properties may be realized to suit a desired separation or catalytic process. © 2012 American Chemical Society.

  19. Effective generation of transgenic pigs and mice by linker based sperm-mediated gene transfer.

    Directory of Open Access Journals (Sweden)

    Shih Ping Yao

    2002-04-01

    Full Text Available Abstract Background Transgenic animals have become valuable tools for both research and applied purposes. The current method of gene transfer, microinjection, which is widely used in transgenic mouse production, has only had limited success in producing transgenic animals of larger or higher species. Here, we report a linker based sperm-mediated gene transfer method (LB-SMGT that greatly improves the production efficiency of large transgenic animals. Results The linker protein, a monoclonal antibody (mAb C, is reactive to a surface antigen on sperm of all tested species including pig, mouse, chicken, cow, goat, sheep, and human. mAb C is a basic protein that binds to DNA through ionic interaction allowing exogenous DNA to be linked specifically to sperm. After fertilization of the egg, the DNA is shown to be successfully integrated into the genome of viable pig and mouse offspring with germ-line transfer to the F1 generation at a highly efficient rate: 37.5% of pigs and 33% of mice. The integration is demonstrated again by FISH analysis and F2 transmission in pigs. Furthermore, expression of the transgene is demonstrated in 61% (35/57 of transgenic pigs (F0 generation. Conclusions Our data suggests that LB-SMGT could be used to generate transgenic animals efficiently in many different species.

  20. The S4---S5 linker - gearbox of TRP channel gating.

    Science.gov (United States)

    Hofmann, Laura; Wang, Hongmei; Zheng, Wang; Philipp, Stephan E; Hidalgo, Patricia; Cavalié, Adolfo; Chen, Xing-Zhen; Beck, Andreas; Flockerzi, Veit

    2017-11-01

    Transient receptor potential (TRP) channels are cation channels which participate in a wide variety of physiological processes in organisms ranging from fungi to humans. They fulfill roles in body homeostasis, are sensors for noxious chemicals and temperature in the mammalian somatosensory system and are activated by light stimulated phospholipase C activity in Drosophila or by hypertonicity in yeast. The transmembrane topology of TRP channels is similar to that of voltage-gated cation channels. TRP proteins assemble as tetramers with each subunit containing six transmembrane helices (S1-S6) and intracellular N- and C-termini. Here we focus on the emerging functions of the cytosolic S4-S5 linker on TRP channel gating. Most of this knowledge comes from pathogenic mutations within the S4-S5 linker that alter TRP channel activities. This knowledge has stimulated forward genetic approaches to identify additional residues around this region which are essential for channel gating and is supported, in part, by recent structures obtained for TRPV1, TRPV2, TRPV6, TRPA1, and TRPP2. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Linker-Induced Anomalous Emission of Organic-Molecule Conjugated Metal-Oxide Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Turkowski, Volodymyr; Babu, Suresh; Le, Duy; Kumar, Amit; Haldar, Manas K.; Wagh, Anil V.; Hu, Zhongjian; Karakoti, Ajay S.; Gesquiere, Andre J.; Law, Benedict; Mallik, Sanku; Rahman, Talat S.; Leuenberger, Michael N.; Seal, Sudipta

    2012-06-26

    Semiconductor nanoparticles conjugated with organic- and dye-molecules to yield high efficiency visible photoluminescence (PL) hold great potential for many future technological applications. We show that folic acid (FA)-conjugated to nanosize TiO2 and CeO2 particles demonstrates a dramatic increase of photoemission intensity at wavelengths between 500 and 700 nm when derivatized using aminopropyl trimethoxysilane (APTMS) as spacer-linker molecules between the metal oxide and FA. Using density-functional theory (DFT) and time-dependent DFT calculations we demonstrate that the strong increase of the PL can be explained by electronic transitions between the titania surface oxygen vacancy (OV) states and the low-energy excited states of the FA/APTMS molecule anchored onto the surface oxygen bridge sites in close proximity to the OVs. We suggest this scenario to be a universal feature for a wide class of metal oxide nanoparticles, including nanoceria, possessing a similar band gap (3 eV) and with a large surface-vacancy-related density of electronic states. We demonstrate that the molecule-nanoparticle linker can play a crucial role in tuning the electronic and optical properties of nanosystems by bringing optically active parts of the molecule and of the surface close to each other.

  2. The interaction between progranulin and prosaposin is mediated by granulins and the linker region between saposin B and C.

    Science.gov (United States)

    Zhou, Xiaolai; Sullivan, Peter M; Sun, Lirong; Hu, Fenghua

    2017-10-01

    The frontotemporal lobar degeneration (FTLD) protein progranulin (PGRN) is essential for proper lysosomal function. PGRN localizes in the lysosomal compartment within the cell. Prosaposin (PSAP), the precursor of lysosomal saposin activators (saposin A, B, C, D), physically interacts with PGRN. Previously, we have shown that PGRN and PSAP facilitate each other's lysosomal trafficking. Here, we report that the interaction between PSAP and PGRN requires the linker region of saposin B and C (BC linker). PSAP protein with the BC linker mutated, fails to interact with PGRN and deliver PGRN to lysosomes in the biosynthetic and endocytic pathways. On the other hand, PGRN interacts with PSAP through multiple granulin motifs. Granulin D and E bind to PSAP with similar affinity as full-length PGRN. Read the Editorial Comment for this article on page 154. © 2017 International Society for Neurochemistry.

  3. Mutations in Biosynthetic Enzymes for the Protein Linker Region of Chondroitin/Dermatan/Heparan Sulfate Cause Skeletal and Skin Dysplasias

    Directory of Open Access Journals (Sweden)

    Shuji Mizumoto

    2015-01-01

    Full Text Available Glycosaminoglycans, including chondroitin, dermatan, and heparan sulfate, have various roles in a wide range of biological events such as cell signaling, cell proliferation, tissue morphogenesis, and interactions with various growth factors. Their polysaccharides covalently attach to the serine residues on specific core proteins through the common linker region tetrasaccharide, -xylose-galactose-galactose-glucuronic acid, which is produced through the stepwise addition of respective monosaccharides by four distinct glycosyltransferases. Mutations in the human genes encoding the glycosyltransferases responsible for the biosynthesis of the linker region tetrasaccharide cause a number of genetic disorders, called glycosaminoglycan linkeropathies, including Desbuquois dysplasia type 2, spondyloepimetaphyseal dysplasia, Ehlers-Danlos syndrome, and Larsen syndrome. This review focused on recent studies on genetic diseases caused by defects in the biosynthesis of the common linker region tetrasaccharide.

  4. Comparative Enactment of Formaldehyde-free and Formaldehyde-based Cross-linkers on Cotton Woven Fabrics

    Directory of Open Access Journals (Sweden)

    Nawshin Farzana

    2017-04-01

    Full Text Available The performances of formaldehyde-based and non-formaldehyde cross-linkers on pretreated cotton woven fabric were assessed and compared in this research. Fixapret CL was considered as the formaldehyde-based resin and Fixapret NF as the formaldehyde-free resin. Dry cross-linking method was adopted for the application of cross-linkers. Different properties of resin treated fabrics investigated and compared were as follows: DP (durable press rating, wrinkle recovery, stiff ness, tensile strength, tear strength, shrinkage, skewness, hydrophobicity, whiteness and yellowness index. Marginally low performances in smoothness appearance and dimensional stability on fabric were exhibited with formaldehyde-free cross-linkers although indicating lower amount of the strength loss percentage. The formaldehyde-based compounds imparted more yellowing tendency to the treated fabric. The formaldehyde-free resins may be a good choice of replacements considering the overall eff ectiveness on fabric

  5. The P-glycoprotein (ABCB1) linker domain encodes high-affinity binding sequences to alpha- and beta-tubulins.

    Science.gov (United States)

    Georges, Elias

    2007-06-26

    P-Glycoprotein (or ABCB1) has been shown to cause multidrug resistance in tumor cell lines selected with lipophilic anticancer drugs. ABCB1 encodes a duplicated molecule with two hydrophobic and hydrophilic domains linked by a highly charged region of approximately 90 amino acids, the "linker domain" with as yet unknown function(s). In this report, we demonstrate a role for this domain in binding to other cellular proteins. Using overlapping hexapeptides that encode the entire amino acid sequence of the linker domain of human ABCB1, we show a direct and specific binding between sequences in the linker domain and several intracellular proteins. Three different polypeptide sequences [617EKGIYFKLVTM627 (LDS617-627), 657SRSSLIRKRSTRRSVRGSQA676 (LDS657-676), and 693PVSFWRIMKLNLT705 (LDS693-705)] in the linker domain interacted tightly with several proteins with apparent molecular masses of approximately 80, 57, and 30 kDa. Interestingly, only the 57 kDa protein (or P57) interacted with all three different sequences of the linker domain. Purification and partial N-terminal amino acid sequencing of P57 showed that it encodes the N-terminal amino acids of alpha- and beta-tubulins. The identity of the P57 interacting protein as tubulins was further confirmed by Western blotting using monoclonal antibodies to alpha- and beta-tubulin. Taken together, the results of this study provide the first evidence for ABCB1 protein interaction mediated by sequences in the linker domain. These findings are likely to provide further insight into the functions of ABCB1 in normal and drug resistant tumor cells.

  6. The S4-S5 linker acts as a signal integrator for HERG K+ channel activation and deactivation gating.

    Directory of Open Access Journals (Sweden)

    Chai Ann Ng

    Full Text Available Human ether-à-go-go-related gene (hERG K(+ channels have unusual gating kinetics. Characterised by slow activation/deactivation but rapid inactivation/recovery from inactivation, the unique gating kinetics underlie the central role hERG channels play in cardiac repolarisation. The slow activation and deactivation kinetics are regulated in part by the S4-S5 linker, which couples movement of the voltage sensor domain to opening of the activation gate at the distal end of the inner helix of the pore domain. It has also been suggested that cytosolic domains may interact with the S4-S5 linker to regulate activation and deactivation kinetics. Here, we show that the solution structure of a peptide corresponding to the S4-S5 linker of hERG contains an amphipathic helix. The effects of mutations at the majority of residues in the S4-S5 linker of hERG were consistent with the previously identified role in coupling voltage sensor movement to the activation gate. However, mutations to Ser543, Tyr545, Gly546 and Ala548 had more complex phenotypes indicating that these residues are involved in additional interactions. We propose a model in which the S4-S5 linker, in addition to coupling VSD movement to the activation gate, also contributes to interactions that stabilise the closed state and a separate set of interactions that stabilise the open state. The S4-S5 linker therefore acts as a signal integrator and plays a crucial role in the slow deactivation kinetics of the channel.

  7. The role of the N-D1 linker of the N-ethylmaleimide-sensitive factor in the SNARE disassembly.

    Directory of Open Access Journals (Sweden)

    Cui-Cui Liu

    Full Text Available N-ethylmaleimide-sensitive factor (NSF is a member of the type II AAA+ (ATPase associated with various cellular activities family. It plays a critical role in intracellular membrane trafficking by disassembling soluble NSF attachment protein receptor (SNARE complexes. Each NSF protomer consists of an N-terminal domain (N domain followed by two AAA ATPase domains (D1 and D2 in tandem. The N domain is required for SNARE/α-SNAP binding and the D1 domain accounts for the majority of ATP hydrolysis. Little is known about the role of the N-D1 linker in the NSF function. This study presents detailed mutagenesis analyses of NSF N-D1 linker, dissecting its role in the SNARE disassembly, the SNARE/α-SNAP complex binding, the basal ATPase activity and the SNARE/α-SNAP stimulated ATPase activity. Our results show that the N-terminal region of the N-D1 linker associated mutants cause severe defect in SNARE complex disassembly, but little effects on the SNARE/α-SNAP complex binding, the basal and the SNARE/α-SNAP stimulated ATPase activity, suggesting this region may be involved in the motion transmission from D1 to N domain. Mutating the residues in middle and C-terminal region of the N-D1 linker increases the basal ATPase activity, indicating it may play a role in autoinhibiting NSF activity until it encounters SNARE/α-SNAP complex substrate. Moreover, mutations at the C-terminal sequence GIGG exhibit completely abolished or severely reduced activities of the substrate binding, suggesting that the flexibility of N-D1 linker is critical for the movement of the N domain that is required for the substrate binding. Taken together, these data suggest that the whole N-D1 linker is critical for the biological function of NSF to disassemble SNARE complex substrate with different regions responsible for different roles.

  8. A new 18F-labeled BBN-RGD peptide heterodimer with a symmetric linker for prostate cancer imaging.

    Science.gov (United States)

    Yan, Yongjun; Chen, Kai; Yang, Min; Sun, Xilin; Liu, Shuanglong; Chen, Xiaoyuan

    2011-07-01

    A peptide heterodimer comprises two different receptor-targeting peptide ligands. Molecular imaging probes based on dual-receptor targeting peptide heterodimers exhibit improved tumor targeting efficacy for multi-receptor expressing tumors compared with their parent single-receptor targeting peptide monomers. Previously we have developed bombesin (BBN)-RGD (Arg-Gly-Asp) peptide heterodimers, in which BBN and RGD are covalently connected with an asymmetric glutamate linker (J Med Chem 52:425-432, 2009). Although (18)F-labeled heterodimers showed significantly better microPET imaging quality than (18)F-labeled RGD and BBN monomers in a PC-3 xenograft model which co-expresses gastrin-releasing peptide receptor (GRPR) and integrin αvβ3, tedious heterodimer synthesis due to the asymmetric nature of glutamate linker restricts their clinical applications. In this study, we report the use of a symmetric linker AEADP [AEADP = 3,3'-(2-aminoethylazanediyl)dipropanoic acid] for the synthesis of BBN-RGD peptide heterodimer. The (18)F-labeled heterodimer ((18)F-FB-AEADP-BBN-RGD) showed comparable microPET imaging results with glutamate linked BBN-RGD heterodimers, indicating that the replacement of glutamate linker with AEADP linker did not affect the biological activities of BBN-RGD heterodimer. The heterodimer synthesis is rather easy and straightforward. Because tumors often co-express multiple receptors, the use of a symmetric linker provides a general method of fast assembly of various peptide heterodimers for imaging multi-receptor expressing tumors.

  9. Silyl-based alkyne-modifying linker for the preparation of C-terminal acetylene-derivatized protected peptides.

    Science.gov (United States)

    Strack, Martin; Langklotz, Sina; Bandow, Julia E; Metzler-Nolte, Nils; Albada, H Bauke

    2012-11-16

    A novel linker for the synthesis of C-terminal acetylene-functionalized protected peptides is described. This SAM1 linker is applied in the manual Fmoc-based solid-phase peptide synthesis of Leu-enkephalin and in microwave-assisted automated synthesis of Maculatin 2.1, an antibacterial peptide that contains 18 amino acid residues. For the cleavage, treatment with tetramethylammonium fluoride results in protected acetylene-derivatized peptides. Alternatively, a one-pot cleavage-click procedure affords the protected 1,2,3-triazole conjugate in high yields after purification.

  10. Characterization of the pore structure of aqueous three-dimensional polyacrylamide gels with a novel cross-linker.

    Science.gov (United States)

    Patras, G; Qiao, G G; Solomon, D H

    2000-11-01

    The properties of polyacrylamide hydrogels synthesized with a novel hexafunctional (three double bonds) cross-linker, hexahydro-1,3,5-triacryloyl-s-triazine (1a), was evaluated and compared to the currently used tetrafunctional (two double bonds) cross-linker N,N-methylenebisacrylamide (Bis). A variety of characterization techniques that require very little sample preparation and data handling were chosen and include polymerization temperature profiles and conversions, water swelling, differential scanning calorimetry (DSC), polyacrylamide gel electrophoresis (PAGE), Gradiflow electrophoretic separation process and scanning electron microscopy (SEM). The alternative use of 1a compared to Bis results in polyacrylamide gels with larger pore sizes and a broad pore size distribution.

  11. Preparation of value-added metal-organic frameworks (MOFs) using waste PET bottles as source of acid linker

    CSIR Research Space (South Africa)

    Dyosiba, Xoliswa

    2016-12-01

    Full Text Available of Value-added Metal-organic Frameworks (MOFs) Using Waste PET Bottles as Source of Acid Linker Xoliswa Dyosiba, Jianwei Ren, Nicholas M. Musyoka, Henrietta W. Langmi, Mkhulu Mathe, Maurice S. Onyango PII: S2214-9937(16)30053-7 DOI: doi:10.1016/j..., Hen- rietta W. Langmi, Mkhulu Mathe, Maurice S. Onyango, Preparation of Value-added Metal-organic Frameworks (MOFs) Using Waste PET Bottles as Source of Acid Linker, Sustainable Materials and Technologies (2016), doi:10.1016/j.susmat.2016...

  12. Iminodiacetic acid as bifunctional linker for dimerization of cyclic RGD peptides.

    Science.gov (United States)

    Xu, Dong; Zhao, Zuo-Quan; Chen, Shu-Ting; Yang, Yong; Fang, Wei; Liu, Shuang

    2017-05-01

    In this study, I2P-RGD2 was used as the example to illustrate a novel approach for dimerization of cyclic RGD peptides. The main objective of this study was to explore the impact of bifunctional linkers (glutamic acid vs. iminodiacetic acid) on tumor-targeting capability and excretion kinetics of the 99mTc-labeled dimeric cyclic RGD peptides. HYNIC-I2P-RGD2 was prepared by reacting I2P-RGD2 with HYNIC-OSu in the presence of diisopropylethylamine, and was evaluated for its αvβ3 binding affinity against 125I-echistatin bound to U87MG glioma cells. 99mTc-I2P-RGD2 was prepared with high specific activity (~185GBq/μmol). The athymic nude mice bearing U87MG glioma xenografts were used to evaluate its biodistribution properties and image quality in comparison with those of 99mTc-3P-RGD2. The IC50 value for HYNIC-I2P-RGD2 was determined to be 39±6nM, which was very close to that (IC50=33±5nM) of HYNIC-3P-RGD2. Replacing glutamic acid with iminodiacetic acid had little impact on αvβ3 binding affinity of cyclic RGD peptides. 99mTc-I2P-RGD2 and 99mTc-3P-RGD2 shared similar tumor uptake values over the 2h period, and its αvβ3-specificity was demonstrated by a blocking experiment. The uptake of 99mTc-I2P-RGD2 was significantly lower than 99mTc-3P-RGD2 in the liver and kidneys. The U87MG glioma tumors were visualized by SPECT with excellent contrast using both 99mTc-I2P-RGD2 and 99mTc-3P-RGD2. Iminodiacetic acid is an excellent bifunctional linker for dimerization of cyclic RGD peptides. Bifunctional linkers have significant impact on the excretion kinetics of 99mTc radiotracers. Because of its lower liver uptake and better tumor/liver ratios, 99mTc-I2P-RGD2 may have advantages over 99mTc-3P-RGD2 for diagnosis of tumors in chest region. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Surface modification of g-C3N4 by hydrazine: Simple way for noble-metal free hydrogen evolution catalysts

    KAUST Repository

    Chen, Yin

    2015-11-02

    The graphitic carbon nitride (g-C3N4) usually is thought to be an inert material and it’s difficult to have the surface terminated NH2 groups functionalized. By modifying the g-C3N4 surface with hydrazine, the diazanyl group was successfully introduced onto the g-C3N4 surface, which allows the introduction with many other function groups. Here we illustrated that by reaction of surface hydrazine group modified g-C3N4 with CS2 under basic condition, a water electrolysis active group C(=S)SNi can be implanted on the g-C3N4 surface, and leads to a noble metal free hydrogen evolution catalyst. This catalyst has 40% hydrogen evolution efficiency compare to the 3 wt% Pt photo precipitated g-C3N4, with only less than 0.2 wt% nickel.

  14. Proceedings of the Conference on the Environmental Chemistry of Hydrazine Fuels (3rd) Held in Panama City Beach, Florida on 15-17 September 1987

    Science.gov (United States)

    1988-01-01

    centre came from redox titrimetry in which -9 equivalents of Fe(CN)6 3- were consumed on titration with a solution of the complex in 2M NaOH, pointing...hydrogen bonding interaction between kaolinite surfaces and intercalated potassium acetate, hydrazine, formamide, and urea." J. Coil. Interface Sci. 21...saturated potassium hydroxide. The crude SDMH was dried over barium oxide overnight and then fractionally distilled from fresh barium oxide (bp 76.5 4C, 660

  15. Synthesis of ubiquitylated histone H3 using a thiirane linker for chemical ligation.

    Science.gov (United States)

    Kawakami, Toru; Mishima, Yuichi; Hojo, Hironobu; Suetake, Isao

    2017-07-01

    Post-translational modifications of histone proteins, which form nucleosome cores, play an important role in gene regulation. Ubiquitin modification is one such modification. We previously reported on the use of a thiirane linker to introduce a 1,2-aminothiol moiety at a cysteine residue for native chemical ligation with peptide thioesters, which permitted isopeptide mimetics to be produced. In this report, we describe the preparation of the ubiquitylated full length histone H3 at the 18 position and the construction of tetranucleosomes with recombinant histones H2A, H2B, H4, and DNA, which are slightly more stable than those that are prepared without ubiquitin modification. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

  16. Design of antiviral stapled peptides containing a biphenyl cross-linker.

    Science.gov (United States)

    Muppidi, Avinash; Zhang, Hongtao; Curreli, Francesca; Li, Nan; Debnath, Asim K; Lin, Qing

    2014-04-01

    Here we report the design and synthesis of a panel of stapled peptides containing a distance-matching biphenyl cross-linker based upon a peptide capsid assembly inhibitor reported previously. Compared with the linear peptide, the biphenyl-stapled peptides exhibited significantly enhanced cell penetration and potent antiviral activity in the cell-based infection assays. Isothermal titration calorimetry and surface plasmon resonance experiments revealed that the most active stapled CAI peptide binds to the C-terminal domain of HIV capsid protein as well as envelop glycoprotein gp120 with low micromolar binding affinities, and as a result, inhibits both the HIV-1 virus entry and the virus assembly. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Efficient loading of primary alcohols onto a solid phase using a trityl bromide linker

    DEFF Research Database (Denmark)

    Crestey, François; Ottesen, Lars Korsgaard; Jaroszewski, Jerzy Witold

    2008-01-01

    The Letter describes an improved, rapid and mild strategy for the loading of primary alcohols onto a polystyrene trityl resin via a highly reactive trityl bromide linker. This protocol facilitates an efficient resin loading even of acid-sensitive or heat-labile alcohols, which otherwise require...... expensive or non-commercial resin types. Secondary alcohols were only attached in moderate to low yields, while attempts to load a tertiary alcohol expectedly failed. Importantly, selective attachment of diols via a primary alcohol group in the presence of more hindered alcohol groups proved possible....... The effects of activation time and reagent excess as well as alcohol structure were investigated. This improved method provides a convenient access to O-linked resin-bound N-Fmoc-protected amino alcohols that may be employed in SPS of peptides with C-terminal alcohol functionalities. In the case...

  18. H-DROP: an SVM based helical domain linker predictor trained with features optimized by combining random forest and stepwise selection.

    Science.gov (United States)

    Ebina, Teppei; Suzuki, Ryosuke; Tsuji, Ryotaro; Kuroda, Yutaka

    2014-08-01

    Domain linker prediction is attracting much interest as it can help identifying novel domains suitable for high throughput proteomics analysis. Here, we report H-DROP, an SVM-based Helical Domain linker pRediction using OPtimal features. H-DROP is, to the best of our knowledge, the first predictor for specifically and effectively identifying helical linkers. This was made possible first because a large training dataset became available from IS-Dom, and second because we selected a small number of optimal features from a huge number of potential ones. The training helical linker dataset, which included 261 helical linkers, was constructed by detecting helical residues at the boundary regions of two independent structural domains listed in our previously reported IS-Dom dataset. 45 optimal feature candidates were selected from 3,000 features by random forest, which were further reduced to 26 optimal features by stepwise selection. The prediction sensitivity and precision of H-DROP were 35.2 and 38.8%, respectively. These values were over 10.7% higher than those of control methods including our previously developed DROP, which is a coil linker predictor, and PPRODO, which is trained with un-differentiated domain boundary sequences. Overall, these results indicated that helical linkers can be predicted from sequence information alone by using a strictly curated training data set for helical linkers and carefully selected set of optimal features. H-DROP is available at http://domserv.lab.tuat.ac.jp.

  19. Probing the relation between protein–protein interactions and DNA binding for a linker mutant of the bacterial nucleoid protein H-NS

    NARCIS (Netherlands)

    Giangrossi, M.; Wintraecken, K.; Spurio, R.; Vries, de R.J.

    2014-01-01

    We have investigated the relationship between oligomerization in solution and DNA binding for the bacterial nucleoid protein H-NS. This was done by comparing oligomerization and DNA binding of H-NS with that of a H-NS D68V-D71V linker mutant. The double linker mutation D68V-D71V, that makes the

  20. Synthesis of Selective Butyrylcholinesterase Inhibitors Coupled between α-Lipoic Acid and Polyphenols by Using 2-(Piperazin-1-yl)ethanol Linker

    Energy Technology Data Exchange (ETDEWEB)

    Yeun, Go Heun; Lee, Seung Hwan; LIm, Yong Bae; Lee, Hye Sook; Lee, Bong Ho; Park, Jeong Ho [Hanbat National Univ., Daejeon (Korea, Republic of); Won, Mooho [Kangwon National Univ., Chuncheon (Korea, Republic of)

    2013-04-15

    In the previous paper (Bull. Korean Chem. Soc., 2011, 32, 2997), the hybrid molecules between α-lipoic acid (ALA) and polyphenols (PPs) connected with neutral 2-(2-aminoethoxy)ethanol linker (linker-1) showed new biological activity such as butyrylcholinesterase (BuChE) inhibition. In order to increase the binding affinity of the hybrid compounds to cholinesterase (ChE), the neutral 2-(2-aminoethoxy)ethanol (linker 1) was switched to the cationic 2-(piperazin-1-yl)ethanol linker (linker 2). The IC{sub 50} values of the linker-2 hybrid molecules for BuChE inhibition were lower than those of linker-1 hybrid molecules (except 9-2) and they also had the same great selectivity for BuChE over AChE (> 800 fold) as linker-1 hybrid molecules. ALA-acetyl caffeic acid (10-2, ALA-AcCA) was shown as an effective inhibitor of BuChE (IC{sub 50} = 0.44 ± 0.24 μM). A kinetic study using 7-2 showed that it is the same mixed type inhibition as 7-1. Its inhibition constant (Ki) to BuChE is 4.3 ± 0.09 μM.

  1. Temperature-triggered release of a liquid cross-linker micro-encapsulated in a glassy polymer for low temperature curing

    NARCIS (Netherlands)

    Senatore, D.; Cate, A.T. ten; Laven, J.; Benthem, R.A.T.M. van; With, G. de

    2013-01-01

    In order to prevent a liquid epoxy cross-linker from premature, Arrhenius-law predicted, reaction with an acid-functional polyester resin, the liquid cross-linker has been physically separated from the resin by encapsulation while release is only possible by a temperature-controlled trigger. The

  2. Effect of biointerfacing linker chemistries on the sensitivity of silicon nanowires for protein detection.

    Science.gov (United States)

    Dorvel, Brian; Reddy, Bobby; Bashir, Rashid

    2013-10-15

    Point-of-care diagnostics show promise in removing reliance on centralized lab testing facilities and may help increase both the survival rate for infectious diseases as well as monitoring of chronic illnesses. CMOS compatible diagnostic platforms are currently being considered as possible solutions as they can be easily miniaturized and can be cost-effective. Top-down fabricated silicon nanowires are a CMOS-compatible technology which have demonstrated high sensitivities in detecting biological analytes, such as proteins, DNA, and RNA. However, the reported response of nanowires to these analytes has varied widely since several different functionalization protocols have been attempted with little characterization and comparison. Here we report protocols for fabrication and functionalization of silicon nanowires which yield highly stable nanowires in aqueous solutions and limits of detection to ∼1 pg/mL of the model protein used in the study. A thorough characterization was done into optimizing the release of the silicon nanowires using combined dry and wet etch techniques, which yielded nanowires that could be directly compared to increase output statistics. Moreover, a range of different linker chemistries were tried for reacting the primary antibody, and its response to target and nonspecific antigens, with polyethylene glycol based linker BS(PEG)5 providing the best response. Consequently, this chemistry was used to characterize different oxide thicknesses and their responses to the mouse IgG antigen, which with the smallest oxide thickness yielded 0.1-1 pg/mL limits of detection and a dynamic range over 3 orders of magnitude.

  3. Linker Flexibility Facilitates Module Exchange in Fungal Hybrid PKS-NRPS Engineering.

    Science.gov (United States)

    Nielsen, Maria Lund; Isbrandt, Thomas; Petersen, Lene Maj; Mortensen, Uffe Hasbro; Andersen, Mikael Rørdam; Hoof, Jakob Blæsbjerg; Larsen, Thomas Ostenfeld

    2016-01-01

    Polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) each give rise to a vast array of complex bioactive molecules with further complexity added by the existence of natural PKS-NRPS fusions. Rational genetic engineering for the production of natural product derivatives is desirable for the purpose of incorporating new functionalities into pre-existing molecules, or for optimization of known bioactivities. We sought to expand the range of natural product diversity by combining modules of PKS-NRPS hybrids from different hosts, hereby producing novel synthetic natural products. We succeeded in the construction of a functional cross-species chimeric PKS-NRPS expressed in Aspergillus nidulans. Module swapping of the two PKS-NRPS natural hybrids CcsA from Aspergillus clavatus involved in the biosynthesis of cytochalasin E and related Syn2 from rice plant pathogen Magnaporthe oryzae lead to production of novel hybrid products, demonstrating that the rational re-design of these fungal natural product enzymes is feasible. We also report the structure of four novel pseudo pre-cytochalasin intermediates, niduclavin and niduporthin along with the chimeric compounds niduchimaeralin A and B, all indicating that PKS-NRPS activity alone is insufficient for proper assembly of the cytochalasin core structure. Future success in the field of biocombinatorial synthesis of hybrid polyketide-nonribosomal peptides relies on the understanding of the fundamental mechanisms of inter-modular polyketide chain transfer. Therefore, we expressed several PKS-NRPS linker-modified variants. Intriguingly, the linker anatomy is less complex than expected, as these variants displayed great tolerance with regards to content and length, showing a hitherto unreported flexibility in PKS-NRPS hybrids, with great potential for synthetic biology-driven biocombinatorial chemistry.

  4. Nile tilapia skin collagen sponge modified with chemical cross-linkers as a biomedical hemostatic material.

    Science.gov (United States)

    Sun, Leilei; Li, Bafang; Jiang, Dandan; Hou, Hu

    2017-11-01

    Nile tilapia skin collagen sponges were fabricated by freeze-drying technology and modified with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide (EDC/NHS), genipin+PBS, genipin+ethanol, tea polyphenol (TP), nordihydroguaiaretic acid (NDGA) and diphenyl phosphoryl azide (DPPA). Physicochemical and biological properties, micromorphology and compatibility before and after modification were investigated to evaluate collagen sponge as a hemostatic biomedical material. The mechanical property of collagen sponges strengthened after cross-linking. The elongation at break of cross-linked collagen sponges decreased except for EDC/NHS, which was close to that of non-crosslinked. The collagen sponge cross-linked with EDC/NHS exhibited the highest hygroscopicity in comparison with other cross-linkers. The resistance to collagenase biodegradation of collagen sponges after cross-linking strengthened significantly except for NDGA. Collagen sponges cross-linked with EDC/NHS, TP and NDGA maintained high porosity (97-98%), similar to non-crosslinked (98.42%). Collagen sponges could shorten the blood coagulation time. From the variations of the FTIR spectrum pattern and SEM, DPPA could change the secondary structure of collagen and destroy the spongy structure of collagen sponge, which was not suitable for the cross-linking of collagen sponge. Whereas, EDC/NHS was recognized as a perfect cross-linker owing to its excellent properties and porous microstructure. All fabricated collagen sponges were recognized to be biocompatible by the hemolysis assay in vitro. Therefore, collagen sponge modified with EDC/NHS could be used as a perfect biomedical hemostatic material. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Cytoskeletal Linker Protein Dystonin Is Not Critical to Terminal Oligodendrocyte Differentiation or CNS Myelination.

    Directory of Open Access Journals (Sweden)

    Samantha F Kornfeld

    Full Text Available Oligodendrocyte differentiation and central nervous system myelination require massive reorganization of the oligodendrocyte cytoskeleton. Loss of specific actin- and tubulin-organizing factors can lead to impaired morphological and/or molecular differentiation of oligodendrocytes, resulting in a subsequent loss of myelination. Dystonin is a cytoskeletal linker protein with both actin- and tubulin-binding domains. Loss of function of this protein results in a sensory neuropathy called Hereditary Sensory Autonomic Neuropathy VI in humans and dystonia musculorum in mice. This disease presents with severe ataxia, dystonic muscle and is ultimately fatal early in life. While loss of the neuronal isoforms of dystonin primarily leads to sensory neuron degeneration, it has also been shown that peripheral myelination is compromised due to intrinsic Schwann cell differentiation abnormalities. The role of this cytoskeletal linker in oligodendrocytes, however, remains unclear. We sought to determine the effects of the loss of neuronal dystonin on oligodendrocyte differentiation and central myelination. To address this, primary oligodendrocytes were isolated from a severe model of dystonia musculorum, Dstdt-27J, and assessed for morphological and molecular differentiation capacity. No defects could be discerned in the differentiation of Dstdt-27J oligodendrocytes relative to oligodendrocytes from wild-type littermates. Survival was also compared between Dstdt-27J and wild-type oligodendrocytes, revealing no significant difference. Using a recently developed migration assay, we further analysed the ability of primary oligodendrocyte progenitor cell motility, and found that Dstdt-27J oligodendrocyte progenitor cells were able to migrate normally. Finally, in vivo analysis of oligodendrocyte myelination was done in phenotype-stage optic nerve, cerebral cortex and spinal cord. The density of myelinated axons and g-ratios of Dstdt-27J optic nerves was normal, as

  6. Comprehensive DFT and MP2 Level Investigations of Reaction of 2,3-Dihydro-1,5-benzodiazepine-2-thiones with Hydrazine

    Science.gov (United States)

    Okovytyy, Sergiy I.; Sviatenko, Liudmyla K.; Gaponov, Alexandr O.; Tarabara, Igor N.; Kasyan, Lilija I.; Leszczynski, Jerzy

    2009-09-01

    Density functional theory approach was used for the 4-phenyl-2,3-dihydro-1,5-benzodiazepine-2-thione compound to determine the mechanism of hydrazinolysis of 4-substituted 2,3-dihydro-1,5-benzodiazepine-2-thiones. Single-point calculations at the MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) level were performed for the more accurate energy prediction. The solvent effect was taken into account by carrying out single-point calculations using the PCM methodology. The obtained results show that in the investigating mechanism the first step consists of the hydrazine molecule addition to the thiocarbonyl bond of the 4-phenyl-2,3-dihydro-1,5-benzodiazepine-2-thione following removal of H2S. Further addition of another hydrazine molecule to the azomethyne bond and cyclization with pyrazole ring formation occur, and then the diazepine ring-opening and the removal of hydrazine molecule proceed. Finally, imine-enamine tautomerization leads to 5-N-(2-aminophenyl-1-amino)-3-phenylpyrazole as a main product that is in agreement with the experimental observation. The cyclization step is a rate-determining step of this reaction.

  7. Non-degenerate n-type doping by hydrazine treatment in metal work function engineered WSe2 field-effect transistor

    Science.gov (United States)

    Lee, Inyeal; Rathi, Servin; Li, Lijun; Lim, Dongsuk; Atif Khan, Muhammad; Kannan, E. S.; Kim, Gil-Ho

    2015-11-01

    We report a facile and highly effective n-doping method using hydrazine solution to realize enhanced electron conduction in a WSe2 field-effect transistor (FET) with three different metal contacts of varying work functions—namely, Ti, Co, and Pt. Before hydrazine treatment, the Ti- and Co-contacted WSe2 FETs show weak ambipolar behaviour with electron dominant transport, whereas in the Pt-contacted WSe2 FETs, the p-type unipolar behaviour was observed with the transport dominated by holes. In the hydrazine treatment, a p-type WSe2 FET (Pt contacted) was converted to n-type with enhanced electron conduction, whereas highly n-doped properties were achieved for both Ti- and Co-contacted WSe2 FETs with on-current increasing by three orders of magnitude for Ti. All n-doped WSe2 FETs exhibited enhanced hysteresis in their transfer characteristics, which opens up the possibility of developing memories using transition metal dichalcogenides.

  8. Role of Linkers between Zinc Fingers in Spacing Recognition by Plant TFIIIA-Type Zinc-Finger Proteins

    Directory of Open Access Journals (Sweden)

    Setsuko Fukushima

    2012-01-01

    Full Text Available The EPF family of plant TFIIIA-type zinc-finger (ZF proteins (ZPTs is characterized by long linkers separating ZF motifs. We previously reported that two-fingered ZPTs bind to two tandem core sites that are separated by several base pairs, each ZF making contact with one core site. Here we report further characterization of DNA-binding activities of ZPTs using four family members, ZPT2-14, ZPT2-7, ZPT2-8, and ZPT2-2, having inter-ZF linkers of different lengths and sequences, to investigate the correlation of the length and/or sequence of the linker with preference for the spacing between core sites in target DNAs. Selected and amplified binding site (SAAB-imprinting assays and gel mobility shift assays prompted three conclusions. (1 The four ZPTs have common specificity for core binding sites—two AGT(G/(CACTs separated by several nucleotides. (2 The four ZPTs prefer a spacing of 10 bases between the core sites, but each ZPT has its own preference for suboptimal spacing. (3 At a particular spacing, two zinc fingers may bind to the core sites on both strands. The results provide new information about how the diversity in linker length/sequence affects DNA-sequence recognition in this protein family.

