WorldWideScience

Sample records for side chain replacements

  1. Side Chain Engineering in Solution-Processable Conjugated Polymers

    KAUST Repository

    Mei, Jianguo; Bao, Zhenan

    2014-01-01

    Side chains in conjugated polymers have been primarily utilized as solubilizing groups. However, these side chains have roles that are far beyond. We advocate using side chain engineering to tune a polymer's physical properties, including absorption

  2. Side chain polysiloxanes with phthalocyanine moieties

    Directory of Open Access Journals (Sweden)

    T. Ganicz

    2012-05-01

    Full Text Available Side chain polysiloxane with 5-(pentyloxy-3-methyloxy-9,10,16,17,23,24-hexakis(octenyloxyphthalocyanine moieties is synthesized by hydrosilylation reaction. The phase behavior and thermooptical properties of the polysiloxane and starting 2-(pent-4-enyloxy-3-methyloxy-9,10,16,17,23,24-hexakis(octenyloxyphthalocyanine is examined by POM (Polarizing optical microscopy, TOA (thermooptical analysis, DSC (differential scanning calorimetry, AFM (atomic force microscopy and SAXS (small angle X-ray scattering studies. The effect of the attachment of phthalocyanine to polysiloxane chains over phase transitions and phase morphology is discussed in details.

  3. Side Chain Cyclized Aromatic Amino Acids

    DEFF Research Database (Denmark)

    Van der Poorten, Olivier; Knuhtsen, Astrid; Sejer Pedersen, Daniel

    2016-01-01

    Constraining the conformation of flexible peptides is a proven strategy to increase potency, selectivity, and metabolic stability. The focus has mostly been on constraining the backbone dihedral angles; however, the correct orientation of the amino acid side chains (χ-space) that constitute...... the peptide pharmacophore is equally important. Control of χ-space utilizes conformationally constrained amino acids that favor, disfavor, or exclude the gauche (-), the gauche (+), or the trans conformation. In this review we focus on cyclic aromatic amino acids in which the side chain is connected...... to the peptide backbone to provide control of χ(1)- and χ(2)-space. The manifold applications for cyclized analogues of the aromatic amino acids Phe, Tyr, Trp, and His within peptide medicinal chemistry are showcased herein with examples of enzyme inhibitors and ligands for G protein-coupled receptors....

  4. Side Chain Engineering in Solution-Processable Conjugated Polymers

    KAUST Repository

    Mei, Jianguo

    2014-01-14

    Side chains in conjugated polymers have been primarily utilized as solubilizing groups. However, these side chains have roles that are far beyond. We advocate using side chain engineering to tune a polymer\\'s physical properties, including absorption, emission, energy level, molecular packing, and charge transport. To date, numerous flexible substituents suitable for constructing side chains have been reported. In this Perspective article, we advocate that the side chain engineering approach can advance better designs for next-generation conjugated polymers. © 2013 American Chemical Society.

  5. SCit: web tools for protein side chain conformation analysis.

    Science.gov (United States)

    Gautier, R; Camproux, A-C; Tufféry, P

    2004-07-01

    SCit is a web server providing services for protein side chain conformation analysis and side chain positioning. Specific services use the dependence of the side chain conformations on the local backbone conformation, which is described using a structural alphabet that describes the conformation of fragments of four-residue length in a limited library of structural prototypes. Based on this concept, SCit uses sets of rotameric conformations dependent on the local backbone conformation of each protein for side chain positioning and the identification of side chains with unlikely conformations. The SCit web server is accessible at http://bioserv.rpbs.jussieu.fr/SCit.

  6. Rational Design of Coordination Polymers with Flexible Oxyethylene Side Chains

    International Nuclear Information System (INIS)

    Choi, Eun Young; Gao, Chunji; Lee, Suck Hyun; Kwon, O Pil

    2012-01-01

    We rationally designed and synthesized metallopolymers with organic 1,4-benzenedicarboxylic acid (BDC) linkers with different lengths of oxyethylene side chains in order to examine the influence of side chains on the coordination characteristics. While in a previous report the BDC linkers with alkyl side chains were found to form three-dimensional (3D) isoreticular metal-organic framework (IRMOF) structures or one-dimensional (1D) coordination polymeric structures with short -O(CH 2 ) 6 CH 3 or long -O(CH 2 ) 9 CH 3 side chains, respectively, new BDC linkers with oxyethylene side chains of the same lengths, -(OCH 2 CH 2 ) 2 CH 3 and -(OCH 2 CH 2 ) 3 CH 3 , form only 3D IRMOF structures. This result is attributed to the higher flexibility and smaller volume of oxyethylene side chains compared to alkyl side chains

  7. Modelling antibody side chain conformations using heuristic database search.

    Science.gov (United States)

    Ritchie, D W; Kemp, G J

    1997-01-01

    We have developed a knowledge-based system which models the side chain conformations of residues in the variable domains of antibody Fv fragments. The system is written in Prolog and uses an object-oriented database of aligned antibody structures in conjunction with a side chain rotamer library. The antibody database provides 3-dimensional clusters of side chain conformations which can be copied en masse into the model structure. The object-oriented database architecture facilitates a navigational style of database access, necessary to assemble side chains clusters. Around 60% of the model is built using side chain clusters and this eliminates much of the combinatorial complexity associated with many other side chain placement algorithms. Construction and placement of side chain clusters is guided by a heuristic cost function based on a simple model of side chain packing interactions. Even with a simple model, we find that a large proportion of side chain conformations are modelled accurately. We expect our approach could be used with other homologous protein families, in addition to antibodies, both to improve the quality of model structures and to give a "smart start" to the side chain placement problem.

  8. SCit: web tools for protein side chain conformation analysis

    OpenAIRE

    Gautier, R.; Camproux, A.-C.; Tufféry, P.

    2004-01-01

    SCit is a web server providing services for protein side chain conformation analysis and side chain positioning. Specific services use the dependence of the side chain conformations on the local backbone conformation, which is described using a structural alphabet that describes the conformation of fragments of four-residue length in a limited library of structural prototypes. Based on this concept, SCit uses sets of rotameric conformations dependent on the local backbone conformation of each...

  9. Integrated planning in supply chains with buy-side and sell-side

    Indian Academy of Sciences (India)

    Supply chain management; dynamic pricing; partner selection; supply chain planning; electronic marketplaces. Abstract. In this paper we develop a quadratic programming model for partner selection and planning in integrated supply chain networks embedded with both sell-side and buy-side electronic marketplaces.

  10. Simultaneous in vivo truncation of pectic side chains

    DEFF Research Database (Denmark)

    Øbro, Jens; Borkhardt, Bernhard; Harholt, Jesper

    2009-01-01

    . These modifications often prevent gelation, which has been a major functional requirement of commercial pectins until recently. We have previously shown that modification of pectin is possible through heterologous expression of pectin degrading enzymes in planta. To test the effect of simultaneous modification......Despite the wide occurrence of pectin in nature only a few source materials have been used to produce commercial pectins. One of the reasons for this is that many plant species contain pectins with high levels of neutral sugar side chains or that are highly substituted with acetyl or other groups...... of the two main neutral pectic side chains in pectic rhamnogalacturonan I (RGI), we constitutively expressed two different enzymes in Arabidopsis thaliana that would either modify the galactan or the arabinan side chains, or both side chains simultaneously. Our analysis showed that the simultaneous...

  11. A protein-dependent side-chain rotamer library.

    KAUST Repository

    Bhuyan, M.S.

    2011-12-14

    Protein side-chain packing problem has remained one of the key open problems in bioinformatics. The three main components of protein side-chain prediction methods are a rotamer library, an energy function and a search algorithm. Rotamer libraries summarize the existing knowledge of the experimentally determined structures quantitatively. Depending on how much contextual information is encoded, there are backbone-independent rotamer libraries and backbone-dependent rotamer libraries. Backbone-independent libraries only encode sequential information, whereas backbone-dependent libraries encode both sequential and locally structural information. However, side-chain conformations are determined by spatially local information, rather than sequentially local information. Since in the side-chain prediction problem, the backbone structure is given, spatially local information should ideally be encoded into the rotamer libraries. In this paper, we propose a new type of backbone-dependent rotamer library, which encodes structural information of all the spatially neighboring residues. We call it protein-dependent rotamer libraries. Given any rotamer library and a protein backbone structure, we first model the protein structure as a Markov random field. Then the marginal distributions are estimated by the inference algorithms, without doing global optimization or search. The rotamers from the given library are then re-ranked and associated with the updated probabilities. Experimental results demonstrate that the proposed protein-dependent libraries significantly outperform the widely used backbone-dependent libraries in terms of the side-chain prediction accuracy and the rotamer ranking ability. Furthermore, without global optimization/search, the side-chain prediction power of the protein-dependent library is still comparable to the global-search-based side-chain prediction methods.

  12. A protein-dependent side-chain rotamer library.

    KAUST Repository

    Bhuyan, M.S.; Gao, Xin

    2011-01-01

    Protein side-chain packing problem has remained one of the key open problems in bioinformatics. The three main components of protein side-chain prediction methods are a rotamer library, an energy function and a search algorithm. Rotamer libraries summarize the existing knowledge of the experimentally determined structures quantitatively. Depending on how much contextual information is encoded, there are backbone-independent rotamer libraries and backbone-dependent rotamer libraries. Backbone-independent libraries only encode sequential information, whereas backbone-dependent libraries encode both sequential and locally structural information. However, side-chain conformations are determined by spatially local information, rather than sequentially local information. Since in the side-chain prediction problem, the backbone structure is given, spatially local information should ideally be encoded into the rotamer libraries. In this paper, we propose a new type of backbone-dependent rotamer library, which encodes structural information of all the spatially neighboring residues. We call it protein-dependent rotamer libraries. Given any rotamer library and a protein backbone structure, we first model the protein structure as a Markov random field. Then the marginal distributions are estimated by the inference algorithms, without doing global optimization or search. The rotamers from the given library are then re-ranked and associated with the updated probabilities. Experimental results demonstrate that the proposed protein-dependent libraries significantly outperform the widely used backbone-dependent libraries in terms of the side-chain prediction accuracy and the rotamer ranking ability. Furthermore, without global optimization/search, the side-chain prediction power of the protein-dependent library is still comparable to the global-search-based side-chain prediction methods.

  13. Difference between right and left side in total knee and unicondylar knee replacement: An interesting observation

    Directory of Open Access Journals (Sweden)

    Vasudevan Thirumal Selvan

    2005-02-01

    Full Text Available We report an observation made about the differences between right and left side in case of total knee and unicondylar knee replacement. It was found that unicondylar knee replacement was performed more commonly on the left side (66%, as compared to only 34% on right side, where as total knee replacement was more common on the right side (64% as compared to 36% on left side. The exact clinical utility of this difference is yet to be known.

  14. The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes

    KAUST Repository

    Giovannitti, Alexander

    2018-04-24

    We report a design strategy that allows the preparation of solution processable n-type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol-based side chain. A series of random copolymers was prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90, and 100 with respect to the alkyl side chains. These were characterized to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions, and performance in OECTs when operated in aqueous electrolytes. We observed that glycol side chain percentages of >50% are required to achieve volumetric charging, while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.

  15. The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes

    KAUST Repository

    Giovannitti, Alexander; Maria, Iuliana P.; Hanifi, David; Donahue, Mary J.; Bryant, Daniel; Barth, Katrina J.; Makdah, Beatrice E.; Savva, Achilleas; Moia, Davide; Zetek, Matyá š; Barnes, Piers R.F.; Reid, Obadiah G.; Inal, Sahika; Rumbles, Garry; Malliaras, George G.; Nelson, Jenny; Rivnay, Jonathan; McCulloch, Iain

    2018-01-01

    We report a design strategy that allows the preparation of solution processable n-type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol-based side chain. A series of random copolymers was prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90, and 100 with respect to the alkyl side chains. These were characterized to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions, and performance in OECTs when operated in aqueous electrolytes. We observed that glycol side chain percentages of >50% are required to achieve volumetric charging, while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.

  16. Liquid crystal polymers: evidence of hairpin defects in nematic main chains, comparison with side chain polymers

    Science.gov (United States)

    Li, M. H.; Brûlet, A.; Keller, P.; Cotton, J. P.

    1996-09-01

    This article describes the conformation of two species of liquid crystalline polymers as revealed by small angle neutron scattering. The results obtained with side chain polymers are recalled. The procedure used to analyze the scattering data of main chains in the nematic phase is reported in this paper. It permits a demonstration of the existence of hairpins. Comparison of both polymer species shows that in the isotropic phase, the two polymers adopt a random coil conformation. In the nematic phase, the conformations are very different; the side chains behave as a melt of penetrable random coils whereas the main chains behave as a nematic phase of non penetrable cylinders.

  17. Photoinduced Circular Anisotropy in Side-Chain Azobenzene Polyesters

    DEFF Research Database (Denmark)

    Nikolova, L.; Todorov, T.; Ivanov, M.

    1997-01-01

    We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time...

  18. Access to Functionalized Steroid Side Chains via Modified Julia Olefination

    Science.gov (United States)

    Izgu, Enver Cagri; Burns, Aaron C.; Hoye, Thomas R.

    2011-01-01

    Various functionalized steroidal side chains were conveniently accessed by a modified Julia olefination strategy using a common sulfone donor and an appropriate α-branched aldehyde acceptor. For the coupling of these hindered classes of reaction partners (and in contrast to typically observed trends), the benzothiazolyl(BT)-sulfone anion gave superior outcomes compared to the phenyltetrazolyl(PT)-sulfone anion. PMID:21244047

  19. TROSY of side-chain amides in large proteins

    Science.gov (United States)

    Liu, Aizhuo; Yao, Lishan; Li, Yue; Yan, Honggao

    2012-01-01

    By using the mixed solvent of 50% H2O/50% D2O and employing deuterium decoupling, TROSY experiments exclusively detect NMR signals from semideuterated isotopomers of carboxamide groups with high sensitivities for proteins with molecular weights up to 80 kDa. This isotopomer-selective strategy extends TROSY experiments from exclusively detecting backbone to both backbone and side-chain amides, particularly in large proteins. Because of differences in both TROSY effect and dynamics between 15N–HE{DZ} and 15N–HZ{DE} isotopomers of the same carboxamide, the 15N transverse magnetization of the latter relaxes significantly faster than that of the former, which provides a direct and reliable stereospecific distinction between the two configurations. The TROSY effects on the 15N–HE{DZ} isotopomers of side-chain amides are as significant as on backbone amides. PMID:17347000

  20. Side-chain liquid crystalline polyesters for optical information storage

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Holme, Christian; Hvilsted, Søren

    1996-01-01

    and holographic storage in one particular polyester are described in detail and polarized Fourier transform infrared spectroscopic data complementing the optical data are presented. Optical and atomic force microscope investigations point to a laser-induced aggregation as responsible for permanent optical storage.......Azobenzene side-chain liquid crystalline polyester structures suitable for permanent optical storage are described. The synthesis and characterization of the polyesters together with differential scanning calorimetry and X-ray investigations are discussed. Optical anisotropic investigations...

  1. Highly conductive side chain block copolymer anion exchange membranes.

    Science.gov (United States)

    Wang, Lizhu; Hickner, Michael A

    2016-06-28

    Block copolymers based on poly(styrene) having pendent trimethyl styrenylbutyl ammonium (with four carbon ring-ionic group alkyl linkers) or benzyltrimethyl ammonium groups with a methylene bridge between the ring and ionic group were synthesized by reversible addition-fragmentation radical (RAFT) polymerization as anion exchange membranes (AEMs). The C4 side chain polymer showed a 17% increase in Cl(-) conductivity of 33.7 mS cm(-1) compared to the benzyltrimethyl ammonium sample (28.9 mS cm(-1)) under the same conditions (IEC = 3.20 meq. g(-1), hydration number, λ = ∼7.0, cast from DMF/1-propanol (v/v = 3 : 1), relative humidity = 95%). As confirmed by small angle X-ray scattering (SAXS), the side chain block copolymers with tethered ammonium cations showed well-defined lamellar morphologies and a significant reduction in interdomain spacing compared to benzyltrimethyl ammonium containing block copolymers. The chemical stabilities of the block copolymers were evaluated under severe, accelerated conditions, and degradation was observed by (1)H NMR. The block copolymer with C4 side chain trimethyl styrenylbutyl ammonium motifs displayed slightly improved stability compared to that of a benzyltrimethyl ammonium-based AEM at 80 °C in 1 M NaOD aqueous solution for 30 days.

  2. Investigating side chain mediated electroluminescence from carbazole-modified polyfluorene.

    Science.gov (United States)

    Liao, Jin-Long; Chen, Xiwen; Liu, Ching-Yang; Chen, Show-An; Su, Chiu-Huen; Su, An-Chung

    2007-09-06

    In molecular design of electroluminescent (EL) conjugated polymers, introducing a charge transport moiety on a side chain is found to be a promising method for balancing electron and hole fluxes in EL devices without changing the emitting color if there is no interaction between moiety and main chain. In the case of grafting a carbazole (Cz) moiety (hole transporting) on blue emitting polyfluorene, a green emission appears with intensity comparable to the blue emission, which was attributed to a possible interaction between main chain and Cz as previously reported by us. Here, a detailed study of its EL mechanism was carried out by means of time-resolved EL with the assistance of molecular simulation and thermally stimulated current measurements; exploration of how main chain segments interact with the transport moiety was performed. We found the Cz groups in Cz100PF play multiple roles: they act as (1) hole transporter to improve hole injection, (2) hole trapping site for efficient electron-hole recombination to yield blue-emitting excitons, and (3) source of green emission from electroplex formed via electric field-mediated interaction of the Cz/Cz radical cation with an electron in the nearby PF backbone. In combination, these observations suggest that integrated consideration for both intramolecular and intermolecular interactions provides a new route of molecular design of efficient EL polymers.

  3. Prediction of methyl-side Chain Dynamics in Proteins

    International Nuclear Information System (INIS)

    Ming Dengming; Brueschweiler, Rafael

    2004-01-01

    A simple analytical model is presented for the prediction of methyl-side chain dynamics in comparison with S 2 order parameters obtained by NMR relaxation spectroscopy. The model, which is an extension of the local contact model for backbone order parameter prediction, uses a static 3D protein structure as input. It expresses the methyl-group S 2 order parameters as a function of local contacts of the methyl carbon with respect to the neighboring atoms in combination with the number of consecutive mobile dihedral angles between the methyl group and the protein backbone. For six out of seven proteins the prediction results are good when compared with experimentally determined methyl-group S 2 values with an average correlation coefficient r-bar=0.65±0.14. For the unusually rigid cytochrome c 2 no significant correlation between prediction and experiment is found. The presented model provides independent support for the reliability of current side-chain relaxation methods along with their interpretation by the model-free formalism

  4. Ion-Exchange Membranes Based on Polynorbornenes with Fluorinated Imide Side Chain Groups

    Directory of Open Access Journals (Sweden)

    Arlette A. Santiago

    2012-01-01

    Full Text Available The electrochemical characteristics of cation-exchange membranes based on polynorbornenes with fluorinated and sulfonated dicarboximide side chain groups were reported. This study was extended to a block copolymer containing structural units with phenyl and 4-oxybenzenesulfonic acid, 2,3,5,6-tetrafluorophenyl moieties replacing the hydrogen atom of the dicarboximide group. A thorough study on the electrochemical characteristics of the membranes involving electromotive forces of concentration cells and proton conductivity is reported. The proton permselectivity of the membranes is also discussed.

  5. The dominant role of side chains in supramolecular double helical organisation in synthetic tripeptides

    Science.gov (United States)

    Sharma, Ankita; Tiwari, Priyanka; Dutt Konar, Anita

    2018-06-01

    Peptide self-assembled nanostructures have attracted attention recently owing to their promising applications in diversified avenues. To validate the importance of sidechains in supramolecular architectural stabilization, herein this report describes the self-assembly propensities involving weak interactions in a series of model tripeptides Boc-Xaa-Aib-Yaa-OMe I-IV, (where Xaa = 4-F-Phe/NMeSer/Ile & Yaa = Tyr in peptide I-III respectively and Xaa = 4-F-Phe & Yaa = Ile in peptide IV) differing in terminal side chains. The solid state structural analysis reveals that tripeptide (I) displays supramolecular preference for double helical architecture. However, when slight modification has been introduced in the N-terminal side chains disfavour the double helical organisation (Peptide II and III). Indeed the peptides display sheet like ensemble within the framework. Besides replacement of C-terminal Tyr by Ile in peptide I even do not promote the architecture, emphasizing the dominant role of balance of side chains in stabilizing double helical organisation. The CD measurements, concentration dependant studies, NMR titrations and ROESY spectra are well in agreement with the solid state conformational investigation. Moreover the morphological experiments utilizing FE-SEM, support the heterogeneity present in the peptides. Thus this work may not only hold future promise in understanding the structure and function of neurodegenerative diseases but also assist in rational design of protein modification in biologically active peptides.

  6. Beta-scission of side-chain alkoxyl radicals on peptides and proteins results in the loss of side-chains as aldehydes and ketones

    DEFF Research Database (Denmark)

    Headlam, Henrietta A; Davies, Michael Jonathan

    2002-01-01

    Exposure of proteins to radicals in the presence of O(2) results in side-chain oxidation and backbone fragmentation; the interrelationship between these processes is not fully understood. Recently, initial attack on Ala side-chains was shown to give alpha-carbon radicals (and hence backbone cleav...

  7. Light scattering of thin azobenzene side-chain polyester layers

    DEFF Research Database (Denmark)

    Kerekes, Á.; Lörincz, E.; Ramanujam, P.S.

    2002-01-01

    Light scattering properties of liquid crystalline and amorphous azobenzene side-chain polyester layers used for optical data storage were examined by means of transmissive scatterometry. Comparative experiments show that the amorphous polyester has significantly lower light scattering...... characteristics than the liquid crystalline polyester. The amorphous samples have negligible polarization part orthogonal to the incident beam. the liquid crystalline samples have relative high orthogonal polarization part in light scattering, The light scattering results can be used to give a lower limit...... for the domain size in thin liquid crystalline polyester layers being responsible for the dominant light scattering. The characteristic domain Sizes obtained from the Fourier transformation of polarization microscopic Pictures confirm these values....

  8. Solvent Exchange Rates of Side-chain Amide Protons in Proteins

    International Nuclear Information System (INIS)

    Rajagopal, Ponni; Jones, Bryan E.; Klevit, Rachel E.

    1998-01-01

    Solvent exchange rates and temperature coefficients for Asn/Gln side-chain amide protons have been measured in Escherichia coli HPr. The protons of the eight side-chain amide groups (two Asn and six Gln) exhibit varying exchange rates which are slower than some of the fast exchanging backbone amide protons. Differences in exchange rates of the E and Z protons of the same side-chain amide group are obtained by measuring exchange rates at pH values > 8. An NOE between a side-chain amide proton and a bound water molecule was also observed

  9. Incidence and factors associated with infective endocarditis in patients undergoing left-sided heart valve replacement

    DEFF Research Database (Denmark)

    Østergaard, Lauge; Valeur, Nana; Ihlemann, Nikolaj

    2018-01-01

    Aims: Patients with left-sided heart valve replacement are considered at high-risk of infective endocarditis (IE). However, data on the incidence and risk factors associated with IE are sparse. Methods and results: Through Danish administrative registries, we identified patients who underwent left.......35-2.15), and cardiac implantable electronic device (CIED) (HR = 1.57, 95% CI 1.19-2.06) were among factors associated with an increased risk of IE. Conclusion: Infective endocarditis after left-sided heart valve replacement is not uncommon and occurs in about 1/20 over 10 years. Male, bioprosthetic valve, and heart...

  10. Synthesis and characterization of novel side-chain liquid crystalline polycarbonates, 4 - Synthesis of side-chain liquid crystalline polycarbonates with mesogenic groups having tails of different lengths

    NARCIS (Netherlands)

    Jansen, J.C.; Addink, R.; Nijenhuis, K.T.; Mijs, W.J.

    1999-01-01

    Side-chain liquid crystalline polycarbonates with alkoxyphenylbenzoate side groups, having a short spacer and tails ranging from 1 to 8 C-atoms, were synthesized. The polymers were prepared by an organo-zinc catalysed copolymerization of carbon dioxide and mesogenic 4-alkoxyphenyl

  11. Synthesis and characterization of novel side-chain liquid crystalline polycarbonates, 5 - Mesophase characterization of side-chain liquid crystalline polycarbonates with tails of different lengths

    NARCIS (Netherlands)

    Jansen, J.C.; Addink, R.; Nijenhuis, K.T.; Mijs, W.J.

    1999-01-01

    The mesomorphic properties and thermal stability of side-chain LC polycarbonates with alkoxyphenyl benzoate side groups having a short spacer and alkoxy tails ranging from 1 to 8 carbon atoms were studied by DSC, X-ray diffraction and polarized light optical microscopy. All polymers have a smectic A

  12. THE DEAD-END ELIMINATION THEOREM AND ITS USE IN PROTEIN SIDE-CHAIN POSITIONING

    NARCIS (Netherlands)

    DESMET, J; DEMAEYER, M; HAZES, B; LASTERS, [No Value

    1992-01-01

    THE prediction of a protein's tertiary structure is still a considerable problem because the huge amount of possible conformational space' makes it computationally difficult. With regard to side-chain modelling, a solution has been attempted by the grouping of side-chain conformations into

  13. The influence of aliphatic side chain of anacardic acid on molecular ...

    African Journals Online (AJOL)

    Interestingly, the presence of the aliphatic side chain in AnMcr resulted in more uniform imprinted beads as compared to particle agglomerates obtained from SaMcr in the presence of propranolol template. Therefore, the aliphatic side chain of anacardic acid improves both molecular recognition of imprinted polymers as ...

  14. Microphase Separation within a Comb Copolymer with Attractive Side Chains : A Computer Simulation Study

    NARCIS (Netherlands)

    Vasilevskaya, V.V.; Klochkov, A.A.; Khalatur, P.G.; Khokhlov, A.R.; Brinke, G. ten

    2001-01-01

    Computer simulation modelling of a flexible comb copolymer with attractive interactions between the monomer units of the side chains is performed. The conditions for the coil-globule transition, induced by the increase of attractive interaction, ε, between side chain monomer units, are analysed for

  15. Using supply side evidence to inform oral artemisinin monotherapy replacement in Myanmar: a case study.

    Science.gov (United States)

    Khin, Hnin Su Su; Aung, Tin; Aung, Moe; Thi, Aung; Boxshall, Matt; White, Chris

    2016-08-18

    In 2012, alarmingly high rates of oral artemisinin monotherapy availability and use were detected along Eastern Myanmar, threatening efforts to halt the spread of artemisinin resistance in the Greater Mekong Subregion (GMS), and globally. The aim of this paper is to exemplify how the use of supply side evidence generated through the ACTwatch project shaped the artemisinin monotherapy replacement malaria (AMTR) project's design and interventions to rapidly displace oral artemisinin monotherapy with subsidized, quality-assured ACT in the private sector. The AMTR project was implemented as part of the Myanmar artemisinin resistance containment (MARC) framework along Eastern Myanmar. Guided by outlet survey and supply chain evidence, the project implemented a high-level subsidy, including negotiations with a main anti-malarial distributor, with the aim of squeezing oral artemisinin monotherapy out of the market through price competition and increased availability of quality-assured artemisinin-based combinations. This was complemented with a plethora of demand-creation activities targeting anti-malarial providers and consumers. Priority outlet types responsible for the distribution of oral artemisinin monotherapy were identified by the outlet survey, and this evidence was used to target the AMTR project's supporting interventions. The widespread availability and use of oral artemisinin monotherapy in Myanmar has been a serious threat to malaria control and elimination in the country and across the region. Practical anti-malarial market evidence was rapidly generated and used to inform private sector approaches to address these threats. The program design approach outlined in this paper is illustrative of the type of evidence generation and use that will be required to ensure effective containment of artemisinin drug resistance and progress toward regional and global malaria elimination goals.

  16. Automated side-chain model building and sequence assignment by template matching

    International Nuclear Information System (INIS)

    Terwilliger, Thomas C.

    2002-01-01

    A method for automated macromolecular side-chain model building and for aligning the sequence to the map is described. An algorithm is described for automated building of side chains in an electron-density map once a main-chain model is built and for alignment of the protein sequence to the map. The procedure is based on a comparison of electron density at the expected side-chain positions with electron-density templates. The templates are constructed from average amino-acid side-chain densities in 574 refined protein structures. For each contiguous segment of main chain, a matrix with entries corresponding to an estimate of the probability that each of the 20 amino acids is located at each position of the main-chain model is obtained. The probability that this segment corresponds to each possible alignment with the sequence of the protein is estimated using a Bayesian approach and high-confidence matches are kept. Once side-chain identities are determined, the most probable rotamer for each side chain is built into the model. The automated procedure has been implemented in the RESOLVE software. Combined with automated main-chain model building, the procedure produces a preliminary model suitable for refinement and extension by an experienced crystallographer

  17. The C8 side chain is one of the key functional group of Garcinol for its anti-cancer effects.

    Science.gov (United States)

    Zhou, Xin-Ying; Cao, Jing; Han, Chao-Ming; Li, Shu-Wen; Zhang, Chen; Du, Yin-Duan; Zhou, Qian-Qian; Zhang, Xin-Yan; Chen, Xin

    2017-04-01

    Garcinol from the fruit rind of Garcinia indica shows anti-carcinogenic and anti-inflammatory properties, but its mechanism and key functional groups were still need to be identified. Our previous computer modeling suggested that the C8 side chain of Garcinol is so large that it may influence the bioactivity of the compound. 8-Me Garcinol, a derivative of Garcinol in which the bulky side chain at the C8 position of Garcinol is replaced with a much smaller methyl group, was synthesized through a 12-step procedure starting from 1,3-cyclohexanedione. The antitumor activity of Garcinol and 8-Me Garcinol was evaluated in vitro by MTT, cell cycle and cell apoptosis assays. The results showed that 8-Me Garcinol had weaker inhibitory activity on cells proliferation, and little effects on cell cycle and apoptosis in oral cancer cell line SCC15 cells when compared with Garcinol. All of the results indicated 8-Me Garcinol exerts weaker antitumor activity than Garcinol, and the C8 side chain might be an important active site in Garcinol. Changing the C8 side chain will affect the inhibitory effect of Garcinol. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

    KAUST Repository

    Cabanetos, Clement; El Labban, Abdulrahman; Bartelt, Jonathan A.; Douglas, Jessica D.; Mateker, William R.; Frechet, Jean; McGehee, Michael D.; Beaujuge, Pierre

    2013-01-01

    role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones

  19. Effect of side chain position on solar cell performance in cyclopentadithiophene-based copolymers

    International Nuclear Information System (INIS)

    Lee, Sang Kyu; Seo, Jung Hwa; Cho, Nam Sung; Cho, Shinuk

    2012-01-01

    The photovoltaic properties of a series of low band-gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor (D–A) conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl-benzothiadiazole. The base polymer, which has no alkyl side chains, yielded promising power conversion efficiency of 3.8%. Polymers with alkyl side chains, however, exhibited significantly decreased performance. In addition, the effects of processing additive became negligible. The results indicate that substituted side chains, which were introduced to improve solubility, critically affected the optical and electronic properties of D–A conjugated copolymers. Furthermore, the position of the side chain was also very important for controlling the morphological properties of the D–A conjugated copolymers. - Highlights: ► Effect of side chain position on solar cell performance was investigated. ► Polymer without alkyl chains yielded promising power conversion efficiency of 3.8%. ► Position of side chains critically affected the optical and electronic properties.

  20. Charge photogeneration and transport in side-chain carbazole polymers and co-polymers

    KAUST Repository

    Li, Huawei; Termine, Roberto; Godbert, Nicolas; Angiolini, Luigi; Giorgini, Loris; Golemme, Attilio

    2011-01-01

    The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10-3cm2V-1s-1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. © 2011 Elsevier B.V. All rights reserved.

  1. Charge photogeneration and transport in side-chain carbazole polymers and co-polymers

    KAUST Repository

    Li, Huawei

    2011-07-01

    The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10-3cm2V-1s-1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. © 2011 Elsevier B.V. All rights reserved.

  2. Residue-Specific Side-Chain Polymorphisms via Particle Belief Propagation.

    Science.gov (United States)

    Ghoraie, Laleh Soltan; Burkowski, Forbes; Li, Shuai Cheng; Zhu, Mu

    2014-01-01

    Protein side chains populate diverse conformational ensembles in crystals. Despite much evidence that there is widespread conformational polymorphism in protein side chains, most of the X-ray crystallography data are modeled by single conformations in the Protein Data Bank. The ability to extract or to predict these conformational polymorphisms is of crucial importance, as it facilitates deeper understanding of protein dynamics and functionality. In this paper, we describe a computational strategy capable of predicting side-chain polymorphisms. Our approach extends a particular class of algorithms for side-chain prediction by modeling the side-chain dihedral angles more appropriately as continuous rather than discrete variables. Employing a new inferential technique known as particle belief propagation, we predict residue-specific distributions that encode information about side-chain polymorphisms. Our predicted polymorphisms are in relatively close agreement with results from a state-of-the-art approach based on X-ray crystallography data, which characterizes the conformational polymorphisms of side chains using electron density information, and has successfully discovered previously unmodeled conformations.

  3. Automated side-chain model building and sequence assignment by template matching.

    Science.gov (United States)

    Terwilliger, Thomas C

    2003-01-01

    An algorithm is described for automated building of side chains in an electron-density map once a main-chain model is built and for alignment of the protein sequence to the map. The procedure is based on a comparison of electron density at the expected side-chain positions with electron-density templates. The templates are constructed from average amino-acid side-chain densities in 574 refined protein structures. For each contiguous segment of main chain, a matrix with entries corresponding to an estimate of the probability that each of the 20 amino acids is located at each position of the main-chain model is obtained. The probability that this segment corresponds to each possible alignment with the sequence of the protein is estimated using a Bayesian approach and high-confidence matches are kept. Once side-chain identities are determined, the most probable rotamer for each side chain is built into the model. The automated procedure has been implemented in the RESOLVE software. Combined with automated main-chain model building, the procedure produces a preliminary model suitable for refinement and extension by an experienced crystallographer.

  4. Theoretical predictions for side-chain liquid-crystal polymers and comparison to experiment

    International Nuclear Information System (INIS)

    Dowell, F.

    1988-01-01

    This paper presents results from a new unique microscopic molecular theory for side-chain liquid-crystalline polymers (LCPs) in the nematic (N) and multiple smectic-A (SA) LC phases and the isotropic (I) liquid phase. There are no ad hoc or arbitrarily adjustable parameters in this theory. The agreement between the theoretical and experimental values for various properties (including transition temperatures and quadratic characteristic radii) is very good (relative deviations between 0% and less than 6.2%). The theoretical results also show--for the first time--that the N and I phases for these LCPs involve the packing of plate-like sections of backbones and side chains and that the local bilayer SA phase involves packing of side-chains within a plate-like section. This type of packing is predicted to be typical for side-chain LCPs. This theory can predict--for the first time--whether the side chains of a molecule pack on the same or alternating opposite sides of the backbone and whether side chains on different molecules interdigitate (overlap) with each other. 13 refs., 1 fig., 4 tabs

  5. Studies on the Model Synthesis of the Brassinolide and Dolicholide Side Chains

    Institute of Scientific and Technical Information of China (English)

    Li Zeng PENG; Feng Zhi ZHANG; Tian Sheng MEI; Yu Lin LI

    2003-01-01

    A stereoselective synthesis of brassinolide and dolicholide, which involves constructionof the side chain enantiomers by a highly stereoselective aldol reaction of aldehyde 5 with theanion of α-silyloxy ketone 6 is described.

  6. Effect of side chain length on the stability and structural properties of 3

    African Journals Online (AJOL)

    thiophene (DOOPT) and their dimers studied by Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The DFT calculations suggest that dimers of the dialkoxyphenylthiophenes with longer side chains are thermodynamically more ...

  7. Cylindrical polymer brushes with dendritic side chains by iterative anionic reactions

    KAUST Repository

    Zhang, Hefeng; Qu, Chengke; He, Junpo

    2015-01-01

    We report in this paper an easy method for the synthesis of cylindrical polymer brushes with dendritic side chains through anionic reaction. The synthesis is accomplished by iteratively grafting a living block copolymer, polyisoprene-. b

  8. From Labdanes to Drimanes. Degradation of the Side Chain of Dihydrozamoranic Acid.

    Directory of Open Access Journals (Sweden)

    Pedro M. Rocha

    2004-04-01

    Full Text Available A new route for the degradation of the saturated side chain of dihydrozamoranic acid has been devised, giving an advanced intermediate, compound 14, useful for the synthesis of insect antifeedants such as warburganal and polygodial.

  9. From labdanes to drimanes. Degradation of the side chain of dihydrozamoranic acid.

    Science.gov (United States)

    Rodilla, Jesús M L; Díez, D; Urones, J G; Rocha, Pedro M

    2004-04-30

    A new route for the degradation of the saturated side chain of dihydrozamoranic acid has been devised, giving an advanced intermediate, compound 14, useful for the synthesis of insect antifeedants such as warburganal and polygodial.

  10. Synthesis and solution self-assembly of side-chain cobaltocenium-containing block copolymers.

    Science.gov (United States)

    Ren, Lixia; Hardy, Christopher G; Tang, Chuanbing

    2010-07-07

    The synthesis of side-chain cobaltocenium-containing block copolymers and their self-assembly in solution was studied. Highly pure monocarboxycobaltocenium was prepared and subsequently attached to side chains of poly(tert-butyl acrylate)-block-poly(2-hydroxyethyl acrylate), yielding poly(tert-butyl acrylate)-block-poly(2-acryloyloxyethyl cobaltoceniumcarboxylate). The cobaltocenium block copolymers exhibited vesicle morphology in the mixture of acetone and water, while micelles of nanotubes were formed in the mixture of acetone and chloroform.

  11. Synthesis and antimalarial activity of new chloroquine analogues carrying a multifunctional linear side chain

    OpenAIRE

    Iwaniuk, Daniel P.; Whetmore, Eric D.; Rosa, Nicholas; Ekoue-Kovi, Kekeli; Alumasa, John; de Dios, Angel C.; Roepe, Paul D.; Wolf, Christian

    2009-01-01

    We report the synthesis and in vitro antimalarial activity of several new 4-amino-and 4-alkoxy-7-chloroquinolines carrying a linear dibasic side chain. Many of these chloroquine analogues have submicromolar antimalarial activity versus HB3 (chloroquine sensitive) and Dd2 (chloroquine resistant strain of P. falciparum) and low resistance indices were obtained in most cases. Importantly, compounds 11–15 and 24 proved to be more potent against Dd2 than chloroquine. Branching of the side chain st...

  12. Linear rheology and structure of molecular bottlebrushes with short side chains

    International Nuclear Information System (INIS)

    López-Barrón, Carlos R.; Brant, Patrick; Crowther, Donna J.; Eberle, Aaron P. R.

    2015-01-01

    We investigate the microstructure and linear viscoelasticity of model molecular bottlebrushes (BBs) using rheological and small-angle X-ray and neutron scattering measurements. Our polymers have short atactic polypropylene (aPP) side chains of molecular weight ranging from 119 g/mol to 259 g/mol and narrow molecular weight distribution (M w /M n 1.02–1.05). The side chain molecular weights are a small fraction of the entanglement molecular weight of the corresponding linear polymer (M e,aPP = 7.05 kg/mol), and as such, they are unentangled. The morphology of the aPP BBs is characterized as semiflexible thick chains with small side chain interdigitation. Their dynamic master curves, obtained by time-temperature superposition, reveal two sequential relaxation processes corresponding to the segmental relaxation and the relaxation of the BB backbone. Due to the short length of the side chains, their fast relaxation could not be distinguished from the glassy relaxation. The fractional free volume is an increasing function of the side chain length (N SC ). Therefore, the glassy behavior of these polymers as well as their molecular friction and dynamic properties are influenced by their N SC values. The apparent flow activation energies are a decreasing function of N SC , and their values explain the differences in zero-shear viscosity measured at different temperatures

  13. Exploring the impact of the side-chain length on peptide/RNA binding events.

    Science.gov (United States)

    Sbicca, Lola; González, Alejandro López; Gresika, Alexandra; Di Giorgio, Audrey; Closa, Jordi Teixido; Tejedor, Roger Estrada; Andréola, Marie-Line; Azoulay, Stéphane; Patino, Nadia

    2017-07-19

    The impact of the amino-acid side-chain length on peptide-RNA binding events has been investigated using HIV-1 Tat derived peptides as ligands and the HIV-1 TAR RNA element as an RNA model. Our studies demonstrate that increasing the length of all peptide side-chains improves unexpectedly the binding affinity (K D ) but reduces the degree of compactness of the peptide-RNA complex. Overall, the side-chain length appears to modulate in an unpredictable way the ability of the peptide to compete with the cognate TAR RNA partner. Beyond the establishment of non-intuitive fundamental relationships, our results open up new perspectives in the design of effective RNA ligand competitors, since a large number of them have already been identified but few studies report on the modulation of the biological activity by modifying in the same way the length of all chains connecting RNA recognition motives to the central scaffold of a ligand.

  14. Sparse networks of directly coupled, polymorphic, and functional side chains in allosteric proteins.

    Science.gov (United States)

    Soltan Ghoraie, Laleh; Burkowski, Forbes; Zhu, Mu

    2015-03-01

    Recent studies have highlighted the role of coupled side-chain fluctuations alone in the allosteric behavior of proteins. Moreover, examination of X-ray crystallography data has recently revealed new information about the prevalence of alternate side-chain conformations (conformational polymorphism), and attempts have been made to uncover the hidden alternate conformations from X-ray data. Hence, new computational approaches are required that consider the polymorphic nature of the side chains, and incorporate the effects of this phenomenon in the study of information transmission and functional interactions of residues in a molecule. These studies can provide a more accurate understanding of the allosteric behavior. In this article, we first present a novel approach to generate an ensemble of conformations and an efficient computational method to extract direct couplings of side chains in allosteric proteins, and provide sparse network representations of the couplings. We take the side-chain conformational polymorphism into account, and show that by studying the intrinsic dynamics of an inactive structure, we are able to construct a network of functionally crucial residues. Second, we show that the proposed method is capable of providing a magnified view of the coupled and conformationally polymorphic residues. This model reveals couplings between the alternate conformations of a coupled residue pair. To the best of our knowledge, this is the first computational method for extracting networks of side chains' alternate conformations. Such networks help in providing a detailed image of side-chain dynamics in functionally important and conformationally polymorphic sites, such as binding and/or allosteric sites. © 2014 Wiley Periodicals, Inc.

  15. Synthesis and Antiplasmodial Activity of Novel Chloroquine Analogues with Bulky Basic Side Chains.

    Science.gov (United States)

    Tasso, Bruno; Novelli, Federica; Tonelli, Michele; Barteselli, Anna; Basilico, Nicoletta; Parapini, Silvia; Taramelli, Donatella; Sparatore, Anna; Sparatore, Fabio

    2015-09-01

    Chloroquine is commonly used in the treatment and prevention of malaria, but Plasmodium falciparum, the main species responsible for malaria-related deaths, has developed resistance against this drug. Twenty-seven novel chloroquine (CQ) analogues characterized by a side chain terminated with a bulky basic head group, i.e., octahydro-2H-quinolizine and 1,2,3,4,5,6-hexahydro-1,5-methano-8H-pyrido[1,2-a][1,5]diazocin-8-one, were synthesized and tested for activity against D-10 (CQ-susceptible) and W-2 (CQ-resistant) strains of P. falciparum. Most compounds were found to be active against both strains with nanomolar or sub-micromolar IC50 values. Eleven compounds were found to be 2.7- to 13.4-fold more potent than CQ against the W-2 strain; among them, four cytisine derivatives appear to be of particular interest, as they combine high potency with low cytotoxicity against two human cell lines (HMEC-1 and HepG2) along with easier synthetic accessibility. Replacement of the 4-NH group with a sulfur bridge maintained antiplasmodial activity at a lower level, but produced an improvement in the resistance factor. These compounds warrant further investigation as potential drugs for use in the fight against malaria. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. ω-Turn: a novel β-turn mimic in globular proteins stabilized by main-chain to side-chain C−H···O interaction.

    Science.gov (United States)

    Dhar, Jesmita; Chakrabarti, Pinak; Saini, Harpreet; Raghava, Gajendra Pal Singh; Kishore, Raghuvansh

    2015-02-01

    Mimicry of structural motifs is a common feature in proteins. The 10-membered hydrogen-bonded ring involving the main-chain C − O in a β-turn can be formed using a side-chain carbonyl group leading to Asx-turn. We show that the N − H component of hydrogen bond can be replaced by a C(γ) -H group in the side chain, culminating in a nonconventional C − H···O interaction. Because of its shape this β-turn mimic is designated as ω-turn, which is found to occur ∼ three times per 100 residues. Three residues (i to i + 2) constitute the turn with the C − H···O interaction occurring between the terminal residues, constraining the torsion angles ϕi + 1, ψi + 1, ϕi + 2 and χ'1(i + 2) (using the interacting C(γ) atom). Based on these angles there are two types of ω-turns, each of which can be further divided into two groups. C(β) -branched side-chains, and Met and Gln have high propensities to occur at i + 2; for the last two residues the carbonyl oxygen may participate in an additional interaction involving the S and amino group, respectively. With Cys occupying the i + 1 position, such turns are found in the metal-binding sites. N-linked glycosylation occurs at the consensus pattern Asn-Xaa-Ser/Thr; with Thr at i + 2, the sequence can adopt the secondary structure of a ω-turn, which may be the recognition site for protein modification. Location between two β-strands is the most common occurrence in protein tertiary structure, and being generally exposed ω-turn may constitute the antigenic determinant site. It is a stable scaffold and may be used in protein engineering and peptide design. © 2014 Wiley Periodicals, Inc.

  17. An in-situ FTIR study of the side-chain alkylation of toluene with methanol

    International Nuclear Information System (INIS)

    King, S.T.; Garces, J.

    1985-01-01

    The side-chain alkylation of toluene with methanol to styrene and ethylbenzene can be an economically attractive industrial process if it has high enough conversion and selectivity. This process has been investigated by many others using zeolites or metal oxides as the catalyst. It has been generally accepted that high basicity in certain size pores in the catalyst is required for such side-chain alkylation. However, the actual reaction mechanism is still not understood. In this paper the results of an in-situ FT-IR study of the side-chain alkylation in Li, Na, K, Rb and Cs exchanged X zeolites is discussed. It was found that the KX, RbX and CsX zeolites, which are capable of side-chain alkylation, also form surface formate and a surface precursor of formate from methanol decomposition. While the surface formate itself is not the alkylation agent, the observed formate precursor may be the intermediate for side-chain alkylation

  18. Modified melanocortin tetrapeptide Ac-His-dPhe-Arg-Trp-NH at the arginine side chain with ureas and thioureas.

    Science.gov (United States)

    Joseph, C G; Sorensen, N B; Wood, M S; Xiang, Z; Moore, M C; Haskell-Luevano, C

    2005-11-01

    The Ac-His-dPhe-Arg-Trp-NH2 tetrapeptide is a nonselective melanocortin agonist and replacement of Arg in the tetrapeptide with acidic, basic or neutral amino acids results in reduced potency at the melanocortin receptor (MCR) isoforms (MC1R and MC3-5R). To determine the importance of the positive charge and the guanidine moiety for melanocortin activity, a series of urea- and thiourea-substituted tetrapeptides were designed. Replacement of Arg with Lys or ornithine reduced agonist activity at the mouse mMC1 and mMC3-5 receptors, thus supporting the hypothesis that the guanidine moiety is important for receptor potency, particularly at the MC3-5 receptors. The Arg side chain-modified tetrapeptides examined in this study include substituted phenyl, naphthyl, and aliphatic urea and thiourea residues using a Lys side-chain template. These ligands elicit full-agonist pharmacology at the mouse MCRs examined in this study.

  19. Can understanding the packing of side chains improve the design of protein-protein interactions?

    Science.gov (United States)

    Zhou, Alice; O'Hern, Corey; Regan, Lynne

    2011-03-01

    With the long-term goal to improve the design of protein-protein interactions, we have begun extensive computational studies to understand how side-chains of key residues of binding partners geometrically fit together at protein-peptide interfaces, e.g. the tetratrico-peptide repeat protein and its cognate peptide). We describe simple atomic-scale models of hydrophobic dipeptides, which include hard-core repulsion, bond length and angle constraints, and Van der Waals attraction. By completely enumerating all minimal energy structures in these systems, we are able to reproduce important features of the probability distributions of side chain dihedral angles of hydrophic residues in the protein data bank. These results are the crucial first step in developing computational models that can predict the side chain conformations of residues at protein-peptide interfaces. CSO acknowledges support from NSF grant no. CMMT-1006527.

  20. Record high hole mobility in polymer semiconductors via side-chain engineering.

    Science.gov (United States)

    Kang, Il; Yun, Hui-Jun; Chung, Dae Sung; Kwon, Soon-Ki; Kim, Yun-Hi

    2013-10-09

    Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm(2)/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π-π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature.

  1. Asymmetric functional contributions of acidic and aromatic side chains in sodium channel voltage-sensor domains

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Elstone, Fisal D; Niciforovic, Ana P

    2014-01-01

    largely enigmatic. To this end, natural and unnatural side chain substitutions were made in the S2 hydrophobic core (HC), the extracellular negative charge cluster (ENC), and the intracellular negative charge cluster (INC) of the four VSDs of the skeletal muscle sodium channel isoform (NaV1......Voltage-gated sodium (NaV) channels mediate electrical excitability in animals. Despite strong sequence conservation among the voltage-sensor domains (VSDs) of closely related voltage-gated potassium (KV) and NaV channels, the functional contributions of individual side chains in Nav VSDs remain.......4). The results show that the highly conserved aromatic side chain constituting the S2 HC makes distinct functional contributions in each of the four NaV domains. No obvious cation-pi interaction exists with nearby S4 charges in any domain, and natural and unnatural mutations at these aromatic sites produce...

  2. Incorporation of basic side chains into cryptolepine scaffold: structure-antimalarial activity relationships and mechanistic studies.

    Science.gov (United States)

    Lavrado, João; Cabal, Ghislain G; Prudêncio, Miguel; Mota, Maria M; Gut, Jiri; Rosenthal, Philip J; Díaz, Cecília; Guedes, Rita C; dos Santos, Daniel J V A; Bichenkova, Elena; Douglas, Kenneth T; Moreira, Rui; Paulo, Alexandra

    2011-02-10

    The synthesis of cryptolepine derivatives containing basic side-chains at the C-11 position and their evaluations for antiplasmodial and cytotoxicity properties are reported. Propyl, butyl, and cycloalkyl diamine side chains significantly increased activity against chloroquine-resistant Plasmodium falciparum strains while reducing cytotoxicity when compared with the parent compound. Localization studies inside parasite blood stages by fluorescence microscopy showed that these derivatives accumulate inside the nucleus, indicating that the incorporation of a basic side chain is not sufficient enough to promote selective accumulation in the acidic digestive vacuole of the parasite. Most of the compounds within this series showed the ability to bind to a double-stranded DNA duplex as well to monomeric hematin, suggesting that these are possible targets associated with the observed antimalarial activity. Overall, these novel cryptolepine analogues with substantially improved antiplasmodial activity and selectivity index provide a promising starting point for development of potent and highly selective agents against drug-resistant malaria parasites.

  3. Histidine side-chain dynamics and protonation monitored by C-13 CPMG NMR relaxation dispersion

    DEFF Research Database (Denmark)

    Hass, M. A. S.; Yilmaz, A.; Christensen, Hans Erik Mølager

    2009-01-01

    the chemical shift titration experiments, and the CPMG derived exchange rates agree with those obtained previously from N-15 backbone relaxation measurements. Compared to measurements of backbone nuclei, C-13(epsilon 1) dispersion provides a more direct method to monitor interchanging protonation states...... or other kinds of conformational changes of histidine side chains or their environment. Advantages and shortcomings of using the C-13(epsilon 1) dispersion experiments in combination with chemical shift titration experiments to obtain information on exchange dynamics of the histidine side chains...

  4. Synthesis and antimalarial activity of new chloroquine analogues carrying a multifunctional linear side chain.

    Science.gov (United States)

    Iwaniuk, Daniel P; Whetmore, Eric D; Rosa, Nicholas; Ekoue-Kovi, Kekeli; Alumasa, John; de Dios, Angel C; Roepe, Paul D; Wolf, Christian

    2009-09-15

    We report the synthesis and in vitro antimalarial activity of several new 4-amino- and 4-alkoxy-7-chloroquinolines carrying a linear dibasic side chain. Many of these chloroquine analogues have submicromolar antimalarial activity versus HB3 (chloroquine sensitive) and Dd2 (chloroquine resistant strain of Plasmodium falciparum) and low resistance indices were obtained in most cases. Importantly, compounds 11-15 and 24 proved to be more potent against Dd2 than chloroquine. Branching of the side chain structure proved detrimental to the activity against the CQR strain.

  5. Exploring backbone-cation alkyl spacers for multi-cation side chain anion exchange membranes

    Science.gov (United States)

    Zhu, Liang; Yu, Xuedi; Hickner, Michael A.

    2018-01-01

    In order to systematically study how the arrangement of cations on the side chain and length of alkyl spacers between cations impact the performance of multi-cation AEMs for alkaline fuel cells, a series of polyphenylene oxide (PPO)-based AEMs with different cationic side chains were synthesized. This work resulted in samples with two or three cations in a side chain pendant to the PPO backbone. More importantly, the length of the spacer between cations varied from 3 methylene (-CH2-) (C3) groups to 8 methylene (C8) groups. The highest conductivity, up to 99 mS/cm in liquid water at room temperature, was observed for the triple-cation side chain AEM with pentyl (C5) or hexyl (C6) spacers. The multi-cation AEMs were found to have decreased water uptake and ionic conductivity when the spacer chains between cations were lengthened from pentyl (C5) or hexyl (C6) to octyl (C8) linking groups. The triple-cation membranes with pentyl (C5) or hexyl (C6) groups between cations showed greatest stability after immersion in 1 M NaOH at 80 °C for 500 h.

  6. Synthesis of porphyryl boronates with (un)saturated side-chains

    OpenAIRE

    SENGE, MATHIAS; SERGEEVA, NATALIA

    2008-01-01

    PUBLISHED Porphyrins with (un)saturated side?chains containing boron residues were developed as synthons for porphyrin functionalization. Porphyrins with mono and bis-substituted unsaturated boronyl residues were prepared in good yields (52?66 %) using a cross?metathesis approach in the presence of Grubbs I-generation catalysts. In all cases complete E?stereoselectivity (100 %) was observed. Furthermore, formal cross?metathesis products with ?,??unsaturated chains smoothly underwent additi...

  7. side chains

    African Journals Online (AJOL)

    USER

    The effect of ionic exchange degree of aluminated mesoporous materials H(X)- ... zeolites catalysts in cumene conversion and observed distinct differences in the ... with HCl acid solution with varied concentration going from 0.01 N to 0.5 N by .... 14. 16. 18. 20. Number of pulse. Cu m en e co n v ersio n. (%. ) 673. 673. 623.

  8. side chains

    African Journals Online (AJOL)

    USER

    Metropolis Monte Carlo (MC) simulations using only ion-water pair ... the subjects of numerous experimental [42] and theoretical investigations. .... The probability of finding the O-Fe(III)-O angle (θ) in the first hydration shell, the first-shell.

  9. Simulation study of the initial crystallization processes of poly(3-hexylthiophene) in solution: ordering dynamics of main chains and side chains.

    Science.gov (United States)

    Takizawa, Yuumi; Shimomura, Takeshi; Miura, Toshiaki

    2013-05-23

    We study the initial nucleation dynamics of poly(3-hexylthiophene) (P3HT) in solution, focusing on the relationship between the ordering process of main chains and that of side chains. We carried out Langevin dynamics simulation and found that the initial nucleation processes consist of three steps: the ordering of ring orientation, the ordering of main-chain vectors, and the ordering of side chains. At the start, the normal vectors of thiophene rings aligned in a very short time, followed by alignment of main-chain end-to-end vectors. The flexible side-chain ordering took almost 5 times longer than the rigid-main-chain ordering. The simulation results indicated that the ordering of side chains was induced after the formation of the regular stack structure of main chains. This slow ordering dynamics of flexible side chains is one of the factors that cause anisotropic nuclei growth, which would be closely related to the formation of nanofiber structures without external flow field. Our simulation results revealed how the combined structure of the planar and rigid-main-chain backbones and the sparse flexible side chains lead to specific ordering behaviors that are not observed in ordinary linear polymer crystallization processes.

  10. Arabidopsis GUX Proteins Are Glucuronyltransferases Responsible for the Addition of Glucuronic Acid Side Chains onto Xylan

    Science.gov (United States)

    Xylan, the second most abundant cell wall polysaccharide, is composed of a linear backbone of β-(1,4)-linked xylosyl residues that are often substituted with sugar side chains, such as glucuronic acid (GlcA) and methylglucuronic acid (MeGlcA). It has recently been shown that muta...

  11. Synthesis of β-1,4-Linked Galactan Side-Chains of Rhamnogalacturonan I

    DEFF Research Database (Denmark)

    Andersen, Mathias Christian Franch; Kracun, Stjepan; Rydahl, Maja

    2016-01-01

    The synthesis of linear- and (1→6)-branched-β-(1→4)-D-galactans, side chains of the pectic polysaccharide rhamnogalacturonan I is described. The strategy relies on iterative couplings of n-pentenyl disaccharides followed by a late stage glycosylation of a common hexasaccharide core. Reaction...

  12. Side-chain degradation of ultrapure π-conjugated oligomers: implications for organic electronics

    NARCIS (Netherlands)

    Abbel, R.J.; Wolffs, M.; Bovee, R.A.A.; Dongen, van J.L.J.; Lou, X.W.; Henze, O.; Feast, W.J.; Meijer, E.W.; Schenning, A.P.H.J.

    2009-01-01

    The degrdn. of two defect-free pi-conjugated oligomers and the participation of their solubilizing side chains in the process are studied in unprecedented detail. The detected intermediate products reveal a mechanism of successive shortening of alkyl and oligo(ethylene glycol) substituents.

  13. Novel biphotonic holographic storage in a side-chain liquid crystalline polyester

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Hvilsted, S.; Andruzzi, F.