  9. Mapping of post-translational modifications of spermatid-specific linker histone H1-like protein, HILS1.

    Science.gov (United States)

    Mishra, Laxmi N; Gupta, Nikhil; Rao, Satyanarayana M R

    2015-10-14

    In mammalian spermiogenesis, haploid round spermatids undergo dramatic biochemical and morphological changes and transform into motile mature spermatozoa. A majority of the histones are replaced by transition proteins during mid-spermiogenesis and later replaced by protamines, which occupy the sperm chromatin. In mammals, 11 linker histone H1 subtypes have been reported. Among them, H1t, HILS1, and H1T2 are uniquely expressed in testis, with the expression of HILS1 and H1T2 restricted to spermiogenesis. However, there is a lack of knowledge about linker histone role in the nuclear reorganization during mammalian spermiogenesis. Here, we report a method for separation of endogenous HILS1 protein from other rat testis linker histones by reversed-phase high-performance liquid chromatography (RP-HPLC) and identification of 15 novel post-translational modifications of HILS1, which include lysine acetylation and serine/threonine/tyrosine phosphorylation sites. Immunofluorescence studies demonstrate the presence of linker histone HILS1 and HILS1Y78p during different steps of spermiogenesis from early elongating to condensing spermatids. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Conformational rearrangements in the S6 domain and C-linker during gating in CNGA1 channels.

    NARCIS (Netherlands)

    Nair, A.V.; Nguyen, C.H.; Mazzolini, M.

    2009-01-01

    This work completes previous findings and, using cysteine scanning mutagenesis (CSM) and biochemical methods, provides detailed analysis of conformational changes of the S6 domain and C-linker during gating of CNGA1 channels. Specific residues between Phe375 and Val424 were mutated to a cysteine in

  11. Onset of grain filling is associated with a change in properties of linker histone variants in maize kernels

    DEFF Research Database (Denmark)

    Kalamajka, R.; Finnie, Christine; Grasser, K.D.

    2010-01-01

    In maize kernel development, the onset of grain-filling represents a major developmental switch that correlates with a massive reprogramming of gene expression. We have isolated chromosomal linker histones from developing maize kernels before (11 days after pollination, dap) and after (16 dap) in...

  12. The interdomain flexible linker of the polypeptide GalNAc transferases dictates their long-range glycosylation preferences

    DEFF Research Database (Denmark)

    Rivas, Matilde De Las; Lira-Navarrete, Erandi; Daniel, Earnest James Paul

    2017-01-01

    The polypeptide GalNAc-transferases (GalNAc-Ts), that initiate mucin-type O-glycosylation, consist of a catalytic and a lectin domain connected by a flexible linker. In addition to recognizing polypeptide sequence, the GalNAc-Ts exhibit unique long-range N- A nd/or C-terminal prior glycosylation ...

  13. Linker dependent intercalation of bisbenzimidazole-aminosugars in an RNA duplex; selectivity in RNA vs. DNA binding.

    Science.gov (United States)

    Ranjan, Nihar; Arya, Dev P

    2016-12-15

    Neomycin and Hoechst 33258 are two well-known nucleic acid binders that interact with RNA and DNA duplexes with high affinities respectively. In this manuscript, we report that covalent attachment of bisbenzimidazole unit derived from Hoechst 33258 to neomycin leads to intercalative binding of the bisbenzimidazole unit (oriented at 64-74° with respected to the RNA helical axis) in a linker length dependent manner. The dual binding and intercalation of conjugates were supported by thermal denaturation, CD, LD and UV-Vis absorption experiments. These studies highlight the importance of linker length in dual recognition by conjugates, for effective RNA recognition, which can lead to novel ways of recognizing RNA structures. Additionally, the ligand library screens also identify DNA and RNA selective compounds, with compound 9, containing a long linker, showing a 20.3°C change in RNA duplex T m with only a 13.0°C change in T m for the corresponding DNA duplex. Significantly, the shorter linker in compound 3 shows almost the reverse trend, a 23.8°C change in DNA T m , with only a 9.1°C change in T m for the corresponding RNA duplex. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Photochemical Reactions of the LOV and LOV-Linker Domains of the Blue Light Sensor Protein YtvA

    NARCIS (Netherlands)

    Choi, S.; Nakasone, Y.; Hellingwerf, K.J.; Terazima, M.

    2016-01-01

    YtvA is a blue light sensor protein composed of an N-terminal LOV (light-oxygen-voltage) domain, a linker helix, and the C-terminal sulfate transporter and anti-sigma factor antagonist domain. YtvA is believed to act as a positive regulator for light and salt stress responses by regulating the

  15. Oriented immobilization of proteins on hydroxyapatite surface using bifunctional bisphosphonates as linkers.

    Science.gov (United States)

    Yewle, Jivan N; Wei, Yinan; Puleo, David A; Daunert, Sylvia; Bachas, Leonidas G

    2012-06-11

    Oriented immobilization of proteins is an important step in creating protein-based functional materials. In this study, a method was developed to orient proteins on hydroxyapatite (HA) surfaces, a widely used bone implant material, to improve protein bioactivity by employing enhanced green fluorescent protein (EGFP) and β-lactamase as model proteins. These proteins have a serine or threonine at their N-terminus that was oxidized with periodate to obtain a single aldehyde group at the same location, which can be used for the site-specific immobilization of the protein. The HA surface was modified with bifunctional hydrazine bisphosphonates (HBPs) of various length and lipophilicity. The number of functional groups on the HBP-modified HA surface, determined by a 2,4,6-trinitrobenzenesulfonic acid (TNBS) assay, was found to be 2.8 × 10(-5) mol/mg of HA and unaffected by the length of HBPs. The oxidized proteins were immobilized on the HBP-modified HA surface in an oriented manner through formation of a hydrazone bond. The relative protein immobilization amounts through various HBPs were determined by fluorescence and bicinchoninic acid (BCA) assay and showed no significant effect by length and lipophilicity of HBPs. The relative amount of HBP-immobilized EGFP was found to be 10-15 fold that of adsorbed EGFP, whereas the relative amount of β-lactamase immobilized through HBPs (2, 3, 4, 6, and 7) was not significantly different than adsorbed β-lactamase. The enzymatic activity of HBP-immobilized β-lactamase was measured with cefazolin as substrate, and it was found that the catalytic efficiency of HBP-immobilized β-lactamase improved 2-5 fold over adsorbed β-lactamase. The results obtained demonstrate the feasibility of our oriented immobilization approach and showed an increased activity of the oriented proteins in comparison with adsorbed proteins on the same hydroxyapatite surface matrix.

  16. Ruthenium nanoparticles confined in SBA-15 as highly efficient catalyst for hydrolytic dehydrogenation of ammonia borane and hydrazine borane

    Science.gov (United States)

    Yao, Qilu; Lu, Zhang-Hui; Yang, Kangkang; Chen, Xiangshu; Zhu, Meihua

    2015-10-01

    Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption, and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)-1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol-1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively.

  17. Removal of Lead from Water Using Calcium Alginate Beads Doped with Hydrazine Sulphate-Activated Red Mud as Adsorbent

    Directory of Open Access Journals (Sweden)

    A. Naga Babu

    2017-01-01

    Full Text Available Calcium alginate beads doped with hydrazine sulphate-treated red mud are investigated as adsorbent for extracting lead ions from water using batch methods of extraction. Different extraction conditions are optimised for maximum lead extraction. Substantial amount of lead is removed, and the adsorption ability is found to be 138.6 mg/g. Surface characterization using FTIR, EDX, and FESEM confirms that lead is “onto” the surface of the adsorbent. Thermodynamic parameters, adsorption isotherms, and kinetics of adsorption are analysed. Adsorption is “physisorption” in nature and spontaneous. The adsorbent developed can be regenerated using 0.1 M HCl. Thus regenerated adsorbent can be used as the adsorbent for further removal of lead at least 10 times, and this enables the complete removal of lead from water by repetitive use of the regenerated adsorbent. The beads facilitate the easy filtration. The methodology developed is successfully applied for removing lead from industrial waste waters.

  18. Synthesis of non-hydrazine solution processed Cu2(ZnSn)S4 thin films for solar cells applications

    Science.gov (United States)

    Gupta, Indu; Gupta, Preeti; Mohanty, Bhaskar Chandra

    2017-05-01

    Solution processing provides a versatile and inexpensive means to prepare Cu2ZnSnS4 (CZTS) thin films for photovoltaic applications. Differently with the reported growth of CZTS films from hydrazine based toxic solutions, we demonstrate a simple non-toxic ethanol based solution approach to synthesize the films. Using the chemical bath deposition (CBD) method, the CZTS thin films were grown from metal salts (copper chloride, zinc chloride, and tin chloride) in ethanol and monoethanol amine (MEA) and thioacetamide in ethanol as sulfur source in a single dip followed by sulfurization. The structure, composition, morphology and optical properties of the CZTS film were studied by X-ray diffraction, scanning electron microscopy and UV-vis spectroscopy. The results revealed that a post-deposition sulfurization is necessary to the phase formation and among all, sulfurization at 450°C for 60 min yielded phase pure CZTS films having kesterite structure, relatively compact morphology and an optical band gap of ˜1.52 eV indicating its suitability for solar cell applications. The results clearly validate the CBD method as a potential scalable route of preparation of CZTS thin films.

  19. Synthesis and X-ray studies of ruthenium(II complexes containing hydrazine and benzyl isocyanide ligands

    Directory of Open Access Journals (Sweden)

    V.N. Nesterov

    2013-09-01

    Full Text Available The reaction of the polymeric species [{RuCl2(COD}x] (1; x > 2; COD = cyclo-octa-1,5-diene and hydrazine hydrate in methanol under reflux gave a pale pink solution from which the salt [Ru(COD(N2H44][BPh4]2.CH3OH (2 was isolated on addition of NaBPh4. Treatment of 2 in refluxing acetone in the presence of the ligand benzyl isocyanide give a complex of stoichiometry [Ru(NH2N=CMe22(PhCH2NC4][BPh4]2 (3 on the substitution of the labile COD ligand. The two compounds have been characterized by elemental analyses, IR and NMR measurements and single-crystal X-ray diffraction studies. The ruthenium in both compounds has a distorted octahedral coordination geometry.DOI: http://dx.doi.org/10.4314/bcse.v27i3.9

  20. Key study on the potential of hydrazine bisborane for solid- and liquid-state chemical hydrogen storage.

    Science.gov (United States)

    Pylypko, Sergii; Petit, Eddy; Yot, Pascal G; Salles, Fabrice; Cretin, Marc; Miele, Philippe; Demirci, Umit B

    2015-05-04

    Hydrazine bisborane N2H4(BH3)2 (HBB; 16.8 wt %) recently re-emerged as a potential hydrogen storage material. However, such potential is controversial: HBB was seen as a hazardous compound up to 2010, but now it would be suitable for hydrogen storage. In this context, we focused on fundamentals of HBB because they are missing in the literature and should help to shed light on its effective potential while taking into consideration any risk. Experimental/computational methods were used to get a complete characterization data sheet, including, e.g., XRD, NMR, FTIR, Raman, TGA, and DSC. From the reported results and discussion, it is concluded that HBB has potential in the field of chemical hydrogen storage given that both thermolytic and hydrolytic dehydrogenations were analyzed. In solid-state chemical hydrogen storage, it cannot be used in the pristine state (risk of explosion during dehydrogenation) but can be used for the synthesis of derivatives with improved dehydrogenation properties. In liquid-state chemical hydrogen storage, it can be studied for room-temperature dehydrogenation, but this requires the development of an active and selective metal-based catalyst. HBB is a thus a candidate for chemical hydrogen storage.

  1. Luminescent detection of hydrazine and hydrazine derivatives

    Science.gov (United States)

    Swager, Timothy M [Newton, MA; Thomas, III, Samuel W.

    2012-04-17

    The present invention generally relates to methods for modulating the optical properties of a luminescent polymer via interaction with a species (e.g., an analyte). In some cases, the present invention provides methods for determination of an analyte by monitoring a change in an optical signal of a luminescent polymer upon exposure to an analyte. Methods of the present invention may be useful for the vapor phase detection of analytes such as explosives and toxins. The present invention also provides methods for increasing the luminescence intensity of a polymer, such as a polymer that has been photobleached, by exposing the luminescent polymer to a species such as a reducing agent.

  2. Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage.

    Science.gov (United States)

    Yan, Yong; Yang, Sihai; Blake, Alexander J; Schröder, Martin

    2014-02-18

    Hydrogen (H2) is a promising alternative energy carrier because of its environmental benefits, high energy density, and abundance. However, development of a practical storage system to enable the "Hydrogen Economy" remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers. MOFs show promise for H2 storage owing to their high surface area and tuneable properties. In this Account, we summarize our research on novel porous materials with enhanced H2 storage properties and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions. We synthesized a series of materials by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These materials exhibit high structural stability and permanent porosity. Varying the organic linker modulates the pore size, geometry, and functionality to control the overall H2 adsorption. Our top-performing material in this series has a H2 storage capacity of 77.8 mg g(-1) at 77 K, 60 bar. H2 adsorption at low, medium, and high pressures correlates with the isosteric heat of adsorption, surface area, and pore volume, respectively. Another series, using tribranched C3-symmetric hexacarboxylate ligands with Cu(II), gives highly porous (3,24)-connected frameworks incorporating {Cu(II)2} paddlewheels. Increasing the length of the hexacarboxylate struts directly tunes the porosity of the resultant material from micro- to mesoporosity. These materials show exceptionally high H2 uptakes owing to their high surface area and pore volume. The first member of this family reported adsorbs 111 mg g(-1) of H2, or 55.9 g L(-1), at 77 K, 77 bar, while at 77 K, 1 bar, the material adsorbs 2.3 wt % H2. We and others have since achieved enhanced H2 adsorption in these

  3. Active inclusion bodies of acid phosphatase PhoC: aggregation induced by GFP fusion and activities modulated by linker flexibility.

    Science.gov (United States)

    Huang, Ziliang; Zhang, Chong; Chen, Shuo; Ye, Fengchun; Xing, Xin-Hui

    2013-03-14

    Biologically active inclusion bodies (IBs) have gained much attention in recent years. Fusion with IB-inducing partner has been shown to be an efficient strategy for generating active IBs. To make full use of the advantages of active IBs, one of the key issues will be to improve the activity yield of IBs when expressed in cells, which would need more choices on IB-inducing fusion partners and approaches for engineering IBs. Green fluorescent protein (GFP) has been reported to aggregate when overexpressed, but GFP fusion has not been considered as an IB-inducing approach for these fusion proteins so far. In addition, the role of linker in fusion proteins has been shown to be important for protein characteristics, yet impact of linker on active IBs has never been reported. Here we report that by fusing GFP and acid phosphatase PhoC via a linker region, the resultant PhoC-GFPs were expressed largely as IBs. These IBs show high levels of specific fluorescence and specific PhoC activities (phosphatase and phosphotransferase), and can account for up to over 80% of the total PhoC activities in the cells. We further demonstrated that the aggregation of GFP moiety in the fusion protein plays an essential role in the formation of PhoC-GFP IBs. In addition, PhoC-GFP IBs with linkers of different flexibility were found to exhibit different levels of activities and ratios in the cells, suggesting that the linker region can be utilized to manipulate the characteristics of active IBs. Our results show that active IBs of PhoC can be generated by GFP fusion, demonstrating for the first time the potential of GFP fusion to induce active IB formation of another soluble protein. We also show that the linker sequence in PhoC-GFP fusion proteins plays an important role on the regulation of IB characteristics, providing an alternative and important approach for engineering of active IBs with the goal of obtaining high activity yield of IBs.

  4. Truncated Variants of Gaussia Luciferase with Tyrosine Linker for Site-Specific Bioconjugate Applications.

    Science.gov (United States)

    Hunt, Eric A; Moutsiopoulou, Angeliki; Ioannou, Stephanie; Ahern, Katelyn; Woodward, Kristen; Dikici, Emre; Daunert, Sylvia; Deo, Sapna K

    2016-06-08

    Gaussia luciferase (Gluc)-with its many favorable traits such as small size, bright emission, and exceptional stability-has become a prominent reporter protein for a wide range of bioluminescence-based detection applications. The ten internal cysteine residues crucial to functional structure formation, however, make expression of high quantities of soluble protein in bacterial systems difficult. In addition to this challenge, the current lack of structural data further complicates the use of Gluc for in vitro applications, such as biosensors, or cellular delivery, both of which rely heavily on robust and reproducible bioconjugation techniques. While Gluc is already appreciably small for a luciferase, a reduction in size that still retains significant bioluminescent activity, in conjunction with a more reproducible bioorthogonal method of chemical modification and facile expression in bacteria, would be very beneficial in biosensor design and cellular transport studies. We have developed truncated variants of Gluc, which maintain attractive bioluminescent features, and have characterized their spectral and kinetic properties. These variants were purified in high quantities from a bacterial system. Additionally, a C-terminal linker has been incorporated into these variants that can be used for reliable, specific modification through tyrosine-based bioconjugation techniques, which leave the sensitive network of cysteine residues undisturbed.

  5. Nucleosome–nucleosome interactions via histone tails and linker DNA regulate nuclear rigidity

    Science.gov (United States)

    Shimamoto, Yuta; Tamura, Sachiko; Masumoto, Hiroshi; Maeshima, Kazuhiro

    2017-01-01

    Cells, as well as the nuclei inside them, experience significant mechanical stress in diverse biological processes, including contraction, migration, and adhesion. The structural stability of nuclei must therefore be maintained in order to protect genome integrity. Despite extensive knowledge on nuclear architecture and components, however, the underlying physical and molecular mechanisms remain largely unknown. We address this by subjecting isolated human cell nuclei to microneedle-based quantitative micromanipulation with a series of biochemical perturbations of the chromatin. We find that the mechanical rigidity of nuclei depends on the continuity of the nucleosomal fiber and interactions between nucleosomes. Disrupting these chromatin features by varying cation concentration, acetylating histone tails, or digesting linker DNA results in loss of nuclear rigidity. In contrast, the levels of key chromatin assembly factors, including cohesin, condensin II, and CTCF, and a major nuclear envelope protein, lamin, are unaffected. Together with in situ evidence using living cells and a simple mechanical model, our findings reveal a chromatin-based regulation of the nuclear mechanical response and provide insight into the significance of local and global chromatin structures, such as those associated with interdigitated or melted nucleosomal fibers. PMID:28428255

  6. Linker histone H1 and H3K56 acetylation are antagonistic regulators of nucleosome dynamics.

    Science.gov (United States)

    Bernier, Morgan; Luo, Yi; Nwokelo, Kingsley C; Goodwin, Michelle; Dreher, Sarah J; Zhang, Pei; Parthun, Mark R; Fondufe-Mittendorf, Yvonne; Ottesen, Jennifer J; Poirier, Michael G

    2015-12-09

    H1 linker histones are highly abundant proteins that compact nucleosomes and chromatin to regulate DNA accessibility and transcription. However, the mechanisms that target H1 regulation to specific regions of eukaryotic genomes are unknown. Here we report fluorescence measurements of human H1 regulation of nucleosome dynamics and transcription factor (TF) binding within nucleosomes. H1 does not block TF binding, instead it suppresses nucleosome unwrapping to reduce DNA accessibility within H1-bound nucleosomes. We then investigated H1 regulation by H3K56 and H3K122 acetylation, two transcriptional activating histone post translational modifications (PTMs). Only H3K56 acetylation, which increases nucleosome unwrapping, abolishes H1.0 reduction of TF binding. These findings show that nucleosomes remain dynamic, while H1 is bound and H1 dissociation is not required for TF binding within the nucleosome. Furthermore, our H3K56 acetylation measurements suggest that a single-histone PTM can define regions of the genome that are not regulated by H1.

  7. Linker-Region Modified Derivatives of the Deoxyhypusine Synthase Inhibitor CNI-1493 Suppress HIV-1 Replication.

    Science.gov (United States)

    Schröder, Marcus; Kolodzik, Adrian; Windshügel, Björn; Krepstakies, Marcel; Priyadarshini, Poornima; Hartjen, Philip; van Lunzen, Jan; Rarey, Matthias; Hauber, Joachim; Meier, Chris

    2016-02-01

    The inhibition of cellular factors that are involved in viral replication may be an important alternative to the commonly used strategy of targeting viral enzymes. The guanylhydrazone CNI-1493, a potent inhibitor of the deoxyhypusine synthase (DHS), prevents the activation of the cellular factor eIF-5A and thereby suppresses HIV replication and a number of other diseases. Here, we report on the design, synthesis and biological evaluation of a series of CNI-1493 analogues. The sebacoyl linker in CNI-1493 was replaced by different alkyl or aryl dicarboxylic acids. Most of the tested derivatives suppress HIV-1 replication efficiently in a dose-dependent manner without showing toxic side effects. The unexpected antiviral activity of the rigid derivatives point to a second binding mode as previously assumed for CNI-1493. Moreover, the chemical stability of CNI-1493 was analysed, showing a successive hydrolysis of the imino bonds. By molecular dynamics simulations, the behaviour of the parent CNI-1493 in solution and its interactions with DHS were investigated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact.

    Science.gov (United States)

    Gorji, Mohammad Saleh; Razak, Khairunisak Abdul; Cheong, Kuan Yew

    2013-10-15

    Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Graft linker immobilization for spatial control of protein immobilization inside fused microchips.

    Science.gov (United States)

    Shirai, Kentaro; Renberg, Björn; Sato, Kae; Mawatari, Kazuma; Konno, Tomohiro; Ishihara, Kazuhiko; Kitamori, Takehiko

    2009-12-01

    Fused silica glass microchips have several attractive features for lab-on-a-chip applications; they can be machined with excellent precision down to nanospace; are stable; transparent and can be modified with a range of silanization agents to change channel surface properties. For immobilization, however, ligands must be added after bonding, since the harsh bonding conditions using heat or hydrofluoric acid would remove all prior immobilized ligands. For spatial control over immobilization, UV-mediated immobilization offers several advantages; spots can be created in parallel, the feature size can be made small, and spatial control over patterns and positions is excellent. However, UV sensitive groups are often based on hydrophobic chemical moieties, which unfortunately result in greater non-specific binding of biomolecules, especially proteins. Here, we present techniques in which any -CH(x) (x=1,2,3) containing surface coating can be used as foundation for grafting a hydrophilic linker with a chemical anchor, a carboxyl group, to which proteins and amine containing molecules can be covalently coupled. Hence, the attractive features of many well-known protein and biomolecule repelling polymer coatings can be utilized while achieving site-specific immobilization only to pre-determined areas within the bonded microchips.

  10. Gel Point Suppression in RAFT Polymerization of Pure Acrylic Cross-Linker Derived from Soybean Oil.

    Science.gov (United States)

    Yan, Mengguo; Huang, Yuerui; Lu, Mingjia; Lin, Fang-Yi; Hernández, Nacú B; Cochran, Eric W

    2016-08-08

    Here we report the reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylated epoxidized soybean oil (AESO), a cross-linker molecule, to high conversion (>50%) and molecular weight (>100 kDa) without macrogelation. Surprisingly, gelation is suppressed in this system far beyond the expectations predicated both on Flory-Stockmeyer theory and multiple other studies of RAFT polymerization featuring cross-linking moieties. By varying AESO and initiator concentrations, we show how intra- versus intermolecular cross-linking compete, yielding a trade-off between the degree of intramolecular linkages and conversion at gel point. We measured polymer chain characteristics, including molecular weight, chain dimensions, polydispersity, and intrinsic viscosity, using multidetector gel permeation chromatography and NMR to track polymerization kinetics. We show that not only the time and conversion at macrogelation, but also the chain architecture, is largely affected by these reaction conditions. At maximal AESO concentration, the gel point approaches that predicted by the Flory-Stockmeyer theory, and increases in an exponential fashion as the AESO concentration decreases. In the most dilute solutions, macrogelation cannot be detected throughout the entire reaction. Instead, cyclization/intramolecular cross-linking reactions dominate, leading to microgelation. This work is important, especially in that it demonstrates that thermoplastic rubbers could be produced based on multifunctional renewable feedstocks.

  11. Chitosan hydrogel formation using laccase activated phenolics as cross-linkers.

    Science.gov (United States)

    Huber, Daniela; Tegl, Gregor; Baumann, Martina; Sommer, Eva; Gorji, Elham Ghorbani; Borth, Nicole; Schleining, Gerhard; Nyanhongo, Gibson S; Guebitz, Georg M

    2017-02-10

    Chitosan hydrogels are gaining increasing interest for biomedical applications due to attractive properties such as biocompatibility. In order to replace toxic chemical cross-linkers for hydrogel formation, we investigated the cross-linking potential of laccase oxidized phenolics. HPLC-TOF-MS and ATR-FTIR demonstrated that phenolics were bond to glucosamine as chitosan model substrate. Phenolics concentrations required for hydrogel formation varied from 500μM for catechol to 5000μM for sinapic acid. The hydrogels showed different swelling and release properties assessed using methylene blue release as a model. Laccase oxidized caffeic acid and pyrogallol-chitosan hydrogels showed excellent behavior in up-taking water with a swelling of 208.7% for caffeic acid. Biocompatibility results did not show any significant inhibition of growth of HEK293 cell line when phenolics like catechol or eugenol were used. Therefore, this study demonstrates that laccase oxidized phenolics are potential cross-linking agents of chitosan as a novel green approach to synthesizing chitosan hydrogels. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. On the Efficiency of NHS Ester Cross-Linkers for Stabilizing Integral Membrane Protein Complexes

    Science.gov (United States)

    Chen, Fan; Gerber, Sabina; Korkhov, Volodymyr M.; Mireku, Samantha; Bucher, Monika; Locher, Kaspar P.; Zenobi, Renato

    2015-03-01

    We have previously presented a straightforward approach based on high-mass matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) to study membrane proteins. In addition, the stoichiometry of integral membrane protein complexes could be determined by MALDI-MS, following chemical cross-linking via glutaraldehyde. However, glutaraldehyde polymerizes in solution and reacts nonspecifically with various functional groups of proteins, limiting its usefulness for structural studies of protein complexes. Here, we investigated the capability of N-hydroxysuccinimide (NHS) esters, which react much more specifically, to cross-link membrane protein complexes such as PglK and BtuC2D2. We present clear evidence that NHS esters are capable of stabilizing membrane protein complexes in situ, in the presence of detergents such as DDM, C12E8, and LDAO. The stabilization efficiency strongly depends on the membrane protein structure (i.e, the number of primary amine groups and the distances between primary amines). A minimum number of primary amine groups is required, and the distances between primary amines govern whether a cross-linker with a specific spacer arm length is able to bridge two amine groups.

  13. Lanthanide metal-organic frameworks based on a thiophenedicarboxylate linker: Characterization and luminescence

    Science.gov (United States)

    Calderone, Paul J.; Plonka, Anna M.; Banerjee, Debasis; Nizami, Quddus A.; Parise, John B.

    2013-01-01

    Three topologically-related lanthanide thiophenedicarboxylate (TDC) metal-organic frameworks were synthesized using an identical metal:linker:solvet ratio. Nd(TDC)3(EtOH)3(H2O)·H2O (1; space group Cc, a = 24.035(2) Å, b = 10.063(1) Å, c = 18.998(1) Å, β = 132.41(1)°) contains the same metal-TDC coordination modes as two other compounds which have the isostructural formula Ln(TDC)3(EtOH)3(H2O)·H2O; Ln = Tb (2; space group P¯ 1, a = 12.807(9) Å, b = 14.557(1) Å, c = 19.128(1) Å, α = 106.66(2)°, β = 105.62(2)°, γ = 93.691(2)°), Dy (3; space group P¯ 1, a = 12.793(8) Å, b = 14.682(1) Å, c = 19.077(1) Å, α = 107.12(1)°, β = 105.54(1)°, γ = 93.518(2)°). An equimolar solvent mixture of water and ethanol causes both types of solvent molecules coordinating to metal centers. The fluorescence spectra of compounds 2 and 3 show characteristic bands related to their respective metal ions, but Dy-based 3 is very weak compared to Tb-based 2, indicating coordinating solvent molecules may be quenching Dy fluorescence.

  14. New bis(azobenzocrown)s with dodecylmethylmalonyl linkers as ionophores for sodium selective potentiometric sensors.

    Science.gov (United States)

    Luboch, Elżbieta; Jeszke, Maciej; Szarmach, Mirosław; Łukasik, Natalia

    2016-01-01

    Novel biscrowns 1 and 2 were synthesized from 13-membered azobenzocrown ethers containing bromoalkylenoxy chains in para position relative to the azo group. The synthesized diester molecules are dodecylmethylmalonic acid derivatives differing by the linker length. The synthesized compounds have the potential of being used as sodium ionophores in ion-selective electrodes. They were characterized and used as ionophores in classic and miniature, solid contact (screen-printed and glassy carbon) membrane ion-selective electrodes. Compound 3, a similar monoester derivative of 13-membered azobenzocrown, was synthesized and used in membrane electrodes for comparison. Lipophilicity of new ionophores was determined by TLC. Lipophilicity of bis(azobenzocrown)s was found to be within the range of logPTLC = 12-13. It was observed that the particularly important selectivity coefficients logKNa,K determined for new electrodes, being logKNa,K = -2.5 and -2.6 (SSM, 0.1 M), are better than those of the electrodes featuring seven out of the nine commercially available sodium ionophores. It was concluded that the ionophore 1 creates, in acetone, with sodium iodide, complex of 1:1 stoichiometry (sandwich complex) with stability constant (logK) ca. 3.0.

  15. A Class of Rigid Linker-bearing Glucosides for Membrane Protein Structural Study

    Science.gov (United States)

    Sadaf, Aiman; Mortensen, Jonas S.; Capaldi, Stefano; Tikhonova, Elena; Hariharan, Parameswaran; de Castro Ribeiro, Orquidea; Loland, Claus J; Guan, Lan; Byrne, Bernadette

    2015-01-01

    Membrane proteins are amphipathic bio-macromolecules incompatible with the polar environments of aqueous media. Conventional detergents encapsulate the hydrophobic surfaces of membrane proteins allowing them to exist in aqueous solution. Membrane proteins stabilized by detergent micelles are used for structural and functional analysis. Despite the availability of a large number of detergents, only a few agents are sufficiently effective at maintaining the integrity of membrane proteins to allow successful crystallization. In the present study, we describe a novel class of synthetic amphiphiles with a branched tail group and a triglucoside head group. These head and tail groups were connected via an amide or ether linkage by using a tris(hydroxylmethyl)aminomethane (TRIS) or neopentyl glycol (NPG) linker to produce TRIS-derived triglucosides (TDTs) and NPG-derived triglucosides (NDTs), respectively. Members of this class conferred enhanced stability on target membrane proteins compared to conventional detergents. Because of straightforward synthesis of the novel agents and their favourable effects on a range of membrane proteins, these agents should be of wide applicability to membrane protein science. PMID:27110345

  16. Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically.

    Science.gov (United States)

    Channon, Robert B; Joseph, Maxim B; Bitziou, Eleni; Bristow, Anthony W T; Ray, Andrew D; Macpherson, Julie V

    2015-10-06

    The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems.

  17. The structural kinetics of switch-1 and the neck linker explain the functions of kinesin-1 and Eg5.

    Science.gov (United States)

    Muretta, Joseph M; Jun, Yonggun; Gross, Steven P; Major, Jennifer; Thomas, David D; Rosenfeld, Steven S

    2015-12-01

    Kinesins perform mechanical work to power a variety of cellular functions, from mitosis to organelle transport. Distinct functions shape distinct enzymologies, and this is illustrated by comparing kinesin-1, a highly processive transport motor that can work alone, to Eg5, a minimally processive mitotic motor that works in large ensembles. Although crystallographic models for both motors reveal similar structures for the domains involved in mechanochemical transduction--including switch-1 and the neck linker--how movement of these two domains is coordinated through the ATPase cycle remains unknown. We have addressed this issue by using a novel combination of transient kinetics and time-resolved fluorescence, which we refer to as "structural kinetics," to map the timing of structural changes in the switch-1 loop and neck linker. We find that differences between the structural kinetics of Eg5 and kinesin-1 yield insights into how these two motors adapt their enzymologies for their distinct functions.

  18. Aminosilane as a Molecular Linker between the Electron-Transport Layer and Active Layer for Efficient Inverted Polymer Solar Cells.

    Science.gov (United States)

    Fu, Ping; Guo, Xin; Wang, Shengyang; Ye, Yun; Li, Can

    2017-04-19

    Interfacial modification is crucial for improving the photovoltaic performance. In this work, we present an aminosilane as a molecular linker between the ZnO electron-transport layer and fullerene derivative phenyl-C71-butyric acid methyl ester (PC71BM)-based active layer for efficient inverted polymer solar cells. An enhancement in the power-conversion efficiency (PCE), from 8.47 to 9.46%, was achieved on using PTB7-Th as donors. The aminosilane molecular linker provides dual functionalities for enhanced PCE, including (1) passivating the ZnO surface and decreasing the surface work function of ZnO for energy-level alignment and (2) bonding onto the fullerene derivative PC71BM-based active layer to reduce the interface contact resistance.

  19. De novo transcriptome analysis of the red seaweed Gracilaria chilensis and identification of linkers associated with phycobilisomes.

    Science.gov (United States)

    Vorphal, María Alejandra; Gallardo-Escárate, Cristian; Valenzuela-Muñoz, Valentina; Dagnino-Leone, Jorge; Vásquez, José Aleikar; Martínez-Oyanedel, José; Bunster, Marta

    2017-02-01

    This work reports the results of the Illumina RNA-Seq of a wild population of female haploid plants of Gracilaria chilensis (Bird et al., 1986) (Rhodophyta, Gigartinalis). Most transcripts were de novo assembled in 12,331 contigs with an average length of 1756bp, showing that 96.64% of the sequences were annotated with known proteins. In particular, the identification of linker proteins of phycobilisomes (PBS) is reported. Linker proteins have primary been identified in cyanobacteria but the information available about them in eukaryotic red alga is not complete, and this is the first report in G. chilensis. This resource will also provide the basis for the study of metabolic pathways related to polysaccharide production. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Covalent stabilization of alginate hydrogel beads via Staudinger ligation: Assessment of poly(ethylene glycol) and alginate cross-linkers

    OpenAIRE

    Gattás-Asfura, Kerim M.; Fraker, Christopher A.; Stabler, Cherie L.

    2011-01-01

    Cellular encapsulation within alginate hydrogel capsules has broad applications in tissue engineering. In seeking to improve the inherent instability of ionically cross-linked alginate hydrogels, we previously demonstrated the covalent stabilization of Ba2+ cross-linked alginate-azide beads via chemoselective Staudinger ligation using a 1-methyl-2-diphenylphosphino-terephthalate (MDT) terminated poly(ethylene glycol) linker. In this study, we functionalized variant PEG, linear and branched, a...

  1. Plasmin inhibitors with hydrophobic amino acid-based linker between hydantoin moiety and benzimidazole scaffold enhance inhibitory activity.

    Science.gov (United States)

    Teno, Naoki; Gohda, Keigo; Yamashita, Yukiko; Otsubo, Tadamune; Yamaguchi, Masafumi; Wanaka, Keiko; Tsuda, Yuko

    2016-05-01

    In this letter we report the design and synthesis of a series of plasmin inhibitors, which share the amino acid-based linker with limited free rotation between the hydantoin moiety and the benzimidazole scaffold. Our studies led to potent plasmin inhibitors and yielded important new insights into their structure-activity relationship for binding to the active site of plasmin. Copyright © 2016. Published by Elsevier Ltd.

  2. Targeting C-myc G-Quadruplex: Dual Recognition by Aminosugar-Bisbenzimidazoles with Varying Linker Lengths

    Directory of Open Access Journals (Sweden)

    Nihar Ranjan

    2013-11-01

    Full Text Available G-quadruplexes are therapeutically important biological targets. In this report, we present biophysical studies of neomycin-Hoechst 33258 conjugates binding to a G-quadruplex derived from the C-myc promoter sequence. Our studies indicate that conjugation of neomycin to a G-quadruplex binder, Hoechst 33258, enhances its binding. The enhancement in G-quadruplex binding of these conjugates varies with the length and composition of the linkers joining the neomycin and Hoechst 33258 units.

  3. Optimizing the relaxivity of GdIII complexes appended to InP/ZnS quantum dots by linker tuning.

    Science.gov (United States)

    Stasiuk, Graeme J; Tamang, Sudarsan; Imbert, Daniel; Gateau, Christelle; Reiss, Peter; Fries, Pascal; Mazzanti, Marinella

    2013-06-21

    Three bimodal MRI/optical nanosized contrast agents with high per-nanoparticle relaxivity (up to 2523 mM(-1) s(-1) at 35 MHz and 932 mM(-1) s(-1) at 200 MHz) have been prepared connecting up to 115 tris-aqua Gd(III) complexes to fluorescent non-toxic InP/ZnS quantum dots. The structure of the linker has an important effect on the relaxivity of the final multimeric contrast agent.