    1993-01-01

    We report novel biphotonic holographic storage of text and gratings on unoriented films of a side-chain liquid crystalline polyester capable of high density storage and complete erasure. The holograms have a typical size of 1 mm. The recording utilizes unusual photochemistry involving azo dye...

  14. Light-induced circular birefringence in cyanoazobenzene side-chain liquid-crystalline polyester films

    DEFF Research Database (Denmark)

    Naydenova, I; Nikolova, L; Ramanujam, P.S.

    1999-01-01

    We report the inducement of large circular birefringence (optical activity) in films of a cyanoazobenzene side-chain liquid-crystalline polyester on illumination with circularly polarized light. The polyester has no chiral groups and is initially isotropic. The induced optical rotation is up to 5...

  15. Liquid-crystalline side chain block copolymers - synthesis, morphology and LC behavior

    NARCIS (Netherlands)

    Arnold, M.; Poser, S.; Fischer, H.R.; Frank, W.; Utschick, H.

    1994-01-01

    Side-chain liq.-cryst. 2-hydroxyethyl methacrylate-styrene diblock copolymer (I) was prepd. by polymn. of 2-(trimethylsiloxy)ethyl methacrylate with styrene with further treatment with cholesteryl chloroformate. Morphol. and phase behavior of I were investigated. [on SciFinder (R)

  16. Influence of structures of polymer backbones on cooperative photoreorientation behavior of p-cyanoazobenzene side chains

    DEFF Research Database (Denmark)

    Han, Mina; Kidowaki, Masatoshi; Ichimura, Kunihiro

    2001-01-01

    Photoinduced orientational behavior of a polymethacrylate (CN6) and a polyester (p6a12) with p-cyanoazobenzene side chains was studied to reveal the structural effect of the liquid crystalline polymer backbones. Irradiation with linearly polarized W light resulted in the reorientation of the azob...

  17. New approaches towards the synthesis of the side-chain of mycolactones A and B

    NARCIS (Netherlands)

    van Summeren, RP; Feringa, BL; Minnaard, AJ; Summeren, Ruben P. van

    2005-01-01

    New approaches towards the synthesis of the C1' - C16' side-chain of mycolactones A and B from Mycobacterium ulcerans are reported. Chiral building block 4 ( Fig. 2) with the correct stereochemistry was obtained starting from naturally occurring monosaccharides, i.e. D-glucose or L-rhamnose. The

  18. Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers

    KAUST Repository

    El Labban, Abdulrahman; Warnan, Julien; Cabanetos, Clement; Ratel, Olivier; Tassone, Christopher J.; Toney, Michael F.; Beaujuge, Pierre

    2014-01-01

    -effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device

  19. Conjugation of diisocyanate side chains to dimethacrylate reduces polymerization shrinkage and increases the hardness of composite resins

    Directory of Open Access Journals (Sweden)

    Yih-Dean Jan

    2014-04-01

    Conclusion: Conjugation of diisocyanate side chains to dimethacrylate represents an effective means of reducing polymerization shrinkage and increasing the surface hardness of dental composite resins.

  20. Arginine side chain interactions and the role of arginine as a gating charge carrier in voltage sensitive ion channels

    Science.gov (United States)

    Armstrong, Craig T.; Mason, Philip E.; Anderson, J. L. Ross; Dempsey, Christopher E.

    2016-02-01

    Gating charges in voltage-sensing domains (VSD) of voltage-sensitive ion channels and enzymes are carried on arginine side chains rather than lysine. This arginine preference may result from the unique hydration properties of the side chain guanidinium group which facilitates its movement through a hydrophobic plug that seals the center of the VSD, as suggested by molecular dynamics simulations. To test for side chain interactions implicit in this model we inspected interactions of the side chains of arginine and lysine with each of the 19 non-glycine amino acids in proteins in the protein data bank. The arginine guanidinium interacts with non-polar aromatic and aliphatic side chains above and below the guanidinium plane while hydrogen bonding with polar side chains is restricted to in-plane positions. In contrast, non-polar side chains interact largely with the aliphatic part of the lysine side chain. The hydration properties of arginine and lysine are strongly reflected in their respective interactions with non-polar and polar side chains as observed in protein structures and in molecular dynamics simulations, and likely underlie the preference for arginine as a mobile charge carrier in VSD.

  1. Nanophase separation in side chain polymers: new evidence from structure and dynamics

    International Nuclear Information System (INIS)

    Hiller, S; Pascui, O; Budde, H; Kabisch, O; Reichert, D; Beiner, M

    2004-01-01

    New evidence for a nanophase separation of incompatible main and side chain parts in amorphous poly(n-alkyl methacrylates) with long alkyl groups are presented. Independent indications for the existence of alkyl nanodomains with a typical dimension in the 1 nm range from studies on dynamics and structure are reported. Results from nuclear magnetic resonance (NMR) experiments are compared with data from different relaxation spectroscopy methods on poly(n-decyl methacrylate). The NMR results in combination with relaxation spectroscopy data support the existence of an independent polyethylene-like glass transition, α PE , within the alkyl nanodomains in addition to the conventional glass transition a at higher temperatures. X-ray scattering data show that the situation in homopolymers is similar to that for random poly(n-alkyl methacrylate) copolymers with the same average length of the alkyl group in the side chains. Scattering data for a series of n-butyl methacrylate samples with polymerization degrees reaching from P=1 to 405 indicate that nanophase separation is chain-length independent above P=25, while the nanophase separation tends to disappear below P=6. Insensitivity of structural aspects in nanophase-separated poly(n-alkyl methacrylates) to changes in the molecular microstructure and consistency of NMR results with independent conclusions from relaxation spectroscopy underline the general importance of nanophase separation effects in a broad class of side chain polymers

  2. Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes

    Science.gov (United States)

    Raithel, Dominic; Simine, Lena; Pickel, Sebastian; Schötz, Konstantin; Panzer, Fabian; Baderschneider, Sebastian; Schiefer, Daniel; Lohwasser, Ruth; Köhler, Jürgen; Thelakkat, Mukundan; Sommer, Michael; Köhler, Anna; Rossky, Peter J.; Hildner, Richard

    2018-03-01

    The backbone conformation of conjugated polymers affects, to a large extent, their optical and electronic properties. The usually flexible substituents provide solubility and influence the packing behavior of conjugated polymers in films or in bad solvents. However, the role of the side chains in determining and potentially controlling the backbone conformation, and thus the optical and electronic properties on the single polymer level, is currently under debate. Here, we investigate directly the impact of the side chains by studying the bulky-substituted poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) and the common poly(3-hexylthiophene) (P3HT), both with a defined molecular weight and high regioregularity, using low-temperature single-chain photoluminescence (PL) spectroscopy and quantum-classical simulations. Surprisingly, the optical transition energy of PDOPT is significantly (˜2,000 cm‑1 or 0.25 eV) red-shifted relative to P3HT despite a higher static and dynamic disorder in the former. We ascribe this red shift to a side-chain induced backbone planarization in PDOPT, supported by temperature-dependent ensemble PL spectroscopy. Our atomistic simulations reveal that the bulkier 2,5-dioctylphenyl side chains of PDOPT adopt a clear secondary helical structural motif and thus protect conjugation, i.e., enforce backbone planarity, whereas, for P3HT, this is not the case. These different degrees of planarity in both thiophenes do not result in different conjugation lengths, which we found to be similar. It is rather the stronger electronic coupling between the repeating units in the more planar PDOPT which gives rise to the observed spectral red shift as well as to a reduced calculated electron‑hole polarization.

  3. Abnormal viscoelastic behavior of side-chain liquid-crystal polymers

    Science.gov (United States)

    Gallani, J. L.; Hilliou, L.; Martinoty, P.; Keller, P.

    1994-03-01

    We show that, contrary to what is commonly believed, the isotropic phase of side-chain liquid-crystal polymers has viscoelastic properties which are totally different from those of ordinary flexible melt polymers. The results can be explained by the existence of a transient network created by the dynamic association of mesogenic groups belonging to different chains. The extremely high sensitivity of the compound to the state of the surfaces with which it is in contact offers us an unexpected method of studying surface states.

  4. Effect of side chain length on charge transport, morphology, and photovoltaic performance of conjugated polymers in bulk heterojunction solar cells

    NARCIS (Netherlands)

    Duan, C.; Willems, R.E.M.; van Franeker, J.J.; Bruijnaers, B.J.; Wienk, M.M.; Janssen, R.A.J.

    2016-01-01

    The effect of side chain length on the photovoltaic properties of conjugated polymers is systematically investigated with two sets of polymers that bear different alkyl side chain lengths based on benzodithiophene and benzo[2,1,3]thiadiazole or 5,6-difluorobenzo[2,1,3]thiadiazole. Characterization

  5. The Influence of Side-Chain Position on the Optoelectronic Properties of a Red-Emitting Conjugated Polymer

    NARCIS (Netherlands)

    Lu, Li Ping; Finlayson, Chris E.; Kabra, Dinesh; Albert-Seifried, Sebastian; Song, Myoung Hoon; Havenith, Remco W. A.; Tu, Guoli; Huck, Wilhelm T. S.; Friend, Richard H.

    2013-01-01

    A study of the organic semiconductor F8TBT is presented, directly comparing a conventional form (F8TBT-out) with a form with varied alkyl side-chain position (F8TBT-in), in terms of optical properties and device performance in light-emitting-diodes (LEDs). Computational simulations of the side-chain

  6. Molecular origin of urea driven hydrophobic polymer collapse and unfolding depending on side chain chemistry.

    Science.gov (United States)

    Nayar, Divya; Folberth, Angelina; van der Vegt, Nico F A

    2017-07-19

    Osmolytes affect hydrophobic collapse and protein folding equilibria. The underlying mechanisms are, however, not well understood. We report large-scale conformational sampling of two hydrophobic polymers with secondary and tertiary amide side chains using extensive molecular dynamics simulations. The calculated free energy of unfolding increases with urea for the secondary amide, yet decreases for the tertiary amide, in agreement with experiment. The underlying mechanism is rooted in opposing entropic driving forces: while urea screens the hydrophobic macromolecular interface and drives unfolding of the tertiary amide, urea's concomitant loss in configurational entropy drives collapse of the secondary amide. Only at sufficiently high urea concentrations bivalent urea hydrogen bonding interactions with the secondary amide lead to further stabilisation of its collapsed state. The observations provide a new angle on the interplay between side chain chemistry, urea hydrogen bonding, and the role of urea in attenuating or strengthening the hydrophobic effect.

  7. Correlation between protein secondary structure, backbone bond angles, and side-chain orientations

    Science.gov (United States)

    Lundgren, Martin; Niemi, Antti J.

    2012-08-01

    We investigate the fine structure of the sp3 hybridized covalent bond geometry that governs the tetrahedral architecture around the central Cα carbon of a protein backbone, and for this we develop new visualization techniques to analyze high-resolution x-ray structures in the Protein Data Bank. We observe that there is a correlation between the deformations of the ideal tetrahedral symmetry and the local secondary structure of the protein. We propose a universal coarse-grained energy function to describe the ensuing side-chain geometry in terms of the Cβ carbon orientations. The energy function can model the side-chain geometry with a subatomic precision. As an example we construct the Cα-Cβ structure of HP35 chicken villin headpiece. We obtain a configuration that deviates less than 0.4 Å in root-mean-square distance from the experimental x-ray structure.

  8. MgO encapsulated mesoporous zeolite for the side chain alkylation of toluene with methanol.

    Science.gov (United States)

    Jiang, Nanzhe; Jin, Hailian; Jeong, Eun-Young; Park, Sang-Eon

    2010-01-01

    Side chain alkylation of toluene with methanol was studied over mesoporous zeolite supported MgO catalysts. MgO were supported onto the carbon templated mesoporous silicalite-1 by direct synthesis route under microwave conditions. This direct synthesis route yields the majority of MgO highly dispersed into the mesopores of the silicalite-1 crystals. The vapor phase alkylation of toluene with methanol was performed over these catalysts under vapor phase conditions at atmospheric pressure. Mesoporous silicalite-1 supported MgO catalysts gave improved yields towards side chain alkylated products compared to the bulk MgO. The higher activity exhibited by 5% MgO supported on mesoporous silicalite compared to the one with 1% MgO can be attributed to the large number of weak basic sites observed from the CO2 TPD.

  9. Absolute rate constants for the reaction of hypochlorous acid with protein side chains and peptide bonds

    DEFF Research Database (Denmark)

    Pattison, D I; Davies, Michael Jonathan

    2001-01-01

    , absolute second-order rate constants for the reactions of HOCl with protein side chains, model compounds, and backbone amide (peptide) bonds have been determined at physiological pH values. The reactivity of HOCl with potential reactive sites in proteins is summarized by the series: Met (3.8 x 10(7) M(-1......Hypochlorous acid (HOCl) is a potent oxidant, which is produced in vivo by activated phagocytes. This compound is an important antibacterial agent, but excessive or misplaced production has been implicated in a number of human diseases, including atherosclerosis, arthritis, and some cancers....... Proteins are major targets for this oxidant, and such reaction results in side-chain modification, backbone fragmentation, and cross-linking. Despite a wealth of qualitative data for such reactions, little absolute kinetic data is available to rationalize the in vitro and in vivo data. In this study...

  10. Azobenzene side-chain liquid crystalline polyesters with outstanding optical storage properties

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Pedersen, M; Holme, NCR

    1998-01-01

    A flexible azobenzene side-chain liquid crystalline (SCLC) polyester architecture employed for reversible optical storage is described. The modular design allows four structural parameters to be individually modified. These parameters: i- the methylene side-chain spacer length, ii- the substituent......,000 are routinely obtained by melt transesterification of the novel diols and selected diacid precursors (parameter iii). Prominent storage features include no prealignment of thin SCLC polyester films prior to the writing process, and sensitivity in a broad laser wavelength window (415-532 nm). Additionally...... sign of fatigue. The non-destructive read out is performed with red light (600-750 nm). Finally, erasing the information can be achieved by heating the polyester film to 80 degrees C or irradiating it briefly with UV-light. In the latter case at least 10,000 write, read and erase cycles are possible...

  11. Electron detachment of the hydrogen-bonded amino acid side-chain guanine complexes

    Science.gov (United States)

    Wang, Jing; Gu, Jiande; Leszczynski, Jerzy

    2007-07-01

    The photoelectron spectra of the hydrogen-bonded amino acid side-chain-guanine complexes has been studied at the partial third order (P3) self-energy approximation of the electron propagator theory. The correlation between the vertical electron detachment energy and the charge distributions on the guanine moiety reveals that the vertical electron detachment energy (VDE) increases as the positive charge distribution on the guanine increases. The low VDE values determined for the negatively charged complexes of the guanine-side-chain-group of Asp/Glu suggest that the influence of the H-bonded anionic groups on the VDE of guanine could be more important than that of the anionic backbone structure. The even lower vertical electron detachment energy for guanine is thus can be expected in the H-bonded protein-DNA systems.

  12. Genetic stability of gene targeted immunoglobulin loci. I. Heavy chain isotype exchange induced by a universal gene replacement vector.

    Science.gov (United States)

    Kardinal, C; Selmayr, M; Mocikat, R

    1996-11-01

    Gene targeting at the immunoglobulin loci of B cells is an efficient tool for studying immunoglobulin expression or generating chimeric antibodies. We have shown that vector integration induced by human immunoglobulin G1 (IgG1) insertion vectors results in subsequent vector excision mediated by the duplicated target sequence, whereas replacement events which could be induced by the same constructs remain stable. We could demonstrate that the distribution of the vector homology strongly influences the genetic stability obtained. To this end we developed a novel type of a heavy chain replacement vector making use of the heavy chain class switch recombination sequence. Despite the presence of a two-sided homology this construct is universally applicable irrespective of the constant gene region utilized by the B cell. In comparison to an integration vector the frequency of stable incorporation was strongly increased, but we still observed vector excision, although at a markedly reduced rate. The latter events even occurred with circular constructs. Linearization of the construct at various sites and the comparison with an integration vector that carries the identical homology sequence, but differs in the distribution of homology, revealed the following features of homologous recombination of immunoglobulin genes: (i) the integration frequency is only determined by the length of the homology flank where the cross-over takes place; (ii) a 5' flank that does not meet the minimum requirement of homology length cannot be complemented by a sufficient 3' flank; (iii) free vector ends play a role for integration as well as for replacement targeting; (iv) truncating recombination events are suppressed in the presence of two flanks. Furthermore, we show that the switch region that was used as 3' flank is non-functional in an inverted orientation.

  13. Optimization of the alkyl side chain length of fluorine-18-labeled 7α-alkyl-fluoroestradiol

    International Nuclear Information System (INIS)

    Okamoto, Mayumi; Shibayama, Hiromitsu; Naka, Kyosuke; Kitagawa, Yuya; Ishiwata, Kiichi; Shimizu, Isao; Toyohara, Jun

    2016-01-01

    Introduction: Several lines of evidence suggest that 7α-substituted estradiol derivatives bind to the estrogen receptor (ER). In line with this hypothesis, we designed and synthesized 18 F-labeled 7α-fluoroalkylestradiol (Cn-7α-[ 18 F]FES) derivatives as molecular probes for visualizing ERs. Previously, we successfully synthesized 7α-(3-[ 18 F]fluoropropyl)estradiol (C3-7α-[ 18 F]FES) and showed promising results for quantification of ER density in vivo, although extensive metabolism was observed in rodents. Therefore, optimization of the alkyl side chain length is needed to obtain suitable radioligands based on Cn-7α-substituted estradiol pharmacophores. Methods: We synthesized fluoromethyl (23; C1-7α-[ 18 F]FES) to fluorohexyl (26; C6-7α-[ 18 F]FES) derivatives, except fluoropropyl (C3-7α-[ 18 F]FES) and fluoropentyl derivatives (C5-7α-[ 18 F]FES), which have been previously synthesized. In vitro binding to the α-subtype (ERα) isoform of ERs and in vivo biodistribution studies in mature female mice were carried out. Results: The in vitro IC 50 value of Cn-7α-FES tended to gradually decrease depending on the alkyl side chain length. C1-7α-[ 18 F]FES (23) showed the highest uptake in ER-rich tissues such as the uterus. Uterus uptake also gradually decreased depending on the alkyl side chain length. As a result, in vivo uterus uptake reflected the in vitro ERα affinity of each compound. Bone uptake, which indicates de-fluorination, was marked in 7α-(2-[ 18 F]fluoroethyl)estradiol (C2-7α-[ 18 F]FES) (24) and 7α-(4-[ 18 F]fluorobutyl)estradiol (C4-7α-[ 18 F]FES) (25) derivatives. However, C1-7α-[ 18 F]FES (23) and C6-7α-[ 18 F]FES (26) showed limited uptake in bone. As a result, in vivo bone uptake (de-fluorination) showed a bell-shaped pattern, depending on the alkyl side chain length. C1-7α-[ 18 F]FES (23) showed the same levels of uptake in uterus and bone compared with those of 16α-[ 18 F]fluoro-17β-estradiol. Conclusions: The optimal alkyl

  14. Comparing side chain packing in soluble proteins, protein-protein interfaces, and transmembrane proteins.

    Science.gov (United States)

    Gaines, J C; Acebes, S; Virrueta, A; Butler, M; Regan, L; O'Hern, C S

    2018-05-01

    We compare side chain prediction and packing of core and non-core regions of soluble proteins, protein-protein interfaces, and transmembrane proteins. We first identified or created comparable databases of high-resolution crystal structures of these 3 protein classes. We show that the solvent-inaccessible cores of the 3 classes of proteins are equally densely packed. As a result, the side chains of core residues at protein-protein interfaces and in the membrane-exposed regions of transmembrane proteins can be predicted by the hard-sphere plus stereochemical constraint model with the same high prediction accuracies (>90%) as core residues in soluble proteins. We also find that for all 3 classes of proteins, as one moves away from the solvent-inaccessible core, the packing fraction decreases as the solvent accessibility increases. However, the side chain predictability remains high (80% within 30°) up to a relative solvent accessibility, rSASA≲0.3, for all 3 protein classes. Our results show that ≈40% of the interface regions in protein complexes are "core", that is, densely packed with side chain conformations that can be accurately predicted using the hard-sphere model. We propose packing fraction as a metric that can be used to distinguish real protein-protein interactions from designed, non-binding, decoys. Our results also show that cores of membrane proteins are the same as cores of soluble proteins. Thus, the computational methods we are developing for the analysis of the effect of hydrophobic core mutations in soluble proteins will be equally applicable to analyses of mutations in membrane proteins. © 2018 Wiley Periodicals, Inc.

  15. Topological side-chain classification of beta-turns: ideal motifs for peptidomimetic development.

    Science.gov (United States)

    Tran, Tran Trung; McKie, Jim; Meutermans, Wim D F; Bourne, Gregory T; Andrews, Peter R; Smythe, Mark L

    2005-08-01

    Beta-turns are important topological motifs for biological recognition of proteins and peptides. Organic molecules that sample the side chain positions of beta-turns have shown broad binding capacity to multiple different receptors, for example benzodiazepines. Beta-turns have traditionally been classified into various types based on the backbone dihedral angles (phi2, psi2, phi3 and psi3). Indeed, 57-68% of beta-turns are currently classified into 8 different backbone families (Type I, Type II, Type I', Type II', Type VIII, Type VIa1, Type VIa2 and Type VIb and Type IV which represents unclassified beta-turns). Although this classification of beta-turns has been useful, the resulting beta-turn types are not ideal for the design of beta-turn mimetics as they do not reflect topological features of the recognition elements, the side chains. To overcome this, we have extracted beta-turns from a data set of non-homologous and high-resolution protein crystal structures. The side chain positions, as defined by C(alpha)-C(beta) vectors, of these turns have been clustered using the kth nearest neighbor clustering and filtered nearest centroid sorting algorithms. Nine clusters were obtained that cluster 90% of the data, and the average intra-cluster RMSD of the four C(alpha)-C(beta) vectors is 0.36. The nine clusters therefore represent the topology of the side chain scaffold architecture of the vast majority of beta-turns. The mean structures of the nine clusters are useful for the development of beta-turn mimetics and as biological descriptors for focusing combinatorial chemistry towards biologically relevant topological space.

  16. Carbon-14 methylation of the 2-methylbutyryl side chain of mevinolin and its analogs

    International Nuclear Information System (INIS)

    Prakash, S.R.; Ellsworth, R.L.

    1988-01-01

    A one step procedure for the preparation of three labeled mevinolin analogs possessing the 2,2-dimethylbutyryloxy side chain is described. Three lactones were converted into potassium salts of their corresponding di or trihydroxy carboxylic acids from which anionic ester enolates were generated and alkylated with [ 14 ]methyl iodide. Workup and purification by reverse phase HPLC provided the three radiochemically pure mevinolin analogs. The labeled lactones were converted into ammonium salts of their corresponding di or trihydroxy acids. (author)

  17. An exceptional series of phase transitions in hydrophobic amino acids with linear side chains

    Czech Academy of Sciences Publication Activity Database

    Görbitz, C.H.; Karen, P.; Dušek, Michal; Petříček, Václav

    2016-01-01

    Roč. 3, Sep (2016), s. 341-353 ISSN 2052-2525 R&D Projects: GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : amino acids * disorder * hydrogen bonding * modulated phases * phase transitions * side-chain stacking * polymorphism * molecular crystals Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.793, year: 2016

  18. Side-chain liquid-crystalline polyesters for optical information storage

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Andruzzi, F.; Ramanujam, P.S.

    1992-01-01

    We report erasable holographic recording with a resolution of at least 2500 lines/mm on unoriented films of side-chain liquid-crystalline polyesters. Recording energies of approximately 1 J/cm2 have been used. We have obtained a diffraction efficiency of approximately 30% with polarization record...... recording of holograms. The holograms can be erased by heating them to approximately 80-degrees-C for approximately 2 min and are available for rerecording....

  19. Mesogenic polybuthadiene diols with thiol side-chain units: synthesis and thermal behaviour

    Czech Academy of Sciences Publication Activity Database

    Bubnov, Alexej; Kašpar, Miroslav; Sedláková, Zdeňka

    2010-01-01

    Roč. 83, č. 1 (2010), 16-27 ISSN 0141-1594 R&D Projects: GA AV ČR IAA100100911; GA AV ČR(CZ) GA202/09/0047; GA MŠk OC 175 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : mesogenic polymer * phase transition * polybutadiene diol * side -chain polymer Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.006, year: 2010

  20. Exploiting the CNC side chain in heterocyclic rearrangements: synthesis of 4(5)-acylamino-imidazoles.

    Science.gov (United States)

    Piccionello, Antonio Palumbo; Buscemi, Silvestre; Vivona, Nicolò; Pace, Andrea

    2010-08-06

    A new variation on the Boulton-Katritzky reaction is reported, namely, involving use of a CNC side chain. A novel Montmorillonite-K10 catalyzed nonreductive transamination of a 3-benzoyl-1,2,4-oxadiazole afforded a 3-(alpha-aminobenzyl)-1,2,4-oxadiazole, which was condensed with benzaldehydes to afford the corresponding imines. In the presence of strong base, these imines underwent Boulton-Katritzky-type rearrangement to afford novel 4(5)-acylaminoimidazoles.

  1. Synthesis of side-chain polystyrenes for all organic solution processed OLEDs

    OpenAIRE

    Lorente Sánchez, Alejandro Jose (Dr.)

    2017-01-01

    In the present work side-chain polystyrenes were synthesized and characterized, in order to be applied in multilayer OLEDs fabricated by solution process techniques. Manufacture of optoelectronic devices by solution process techniques is meant to decrease significantly fabrication cost and allow large scale production of such devices. This dissertation focusses in three series, enveloped in two material classes. The two classes differ to each other in the type of charge transport exhibited...

  2. Contribution of cutinase serine 42 side chain to the stabilization of the oxyanion transition state.

    Science.gov (United States)

    Nicolas, A; Egmond, M; Verrips, C T; de Vlieg, J; Longhi, S; Cambillau, C; Martinez, C

    1996-01-16

    Cutinase from the fungus Fusarium solani pisi is a lipolytic enzyme able to hydrolyze both aggregated and soluble substrates. It therefore provides a powerful tool for probing the mechanisms underlying lipid hydrolysis. Lipolytic enzymes have a catalytic machinery similar to those present in serine proteinases. It is characterized by the triad Ser, His, and Asp (Glu) residues, by an oxyanion binding site that stabilizes the transition state via hydrogen bonds with two main chain amide groups, and possibly by other determinants. It has been suggested on the basis of a covalently bond inhibitor that the cutinase oxyanion hole may consist not only of two main chain amide groups but also of the Ser42 O gamma side chain. Among the esterases and the serine and the cysteine proteases, only Streptomyces scabies esterase, subtilisin, and papain, respectively, have a side chain residue which is involved in the oxyanion hole formation. The position of the cutinase Ser42 side chain is structurally conserved in Rhizomucor miehei lipase with Ser82 O gamma, in Rhizopus delemar lipase with Thr83 O gamma 1, and in Candida antartica B lipase with Thr40 O gamma 1. To evaluate the increase in the tetrahedral intermediate stability provided by Ser42 O gamma, we mutated Ser42 into Ala. Furthermore, since the proper orientation of Ser42 O gamma is directed by Asn84, we mutated Asn84 into Ala, Leu, Asp, and Trp, respectively, to investigate the contribution of this indirect interaction to the stabilization of the oxyanion hole. The S42A mutation resulted in a drastic decrease in the activity (450-fold) without significantly perturbing the three-dimensional structure. The N84A and N84L mutations had milder kinetic effects and did not disrupt the structure of the active site, whereas the N84W and N84D mutations abolished the enzymatic activity due to drastic steric and electrostatic effects, respectively.

  3. Improving proton conduction pathways in di- and triblock copolymer membranes: Branched versus linear side chains

    Science.gov (United States)

    Dorenbos, G.

    2017-06-01

    Phase separation within a series of polymer membranes in the presence of water is studied by dissipative particle dynamics. Each polymer contains hydrophobic A beads and hydrophilic C beads. Three parent architectures are constructed from a backbone composed of connected hydrophobic A beads to which short ([C]), long ([A3C]), or symmetrically branched A5[AC][AC] side chains spring off. Three di-block copolymer derivatives are constructed by covalently bonding an A30 block to each parent architecture. Also three tri-blocks with A15 blocks attached to both ends of each parent architecture are modeled. Monte Carlo tracer diffusion calculations through the water containing pores for 1226 morphologies reveal that water diffusion for parent architectures is slowest and diffusion through the di-blocks is fastest. Furthermore, diffusion increases with side chain length and is highest for branched side chains. This is explained by the increase of water pore size with , which is the average number of bonds that A beads are separated from a nearest C bead. Optimization of within the amphiphilic parent architecture is expected to be essential in improving proton conduction in polymer electrolyte membranes.

  4. Systematic and efficient side chain optimization for molecular docking using a cheapest-path procedure.

    Science.gov (United States)

    Schumann, Marcel; Armen, Roger S

    2013-05-30

    Molecular docking of small-molecules is an important procedure for computer-aided drug design. Modeling receptor side chain flexibility is often important or even crucial, as it allows the receptor to adopt new conformations as induced by ligand binding. However, the accurate and efficient incorporation of receptor side chain flexibility has proven to be a challenge due to the huge computational complexity required to adequately address this problem. Here we describe a new docking approach with a very fast, graph-based optimization algorithm for assignment of the near-optimal set of residue rotamers. We extensively validate our approach using the 40 DUD target benchmarks commonly used to assess virtual screening performance and demonstrate a large improvement using the developed side chain optimization over rigid receptor docking (average ROC AUC of 0.693 vs. 0.623). Compared to numerous benchmarks, the overall performance is better than nearly all other commonly used procedures. Furthermore, we provide a detailed analysis of the level of receptor flexibility observed in docking results for different classes of residues and elucidate potential avenues for further improvement. Copyright © 2013 Wiley Periodicals, Inc.

  5. An exceptional series of phase transitions in hydrophobic amino acids with linear side chains

    Directory of Open Access Journals (Sweden)

    Carl Henrik Görbitz

    2016-09-01

    Full Text Available The solid-state phase transitions and intermediate structures of S-2-aminobutanoic acid (l-2-aminobutyric acid, S-2-aminopentanoic acid (l-norvaline, S-2-aminohexanoic acid (l-norleucine and l-methionine between 100 and 470 K, identified by differential scanning calorimetry, have been characterized in a comprehensive single-crystal X-ray diffraction investigation. Unlike other enantiomeric amino acids investigated until now, this group featuring linear side chains displays up to five distinct phases. The multiple transitions between them involve a number of different processes: alteration of the hydrogen-bond pattern, to our knowledge the first example of this observed for an amino acid, sliding of molecular bilayers, seen previously only for racemates and quasiracemates, concerted side-chain rearrangements and abrupt as well as gradual modifications of the side-chain disorder. Ordering of l-norleucine upon cooling even proceeds via an incommensurately modulated structure. l-Methionine has previously been described as being fully ordered at room temperature. An accurate refinement now reveals extensive disorder for both molecules in the asymmetric unit, while two previously unknown phases occur above room temperature.

  6. Boosting the ambipolar performance of solution-processable polymer semiconductors via hybrid side-chain engineering.

    Science.gov (United States)

    Lee, Junghoon; Han, A-Reum; Yu, Hojeong; Shin, Tae Joo; Yang, Changduk; Oh, Joon Hak

    2013-06-26

    Ambipolar polymer semiconductors are highly suited for use in flexible, printable, and large-area electronics as they exhibit both n-type (electron-transporting) and p-type (hole-transporting) operations within a single layer. This allows for cost-effective fabrication of complementary circuits with high noise immunity and operational stability. Currently, the performance of ambipolar polymer semiconductors lags behind that of their unipolar counterparts. Here, we report on the side-chain engineering of conjugated, alternating electron donor-acceptor (D-A) polymers using diketopyrrolopyrrole-selenophene copolymers with hybrid siloxane-solubilizing groups (PTDPPSe-Si) to enhance ambipolar performance. The alkyl spacer length of the hybrid side chains was systematically tuned to boost ambipolar performance. The optimized three-dimensional (3-D) charge transport of PTDPPSe-Si with pentyl spacers yielded unprecedentedly high hole and electron mobilities of 8.84 and 4.34 cm(2) V(-1) s(-1), respectively. These results provide guidelines for the molecular design of semiconducting polymers with hybrid side chains.

  7. Controlling the mode of operation of organic transistors through side-chain engineering

    KAUST Repository

    Giovannitti, Alexander

    2016-10-11

    Electrolyte-gated organic transistors offer low bias operation facilitated by direct contact of the transistor channel with an electrolyte. Their operation mode is generally defined by the dimensionality of charge transport, where a field-effect transistor allows for electrostatic charge accumulation at the electrolyte/semiconductor interface, whereas an organic electrochemical transistor (OECT) facilitates penetration of ions into the bulk of the channel, considered a slow process, leading to volumetric doping and electronic transport. Conducting polymer OECTs allow for fast switching and high currents through incorporation of excess, hygroscopic ionic phases, but operate in depletion mode. Here, we show that the use of glycolated side chains on a thiophene backbone can result in accumulation mode OECTs with high currents, transconductance, and sharp subthreshold switching, while maintaining fast switching speeds. Compared with alkylated analogs of the same backbone, the triethylene glycol side chains shift the mode of operation of aqueous electrolyte-gated transistors from interfacial to bulk doping/transport and show complete and reversible electrochromism and high volumetric capacitance at low operating biases. We propose that the glycol side chains facilitate hydration and ion penetration, without compromising electronic mobility, and suggest that this synthetic approach can be used to guide the design of organic mixed conductors.

  8. Controlling the mode of operation of organic transistors through side-chain engineering

    Science.gov (United States)

    Giovannitti, Alexander; Sbircea, Dan-Tiberiu; Inal, Sahika; Nielsen, Christian B.; Bandiello, Enrico; Hanifi, David A.; Sessolo, Michele; Malliaras, George G.; McCulloch, Iain; Rivnay, Jonathan

    2016-01-01

    Electrolyte-gated organic transistors offer low bias operation facilitated by direct contact of the transistor channel with an electrolyte. Their operation mode is generally defined by the dimensionality of charge transport, where a field-effect transistor allows for electrostatic charge accumulation at the electrolyte/semiconductor interface, whereas an organic electrochemical transistor (OECT) facilitates penetration of ions into the bulk of the channel, considered a slow process, leading to volumetric doping and electronic transport. Conducting polymer OECTs allow for fast switching and high currents through incorporation of excess, hygroscopic ionic phases, but operate in depletion mode. Here, we show that the use of glycolated side chains on a thiophene backbone can result in accumulation mode OECTs with high currents, transconductance, and sharp subthreshold switching, while maintaining fast switching speeds. Compared with alkylated analogs of the same backbone, the triethylene glycol side chains shift the mode of operation of aqueous electrolyte-gated transistors from interfacial to bulk doping/transport and show complete and reversible electrochromism and high volumetric capacitance at low operating biases. We propose that the glycol side chains facilitate hydration and ion penetration, without compromising electronic mobility, and suggest that this synthetic approach can be used to guide the design of organic mixed conductors. PMID:27790983

  9. Cylindrical polymer brushes with dendritic side chains by iterative anionic reactions

    KAUST Repository

    Zhang, Hefeng

    2015-05-01

    We report in this paper an easy method for the synthesis of cylindrical polymer brushes with dendritic side chains through anionic reaction. The synthesis is accomplished by iteratively grafting a living block copolymer, polyisoprene-. b-polystyrenyllithium (PI-. b-PSLi), to the main chain and subsequently to the branches in a divergent way. PI segment is short and serves as a precursor for multifunctional branching unit. The grafting reaction involves two successive steps: i) epoxidation of internal double bonds of PI segments, either in main chain or side chains; ii) ring-opening addition to the resulting epoxy group by the living PI-. b-PSLi. Repeating the two steps affords a series of cylindrical polymer brushes with up to 3rd generation and extremely high molecular weight. The branching multiplicity depends on the average number of oxirane groups per PI segment, usually ca. 8 in the present work. The high branching multiplicity leads to tremendous increase in molecular weights of the cylindrical products with generation growth. Several series of cylindrical polymer brushes with tunable aspect ratios are prepared using backbones and branches with controlled lengths. Shape anisotropy is investigated in dilute solution using light scattering technique. Worm-like single molecular morphology with large persistence length is observed on different substrates by atomic force microscopy.

  10. A possibility for generation of two species of charge carriers along main-chain and side-chains for a π-conjugated polymer

    International Nuclear Information System (INIS)

    Kudo, Yuki; Kawabata, Kohsuke; Goto, Hiromasa

    2013-01-01

    Iodide doping produces charge carriers in π-conjugated polymers. Solitons can be generated in the case of polyacetylene, and polarons in the case of aromatic-type conjugated polymers. We synthesized a conjugated main-chain/side-chain polymer, which consists of polyene in the main-chain and aromatic-type conjugated units in the side-chains. Based on the SSH (Su, Schrieffer, Heeger) theoretical model of solitons in one-dimensional conjugated polymers, we experimentally carried out chemical doping to the main-chain/side-chains conjugated polymer. Generation of the charge carriers was examined by electron spin resonance spectroscopy. This study may lead to realization of a dual doping system of solitons and polarons in π-conjugation expanded to two-dimensional directions in polymers.

  11. Semi-crystalline photovoltaic polymers with siloxane-terminated hybrid side-chains

    Institute of Scientific and Technical Information of China (English)

    Yuxiang Li; Seyeong Song; Song Yi Park; Jin Young Kim; Han Young Woo

    2017-01-01

    Three types of semi-cry stalline photovoltaic polymers were synthesized by incorporating a siloxane-terminated organic/inorganic hybrid side-chain and changing the number of fluorine substituents.A branch point away from a polymer main backbone in the siloxane-containing side-chains and the intra-and/or interchain noncovalent coulombic interactions enhance a chain planarity and facile interchain organization.The resulting polymers formed strongly agglomerated films with high roughness,suggesting strong intermolecular interactions.The optical band gap of ca.1.7 eV was measured for all polymers with a pronounced shoulder peak due to tight π-π stacking.With increasing the fluorine substituents,the frontier energy levels decreased and preferential face-on orientation was observed.The siloxane-terminated side-chains and fluorine substitution promoted the intermolecular packing,showing well resolved lamellar scatterings up to(300) for this series of polymers in the grazing incidence wide angle X-ray scattering measurements.The PPsiDTBT,PPsiDTFBT and PPsiDT2 FBT devices showed a power conversion efficiency of 3.16%,4.40%and 5.65%,respectively,by blending with PC71BM.Langevin-type bimolecular charge recombination was similar for three polymeric solar cells.The main loss in the photocurrent generation for PPsiDTBT:PC71BM was interpreted to originate from the trap assisted charge recombination by measuring light-intensity dependent short-circuit current density(JSC) and open-circuit voltage(VOc).Our results provide a new insight into the rational selection of solubilizing substituents for optimizing crystalline interchain packing with appropriate miscibility with PC71 BM for further optimizing polymer solar cells.

  12. Semi-crystalline photovoltaic polymers with siloxane-terminated hybrid side-chains

    Institute of Scientific and Technical Information of China (English)

    Yuxiang Li; Seyeong Song; Song Yi Park; Jin Young Kim; Han Young Woo

    2017-01-01

    Three types of semi-crystalline photovoltaic polymers were synthesized by incorporating a siloxane-terminated organic/inorganic hybrid side-chain and changing the number of fluorine substituents.A branch point away from a polymer main backbone in the siloxane-containing side-chains and the intra-and/or interchain noncovalent coulombic interactions enhance a chain planarity and facile interchain organization.The resulting polymers formed strongly agglomerated films with high roughness,suggesting strong intermolecular interactions.The optical band gap of ca.1.7 eV was measured for all polymers with a pronounced shoulder peak due to tight π-π stacking.With increasing the fluorine substituents,the frontier energy levels decreased and preferential face-on orientation was observed.The siloxane-terminated side-chains and fluorine substitution promoted the intermolecular packing,showing well resolved lamellar scatterings up to (300) for this series of polymers in the grazing incidence wide angle X-ray scattering measurements.The PPsiDTBT,PPsiDTFBT and PPsiDT2FBT devices showed a power conversion efficiency of 3.16%,4.40% and 5.65%,respectively,by blending with PC71BM.Langevin-type bimolecular charge recombination was similar for three polymeric solar cells.The main loss in the photocurrent generation for PPsiDTBT:PC71BM was interpreted to originate from the trap assisted charge recombination by measuring light-intensity dependent short-circuit current density (Jsc) and open-circuit voltage (Voc).Our results provide a new insight into the rational selection of solubilizing substituents for optimizing crystalline interchain packing with appropriate miscibility with PC71BM for further optimizing polymer solar cells.

  13. Peramivir analogues bearing hydrophilic side chains exhibit higher activities against H275Y mutant than wild-type influenza virus.

    Science.gov (United States)

    Chiu, Din-Chi; Lin, Tzu-Chen; Huang, Wen-I; Cheng, Ting-Jen; Tsai, Keng-Chang; Fang, Jim-Min

    2017-11-29

    Peramivir is an effective anti-influenza drug in the clinical treatment of influenza, but its efficacy toward the H275Y mutant is reduced. The previously reported cocrystal structures of inhibitors in the mutant neuraminidase (NA) suggest that the hydrophobic side chain should be at the origin of reduced binding affinity. In contrast, zanamivir having a hydrophilic glycerol side chain still possesses high affinity toward the H275Y NA. We thus designed five peramivir analogues (5-9) carrying hydrophilic glycol or glycerol side chains, and evaluated their roles in anti-influenza activity, especially for the H275Y mutant. The synthetic sequence involves a key step of (3 + 2) cycloaddition reactions between alkenes and nitrile oxides to construct the scaffold of peramivir carrying the desired hydrophilic side chains and other appropriate functional groups. The molecular docking experiments reveal that the hydrophilic side chain can provide extra hydrogen bonding with the translocated Glu-276 residue in the H275Y NA active site. Thus, the H275Y mutant may be even more sensitive than wild-type virus toward the peramivir analogues bearing hydrophilic side chains. Notably, the peramivir analogue bearing a glycerol side chain inhibits the H275Y mutant with an IC 50 value of 35 nM, which is better than the WSN virus by 9 fold.

  14. Structural and kinetic mapping of side-chain exposure onto the protein energy landscape.

    Science.gov (United States)

    Bernstein, Rachel; Schmidt, Kierstin L; Harbury, Pehr B; Marqusee, Susan

    2011-06-28

    Identification and characterization of structural fluctuations that occur under native conditions is crucial for understanding protein folding and function, but such fluctuations are often rare and transient, making them difficult to study. Native-state hydrogen exchange (NSHX) has been a powerful tool for identifying such rarely populated conformations, but it generally reveals no information about the placement of these species along the folding reaction coordinate or the barriers separating them from the folded state and provides little insight into side-chain packing. To complement such studies, we have performed native-state alkyl-proton exchange, a method analogous to NSHX that monitors cysteine modification rather than backbone amide exchange, to examine the folding landscape of Escherichia coli ribonuclease H, a protein well characterized by hydrogen exchange. We have chosen experimental conditions such that the rate-limiting barrier acts as a kinetic partition: residues that become exposed only upon crossing the unfolding barrier are modified in the EX1 regime (alkylation rates report on the rate of unfolding), while those exposed on the native side of the barrier are modified predominantly in the EX2 regime (alkylation rates report on equilibrium populations). This kinetic partitioning allows for identification and placement of partially unfolded forms along the reaction coordinate. Using this approach we detect previously unidentified, rarely populated conformations residing on the native side of the barrier and identify side chains that are modified only upon crossing the unfolding barrier. Thus, in a single experiment under native conditions, both sides of the rate-limiting barrier are investigated.

  15. Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers

    KAUST Repository

    El Labban, Abdulrahman

    2014-11-26

    (Figure Presented) Alkyl substituents appended to the π-conjugated main chain account for the solution-processability and film-forming properties of most π-conjugated polymers for organic electronic device applications, including field-effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device performance. However, the factors that determine polymer crystallite orientation in thin-films, implying preferential backbone orientation relative to the device substrate, are a matter of some debate, and these structural changes remain difficult to anticipate. In this report, we show how systematic changes in the side-chain pattern of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers can (i) influence the propensity of the polymer to order in the π-stacking direction, and (ii) direct the preferential orientation of the polymer crystallites in thin films (e.g., "face-on" vs "edge-on"). Oriented crystallites, specifically crystallites that are well-ordered in the π-stacking direction, are believed to be a key contributor to improved thin-film device performance in both FETs and BHJ solar cells.

  16. Microscopic theory of light-induced deformation in amorphous side-chain azobenzene polymers.

    Science.gov (United States)

    Toshchevikov, V; Saphiannikova, M; Heinrich, G

    2009-04-16

    We propose a microscopic theory of light-induced deformation of side-chain azobenzene polymers taking into account the internal structure of polymer chains. Our theory is based on the fact that interaction of chromophores with the polarized light leads to the orientation anisotropy of azobenzene macromolecules which is accompanied by the appearance of mechanical stress. It is the first microscopic theory which provides the value of the light-induced stress larger than the yield stress. This result explains a possibility for the inscription of surface relief gratings in glassy side-chain azobenzene polymers. For some chemical architectures, elongation of a sample demonstrates a nonmonotonic behavior with the light intensity and can change its sign (a stretched sample starts to be uniaxially compressed), in agreement with experiments. Using a viscoplastic approach, we show that the irreversible strain of a sample, which remains after the light is switched off, decreases with increasing temperature and can disappear at certain temperature below the glass transition temperature. This theoretical prediction is also confirmed by recent experiments.

  17. Amphiphilic polymer based on fluoroalkyl and PEG side chains for fouling release coating

    Science.gov (United States)

    Cong, W. W.; Wang, K.; Yu, X. Y.; Zhang, H. Q.; Lv, Z.; Gui, T. J.

    2017-12-01

    Under static conditions, fouling release coating could not express good release property to marine organisms. Amphiphilic polymer with mixture of fluorinated monomer and short side group of polyethylene glycol (PEG) was synthesized. And also we studied the ability of amphiphilic polymer to influence the surface properties and how it controlled the adhesion of marine organisms to coated surfaces. By incorporating fluorinated monomer and PEG side chain into the polymer, the effect of incorporating both polar and non-polar groups on fouling-release coating could be studied. The dry surface was characterized by three-dimensional digital microscopy and scanning electron microscopy (SEM), and the morphology of the amphiphilic fouling release coating showed just like flaky petal. The amphiphilic polymer in fouling release coating tended to reconstruct in water, and the ability was examined by static contact angle, which was smaller than the PDMS (polydimethylsiloxane) fouling release coating. Also surface energy was calculated by three solvents, and surface energy of amphiphilic fouling release coating was higher than that of the PDMS fouling release coating. To understand more about its fouling release property, seawater exposure method was adopted in gulf of Qingdao port. Fewer diatoms Navicula were found in biofilm after using amphiphilic fouling release coating. In general, coating containing both PEG and fluorinated side chain possessed certain fouling release property.

  18. Enabling high-mobility, ambipolar charge-transport in a DPP-benzotriazole copolymer by side-chain engineering

    DEFF Research Database (Denmark)

    Gruber, Mathias; Jung, Seok-Heon; Schott, Sam

    2015-01-01

    In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit. We demonstrate that the BTZ unit allows for additional solubilizing side-chains on the co-monomer and show that the introduction of a linear...... side-chain on the DPP-unit leads to an increase in thin-film order and charge-carrier mobility if a sufficiently solubilizing, branched, side chain is attached to the BTZ. We compare two different synthetic routes, direct arylation and Suzuki-polycondensation, by a direct comparison of polymers...

  19. Accessing ns-μs side chain dynamics in ubiquitin with methyl RDCs

    International Nuclear Information System (INIS)

    Fares, Christophe; Lakomek, Nils-Alexander; Walter, Korvin F. A.; Frank, Benedikt T. C.; Meiler, Jens; Becker, Stefan; Griesinger, Christian

    2009-01-01

    This study presents the first application of the model-free analysis (MFA) (Meiler in J Am Chem Soc 123:6098-6107, 2001; Lakomek in J Biomol NMR 34:101-115, 2006) to methyl group RDCs measured in 13 different alignment media in order to describe their supra-τ c dynamics in ubiquitin. Our results indicate that methyl groups vary from rigid to very mobile with good correlation to residue type, distance to backbone and solvent exposure, and that considerable additional dynamics are effective at rates slower than the correlation time τ c . In fact, the average amplitude of motion expressed in terms of order parameters S 2 associated with the supra-τ c window brings evidence to the existence of fluctuations contributing as much additional mobility as those already present in the faster ps-ns time scale measured from relaxation data. Comparison to previous results on ubiquitin demonstrates that the RDC-derived order parameters are dominated both by rotameric interconversions and faster libration-type motions around equilibrium positions. They match best with those derived from a combined J-coupling and residual dipolar coupling approach (Chou in J Am Chem Soc 125:8959-8966, 2003) taking backbone motion into account. In order to appreciate the dynamic scale of side chains over the entire protein, the methyl group order parameters are compared to existing dynamic ensembles of ubiquitin. Of those recently published, the broadest one, namely the EROS ensemble (Lange in Science 320:1471-1475, 2008), fits the collection of methyl group order parameters presented here best. Last, we used the MFA-derived averaged spherical harmonics to perform highly-parameterized rotameric searches of the side chains conformation and find expanded rotamer distributions with excellent fit to our data. These rotamer distributions suggest the presence of concerted motions along the side chains

  20. Revealing the Supramolecular Nature of Side-Chain Terpyridine-Functionalized Polymer Networks

    Directory of Open Access Journals (Sweden)

    Jérémy Brassinne

    2015-01-01

    Full Text Available Nowadays, finely controlling the mechanical properties of polymeric materials is possible by incorporating supramolecular motifs into their architecture. In this context, the synthesis of a side-chain terpyridine-functionalized poly(2-(dimethylaminoethyl methacrylate is reported via reversible addition-fragmentation chain transfer polymerization. By addition of transition metal ions, concentrated aqueous solutions of this polymer turn into metallo-supramolecular hydrogels whose dynamic mechanical properties are investigated by rotational rheometry. Hence, the possibility for the material to relax mechanical constrains via dissociation of transient cross-links is brought into light. In addition, the complex phenomena occurring under large oscillatory shear are interpreted in the context of transient networks.

  1. Influence of water solubility, side chain degradability and side chain configuration on the degradation of phthalic acid esters under methanogenic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Alnervik, M.

    1996-12-31

    Water solubility and degradability of side chains estrifying phthalic acid are factors possible to influence the degradation of phthalic acid esters (PAEs). To investigate the importance of these factors degradation of butyl 2-ethylhexyl phthalate (BEHP), bis(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), dihexyl phthalate (DHP), dioctyl phthalate (DOP) and didecyl phthalate (DDP) were examined under methanogenic conditions as well as was the degradability of the alcohols estrifying these PAEs. We also investigated if the degradation of resistant PAEs could be stimulated by the addition of a degradable PAE. Synthesis of degradation intermediates and two methods for PAE analyses are presented. The investigation showed that all alcohols were degraded to methane and carbon dioxide and that the degradation of PAE occurred in incubations amended with BBP, BEHP, DHP and DBP, whilst DEHP, DOP and DDP were unaffected throughout the experimental period. BBP added to incubations with DEHP, could not stimulate DEHP degradation. In conclusion, the degradability of alcohols estrifying phthalic acid in this study does not affect the anaerobic degradability of PAEs. Water solubility of a PAE can not be rejected as a factor limiting phthalate degradation under methanogenic conditions. Anaerobic degradation of persistent PAEs can not be stimulated by mixing it with a degradable phthalate. 23 refs, 11 figs, 2 tabs

  2. Synthesis and Intramolecular [4+2] Cycloaddition Reactions of 4-Pyridazinecarbonitriles with Alkyne Side Chains

    Directory of Open Access Journals (Sweden)

    Norbert Haider

    1998-01-01

    Full Text Available The preparation of a series of new 3-(alkynyl-X-substituted 4-pyridazinecarbonitriles 2-5 (X = O, NH is described. The compounds are shown to undergo thermally induced intramolecular Diels-Alder reactions with inverse electron demand, affording the fused benzonitriles 6-8. Incorporation of a 1,2-phenylene unit into the side chain, as in the case of compounds 10 and 13, results in a more favorable conformation of the dienophilic substructure and thus to a pronounced acceleration of the [4+2] cycloaddition reaction.

  3. Side Chain and Flexibility Contributions to the Raman Optical Activity Spectra of a Model Cyclic Hexapeptide

    Czech Academy of Sciences Publication Activity Database

    Hudecová, J.; Kapitán, Josef; Baumruk, V.; Hammer, R. P.; Keiderling, T. A.; Bouř, Petr

    2010-01-01

    Roč. 114, č. 28 (2010), s. 7642-7651 ISSN 1089-5639 R&D Projects: GA ČR GA203/06/0420; GA ČR GA202/07/0732; GA AV ČR IAA400550702 Grant - others:GA UK(CZ) 126310 Institutional research plan: CEZ:AV0Z40550506 Keywords : Raman optical activity * ab initio * side chain * flexibility * peptide Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.732, year: 2010

  4. Tuning Thermoresponsive Properties of Cationic Elastin-like Polypeptides by Varying Counterions and Side-Chains.

    Science.gov (United States)

    Petitdemange, Rosine; Garanger, Elisabeth; Bataille, Laure; Bathany, Katell; Garbay, Bertrand; Deming, Timothy J; Lecommandoux, Sébastien

    2017-05-17

    We report the synthesis of methionine-containing recombinant elastin-like polypeptides (ELPs) of different lengths that contain periodically spaced methionine residues. These ELPs were chemoselectively alkylated at all methionine residues to give polycationic derivatives. Some of these samples were found to possess solubility transitions in water, where the temperature of these transitions varied with ELP concentration, nature of the methionine alkylating group, and nature of the sulfonium counterions. These studies show that introduction and controlled spacing of methionine sulfonium residues into ELPs can be used as a means both to tune their solubility transition temperatures in water using a variety of different parameters and to introduce new side-chain functionality.

  5. Mean-field theory of photoinduced molecular reorientation in azobenzene liquid crystalline side-chain polymers

    DEFF Research Database (Denmark)

    Pedersen, T.G.; Johansen, P.M.

    1997-01-01

    . The theory provides an explanation for the high long-term stability of the photoinduced anisotropy as well as a theoretical prediction of the temporal behavior of photoinduced birefringence. The theoretical results agree favorably with measurements in the entire range of writing intensities used......A novel mean-field theory of photoinduced reorientation and optical anisotropy in liquid crystalline side-chain polymers is presented and compared with experiments, The reorientation mechanism is based on photoinduced trans cis isomerization and a multidomain model of the material is introduced...

  6. Mean-field theory of photoinduced formation of surface reliefs in side-chain azobenzene polymers

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Johansen, Per Michael; Holme, N.C.R.

    1998-01-01

    A mean-field model of photoinduced surface reliefs in dye containing side-chain polymers is presented. It is demonstrated that photoinduced ordering of dye molecules subject to anisotropic intermolecular interactions leads to mass transport even when the intensity of the incident light is spatially...... uniform. Theoretical profiles are obtained using a simple variational method and excellent agreement with experimental surface reliefs recorded under various polarization configurations is found. The polarization dependence of both period and shape of the profiles is correctly reproduced by the model....

  7. A Solid-State Deuterium NMR and SFG Study of the Side Chain Dynamics of Peptides Adsorbed onto Surfaces

    Science.gov (United States)

    Breen, Nicholas F.; Weidner, Tobias; Li, Kun; Castner, David G.; Drobny, Gary P.

    2011-01-01

    The artificial amphiphilic peptide LKα14 adopts a helical structure at interfaces, with opposite orientation of its leucine (L, hydrophobic) and lysine (K, hydrophilic) side chains. When adsorbed onto surfaces, different residue side chains necessarily have different proximities to the surface, depending on both their position in the helix and the composition of the surface itself. Deuterating the individual leucine residues (isopropyl-d7) permits the use of solid-state deuterium NMR as a site-specific probe of side chain dynamics. In conjunction with SFG as a probe of the peptide binding face, we demonstrate that the mobility of specific leucine side chains at the interface is quantifiable in terms of their surface proximity. PMID:19764755

  8. A new series of two-ring-based side chain liquid crystalline polymers: synthesis and mesophase characterization

    CSIR Research Space (South Africa)

    Reddy, GSM

    2013-05-01

    Full Text Available A new series of side chain liquid crystalline polymers containing a core, a butamethylenoxy spacer, ester groups, and terminal alkoxy groups were synthesised and their structures were confirmed. The core was constructed with two phenyl rings...

  9. Synthesis and property characterization of two novel side-chain isoindigo copolymers for polymer solar cells

    Directory of Open Access Journals (Sweden)

    X. Liu

    2015-11-01

    Full Text Available Two novel side-chain conjugated polymers, PTBT-TID and PTBT-TTID, based on the new synthetic thiophene-benzne-thiophene (TBT unit, side-chain isoindigo (ID unit, and the introduced thiophene π-bridge, have been designed and synthesized. The photophysical, electrochemical and photovoltaic properties of the two polymers have been systematically investigated. The two polymers possess relatively good solubility as well as excellent thermal stability up to 380°C, and all of the polymer solar cell (PSC devices based on the two polymers obtain high open circuit voltage (Voc of about 0.8 V. The polymer solar cells based on the polymer PTBT-TID show relatively higher efficiencies than the PTBT-TTID-based ones, due to the broader absorption spectrum, a relatively higher hole mobility, a lower HOMO (the highest occupied molecular orbital energy level, a stronger IPCE (the incident photon to current conversion efficiency response and a better microphase separation, Consequently, the device based on PTBT-TID:PC61BM (1:2, by weight gives the best power conversion efficiency (PCE of 2.04%, with a short-circuit current density (Jsc of 5.39 mA·cm–2, an open-circuit voltage (Voc of 0.83 V, and a fill factor (FF of 0.45.

  10. Subcritical Water Hydrolysis of Peptides: Amino Acid Side-Chain Modifications

    Science.gov (United States)

    Powell, Thomas; Bowra, Steve; Cooper, Helen J.