  4. Xe Adsorption and Separation Properties of a Series of Microporous Metal–Organic Frameworks (MOFs) with V-Shaped Linkers

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Debasis; Elsaidi, Sameh K.; Thallapally, Praveen K.

    2017-08-28

    A series of microporous Metal-Organic Frameworks (MOFs) constructed by a V-shaped linker, 4,4’-sul-fonyldibenzoic acid were evaluated for their Xe gas adsorption properties. In particular, a cadmium based MOF exhibit noteworthy Xe adsorption and separation properties in presence of other gases under nuclear reprocessing conditions. The difference in Xe adsorption and separation properties of the materials were attributed towards their topology and pore size.

  5. Direct evidence that the carboxyl-terminal sequence of a bacterial chemoreceptor is an unstructured linker and enzyme tether.

    Science.gov (United States)

    Bartelli, Nicholas L; Hazelbauer, Gerald L

    2011-11-01

    Sensory adaptation in bacterial chemotaxis involves reversible methylation of specific glutamyl residues on chemoreceptors. The reactions are catalyzed by a dedicated methyltransferase and dedicated methylesterase. In Escherichia coli and related organisms, control of these enzymes includes an evolutionarily recent addition of interaction with a pentapeptide activator located at the carboxyl terminus of the receptor polypeptide chain. Effective enzyme activation requires not only the pentapeptide but also a segment of the receptor polypeptide chain between that sequence and the coiled-coil body of the chemoreceptor. This segment has features consistent with a role as a flexible and presumably unstructured linker and enzyme tether, but there has been no direct information about its structure. We used site-directed spin labeling and electron paramagnetic resonance spectroscopy to characterize structural features of the carboxyl-terminal 40 residues of E. coli chemoreceptor Tar. Beginning ∼ 35 residues from the carboxyl terminus and continuing to the end of the protein, spectra of spin-labeled Tar embedded in native membranes or in reconstituted proteoliposomes, exhibited mobilities characteristic of unstructured, disordered segments. Binding of methyltransferase substantially reduced mobility for positions in or near the pentapeptide but mobility for the linker sequence remained high, being only modestly reduced in a gradient of decreasing effects for 10-15 residues, a pattern consistent with the linker providing a flexible arm that would allow enzyme diffusion within defined limits. Thus, our data identify that the carboxyl-terminal linker between the receptor body and the pentapeptide is an unstructured, disordered segment that can serve as a flexible arm and enzyme tether. Copyright © 2011 The Protein Society.

  6. Facile synthesis of one-dimensional organometallic-organic hybrid polymers based on a diphosphorus complex and flexible bipyridyl linkers.

    Science.gov (United States)

    Elsayed Moussa, M; Attenberger, B; Peresypkina, E V; Fleischmann, M; Balázs, G; Scheer, M

    2016-08-21

    The selective synthesis of a series of new "ladderlike" one-dimensional organometallic-organic hybrid polymers is shown. The polymers are obtained from the reaction of the diphosphorus ligand complex [Cp2Mo2(CO)4(η(2)-P2)] with the copper salt [Cu(CH3CN)4]BF4 in the presence of flexible organic bipyridyl linkers in high selectivity. This unique behaviour is supported by DFT calculations.

  7. The interdomain flexible linker of the polypeptide GalNAc transferases dictates their long-range glycosylation preferences.

    Science.gov (United States)

    Rivas, Matilde de Las; Lira-Navarrete, Erandi; Daniel, Earnest James Paul; Compañón, Ismael; Coelho, Helena; Diniz, Ana; Jiménez-Barbero, Jesús; Peregrina, Jesús M; Clausen, Henrik; Corzana, Francisco; Marcelo, Filipa; Jiménez-Osés, Gonzalo; Gerken, Thomas A; Hurtado-Guerrero, Ramon

    2017-12-05

    The polypeptide GalNAc-transferases (GalNAc-Ts), that initiate mucin-type O-glycosylation, consist of a catalytic and a lectin domain connected by a flexible linker. In addition to recognizing polypeptide sequence, the GalNAc-Ts exhibit unique long-range N- and/or C-terminal prior glycosylation (GalNAc-O-Ser/Thr) preferences modulated by the lectin domain. Here we report studies on GalNAc-T4 that reveal the origins of its unique N-terminal long-range glycopeptide specificity, which is the opposite of GalNAc-T2. The GalNAc-T4 structure bound to a monoglycopeptide shows that the GalNAc-binding site of its lectin domain is rotated relative to the homologous GalNAc-T2 structure, explaining their different long-range preferences. Kinetics and molecular dynamics simulations on several GalNAc-T2 flexible linker constructs show altered remote prior glycosylation preferences, confirming that the flexible linker dictates the rotation of the lectin domain, thus modulating the GalNAc-Ts' long-range preferences. This work for the first time provides the structural basis for the different remote prior glycosylation preferences of the GalNAc-Ts.

  8. A One-Pot Chemically Cleavable Bis-Linker Tether Strategy for the Synthesis of Heterodimeric Peptides.

    Science.gov (United States)

    Patil, Nitin A; Tailhades, Julien; Karas, John A; Separovic, Frances; Wade, John D; Hossain, Mohammed Akhter

    2016-11-14

    Heterodimeric peptides linked by disulfide bonds are attractive drug targets. However, their chemical assembly can be tedious, time-consuming, and low yielding. Inspired by the cellular synthesis of pro-insulin in which the two constituent peptide chains are expressed as a single-chain precursor separated by a connecting C-peptide, we have developed a novel chemically cleavable bis-linker tether which allows the convenient assembly of two peptide chains as a single "pro"-peptide on the same solid support. Following the peptide cleavage and post-synthetic modifications, this bis-linker tether can be removed in one-step by chemical means. This method was used to synthesize a drug delivery-cargo conjugate, TAT-PKCi peptide, and a two-disulfide bridged heterodimeric peptide, thionin (7-19)-(24-32R), a thionin analogue. To our knowledge, this is the first report of a one-pot chemically cleavable bis-linker strategy for the facile synthesis of cross-bridged two-chain peptides. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Diketopyrrolopyrrole Polymers with Thienyl and Thiazolyl Linkers for Application in Field-Effect Transistors and Polymer Solar Cells.

    Science.gov (United States)

    Yu, Yaping; Wu, Yang; Zhang, Andong; Li, Cheng; Tang, Zheng; Ma, Wei; Wu, Yonggang; Li, Weiwei

    2016-11-09

    Conjugated polymers consisting of diketopyrrolopyrrole (DPP) units have been successfully applied in field-effect transistors (FETs) and polymer solar cells (PSCs), while most of the DPP polymers were designed as symmetric structures containing identical aromatic linkers. In this manuscript, we design a new asymmetric DPP polymer with varied aromatic linkers in the backbone for application in FETs and PSCs. The designation provides the chance to finely adjust the energy levels of conjugated polymers so as to influence the device performance. The asymmetric polymer exhibits highly crystalline properties, high hole mobilities of 3.05 cm(2) V(-1) s(-1) in FETs, and a high efficiency of 5.9% in PSCs with spectra response from 300 to 850 nm. Morphology investigation demonstrates that the asymmetric polymer has a large crystal domain in blended thin films, indicating that the solar cell performance can be further enhanced by optimizing the microphase separation. The study reveals that the asymmetric design via adjusting the aromatic linkers in DPP polymers is a useful route toward flexible electronic devices.

  10. Linker-extended native cyanovirin-N facilitates PEGylation and potently inhibits HIV-1 by targeting the glycan ligand.

    Directory of Open Access Journals (Sweden)

    Jia Chen

    Full Text Available Cyanovirin-N (CVN potently inhibits human immunodeficiency virus type 1 (HIV-1 infection, but both cytotoxicity and immunogenicity have hindered the translation of this protein into a viable therapeutic. A molecular docking analysis suggested that up to 12 residues were involved in the interaction of the reverse parallel CVN dimer with the oligosaccharide targets, among which Leu-1 was the most prominent hot spot residue. This finding provided a possible explanation for the lack of anti-HIV-1 activity observed with N-terminal PEGylated CVN. Therefore, linker-CVN (LCVN was designed as a CVN derivative with a flexible and hydrophilic linker (Gly4Ser3 at the N-terminus. The N-terminal α-amine of LCVN was PEGylated to create 10 K PEG-aldehyde (ALD-LCVN. LCVN and 10 K PEG-ALD-LCVN retained the specificity and affinity of CVN for high mannose N-glycans. Moreover, LCVN exhibited significant anti-HIV-1 activity with attenuated cytotoxicity in the HaCaT keratinocyte cell line and MT-4 T lymphocyte cell lines. 10 K PEG-ALD-LCVN also efficiently inactivated HIV-1 with remarkably decreased cytotoxicity and pronounced cell-to-cell fusion inhibitory activity in vitro. The linker-extended CVN and the mono-PEGylated derivative were determined to be promising candidates for the development of an anti-HIV-1 agent. This derivatization approach provided a model for the PEGylation of biologic candidates without introducing point mutations.

  11. Analysis of the linker region joining the adenylation and carrier protein domains of the modular nonribosomal peptide synthetases.

    Science.gov (United States)

    Miller, Bradley R; Sundlov, Jesse A; Drake, Eric J; Makin, Thomas A; Gulick, Andrew M

    2014-10-01

    Nonribosomal peptide synthetases (NRPSs) are multimodular proteins capable of producing important peptide natural products. Using an assembly line process, the amino acid substrate and peptide intermediates are passed between the active sites of different catalytic domains of the NRPS while bound covalently to a peptidyl carrier protein (PCP) domain. Examination of the linker sequences that join the NRPS adenylation and PCP domains identified several conserved proline residues that are not found in standalone adenylation domains. We examined the roles of these proline residues and neighboring conserved sequences through mutagenesis and biochemical analysis of the reaction catalyzed by the adenylation domain and the fully reconstituted NRPS pathway. In particular, we identified a conserved LPxP motif at the start of the adenylation-PCP linker. The LPxP motif interacts with a region on the adenylation domain to stabilize a critical catalytic lysine residue belonging to the A10 motif that immediately precedes the linker. Further, this interaction with the C-terminal subdomain of the adenylation domain may coordinate movement of the PCP with the conformational change of the adenylation domain. Through this work, we extend the conserved A10 motif of the adenylation domain and identify residues that enable proper adenylation domain function. © 2014 Wiley Periodicals, Inc.

  12. Analysis of the Linker Region Joining the Adenylation and Carrier Protein Domains of the Modular Non-Ribosomal Peptide Synthetases

    Science.gov (United States)

    Miller, Bradley R.; Sundlov, Jesse A.; Drake, Eric J.; Makin, Thomas A.; Gulick, Andrew M.

    2014-01-01

    Non-Ribosomal Peptide Synthetases (NRPSs) are multi-modular proteins capable of producing important peptide natural products. Using an assembly-line process the amino acid substrate and peptide intermediates are passed between the active sites of different catalytic domains of the NRPS while bound covalently to a peptidyl carrier protein (PCP) domain. Examination of the linker sequences that join the NRPS adenylation and PCP domains identified several conserved proline residues that are not found in standalone adenylation domains. We examined the roles of these proline residues and neighboring conserved sequences through mutagenesis and biochemical analysis of the reaction catalyzed by the adenylation domain and the fully reconstituted NRPS pathway. In particular, we identified a conserved LPxP motif at the start of the adenylation-PCP linker. The LPxP motif interacts with a region on the adenylation domain to stabilize a critical catalytic lysine residue belonging to the A10 motif that immediately precedes the linker. Further, this interaction with the C-terminal sub-domain of the adenylation domain may coordinate movement of the PCP with the conformational change of the adenylation domain. Through this work, we extend the conserved A10 motif of the adenylation domain and identify residues that enable proper adenylation domain function. PMID:24975514

  13. Defect Creation by Linker Fragmentation in Metal-Organic Frameworks and Its Effects on Gas Uptake Properties

    Energy Technology Data Exchange (ETDEWEB)

    Barin, G; Krungleviciute, V; Gutov, O; Hupp, JT; Yildirim, T; Farha, OK

    2014-07-07

    We successfully demonstrate an approach based on linker fragmentation to create defects and tune the pore volumes and surface areas of two metal-organic frameworks, NU-125 and HKUST-1, both of which feature copper paddlewheel nodes. Depending on the linker fragment composition, the defect can be either a vacant site or a functional group that the original linker does not have. In the first case, we show that both surface area and pore volume increase, while in the second case they decrease. The effect of defects on the high-pressure gas uptake is also studied over a large temperature and pressure range for different gases. We found that despite an increase in pore volume and surface area in structures with vacant sites, the absolute adsorption for methane decreases for HKUST-1 and slightly increases for NU-125. However, the working capacity (deliverable amount between 65 and 5 bar) in both cases remains similar to parent frameworks due to lower uptakes at low pressures. In the case of NU-125, the effect of defects became more pronounced at lower temperatures, reflecting the greater surface areas and pore volumes of the altered forms.

  14. Design, synthesis and biological evaluation of benzamide and phenyltetrazole derivatives with amide and urea linkers as BCRP inhibitors.

    Science.gov (United States)

    Gujarati, Nehaben A; Zeng, Leli; Gupta, Pranav; Chen, Zhe-Sheng; Korlipara, Vijaya L

    2017-10-15

    Breast cancer resistant protein (BCRP/ABCG2), a 72kDa plasma membrane transporter protein is a member of ABC transporter superfamily. Increased expression of BCRP causes increased efflux and therefore, reduced intracellular accumulation of many unrelated chemotherapeutic agents leading to multidrug resistance (MDR). A series of 31 benzamide and phenyltetrazole derivatives with amide and urea linkers has been synthesized to serve as potential BCRP inhibitors in order to overcome BCRP-mediated MDR. The target derivatives were tested for their cytotoxicity and reversal effects in human non-small cell lung cancer cell line H460 and mitoxantrone resistant cell line H460/MX20 using the MTT assay. In the benzamide series, compounds 6 and 7 exhibited a fold resistance of 1.51 and 1.62, respectively at 10µM concentration which is similar to that of FTC, a known BCRP inhibitor. Compounds 27 and 31 were the most potent analogues in the phenyltetrazole series with amide linker with a fold resistance of 1.39 and 1.32, respectively at 10µM concentration. For the phenyltetrazole series with urea linker, 38 exhibited a fold resistance of 1.51 which is similar than that of FTC and is the most potent compound in this series. The target compounds did not exhibit reversal effect in P-gp overexpressing resistant cell line SW620/Ad300 suggesting that they are selective BCRP inhibitors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Design of Tail-Clamp Peptide Nucleic Acid Tethered with Azobenzene Linker for Sequence-Specific Detection of Homopurine DNA

    Directory of Open Access Journals (Sweden)

    Shinjiro Sawada

    2017-10-01

    Full Text Available DNA carries genetic information in its sequence of bases. Synthetic oligonucleotides that can sequence-specifically recognize a target gene sequence are a useful tool for regulating gene expression or detecting target genes. Among the many synthetic oligonucleotides, tail-clamp peptide nucleic acid (TC-PNA offers advantages since it has two homopyrimidine PNA strands connected via a flexible ethylene glycol-type linker that can recognize complementary homopurine sequences via Watson-Crick and Hoogsteen base pairings and form thermally-stable PNA/PNA/DNA triplex structures. Here, we synthesized a series of TC-PNAs that can possess different lengths of azobenzene-containing linkers and studied their binding behaviours to homopurine single-stranded DNA. Introduction of azobenzene at the N-terminus amine of PNA increased the thermal stability of PNA-DNA duplexes. Further extension of the homopyrimidine PNA strand at the N-terminus of PNA-AZO further increased the binding stability of the PNA/DNA/PNA triplex to the target homopurine sequence; however, it induced TC-PNA/DNA/TC-PNA complex formation. Among these TC-PNAs, 9W5H-C4-AZO consisting of nine Watson-Crick bases and five Hoogsteen bases tethered with a beta-alanine conjugated azobenzene linker gave a stable 1:1 TC-PNA/ssDNA complex and exhibited good mismatch recognition. Our design for TC-PNA-AZO can be utilized for detecting homopurine sequences in various genes.

  16. The effect of cyclic thiourea functionalization and β,β‧-dialkylbithiophene linker on the performance of triphenylamine dyes

    Science.gov (United States)

    Guo, Yinju; Su, Jianli; An, Zhongwei; Chen, Xinbing; Chen, Pei

    2015-08-01

    Four new dyes (T-C1, T-C6, S-C1 and S-C6) with β,β‧-dialkylbithiophene as π-linkers were synthesized and utilized in dye-sensitized solar cells (DSSCs). Compared with the reference dyes (T-C0 and AZ6) with bithiophene as π-linkers, these dyes show blue-shifted absorption bands, and their DSSCs produce lower short-circuit current and high open-circuit voltage. These may be caused by the increase of dihedral angle between two thiophenes. On the one hand, the molecular conjugations are decreased; on the other hand, steric effect of the whole structures are increased. Compared with the triphenylamine dyes (T-C0, T-C1 and T-C6), the cyclic thiourea functionalized dyes (AZ6, S-C1 and S-C6) exhibit better photophysical and photovoltaic performances. However, the superiority of cyclic thiourea functionalization is gradually disappearing with the increased steric effect of the π-linkers.

  17. 2-{[2-(2-Hy-droxy-3-meth-oxy-benzyl-idene)hydrazin-1-yl-idene]meth-yl}-6-meth-oxy-phenol.

    Science.gov (United States)

    Lu, Rong; Wang, Wenxia; Lü, Xingqiang; Zhao, Shunsheng

    2011-10-01

    The title compound, C(16)H(16)N(2)O(4), was obtained from the reaction of hydrazine hydrate and o-vanilin in absolute ethanol. The mol-ecule is almost planar (except for the methyl H atoms), with a mean deviation from the plane of 0.0259 Å. The mol-ecular structure also exhibits an approximate non-crystallographic twofold axis. Intra-molecular O-H⋯N hydrogen bonds occur. In the crystal, inter-molecular C-H⋯O hydrogen bonds generate mol-ecular zigzag sheets. The sheets stack through C-H⋯π inter-actions, leading to a three-dimensional-network.

  18. The linker between LOV2-Jα and STK plays an essential role in the kinase activation by blue light in Arabidopsis phototropin1, a plant blue light receptor.

    Science.gov (United States)

    Kashojiya, Sachiko; Yoshihara, Shizue; Okajima, Koji; Tokutomi, Satoru

    2016-01-01

    Phototropin (phot), a blue light receptor in plants, is composed of several domains: LOV1, LOV2, and a serine/threonine kinase (STK). LOV2 is the main regulator of light activation of STK. However, the detailed mechanism remains unclear. In this report, we focused on the linker region between LOV2 and STK excluding the Jα-helix. Spectroscopy and a kinase assay for the substituents in the linker region of Arabidopsis phot1 LOV2-STK indicated that the linker is involved in the activation of STK. A putative module in the middle of the linker would be critical for intramolecular signaling and/or regulation of STK. © 2015 Federation of European Biochemical Societies.

  19. The PathLinker app: Connect the dots in protein interaction networks [version 1; referees: 1 approved, 2 approved with reservations

    Directory of Open Access Journals (Sweden)

    Daniel P. Gil

    2017-01-01

    Full Text Available PathLinker is a graph-theoretic algorithm for reconstructing the interactions in a signaling pathway of interest. It efficiently computes multiple short paths within a background protein interaction network from the receptors to transcription factors (TFs in a pathway. We originally developed PathLinker to complement manual curation of signaling pathways, which is slow and painstaking. The method can be used in general to connect any set of sources to any set of targets in an interaction network. The app presented here makes the PathLinker functionality available to Cytoscape users. We present an example where we used PathLinker to compute and analyze the network of interactions connecting proteins that are perturbed by the drug lovastatin.

  20. The electron injection rate in CdSe quantum dot sensitized solar cells: from a bifunctional linker and zinc oxide morphology.

    Science.gov (United States)

    Ding, Wei-Lu; Peng, Xing-Liang; Sun, Zhu-Zhu; Li, Ze-Sheng

    2017-11-09

    Herein, we have investigated the effect of both the bifunctional linker (L1, L2, L3, and L4) and ZnO morphology (porous nanoparticles (NPs), nanowires (NWs), and nanotubes (NTs-A and NTs-Z)) on the electron injection in CdSe QD sensitized solar cells by first-principles simulation. Via calculating the partitioned interfaces formed by different components (linker/QDs and ZnO/linker), we found that the electronic states of QDs and every ZnO substrate are insensitive to any linker, while the frontier orbitals of L1-L4 (with increased delocalization) manifest a systematical negative-shift. Because of the lowest unoccupied molecular orbital (LUMO) of L1 compared to its counterparts aligned in the region of the virtual states of QDs or the substrate with a high density of states, it always yields a stronger electronic coupling with QDs and varied substrates. After characterization of the complete ZnO/linker/QD system, we found that the electron injection time (τ) vastly depends on both the linker and substrate. On the one hand, L1 bridged QDs and every substrate always achieve the shortest τ compared to their counterpart associated cases. On the other hand, NW supported systems always yield the shortest τ no matter what the linker is. Overall, the NW/L1/QD system achieves the fastest injection by ∼160 fs. This essentially stems from the shortest molecular length of L1 decreasing the distance between QDs and the substrate, subsequently improving the interfacial coupling. Meanwhile, the NW supported cases generate the less sensitive virtual states for both the QDs and NWs, ensuring a less variable interfacial coupling. These facts combined can provide understanding of the effects contributed from the linker and the oxide semiconductor morphology on charge transfer with the aim of choosing an appropriate component with fast directional electron injection.

  1. Site-Dependent Degradation of a Non-Cleavable Auristatin-Based Linker-Payload in Rodent Plasma and Its Effect on ADC Efficacy

    OpenAIRE

    Dorywalska, Magdalena; Strop, Pavel; Melton-Witt, Jody A.; Hasa-Moreno, Adela; Farias, Santiago E.; Galindo Casas, Meritxell; Delaria, Kathy; Lui, Victor; Poulsen, Kris; Sutton, Janette; Bolton, Gary; Zhou, Dahui; Moine, Ludivine; Dushin, Russell; Tran, Thomas-Toan

    2015-01-01

    The efficacy of an antibody-drug conjugate (ADC) is dependent on the properties of its linker-payload which must remain stable while in systemic circulation but undergo efficient processing upon internalization into target cells. Here, we examine the stability of a non-cleavable Amino-PEG6-based linker bearing the monomethyl auristatin D (MMAD) payload site-specifically conjugated at multiple positions on an antibody. Enzymatic conjugation with transglutaminase allows us to create a stable am...

  2. Reassembly and co-crystallization of a family 9 processive endoglucanase from its component parts: structural and functional significance of the intermodular linker

    Directory of Open Access Journals (Sweden)

    Svetlana Petkun

    2015-09-01

    Full Text Available Non-cellulosomal processive endoglucanase 9I (Cel9I from Clostridium thermocellum is a modular protein, consisting of a family-9 glycoside hydrolase (GH9 catalytic module and two family-3 carbohydrate-binding modules (CBM3c and CBM3b, separated by linker regions. GH9 does not show cellulase activity when expressed without CBM3c and CBM3b and the presence of the CBM3c was previously shown to be essential for endoglucanase activity. Physical reassociation of independently expressed GH9 and CBM3c modules (containing linker sequences restored 60–70% of the intact Cel9I endocellulase activity. However, the mechanism responsible for recovery of activity remained unclear. In this work we independently expressed recombinant GH9 and CBM3c with and without their interconnecting linker in Escherichia coli. We crystallized and determined the molecular structure of the GH9/linker-CBM3c heterodimer at a resolution of 1.68 Å to understand the functional and structural importance of the mutual spatial orientation of the modules and the role of the interconnecting linker during their re-association. Enzyme activity assays and isothermal titration calorimetry were performed to study and compare the effect of the linker on the re-association. The results indicated that reassembly of the modules could also occur without the linker, albeit with only very low recovery of endoglucanase activity. We propose that the linker regions in the GH9/CBM3c endoglucanases are important for spatial organization and fixation of the modules into functional enzymes.

  3. Post-translational modifications of linker histone H1 variants in mammals

    Science.gov (United States)

    Starkova, T. Yu; Polyanichko, A. M.; Artamonova, T. O.; Khodorkovskii, M. A.; Kostyleva, E. I.; Chikhirzhina, E. V.; Tomilin, A. N.

    2017-02-01

    The covalent modifications of the linker histone H1 and the core histones are thought to play an important role in the control of chromatin functioning. Histone H1 variants from K562 cell line (hH1), mouse (mH1) and calf (cH1) thymi were studied by matrix-activated laser desorption/ionization fourier transform ion cyclotron resonance mass-spectroscopy (MALDI-FT-ICR-MS). The proteomics analysis revealed novel post-translational modifications of the histone H1, such as meK34-mH1.4, meK35-cH1.1, meK35-mH1.1, meK75-hH1.2, meK75-hH1.3, acK26-hH1.4, acK26-hH1.3 and acK17-hH1.1. The comparison of the hH1, mH1 and cH1 proteins has demonstrated that the types and positions of the post-translational modifications of the globular domains of the H1.2-H1.4 variants are very conservative. However, the post-translational modifications of the N- and C-terminal tails of H1.2, H1.3 and H1.4 are different. The differences of post-translational modifications in the N- and C-terminal tails of H1.2, H1.3 and H1.4 likely lead to the differences in DNA-H1 and H1-protein interactions.

  4. Small epitope-linker modules for PCR-based C-terminal tagging in Saccharomyces cerevisiae.

    Science.gov (United States)

    Funakoshi, Minoru; Hochstrasser, Mark

    2009-03-01

    PCR-mediated gene modification is a powerful approach to the functional analysis of genes in Saccharomyces cerevisiae. One application of this method is epitope-tagging of a gene to analyse the corresponding protein by immunological methods. However, the number of epitope tags available in a convenient format is still low, and interference with protein function by the epitope, particularly if it is large, is not uncommon. To address these limitations and broaden the utility of the method, we constructed a set of convenient template plasmids designed for PCR-based C-terminal tagging with 10 different, relatively short peptide sequences that are recognized by commercially available monoclonal antibodies. The encoded tags are FLAG, 3 x FLAG, T7, His-tag, Strep-tag II, S-tag, Myc, HSV, VSV-G and V5. The same pair of primers can be used to construct tagged alleles of a gene of interest with any of the 10 tags. In addition, a six-glycine linker sequence is inserted upstream of these tags to minimize the influence of the tag on the target protein and maximize its accessibility for antibody binding. Three marker genes, HIS3MX6, kanMX6 and hphMX4, are available for each epitope. We demonstrate the utility of the new tags for both immunoblotting and one-step affinity purification of the regulatory particle of the 26S proteasome. The set of plasmids has been deposited in the non-profit plasmid repository Addgene (http://www.addgene.org).

  5. Post-translational modifications of linker histone H1 variants in mammals.

    Science.gov (United States)

    Starkova, T Yu; Polyanichko, A M; Artamonova, T O; Khodorkovskii, M A; Kostyleva, E I; Chikhirzhina, E V; Tomilin, A N

    2017-02-16

    The covalent modifications of the linker histone H1 and the core histones are thought to play an important role in the control of chromatin functioning. Histone H1 variants from K562 cell line (hH1), mouse (mH1) and calf (cH1) thymi were studied by matrix-activated laser desorption/ionization fourier transform ion cyclotron resonance mass-spectroscopy (MALDI-FT-ICR-MS). The proteomics analysis revealed novel post-translational modifications of the histone H1, such as meK34-mH1.4, meK35-cH1.1, meK35-mH1.1, meK75-hH1.2, meK75-hH1.3, acK26-hH1.4, acK26-hH1.3 and acK17-hH1.1. The comparison of the hH1, mH1 and cH1 proteins has demonstrated that the types and positions of the post-translational modifications of the globular domains of the H1.2-H1.4 variants are very conservative. However, the post-translational modifications of the N- and C-terminal tails of H1.2, H1.3 and H1.4 are different. The differences of post-translational modifications in the N- and C-terminal tails of H1.2, H1.3 and H1.4 likely lead to the differences in DNA-H1 and H1-protein interactions.

  6. Preparation and in vivo evaluation of novel linkers for {sup 211}At labeling of proteins

    Energy Technology Data Exchange (ETDEWEB)

    Talanov, Vladimir S. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Yordanov, Alexander T. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Garmestani, Kayhan [Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Milenic, Diane E. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Arora, Hans C. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Plascjak, Paul S. [Department of Nuclear Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892 (United States); Eckelman, William C. [Department of Nuclear Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892 (United States); Waldmann, Thomas A. [Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Brechbiel, Martin W. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States)]. E-mail: martinwb@mail.nih.gov

    2004-11-01

    The syntheses, radiolabeling, antibody conjugation and in vivo evaluation of new linkers for {sup 211}At labeling of monoclonal antibodies are described. Syntheses of the N-succinimidyl esters and labeling with {sup 211}At to form succinimidyl 4-methoxymethyl-3-[{sup 211}At]astatobenzoate (9) and succinimidyl 4-methylthiomethyl-3-[{sup 211}At]astatobenzoate (11) from the corresponding bromo-aryl esters is reported. Previously reported succinimidyl N-{l_brace}4-[{sup 211}At]astatophenethyl{r_brace}succinamate (SAPS) is employed as a standard of in vivo stability. Each agent is conjugated with Herceptin in parallel with their respective {sup 125}I analogue, succinimidyl 4-methoxymethyl-3-[{sup 125}I]iodobenzoate (10), succinimidyl 4-methylthiomethyl-3-[{sup 125}I]iodobenzoate (12) and succinimidyl N-{l_brace}4-[{sup 125}I]iodophenethyl{r_brace}succinamate (SIPS), respectively, for comparative assessment in LS-174T xenograft-bearing mice. With 9 and 11, inclusion of an electron pair donor in the ortho position does not appear to provide in vivo stability comparable to SAPS. Variables in radiolabeling chemistry of these three agents with {sup 211}At are notable. Sequential elimination of acetic acid and oxidizing agent, N-chlorosuccinimide (NCS), from the {sup 211}At radiolabeling protocol for forming SAPS improves yield, product purity and consistency. NCS appears to be critical for the radiolabeling of 6 with {sup 211}At. Formation of 11, however, is found to require the absence of NCS. Elimination of acetic acid is found to have no effect on radiolabeling efficiency or yield for either of these reactions.

  7. Preparation of FeO(OH Modified with Polyethylene Glycol and Its Catalytic Activity on the Reduction of Nitrobenzene with Hydrazine Hydrate

    Directory of Open Access Journals (Sweden)

    Ke Ying Cai

    2016-10-01

    Full Text Available Iron oxyhydroxide was prepared by dropping ammonia water to Fe(NO33.9H2O dispersed in polyethylene glycol (PEG 1000. The catalyst was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and laser particle size analyzer. The results showed the catalyst modified with polyethylene glycol was amorphous. The addition of PEG during the preparation make the particle size of the catalyst was smaller and more uniform. The catalytic performance was tested in the reduction of nitroarenes to corresponding amines with hydrazine hydrate, and the catalyst showed excellent activity and stability. Copyright © 2016 BCREC GROUP. All rights reserved Received: 2nd February 2016; Revised: 26th April 2016; Accepted: 7th June 2016 How to Cite: Cai, K.Y., Liu, Y.S., Song, M., Zhou, Y.M., Liu, Q., Wang, X.H. (2016. Preparation of FeO(OH Modified with Polyethylene Glycol and Its Catalytic Activity on the Reduction of Nitrobenzene with Hydrazine Hydrate. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3: 363-368 (doi:10.9767/bcrec.11.3.576.363-368 Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.576.363-368

  8. Hydrazine-hydrothermal syntheses, characterizations and photoelectrochemical properties of two quaternary chalcogenidoantimonates(III) BaCuSbQ{sub 3} (Q = S, Se)

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang; Hou, Peipei [State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Chai, Wenxiang [College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018 (China); Tian, Jiawei; Zheng, Xuerong; Shen, Yaying; Zhi, Mingjia; Zhou, Chunmei [State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Liu, Yi, E-mail: liuyimse@zju.edu.cn [State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2016-09-15

    Two isostructural quaternary chalcogenidoantimonates(III) BaCuSbQ{sub 3} (Q = S, Se): BaCuSbS{sub 3} (1) and BaCuSbSe{sub 3} (2) have been successfully synthesized through a facile hydrazine-hydrothermal method. Both two compounds crystallize in the orthorhombic space group and feature a three-dimensional (3D) channeled [Cu{sub 2}Sb{sub 2}Q{sub 6}]{sup 4-} framework, which is constructed by the distorted tetrahedral CuQ{sub 4} and pyramid SbQ{sub 3} units via vertex sharing. Both optical properties and theoretical studies show 1 and 2 are semiconductors with narrow band gaps. In addition, their photoelectrochemical properties have been investigated. - Highlights: • BaCuSbQ{sub 3} (Q = S, Se) were synthesized through a hydrazine-hydrothermal method. • BaCuSbQ{sub 3} (Q = S, Se) feature a 3D framework by single-crystal X-ray diffraction. • Experimental and theoretical studies confirm BaCuSbQ{sub 3} (Q = S, Se) are semiconductors. • Photoelectrochemical properties of BaCuSbQ{sub 3} (Q = S, Se) have been investigated.

  9. Electrochemical Detection of Hydrazine and 4-Nitrophenol Based on Layer-by-Layer Assembled Multilayer Films of Reduced Graphene Oxide/Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Shuohan HUANG

    2015-05-01

    Full Text Available Based on poly sodium 4-styrenesulfonate (PSS functionalized reduced graphene oxide (RGO and polyamidoamine (PAMAM dendrimer protected gold nanoparticles (AuNPs, a novel electrochemical sensing platform for sensitive detection of 4-nitrophenol and hydrazine was fabricated via electrostatic layer-by-layer (LBL self-assembly on a gold electrode modified with a first layer of poly (diallyldimethylammonium chloride (PDDA. The resulting nanocomposites were characterized by Raman and UV-Vis spectroscopes. Besides, electrochemical measurements were employed to investigate the electrocatalytic and sensing properties of the as-prepared modified electrode. The results indicate that the LBL assembled PSS-RGO/PAMAM-AuNPs multilayer films possess excellent electrocatalytic activities towards the reduction of 4-nitrophenol (4-NP and the oxidation of hydrazine and also show good analytical performance for the amperometric detection of the potential poisonous substances. In addition, the combination of the reduced graphene oxide and gold nanoparticles in the LBL assembly films and their synergistic effect may account for the increased electrochemical activities.

  10. Casitas B-lineage lymphoma linker helix mutations found in myeloproliferative neoplasms affect conformation.

    Science.gov (United States)

    Buetow, Lori; Tria, Giancarlo; Ahmed, Syed Feroj; Hock, Andreas; Dou, Hao; Sibbet, Gary J; Svergun, Dmitri I; Huang, Danny T

    2016-09-08

    Casitas B-lineage lymphoma (Cbl or c-Cbl) is a RING ubiquitin ligase that negatively regulates protein tyrosine kinase (PTK) signalling. Phosphorylation of a conserved residue (Tyr371) on the linker helix region (LHR) between the substrate-binding and RING domains is required to ubiquitinate PTKs, thereby flagging them for degradation. This conserved Tyr is a mutational hotspot in myeloproliferative neoplasms. Previous studies have revealed that select point mutations in Tyr371 can potentiate transformation in cells and mice but not all possible mutations do so. To trigger oncogenic potential, Cbl Tyr371 mutants must perturb the LHR-substrate-binding domain interaction and eliminate PTK ubiquitination. Although structures of native and pTyr371-Cbl are available, they do not reveal how Tyr371 mutations affect Cbl's conformation. Here, we investigate how Tyr371 mutations affect Cbl's conformation in solution and how this relates to Cbl's ability to potentiate transformation in cells. To explore how Tyr371 mutations affect Cbl's properties, we used surface plasmon resonance to measure Cbl mutant binding affinities for E2 conjugated with ubiquitin (E2-Ub), small angle X-ray scattering studies to investigate Cbl mutant conformation in solution and focus formation assays to assay Cbl mutant transformation potential in cells. Cbl Tyr371 mutants enhance E2-Ub binding and cause Cbl to adopt extended conformations in solution. LHR flexibility, RING domain accessibility and transformation potential are associated with the extent of LHR-substrate-binding domain perturbation affected by the chemical nature of the mutation. More disruptive mutants like Cbl Y371D or Y371S are more extended and the RING domain is more accessible, whereas Cbl Y371F mimics native Cbl in solution. Correspondingly, the only Tyr371 mutants that potentiate transformation in cells are those that perturb the LHR-substrate-binding domain interaction. c-Cbl's LHR mutations are only oncogenic when they

  11. Integrity of the Linker of Nucleoskeleton and Cytoskeleton Is Required for Efficient Herpesvirus Nuclear Egress.

    Science.gov (United States)

    Klupp, Barbara G; Hellberg, Teresa; Granzow, Harald; Franzke, Kati; Dominguez Gonzalez, Beatriz; Goodchild, Rose E; Mettenleiter, Thomas C

    2017-10-01

    Herpesvirus capsids assemble in the nucleus, while final virion maturation proceeds in the cytoplasm. This requires that newly formed nucleocapsids cross the nuclear envelope (NE), which occurs by budding at the inner nuclear membrane (INM), release of the primary enveloped virion into the perinuclear space (PNS), and subsequent rapid fusion with the outer nuclear membrane (ONM). During this process, the NE remains intact, even at late stages of infection. In addition, the spacing between the INM and ONM is maintained, as is that between the primary virion envelope and nuclear membranes. The linker of nucleoskeleton and cytoskeleton (LINC) complex consists of INM proteins with a luminal SUN (Sad1/UNC-84 homology) domain connected to ONM proteins with a KASH (Klarsicht, ANC-1, SYNE homology) domain and is thought to be responsible for spacing the nuclear membranes. To investigate the role of the LINC complex during herpesvirus infection, we generated cell lines constitutively expressing dominant negative (dn) forms of SUN1 and SUN2. Ultrastructural analyses revealed a significant expansion of the PNS and the contiguous intracytoplasmic lumen, most likely representing endoplasmic reticulum (ER), especially in cells expressing dn-SUN2. After infection, primary virions accumulated in these expanded luminal regions, also very distant from the nucleus. The importance of the LINC complex was also confirmed by reduced progeny virus titers in cells expressing dn-SUN2. These data show that the intact LINC complex is required for efficient nuclear egress of herpesviruses, likely acting to promote fusion of primary enveloped virions with the ONM. IMPORTANCE While the viral factors for primary envelopment of nucleocapsids at the inner nuclear membrane are known to the point of high-resolution structures, the roles of cellular components and regulators remain enigmatic. Furthermore, the machinery responsible for fusion with the outer nuclear membrane is unsolved. We show here

  12. Linker 2 of the eukaryotic pre-ribosomal processing factor Mrd1p is an essential interdomain functionally coupled to upstream RNA Binding Domain 2 (RBD2).

    Science.gov (United States)

    Lackmann, Fredrik; Belikov, Sergey; Wieslander, Lars

    2017-01-01

    Ribosome synthesis is an essential process in all cells. In Sacharomyces cerevisiae, the precursor rRNA, 35S pre-rRNA, is folded and assembled into a 90S pre-ribosomal complex. The 40S ribosomal subunit is processed from the pre-ribosomal complex. This requires concerted action of small nucleolar RNAs, such as U3 snoRNA, and a large number of trans-acting factors. Mrd1p, one of the essential small ribosomal subunit synthesis factors is required for cleavage of the 35S pre-rRNA to generate 18S rRNA of the small ribosomal subunit. Mrd1p is evolutionary conserved in all eukaryotes and in yeast it contains five RNA Binding Domains (RBDs) separated by linker regions. One of these linkers, Linker 2 between RBD2 and RBD3, is conserved in length, predicted to be structured and contains conserved clusters of amino acid residues. In this report, we have analysed Linker 2 mutations and demonstrate that it is essential for Mrd1p function during pre-ribosomal processing. Extensive changes of amino acid residues as well as specific changes of conserved clusters of amino acid residues were found to be incompatible with synthesis of pre-40S ribosomes and cell growth. In addition, gross changes in primary sequence of Linker 2 resulted in Mrd1p instability, leading to degradation of the N-terminal part of the protein. Our data indicates that Linker 2 is functionally coupled to RBD2 and argues for that these domains constitute a functional module in Mrd1p. We conclude that Linker 2 has an essential role for Mrd1p beyond just providing a defined length between RBD2 and RBD3.

  13. Kv Channel S1-S2 Linker Working as a Binding Site of Human β-Defensin 2 for Channel Activation Modulation*

    Science.gov (United States)

    Feng, Jing; Yang, Weishan; Xie, Zili; Xiang, Fang; Cao, Zhijian; Li, Wenxin; Hu, Hongzhen; Chen, Zongyun; Wu, Yingliang

    2015-01-01

    Among the three extracellular domains of the tetrameric voltage-gated K+ (Kv) channels consisting of six membrane-spanning helical segments named S1–S6, the functional role of the S1-S2 linker still remains unclear because of the lack of a peptide ligand. In this study, the Kv1.3 channel S1-S2 linker was reported as a novel receptor site for human β-defensin 2 (hBD2). hBD2 shifts the conductance-voltage relationship curve of the human Kv1.3 channel in a positive direction by nearly 10.5 mV and increases the activation time constant for the channel. Unlike classical gating modifiers of toxin peptides from animal venoms, which generally bind to the Kv channel S3-S4 linker, hBD2 only targets residues in both the N and C termini of the S1-S2 linker to influence channel gating and inhibit channel currents. The increment and decrement of the basic residue number in a positively charged S4 sensor of Kv1.3 channel yields conductance-voltage relationship curves in the positive direction by ∼31.2 mV and 2–4 mV, which suggests that positively charged hBD2 is anchored in the channel S1-S2 linker and is modulating channel activation through electrostatic repulsion with an adjacent S4 helix. Together, these findings reveal a novel peptide ligand that binds with the Kv channel S1-S2 linker to modulate channel activation. These findings also highlight the functional importance of the Kv channel S1-S2 linker in ligand recognition and modification of channel activation. PMID:25944908

  14. Linker 2 of the eukaryotic pre-ribosomal processing factor Mrd1p is an essential interdomain functionally coupled to upstream RNA Binding Domain 2 (RBD2.

    Directory of Open Access Journals (Sweden)

    Fredrik Lackmann

    Full Text Available Ribosome synthesis is an essential process in all cells. In Sacharomyces cerevisiae, the precursor rRNA, 35S pre-rRNA, is folded and assembled into a 90S pre-ribosomal complex. The 40S ribosomal subunit is processed from the pre-ribosomal complex. This requires concerted action of small nucleolar RNAs, such as U3 snoRNA, and a large number of trans-acting factors. Mrd1p, one of the essential small ribosomal subunit synthesis factors is required for cleavage of the 35S pre-rRNA to generate 18S rRNA of the small ribosomal subunit. Mrd1p is evolutionary conserved in all eukaryotes and in yeast it contains five RNA Binding Domains (RBDs separated by linker regions. One of these linkers, Linker 2 between RBD2 and RBD3, is conserved in length, predicted to be structured and contains conserved clusters of amino acid residues. In this report, we have analysed Linker 2 mutations and demonstrate that it is essential for Mrd1p function during pre-ribosomal processing. Extensive changes of amino acid residues as well as specific changes of conserved clusters of amino acid residues were found to be incompatible with synthesis of pre-40S ribosomes and cell growth. In addition, gross changes in primary sequence of Linker 2 resulted in Mrd1p instability, leading to degradation of the N-terminal part of the protein. Our data indicates that Linker 2 is functionally coupled to RBD2 and argues for that these domains constitute a functional module in Mrd1p. We conclude that Linker 2 has an essential role for Mrd1p beyond just providing a defined length between RBD2 and RBD3.

  15. Direct demonstration of the flexibility of the glycosylated proline-threonine linker in the Cellulomonas fimi Xylanase Cex through NMR spectroscopic analysis.

    Science.gov (United States)

    Poon, David K Y; Withers, Stephen G; McIntosh, Lawrence P

    2007-01-19

    The modular xylanase Cex (or CfXyn10A) from Cellulomonas fimi consists of an N-terminal catalytic domain and a C-terminal cellulose-binding domain, joined by a glycosylated proline-threonine (PT) linker. To characterize the conformation and dynamics of the Cex linker and the consequences of its modification, we have used NMR spectroscopy to study full-length Cex in its nonglycosylated ( approximately 47 kDa) and glycosylated ( approximately 51 kDa) forms. The PT linker lacks any predominant structure in either form as indicated by random coil amide chemical shifts. Furthermore, heteronuclear (1)H-(15)N nuclear Overhauser effect relaxation measurements demonstrate that the linker is flexible on the ns-to-ps time scale and that glycosylation partially dampens this flexibility. The catalytic and cellulose-binding domains also exhibit identical amide chemical shifts whether in isolation or in the context of either unmodified or glycosylated full-length Cex. Therefore, there are no noncovalent interactions between the two domains of Cex or between either domain and the linker. This conclusion is supported by the distinct (15)N relaxation properties of the two domains, as well as their differential alignment within a magnetic field by Pf1 phage particles. These data demonstrate that the PT linker is a flexible tether, joining the structurally independent catalytic and cellulose-binding domains of Cex in an ensemble of conformations; however, more extended forms may predominate because of restrictions imparted by the alternating proline residues. This supports the postulate that the binding-domain anchors Cex to the surface of cellulose, whereas the linker provides flexibility for the catalytic domain to hydrolyze nearby hemicellulose (xylan) chains.

  16. A New Triglycyl Peptide Linker for Antibody-Drug Conjugates (ADCs) with Improved Targeted Killing of Cancer Cells.

    Science.gov (United States)

    Singh, Rajeeva; Setiady, Yulius Y; Ponte, Jose; Kovtun, Yelena V; Lai, Katharine C; Hong, E Erica; Fishkin, Nathan; Dong, Ling; Jones, Gregory E; Coccia, Jennifer A; Lanieri, Leanne; Veale, Karen; Costoplus, Juliet A; Skaletskaya, Anna; Gabriel, Rabih; Salomon, Paulin; Wu, Rui; Qiu, Qifeng; Erickson, Hans K; Lambert, John M; Chari, Ravi V J; Widdison, Wayne C

    2016-06-01

    A triglycyl peptide linker (CX) was designed for use in antibody -: drug conjugates (ADC), aiming to provide efficient release and lysosomal efflux of cytotoxic catabolites within targeted cancer cells. ADCs comprising anti-epithelial cell adhesion molecule (anti-EpCAM) and anti-EGFR antibodies with maytansinoid payloads were prepared using CX or a noncleavable SMCC linker (CX and SMCC ADCs). The in vitro cytotoxic activities of CX and SMCC ADCs were similar for several cancer cell lines; however, the CX ADC was more active (5-100-fold lower IC50) than the SMCC ADC in other cell lines, including a multidrug-resistant line. Both CX and SMCC ADCs showed comparable MTDs and pharmacokinetics in CD-1 mice. In Calu-3 tumor xenografts, antitumor efficacy was observed with the anti-EpCAM CX ADC at a 5-fold lower dose than the corresponding SMCC ADC in vivo Similarly, the anti-EGFR CX ADC showed improved antitumor activity over the respective SMCC conjugate in HSC-2 and H1975 tumor models; however, both exhibited similar activity against FaDu xenografts. Mechanistically, in contrast with the charged lysine-linked catabolite of SMCC ADC, a significant fraction of the carboxylic acid catabolite of CX ADC could be uncharged in the acidic lysosomes, and thus diffuse out readily into the cytosol. Upon release from tumor cells, CX catabolites are charged at extracellular pH and do not penetrate and kill neighboring cells, similar to the SMCC catabolite. Overall, these data suggest that CX represents a promising linker option for the development of ADCs with improved therapeutic properties. Mol Cancer Ther; 15(6); 1311-20. ©2016 AACR. ©2016 American Association for Cancer Research.

  17. Stability, Intracellular Delivery, and Release of siRNA from Chitosan Nanoparticles Using Different Cross-Linkers.

    Directory of Open Access Journals (Sweden)

    Maria Abdul Ghafoor Raja

    Full Text Available Chitosan (CS nanoparticles have been extensively studied for siRNA delivery; however, their stability and efficacy are highly dependent on the types of cross-linker used. To address this issue, three common cross-linkers; tripolyphosphate (TPP, dextran sulphate (DS and poly-D-glutamic acid (PGA were used to prepare siRNA loaded CS-TPP/DS/PGA nanoparticles by ionic gelation method. The resulting nanoparticles were compared with regard to their physicochemical properties including particle size, zeta potential, morphology, binding and encapsulation efficiencies. Among all the formulations prepared with different cross linkers, CS-TPP-siRNA had the smallest particle size (ranged from 127 ± 9.7 to 455 ± 12.9 nm with zeta potential ranged from +25.1 ± 1.5 to +39.4 ± 0.5 mV, and high entrapment (>95% and binding efficiencies. Similarly, CS-TPP nanoparticles showed better siRNA protection during storage at 4˚C and as determined by serum protection assay. TEM micrographs revealed the assorted morphology of CS-TPP-siRNA nanoparticles in contrast to irregular morphology displayed by CS-DS-siRNA and CS-PGA-siRNA nanoparticles. All siRNA loaded CS-TPP/DS/PGA nanoparticles showed initial burst release followed by sustained release of siRNA. Moreover, all the formulations showed low and concentration-dependent cytotoxicity with human colorectal cancer cells (DLD-1, in vitro. The cellular uptake studies with CS-TPP-siRNA nanoparticles showed successful delivery of siRNA within cytoplasm of DLD-1 cells. The results demonstrate that ionically cross-linked CS-TPP nanoparticles are biocompatible non-viral gene delivery system and generate a solid ground for further optimization studies, for example with regard to steric stabilization and targeting.

  18. Hydrazine Sulfate (PDQ)

    Science.gov (United States)

    ... health professional versions have detailed information written in technical language. The patient versions are written in easy- ... citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230, ...

  19. Hydrazine APU Starter Development.

    Science.gov (United States)

    1983-06-01

    would not rotate and was removed for inspection. Run 18 - For this series the phenolic blades were lubricated with Molycote Z applied as a spray prior... pyrolytic carbon blades fabricated by Hitco. Using the results of the previous tests, the blades were vented on the back side and set up to operate with...delamination of the reinforced pyrolytic material at one end of each blade on the high pressure side of the blade near the stator interface. The

  20. Construction of Covalent Organic Frameworks Bearing Three Different Kinds of Pores through the Heterostructural Mixed Linker Strategy.

    Science.gov (United States)

    Pang, Zhong-Fu; Xu, Shun-Qi; Zhou, Tian-You; Liang, Rong-Ran; Zhan, Tian-Guang; Zhao, Xin

    2016-04-13

    It is very important to create novel topologies and improve structural complexity for covalent organic frameworks (COFs) that might lead to unprecedented properties and applications. Despite the progress achieved over the past decade, the structural diversity and complexity of COFs are quite limited. In this Communication, we report the construction of COFs bearing three different kinds of pores through the heterostructural mixed linker strategy involving the condensation of a D2h-symmetric tetraamine and two C2-symmetric dialdehydes of different lengths. The complicated structures of the triple-pore COFs have been confirmed by powder X-ray diffraction and pore size distribution analyses.

  1. Biocompatible artificial DNA linker that is read through by DNA polymerases and is functional in Escherichia coli.

    Science.gov (United States)

    El-Sagheer, Afaf H; Sanzone, A Pia; Gao, Rachel; Tavassoli, Ali; Brown, Tom

    2011-07-12

    A triazole mimic of a DNA phosphodiester linkage has been produced by templated chemical ligation of oligonucleotides functionalized with 5'-azide and 3'-alkyne. The individual azide and alkyne oligonucleotides were synthesized by standard phosphoramidite methods and assembled using a straightforward ligation procedure. This highly efficient chemical equivalent of enzymatic DNA ligation has been used to assemble a 300-mer from three 100-mer oligonucleotides, demonstrating the total chemical synthesis of very long oligonucleotides. The base sequences of the DNA strands containing this artificial linkage were copied during PCR with high fidelity and a gene containing the triazole linker was functional in Escherichia coli.

  2. Design, Synthesis, and Biological Evaluation of a Novel Water-soluble Prodrug of Docetaxel with Amino Acid as a Linker.

    Science.gov (United States)

    Ma, Huan; Chen, Gang; Wang, Tao; Li, Qingeng; Liu, Yan

    2016-09-01

    The synthesis and preliminary evaluation of derivatives of docetaxel with novel amino acid as a linker named as LK-193˜LK-196 was described. The C2'-modified compound LK-196 behaves as a prodrug; that is, docetaxel is generated upon exposure to human plasma. The compound was also found to have greatly improved water solubility. The pharmacodynamic results showed LK-196 had the self-evident inhibitory effect on tumor growth in vivo, which is a promising candidate for further biological evaluation. © 2016 John Wiley & Sons A/S.

  3. Last-Step Enzymatic [(18) F]-Fluorination of Cysteine-Tethered RGD Peptides Using Modified Barbas Linkers.

    Science.gov (United States)

    Zhang, Qingzhi; Dall'Angelo, Sergio; Fleming, Ian N; Schweiger, Lutz F; Zanda, Matteo; O'Hagan, David

    2016-07-25

    We report a last-step fluorinase-catalyzed [(18) F]-fluorination of a cysteine-containing RGD peptide. The peptide was attached through sulfur to a modified and more hydrophilic variant of the recently disclosed Barbas linker which was itself linked to a chloroadenosine moiety via a PEGylated chain. The fluorinase was able to use this construct as a substrate for a transhalogenation reaction to generate [(18) F]-radiolabeled RGD peptides, which retained high affinity to cancer-cell relevant αv β3 integrins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Deconjugation of N-glucuronide conjugated metabolites with hydrazine hydrate - Biomarkers for exposure to the food-borne carcinogen 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lauritz

    2007-01-01

    of PhIP metabolites were unsusceptible to treatment with beta-glucuronidase indicating that these are N-glucuronides. Treatment of the conjugates with hydrazine hydrate, however, resulted in complete hydrolysis of the glucuronic acid conjugates as well as in reduction to the parent amine of metabolites...

  5. Photo-control of peptide conformation on a timescale of seconds with a conformationally constrained, blue-absorbing, photo-switchable linker.

    Science.gov (United States)

    Beharry, Andrew A; Sadovski, Oleg; Woolley, G Andrew

    2008-12-07

    Azobenzene derivatives can be used to reversibly photo-regulate conformation and activity when introduced as intramolecular bridges in peptides and proteins. Here we report the design, synthesis, and characterization of an azobenzene derivative that absorbs between 400-450 nm in aqueous solution to produce the cis isomer, and relaxes back to the trans isomer with a half-life of a few seconds at room temperature. In the trans form, the linker can span a distance of approximately 25 A, so that it can bridge Cys residues spaced i, i + 15 in an alpha-helix. Switching of the azobenzene cross-linker from trans to cis causes a decrease in the helix content of peptides where the linker is attached via Cys residues spaced at i, i + 15 and i, i + 14 positions, no change in helix content with Cys residues spaced i, i + 11 and an increase in helix content in a peptide with Cys residues spaced at i, i + 7. In the presence of 10 mM reduced glutathione, the azobenzene cross-linker continued to photo-switch after 24 hours. This cross-linker design thus expands the possibilities for fast photo-control of peptide and protein structure in biochemical systems.

  6. Modelling a Linker Mix-and-Match Approach for Controlling the Optical Excitation Gaps and Band Alignment of Zeolitic Imidazolate Frameworks.

    Science.gov (United States)

    Grau-Crespo, Ricardo; Aziz, Alex; Collins, Angus W; Crespo-Otero, Rachel; Hernández, Norge C; Rodriguez-Albelo, L Marleny; Ruiz-Salvador, A Rabdel; Calero, Sofia; Hamad, Said

    2016-12-23

    Tuning the electronic structure of metal-organic frameworks is the key to extending their functionality to the photocatalytic conversion of absorbed gases. Herein we discuss how the band edge positions in zeolitic imidazolate frameworks (ZIFs) can be tuned by mixing different imidazole-based linkers within the same structure. We present the band alignment for a number of known and hypothetical Zn-based ZIFs with respect to the vacuum level. Structures with a single type of linker exhibit relatively wide band gaps; however, by mixing linkers of a low-lying conduction edge with linkers of a high-lying valence edge, we can predict materials with ideal band positions for visible-light water splitting and CO2 reduction photocatalysis. By introducing copper in the tetrahedral position of the mixed-linker ZIFs, it would be possible to increase both photo-absorption and the electron-hole recombination times. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  7. One-pot DNA construction for synthetic biology: the Modular Overlap-Directed Assembly with Linkers (MODAL) strategy.

    Science.gov (United States)

    Casini, Arturo; MacDonald, James T; De Jonghe, Joachim; Christodoulou, Georgia; Freemont, Paul S; Baldwin, Geoff S; Ellis, Tom

    2014-01-01

    Overlap-directed DNA assembly methods allow multiple DNA parts to be assembled together in one reaction. These methods, which rely on sequence homology between the ends of DNA parts, have become widely adopted in synthetic biology, despite being incompatible with a key principle of engineering: modularity. To answer this, we present MODAL: a Modular Overlap-Directed Assembly with Linkers strategy that brings modularity to overlap-directed methods, allowing assembly of an initial set of DNA parts into a variety of arrangements in one-pot reactions. MODAL is accompanied by a custom software tool that designs overlap linkers to guide assembly, allowing parts to be assembled in any specified order and orientation. The in silico design of synthetic orthogonal overlapping junctions allows for much greater efficiency in DNA assembly for a variety of different methods compared with using non-designed sequence. In tests with three different assembly technologies, the MODAL strategy gives assembly of both yeast and bacterial plasmids, composed of up to five DNA parts in the kilobase range with efficiencies of between 75 and 100%. It also seamlessly allows mutagenesis to be performed on any specified DNA parts during the process, allowing the one-step creation of construct libraries valuable for synthetic biology applications.

  8. Improved expression and purification of sigma 1 receptor fused to maltose binding protein by alteration of linker sequence.

    Science.gov (United States)

    Gromek, Katarzyna A; Meddaugh, Hannah R; Wrobel, Russell L; Suchy, Fabian P; Bingman, Craig A; Primm, John G; Fox, Brian G

    2013-06-01

    Sigma 1 receptor (S1R) is a eukaryotic membrane protein that functions as an inter-organelle signaling modulator and chaperone. Here we report an improved expression of S1R in Escherichia coli as a fusion to maltose binding protein (MBP) and a high-yield purification. Variants with linking amino acid sequences consisting of 0-5 alanine residues between MBP and S1R were created and tested in several E. coli expression strains in order to determine the best combination of construct and host for production of active MBP-S1R. Among the linker variations, the protein containing a 4-Ala linker exhibited superior expression characteristics (MBP-4A-S1R); this construct was most productively paired with E. coli B834-pRARE2 and a chemically defined growth and expression medium. A 3-step purification was developed, including extraction from the E. coli membrane fraction using a mixture of Triton X-100 and n-dodecyl-beta-D-maltopyranoside identified by screening constrainted by retention of binding function, and purification by amylose affinity and gel filtration chromatographies. This procedure yields ∼3.5mg of purified fusion protein per L of bacterial culture medium. Purified MBP-4A-S1R showed a 175-fold purification from the starting cellular lysate with respect to specific ligand binding activity, and is stable during concentration and freeze-thaw cycling. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Novel roles of Caenorhabditis elegans heterochromatin protein HP1 and linker histone in the regulation of innate immune gene expression.

    Science.gov (United States)

    Studencka, Maja; Konzer, Anne; Moneron, Gael; Wenzel, Dirk; Opitz, Lennart; Salinas-Riester, Gabriela; Bedet, Cecile; Krüger, Marcus; Hell, Stefan W; Wisniewski, Jacek R; Schmidt, Henning; Palladino, Francesca; Schulze, Ekkehard; Jedrusik-Bode, Monika

    2012-01-01

    Linker histone (H1) and heterochromatin protein 1 (HP1) are essential components of heterochromatin which contribute to the transcriptional repression of genes. It has been shown that the methylation mark of vertebrate histone H1 is specifically recognized by the chromodomain of HP1. However, the exact biological role of linker histone binding to HP1 has not been determined. Here, we investigate the function of the Caenorhabditis elegans H1 variant HIS-24 and the HP1-like proteins HPL-1 and HPL-2 in the cooperative transcriptional regulation of immune-relevant genes. We provide the first evidence that HPL-1 interacts with HIS-24 monomethylated at lysine 14 (HIS-24K14me1) and associates in vivo with promoters of genes involved in antimicrobial response. We also report an increase in overall cellular levels and alterations in the distribution of HIS-24K14me1 after infection with pathogenic bacteria. HIS-24K14me1 localization changes from being mostly nuclear to both nuclear and cytoplasmic in the intestinal cells of infected animals. Our results highlight an antimicrobial role of HIS-24K14me1 and suggest a functional link between epigenetic regulation by an HP1/H1 complex and the innate immune system in C. elegans.

  10. The HCN4 channel mutation D553N associated with bradycardia has a C-linker mediated gating defect.

    Science.gov (United States)

    Netter, Michael F; Zuzarte, Marylou; Schlichthörl, Günter; Klöcker, Nikolaj; Decher, Niels

    2012-01-01

    The D553N mutation located in the C-linker of the cardiac pacemaker channel HCN4 is thought to cause sino-atrial dysfunction via a pronounced dominant-negative trafficking defect. Since HCN4 mutations usually have a minor defect in channel gating, it was our aim to further characterize the disease causing mechanism of D553N. Fluorescence microscopy, FACS, TEVC and patch-clamp recordings were performed to characterize D553N. Surprisingly, we found that D553N channels reach the plasma membrane and have no apparent trafficking defect. Co-expression of D553N with HCN4 also revealed no dominant-negative effect on wild-type channels. Consistent with the normal cell surface expression of D553N, it was possible to extensively characterize D553N mutants in Xenopus oocytes and mammalian cells. D553N channels generate currents with reduced amplitude, while the kinetics of activation and deactivation are not altered. While the regulation of D553N by tyrosine kinases is normal, we observed a change in the cAMP regulation which however cannot account for the strong loss-of-function of the mutant. The pronounced current reduction and the regular surface expression indicate a major gating defect of the C-linker gate. We hypothesize that the D553N mutation stabilizes a previously reported salt bridge important for the gating of the channel. Copyright © 2012 S. Karger AG, Basel.

  11. Comparative photophysical investigation of oxygen and sulfur as covalent linkers on octaalkylamino substituted zinc(II) phthalocyanines.

    Science.gov (United States)

    Strassert, Cristian Alejandro; Bilmes, Gabriel Mario; Awruch, Josefina; Dicelio, Lelia Elina

    2008-06-01

    This work describes a systematic comparison of oxygen and sulfur as covalent linkers on octasubstituted zinc(II) phthalocyaninates. Most photophysical parameters that make phthalocyanines technologically relevant, e.g. molar absorption coefficients, fluorescence, triplet and singlet oxygen quantum yields, are essentially unaffected by the substitution. The energy content of the first triplet state was observed to be close to the first singlet state of molecular oxygen for both spacers, as follows from photoacoustic determinations. Nonetheless, a bathochromic shift of 30 nm in the absorption and emission maxima, and of 60 nm in the triplet-triplet absorption spectra were observed when alkyloxyl and alkylsulfanyl moieties were alternatively present. Fluorescence quantum yields proved to be much more sensitive towards aggregation than the absorption spectra. Therefore, a novel fluorescence data analysis provided aggregation parameters and photophysical properties of the monomeric species. It was observed that the tendency towards dimerization is slightly higher with sulfur linkers. These results set a foundation for the rational design of conveniently substituted phthalocyaninates with different connectors between the macrocycle and the side chains.

  12. Probing the Influence of Linker Length and Flexibility in the Design and Synthesis of New Trehalase Inhibitors

    Directory of Open Access Journals (Sweden)

    Giampiero D’Adamio

    2018-02-01

    Full Text Available This work aims to synthesize new trehalase inhibitors selective towards the insect trehalase versus the porcine trehalase, in view of their application as potentially non-toxic insecticides and fungicides. The synthesis of a new pseudodisaccharide mimetic 8, by means of a stereoselective α-glucosylation of the key pyrrolizidine intermediate 13, was accomplished. The activity of compound 8 as trehalase inhibitor towards C. riparius trehalase was evaluated and the results showed that 8 was active in the μM range and showed a good selectivity towards the insect trehalase. To reduce the overall number of synthetic steps, simpler and more flexible disaccharide mimetics 9–11 bearing a pyrrolidine nucleus instead of the pyrrolizidine core were synthesized. The biological data showed the key role of the linker chain’s length in inducing inhibitory properties, since only compounds 9 (α,β-mixture, bearing a two-carbon atom linker chain, maintained activity as trehalase inhibitors. A proper change in the glucosyl donor-protecting groups allowed the stereoselective synthesis of the β-glucoside 9β, which was active in the low micromolar range (IC50 = 0.78 μM and 12-fold more potent (and more selective than 9α towards the insect trehalase.

  13. The effect of varying the peptide linker length in a single chain variable fragment antibody against wogonin glucuronide.

    Science.gov (United States)

    Paudel, Madan Kumar; Sakamoto, Seiichi; Van Huy, Le; Tanaka, Hiroyuki; Miyamoto, Tomofumi; Morimoto, Satoshi

    2017-06-10

    Peptide linkers of three different lengths were constructed to join the variable regions of the heavy chain (VH) and the light chain (VL) in a single-chain variable fragment antibody (scFv) specific for wogonin glucuronide (Wgn) that has the structure VH-(GGGGS) n -VL (n=3, 5, or 7). The scFv antibodies, which were expressed in Escherichia coli, were derived from an anti-Wgn monoclonal antibody (315A). An indirect competitive enzyme-linked immunosorbent assay (icELISA) was used to evaluate their reactivity and sensitivity, which is also used for quantitative analysis of Wgn. Our results, showed that the reactivity and specificity of the three different scFvs were, in fact, similar. Subsequently, the scFv having a VH-(GGGGS) 3 -VL linker which was slightly better that other two scFvs against Wgn, was applied to indirect competitive ELISA (icELISA) to analyze Scutellariae Radix (S. Radix). The utility of the icELISA was demonstrated for quality control and analysis of S. Radix in this report. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Just a Flexible Linker? The Structural and Dynamic Properties of CBP-ID4 Revealed by NMR Spectroscopy.

    Science.gov (United States)

    Piai, Alessandro; Calçada, Eduardo O; Tarenzi, Thomas; Grande, Alessandro Del; Varadi, Mihaly; Tompa, Peter; Felli, Isabella C; Pierattelli, Roberta

    2016-01-19

    Here, we present a structural and dynamic description of CBP-ID4 at atomic resolution. ID4 is the fourth intrinsically disordered linker of CREB-binding protein (CBP). In spite of the largely disordered nature of CBP-ID4, NMR chemical shifts and relaxation measurements show a significant degree of α-helix sampling in the protein regions encompassing residues 2-25 and 101-128 (1852-1875 and 1951-1978 in full-length CBP). Proline residues are uniformly distributed along the polypeptide, except for the two α-helical regions, indicating that they play an active role in modulating the structural features of this CBP fragment. The two helical regions are lacking known functional motifs, suggesting that they represent thus-far uncharacterized functional modules of CBP. This work provides insights into the functions of this protein linker that may exploit its plasticity to modulate the relative orientations of neighboring folded domains of CBP and fine-tune its interactions with a multitude of partners. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  15. Parsing the roles of neck-linker docking and tethered head diffusion in the stepping dynamics of kinesin.

    Science.gov (United States)

    Zhang, Zhechun; Goldtzvik, Yonathan; Thirumalai, D

    2017-11-14

    Kinesin walks processively on microtubules (MTs) in an asymmetric hand-over-hand manner consuming one ATP molecule per 16-nm step. The individual contributions due to docking of the approximately 13-residue neck linker to the leading head (deemed to be the power stroke) and diffusion of the trailing head (TH) that contributes in propelling the motor by 16 nm have not been quantified. We use molecular simulations by creating a coarse-grained model of the MT-kinesin complex, which reproduces the measured stall force as well as the force required to dislodge the motor head from the MT, to show that nearly three-quarters of the step occurs by bidirectional stochastic motion of the TH. However, docking of the neck linker to the leading head constrains the extent of diffusion and minimizes the probability that kinesin takes side steps, implying that both the events are necessary in the motility of kinesin and for the maintenance of processivity. Surprisingly, we find that during a single step, the TH stochastically hops multiple times between the geometrically accessible neighboring sites on the MT before forming a stable interaction with the target binding site with correct orientation between the motor head and the [Formula: see text] tubulin dimer.

  16. Effect of amide-triazole linkers on the electrochemical and biological properties of ferrocene-carbohydrate conjugates.

    Science.gov (United States)

    Deepthi, Sadanala Bhavya; Trivedi, Rajiv; Giribabu, Lingamallu; Sujitha, Pombala; Kumar, C Ganesh

    2013-01-28

    Amide-triazole linker incorporated ferrocene-carbohydrate conjugates were prepared by adopting a regiospecific copper(II)-catalysed 1,3-cycloaddition of ferrocenoyl propargylamide and isopropylidene/acetyl protected carbohydrate azides. Hydrophilic ferrocene glycoside with an amide-triazole linker was synthesised by deacetylation of the hydroxyl groups. All the new compounds were characterised by UV-visible and electrochemical studies and they were found to be stable in organic solvents as well as in the buffer system under physiological conditions (pH = 7.0). The diffusion coefficient (D(f)) of the conjugates was also calculated by means of cyclic voltammetric studies. It was observed that while the molecular weight of the compounds had no significant effect on the diffusion coefficient, the hydrophobic/hydrophilic nature of the carbohydrate scaffold displayed varied diffusion coefficient values. Stabilization of the compounds in buffer solution under physiological pH led to almost identical diffusion coefficient values. The compounds derived from xylose and ribose exhibited cytotoxicity on hormone-dependent and hormone-independent breast cancer cell lines, whereas the conjugates derived from glucose and galactose were found to be non-toxic in nature. The compounds did not show any antimicrobial activity against Gram-positive and Gram-negative pathogens.

  17. Improving the performance of DomainDiscovery of protein domain boundary assignment using inter-domain linker index

    Directory of Open Access Journals (Sweden)

    Zomaya Albert Y

    2006-12-01

    Full Text Available Abstract Background Knowledge of protein domain boundaries is critical for the characterisation and understanding of protein function. The ability to identify domains without the knowledge of the structure – by using sequence information only – is an essential step in many types of protein analyses. In this present study, we demonstrate that the performance of DomainDiscovery is improved significantly by including the inter-domain linker index value for domain identification from sequence-based information. Improved DomainDiscovery uses a Support Vector Machine (SVM approach and a unique training dataset built on the principle of consensus among experts in defining domains in protein structure. The SVM was trained using a PSSM (Position Specific Scoring Matrix, secondary structure, solvent accessibility information and inter-domain linker index to detect possible domain boundaries for a target sequence. Results Improved DomainDiscovery is compared with other methods by benchmarking against a structurally non-redundant dataset and also CASP5 targets. Improved DomainDiscovery achieves 70% accuracy for domain boundary identification in multi-domains proteins. Conclusion Improved DomainDiscovery compares favourably to the performance of other methods and excels in the identification of domain boundaries for multi-domain proteins as a result of introducing support vector machine with benchmark_2 dataset.

  18. Chemical Synthesis, Crystal Structure and Enzymatic Evaluation of a Dinucleotide Spore Photoproduct Analogue Containing a Formacetal Linker

    Science.gov (United States)

    Lin, Gengjie; Chen, Chun-Hsing; Pink, Maren; Pu, Jingzhi; Li, Lei

    2011-01-01

    Spore photoproduct (SP) is the exclusive DNA photodamage product found in bacterial endospores. Its photoformation and repair by a metal-loenzyme spore photoproduct lyase (SPL) composes the unique SP biochemistry. Despite the fact that the SP was discovered almost 50 years ago, its crystal structure is still unknown and the lack of structural information greatly hinders the study of SP biochemistry. Employing a formacetal linker and organic synthesis, we successfully prepared a dinucleotide SP isostere 5R-CH2SP, which contains a neutral CH2 moiety between the two thymine residues instead of a phosphate. The neutral linker dramatically facilitates the crystallization process, allowing us to obtain the crystal structure for this intriguing thymine dimer half a century after its discovery. Further ROESY spectroscopic, DFT computational, and enzymatic studies of this 5R-CH2SP compound prove that it possesses similar properties with the 5R-SP species, suggesting that the revealed structure truly reflects that of SP generated in Nature. PMID:21780208

  19. Structural, luminescent, and magnetic properties of three novel three-dimensional metal-organic frameworks based on hexadentate N,N'-bis(4-picolinoyl)hydrazine.

    Science.gov (United States)

    Fang, Zhen-Lan; Yu, Rong-Min; He, Jian-Gang; Zhang, Qi-Sheng; Zhao, Zhen-Guo; Lu, Can-Zhong

    2009-08-17

    Three novel microporous three-dimensional (3-D) metal-organic framework materials [ML](n) [M = Ni, Co, Cd; L = N,N'-bis(4-picolinoyl)hydrazine] were obtained from hydrothermal reactions. The organic ligand L was formed through the in situ ring-opening hydrolysis reaction of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole with the assistance of metal ions. Single-crystal X-ray diffraction studies reveal that complexes 1-3 adopt 6-connected 3-D networks of distorted alpha-Po topology, which are built from non-interpenetrated (4,4) grids cross-linked by zigzag chains. These isomorphic complexes are all of high thermal stability, but some other physical properties are quite different because of their different metal centers. Antiferromagnetic exchange was observed between Ni(II) centers of complex 1, while ferromagnetic for Co(II) centers of complex 2. Complex 3 exhibits strong fluorescence emission.

  20. An all-atom model of the chromatin fiber containing linker histones reveals a versatile structure tuned by the nucleosomal repeat length.

    Directory of Open Access Journals (Sweden)

    Hua Wong

    Full Text Available In the nucleus of eukaryotic cells, histone proteins organize the linear genome into a functional and hierarchical architecture. In this paper, we use the crystal structures of the nucleosome core particle, B-DNA and the globular domain of H5 linker histone to build the first all-atom model of compact chromatin fibers. In this 3D jigsaw puzzle, DNA bending is achieved by solving an inverse kinematics problem. Our model is based on recent electron microscopy measurements of reconstituted fiber dimensions. Strikingly, we find that the chromatin fiber containing linker histones is a polymorphic structure. We show that different fiber conformations are obtained by tuning the linker histone orientation at the nucleosomes entry/exit according to the nucleosomal repeat length. We propose that the observed in vivo quantization of nucleosomal repeat length could reflect nature's ability to use the DNA molecule's helical geometry in order to give chromatin versatile topological and mechanical properties.