    2017-09-01

    Previously we have shown that subcritical water may be used as an alternative to enzymatic digestion in the proteolysis of proteins for bottom-up proteomics. Subcritical water hydrolysis of proteins was shown to result in protein sequence coverages greater than or equal to that obtained following digestion with trypsin; however, the percentage of peptide spectral matches for the samples treated with trypsin were consistently greater than for those treated with subcritical water. This observation suggests that in addition to cleavage of the peptide bond, subcritical water treatment results in other hydrolysis products, possibly due to modifications of amino acid side chains. Here, a model peptide comprising all common amino acid residues (VQSIKCADFLHYMENPTWGR) and two further model peptides (VCFQYMDRGDR and VQSIKADFLHYENPTWGR) were treated with subcritical water with the aim of probing any induced amino acid side-chain modifications. The hydrolysis products were analyzed by direct infusion electrospray tandem mass spectrometry, either collision-induced dissociation or electron transfer dissociation, and liquid chromatography collision-induced dissociation tandem mass spectrometry. The results show preferential oxidation of cysteine to sulfinic and sulfonic acid, and oxidation of methionine. In the absence of cysteine and methionine, oxidation of tryptophan was observed. In addition, water loss from aspartic acid and C-terminal amidation were observed in harsher subcritical water conditions. [Figure not available: see fulltext.

  11. Controlling the morphology and efficiency of hybrid ZnO: Polythiophene solar cells via side chain functionalization

    NARCIS (Netherlands)

    Oosterhout, S.D.; Koster, L.J.A.; Bavel, van S.S.; Loos, J.; Stenzel, O.; Thiedmann, R.; Schmidt, V.; Campo, B.J.; Cleij, T.J.; Lutzen, L.; Vanderzande, D.J.M.; Wienk, M.M.; Janssen, R.A.J.

    2011-01-01

    The efficiency of polymer – metal oxide hybrid solar cells depends critically on the intimacy of mixing of the two semiconductors. The effect of side chain functionalization on the morphology and performance of conjugated polymer:ZnO solar cells is investigated. Using an ester-functionalized side

  12. Controlling the Morphology and Efficiency of Hybrid ZnO : Polythiophene Solar Cells Via Side Chain Functionalization

    NARCIS (Netherlands)

    Oosterhout, Stefan D.; Koster, L. Jan Anton; van Bavel, Svetlana S.; Loos, Joachim; Stenzel, Ole; Thiedmann, Ralf; Schmidt, Volker; Campo, Bert; Cleij, Thomas J.; Lutzen, Laurence; Vanderzande, Dirk; Wienk, Martijn M.; Janssen, Rene A. J.

    2011-01-01

    The efficiency of polymer - metal oxide hybrid solar cells depends critically on the intimacy of mixing of the two semiconductors. The effect of side chain functionalization on the morphology and performance of conjugated polymer:ZnO solar cells is investigated. Using an ester-functionalized side

  13. Effect of the Side Chains and Anode Material on Thermal Stability and Performance of Bulk-Heterojunction Solar Cells Using DPP(TBFu2 Derivatives as Donor Materials

    Directory of Open Access Journals (Sweden)

    Alexander Kovalenko

    2015-01-01

    Full Text Available An optimized fabrication of bulk-heterojunction solar cells (BHJ SCs based on previously reported diketopyrrolopyrrole donor, ethyl-hexylated DPP(TBFu2, as well as two new DPP(TBFu2 derivatives with ethyl-hexyl acetate and diethyl acetal solubilizing side-chains and PC60BM as an acceptor is demonstrated. Slow gradual annealing of the solar cell causing the effective donor-acceptor reorganization, and as a result higher power conversion efficiency (PCE, is described. By replacing a hole transporting layer PEDOT:PSS with MoO3 we obtained higher PCE values as well as higher thermal stability of the anode contact interface. DPP(TBFu2 derivative containing ethyl-hexyl acetate solubilizing side-chains possessed the best as-cast self-assembly and high crystallinity. However, the presence of ethyl-hexyl acetate and diethyl acetal electrophilic side-chains stabilizes HOMO energy of isolated DPP(TBFu2 donors with respect to the ethyl-hexylated one, according to cyclic voltammetry.

  14. A stability study of polymer solar cells using conjugated polymers with different donor or acceptor side chain patterns

    DEFF Research Database (Denmark)

    Heckler, Ilona Maria; Kesters, Jurgen; Defour, Maxime

    2016-01-01

    -phenylethyl group. It is shown that the exchange of the hexyl chain on the DTBT moiety has a negative impact on the stability of the polymer as well as on the performance of the resulting PSCs. On the other hand, partial exchange of the 2-hexyldecyl side chain of the BDT unit by a 2-hydroxyethyl group results......)benzo[c][1,2,5]thiadiazole (DTBT), specifically selected because of its suitability for roll-coating in the ambient environment, is investigated in terms of operational stability via partial exchange (5 or 10%) of the alkyl side chain on either the donor or the acceptor monomer with a 2-hydroxyethyl or 2...

  15. Replacement

    Directory of Open Access Journals (Sweden)

    S. Radhakrishnan

    2014-03-01

    Full Text Available The fishmeal replaced with Spirulina platensis, Chlorella vulgaris and Azolla pinnata and the formulated diet fed to Macrobrachium rosenbergii postlarvae to assess the enhancement ability of non-enzymatic antioxidants (vitamin C and E, enzymatic antioxidants (superoxide dismutase (SOD and catalase (CAT and lipid peroxidation (LPx were analysed. In the present study, the S. platensis, C. vulgaris and A. pinnata inclusion diet fed groups had significant (P < 0.05 improvement in the levels of vitamins C and E in the hepatopancreas and muscle tissue. Among all the diets, the replacement materials in 50% incorporated feed fed groups showed better performance when compared with the control group in non-enzymatic antioxidant activity. The 50% fishmeal replacement (best performance diet fed groups taken for enzymatic antioxidant study, in SOD, CAT and LPx showed no significant increases when compared with the control group. Hence, the present results revealed that the formulated feed enhanced the vitamins C and E, the result of decreased level of enzymatic antioxidants (SOD, CAT and LPx revealed that these feeds are non-toxic and do not produce any stress to postlarvae. These ingredients can be used as an alternative protein source for sustainable Macrobrachium culture.

  16. Unusual Photo-Induced Behaviour in a Side Chain Liquid Crystalline Azo-Polyester

    DEFF Research Database (Denmark)

    López, D; Rodríguez, F.J.; Sánchez, C.

    2006-01-01

    An unusual behaviour has been observed in the photo-indueed response of an azobenzene side chain liquid erystalline polyester (P6d4). Room temperature irradiation with linearly polarised 488 nm light does not induce any birefringence (An) in films of this polymer that have been quenehed from...... the isotropie state. However, using the same irradiation conditions An is indueed in quenehed films that have been kept in darkness for a few minutes. Besides, no photo-induced An is observed in films irradiated with 488 nm light that have been previously irradiated with UV light. In this ease, An can...... be reeorded if the UV irradiated films have been kept in darkness for several hours. In another set of experiments performed with the P6d4 polymer, irradiation with high intensity linearly polarised 488 nm light induces an initial increase of An and then it goes back to zero. Subsequent irradiation...

  17. High Performance All-Polymer Solar Cell via Polymer Side-Chain Engineering

    KAUST Repository

    Zhou, Yan; Kurosawa, Tadanori; Ma, Wei; Guo, Yikun; Fang, Lei; Vandewal, Koen; Diao, Ying; Wang, Chenggong; Yan, Qifan; Reinspach, Julia; Mei, Jianguo; Appleton, Anthony Lucas; Koleilat, Ghada I.; Gao, Yongli; Mannsfeld, Stefan C. B.; Salleo, Alberto; Ade, Harald; Zhao, Dahui; Bao, Zhenan

    2014-01-01

    An average PCE of 4.2% for all-polymer solar cells from 20 devices with an average J SC of 8.8 mA cm-2 are obtained with a donor-acceptor pair despite a low LUMO-LUMO energy offset of less than 0.1 eV. Incorporation of polystyrene side chains into the donor polymer is found to assist in reducing the phase separation domain length scale, and results in more than 20% enhancement of PCE. We observe a direct correlation between the short circuit current (J SC) and the length scale of BHJ phase separation, which is obtained by resonance soft X-ray scattering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Rotator side chains trigger cooperative transition for shape and function memory effect in organic semiconductors.

    Science.gov (United States)

    Chung, Hyunjoong; Dudenko, Dmytro; Zhang, Fengjiao; D'Avino, Gabriele; Ruzié, Christian; Richard, Audrey; Schweicher, Guillaume; Cornil, Jérôme; Beljonne, David; Geerts, Yves; Diao, Ying

    2018-01-18

    Martensitic transition is a solid-state phase transition involving cooperative movement of atoms, mostly studied in metallurgy. The main characteristics are low transition barrier, ultrafast kinetics, and structural reversibility. They are rarely observed in molecular crystals, and hence the origin and mechanism are largely unexplored. Here we report the discovery of martensitic transition in single crystals of two different organic semiconductors. In situ microscopy, single-crystal X-ray diffraction, Raman and nuclear magnetic resonance spectroscopy, and molecular simulations combined indicate that the rotating bulky side chains trigger cooperative transition. Cooperativity enables shape memory effect in single crystals and function memory effect in thin film transistors. We establish a molecular design rule to trigger martensitic transition in organic semiconductors, showing promise for designing next-generation smart multifunctional materials.

  19. Novel side-chain liquid crystalline polyester architecture for reversible optical storage

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Andruzzi, Fulvio; Kulinna, Chrisian

    1995-01-01

    New side-chain liquid crystalline polyesters have been prepared by melt transesterification of diphenyl tetradecanedioate and a series of mesogenic 2-[omega-[4-[(4-cyanophenyl)azo]phenoxyl] alkyl]-1,3-propanediols, where the alkyl spacer is hexa-, octa-, and decamethylene in turn. The polyesters...... have molecular masses in the range 5000-89 000. Solution C-13 NMR spectroscopy has been employed to identify carbons of polyester repeat units and of both types of end groups. Polyester phases and phase transitions have been investigated in detail by polarizing optical microscopy and differential...... scanning calorimetry for the hexamethylene spacer architecture with different molecular masses. Using FTIR polarization spectroscopy, the segmental orientation in unoriented polyester films induced by argon ion laser irradiation has been followed and an irradiation-dependent order parameter...

  20. Side chain and backbone contributions of Phe508 to CFTR folding

    Energy Technology Data Exchange (ETDEWEB)

    Thibodeau, Patrick H.; Brautigam, Chad A.; Machius, Mischa; Thomas, Philip J. (U. of Texas-SMED)

    2010-12-07

    Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), an integral membrane protein, cause cystic fibrosis (CF). The most common CF-causing mutant, deletion of Phe508, fails to properly fold. To elucidate the role Phe508 plays in the folding of CFTR, missense mutations at this position were generated. Only one missense mutation had a pronounced effect on the stability and folding of the isolated domain in vitro. In contrast, many substitutions, including those of charged and bulky residues, disrupted folding of full-length CFTR in cells. Structures of two mutant nucleotide-binding domains (NBDs) reveal only local alterations of the surface near position 508. These results suggest that the peptide backbone plays a role in the proper folding of the domain, whereas the side chain plays a role in defining a surface of NBD1 that potentially interacts with other domains during the maturation of intact CFTR.

  1. Lithiated short side chain perfluorinated sulfonic ionomeric membranes: Water content and conductivity

    Science.gov (United States)

    Navarrini, Walter; Scrosati, Bruno; Panero, Stefania; Ghielmi, Alessandro; Sanguineti, Aldo; Geniram, Giuliana

    In view of possible applications as single-ion electrolyte for lithium batteries, some aspects of the lithium form of Hyflon Ion ionomer, a sulfonic short side chain (SSC) electrolyte, have been investigated. The synthesis of the ionomer and the successive membrane preparation is reported. An appropriate methodology for the direct salification of the ionomeric membrane from the SO 2F form to lithium salt, using lithium hydroxide in absence of organic solvent has been found. Utilizing these SSC lithium ionomer membranes and though a particular methodology for the dehydration of the lithium ion membrane in non-aqueous media, it has been possible to achieve an ionic conductivity of 10 -3 S cm -1 at room temperature [W. Navarrini, S. Panero, B. Scrosati, A. Sanguineti, European Patent 1,403,958 A1 (2003)]. Surprisingly it was observed that the membrane ionic conductivity depends on the dehydration methodologies adopted.

  2. High Performance All-Polymer Solar Cell via Polymer Side-Chain Engineering

    KAUST Repository

    Zhou, Yan

    2014-03-24

    An average PCE of 4.2% for all-polymer solar cells from 20 devices with an average J SC of 8.8 mA cm-2 are obtained with a donor-acceptor pair despite a low LUMO-LUMO energy offset of less than 0.1 eV. Incorporation of polystyrene side chains into the donor polymer is found to assist in reducing the phase separation domain length scale, and results in more than 20% enhancement of PCE. We observe a direct correlation between the short circuit current (J SC) and the length scale of BHJ phase separation, which is obtained by resonance soft X-ray scattering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. White emission from liquid-crystalline copolymers containing oxadiazole moieties in the side chain

    Science.gov (United States)

    Kawamoto, Masuki; Tsukamoto, Takuji; Kinoshita, Motoi; Ikeda, Tomiki

    2006-09-01

    A liquid-crystalline polymer in the side chain was synthesized through copolymerization of a bipolar carrier-transporting monomer with a liquid-crystalline monomer containing oxadiazole moieties substituted with trifluoromethyl groups. A single-layer light-emitting diode of indium tin oxide (ITO)/copolymer/MgAg emitted white light with a maximum luminous efficiency of 0.1cd/A. The origin of the white emission in the copolymer is the electroplex between bipolar carrier-transporting moieties and strong electron-withdrawing moieties. Furthermore, a simple multilayer device with configuration of ITO/poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)/copolymer/MgAg device showed white emission with CIE 1931 chromaticity coordinates (x,y): (0.30, 0.33).

  4. Diffraction from polarization holographic gratings with surface relief in side-chain azobenzene polyesters

    DEFF Research Database (Denmark)

    Naydenova, I; Nikolova, L; Todorov, T

    1998-01-01

    We investigate the polarization properties of holographic gratings in side-chain azobenzene polyesters in which an anisotropic grating that is due to photoinduced linear and circular birefringence is recorded in the volume of the material and a relief grating appears on the surface. A theoretical...... model is proposed to explain the experimental results, making it possible to understand the influence of the different photoinduced effects. It is shown that at low intensity the polarization properties of the diffraction at these gratings are determined by the interaction of the linear and circular...... photobirefringences, and at larger intensity the influence of the surface relief dominates the effect of the circular anisotropy. Owing to the high recording efficiency of the polyesters, the +/-1-order diffracted waves change the polarization interference pattern during the holographic recording, resulting...

  5. Protein structure modelling and evaluation based on a 4-distance description of side-chain interactions

    Directory of Open Access Journals (Sweden)

    Inbar Yuval

    2010-07-01

    Full Text Available Abstract Background Accurate evaluation and modelling of residue-residue interactions within and between proteins is a key aspect of computational structure prediction including homology modelling, protein-protein docking, refinement of low-resolution structures, and computational protein design. Results Here we introduce a method for accurate protein structure modelling and evaluation based on a novel 4-distance description of residue-residue interaction geometry. Statistical 4-distance preferences were extracted from high-resolution protein structures and were used as a basis for a knowledge-based potential, called Hunter. We demonstrate that 4-distance description of side chain interactions can be used reliably to discriminate the native structure from a set of decoys. Hunter ranked the native structure as the top one in 217 out of 220 high-resolution decoy sets, in 25 out of 28 "Decoys 'R' Us" decoy sets and in 24 out of 27 high-resolution CASP7/8 decoy sets. The same concept was applied to side chain modelling in protein structures. On a set of very high-resolution protein structures the average RMSD was 1.47 Å for all residues and 0.73 Å for buried residues, which is in the range of attainable accuracy for a model. Finally, we show that Hunter performs as good or better than other top methods in homology modelling based on results from the CASP7 experiment. The supporting web site http://bioinfo.weizmann.ac.il/hunter/ was developed to enable the use of Hunter and for visualization and interactive exploration of 4-distance distributions. Conclusions Our results suggest that Hunter can be used as a tool for evaluation and for accurate modelling of residue-residue interactions in protein structures. The same methodology is applicable to other areas involving high-resolution modelling of biomolecules.

  6. Energetically Unfavorable Amide Conformations for N6-Acetyllysine Side Chains in Refined Protein Structures

    Science.gov (United States)

    Genshaft, Alexander; Moser, Joe-Ann S.; D'Antonio, Edward L.; Bowman, Christine M.; Christianson, David W.

    2013-01-01

    The reversible acetylation of lysine to form N6-acetyllysine in the regulation of protein function is a hallmark of epigenetics. Acetylation of the positively charged amino group of the lysine side chain generates a neutral N-alkylacetamide moiety that serves as a molecular “switch” for the modulation of protein function and protein-protein interactions. We now report the analysis of 381 N6-acetyllysine side chain amide conformations as found in 79 protein crystal structures and 11 protein NMR structures deposited in the Protein Data Bank (PDB) of the Research Collaboratory for Structural Bioinformatics. We find that only 74.3% of N6-acetyllysine residues in protein crystal structures and 46.5% in protein NMR structures contain amide groups with energetically preferred trans or generously trans conformations. Surprisingly, 17.6% of N6-acetyllysine residues in protein crystal structures and 5.3% in protein NMR structures contain amide groups with energetically unfavorable cis or generously cis conformations. Even more surprisingly, 8.1% of N6-acetyllysine residues in protein crystal structures and 48.2% in NMR structures contain amide groups with energetically prohibitive twisted conformations that approach the transition state structure for cis-trans isomerization. In contrast, 109 unique N-alkylacetamide groups contained in 84 highly-accurate small molecule crystal structures retrieved from the Cambridge Structural Database exclusively adopt energetically preferred trans conformations. Therefore, we conclude that cis and twisted N6-acetyllysine amides in protein structures deposited in the PDB are erroneously modeled due to their energetically unfavorable or prohibitive conformations. PMID:23401043

  7. Computational mining for hypothetical patterns of amino acid side chains in protein data bank (PDB)

    Science.gov (United States)

    Ghani, Nur Syatila Ab; Firdaus-Raih, Mohd

    2018-04-01

    The three-dimensional structure of a protein can provide insights regarding its function. Functional relationship between proteins can be inferred from fold and sequence similarities. In certain cases, sequence or fold comparison fails to conclude homology between proteins with similar mechanism. Since the structure is more conserved than the sequence, a constellation of functional residues can be similarly arranged among proteins of similar mechanism. Local structural similarity searches are able to detect such constellation of amino acids among distinct proteins, which can be useful to annotate proteins of unknown function. Detection of such patterns of amino acids on a large scale can increase the repertoire of important 3D motifs since available known 3D motifs currently, could not compensate the ever-increasing numbers of uncharacterized proteins to be annotated. Here, a computational platform for an automated detection of 3D motifs is described. A fuzzy-pattern searching algorithm derived from IMagine an Amino Acid 3D Arrangement search EnGINE (IMAAAGINE) was implemented to develop an automated method for searching of hypothetical patterns of amino acid side chains in Protein Data Bank (PDB), without the need for prior knowledge on related sequence or structure of pattern of interest. We present an example of the searches, which is the detection of a hypothetical pattern derived from known structural motif of C2H2 structural pattern from zinc fingers. The conservation of particular patterns of amino acid side chains in unrelated proteins is highlighted. This approach can act as a complementary method for available structure- and sequence-based platforms and may contribute in improving functional association between proteins.

  8. Side-chain-controlled self-assembly of polystyrene-polypeptide miktoarm star copolymers

    KAUST Repository

    Junnila, Susanna

    2012-03-27

    We show how the self-assembly of miktoarm star copolymers can be controlled by modifying the side chains of their polypeptide arms, using A 2B and A 2B 2 type polymer/polypeptide hybrids (macromolecular chimeras). Initially synthesized PS 2PBLL and PS 2PBLL 2 (PS, polystyrene; PBLL, poly(ε-tert-butyloxycarbonyl-l-lysine) ) miktoarms were first deprotected to PS 2PLLHCl and PS 2PLLHCl 2 miktoarms (PLLHCl, poly(l-lysine hydrochloride)) and then complexed ionically with sodium dodecyl sulfonate (DS) to give the supramolecular complexes PS 2PLL(DS) and PS 2(PLL(DS)) 2. The solid-state self-assemblies of these six miktoarm systems were studied by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and small- and wide-angle X-ray scattering (SAXS, WAXS). The side chains of the polypeptide arms were observed to have a large effect on the solubility, polypeptide conformation, and self-assembly of the miktoarms. Three main categories were observed: (i) lamellar self-assemblies at the block copolymer length scale with packed layers of α-helices in PS 2PBLL and PS 2PBLL 2; (ii) charge-clustered polypeptide micelles with less-defined conformations in a nonordered lattice within a PS matrix in PS 2PLLHCl and PS 2PLLHCl 2; (iii) lamellar polypeptide-surfactant self-assemblies with β-sheet conformation in PS 2PLL(DS) and PS 2(PLL(DS)) 2 which dominate over the formation of block copolymer scale structures. Differences between the 3- and 4-arm systems illustrate how packing frustration between the coil-like PS arms and rigid polypeptide conformations can be relieved by the right number of arms, leading to differences in the extent of order. © 2012 American Chemical Society.

  9. DMFC Performance of Polymer Electrolyte Membranes Prepared from a Graft-Copolymer Consisting of a Polysulfone Main Chain and Styrene Sulfonic Acid Side Chains

    Directory of Open Access Journals (Sweden)

    Nobutaka Endo

    2016-08-01

    Full Text Available Polymer electrolyte membranes (PEMs for direct methanol fuel cell (DMFC applications were prepared from a graft-copolymer (PSF-g-PSSA consisting of a polysulfone (PSF main chain and poly(styrene sulfonic acid (PSSA side chains with various average distances between side chains (Lav and side chain lengths (Lsc. The polymers were synthesized by grafting ethyl p-styrenesulfonate (EtSS on macro-initiators of chloromethylated polysulfone with different contents of chloromethyl (CM groups, and by changing EtSS content in the copolymers by using atom transfer radical polymerization (ATRP. The DMFC performance tests using membrane electrode assemblis (MEAs with the three types of the PEMs revealed that: a PSF-g-PSSA PEM (SF-6 prepared from a graft copolymer with short average distances between side chains (Lav and medium Lsc had higher DMFC performance than PEMs with long Lav and long Lsc or with short Lav and short Lsc. SF-6 had about two times higher PDmax (68.4 mW/cm2 than Nafion® 112 at 30 wt % of methanol concentration. Furthermore, it had 58.2 mW/cm2 of PDmax at 50 wt % of methanol concentration because of it has the highest proton selectivity during DMFC operation of all the PSF-g-PSSA PEMs and Nafion® 112.

  10. Multi-functionalized side-chain supramolecular polymers: A methodology towards tunable functional materials

    Science.gov (United States)

    Nair, Kamlesh Prabhakaran

    Even as we see a significant growth in the field of supramolecular polymers in the last ten years, multi-functionalized systems have been scarcely studied. Noncovalent multi-functionalization provides unique advantages such as rapid materials optimization via reversible functionalization as well as for the tuning of materials properties by exploiting the differences in the nature of these reversible interactions. This thesis involves the design principles, synthesis & methodology of supramolecular side-chain multi-functionalized polymers. The combination of a functionally tolerant & controlled polymerization technique such as ROMP with multiple noncovalent interactions such as hydrogen bonding, metal coordination and ionic interactions has been successfully used to synthesize these polymers. Furthermore, the orthogonality between the above interactions in block/random copolymers has been studied in detail. It has been found that the studied interactions were orthogonal to each other. To validate the viability of this methodology using multiple orthogonal interactions towards materials design noncovalent crosslinking of polymers has been used as a potential application. Three classes of networks have been studied: complementary multiple hydrogen bonded networks, metal crosslinked networks, & multi-functionalized hydrogen bonded and metal coordinated networks. The first room temperature decrosslinking by exclusive complementary hydrogen bonded interactions has been successfully achieved. Furthermore network properties have been successfully tuned by varying the network micro-structure which in turn was tuned by the hydrogen bonding motifs used for inter-chain crosslinking. By combining two different noncovalent interactions used for inter-chain crosslinking, it was possible to make multi-functionalized materials whose properties could be controlled by varying the crosslinking strategy. Hence by employing multi-functionalization methodology, important materials

  11. The power of hard-sphere models: explaining side-chain dihedral angle distributions of Thr and Val.

    Science.gov (United States)

    Zhou, Alice Qinhua; O'Hern, Corey S; Regan, Lynne

    2012-05-16

    The energy functions used to predict protein structures typically include both molecular-mechanics and knowledge-based terms. In contrast, our approach is to develop robust physics- and geometry-based methods. Here, we investigate to what extent simple hard-sphere models can be used to predict side-chain conformations. The distributions of the side-chain dihedral angle χ(1) of Val and Thr in proteins of known structure show distinctive features: Val side chains predominantly adopt χ(1) = 180°, whereas Thr side chains typically adopt χ(1) = 60° and 300° (i.e., χ(1) = ±60° or g- and g(+) configurations). Several hypotheses have been proposed to explain these differences, including interresidue steric clashes and hydrogen-bonding interactions. In contrast, we show that the observed side-chain dihedral angle distributions for both Val and Thr can be explained using only local steric interactions in a dipeptide mimetic. Our results emphasize the power of simple physical approaches and their importance for future advances in protein engineering and design. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  12. Characterization of threonine side chain dynamics in an antifreeze protein using natural abundance {sup 13}C NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Daley, Margaret E.; Sykes, Brian D. [University of Alberta, Department of Biochemistry, CIHR Group in Protein Structure and Function and Protein Engineering Network of Centres of Excellence (Canada)

    2004-06-15

    The dynamics of threonine side chains of the Tenebrio molitor antifreeze protein (TmAFP) were investigated using natural abundance {sup 13}C NMR. In TmAFP, the array of threonine residues on one face of the protein is responsible for conferring its ability to bind crystalline ice and inhibit its growth. Heteronuclear longitudinal and transverse relaxation rates and the {sup 1}H-{sup 13}C NOE were determined in this study. The C{alpha}H relaxation measurements were compared to the previously measured {sup 15}N backbone parameters and these are found to be in agreement. For the analysis of the threonine side chain motions, the model of restricted rotational diffusion about the {chi}{sub 1} dihedral angle was employed [London and Avitabile (1978) J. Am. Chem. Soc., 100, 7159-7165]. We demonstrate that the motion experienced by the ice binding threonine side chains is highly restricted, with an approximate upper limit of less than {+-}25 deg.

  13. Characterization of threonine side chain dynamics in an antifreeze protein using natural abundance 13C NMR spectroscopy

    International Nuclear Information System (INIS)

    Daley, Margaret E.; Sykes, Brian D.

    2004-01-01

    The dynamics of threonine side chains of the Tenebrio molitor antifreeze protein (TmAFP) were investigated using natural abundance 13 C NMR. In TmAFP, the array of threonine residues on one face of the protein is responsible for conferring its ability to bind crystalline ice and inhibit its growth. Heteronuclear longitudinal and transverse relaxation rates and the 1 H- 13 C NOE were determined in this study. The CαH relaxation measurements were compared to the previously measured 15 N backbone parameters and these are found to be in agreement. For the analysis of the threonine side chain motions, the model of restricted rotational diffusion about the χ 1 dihedral angle was employed [London and Avitabile (1978) J. Am. Chem. Soc., 100, 7159-7165]. We demonstrate that the motion experienced by the ice binding threonine side chains is highly restricted, with an approximate upper limit of less than ±25 deg

  14. From Semi- to Full-Two-Dimensional Conjugated Side-Chain Design: A Way toward Comprehensive Solar Energy Absorption

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Pengjie [Department; School; Wang, Huan [Department; Qu, Shiwei [Department; Mo, Daize [Department; Meng, Hong [School; Chen, Wei [Materials; Institute; He, Feng [Department

    2017-12-05

    Two polymers with fully two-dimensional (2D) conjugated side chains, 2D-PTB-Th and 2D-PTB-TTh, were synthesized and characterized through simultaneously integrating the 2D-TT and the 2D-BDT monomers onto the polymer backbone. Resulting from the synergistic effect from the conjugated side chains on both monomers, the two polymers showed remarkably efficient absorption of the sunlight and improved pi-pi intermolecular interactions for efficient charge carrier transport. The optimized bulk heterojunction device based on 2D-PTB-Th and PC71BM shows a higher PCE of 9.13% compared to PTB7-Th with a PCE of 8.26%, which corresponds to an approximately 10% improvement in solar energy conversion. The fully 2D-conjugated side-chain concept reported here developed a new molecular design strategy for polymer materials with enhanced sunlight absorption and efficient solar energy conversion.

  15. Role of Side-Chain Molecular Features in Tuning Lower Critical Solution Temperatures (LCSTs) of Oligoethylene Glycol Modified Polypeptides.

    Science.gov (United States)

    Gharakhanian, Eric G; Deming, Timothy J

    2016-07-07

    A series of thermoresponsive polypeptides has been synthesized using a methodology that allowed facile adjustment of side-chain functional groups. The lower critical solution temperature (LCST) properties of these polymers in water were then evaluated relative to systematic molecular modifications in their side-chains. It was found that in addition to the number of ethylene glycol repeats in the side-chains, terminal and linker groups also have substantial and predictable effects on cloud point temperatures (Tcp). In particular, we found that the structure of these polypeptides allowed for inclusion of polar hydroxyl groups, which significantly increased their hydrophilicity and decreased the need to use long oligoethylene glycol repeats to obtain LCSTs. The thioether linkages in these polypeptides were found to provide an additional structural feature for reversible switching of both polypeptide conformation and thermoresponsive properties.

  16. Structural effects of a light emitting copolymer having perylene moieties in the side chain on the electroluminescent characteristics

    International Nuclear Information System (INIS)

    Lee, Chang Ho; Ryu, Seung Hoon; Jang, Hee Dong; Oh, Se Young

    2004-01-01

    We have synthesized a novel side chain light emitting copolymer. The side chain light emitting copolymer has a perylene moiety as an emitting unit and methylmethacrylate (MMA) as a spacer to decrease the concentration quenching of light emitting site in the polymer intrachain. These polymers are very soluble in most organic solvents such as monochlorobenzene, tetrahydrofuran, chloroform and benzene. The single-layered electroluminescent (EL) device consisting of ITO/carrier transporting copolymer and light emitting copolymer/Al was manufactured. The carrier transporting copolymer has triphenylamine moiety as a hole transporting unit and triazine moiety as an electron transporting unit in the polymer side chain. This device exhibits maximum external quantum efficiency when the MMA contents of light emitting copolymer is 30 wt.%. In particular, the device emits more blue light as MMA contents increase

  17. The Influence of Conjugated Polymer Side Chain Manipulation on the Efficiency and Stability of Polymer Solar Cells

    DEFF Research Database (Denmark)

    Heckler, Ilona Maria; Kesters, Jurgen; Defour, Maxime

    2016-01-01

    ]thiazole (TzTz) acceptor units, were selected toward effective device scalability by roll-coating. The influence of the partial exchange (5% or 10%) of the solubilizing 2-hexyldecyloxy by alternative 2-phenylethoxy groups on efficiency and stability was investigated. With an increasing 2-phenylethoxy ratio...... studies under constant sun irradiance showed a diminishing initial degradation rate for the BT-based devices upon including the alternative side chains, whereas the (more stable) TzTz-based devices degraded at a faster rate from the start of the experiment upon partly exchanging the side chains. No clear......The stability of polymer solar cells (PSCs) can be influenced by the introduction of particular moieties on the conjugated polymer side chains. In this study, two series of donor-acceptor copolymers, based on bis(thienyl)dialkoxybenzene donor and benzo[c][1,2,5]thiadiazole (BT) or thiazolo[5,4-d...

  18. Unique contributions of an arginine side chain to ligand recognition in a glutamate-gated chloride channel

    DEFF Research Database (Denmark)

    Lynagh, Timothy; Komnatnyy, Vitaly V; Pless, Stephan A

    2017-01-01

    Glutamate recognition by neurotransmitter receptors often relies on arginine (Arg) residues in the binding site, leading to the assumption that charge-charge interactions underlie ligand recognition. However, assessing the precise chemical contribution of Arg side chains to protein function......-gated chloride channel from the nematode Haemonchus contortus. Our data unveil a surprisingly small contribution of charge at a conserved arginine side chain previously suggested to form a salt bridge with the ligand, glutamate. Instead, our data show that Arg contributes crucially to ligand sensitivity via...

  19. Fabrication of narrow surface relief features in a side-chain azobenzene polyester with a scanning near-field microscope

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Holme, N. C. R.; Pedersen, M.

    2001-01-01

    We show that it is possible to fabricate topographic submicron features in a side-chain azobenzene polyester with a scanning near-field optical microscope, Through irradiation at a wavelength of 488 run at intensity levels of 12 W/cm(2), topographic features as narrow as 240 nm and as high as 6 nm...... have been reproducibly recorded in a thin film of the polyester. These observations are consistent with the fact that at low intensities peaks are produced evolving into formation of trenches at high intensities in the case of amorphous side-chain azobenzene polyesters. This may find applications...

  20. Proton conducting graft copolymers with tunable length and density of phosphonated side chains for fuel cell membranes

    DEFF Research Database (Denmark)

    Dimitrov, Ivaylo; Takamuku, Shogo; Jankova Atanasova, Katja

    2014-01-01

    Polysulfones functionalized with highly phosphonated poly(pentafluorostyrene) side chains of different lengths were synthesized applying controlled polymerization and modification methods. The graft copolymers' thermal properties were evaluated by differential scanning calorimetry and thermal...... gravimetrical analyses. The proton conductivity of membrane prepared from the graft copolymer with the shortest phosphonated side chains was 134 mS cm(-1) at 100 degrees C under fully immersed conditions. The graft copolymer TEM image shows a nanophase separation of ion-rich segments within the polysulfone...

  1. Structure and isotopic ratios of aliphatic side chains in the insoluble organic matter of the Murchison carbonaceous chondrite

    Science.gov (United States)

    Huang, Yongsong; Alexandre, Marcelo R.; Wang, Yi

    2007-07-01

    We report in this paper the first molecular and isotopic characterization of individual aliphatic side chains from the insoluble organic matter (IOM) in the Murchison carbonaceous chondrite using a novel combined approach of RuO 4 oxidation and solid phase microextraction (SPME). The aliphatic side chains in the IOM of Murchison were first released by oxidizing aromatic structures using RuO 4. Because the IOM of carbonaceous chondrites contains predominantly short (C 1 to C 9) aliphatic substitutions, the resulting low molecular weight monocarboxylic acids (MCAs) are highly volatile and water-soluble. The conventional aqueous extraction and derivatization procedures following RuO 4 oxidation are unable to recover MCAs for subsequent analyses. We overcame this problem by employing SPME to directly capture the MCAs from the aqueous solution. We selected a SPME fiber with greater affinity for longer chain monoacids to compensate for the exponential decline of monoacid concentrations with increasing carbon numbers in meteorite IOM, allowing more accurate identification and quantification for the less abundant monoacids. We also determined the carbon and hydrogen isotopic ratios of individual MCAs derived from Murchinson IOM. Our results reveal significant similarity in both molecular structures and hydrogen isotopic ratios between the IOM aliphatic side chains and water-soluble MCAs in Murchison, suggesting that these compounds had common precursors. Our combined new approach of RuO 4 oxidation-SPME provides a new way to probe the molecular and isotopic characteristics of aliphatic side chains in carbonaceous chondrites.

  2. Effect of side chain length and degree of polymerization on the decomposition and crystallization behaviour of chlorinated poly(vinyl ester) oligomers

    International Nuclear Information System (INIS)

    Heinze, D.; Mang, Th.; Popescu, C.; Weichold, O.

    2016-01-01

    Highlights: • Thermal behaviour of telomerized polyvinyl esters is investigated. • Thermal stability relies mainly on the contribution of side chains. • At equal molecular weights thermal stability is dictated by length of side chain. • Increasing the length of side chains improves also the packing degree of polymer. - Abstract: Four members of a homologous series of chlorinated poly(vinyl ester) oligomers CCl_3–(CH_2CH (OCO(CH_2)_mCH_3))_n–Cl with degrees of polymerization of 10 and 20 were prepared by telomerisation using carbon tetrachloride. The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate) to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain length and of the degree of polymerization on the thermal stability and crystallization behaviour of the synthesized compounds was investigated. All oligomers degrade in two major steps by first losing HCl and side chains with subsequent breakdown of the backbone. The members with short side chains, up to poly(vinyl octanoate), are amorphous and show internal plasticization, whereas those with high number of side chain carbon atoms are semi-crystalline due to side-chain crystallization. A better packing for poly(vinyl stearate) is also noticeable. The glass transition and melting temperatures as well as the onset temperature of decomposition are influenced to a larger extent by the side chain length than by the degree of polymerization. Thermal stability is improved if both the size and number of side chains increase, but only a long side chain causes a significant increase of the resistance to degradation. This results in a stabilization of PVAc so that oligomers from poly(vinyl octanoate) on are stable under atmospheric conditions. Thus, the way to design stable, chlorinated PVEs oligomers is to use a long n-alkyl side chain.

  3. Effect of side chain length and degree of polymerization on the decomposition and crystallization behaviour of chlorinated poly(vinyl ester) oligomers

    Energy Technology Data Exchange (ETDEWEB)

    Heinze, D.; Mang, Th. [Aachen University of Applied Sciences, Heinrich-Mussmann-Str. 1, 52428 Jülich (Germany); Popescu, C., E-mail: crisan.popescu@kao.com [KAO Germany GmbH, Pfungstädterstr. 98-100, 64297 Darmstadt (Germany); Weichold, O., E-mail: weichold@ibac.rwth-aachen.de [Institute of Building Materials Research, Schinkelstr. 3, 52062 Aachen (Germany)

    2016-08-10

    Highlights: • Thermal behaviour of telomerized polyvinyl esters is investigated. • Thermal stability relies mainly on the contribution of side chains. • At equal molecular weights thermal stability is dictated by length of side chain. • Increasing the length of side chains improves also the packing degree of polymer. - Abstract: Four members of a homologous series of chlorinated poly(vinyl ester) oligomers CCl{sub 3}–(CH{sub 2}CH (OCO(CH{sub 2}){sub m}CH{sub 3})){sub n}–Cl with degrees of polymerization of 10 and 20 were prepared by telomerisation using carbon tetrachloride. The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate) to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain length and of the degree of polymerization on the thermal stability and crystallization behaviour of the synthesized compounds was investigated. All oligomers degrade in two major steps by first losing HCl and side chains with subsequent breakdown of the backbone. The members with short side chains, up to poly(vinyl octanoate), are amorphous and show internal plasticization, whereas those with high number of side chain carbon atoms are semi-crystalline due to side-chain crystallization. A better packing for poly(vinyl stearate) is also noticeable. The glass transition and melting temperatures as well as the onset temperature of decomposition are influenced to a larger extent by the side chain length than by the degree of polymerization. Thermal stability is improved if both the size and number of side chains increase, but only a long side chain causes a significant increase of the resistance to degradation. This results in a stabilization of PVAc so that oligomers from poly(vinyl octanoate) on are stable under atmospheric conditions. Thus, the way to design stable, chlorinated PVEs oligomers is to use a long n-alkyl side chain.

  4. The role of side chain conformational flexibility in surface recognition by Tenebrio molitor antifreeze protein

    Science.gov (United States)

    Daley, Margaret E.; Sykes, Brian D.

    2003-01-01

    Two-dimensional nuclear magnetic resonance spectroscopy was used to investigate the flexibility of the threonine side chains in the β-helical Tenebrio molitor antifreeze protein (TmAFP) at low temperatures. From measurement of the 3Jαβ 1H-1H scalar coupling constants, the χ1 angles and preferred rotamer populations can be calculated. It was determined that the threonines on the ice-binding face of the protein adopt a preferred rotameric conformation at near freezing temperatures, whereas the threonines not on the ice-binding face sample many rotameric states. This suggests that TmAFP maintains a preformed ice-binding conformation in solution, wherein the rigid array of threonines that form the AFP-ice interface matches the ice crystal lattice. A key factor in binding to the ice surface and inhibition of ice crystal growth appears to be the close surface-to-surface complementarity between the AFP and crystalline ice, and the lack of an entropic penalty associated with freezing out motions in a flexible ligand. PMID:12824479

  5. Anti-Biofouling Properties of Comblike Block Copolymers with Amphiphilic Side Chains

    International Nuclear Information System (INIS)

    Krishnan, S.; Ayothi, R.; Hexemer, A.; Finlay, J.; Sohn, K.; Perry, R.; Ober, C.; Kramer, E.; Callow, M.

    2006-01-01

    Surfaces of novel block copolymers with amphiphilic side chains were studied for their ability to influence the adhesion of marine organisms. The surface-active polymer, obtained by grafting fluorinated molecules with hydrophobic and hydrophilic blocks to a block copolymer precursor, showed interesting bioadhesion properties. Two different algal species, one of which adhered strongly to hydrophobic surfaces, and the other, to hydrophilic surfaces, showed notably weak adhesion to the amphiphilic surfaces. Both organisms are known to secrete adhesive macromolecules, with apparently different wetting characteristics, to attach to underwater surfaces. The ability of the amphiphilic surface to undergo an environment-dependent transformation in surface chemistry when in contact with the extracellular polymeric substances is a possible reason for its antifouling nature. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) was used, in a new approach based on angle-resolved X-ray photoelectron spectroscopy (XPS), to determine the variation in chemical composition within the top few nanometers of the surface and also to study the surface segregation of the amphiphilic block. A mathematical model to extract depth-profile information from the normalized NEXAFS partial electron yield is developed

  6. Kerr effect in the isotropic phase of a side-chain polymeric liquid crystal

    Science.gov (United States)

    Reys, V.; Dormoy, Y.; Collin, D.; Keller, P.; Martinoty, P.

    1992-02-01

    The birefringence induced by a pulsed electrical field was used to study the pretransitional effects associated with the isotropic phase of a side-chain polysiloxane. The results obtained show that these effects are characterised by a conventional value of the static exponent and an abnormal value of the dynamic exponent, which shows that the dynamic theory of low molecular weight liquid crystals does not apply. The results also reveal competition between the dipolar moments induced by the electrical field and the permanent moments of the mesogenic molecules. La biréfringence induite par un champ électrique impulsionnel a été utilisée pour étudier les effets prétransitionnels associés à la phase isotrope d'un polysiloxane à chaînes latérales. Les résultats obtenus montrent que ces effets sont caractérisés par une valeur classique de l'exposant statique et une valeur anormale de l'exposant dynamique. Ce dernier résultat montre que la théorie dynamique des cristaux liquides de bas poids moléculaire n'est pas applicable au cas présent. Les expériences mettent également en évidence une compétition entre les moments dipolaires induits par le champ électrique et les moments permanents des molécules mésogènes.

  7. Effect of alkyl side chain location and cyclicity on the aerobic biotransformation of naphthenic acids.

    Science.gov (United States)

    Misiti, Teresa M; Tezel, Ulas; Pavlostathis, Spyros G

    2014-07-15

    Aerobic biodegradation of naphthenic acids is of importance to the oil industry for the long-term management and environmental impact of process water and wastewater. The effect of structure, particularly the location of the alkyl side chain as well as cyclicity, on the aerobic biotransformation of 10 model naphthenic acids (NAs) was investigated. Using an aerobic, mixed culture, enriched with a commercial NA mixture (NA sodium salt; TCI Chemicals), batch biotransformation assays were conducted with individual model NAs, including eight 8-carbon isomers. It was shown that NAs with a quaternary carbon at the α- or β-position or a tertiary carbon at the β- and/or β'-position are recalcitrant or have limited biodegradability. In addition, branched NAs exhibited lag periods and lower degradation rates than nonbranched or simple cyclic NAs. Two NA isomers used in a closed bottle, aerobic biodegradation assay were mineralized, while 21 and 35% of the parent compound carbon was incorporated into the biomass. The NA biodegradation probability estimated by two widely used models (BIOWIN 2 and 6) and a recently developed model (OCHEM) was compared to the biodegradability of the 10 model NAs tested in this study as well as other related NAs. The biodegradation probability estimated by the OCHEM model agreed best with the experimental data and was best correlated with the measured NA biodegradation rate.

  8. Poly(Amido Amine)s Containing Agmatine and Butanol Side Chains as Efficient Gene Carriers.

    Science.gov (United States)

    Won, Young-Wook; Ankoné, Marc; Engbersen, Johan F J; Feijen, Jan; Kim, Sung Wan

    2016-04-01

    A new type of bioreducible poly(amido amine) copolymer is synthesized by the Michael addition polymerization of cystamine bisacrylamide (CBA) with 4-aminobutylguanidine (agmatine, AGM) and 4-aminobutanol (ABOL). Since the positively charged guanidinium groups of AGM and the hydroxybutyl groups of ABOL in the side chains have shown to improve the overall transfection efficiency of poly(amido amine)s, it is hypothesized that poly(CBA-ABOL/AGM) synthesized at the optimal ratio of both components would result in high transfection efficiency and minimal toxicity. In this study, a series of the poly(CBA-ABOL/AGM) copolymers is synthesized as gene carriers. The polymers are characterized and luciferase transfection efficiencies of the polymers in various cell lines are investigated to select the ideal ratio between AGM and ABOL. The poly(CBA-ABOL/AGM) containing 80% AGM and 20% ABOL has shown the best transfection efficiency with the lowest cytotoxicity, indicating that this polymer is very promising as a potent and nontoxic gene carrier. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. A rigid disulfide-linked nitroxide side chain simplifies the quantitative analysis of PRE data

    Energy Technology Data Exchange (ETDEWEB)

    Fawzi, Nicolas L. [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States); Fleissner, Mark R. [University of California, Jules Stein Eye Institute and Department of Chemistry and Biochemistry (United States); Anthis, Nicholas J. [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States); Kalai, Tamas; Hideg, Kalman [University of Pecs, Institute of Organic and Medicinal Chemistry (Hungary); Hubbell, Wayne L., E-mail: hubbellw@jsei.ucla.edu [University of California, Jules Stein Eye Institute and Department of Chemistry and Biochemistry (United States); Clore, G. Marius, E-mail: mariusc@mail.nih.gov [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States)

    2011-09-15

    The measurement of {sup 1}H transverse paramagnetic relaxation enhancement (PRE) has been used in biomolecular systems to determine long-range distance restraints and to visualize sparsely-populated transient states. The intrinsic flexibility of most nitroxide and metal-chelating paramagnetic spin-labels, however, complicates the quantitative interpretation of PREs due to delocalization of the paramagnetic center. Here, we present a novel, disulfide-linked nitroxide spin label, R1p, as an alternative to these flexible labels for PRE studies. When introduced at solvent-exposed {alpha}-helical positions in two model proteins, calmodulin (CaM) and T4 lysozyme (T4L), EPR measurements show that the R1p side chain exhibits dramatically reduced internal motion compared to the commonly used R1 spin label (generated by reacting cysteine with the spin labeling compound often referred to as MTSL). Further, only a single nitroxide position is necessary to account for the PREs arising from CaM S17R1p, while an ensemble comprising multiple conformations is necessary for those observed for CaM S17R1. Together, these observations suggest that the nitroxide adopts a single, fixed position when R1p is placed at solvent-exposed {alpha}-helical positions, greatly simplifying the interpretation of PRE data by removing the need to account for the intrinsic flexibility of the spin label.

  10. A rigid disulfide-linked nitroxide side chain simplifies the quantitative analysis of PRE data

    International Nuclear Information System (INIS)

    Fawzi, Nicolas L.; Fleissner, Mark R.; Anthis, Nicholas J.; Kálai, Tamás; Hideg, Kálmán; Hubbell, Wayne L.; Clore, G. Marius

    2011-01-01

    The measurement of 1 H transverse paramagnetic relaxation enhancement (PRE) has been used in biomolecular systems to determine long-range distance restraints and to visualize sparsely-populated transient states. The intrinsic flexibility of most nitroxide and metal-chelating paramagnetic spin-labels, however, complicates the quantitative interpretation of PREs due to delocalization of the paramagnetic center. Here, we present a novel, disulfide-linked nitroxide spin label, R1p, as an alternative to these flexible labels for PRE studies. When introduced at solvent-exposed α-helical positions in two model proteins, calmodulin (CaM) and T4 lysozyme (T4L), EPR measurements show that the R1p side chain exhibits dramatically reduced internal motion compared to the commonly used R1 spin label (generated by reacting cysteine with the spin labeling compound often referred to as MTSL). Further, only a single nitroxide position is necessary to account for the PREs arising from CaM S17R1p, while an ensemble comprising multiple conformations is necessary for those observed for CaM S17R1. Together, these observations suggest that the nitroxide adopts a single, fixed position when R1p is placed at solvent-exposed α-helical positions, greatly simplifying the interpretation of PRE data by removing the need to account for the intrinsic flexibility of the spin label.

  11. QSAR studies of some side chain modified 7-chloro-4-aminoquinolines as antimalarial agents

    Directory of Open Access Journals (Sweden)

    Nitendra K. Sahu

    2014-11-01

    Full Text Available The quantitative structure–activity relationship (QSAR analyses were carried out for a series of new side chain modified 4-amino-7-chloroquinolines to find out the structural requirements of their antimalarial activities against both chloroquine sensitive (HB3 and resistant (Dd2 Plasmodium falciparum strain. The statistically significant best 2D QSAR models for Dd2, having correlation coefficient (r2 = 0.9188 and cross validated squared correlation coefficient (q2 = 0.8349 with external predictive ability (pred_r2 = 0.7258 and for HB3, having r2 = 0.9024, q2 = 0.8089 and pred_r2 = 0.7463 were developed by multiple linear regression coupled with genetic algorithm (GA–MLR and stepwise (SW–MLR forward algorithm, respectively. The results of the present study may be useful on the designing of more potent analogues as antimalarial agents.

  12. UV resonance Raman finds peptide bond-Arg side chain electronic interactions.

    Science.gov (United States)

    Sharma, Bhavya; Asher, Sanford A

    2011-05-12

    We measured the UV resonance Raman excitation profiles and Raman depolarization ratios of the arginine (Arg) vibrations of the amino acid monomer as well as Arg in the 21-residue predominantly alanine peptide AAAAA(AAARA)(3)A (AP) between 194 and 218 nm. Excitation within the π → π* peptide bond electronic transitions result in UVRR spectra dominated by amide peptide bond vibrations. The Raman cross sections and excitation profiles indicate that the Arg side chain electronic transitions mix with the AP peptide bond electronic transitions. The Arg Raman bands in AP exhibit Raman excitation profiles similar to those of the amide bands in AP which are conformation specific. These Arg excitation profiles distinctly differ from the Arg monomer. The Raman depolarization ratios of Arg in monomeric solution are quite simple with ρ = 0.33 indicating enhancement by a single electronic transition. In contrast, we see very complex depolarization ratios of Arg in AP that indicate that the Arg residues are resonance enhanced by multiple electronic transitions.

  13. Effects of hydrophobic helix length and side chain chemistry on biomimicry in peptoid analogues of SP-C.

    Science.gov (United States)

    Brown, Nathan J; Wu, Cindy W; Seurynck-Servoss, Shannon L; Barron, Annelise E

    2008-02-12

    The hydrophobic proteins of lung surfactant (LS), SP-B and SP-C, are critical constituents of an effective surfactant replacement therapy for the treatment of respiratory distress syndrome. Because of concerns and difficulties associated with animal-derived surfactants, recent investigations have focused on the creation of synthetic analogues of the LS proteins. However, creating an accurate mimic of SP-C that retains its biophysical surface activity is extraordinarily challenging given the lipopeptide's extreme hydrophobicity and propensity to misfold and aggregate. One successful approach that overcomes these difficulties is the use of poly-N-substituted glycines, or peptoids, to mimic SP-C. To develop a non-natural, bioactive mimic of SP-C and to investigate the effects of side chain chemistry and length of the helical hydrophobic region, we synthesized, purified, and performed in vitro testing of two classes of peptoid SP-C mimics: those having a rigid alpha-chiral aromatic helix and those having a biomimetic alpha-chiral aliphatic helix. The length of the two classes of mimics was also systematically altered. Circular dichroism spectroscopy gave evidence that all of the peptoid-based mimics studied here emulated SP-C's secondary structure, forming stable helical structures in solution. Langmuir-Wilhelmy surface balance, fluorescence microscopy, and pulsating bubble surfactometry experiments provide evidence that the aromatic-based SP-C peptoid mimics, in conjunction with a synthetic lipid mixture, have superior surface activity and biomimetic film morphology in comparison to the aliphatic-based mimics and that there is an increase in surface activity corresponding to increasing helical length.

  14. DISTRIBUTION OF GBM HEPARAN-SULFATE PROTEOGLYCAN CORE PROTEIN AND SIDE-CHAINS IN HUMAN GLOMERULAR-DISEASES

    NARCIS (Netherlands)

    VANDENBORN, J; VANDENHEUVEL, LPWJ; BAKKER, MAH; VEERKAMP, JH; ASSMANN, KJM; WEENING, JJ; BERDEN, JHM

    Using monoclonal antibodies (mAbs) recognizing either the core protein or the heparan sulfate (HS) side chain of human GBM heparan sulfate proteoglycan (HSPG), we investigated their glomerular distribution on cryostat sections of human kidney tissues. The study involved 95 biopsies comprising twelve

  15. 26 kDa endochitinase from barley seeds: an interaction of the ionizable side chains essential for catalysis

    DEFF Research Database (Denmark)

    Ohnishi, Tsuneo; Juffer, André H; Tamoi, Masahiro

    2005-01-01

    to be abnormally low (-2.4), suggesting that these side chains may interact with each other. Mutation of Glu203 to alanine (E203A) completely eliminated the enzymatic activity and impaired the thermal stability (deltaT(m) = 6.4 degrees C) of the enzyme. Substrate binding ability was also affected by the Glu203...

  16. The influence of chirality in the amide side chain on the carbonyl orientation in rotational isomers of 3-carbamoylpyridinium halides

    NARCIS (Netherlands)

    Bastiaansen, L.A.M.; Vermeulen, T.J.M.; Buck, H.M.; Smeets, W.J.J.; Kanters, J.A.

    1988-01-01

    The direction of the carbonyl orientation in solid amide rotamers of 3-(N-methyl-N-a-methylbenzylcarbamoyl)-1,2,4-trimethylpyridinium iodide is governed by the (R)- or (S)-chirality in the amide side chain; X-ray structures and c.d. spectra are correlated.

  17. Synthesis of deuterium-labeled plant sterols and analysis of their side-chain mobility by solid state deuterium NMR

    International Nuclear Information System (INIS)

    Marsan, M.P.; Muller, I.; Milon, A.

    1996-01-01

    Sitosterol and stigmasterol, plant sterols, were deuterated at specific positions. Orientation and mobility of the deuterated sitosterol and stigmasterol (and two of their diasteromers) on oriented lipid bilayers were analyzed by deuterium NMR spectroscopy. Orientation and mobility of the side chains was revealed by these studies

  18. Interplay Between Side Chain Pattern, Polymer Aggregation, and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk-Heterojunction Solar Cells

    KAUST Repository

    Dyer-Smith, Clare; Howard, Ian A.; Cabanetos, Clement; El Labban, Abdulrahman; Beaujuge, Pierre; Laquai, Fré dé ric

    2015-01-01

    Poly(benzo[1,2-b:4,5-b′]dithiophene–alt–thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with linear side-chains yield bulk-heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl-C71-butyric acid methyl

  19. Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics

    KAUST Repository

    Kiefer, David; Giovannitti, Alexander; Sun, Hengda; Biskup, Till; Hofmann, Anna; Koopmans, Marten; Cendra, Camila; Weber, Stefan; Anton Koster, L. Jan; Olsson, Eva; Rivnay, Jonathan; Fabiano, Simone; McCulloch, Iain; Mü ller, Christian

    2018-01-01

    (gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole–dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively

  20. Effect of Non-fullerene Acceptors' Side Chains on the Morphology and Photovoltaic Performance of Organic Solar Cells.

    Science.gov (United States)

    Zhang, Cai'e; Feng, Shiyu; Liu, Yahui; Hou, Ran; Zhang, Zhe; Xu, Xinjun; Wu, Youzhi; Bo, Zhishan

    2017-10-04

    Three indacenodithieno[3,2-b]thiophene (IT) cored small molecular acceptors (ITIC-SC6, ITIC-SC8, and ITIC-SC2C6) were synthesized, and the influence of side chains on their performances in solar cells was systematically probed. Our investigations have demonstrated the variation of side chains greatly affects the charge dissociation, charge mobility, and morphology of the donor:acceptor blend films. ITIC-SC2C6 with four branched side chains showed improved solubility, which can ensure the polymer donor to form favorable fibrous nanostructure during the drying of the blend film. Consequently, devices based on PBDB-ST:ITIC-SC2C6 demonstrated higher charge mobility, more effective exciton dissociation, and the optimal power conversion efficiency up to 9.16% with an FF of 0.63, a J sc of 15.81 mA cm -2 , and a V oc of 0.92 V. These results reveal that the side chain engineering is a valid way of tuning the morphology of blend films and further improving PCE in polymer solar cells.

  1. Conjugation of diisocyanate side chains to dimethacrylate reduces polymerization shrinkage and increases the hardness of composite resins.

    Science.gov (United States)

    Jan, Yih-Dean; Lee, Bor-Shiunn; Lin, Chun-Pin; Tseng, Wan-Yu

    2014-04-01

    Polymerization shrinkage is one of the main causes of dental restoration failure. This study tried to conjugate two diisocyanate side chains to dimethacrylate resins in order to reduce polymerization shrinkage and increase the hardness of composite resins. Diisocyanate, 2-hydroxyethyl methacrylate, and bisphenol A dimethacrylate were reacted in different ratios to form urethane-modified new resin matrices, and then mixed with 50 wt.% silica fillers. The viscosities of matrices, polymerization shrinkage, surface hardness, and degrees of conversion of experimental composite resins were then evaluated and compared with a non-modified control group. The viscosities of resin matrices increased with increasing diisocyanate side chain density. Polymerization shrinkage and degree of conversion, however, decreased with increasing diisocyanate side chain density. The surface hardness of all diisocyanate-modified groups was equal to or significantly higher than that of the control group. Conjugation of diisocyanate side chains to dimethacrylate represents an effective means of reducing polymerization shrinkage and increasing the surface hardness of dental composite resins. Copyright © 2012. Published by Elsevier B.V.