  1. Next-generation bis-locked nucleic acids with stacking linker and 2'-glycylamino-LNA show enhanced DNA invasion into supercoiled duplexes

    DEFF Research Database (Denmark)

    Geny, Sylvain; Moreno, Pedro M D; Krzywkowski, Tomasz

    2016-01-01

    nucleobases, a new strategy previously not applied for any type of clamp-constructs. Although the Hoogsteen-arm limits the invasion, upon incorporation of the stacking linker, bisLNA invasion is significantly more efficient than for non-clamp, or nucleotide-linker containing LNA-constructs. Further...... improvements were obtained by substituting LNA with 2'-glycylamino-LNA, contributing a positive charge. For regular bisLNAs a 14-nt tail significantly enhances invasion. However, when two stacking linkers were incorporated, tail-less bisLNAs were able to efficiently invade. Finally, successful targeting...... of plasmids inside bacteria clearly demonstrates that strand invasion can take place in a biologically relevant context....

  2. Air oxidation of hydrazine. 1. Reaction kinetics on natural kaolinites, halloysites, and model substituent layers with varying iron and titanium oxide and O- center contents

    Science.gov (United States)

    Coyne, L.; Mariner, R.; Rice, A.

    1991-01-01

    Air oxidation of hydrazine was studied by using a group of kaolinites, halloysites, and substituent oxides as models for the tetrahedral and octahedral sheets. The rate was found to be linear with oxygen. The stoichiometry showed that oxygen was the primary oxidant and that dinitrogen was the only important nitrogen-containing product. The rates on kaolinites were strongly inhibited by water. Those on three-dimensional silica and gibbsite appeared not to be. That on a supposedly layered silica formed from a natural kaolinite by acid leaching showed transitional behavior--slowed relative to that expected from a second-order reaction relative to that on the gibbsite and silica but faster than those on the kaolinites. The most striking result of the reaction was the marked increase in the rate of reaction of a constant amount of hydrazine as the amount of clay was increased. The increase was apparent (in spite of the water inhibition at high conversions) over a 2 order of magnitude variation of the clay weight. The weight dependence was taken to indicate that the role of the clay is very important, that the number of reactive centers is very small, or that they may be deactivated over the course of the reaction. In contrast to the strong dependence on overall amount of clay, the variation of amounts of putative oxidizing centers, such as structural Fe(III), admixed TiO2 or Fe2O3, or O- centers, did not result in alteration of the rate commensurate with the degree of variation of the entity in question. Surface iron does play some role, however, as samples that were pretreated with a reducing agent were less active as catalysts than the parent material. These results were taken to indicate either that the various centers interact to such a degree that they cannot be considered independently or that the reaction might proceed by way of surface complexation, rather than single electron transfers.

  3. Maximizing the Photocatalytic Activity of Metal-Organic Frameworks with Aminated-Functionalized Linkers: Substoichiometric Effects in MIL-125-NH2.

    Science.gov (United States)

    Chambers, Matthew B; Wang, Xia; Ellezam, Laura; Ersen, Ovidiu; Fontecave, Marc; Sanchez, Clément; Rozes, Laurence; Mellot-Draznieks, Caroline

    2017-06-21

    Despite the promise of utilizing metal-organic frameworks (MOFs) as highly tunable photocatalytic materials, systematic studies that interrogate the relationship between their catalytic performances and the amount of functionalized linkers are lacking. Aminated linkers are known to enhance the absorption of light and afford photocatalysis with MOFs under visible-light irradiation. However, the manner in which the photocatalytic performances are impacted by the amount of such linkers is poorly understood. Here, we assess the photocatalytic activity of MIL-125, a TiO2/1,4-benzenedicarboxylate (bdc) MOF for the oxidation of benzyl alcohol to benzaldehyde when increasing amounts of bdc-NH2 linkers (0%, 20%, 46%, 70%, and 100%) are incorporated in the framework. Analytical TEM allowed assessing the homogeneous localization of bdc-NH2 in these mixed-linker MOFs. Steady state reaction rates reveal two regimes of catalytic performances: a first linear regime up to ∼50% bdc-NH2 into the hybrid framework whereby increased amounts of bdc-NH2 yielded increased photocatalytic rates, followed by a plateau up to 100% bdc-NH2. This unexpected "saturation" of the catalytic activity above ∼50% bdc-NH2 content in the framework whatever the wavelength filters used demonstrates that amination of all linkers of the MOF is not required to obtain the maximum photocatalytic activity. This is rationalized on the basis of mixed-valence Ti3+/Ti4+ intermediate catalytic centers revealed by electron spin resonance (ESR) measurements and recent knowledge of lifetime excited states in MIL-125-type of solids.

  4. Substitutions in conserved regions preceding and within the linker affect activity and flexibility of tRNase ZL, the long form of tRNase Z.

    Directory of Open Access Journals (Sweden)

    Makenzie Saoura

    Full Text Available The enzyme tRNase Z, a member of the metallo-β-lactamase family, endonucleolytically removes 3' trailers from precursor tRNAs, preparing them for CCA addition and aminoacylation. The short form of tRNase Z, tRNase ZS, functions as a homodimer and is found in all prokaryotes and some eukaryotes. The long form, tRNase ZL, related to tRNase ZS through tandem duplication and found only in eukaryotes, possesses ~2,000-fold greater catalytic efficiency than tRNase ZS. tRNase ZL consists of related but diverged amino and carboxy domains connected by a flexible linker (also referred to as a flexible tether and functions as a monomer. The amino domain retains the flexible arm responsible for substrate recognition and binding while the carboxy domain retains the active site. The linker region was explored by Ala-scanning through two conserved regions of D. melanogaster tRNase Z: NdomTprox, located at the carboxy end of the amino domain proximal to the linker, and Tflex, a flexible site in the linker. Periodic substitutions in a hydrophobic patch (F329 and L332 at the carboxy end of NdomTprox show 2,700 and 670-fold impairment relative to wild type, respectively, accompanied by reduced linker flexibility at N-T inside the Ndom- linker boundary. The Ala substitution for N378 in the Tflex region has 10-fold higher catalytic efficiency than wild type and locally decreased flexibility, while the Ala substitution at R382 reduces catalytic efficiency ~50-fold. These changes in pre-tRNA processing kinetics and protein flexibility are interpreted in light of a recent crystal structure for S. cerevisiae tRNase Z, suggesting transmission of local changes in hydrophobicity into the skeleton of the amino domain.

  5. The influence of different linker modifications on the catalytic activity and cellulose affinity of cellobiohydrolase Cel7A from Hypocrea jecorina

    DEFF Research Database (Denmark)

    Badino, Silke Flindt; Bathke, Jenny Kim; Sørensen, Trine Holst

    2017-01-01

    , of the linker and its glycans, have been widely discussed, but experimental evidence remains sparse. One of the most studied cellulose degrading enzymes is the multi-domain cellobiohydrolase Cel7A from Hypocrea jecorina. Here, we designed variants of Cel7A with mutations in the linker region to elucidate...... interactions. However, a variant with several inserted glycosylation sites near the CBM also showed lower affinity for the substrate compared to the wild-type, and we suggest that substrate interactions of the glycans depend on their exact location as well as other factors such as changes in structure...

  6. Yeast linker histone Hho1p is required for efficient RNA polymerase I processivity and transcriptional silencing at the ribosomal DNA

    OpenAIRE

    Levy, Anat; Eyal, Miri; Hershkovits, Gitit; Salmon-Divon, Mali; Klutstein, Michael; Katcoff, Don Jay

    2008-01-01

    Nucleosome core particles in eukaryotes are linked by a stretch of DNA that is usually associated with a linker histone. Here, we show in yeast, that the presence of yeast linker histone Hho1p represses expression of a pol II transcribed gene (MET15) embedded in the rDNA. In vivo deletions of Hho1p sequences showed that the second globular domain is sufficient for that repression, whereas the presence of the N terminus is required for its derepression. In contrast, a run-on assay confirmed by...

  7. Study of Supported Nickel Catalysts Prepared by Aqueous Hydrazine Method. Hydrogenating Properties and Hydrogen Storage: Support Effect. Silver Additive Effect; Catalyseurs de nickel supportes prepares par la methode de l'hydrazine aqueuse. Proprietes hydrogenantes et stockage d'hydrogene. Effet du support. Effet de l'ajout d'argent

    Energy Technology Data Exchange (ETDEWEB)

    Wojcieszak, R

    2006-06-15

    We have studied Ni or NiAg nano-particles obtained by the reduction of nickel salts (acetate or nitrate) by hydrazine and deposited by simple or EDTA-double impregnation on various supports ({gamma}-Al{sub 2}O{sub 3}, amorphous or crystallized SiO{sub 2}, Nb{sub 2}O{sub 5}, CeO{sub 2} and carbon). Prepared catalysts were characterized by different methods (XRD, XPS, low temperature adsorption and desorption of N{sub 2}, FTIR and FTIR-Pyridine, TEM, STEM, EDS, H{sub 2}-TPR, H{sub 2}-adsorption, H{sub 2}-TPD, isopropanol decomposition) and tested in the gas phase hydrogenation of benzene or as carbon materials in the hydrogen storage at room temperature and high pressure. The catalysts prepared exhibited better dispersion and activity than classical catalysts. TOF's of NiAg/SiO{sub 2} or Ni/carbon catalysts were similar to Pt catalysts in benzene hydrogenation. Differences in support acidity or preparation method and presence of Ag as metal additive play a crucial role in the chemical reduction of Ni by hydrazine and in the final properties of the materials. Ni/carbon catalysts could store significant amounts of hydrogen at room temperature and high pressure (0.53%/30 bars), probably through the hydrogen spillover effect. (author)

  8. Highly Polarizable Triiodide Anions (I3(-)) as Cross-Linkers for Coordination Polymers: Closing the Semiconductive Band Gap.

    Science.gov (United States)

    He, Jun; Cao, Peng; Wu, Chao; Huang, Jiahong; Huang, Jian; He, Yonghe; Yu, Lin; Zeller, Matthias; Hunter, Allen D; Xu, Zhengtao

    2015-07-06

    From a hydrothermal reaction using CuI, KI, and 3,3'5,5'-tetramethyl-4,4'-bipyrazole (TMBP), the triiodide anion I3(-) has been integrated into the water-stable 2D coordination polymer Cu(TMBP)I3 (1). In contrast with other metal triiodide complexes, 1 features remarkably small distortions in the bond distances associated with the I3(-) units (i.e., the Cu-I and I-I bonds), which effectively link up the copper(I) centers into infinite CuI3 chains. The electronic band gaps and electrical conductivity data are also found to be consistent with the I3(-) ion acting as an effective linker across the copper(I) centers.

  9. X-ray crystallographic analysis and DFT calculations of three 'propylene linker' dimers linked by one polystep reaction

    Science.gov (United States)

    Shi, Yan; Tan, Xue-Jie; Xing, Dian-Xiang; Sui, Qi-Cheng; Liu, Bin; Feng, Wen-Quan; Liu, Yun

    2017-06-01

    In this manuscript, we report the synthesis, NMR and single-crystal structures of three propylene linking dimers related with the hydrolytic degradation of one 5,6-dehydronorcantharimide dimer. Special attention was paid to the conformation of propylene linkers in order to understand their changes in the reaction. Statistical analysis of CSD database revealed that a-a, g-a and g-g conformations may have similar stability in most cases and various complicated unpredictable non-covalent interactions may play important role in the formation of final rotamers. In order to reproduce all stable conformations and the energy barriers separating them, full range two-dimensional fully relaxed potential-energy surfaces (PES) scans of six 'propylene linker' dimers were calculated starting from the most stable crystal structures. The PES were scanned along both bridge Csbnd C single bond torsional angles (denoted as θ1 and θ2), while all other internal coordinates were optimized at the DFT/B3LYP/3-21G* level in gas phase. Then all energy minima were re-optimized again at the DFT/B3LYP/6-311 + G(d,p) level both in gas and ethanol solutions in order to evaluate the really stable rotamers. At last, 1D or 2D relaxed PES scans were performed between local stable rotamers to get reliable energy barriers. This method represents a less time-consuming and more reliable approach to the determination of conformational stability of propanediyl bridging chains. The combination of experimental, statistical and theoretical results shows that the observed conformation is jointly determined by the energy levels of the minima, energy barriers separating them, non-covalent interactions and somewhat randomness.

  10. Galangin enhances TGF-β1-mediated growth inhibition by suppressing phosphorylation of threonine 179 residue in Smad3 linker region.

    Science.gov (United States)

    Kwak, Mi-Kyung; Yang, Kyung-Min; Park, Jinah; Lee, Siyoung; Park, Yuna; Hong, Eunji; Sun, Eun Jin; An, Haein; Park, Sujin; Pang, Kyoungwha; Lee, Jihee; Kang, Jin Muk; Kim, Pyunggang; Ooshima, Akira; Kim, Seong-Jin

    2017-12-16

    Smad3 linker phosphorylation is a candidate target for several kinases that play important roles in cancer cell initiation, proliferation and progression. Also, Smad3 is an essential intracellular mediator of TGF-β1-induced transcriptional responses during carcinogenesis. Therefore, it is highly advantageous to identify and develop inhibitors targeting Smad3 linker phosphorylation for the treatment of cancers. Galangin (3,5,7-trihydroxyflavone) has been known to be an active flavonoid showing a cytotoxic effect on several cancer cells. However, the mechanism of action of galangin in various cancers remains unclear, and there has been no report concerning regulation of Smad3 phosphorylation by galangin. In the present study, we show that galangin significantly induced apoptosis and inhibited cell proliferation in the presence of TGF-β1 in both human prostate and pancreatic cancer cell lines. Particularly, galangin effectively inhibits phosphorylation of the Thr-179 site at Smad3 linker region through suppression of CDK4 phosphorylation. Thus, galangin can be a promising candidate as a selective inhibitor to suppress phosphorylation of Smad3 linker region. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. An enzyme-activatable probe with a self-immolative linker for rapid and sensitive alkaline phosphatase detection and cell imaging through a cascade reaction.

    Science.gov (United States)

    Zhang, Hongmei; Xu, Chenglong; Liu, Jie; Li, Xiaohong; Guo, Lin; Li, Xinming

    2015-04-25

    We report the design and synthesis of a novel probe (1) for ALP assay by incorporating a self-immolative linker between a phosphate moiety and resorufin. Because of its good biocompatibility and rapid cell internalization, this probe also exhibited great potential for real-time monitoring of endogenous phosphatase activity in living cells.

  12. A versatile puromycin-linker using cnvK for high-throughput in vitro selection by cDNA display.

    Science.gov (United States)

    Mochizuki, Yuki; Suzuki, Takeru; Fujimoto, Kenzo; Nemoto, Naoto

    2015-10-20

    cDNA display is a powerful in vitro display technology used to explore functional peptides and proteins from a huge library by in vitro selection. In addition to expediting the in vitro selection cycle by using cDNA display, easy and rapid functional analysis of selected candidate clones is crucial for high-throughput screening of functional peptides and proteins. In this report, a versatile puromycin-linker employing an ultrafast photo-cross-linker, 3-cyanovinylcarbazole nucleoside, is introduced. Its utility for both in vitro selection using cDNA display and protein-protein interaction analysis using a surface plasmon resonance (SPR) system is described. Using this versatile puromycin-linker, we demonstrated the model in vitro selection of the FLAG epitope and a SPR-based assay to measure the dissociation constant between the B domain of protein A and immunoglobulin G. Improvement of the puromycin-linker as described herein should make the cDNA display method easier to utilize for design of protein or peptide based affinity reagents. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Traceless Azido Linker for the Solid-Phase Synthesis of NH-1,2,3-Triazoles via Cu-Catalyzed Azide-Alkyne Cycloaddition Reactions

    DEFF Research Database (Denmark)

    Cohrt, Anders Emil; Jensen, Jakob Feldthusen; Nielsen, Thomas Eiland

    2010-01-01

    A broadly useful acid-labile traceless azido linker for the solid-phase synthesis of NH-1,2,3-triazoles is presented. A variety of alkynes were efficiently immobilized on a range of polymeric supports by Cu(I)-mediated azide-alkyne cycloadditions. Supported triazoles showed excellent compatibility...

  14. Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R- and (S-aminopropanediol as an acyclic linker

    Directory of Open Access Journals (Sweden)

    Daniel Lachmann

    2010-02-01

    Full Text Available The Nile Blue chromophore was incorporated into oligonucleotides using “click” chemistry for the postsynthetic modification of oligonucleotides. These were synthesized using DNA building block 3 bearing an alkyne group and reacted with the azide 4. (R-3-amino-1,2-propanediol was applied as the linker between the phosphodiester bridges. Two sets of DNA duplexes were prepared. One set carried the chromophore in an A-T environment, the second set in a G-C environment. Both were characterized by optical spectroscopy. Sequence-dependent fluorescence quenching was applied as a sensitive tool to compare the stacking interactions with respect to the chirality of the acyclic linker attachment. The results were compared to recent results from duplexes that carried the Nile Blue label in a sequentially and structurally identical context, except for the opposite chirality of the linker ((S-3-amino-1,2-propandiol. Only minor, negligible differences were observed. Melting temperatures, UV–vis absorption spectra together with fluorescence quenching data indicate that Nile Blue stacks perfectly between the adjacent base pairs regardless of whether it has been attached via an S- or R-configured linker. This result was supported by geometrically optimized DNA models.

  15. An aptly positioned azido group in the spacer of a protein cross-linker for facile mapping of lysines in close proximity

    NARCIS (Netherlands)

    Kasper, P.T.; Back, J.W.; Vitale, M.R.; Hartog, A.F.; Roseboom, W.; de Koning, L.J.; van Maarseveen, J.H.; Muijsers, A.O.; de Koster, C.G.; de Jong, L.

    2007-01-01

    Cross-links between amino acid residues in close proximity can provide distance constraints for the validation of models of the 3D structure proteins. The mapping of cross-links by the identification of linked peptides in proteolytic digests is facilitated by cleavable cross-linkers that enable

  16. Biological evaluation of tetracationic compounds based on two 1,4-diazabicyclo[2.2.2]octane moieties connected by different linkers.

    Science.gov (United States)

    Burakova, Ekaterina A; Saranina, Irina V; Tikunova, Nina V; Nazarkina, Zhanna K; Laktionov, Pavel P; Karpinskaya, Lubov' A; Anikin, Vadim B; Zarubaev, Vladimir V; Silnikov, Vladimir N

    2016-11-15

    A series of 1,4-diazabicyclo[2.2.2]octane derivatives differing by linker moiety was evaluated for activity against several strains of both Gram-positive and Gram-negative bacteria including drug-resistant strains, one strain of fungus and influenza virus A/Puerto Rico/8/34 (H1N1). All compounds exhibited high antibacterial activity against all bacteria except Proteus vulgaris. The minimum inhibitory concentrations (MICs) of compound 1c with an o-phenylenebismethyl linker and compound 1e with a propylene aliphatic linker were found to be low and were comparable or better to the reference drug ciprofloxacin for Pseudomonas aeruginosa and Staphylococcus aureus. Additionally, a time-kill assay was performed to examine the bactericidal kinetics. Compounds 1c and 1e displayed rapid killing effects against St. aureus and Ps. aeruginosa after 2h. Furthermore, compounds 1a-c with aromatic linkers and compound 1e showed the highest antiviral activity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. A NbO-type metal-organic framework derived from a polyyne-coupled di-isophthalate linker formed in situ.

    Science.gov (United States)

    Zhao, Dan; Yuan, Daqiang; Yakovenko, Andrey; Zhou, Hong-Cai

    2010-06-21

    A NbO-type metal-organic framework, PCN-46, was constructed based on a polyyne-coupled di-isophthalate linker formed in situ. Its lasting porosity was confirmed by N(2) adsorption isotherm, and its H(2), CH(4) and CO(2) adsorption capacity was examined at 77 K and 298 K over a wide pressure range (0-110 bar).

  18. A Series of Robust Copper-Based Triazolyl Isophthalate MOFs: Impact of Linker Functionalization on Gas Sorption and Catalytic Activity †

    Science.gov (United States)

    Junghans, Ulrike; Kobalz, Merten; Erhart, Oliver; Preißler, Hannes; Lincke, Jörg; Möllmer, Jens; Krautscheid, Harald; Gläser, Roger

    2017-01-01

    The synthesis and characterization of an isomorphous series of copper-containing microporous metal-organic frameworks (MOFs) based on triazolyl isophthalate linkers with the general formula ∞3[Cu4(μ3-OH)2(R1-R2-trz-ia)3(H2O)x] are presented. Through size adjustment of the alkyl substituents R1 and/or R2 at the linker, the impact of linker functionalization on structure-property relationships was studied. Due to the arrangement of the substituents towards the cavities, the porosity (pore fraction 28%–39%), as well as the pore size can be adjusted by the size of the substituents of the triazole ring. Thermal analysis and temperature-dependent PXRD studies reveal a thermal stability of the MOFs up to 230 °C due to increasing framework stability through fine-tuning of the linker substitution pattern. Adsorption of CO2 (298 K) shows a decreasing maximum loading with increasing steric demand of the substituents of the triazole ring. Furthermore, the selective oxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) is studied over the MOFs at 323 K in liquid chloroform. The catalytic activity increases with the steric demand of the substituents. Additionally, these isomorphous MOFs exhibit considerable robustness under oxidizing conditions confirmed by CO2 adsorption studies, as well as by the catalytic selective oxidation experiments. PMID:28772698

  19. Ferrocene-donor and 4,5-dicyanoimidazole-acceptor moieties in charge-transfer chromophores with π linkers tailored for second-order nonlinear optics.

    Science.gov (United States)

    Kulhánek, Jiří; Bureš, Filip; Kuznik, Wojciech; Kityk, Iwan V; Mikysek, Tomáš; Růžička, Aleš

    2013-02-01

    A series of new nonlinear optical chromophores (1-15) that were comprised of ferrocene-donor and 4,5-dicyanoimidazole-acceptor moieties and various π linkers of different length were synthesized. Support for the presence of significant DA interactions in these NLO-phores was obtained from the evaluation of the quinoid character of the 1,4-phenylene moieties and their electronic absorption spectra, which featured intense high-energy (HE) bands that were accompanied by less-intense low-energy (LE) bands. The redox behavior of these compounds was investigated by cyclic voltammetry (CV) and by rotating-disc voltammetry (RDV); their electrochemical gaps decreased steadily from 2.64 to 2.09 V. In addition to the experimentally obtained data, DFT calculations of their absorption spectra, HOMO/LUMO levels, and second-order polarizabilities (β) (-2ω,ω,ω) were performed. A structure-property relationship study that was performed by systematically altering the π linker revealed that the intramolecular charge-transfer and nonlinear optical properties of these inorganic-organic hybrid D-π-A systems (1-15) were primarily affected by: 1) The presence of olefinic/acetylenic subunits; 2) the length of the π linker; and 3) the spatial arrangement (planarity) of the π linker. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. The ortho backbone amide linker (o-BAL) is an easily prepared and highly acid-labile handle for solid-phase synthesis

    DEFF Research Database (Denmark)

    Boas, Ulrik; Brask, Jesper; Christensen, J.B.

    2002-01-01

    The tris(alkoxy)benzyl backbone amide linker (BAL) has found widespread application in solid-phase synthesis. The key intermediate for preparation of para BAL (p-BAL) is 2,6-dimethoxy-4-hydroxybenzaldehyde; several reports on its synthesis have appeared. However, the ortho analogue of the handle (o...

  1. Processing and targeting of proteins derived from polyprotein with 2A and LP4/2A as peptide linkers in a maize expression system.

    Directory of Open Access Journals (Sweden)

    He Sun

    Full Text Available In the transformation of multiple genes, gene fusion is an attractive alternative to other methods, including sexual crossing, re-transformation, and co-transformation, among others. The 2A peptide from the foot-and-mouth disease virus (FMDV causes the co-translational "cleavage" of polyprotein and operates in a wide variety of eukaryotic cells. LP4, a linker peptide that originates from a natural polyprotein occurring in the seed of Impatiens balsamina, can be split between the first and second amino acids in post-translational processing. LP4/2A is a hybrid linker peptide that contains the first nine amino acids of LP4 and 20 amino acids of 2A. The three linkers have been used as a suitable technique to link the expression of genes in some transgenic plants, but to date the cleavage efficiency of three linkers have not been comprehensively demonstrated in the same transformation system, especially in the staple crop. To verify the functions of 2A, LP4, and LP4/2A linker peptides in transgenic maize, six fusion protein vectors that each encoded a single open reading frame (ORF incorporating two report genes, Green Fluorescent Protein (GFP and β-glucuronidase (GUS, separated by 2A (or modified 2A, LP4 or LP4/2A were assembled to compare the cleavage efficiency of the three linkers in a maize transient expression system. The results demonstrated the more protein production and higher cleavage splicing efficiency with the polyprotein construct linked by the LP4/2A peptide than those of the polyprotein constructs linked by 2A or LP4 alone. Seven other fusion proteins that each encoded a single ORF incorporating two different genes GFP and Red Fluorecent Protein (RFP with different signal peptides were assembled to study the subcellular localization of genes linked by LP4/2A. The subcellular localization experiments suggested that both types of signal peptide, co-translational and post-translational, could lead their proteins to the target

  2. Desorption of 3,3′-diindolylmethane from imprinted particles: An impact of cross-linker structure on binding capacity and selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Klejn, Dorota; Luliński, Piotr; Maciejewska, Dorota, E-mail: dorota.maciejewska@wum.edu.pl

    2015-11-01

    Here, seven cross-linkers (six polar diacrylates or dimethacrylates of different lengths between double bonds, and one aromatic-divinylbenzene) were used to examine the impact of the cross-linker on binding capacity and selectivity of 3,3′-diindolylmethane (DIM) imprinted material. DIM participates in the suppression of viability of human ovarian and human breast cancer cell lines, but has low bioavailability. The investigations of novel imprinted polymer matrices for improvement of DIM release could allow to utilize not only a potency of DIM but also similar alkaloids, which are the important compounds with pharmacological activity. The bulk, thermal radical copolymerization of the cross-linkers in the presence of 3,3′-diindolylmethane (the template) and allylamine (the functional monomer) in dimethyl sulfoxide or in carbon tetrachloride (porogens) was carried out. The binding capacities of imprinted and non-imprinted polymers were compared, and two polymers (these were prepared using ethylene glycol dimethacrylate and polyethylene glycol dimethacrylate as the cross-linkers) with the highest selectivity and binding capacity were selected to desorption test. The desorption profile of polymer prepared using polyethylene glycol dimethacrylate as the cross-linker revealed sustained release of 3,3′-diindolylmethane, and this system was selected for further optimization of the cross-linker amounts. The morphology and structure of the selected particles were analyzed using SEM micrographs, {sup 13}C CP/MAS NMR spectroscopy, and BET measurements. The desorption of 3,3′-diindolylmethane from poly(allylamine-co-polyethylene glycol dimethacrylate) particles was in accordance with pseudo-second-order kinetics and the simplified Higuchi model indicated the diffusion controlled release of 3,3′-diindolylmethane. - Graphical abstract: Sustained release of 3,3′-diindolylmethane from cavity in imprinted poly(allylamine-co-polyethylene glycol dimethacrylate

  3. Structural Modification on the Lys Linker Enhanced Tumor to Kidney Uptake Ratios of Tc-99m-Labeled RGD-Conjugated Alpha-MSH Hybrid Peptides

    Science.gov (United States)

    Yang, Jianquan; Lu, Jie; Miao, Yubin

    2012-01-01

    The purpose of this study was to examine whether the structural modification on the positively-charged Lys linker could reduce the kidney uptake of 99mTc-labeled Arg-Gly-Asp (RGD)-conjugated alpha-melanocyte stimulating hormone (α-MSH) hybrid peptides. The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys3,4,10, D-Phe7, Arg11]α-MSH3–13 {(Arg11)CCMSH} through a neutral Glycine linker to eliminate the positively-charged amino side chain of Lys linker, or without linker to - delete the Lys linker. The receptor binding affinity of RGD-Gly-(Arg11)CCMSH and RGD-(Arg11)CCMSH was determined in B16/F1 melanoma cells. The melanoma targeting and imaging properties of 99mTc-RGD-Gly-(Arg11)CCMSH and 99mTc-RGD-(Arg11)CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The structural modification on the Lys linker retained low nanomolar receptor binding affinity of RGD-Gly-(Arg11)CCMSH and RGD-(Arg11)CCMSH (1.5 and 1.0 nM, respectively). The structural modification on the Lys linker dramatically decreased the renal uptake of 99mTc-RGD-Gly-(Arg11)CCMSH and 99mTc-RGD-(Arg11)CCMSH by 79% and 77% at 4 h post-injection compared to 99mTc-RGD-Lys-(Arg11)CCMSH. 99mTc-RGD-(Arg11)CCMSH displayed higher melanoma uptake (16.12 ± 3.09% ID/g) than 99mTc-RGD-Gly-(Arg11)CCMSH (11.50 ± 1.01% ID/g) at 2 post-injection. The tumor uptake of 99mTc-RGD-(Arg11)CCMSH was 1.4 times the tumor uptake of 99mTc-RGD-Gly-(Arg11)CCMSH at 2 post-injection. Dramatically enhanced tumor to kidney uptake ratio of 99mTc-RGD-(Arg11)CCMSH suggests that 188Re-RGD-(Arg11)CCMSH may behave in a similar fashion warranting future evaluation for melanoma treatment. PMID:22452443

  4. Structural modification on the Lys linker enhanced tumor to kidney uptake ratios of 99mTc-labeled RGD-conjugated α-MSH hybrid peptides.

    Science.gov (United States)

    Yang, Jianquan; Lu, Jie; Miao, Yubin

    2012-05-07

    The purpose of this study was to examine whether the structural modification on the positively charged Lys linker could reduce the kidney uptake of (99m)Tc-labeled Arg-Gly-Asp (RGD)-conjugated α-melanocyte stimulating hormone (α-MSH) hybrid peptides. The RGD motif {cyclic(Arg-Gly-Asp-D-Tyr-Asp)} was coupled to [Cys(3,4,10), D-Phe(7), Arg(11)]α-MSH(3-13) {(Arg(11))CCMSH} through a neutral glycine linker to eliminate the positively charged amino side chain of the Lys linker or without a linker to delete the Lys linker. The receptor binding affinity of RGD-Gly-(Arg(11))CCMSH and RGD-(Arg(11))CCMSH was determined in B16/F1 melanoma cells. The melanoma targeting and imaging properties of (99m)Tc-RGD-Gly-(Arg(11))CCMSH and (99m)Tc-RGD-(Arg(11))CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The structural modification on the Lys linker retained a low nanomolar receptor binding affinity of RGD-Gly-(Arg(11))CCMSH and RGD-(Arg(11))CCMSH (1.5 and 1.0 nM, respectively). The structural modification on the Lys linker dramatically decreased the renal uptake of (99m)Tc-RGD-Gly-(Arg(11))CCMSH and (99m)Tc-RGD-(Arg(11))CCMSH by 79% and 77% at 4 h postinjection compared to (99m)Tc-RGD-Lys-(Arg(11))CCMSH. (99m)Tc-RGD-(Arg(11))CCMSH displayed a higher melanoma uptake (16.12 ± 3.09% ID/g) than (99m)Tc-RGD-Gly-(Arg(11))CCMSH (11.50 ± 1.01% ID/g) at 2 postinjection. The tumor uptake of (99m)Tc-RGD-(Arg(11))CCMSH was 1.4 times the tumor uptake of (99m)Tc-RGD-Gly-(Arg(11))CCMSH at 2 postinjection. A dramatically enhanced tumor-to-kidney uptake ratio of (99m)Tc-RGD-(Arg(11))CCMSH suggests that (188)Re-RGD-(Arg(11))CCMSH may behave in a similar fashion warranting future evaluation for melanoma treatment.

  5. Interleukin 1 β-induced SMAD2/3 linker modifications are TAK1 dependent and delay TGFβ signaling in primary human mesenchymal stem cells.

    Science.gov (United States)

    van den Akker, Guus G; van Beuningen, Henk M; Vitters, Elly L; Koenders, Marije I; van de Loo, Fons A; van Lent, Peter L; Blaney Davidson, Esmeralda N; van der Kraan, Peter M

    2017-12-01

    Chondrogenic differentiation of mesenchymal stem cells (MSC) requires transforming growth factor beta (TGFβ) signaling. TGFβ binds to the type I receptor activin-like kinase (ALK)5 and results in C-terminal SMAD2/3 phosphorylation (pSMAD2/3C). In turn pSMAD2/3C translocates to the nucleus and regulates target gene expression. Inflammatory mediators are known to exert an inhibitory effect on MSC differentiation. In this study we investigated the effect of interleukin 1 β (IL1β) on SMAD2/3 signaling dynamics and post-translational modifications. Co-stimulation of MSC with TGFβ and IL1β did not affect peak pSMAD2C levels at 1h post-stimulation. Surprisingly, SMAD3 transcriptional activity, as determined by the CAGA12-luciferase reporter construct, was enhanced by co-stimulation of TGFβ and IL1β compared to TGFβ alone. Furthermore, IL1β stimulation induced CAGA12-luciferase activity in a SMAD dependent way. As SMAD function can be modulated independent of canonical TGFβ signaling through the SMAD linker domain, we studied SMAD2 linker phosphorylation at specific threonine and serine residues. SMAD2 linker threonine and serine modifications were observed within 1h following TGFβ, IL1β or TGFβ and IL1β stimulation. Upon co-stimulation linker modified SMAD2 accumulated in the cytoplasm and SMAD2/3 target gene transcription (ID1, JUNB) at 2-4h was inhibited. A detailed time course analysis of IL1β-induced SMAD2 linker modifications revealed a distinct temperospatial pattern compared to TGFβ. Co-stimulation with both factors resulted in a similar kinetic profile as TGFβ alone. Nevertheless, IL1β did subtly alter TGFβ-induced pSMAD2C levels between 8 and 24h post-stimulation, which was reflected by TGFβ target gene expression (PAI1, JUNB). Direct evidence for the importance of SMAD3 linker modifications for the effect of IL1β on TGFβ signaling was obtained by over-expression of SMAD3 or a SMAD3 linker phospho-mutant. Finally, an inhibitor screening was

  6. Linker-based control of electron propagation through ferrocene moieties covalently anchored onto insulator-based nanopores derived from a polystyrene-poly(methylmethacrylate) diblock copolymer.

    Science.gov (United States)

    Li, Feng; Pandey, Bipin; Ito, Takashi

    2012-12-04

    This paper reports the effects of linker length on electron propagation through ferrocene moieties covalently anchored onto insulator-based cylindrical nanopores derived from a cylinder-forming polystyrene-poly(methylmethacrylate) diblock copolymer. These nanopores (24 nm in diameter, 30 nm long) aligned perpendicular to an underlying gold electrode were modified via esterification of their surface COOH groups with OH-terminated ferrocene derivatives having different alkyl linkers (FcCO(CH(2))(n)OH; n = 2, 5, 15). Cyclic voltammograms were measured in 0.1 M NaBF(4) at different scan rates to assess the efficiency of electron propagation through the ferrocene moieties. The redox peaks of the anchored ferrocenes were observed at nanoporous films decorated with FcCO(CH(2))(15)OH and FcCO(CH(2))(5)OH, but not at those with FcCO(CH(2))(2)OH. Importantly, the higher electron propagation efficiency was observed in the use of the longer linker, as shown by the apparent diffusion coefficients (ca. 10(-12) cm(2)/s for n = 15; ca. 10(-13) cm(2)/s for n = 5; no electron propagation for n = 2). The observed electron propagation resulted from electron hopping across relatively large spacing that was controlled by the motion of anchored redox sites (bounded diffusion). The longer linker led to the larger physical displacement range of anchored ferrocene moieties, facilitating the approach of the adjacent ferrocene moieties within a distance required for electron self-exchange reaction. The linker-based control of redox-involved electron propagation on nanostructured, insulating surfaces will provide a means for designing novel molecular electronics and electrochemical sensors.

  7. Immolation of p-Aminobenzyl Ether Linker and Payload Potency and Stability Determine the Cell-Killing Activity of Antibody-Drug Conjugates with Phenol-Containing Payloads.

    Science.gov (United States)

    Zhang, Donglu; Le, Hoa; Cruz-Chuh, Josefa Dela; Bobba, Sudheer; Guo, Jun; Staben, Leanna; Zhang, Chenghong; Ma, Yong; Kozak, Katherine R; Lewis Phillips, Gail D; Vollmar, Breanna S; Sadowsky, Jack D; Vandlen, Richard; Wei, BinQing; Su, Dian; Fan, Peter; Dragovich, Peter S; Khojasteh, S Cyrus; Hop, Cornelis E C A; Pillow, Thomas H

    2018-02-07

    The valine-citrulline (Val-Cit) dipeptide and p-aminobenzyl (PAB) spacer have been commonly used as a cleavable self-immolating linker in ADC design including in the clinically approved ADC, brentuximab vedotin (Adcetris). When the same linker was used to connect to the phenol of the cyclopropabenzindolone (CBI) (P1), the resulting ADC1 showed loss of potency in CD22 target-expressing cancer cell lines (e.g., BJAB, WSU-DLCL2). In comparison, the conjugate (ADC2) of a cyclopropapyrroloindolone (CPI) (P2) was potent despite the two corresponding free drugs having similar picomolar cell-killing activity. Although the corresponding spirocyclization products of P1 and P2, responsible for DNA alkylation, are a prominent component in buffer, the linker immolation was slow when the PAB was connected as an ether (PABE) to the phenol in P1 compared to that in P2. Additional immolation studies with two other PABE-linked substituted phenol compounds showed that electron-withdrawing groups accelerated the immolation to release an acidic phenol-containing payload (to delocalize the negative charge on the anticipated anionic phenol oxygen during immolation). In contrast, efficient immolation of LD4 did not result in an active ADC4 because the payload (P4) had a low potency to kill cells. In addition, nonimmolation of LD5 did not affect the cell-killing potency of its ADC5 since immolation is not required for DNA alkylation by the center-linked pyrrolobenzodiazepine. Therefore, careful evaluation needs to be conducted when the Val-Cit-PAB linker is used to connect antibodies to a phenol-containing drug as the linker immolation, as well as payload potency and stability, affects the cell-killing activity of an ADC.

  8. Self-assembling complexes between binary mixtures of lipids with different linkers and nucleic acids promote universal mRNA, DNA and siRNA delivery.

    Science.gov (United States)

    Colombani, Thibault; Peuziat, Pauline; Dallet, Laurence; Haudebourg, Thomas; Mével, Mathieu; Berchel, Mathieu; Lambert, Olivier; Habrant, Damien; Pitard, Bruno

    2017-03-10

    Protein expression and RNA interference require efficient delivery of DNA or mRNA and small double stranded RNA into cells, respectively. Although cationic lipids are the most commonly used synthetic delivery vectors, a clear need still exists for a better delivery of various types of nucleic acids molecules to improve their biological activity. To optimize the transfection efficiency, a molecular approach consisting in modifying the chemical structure of a given cationic lipid is usually performed, but an alternative strategy could rely on modulating the supramolecular assembly of lipidic lamellar phases sandwiching the nucleic acids molecules. To validate this new concept, we synthesized on one hand two paromomycin-based cationic lipids, with either an amide or a phosphoramide linker, and on the other hand two imidazole-based neutral lipids, having as well either an amide or a phosphoramide function as linker. Combinations of cationic and helper lipids containing the same amide or phosphoramide linkers led to the formation of homogeneous lamellar phases, while hybrid lamellar phases were obtained when the linkers on the cationic and helper lipids were different. Cryo-transmission electron microscopy and fluorescence experiments showed that liposomes/nucleic acids complexes resulting from the association of nucleic acids with hybrid lamellar phases led to complexes that were more stable in the extracellular compartment compared to those obtained with homogeneous systems. In addition, we observed that the most active supramolecular assemblies for the delivery of DNA, mRNA and siRNA were obtained when the cationic and helper lipids possess linkers of different natures. The results clearly show that this supramolecular strategy modulating the property of the lipidic lamellar phase constitutes a new approach for increasing the delivery of various types of nucleic acid molecules. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Synthesis of Au nanoparticles decorated graphene oxide nanosheets: Noncovalent functionalization by TWEEN 20 in situ reduction of aqueous chloroaurate ions for hydrazine detection and catalytic reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Wenbo [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China); Ning, Rui [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Qin, Xiaoyun; Zhang, Yingwei; Chang, Guohui; Liu, Sen; Luo, Yonglan [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China); Sun, Xuping, E-mail: sunxp@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer TWEEN 20 is used as a stabilizing agent for GO as well as a reducing and immobilizing agent for Au nanoparticles. Black-Right-Pointing-Pointer The hydrazine sensor based on the nanocomposites has a fast amperometric response. Black-Right-Pointing-Pointer The detection limit of the hydrazine sensor is estimated to be 78 nM. Black-Right-Pointing-Pointer The nanocomposites also exhibit good catalytic activity toward 4-nitrophenol reduction. - Abstract: In this paper, we develop a cost-effective and simple route for the synthesis of Au nanoparticles (AuNPs) decorated graphene oxide (GO) nanosheets using polyoxyethylene sorbitol anhydride monolaurate (TWEEN 20) as a stabilizing agent for GO as well as a reducing and immobilizing agent for AuNPs. The AuNPs assemble on the surface of TWEEN-functionalized GO by the in situ reduction of HAuCl{sub 4} aqueous solution. The morphologies of these composites were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the resultant AuNPs decorated GO nanosheets (AuNPs/TWEEN/GO) exhibit remarkable catalytic performance for hydrazine oxidation. This hydrazine sensor has a fast amperometric response time of less than 3 s. The linear range is estimated to be from 5 {mu}M to 3 mM (r = 0.999), and the detection limit is estimated to be 78 nM at a signal-to-noise ratio of 3. The AuNPs/TWEEN/GO composites also exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activity via a synergistic effect.

  10. Mechanism of the Fischer reaction. Rearrangement of cyclohexanone N-methylphenylhydrazone and N,N'-dimethyl-N-phenyl-N'-(1-cyclohexenyl)hydrazine to 9-methyl-1,2,3,4-tetrahydrocarbazole

    Energy Technology Data Exchange (ETDEWEB)

    Przheval' skii, N.M.; Kletskii, M.E.; Grandberg, I.I.; Kostromina, L.Yu.

    1985-12-01

    The kinetics of the thermal and acid-catalyzed Fischer reaction of cyclohexanone N-methylphenylhydrazone and N,N'-dimethyl-N-phenyl-N'-(1-cyclohexenyl)hydrazine were studied by a spectrophotometric method. Formation of the carbon-carbon bond proceeds by a (3,3)-sigmatropic shift mechanism. This conclusion was confirmed by MINDO/3 calculations of the rearrangement of a model divinylhydrazine.

  11. A QSAR/QSTR study on the human health impact of the rocket fuel 1,1-dimethyl hydrazine and its transformation products Multicriteria hazard ranking based on partial order methodologies.

    Science.gov (United States)

    Carlsen, Lars; Kenessov, Bulat N; Batyrbekova, Svetlana Ye

    2009-05-01

    The possible impact of the rocket fuel 1,1-dimethyl hydrazine (heptyl) (1) and its transformation products on human health has been studied using (Quantitative) Structure Activity/Toxicity ((Q)SAR/(Q)STR) modelling, including both ADME models and models for acute toxicity, organ specific adverse haematological effects, the cardiovascular and gastrointestinal systems, the kidneys, the liver and the lungs, as well as a model predicting the biological activity of the compounds. It was predicted that all compounds studied are readily bioavailable through oral intake and that significant amounts of the compounds will be freely available in the systemic circulation. In general, the compounds are not predicted to be acutely toxic apart from hydrogen cyanide, whereas several compounds are predicted to cause adverse organ specific human health effects. Further, several compounds are predicted to exhibit high probabilities for potential carcinogenicity, mutagenicity, teratogenicity and/or embryotoxicity. The compounds were ranked based on their predicted human health impact using partial order ranking methodologies that highlight which compounds on a cumulative basis should receive the major attention, i.e., N-nitroso dimethyl amine, 1,1,4,4-tetramethyl tetrazene, trimethyl, trimethyl hydrazine, acetaldehyde dimethyl hydrazone, 1, 1-formyl 2,2-dimethyl hydrazine and formaldehyde dimethyl hydrazone, respectively. Copyright © 2009 Elsevier B.V. All rights reserved.

  12. Non-adiabatic behavior in the homolytic and heterolytic bond dissociation of protonated hydrazine: A guided ion beam and theoretical investigation.

    Science.gov (United States)

    McNary, Christopher P; Armentrout, P B

    2017-09-28

    Threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer was performed on protonated hydrazine and its perdeuterated variant. The dominant dissociation pathways observed were endothermic homolytic and heterolytic cleavages of the N-N bond. The data were analyzed using a statistical model after accounting for internal and kinetic energy distributions, multiple collisions, and kinetic shifts to obtain 0 K bond dissociation energies. Comparison with literature thermochemistry demonstrates that both channels behave non-adiabatically. Heterolytic bond cleavage yields NH2+ + NH3 products, but the NH2+ fragment is in the spin-restricted excited 1A1 state and not in the spin-forbidden ground 3B1 state, whereas homolytic bond cleavage leads to dissociation to the NH3+ + NH2 product asymptote with NH2 in its excited 2A1 state rather than the energetically favored 2B1 state. The rationale for the non-adiabatic behavior observed in the homolytic bond cleavage is revealed by detailed theoretical calculations of the relevant potential energy surfaces and the relevant occupied valence molecular orbitals. These calculations suggest that the non-adiabatic behavior results from conservation of the σ and π character of the binding and lone pair electrons on the nitrogen atoms.

  13. Synthesis, spectroscopic, anticancer, antibacterial and antifungal studies of Ni(II) and Cu(II) complexes with hydrazine carboxamide, 2-[3-methyl-2-thienyl methylene

    Science.gov (United States)

    Chandra, Sulekh; Vandana; Kumar, Suresh

    2015-01-01

    Schiff's base ligand(L) hydrazine carboxamide, 2-[3-methyl-2-thienyl methylene] and its metal complexes have been synthesized and characterized by elemental analysis, molar conductance, various spectroscopic techniques such as electronic, IR, 1H NMR, mass, EPR. Molar conductance of complexes in DMF solution corresponds to non-electrolyte. Complexes have general composition [M(L)2X2], where M = Ni(II) and Cu(II), X = Cl-, NO3-, CH3COO- and ½SO42-. On the basis of above spectral studies, an octahedral geometry has been assigned for Ni(II) complexes and tetragonal geometry for Cu(II) complexes except [Cu(L)2SO4] which possesses five coordinated trigonal bipyramidal geometry. These metal complexes were also tested for their anticancer, antibacterial and antifungal activities to assess their inhibition potential. Anticancer activity of ligand and its metal complexes were evaluated using SRB fluorometric assay and Adriamycin (ADR) was applied as positive control. Schiff's base ligand and its metal complexes were screened for their antibacterial and antifungal activity against Escherichia coli, Bacillus cereus and Aspergillus niger, Aspergillus flavus, respectively. Kirby-Bauer single disk susceptibility test was used for antibacterial activity and well diffusion method for antifungal activity of the compounds on the used fungi.

  14. In-Doped ZnO Hexagonal Stepped Nanorods and Nanodisks as Potential Scaffold for Highly-Sensitive Phenyl Hydrazine Chemical Sensors

    Directory of Open Access Journals (Sweden)

    Ahmad Umar

    2017-11-01

    Full Text Available Herein, we report the growth of In-doped ZnO (IZO nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The as-grown IZO nanomaterials were investigated by several techniques in order to examine their morphological, structural, compositional and optical properties. The detailed investigations confirmed that the grown nanomaterials, i.e., nanorods and nanodisks possess well-crystallinity with wurtzite hexagonal phase and grown in high density. The room-temperature PL spectra exhibited a suppressed UV emissions with strong green emissions for both In-doped ZnO nanomaterials, i.e., nanorods and nanodisks. From an application point of view, the grown IZO nanomaterials were used as a potential scaffold to fabricate sensitive phenyl hydrazine chemical sensors based on the I–V technique. The observed sensitivities of the fabricated sensors based on IZO nanorods and nanodisks were 70.43 μA·mM−1·cm−2 and 130.18 μA·mM−1·cm−2, respectively. For both the fabricated sensors, the experimental detection limit was 0.5 μM, while the linear range was 0.5 μM–5.0 mM. The observed results revealed that the simply grown IZO nanomaterials could efficiently be used to fabricate highly sensitive chemical sensors.

  15. In-Doped ZnO Hexagonal Stepped Nanorods and Nanodisks as Potential Scaffold for Highly-Sensitive Phenyl Hydrazine Chemical Sensors.

    Science.gov (United States)

    Umar, Ahmad; Kim, Sang Hoon; Kumar, Rajesh; Al-Assiri, Mohammad S; Al-Salami, A E; Ibrahim, Ahmed A; Baskoutas, Sotirios

    2017-11-21

    Herein, we report the growth of In-doped ZnO (IZO) nanomaterials, i.e., stepped hexagonal nanorods and nanodisks by the thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The as-grown IZO nanomaterials were investigated by several techniques in order to examine their morphological, structural, compositional and optical properties. The detailed investigations confirmed that the grown nanomaterials, i.e., nanorods and nanodisks possess well-crystallinity with wurtzite hexagonal phase and grown in high density. The room-temperature PL spectra exhibited a suppressed UV emissions with strong green emissions for both In-doped ZnO nanomaterials, i.e., nanorods and nanodisks. From an application point of view, the grown IZO nanomaterials were used as a potential scaffold to fabricate sensitive phenyl hydrazine chemical sensors based on the I-V technique. The observed sensitivities of the fabricated sensors based on IZO nanorods and nanodisks were 70.43 μA·mM-1 cm-2 and 130.18 μA·mM-1 cm-2, respectively. For both the fabricated sensors, the experimental detection limit was 0.5 μM, while the linear range was 0.5 μM-5.0 mM. The observed results revealed that the simply grown IZO nanomaterials could efficiently be used to fabricate highly sensitive chemical sensors.

  16. Synthesis, spectroscopic, DFT and optoelectronic studies of 2-benzylidene-3-hydroxy -1-(5,6-diphenyl-1,2,4-triazine-3-yl)hydrazine metal complexes

    Science.gov (United States)

    Taha, A.; Farag, A. A. M.; Adly, O. M. I.; Roushdy, N.; Shebl, Magdy; Ahmed, H. M.

    2017-07-01

    Metal complexes of Ni(II) and Cu(II) with a new Schiff base, 2-benzylidene-3-hydroxy -1-(5,6-diphenyl-1,2,4-triazine-3-yl)hydrazine (HBDHT) have been synthesized and characterized by elemental analysis and spectroscopic methods. The results adopt octahedral and square planar structures for Ni(II) and Cu(II) complexes, respectively with the formula, [Ni(BDHT)(NO3)(H2O)2)]·H2O and [Cu(BDHT)(H2O)](NO3)·H2O. The emission spectra arising from S1 state is assigned to π∗ →π and LUMO→HOMO transition character for investigated molecules. Structural parameters of the synthesized compounds were calculated on the basis of DFT level implemented in the Gaussian 09 program. The size of the prepared nano particles was obtained by scanning electron microscopy (SEM) and particle size analyzer. Analysis of the absorption coefficient near the fundamental absorption edge emphasizes two indirect allowed transitions n → π∗ and π → π∗ with energy gaps of 1.1 and 2.55 eV. The forward bias current of the prepared heterojunction shows diode-like behavior with appreciable rectification characteristics. The extracted heterojunction parameters show light dependence which supporting the achievability for the optical sensor in several optoelectronic applications.

  17. Non-adiabatic behavior in the homolytic and heterolytic bond dissociation of protonated hydrazine: A guided ion beam and theoretical investigation

    Science.gov (United States)

    McNary, Christopher P.; Armentrout, P. B.

    2017-09-01

    Threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer was performed on protonated hydrazine and its perdeuterated variant. The dominant dissociation pathways observed were endothermic homolytic and heterolytic cleavages of the N-N bond. The data were analyzed using a statistical model after accounting for internal and kinetic energy distributions, multiple collisions, and kinetic shifts to obtain 0 K bond dissociation energies. Comparison with literature thermochemistry demonstrates that both channels behave non-adiabatically. Heterolytic bond cleavage yields NH2+ + NH3 products, but the NH2+ fragment is in the spin-restricted excited 1A1 state and not in the spin-forbidden ground 3B1 state, whereas homolytic bond cleavage leads to dissociation to the NH3+ + NH2 product asymptote with NH2 in its excited 2A1 state rather than the energetically favored 2B1 state. The rationale for the non-adiabatic behavior observed in the homolytic bond cleavage is revealed by detailed theoretical calculations of the relevant potential energy surfaces and the relevant occupied valence molecular orbitals. These calculations suggest that the non-adiabatic behavior results from conservation of the σ and π character of the binding and lone pair electrons on the nitrogen atoms.

  18. Directing the breathing behavior of pillared-layered metal-organic frameworks via a systematic library of functionalized linkers bearing flexible substituents.

    Science.gov (United States)

    Henke, Sebastian; Schneemann, Andreas; Wütscher, Annika; Fischer, Roland A

    2012-06-06

    Flexible metal-organic frameworks (MOFs), also referred to as soft porous crystals (SPCs), show reversible structural transitions dependent on the nature and quantity of adsorbed guest molecules. In recent studies it has been reported that covalent functionalization of the organic linker can influence or even integrate framework flexibility ("breathing") in MOFs. However, rational fine-tuning of such responsive properties is very desirable but challenging as well. Here we present a powerful approach for the targeted manipulation of responsiveness and framework flexibility of an important family of pillared-layered MOFs based on the parent structure [Zn(2)(bdc)(2)(dabco)](n) (bdc = 1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane). A library of functionalized bdc-type linkers (fu-bdc), which bear additional dangling side groups at different positions of the benzene core (alkoxy groups of varying chain length with diverse functionalities and polarity), was generated. Synthesis of the materials [Zn(2)(fu-bdc)(2)(dabco)](n) yields the respective collection of highly responsive MOFs. The parent MOF is only weakly flexible; however, the substituted frameworks of [Zn(2)(fu-bdc)(2)(dabco)](n) contract drastically upon guest removal and expand again upon adsorption of DMF (N,N-dimethylformamide), EtOH, or CO(2), etc., while N(2) is hardly adsorbed and does not open the narrow-pored form. These "breathing" dynamics are attributed to the dangling side chains that act as immobilized "guests", which interact with mobile guest molecules as well as with themselves and with the framework backbone. The structural details of the guest-free, contracted form and the gas sorption behavior (phase transition pressure, hysteresis loop) are highly dependent on the nature of the substituent at the linker and can therefore be adjusted using our approach. Combining our library of functionalized linkers with the concept of mixed-component MOFs (solid solutions) offers very rich

  19. Multivalent peptidic linker enables identification of preferred sites of conjugation for a potent thialanstatin antibody drug conjugate.

    Directory of Open Access Journals (Sweden)

    Sujiet Puthenveetil

    Full Text Available Antibody drug conjugates (ADCs are no longer an unknown entity in the field of cancer therapy with the success of marketed ADCs like ADCETRIS and KADCYLA and numerous others advancing through clinical trials. The pursuit of novel cytotoxic payloads beyond the mictotubule inhibitors and DNA damaging agents has led us to the recent discovery of an mRNA splicing inhibitor, thailanstatin, as a potent ADC payload. In our previous work, we observed that the potency of this payload was uniquely tied to the method of conjugation, with lysine conjugates showing much superior potency as compared to cysteine conjugates. However, the ADC field is rapidly shifting towards site-specific ADCs due to their advantages in manufacturability, characterization and safety. In this work we report the identification of a highly efficacious site-specific thailanstatin ADC. The site of conjugation played a critical role on both the in vitro and in vivo potency of these ADCs. During the course of this study, we developed a novel methodology of loading a single site with multiple payloads using an in situ generated multi-drug carrying peptidic linker that allowed us to rapidly screen for optimal conjugation sites. Using this methodology, we were able to identify a double-cysteine mutant ADC delivering four-loaded thailanstatin that was very efficacious in a gastric cancer xenograft model at 3mg/kg and was also shown to be efficacious against T-DM1 resistant and MDR1 overexpressing tumor cell lines.

  20. Solid phase synthesis of mitochondrial triphenylphosphonium-vitamin E metabolite using a lysine linker for reversal of oxidative stress.

    Directory of Open Access Journals (Sweden)

    Mohanad Mossalam

    Full Text Available Mitochondrial targeting of antioxidants has been an area of interest due to the mitochondria's role in producing and metabolizing reactive oxygen species. Antioxidants, especially vitamin E (α-tocopherol, have been conjugated to lipophilic cations to increase their mitochondrial targeting. Synthetic vitamin E analogues have also been produced as an alternative to α-tocopherol. In this paper, we investigated the mitochondrial targeting of a vitamin E metabolite, 2,5,7,8-tetramethyl-2-(2'-carboxyethyl-6-hydroxychroman (α-CEHC, which is similar in structure to vitamin E analogues. We report a fast and efficient method to conjugate the water-soluble metabolite, α-CEHC, to triphenylphosphonium cation via a lysine linker using solid phase synthesis. The efficacy of the final product (MitoCEHC to lower oxidative stress was tested in bovine aortic endothelial cells. In addition the ability of MitoCEHC to target the mitochondria was examined in type 2 diabetes db/db mice. The results showed mitochondrial accumulation in vivo and oxidative stress decrease in vitro.

  1. Multivalent peptidic linker enables identification of preferred sites of conjugation for a potent thialanstatin antibody drug conjugate.

    Science.gov (United States)

    Puthenveetil, Sujiet; He, Haiyin; Loganzo, Frank; Musto, Sylvia; Teske, Jesse; Green, Michael; Tan, Xingzhi; Hosselet, Christine; Lucas, Judy; Tumey, L Nathan; Sapra, Puja; Subramanyam, Chakrapani; O'Donnell, Christopher J; Graziani, Edmund I

    2017-01-01

    Antibody drug conjugates (ADCs) are no longer an unknown entity in the field of cancer therapy with the success of marketed ADCs like ADCETRIS and KADCYLA and numerous others advancing through clinical trials. The pursuit of novel cytotoxic payloads beyond the mictotubule inhibitors and DNA damaging agents has led us to the recent discovery of an mRNA splicing inhibitor, thailanstatin, as a potent ADC payload. In our previous work, we observed that the potency of this payload was uniquely tied to the method of conjugation, with lysine conjugates showing much superior potency as compared to cysteine conjugates. However, the ADC field is rapidly shifting towards site-specific ADCs due to their advantages in manufacturability, characterization and safety. In this work we report the identification of a highly efficacious site-specific thailanstatin ADC. The site of conjugation played a critical role on both the in vitro and in vivo potency of these ADCs. During the course of this study, we developed a novel methodology of loading a single site with multiple payloads using an in situ generated multi-drug carrying peptidic linker that allowed us to rapidly screen for optimal conjugation sites. Using this methodology, we were able to identify a double-cysteine mutant ADC delivering four-loaded thailanstatin that was very efficacious in a gastric cancer xenograft model at 3mg/kg and was also shown to be efficacious against T-DM1 resistant and MDR1 overexpressing tumor cell lines.

  2. Synthesis of Cassava Waste Pulp-Acrylamide Super Absorbent: Effect of Initiator and Cross-Linker Concentration

    Directory of Open Access Journals (Sweden)

    Zainal Alim Mas’ud

    2013-05-01

    Full Text Available Cassava waste pulp (CWP contains high carbohydrates that can be modified into super absorbent polymer (SAP through grafting and cross-linking copolymerization. Acrylamide (AM was grafted onto CWP with ammonium persulfate (APS as the initiator and N,N'-methylene-bis-acrylamide (MBA as the cross-linker under atmospheric nitrogen. The effect of APS and MBA concentrations on water absorption capacity of saponified SAP was studied, while the evaluation of grafting ratio (GR and grafting efficiency (GRE was conducted on unsaponified SAP. The grafting success was indicated by the occurrence of IR peaks at wave numbers of 573, 765, 858, and 1667 cm-1. In the saponified SAP, the very intense characteristic band at 1562 cm-1 is due to C=O asymmetric stretching in the carboxylate anion. Saponification increases significantly water absorption capacity compared to that of unsaponified SAP (from 39.79 g/g to 578.23 g/g. The highest water absorption capacity is reached at 0.74% APS and 0.09% MBA. The percentage of GRE and GR tends to increase with increasing APS concentration until reaching the highest value and then decreases. Effect of MBA concentration on water absorption capacity, GR, and on GRE is similar to the effect of initiator concentration on GR and GRE.

  3. Phosphonate self-assembled monolayers as organic linkers in solid-state quantum dot sensetized solar cells

    KAUST Repository

    Ardalan, Pendar

    2010-06-01

    We have employed X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, infrared (IR) spectroscopy, water contact angle (WCA) measurements, ellipsometry, and electrical measurements to study the effects of self-assembled monolayers (SAMs) with phosphonic acid headgroups on the bonding and performance of cadmium sulfide (CdS) solid-state quantum dot sensitized solar cells (QDSSCs). ∼2 to ∼6 nm size CdS quantum dots (QDs) were grown on the SAM-passivated TiO2 surfaces by successive ionic layer adsorption and reaction (SILAR). Our results show differences in the bonding of the CdS QDs at the TiO2 surfaces with a SAM linker. Moreover, our data indicate that presence of a SAM increases the CdS uptake on TiO2 as well as the performance of the resulting devices. Importantly, we observe ∼2 times higher power conversion efficiencies in the devices with a SAM compared to those that lack a SAM. © 2010 IEEE.

  4. Mutations in linker for activation of T cells (LAT) lead to a novel form of severe combined immunodeficiency.

    Science.gov (United States)

    Bacchelli, Chiara; Moretti, Federico A; Carmo, Marlene; Adams, Stuart; Stanescu, Horia C; Pearce, Kerra; Madkaikar, Manisha; Gilmour, Kimberly C; Nicholas, Adeline K; Woods, C Geoffrey; Kleta, Robert; Beales, Phil L; Qasim, Waseem; Gaspar, H Bobby

    2017-02-01

    Signaling through the T-cell receptor (TCR) is critical for T-cell development and function. Linker for activation of T cells (LAT) is a transmembrane adaptor signaling molecule that is part of the TCR complex and essential for T-cell development, as demonstrated by LAT-deficient mice, which show a complete lack of peripheral T cells. We describe a pedigree affected by a severe combined immunodeficiency phenotype with absent T cells and normal B-cell and natural killer cell numbers. A novel homozygous frameshift mutation in the gene encoding for LAT was identified in this kindred. Genetic, molecular, and functional analyses were used to identify and characterize the LAT defect. Clinical and immunologic analysis of patients was also performed and reported. Homozygosity mapping was used to identify potential defective genes. Sanger sequencing of the LAT gene showed a mutation that resulted in a premature stop codon and protein truncation leading to complete loss of function and loss of expression of LAT in the affected family members. We also demonstrate loss of LAT expression and lack of TCR signaling restoration in LAT-deficient cell lines reconstituted with a synthetic LAT gene bearing this severe combined immunodeficiency mutation. For the first time, the results of this study show that inherited LAT deficiency should be considered in patients with combined immunodeficiency with T-cell abnormalities. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  5. Optimization and characterization of biomolecule immobilization on silicon substrates using (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde linker

    Energy Technology Data Exchange (ETDEWEB)

    Gunda, Naga Siva Kumar [Department of Mechanical Engineering, University of Alberta, Edmonton, Canada T6G 2G8 (Canada); Singh, Minashree [Department of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada T6G 1C9 (Canada); Norman, Lana [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada T6G 2V4 (Canada); Kaur, Kamaljit [Department of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada T6G 1C9 (Canada); Mitra, Sushanta K., E-mail: sushanta.mitra@ualberta.ca [Department of Mechanical Engineering, University of Alberta, Edmonton, Canada T6G 2G8 (Canada)

    2014-06-01

    In the present work, we developed and optimized a technique to produce a thin, stable silane layer on silicon substrate in a controlled environment using (3-aminopropyl)triethoxysilane (APTES). The effect of APTES concentration and silanization time on the formation of silane layer is studied using spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR). Biomolecules of interest are immobilized on optimized silane layer formed silicon substrates using glutaraldehyde linker. Surface analytical techniques such as ellipsometry, FTIR, contact angle measurement system, and atomic force microscopy are employed to characterize the bio-chemically modified silicon surfaces at each step of the biomolecule immobilization process. It is observed that a uniform, homogenous and highly dense layer of biomolecules are immobilized with optimized silane layer on the silicon substrate. The developed immobilization method is successfully implemented on different silicon substrates (flat and pillar). Also, different types of biomolecules such as anti-human IgG (rabbit monoclonal to human IgG), Listeria monocytogenes, myoglobin and dengue capture antibodies were successfully immobilized. Further, standard sandwich immunoassay (antibody–antigen–antibody) is employed on respective capture antibody coated silicon substrates. Fluorescence microscopy is used to detect the respective FITC tagged detection antibodies bound to the surface after immunoassay.

  6. Introducing RGD peptides on PHBV films through PEG-containing cross-linkers to improve the biocompatibility.

    Science.gov (United States)

    Wang, Yan-Yan; Lü, Lan-Xin; Shi, Jun-Cai; Wang, Hai-Feng; Xiao, Zhong-Dang; Huang, Ning-Ping

    2011-03-14

    Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable polyester, has been a good candidate of biomaterial employed in tissue engineering. However, the PHBV film is hydrophobic and has no recognition sites for cell attachment. In this study, PHBV films are activated by ammonia plasma treatment to produce amino groups on the surface, followed by sequential reactions with a heterobifunctional cross-linker containing a segment of poly(ethylene glycol) (PEG) and further with RGD-containing peptides. XPS analyses of modified surfaces after each reaction step reveal that the RGD-containing peptides have been covalently grafted onto PHBV films. The result of cell viability assay indicates that the RGD-modified PHBV films exhibit a distinctly improved cellular compatibility. Moreover, according to the results of serum adsorption tests by optical waveguide lightmode spectroscopy (OWLS) and fibrinogen adsorption tests by enzyme-linked immunosorbent assay (ELISA) on unmodified and modified PHBV surfaces, the introduced PEG chains can significantly decrease the nonspecific adsorption of proteins from serum and fibrinogen from plasma, thus decreasing the risk of thrombus formation and improving the blood compatibility of implanted materials.

  7. Bonding efficacy of etch-and-rinse adhesives after dentin biomodification using ethanol saturation and collagen cross-linker pretreatment.

    Science.gov (United States)

    Sharma, Pallavi; Nagpal, Rajni; Tyagi, Shashi Prabha; Manuja, Naveen

    2015-01-01

    To evaluate whether the application of two simplified etch-and-rinse adhesives to biomodified dentin using ethanol-wet bonding (EWB) and collagen cross-linker (CCL) pretreatment improves their sealing ability. In 176 extracted human molars, the pulp-chambers were deroofed, and teeth were sectioned horizontally. Samples were randomly divided into eight groups according to four bonding techniques using two simplified etch-and-rinse adhesives; Adper Single Bond 2 (ASB) and XP Bond (XPB). The bonding protocols included: (a) Water-wet bonding (WWB); (b) EWB; (c) WWB and CCL application; (d) EWB and CCL application. After composite resin restorations, dye leakage evaluation and scanning electron microscope analysis were done. Leakage scores were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests at a significance level of P adhesives, least dye leakage was observed in EWB groups (b and d) (P = 0.918 and P = 0.399 respectively) which showed no significant difference, while maximum leakage scores were seen in WWB groups (a and c). Regardless of CCL application and adhesives used, EWB technique depicted (P = 0.003 and P = 0.004) significantly greater sealing ability than WWB. Bonding of ASB and XPB using EWB significantly improved their sealing ability. Biomodification using CCL pretreatment had no significant effect on the sealing ability of adhesives bonded with either WWB or EWB.

  8. Tetraphenylethylene Foldamers with Double Hairpin-Turn Linkers, TNT-Binding Mode and Detection of Highly Diluted TNT Vapor.

    Science.gov (United States)

    Xiong, Jia-Bin; Feng, Hai-Tao; Wang, Jin-Hua; Zhang, Chun; Li, Bao; Zheng, Yan-Song

    2018-02-06

    Tetraphenylethylene (TPE) foldamers with double hairpin-turn linkers showing an aggregation-induced emission (AIE) effect have been synthesized for the first time. A crystal structure of a foldamer-TNT complex has been obtained, enabling unprecedented direct observation of the interactions between TNT molecules and the chromophores of the foldamer. Instead of π-π stacking interactions, which have often been considered to be the key mechanism in the binding of TNT by chromophoric receptors, strong n-π interactions between the nitro groups of TNT and the aromatic rings of the foldamer have been found. Exceptionally, by addition of 1 % NaF to a suspension of the foldamer in H 2 O/THF (95:5), the fluorescence quenching efficiency by TNT vapor significantly increased from about 20 % to more than 90 %. Even after diluting TNT-saturated air at 25 °C by a factor of 2×10 4 , an obvious quenching response was observed, indicating that ultratrace TNT vapor (down to 3.4 fg per mL of air) could be detected. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Influence of vibronic contribution on light harvesting efficiency of NKX-2587 derivatives with oligothiophene as π-conjugated linker

    Science.gov (United States)

    Yang, Pan; Zhang, Yang; Li, Ming; Shen, Wei; He, Rongxing

    2018-01-01

    Based on the NKX-2587 molecule we designed ten sensitizers with 1-10 thiophene moieties to investigate how the number of thiophene unit in the spacer influences the absorption spectra of sensitizer in dye sensitized solar cells (DSSCs). The parameters of short-circuit current density (Jsc), open circuit voltage (Voc), the light harvesting efficiency (LHE), injection driving force (Δ Ginject), and transferred electron number (nc), were calculated and discussed in detail. Results indicated that the increasing of thiophene units makes for the enhancement of oscillator strengths (f), although the red shift of vertical electronic absorption spectra is small. For the designed sensitizers with 1-5 thiophene units, their ΔGinject and nc raise gradually with the increasing of thiophene number. However, for those sensitizers with 6-10 thiophene units, the ΔGinject and nc decrease continuously with the increasing of thiophene units. In order to study how the oligothiophene as π-conjugated linker affects light harvesting efficiency of DSSCs, the vibrationally resolved electronic spectra of five metal-free NKX-2587 derivatives with 1-5 thiophene units were simulated within the Franck-Condon approximation including the Herzberg-Teller and Duschinsky effects. The present theoretical results provided helpful guidance for understanding the sources of spectral intensities of dye molecules, and a valuable method for rational design of new molecules to improve the energy conversion efficiency (η) of DSSCs.

  10. Polydopamine Thin Films as Protein Linker Layer for Sensitive Detection of Interleukin-6 by Surface Plasmon Enhanced Fluorescence Spectroscopy.

    Science.gov (United States)

    Toma, Mana; Tawa, Keiko

    2016-08-31

    Polydopamine (PDA) thin films are introduced to the surface modification of biosensor surfaces utilizing surface plasmon enhanced fluorescence spectroscopy (SPFS) as the linker layer of capture antibody on to the sensor surfaces. The capture antibody can be directly attached to the sensor surface without using any coupling agent by functionalizing the gold sensor surface with PDA thin films. The PDA coating is performed by a single-step preparation process by applying the dopamine solution on the sensor surface, which requires an extremely short incubation time (10 min). The real-time in situ measurement of the adsorption kinetics of the capture antibody onto the PDA-coated sensor surface is studied by surface plasmon resonance (SPR) spectroscopy. It reveals that the immobilization of capture antibody immediately occurs after introduction of a solution containing capture antibody, and the sensor surface is fully covered with the capture antibody. The sensitive detection of the cytokine marker interleukin-6 (IL-6) is performed by SPFS using a sandwich assay format with fluorescently labeled detection antibody. The sensor chips functionalized by PDA chemistry exhibited sensitive sensor responses with low nonspecific adsorption of the detection antibody onto the sensor surface. The detection limit of IL-6 with the developed SPFS biosensor is determined to be 2 pg/mL (100 fM), which is within the range of the diagnostic criteria. Our observation elucidates the remarkable utility of PDA coatings for chemical modification of the metallic sensor surfaces by a simple, brief, and inexpensive manner.

  11. Demonstration of Improved Charge Transfer in Graphene/Au Nanorods Plasmonic Hybrids Stabilized by Benzyl Thiol Linkers

    Directory of Open Access Journals (Sweden)

    Giuseppe Valerio Bianco

    2016-01-01

    Full Text Available Hybrids based on graphene decorated with plasmonic gold (Au nanostructures are being investigated as possible materials combination to add to graphene functionalities of tunable plasmon resonance and enhanced absorption at selected wavelength in the visible-near-infrared region of the spectrum. Here, we report a solution drop-casting approach for fabricating stable hybrids based on chemical vapor deposition (CVD graphene and Au nanorods, which are able to activate effective charge transfer from graphene. We demonstrate that CVD graphene functionalization by benzyl thiol (BZT provides the linker to strong anchoring, via S-Au bonds, Au nanorods to graphene. Optical measurements by spectroscopic ellipsometry give evidence of the introduction of plasmon resonances at 1.85 and 2.25 eV in the Au nanorods/BZT/graphene hybrids, which enable surface enhanced Raman scattering (SERS detection. Furthermore, an effective electron transfer from graphene to Au nanorods, resulting in an enhancement of p-type doping of graphene with a consequent decrease of its sheet resistance, is probed by Raman spectroscopy and corroborated by electrical measurements.

  12. Facile linker free growth of CdS nanoshell on 1-D ZnO: Solar cell application

    Science.gov (United States)

    Kamble, Archana; Sinha, Bhavesh; Chung, Kookchae; More, Anup; Vanalakar, Sharad; Hong, Chang Woo; Kim, Jin Hyeok; Patil, Pramod

    2015-03-01

    One dimensional type-II core/shell heterostructures are widely employed in solar cells because of their adventitious role in both light absorption and charge separation. Here we report a facile two step chemical approach to synthesizing ZnO/CdS core/shell nanorod arrays. ZnO nanorods (ZNR) with a high aspect ratio were grown using a hydrothermal technique where a uniform CdS shell was deposited using a facile, linker free, one pot, Hexamethylenetetramine (HMTA) based reflux technique for the first time. Though the reflux technique is quite similar to the chemical bath deposition technique (CBD), we obtained more uniform CdS coating and improved solar cell performance with the ZnO/CdS heterostructure compared to CBD-grown ZnO/CdS heterostructures. To obtain a conformal coating of CdS, we optimized the CdS deposition time. Formation of pure phase ZnO/CdS core/shell heterostructure was confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy (XPS) depth analysis. Improved solar cell performance of 1.23% was obtained for ZnO/CdS core/shell structures with ZnS surface treatment. [Figure not available: see fulltext.