  2. Siloxane-Terminated Solubilizing Side Chains: Bringing Conjugated Polymer Backbones Closer and Boosting Hole Mobilities in Thin-Film Transistors

    KAUST Repository

    Mei, Jianguo; Kim, Do Hwan; Ayzner, Alexander L.; Toney, Michael F.; Bao, Zhenan

    2011-01-01

    We introduce a novel siloxane-terminated solubilizing group and demonstrate its effectiveness as a side chain in an isoindigo-based conjugated polymer. An average hole mobility of 2.00 cm 2 V -1 s -1 (with a maximum mobility of 2.48 cm 2 V -1 s -1

  3. Molecular dynamics simulation of radiation grafted FEP films as proton exchange membranes: Effects of the side chain length

    DEFF Research Database (Denmark)

    Li, Xue; Zhao, Yang; Li, Weiwei

    2017-01-01

    In order to study the microstructure of the prepared potential proton exchange membrane (PEM), molecular dynamics (MD) simulations were used to lucubrate the transport behavior of water molecules and hydronium ions inside the hydrated sulfonated styrene grafted fluorinated ethylene propylene (FEP...... whereas larger water clusters formed. The results of the mean square displacements (MSDs) show that the proton conductivities of the membranes with the proposed side chain lengths were about three fifths of the experimental data, of which the membrane with side chain length of 7 sulfonic styrene units...... was supposed to exhibit the highest proton conductivity, that is 115.69 mS cm-1. All of the supposed membrane models presented good proton conductivity that could definitely meet the application requirements of the proton exchange membranes. The MD simulations can provide an insight to the chain structure...

  4. Solvent dielectric effect and side chain mutation on the structural stability of Burkholderia cepacia lipase active site: a quantum mechanical/molecular mechanics study.

    Science.gov (United States)

    Tahan, A; Monajjemi, M

    2011-12-01

    Quantum mechanical and molecular dynamics methods were used to analyze the structure and stability of neutral and zwitterionic configurations of the extracted active site sequence from a Burkholderia cepacia lipase, histidyl-seryl-glutamin (His86-Ser87-Gln88) and its mutated form, histidyl-cysteyl-glutamin (His86-Cys87-Gln88) in vacuum and different solvents. The effects of solvent dielectric constant, explicit and implicit water molecules and side chain mutation on the structure and stability of this sequence in both neutral and zwitterionic forms are represented. The quantum mechanics computations represent that the relative stability of zwitterionic and neutral configurations depends on the solvent structure and its dielectric constant. Therefore, in vacuum and the considered non-polar solvents, the neutral form of the interested sequences is more stable than the zwitterionic form, while their zwitterionic form is more stable than the neutral form in the aqueous solution and the investigated polar solvents in most cases. However, on the potential energy surfaces calculated, there is a barrier to proton transfer from the positively charged ammonium group to the negatively charged carboxylat group or from the ammonium group to the adjacent carbonyl oxygen and or from side chain oxygen and sulfur to negatively charged carboxylat group. Molecular dynamics simulations (MD) were also performed by using periodic boundary conditions for the zwitterionic configuration of the hydrated molecules in a box of water molecules. The obtained results demonstrated that the presence of explicit water molecules provides the more compact structures of the studied molecules. These simulations also indicated that side chain mutation and replacement of sulfur with oxygen leads to reduction of molecular flexibility and packing.

  5. On the turn-inducing properties of asparagine: the structuring role of the amide side chain, from isolated model peptides to crystallized proteins.

    Science.gov (United States)

    Habka, S; Sohn, W Y; Vaquero-Vara, V; Géléoc, M; Tardivel, B; Brenner, V; Gloaguen, E; Mons, M

    2018-01-31

    Asparagine (Asn) is a powerful turn-inducer residue, with a large propensity to occupy the second position in the central region of β-turns of proteins. The present work aims at investigating the role of a local anchoring between the Asn side chain and the main chain in this remarkable property. For this purpose, the H-bonding patterns of an asparagine residue in an isolated protein chain fragment forming a γ- or a β-turn have been determined using IR/UV double resonance gas phase spectroscopy on laser-desorbed, jet-cooled short models in conjunction with relevant quantum chemistry calculations. These gas phase data provide evidence for an original double anchoring linking the Asn primary amide side chain (SC), which adopts a gauche+ rotameric form, to its main chain (MC) local environment. From both IR spectroscopic evidence (H-bond induced red shifts) and quantum chemistry, Asn SC is found to behave as a stronger H-bond acceptor than donor, resulting in stronger MC→SC H-bonds than SC→MC ones. These gas phase structural data, relevant to a hydrophobic environment, have been used as a reference to assess the anchoring taking place in high resolution crystallized proteins of the Protein Data Bank. This approach reveals that, when the SC adopts a gauche+ orientation, the stronger MC→SC bonds are preserved in many cases whereas the SC→MC bonds are always disrupted, in qualitative agreement with the gas phase ranking of these interactions. Most interestingly, when Asn occupies the second position of central part of a β-turn (i.e., the very turn-inducer position), the MC→SC H-bonds are also disrupted and replaced by a water-mediated SC to MC anchoring. Owing to the specific features of the hydrated Asn side chain, we propose that it could be a turn precursor structure, able to facilitate turn formation in the early events of the folding process.

  6. Role of Loop-Clamping Side Chains in Catalysis by Triosephosphate Isomerase.

    Science.gov (United States)

    Zhai, Xiang; Amyes, Tina L; Richard, John P

    2015-12-09

    The side chains of Y208 and S211 from loop 7 of triosephosphate isomerase (TIM) form hydrogen bonds to backbone amides and carbonyls from loop 6 to stabilize the caged enzyme-substrate complex. The effect of seven mutations [Y208T, Y208S, Y208A, Y208F, S211G, S211A, Y208T/S211G] on the kinetic parameters for TIM catalyzed reactions of the whole substrates dihydroxyacetone phosphate and d-glyceraldehyde 3-phosphate [(k(cat)/K(m))(GAP) and (k(cat)/K(m))DHAP] and of the substrate pieces glycolaldehyde and phosphite dianion (k(cat)/K(HPi)K(GA)) are reported. The linear logarithmic correlation between these kinetic parameters, with slope of 1.04 ± 0.03, shows that most mutations of TIM result in an identical change in the activation barriers for the catalyzed reactions of whole substrate and substrate pieces, so that the transition states for these reactions are stabilized by similar interactions with the protein catalyst. The second linear logarithmic correlation [slope = 0.53 ± 0.16] between k(cat) for isomerization of GAP and K(d)(⧧) for phosphite dianion binding to the transition state for wildtype and many mutant TIM-catalyzed reactions of substrate pieces shows that ca. 50% of the wildtype TIM dianion binding energy, eliminated by these mutations, is expressed at the wildtype Michaelis complex, and ca. 50% is only expressed at the wildtype transition state. Negative deviations from this correlation are observed when the mutation results in a decrease in enzyme reactivity at the catalytic site. The main effect of Y208T, Y208S, and Y208A mutations is to cause a reduction in the total intrinsic dianion binding energy, but the effect of Y208F extends to the catalytic site.

  7. Side chain requirements for affinity and specificity in D5, an HIV-1 antibody derived from the VH1-69 germline segment.

    Science.gov (United States)

    Stewart, Alex; Harrison, Joseph S; Regula, Lauren K; Lai, Jonathan R

    2013-04-08

    Analysis of factors contributing to high affinity antibody-protein interactions provides insight into natural antibody evolution, and guides the design of antibodies with new or enhanced function. We previously studied the interaction between antibody D5 and its target, a designed protein based on HIV-1 gp41 known as 5-Helix, as a model system [Da Silva, G. F.; Harrison, J. S.; Lai, J. R., Biochemistry, 2010, 49, 5464-5472]. Antibody D5 represents an interesting case study because it is derived from the VH1-69 germline segment; this germline segment is characterized by a hydrophobic second heavy chain complementarity determining region (HCDR2) that constitutes the major functional paratope in D5 and several antibodies derived from the same progenitor. Here we explore side chain requirements for affinity and specificity in D5 using phage display. Two D5-based libraries were prepared that contained diversity in all three light chain complementarity determining regions (LCDRs 1-3), and in the third HCDR (HCDR3). The first library allowed residues to vary among a restricted set of six amino acids (Tyr/Ala/Asp/Ser/His/Pro; D5-Lib-I). The second library was designed based on a survey of existing VH1-69 antibody structures (D5-Lib-II). Both libraries were subjected to multiple rounds of selection against 5-Helix, and individual clones characterized. We found that selectants from D5-Lib-I generally had moderate affinity and specificity, while many clones from D5-Lib-II exhibited D5-like properties. Additional analysis of the D5-Lib-II functional population revealed position-specific biases for particular amino acids, many that differed from the identity of those side chains in D5. Together these results suggest that there is some permissiveness for alternative side chains in the LCDRs and HCDR3 of D5, but that replacement with a minimal set of residues is not tolerated in this scaffold for 5-Helix recognition. This work provides novel information about this high

  8. Asymmetric Alkyl Side-Chain Engineering of Naphthalene Diimide-Based n-Type Polymers for Efficient All-Polymer Solar Cells.

    Science.gov (United States)

    Jia, Tao; Li, Zhenye; Ying, Lei; Jia, Jianchao; Fan, Baobing; Zhong, Wenkai; Pan, Feilong; He, Penghui; Chen, Junwu; Huang, Fei; Cao, Yong

    2018-02-13

    The design and synthesis of three n-type conjugated polymers based on a naphthalene diimide-thiophene skeleton are presented. The control polymer, PNDI-2HD, has two identical 2-hexyldecyl side chains, and the other polymers have different alkyl side chains; PNDI-EHDT has a 2-ethylhexyl and a 2-decyltetradecyl side chain, and PNDI-BOOD has a 2-butyloctyl and a 2-octyldodecyl side chain. These copolymers with different alkyl side chains exhibit higher melting and crystallization temperatures, and stronger aggregation in solution, than the control copolymer PNDI-2HD that has the same side chain. Polymer solar cells based on the electron-donating copolymer PTB7-Th and these novel copolymers exhibit nearly the same open-circuit voltage of 0.77 V. Devices based on the copolymer PNDI-BOOD with different side chains have a power-conversion efficiency of up to 6.89%, which is much higher than the 4.30% obtained with the symmetric PNDI-2HD. This improvement can be attributed to the improved charge-carrier mobility and the formation of favorable film morphology. These observations suggest that the molecular design strategy of incorporating different side chains can provide a new and promising approach to developing n-type conjugated polymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. "There is a chain of connections": using syndemics theory to understand HIV treatment side effects.

    Science.gov (United States)

    Gagnon, Marilou

    2018-07-01

    Side effects are central to the experience of living longer with HIV but rarely have they been studied alone. Unlike other aspects of that experience, like quality of life, treatment adherence, chronicity, episodic disability, aging, health, and viral load suppression, side effects have not benefited from the same level of empirical and theoretical engagement from qualitative researchers. In this paper, we draw on syndemics theory and 50 qualitative interviews to better understand the experience of HIV treatment side effects. Two main categories were identified in the data: side effects as a product and side effects as a risk factor. The first category suggests that side effects are not just the product of taking antiretroviral drugs. They are also the product of particular conditions and tend to cluster with other health problems. The second category puts forward the idea that side effects can act as a syndemic risk factor by exposing PLWH to a greater risk of developing health problems and creating conditions in which psychosocial issues are more likely to emerge. The paper concludes by calling for more research on the complex nature of side effects and for the development of comprehensive approaches for the assessment and management of side effects.

  10. Siloxane-Terminated Solubilizing Side Chains: Bringing Conjugated Polymer Backbones Closer and Boosting Hole Mobilities in Thin-Film Transistors

    KAUST Repository

    Mei, Jianguo

    2011-12-21

    We introduce a novel siloxane-terminated solubilizing group and demonstrate its effectiveness as a side chain in an isoindigo-based conjugated polymer. An average hole mobility of 2.00 cm 2 V -1 s -1 (with a maximum mobility of 2.48 cm 2 V -1 s -1), was obtained from solution-processed thin-film transistors, one of the highest mobilities reported to date. In contrast, the reference polymer with a branched alkyl side chain gave an average hole mobility of 0.30 cm 2 V -1 s -1 and a maximum mobility of 0.57 cm 2 V -1 s -1. This is largely explained by the polymer packing: our new polymer exhibited a π-π stacking distance of 3.58 Å, while the reference polymer showed a distance of 3.76 Å. © 2011 American Chemical Society.

  11. Fused-Ring Acceptors with Asymmetric Side Chains for High-Performance Thick-Film Organic Solar Cells.

    Science.gov (United States)

    Feng, Shiyu; Zhang, Cai'e; Liu, Yahui; Bi, Zhaozhao; Zhang, Zhe; Xu, Xinjun; Ma, Wei; Bo, Zhishan

    2017-11-01

    A kind of new fused-ring electron acceptor, IDT-OB, bearing asymmetric side chains, is synthesized for high-efficiency thick-film organic solar cells. The introduction of asymmetric side chains can increase the solubility of acceptor molecules, enable the acceptor molecules to pack closely in a dislocated way, and form favorable phase separation when blended with PBDB-T. As expected, PBDB-T:IDT-OB-based devices exhibit high and balanced hole and electron mobility and give a high power conversion efficiency (PCE) of 10.12%. More importantly, the IDT-OB-based devices are not very sensitive to the film thickness, a PCE of 9.17% can still be obtained even the thickness of active layer is up to 210 nm. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

    KAUST Repository

    Moia, Davide; Giovannitti, Alexander; Szumska, Anna A.; Schnurr, Martin; Rezasoltani, Elham; Maria, Iuliana P.; Barnes, Piers R. F.; McCulloch, Iain; Nelson, Jenny

    2017-01-01

    conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

  13. Improvement in carrier mobility and photovoltaic performance through random distribution of segments of linear and branched side chains

    Energy Technology Data Exchange (ETDEWEB)

    Egbe, Daniel A.M.; Adam, Getachew; Pivrikas, Almantas; Ulbricht, Christoph; Ramil, Alberto M.; Sariciftci, Niyazi Serdar [Johannes Kepler Univ., Linz (AT). Linz Inst. for Organic Solar Cells (LIOS); Hoppe, Harald [Technische Univ. Ilmenau (Germany). Inst. of Physics and Inst. of Micro- and Nanotechnologies; Rathgeber, Silke [Mainz Univ. (Germany). Inst. of Physics

    2010-07-01

    The random distribution of segments of linear octyloxy side chains and of branched 2-ethylhexyloxy side chains, on the backbone of anthracene containing poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) (PPE-PPV) has resulted in a side chain based statistical copolymer, denoted AnE-PVstat, showing optimized features as compared to the well defined homologues AnE-PVaa, -ab, -ba and -bb, whose constitutional units are incorporated into its backbone. WAXS studies on AnE-P's demonstrate the highest degree of order at the self-assembly state of AnE-PVstat, which is confirmed by its highly structured thin film absorption band. Electric field independent charge carrier mobility ({mu}{sub hole}) for AnE-PVstat was demonstrated by CELIV and OFET measurements, both methods resulting in similar {mu}{sub hole} values of up to 5.43 x 10{sup -4} cm{sup 2}/Vs. Upon comparison, our results show that charge carrier mobility as measured by CELIV technique is predominantly an intrachain process and less an interchain one, which is in line with past photoconductivity results from PPE-PPV based materials. The present side chain distribution favors efficient solar cell active layer phase separation. As a result, a smaller amount of PC{sub 60}BM is needed to achieve relatively high energy conversion efficiencies above 3 %. The efficiency of {eta}{sub AM1.5} {approx} 3.8 % obtained for AnE-PVstat:PC{sub 60}BM blend is presently the state-of-art value for PPV-based materials. (orig.)

  14. Aromatic Side Chain Water-to-Lipid Transfer Free Energies Show a Depth Dependence across the Membrane Normal.

    Science.gov (United States)

    McDonald, Sarah K; Fleming, Karen G

    2016-06-29

    Quantitating and understanding the physical forces responsible for the interactions of biomolecules are fundamental to the biological sciences. This is especially challenging for membrane proteins because they are embedded within cellular bilayers that provide a unique medium in which hydrophobic sequences must fold. Knowledge of the energetics of protein-lipid interactions is thus vital to understand cellular processes involving membrane proteins. Here we used a host-guest mutational strategy to calculate the Gibbs free energy changes of water-to-lipid transfer for the aromatic side chains Trp, Tyr, and Phe as a function of depth in the membrane. This work reveals an energetic gradient in the transfer free energies for Trp and Tyr, where transfer was most favorable to the membrane interfacial region and comparatively less favorable into the bilayer center. The transfer energetics follows the concentration gradient of polar atoms across the bilayer normal that naturally occurs in biological membranes. Additional measurements revealed nearest-neighbor coupling in the data set are influenced by a network of aromatic side chains in the host protein. Taken together, these results show that aromatic side chains contribute significantly to membrane protein stability through either aromatic-aromatic interactions or placement at the membrane interface.

  15. Interplay Between Side Chain Pattern, Polymer Aggregation, and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk-Heterojunction Solar Cells

    KAUST Repository

    Dyer-Smith, Clare

    2015-05-01

    Poly(benzo[1,2-b:4,5-b′]dithiophene–alt–thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with linear side-chains yield bulk-heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor, while a PBDTTPD polymer with a combination of branched and linear substituents yields a doubling of the PCE to 8%. Using transient optical spectroscopy it is shown that while the exciton dissociation and ultrafast charge generation steps are not strongly affected by the side chain modifications, the polymer with branched side chains exhibits a decreased rate of nongeminate recombination and a lower fraction of sub-nanosecond geminate recombination. In turn the yield of long-lived charge carriers increases, resulting in a 33% increase in short circuit current (J sc). In parallel, the two polymers show distinct grazing incidence X-ray scattering spectra indicative of the presence of stacks with different orientation patterns in optimized thin-film BHJ devices. Independent of the packing pattern the spectroscopic data also reveals the existence of polymer aggregates in the pristine polymer films as well as in both blends which trap excitons and hinder their dissociation.

  16. The Influence of Conjugated Polymer Side Chain Manipulation on the Efficiency and Stability of Polymer Solar Cells.

    Science.gov (United States)

    Heckler, Ilona M; Kesters, Jurgen; Defour, Maxime; Madsen, Morten V; Penxten, Huguette; D'Haen, Jan; Van Mele, Bruno; Maes, Wouter; Bundgaard, Eva

    2016-03-09

    The stability of polymer solar cells (PSCs) can be influenced by the introduction of particular moieties on the conjugated polymer side chains. In this study, two series of donor-acceptor copolymers, based on bis(thienyl)dialkoxybenzene donor and benzo[ c ][1,2,5]thiadiazole (BT) or thiazolo[5,4- d ]thiazole (TzTz) acceptor units, were selected toward effective device scalability by roll-coating. The influence of the partial exchange (5% or 10%) of the solubilizing 2-hexyldecyloxy by alternative 2-phenylethoxy groups on efficiency and stability was investigated. With an increasing 2-phenylethoxy ratio, a decrease in solar cell efficiency was observed for the BT-based series, whereas the efficiencies for the devices based on the TzTz polymers remained approximately the same. The photochemical degradation rate for PSCs based on the TzTz polymers decreased with an increasing 2-phenylethoxy ratio. Lifetime studies under constant sun irradiance showed a diminishing initial degradation rate for the BT-based devices upon including the alternative side chains, whereas the (more stable) TzTz-based devices degraded at a faster rate from the start of the experiment upon partly exchanging the side chains. No clear trends in the degradation behavior, linked to the copolymer structural changes, could be established at this point, evidencing the complex interplay of events determining PSCs' lifetime.

  17. The Influence of Conjugated Polymer Side Chain Manipulation on the Efficiency and Stability of Polymer Solar Cells

    Directory of Open Access Journals (Sweden)

    Ilona M. Heckler

    2016-03-01

    Full Text Available The stability of polymer solar cells (PSCs can be influenced by the introduction of particular moieties on the conjugated polymer side chains. In this study, two series of donor-acceptor copolymers, based on bis(thienyldialkoxybenzene donor and benzo[c][1,2,5]thiadiazole (BT or thiazolo[5,4-d]thiazole (TzTz acceptor units, were selected toward effective device scalability by roll-coating. The influence of the partial exchange (5% or 10% of the solubilizing 2-hexyldecyloxy by alternative 2-phenylethoxy groups on efficiency and stability was investigated. With an increasing 2-phenylethoxy ratio, a decrease in solar cell efficiency was observed for the BT-based series, whereas the efficiencies for the devices based on the TzTz polymers remained approximately the same. The photochemical degradation rate for PSCs based on the TzTz polymers decreased with an increasing 2-phenylethoxy ratio. Lifetime studies under constant sun irradiance showed a diminishing initial degradation rate for the BT-based devices upon including the alternative side chains, whereas the (more stable TzTz-based devices degraded at a faster rate from the start of the experiment upon partly exchanging the side chains. No clear trends in the degradation behavior, linked to the copolymer structural changes, could be established at this point, evidencing the complex interplay of events determining PSCs’ lifetime.

  18. Impact of the Nature of the Side-Chains on the Polymer-Fullerene Packing in the Mixed Regions of Bulk Heterojunction Solar Cells

    KAUST Repository

    Wang, Tonghui; Ravva, Mahesh Kumar; Bredas, Jean-Luc

    2016-01-01

    Polymer-fullerene packing in mixed regions of a bulk heterojunction solar cell is expected to play a major role in exciton-dissociation, charge-separation, and charge-recombination processes. Here, molecular dynamics simulations are combined with density functional theory calculations to examine the impact of nature and location of polymer side-chains on the polymer-fullerene packing in mixed regions. The focus is on poly-benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione (PBDTTPD) as electron-donating material and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as electron-accepting material. Three polymer side-chain patterns are considered: i) linear side-chains on both benzodithiophene (BDT) and thienopyrroledione (TPD) moieties; ii) two linear side-chains on BDT and a branched side-chain on TPD; and iii) two branched side-chains on BDT and a linear side-chain on TPD. Increasing the number of branched side-chains is found to decrease the polymer packing density and thereby to enhance PBDTTPD–PC61 BM mixing. The nature and location of side-chains are found to play a determining role in the probability of finding PC61BM molecules close to either BDT or TPD. The electronic couplings relevant for the exciton-dissociation and charge-recombination processes are also evaluated. Overall, the findings are consistent with the experimental evolution of the PBDTTPD–PC61BM solar-cell performance as a function of side-chain patterns. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  19. Impact of the Nature of the Side-Chains on the Polymer-Fullerene Packing in the Mixed Regions of Bulk Heterojunction Solar Cells

    KAUST Repository

    Wang, Tonghui

    2016-06-20

    Polymer-fullerene packing in mixed regions of a bulk heterojunction solar cell is expected to play a major role in exciton-dissociation, charge-separation, and charge-recombination processes. Here, molecular dynamics simulations are combined with density functional theory calculations to examine the impact of nature and location of polymer side-chains on the polymer-fullerene packing in mixed regions. The focus is on poly-benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione (PBDTTPD) as electron-donating material and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as electron-accepting material. Three polymer side-chain patterns are considered: i) linear side-chains on both benzodithiophene (BDT) and thienopyrroledione (TPD) moieties; ii) two linear side-chains on BDT and a branched side-chain on TPD; and iii) two branched side-chains on BDT and a linear side-chain on TPD. Increasing the number of branched side-chains is found to decrease the polymer packing density and thereby to enhance PBDTTPD–PC61 BM mixing. The nature and location of side-chains are found to play a determining role in the probability of finding PC61BM molecules close to either BDT or TPD. The electronic couplings relevant for the exciton-dissociation and charge-recombination processes are also evaluated. Overall, the findings are consistent with the experimental evolution of the PBDTTPD–PC61BM solar-cell performance as a function of side-chain patterns. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  20. Fine-tuning blend morphology via alkylthio side chain engineering towards high performance non-fullerene polymer solar cells

    Science.gov (United States)

    Li, Ling; Feng, Liuliu; Yuan, Jun; Peng, Hongjian; Zou, Yingping; Li, Yongfang

    2018-03-01

    Two medium bandgap polymers (ffQx-TS1, ffQx-TS2) were designed and synthesized to investigate the influence of different alkylthio side chain on the morphology and photovoltaic performance of non-fullerene polymer solar cells (PSCs). Both polymers exhibit similar molecular weights and comparable the highest occupied molecular orbital (HOMO) energy level. However, the polymer with straight alkylthio chain delivers a root-mean-square (RMS) of 0.86 nm, which is slightly lower than that with branched chain (1.40 nm). The lower RMS benefits the ohmic contact between the active lay and interface layer, thus enhanced short circuit current (Jsc) (from 13.54 mA cm-1 to 15.25 mA cm-1) could be obtained. Due to the enhancement of Jsc, better power conversion efficiency (PCE) of 7.69% for ffQx-TS2 could be realized. These results indicated that alkylthio side chain engineering is a promising method to improve photovoltaic performance.

  1. Influence of the side chain and substrate on polythiophene thin film surface, bulk, and buried interfacial structures.

    Science.gov (United States)

    Xiao, Minyu; Jasensky, Joshua; Zhang, Xiaoxian; Li, Yaoxin; Pichan, Cayla; Lu, Xiaolin; Chen, Zhan

    2016-08-10

    The molecular structures of organic semiconducting thin films mediate the performance of various devices composed of such materials. To fully understand how the structures of organic semiconductors alter on substrates due to different polymer side chains and different interfacial interactions, thin films of two kinds of polythiophene derivatives with different side-chains, poly(3-hexylthiophene) (P3HT) and poly(3-potassium-6-hexanoate thiophene) (P3KHT), were deposited and compared on various surfaces. A combination of analytical tools was applied in this research: contact angle goniometry and X-ray photoelectron spectroscopy (XPS) were used to characterize substrate dielectric surfaces with varied hydrophobicity for polymer film deposition; X-ray diffraction and UV-vis spectroscopy were used to examine the polythiophene film bulk structure; sum frequency generation (SFG) vibrational spectroscopy was utilized to probe the molecular structures of polymer film surfaces in air and buried solid/solid interfaces. Both side-chain hydrophobicity and substrate hydrophobicity were found to mediate the crystallinity of the polythiophene film, as well as the orientation of the thiophene ring within the polymer backbone at the buried polymer/substrate interface and the polymer thin film surface in air. For the same type of polythiophene film deposited on different substrates, a more hydrophobic substrate surface induced thiophene ring alignment with the surface normal at both the buried interface and on the surface in air. For different films (P3HT vs. P3KHT) deposited on the same dielectric substrate, a more hydrophobic polythiophene side chain caused the thiophene ring to align more towards the surface at the buried polymer/substrate interface and on the surface in air. We believe that the polythiophene surface, bulk, and buried interfacial molecular structures all influence the hole mobility within the polythiophene film. Successful characterization of an organic conducting

  2. Thermoresponsive Poly(2-oxazoline) Molecular Brushes by Living Ionic Polymerization: Kinetic Investigations of Pendant Chain Grafting and Cloud Point Modulation by Backbone and Side Chain Length Variation

    KAUST Repository

    Zhang, Ning

    2012-04-17

    Molecular brushes of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-iso-propenyl-2-oxazoline to form the backbone and subsequent living cationic ring-opening polymerization of 2-n- or 2-iso-propyl-2-oxazoline for pendant chain grafting. In situ kinetic studies indicate that the initiation efficiency and polymerization rates are independent from the number of initiator functions per initiator molecule. This was attributed to the high efficiency of oxazolinium salt and the stretched conformation of the backbone, which is caused by the electrostatic repulsion of the oxazolinium moieties along the macroinitiator. The resulting molecular brushes showed thermoresponsive properties, that is, having a defined cloud point (CP). The dependence of the CP as a function of backbone and side chain length as well as concentration was studied. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Substituted group and side chain effects for the porphyrin and zinc(II)–porphyrin derivatives: A DFT and TD-DFT study

    International Nuclear Information System (INIS)

    Tai, Chin-Kuen; Chuang, Wen-Hua; Wang, Bo-Cheng

    2013-01-01

    The DFT/B3LYP/LANL2DZ and TD-DFT calculations have been performed to generate the optimized structures, electronic and photo-physical properties for the porphyrin and zinc(II)–porphyrin (metalloporphyrin) derivatives. The substituted group and side chain effects for these derivatives are discussed in this study. According to the calculation results, the side chain moiety extends the π-delocalization length from the porphyrin core to the side chain moiety. The substituted group with a stronger electron-donating ability increases the energy level of highest occupied molecular orbital (E HOMO ). The side chain moiety with a lower resonance energy decreases E HOMO , the energy level of the lowest unoccupied molecular orbital (E LUMO ), and the energy gap (E g ) between HOMO and LUMO in the porphyrin and zinc(II)–porphyrin derivatives. The natural bonding orbital (NBO) analysis determines the possible electron transfer mechanism from the electron-donating to -withdrawing groups (the side chain moiety) in these porphyrin derivatives. The projected density of state (PDOS) analysis shows that the electron-donating group affects the electron density distribution in both HOMO and LUMO, and the side chain moiety influence the electron density distribution in LUMO. The calculated photo-physical properties (absorption wavelengths and the related oscillator strength, f) in dichloromethane environment for porphyrin and zinc(II)–porphyrin derivatives have been simulated by using the TD-DFT method within the Polarizable Continuum Model (PCM). The present of both of the substituted group and the side chain moiety in these derivatives results in a red shift and broadening of the range of the absorption peaks of the Q/Soret band as compared to porphin. -- Highlights: • Side chain moiety extends the π-delocalization for the porphyrins. • Substituted group increases the energy of highest occupied molecular orbital. • Side chain moiety influences the Q/Soret band of

  4. Modification of eucalyptus pulp fiber using silane coupling agents with aliphatic side chains of different length

    Science.gov (United States)

    The objective of this work was to evaluate the effect of three silane coupling agents with different aliphatic chain lengths on the hydrophobicity of eucalyptus pulp fiber. The three silanes coupling agents used (isobutyltrimethoxysilane, methyltrimethoxysilane, and n-octyltriethoxysilane [OTES]) we...

  5. effect of side chain length on the stability and structural properties of 3

    African Journals Online (AJOL)

    Preferred Customer

    We report on the effect of the alkoxy chain length on the thermodynamic ... studied by Hartree-Fock (HF) and Density Functional Theory (DFT) methods. ..... with longer alkoxy substituents on the phenyl ring have lesser value of change in Gibbs ...

  6. Naphthalenetetracarboxylic diimide layer-based transistors with nanometer oxide and side chain dielectrics operating below one volt.

    Science.gov (United States)

    Jung, Byung Jun; Martinez Hardigree, Josue F; Dhar, Bal Mukund; Dawidczyk, Thomas J; Sun, Jia; See, Kevin Cua; Katz, Howard E

    2011-04-26

    We designed a new naphthalenetetracarboxylic diimide (NTCDI) semiconductor molecule with long fluoroalkylbenzyl side chains. The side chains, 1.2 nm long, not only aid in self-assembly and kinetically stabilize injected electrons but also act as part of the gate dielectric in field-effect transistors. On Si substrates coated only with the 2 nm thick native oxide, NTCDI semiconductor films were deposited with thicknesses from 17 to 120 nm. Top contact Au electrodes were deposited as sources and drains. The devices showed good transistor characteristics in air with 0.1-1 μA of drain current at 0.5 V of V(G) and V(DS) and W/L of 10-20, even though channel width (250 μm) is over 1000 times the distance (20 nm) between gate and drain electrodes. The extracted capacitance-times-mobility product, an expression of the sheet transconductance, can exceed 100 nS V(-1), 2 orders of magnitude higher than typical organic transistors. The vertical low-frequency capacitance with gate voltage applied in the accumulation regime reached as high as 650 nF/cm(2), matching the harmonic sum of capacitances of the native oxide and one side chain and indicating that some gate-induced carriers in such devices are distributed among all of the NTCDI core layers, although the preponderance of the carriers are still near the gate electrode. Besides demonstrating and analyzing thickness-dependent NTCDI-based transistor behavior, we also showed <1 V detection of dinitrotoluene vapor by such transistors.

  7. Smectic order and backbone anisotropy of a side-chain liquid crystalline polymer by Small-Angle Neutron Scattering

    Science.gov (United States)

    Noirez, L.; Pépy, G.; Keller, P.; Benguigui, L.

    1991-07-01

    We have simultaneously measured, for the first time, the extension of the polymer backbone of a side-chain liquid crystalline polymer and the intensity of the 001 Bragg reflection, which gives the smectic order parameter Psi as a function of temperature in the smectic phase. We have qualitatively demonstrated that the more the smectic phase is ordered, the more the polymer backbone is localized between the mesogenic layers. It is shown that the Landau theory allows us to relate the radius of gyration parallel to the magnetic field of the polymer backbone to the smectic order parameter. We also show that the Renz-Warner theory is suitable at low temperatures.

  8. Side chain engineering of fused aromatic thienopyrazine based low band-gap polymers for enhanced charge carrier mobility

    KAUST Repository

    Mondal, Rajib

    2011-01-01

    A strategic side-chain engineering approach leads to the two orders of magnitude enhancement of charge carrier mobility in phenanthrene based fused aromatic thienopyrazine polymers. Hole carrier mobility up to 0.012 cm 2/Vs can be obtained in thin film transistor devices. Polymers were also utilized to fabricate bulk heterojunction photovoltaic devices and the maximum PCE obtained in these OPV\\'s was 1.15%. Most importantly, performances of the devices were correlated with thin morphological analysis performed by atomic force microscopy and grazing incidence X-ray scattering. © 2011 The Royal Society of Chemistry.

  9. A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

    OpenAIRE

    Moia, Davide; Giovannitti, Alexander; Szumska, Anna A.; Schnurr, Martin; Rezasoltani, Elham; Maria, Iuliana P.; Barnes, Piers R. F.; McCulloch, Iain; Nelson, Jenny

    2017-01-01

    We report a neutral salt water based battery which uses p-type and n-type solution processed polymer films as the cathode and the anode of the cell. The specific capacity of the electrodes (approximately 30 mAh cm-3) is achieved via formation of bipolarons in both the p-type and n-type polymers. By engineering ethylene glycol and zwitterion based side chains attached to the polymer backbone we facilitate rapid ion transport through the non-porous polymer films. This, combined with efficient t...

  10. Synthesis and characterisation of new types of side chain cholesteryl polymers.

    Science.gov (United States)

    Wang, Bin; Du, Haiyan; Zhang, Junhua

    2011-01-01

    A series of cholesterol derivatives have been synthesised via the alkylation reaction of the 3-hydroxyl group with the aliphatic bromide compounds with different chain lengths, namely 3β-alkyloxy-cholesterol. The double bond between the C5 and C6 positions in these cholesterol derivatives was oxidised into epoxy, followed by an epoxy-ring-opening reaction with the treatment with acrylic acid, resulting in a series of 3β-alkyloxy-5α-hydroxy-6β-acryloyloxycholesterol, C(n)OCh (n=1, 2, 4, 6, 8, 10, 12), The acrylate group is connected to the C6 position, which is confirmed by the single crystal structure analysis. The corresponding polymers, PC(n)OCh, were prepared via free radical polymerisation. The structure of monomers and the resulting polymers were characterised with nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The thermal properties of PC(n)OCh were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). To determine the secondary structure of polymers, circular dichroism (CD) spectra were performed. It was found that not all monomers produce high-molecular-weight polymers because of steric hindrance. However, all polymers have a helical structure, which can be enhanced by increasing the alkoxy chain length. In addition, increasing the alkoxy chain length decreases the glass transition temperature and increases the decomposition temperature of the polymers. Copyright © 2010 Elsevier Inc. All rights reserved.

  11. Total synthesis of a CD-ring: side-chain building block for preparing 17-epi-calcitriol derivatives from the Hajos-Parrish dione.

    Science.gov (United States)

    Michalak, Karol; Wicha, Jerzy

    2011-08-19

    An efficient synthesis of the key building block for 17-epi-calctriol from the Hajos-Parrish dione involving a sequence of diastereoselective transformation of the azulene core and the side-chain construction is presented.

  12. Effect of Side Chains on Molecular Conformation of Anthracene-Ethynylene-Phenylene-Vinylene Oligomers: A Comparative Density Functional Study With and Without Dispersion Interaction.

    Science.gov (United States)

    Dong, Chuanding; Hoppe, Harald; Beenken, Wichard J D

    2016-06-02

    Using density functional calculations with and without dispersion interaction, we studied the effects of linear octyl and branched 2-ethylhexyl side chains on the oligomer conformation of the conjugated copolymer poly(p-anthracene-ethynylene)-alt-poly(p-phenylene-vinylene). With dispersion included, the branched side chains can cause significant bending of the oligomer backbone, while without dispersion they induce mainly torsional disorder. The oligomers with mainly linear side chains keep good planarity when optimized with and without dispersion. Despite their dramatically different conformations, the calculated absorption spectra of the oligomers with various side chain combinations are very similar, indicating that the conformation of the copolymer is not the main reason for the experimentally observed different spectra of ordered and disordered phases.

  13. 4-N, 4-S & 4-O Chloroquine Analogues: Influence of Side Chain Length and Quinolyl Nitrogen pKa on Activity vs. Chloroquine Resistant Malaria+, #

    OpenAIRE

    Natarajan, Jayakumar K.; Alumasa, John; Yearick, Kimberly; Ekoue-Kovi, Kekeli A.; Casabianca, Leah B.; de Dios, Angel C.; Wolf, Christian; Roepe, Paul D.

    2008-01-01

    Using predictions from heme – quinoline antimalarial complex structures, previous modifications of chloroquine (CQ), and hypotheses for chloroquine resistance (CQR), we synthesize and assay CQ analogues that test structure – function principles. We vary side chain length for both monoethyl and diethyl 4N CQ derivatives. We alter the pKa of the quinolyl N by introducing alkylthio or alkoxy substituents into the 4 position, and vary side chain length for these analogues. We introduce an additio...

  14. Side chain variations radically alter the diffusion of poly(2-alkyl-2-oxazoline) functionalised nanoparticles through a mucosal barrier.

    Science.gov (United States)

    Mansfield, Edward D H; de la Rosa, Victor R; Kowalczyk, Radoslaw M; Grillo, Isabelle; Hoogenboom, Richard; Sillence, Katy; Hole, Patrick; Williams, Adrian C; Khutoryanskiy, Vitaliy V

    2016-08-16

    Functionalised nanomaterials are gaining popularity for use as drug delivery vehicles and, in particular, mucus penetrating nanoparticles may improve drug bioavailability via the oral route. To date, few polymers have been investigated for their muco-penetration, and the effects of systematic structural changes to polymer architectures on the penetration and diffusion of functionalised nanomaterials through mucosal tissue have not been reported. We investigated the influence of poly(2-oxazoline) alkyl side chain length on nanoparticle diffusion; poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline), and poly(2-n-propyl-2-oxazoline) were grafted onto the surface of thiolated silica nanoparticles and characterised by FT-IR, Raman and NMR spectroscopy, thermogravimetric analysis, and small angle neutron scattering. Diffusion coefficients were determined in water and in a mucin dispersion (using Nanoparticle Tracking Analysis), and penetration through a mucosal barrier was assessed using an ex vivo fluorescence technique. The addition of a single methylene group in the side chain significantly altered the penetration and diffusion of the materials in both mucin dispersions and mucosal tissue. Nanoparticles functionalised with poly(2-methyl-2-oxazoline) were significantly more diffusive than particles with poly(2-ethyl-2-oxazoline) while particles with poly(2-n-propyl-2-oxazoline) showed no significant increase compared to the unfunctionalised particles. These data show that variations in the polymer structure can radically alter their diffusive properties with clear implications for the future design of mucus penetrating systems.

  15. Self-Assembly of Amphiphilic Block Copolypeptoids with C 2 -C 5 Side Chains in Aqueous Solution

    KAUST Repository

    Fetsch, Corinna

    2014-12-22

    © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Nowadays, amphiphilic molecules play an important role in our life. In medical applications, amphiphilic block copolymers have attracted much attention as excipients in drug delivery systems. Here, the polymers are used as emulsifiers, micelles, or polymersomes with a hydrophilic corona block and a hydrophobic core or membrane. The aggregation behavior in aqueous solutions of a series of different amphiphilic block copolypeptoids comprising polysarcosine as a hydrophilic part is here reported. The formation of aggregates is investigated with 1H NMR spectroscopy and dynamic light scattering, and the determination of the critical micelle concentration (cmc) is performed using pyrene fluorescence spectroscopy. For the different block copolypeptoids cmc values ranging from 0.6 × 10-6 M to 0.1 × 10-3 M are found. The tendency to form micelles increases with increasing hydrophobicity at the nitrogen side chain in the hydrophobic moiety. Furthermore, in the case of the same hydrophobic side chain, a decreasing hydrophilic/lipophilic balance leads to the formation of larger aggregates. The aggregates formed in the buffer are able to solubilize the hydrophobic model compounds Reichardt\\'s dye and pyrene, and exhibit versatile microenvironments. Final investigations about the cytotoxicity reveal that the block copolypeptoids are well tolerated by mammalian cells up to high concentrations.

  16. Triblock Copolymers with Grafted Fluorine-Free Amphiphilic Non-Ionic Side Chains for Antifouling and Fouling-Release Applications

    Energy Technology Data Exchange (ETDEWEB)

    Y Cho; H Sundaram; C Weinman; M Paik; M Dimitriou; J Finlay; M Callow; J Callow; E Kramer; C Ober

    2011-12-31

    Fluorine-free, amphiphilic, nonionic surface active block copolymers (SABCs) were synthesized through chemical modification of a polystyrene-block-poly(ethylene-ran-butylene)-block-polyisoprene triblock copolymer precursor with selected amphiphilic nonionic Brij and other surfactants. Amphiphilicity was imparted by a hydrophobic aliphatic group combined with a hydrophilic poly(ethylene glycol) (PEG) group-containing moiety. The surfaces were characterized by dynamic water contact angle, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) analysis. In biofouling assays, settlement (attachment) of both spores of the green alga Ulva and cells of the diatom Navicula on SABCs modified with Brij nonionic side chains was significantly reduced relative to a PDMS standard, with a nonionic surfactant combining a PEG group and an aliphatic moiety demonstrating the best performance. Additionally, a fouling-release assay using sporelings (young plants) of Ulva and Navicula suggested that the SABC derived from nonionic Brij side chains also out-performed PDMS as a fouling-release material. Good antifouling and fouling-release properties were not demonstrated for the other two amphiphilic surfaces derived from silicone and aromatic group containing nonionic surfactants included in this study. The results suggest that small differences in chemical surface functionality impart more significant changes with respect to the antifouling settlement and fouling-release performance of materials than overall wettability behavior.

  17. A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

    KAUST Repository

    Moia, Davide

    2017-11-28

    We report a neutral salt water based battery which uses p-type and n-type solution processed polymer films as the cathode and the anode of the cell. The specific capacity of the electrodes (approximately 30 mAh cm-3) is achieved via formation of bipolarons in both the p-type and n-type polymers. By engineering ethylene glycol and zwitterion based side chains attached to the polymer backbone we facilitate rapid ion transport through the non-porous polymer films. This, combined with efficient transport of electronic charge via the conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

  18. Controlling the morphology of side chain liquid crystalline block copolymer thin films through variations in liquid crystalline content.

    Science.gov (United States)

    Verploegen, Eric; Zhang, Tejia; Jung, Yeon Sik; Ross, Caroline; Hammond, Paula T

    2008-10-01

    In this paper, we describe methods for manipulating the morphology of side-chain liquid crystalline block copolymers through variations in the liquid crystalline content. By systematically controlling the covalent attachment of side chain liquid crystals to a block copolymer (BCP) backbone, the morphology of both the liquid crystalline (LC) mesophase and the phase-segregated BCP microstructures can be precisely manipulated. Increases in LC functionalization lead to stronger preferences for the anchoring of the LC mesophase relative to the substrate and the intermaterial dividing surface. By manipulating the strength of these interactions, the arrangement and ordering of the ultrathin film block copolymer nanostructures can be controlled, yielding a range of morphologies that includes perpendicular and parallel cylinders, as well as both perpendicular and parallel lamellae. Additionally, we demonstrate the utilization of selective etching to create a nanoporous liquid crystalline polymer thin film. The unique control over the orientation and order of the self-assembled morphologies with respect to the substrate will allow for the custom design of thin films for specific nanopatterning applications without manipulation of the surface chemistry or the application of external fields.

  19. Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

    International Nuclear Information System (INIS)

    Cho, Woosum; Lee, Jae Wook; Gal, Yeong-Soon; Kim, Mi-Ra; Jin, Sung Ho

    2014-01-01

    Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I 2 ), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (J sc , 10.75 mA cm −2 ) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm −2 irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte

  20. Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Woosum [Department of Chemistry Education, and Department of Frontier Materials Chemistry, and Institute for Plastic Information and Energy Materials, Pusan National University, Busan 609-735 (Korea, Republic of); Lee, Jae Wook, E-mail: jlee@donga.ac.kr [Department of Chemistry, Dong-A University, Busan 604-714 (Korea, Republic of); Gal, Yeong-Soon [Polymer Chemistry Lab, College of General Education, Kyungil University, Hayang 712-701 (Korea, Republic of); Kim, Mi-Ra, E-mail: mrkim2@pusan.ac.kr [Department of Polymer Science and Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Jin, Sung Ho, E-mail: shjin@pusan.ac.kr [Department of Chemistry Education, and Department of Frontier Materials Chemistry, and Institute for Plastic Information and Energy Materials, Pusan National University, Busan 609-735 (Korea, Republic of)

    2014-02-14

    Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I{sub 2}), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (J{sub sc}, 10.75 mA cm{sup −2}) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm{sup −2} irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte.

  1. Amide side chain amphiphilic polymers disrupt surface established bacterial bio-films and protect mice from chronic Acinetobacter baumannii infection.

    Science.gov (United States)

    Uppu, Divakara S S M; Samaddar, Sandip; Ghosh, Chandradhish; Paramanandham, Krishnamoorthy; Shome, Bibek R; Haldar, Jayanta

    2016-01-01

    Bacterial biofilms represent the root-cause of chronic or persistent infections in humans. Gram-negative bacterial infections due to nosocomial and opportunistic pathogens such as Acinetobacter baumannii are more difficult to treat because of their inherent and rapidly acquiring resistance to antibiotics. Due to biofilm formation, A. baumannii has been noted for its apparent ability to survive on artificial surfaces for an extended period of time, therefore allowing it to persist in the hospital environment. Here we report, maleic anhydride based novel cationic polymers appended with amide side chains that disrupt surface established multi-drug resistant A. baumannii biofilms. More importantly, these polymers significantly (p polymers also show potent antibacterial efficacy against methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterococci (VRE) and multi-drug resistant clinical isolates of A. baumannii with minimal toxicity to mammalian cells. We observe that optimal hydrophobicity dependent on the side chain chemical structure of these polymers dictate the selective toxicity to bacteria. Polymers interact with the bacterial cell membranes by causing membrane depolarization, permeabilization and energy depletion. Bacteria develop rapid resistance to erythromycin and colistin whereas no detectable development of resistance occurs against these polymers even after several passages. These results suggest the potential use of these polymeric biomaterials in disinfecting biomedical device surfaces after the infection has become established and also for the topical treatment of chronic bacterial infections. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Novel Random PBS-Based Copolymers Containing Aliphatic Side Chains for Sustainable Flexible Food Packaging

    Directory of Open Access Journals (Sweden)

    Giulia Guidotti

    2017-12-01

    Full Text Available In the last decade, there has been an increased interest from the food packaging industry toward the development and application of biodegradable and biobased plastics, to contribute to the sustainable economy and to reduce the huge environmental problem afflicting the planet. In this framework, the present paper describes the synthesis of novel PBS (poly(butylene succinate-based random copolymers with different composition containing glycol sub-units characterized by alkyl pendant groups of different length. The prepared samples were subjected to molecular, thermal, diffractometric and mechanical characterization. The barrier performances to O2, CO2 and N2 gases were also evaluated, envisioning for these new materials an application in food packaging. The presence of the side alkyl groups did not alter the thermal stability, whereas it significantly reduced the sample crystallinity degree, making these materials more flexible. The barrier properties were found to be worse than PBS; however, some of them were comparable to, or even better than, those of Low Density Polyethylene (LDPE, widely employed for flexible food packaging. The entity of variations in the final properties due to copolymerization were more modest in the case of the co-unit with short side methyl groups, which, when included in the PBS crystal lattice, causes a more modest decrement of crystallinity degree.

  3. Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

    KAUST Repository

    Cabanetos, Clement

    2013-03-27

    While varying the size and branching of solubilizing side chains in π-conjugated polymers impacts their self-assembling properties in thin-film devices, these structural changes remain difficult to anticipate. This report emphasizes the determining role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones in the BDT motifs induces a critical change in polymer self-assembly and backbone orientation in thin films that correlates with a dramatic drop in solar cell efficiency. In contrast, we show that for polymers with branched alkyl-substituted BDT motifs, controlling the number of aliphatic carbons in the linear N-alkyl-substituted TPD motifs is a major contributor to improved material performance. With this approach, PBDTTPD polymers were found to reach power conversion efficiencies of 8.5% and open-circuit voltages of 0.97 V in BHJ devices with PC71BM, making PBDTTPD one of the best polymer donors for use in the high-band-gap cell of tandem solar cells. © 2013 American Chemical Society.

  4. 5-Ethynyl-2'-deoxycytidine: a DNA building block with a 'clickable' side chain.

    Science.gov (United States)

    Seela, Frank; Mei, Hui; Xiong, Hai; Budow, Simone; Eickmeier, Henning; Reuter, Hans

    2012-10-01

    The title compound [systematic name: 4-amino-1-(2-deoxy-β-D-erythro-pentofuranosyl)-5-ethynylpyrimidin-2(1H)-one], C(11)H(13)N(3)O(4), shows two conformations in the crystalline state. The N-glycosylic bonds of both conformers adopt similar conformations, with χ = -149.2 (1)° for conformer (I-1) and -151.4 (1)° for conformer (I-2), both in the anti range. The sugar residue of (I-1) shows a C2'-endo envelope conformation ((2)E, S-type), with P = 164.7 (1)° and τ(m) = 36.9 (1)°, while (I-2) shows a major C3'-exo sugar pucker (C3'-exo-C2'-endo, (3)T(2), S-type), with P = 189.2 (1)° and τ(m) = 33.3 (1)°. Both conformers participate in the formation of a layered three-dimensional crystal structure with a chain-like arrangement of the conformers. The ethynyl groups do not participate in hydrogen bonding, but are arranged in proximal positions.

  5. Role of Side Chains in β-Sheet Self-Assembly into Peptide Fibrils. IR and VCD Spectroscopic Studies of Glutamic Acid-Containing Peptides.

    Science.gov (United States)

    Tobias, Fernando; Keiderling, Timothy A

    2016-05-10

    Poly(glutamic acid) at low pH self-assembles after incubation at higher temperature into fibrils composed of antiparallel sheets that are stacked in a β2-type structure whose amide carbonyls have bifurcated H-bonds involving the side chains from the next sheet. Oligomers of Glu can also form such structures, and isotope labeling has provided insight into their out-of-register antiparallel structure [ Biomacromolecules 2013 , 14 , 3880 - 3891 ]. In this paper we report IR and VCD spectra and transmission electron micrograph (TEM) images for a series of alternately sequenced oligomers, Lys-(Aaa-Glu)5-Lys-NH2, where Aaa was varied over a variety of polar, aliphatic, or aromatic residues. Their spectral and TEM data show that these oligopeptides self-assemble into different structures, both local and morphological, that are dependent on both the nature of the Aaa side chains and growth conditions employed. Such alternate peptides substituted with small or polar residues, Ala and Thr, do not yield fibrils; but with β-branched aliphatic residues, Val and Ile, that could potentially pack with Glu side chains, these oligopeptides do show evidence of β2-stacking. By contrast, for Leu, with longer side chains, only β1-stacking is seen while with even larger Phe side chains, either β-form can be detected separately, depending on preparation conditions. These structures are dependent on high temperature incubation after reducing the pH and in some cases after sonication of initial fibril forms and reincubation. Some of these fibrillar peptides, but not all, show enhanced VCD, which can offer evidence for formation of long, multistrand, often twisted structures. Substitution of Glu with residues having selected side chains yields a variety of morphologies, leading to both β1- and β2-structures, that overall suggests two different packing modes for the hydrophobic side chains depending on size and type.

  6. Detection of Side Chain Rearrangements Mediating the Motions of Transmembrane Helices in Molecular Dynamics Simulations of G Protein-Coupled Receptors

    Directory of Open Access Journals (Sweden)

    Zied Gaieb

    Full Text Available Structure and dynamics are essential elements of protein function. Protein structure is constantly fluctuating and undergoing conformational changes, which are captured by molecular dynamics (MD simulations. We introduce a computational framework that provides a compact representation of the dynamic conformational space of biomolecular simulations. This method presents a systematic approach designed to reduce the large MD simulation spatiotemporal datasets into a manageable set in order to guide our understanding of how protein mechanics emerge from side chain organization and dynamic reorganization. We focus on the detection of side chain interactions that undergo rearrangements mediating global domain motions and vice versa. Side chain rearrangements are extracted from side chain interactions that undergo well-defined abrupt and persistent changes in distance time series using Gaussian mixture models, whereas global domain motions are detected using dynamic cross-correlation. Both side chain rearrangements and global domain motions represent the dynamic components of the protein MD simulation, and are both mapped into a network where they are connected based on their degree of coupling. This method allows for the study of allosteric communication in proteins by mapping out the protein dynamics into an intramolecular network to reduce the large simulation data into a manageable set of communities composed of coupled side chain rearrangements and global domain motions. This computational framework is suitable for the study of tightly packed proteins, such as G protein-coupled receptors, and we present an application on a seven microseconds MD trajectory of CC chemokine receptor 7 (CCR7 bound to its ligand CCL21. Keywords: Molecular dynamics, Change-point detection, Side chain reorganization, Helical domain motion, Intramolecular network, Membrane proteins, GPCR, GPCR computational modeling, GPCR allostery

  7. Backbone and stereospecific (13)C methyl Ile (δ1), Leu and Val side-chain chemical shift assignments of Crc.

    Science.gov (United States)

    Sharma, Rakhi; Sahu, Bhubanananda; Ray, Malay K; Deshmukh, Mandar V

    2015-04-01

    Carbon catabolite repression (CCR) allows bacteria to selectively assimilate a preferred compound among a mixture of several potential carbon sources, thus boosting growth and economizing the cost of adaptability to variable nutrients in the environment. The RNA-binding catabolite repression control (Crc) protein acts as a global post-transcriptional regulator of CCR in Pseudomonas species. Crc triggers repression by inhibiting the expression of genes involved in transport and catabolism of non-preferred substrates, thus indirectly favoring assimilation of preferred one. We report here a nearly complete backbone and stereospecific (13)C methyl side-chain chemical shift assignments of Ile (δ1), Leu and Val of Crc (~ 31 kDa) from Pseudomonas syringae Lz4W.

  8. Side-chain interactions form late and cooperatively in the binding reaction between disordered peptides and PDZ domains

    DEFF Research Database (Denmark)

    Haq, S Raza; Chi, Celestine N; Bach, Anders

    2012-01-01

    Intrinsically disordered proteins are very common and mediate numerous protein-protein and protein-DNA interactions. While it is clear that these interactions are instrumental for the life of the mammalian cell, there is a paucity of data regarding their molecular binding mechanisms. We have here...... used short peptides as a model system for intrinsically disordered proteins. Linear free-energy relationships based on rate and equilibrium constants for the binding of these peptides to ordered target proteins, PDZ domains, demonstrate that native side-chain interactions form mainly after the rate......-limiting barrier for binding, in a cooperative fashion. This finding suggests that these disordered peptides first form a weak encounter complex with non-native interactions. The data do not support the recent notion that the affinities of intrinsically disordered proteins towards their targets are generally...

  9. Pressure dependence of side chain 13C chemical shifts in model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    Science.gov (United States)

    Beck Erlach, Markus; Koehler, Joerg; Crusca, Edson; Munte, Claudia E; Kainosho, Masatsune; Kremer, Werner; Kalbitzer, Hans Robert

    2017-10-01

    For evaluating the pressure responses of folded as well as intrinsically unfolded proteins detectable by NMR spectroscopy the availability of data from well-defined model systems is indispensable. In this work we report the pressure dependence of 13 C chemical shifts of the side chain atoms in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH 2 (Xxx, one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of a number of nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The size of the polynomial pressure coefficients B 1 and B 2 is dependent on the type of atom and amino acid studied. For H N , N and C α the first order pressure coefficient B 1 is also correlated to the chemical shift at atmospheric pressure. The first and second order pressure coefficients of a given type of carbon atom show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure also are weakly correlated. The downfield shifts of the methyl resonances suggest that gauche conformers of the side chains are not preferred with pressure. The valine and leucine methyl groups in the model peptides were assigned using stereospecifically 13 C enriched amino acids with the pro-R carbons downfield shifted relative to the pro-S carbons.

  10. Involvement of a cytosine side chain in proton transfer in the rate-determining step of ribozyme self-cleavage

    Science.gov (United States)

    Shih, I-hung; Been, Michael D.

    2001-01-01

    Ribozymes of hepatitis delta virus have been proposed to use an active-site cytosine as an acid-base catalyst in the self-cleavage reaction. In this study, we have examined the role of cytosine in more detail with the antigenomic ribozyme. Evidence that proton transfer in the rate-determining step involved cytosine 76 (C76) was obtained from examining cleavage activity of the wild-type and imidazole buffer-rescued C76-deleted (C76Δ) ribozymes in D2O and H2O. In both reactions, a similar kinetic isotope effect and shift in the apparent pKa indicate that the buffer is functionally substituting for the side chain in proton transfer. Proton inventory of the wild-type reaction supported a mechanism of a single proton transfer at the transition state. This proton transfer step was further characterized by exogenous base rescue of a C76Δ mutant with cytosine and imidazole analogues. For the imidazole analogues that rescued activity, the apparent pKa of the rescue reaction, measured under kcat/KM conditions, correlated with the pKa of the base. From these data a Brønsted coefficient (β) of 0.51 was determined for the base-rescued reaction of C76Δ. This value is consistent with that expected for proton transfer in the transition state. Together, these data provide strong support for a mechanism where an RNA side chain participates directly in general acid or general base catalysis of the wild-type ribozyme to facilitate RNA cleavage. PMID:11171978

  11. Conformational exchange of aromatic side chains characterized by L-optimized TROSY-selected ¹³C CPMG relaxation dispersion.