  13. Organic linkers on oxide surfaces: Adsorption and chemical bonding of phthalic anhydride on MgO(100)

    Science.gov (United States)

    Mohr, Susanne; Doepper, Tibor; Xu, Tao; Tariq, Quratulain; Lytken, Ole; Laurin, Mathias; Steinrueck, Hans-Peter; Goerling, Andreas; Libuda, Joerg

    2016-04-01

    To elucidate the adsorption behavior and interaction mechanisms of organic linker units on oxide surfaces, we have performed a model study under ultrahigh vacuum (UHV) conditions. We apply infrared reflection absorption spectroscopy (IRAS) in combination with density-functional theory (DFT), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). Phthalic anhydride (PAA) was deposited at temperatures between 100 and 300 K by physical vapor deposition (PVD) onto an ordered MgO(100) film grown on Ag(100). At 100 K, the first monolayer adsorbs molecularly with the molecular plane aligned parallel to the surface. Subsequent growth of a multilayer film at low temperature also occurs with preferential molecular alignment parallel to the surface. At 240 K, the multilayer desorbs without decomposition. At 300 K, a mixed monolayer of chemically modified ring-opened and intact phthalic anhydride exists on the surface. The chemically modified species binds in a strongly tilted geometry via opening of the anhydride ring to form a bis-carboxylate species. This species additionally stabilizes the coadsorbed molecular PAA via intermolecular interactions. Finally, surface defects and hydroxyl groups are found to increase the amount of surface bis-carboxylate at 300 K, whereas the relative amount of coadsorbed molecular PAA decreases.

  14. Hsp70 oligomerization is mediated by an interaction between the interdomain linker and the substrate-binding domain.

    Directory of Open Access Journals (Sweden)

    Francesco A Aprile

    Full Text Available Oligomerization in the heat shock protein (Hsp 70 family has been extensively documented both in vitro and in vivo, although the mechanism, the identity of the specific protein regions involved and the physiological relevance of this process are still unclear. We have studied the oligomeric properties of a series of human Hsp70 variants by means of nanoelectrospray ionization mass spectrometry, optical spectroscopy and quantitative size exclusion chromatography. Our results show that Hsp70 oligomerization takes place through a specific interaction between the interdomain linker of one molecule and the substrate-binding domain of a different molecule, generating dimers and higher-order oligomers. We have found that substrate binding shifts the oligomerization equilibrium towards the accumulation of functional monomeric protein, probably by sequestering the helical lid sub-domain needed to stabilize the chaperone: substrate complex. Taken together, these findings suggest a possible role of chaperone oligomerization as a mechanism for regulating the availability of the active monomeric form of the chaperone and for the control of substrate binding and release.

  15. PARP1-dependent eviction of the linker histone H1 mediates immediate early gene expression during neuronal activation.

    Science.gov (United States)

    Azad, Gajendra Kumar; Ito, Kenji; Sailaja, Badi Sri; Biran, Alva; Nissim-Rafinia, Malka; Yamada, Yasuhiro; Brown, David T; Takizawa, Takumi; Meshorer, Eran

    2017-12-28

    Neuronal stimulation leads to immediate early gene (IEG) expression through calcium-dependent mechanisms. In recent years, considerable attention has been devoted to the transcriptional responses after neuronal stimulation, but relatively little is known about the changes in chromatin dynamics that follow neuronal activation. Here, we use fluorescence recovery after photobleaching, biochemical fractionations, and chromatin immunoprecipitation to show that KCl-induced depolarization in primary cultured cortical neurons causes a rapid release of the linker histone H1 from chromatin, concomitant with IEG expression. H1 release is repressed by PARP inhibition, PARP1 deletion, a non-PARylatable H1, as well as phosphorylation inhibitions and a nonphosphorylatable H1, leading to hindered IEG expression. Further, H1 is replaced by PARP1 on IEG promoters after neuronal stimulation, and PARP inhibition blocks this reciprocal binding response. Our results demonstrate the relationship between neuronal excitation and chromatin plasticity by identifying the roles of polyadenosine diphosphate ribosylation and phosphorylation of H1 in regulating H1 chromatin eviction and IEG expression in stimulated neurons. © 2018 Azad et al.

  16. Data on face-to-face contacts in an office building suggests a low-cost vaccination strategy based on community linkers

    CERN Document Server

    Génois, Mathieu; Fournet, Julie; Panisson, André; Bonmarin, Isabelle; Barrat, Alain

    2014-01-01

    Empirical data on contacts between individuals in social contexts play an important role in the information of models describing human behavior and how epidemics spread in populations. Here, we analyze data on face-to-face contacts collected in an office building. The statistical properties of contacts are similar to other social situations, but important differences are observed in the contact network structure. In particular, the contact network is strongly shaped by the organization of the offices in departments, which has consequences in the design of accurate agent-based models of epidemic spread. We then consider the contact network as a potential substrate for infectious disease spread and show that its sparsity tends to prevent outbreaks of fast-spreading epidemics. Moreover, we define three typical behaviors according to the fraction $f$ of links each individual shares outside its own department: residents, wanderers and linkers. Linkers ($f\\sim 50%$) act as bridges in the network and have large betw...

  17. Modulation of domain-domain interaction and protein function by a charged linker: a case study of mycobacteriophage D29 endolysin.

    Science.gov (United States)

    Pohane, Amol Arunrao; Patidar, Neelam Devidas; Jain, Vikas

    2015-03-12

    Phage-encoded cell wall peptidoglycan hydrolyzing enzymes, called endolysins, are essential for efficient release of virions from bacteria, and show species-specific killing of the host. We have demonstrated previously that the interaction between N-terminal catalytic and C-terminal cell wall binding domains of mycobacteriophage D29 endolysin makes the enzyme inactive in Escherichiacoli. Here, we demonstrate that such interaction occurs intramolecularly and is facilitated by a charged linker that connects the two domains. We also show that linker composition is crucial for the inactivation of PG hydrolase in E. coli. Such knowledge will immensely help in bioengineering of endolysins with narrow or broad spectrum antimicrobial activity. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  18. Calculated photo-isomerization efficiencies of functionalized azobenzene derivatives in solar energy materials: azo-functional organic linkers for porous coordinated polymers

    Science.gov (United States)

    Neukirch, Amanda J.; Park, Jinhee; Zobac, Vladmir; Wang, Hong; Jelinek, Pavel; Prezhdo, Oleg V.; Zhou, Hong-Cai; Lewis, James P.

    2015-04-01

    Recently, we used a local orbital density functional theory code called FIREBALL, to study the photoisomerization process in azobenzene derivatives for solar energy materials. Azobenzene functional groups undergo photoisomerization upon light irradiation or application of heat. Zhou et al (2012 J. Am. Chem. Soc. 134 99-102) showed that these azobenzenes can then be introduced into metal-organic frameworks via an organic linker in order to create a reversible switch for CO2 adsorption. In this manuscript, we examined how the addition of organic linkers (isophthalic acid) changes the relaxation times, isomerization mechanism, and quantum yield for both the cis↔trans pathways. We then tuned these properties by substituting functional groups, finding an increase in quantum yield as well as improved optical properties.

  19. Effect of Redox “Non-Innocent” Linker on the Catalytic Activity of Copper-Catecholate-Decorated Metal–Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xuan [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Vermeulen, Nicolaas A. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Huang, Zhiyuan [Chemical Sciences & amp, Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Cui, Yuexing [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Liu, Jian [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Krzyaniak, Matthew D. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Li, Zhanyong [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Noh, Hyunho [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Wasielewski, Michael R. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Delferro, Massimiliano [Chemical Sciences & amp, Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Farha, Omar K. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia

    2017-12-19

    Two new UiO-68 type of Zr-MOFs featuring redox non-innocent catechol-based linkers of different redox activities have been synthesized through a de novo mixed-linker strategy. Metalation of the MOFs with Cu(II) precursors triggers the reduction of Cu(II) by the phenyl-catechol groups to Cu(I) with the concomitant formation of semiquinone radicals as evidenced by EPR and XPS characterization. The MOF-supported catalysts are selective toward the allylic oxidation of cyclohexene and it is found that the presence of in situ-generated Cu(I) species exhibits enhanced catalytic activity as compared to a similar MOF with Cu(II) metalated naphthalenyl-dihydroxy groups. This work unveils the importance of metal-support redox interactions in the catalytic activity of MOF-supported catalysts which are not easily accessible in traditional metal oxide supports.

  20. The Influence of the Linker Geometry in Bis(3-hydroxy-N-methyl-pyridin-2-one) Ligands on Solution-Phase Uranyl Affinity

    Energy Technology Data Exchange (ETDEWEB)

    Szigethy, Geza; Raymond, Kenneth

    2010-08-12

    Seven water-soluble, tetradentate bis(3-hydroxy-N-methyl-pyridin-2-one) (bis-Me-3,2-HOPO) ligands were synthesized that vary only in linker geometry and rigidity. Solution phase thermodynamic measurements were conducted between pH 1.6 and pH 9.0 to determine the effects of these variations on proton and uranyl cation affinity. Proton affinity decreases by introduction of the solubilizing triethylene glycol group as compared to un-substituted reference ligands. Uranyl affinity was found to follow no discernable trends with incremental geometric modification. The butyl-linked 4Li-Me-3,2-HOPO ligand exhibited the highest uranyl affinity, consistent with prior in vivo decorporation results. Of the rigidly-linked ligands, the o-phenylene linker imparted the best uranyl affinity to the bis-Me-3,2-HOPO ligand platform.

  1. Flexibility between the protease and helicase domains of the dengue virus NS3 protein conferred by the linker region and its functional implications.

    Science.gov (United States)

    Luo, Dahai; Wei, Na; Doan, Danny N; Paradkar, Prasad N; Chong, Yuwen; Davidson, Andrew D; Kotaka, Masayo; Lescar, Julien; Vasudevan, Subhash G

    2010-06-11

    The dengue virus (DENV) NS3 protein is essential for viral polyprotein processing and RNA replication. It contains an N-terminal serine protease region (residues 1-168) joined to an RNA helicase (residues 180-618) by an 11-amino acid linker (169-179). The structure at 3.15 A of the soluble NS3 protein from DENV4 covalently attached to 18 residues of the NS2B cofactor region (NS2B(18)NS3) revealed an elongated molecule with the protease domain abutting subdomains I and II of the helicase (Luo, D., Xu, T., Hunke, C., Grüber, G., Vasudevan, S. G., and Lescar, J. (2008) J. Virol. 82, 173-183). Unexpectedly, using similar crystal growth conditions, we observed an alternative conformation where the protease domain has rotated by approximately 161 degrees with respect to the helicase domain. We report this new crystal structure bound to ADP-Mn(2+) refined to a resolution of 2.2 A. The biological significance for interdomain flexibility conferred by the linker region was probed by either inserting a Gly residue between Glu(173) and Pro(174) or replacing Pro(174) with a Gly residue. Both mutations resulted in significantly lower ATPase and helicase activities. We next increased flexibility in the linker by introducing a Pro(176) to Gly mutation in a DENV2 replicon system. A 70% reduction in luciferase reporter signal and a similar reduction in the level of viral RNA synthesis were observed. Our results indicate that the linker region has evolved to an optimum length to confer flexibility to the NS3 protein that is required both for polyprotein processing and RNA replication.

  2. Influence of the metal complex-to-peptide linker on the synthesis and properties of bioactive CpMn(CO)3 peptide conjugates.

    Science.gov (United States)

    Splith, Katrin; Neundorf, Ines; Hu, Wanning; Peindy N'Dongo, Harmel W; Vasylyeva, Vera; Merz, Klaus; Schatzschneider, Ulrich

    2010-03-14

    By combining organometallic groups and peptides, a large number of conjugates with interesting new biological properties can be prepared. Especially, attachment to cell-penetrating peptides (CPP) that act as efficient cell delivery vehicles has come to the fore. However, the presence of the metal moiety in such systems can interfere with standard conjugate synthesis procedures which therefore need to be optimized for every new compound. In this work, we report on the preparation of six new cymantrene-sC18 peptide bioconjugates that were prepared by solid phase peptide synthesis (SPPS) techniques. The cymantrene complexes were chosen for their different linker to the peptide, to study the influence of the linker group on cellular uptake and cell viability of the conjugates. Interestingly, the attachment of the metal complex leads to a non-standard cleavage of the Rink amide linker used in the SPPS protocol under trifluoroacetic acid (TFA) treatment, resulting in peptide amides that are N-alkylated at the C-terminus. Furthermore, we found that depending on the type of cymantrene moiety attached, the formation of reactive carbocations which result from decomposition of the resin linker is facilitated and can alkylate the metal complex moiety. Both effects were analyzed by MS/MS studies and cleavage mixtures for efficient elimination of this byproduct formation were identified. Moreover, initial biological testing of the cytotoxicity of one of the bioconjugates gave promising results. Concentration-dependent cell viability studies of Cym1-sC18 on human MCF-7 breast adenocarcinoma cells gave an IC(50) value of 59.8 (+/- 6.7) microM and demonstrate their potential in anticancer chemotherapy.

  3. 55 Amino acid linker between helicase and carboxyl terminal domains of RIG-I functions as a critical repression domain and determines inter-domain conformation.

    Science.gov (United States)

    Kageyama, Maiko; Takahasi, Kiyohiro; Narita, Ryo; Hirai, Reiko; Yoneyama, Mitsutoshi; Kato, Hiroki; Fujita, Takashi

    2011-11-11

    In virus-infected cells, viral RNA with non-self structural pattern is recognized by DExD/Hbox RNA helicase, RIG-I. Once RIG-I senses viral RNA, it triggers a signaling cascade, resulting in the activation of genes including type I interferon, which activates antiviral responses. Overexpression of N-terminal caspase activation and recruitment domain (CARD) is sufficient to activate signaling; however basal activity of full-length RIG-I is undetectable. The repressor domain (RD), initially identified as a.a. 735-925, is responsible for diminished basal activity; therefore, it is suggested that RIG-I is under auto-repression in uninfected cells and the repression is reversed upon its encounter with viral RNA. In this report, we further delimited RD to a.a. 747-801, which corresponds to a linker connecting the helicase and the C-terminal domain (CTD). Alanine substitutions of the conserved residues in the linker conferred constitutive activity to full-length RIG-I. We found that the constitutive active mutants do not exhibit ATPase activity, suggesting that ATPase is required for de-repression but not signaling itself. Furthermore, trypsin digestion of recombinant RIG-I revealed that the wild-type, but not linker mutant conforms to the trypsin-resistant structure, containing CARD and helicase domain. The result strongly suggests that the linker is responsible for maintaining RIG-I in a "closed" structure to minimize unwanted production of interferon in uninfected cells. These findings shed light on the structural regulation of RIG-I function. Copyright © 2011 Elsevier Inc. All rights reserved.

  4. Tailoring the dependency between rigidity and water uptake of a microfabricated hydrogel with the conformational rigidity of a polymer cross-linker.

    Science.gov (United States)

    Schmidt, John J; Jeong, Jae Hyun; Chan, Vincent; Cha, Chaenyung; Baek, Kwanghyun; Lai, Mei-Hsiu; Bashir, Rashid; Kong, Hyunjoon

    2013-05-13

    Many diverse applications utilize hydrogels as carriers, sensors, and actuators, and these applications rely on the refined control of physical properties of the hydrogel, such as elastic modulus and degree of swelling. Often, hydrogel properties are interdependent; for example, when elastic modulus is increased, degree of swelling is decreased. Controlling these inverse dependencies remains a major barrier for broader hydrogel applications. We hypothesized that polymer cross-linkers with varied chain flexibility would allow us to tune the inverse dependency between the elastic modulus and the degree of swelling of the hydrogels. We examined this hypothesis by using alginate and poly(acrylic acid) (PAA) modified with a controlled number of methacrylic groups as model inflexible and flexible cross-linkers, respectively. Interestingly, the polyacrylamide hydrogel cross-linked by the inflexible alginate methacrylates exhibited less dependency between the degree of swelling and the elastic modulus than the hydrogel cross-linked by flexible PAA methacrylates. This critical role of the cross-linker's inflexibility was related to the difference of the degree of hydrophobic association between polymer cross-linkers, as confirmed with pyrene probes added in pregel solutions. Furthermore, hydrogels cross-linked with alginate methacrylates could tune the projection area of adhered cells by solely altering elastic moduli. In contrast, gels cross-linked with PAA methacrylates failed to modulate the cellular adhesion morphology due to a lower, and smaller, elastic modulus range to be controlled. Overall, the results of this study will significantly advance the controllability of hydrogel properties and greatly enhance the performance of hydrogels in various biological applications.

  5. Ionic Liquid-Derived Imidazolium Cation Linkers for the Layer-by-Layer Assembly of Polyoxometalate-MWCNT Composite Electrodes with High Power Capability.

    Science.gov (United States)

    Genovese, Matthew; Lian, Keryn

    2016-07-27

    Imidazolium cations derived from ionic liquids were demonstrated as effective linker molecules for the layer-by-layer (LbL) deposition of polyoxometalates (POMs) to increase the charge storage of multi-walled carbon nanotube (MWCNT) electrodes. MWCNTs modified with GeMo12O40(4-) (GeMo12) via an imidazolium cation linker demonstrated highly reversible redox reactions and a capacitance of 84 F cm(-3), close to 4 times larger than bare CNT. Compared to CNT-GeMo12 composites fabricated with a conventional polyelectrolyte linker poly(diallyldimethylammonium chloride), (PDDA), the imidazolium cations resulted in lower POM loading, but higher conductivity and in turn superior performance at fast charge-discharge conditions. A polymerized imidazolium linker (PIL) was also synthesized based on the ethyl-vinyl-imidazolium monomer. CNT-GeMo12 composites fabricated with this PIL achieved high POM loading comparable to PDDA, while still maintaining the good conductivity and high rate capabilities shown by the monomer imidazolium units. The high conductivity imparted by the PIL is especially valuable for the fabrication of multilayer POM composites. Dual-layer GeMo12 O40(4-)-SiMo12O40(4-) (GeMo12-SiMo12) electrodes built with this PIL demonstrated a combined contribution of the individual POMs resulting in a capacitance of 191 F cm(-3), over nine times larger than bare MWCNT. The PIL dual layer composites also maintained 72% of this capacitance at a fast rate of 2 V s(-1), compared to just over 50% retention for similar electrodes fabricated with PDDA.

  6. Surface expression and subunit specific control of steady protein levels by the Kv7.2 helix A-B linker.

    Directory of Open Access Journals (Sweden)

    Paloma Aivar

    Full Text Available Kv7.2 and Kv7.3 are the main components of the neuronal voltage-dependent M-current, which is a subthreshold potassium conductance that exerts an important control on neuronal excitability. Despite their predominantly intracellular distribution, these channels must reach the plasma membrane in order to control neuronal activity. Thus, we analyzed the amino acid sequence of Kv7.2 to identify intrinsic signals that may control its surface expression. Removal of the interlinker connecting helix A and helix B of the intracellular C-terminus produces a large increase in the number of functional channels at the plasma membrane. Moreover, elimination of this linker increased the steady-state amount of protein, which was not associated with a decrease of protein degradation. The magnitude of this increase was inversely correlated with the number of helix A - helix B linkers present in the tetrameric channel assemblies. In contrast to the remarkable effect on the amount of Kv7.2 protein, removal of the Kv7.2 linker had no detectable impact on the steady-state levels of Kv7.3 protein.

  7. Discovery of a 2-hydroxyacetophenone derivative as an outstanding linker to enhance potency and β-selectivity of liver X receptor agonist.

    Science.gov (United States)

    Koura, Minoru; Yamaguchi, Yuki; Kurobuchi, Sayaka; Sumida, Hisashi; Watanabe, Yuichiro; Enomoto, Takashi; Matsuda, Takayuki; Okuda, Ayumu; Koshizawa, Tomoaki; Matsumoto, Yuki; Shibuya, Kimiyuki

    2016-08-15

    Our research found that the 2-hydroxyacetophenone derivative is an outstanding linker between the 1,1-bistrifluoromethylcarbinol moiety and the imidazolidine-2,4-dione moiety to enhance the potency and β-selectivity of liver X receptor (LXR) agonist in our head-to-tail molecular design. The incorporation of this linker is 20-fold more potent than our previous compound (2) for LXR β agonistic activity (EC50) in a GAL-4 luciferase assay. Furthermore, we also identified 5-[5-(1-methylethoxy)pyridyl-2-yl]-5-methylimidazoline-2,4-dione (54), which lowers the lipophilicity of 2-hydroxyacetophenone derivative. We revealed that a combination of our newly developed linker and hydantoin (54) plays a pivotal role in improving the potency and selectivity of LXRβ. The optically separated (-)-56 increases high-density lipoprotein cholesterol levels without elevating plasma triglyceride levels and results in a decrease of the lipid accumulation area in the aortic arch in a high-fat- and cholesterol-fed low-density lipoprotein receptor knock-out mice. In this manuscript, we report that (-)-56 is a highly potent and β-selective LXR agonist for use in the treatment of atherosclerosis. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Single Particle Electron Microscopy Analysis of the Bovine Anion Exchanger 1 Reveals a Flexible Linker Connecting the Cytoplasmic and Membrane Domains

    Science.gov (United States)

    Abuladze, Natalia; Atanasov, Ivo; Ge, Peng; Narla, Mohandas; Pushkin, Alexander; Zhou, Z. Hong; Kurtz, Ira

    2013-01-01

    Anion exchanger 1 (AE1) is the major erythrocyte membrane protein that mediates chloride/bicarbonate exchange across the erythrocyte membrane facilitating CO2 transport by the blood, and anchors the plasma membrane to the spectrin-based cytoskeleton. This multi-protein cytoskeletal complex plays an important role in erythrocyte elasticity and membrane stability. An in-frame AE1 deletion of nine amino acids in the cytoplasmic domain in a proximity to the membrane domain results in a marked increase in membrane rigidity and ovalocytic red cells in the disease Southeast Asian Ovalocytosis (SAO). We hypothesized that AE1 has a flexible region connecting the cytoplasmic and membrane domains, which is partially deleted in SAO, thus causing the loss of erythrocyte elasticity. To explore this hypothesis, we developed a new non-denaturing method of AE1 purification from bovine erythrocyte membranes. A three-dimensional (3D) structure of bovine AE1 at 2.4 nm resolution was obtained by negative staining electron microscopy, orthogonal tilt reconstruction and single particle analysis. The cytoplasmic and membrane domains are connected by two parallel linkers. Image classification demonstrated substantial flexibility in the linker region. We propose a mechanism whereby flexibility of the linker region plays a critical role in regulating red cell elasticity. PMID:23393575

  9. Single particle electron microscopy analysis of the bovine anion exchanger 1 reveals a flexible linker connecting the cytoplasmic and membrane domains.

    Directory of Open Access Journals (Sweden)

    Jiansen Jiang

    Full Text Available Anion exchanger 1 (AE1 is the major erythrocyte membrane protein that mediates chloride/bicarbonate exchange across the erythrocyte membrane facilitating CO₂ transport by the blood, and anchors the plasma membrane to the spectrin-based cytoskeleton. This multi-protein cytoskeletal complex plays an important role in erythrocyte elasticity and membrane stability. An in-frame AE1 deletion of nine amino acids in the cytoplasmic domain in a proximity to the membrane domain results in a marked increase in membrane rigidity and ovalocytic red cells in the disease Southeast Asian Ovalocytosis (SAO. We hypothesized that AE1 has a flexible region connecting the cytoplasmic and membrane domains, which is partially deleted in SAO, thus causing the loss of erythrocyte elasticity. To explore this hypothesis, we developed a new non-denaturing method of AE1 purification from bovine erythrocyte membranes. A three-dimensional (3D structure of bovine AE1 at 2.4 nm resolution was obtained by negative staining electron microscopy, orthogonal tilt reconstruction and single particle analysis. The cytoplasmic and membrane domains are connected by two parallel linkers. Image classification demonstrated substantial flexibility in the linker region. We propose a mechanism whereby flexibility of the linker region plays a critical role in regulating red cell elasticity.

  10. Interactions of the periplasmic binding protein CeuE with Fe(III) n-LICAM4- siderophore analogues of varied linker length

    Science.gov (United States)

    Wilde, Ellis J.; Hughes, Adam; Blagova, Elena V.; Moroz, Olga V.; Thomas, Ross P.; Turkenburg, Johan P.; Raines, Daniel J.; Duhme-Klair, Anne-Kathrin; Wilson, Keith S.

    2017-04-01

    Bacteria use siderophores to mediate the transport of essential Fe(III) into the cell. In Campylobacter jejuni the periplasmic binding protein CeuE, an integral part of the Fe(III) transport system, has adapted to bind tetradentate siderophores using a His and a Tyr side chain to complete the Fe(III) coordination. A series of tetradentate siderophore mimics was synthesized in which the length of the linker between the two iron-binding catecholamide units was increased from four carbon atoms (4-LICAM4-) to five, six and eight (5-, 6-, 8-LICAM4-, respectively). Co-crystal structures with CeuE showed that the inter-planar angles between the iron-binding catecholamide units in the 5-, 6- and 8-LICAM4- structures are very similar (111°, 110° and 110°) and allow for an optimum fit into the binding pocket of CeuE, the inter-planar angle in the structure of 4-LICAM4- is significantly smaller (97°) due to restrictions imposed by the shorter linker. Accordingly, the protein-binding affinity was found to be slightly higher for 5- compared to 4-LICAM4- but decreases for 6- and 8-LICAM4-. The optimum linker length of five matches that present in natural siderophores such as enterobactin and azotochelin. Site-directed mutagenesis was used to investigate the relative importance of the Fe(III)-coordinating residues H227 and Y288.

  11. Carbon Dioxide Capture by a Metal-Organic Framework with Nitrogen-Rich Channels Based on Rationally Designed Triazole-Functionalized Tetraacid Organic Linker.

    Science.gov (United States)

    Seth, Saona; Savitha, Govardhan; Moorthy, Jarugu Narasimha

    2015-07-20

    A semirigid tetraacid linker H4L functionalized with 1,2,3-triazole was rationally designed and synthesized to access nitrogen-rich MOFs for selective adsorption of CO2. The cadmium MOF, that is, Cd-L, obtained by the reaction of H4L with Cd(NO3)2, is found to be a 3D porous framework structure that is robust to desolvation. Crystal structure analysis reveals channels that are decorated by the triazole moieties of L. Gas adsorption studies show that Cd-L MOF permits remarkable CO2 uptake to the extent of 99 and 1000 cc/g at 1 and 30 bar, respectively, at 0 °C. While literature survey reveals that MIL-112, constructed from a 1,2,3-triazole functionalized linker, exhibits no porosity to gas adsorption due to structural flexibility, the results with Cd-L MOF described herein emphasize how rigidification of the organic linker improves gas uptake properties of the resultant MOF.

  12. Investigating the role of chain and linker length on the catalytic activity of an H 2 production catalyst containing a β-hairpin peptide

    Energy Technology Data Exchange (ETDEWEB)

    Reback, Matthew L.; Ginovska, Bojana; Buchko, Garry W.; Dutta, Arnab; Priyadarshani, Nilusha; Kier, Brandon L.; Helm, Monte L.; Raugei, Simone; Shaw, Wendy J.

    2016-06-02

    Building on our recent report of an active H2 production catalyst [Ni(PPh2NProp-peptide)2]2+ (Prop=para-phenylpropionic acid, peptide (R10)=WIpPRWTGPR-NH2, p=D-proline, and P2N=1-aza-3,6-diphosphacycloheptane) that contains structured -hairpin peptides, here we investigate how H2 production is effected by: (1) the length of the hairpin (eight or ten residues) and (2) limiting the flexibility between the peptide and the core complex by altering the length of the linker: para-phenylpropionic acid (three carbons) or para-benzoic acid (one carbon). Reduction of the peptide chain length from ten to eight residues increases or maintains the catalytic current for H2 production for all complexes, suggesting a non-productive steric interaction at longer peptide lengths. While the structure of the hairpin appears largely intact for the complexes, NMR data are consistent with differences in dynamic behavior which may contribute to the observed differences in catalytic activity. Molecular dynamics simulations demonstrate that complexes with a one-carbon linker have the desired effect of restricting the motion of the hairpin relative to the complex; however, the catalytic currents are significantly reduced compared to complexes containing a three-carbon linker as a result of the electron withdrawing nature of the -COOH group. These results demonstrate the complexity and interrelated nature of the outer coordination sphere on catalysis.

  13. The role of H1 linker histone subtypes in preserving the fidelity of elaboration of mesendodermal and neuroectodermal lineages during embryonic development.

    Directory of Open Access Journals (Sweden)

    Giang D Nguyen

    Full Text Available H1 linker histone proteins are essential for the structural and functional integrity of chromatin and for the fidelity of additional epigenetic modifications. Deletion of H1c, H1d and H1e in mice leads to embryonic lethality by mid-gestation with a broad spectrum of developmental alterations. To elucidate the cellular and molecular mechanisms underlying H1 linker histone developmental functions, we analyzed embryonic stem cells (ESCs depleted of H1c, H1d and H1e subtypes (H1-KO ESCs by utilizing established ESC differentiation paradigms. Our study revealed that although H1-KO ESCs continued to express core pluripotency genes and the embryonic stem cell markers, alkaline phosphatase and SSEA1, they exhibited enhanced cell death during embryoid body formation and during specification of mesendoderm and neuroectoderm. In addition, we demonstrated deregulation in the developmental programs of cardiomyocyte, hepatic and pancreatic lineage elaboration. Moreover, ectopic neurogenesis and cardiomyogenesis occurred during endoderm-derived pancreatic but not hepatic differentiation. Furthermore, neural differentiation paradigms revealed selective impairments in the specification and maturation of glutamatergic and dopaminergic neurons with accelerated maturation of glial lineages. These impairments were associated with deregulation in the expression profiles of pro-neural genes in dorsal and ventral forebrain-derived neural stem cell species. Taken together, these experimental observations suggest that H1 linker histone proteins are critical for the specification, maturation and fidelity of organ-specific cellular lineages derived from the three cardinal germ layers.

  14. An Externally Accessible Linker Region in the Sodium-Coupled Phosphate Transporter PiT-1 (SLC20A1 is Important for Transport Function

    Directory of Open Access Journals (Sweden)

    Silvia Ravera

    2013-07-01

    Full Text Available Background/Aims: Members of the SLC20 cotransporter family (PiT-1, PiT-2 are ubiquitously expressed in mammalian tissue and are thought to perform housekeeping functions for intracellular Pi homeostasis as well as being implicated in vascular calcification and renal Pi reabsorption. The aims of this study were to investigate the topology of a linker region in PiT-1 between the predicted 2nd and 3rd transmembrane domains and to investigate the functional consequences of cysteine substitutions in this region. Methods: Cysteines were substituted at 18 sites in the Xenopus PiT-1 isoform and the mutants were expressed in Xenopus laevis oocytes. Transport function of the mutants was investigated by 32P tracer or two electrode voltage clamp before and after thiol modification of the novel Cys. Results: Exposure to the thiol reactive reagent resulted in diminished transport function for 7 mutants. The apparent accessibility of 5 of the mutated sites, estimated from the rate of functional thiol modification, was site-dependent. Cysteine substitution at some sites also altered the apparent affinity for Pi and cation (Na+/Li+ and substrate (phosphate/arsenate selectivity, further underscoring the importance of this linker in defining PiT-1 transport characteristics. Conclusions: The external accessibility of a linker in PiT-1 was confirmed and sites were identified that determine substrate selectivity and transport function.

  15. Preparation of 3-benzyloxy-2-pyridinone functional linkers: Tools for the synthesis of 3,2-hydroxypyridinone (HOPO) and HOPO/hydroxamic acid chelators.

    Science.gov (United States)

    Gibson, Sarah; Fernando, Rasika; Jacobs, Hollie K; Gopalan, Aravamudan S

    2015-12-08

    In contrast to 2,3-dihydroxypyridine, the 3-benzyloxy protected derivative, 2, undergoes facile alkylation at ambient temperatures with a variety of functionalized alkyl halides in good yields. This alkylation has been used to prepare a number of linkers that permit the attachment of 3,2-HOPO moieties onto various scaffolds using a wide range of coupling methods. The Mitsunobu reaction of 2 with representative alcohols was found to be of limited value due to competing O-alkylation that led to product mixtures. The phthalimide 3j can be converted in two steps to HOPO isocyanate 6 in excellent yields. Isocyanate 6 can be coupled to amines at room temperature or to alcohols in refluxing dichloroethane to obtain the corresponding urea or carbamate linked ligand systems. The coupling of isocyanate 6 with TREN followed by deprotection gave the tris-HOPO 10, an interesting target as it has both cationic and anionic binding sites. The HOPO hydroxylamine linker 11 was shown to be especially valuable as its coupling with carboxylic acids proceeds with the concomitant generation of an additional hydroxamate ligand moiety in the framework. The utility of this linker was shown by the preparation of two mixed HOPO-hydroxamate chelators, 16 and 19, based on the structure of desferrioxamine, a well-known trihydroxamate siderophore.

  16. Combining reactive triblock copolymers with functional cross-linkers: A versatile pathway to disulfide stabilized-polyplex libraries and their application as pDNA vaccines.

    Science.gov (United States)

    Heller, Philipp; Hobernik, Dominika; Lächelt, Ulrich; Schinnerer, Meike; Weber, Benjamin; Schmidt, Manfred; Wagner, Ernst; Bros, Matthias; Barz, Matthias

    2017-07-28

    Therapeutic nucleic acids such as pDNA hold great promise for the treatment of multiple diseases. These therapeutic interventions are, however, compromised by the lack of efficient and safe non-viral delivery systems, which guarantee stability during blood circulation together with high transfection efficiency. To provide these desired properties within one system, we propose the use of reactive triblock copolypept(o)ides, which include a stealth-like block for efficient shielding, a hydrophobic block based on reactive disulfides for cross-linking and a cationic block for complexation of pDNA. After the complexation step, bifunctional cross-linkers can be employed to bio-reversibly stabilize derived polyplexes by disulfide bond formation and to introduce endosomolytic moieties at the same time. Cross-linked polyplexes show no aggregation in human blood serum. Upon cellular uptake and cleavage of disulfide bonds, the cross-linkers can interact with the endosomal membrane, leading to lysis and efficient endosomal translocation. In principal, the approach allows for the combination of one polymer with various different cross-linkers and thus enables the fast forward creation of a polyplex library. Here, we provide a first insight into the potential of this concept and use a screening strategy to identify a lead candidate, which is able to transfect dendritic cells with a model DNA vaccine. Copyright © 2017. Published by Elsevier B.V.

  17. A new bis-tetraamine ligand with a chromophoric 4-(9-anthracenyl)-2,6-dimethylpyridinyl linker for glyphosate and ATP sensing.

    Science.gov (United States)

    Pouessel, Jacky; Abada, Sabah; Le Bris, Nathalie; Elhabiri, Mourad; Charbonnière, Loïc J; Tripier, Raphaël

    2013-04-14

    The synthesis of a new linear bis-tetraamine ligand L1, based on two 1,4,8,11-tetraazaundecane units grafted at the 2 and 6 positions of a pyridinyl linker substituted by an anthracenyl fluorophore in the para position, is described and anion complexation studies of L1 with anionic substrates are reported. The protonation pattern and the study of the binding properties of L1 in an aqueous medium with two anionic substrates, the nucleotide adenosine triphosphate (ATP) and the herbicide glyphosate (N-(phosphonomethyl)glycine, PMG), were investigated by means of potentiometry, NMR spectroscopy and absorption and emission spectroscopic techniques. To decipher the impact of the chromophoric linker on the complexation process and to highlight its optical properties, a comparison is established with its previously reported analog L2 devoid of the anthracenyl group. The results unambiguously show that the protonation and complexation properties are preserved despite the presence of the bulky linker, allowing for the use of L1 as a fluorescent sensor for ATP and PMG.

  18. Stabilization of Resveratrol in Blood Circulation by Conjugation to mPEG and mPEG-PLA Polymers: Investigation of Conjugate Linker and Polymer Composition on Stability, Metabolism, Antioxidant Activity and Pharmacokinetic Profile: e0118824

    National Research Council Canada - National Science Library

    Basavaraj Siddalingappa; Heather A E Benson; David H Brown; Kevin T Batty; Yan Chen

    2015-01-01

    .... But undergoes rapid metabolism in the body (half life 0.13h). Hence Polymer conjugation utilizing different chemical linkers and polymer compositions was investigated for enhanced pharmacokinetic profile of resveratrol...

  19. Stabilization of resveratrol in blood circulation by conjugation to mPEG and mPEG-PLA polymers: investigation of conjugate linker and polymer composition on stability, metabolism, antioxidant activity and pharmacokinetic profile

    National Research Council Canada - National Science Library

    Siddalingappa, Basavaraj; Benson, Heather A E; Brown, David H; Batty, Kevin T; Chen, Yan

    2015-01-01

    .... But undergoes rapid metabolism in the body (half life 0.13h). Hence Polymer conjugation utilizing different chemical linkers and polymer compositions was investigated for enhanced pharmacokinetic profile of resveratrol...