    Science.gov (United States)

    Weininger, Ulrich; Respondek, Michal; Akke, Mikael

    2012-09-01

    Protein dynamics on the millisecond time scale commonly reflect conformational transitions between distinct functional states. NMR relaxation dispersion experiments have provided important insights into biologically relevant dynamics with site-specific resolution, primarily targeting the protein backbone and methyl-bearing side chains. Aromatic side chains represent attractive probes of protein dynamics because they are over-represented in protein binding interfaces, play critical roles in enzyme catalysis, and form an important part of the core. Here we introduce a method to characterize millisecond conformational exchange of aromatic side chains in selectively (13)C labeled proteins by means of longitudinal- and transverse-relaxation optimized CPMG relaxation dispersion. By monitoring (13)C relaxation in a spin-state selective manner, significant sensitivity enhancement can be achieved in terms of both signal intensity and the relative exchange contribution to transverse relaxation. Further signal enhancement results from optimizing the longitudinal relaxation recovery of the covalently attached (1)H spins. We validated the L-TROSY-CPMG experiment by measuring fast folding-unfolding kinetics of the small protein CspB under native conditions. The determined unfolding rate matches perfectly with previous results from stopped-flow kinetics. The CPMG-derived chemical shift differences between the folded and unfolded states are in excellent agreement with those obtained by urea-dependent chemical shift analysis. The present method enables characterization of conformational exchange involving aromatic side chains and should serve as a valuable complement to methods developed for other types of protein side chains.

  12. Off-resonance rotating-frame relaxation dispersion experiment for 13C in aromatic side chains using L-optimized TROSY-selection

    DEFF Research Database (Denmark)

    Weininger, Ulrich; Brath, Ulrika; Modig, Kristofer

    2014-01-01

    Protein dynamics on the microsecond-millisecond time scales often play a critical role in biological function. NMR relaxation dispersion experiments are powerful approaches for investigating biologically relevant dynamics with site-specific resolution, as shown by a growing number of publications...... on enzyme catalysis, protein folding, ligand binding, and allostery. To date, the majority of studies has probed the backbone amides or side-chain methyl groups, while experiments targeting other sites have been used more sparingly. Aromatic side chains are useful probes of protein dynamics, because...... they are over-represented in protein binding interfaces, have important catalytic roles in enzymes, and form a sizable part of the protein interior. Here we present an off-resonance R 1ρ experiment for measuring microsecond to millisecond conformational exchange of aromatic side chains in selectively (13)C...

  13. 4-N-, 4-S-, and 4-O-chloroquine analogues: influence of side chain length and quinolyl nitrogen pKa on activity vs chloroquine resistant malaria.

    Science.gov (United States)

    Natarajan, Jayakumar K; Alumasa, John N; Yearick, Kimberly; Ekoue-Kovi, Kekeli A; Casabianca, Leah B; de Dios, Angel C; Wolf, Christian; Roepe, Paul D

    2008-06-26

    Using predictions from heme-quinoline antimalarial complex structures, previous modifications of chloroquine (CQ), and hypotheses for chloroquine resistance (CQR), we synthesize and assay CQ analogues that test structure-function principles. We vary side chain length for both monoethyl and diethyl 4-N CQ derivatives. We alter the pKa of the quinolyl N by introducing alkylthio or alkoxy substituents into the 4 position and vary side chain length for these analogues. We introduce an additional titratable amino group to the side chain of 4-O analogues with promising CQR strain selectivity and increase activity while retaining selectivity. We solve atomic resolution structures for complexes formed between representative 4-N, 4-S, and 4-O derivatives vs mu-oxo dimeric heme, measure binding constants for monomeric vs dimeric heme, and quantify hemozoin (Hz) formation inhibition in vitro. The data provide additional insight for the design of CQ analogues with improved activity vs CQR malaria.

  14. 4-N, 4-S & 4-O Chloroquine Analogues: Influence of Side Chain Length and Quinolyl Nitrogen pKa on Activity vs. Chloroquine Resistant Malaria+, #

    Science.gov (United States)

    Natarajan, Jayakumar K.; Alumasa, John; Yearick, Kimberly; Ekoue-Kovi, Kekeli A.; Casabianca, Leah B.; de Dios, Angel C.; Wolf, Christian; Roepe, Paul D.

    2009-01-01

    Using predictions from heme – quinoline antimalarial complex structures, previous modifications of chloroquine (CQ), and hypotheses for chloroquine resistance (CQR), we synthesize and assay CQ analogues that test structure – function principles. We vary side chain length for both monoethyl and diethyl 4N CQ derivatives. We alter the pKa of the quinolyl N by introducing alkylthio or alkoxy substituents into the 4 position, and vary side chain length for these analogues. We introduce an additional titratable amino group to the side chain of 4O analogues with promising CQR strain selectivity and increase activity while retaining selectivity. We solve atomic resolution structures for complexes formed between representative 4N, 4S and 4O derivatives vs. μ-oxo dimeric heme, measure binding constants for monomeric vs. dimeric heme, and quantify hemozoin (Hz) formation inhibition in vitro. The data provide additional insight for the design of CQ analogues with improved activity vs. CQR malaria. PMID:18512900

  15. Optical anisotropy of polyimide and polymethacrylate containing photocrosslinkable chalcone group in the side chain under irradiation of a linearly polarized UV light

    CERN Document Server

    Choi, D H

    2002-01-01

    Photocrosslinkable soluble polyimide and polymethacrylate compound were synthesized for studying the optically induced anisotropy of the thin films. Chalcone group was introduced into the side chain unit of two polymers. We observed a photodimerization behavior between the double bonds in the chalcone group and an optical anisotropy of these materials by irradiation of a linearly polarized UV light (LPL). Optical anisotropy of the thin film was also investigated by using polarized UV absorption spectroscopy.The dynamic property of optical anisotropy in photoreactive polyimide was compared to that in polymethacrylate containing chalcone group in the side chain.

  16. Bis(thienothiophenyl) diketopyrrolopyrrole-based conjugated polymers with various branched alkyl side chains and their applications in thin-film transistors and polymer solar cells.

    Science.gov (United States)

    Shin, Jicheol; Park, Gi Eun; Lee, Dae Hee; Um, Hyun Ah; Lee, Tae Wan; Cho, Min Ju; Choi, Dong Hoon

    2015-02-11

    New thienothiophene-flanked diketopyrrolopyrrole and thiophene-containing π-extended conjugated polymers with various branched alkyl side-chains were successfully synthesized. 2-Octyldodecyl, 2-decyltetradecyl, 2-tetradecylhexadecyl, 2-hexadecyloctadecyl, and 2-octadecyldocosyl groups were selected as the side-chain moieties and were anchored to the N-positions of the thienothiophene-flanked diketopyrrolopyrrole unit. All five polymers were found to be soluble owing to the bulkiness of the side chains. The thin-film transistor based on the 2-tetradecylhexadecyl-substituted polymer showed the highest hole mobility of 1.92 cm2 V(-1) s(-1) due to it having the smallest π-π stacking distance between the polymer chains, which was determined by grazing incidence X-ray diffraction. Bulk heterojunction polymer solar cells incorporating [6,6]-phenyl-C71-butyric acid methyl ester as the n-type molecule and the additive 1,8-diiodooctane (1 vol %) were also constructed from the synthesized polymers without thermal annealing; the device containing the 2-octyldodecyl-substituted polymer exhibited the highest power conversion efficiency of 5.8%. Although all the polymers showed similar physical properties, their device performance was clearly influenced by the sizes of the branched alkyl side-chain groups.

  17. Reaction mechanisms in the radiolysis of peptides, polypeptides and proteins II reactions at side-chain loci in model systems

    International Nuclear Information System (INIS)

    Garrison, W.M.

    1983-11-01

    The major emphasis in radiation biology at the molecular level has been on the nucleic acid component of the nucleic acid-protein complex because of its primary genetic importance. But there is increasing evidence that radiation damage to the protein component also has important biological implications. Damage to capsid protein now appears to be a major factor in the radiation inactivation of phage and other viruses. And, there is increasing evidence that radiation-chemical change in the protein component of chromation leads to changes in the stability of the repressor-operator complexes involved in gene expression. Knowledge of the radiation chemistry of protein is also of importance in other fields such as the application of radiation sterilization to foods and drugs. Recent findings that a class of compounds, the α,α'-diaminodicarboxylic acids, not normally present in food proteins, are formed in protein radiolysis is of particular significance since certain of their peptide derivatives have been showing to exhibit immunological activity. The purpose of this review is to bring together and to correlate our present knowledge of products and mechanisms in the radiolysis of peptides, polypeptides and proteins both aqueous and solid-state. In part 1 we presented a discussion of the radiation-induced reactions of the peptide main-chain in model peptide and polypeptide systems. Here in part 2 the emphasis is on the competing radiation chemistry at side-chain loci of peptide derivatives of aliphatic, aromatic-unsaturated and sulfur-containing amino acids in similar systems. Information obtained with the various experimental techniques of product analysis, competition kinetics, spin-trapping, pulse radiolysis, and ESR spectroscopy are included

  18. PMMA-g-OEtOx Graft Copolymers: Influence of Grafting Degree and Side Chain Length on the Conformation in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Irina Muljajew

    2018-03-01

    Full Text Available Depending on the degree of grafting (DG and the side chain degree of polymerization (DP, graft copolymers may feature properties similar to statistical copolymers or to block copolymers. This issue is approached by studying aqueous solutions of PMMA-g-OEtOx graft copolymers comprising a hydrophobic poly(methyl methacrylate (PMMA backbone and hydrophilic oligo(2-ethyl-2-oxazoline (OEtOx side chains. The graft copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT copolymerization of methyl methacrylate (MMA and OEtOx-methacrylate macromonomers of varying DP. All aqueous solutions of PMMA-g-OEtOx (9% ≤ DG ≤ 34%; 5 ≤ side chain DP ≤ 24 revealed lower critical solution temperature behavior. The graft copolymer architecture significantly influenced the aggregation behavior, the conformation in aqueous solution and the coil to globule transition, as verified by means of turbidimetry, dynamic light scattering, nuclear magnetic resonance spectroscopy, and analytical ultracentrifugation. The aggregation behavior of graft copolymers with a side chain DP of 5 was significantly affected by small variations of the DG, occasionally forming mesoglobules above the cloud point temperature (Tcp, which was around human body temperature. On the other hand, PMMA-g-OEtOx with elongated side chains assembled into well-defined structures below the Tcp (apparent aggregation number (Nagg = 10 that were able to solubilize Disperse Orange 3. The thermoresponsive behavior of aqueous solutions thus resembled that of micelles comprising a poly(2-ethyl-2-oxazoline (PEtOx shell (Tcp > 60 °C.

  19. Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics

    KAUST Repository

    Kiefer, David

    2018-01-05

    N-doping of conjugated polymers either requires a high dopant fraction or yields a low electrical conductivity because of their poor compatibility with molecular dopants. We explore n-doping of the polar naphthalenediimide–bithiophene copolymer p(gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole–dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively high doping efficiency of 13% for n-dopants, which leads to a high electrical conductivity of more than 10–1 S cm–1 for a dopant concentration of only 10 mol % when measured in an inert atmosphere. We find that the doped polymer is able to maintain its electrical conductivity for about 20 min when exposed to air and recovers rapidly when returned to a nitrogen atmosphere. Overall, solution coprocessing of p(gNDI-gT2) and N-DMBI results in a larger thermoelectric power factor of up to 0.4 μW K–2 m–1 compared to other NDI-based polymers.

  20. Influence of α-methyl group on molecular aggregation structure and surface physicochemical properties of fluoroalkyl side chain polymers

    International Nuclear Information System (INIS)

    Honda, K; Yamaguchi, H; Takahara, A; Sakata, O; Sasaki, S; Takata, M; Morita, M

    2009-01-01

    Influence of α-methyl group on molecular aggregation states and surface physicochemical properties of poly(fluoroalkyl acrylate)s [PFA-C y , where y is fluoromethylene number in R f group] and poly(fluoroalkykl methacrylate)s [PFMA-C y ] thin films were systematically investigated. Spin-coated PFA-C y and PFMA-C y thin films were characterized by dynamic contact angle measurements and grazing-incidence wide-angle X-ray diffraction (GIWAXD) measurements. GIWAXD data revealed that fluoroalkyl side chains of PFA-C y and PFMA-C y with y≥8 formed regular structures in the surface region as well as bulk one. However, the degree of orientation and ordering of the R f groups of PFMA-C 8 thin films was low. Also, the receding contact angle (θ r ) of PFMA-C 8 thin films was lower than that of PFA-C 8 ones. By annealing treatment, the θ r of PFMA-C 8 was increased. These results suggest that the R f groups of PFMA-C 8 were disordered due to presence of the α-methyl group. The R f groups became ordered to pack closely each other by annealing treatment, so that the water repellency was increased.

  1. Factors Governing Intercalation of Fullerenes and Other Small Molecules Between the Side Chains of Semiconducting Polymers Used in Solar Cells

    KAUST Repository

    Miller, Nichole Cates

    2012-08-22

    While recent reports have established signifi cant miscibility in polymer:fullerene blends used in organic solar cells, little is actually known about why polymers and fullerenes mix and how their mixing can be controlled. Here, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and molecular simulations are used to study mixing in a variety of polymer:molecule blends by systematically varying the polymer and smallmolecule properties. It is found that a variety of polymer:fullerene blends mix by forming bimolecular crystals provided there is suffi cient space between the polymer side chains to accommodate a fullerene. Polymer:tetrafl uoro-tetracyanoquinodimethane (F4-TCNQ) bimolecular crystals were also observed, although bimolecular crystals did not form in the other studied polymer:nonfullerene blends, including those with both conjugated and non-conjugated small molecules. DSC and molecular simulations demonstrate that strong polymer-fullerene interactions can exist, and the calculations point to van der Waals interactions as a signifi cant driving force for molecular mixing. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Effect of Side Chain Functional Group on Interactions in Ionic Liquid Systems: Insights from Infinite Dilution Thermodynamic Data.

    Science.gov (United States)

    Paduszyński, Kamil; Królikowska, Marta

    2017-11-02

    Measurements of infinite dilution activity coefficients of 48 molecular solutes (including alkanes, alkenes, alkynes, aromatics, ethers, alcohols, water, ketones, pyridine, thiophene, acetonitrile, and 1-nitropropane) in two ionic liquids (ILs), namely, 1-(2-hydroxyethyl)-3-methylimidazolium dicyanamide and 1-(2-chloroethyl)-3-methylimidazolium dicyanamide, are reported in the temperature range from T = 308.15 to 358.15 K. Comparative analysis of an effect of OH/Cl substitution of terminal carbon in side chains of imidazolium cations is presented and discussed in terms of different types of intermolecular forces acting between ILs and solutes. The new data also are confronted to those published previously for a "plain" counterpart of the studied ILs, namely, 1-ethyl-3-methylimidazolium dicyanamide. Infinite dilution capacity and selectivity of the studied ILs are presented to evaluate them as separating agents in extraction of aromatics from alkanes and sulfur compounds from alkanes. Three modeling approaches, namely, linear solvation energy relationship (LSER), regular solution theory, and conductor-like screening model for real solvents (COSMO-RS), are tested for their capabilities of capturing the substitution effects detected experimentally.

  3. Alanine scan of the peptide antibiotic feglymycin: assessment of amino acid side chains contributing to antimicrobial activity.

    Science.gov (United States)

    Hänchen, Anne; Rausch, Saskia; Landmann, Benjamin; Toti, Luigi; Nusser, Antje; Süssmuth, Roderich D

    2013-03-18

    The antibiotic feglymycin is a linear 13-mer peptide synthesized by the bacterium Streptomyces sp. DSM 11171. It mainly consists of the nonproteinogenic amino acids 4-hydroxyphenylglycine and 3,5-dihydroxyphenylglycine. An alanine scan of feglymycin was performed by solution-phase peptide synthesis in order to assess the significance of individual amino acid side chains for biological activity. Hence, 13 peptides were synthesized from di- and tripeptide building blocks, and subsequently tested for antibacterial activity against Staphylococcus aureus strains. Furthermore we tested the inhibition of peptidoglycan biosynthesis enzymes MurA and MurC, which are inhibited by feglymycin. Whereas the antibacterial activity is significantly based on the three amino acids D-Hpg1, L-Hpg5, and L-Phe12, the inhibitory activity against MurA and MurC depends mainly on L-Asp13. The difference in the position dependence for antibacterial activity and enzyme inhibition suggests multiple molecular targets in the modes of action of feglymycin. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A stochastic algorithm for global optimization and for best populations: A test case of side chains in proteins

    Science.gov (United States)

    Glick, Meir; Rayan, Anwar; Goldblum, Amiram

    2002-01-01

    The problem of global optimization is pivotal in a variety of scientific fields. Here, we present a robust stochastic search method that is able to find the global minimum for a given cost function, as well as, in most cases, any number of best solutions for very large combinatorial “explosive” systems. The algorithm iteratively eliminates variable values that contribute consistently to the highest end of a cost function's spectrum of values for the full system. Values that have not been eliminated are retained for a full, exhaustive search, allowing the creation of an ordered population of best solutions, which includes the global minimum. We demonstrate the ability of the algorithm to explore the conformational space of side chains in eight proteins, with 54 to 263 residues, to reproduce a population of their low energy conformations. The 1,000 lowest energy solutions are identical in the stochastic (with two different seed numbers) and full, exhaustive searches for six of eight proteins. The others retain the lowest 141 and 213 (of 1,000) conformations, depending on the seed number, and the maximal difference between stochastic and exhaustive is only about 0.15 Kcal/mol. The energy gap between the lowest and highest of the 1,000 low-energy conformers in eight proteins is between 0.55 and 3.64 Kcal/mol. This algorithm offers real opportunities for solving problems of high complexity in structural biology and in other fields of science and technology. PMID:11792838

  5. On the calculation of {sup 3}J{sub {alpha}{beta}}-coupling constants for side chains in proteins

    Energy Technology Data Exchange (ETDEWEB)

    Steiner, Denise [Swiss Federal Institute of Technology, Laboratory of Physical Chemistry, ETH (Switzerland); Allison, Jane R. [Massey University Albany, Centre for Theoretical Chemistry and Physics, Institute for Natural Sciences (New Zealand); Eichenberger, Andreas P.; Gunsteren, Wilfred F. van, E-mail: wfvgn@igc.phys.chem.ethz.ch [Swiss Federal Institute of Technology, Laboratory of Physical Chemistry, ETH (Switzerland)

    2012-07-15

    Structural knowledge about proteins is mainly derived from values of observables, measurable in NMR spectroscopic or X-ray diffraction experiments, i.e. absorbed or scattered intensities, through theoretically derived relationships between structural quantities such as atom positions or torsional angles on the one hand and observable quantities such as squared structure factor amplitudes, NOE intensities or {sup 3}J-coupling constants on the other. The standardly used relation connecting {sup 3}J-couplings to torsional angles is the Karplus relation, which is used in protein structure refinement as well as in the evaluation of simulated properties of proteins. The accuracy of the simple and generalised Karplus relations is investigated using side-chain structural and {sup 3}J{sub {alpha}{beta}}-coupling data for three different proteins, Plastocyanin, Lysozyme, and FKBP, for which such data are available. The results show that the widely used Karplus relations are only a rough estimate for the relation between {sup 3}J{sub {alpha}{beta}}-couplings and the corresponding {chi}{sub 1}-angle in proteins.

  6. Atomic force and optical near-field microscopic investigations of polarization holographic gratings in a liquid crystalline azobenzene side-chain polyester

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Holme, N.C.R.; Hvilsted, S.

    1996-01-01

    Atomic force and scanning near-field optical microscopic investigations have been carried out on a polarization holographic grating recorded in an azobenzene side-chain Liquid crystalline polyester. It has been found that immediately following laser irradiation, a topographic surface grating...

  7. Synthesis and anti-HIV activity of novel N-1 side chain-modified analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT).

    Science.gov (United States)

    Pontikis, R; Benhida, R; Aubertin, A M; Grierson, D S; Monneret, C

    1997-06-06

    A series of 33 N-1 side chain-modified analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (1, HEPT) were synthesized and evaluated for their anti-HIV-1 activity. In particular, the influence of substitution of the terminal hydroxy group of the acyclic structure of HEPT and the structural rigidity of this side chain were investigated. Halo (7, 8), azido (9), and amino (10-15) derivatives were synthesized from HEPT via the p-tosylate derivative 6. Acylation of the primary amine 15 afforded the amido analogs 16-20. The diaryl derivatives 26-29 were prepared by reaction of HEPT, or of the 6-(2-pyridylthio) analog 23, with diaryl disulfides in the presence of tri-n-butylphosphine. Compounds 39-41, in which the N-1 side chain is rigidified by incorporation of an E-configured double bond, were obtained by palladium(0)-catalyzed coupling of several different 6-(arylthio)uracil derivatives (37, 38) with allyl acetates 33. Compounds 13, 40a,c,d,f, and 41, incorporating an aromatic ring at the end of the acyclic side chain, were found to be more potent than the known diphenyl-substituted HEPT analog BPT (2), two of them, 40c,d, being 10-fold more active.

  8. Synthesis and Catalytic Properties of Non-Cross-Linked and Cross-Linked Poly(alkylmethyldiallylammonium bromides) Having Decyl, Octyl, and Hexyl Side Chains

    NARCIS (Netherlands)

    Wang, G.J; Engberts, J.B.F.N.

    1995-01-01

    A family of non-cross-linked and cross-linked copolymers containing decyl, octyl, and hexyl groups as side chains ((CL)-CopolC1-10, (CL)-CopolC1-8, and (CL)-CopolC1-6, respectively) were synthesized by radical-initiated cyclocopolymerization of alkylmethyldiallylammonium bromide monomers without and

  9. The influence of the side-chain sequence on the structure-activity correlations of immunomodulatory branched polypeptides. Synthesis and conformational analysis of new model polypeptides.

    Science.gov (United States)

    Mezö, G; Hudecz, F; Kajtár, J; Szókán, G; Szekerke, M

    1989-10-01

    New branched polypeptides were synthesized for a detailed study of the influence of the side-chain structure on the conformation and biological properties. The first subset of polypeptides were prepared by coupling of tetrapeptides to poly[L-Lys]. These polymers contain either DL-Ala3-X [poly[Lys-(X-DL-Ala3)n

  10. Positioning of the carboxamide side chain in 11-oxo-11H-indeno[1,2-b]quinolinecarboxamide anticancer agents: effects on cytotoxicity.

    Science.gov (United States)

    Deady, L W; Desneves, J; Kaye, A J; Finlay, G J; Baguley, B C; Denny, W A

    2001-02-01

    A series of 11-oxo-11H-indeno[1,2-b]quinolines bearing a carboxamide-linked cationic side chain at various positions on the chromophore was studied to determine structure-activity relationships between cytotoxicity and the position of the side chain. The compounds were prepared by Pfitzinger synthesis from an appropriate isatin and 1-indanone, followed by various oxidative steps, to generate the required carboxylic acids. The 4- and 6-carboxamides (with the side chain on a terminal ring, off the short axis of the chromophore) were effective cytotoxins. The dimeric 4- and 6-linked analogues were considerably more cytotoxic than the parent monomers, but had broadly similar activities. In contrast, analogues with side chains at the 8-position (on a terminal ring but off the long axis of the chromophore) or 10-position (off the short axis of the chromophore but in a central ring) were drastically less effective. The 4,10- and 6,10-biscarboxamides had activities between those of the corresponding parent monocarboxamides. The first of these showed good activity against advanced subcutaneous colon 38 tumours in mice.

  11. Probing the effects of the ester functional group, alkyl side chain length and anions on the bulk nanostructure of ionic liquids: a computational study.

    Science.gov (United States)

    Fakhraee, Mostafa; Gholami, Mohammad Reza

    2016-04-14

    The effects of ester addition on nanostructural properties of biodegradable ILs composed of 1-alkoxycarbonyl-3-alkyl-imidazolium cations ([C1COOCnC1im](+), n = 1, 2, 4) combined with [Br](-), [NO3](-), [BF4](-), [PF6](-), [TfO](-), and [Tf2N](-) were explored by using the molecular dynamics (MD) simulations and quantum theory of atoms in molecules (QTAIM) analysis at 400 K. Various thermodynamic properties of these ILs were extensively computed in our earlier work (Ind. Eng. Chem. Res., 2015, 54, 11678-11700). Nano-scale segregation analysis demonstrates the formation of a small spherical island-like hydrocarbon within the continuous ionic domain for ILs with short alkyl side chain ([C1COOC1C1im]), and a sponge-like nanostructure for the compound with long alkyl side chain ([C1COOC4C1im]). Ester-functionalized ILs with ethyl side chain ([C1COOC2C1im]) are the turning point between two different morphologies. Non-polar channels were observed for [C1COOC4C1im] ILs composed of smaller anions such as [Br] and [NO3], whereas clustering organization was found for the other anions. Formation of the spherical micelle-like nanostructure was seen for lengthened cations. Finally, the incorporation of an ester group into the alkyl side chain of the cation leads to stronger segregation between charged and uncharged networks, which consequently increased the possibility of self-assembly and micelle formation.

  12. Structural optimization and evaluation of butenolides as potent antifouling agents: modification of the side chain affects the biological activities of compounds

    KAUST Repository

    Li, Yongxin

    2012-09-01

    A recent global ban on the use of organotin compounds as antifouling agents has increased the need for safe and effective antifouling compounds. In this study, a series of new butenolide derivatives with various amine side chains was synthesized and evaluated for their anti-larval settlement activities in the barnacle, Balanus amphitrite. Side chain modification of butenolide resulted in butenolides 3c-3d, which possessed desirable physico-chemical properties and demonstrated highly effective non-toxic anti-larval settlement efficacy. A structure-activity relationship analysis revealed that varying the alkyl side chain had a notable effect on anti-larval settlement activity and that seven to eight carbon alkyl side chains with a tert-butyloxycarbonyl (Boc) substituent on an amine terminal were optimal in terms of bioactivity. Analysis of the physico-chemical profile of butenolide analogues indicated that lipophilicity is a very important physico-chemical parameter contributing to bioactivity. © 2012 Copyright Taylor and Francis Group, LLC.

  13. Collision-Induced Dissociation of Deprotonated Peptides. Relative Abundance of Side-Chain Neutral Losses, Residue-Specific Product Ions, and Comparison with Protonated Peptides.

    Science.gov (United States)

    Liang, Yuxue; Neta, Pedatsur; Yang, Xiaoyu; Stein, Stephen E

    2018-03-01

    High-accuracy MS/MS spectra of deprotonated ions of 390 dipeptides and 137 peptides with three to six residues are studied. Many amino acid residues undergo neutral losses from their side chains. The most abundant is the loss of acetaldehyde from threonine. The abundance of losses from the side chains of other amino acids is estimated relative to that of threonine. While some amino acids lose the whole side chain, others lose only part of it, and some exhibit two or more different losses. Side-chain neutral losses are less abundant in the spectra of protonated peptides, being significant mainly for methionine and arginine. In addition to the neutral losses, many amino acid residues in deprotonated peptides produce specific negative ions after peptide bond cleavage. An expanded list of fragment ions from protonated peptides is also presented and compared with those of deprotonated peptides. Fragment ions are mostly different for these two cases. These lists of fragments are used to annotate peptide mass spectral libraries and to aid in the confirmation of specific amino acids in peptides. Graphical Abstract ᅟ.

  14. Structural optimization and evaluation of butenolides as potent antifouling agents: modification of the side chain affects the biological activities of compounds

    KAUST Repository

    Li, Yongxin; Zhang, Fengying; Xu, Ying; Matsumura, Kiyotaka; Han, Zhuang; Liu, Lingli; Lin, Wenhan; Jia, Yanxing; Qian, Pei Yuan

    2012-01-01

    A recent global ban on the use of organotin compounds as antifouling agents has increased the need for safe and effective antifouling compounds. In this study, a series of new butenolide derivatives with various amine side chains was synthesized and evaluated for their anti-larval settlement activities in the barnacle, Balanus amphitrite. Side chain modification of butenolide resulted in butenolides 3c-3d, which possessed desirable physico-chemical properties and demonstrated highly effective non-toxic anti-larval settlement efficacy. A structure-activity relationship analysis revealed that varying the alkyl side chain had a notable effect on anti-larval settlement activity and that seven to eight carbon alkyl side chains with a tert-butyloxycarbonyl (Boc) substituent on an amine terminal were optimal in terms of bioactivity. Analysis of the physico-chemical profile of butenolide analogues indicated that lipophilicity is a very important physico-chemical parameter contributing to bioactivity. © 2012 Copyright Taylor and Francis Group, LLC.

  15. Methanol to olefin Conversion on HSAPO-34 zeolite from periodic density functional theory calculations: a complete cycle of side chain hydrocarbon pool mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.M.; Wang, Y.D.; Xie, Z.K.; Liu, Z.P. [SINOPEC, Shanghai (China)

    2009-03-15

    For its unique position in the coal chemical industry, the methanol to olefin (MTO) reaction has been a hot topic in zeolite catalysis. Due to the complexities of catalyst structure and reaction networks, many questions such as how the olefin chain is built from methanol remain elusive. On the basis of periodic density functional theory calculations, this work establishes the first complete catalytic cycle for MTO reaction via hexamethylbenzene (HMB) trapped in HSAPO-34 zeolite based on the so-called side chain hydrocarbon pool mechanism. The cycle starts from the methylation of HMB that leads to heptamethylbenzenium ion (heptaMB{sup +}) intermediate. This is then followed by the growth of side chain via repeated deprotonation of benzenium ions and methylation of the exocyclic double bond. Ethene and propene can finally be released from the side ethyl and isopropyl groups of benzenium ions by deprotonation and subsequent protonation steps. We demonstrate that (i) HMB/HSAPO-34 only yields propene as the primary product based on the side chain hydrocarbon pool mechanism and (ii) an indirect proton-shift step mediated by water that is always available in the system is energetically more favorable than the traditionally regarded internal hydrogen-shift step. Finally, the implications of our results toward understanding the effect of acidity of zeolite on MTO activity are also discussed.

  16. Application of the Solid-Phase Julia–Lythgoe Olefination in Vitamin D Side-Chain Construction

    Directory of Open Access Journals (Sweden)

    Pierre J. De Clercq

    2006-08-01

    Full Text Available An example of the Julia–Lythgoe attachment of the vitamin D side chain to a solid-phase linked Inhoffen–Lythgoe diol derived CD-ring fragment is reported.

  17. Critical roles of hydrophobicity and orientation of side chains for inactivation of sarcoplasmic reticulum Ca2+-ATPase with thapsigargin and thapsigargin analogs

    DEFF Research Database (Denmark)

    Winther, Anne-Marie Lund; Liu, Huizhen; Sonntag, Yonathan

    2010-01-01

    fluorescence data to show how Tg and chemical analogs of the compound with modified or removed side chains bind to isolated SERCA 1a membranes. This occurs by uptake via the membrane lipid followed by insertion into a resident intramembranous binding site with few adaptative changes. Our binding data indicate...... that a balanced hydrophobicity and accurate positioning of the side chains, provided by the central guaianolide ring structure, defines a pharmacophore of Tg that governs both high affinity and access to the protein-binding site. Tg analogs substituted with long linkers at O-8 extend from the binding site between...... transmembrane segments to the putative N-terminal Ca(2+) entry pathway. The long chain analogs provide a rational basis for the localization of the linker, the presence of which is necessary for enabling prostate-specific antigen to cleave peptide-conjugated prodrugs targeting SERCA of cancer cells (Denmeade, S...

  18. Evaluating Force Fields for the Computational Prediction of Ionized Arginine and Lysine Side-Chains Partitioning into Lipid Bilayers and Octanol.

    Science.gov (United States)

    Sun, Delin; Forsman, Jan; Woodward, Clifford E

    2015-04-14

    Abundant peptides and proteins containing arginine (Arg) and lysine (Lys) amino acids can apparently permeate cell membranes with ease. However, the mechanisms by which these peptides and proteins succeed in traversing the free energy barrier imposed by cell membranes remain largely unestablished. Precise thermodynamic studies (both theoretical and experimental) on the interactions of Arg and Lys residues with model lipid bilayers can provide valuable clues to the efficacy of these cationic peptides and proteins. We have carried out molecular dynamics simulations to calculate the interactions of ionized Arg and Lys side-chains with the zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayer for 10 widely used lipid/protein force fields: CHARMM36/CHARMM36, SLIPID/AMBER99SB-ILDN, OPLS-AA/OPLS-AA, Berger/OPLS-AA, Berger/GROMOS87, Berger/GROMOS53A6, GROMOS53A6/GROMOS53A6, nonpolarizable MARTINI, polarizable MARTINI, and BMW MARTINI. We performed umbrella sampling simulations to obtain the potential of mean force for Arg and Lys side-chains partitioning from water to the bilayer interior. We found significant differences between the force fields, both for the interactions between side-chains and bilayer surface, as well as the free energy cost for placing the side-chain at the center of the bilayer. These simulation results were compared with the Wimley-White interfacial scale. We also calculated the free energy cost for transferring ionized Arg and Lys side-chains from water to both dry and wet octanol. Our simulations reveal rapid diffusion of water molecules into octanol whereby the equilibrium mole fraction of water in the wet octanol phase was ∼25%. Surprisingly, our free energy calculations found that the high water content in wet octanol lowered the water-to-octanol partitioning free energies for cationic residues by only 0.6 to 0.7 kcal/mol.

  19. Contributions of a disulfide bond and a reduced cysteine side chain to the intrinsic activity of the high-density lipoprotein receptor SR-BI.

    Science.gov (United States)

    Yu, Miao; Lau, Thomas Y; Carr, Steven A; Krieger, Monty

    2012-12-18

    The high-density lipoprotein (HDL) receptor scavenger receptor class B, type I (SR-BI), binds HDL and mediates selective cholesteryl ester uptake. SR-BI's structure and mechanism are poorly understood. We used mass spectrometry to assign the two disulfide bonds in SR-BI that connect cysteines within the conserved Cys(321)-Pro(322)-Cys(323) (CPC) motif and connect Cys(280) to Cys(334). We used site-specific mutagenesis to evaluate the contributions of the CPC motif and the side chain of extracellular Cys(384) to HDL binding and lipid uptake. The effects of CPC mutations on activity were context-dependent. Full wild-type (WT) activity required Pro(322) and Cys(323) only when Cys(321) was present. Reduced intrinsic activities were observed for CXC and CPX, but not XXC, XPX, or XXX mutants (X ≠ WT residue). Apparently, a free thiol side chain at position 321 that cannot form an intra-CPC disulfide bond with Cys(323) is deleterious, perhaps because of aberrant disulfide bond formation. Pro(322) may stabilize an otherwise strained CPC disulfide bond, thus supporting WT activity, but this disulfide bond is not absolutely required for normal activity. C(384)X (X = S, T, L, Y, G, or A) mutants exhibited altered activities that varied with the side chain's size: larger side chains phenocopied WT SR-BI treated with its thiosemicarbazone inhibitor BLT-1 (enhanced binding, weakened uptake); smaller side chains produced almost inverse effects (increased uptake:binding ratio). C(384)X mutants were BLT-1-resistant, supporting the proposal that Cys(384)'s thiol interacts with BLT-1. We discuss the implications of our findings on the functions of the extracellular loop cysteines in SR-BI and compare our results to those presented by other laboratories.

  20. Solid-State Organization and Ambipolar Field-Effect Transistors of Benzothiadiazole-Cyclopentadithiophene Copolymer with Long Branched Alkyl Side Chains

    Directory of Open Access Journals (Sweden)

    Martin Baumgarten

    2013-06-01

    Full Text Available The solid-state organization of a benzothiadiazole-cyclopentadithiophene copolymer with long, branched decyl-tetradecyl side chains (CDT-BTZ-C14,10 is investigated. The C14,10 substituents are sterically demanding and increase the π-stacking distance to 0.40 nm from 0.37 nm for the same polymer with linear hexadecyls (C16. Despite the bulkiness, the C14,10 side chains tend to crystallize, leading to a small chain-to-chain distance between lamellae stacks and to a crystal-like microstructure in the thin film. Interestingly, field-effect transistors based on solution processed layers of CDT-BTZ-C14,10 show ambipolar behavior in contrast to CDT-BTZ-C16 with linear side chains, for which hole transport was previously observed. Due to the increased π-stacking distance, the mobilities are only 6 × 10−4 cm²/Vs for electrons and 6 × 10−5 cm²/Vs for holes, while CDT-BTZ-C16 leads to values up to 5.5 cm²/Vs. The ambipolarity is attributed to a lateral shift between stacked backbones provoked by the bulky C14,10 side chains. This reorganization is supposed to change the transfer integrals between the C16 and C14,10 substituted polymers. This work shows that the electronic behavior in devices of one single conjugated polymer (in this case CDT-BTZ can be controlled by the right choice of the substituents to place the backbones in the desired packing.

  1. The normally expressed kappa immunoglobulin light chain gene repertoire and somatic mutations studied by single-sided specific polymerase chain reaction (PCR); frequent occurrence of features often assigned to autoimmunity

    DEFF Research Database (Denmark)

    Juul, L; Hougs, L; Andersen, V

    1997-01-01

    The expressed human kappa light chain gene repertoire utilized by healthy individuals was studied by two different single-sided specific PCR techniques to avoid bias for certain V genes. A total of 103 rearranged kappa sequences from peripheral blood mononuclear cells from healthy individuals were...

  2. Autoantibodies against Cytochrome P450 Side-Chain Cleavage Enzyme in Dogs (Canis lupus familiaris) Affected with Hypoadrenocorticism (Addison's Disease).

    Science.gov (United States)

    Boag, Alisdair M; Christie, Michael R; McLaughlin, Kerry A; Syme, Harriet M; Graham, Peter; Catchpole, Brian

    2015-01-01

    Canine hypoadrenocorticism likely arises from immune-mediated destruction of adrenocortical tissue, leading to glucocorticoid and mineralocorticoid deficiency. In humans with autoimmune Addison's disease (AAD) or autoimmune polyendocrine syndrome (APS), circulating autoantibodies have been demonstrated against enzymes associated with adrenal steroid synthesis. The current study investigates autoantibodies against steroid synthesis enzymes in dogs with spontaneous hypoadrenocorticism. Coding regions of canine CYP21A2 (21-hydroxylase; 21-OH), CYP17A1 (17-hydroxylase; 17-OH), CYP11A1 (P450 side-chain cleavage enzyme; P450scc) and HSD3B2 (3β hydroxysteroid dehydrogenase; 3βHSD) were amplified, cloned and expressed as 35S-methionine radiolabelled recombinant protein. In a pilot study, serum samples from 20 dogs with hypoadrenocorticism and four unaffected control dogs were screened by radio-immunoprecipitation assay. There was no evidence of reactivity against 21-OH, 17-OH or 3βHSD, but five dogs with hypoadrenocorticism showed immunoreactivity to P450scc compared with controls. Serum samples were subsequently obtained from 213 dogs diagnosed with hypoadrenocorticism and 110 dogs from a hospital control population. Thirty control dogs were randomly selected to establish a threshold for antibody positivity (mean + 3 × standard deviation). Dogs with hypoadrenocorticism were more likely to be P450scc autoantibody positive than hospital controls (24% vs. 1.2%, respectively; p = 0.0016). Sex was significantly associated with the presence of P450scc autoantibodies in the case population, with 30% of females testing positive compared with 17% of males (p = 0.037). Significant associations with breed (p = 0.015) and DLA-type (DQA1*006:01 allele; p = 0.017) were also found. This cross-sectional study indicates that P450scc autoantibodies are present in a proportion of dogs affected with hypoadrenocorticism.

  3. Autoantibodies against Cytochrome P450 Side-Chain Cleavage Enzyme in Dogs (Canis lupus familiaris Affected with Hypoadrenocorticism (Addison's Disease.

    Directory of Open Access Journals (Sweden)

    Alisdair M Boag

    Full Text Available Canine hypoadrenocorticism likely arises from immune-mediated destruction of adrenocortical tissue, leading to glucocorticoid and mineralocorticoid deficiency. In humans with autoimmune Addison's disease (AAD or autoimmune polyendocrine syndrome (APS, circulating autoantibodies have been demonstrated against enzymes associated with adrenal steroid synthesis. The current study investigates autoantibodies against steroid synthesis enzymes in dogs with spontaneous hypoadrenocorticism. Coding regions of canine CYP21A2 (21-hydroxylase; 21-OH, CYP17A1 (17-hydroxylase; 17-OH, CYP11A1 (P450 side-chain cleavage enzyme; P450scc and HSD3B2 (3β hydroxysteroid dehydrogenase; 3βHSD were amplified, cloned and expressed as 35S-methionine radiolabelled recombinant protein. In a pilot study, serum samples from 20 dogs with hypoadrenocorticism and four unaffected control dogs were screened by radio-immunoprecipitation assay. There was no evidence of reactivity against 21-OH, 17-OH or 3βHSD, but five dogs with hypoadrenocorticism showed immunoreactivity to P450scc compared with controls. Serum samples were subsequently obtained from 213 dogs diagnosed with hypoadrenocorticism and 110 dogs from a hospital control population. Thirty control dogs were randomly selected to establish a threshold for antibody positivity (mean + 3 × standard deviation. Dogs with hypoadrenocorticism were more likely to be P450scc autoantibody positive than hospital controls (24% vs. 1.2%, respectively; p = 0.0016. Sex was significantly associated with the presence of P450scc autoantibodies in the case population, with 30% of females testing positive compared with 17% of males (p = 0.037. Significant associations with breed (p = 0.015 and DLA-type (DQA1*006:01 allele; p = 0.017 were also found. This cross-sectional study indicates that P450scc autoantibodies are present in a proportion of dogs affected with hypoadrenocorticism.

  4. Quasi-elastic neutron scattering study of a re-entrant side-chain liquid-crystal polyacrylate

    Science.gov (United States)

    Benguigui, L.; Noirez, L.; Kahn, R.; Keller, P.; Lambert, M.; Cohen de Lara, E.

    1991-04-01

    We present a first investigation of the dynamics of a side chain liquid crystal polyacrylate in the isotropic (I), nematic (N), smectic A (SA), and re-entrant nematic (NRe) phases by means of quasi-elastic neutron scattering. The motion or/and the mobility of the mesogen protons decreases as soon as the temperature decreases after the isotropic-nematic transition. The I-N and SA-NRe transitions corrspond to a jump in the curve of the Elastic Incoherent Structure Factor (ratio: elastic scattering/ total scattering) versus temperature, on the other hand the transition N-SA occurs without any change of slope. We conclude that the local order is very similar in the nematic and the smectic A phases. Nous présentons une première étude dynamique par diffusion quasi-élastique des neutrons, d'un échantillon de polyacrylate mésomorphe en peigne dans chacune des phases : isotrope, nématique, smectique et nématique rentrante. On montre que le mouvement et/ou la mobilité des protons du mésogène se restreint à mesure que la température diminue après la transition isotrope-nématique. Contrairement à la transition N-SA, les transitions I-N et SA-NRe correspondent à une discontinuité dans la courbe du Facteur de Structure Incohérent Elastique (rapport : intensité élastique/intensité totale) en fonction de la température ; l'ordre local semble donc très proche pour les phases nématique et smectique.

  5. Biosynthesis and incorporation of side-chain-truncated lignin monomers to reduce lignin polymerization and enhance saccharification.

    Science.gov (United States)

    Eudes, Aymerick; George, Anthe; Mukerjee, Purba; Kim, Jin S; Pollet, Brigitte; Benke, Peter I; Yang, Fan; Mitra, Prajakta; Sun, Lan; Cetinkol, Ozgül P; Chabout, Salem; Mouille, Grégory; Soubigou-Taconnat, Ludivine; Balzergue, Sandrine; Singh, Seema; Holmes, Bradley M; Mukhopadhyay, Aindrila; Keasling, Jay D; Simmons, Blake A; Lapierre, Catherine; Ralph, John; Loqué, Dominique

    2012-06-01

    Lignocellulosic biomass is utilized as a renewable feedstock in various agro-industrial activities. Lignin is an aromatic, hydrophobic and mildly branched polymer integrally associated with polysaccharides within the biomass, which negatively affects their extraction and hydrolysis during industrial processing. Engineering the monomer composition of lignins offers an attractive option towards new lignins with reduced recalcitrance. The presented work describes a new strategy developed in Arabidopsis for the overproduction of rare lignin monomers to reduce lignin polymerization degree (DP). Biosynthesis of these 'DP reducers' is achieved by expressing a bacterial hydroxycinnamoyl-CoA hydratase-lyase (HCHL) in lignifying tissues of Arabidopsis inflorescence stems. HCHL cleaves the propanoid side-chain of hydroxycinnamoyl-CoA lignin precursors to produce the corresponding hydroxybenzaldehydes so that plant stems expressing HCHL accumulate in their cell wall higher amounts of hydroxybenzaldehyde and hydroxybenzoate derivatives. Engineered plants with intermediate HCHL activity levels show no reduction in total lignin, sugar content or biomass yield compared with wild-type plants. However, cell wall characterization of extract-free stems by thioacidolysis and by 2D-NMR revealed an increased amount of unusual C₆C₁ lignin monomers most likely linked with lignin as end-groups. Moreover the analysis of lignin isolated from these plants using size-exclusion chromatography revealed a reduced molecular weight. Furthermore, these engineered lines show saccharification improvement of pretreated stem cell walls. Therefore, we conclude that enhancing the biosynthesis and incorporation of C₆C₁ monomers ('DP reducers') into lignin polymers represents a promising strategy to reduce lignin DP and to decrease cell wall recalcitrance to enzymatic hydrolysis. © 2012 The Authors. Plant Biotechnology Journal © 2012 Society for Experimental Biology, Association of Applied

  6. Anterior Myocardial Territory May Replace the Heart as Organ at Risk in Intensity-Modulated Radiotherapy for Left-Sided Breast Cancer

    International Nuclear Information System (INIS)

    Tan Wenyong; Liu Dong; Xue Chenbin; Xu Jiaozhen; Li Beihui; Chen Zhengwang; Hu Desheng; Wang Xionghong

    2012-01-01

    Purpose: We investigated whether the heart could be replaced by the anterior myocardial territory (AMT) as the organ at risk (OAR) in intensity-modulated radiotherapy (IMRT) of the breast for patients with left-sided breast cancer. Methods and Materials: Twenty-three patients with left-sided breast cancer who received postoperative radiation after breast-conserving surgery were studied. For each patient, we generated five IMRT plans including heart (H), left ventricle (LV), AMT, LV+AMT, and H+LV as the primary OARs, respectively, except both lungs and right breast, which corresponded to IMRT(H), IMRT(LV), IMRT(AMT), IMRT(LV+AMT), and IMRT(H+LV). For the planning target volumes and OARs, the parameters of dose–volume histograms were compared. Results: The homogeneity index, conformity index, and coverage index were not compromised significantly in IMRT(AMT), IMRT(LV) and IMRT(LV+ AMT), respectively, when compared with IMRT(H). The mean dose to the heart, LV, and AMT decreased 5.3–21.5% (p < 0.05), 19.9–29.5% (p < 0.05), and 13.3–24.5% (p < 0.05), respectively. Similarly, the low (e.g., V5%), middle (e.g., V20%), and high (e.g., V30%) dose-volume of the heart, LV, and AMT decreased with different levels. The mean dose and V10% of the right lung increased by 9.2% (p < 0.05) and 27.6% (p < 0.05), respectively, in IMRT(LV), and the mean dose and V5% of the right breast decreased significantly in IMRT(AMT) and IMRT(LV+AMT). IMRT(AMT) was the preferred plan and was then compared with IMRT(H+LV); the majority of dose–volume histogram parameters of OARs including the heart, LV, AMT, both lungs, and the right breast were not statistically different. However, the low dose-volume of LV increased and the middle dose-volume decreased significantly (p < 0.05) in IMRT(AMT). Also, those of the right lung (V10%, V15%) and right breast (V5%, V10%) decreased significantly (p < 0.05). Conclusions: The AMT may replace the heart as the OAR in left-sided breast IMRT after breast

  7. Phenylpropanoid 2,3-dioxygenase involved in the cleavage of the ferulic acid side chain to form vanillin and glyoxylic acid in Vanilla planifolia.

    Science.gov (United States)

    Negishi, Osamu; Negishi, Yukiko

    2017-09-01

    Enzyme catalyzing the cleavage of the phenylpropanoid side chain was partially purified by ion exchange and gel filtration column chromatography after (NH 4 ) 2 SO 4 precipitation. Enzyme activities were dependent on the concentration of dithiothreitol (DTT) or glutathione (GSH) and activated by addition of 0.5 mM Fe 2+ . Enzyme activity for ferulic acid was as high as for 4-coumaric acid in the presence of GSH, suggesting that GSH acts as an endogenous reductant in vanillin biosynthesis. Analyses of the enzymatic reaction products with quantitative NMR (qNMR) indicated that an amount of glyoxylic acid (GA) proportional to vanillin was released from ferulic acid by the enzymatic reaction. These results suggest that phenylpropanoid 2,3-dioxygenase is involved in the cleavage of the ferulic acid side chain to form vanillin and GA in Vanilla planifolia.

  8. The probability distribution of side-chain conformations in [Leu] and [Met]enkephalin determines the potency and selectivity to mu and delta opiate receptors

    DEFF Research Database (Denmark)

    Nielsen, Bjørn Gilbert; Jensen, Morten Østergaard; Bohr, Henrik

    2003-01-01

    The structure of enkephalin, a small neuropeptide with five amino acids, has been simulated on computers using molecular dynamics. Such simulations exhibit a few stable conformations, which also have been identified experimentally. The simulations provide the possibility to perform cluster analysis...... in the space defined by potentially pharmacophoric measures such as dihedral angles, side-chain orientation, etc. By analyzing the statistics of the resulting clusters, the probability distribution of the side-chain conformations may be determined. These probabilities allow us to predict the selectivity...... of [Leu]enkephalin and [Met]enkephalin to the known mu- and delta-type opiate receptors to which they bind as agonists. Other plausible consequences of these probability distributions are discussed in relation to the way in which they may influence the dynamics of the synapse....

  9. Effects of side-chain and electron exchange correlation on the band structure of perylene diimide liquid crystals: a density functional study.

    Science.gov (United States)

    Arantes, J T; Lima, M P; Fazzio, A; Xiang, H; Wei, Su-Huai; Dalpian, G M

    2009-04-23

    The structural and electronic properties of perylene diimide liquid crystal PPEEB are studied using ab initio methods based on the density functional theory (DFT). Using available experimental crystallographic data as a guide, we propose a detailed structural model for the packing of solid PPEEB. We find that due to the localized nature of the band edge wave function, theoretical approaches beyond the standard method, such as hybrid functional (PBE0), are required to correctly characterize the band structure of this material. Moreover, unlike previous assumptions, we observe the formation of hydrogen bonds between the side chains of different molecules, which leads to a dispersion of the energy levels. This result indicates that the side chains of the molecular crystal not only are responsible for its structural conformation but also can be used for tuning the electronic and optical properties of these materials.

  10. Synthesis of novel vitamin K derivatives with alkylated phenyl groups introduced at the ω-terminal side chain and evaluation of their neural differentiation activities.

    Science.gov (United States)

    Sakane, Rie; Kimura, Kimito; Hirota, Yoshihisa; Ishizawa, Michiyasu; Takagi, Yuta; Wada, Akimori; Kuwahara, Shigefumi; Makishima, Makoto; Suhara, Yoshitomo

    2017-11-01

    Vitamin K is an essential cofactor of γ-glutamylcarboxylase as related to blood coagulation and bone formation. Menaquinone-4, one of the vitamin K homologues, is biosynthesized in the body and has various biological activities such as being a ligand for steroid and xenobiotic receptors, protection of neuronal cells from oxidative stress, and so on. From this background, we focused on the role of menaquinone in the differentiation activity of progenitor cells into neuronal cells and we synthesized novel vitamin K derivatives with modification of the ω-terminal side chain. We report here new vitamin K analogues, which introduced an alkylated phenyl group at the ω-terminal side chain. These compounds exhibited potent differentiation activity as compared to control. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  11. Stereospecific assignment of the NH2 resonances from the primary amides of asparagine and glutamine side chains in isotopically labeled proteins

    International Nuclear Information System (INIS)

    McIntosh, Lawrence P.; Brun, Emmanuel; Kay, Lewis E.

    1997-01-01

    An HMQC-based pulse scheme is presented for the stereospecific assignment of asparagine and glutamine side-chain amide protons. The approach makes use of the recently developed quantitative-J correlation spectroscopy [Bax, A. et al. (1994) Methods Enzymol., 239,79-105] to distinguish the E and Z primary amide protons and, as such, eliminates the need for assignments derived from more time-consuming and potentially ambiguous NOE methods. An application of this method to a uniformly 15N,13C-labeled cellulose-binding domain is presented. When used in combination with a NOESY-HSQC experiment, the predominant χ2 dihedral angles of two asparagine side chains in this protein can also be defined

  12. Estimating side-chain order in methyl-protonated, perdeuterated proteins via multiple-quantum relaxation violated coherence transfer NMR spectroscopy

    International Nuclear Information System (INIS)

    Sun Hechao; Godoy-Ruiz, Raquel; Tugarinov, Vitali

    2012-01-01

    Relaxation violated coherence transfer NMR spectroscopy (Tugarinov et al. in J Am Chem Soc 129:1743–1750, 2007) is an established experimental tool for quantitative estimation of the amplitudes of side-chain motions in methyl-protonated, highly deuterated proteins. Relaxation violated coherence transfer experiments monitor the build-up of methyl proton multiple-quantum coherences that can be created in magnetically equivalent spin-systems as long as their transverse magnetization components relax with substantially different rates. The rate of this build-up is a reporter of the methyl-bearing side-chain mobility. Although the build-up of multiple-quantum 1 H coherences is monitored in these experiments, the decay of the methyl signal during relaxation delays occurs when methyl proton magnetization is in a single-quantum state. We describe a relaxation violated coherence transfer approach where the relaxation of multiple-quantum 1 H– 13 C methyl coherences during the relaxation delay period is quantified. The NMR experiment and the associated fitting procedure that models the time-dependence of the signal build-up, are applicable to the characterization of side-chain order in [ 13 CH 3 ]-methyl-labeled, highly deuterated protein systems up to ∼100 kDa in molecular weight. The feasibility of extracting reliable measures of side-chain order is experimentally verified on methyl-protonated, perdeuterated samples of an 8.5-kDa ubiquitin at 10°C and an 82-kDa Malate Synthase G at 37°C.

  13. Side-chain amino-acid-based pH-responsive self-assembled block copolymers for drug delivery and gene transfer.

    Science.gov (United States)

    Kumar, Sonu; Acharya, Rituparna; Chatterji, Urmi; De, Priyadarsi

    2013-12-10

    Developing safe and effective nanocarriers for multitype of delivery system is advantageous for several kinds of successful biomedicinal therapy with the same carrier. In the present study, we have designed amino acid biomolecules derived hybrid block copolymers which can act as a promising vehicle for both drug delivery and gene transfer. Two representative natural chiral amino acid-containing (l-phenylalanine and l-alanine) vinyl monomers were polymerized via reversible addition-fragmentation chain transfer (RAFT) process in the presence of monomethoxy poly(ethylene glycol) based macro-chain transfer agents (mPEGn-CTA) for the synthesis of well-defined side-chain amino-acid-based amphiphilic block copolymers, monomethoxy poly(ethylene glycol)-b-poly(Boc-amino acid methacryloyloxyethyl ester) (mPEGn-b-P(Boc-AA-EMA)). The self-assembled micellar aggregation of these amphiphilic block copolymers were studied by fluorescence spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Potential applications of these hybrid polymers as drug carrier have been demonstrated in vitro by encapsulation of nile red dye or doxorubicin drug into the core of the micellar nanoaggregates. Deprotection of side-chain Boc- groups in the amphiphilic block copolymers subsequently transformed them into double hydrophilic pH-responsive cationic block copolymers having primary amino groups in the side-chain terminal. The DNA binding ability of these cationic block copolymers were further investigated by using agarose gel retardation assay and AFM. The in vitro cytotoxicity assay demonstrated their biocompatible nature and these polymers can serve as "smart" materials for promising bioapplications.

  14. Diketopyrrolopyrrole-Based Conjugated Polymer Entailing Triethylene Glycols as Side Chains with High Thin-Film Charge Mobility without Post-Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Si-Fen [Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; University of Chinese Academy of Sciences, Beijing 100049 P. R. China; Liu, Zi-Tong [Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; Cai, Zheng-Xu [Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; Dyson, Matthew J. [Department of Materials and Centre for Plastic Electronics, Imperial College London, London SW72AZ UK; Stingelin, Natalie [Department of Materials and Centre for Plastic Electronics, Imperial College London, London SW72AZ UK; Chen, Wei [Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue Lemont IL 60439 USA; Institute for Molecular Engineering, The University of Chicago, 5640 South Ellis Avenue Chicago IL 60637 USA; Ju, Hua-Jun [Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; Zhang, Guan-Xin [Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; Zhang, De-Qing [Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; University of Chinese Academy of Sciences, Beijing 100049 P. R. China

    2017-04-18

    Side chain engineering of conjugated donor-acceptor polymers is a new way to manipulate their optoelectronic properties. Two new diketopyrrolopyrrole (DPP)-terthiophene-based conjugated polymers PDPP3T-1 and PDPP3T-2, with both hydrophilic triethylene glycol (TEG) and hydrophobic alkyl chains, are reported. It is demonstrated that the incorporation of TEG chains has a significant effect on the interchain packing and thin-film morphology with noticeable effect on charge transport. Polymer chains of PDPP3T-1 in which TEG chains are uniformly distributed can self-assemble spontaneously into a more ordered thin film. As a result, the thin film of PDPP3T-1 exhibits high saturated hole mobility up to 2.6 cm(2) V-1 s(-1) without any post-treatment. This is superior to those of PDPP3T with just alkyl chains and PDPP3T-2. Moreover, the respective field effect transistors made of PDPP3T-1 can be utilized for sensing ethanol vapor with high sensitivity (down to 100 ppb) and good selectivity.