  20. Preparation of CuO/NiO composite nanofibers by electrospinning and their application for electro-catalytic oxidation of hydrazine

    Science.gov (United States)

    Hosseini, Sayed Reza; Ghasemi, Shahram; Kamali-Rousta, Mina

    2017-03-01

    In present work, polyvinyl alcohol/copper acetate-nickel acetate composite nanofibers (PVA/Cu(OAc)2-Ni(OAc)2 NFs) with various weight percentages of Cu(OAc)2:Ni(OAc)2 such as 25:75, 50:50 and 75:25 are fabricated by electrospinning method. After this, the CuO/NiO composite NFs are produced after thermal treatment. A calcination temperature at about 600 °C is determined by thermal gravimetric analysis. Field-emission scanning electron microscopy (FE-SEM) for morphology characterization indicates that large quantities of the prepared PVA/Cu(OAc)2-Ni(OAc)2 composite fibers have smooth and bead-free surfaces. Fourier transform infrared spectroscopy, FE-SEM and energy dispersive X-ray spectroscopy are used to characterize the CuO/NiO composites. According to FE-SEM results, with increasing of Cu(OAc)2 content in polymeric solution, the fibers don't remain as continuous structures after calcination and accumulate in the form of nanoparticles. Also, a carbon paste electrode (CPE) bulky modified with CuO/NiO composites is used for investigation of the electro-catalytic oxidation of hydrazine hydrate in NaOH solution. The catalytic activities of the synthesized catalysts are studied through cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The obtained results demonstrate that the most appropriate proportion of Cu(OAc)2:Ni(OAc)2 in electrospinning solution to enhance the electro-catalytic ability is 25:75.

  1. Design and construction of new potentiometric sensors for determination of Al3+ ion based on (Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine.

    Science.gov (United States)

    Mizani, F; Salmanzadeh Ardabili, S; Ganjaliab, M R; Faridbod, F; Payehghadr, M; Azmoodeh, M

    2015-04-01

    (Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine (L) was used as an active component of PVC membrane electrode (PME), coated graphite electrode (CGE) and coated silver wire electrode (CWE) for sensing Al(3+) ion. The electrodes exhibited linear Nernstian responses to Al(3+) ion in the concentration range of 1.0×10(-6) to 1.0×10(-1)M (for PME, LOD=8.8×10(-7)M), 5.5×10(-7) to 2.0×10(-1)M (for CWE, LOD=3.3×10(-7)M) and 1.5×10(-7) to 1.0×10(-1)M (for CGE, LOD=9.2×10(-8)M). The best performances were observed with the membranes having the composition of L:PVC:NPOE:NaTPB in the ratio of 5:35:57:3 (w/w; mg). The electrodes have a response time of 6s and an applicable pH range of 3.5-9.1. The sensors have a lifetime of about 15weeks and exhibited excellent selectivity over a number of mono-, bi-, and tri-valent cations including alkali, alkaline earth metal, heavy and transition metal ions. Analytical utility of the proposed sensor has been further tested by using it as an indicator electrode in the potentiometric titration of Al(3+) with EDTA. The electrode was also successfully applied for the determination of Al(3+) ion in real and pharmaceutical samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. The Specialized Hsp70 (HscA) Interdomain Linker Binds to Its Nucleotide-Binding Domain and Stimulates ATP Hydrolysis in Both cis and trans Configurations

    Science.gov (United States)

    2015-01-01

    Proteins from the isc operon of Escherichia coli constitute the machinery used to synthesize iron–sulfur (Fe–S) clusters for delivery to recipient apoproteins. Efficient and rapid [2Fe-2S] cluster transfer from the holo-scaffold protein IscU depends on ATP hydrolysis in the nucleotide-binding domain (NBD) of HscA, a specialized Hsp70-type molecular chaperone with low intrinsic ATPase activity (0.02 min−1 at 25 °C, henceforth reported in units of min–1). HscB, an Hsp40-type cochaperone, binds to HscA and stimulates ATP hydrolysis to promote cluster transfer, yet while the interactions between HscA and HscB have been investigated, the role of HscA’s interdomain linker in modulating ATPase activity has not been explored. To address this issue, we created three variants of the 40 kDa NBD of HscA: NBD alone (HscA386), NBD with a partial linker (HscA389), and NBD with the full linker (HscA395). We found that the rate of ATP hydrolysis of HscA395 (0.45 min–1) is nearly 15-fold higher than that of HscA386 (0.035 min–1), although their apparent affinities for ATP are equivalent. HscA395, which contains the full covalently linked linker peptide, exhibited intrinsic tryptophan fluorescence emission and basal thermostability that were higher than those of HscA386. Furthermore, HscA395 displayed narrower 1HN line widths in its two-dimensional 1H–15N TROSY-HSQC spectrum in comparison to HscA386, indicating that the peptide in the cis configuration binds to and stabilizes the structure of the NBD. The addition to HscA386 of a synthetic peptide with a sequence identical to that of the interdomain linker (L387LLDVIPLS395) stimulated its ATPase activity and induced widespread NMR chemical shift perturbations indicative of a binding interaction in the trans configuration. PMID:25372495

  3. Problematic alcohol use associates with sodium channel and clathrin linker 1 (SCLT1) in trauma-exposed populations.

    Science.gov (United States)

    Almli, Lynn M; Lori, Adriana; Meyers, Jacquelyn L; Shin, Jaemin; Fani, Negar; Maihofer, Adam X; Nievergelt, Caroline M; Smith, Alicia K; Mercer, Kristina B; Kerley, Kimberly; Leveille, Jennifer M; Feng, Hao; Abu-Amara, Duna; Flory, Janine D; Yehuda, Rachel; Marmar, Charles R; Baker, Dewleen G; Bradley, Bekh; Koenen, Karestan C; Conneely, Karen N; Ressler, Kerry J

    2017-10-30

    Excessive alcohol use is extremely prevalent in the United States, particularly among trauma-exposed individuals. While several studies have examined genetic influences on alcohol use and related problems, this has not been studied in the context of trauma-exposed populations. We report results from a genome-wide association study of alcohol consumption and associated problems as measured by the alcohol use disorders identification test (AUDIT) in a trauma-exposed cohort. Results indicate a genome-wide significant association between total AUDIT score and rs1433375 [N = 1036, P = 2.61 × 10-8 (dominant model), P = 7.76 × 10-8 (additive model)], an intergenic single-nucleotide polymorphism located 323 kb upstream of the sodium channel and clathrin linker 1 (SCLT1) at 4q28. rs1433375 was also significant in a meta-analysis of two similar, but independent, cohorts (N = 1394, P = 0.0004), the Marine Resiliency Study and Systems Biology PTSD Biomarkers Consortium. Functional analysis indicated that rs1433375 was associated with SCLT1 gene expression and cortical-cerebellar functional connectivity measured via resting state functional magnetic resonance imaging. Together, findings suggest a role for sodium channel regulation and cerebellar functioning in alcohol use behavior. Identifying mechanisms underlying risk for problematic alcohol use in trauma-exposed populations is critical for future treatment and prevention efforts. © 2017 Society for the Study of Addiction.

  4. P-21-activated protein kinase-1 functions as a linker between insulin and Wnt signaling pathways in the intestine.

    Science.gov (United States)

    Sun, J; Khalid, S; Rozakis-Adcock, M; Fantus, I G; Jin, T

    2009-09-03

    Hyperinsulinemia and type II diabetes are associated with an increased risk of developing colorectal tumors. We found previously that in intestinal cells, insulin or insulin-like growth factor-1 stimulates c-Myc and cyclin D1 protein expression through both Akt-dependent and Akt-independent mechanisms. The effect of Akt is attributed to the stimulation of c-Myc translation by mammalian target of rapamycin. However, Akt-independent stimulation was, associated with an increase in beta-catenin (beta-cat) in the nucleus and an increased association between beta-cat and T-cell factor binding sites on the c-Myc promoter, detected by chromatin immunoprecipitation. In this study, we show that insulin stimulated the phosphorylation/activation of p-21-activated protein kinase-1 (PAK-1) in an Akt-independent manner in vitro and in an in vivo hyperinsulinemic mouse model. Significantly, shRNA (small hairpin RNA)-mediated PAK-1 knockdown attenuated both basal and insulin-stimulated c-Myc and cyclin D1 expression, associated with a marked reduction in extracellular signal-regulated kinase activation and beta-cat phosphorylation at Ser675. Furthermore, PAK-1 silencing led to a complete blockade of insulin-stimulated beta-cat binding to the c-Myc promoter and cellular growth. Finally, inhibition of MEK, a downstream target of PAK-1, blocked insulin-stimulated nuclear beta-cat accumulation and c-Myc expression. Our observations suggest that PAK-1 serves as an important linker between insulin and Wnt signaling pathways.

  5. Merlin, a "magic" linker between extracellular cues and intracellular signaling pathways that regulate cell motility, proliferation, and survival.

    Science.gov (United States)

    Stamenkovic, Ivan; Yu, Qin

    2010-09-01

    Genetic alterations of neurofibromatosis type 2 (NF2) gene lead to the development of schwannomas, meningiomas, and ependymomas. Mutations of NF2 gene were also found in thyroid cancer, mesothelioma, and melanoma, suggesting that it functions as a tumor suppressor in a wide spectrum of cells. The product of NF2 gene is merlin (moesin-ezrin-radixin-like protein), a member of the Band 4.1 superfamily proteins. Merlin shares significant sequence homology with the ERM (Ezrin-Radixin-Moesin) family proteins and serves as a linker between transmembrane proteins and the actin-cytoskeleton. Merlin is a multifunctional protein and involved in integrating and regulating the extracellular cues and intracellular signaling pathways that control cell fate, shape, proliferation, survival, and motility. Recent studies showed that merlin regulates the cell-cell and cell-matrix adhesions and functions of the cell surface adhesion/extracellular matrix receptors including CD44 and that merlin and CD44 antagonize each other's function and work upstream of the mammalian Hippo signaling pathway. Furthermore, merlin plays important roles in stabilizing the contact inhibition of proliferation and in regulating activities of several receptor tyrosine kinases. Accumulating data also suggested an emerging role of merlin as a negative regulator of growth and progression of several non-NF2 associated cancer types. Together, these recent advances have improved our basic understanding about merlin function, its regulation, and the major signaling pathways regulated by merlin and provided the foundation for future translation of these findings into the clinic for patients bearing the cancers in which merlin function and/or its downstream signaling pathways are impaired or altered.

  6. A long-linker conjugate of fluorescein and triphenylphosphonium as mitochondria-targeted uncoupler and fluorescent neuro- and nephroprotector.

    Science.gov (United States)

    Antonenko, Yuri N; Denisov, Stepan S; Silachev, Denis N; Khailova, Ljudmila S; Jankauskas, Stanislovas S; Rokitskaya, Tatyana I; Danilina, Tatyana I; Kotova, Elena A; Korshunova, Galina A; Plotnikov, Egor Y; Zorov, Dmitry B

    2016-11-01

    Limited uncoupling of oxidative phosphorylation is known to be beneficial in various laboratory models of diseases. Linking a triphenyl-phosphonium cation to fluorescein through a decyl (C10) spacer yields a fluorescent uncoupler, coined mitoFluo, that selectively accumulates in energized mitochondria (Denisov et al., Chem.Commun. 2014). Proton-transport activity of mitoFluo was tested in liposomes reconstituted with bacteriorhodopsin. To examine the uncoupling action on mitochondria, we monitored mitochondrial membrane potential in parallel with oxygen consumption. Neuro- and nephroprotecting activity was detected by a limb-placing test and a kidney ischemia/reperfusion protocol, respectively. We compared mitoFluo properties with those of its newly synthesized analog having a short (butyl) spacer (C4-mitoFluo). MitoFluo, but not C4-mitoFluo, caused collapse of mitochondrial membrane potential resulting in stimulation of mitochondrial respiration. The dramatic difference in the uncoupling activity of mitoFluo and C4-mitoFluo was in line with the difference in their protonophoric activity on a lipid membrane. The accumulation of mitoFluo in mitochondria was more pronounced than that of C4-mitoFluo. MitoFluo decreased the rate of ROS production in mitochondria. MitoFluo was effective in preventing consequences of brain trauma in rats: it suppressed trauma-induced brain swelling and reduced a neurological deficit. Besides, mitoFluo attenuated acute kidney injury after ischemia/reperfusion in rats. A long alkyl linker was proved mandatory for mitoFluo to be a mitochondria- targeted uncoupler. MitoFluo showed high protective efficacy in certain models of oxidative stress-related diseases. MitoFluo is a candidate for developing therapeutic and fluorescence imaging agents to treat brain and kidney pathologies. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Preparation and in vivo evaluation of a novel stabilized linker for {sup 211}At labeling of protein

    Energy Technology Data Exchange (ETDEWEB)

    Talanov, Vladimir S. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States)]. E-mail: vstalanov@msrce.howard.edu; Garmestani, Kayhan [Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Regino, Celeste A.S. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Milenic, Diane E. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Plascjak, Paul S. [Department of Nuclear Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892 (United States); Waldmann, Thomas A. [Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Brechbiel, Martin W. [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States)]. E-mail: martinwb@mail.nih.gov

    2006-05-15

    Significant improvement of in vivo stability of {sup 211}At-labeled radioimmunoconjugates achieved upon employment of a recently reported new linker, succinimidyl N-2-(4-[{sup 211}At]astatophenethyl)succinamate (SAPS), prompted additional studies of its chemistry. The {sup 211}At radiolabeling of succinimidyl N-2-(4-tributylstannylphenethyl)succinamate (1) was noted to decline after storage at -15{sup o}C for greater than 6 months. Compound 1 was found to degrade via a ring closure reaction with the formation of N-2-(4-tributylstannylphenethyl)succinimide (3), and a modified procedure for the preparation of 1 was developed. The N-methyl structural analog of 1, succinimidyl N-2-(4-tributylstannylphenethyl)-N-methyl succinamate (SPEMS), was synthesized to investigate the possibility of improving the stability of reagent-protein linkage chemistry. Radiolabeling of SPEMS with {sup 211}At generates succinimidyl N-2-(4-[{sup 211}At]astatophenethyl)-N-methyl succinamate (Methyl-SAPS), with yields being consistent for greater than 1 year. Radiolabelings of 1 and SPEMS with {sup 125}I generated succinimidyl N-2-(4-[{sup 125}I]iodophenethyl)succinamate (SIPS) and succinimidyl N-2-(4-[{sup 125}I]iodophenethyl)-N-methyl succinamate (Methyl-SIPS), respectively, and showed no decline in yields. Methyl-SAPS, SAPS, Methyl-SIPS and SIPS were conjugated to Herceptin for a comparative assessment in LS-174T xenograft-bearing mice. The conjugates of Herceptin with Methyl-SAPS or Methyl-SIPS demonstrated immunoreactivity equivalent to if not superior to the SAPS and SIPS paired analogs. The in vivo studies also revealed that the N-methyl modification resulted in a superior statinated product.

  8. Synthesis of zincphthalocyanine-based conjugated microporous polymers with rigid-linker as novel and green heterogeneous photocatalysts.

    Science.gov (United States)

    Cai, Lijun; Li, Yanwei; Li, Yanhui; Wang, Hengguo; Yu, Yang; Liu, Ying; Duan, Qian

    2018-01-20

    The novel zincphthalocyanine-based conjugated microporous polymers with rigid-linker (α-ZnPc-CMP and β-ZnPc-CMP) were synthesized by copolymerization of zinc phthalocyanine (ZnPc) and 4, 6-diaminoresorcinol dihydrochloride (DADHC). The α-ZnPc-CMP and β-ZnPc-CMP were utilized as heterogeneous photocatalysts to degrade Rhodamine B (RhB) in aqueous solution. It is the first time for MPc-based CMPs used as heterogeneous photocatalysts for photodegradation of RhB to date. The highly ordered skeletal alignment and two-dimensional open-channel structure of α-ZnPc-CMP and β-ZnPc-CMP not only solve the aggregation of ZnPc and enhance its photocatalytic activity, but also facilitate the recycling and avoid the secondary pollution. The chemical structures and morphologies of α-ZnPc-CMP and β-ZnPc-CMP were well characterized by Fourier transform infrared spectra (FT-IR), solid-state 13C nuclear magnetic resonance (13C NMR), scanning electron microscopy (SEM), N2-sorption/ desorption and X-ray diffraction (XRD). The solubility experiments and thermogravimetric analysis (TGA) showed they have good chemical stability and recyclability. Furthermore, the photocatalytic tests indicated α-ZnPc-CMP and β-ZnPc-CMP have excellent photocatalytic performances for degradation of RhB (3 h, degraded 98 and 97.47%) in the presence of H2O2 under visible-light irradiation. All results reveal that α-ZnPc-CMP and β-ZnPc-CMP have great potential as photocatalysts on the degradation of organic dye contaminants. Moreover, the possible reaction mechanism of α-ZnPc-CMP and β-ZnPc-CMP as photocatalysts for the degradation of RhB is proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Stomach Chitinase from Japanese Sardine Sardinops melanostictus: Purification, Characterization, and Molecular Cloning of Chitinase Isozymes with a Long Linker.

    Science.gov (United States)

    Kawashima, Satoshi; Ikehata, Hiroki; Tada, Chihiro; Ogino, Tomohiro; Kakizaki, Hiromi; Ikeda, Mana; Fukushima, Hideto; Matsumiya, Masahiro

    2016-01-20

    Fish express two different chitinases, acidic fish chitinase-1 (AFCase-1) and acidic fish chitinase-2 (AFCase-2), in the stomach. AFCase-1 and AFCase-2 have different degradation patterns, as fish efficiently degrade chitin ingested as food. For a comparison with the enzymatic properties and the primary structures of chitinase isozymes obtained previously from the stomach of demersal fish, in this study, we purified chitinase isozymes from the stomach of Japanese sardine Sardinops melanostictus, a surface fish that feeds on plankton, characterized the properties of these isozymes, and cloned the cDNAs encoding chitinases. We also predicted 3D structure models using the primary structures of S. melanostictus stomach chitinases. Two chitinase isozymes, SmeChiA (45 kDa) and SmeChiB (56 kDa), were purified from the stomach of S. melanostictus. Moreover, two cDNAs, SmeChi-1 encoding SmeChiA, and SmeChi-2 encoding SmeChiB were cloned. The linker regions of the deduced amino acid sequences of SmeChi-1 and SmeChi-2 (SmeChi-1 and SmeChi-2) are the longest among the fish stomach chitinases. In the cleavage pattern groups toward short substrates and the phylogenetic tree analysis, SmeChi-1 and SmeChi-2 were classified into AFCase-1 and AFCase-2, respectively. SmeChi-1 and SmeChi-2 had catalytic domains that consisted of a TIM-barrel (β/α)₈-fold structure and a deep substrate-binding cleft. This is the first study showing the 3D structure models of fish stomach chitinases.

  10. Anodic Oxidation and Amperometric Sensing of Hydrazine at a Glassy Carbon Electrode Modified with Cobalt (II Phthalocyanine–cobalt (II Tetraphenylporphyrin (CoPc- (CoTPP4 Supramolecular Complex

    Directory of Open Access Journals (Sweden)

    Kenneth I. Ozoemena

    2006-08-01

    Full Text Available This paper describes the electrocatalytic behaviour of a glassy carbon electrode (GCEmodified with cobalt(IIphthalocyanine (CoPc complex peripherally tetrasubstituted withcobalt(IItetraphenylporphyrin (CoTPP complexes via ether linkages (i.e., CoPc-(CoTPP4. Thefeatures of the immobilised pentamer were interrogated with cyclic voltammetry andelectrochemical impedance spectroscopy (EIS using [Fe(CN6]3-/4- as redox probe revealedenhanced electron transfer properties with kapp ≈ 18 x 10-6 cms-1 compared to that of the bareGCE (4.7 x 10-6 cms-1. The viability of this supramolecular complex as a redox mediator for theanodic oxidation and sensitive amperometric determination of hydrazine in alkaline conditions isdescribed. The electrocatalytic oxidation of hydrazine by GCE-CoPc-(CoTPP4 was characterisedwith satisfactory catalytic current response with low non-Faradaic current (ca. 30 times lowerthan the bare GCE and at much lower oxidation potential (ca. 300 mV lower than the bareGCE. A mechanism for the studied electrocatalytic reaction was proposed based on thespectrophotometric evidence that revealed the major involvement of the Co(III/Co(II redox coupleof the central CoPc species rather than the CoTPP component of the pentamer. Rate constant forthe anodic oxidation of hydrazine was estimated from chronoamperometry as ~ 3x103 M-1s-1. Theproposed amperometric sensor displayed excellent charateristics towards the determination ofhydrazine in 0.2 M NaOH ; such as low overpotentials ( 100 mV vs Ag|AgCl, very fastamperometric response time (1 s, linear concentration range of up to 230 μM, with micromolardetection limit, high sensitivity and stability.

  11. Metal-Organic Frameworks with Internal Urea-Functionalized Dicarboxylate Linkers for SO2 and NH3 Adsorption.

    Science.gov (United States)

    Glomb, Sebastian; Woschko, Dennis; Makhloufi, Gamall; Janiak, Christoph

    2017-10-25

    Introduction of a urea R-NH-CO-NH-R group as a seven-membered diazepine ring at the center of 4,4'-biphenyl-dicarboxylic acid leads to a urea-functionalized dicarboxylate linker (L12-) from which four zinc metal-organic frameworks (MOFs) could be obtained, having a {Zn4(μ4-O)(O2C-)6} SBU and IRMOF-9 topology (compound [Zn4(μ4-O)(L1)3], 1, from dimethylformamide, DMF) or a {Zn2(O2C-)4} paddle-wheel SBU in a 2D-network (compound [Zn2(L1)2(DEF)2·2.5DEF], 2, from diethylformamide, DEF). Pillaring of the 2D-network of 2 with 4,4'-bipyridine (bipy) or 1,2-bis(4-pyridyl)ethane (bpe) gives 3D frameworks with rhombohedrally distorted pcu-a topologies ([Zn2(L1)2(bipy)], 3 and [Zn2(L1)2(bpe)], 4, respectively). The 3D-frameworks 1, 3, and 4 are 2-fold interpenetrated with ∼50% solvent-accessible volume, albeit of apparently dynamic porous character, such that N2 adsorption at 77 K does not occur, while H2 at 77 K (up to ∼1 wt %) and CO2 at 293 K (∼5 wt %) are adsorbed with large hystereses in these flexible MOFs. The urea-functionalized MOF 3 exhibits an uptake of 10.9 mmol g-1 (41 wt %) of SO2 at 293 K, 1 bar, which appears to be the highest value observed so far. Compounds 3 and 4 adsorb 14.3 mmol g-1 (20 wt %) and 17.8 mmol g-1 (23 wt %) NH3, respectively, which is at the top of the reported values. These high uptake values are traced to the urea functionality and its hydrogen-bonding interactions to the adsorbents. The gas uptake capacities follow the specific porosity of the frameworks, in combination with pore aperture size and affinity constants from fits of the adsorption isotherms.

  12. The amino acid linker between the endonuclease and helicase domains of adeno-associated virus type 5 Rep plays a critical role in DNA-dependent oligomerization.

    Science.gov (United States)

    Maggin, Jenna E; James, Jeffrey A; Chappie, Joshua S; Dyda, Fred; Hickman, Alison Burgess

    2012-03-01

    The adeno-associated virus (AAV) genome encodes four Rep proteins, all of which contain an SF3 helicase domain. The larger Rep proteins, Rep78 and Rep68, are required for viral replication, whereas Rep40 and Rep52 are needed to package AAV genomes into preformed capsids; these smaller proteins are missing the site-specific DNA-binding and endonuclease domain found in Rep68/78. Other viral SF3 helicases, such as the simian virus 40 large T antigen and the papillomavirus E1 protein, are active as hexameric assemblies. However, Rep40 and Rep52 have not been observed to form stable oligomers on their own or with DNA, suggesting that important determinants of helicase multimerization lie outside the helicase domain. Here, we report that when the 23-residue linker that connects the endonuclease and helicase domains is appended to the adeno-associated virus type 5 (AAV5) helicase domain, the resulting protein forms discrete complexes on DNA consistent with single or double hexamers. The formation of these complexes does not require the Rep binding site sequence, nor is it nucleotide dependent. These complexes have stimulated ATPase and helicase activities relative to the helicase domain alone, indicating that they are catalytically relevant, a result supported by negative-stain electron microscopy images of hexameric rings. Similarly, the addition of the linker region to the AAV5 Rep endonuclease domain also confers on it the ability to bind and multimerize on nonspecific double-stranded DNA. We conclude that the linker is likely a key contributor to Rep68/78 DNA-dependent oligomerization and may play an important role in mediating Rep68/78's conversion from site-specific DNA binding to nonspecific DNA unwinding.

  13. Sequences in Linker-1 domain of the multidrug resistance associated protein (MRP1 or ABCC1) bind to tubulin and their binding is modulated by phosphorylation.

    Science.gov (United States)

    Ambadipudi, Raghuram; Georges, Elias

    2017-01-22

    The multidrug resistant associated protein 1 (or MRP1, ABCC1) encodes two cytoplasmic linker domains (L0 and L1) composed of highly charged sequences with multiple protein kinase A/C phosphorylation sites. In this report we made use of the scanning peptide approach to identify MRP1 linker L1 (L1MRP1) interacting proteins. Scanning heptapeptides covering L1MRP1 126 amino acids (Ile846- Leu972) were synthesized and used in pull-down assays to isolate proteins from cell extracts (human multidrug resistant SCLC cell line; H69/AR). The results show four high affinity binding sequences in L1MRP1 domain [866FLRTYAST867; 906SAGKQLQRQLSSS912; 925ISRHHNSTA927 and 954AQTGQVKLSVYW959] that bound ∼55 kDa and 110 kDa polypeptides. The latter polypeptides were identified by mass spectrometry as α- and β-tubulin monomers and dimers. Western blotting with monoclonal antibodies to α- and β-tubulin proteins confirmed the mass-spectrometry results. Moreover, using recombinant full-length GST-Linker 1 fusion polypeptide (GST-L1MRP1), we confirmed the peptide scanning approach demonstrating specific binding of tubulin to GST-L1MRP1. Intriguingly, substitutions of serine residues in L1MRP1 by aspartic acid, but not alanine, abolished its binding to tubulin, suggesting that phosphorylation of Ser871, 915, 930, and 961 within L1MRP1 may modulate its binding to tubulin. Taken together, the results of this study suggest possible interaction between MRP1 and tubulin that is modulated by phosphorylation of specific sequences in the L1MRP1 domain. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Expression profiles of a banana fruit linker histone H1 gene MaHIS1 and its interaction with a WRKY transcription factor.

    Science.gov (United States)

    Wang, Jun-ning; Kuang, Jian-fei; Shan, Wei; Chen, Jiao; Xie, Hui; Lu, Wang-jin; Chen, Jian-wen; Chen, Jian-ye

    2012-08-01

    Chromatin remodeling-related proteins, such as linker histone H1, involving in fruit ripening and stress responses are poorly understood. In the present study, a novel cDNA encoding linker histone H1 gene, designated as MaHIS1 was isolated and characterized from banana fruit. The full-length cDNA sequence was 1,253 bp with an open-reading frame (ORF) of 948 bp, encoding 315 amino acids with a molecular weight of 31.98 kDa and a theoretical isoelectric point of 10.67. Subcellular localization analysis showed that MaHIS1 was a nucleus-localized protein. Real-time PCR analysis indicated that expression of MaHIS1 gene is induced by external and internal ethylene during fruit postharvest ripening. Accumulation of MaHIS1 transcript was also obviously enhanced by exogenous hormones, including methyl jasmonate, abscisic acid, and hydrogen peroxide (H₂O₂), as well as stresses, such as chilling and pathogen Colletotrichum musae infection. Moreover, yeast two-hybrid and bimolecular fluorescence complementation assays showed that MaHIS1 could interact with a transcription factor (TF) MaWRKY1. Taken together, our results suggest that MaHIS1 may be related to ripening and stress responses of banana fruit, and be likely functionally coordinating with MaWRKY1 in these physiological processes. MaHIS1 may be related to ripening and stress responses of banana fruit, and it also could interact with WRKY TF, which expands the very limited information regarding the functions of linker histone H1 in fruits.

  15. Functional extension of amino acid triads from the fourth transmembrane segment (S4) into its external linker in Shaker K(+) channels.

    Science.gov (United States)

    Yang, Ya-Chin; Lin, Shin; Chang, Po-Chun; Lin, Hsiao-Chun; Kuo, Chung-Chin

    2011-10-28

    The highly conserved fourth transmembrane segment (S4) is the primary voltage sensor of the voltage-dependent channel and would move outward upon membrane depolarization. S4 comprises repetitive amino acid triads, each containing one basic (presumably charged and voltage-sensing) followed by two hydrophobic residues. We showed that the triad organization is functionally extended into the S3-4 linker right external to S4 in Shaker K(+) channels. The arginine (and lysine) substitutes for the third and the sixth residues (Ala-359 and Met-356, respectively) external to the outmost basic residue (Arg-362) in S4 dramatically and additively stabilize S4 in the resting conformation. Also, Leu-361 and Leu-358 play a very similar role in stabilization of S4 in the resting position, presumably by their hydrophobic side chains. Moreover, the double mutation A359R/E283A leads to a partially extruded position of S4 and consequently prominent closed-state inactivation, suggesting that Glu-283 in S2 may coordinate with the arginines in the extruded S4 upon depolarization. We conclude that the triad organization extends into the S3-4 linker for about six amino acids in terms of their microenvironment. These approximately six residues should retain the same helical structure as S4, and their microenvironment serves as part of the "gating canal" accommodating the extruding S4. Upon depolarization, S4 most likely moves initially as a sliding helix and follows the path that is set by the approximately six residues in the S3-4 linker in the resting state, whereas further S4 translocation could be more like, for example, a paddle, without orderly coordination from the contiguous surroundings.

  16. The Domain II S4-S5 Linker in Nav1.9: A Missense Mutation Enhances Activation, Impairs Fast Inactivation, and Produces Human Painful Neuropathy.

    Science.gov (United States)

    Han, Chongyang; Yang, Yang; de Greef, Bianca T A; Hoeijmakers, Janneke G J; Gerrits, Monique M; Verhamme, Camiel; Qu, Jian; Lauria, Giuseppe; Merkies, Ingemar S J; Faber, Catharina G; Dib-Hajj, Sulayman D; Waxman, Stephen G

    2015-06-01

    Painful small fiber neuropathy is a challenging medical condition with no effective treatment. Non-genetic causes can be identified in one half of the subjects. Gain-of-function variants of sodium channels Nav1.7 and Nav1.8 have recently been associated with painful small fiber neuropathy. More recently, mutations of sodium channel Nav1.9 have been linked to human pain disorders, with two gain-of-function mutations found in patients with painful small fiber neuropathy. Here we report a novel Nav1.9 mutation, a glycine 699 substitution by arginine (G699R) in the domain II S4-S5 linker, identified in a patient with painful small fiber neuropathy. In this study, we assayed the mutant channels by voltage-clamp in superior cervical ganglion neurons, which do not produce endogenous Nav1.8 or Nav1.9 currents, and provide a novel platform where Nav1.9 is expressed at relatively high levels. Voltage-clamp analysis showed that the mutation hyperpolarizes (-10.1 mV) channel activation, depolarizes (+6.3 mV) steady-state fast inactivation, slows deactivation, and enhances ramp responses compared with wild-type Nav1.9 channels. Current-clamp analysis showed that the G699R mutant channels render dorsal root ganglion neurons hyperexcitable, via depolarized resting membrane potential, reduced current threshold and increased evoked firing. These observations show that the domain II S4-S5 linker plays an important role in the gating of Nav1.9 and demonstrates that a mutation in this linker is linked to a common pain disorder.

  17. In-vitro DNA binding and cleavage studies with pBR322 of N,N-Bis(3{beta}-acetoxy-5{alpha}-cholest-6-yl-idene)hydrazine

    Energy Technology Data Exchange (ETDEWEB)

    Tabassum, Zishan [School of Industrial Technology, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Muddassir, Mohd [Department of Chemistry, Aligarh Muslim University, Aligarh 202002, U.P. (India); Sulaiman, Othman [School of Industrial Technology, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Arjmand, Farukh, E-mail: farukh_arjmand@yahoo.co.in [Department of Chemistry, Aligarh Muslim University, Aligarh 202002, U.P. (India)

    2012-08-15

    The DNA binding studies of the triterpenoid derivative, cholesterol, N,N-Bis(3{beta}-acetoxy-5{alpha}-cholest-6-yl-idene)hydrazine (L) with CT DNA were carried out by employing different optical methods viz, UV-vis and fluorescence spectroscopy. The ligand binds to DNA through hydrophobic interaction with K{sub b} value found to be 4.7 Multiplication-Sign 10{sup 3} M{sup -1}. These observations have been validated also by fluorescence spectroscopy. (L) exhibits a remarkable DNA cleavage activity with pBR322 DNA in the presence of different activators and the DNA is probably cleaved by an other than oxidative mechanism, possibly by a discernable hydrolytic pathway. In the presence of major and minor groove binding agents, (L) prefers major groove binding of the DNA. - Highlights: Black-Right-Pointing-Pointer DNA binding studies of the triterpenoid derivative, cholesterol, N,N-Bis(3{beta}-acetoxy-5{alpha}-cholest-6-yl-idene)hydrazine. Black-Right-Pointing-Pointer The ligand binds to DNA through hydrophobic interaction with K{sub b} value found to be 4.7 Multiplication-Sign 10{sup 3} M{sup -1}. Black-Right-Pointing-Pointer DNA is probably cleaved by an other than oxidative mechanism, possibly by a discernable hydrolytic pathway. Black-Right-Pointing-Pointer In the presence of major and minor groove binding agents, the (L) prefers major groove binding of the DNA.

  18. Butane-1,2,3,4-tetraol-based amphiphilic stereoisomers for membrane protein study: importance of chirality in the linker region

    DEFF Research Database (Denmark)

    Das, Manabendra; Du, Yang; Mortensen, Jonas S.

    2017-01-01

    Amphiphile selection is a crucial step in membrane protein structural and functional study. As conventional detergents have limited scope and utility, novel agents with enhanced efficacy need to be developed. Although a large number of novel agents have been reported, so far there has been...... of the targeted membrane proteins depending on the chirality of the linker region. These findings indicate an important role for detergent stereochemistry in membrane protein stabilization. In addition, we generally observed enhanced detergent efficacy with increasing alkyl chain length, reinforcing...

  19. Affinities of bispyridinium non-oxime compounds to [(3)H]epibatidine binding sites of Torpedo californica nicotinic acetylcholine receptors depend on linker length.

    Science.gov (United States)

    Niessen, K V; Seeger, T; Tattersall, J E H; Timperley, C M; Bird, M; Green, C; Thiermann, H; Worek, F

    2013-12-05

    The toxicity of organophosphorus nerve agents or pesticides arises from accumulation of acetylcholine and overstimulation of both muscarinic and nicotinic acetylcholine receptors (mAChRs and nAChRs) due to inhibition of acetylcholinesterase (AChE). Standard treatment by administration of atropine and oximes, e.g., obidoxime or pralidoxime, focuses on antagonism of mAChRs and reactivation of AChE, whereas nicotinic malfunction is not directly treated. An alternative approach would be to use nAChR active substances to counteract the effects of accumulated acetylcholine. Promising in vitro and in vivo results were obtained with the bispyridinium compounds SAD-128 (1,1'-oxydimethylene bis(4-tert-butylpyridinium) dichloride) and MB327 (1,1'-(propane-1,3-diyl)bis(4-tert-butylpyridinium) di(iodide)), which were partly attributed to their interaction with nAChRs. In this study, a homologous series of unsubstituted and 4-tert-butyl-substituted bispyridinium compounds with different alkane linker lengths was investigated in competition binding experiments using [(3)H]epibatidine as a reporter ligand. Additionally, the effect of the well-characterised MB327 on the [(3)H]epibatidine equilibrium dissociation (KD) constant in different buffers was determined. This study demonstrated that divalent cations increased the affinity of [(3)H]epibatidine. Since quaternary ammonium molecules are known to inhibit AChE, the obtained affinity constants of the tested bispyridinium compounds were compared with the inhibition of human AChE. In competition experiments, bispyridinium derivatives of longer linker length displaced [(3)H]epibatidine and inhibited AChE strongly. Bispyridinium compounds with short linkers, at most, have an allosteric interaction with the [(3)H]epibatidine binding sites and barely inhibited AChE. In dependence on alkane linker length, the bispyridinium compounds seemed to interact at different binding sites. However, the exact binding sites of the bispyridinium

  20. Saccharomyces cerevisiae Linker Histone Hho1p Functionally Interacts with Core Histone H4 and Negatively Regulates the Establishment of Transcriptionally Silent Chromatin*

    OpenAIRE

    Yu, Qun; Kuzmiak, Holly; Zou, Yanfei; Olsen, Lars; Defossez, Pierre-Antoine; Bi, Xin

    2009-01-01

    Saccharomyces cerevisiae linker histone Hho1p is not essential for cell viability, and very little is known about its function in vivo. We show that deletion of HHO1 (hho1Δ) suppresses the defect in transcriptional silencing caused by a mutation in the globular domain of histone H4. hho1Δ also suppresses the reduction in HML silencing by the deletion of SIR1 that is involved in the establishment of silent chromatin at HML. We further show that hho1Δ suppresses chan...