  15. Side-chain tunability of furan-containing low-band-gap polymers provides control of structural order in efficient solar cells

    KAUST Repository

    Yiu, Alan T.; Beaujuge, Pierre; Lee, Olivia P.; Woo, Claire; Toney, Michael F.; Frechet, Jean

    2012-01-01

    The solution-processability of conjugated polymers in organic solvents has classically been achieved by modulating the size and branching of alkyl substituents appended to the backbone. However, these substituents impact structural order and charge transport properties in thin-film devices. As a result, a trade-off must be found between material solubility and insulating alkyl content. It was recently shown that the substitution of furan for thiophene in the backbone of the polymer PDPP2FT significantly improves polymer solubility, allowing for the use of shorter branched side chains while maintaining high device efficiency. In this report, we use PDPP2FT to demonstrate that linear alkyl side chains can be used to promote thin-film nanostructural order. In particular, linear side chains are shown to shorten π-π stacking distances between backbones and increase the correlation lengths of both π-π stacking and lamellar spacing, leading to a substantial increase in the efficiency of bulk heterojunction solar cells. © 2011 American Chemical Society.

  16. Side-chain tunability of furan-containing low-band-gap polymers provides control of structural order in efficient solar cells

    KAUST Repository

    Yiu, Alan T.

    2012-02-01

    The solution-processability of conjugated polymers in organic solvents has classically been achieved by modulating the size and branching of alkyl substituents appended to the backbone. However, these substituents impact structural order and charge transport properties in thin-film devices. As a result, a trade-off must be found between material solubility and insulating alkyl content. It was recently shown that the substitution of furan for thiophene in the backbone of the polymer PDPP2FT significantly improves polymer solubility, allowing for the use of shorter branched side chains while maintaining high device efficiency. In this report, we use PDPP2FT to demonstrate that linear alkyl side chains can be used to promote thin-film nanostructural order. In particular, linear side chains are shown to shorten π-π stacking distances between backbones and increase the correlation lengths of both π-π stacking and lamellar spacing, leading to a substantial increase in the efficiency of bulk heterojunction solar cells. © 2011 American Chemical Society.

  17. Enhanced performance and durability of low catalyst loading PEM water electrolyser based on a short-side chain perfluorosulfonic ionomer

    International Nuclear Information System (INIS)

    Siracusano, Stefania; Baglio, Vincenzo; Van Dijk, Nicholas; Merlo, Luca; Aricò, Antonino Salvatore

    2017-01-01

    Graphical abstract: Tripling current density (>3 A·cm"−"2) with respect to the state of the art of commercial PEM electrolyser can be achieved also in the presence of a significant reduction, about 4-fold, of the total noble metal loading (0.5 mg·cm"−"2) while achieving high efficiency (>80%) and proper durability. - Highlights: • Current density >3 A·cm"−"2 is achieved in electrolysis cells with efficiency >80%. • A 4-fold reduction of noble metal loading is demonstrated in electrolysis cells. • Degradation rate <5 μV/h is achieved in a 1000 h durability test at 1 A·cm"−"2. • Degradation associated to a change in Lewis acidity characteristics is observed. - Abstract: Water electrolysis supplied by renewable energy is the foremost technology for producing “green” hydrogen for fuel cell vehicles. In addition, the ability to rapidly follow an intermittent load makes electrolysis an ideal solution for grid-balancing caused by differences in supply and demand for energy generation and consumption. Membrane-electrode assemblies (MEAs) designed for polymer electrolyte membrane (PEM) water electrolysis, based on a novel short-side chain (SSC) perfluorosulfonic acid (PFSA) membrane, Aquivion®, with various cathode and anode noble metal loadings, were investigated in terms of both performance and durability. Utilizing a nanosized Ir_0_._7Ru_0_._3O_x solid solution anode catalyst and a supported Pt/C cathode catalyst, in combination with the Aquivion® membrane, gave excellent electrolysis performances exceeding 3.2 A·cm"−"2 at 1.8 V terminal cell voltage (∼80% efficiency) at 90 °C in the presence of a total catalyst loading of 1.6 mg⋅cm"−"2. A very small loss of efficiency, corresponding to 30 mV voltage increase, was recorded at 3 A⋅cm"−"2 using a total noble metal catalyst loading of less than 0.5 mg·cm"−"2 (compared to the industry standard of 2 mg·cm"−"2). Steady-state durability tests, carried out for 1000 h at 1 A

  18. Pronounced Side Chain Effects in Triple Bond-Conjugated Polymers Containing Naphthalene Diimides for n-Channel Organic Field-Effect Transistors

    KAUST Repository

    Nam, Sungho

    2018-03-23

    Three triple bond-conjugated naphthalene diimide (NDI) copolymers, poly{[N,N′-bis(2-R1)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-[(2,5-bis(2-R2)-1,4-phenylene)bis(ethyn-2,1-diyl)]} (PNDIR1-R2), were synthesized via Sonogashira coupling polymerization with varying alkyl side chains at the nitrogen atoms of the imide ring and 2,5-positions of the 1,4-diethynylbenzene moiety. Considering their identical polymer backbone structures, the side chains were found to have a strong influence on the surface morphology/nanostructure, thus playing a critical role in charge-transporting properties of the three NDI-based copolymers. Among the polymers, the one with an octyldodecyl (OD) chain at the nitrogen atoms of imide ring and a hexadecyloxy (HO) chain at the 2,5-positions of 1,4-diethynylbenzene, P(NDIOD-HO), exhibited the highest electron mobility of 0.016 cm2 V–1 s–1, as compared to NDI-based copolymers with an ethylhexyl chain at the 2,5-positions of 1,4-diethynylbenzene. The enhanced charge mobility in the P(NDIOD-HO) layers is attributed to the well-aligned nano-fiber-like surface morphology and highly ordered packing structure with a dominant edge-on orientation, thus enabling efficient in-plane charge transport. Our results on the molecular structure–charge transport property relationship in these materials may provide an insight into novel design of n-type conjugated polymers for applications in the organic electronics of the future.

  19. Fluorinated polyimides grafted with poly(ethylene glycol) side chains by the RAFT-mediated process and their membranes

    International Nuclear Information System (INIS)

    Chen Yiwang; Chen Lie; Nie Huarong; Kang, E.T.; Vora, R.H.

    2005-01-01

    Graft polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) from fluorinated polyimide (FPI) was carried out by the reversible addition-fragmentation chain transfer (RAFT)-mediated process. The peroxides generated by the ozone treatment on FPI facilitated the thermally-initiated graft copolymerization from FPI backbone. The 'living' character of the graft chain growing was ascertained in the subsequent chain extension of PEGMA. Nuclear magnetic resonance (NMR) and molecular weight measurements were used to characterize the chemical composition and structure of the copolymers. Microfiltration (MF) membranes were fabricated from the FPI-g-PEGMA comb copolymers by phase inversion in aqueous media. Surface composition analysis of the membranes scanned by X-ray photoelectron spectroscopy (XPS) revealed a substantial surface enrichment of the hydrophilic components. The pore size distribution of the resulting membranes was found to be much more uniform than that of the corresponding membranes cast from FPI-g-PEGMA prepared by the conventional radical polymerization process in the absence of the chain transfer agent. The morphology of the membranes was characterized by scanning electron microscopy (SEM)

  20. On the interaction of the morphological structure and the LC behaviour of LC side chain block copolymers

    NARCIS (Netherlands)

    Fischer, H.R.; Poser, S.; Arnold, M.

    1995-01-01

    The interaction between morphological structure and phase behaviour of a LC side group block copolymer has been investigated using DSC, TEM and small angle X-ray diffraction. All samples of Polystyrene-block-2-(3-cholesteryloxycarbonyloxy)ethyl methacrylate (PS-b-PChEMA) show a phase separation

  1. On the interaction of the morphological structure and the LC behaviour of LC side chain block copolymers

    NARCIS (Netherlands)

    Fischer, H.R.; Arnold, M.

    1995-01-01

    The interaction between morphological structure and phase behaviour of a group of LC side group block copolymers have been investigated using DSC, TEM and small angle X-ray diffraction. Generally, phase separation between the two blocks was observed. It was found that in the case of those samples,

  2. Acidic-basic properties of three alanine-based peptides containing acidic and basic side chains: comparison between theory and experiment.

    Science.gov (United States)

    Makowska, Joanna; Bagińska, Katarzyna; Liwo, Adam; Chmurzyński, Lech; Scheraga, Harold A

    2008-01-01

    The purpose of this work was to evaluate the effect of the nature of the ionizable end groups, and the solvent, on their acid-base properties in alanine-based peptides. Hence, the acid-base properties of three alanine-based peptides: Ac-KK-(A)(7)-KK-NH(2) (KAK), Ac-OO-(A)(7)-DD-NH(2) (OAD), Ac-KK-(A)(7)-EE-NH(2) (KAE), where A, D, E, K, and O denote alanine, aspartic acid, glutamic acid, lysine, and ornithine, respectively, were determined in water and in methanol by potentiometry. With the availability of these data, the ability of two theoretical methods to simulate pH-metric titration of those peptides was assessed: (i) the electrostatically driven Monte Carlo method with the ECEPP/3 force field and the Poisson-Boltzmann approach to compute solvation energy (EDMC/PB/pH), and (ii) the molecular dynamics method with the AMBER force field and the Generalized Born model (MD/GB/pH). For OAD and KAE, pK(a1) and pK(a2) correspond to the acidic side chains. For all three compounds in both solvents, the pK(a1) value is remarkably lower than the pK(a) of a compound modeling the respective isolated side chain, which can be explained by the influence of the electrostatic field from positively charged ornithine or lysine side chains. The experimental titration curves are reproduced well by the MD/GB/pH approach, the agreement being better if restraints derived from NMR measurements are incorporated in the conformational search. Poorer agreement is achieved by the EDMC/PB/pH method.

  3. Chemoenzymatic synthesis of statine side chain building blocks and application in the total synthesis of the cholesterol-lowering compound solistatin.

    Science.gov (United States)

    Rieder, Oliver; Wolberg, Michael; Foegen, Silke E; Müller, Michael

    2017-09-20

    The synthesis and enzymatic reduction of several 6-substituted dioxohexanoates are presented. Two-step syntheses of tert-butyl 6-bromo-3,5-dioxohexanoate and the corresponding 6-hydroxy compound have been achieved in 89% and 59% yield, respectively. Regio- and enantioselective reduction of these diketones and of the 6-chloro derivative with alcohol dehydrogenase from Lactobacillus brevis (LBADH) gave the (5S)-5-hydroxy-3-oxo products with enantiomeric excesses of 91%, 98.4%, and >99.5%, respectively. Chain elongation of the reduction products by one carbon via cyanide addition, and by more than one carbon by Julia-Kocienski olefination, gave access to well-established statine side-chain building blocks. Application in the synthesis of the cholesterol-lowering natural compound solistatin is given. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. New theories for smectic and nematic liquid-crystal polymers: Backbone LCPs [liquid crystalline polymers] and their mixtures and side-chain LCPs

    International Nuclear Information System (INIS)

    Dowell, F.

    1987-01-01

    A summary of predictions and explanations from statistical-physics theories for both backbone and side-chain liquid crystalline polymers (LCPs) and for mixtures with backbone LCPs are presented. Trends in the thermodynamic and molecular ordering properties have been calculated as a function of pressure, density, temperature, and molecule chemical structures (including degree of polymerization and the following properties of the chemical structures of the repeat units: lengths and shapes, intra-chain rotation energies, dipole moments, site-site polarizabilities and Lennard-Jones potentials, etc.) in nematic and multiple smectic-A LC phases and in the isotropic liquid phase. The theoretical results are found to be in good agreement with existing experimental data. These theories can also be applied to combined LCPs. Since these theories have no ad hoc or arbitrarily adjustable parameters, these theories can be used to design new LCPs and new solvents as well as to predict and explain properties. 27 refs., 4 tabs

  5. Utilizing alkoxyphenyl substituents for side-chain engineering of efficient benzo[1,2-b:4,5-b ']dithiophene-based small molecule organic solar cells

    DEFF Research Database (Denmark)

    Du, Zhengkun; Chen, Weichao; Qiu, Meng

    2015-01-01

    -processed organic solar cells (OSCs) as an electron donor material, in which an alkoxyphenyl group was introduced as a weak electrondonating side chain of the BDT moiety. The DCA3TBDTP molecule exhibited good solubility, a deep highest occupied molecular orbital (HOMO) level (-5.25 eV), an appropriate optical band......-gap (1.82 eV) and a high decomposition temperature (362 degrees C). By applying the simple solution spin-coating fabrication process, the bulk heterojunction (BHJ) OSCs based on DCA3TBDTP and [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) exhibited a good power conversion efficiency (PCE) of 4...

  6. Influence of Side Chain Position on the Electrical Properties of Organic Solar Cells Based on Dithienylbenzothiadiazole-alt-phenylene Conjugated Polymers

    DEFF Research Database (Denmark)

    Livi, Francesco; Zawacka, Natalia Klaudia; Angmo, Dechan

    2015-01-01

    backbone for polymer solar cells. All the polymers were roll slot die coated under ambient conditions on flexible ITO-free plastic substrates to give inverted polymer solar cell devices with an upscaled active area of 1 cm2. The best characteristics were found for the polymer carrying alkoxy side chains...... showed excellent performance under constant illumination and high temperature (exhibiting stable photovoltaic properties even after 670 h under conditions similar to ISOS-L-2 lifetime protocol). This makes P7 a good candidate for further upscaling and device optimization. The photovoltaic performance...

  7. Comparison of the Photovoltaic Characteristics and Nanostructure of Fullerenes Blended with Conjugated Polymers with Siloxane-Terminated and Branched Aliphatic Side Chains

    KAUST Repository

    Kim, Do Hwan

    2013-02-12

    All-organic bulk heterojunction solar cells based on blends of conjugated polymers with fullerenes have recently surpassed the 8% efficiency mark and are well on their way to the industrially relevant ∼15% threshold. Using a low band-gap conjugated polymer, we have recently shown that polymer side chain engineering can lead to dramatic improvement in the in-plane charge carrier mobility. In this article, we investigate the effectiveness of siloxy side chain derivatization in controlling the photovoltaic performance of polymer:[6,6]-phenyl-C[71]-butyric acid methyl ester (PC71BM) blends and hence its influence on charge transport in the out-of-plane direction relevant for organic solar cells. We find that, in neat blends, the photocurrent of the polymer with siloxy side chains (PII2T-Si) is 4 times greater than that in blends using the polymer with branched aliphatic side chains (PII2T-ref). This difference is due to a larger out-of-plane hole mobility for PII2T-Si brought about by a largely face-on crystallite orientation as well as more optimal nanoscale polymer:PC71BM mixing. However, upon incorporating a common processing additive, 1,8-diiodooctane (DIO), into the spin-casting blend solution and following optimization, the PII2T-ref:PC71BM OPV device performance undergoes a large improvement and becomes the better-performing device, almost independent of DIO concentration (>1%). We find that the precise amount of DIO plays a larger role in determining the efficiency of PII2T-Si:PC71BM, and even at its maximum, the device performance lags behind optimized PII2T-ref:PC71BM blends. Using a combination of atomic force microscopy and small- and wide-angle X-ray scattering, we are able to elucidate the morphological modifications associated with the DIO-induced changes in both the nanoscale morphology and the molecular packing in blend films. © 2012 American Chemical Society.

  8. The interplay between transient a-helix formation and side chain rotamer distributions in disordered proteins probed by methyl chemical shifts

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Iesmantavicius, Vytautas; Poulsen, Flemming M

    2011-01-01

    and retinoid receptors (ACTR). We find that small differences in the methyl carbon chemical shifts due to the ¿-gauche effect may provide information about the side chain rotamer distributions. However, the effects of neighboring residues on the methyl group chemical shifts obscure the direct observation...... of ¿-gauche effect. To overcome this, we reference the chemical shifts to those in a more disordered state resulting in residue specific random coil chemical shifts. The (13)C secondary chemical shifts of the methyl groups of valine, leucine, and isoleucine show sequence specific effects, which allow...

  9. In vitro degradability and total gas production of biodiesel chain byproducts used as a replacement for cane sugar feed

    Directory of Open Access Journals (Sweden)

    Milenna Nunes Moreira

    2014-09-01

    Full Text Available This study aimed to determine the in vitro degradability of dry matter and the total gas production of oil seed press cake from biodiesel production (Gossypium hirsutum L., Helianthus annuus L., Ricinus communis, Moringa oleífera L. and Pinhão manso curcas L. at four different levels of replacement (0, 30, 50, and 70% for cane sugar (Saccharum officinarum RB. in ruminant feed. Inocula were prepared using the ruminal fluid of three Holstein cows, and data were collected after 48 hours of incubation. The byproducts of Moringa had the highest degradability, and castor presented the lowest values at all evaluated levels of replacement. Castor bean byproduct showed the highest total gas production, cotton showed the lowest production, and the byproduct of Moringa at the 70% level showed the best ruminal fermentation results. These results demonstrate that the use of oil seed press cake from biodiesel production (Helianthus annuus L. and Ricinus communis can replace cane sugar in ruminant feed.

  10. Blocking of proteolytic processing and deletion of glycosaminoglycan side chain of mouse DMP1 by substituting critical amino acid residues.

    Science.gov (United States)

    Peng, Tao; Huang, Bingzhen; Sun, Yao; Lu, Yongbo; Bonewald, Lynda; Chen, Shuo; Butler, William T; Feng, Jerry Q; D'Souza, Rena N; Qin, Chunlin

    2009-01-01

    Dentin matrix protein 1 (DMP1) is present in the extracellular matrix (ECM) of dentin and bone as processed NH(2)- and COOH-terminal fragments, resulting from proteolytic cleavage at the NH(2) termini of 4 aspartic acid residues during rat DMP1 processing. One cleavage site residue, Asp(181) (corresponding to Asp(197) of mouse DMP1), and its flanking region are highly conserved across species. We speculate that cleavage at the NH(2) terminus of Asp(197) of mouse DMP1 represents an initial, first-step scission in the whole cascade of proteolytic processing. To test if Asp(197) is critical for initiating the proteolytic processing of mouse DMP1, we substituted Asp(197) with Ala(197) by mutating the corresponding nucleotides of mouse cDNA that encode this amino acid residue. This mutant DMP1 cDNA was cloned into a pcDNA3.1 vector. Data from transfection experiments indicated that this single substitution blocked the proteolytic processing of mouse DMP1 in HEK-293 cells, indicating that cleavage at the NH(2) terminus of Asp(197) is essential for exposing other cleavage sites for the conversion of DMP1 to its fragments. The NH(2)-terminal fragment of DMP1 occurs as a proteoglycan form (DMP1-PG) that contains a glycosaminoglycan (GAG) chain. Previously, we showed that a GAG chain is linked to Ser(74) in rat DMP1 (Ser(89) in mouse DMP1). To confirm that mouse DMP1-PG possesses a single GAG chain attached to Ser(89), we substituted Ser(89) by Gly(89). Data from transfection analysis indicated that this substitution completely prevented formation of the GAG-containing form, confirming that DMP1-PG contains a single GAG chain attached to Ser(89) in mouse DMP1. Copyright 2008 S. Karger AG, Basel.

  11. Highly crystalline films of PCPDTBT with branched side chains by solvent vapor crystallization: influence on opto-electronic properties.

    Science.gov (United States)

    Fischer, Florian S U; Trefz, Daniel; Back, Justus; Kayunkid, Navaphun; Tornow, Benjamin; Albrecht, Steve; Yager, Kevin G; Singh, Gurpreet; Karim, Alamgir; Neher, Dieter; Brinkmann, Martin; Ludwigs, Sabine

    2015-02-18

    PCPDTBT, a marginally crystallizable polymer, is crystallized into a new crystal structure using solvent-vapor annealing. Highly ordered areas with three different polymer-chain orientations are identified using TEM/ED, GIWAXS, and polarized Raman spectroscopy. The optical and structural properties differ significantly from films prepared by standard device preparation protocols. Bilayer solar cells, however, show similar performance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Beta-scission of alkoxyl radicals on peptides and proteins can give rise to backbone cleavage and loss of side-chains

    International Nuclear Information System (INIS)

    Headlam, H.A.; Davies, M.J.; Mortimer, A.; Easton, C.J.

    2000-01-01

    Full text: Exposure of proteins to radicals in the presence of O 2 brings about multiple changes including side-chain oxidation, backbone fragmentation, cross-linking, unfolding, changes in hydrophobicity and conformation, altered susceptibility to proteolytic enzymes and formation of new reactive groups (e.g. hydroperoxides and 3,4-dihydroxyphenylalanine). All of these processes can result in loss of structural or enzymatic activity. The mechanisms that give rise to backbone cleavage are only partly understood. Whilst it is known that direct hydrogen atom abstraction at a-carbon sites gives backbone cleavages it has also been proposed that initial attack at side-chain sites might also give rise to backbone cleavage. In this study we have examined whether initial attack at the β- (C-3) position can give rise to α-carbon radicals (and hence backbone cleavage) via the formation, and subsequent β- scission, of C-3 alkoxyl radicals. This process has been observed previously with protected amino acids in organic solvents (J. Chem. Soc. Perkin Trans. 2, 1997, 503-507) but the occurrence of such reactions with proteins in aqueous solution has not been explored. Alkoxyl radicals were generated at the C-3 position of a variety of protected amino acids and small peptides by two methods: metal-ion catalysed decomposition of hydroperoxides formed as a result of γ-radiolysis in the presence of O 2 , and UV photolysis of nitrate esters. In most cases radicals have been detected by EPR spectroscopy using nitroso and nitrone spin traps, which can be assigned by comparison with literature data to α-carbon radicals; in some case assignments were confirmed by the generation of the putative species by other routes. With Ala peptide hydroperoxides and nitrate esters, and MNP as the spin trap, the major radical detected in each case has been assigned to the adduct of an α-carbon radical with partial structure - NH- . CH-C(O) - consistent with the rapid occurrence of the above

  13. Partial molar volumes of proteins: amino acid side-chain contributions derived from the partial molar volumes of some tripeptides over the temperature range 10-90 degrees C.

    Science.gov (United States)

    Häckel, M; Hinz, H J; Hedwig, G R

    1999-11-15

    The partial molar volumes of tripeptides of sequence glycyl-X-glycine, where X is one of the amino acids alanine, leucine, threonine, glutamine, phenylalanine, histidine, cysteine, proline, glutamic acid, and arginine, have been determined in aqueous solution over the temperature range 10-90 degrees C using differential scanning densitometry . These data, together with those reported previously, have been used to derive the partial molar volumes of the side-chains of all 20 amino acids. The side-chain volumes are critically compared with literature values derived using partial molar volumes for alternative model compounds. The new amino acid side-chain volumes, along with that for the backbone glycyl group, were used to calculate the partial specific volumes of several proteins in aqueous solution. The results obtained are compared with those observed experimentally. The new side-chain volumes have also been used to re-determine residue volume changes upon protein folding.

  14. Introduction of a methoxymethyl side chain into p-phenylenediamine attenuates its sensitizing potency and reduces the risk of allergy induction

    Energy Technology Data Exchange (ETDEWEB)

    Goebel, Carsten, E-mail: goebel.c.1@pg.com [The Procter and Gamble Co., Central Product Safety and Communications, Darmstadt (Germany); Troutman, John [The Procter and Gamble Co., Central Product Safety, Cincinnati, OH (United States); Hennen, Jenny [Dept. of Environmental Toxicology, Trier University, Trier (Germany); Rothe, Helga; Schlatter, Harald [The Procter and Gamble Co., Central Product Safety and Communications, Darmstadt (Germany); Gerberick, G. Frank [The Procter and Gamble Co., Central Product Safety, Cincinnati, OH (United States); Blömeke, Brunhilde [Dept. of Environmental Toxicology, Trier University, Trier (Germany)

    2014-02-01

    The strong sensitizing potencies of the most important primary intermediates of oxidative hair dyes, p-phenylenediamine (PPD) and p-toluylenediamine (PTD, i.e. 2-methyl-PPD) are well established. They are considered as the key sensitizers in hair dye allergic contact dermatitis. While modification of their molecular structure is expected to alter their sensitizing properties, it may also impair their color performance. With introduction of a methoxymethyl side chain we found the primary intermediate 2-methoxymethyl-p-phenylenediamine (ME-PPD) with excellent hair coloring performance but significantly reduced sensitizing properties compared to PPD and PTD: In vitro, ME-PPD showed an attenuated innate immune response when analyzed for its protein reactivity and dendritic cell activation potential. In vivo, the effective concentration of ME-PPD necessary to induce an immune response 3-fold above vehicle control (EC3 value) in the local lymph node assay (LLNA) was 4.3%, indicating a moderate skin sensitizing potency compared to values of 0.1 and 0.17% for PPD and PTD, respectively. Finally, assessing the skin sensitizing potency of ME-PPD under consumer hair dye usage conditions through a quantitative risk assessment (QRA) indicated an allergy induction risk negligible compared to PPD or PTD. - Highlights: • Methoxymethyl side chain in p-phenylenediamine reduces its strong skin sensitizing properties. • Reduced protein reactivity and dendritic cell activation. • Reduced skin sensitizing potency in local lymph node assay (LLNA). • Negligible allergy induction risk under hair dye usage conditions.

  15. Introduction of a methoxymethyl side chain into p-phenylenediamine attenuates its sensitizing potency and reduces the risk of allergy induction

    International Nuclear Information System (INIS)

    Goebel, Carsten; Troutman, John; Hennen, Jenny; Rothe, Helga; Schlatter, Harald; Gerberick, G. Frank; Blömeke, Brunhilde

    2014-01-01

    The strong sensitizing potencies of the most important primary intermediates of oxidative hair dyes, p-phenylenediamine (PPD) and p-toluylenediamine (PTD, i.e. 2-methyl-PPD) are well established. They are considered as the key sensitizers in hair dye allergic contact dermatitis. While modification of their molecular structure is expected to alter their sensitizing properties, it may also impair their color performance. With introduction of a methoxymethyl side chain we found the primary intermediate 2-methoxymethyl-p-phenylenediamine (ME-PPD) with excellent hair coloring performance but significantly reduced sensitizing properties compared to PPD and PTD: In vitro, ME-PPD showed an attenuated innate immune response when analyzed for its protein reactivity and dendritic cell activation potential. In vivo, the effective concentration of ME-PPD necessary to induce an immune response 3-fold above vehicle control (EC3 value) in the local lymph node assay (LLNA) was 4.3%, indicating a moderate skin sensitizing potency compared to values of 0.1 and 0.17% for PPD and PTD, respectively. Finally, assessing the skin sensitizing potency of ME-PPD under consumer hair dye usage conditions through a quantitative risk assessment (QRA) indicated an allergy induction risk negligible compared to PPD or PTD. - Highlights: • Methoxymethyl side chain in p-phenylenediamine reduces its strong skin sensitizing properties. • Reduced protein reactivity and dendritic cell activation. • Reduced skin sensitizing potency in local lymph node assay (LLNA). • Negligible allergy induction risk under hair dye usage conditions

  16. Introduction of a tryptophan side chain into subsite +1 enhances transglycosylation activity of a GH-18 chitinase from Arabidopsis thaliana, AtChiC

    DEFF Research Database (Denmark)

    Umemoto, Naoyuki; Ohnuma, Takayuki; Mizuhara, Mamiko

    2013-01-01

    A tryptophan side chain was introduced into subsite +1 of family GH-18 (class V) chitinases from Nicotiana tabacum and Arabidopsis thaliana (NtChiV and AtChiC, respectively) by the mutation of a glycine residue to tryptophan (G74W-NtChiV and G75W-AtChiC). The specific activity toward glycol chitin...... of the two mutant enzymes was 70-71% of that of the wild type. Using chitin oligosaccharides, (GlcNAc)(n) (n = 4, 5 and 6), as the substrates, we found the transglycosylation reaction to be significantly enhanced in G74W-NtChiV and G75W-AtChiC when compared with the corresponding wild-type enzymes....... The introduced tryptophan side chain might protect the oxazolinium ion intermediate from attack by a nucleophilic water molecule. The enhancement of transglycosylation activity was much more distinct in G75W-AtChiC than in G74W-NtChiV. Nuclear magnetic resonance titration experiments using the inactive double...

  17. Succinimide Formation from an NGR-Containing Cyclic Peptide: Computational Evidence for Catalytic Roles of Phosphate Buffer and the Arginine Side Chain

    Directory of Open Access Journals (Sweden)

    Ryota Kirikoshi

    2017-02-01

    Full Text Available The Asn-Gly-Arg (NGR motif and its deamidation product isoAsp-Gly-Arg (isoDGR have recently attracted considerable attention as tumor-targeting ligands. Because an NGR-containing peptide and the corresponding isoDGR-containing peptide target different receptors, the spontaneous NGR deamidation can be used in dual targeting strategies. It is well known that the Asn deamidation proceeds via a succinimide derivative. In the present study, we computationally investigated the mechanism of succinimide formation from a cyclic peptide, c[CH2CO-NGRC]-NH2, which has recently been shown to undergo rapid deamidation in a phosphate buffer. An H2PO4− ion was explicitly included in the calculations. We employed the density functional theory using the B3LYP functional. While geometry optimizations were performed in the gas phase, hydration Gibbs energies were calculated by the SM8 (solvation model 8 continuum model. We have found a pathway leading to the five-membered ring tetrahedral intermediate in which both the H2PO4− ion and the Arg side chain act as catalyst. This intermediate, once protonated at the NH2 group on the five-membered ring, was shown to easily undergo NH3 elimination leading to the succinimide formation. This study is the first to propose a possible catalytic role for the Arg side chain in the NGR deamidation.

  18. Evidence for side-chain π-delocalization in a planar substituted benzene: an experimental and theoretical charge density study on 2,5-dimethoxybenzaldehyde thiosemicarbazone.

    Science.gov (United States)

    Farrugia, Louis J; Khalaji, Aliakbar Dehno

    2011-11-17

    The charge density in 2,5-dimethoxybenzaldehyde thiosemicarbazone (1) has been studied experimentally using Mo-K(α) X-ray diffraction at 100 K, and by theory using DFT calculations at the B3LYP/6-311++G(2d,2p) level. The quantum theory of atoms in molecules (QTAIM) was used to investigate the extent of π-delocalization in the thioamide side-chain, which is virtually coplanar with the benzene ring. The experimental and theoretical ellipticity profiles along the bond paths were in excellent agreement, and showed that some of the formal single bonds in the side-chain have significant π-bond character. This view was supported by the magnitudes of the topological bond orders and by the delocalization indices δ(Ω(A), Ω(B)). An orbital decomposition of δ(Ω(A), Ω(B)) demonstrated that there was significant π-character in all the interchain non-H chemical bonds. On the other hand, the source function referenced at the interchain bond critical points could not provide any evidence for π-delocalization, showing instead only limited σ-delocalization between nearest neighbors. Overall, the topological evidence and the atomic graphs of the oxygen atoms did not provide convincing evidence for π-delocalization involving the methoxy substituents.

  19. Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C61-butyric acid methyl ester and its bis-adduct

    International Nuclear Information System (INIS)

    Akaike, Kouki; Kanai, Kaname; Ouchi, Yukio; Seki, Kazuhiko

    2013-01-01

    Highlights: ► Electronic structure of spin-coated films of PCBM and bis-PCBM was investigated. ► Ionization energy and electron affinity of bis-PCBM are smaller than those of PCBM. ► Electron donation from the side chain to C 60 -backbone raises the HOMO and LUMO. ► Open circuit voltages of PCBM-based solar cells relates to electron affinities. - Abstract: We investigated the electronic structure of spin-coated films of two soluble fullerenes; [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and its bis-adduct (bis-PCBM) using ultraviolet photoelectron spectroscopy, inverse photoemission spectroscopy and molecular orbital calculations. The ionization energy and electron affinity of spin-coated films of bis-PCBM were determined to be 6.01 eV and 3.4 eV, respectively. Analysis of electron density suggested the stronger electron donation from the two side chains to fullerene-backbone in a bis-PCBM molecule, compared with PCBM. The electron donation raises the energies of the frontier orbitals of bis-PCBM, which mainly consist of π-orbitals of fullerene-backbone. As a result, the ionization energy and electron affinity of bis-PCBM are smaller than those of PCBM. Moreover, we also concluded that the larger open circuit voltage observed for bis-PCBM based organic photovoltaics was explained by the higher-lying unoccupied molecular orbital of bis-PCBM

  20. Regioselectively nucleus and/or side-chain fluorinated 2-(Phenanthryl)propionic acids by an effective combination of radical and organometallic chemistry.

    Science.gov (United States)

    Ricci, Giacomo; Ruzziconi, Renzo

    2005-01-21

    Regioselectively nucleus and/or side-chain fluorinated 2-(phenanthr-1-yl)- and 2-(phenanthr-2-yl)propionic acids 1-5 were prepared using phenanthren-1(2H)-ones 6a-c as key intermediates. Thus, ethyl 2-(fluorophenanthryl)propionates 11 were obtained in good yields by Reformatsky reaction of 6a-c with ethyl 2-bromopropionate followed by dehydratation and DDQ-promoted aromatization of the resulting beta-hydroxyesters. Side-chain alkyl 2-hydroxy-2-(phenanthr-1-yl)propionates 14 were obtained by bromine/lithium permutation of dihydrophenanthryl bromides 12a-c with butyllithium followed by quenching of the lithiated intermediates with methyl pyruvate or ethyl 3,3,3-trifluoropyruvate and subsequent DDQ-promoted aromatization. The alkyl 2-hydroxy-2-(phenanthr-1-yl)propionates 25 were prepared by reacting 8-bromo-1,3-difluorophenanthrene 24 with butyllithium for 10 seconds at -110 degrees C and subsequent addition of the suitable pyruvate to the lithiated intermediates. Alkyl 2-hydroxy-2-(phenanthr-2-yl)propionates 26 and 29 were suitably obtained by site-selective metalation of 1,3-difluorophenanthrene 28 and the bromophenanthrene 24, respectively, with LDA followed by quenching of the metalated intermediates with the suitable alkyl pyruvate. Fluorination of the above alpha-hydroxypropionates with DAST, followed by the alkaline hydrolysis, allowed the expected 2-(phenanthryl)propionic acids 1-5 to be obtained in satisfactory overall yields.

  1. Synthesis and evaluation of new long alkyl side chain acetamide, isoxazolidine and isoxazoline derivatives as corrosion inhibitors

    International Nuclear Information System (INIS)

    Yildirim, A.; Cetin, M.

    2008-01-01

    2-(Alkylsulfanyl)-N-(pyridin-2-yl) acetamide derivatives were synthesized via amidation reaction of acyl chlorides bearing S atom in the long chain with 2-aminopyridine. Derivatives of isoxazolidine and isoxazoline were synthesized through 1,3-dipolar cycloaddition reactions with three different long chain alkenes containing O or S as hetero atoms and C,N-diphenyl nitrone or benzonitrile-N-oxide, respectively. Synthesized compounds were characterized with their FT-IR, 1 H NMR spectra and then their physical properties and corrosion prevention efficiencies were investigated. All compounds were tested with steel coupons in acidic medium by gravimetric method, and also some of them were tested with steel stripe in paraffin based mineral oil medium via standard method. Acidic test was done with a medium concentration of 2 M HCl for 20 h at room temperature. Mineral oil was used and the test in this medium was done at 60 deg. C constant temperature but varying time from 42 to 63 h. The best inhibition was generally obtained at 50 ppm inhibitor concentration in the acidic medium. All tested inhibitors except two of them in oil medium also showed promising inhibition efficiencies

  2. Roles of head group architecture and side chain length on colorimetric response of polydiacetylene vesicles to temperature, ethanol and pH.

    Science.gov (United States)

    Charoenthai, Nipaphat; Pattanatornchai, Thanutpon; Wacharasindhu, Sumrit; Sukwattanasinitt, Mongkol; Traiphol, Rakchart

    2011-08-15

    In this contribution, we report the relationship between molecular structures of polydiacetylene (PDA) vesicles, fabricated by using three monomers, 10,12-tricosadiynoic acid (TCDA), 10,12-pentacosadiynoic acid (PCDA) and N-(2-aminoethyl)pentacosa-10,12-diynamide (AEPCDA), and their color-transition behaviors. The modification of side chain length and head group of the PDA vesicles strongly affects the colorimetric response to temperature, ethanol and pH. A shorter side chain of poly(TCDA) yields weaker inter- and intra-chain dispersion interactions in the bilayers compared to the system of poly(PCDA), which in turn results in a faster color transition upon exposure to all stimuli. A change of head group in poly(AEPCDA) slightly reduces the transition temperature. Interestingly, the colorimetric response of poly(AEPCDA) vesicles to the addition of ethanol is found to occur in a two-step fashion while the response of poly(PCDA) vesicles takes place in a one-step process. The amount of ethanol required for inducing complete color-transition of poly(AEPCDA) vesicles is also much higher, about 87% v/v. The increase of pH to ~9 and ~10 causes a color-transition of poly(TCDA) and poly(PCDA) vesicles, respectively. The poly(AEPCDA) vesicles, on the other hand, change color upon decreasing pH to ~0. The colorimetric response also occurs in a multi-step fashion. These discrepancies are attributed to the architecture of surface layers of poly(AEPCDA), constituting amine and amide groups separated by ethyl linkers. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Oxidative cleavage of the octyl side chain of 1-(3,4-dichlorobenzyl)-5-octylbiguanide (OPB-2045) in rat and dog liver preparations.

    Science.gov (United States)

    Umehara, K; Kudo, S; Hirao, Y; Morita, S; Uchida, M; Odomi, M; Miyamoto, G

    2000-08-01

    The metabolism of 1-(3,4-dichlorobenzyl)-5-octylbiguanide (OPB-2045), a new potent biguanide antiseptic, was investigated using rat and dog liver preparations to elucidate the mechanism of OPB-2045 metabolite formation, in which the octyl side chain is reduced to four, five, or six carbon atoms. Chemical structures of metabolites were characterized by 1H NMR, fast atom bombardment/mass spectrometry, and liquid chromatography/electrospray ionization-tandem mass spectrometry. Three main metabolites were observed during incubation of OPB-2045 with rat liver S9: 2-octanol (M-1), 3-octanol (M-2), and 4-octanol (M-3). In the incubation of OPB-2045 with dog liver S9, eight metabolites were observed, seven of which being M-1, M-2, M-3, 2-octanone (M-4), threo-2,3-octandiol (M-5), erythro-2,3-octandiol (M-6), and 1,2-octandiol (M-7). M-5 and M-6 were further biotransformed to a ketol derivative and C-C bond cleavage metabolite (hexanoic acid derivative), an in vivo end product, in the incubation with dog liver microsomes. The reactions required NADPH as a cofactor and were significantly inhibited by the various inhibitors of cytochrome P450 (i.e., CO, n-octylamine, SKF 525-A, metyrapone, and alpha-naphthoflavone). The results indicate that the degraded products of OPB-2045 are produced by C-C bond cleavage after monohydroxylation, dihydroxylation, and ketol formation at the site of the octyl side chain with possible involvement of cytochrome P450 systems. This aliphatic C-C bond cleavage by sequential oxidative reactions may play an important role in the metabolism of other drugs or endogenous compounds that possess aliphatic chains.

  4. Postprandial glycaemic and insulinaemic responses in adults after consumption of dairy desserts and pound cakes containing short-chain fructo-oligosaccharides used to replace sugars.

    Science.gov (United States)

    Lecerf, J M; Clerc, E; Jaruga, A; Wagner, A; Respondek, F

    2015-01-01

    The present studies aimed to evaluate the glycaemic and insulinaemic responses, in healthy adults, to short-chain fructo-oligosaccharides (scFOS) from sucrose used to replace sugars in foods. Two study populations aged 18-50 years were recruited and they consumed dairy desserts or pound cakes containing either standard sugar content or scFOS to replace 30 % of the sugar content. For each study, the two products were tested once under a double-blind and cross-over design with at least 7 d between the two tests. Glucose and insulin were measured using standard methods in blood samples collected with a venous catheter for 120 min during a kinetic test. For the dairy desserts, replacing 30 % of the sugars with scFOS significantly reduced postprandial glycaemic (AUC0-120 min; P = 0·020) and insulinaemic (AUC0-120 min; P = 0·003) responses. For the pound cakes, the glycaemic response was not altered (AUC0-120 min; P =  0·322) while the insulinaemic response tended to be lower (AUC0-120 min; P = 0·067). This study showed that scFOS can be used to replace sugars with the benefit of lowering the postprandial glycaemic response without increasing the insulinaemic response. The effect might be modulated by other parameters (e.g. fat content) of the food matrices.

  5. Molecular Design for Preparation of Hexagonal-Ordered Porous Films Based on Side-chain Type Liquid-Crystalline Star Polymer.

    Science.gov (United States)

    Naka, Yumiko; Takayama, Hiromu; Koyama, Teruhisa; Le, Khoa V; Sasaki, Takeo

    2018-05-02

    Fabrication of regularly porous films by the breath-figure method has attracted much attention. The simple, low-cost technique uses the condensation of water droplets to produce these structures, but the phenomenon itself is complex, requiring control over many interacting parameters that change throughout the process. Developing a unified understanding for the molecular design of polymers to prepare ordered porous films is challenging, but required for further advancements. In this article, the effects of the chemical structure of polymers in the breath-figure technique were systematically explored using side-chain type liquid-crystalline (LC) star polymers. The formation of porous films was affected by the structure of the polymers. Although the entire film surface of poly(11-[4-(4-cyanobiphenyl)oxy]undecyl methacrylate) (P11CB) had a hexagonal ordered porous structure over a certain Mn value, regularly arranged holes did not easily form in poly(methyl methacrylate) (PMMA), even though the main chain of PMMA is similar to that of P11CB. Comparing P11CB and poly(11-[(1,1'-biphenyl)-4-yloxy]undecyl methacrylate) (P11B) (P11CB without cyano groups) showed that the local polar groups in hydrophobic polymers promoted the formation of ordered porous films. No holes formed in poly(4-cyanobiphenyl methacrylate) (P0CB) (P11CB without alkyl spacers) films due to its hydrophilicity. The introduction of alkyl chains in P0CB allowed the preparation of honeycomb-structured films by increasing the internal tension. However, alkyl chains in the side chain alone did not result in a porous structure, as in the case of poly(11-[(1,1'-biphenyl)-4-yloxy]undecyl methacrylate) (P11). Aromatic rings are also required to increase the Tg and improve film formability. In the present study, suitable molecular designs of polymers were found, specifically hydrophobic polymers with local polar groups, to form a regularly porous structure. Development of clear guidelines for the molecular

  6. Alkyl side chain on the 1-methylimidazolium ring of countercation modulating thermal and magnetic properties of metal-dithiolene complexes

    Science.gov (United States)

    Duan, Hai-Bao; Yu, Shan-Shan; Cai, Ying; Zhang, Hui

    2015-05-01

    Two low-dimensional ion-pair compounds [1,5-bis(1-methylimidazolium)pentane][Ni(mnt)2]2 (1) and [1,9-bis(1-methylimidazolium)nonane][Ni(mnt)2]2 (2) (mnt2- = maleonitriledithiolate) were designed and synthesized. The cations and anions formed mixed column along the crystallographic a-axis direction in the crystal of 1·0.5DMF. Two compounds display different thermal and magnetic behaviors. Multi-step solid to solid state phase transition was observed for 1 by DSC. 1 exhibits weak paramagnetism over the temperature range of 2-400 K and 2 shows spin gap in the low-temperature phase. Thus by changing of the alky chain length of the counter-cation allows the modulation thermal and magnetic behaviors for such system.

  7. A novel α-galactosidase from Fusarium oxysporum and its application in determining the structure of the gum arabic side chain.

    Science.gov (United States)

    Maruta, Akiho; Yamane, Mirei; Matsubara, Midori; Suzuki, Shiho; Nakazawa, Masami; Ueda, Mitsuhiro; Sakamoto, Tatsuji

    2017-08-01

    We previously reported that Fusarium oxysporum 12S produces two bifunctional proteins, FoAP1 and FoAP2, with α-d-galactopyranosidase (GPase) and β-l-arabinopyranosidase (APase) activities. The aim of this paper was to purify a third GPase, FoGP1, from culture supernatant of F. oxysporum 12S, to characterize it, and to determine its mode of action towards gum arabic. A cDNA encoding FoGP1 was cloned and the protein was overexpressed in Escherichia coli. Module sequence analysis revealed the presence of a GH27 domain in FoGP1. The recombinant enzyme (rFoGP1) showed a GPase/APase activity ratio of 330, which was quite different from that of FoAP1 (1.7) and FoAP2 (0.2). Among the natural substrates tested, rFoGP1 showed the highest activity towards gum arabic. In contrast to other well-characterized GPases, rFoGP1 released a small amount of galactose from α-galactosyl oligosaccharides such as raffinose and exhibited no activity toward galactomannans, which are highly substituted with α-galactosyl side chains. This indicated that FoGP1 is an unusual type of GPase. rFoGP1 released 30% of the total galactose from gum arabic, suggesting the existence of a large number of α-galactosyl residues at the non-reducing ends of gum arabic side chains. Together, rFoGP1 and α-l-arabinofuranosidase released four times more arabinose than α-l-arabinofuranosidase acting alone. This suggested that a large number of α-l-arabinofuranosyl residues is capped by α-galactosyl residues. 1 H NMR experiments revealed that rFoGP1 hydrolyzed the α-1,3-galactosidic linkage within the side chain structure of [α-d-Galp-(1→3)-α-l-Araf-(1→] in gum arabic. In conclusion, rFoGP1 is highly active toward α-1,3-galactosyl linkages but negligibly or not active toward α-1,6-galactosyl linkages. The novel FoGP1 might be used to modify the physical properties of gum arabic, which is an industrially important polysaccharide used as an emulsion stabilizer and coating agent. Copyright © 2017

  8. Effects of Odd–Even Side Chain Length of Alkyl-Substituted Diphenylbithiophenes on First Monolayer Thin Film Packing Structure

    KAUST Repository

    Akkerman, Hylke B.

    2013-07-31

    Because of their preferential two-dimensional layer-by-layer growth in thin films, 5,5′bis(4-alkylphenyl)-2,2′-bithiophenes (P2TPs) are model compounds for studying the effects of systematic chemical structure variations on thin-film structure and morphology, which in turn, impact the charge transport in organic field-effect transistors. For the first time, we observed, by grazing incidence X-ray diffraction (GIXD), a strong change in molecular tilt angle in a monolayer of P2TP, depending on whether the alkyl chain on the P2TP molecules was of odd or even length. The monolayers were deposited on densely packed ultrasmooth self-assembled alkane silane modified SiO2 surfaces. Our work shows that a subtle change in molecular structure can have a significant impact on the molecular packing structure in thin film, which in turn, will have a strong impact on charge transport of organic semiconductors. This was verified by quantum-chemical calculations that predict a corresponding odd-even effect in the strength of the intermolecular electronic coupling. © 2013 American Chemical Society.

  9. Effects of Odd–Even Side Chain Length of Alkyl-Substituted Diphenylbithiophenes on First Monolayer Thin Film Packing Structure

    KAUST Repository

    Akkerman, Hylke B.; Mannsfeld, Stefan C. B.; Kaushik, Ananth P.; Verploegen, Eric; Burnier, Luc; Zoombelt, Arjan P.; Saathoff, Jonathan D.; Hong, Sanghyun; Atahan-Evrenk, Sule; Liu, Xueliang; Aspuru-Guzik, Alá n; Toney, Michael F.; Clancy, Paulette; Bao, Zhenan

    2013-01-01

    Because of their preferential two-dimensional layer-by-layer growth in thin films, 5,5′bis(4-alkylphenyl)-2,2′-bithiophenes (P2TPs) are model compounds for studying the effects of systematic chemical structure variations on thin-film structure and morphology, which in turn, impact the charge transport in organic field-effect transistors. For the first time, we observed, by grazing incidence X-ray diffraction (GIXD), a strong change in molecular tilt angle in a monolayer of P2TP, depending on whether the alkyl chain on the P2TP molecules was of odd or even length. The monolayers were deposited on densely packed ultrasmooth self-assembled alkane silane modified SiO2 surfaces. Our work shows that a subtle change in molecular structure can have a significant impact on the molecular packing structure in thin film, which in turn, will have a strong impact on charge transport of organic semiconductors. This was verified by quantum-chemical calculations that predict a corresponding odd-even effect in the strength of the intermolecular electronic coupling. © 2013 American Chemical Society.

  10. Circulating N-Linked Glycoprotein Side-Chain Biomarker, Rosuvastatin Therapy, and Incident Cardiovascular Disease: An Analysis From the JUPITER Trial.

    Science.gov (United States)

    Akinkuolie, Akintunde O; Glynn, Robert J; Padmanabhan, Latha; Ridker, Paul M; Mora, Samia

    2016-07-13

    GlycA, a novel protein glycan biomarker of N-acetyl side chains of acute-phase proteins, was recently associated with incident cardiovascular disease (CVD) in healthy women. Whether GlycA predicts CVD events in the setting of statin therapy in men and women without CVD but with evidence of chronic inflammation is unknown. In the Justfication for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial (NCT00239681), participants with low-density lipoprotein cholesterol 0.20). In the JUPITER trial, increased levels of GlycA were associated with an increased risk of CVD events independent of traditional risk factors and hsCRP. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00239681. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  11. Characterizing hydrophobicity of amino acid side chains in a protein environment via measuring contact angle of a water nanodroplet on planar peptide network.

    Science.gov (United States)

    Zhu, Chongqin; Gao, Yurui; Li, Hui; Meng, Sheng; Li, Lei; Francisco, Joseph S; Zeng, Xiao Cheng

    2016-11-15

    Hydrophobicity of macroscopic planar surface is conventionally characterized by the contact angle of water droplets. However, this engineering measurement cannot be directly extended to surfaces of proteins, due to the nanometer scale of amino acids and inherent nonplanar structures. To measure the hydrophobicity of side chains of proteins quantitatively, numerous parameters were developed to characterize behavior of hydrophobic solvation. However, consistency among these parameters is not always apparent. Herein, we demonstrate an alternative way of characterizing hydrophobicity of amino acid side chains in a protein environment by constructing a monolayer of amino acids (i.e., artificial planar peptide network) according to the primary and the β-sheet secondary structures of protein so that the conventional engineering measurement of the contact angle of a water droplet can be brought to bear. Using molecular dynamics simulations, contact angles θ of a water nanodroplet on the planar peptide network, together with excess chemical potentials of purely repulsive methane-sized Weeks-Chandler-Andersen solute, are computed. All of the 20 types of amino acids and the corresponding planar peptide networks are studied. Expectedly, all of the planar peptide networks with nonpolar amino acids are hydrophobic due to θ [Formula: see text] 90°, whereas all of the planar peptide networks of the polar and charged amino acids are hydrophilic due to θ [Formula: see text] 90°. Planar peptide networks of the charged amino acids exhibit complete-wetting behavior due to θ [Formula: see text] 0°. This computational approach for characterization of hydrophobicity can be extended to artificial planar networks of other soft matter.

  12. Functionalized PHB granules provide the basis for the efficient side-chain cleavage of cholesterol and analogs in recombinant Bacillus megaterium.

    Science.gov (United States)

    Gerber, Adrian; Kleser, Michael; Biedendieck, Rebekka; Bernhardt, Rita; Hannemann, Frank

    2015-07-29

    Cholesterol, the precursor of all steroid hormones, is the most abundant steroid in vertebrates and exhibits highly hydrophobic properties, rendering it a difficult substrate for aqueous microbial biotransformations. In the present study, we developed a Bacillus megaterium based whole-cell system that allows the side-chain cleavage of this sterol and investigated the underlying physiological basis of the biocatalysis. CYP11A1, the side-chain cleaving cytochrome P450, was recombinantly expressed in the Gram-positive soil bacterium B. megaterium combined with the required electron transfer proteins. By applying a mixture of 2-hydroxypropyl-β-cyclodextrin and Quillaja saponin as solubilizing agents, the zoosterols cholesterol and 7-dehydrocholesterol, as well as the phytosterol β-sitosterol could be efficiently converted to pregnenolone or 7-dehydropregnenolone. Fluorescence-microscopic analysis revealed that cholesterol accumulates in the carbon and energy storage-serving poly(3-hydroxybutyrate) (PHB) bodies and that the membrane proteins CYP11A1 and its redox partner adrenodoxin reductase (AdR) are likewise localized to their surrounding phospholipid/protein monolayer. The capacity to store cholesterol was absent in a mutant strain devoid of the PHB-producing polymerase subunit PhaC, resulting in a drastically decreased cholesterol conversion rate, while no effect on the expression of the recombinant proteins could be observed. We established a whole-cell system based on B. megaterium, which enables the conversion of the steroid hormone precursor cholesterol to pregnenolone in substantial quantities. We demonstrate that the microorganism's PHB granules, aggregates of bioplastic coated with a protein/phospholipid monolayer, are crucial for the high conversion rate by serving as substrate storage. This microbial system opens the way for an industrial conversion of the abundantly available cholesterol to any type of steroid hormones, which represent one of the

  13. Hybrid bulk heterojunction solar cells based on poly(3-hexylthiophene) and ZnO nanoparticles modified by side-chain functional polythiophenes

    International Nuclear Information System (INIS)

    Li, Fan; Du, Yanhui; Chen, Yiwang

    2012-01-01

    We report the investigation of the hybrid bulk heterojunction solar cells based on the blend of poly(3-hexylthiophene) (P3HT) and ZnO nanoparticles modified by side-chain thiol functional poly(3-thiophenehexanethiol) (P3HT-SH). Grafting of P3HT-SH onto ZnO nanoparticles can promote the dispersion of ZnO nanoparticles within P3HT matrix and facilitate electron injection process into ZnO nanoparticles, resulting in a more efficient photoinduced charge transfer than that in simple physical mixture of P3HT and non-modified ZnO nanoparticles (P3HT/ZnO). Furthermore, the performance of hybrid photovoltaic device based on P3HT/P3HT-SH-modified ZnO blend exhibits an improved device efficiency compared with P3HT/ZnO even before thermal treatment. After being annealed at 80 °C, the P3HT/P3HT-SH-modified ZnO device shows the power conversion efficiency as high as 0.68%, with the short-circuit current density of 1.89 mA/cm 2 , the open-circuit voltage of 0.599 V and a fill factor of 60.5% under AM 1.5 G illumination with 100 mW/cm 2 light intensity. - Highlights: ► Hybrid solar cells based on poly(3-hexylthiophene) and modified ZnO nanoparticles ► ZnO nanoparticles modified by side-chain functional polythiophenes ► Uniform dispersion and intimate contact between polymers and nanoparticles ► Efficient charge transfer leading to the improvement of device efficiency

  14. Activity of 3-Ketosteroid 9α-Hydroxylase (KshAB) Indicates Cholesterol Side Chain and Ring Degradation Occur Simultaneously in Mycobacterium tuberculosis*

    Science.gov (United States)

    Capyk, Jenna K.; Casabon, Israël; Gruninger, Robert; Strynadka, Natalie C.; Eltis, Lindsay D.

    2011-01-01

    Mycobacterium tuberculosis (Mtb), a significant global pathogen, contains a cholesterol catabolic pathway. Although the precise role of cholesterol catabolism in Mtb remains unclear, the Rieske monooxygenase in this pathway, 3-ketosteroid 9α-hydroxylase (KshAB), has been identified as a virulence factor. To investigate the physiological substrate of KshAB, a rhodococcal acyl-CoA synthetase was used to produce the coenzyme A thioesters of two cholesterol derivatives: 3-oxo-23,24-bisnorchol-4-en-22-oic acid (forming 4-BNC-CoA) and 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid (forming 1,4-BNC-CoA). The apparent specificity constant (kcat/Km) of KshAB for the CoA thioester substrates was 20–30 times that for the corresponding 17-keto compounds previously proposed as physiological substrates. The apparent KmO2 was 90 ± 10 μm in the presence of 1,4-BNC-CoA, consistent with the value for two other cholesterol catabolic oxygenases. The Δ1 ketosteroid dehydrogenase KstD acted with KshAB to cleave steroid ring B with a specific activity eight times greater for a CoA thioester than the corresponding ketone. Finally, modeling 1,4-BNC-CoA into the KshA crystal structure suggested that the CoA moiety binds in a pocket at the mouth of the active site channel and could contribute to substrate specificity. These results indicate that the physiological substrates of KshAB are CoA thioester intermediates of cholesterol side chain degradation and that side chain and ring degradation occur concurrently in Mtb. This finding has implications for steroid metabolites potentially released by the pathogen during infection and for the design of inhibitors for cholesterol-degrading enzymes. The methodologies and rhodococcal enzymes used to generate thioesters will facilitate the further study of cholesterol catabolism. PMID:21987574

  15. A novel branched side-chain-type sulfonated polyimide membrane with flexible sulfoalkyl pendants and trifluoromethyl groups for vanadium redox flow batteries

    Science.gov (United States)

    Li, Jinchao; Liu, Suqin; He, Zhen; Zhou, Zhi

    2017-04-01

    A novel branched side-chain-type sulfonated polyimide (6F-s-bSPI) membrane with accessible branching agents of melamine, hydrophobic trifluoromethyl groups (sbnd CF3), and flexible sulfoalkyl pendants is prepared by a high-temperature polycondensation and post-sulfonation method for use in vanadium redox flow batteries (VRFBs). The chemical structure of the 6F-s-bSPI membrane is confirmed by ATR-FTIR and 1H NMR spectra. The physico-chemical properties of the as-prepared 6F-s-bSPI membrane are systematically investigated and found to be strongly related to the specially designed structure. The 6F-s-bSPI membrane offers a reduced cost and possesses a significantly lowered vanadium ion permeability (1.18 × 10-7 cm2 min-1) compared to the linear SPI (2.25 × 10-7 cm2 min-1) and commercial Nafion 115 (1.36 × 10-6 cm2 min-1) membranes, prolonging the self-discharge duration of the VRFBs. In addition, the VRFB assembled with a 6F-s-bSPI membrane shows higher coulombic (98.3%-99.7%) and energy efficiencies (88.4%-66.12%) than that with a SPI or Nafion 115 membrane under current densities ranging from 20 to 100 mA cm-2. Moreover, the VRFB with a 6F-s-bSPI membrane delivers a stable cycling performance over 100 cycles with no decline in coulombic and energy efficiencies. These results show that the branched side-chain-type structure is a promising design to prepare excellent proton conductive membranes.

  16. Composition of the epicuticular waxes coating the adaxial side of Phyllostachys aurea leaves: Identification of very-long-chain primary amides.

    Science.gov (United States)

    Racovita, Radu C; Jetter, Reinhard

    2016-10-01

    The present study presents comprehensive chemical analyses of cuticular wax mixtures of the bamboo Phyllostachys aurea. The epicuticular and intracuticular waxes were sampled selectively from the adaxial side of leaves on young and old plants and investigated by gas chromatography-mass spectrometry and flame ionization detection. The epi- and intracuticular layers on young and old leaves had wax loads ranging from 1.7 μg/cm(2) to 1.9 μg/cm(2). Typical very-long-chain aliphatic wax constituents were found with characteristic chain length patterns, including alkyl esters (primarily C48), alkanes (primarily C29), fatty acids (primarily C28 and C16), primary alcohols (primarily C28) and aldehydes (primarily C30). Alicyclic wax components were identified as tocopherols and triterpenoids, including substantial amounts of triterpenoid esters. Alkyl esters, alkanes, fatty acids and aldehydes were found in greater amounts in the epicuticular layer, while primary alcohols and most terpenoids accumulated more in the intracuticular wax. Alkyl esters occurred as mixtures of metamers, combining C20 alcohol with various acids into shorter ester homologs (C36C40), and a wide range of alcohols with C22 and C24 acids into longer esters (C42C52). Primary amides were identified, with a characteristic chain length profile peaking at C30. The amides were present exclusively in the epicuticular layer and thus at or near the surface, where they may affect plant-herbivore or plant-pathogen interactions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. A chemical approach for site-specific identification of NMR signals from protein side-chain NH{sub 3}{sup +} groups forming intermolecular ion pairs in protein–nucleic acid complexes

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Kurtis M. [University of Texas Health Science Center at Houston, Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine (United States); Nguyen, Dan; Esadze, Alexandre; Zandrashvili, Levani [University of Texas Medical Branch, Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics (United States); Gorenstein, David G. [University of Texas Health Science Center at Houston, Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine (United States); Iwahara, Junji, E-mail: juiwahar@utmb.edu, E-mail: j.iwahara@utmb.edu [University of Texas Medical Branch, Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics (United States)

    2015-05-15

    Protein–nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein–DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH{sub 3}{sup +} groups forming the intermolecular ion pairs. A characteristic change in their {sup 1}H and {sup 15}N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain {sup 15}N and DNA phosphorodithiaote {sup 31}P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein–RNA complexes as well.

  18. A chemical approach for site-specific identification of NMR signals from protein side-chain NH3+ groups forming intermolecular ion pairs in protein–nucleic acid complexes

    International Nuclear Information System (INIS)

    Anderson, Kurtis M.; Nguyen, Dan; Esadze, Alexandre; Zandrashvili, Levani; Gorenstein, David G.; Iwahara, Junji

    2015-01-01

    Protein–nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein–DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH 3 + groups forming the intermolecular ion pairs. A characteristic change in their 1 H and 15 N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain 15 N and DNA phosphorodithiaote 31 P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein–RNA complexes as well

  19. Why Public Employment Services Always Fail. Double-sided Asymmetric Information and the Replacement of Low-skill Workers in six European Countries

    DEFF Research Database (Denmark)

    Larsen, Christian Albrekt; Vesan, Patrik

    2012-01-01

    It has been a general finding across Europe that very few job matches are facilitated by public employment services (PES).The article explains this failure by highlighting the existence of a double-sided asymmetric information problem on the labour market. It is argued that although a PES...

  20. Activity of 3-ketosteroid 9α-hydroxylase (KshAB) indicates cholesterol side chain and ring degradation occur simultaneously in Mycobacterium tuberculosis.

    Science.gov (United States)

    Capyk, Jenna K; Casabon, Israël; Gruninger, Robert; Strynadka, Natalie C; Eltis, Lindsay D

    2011-11-25

    Mycobacterium tuberculosis (Mtb), a significant global pathogen, contains a cholesterol catabolic pathway. Although the precise role of cholesterol catabolism in Mtb remains unclear, the Rieske monooxygenase in this pathway, 3-ketosteroid 9α-hydroxylase (KshAB), has been identified as a virulence factor. To investigate the physiological substrate of KshAB, a rhodococcal acyl-CoA synthetase was used to produce the coenzyme A thioesters of two cholesterol derivatives: 3-oxo-23,24-bisnorchol-4-en-22-oic acid (forming 4-BNC-CoA) and 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid (forming 1,4-BNC-CoA). The apparent specificity constant (k(cat)/K(m)) of KshAB for the CoA thioester substrates was 20-30 times that for the corresponding 17-keto compounds previously proposed as physiological substrates. The apparent K(m)(O(2)) was 90 ± 10 μM in the presence of 1,4-BNC-CoA, consistent with the value for two other cholesterol catabolic oxygenases. The Δ(1) ketosteroid dehydrogenase KstD acted with KshAB to cleave steroid ring B with a specific activity eight times greater for a CoA thioester than the corresponding ketone. Finally, modeling 1,4-BNC-CoA into the KshA crystal structure suggested that the CoA moiety binds in a pocket at the mouth of the active site channel and could contribute to substrate specificity. These results indicate that the physiological substrates of KshAB are CoA thioester intermediates of cholesterol side chain degradation and that side chain and ring degradation occur concurrently in Mtb. This finding has implications for steroid metabolites potentially released by the pathogen during infection and for the design of inhibitors for cholesterol-degrading enzymes. The methodologies and rhodococcal enzymes used to generate thioesters will facilitate the further study of cholesterol catabolism.

  1. Catalyst-Directed Diastereoselective Isomerization of Allylic Alcohols for the Stereoselective Construction of C(20) in Steroid Side Chains: Scope and Topological Diversification.

    Science.gov (United States)

    Li, Houhua; Mazet, Clément

    2015-08-26

    The stereoselective construction of C20 in steroidal derivatives by a highly diastereoselective Ir-catalyzed isomerization of primary allylic alcohols is reported. A key aspect of this strategy is a straightforward access to geometrically pure steroidal enol tosylate and enol triflate intermediates for subsequent high yielding stereoretentive Negishi cross-coupling reactions to allow structural diversity to be introduced. A range of allylic alcohols participates in the diastereoselective isomerization under the optimized reaction conditions. Electron-rich and electron-poor aryl or heteroaryl substituents are particularly well-tolerated, and the stereospecific nature of the reaction provides indifferently access to the natural C20-(R) and unnatural C20-(S) configurations. Alkyl containing substrates are more challenging as they affect regioselectivity of iridium-hydride insertion. A rationale for the high diastereoselectivities observed is proposed for aryl containing precursors. The scope of our method is further highlighted through topological diversification in the side chain and within the polycyclic domain of advanced and complex steroidal architectures. These findings have the potential to greatly simplify access to epimeric structural analogues of important steroid scaffolds for applications in biological, pharmaceutical, and medical sciences.

  2. Influence of the strength of the smectic order on the backbone anisotropy of side-chain liquid crystal polymers as revealed by SANS

    Science.gov (United States)

    Noirez, L.; Keller, P.; Cotton, J. P.

    1992-06-01

    It is proposed that the strength of the smectic order determines the backbone anisotropy of side-chain liquid crystal polymers. Here this strength increases with the length of the alkyl terminal group of the mesogens. Two liquid crystal polymethacrylates differing only by the mesogenic tails —OCH3 and —OC4H9 are considered. The backbone anisotropy of these polymers is measured by small angle neutron scattering (SANS) whereas the smectic order is evaluated from the intensity of the 001 Bragg peak. Il est proposé que la qualité de l'ordre smectique détermine l'anisotropie du squelette de polymères mésomorphes en peigne confinés dans les lamelles. Ici l'ordre smectique est augmenté en allongeant le groupe alkyl terminal des mésogènes. Nous étudions deux polyméthacrylates cristal liquide qui ne différent que par leurs groupes terminaux : —OCH3 et —OC4H9. L'anisotropie du squellete est mesurée par diffusion de neutrons aux petits angles tandis que l'ordre smectique est évalué à l'aide de l'intensité du pic de Bragg 001.

  3. Is buffer a good proxy for a crowded cell-like environment? A comparative NMR study of calmodulin side-chain dynamics in buffer and E. coli lysate.

    Directory of Open Access Journals (Sweden)

    Michael P Latham

    Full Text Available Biophysical studies of protein structure and dynamics are typically performed in a highly controlled manner involving only the protein(s of interest. Comparatively fewer such studies have been carried out in the context of a cellular environment that typically involves many biomolecules, ions and metabolites. Recently, solution NMR spectroscopy, focusing primarily on backbone amide groups as reporters, has emerged as a powerful technique for investigating protein structure and dynamics in vivo and in crowded "cell-like" environments. Here we extend these studies through a comparative analysis of Ile, Leu, Val and Met methyl side-chain motions in apo, Ca(2+-bound and Ca(2+, peptide-bound calmodulin dissolved in aqueous buffer or in E. coli lysate. Deuterium spin relaxation experiments, sensitive to pico- to nano-second time-scale processes and Carr-Purcell-Meiboom-Gill relaxation dispersion experiments, reporting on millisecond dynamics, have been recorded. Both similarities and differences in motional properties are noted for calmodulin dissolved in buffer or in lysate. These results emphasize that while significant insights can be obtained through detailed "test-tube" studies, experiments performed under conditions that are "cell-like" are critical for obtaining a comprehensive understanding of protein motion in vivo and therefore for elucidating the relation between motion and function.

  4. Photoinduced electron transfer involving eosin-tryptophan conjugates. Long-lived radical pair states for systems incorporating aromatic amino acid side chains

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G. II; Farahat, C.W.; Oh, C. (Boston Univ., MA (United States))

    1994-07-14

    The electron-transfer photochemistry of the covalent derivatives of the dye eosin, in which the xanthene dye is covalently attached to the amino acid L-tryptophan via the thiohydantoin derivative, the tryptophan dipeptide, and an ethyl ester derivative, has been investigated. The singlet excited state of the dye is significantly quenched on attachment of the aromatic amino acid residue. Dye triplet states are also intercepted through intramolecular interaction of excited dye and amino acid pendants. Flash photolysis experiments verify that this interaction involves electron transfer from the indole side chains of tryptophan. Rate constants for electron transfer are discussed in terms of the distance relationships for the eosin chromophore and aromatic redox sites on peptide derivatives, the pathway for [sigma]-[pi] through-bond interaction between redox sites, and the multiplicity and state of protonation for electron-transfer intermediates. Selected electron-transfer photoreactions were studied under conditions of binding of the peptide derivatives in a high molecular weight, water-soluble, globular polymer, poly(vinyl-2-pyrrolidinone). 28 refs., 4 figs., 1 tab.

  5. Amino Acid Functionalization of Doped Single-Walled Carbon Nanotubes: Effects of Dopants and Side Chains as Well as Zwitterionic Stabilizations.

    Science.gov (United States)

    Jiang, Lisha; Zhu, Chang; Fu, Yujie; Yang, Gang

    2017-04-06

    Functionalization of single-walled carbon nanotubes (SWCNTs) is necessitated in a number of conditions such as drug delivery, and here amino acid functionalization of SWCNTs is conducted within the framework of density functional theory. Functionalization efficiencies of Gly are largely determined by dopants, as a combined effect of atomic radius, electronic configuration, and distortion to SWCNTs. Different functionalization sites in Gly have divergent interaction strengths with M/SWCNTs that decline as O b > N > O a , and this trend seems almost independent of the identity of metallic dopants. B/SWCNT behaves distinctly and prefers to the N site. Dopants affect principally interaction strengths, while amino acids regulate significantly both functionalization configurations and interaction energies. Then focus is given to stabilization of zwitterionic amino acids due to enhanced interactions with the widely used zwitterionic drugs. All metallic dopants render zwitterionic Gly to be the most stable, and side chains in amino acids rather than dopants in M/SWCNTs cause more pronounced effects to zwitterionic stabilizations. Charge transfers between amino acids and M/SWCNTs are closely associated with zwitterionic stabilization effects, and different charge transfer mechanisms between M/SWCNTs and metal ions are interpreted. Thus, this work provides a comprehensive understanding of amino acid functionalization of M/SWCNTs.

  6. Fluorescence spectroscopic study of the aggregation behavior of non-cross-linked and cross-linked poly(alkylmethyldiallylammonium bromides) having decyl, octyl, and hexyl side chains in aqueous solution

    NARCIS (Netherlands)

    Wang, G.J; Engberts, J.B.F.N.

    1996-01-01

    The conformational state of a series of non-cross-linked and cross-linked poly(alkylmethyldiallylammonium bromides) bearing decyl, octyl, and hexyl side chains ((CL)-CopolC1-10, (CL)-CopolC1-8, and (CL)-CopolC1-6, respectively) in aqueous solutions were investigated by fluorescence spectroscopy

  7. Electrolytic extraction drives volatile fatty acid chain elongation through lactic acid and replaces chemical pH control in thin stillage fermentation.

    Science.gov (United States)

    Andersen, Stephen J; Candry, Pieter; Basadre, Thais; Khor, Way Cern; Roume, Hugo; Hernandez-Sanabria, Emma; Coma, Marta; Rabaey, Korneel

    2015-01-01

    Volatile fatty acids (VFA) are building blocks for the chemical industry. Sustainable, biological production is constrained by production and recovery costs, including the need for intensive pH correction. Membrane electrolysis has been developed as an in situ extraction technology tailored to the direct recovery of VFA from fermentation while stabilizing acidogenesis without caustic addition. A current applied across an anion exchange membrane reduces the fermentation broth (catholyte, water reduction: H2O + e(-) → ½ H2 + OH(-)) and drives carboxylate ions into a clean, concentrated VFA stream (anolyte, water oxidation: H2O → 2e(-) + 2 H(+) + O2). In this study, we fermented thin stillage to generate a mixed VFA extract without chemical pH control. Membrane electrolysis (0.1 A, 3.22 ± 0.60 V) extracted 28 ± 6 % of carboxylates generated per day (on a carbon basis) and completely replaced caustic control of pH, with no impact on the total carboxylate production amount or rate. Hydrogen generated from the applied current shifted the fermentation outcome from predominantly C2 and C3 VFA (64 ± 3 % of the total VFA present in the control) to majority of C4 to C6 (70 ± 12 % in the experiment), with identical proportions in the VFA acid extract. A strain related to Megasphaera elsdenii (maximum abundance of 57 %), a bacteria capable of producing mid-chain VFA at a high rate, was enriched by the applied current, alongside a stable community of Lactobacillus spp. (10 %), enabling chain elongation of VFA through lactic acid. A conversion of 30 ± 5 % VFA produced per sCOD fed (60 ± 10 % of the reactive fraction) was achieved, with a 50 ± 6 % reduction in suspended solids likely by electro-coagulation. VFA can be extracted directly from a fermentation broth by membrane electrolysis. The electrolytic water reduction products are utilized in the fermentation: OH(-) is used for pH control without added chemicals, and H2 is

  8. Testosterone stimulates progesterone production and STAR, P450 cholesterol side-chain cleavage and LH receptor mRNAs expression in hen (Gallus domesticus) granulosa cells.

    Science.gov (United States)

    Rangel, P L; Rodríguez, A; Rojas, S; Sharp, P J; Gutierrez, C G

    2009-12-01

    The chicken ovary is organized into a hierarchy of yellow yolky follicles that ovulate on successive days. Active or passive immunization of laying hens against testosterone blocks ovulation without affecting follicle development. Testosterone may play a role in pre-ovulatory follicle maturation by stimulating granulosa progesterone production. We assessed whether this stimulus is dose-related and depends on the maturity of the donor follicle, and if it does so by stimulating granulosa cell STAR, P450 cholesterol side-chain cleavage (P450scc), and LH receptor (LHCGR) mRNAs expression. Progesterone production by granulosa cells from F1, F3, and F4 follicles, cultured for 3 h without testosterone was greater in cells collected 11-14 h than 1-4 h after ovulation. These differences in progesterone production were less pronounced after granulosa cells had been cultured for 24 h. Culture of granulosa cells for 3 or 24 h with testosterone (1-100 ng/ml) stimulated progesterone production in cells collected from F4, F3, or F1 follicles 1-4, or 11-14 h after ovulation. Testosterone (0-4000 ng/ml) alone or in combination with LH (0-100 ng/ml) increased progesterone production by F1 granulosa cells, collected 1-4 and 11-14 h after ovulation and cultured for 3 h. Finally, testosterone (10 or 100 ng/ml) increased STAR, P450scc, and LHCGR mRNAs, when added to 3 h cultures of F1 granulosa cells. In conclusion, testosterone stimulates granulosa cell progesterone production in hen pre-ovulatory hierarchical follicles irrespective of maturational state, acting alone or additively with LH. We propose that testosterone promotes granulosa cell maturation to facilitate the pre-ovulatory release of LH.

  9. Sensitivity improvement for correlations involving arginine side-chain Nε/Hε resonances in multi-dimensional NMR experiments using broadband 15N 180o pulses

    International Nuclear Information System (INIS)

    Iwahara, Junji; Clore, G. Marius

    2006-01-01

    Due to practical limitations in available 15 N rf field strength, imperfections in 15 N 180 o pulses arising from off-resonance effects can result in significant sensitivity loss, even if the chemical shift offset is relatively small. Indeed, in multi-dimensional NMR experiments optimized for protein backbone amide groups, cross-peaks arising from the Arg guanidino 15 Nε (∼85 ppm) are highly attenuated by the presence of multiple INEPT transfer steps. To improve the sensitivity for correlations involving Arg Nε-Hε groups, we have incorporated 15 N broadband 180 deg. pulses into 3D 15 N-separated NOE-HSQC and HNCACB experiments. Two 15 N-WURST pulses incorporated at the INEPT transfer steps of the 3D 15 N-separated NOE-HSQC pulse sequence resulted in a ∼1.5-fold increase in sensitivity for the Arg Nε-Hε signals at 800 MHz. For the 3D HNCACB experiment, five 15 N Abramovich-Vega pulses were incorporated for broadband inversion and refocusing, and the sensitivity of Arg 1 Hε- 15 Nε- 13 Cγ/ 13 Cδ correlation peaks was enhanced by a factor of ∼1.7 at 500 MHz. These experiments eliminate the necessity for additional experiments to assign Arg 1 Hε and 15 Nε resonances. In addition, the increased sensitivity afforded for the detection of NOE cross-peaks involving correlations with the 15 Nε/ 1 Hε of Arg in 3D 15 N-separated NOE experiments should prove to be very useful for structural analysis of interactions involving Arg side-chains

  10. Observation of the side chain O-methylation of glutamic acid or aspartic acid containing model peptides by electrospray ionization-mass spectrometry.

    Science.gov (United States)

    Atik, A Emin; Guray, Melda Z; Yalcin, Talat

    2017-03-15

    O-methylation of the side chains of glutamic acid (E) and aspartic acid (D) residues is generally observed modification when an acidified methanol/water (MeOH/dH 2 O) mixture is used as a solvent system during sample preparation for proteomic research. This chemical modification may result misidentification with endogenous protein methylation; therefore, a special care should be taken during sample handling prior to mass spectrometric analysis. In the current study, we systematically examined the extent of E/D methylation and C-terminus carboxyl group of synthetic model peptides in terms of different incubation temperatures, storage times, and added acid types as well as its percentages. To monitor these effects, C-terminus amidated and free acid forms of synthetic model peptides comprised of E or D residue(s) have been analyzed by electrospray ionization-mass spectrometry (ESI-MS). Additionally, LC-MS/MS experiments were performed to confirm the formation of methylated peptide product. The results showed that the rate of methylation was increased as the temperature increases along with prolong incubation times. Moreover, the extent of methylation was remarkably high when formic acid (FA) used as a protonation agent instead of acetic acid (AA). In addition, it was found that the degree of methylation was significantly decreased by lowering acid percentages in ESI solution. More than one acidic residue containing model peptides have been also used to explore the extent of multiple methylation reaction. Lastly, the ethanol (EtOH) and isopropanol (iPrOH) have been substituted separately with MeOH in sample preparation step to investigate the extent of esterification reaction under the same experimental conditions. However, in the positive perspective of view, this method can be used as a simple, rapid and cheap method for methylation of acidic residues under normal laboratory conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Absence of arabinan in the side chains of the pectic polysaccharides strongly associated with cell walls of Nicotiana plumbaginifolia non-organogenic callus with loosely attached constituent cells.

    Science.gov (United States)

    Iwai, H; Ishii, T; Satoh, S

    2001-10-01

    When leaf disks from haploid plants of Nicotiana plumbaginifolia Viv. were transformed with T-DNA and cultured on shoot-inducing medium, nonorganogenic callus. designated nolac (for non-organogenic callus with loosely attached cells), appeared on approximately 7% of leaf disks. In contrast, normal callus was generated on T-DNA-transformed leaf disks from diploid plants and on non-transformed leaf disks from haploid and diploid plants. Transmission electron microscopy revealed that the middle lamellae and the cell walls of one line of mutant callus (nolac-H14) were barely stained by ruthenium red. even after demethylesterification with NaOH, whereas the entire cell wall and the middle lamella were strongly stained in normal callus. In cultures of nolac-H14 callus, the level of sugar components of pectic polysaccharides in the hemicellulose fraction was reduced and that in the culture medium was elevated, as compared with cultures of normal callus. These results indicate that pectic polysaccharides are not retained in the cell walls and middle lamellae of nolac-H14 callus. In nolac-H14, the ratio of arabinose to galactose was low in the pectic polysaccharides purified from all cell wall fractions and from the medium, in particular, in the hemicellulose fractions. The low levels of arabinofuranosyl (T-Araf, 5-Araf, 2,5-Araf, and 3,5-Araf) residues in the pectic polysaccharides of the hemicellulosic fraction of nolac-H,14 indicated that no neutral-sugar side chains, composed mainly of linear arabinan. were present in nolac-H14. Arabinose-rich pectins. which are strongly associated with cellulose-hemicellulose complexes, might play an important role in intercellular attachment in the architecture of the cell wall.

  12. Arteriovenous renal replacement therapy in end-stage left-sided heart failure patients has a detrimental effect on patients with impaired right ventricular function.

    Science.gov (United States)

    Repasos, Evangelos; Kaldara, Elisabeth; Pantsios, Christos; Kapelios, Chris; Nana, Emmeleia; Vernadakis, Spiridon; Melexopoulou, Christina; Malliaras, Konstantinos; Boletis, John; Nanas, John N

    Chronic intermittent renal replacement therapy(RRT) is an alternate method of decongestion for patients presenting with diuretic-resistant, end-stage heart failure(HF) and cardiorenal syndrome. The optimal method of vascular access has not been confirmed. This study investigated the 6-month outcomes of patients with end-stage HF after the creation of arteriovenous communications (AVC) compared with other means of RRT. We treated 40 patients with chronic, intermittent, ambulatory RRT, of whom 15 (37.5%; Group A) underwent creation of AVC, and 25 (62.5%; Group B) received intraperitoneal (n=6) or internal jugular catheters (n=19) with the goal of achieving body weight stabilization and relief from congestion. The characteristics of the two groups were similar. According to Cox regression analysis, the 6-month rate of death or re-hospitalization for HF was significantly higher in Group A (73%) than in Group B (44%); hazard ratio (HR): 2.58; 95% confidence interval (CI) 1.2-6.2; P=0.02. Over a 6-month follow-up, the cumulative survival was significantly shorter (P=0.03) in Group A (13.8±10 weeks) than in Group B (20.7±7 weeks). In the 15 patients who received AVC, the only independent predictor of adverse outcome at 6 months was serum total bilirubin concentration (HR 2.5; 95% CI 1.1-5.7, p=0.02), whereas in the 25 patients who underwent other means of RRT, pulmonary vascular resistance (PVR) was identified as a risk factor for hospitalization or death at 1-year follow-up (HR 1.26; 95% CI 1.1-1.57, p=0.04). In patients with end-stage HF, the creation of AVC for intermittent RRT was followed by a significant increase in morbidity and mortality in comparison to the safe and effective placement of permanent central venous catheters. Patients with elevated PVR seem to comprise a group at high risk for adverse outcomes after central catheter insertion. Copyright © 2016 Hellenic Society of Cardiology. Published by Elsevier B.V. All rights reserved.

  13. Property Enhancement Effects of Side-Chain-Type Naphthalene-Based Sulfonated Poly(arylene ether ketone) on Nafion Composite Membranes for Direct Methanol Fuel Cells.

    Science.gov (United States)

    Wang, Baolong; Hong, Lihua; Li, Yunfeng; Zhao, Liang; Zhao, Chengji; Na, Hui

    2017-09-20

    Nafion/SNPAEK-x composite membranes were prepared by blending raw Nafion and synthesized side-chain-type naphthalene-based sulfonated poly(arylene ether ketone) with a sulfonation degree of 1.35 (SNPAEK-1.35). The incorporation of SNPAEK-1.35 polymer with ion exchange capacity (IEC) of 2.01 mequiv·g -1 into a Nafion matrix has the property enhancement effects, such as increasing IECs, improving proton conductivity, enhancing mechanical properties, reducing methanol crossover, and improving single cell performance of Nafion. Morphology studies show that Nafion/SNPAEK-x composite membranes exhibit a well-defined microphase separation structure depending on the contents of SNPAEK-1.35 polymer. Among them, Nafion/SNPAEK-7.5% with a bicontinuous morphology exhibits the best comprehensive properties. For example, it shows the highest proton conductivities of 0.092 S cm -1 at 25 °C and 0.163 S cm -1 at 80 °C, which are higher than those of recast Nafion with 0.073 S cm -1 at 25 °C and 0.133 S cm -1 at 80 °C, respectively. Nafion/SNPAEK-5.0% and Nafion/SNPAEK-7.5% membranes display an open circuit voltage of 0.77 V and a maximum power density of 47 mW cm -2 at 80 °C, which are much higher than those of recast Nafion of 0.63 V and 24 mW cm -2 under the same conditions. Nafion/SNPAEK-5.0% membrane also has comparable tensile strength (12.7 MPa) to recast Nafion (13.7 MPa), and higher Young's modulus (330 MPa) than that of recast Nafion (240 MPa). By combining their high proton conductivities, comparable mechanical properties, and good single cell performance, Nafion/SNPAEK-x composite membranes have the potential to be polymer electrolyte materials for direct methanol fuel cell applications.

  14. Nano-Mole Scale Side-Chain Signal Assignment by 1H-Detected Protein Solid-State NMR by Ultra-Fast Magic-Angle Spinning and Stereo-Array Isotope Labeling

    KAUST Repository

    Wang, Songlin

    2015-04-09

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52–57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems.

  15. Nano-Mole Scale Side-Chain Signal Assignment by 1H-Detected Protein Solid-State NMR by Ultra-Fast Magic-Angle Spinning and Stereo-Array Isotope Labeling

    KAUST Repository

    Wang, Songlin; Parthasarathy, Sudhakar; Nishiyama, Yusuke; Endo, Yuki; Nemoto, Takahiro; Yamauchi, Kazuo; Asakura, Tetsuo; Takeda, Mitsuhiro; Terauchi, Tsutomu; Kainosho, Masatsune; Ishii, Yoshitaka

    2015-01-01

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52–57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems.

  16. Synthesis and photophysical and electroluminescent properties of poly(1,4-phenylene–ethynylene)-alt-poly(1,4-phenylene–vinylene)s with various dissymmetric substitution of alkoxy side chains

    Czech Academy of Sciences Publication Activity Database

    Bouguerra, N.; Růžička, Aleš; Ulbricht, C.; Enengl, C.; Enengl, S.; Pokorná, Veronika; Výprachtický, Drahomír; Tordin, E.; Aitout, R.; Cimrová, Věra; Egbe, D. A. M.

    2016-01-01

    Roč. 49, č. 2 (2016), s. 455-464 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GA13-26542S; GA ČR(CZ) GAP106/12/0827 Institutional support: RVO:61389013 Keywords : poly(1,4-phenylene-ethynylene)-alt-poly(1,4-phenylene-vinylene)s * dissymmetric side chains * synthesis Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.835, year: 2016

  17. Binding cooperativity between a ligand carbonyl group and a hydrophobic side chain can be enhanced by additional H-bonds in a distance dependent manner: A case study with thrombin inhibitors.

    Science.gov (United States)

    Said, Ahmed M; Hangauer, David G

    2015-01-01

    One of the underappreciated non-covalent binding factors, which can significantly affect ligand-protein binding affinity, is the cooperativity between ligand functional groups. Using four different series of thrombin inhibitors, we reveal a strong positive cooperativity between an H-bond accepting carbonyl functionality and the adjacent P3 hydrophobic side chain. Adding an H-bond donating amine adjacent to the P3 hydrophobic side chain further increases this positive cooperativity thereby improving the Ki by as much as 546-fold. In contrast, adding an amidine multiple H-bond/salt bridge group in the distal S1 pocket does not affect this cooperativity. An analysis of the crystallographic B-factors of the ligand groups inside the binding site indicates that the strong cooperativity is mainly due to a significant mutual reduction in the residual mobility of the hydrophobic side chain and the H-bonding functionalities that is absent when the separation distance is large. This type of cooperativity is important to encode in binding affinity prediction software, and to consider in SAR studies. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  18. Accurate Determination of Leucine and Valine Side-chain Conformations using U-[15N/13C/2H]/[1H-(methine/methyl)-Leu/Val] Isotope Labeling, NOE Pattern Recognition, and Methine Cγ-Hγ/Cβ-Hβ Residual Dipolar Couplings

    International Nuclear Information System (INIS)

    Tang, Chun; Iwahara, Junji; Clore, G. Marius

    2005-01-01

    An isotope labeling scheme is described in which specific protonation of methine and methyl protons of leucine and valine is obtained on a 15 N/ 13 C labeled background with uniform deuteration of all other non-exchangeable protons. The presence of a protonated methine group has little effect on the favorable relaxation properties of the methyl protons of Leu and Val. This labeling scheme permits the rotameric state of leucine side-chains to be readily determined by simple inspection of the pattern of Hγ(i)-H N (i) and Hγ(i)-H N (i+1) NOEs in a 3D 15 N-separated NOE spectrum free of complications arising from spectral overlap and spin-diffusion. In addition, one-bond residual dipolar couplings for the methine 13 C- 1 H bond vectors of Leu and Val can be accurately determined from an intensity J-modulated constant-time HCCH-COSY experiment and used to accurately orient the side-chains of Leu and Val. Incorporation of these data into structure refinement improves the accuracy with which the conformations of Leu and Val side-chains can be established. This is important to ensure optimal packing both within the protein core and at intermolecular interfaces. The impact of the method on protein structure determination is illustrated by application to enzyme IIA Chitobiose , a 34 kDa homotrimeric phosphotransferase protein

  19. Ankle replacement

    Science.gov (United States)

    Ankle arthroplasty - total; Total ankle arthroplasty; Endoprosthetic ankle replacement; Ankle surgery ... Ankle replacement surgery is most often done while you are under general anesthesia. This means you will ...

  20. Side Effects

    Science.gov (United States)

    Side effects are problems that occur when cancer treatment affects healthy tissues or organs. Learn about side effects caused by cancer treatment. Know what signs and symptoms to call your doctor about. Learn about treatments for side effects.

  1. Incidence and outcome of patients starting renal replacement therapy for end-stage renal disease due to multiple myeloma or light-chain deposit disease: an ERA-EDTA Registry study

    DEFF Research Database (Denmark)

    Tsakiris, D.J.; Stel, V.S.; Finne, P.

    2010-01-01

    Background. Information on demographics and survival of patients starting renal replacement therapy (RRT) for end-stage renal disease (ESRD) due to multiple myeloma (MM) or light-chain deposit disease (LCDD) is scarce. The aim of this study was to describe the incidence, characteristics, causes...... causes (non-MM) was observed overtime. Patient survival on RRT was examined, unadjusted and adjusted for age and gender. Results. Of the 159 637 patients on RRT, 2453 (1.54%) had MM or LCDD. The incidence of RRT for ESRD due to MM or LCDD, adjusted for age and gender, increased from 0.70 pmp in 1986...

  2. Pronounced Side Chain Effects in Triple Bond-Conjugated Polymers Containing Naphthalene Diimides for n-Channel Organic Field-Effect Transistors

    KAUST Repository

    Nam, Sungho; Hahm, Suk Gyu; Khim, Dongyoon; Kim, Hwajeong; Sajoto, Tissa; Ree, Moonhor; Marder, Seth R.; Anthopoulos, Thomas D.; Bradley, Donal D.C.; Kim, Youngkyoo

    2018-01-01

    on the surface morphology/nanostructure, thus playing a critical role in charge-transporting properties of the three NDI-based copolymers. Among the polymers, the one with an octyldodecyl (OD) chain at the nitrogen atoms of imide ring and a hexadecyloxy (HO

  3. Studies on the O-polysaccharide of Escherichia albertii O2 characterized by non-stoichiometric O-acetylation and non-stoichiometric side-chain l-fucosylation.

    Science.gov (United States)

    Naumenko, Olesya I; Zheng, Han; Xiong, Yanwen; Senchenkova, Sof'ya N; Wang, Hong; Shashkov, Alexander S; Li, Qun; Wang, Jianping; Knirel, Yuriy A

    2018-05-22

    An O-polysaccharide was isolated from the lipopolysaccharide of Escherichia albertii O2 and studied by chemical methods and 1D and 2D 1 H and 13 C NMR spectroscopy. The following structure of the O-polysaccharide was established: . The O-polysaccharide is characterized by masked regularity owing to a non-stoichiometric O-acetylation of an l-fucose residue in the main chain and a non-stoichiometric side-chain l-fucosylation of a β-GlcNAc residue. A regular linear polysaccharide was obtained by sequential Smith degradation and alkaline O-deacetylation of the O-polysaccharide. The content of the O-antigen gene cluster of E. albertii O2 was found to be essentially consistent with the O-polysaccharide structure established. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Structure activity correlations in the inhibition of brain synaptosomal 3H-norepinephrine uptake by phenethylamine analogs. The role of α-alkyl side chain and methoxyl ring substitutions

    International Nuclear Information System (INIS)

    Makriyannis, A.; Bowerman, D.; Sze, P.Y.; Fournier, D.; Jong, A.P. de

    1982-01-01

    α-Ethylphenethylamine proved to be a weaker inhibitor of rat brain synaptosomal [ 3 H]norepinephrine ([ 3 H]NE) uptake than amphetamine, while 2-amino-tetralin and 2-amino-1,2-dihydronaphtalene, compounds in which the α-side chain ethyl group is tied to the aromatic ring have a similar inhibiting potency as amphetamine. Hallucinogenic polymethoxy substituted phenethylamine analogs have very low inhibitory potencies indicating that inhibition of NE-reuptake in brain noradrenergic neurons is not associated with the drug-induced hallucinogenic syndrome. (Auth.)

  5. Property-based design and synthesis of new chloroquine hybrids via simple incorporation of 2-imino-thiazolidine-4-one or 1h-pyrrol-2, 5-dione fragments on the 4-amino-7-chloroquinoline side chain

    International Nuclear Information System (INIS)

    Rojas, Fernando A.; Kouznetsov, Vladimir V.

    2011-01-01

    In the present work, the syntheses of new 4-amino-7-chloroquinoline N-derivatives were performed by selective modification of the side chain amino group of N-(7-chloroquinoline-4-yl) alkyldiamines, basis framework of chloroquine (CQ) drug through the incorporation of heterocyclic 2-imino-thiazolidine-4-one and 1 H-pyrrol-2,5-dione systems. These potential activity modulators were selected thanks to their characteristic properties, and evaluated by virtual screening employing the OSIRIS and Molinspirations platforms. Designed and synthesized quinolinic derivatives could increase the antimalarial activity of CQ analogues without affecting the lipophilicity as described in literature, suggesting them as candidates for further biological assessments. (author)

  6. Property-based design and synthesis of new chloroquine hybrids via simple incorporation of 2-imino-thiazolidine-4-one or 1h-pyrrol-2, 5-dione fragments on the 4-amino-7-chloroquinoline side chain

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Fernando A; Kouznetsov, Vladimir V., E-mail: kouznet@uis.edu.co [Laboratorio de Quimica Organica y Biomolecular, Escuela de Quimica, Universidad Industrial de Santander, Bucaramanga (Colombia)

    2011-09-15

    In the present work, the syntheses of new 4-amino-7-chloroquinoline N-derivatives were performed by selective modification of the side chain amino group of N-(7-chloroquinoline-4-yl) alkyldiamines, basis framework of chloroquine (CQ) drug through the incorporation of heterocyclic 2-imino-thiazolidine-4-one and {sup 1}H-pyrrol-2,5-dione systems. These potential activity modulators were selected thanks to their characteristic properties, and evaluated by virtual screening employing the OSIRIS and Molinspirations platforms. Designed and synthesized quinolinic derivatives could increase the antimalarial activity of CQ analogues without affecting the lipophilicity as described in literature, suggesting them as candidates for further biological assessments. (author)

  7. Methylobacterium extorquens AM1 produces a novel type of acyl-homoserine lactone with a double unsaturated side chain under methylotrophic growth conditions.

    Science.gov (United States)

    Nieto Penalver, Carlos G; Morin, Danièle; Cantet, Franck; Saurel, Olivier; Milon, Alain; Vorholt, Julia A

    2006-01-23

    Acyl-homoserine lactones (acyl-HSLs) have emerged as important regulatory molecules for many gram-negative bacteria. We have found that Methylobacterium extorquens AM1, a member of the pink-pigmented facultative methylotrophs commonly present on plant surfaces, produces several acyl-HSLs depending upon the carbon source. A novel HSL was discovered with a double unsaturated carbon chain (N-(tetradecenoyl)) (C14:2) and characterized by MS and proton NMR. This long-chain acyl-HSL is synthesized by MlaI that also directs synthesis of C14:1-HSL. The Alphaproteobacterium also produces N-hexanoyl-HSL (C6-HSL) and N-octanoyl-HSL (C8-HSL) via MsaI.

  8. Selectively deuterated liquid crystalline cyanoazobenzene side-chain polyesters. 3. Investigations of laser induced segmental mobility by Fourier transform infrared spectroscopy

    DEFF Research Database (Denmark)

    Kulinna, Christian; Hvilsted, Søren; Hendann, Claudia

    1998-01-01

    The laser-induced anisotropy in thin films of an extensive number of cyanoazobenzene sidechain liquid crystalline polytetradecanedioates, -dodecanedioates, and -adipates selectively deuterated at different positions have been investigated with polarized FTIR spectroscopy. The analysis of the segm......The laser-induced anisotropy in thin films of an extensive number of cyanoazobenzene sidechain liquid crystalline polytetradecanedioates, -dodecanedioates, and -adipates selectively deuterated at different positions have been investigated with polarized FTIR spectroscopy. The analysis...... of the segmental orientation based on dichroic ratios of characteristic absorption bands shows that, in polyesters with long main-chain spacing (tetradecanedioates and dodecanedioates), not only the light sensitive azo chromophore but also the main-chain methylene segment and to a smaller extent the flexible...

  9. Hasegawa, T., et al. Structure-Odor Relationships of α­Santalol Derivatives with Modified Side Chains. Molecules, 2012, 17, 2259-2270

    Directory of Open Access Journals (Sweden)

    Hideo Yamada

    2012-09-01

    Full Text Available The authors are sorry to report that some of the 13C-NMR data reported in their recently published paper [1] were incorrect. While this manuscript was in preparation and pending recording of some 13C-NMR spectra the data of α-santalol was used as a placeholder. Upon revising the manuscript according to the reviewers’ comments, they mistakenly thought that all spectral data had been replaced by the correct measured data. Consequently the authors wish to make at this time the following corrections to the paper.

  10. Knee Replacement

    Science.gov (United States)

    Knee replacement is surgery for people with severe knee damage. Knee replacement can relieve pain and allow you to ... Your doctor may recommend it if you have knee pain and medicine and other treatments are not ...

  11. Myocardial gene expression of microRNA-133a and myosin heavy and light chains, in conjunction with clinical parameters, predict regression of left ventricular hypertrophy after valve replacement in patients with aortic stenosis.

    Science.gov (United States)

    Villar, Ana V; Merino, David; Wenner, Mareike; Llano, Miguel; Cobo, Manuel; Montalvo, Cecilia; García, Raquel; Martín-Durán, Rafael; Hurlé, Juan M; Hurlé, María A; Nistal, J Francisco

    2011-07-01

    Left ventricular (LV) reverse remodelling after valve replacement in aortic stenosis (AS) has been classically linked to the hydraulic performance of the replacement device, but myocardial status at the time of surgery has received little attention. To establish predictors of LV mass (LVM) regression 1 year after valve replacement in a surgical cohort of patients with AS based on preoperative clinical and echocardiographic parameters and the myocardial gene expression profile at surgery. Transcript levels of remodelling-related proteins and regulators were determined in LV intraoperative biopsies from 46 patients with AS by RT-PCR. Using multiple linear regression analysis, an equation was developed (adjusted R²=0.73; pregression analysis identified microRNA-133a as a significant positive predictor of LVM normalisation, whereas β-myosin heavy chain and BMI constituted negative predictors. Hypertrophy regression 1 year after pressure overload release is related to the preoperative myocardial expression of remodelling-related genes, in conjunction with the patient's clinical background. In this scenario, miR-133 emerges as a key element of the reverse remodelling process. Postoperative improvement of valve haemodynamics does not predict the degree of hypertrophy regression or LVM normalisation. These results led us to reconsider the current reverse remodelling paradigm and (1) to include criteria of hypertrophy reversibility in the decision algorithm used to decide timing for the operation; and (2) to modify other prevailing factors (overweight, diabetes, etc) known to maintain LV hypertrophy.

  12. Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C{sub 61}-butyric acid methyl ester and its bis-adduct

    Energy Technology Data Exchange (ETDEWEB)

    Akaike, Kouki, E-mail: akaike@riken.jp [Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Kanai, Kaname [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Yamazaki 2641, Noda 278-8510 (Japan); Ouchi, Yukio; Seki, Kazuhiko [Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

    2013-03-29

    Highlights: ► Electronic structure of spin-coated films of PCBM and bis-PCBM was investigated. ► Ionization energy and electron affinity of bis-PCBM are smaller than those of PCBM. ► Electron donation from the side chain to C{sub 60}-backbone raises the HOMO and LUMO. ► Open circuit voltages of PCBM-based solar cells relates to electron affinities. - Abstract: We investigated the electronic structure of spin-coated films of two soluble fullerenes; [6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM) and its bis-adduct (bis-PCBM) using ultraviolet photoelectron spectroscopy, inverse photoemission spectroscopy and molecular orbital calculations. The ionization energy and electron affinity of spin-coated films of bis-PCBM were determined to be 6.01 eV and 3.4 eV, respectively. Analysis of electron density suggested the stronger electron donation from the two side chains to fullerene-backbone in a bis-PCBM molecule, compared with PCBM. The electron donation raises the energies of the frontier orbitals of bis-PCBM, which mainly consist of π-orbitals of fullerene-backbone. As a result, the ionization energy and electron affinity of bis-PCBM are smaller than those of PCBM. Moreover, we also concluded that the larger open circuit voltage observed for bis-PCBM based organic photovoltaics was explained by the higher-lying unoccupied molecular orbital of bis-PCBM.

  13. Density functional theory study of silodithiophene thiophenepyrrolopyrroledion-based small molecules: The effect of alkyl side chain length in electron donor materials

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Dong Kyun; Yeo, Hak; Kwak, Kyung Won [Dept. of Chemistry, Chung-Ang University, Seoul (Korea, Republic of); Yoon, Young Woon; Kim, Bong Soo [Photo-electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Lee, Kyung Koo [Dept. of Chemistry, Kunsan National University, Gunsan (Korea, Republic of)

    2015-02-15

    Push–pull small molecules are promising electron-donor materials for organic solar cells. Thus, precise prediction of their electronic structures is of paramount importance to control the optical and electrical properties of the solar cells. Various types of alkyl chains are usually introduced to increase solubility and modify the morphology of the resulting molecular films. Here, using density functional theory (DFT) and time-dependent DFT (TD-DFT), we report the precise effect of increasing the length of the alkyl chain on the electronic structure of an electron donor molecule 6,60-((4,4-dialkyl-4H-silolo[3,2-b:4,5-b′]-dithiophene-2,6-diyl) bis(thiophene-5,2-diyl))bis(2,5-alkyl-3-(thiophen-2-yl) -2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) (DTS1TDPP). Alkyl groups were attached to the bridging position (silicon atom) of the fused rings and nitrogen atom of the pyrrolopyrroledione groups. We demonstrate that the alkyl groups do not perturb the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, π-delocalized backbone structure, and UV–Vis absorption spectrum when they are placed at the least steric effect positions.

  14. Tuning Surface Properties of Poly(methyl methacrylate) Film Using Poly(perfluoromethyl methacrylate)s with Short Perfluorinated Side Chains.

    Science.gov (United States)

    Sohn, Eun-Ho; Ha, Jong-Wook; Lee, Soo-Bok; Park, In Jun

    2016-09-27

    To control the surface properties of a commonly used polymer, poly(methyl methacrylate) (PMMA), poly(perfluoromethyl methacrylate)s (PFMMAs) with short perfluorinated side groups (i.e., -CF3, -CF2CF3, -(CF3)2, -CF2CF2CF3) were used as blend components because of their good solubility in organic solvents, low surface energies, and high optical transmittance. The surface energies of the blend films of PFMMA with the -CF3 group and PMMA increased continuously with increasing PMMA contents from 17.6 to 26.0 mN/m, whereas those of the other polymer blend films remained at very low levels (10.2-12.6 mN/m), similar to those of pure PFMMAs, even when the blends contained 90 wt %PMMA. Surface morphology and composition measurements revealed that this result originated from the different blend structures, such as lateral and vertical phase separations. We expect that these PFMMAs will be useful in widening the applicable window of PMMA.

  15. (1)H, (13)C, (15)N backbone and side-chain resonance assignment of Nostoc sp. C139A variant of the heme-nitric oxide/oxygen binding (H-NOX) domain.

    Science.gov (United States)

    Alexandropoulos, Ioannis I; Argyriou, Aikaterini I; Marousis, Kostas D; Topouzis, Stavros; Papapetropoulos, Andreas; Spyroulias, Georgios A

    2016-10-01

    The H-NOX (Heme-nitric oxide/oxygen binding) domain is conserved across eukaryotes and bacteria. In human soluble guanylyl cyclase (sGC) the H-NOX domain functions as a sensor for the gaseous signaling agent nitric oxide (NO). sGC contains the heme-binding H-NOX domain at its N-terminus, which regulates the catalytic site contained within the C-terminal end of the enzyme catalyzing the conversion of GTP (guanosine 5'-triphosphate) to GMP (guanylyl monophosphate). Here, we present the backbone and side-chain assignments of the (1)H, (13)C and (15)N resonances of the 183-residue H-NOX domain from Nostoc sp. through solution NMR.

  16. ¹H, ¹³C, and ¹⁵N backbone and side-chain chemical shift assignment of the toxin Doc in the unbound state.

    Science.gov (United States)

    De Gieter, Steven; Loris, Remy; van Nuland, Nico A J; Garcia-Pino, Abel

    2014-04-01

    Toxin-antitoxin (TA) modules in bacteria are involved in pathogenesis, antibiotic stress response, persister formation and programmed cell death. The toxin Doc, from the phd/doc module, blocks protein synthesis by targeting the translation machinery. Despite a large wealth of biophysical and biochemical data on the regulatory aspects of the operon transcription and role of Doc co-activator and co-repressor, little is still know on the molecular basis of Doc toxicity. Structural information about this toxin is only available for its inhibited state bound to the antitoxin Phd. Here we report the (1)H, (15)N and (13)C backbone and side chain chemical shift assignments of the toxin Doc from of bacteriophage P1 (the model protein from this family of TA modules) in its free state. The BMRB accession number is 18899.

  17. Reactivity of lignin with different composition of aromatic syringyl/guaiacyl structures and erythro/threo side chain structures in β-O-4 type during alkaline delignification: as a basis for the different degradability of hardwood and softwood lignin.

    Science.gov (United States)

    Shimizu, Satoko; Yokoyama, Tomoya; Akiyama, Takuya; Matsumoto, Yuji

    2012-07-04

    The reactivity of lignin during alkaline delignification was quantitatively investigated focusing on the effect of the structural differences between syringyl and guaiacyl aromatic nuclei and between erythro and threo in the side chain of β-O-4 type lignin substructure on the β-O-4 bond cleavage rate. It was known that the ratio of this reaction rate of the erythro to threo isomers of the dimeric β-O-4 type lignin model compound with two guaiacyl aromatic nuclei was ca. 4. However, the presence of a syringyl nucleus strongly influenced the rate, and the ratio of the syringyl type analogue was in the range between 2.7 and 8.0 depending on the reaction temperature. The effect of syringyl nucleus on the enhancement of the reaction rate appeared to be greater when the syringyl nucleus consists of the cleaving ether bond rather than being a member of the carbon framework.

  18. Side-chain dynamics of a detergent-solubilized membrane protein: Measurement of tryptophan and glutamine hydrogen-exchange rates in M13 coat protein by 1H NMR spectroscopy

    International Nuclear Information System (INIS)

    O'Neil, J.D.J.; Sykes, B.D.

    1989-01-01

    M13 coat protein is a small (50 amino acids) lipid-soluble protein that becomes an integral membrane protein during the infection stage of the life cycle of the M13 phage and is therefore used as a model membrane protein. To study side-chain dynamics in the protein, the authors have measured individual hydrogen-exchange rates for a primary amide in the side chain of glutamine-15 and for the indole amine of tryptophan-26. The protein was solubilized with the use of perdeuteriated sodium dodecyl sulfate (SDS), and hydrogen-exchange rates were measured by using 1 H nuclear magnetic resonance spectroscopy. The glutamine-15 syn proton exchanged at a rate identical with that in glutamine model peptides except that the pH corresponding to minimum exchange was elevated by about 1.5 pH units. The tryptophan-26 indole amine proton exchange was biphasic, suggesting that two populations of tryptophan-26 exist. It is suggested that the two populations may reflect protein dimerization or aggregation in the SDS micelles. The pH values of minimum exchange for tryptophan-26 in both environments were also elevated by 1.3-1.9 pH units. This phenomenon is reproduced when small tryptophan- and glutamine-containing hydrophobic peptides are dissolved in the presence of SDS micelles. The electrostatic nature of this phenomenon is proven by showing that the minimum pH for exchange can be reduced by dissolving the hydrophobic peptides in the positively charged detergent micelle dodecyltrimethylammonium bromide

  19. Comparing Demand Side Management approaches

    NARCIS (Netherlands)

    Molderink, Albert; Bakker, Vincent; Hurink, Johann L.; Smit, Gerardus Johannes Maria

    2012-01-01

    Due to increasing energy prices and the greenhouse effect, a more efficient energy supply is desirable, preferably based on renewable sources. To cope with the decrease of flexibility due to the introduction of renewables in production side of the supply chain, a more flexible consumer side is

  20. Effects of partial replacement of dietary starch from barley or corn with lactose on ruminal function, short-chain fatty acid absorption, nitrogen utilization, and production performance of dairy cows.

    Science.gov (United States)

    Chibisa, G E; Gorka, P; Penner, G B; Berthiaume, R; Mutsvangwa, T

    2015-04-01

    In cows fed diets based on corn-alfalfa silage, replacing starch with sugar improves milk production. Although the rate of ruminal fermentation of sugar is more rapid than that of starch, evidence has been found that feeding sugar as a partial replacement for starch does not negatively affect ruminal pH despite increasing diet fermentability. The mechanism(s) for this desirable response are unknown. Our objective was to determine the effects of replacing barley or corn starch with lactose (as dried whey permeate; DWP) on ruminal function, short-chain fatty acid (SCFA) absorption, and nitrogen (N) utilization in dairy cows. Eight lactating cows were used in a replicated 4 × 4 Latin square design with 28-d periods and source of starch (barley vs. corn) and level of DWP (0 vs. 6%, DM basis) as treatment factors. Four cows in 1 Latin square were ruminally cannulated for the measurement of ruminal function, SCFA absorption, and N utilization. Dry matter intake and milk and milk component yields did not differ with diet. The dietary addition of DWP tended to increase ruminal butyrate concentration (13.6 vs. 12.2 mmol/L), and increased the Cl(-)-competitive absorption rates for acetate and propionate. There was no sugar effect on minimum ruminal pH, and the duration and area when ruminal pH was below 5.8. Minimum ruminal pH tended to be lower in cows fed barley compared with those fed corn (5.47 vs. 5.61). The duration when ruminal pH was below pH 5.8 tended to be shorter (186 vs. 235 min/d), whereas the area (pH × min/d) that pH was below 5.8 was smaller (47 vs. 111) on the corn than barley diets. Cows fed the high- compared with the low-sugar diet had lower ruminal NH3-N concentration. Feeding the high-sugar diet tended to increase apparent total-tract digestibility of dry matter and organic matters and increased apparent total-tract digestibility of fat. Apparent total-tract digestibility of N tended to be greater in cows fed barley compared with those fed corn

  1. Replacing penalties

    Directory of Open Access Journals (Sweden)

    Vitaly Stepashin

    2017-01-01

    Full Text Available УДК 343.24The subject. The article deals with the problem of the use of "substitute" penalties.The purpose of the article is to identify criminal and legal criteria for: selecting the replacement punishment; proportionality replacement leave punishment to others (the formalization of replacement; actually increasing the punishment (worsening of legal situation of the convicted.Methodology.The author uses the method of analysis and synthesis, formal legal method.Results. Replacing the punishment more severe as a result of malicious evasion from serving accused designated penalty requires the optimization of the following areas: 1 the selection of a substitute punishment; 2 replacement of proportionality is serving a sentence other (formalization of replacement; 3 ensuring the actual toughening penalties (deterioration of the legal status of the convict. It is important that the first two requirements pro-vide savings of repression in the implementation of the replacement of one form of punishment to others.Replacement of punishment on their own do not have any specifics. However, it is necessary to compare them with the contents of the punishment, which the convict from serving maliciously evaded. First, substitute the punishment should assume a more significant range of restrictions and deprivation of certain rights of the convict. Second, the perfor-mance characteristics of order substitute the punishment should assume guarantee imple-mentation of the new measures.With regard to replacing all forms of punishment are set significant limitations in the application that, in some cases, eliminates the possibility of replacement of the sentence, from serving where there has been willful evasion, a stricter measure of state coercion. It is important in the context of the topic and the possibility of a sentence of imprisonment as a substitute punishment in cases where the original purpose of the strict measures excluded. It is noteworthy that the

  2. Mutations blocking side chain assembly, polymerization, or transport of a Wzy-dependent Streptococcus pneumoniae capsule are lethal in the absence of suppressor mutations and can affect polymer transfer to the cell wall.

    Science.gov (United States)

    Xayarath, Bobbi; Yother, Janet

    2007-05-01

    Extracellular polysaccharides of many bacteria are synthesized by the Wzy polymerase-dependent mechanism, where long-chain polymers are assembled from undecaprenyl-phosphate-linked repeat units on the outer face of the cytoplasmic membrane. In gram-positive bacteria, Wzy-dependent capsules remain largely cell associated via membrane and peptidoglycan linkages. Like many Wzy-dependent capsules, the Streptococcus pneumoniae serotype 2 capsule is branched. In this study, we found that deletions of cps2K, cps2J, or cps2H, which encode a UDP-glucose dehydrogenase necessary for side chain synthesis, the putative Wzx transporter (flippase), and the putative Wzy polymerase, respectively, were obtained only in the presence of suppressor mutations. Most of the suppressor mutations were in cps2E, which encodes the initiating glycosyltransferase for capsule synthesis. The cps2K mutants containing the suppressor mutations produced low levels of high-molecular-weight polymer that was detected only in membrane fractions. cps2K-repaired mutants exhibited only modest increases in capsule production due to the effect of the secondary mutation, but capsule was detectable in both membrane and cell wall fractions. Lethality of the cps2K, cps2J, and cps2H mutations was likely due to sequestration of undecaprenyl-phosphate in the capsule pathway and either preclusion of its turnover for utilization in essential pathways or destabilization of the membrane due to an accumulation of lipid-linked intermediates. The results demonstrate that proper polymer assembly requires not only a functional transporter and polymerase but also complete repeat units. A central role for the initiating glycosyltransferase in controlling capsule synthesis is also suggested.

  3. Knee Replacement

    Science.gov (United States)

    ... days. Medications prescribed by your doctor should help control pain. During the hospital stay, you'll be encouraged to move your ... exercise your new knee. After you leave the hospital, you'll continue physical ... mobility and a better quality of life. And most knee replacements can be ...

  4. Melanocortin tetrapeptide Ac-His-DPhe-Arg-Trp-NH2 modified at the para position of the benzyl side chain (DPhe): importance for mouse melanocortin-3 receptor agonist versus antagonist activity.

    Science.gov (United States)

    Proneth, Bettina; Pogozheva, Irina D; Portillo, Federico P; Mosberg, Henry I; Haskell-Luevano, Carrie

    2008-09-25

    The melanocortin-3 and -4 receptors (MC3R, MC4R) have been implicated in energy homeostasis and obesity. Whereas the physiological role of the MC4R is extensively studied, little is known about the MC3R. One caveat is the limited availability of ligands that are selective for the MC3R. Previous studies identified Ac-His-DPhe(p-I)-Arg-Trp-NH 2, which possessed partial agonist/antagonist pharmacology at the mMC3R while retaining full nanomolar agonist pharmacology at the mMC4R. These data allowed for the hypothesis that the DPhe position in melanocortin tetrapeptides can be used to examine ligand side-chain determinants important for differentiation of mMC3R agonist versus antagonist activity. A series of 15 DPhe (7) modified Ac-His-DPhe (7)-Arg-Trp-NH 2 tetrapeptides has been synthesized and pharmacologically characterized. Most notable results include the identification of modifications that resulted in potent antagonists/partial agonists at the mMC3R and full, potent agonists at the mMC4R. These SAR studies provide experimental evidence that the molecular mechanism of antagonism at the mMC3R differentiates this subtype from the mMC4R.

  5. Improvement in the mechanical properties, proton conductivity, and methanol resistance of highly branched sulfonated poly(arylene ether)/graphene oxide grafted with flexible alkylsulfonated side chains nanocomposite membranes

    Science.gov (United States)

    Liu, Dong; Peng, Jinhua; Li, Zhuoyao; Liu, Bin; Wang, Lei

    2018-02-01

    Sulfonated polymer/graphene oxide (GO) nanocomposites exhibit excellent properties as proton exchange membranes. However, few investigations on highly branched sulfonated poly(arylene ether)s (HBSPE)/GO nanocomposites as proton exchange membranes are reported. In order to obtain HBSPE-based nanocomposite membranes with better dispersibility and properties, a novel GO containing flexible alkylsulfonated side chains (SGO) is designed and prepared for the first time in this work. The HBSPE/SGO nanocomposite membranes with excellent dispersibility are successfully prepared. The properties of these membranes, including the mechanical properties, ion-exchange capacity, water uptake, proton conductivity, and methanol resistance, are characterized. The nanocomposite membranes exhibit higher tensile strength (32.67 MPa), higher proton conductivity (0.39 S cm-1 at 80 °C) and lower methanol permeability (4.89 × 10-7 cm2 s-1) than the pristine membrane. The nanocomposite membranes also achieve a higher maximum power density (82.36 mW cm-2) than the pristine membrane (67.85 mW cm-2) in single-cell direct methanol fuel cell (DMFC) tests, demonstrating their considerable potential for applications in DMFCs.

  6. Replacement rod

    International Nuclear Information System (INIS)

    Hatfield, S.C.

    1989-01-01

    This patent describes in an elongated replacement rod for use with fuel assemblies of the type having two end fittings connected by guide tubes with a plurality of rod and guide tube cell defining spacer grids containing rod support features and mixing vanes. The grids secured to the guide tubes in register between the end fittings at spaced intervals. The fuel rod comprising: an asymmetrically beveled tip; a shank portion having a straight centerline; and a permanently diverging portion between the tip and the shank portion

  7. (¹⁵N ± ¹³C') edited (4, 3)D-H(CC)CONH TOCSY and (4, 3)D-NOESY HNCO experiments for unambiguous side chain and NOE assignments of proteins with high shift degeneracy.

    Science.gov (United States)

    Kumar, Dinesh; Arora, Ashish

    2011-11-01

    Well-resolved and unambiguous through-bond correlations and NOE data are crucial for high-quality protein structure determination by NMR. In this context, we present here (4, 3)D reduced dimensionality (RD) experiments: H(CC)CONH TOCSY and NOESY HNCO--which instead of (15)N shifts exploit the linear combination of (15)N(i) and (13)C'(i-1) shifts (where i is a residue number) to resolve the through-bond (1)H-(1)H correlations and through-space (1)H-(1)H NOEs. The strategy makes use of the fact that (15)N and (13)C' chemical shifts when combined linearly provide a dispersion which is better compared to those of the individual chemical shifts. The extended dispersion thus available in these experiments will help to obtain the unambiguous side chain and accurate NOE assignments especially for medium-sized alpha-helical or partially unstructured proteins [molecular weight (MW) between 12-15 kDa] as well as higher MW (between 15-25 kDa) folded proteins where spectral overlap renders inaccurate and ambiguous NOEs. Further, these reduced dimensionality experiments in combination with routinely used (15)N and (13)C' edited TOCSY and NOESY experiments will provide an alternative way for high-quality NMR structure determination of large unstable proteins (with very high shift degeneracy), which are not at all amenable to 4D NMR. The utility of these experiments has been demonstrated here using (13)C/(15)N labeled ubiquitin (76 aa) protein. Copyright © 2011 John Wiley & Sons, Ltd.

  8. Overexpression of the steroidogenic enzyme cytochrome P450 side chain cleavage in the ventral tegmental area increases 3α,5α-THP and reduces long-term operant ethanol self-administration.

    Science.gov (United States)

    Cook, Jason B; Werner, David F; Maldonado-Devincci, Antoniette M; Leonard, Maggie N; Fisher, Kristen R; O'Buckley, Todd K; Porcu, Patrizia; McCown, Thomas J; Besheer, Joyce; Hodge, Clyde W; Morrow, A Leslie

    2014-04-23

    Neuroactive steroids are endogenous neuromodulators capable of altering neuronal activity and behavior. In rodents, systemic administration of endogenous or synthetic neuroactive steroids reduces ethanol self-administration. We hypothesized this effect arises from actions within mesolimbic brain regions that we targeted by viral gene delivery. Cytochrome P450 side chain cleavage (P450scc) converts cholesterol to pregnenolone, the rate-limiting enzymatic reaction in neurosteroidogenesis. Therefore, we constructed a recombinant adeno-associated serotype 2 viral vector (rAAV2), which drives P450scc expression and neuroactive steroid synthesis. The P450scc-expressing vector (rAAV2-P450scc) or control GFP-expressing vector (rAAV2-GFP) were injected bilaterally into the ventral tegmental area (VTA) or nucleus accumbens (NAc) of alcohol preferring (P) rats trained to self-administer ethanol. P450scc overexpression in the VTA significantly reduced ethanol self-administration by 20% over the 3 week test period. P450scc overexpression in the NAc, however, did not alter ethanol self-administration. Locomotor activity was unaltered by vector administration to either region. P450scc overexpression produced a 36% increase in (3α,5α)-3-hydroxypregnan-20-one (3α,5α-THP, allopregnanolone)-positive cells in the VTA, but did not increase 3α,5α-THP immunoreactivity in NAc. These results suggest that P450scc overexpression and the resultant increase of 3α,5α-THP-positive cells in the VTA reduces ethanol reinforcement. 3α,5α-THP is localized to neurons in the VTA, including tyrosine hydroxylase neurons, but not astrocytes. Overall, the results demonstrate that using gene delivery to modulate neuroactive steroids shows promise for examining the neuronal mechanisms of moderate ethanol drinking, which could be extended to other behavioral paradigms and neuropsychiatric pathology.

  9. 1H NMR study of effects of synergistic anion and metal ion binding on pH titration of the histidinyl side-chain residues of the half-molecules of ovotransferrin

    International Nuclear Information System (INIS)

    Woodworth, R.C.; Butcher, N.D.; Brown, S.A.; Brown-Mason, A.

    1987-01-01

    Separation of ovotransferrin into C-terminal (OTf/2C) and N-terminal (OTf/2N) half-molecules has made possible the resolution of all expected histidinyl C(2)H resonances by proton nuclear magnetic resonance at 250 MHz. The chemical shift of many of the resonances decreases with increasing pH, allowing construction of titration curves, whereas a few resonances fail to titrate. On formation of the Ga/sup III/OTf/2(C 2 O 4 ) ternary complexes, two of the low-field C(2)H resonances in each half-molecule fail to titrate. This behavior implicates the imidazole groups giving rise to these resonances as ligands to the bound metal ion. A third C(2)H resonance in each half-molecule undergoes a marked reduction in pK'/sub a/ on formation of the ternary complex. The imidazole group displaying this resonance is implicated in a proton-relay scheme involved in binding the synergistic anion, oxalate, and a water of hydration on the bound metal ion. The titration curves for the various imidazole resonances have been fit to a four-parameter equation involving estimation of the pK'/sub a/, the limiting chemical shift values, and a Hill constant n. Hill constants of 1, which suggests positive cooperativity in the titration of this residue. The basis for this behavior cannot be rationalized at this time. 13 C NMR studies of [zeta- 13 C]Arg-OTf suggest the Arg side chains may not be intimately involved in formation of the ternary complex

  10. Sensitivity improvement for correlations involving arginine side-chain N{epsilon}/H{epsilon} resonances in multi-dimensional NMR experiments using broadband {sup 15}N 180{sup o} pulses

    Energy Technology Data Exchange (ETDEWEB)

    Iwahara, Junji; Clore, G. Marius [National Institutes of Health, Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Disease (United States)], E-mail: mariusc@intra.niddk.nih.gov

    2006-12-15

    Due to practical limitations in available {sup 15}N rf field strength, imperfections in {sup 15}N 180{sup o} pulses arising from off-resonance effects can result in significant sensitivity loss, even if the chemical shift offset is relatively small. Indeed, in multi-dimensional NMR experiments optimized for protein backbone amide groups, cross-peaks arising from the Arg guanidino {sup 15}N{epsilon} ({approx}85 ppm) are highly attenuated by the presence of multiple INEPT transfer steps. To improve the sensitivity for correlations involving Arg N{epsilon}-H{epsilon} groups, we have incorporated {sup 15}N broadband 180 deg. pulses into 3D {sup 15}N-separated NOE-HSQC and HNCACB experiments. Two {sup 15}N-WURST pulses incorporated at the INEPT transfer steps of the 3D {sup 15}N-separated NOE-HSQC pulse sequence resulted in a {approx}1.5-fold increase in sensitivity for the Arg N{epsilon}-H{epsilon} signals at 800 MHz. For the 3D HNCACB experiment, five {sup 15}N Abramovich-Vega pulses were incorporated for broadband inversion and refocusing, and the sensitivity of Arg{sup 1}H{epsilon}-{sup 15}N{epsilon}-{sup 13}C{gamma}/{sup 13}C{delta} correlation peaks was enhanced by a factor of {approx}1.7 at 500 MHz. These experiments eliminate the necessity for additional experiments to assign Arg {sup 1}H{epsilon} and {sup 15}N{epsilon} resonances. In addition, the increased sensitivity afforded for the detection of NOE cross-peaks involving correlations with the {sup 15}N{epsilon}/{sup 1}H{epsilon} of Arg in 3D {sup 15}N-separated NOE experiments should prove to be very useful for structural analysis of interactions involving Arg side-chains.

  11. Shoulder replacement - discharge

    Science.gov (United States)

    Total shoulder arthroplasty - discharge; Endoprosthetic shoulder replacement - discharge; Partial shoulder replacement - discharge; Partial shoulder arthroplasty - discharge; Replacement - shoulder - discharge; Arthroplasty - shoulder - discharge

  12. Involvement of adenosine monophosphate activated kinase in interleukin-6 regulation of steroidogenic acute regulatory protein and cholesterol side chain cleavage enzyme in the bovine zona fasciculata and zona reticularis.

    Science.gov (United States)

    De Silva, Matharage S I; Dayton, Adam W; Rhoten, Lance R; Mallett, John W; Reese, Jared C; Squires, Mathieu D; Dalley, Andrew P; Porter, James P; Judd, Allan M

    2018-06-01

    In bovine adrenal zona fasciculata (ZF) and NCI-H295R cells, interleukin-6 (IL-6) increases cortisol release, increases expression of steroidogenic acute regulatory protein (StAR), cholesterol side chain cleavage enzyme (P450scc), and steroidogenic factor 1 (SF-1) (increases steroidogenic proteins), and decreases the expression of adrenal hypoplasia congenita-like protein (DAX-1) (inhibits steroidogenic proteins). In contrast, IL-6 decreases bovine adrenal zona reticularis (ZR) androgen release, StAR, P450scc, and SF-1 expression, and increases DAX-1 expression. Adenosine monophosphate (AMP) activated kinase (AMPK) regulates steroidogenesis, but its role in IL-6 regulation of adrenal steroidogenesis is unknown. In the present study, an AMPK activator (AICAR) increased (P < 0.01) NCI-H295R StAR promoter activity, StAR and P450scc expression, and the phosphorylation of AMPK (PAMPK) and acetyl-CoA carboxylase (PACC) (indexes of AMPK activity). In ZR (decreased StAR, P450scc, SF-1, increased DAX-1) (P < 0.01) and ZF tissues (increased StAR, P450scc, SF-1, decreased DAX-1) (P < 0.01), AICAR modified StAR, P450scc, SF-1 and DAX-1 mRNAs/proteins similar to the effects of IL-6. The activity (increased PAMPK and PACC) (P < 0.01) of AMPK in the ZF and ZR was increased by AICAR and IL-6. In support of an AMPK role in IL-6 ZF and ZR effects, the AMPK inhibitor compound C blocked (P < 0.01) the effects of IL-6 on the expression of StAR, P450scc, SF-1, and DAX-1. Therefore, IL-6 modification of the expression of StAR and P450scc in the ZF and ZR may involve activation of AMPK and these changes may be related to changes in the expression of SF-1 and DAX-1. Copyright © 2018 Elsevier Inc. All rights reserved.

  13. Analysis of a quantum Markov chain

    International Nuclear Information System (INIS)

    Marbeau, J.; Gudder, S.

    1990-01-01

    A quantum chain is analogous to a classical stationary Markov chain except that the probability measure is replaced by a complex amplitude measure and the transition probability matrix is replaced by a transition amplitude matrix. After considering the general situation, we study a particular example of a quantum chain whose transition amplitude matrix has the form of a Dirichlet matrix. Such matrices generate a discrete analog of the usual continuum Feynman amplitude. We then compute the probability distribution for these quantum chains

  14. Hip joint replacement

    Science.gov (United States)

    Hip arthroplasty; Total hip replacement; Hip hemiarthroplasty; Arthritis - hip replacement; Osteoarthritis - hip replacement ... Your hip joint is made up of 2 major parts. One or both parts may be replaced during surgery: ...

  15. Accurate Determination of Leucine and Valine Side-chain Conformations using U-[{sup 15}N/{sup 13}C/{sup 2}H]/[{sup 1}H-(methine/methyl)-Leu/Val] Isotope Labeling, NOE Pattern Recognition, and Methine C{gamma}-H{gamma}/C{beta}-H{beta} Residual Dipolar Couplings

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Chun; Iwahara, Junji; Clore, G. Marius [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Laboratory of Chemical Physics (United States)], E-mail: mariusc@intra.niddk.nih.gov

    2005-10-15

    An isotope labeling scheme is described in which specific protonation of methine and methyl protons of leucine and valine is obtained on a {sup 15}N/{sup 13}C labeled background with uniform deuteration of all other non-exchangeable protons. The presence of a protonated methine group has little effect on the favorable relaxation properties of the methyl protons of Leu and Val. This labeling scheme permits the rotameric state of leucine side-chains to be readily determined by simple inspection of the pattern of H{gamma}(i)-H{sub N}(i) and H{gamma}(i)-H{sub N}(i+1) NOEs in a 3D {sup 15}N-separated NOE spectrum free of complications arising from spectral overlap and spin-diffusion. In addition, one-bond residual dipolar couplings for the methine {sup 13}C-{sup 1}H bond vectors of Leu and Val can be accurately determined from an intensity J-modulated constant-time HCCH-COSY experiment and used to accurately orient the side-chains of Leu and Val. Incorporation of these data into structure refinement improves the accuracy with which the conformations of Leu and Val side-chains can be established. This is important to ensure optimal packing both within the protein core and at intermolecular interfaces. The impact of the method on protein structure determination is illustrated by application to enzyme IIA{sup Chitobiose}, a 34 kDa homotrimeric phosphotransferase protein.

  16. Energy Matrix of Structurally Important Side-Chain/Side-Chain Interactions in Proteins

    Czech Academy of Sciences Publication Activity Database

    Berka, K.; Laskowski, R. A.; Hobza, P.; Vondrášek, Jiří

    2010-01-01

    Roč. 6, č. 7 (2010), s. 2191-2203 ISSN 1549-9618 R&D Projects: GA ČR GAP208/10/0725; GA MŠk LC512 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50520701 Keywords : protein structure * DFT method * force fields * interaction energy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.138, year: 2010

  17. Monitoring the vaccine cold chain.

    OpenAIRE

    Cheriyan, E

    1993-01-01

    Maintaining the vaccine cold chain is an essential part of a successful immunisation programme. A continuous electronic temperature monitor helped to identify breaks in the cold chain in the community and the study led to the issue of proper guidelines and replacement of faulty equipment.

  18. Transcatheter aortic valve replacement

    Science.gov (United States)

    ... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

  19. Hip Replacement Surgery

    Science.gov (United States)

    ... Outreach Initiative Breadcrumb Home Health Topics English Español Hip Replacement Surgery Basics In-Depth Download Download EPUB ... PDF What is it? Points To Remember About Hip Replacement Surgery Hip replacement surgery removes damaged or ...

  20. Nicotine replacement therapy

    Science.gov (United States)

    Smoking cessation - nicotine replacement; Tobacco - nicotine replacement therapy ... Before you start using a nicotine replacement product, here are some things to know: The more cigarettes you smoke, the higher the dose you may need to ...

  1. Understanding and reducing the risk of supply chain disruptions.

    Science.gov (United States)

    Clark, Graham

    2012-01-01

    Natural disasters can wreck havoc on business operations. When civil unrest swept the UK in August 2011, the effect on business was stark, losing the retail sector £300m in unexpected costs and lost revenues. On the other side of the world, the natural disaster that hit Japan in early 2011 is estimated to have run up costs in the region of £189bn in repairs. Beyond this, the earthquake and its aftermath shattered supply chains, with technology companies expecting delays of up to six months before business could resume fully. It is impossible to predict incidents like these, but businesses can help mitigate disruption in the supply chain by undertaking business continuity management (BCM). A flexible supply chain is essential when it comes to BCM - whether it means being able to cope with altering transport routes at short notice, or finding or replacing a supplier at the last minute. Understanding the supply chain is critical when responding to major impacts that affect supply chains in multiple points - like IT system failures and country-wide fuel strikes. Businesses should carry out detailed business impact assessments and risk assessments right across the end-to-end supply chain and not just at key single points of failure. It is an intensive process that needs dedicated resources and ownership at the highest level. Recognising this, DHL has designed a 10-step process, which it has implemented across its global supply chain business. This paper provides an overview of what a supply chain really looks like, what can cause disruptions and how far up/down the supply chain companies need to go with their BCM planning.

  2. The TEL-AML1 real-time quantitative polymerase chain reaction (PCR) might replace the antigen receptor-based genomic PCR in clinical minimal residual disease studies in children with acute lymphoblastic leukaemia

    NARCIS (Netherlands)

    de Haas, V.; Breunis, W. B.; dee, R.; Verhagen, O. J. H. M.; Kroes, W.; van Wering, E. R.; van Dongen, J. J. M.; van den Berg, H.; van der Schoot, C. E.

    2002-01-01

    Prospective studies in children with B-precursor acute lymphoblastic leukaemia (ALL) have shown that polymerase chain reaction (PCR)-based detection of minimal residual disease (MRD) using immunoglobin (Ig) and T-cell receptor (TCR) gene rearrangements as targets can be used to identify patients

  3. Reply to the 'Comment on "Relating side chain organization of PNIPAm with its conformation in aqueous methanol"' by A. Pica and G. Graziano, Soft Matter, 2017, 13, DOI: 10.1039/C7SM01065F.

    Science.gov (United States)

    Mukherji, Debashish; Wagner, Manfred; Watson, Mark D; Winzen, Svenja; de Oliveira, Tiago E; Marques, Carlos M; Kremer, Kurt

    2017-11-01

    We have recently proposed preferential binding by a cosolvent as the mechanism for chain collapse under co-non-solvency. Here we summarise our earlier works and provide further evidence that alcohol preferentially binds to PNIPAm, forming cosolvent bridges, and thus drives the transition. We also clarify some of the common misconceptions evoked in this debate with Pica and Graziano (PG), reinforcing the arguments of our earlier reply-comment [Soft Matter, 2017, 13, 2292] and published works.

  4. Mutations Blocking Side Chain Assembly, Polymerization, or Transport of a Wzy-Dependent Streptococcus pneumoniae Capsule Are Lethal in the Absence of Suppressor Mutations and Can Affect Polymer Transfer to the Cell Wall▿

    OpenAIRE

    Xayarath, Bobbi; Yother, Janet

    2007-01-01

    Extracellular polysaccharides of many bacteria are synthesized by the Wzy polymerase-dependent mechanism, where long-chain polymers are assembled from undecaprenyl-phosphate-linked repeat units on the outer face of the cytoplasmic membrane. In gram-positive bacteria, Wzy-dependent capsules remain largely cell associated via membrane and peptidoglycan linkages. Like many Wzy-dependent capsules, the Streptococcus pneumoniae serotype 2 capsule is branched. In this study, we found that deletions ...

  5. Medications and Side Effects

    Science.gov (United States)

    ... to fully work. You might feel some side effects of your medication before your feel the benefits – ... as sleepiness, anxiety or headache) is a side effect or a symptom of your illness. Many side ...

  6. Defining line replaceable units

    NARCIS (Netherlands)

    Parada Puig, J. E.; Basten, R. J I

    2015-01-01

    Defective capital assets may be quickly restored to their operational condition by replacing the item that has failed. The item that is replaced is called the Line Replaceable Unit (LRU), and the so-called LRU definition problem is the problem of deciding on which item to replace upon each type of

  7. Falling chains

    OpenAIRE

    Wong, Chun Wa; Yasui, Kosuke

    2005-01-01

    The one-dimensional fall of a folded chain with one end suspended from a rigid support and a chain falling from a resting heap on a table is studied. Because their Lagrangians contain no explicit time dependence, the falling chains are conservative systems. Their equations of motion are shown to contain a term that enforces energy conservation when masses are transferred between subchains. We show that Cayley's 1857 energy nonconserving solution for a chain falling from a resting heap is inco...

  8. Comment on "Relating side chain organization of PNIPAm with its conformation in aqueous methanol" by D. Mukherji, M. Wagner, M. D. Watson, S. Winzen, T. E. de Oliveira, C. M. Marques and K. Kremer, Soft Matter, 2016, 12, 7995.

    Science.gov (United States)

    Pica, Andrea; Graziano, Giuseppe

    2017-11-01

    In a recent article, Kremer and co-workers have combined NMR measurements and very long, all-atom MD simulations to strengthen their original claim that PNIPAM cononsolvency in water-methanol solutions is driven by the ability of MeOH molecules to bridge different monomers far away along the polymeric chain. In this comment, the results presented by Kremer and co-workers are reviewed, analyzed, and questioned regarding their ability to provide support to the bridging mechanism. Here, some pieces of evidence are provided to show that: (1) the solvent-excluded volume effect plays always a fundamental role in polymer collapse; (2) PNIPAM cononsolvency is caused by the geometric-energetic frustration experienced by the polymer when it can interact with both water and methanol molecules at the same time.

  9. Sympathetic chain Schwannoma

    International Nuclear Information System (INIS)

    Al-Mashat, Faisal M.

    2009-01-01

    Schwannomas are rare, benign, slowly growing tumors arising from Schwann cells that line nerve sheaths. Schwannomas arising from the cervical sympathetic chain are extremely rare. Here, we report a case of a 70-year-old man who presented with only an asymptomatic neck mass. Physical examination revealed a left sided Horner syndrome and a neck mass with transmitted pulsation and anterior displacement of the carotid artery. Computed tomography (CT) showed a well-defined non-enhancing mass with vascular displacement. The nerve of origin of this encapsulated tumor was the sympathetic chain. The tumor was excised completely intact. The pathologic diagnosis was Schwannoma (Antoni type A and Antoni type B). The patient has been well and free of tumor recurrence for 14 months with persistence of asymptomatic left sided Horner syndrome. The clinical, radiological and pathological evaluations, therapy and postoperative complications of this tumor are discussed. (author)

  10. Ankle replacement - discharge

    Science.gov (United States)

    ... total - discharge; Total ankle arthroplasty - discharge; Endoprosthetic ankle replacement - discharge; Osteoarthritis - ankle ... You had an ankle replacement. Your surgeon removed and reshaped ... an artificial ankle joint. You received pain medicine and were ...

  11. Artificial Disc Replacement

    Science.gov (United States)

    ... Spondylolisthesis BLOG FIND A SPECIALIST Treatments Artificial Disc Replacement (ADR) Patient Education Committee Jamie Baisden The disc ... Disc An artificial disc (also called a disc replacement, disc prosthesis or spine arthroplasty device) is a ...

  12. Partial knee replacement - slideshow

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/presentations/100225.htm Partial knee replacement - series—Normal anatomy To use the sharing ... A.M. Editorial team. Related MedlinePlus Health Topics Knee Replacement A.D.A.M., Inc. is accredited ...

  13. Flued head replacement alternatives

    International Nuclear Information System (INIS)

    Smetters, J.L.

    1987-01-01

    This paper discusses flued head replacement options. Section 2 discusses complete flued head replacement with a design that eliminates the inaccessible welds. Section 3 discusses alternate flued head support designs that can drastically reduce flued head installation costs. Section 4 describes partial flued head replacement designs. Finally, Section 5 discusses flued head analysis methods. (orig./GL)

  14. Capital Equipment Replacement Decisions

    OpenAIRE

    Batterham, Robert L.; Fraser, K.I.

    1995-01-01

    This paper reviews the literature on the optimal replacement of capital equipment, especially farm machinery. It also considers the influence of taxation and capital rationing on replacement decisions. It concludes that special taxation provisions such as accelerated depreciation and investment allowances are unlikely to greatly influence farmers' capital equipment replacement decisions in Australia.

  15. Implementing Replacement Cost Accounting

    Science.gov (United States)

    1976-12-01

    cost accounting Clickener, John Ross Monterey, California. Naval Postgraduate School http://hdl.handle.net/10945/17810 Downloaded from NPS Archive...Calhoun IMPLEMENTING REPLACEMENT COST ACCOUNTING John Ross CHckener NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS IMPLEMENTING REPLACEMENT COST ...Implementing Replacement Cost Accounting 7. AUTHORS John Ross Clickener READ INSTRUCTIONS BEFORE COMPLETING FORM 3. RECIPIENT’S CATALOG NUMBER 9. TYRE OF

  16. Side Effects (Management)

    Science.gov (United States)

    ... cancer care is relieving side effects, called symptom management, palliative care, or supportive care. It is important ... treat them. To learn about the symptoms and management of the long-term side effects of cancer ...

  17. Improvements relating to apparatus for emplacing or replacing a gaiter

    International Nuclear Information System (INIS)

    Chilvers, D.; Morrison, D.M.

    1982-01-01

    The invention relates to apparatus for emplacing or replacing a gaiter of the type which may be used in sealing the hot side of an isolation enclosure which is associated with a master-slave manipulator. (author)

  18. Radiation Therapy Side Effects

    Science.gov (United States)

    Radiation therapy has side effects because it not only kills or slows the growth of cancer cells, it can also affect nearby healthy cells. Many people who get radiation therapy experience fatigue. Other side effects depend on the part of the body that is being treated. Learn more about possible side effects.

  19. Aeronautical Information System Replacement -

    Data.gov (United States)

    Department of Transportation — Aeronautical Information System Replacement is a web-enabled, automation means for the collection and distribution of Service B messages, weather information, flight...

  20. Development of Side Coupled Cavities

    International Nuclear Information System (INIS)

    Conto, J.M. de; Carretta, J.M.; Gomez-Martinez, Y.; Micoud, R.

    2008-01-01

    Side coupled Cavities are good candidates for proton accelerations in the 90-180 MeV range, as it has been first proposed for the CERN LINAC4 project. A side coupled Linac is made of a lump chain of resonant cavities, alternatively accelerating and coupling. A side coupled cavity has been designed in a CERN-LPSC collaboration to achieve LINAC4 requirements. After RF studies, a complete thermal study has been done, showing that 10-15% is the absolute maximum duty-cycle achievable by such a cavity. Error studies have been developed. They have shown that a tuning ring is mandatory and that a K equals 3% coupling factor is a good choice. A prototype has been built and each cell has been measured and tuned. A simple and accurate method has been used to get both the resonant frequency and the coupling factor, with a movable tuner and a linear fit. A similar method has been used to get the second order coupling factor. A large dispersion is observed on K. This is mainly due to the shape of the coupling apertures, which are very sensitive to mechanical errors. A future and realistic design must be very careful to guarantee a constant aperture (the important parameter is more the dispersion of k than its exact value). Finally, we analyse how to tune the cavity. This has to checked carefully and probably improved or corrected. Results are expected for mid-2008

  1. Radiation Source Replacement Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, Jeffrey W.; Moran, Traci L.; Bond, Leonard J.

    2010-12-01

    This report summarizes a Radiation Source Replacement Workshop in Houston Texas on October 27-28, 2010, which provided a forum for industry and researchers to exchange information and to discuss the issues relating to replacement of AmBe, and potentially other isotope sources used in well logging.

  2. Single-sided NMR

    CERN Document Server

    Casanova, Federico; Blümich, Bernhard

    2011-01-01

    Single-Sided NMR describes the design of the first functioning single-sided tomograph, the related measurement methods, and a number of applications. One of the key advantages to this method is the speed at which the images are obtained.

  3. CHAIN 2

    International Nuclear Information System (INIS)

    Bailey, D.

    1998-04-01

    The Second Processing Chain (CHAIN2) consists of a suite of ten programs which together provide a full local analysis of the bulk plasma physics within the JET Tokamak. In discussing these ten computational models this report is intended to fulfil two broad purposes. Firstly it is meant to be used as a reference source for any user of CHAIN2 data, and secondly it provides a basic User Manual sufficient to instruct anyone in running the CHAIN2 suite of codes. In the main report text each module is described in terms of its underlying physics and any associated assumptions or limitations, whilst deliberate emphasis is put on highlighting the physics and mathematics of the calculations required in deriving each individual datatype in the standard module PPF output. In fact each datatype of the CHAIN2 PPF output listed in Appendix D is cross referenced to the point in the main text where its evaluation is discussed. An effort is made not only to give the equation used to derive a particular data profile but also to explicitly define which external data sources are involved in the computational calculation

  4. Could wind replace nuclear?

    International Nuclear Information System (INIS)

    2017-01-01

    This article aims at assessing the situation produced by a total replacement of nuclear energy by wind energy, while facing consumption demand at any moment, notably in December. The authors indicate the evolution of the French energy mix during December 2016, and the evolution of the rate between wind energy production and the sum of nuclear and wind energy production during the same month, and then give briefly some elements regarding necessary investments in wind energy to wholly replace nuclear energy. According to them, such a replacement would be ruinous

  5. Slab replacement maturity guidelines.

    Science.gov (United States)

    2014-04-01

    This study investigated the use of maturity method to determine early age strength of concrete in slab : replacement application. Specific objectives were (1) to evaluate effects of various factors on the compressive : maturity-strength relationship ...

  6. Partial knee replacement

    Science.gov (United States)

    ... good range of motion in your knee. The ligaments in your knee are stable. However, most people with knee arthritis have a surgery called a total knee arthroplasty (TKA). Knee replacement is most often done in people age 60 ...

  7. Carbohydrates as Fat Replacers.

    Science.gov (United States)

    Peng, Xingyun; Yao, Yuan

    2017-02-28

    The overconsumption of dietary fat contributes to various chronic diseases, which encourages attempts to develop and consume low-fat foods. Simple fat reduction causes quality losses that impede the acceptance of foods. Fat replacers are utilized to minimize the quality deterioration after fat reduction or removal to achieve low-calorie, low-fat claims. In this review, the forms of fats and their functions in contributing to food textural and sensory qualities are discussed in various food systems. The connections between fat reduction and quality loss are described in order to clarify the rationales of fat replacement. Carbohydrate fat replacers usually have low calorie density and provide gelling, thickening, stabilizing, and other texture-modifying properties. In this review, carbohydrates, including starches, maltodextrins, polydextrose, gums, and fibers, are discussed with regard to their interactions with other components in foods as well as their performances as fat replacers in various systems.

  8. Hip joint replacement - slideshow

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/presentations/100006.htm Hip joint replacement - series—Normal anatomy To use the ... to slide 5 out of 5 Overview The hip joint is made up of two major parts: ...

  9. Tool Inventory and Replacement

    Science.gov (United States)

    Bear, W. Forrest

    1976-01-01

    Vocational agriculture teachers are encouraged to evaluate curriculum offerings, the new trends in business and industry, and develop a master tool purchase and replacement plan over a 3- to 5-year period. (HD)

  10. Knee joint replacement

    Science.gov (United States)

    ... to make everyday tasks easier. Practice using a cane, walker , crutches , or a wheelchair correctly. On the ... ask your doctor Knee joint replacement - discharge Preventing falls Preventing falls - what to ask your doctor Surgical ...

  11. Product Platform Replacements

    DEFF Research Database (Denmark)

    Sköld, Martin; Karlsson, Christer

    2012-01-01

    . To shed light on this unexplored and growing managerial concern, the purpose of this explorative study is to identify operational challenges to management when product platforms are replaced. Design/methodology/approach – The study uses a longitudinal field-study approach. Two companies, Gamma and Omega...... replacement was chosen in each company. Findings – The study shows that platform replacements primarily challenge managers' existing knowledge about platform architectures. A distinction can be made between “width” and “height” in platform replacements, and it is crucial that managers observe this in order...... to challenge their existing knowledge about platform architectures. Issues on technologies, architectures, components and processes as well as on segments, applications and functions are identified. Practical implications – Practical implications are summarized and discussed in relation to a framework...

  12. The effect of problems on supply chain wide efficiency

    Directory of Open Access Journals (Sweden)

    Micheline J. Naude

    2011-11-01

    This article reports on an exploratory empirical study to illustrate the effect of problems at one party in the supply chain on the whole supply chain. The study was done at automotive component manufacturers. To determine how problems at one place permeate through the whole supply chain, correlation testing was done between supply-side, internal operations, and distribution or customer-side problems. The study found that problems experienced at one place in the supply chain had a negative impact throughout the supply chain. Automotive supply chains should therefore be managed more as a system, taking into consideration the effect of decision making and actions at one part of the supply chain on other parts of the supply chain. There should be a supply chain wide co-operative effort to find solutions to inefficiencies at all places in the supply chain.

  13. The replacement research reactor

    International Nuclear Information System (INIS)

    Cameron, R.

    1999-01-01

    As a consequences of the government decision in September 1997. ANSTO established a replacement research reactor project to manage the procurement of the replacement reactor through the necessary approval, tendering and contract management stages This paper provides an update of the status of the project including the completion of the Environmental Impact Statement. Prequalification and Public Works Committee processes. The aims of the project, management organisation, reactor type and expected capabilities are also described

  14. Moving Segmentation Up the Supply-Chain: Supply Chain Segmentation and Artificial Neural Networks

    OpenAIRE

    Erevelles, Sunil; Fukawa, Nobuyuki

    2008-01-01

    This paper explained the concept of supply-side segmentation and transvectional alignment, and applies these concepts in the artificial neural network (ANN). To the best of our knowledge, no research has applied ANN in explaining the heterogeneity of both the supply-side and demand-side of a market in forming relational entity that consists of firms at all levels of the supply chain and the demand chain. The ANN offers a way of operationalizing the concept of supply-side segmentation. In toda...

  15. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    Due to the industrial facilities, heavy metal contents in environmental samples increase ... High performance liquid chromatography (HPLC) ... environmental waters by atomic absorption spectrometry (AAS) is very difficult due to the low.

  16. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    The presence of this lysine lowers the pKa of CysH3[125]β from the normal value for sulfhydryl groups (between 8 and 8.5) to .... However, DTNB has one disadvantage, it contains a disulfide bond, and the .... The pKa of the reacting sulfhydryl group varies between 5.9 and 6.4, with a mean value of. 6.1±0.2. (c) Assignment ...

  17. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    In the last decade, a large number of copper(II) complexes have been prepared and ... of glacial acetic acid, was added dropwise a solution of o-vanillin (6.16 g, 40.50 mmol) in 30 .... maximum indicates clearly antiferromagnetic interactions.

  18. Pendant triazole ring assisted mesogen containing side chain liquid ...

    Indian Academy of Sciences (India)

    Thermal stability of polymers was confirmed by thermogravimetric analysis. Mesomorphic property and phase transition temperature of polymers were ... group and investigated their mesomorphic property and their structure–property relationships. 2. Experimental. 2.1 Materials. Methanol, ethanol, phenol, THF, diethyl ether, ...

  19. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    was added the metal chloride or nitrate solution while stirring. The reaction mixture ... few drops of dilute ethanolic ammonium hydroxide to obtain the respective solid metal-ligand complex. ... indicating formation of thermally stable species.

  20. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    1Egerton University, Department of Chemistry, P.O. Box 536, Njoro, Kenya. 2Egerton ... War [13]. However, there is little data available about the chemical characterization of the essentials of the Ocimum .... Institute for Capacity Development).

  1. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    DETERMINATION OF THE MINOR AND TRACE ELEMENTS IN BIRINIWA'S TIN. PYRITE ... Lead and tin, the major elements, respectively, of the lead/zinc ore and tin ... In Africa, particularly in Nigeria, prior to the advent of modem cosmetics, ...

  2. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    GAS. Laitao Luo*, Zhonghua Gu, Jianjun Guo. Department of Chemistry, Nangchang University, Nangchang, 330047, Jiangxi, P.R. China. (Received June 4 ... KEY WORDS: Purification of exhaust gas, Pt Rh Pd/γ-Al2O3 catalyst, Transition metals .... An ideal d% will result in a useful improvement in catalyst effectiveness.

  3. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    2Department of Chemistry, University of Port Elizabeth, P.O. Box 1600, 6000 Port ... applications of rhenium radiopharmaceuticals in nuclear medicine[5, 6]. ... This report deals with the synthesis of complexes II, and their reactions with 2-.

  4. Microwave heating in peptide side chain modification via cysteine alkylation.

    Science.gov (United States)

    Calce, Enrica; De Luca, Stefania

    2016-09-01

    Microwave irradiation has been successfully applied to a selective synthetic procedure for introducing molecular substituents on peptides, providing a noticeable reduction of the reaction time and also an increased crude peptide purity for some compounds.

  5. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    above systems for environmental decontamination of organophosphates is discussed. ... and carbamates usually contain solvents such as petroleum distillates ... This kind of self-assembly, inherent to microemulsions, results in the .... applied to the soil depends largely on two of its properties: persistence and adsorption.

  6. Analysis of side chain rotational restrictions of membrane-embedded

    NARCIS (Netherlands)

    Strancar, J.; Kavalenka, A.A.; Ziherl, P.; Stopar, D.; Hemminga, M.A.

    2009-01-01

    Site-directed spin-labeling electron spin resonance (SDSL-ESR) is a promising tool for membrane protein structure determination. Here we propose a novel way to translate the local structural constraints gained by SDSL-ESR data into a low-resolution structure of a protein by simulating the

  7. Peptide Nucleic Acids Having Amino Acid Side Chains

    DEFF Research Database (Denmark)

    1998-01-01

    A novel class of compounds, known as peptide nucleic acids, bind complementary DNA and RNA strands more strongly than the corresponding DNA or RNA strands, and exhibit increased sequence specificity and solubility. The peptide nucleic acids comprise ligands selected from a group consisting...

  8. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    aDepartment of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala,. Cameroon. bLaboratoire de Chimie des Substances Naturelles, USM 0502 MNHN - UMR 5154 CNRS, 63 rue Buffon-75005 Paris, France. cDepartment of Organic Chemistry, Faculty of Science, University of Yaounde I, P.O. Box ...

  9. new polythiophenes with oligo(oxyethylene) side chains

    African Journals Online (AJOL)

    USER

    ORGANOSILICON CHEMISTRY I: CYCLOPROPANATION BY CARBENE OR. CARBENOID ... ammonium salt was highly hygroscopic. Related ... which stress the necessity of operating under anhydrous condition, due to rapid hydrolysis of.

  10. Side Effects: Sleep Problems

    Science.gov (United States)

    Sleep problems are a common side effect during cancer treatment. Learn how a polysomnogram can assess sleep problems. Learn about the benefits of managing sleep disorders in men and women with cancer.

  11. Side Effects: Fatigue

    Science.gov (United States)

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  12. Side Effects: Diarrhea

    Science.gov (United States)

    Diarrhea, a side effect of cancer treatment, may cause symptoms such as loose, watery stools. Diarrhea can lead to dehydration and malnutrition in cancer patients. Learn about ways to treat and manage diarrhea during cancer treatment.

  13. Side Effects: Appetite Loss

    Science.gov (United States)

    Cancer treatments may lower your appetite. Side effects such as nausea, fatigue, or mouth sores can also making eating difficult. Learn how to eat well to avoid losing weight or becoming dehydrated, so you stay strong during treatment.

  14. Side Effects: Pain

    Science.gov (United States)

    Controlling pain is an important part of your cancer treatment plan. Learn how to track levels of pain. Find out how pain, a side effect of cancer treatment, is treated using acupuncture, biofeedback, and physical therapy.

  15. Side Effects: Anemia

    Science.gov (United States)

    Anemia is a side effect of cancer treatments, including chemotherapy and radiation therapy. It can make women and men feel fatigued, dizzy, and short of breath. Learn how to manage fatigue caused by anemia during cancer treatment.

  16. Side core lifter

    Energy Technology Data Exchange (ETDEWEB)

    Edelman, Ya A

    1982-01-01

    A side core lifter is proposed which contains a housing with guide slits and a removable core lifter with side projections on the support section connected to the core receiver. In order to preserve the structure of the rock in the core sample by means of guaranteeing rectilinear movement of the core lifter in the rock, the support and core receiver sections are hinged. The device is equipped with a spring for angular shift in the core-reception part.

  17. Heavy Chain Diseases

    Science.gov (United States)

    ... of heavy chain produced: Alpha Gamma Mu Alpha Heavy Chain Disease Alpha heavy chain disease (IgA heavy ... the disease or lead to a remission. Gamma Heavy Chain Disease Gamma heavy chain disease (IgG heavy ...

  18. Method of identification of unbranched chain reaction with cross termination of chain

    International Nuclear Information System (INIS)

    Poluehktov, V.A.; Begishev, I.R.

    1977-01-01

    Gas-phase chlorination of unsymmetrical difluoroethane initiated by gamma quanta of Co 60 has been studied. At decreased temperatures the only hydrogen is replaced by a chlorine atom. Over a wide range of ratios of the initial reagents, the reaction occurs with a chain rupture. An analysis of the kinetics of such a reaction provides a method for identification of an unbranched chain reaction with a cross-rupture of the chain

  19. [Psychoanalysis and Side Effect].

    Science.gov (United States)

    Shirahase, Joichiro

    2015-01-01

    A study of psychoanalysis from the perspective of side effects reveals that its history was a succession of measures to deal with its own side effects. This, however, does not merely suggest that, as a treatment method, psychoanalysis is incomplete and weak: rather, its history is a record of the growth and development of psychoanalysis that discovered therapeutic significance from phenomena that were initially regarded as side effects, made use of these discoveries, and elaborated them as a treatment method. The approach of research seen during the course of these developments is linked to the basic therapeutic approach of psychoanalysis. A therapist therefore does not draw conclusions about a patient's words and behaviors from a single aspect, but continues to make efforts to actively discover a variety of meanings and values from them, and to make the patient's life richer and more productive. This therapeutic approach is undoubtedly one of the unique aspects of psychoanalysis. I discuss the issue of psychoanalysis and side effects with the aim of clarifying this unique characteristic of psychoanalysis. The phenomenon called resistance inevitably emerges during the process of psychoanalytic treatment. Resistance can not only obstruct the progress of therapy; it also carries the risk of causing a variety of disadvantages to the patient. It can therefore be seen as an adverse effect. However, if we re-examine this phenomenon from the perspective of transference, we find that resistance is in fact a crucial tool in psychoanalysis, and included in its main effect, rather than a side effect. From the perspective of minimizing the character of resistance as a side effect and maximizing its character as a main effect, I have reviewed logical organization, dynamic evaluation, the structuring of treatment, the therapist's attitudes, and the training of therapists. I conclude by stating that psychoanalysis has aspects that do not match the perspective known as a side

  20. Prioritizing equipment for replacement.

    Science.gov (United States)

    Capuano, Mike

    2010-01-01

    It is suggested that clinical engineers take the lead in formulating evaluation processes to recommend equipment replacement. Their skill, knowledge, and experience, combined with access to equipment databases, make them a logical choice. Based on ideas from Fennigkoh's scheme, elements such as age, vendor support, accumulated maintenance cost, and function/risk were used.6 Other more subjective criteria such as cost benefits and efficacy of newer technology were not used. The element of downtime was also omitted due to the data element not being available. The resulting Periop Master Equipment List and its rationale was presented to the Perioperative Services Program Council. They deemed the criteria to be robust and provided overwhelming acceptance of the list. It was quickly put to use to estimate required capital funding, justify items already thought to need replacement, and identify high-priority ranked items for replacement. Incorporating prioritization criteria into an existing equipment database would be ideal. Some commercially available systems do have the basic elements of this. Maintaining replacement data can be labor-intensive regardless of the method used. There is usually little time to perform the tasks necessary for prioritizing equipment. However, where appropriate, a clinical engineering department might be able to conduct such an exercise as shown in the following case study.

  1. Thyroid hormone replacement therapy

    NARCIS (Netherlands)

    Wiersinga, W. M.

    2001-01-01

    Thyroid hormone replacement has been used for more than 100 years in the treatment of hypothyroidism, and there is no doubt about its overall efficacy. Desiccated thyroid contains both thyroxine (T(4)) and triiodothyronine (T(3)); serum T(3) frequently rises to supranormal values in the absorption

  2. Can photovoltaic replace nuclear?

    International Nuclear Information System (INIS)

    2017-01-01

    As the French law on energy transition for a green growth predicts that one third of nuclear energy production is to be replaced by renewable energies (wind and solar) by 2025, and while the ADEME proposes a 100 per cent renewable scenario for 2050, this paper proposes a brief analysis of the replacement of nuclear energy by solar photovoltaic energy. It presents and discusses some characteristics of photovoltaic production: production level during a typical day for each month (a noticeable lower production in December), evolution of monthly production during a year, evolution of the rate between nuclear and photovoltaic production. A cost assessment is then proposed for energy storage and for energy production, and a minimum cost of replacement of nuclear by photovoltaic is assessed. The seasonal effect is outlined, as well as the latitude effect. Finally, the authors outline the huge cost of such a replacement, and consider that public support to new photovoltaic installations without an at least daily storage mean should be cancelled

  3. Fluorescent Lamp Replacement Study

    Science.gov (United States)

    2017-07-01

    not be cited for purposes of advertisement. DISPOSITION INSTRUCTIONS: Destroy this document when no longer needed. Do not return to the... recycling , and can be disposed safely in a landfill. (2) LEDs offer reduced maintenance costs and fewer bulb replacements, significantly reducing... recycling . Several fixtures, ballasts and energy efficient fluorescent bulbs that were determined to be in pristine condition were returned to ATC

  4. Replacing Recipe Realism

    OpenAIRE

    Saatsi, J

    2017-01-01

    Many realist writings exemplify the spirit of ‘recipe realism’. Here I characterise recipe realism, challenge it, and propose replacing it with ‘exemplar realism’. This alternative understanding of realism is more piecemeal, robust, and better in tune with scientists’ own attitude towards their best theories, and thus to be preferred.

  5. Working the Dark Side

    DEFF Research Database (Denmark)

    Bjering, Jens Christian Borrebye

    A few days after the terror attacks of 9/11, then Vice President Dick Cheney appeared on television with a call for “working the dark side.” While still unclear what this expression entailed at the time, Cheney's comment appears in retrospect to almost have been prophetic for the years to come....... By analyzing official reports and testimonies from soldiers partaking in the War On Terror, the dissertation's second part—dark arts—focuses on the transformation of the dark side into a productive space in which “information” and the hunt for said information overshadowed all legal, ethical, or political...

  6. Forskningens personlige side

    DEFF Research Database (Denmark)

    Hansen, Finn Thorbjørn

    2008-01-01

    Artiklen omhandler den ontologiske vending inden for universitetspædagogisk forskning, og redegør for hvorfor en mere personlig og eksistentiel side ved forskningen må medtænkes i universitetspædagogikken og -vejledningen. Udgivelsesdato: 24.11.08...

  7. Side loading filter apparatus

    International Nuclear Information System (INIS)

    Reynolds, K.E.

    1981-01-01

    A side loading filter chamber for use with radioactive gases is described. The equipment incorporates an inexpensive, manually operated, mechanism for aligning filter units with a number of laterally spaced wall openings and for removing the units from the chamber. (U.K.)

  8. Side insertable spacer

    International Nuclear Information System (INIS)

    Patterson, J.F.; Ewing, R.H.

    1992-01-01

    This patent describes a spacer for restraining the fuel rods of a nuclear fuel assembly, the assembly being formed of a plurality of parallel, elongated fuel rods so arranged that the assembly is bounded by a polygon having an even number of sides, the rods being so arranged as to lie in a plurality of sets of parallel rows, the rows of each set being perpendicular to one of the sides of the polygon. It comprises a number of spacer combs equal to at least half the number of the sides of the polygon, the spacer combs being superposed on each other, each of the spacer combs comprising: a single base strip having a length equal to that of one of the sides of the polygon and grid strips equal in number to the spaces between rows in one of the sets, and at least a majority of the grid strips being of a length sufficient to extend substantially the full length of the rows; the grid strips being provided with spring members positioned to engage each of the rods; the grid strips being provided with spring members positioned to engage each of the rods; the grid strips being secured to and extending at right angles to the base strip; the grid strips of different combs being positioned at angles to each other, so as to occupy the spaces between rows in different sets

  9. Valve exploiting the principle of a side channel turbine

    Directory of Open Access Journals (Sweden)

    Jandourek Pavel

    2017-01-01

    Full Text Available The article deals with a side channel turbine, which can be used as a suitable substitute for a pressure reducing valve. Reducing valves are a source of hydraulic losses. The aim is to replace them by a side channel turbine. With that in mind, hydraulic losses can be replaced by a production of electrical energy at comparable characteristics of the valve and the turbine. The basis for the design is the loss characteristics of the valve. Thereby creating a kind of turbine valve with speed-controlled flow in dependence of runner revolution.

  10. Glaucoma after corneal replacement.

    Science.gov (United States)

    Baltaziak, Monika; Chew, Hall F; Podbielski, Dominik W; Ahmed, Iqbal Ike K

    Glaucoma is a well-known complication after corneal transplantation surgery. Traditional corneal transplantation surgery, specifically penetrating keratoplasty, has been slowly replaced by the advent of new corneal transplantation procedures: primarily lamellar keratoplasties. There has also been an emergence of keratoprosthesis implants for eyes that are high risk of failure with penetrating keratoplasty. Consequently, there are different rates of glaucoma, pathogenesis, and potential treatment in the form of medical, laser, or surgical therapy. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. The replacement research reactor

    International Nuclear Information System (INIS)

    Cameron, R.; Horlock, K.

    2001-01-01

    The contract for the design, construction and commissioning of the Replacement Research Reactor was signed in July 2000. This was followed by the completion of the detailed design and an application for a construction licence was made in May 2001. This paper will describe the main elements of the design and their relation to the proposed applications of the reactor. The future stages in the project leading to full operation are also described

  12. Apparatus for fuel replacement

    International Nuclear Information System (INIS)

    Imada, Takahiko.

    1974-01-01

    Object: To support a telescope mast such that no deforming load is applied to it even during massive vibration, it is held fixed at the time of fuel replacement to permit satisfactory remote control operation by automatic operation. Structure: The body of the fuel replacement apparatus is provided with telescope mast fixing means comprising a slide base supported for reciprocal movement with respect to a telescope mast, an operating arm pivoted at the slide base, a wrist member mounted on the free end of the operating arm and an engagement member for restricting the slide base and operating arm at the time of loading and unloading the fuel. When loading and unloading the fuel, the slide base and operating arm are restrained by the engagement member to reliably restrict the vibration of the telescope mast. When the fuel replacement apparatus is moved, the means provided on the operating arm is smoothly displaced to follow the swing (vibration) of the telescope mast to prevent the deforming load from being applied to the support portion or other areas. The wrist member supports the telescope mast such that it can be rotated while restraining movement in the axial direction, and it is provided with revolution drive means for rotating the telescope mast under remote control. (Kamimura, M.)

  13. Supply chain reaction

    International Nuclear Information System (INIS)

    Snieckus, Darius

    2000-01-01

    'Logic' (Leading Oil and Gas Industry Competitiveness) is a government-industry supply chain management initiative which aims to improve the competitiveness of the UK's North Sea business by 1 billion UK pounds by 2002 and its export performance by 50% inside 5 years. Much of the article is devoted to the background and views of Logic's chief executive Chris. Freeman. Freeman makes clear that 'unlike Crine, we are not a cost-reduction initiative: that may be one of the outcomes, but we are really focusing on the co-operation side of things'. Logic aims to change the culture of the UK offshore industry through example. Freeman believes that the creation of collaborative success will flag up industry and give credence to Logics objectives

  14. Toleration, Synthesis or Replacement?

    DEFF Research Database (Denmark)

    Holtermann, Jakob v. H.; Madsen, Mikael Rask

    2016-01-01

    , in order to answer is not yet another partisan suggestion, but rather an attempt at making intelligible both the oppositions and the possibilities of synthesis between normative and empirical approaches to law. Based on our assessment and rational reconstruction of current arguments and positions, we...... therefore outline a taxonomy consisting of the following three basic, ideal-types in terms of the epistemological understanding of the interface of law and empirical studies: toleration, synthesis and replacement. This tripartite model proves useful with a view to teasing out and better articulating...

  15. Upgrade, rebuild or replace?

    International Nuclear Information System (INIS)

    Forbes, C.A.

    1990-01-01

    Ageing reactor simulators present some tough decisions for utility managers. Although most utilities have chosen the cheaper, upgrading solution as the best compromise between costs and outage length, some US utilities have found that for them, replacement represents the best option. Simulators may be less than ten years old, but they have limited instructor systems, older low fidelity models that cannot reproduce important training scenarios, and out of date, difficult to maintain computers that do not permit much expansion of the models anyway. Perhaps worse than this is the possibility that the simulator may no longer be a faithful reproduction of the referenced plant, or have poor (or non-existent) documentation. (author)

  16. Chain reaction

    International Nuclear Information System (INIS)

    Balogh, Brian.

    1991-01-01

    Chain Reaction is a work of recent American political history. It seeks to explain how and why America came to depend so heavily on its experts after World War II, how those experts translated that authority into political clout, and why that authority and political discretion declined in the 1970s. The author's research into the internal memoranda of the Atomic Energy Commission substantiates his argument in historical detail. It was not the ravages of American anti-intellectualism, as so many scholars have argued, that brought the experts back down to earth. Rather, their decline can be traced to the very roots of their success after World War II. The need to over-state anticipated results in order to garner public support, incessant professional and bureaucratic specialization, and the sheer proliferation of expertise pushed arcane and insulated debates between experts into public forums at the same time that a broad cross section of political participants found it easier to gain access to their own expertise. These tendencies ultimately undermined the political influence of all experts. (author)

  17. Thermoresponsive Poly(2-Oxazoline) Molecular Brushes by Living Ionic Polymerization: Modulation of the Cloud Point by Random and Block Copolymer Pendant Chains

    KAUST Repository

    Zhang, Ning; Luxenhofer, Robert; Jordan, Rainer

    2012-01-01

    random and block copolymers. Their aqueous solutions displayed a distinct thermoresponsive behavior as a function of the side-chain composition and sequence. The cloud point (CP) of MBs with random copolymer side chains is a linear function

  18. Power Plant Replacement Study

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Gary

    2010-09-30

    This report represents the final report for the Eastern Illinois University power plant replacement study. It contains all related documentation from consideration of possible solutions to the final recommended option. Included are the economic justifications associated with the chosen solution along with application for environmental permitting for the selected project for construction. This final report will summarize the results of execution of an EPC (energy performance contract) investment grade audit (IGA) which lead to an energy services agreement (ESA). The project includes scope of work to design and install energy conservation measures which are guaranteed by the contractor to be self-funding over its twenty year contract duration. The cost recovery is derived from systems performance improvements leading to energy savings. The prime focus of this EPC effort is to provide a replacement solution for Eastern Illinois University's aging and failing circa 1925 central steam production plant. Twenty-three ECMs were considered viable whose net impact will provide sufficient savings to successfully support the overall project objectives.

  19. Cadmium plating replacements

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, M.J.; Groshart, E.C.

    1995-03-01

    The Boeing Company has been searching for replacements to cadmium plate. Two alloy plating systems seem close to meeting the needs of a cadmium replacement. The two alloys, zinc-nickel and tin-zinc are from alloy plating baths; both baths are neutral pH. The alloys meet the requirements for salt fog corrosion resistance, and both alloys excel as a paint base. Currently, tests are being performed on standard fasteners to compare zinc-nickel and tin-zinc on threaded hardware where cadmium is heavily used. The Hydrogen embrittlement propensity of the zinc-nickel bath has been tested, and just beginning for the tin-zinc bath. Another area of interest is the electrical properties on aluminum for tin-zinc and will be discussed. The zinc-nickel alloy plating bath is in production in Boeing Commercial Airplane Group for non-critical low strength steels. The outlook is promising that these two coatings will help The Boeing Company significantly reduce its dependence on cadmium plating.

  20. REPLACEMENT OF FRENCH CARDS

    CERN Multimedia

    Human Resources Division

    2001-01-01

    The French Ministry of Foreign Affairs has informed the Organization that it is shortly to replace all diplomatic cards, special cards and employment permits ('attestations de fonctions') now held by members of the personnel and their families. Between 2 July and 31 December 2001, these cards are to be replaced by secure, computerized equivalents. A 'personnel office' stamped photocopy of the old cards may continue to be used until 31 December 2001. For the purposes of the handover, members of the personnel must go personally to the cards office (33/1-015), between 8:30 and 12:30, in order to fill a 'fiche individuelle' form (in black ink only), which has to be personally signed by themselves and another separately signed by members of their family, taking the following documents for themselves and members of their families already in possession of a French card : A recent identity photograph in 4.5 cm x 3.5 cm format (signed on the back) The French card in their possession an A4 photocopy of the same Fre...

  1. Power Plant Replacement Study

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Gary

    2010-09-30

    This report represents the final report for the Eastern Illinois University power plant replacement study. It contains all related documentation from consideration of possible solutions to the final recommended option. Included are the economic justifications associated with the chosen solution along with application for environmental permitting for the selected project for construction. This final report will summarize the results of execution of an EPC (energy performance contract) investment grade audit (IGA) which lead to an energy services agreement (ESA). The project includes scope of work to design and install energy conservation measures which are guaranteed by the contractor to be self-funding over its twenty year contract duration. The cost recovery is derived from systems performance improvements leading to energy savings. The prime focus of this EPC effort is to provide a replacement solution for Eastern Illinois University’s aging and failing circa 1925 central steam production plant. Twenty-three ECMs were considered viable whose net impact will provide sufficient savings to successfully support the overall project objectives.

  2. Replace with abstract title

    Science.gov (United States)

    Coho, Aleksander; Kioussis, Nicholas

    2003-03-01

    We use the semidiscrete variational generelized Peierls-Nabarro model to study the effect of Cu alloying on the dislocation properties of Al. First-principles density functional theory (DFT) is used to calculate the generalized-stacking-fault (GSF) energy surface when a plane, on which one in four Al atoms has been replaced with a Cu atom, slips over a pure Al plane. Various dislocation core properties (core width, energy, Peierls stress, dissociation tendency) are investigated and compared with the pure Al case. Cu alloying lowers the intrinsic stacking fault (ISF) energy, which makes dislocations more likely to dissociate into partials. We also try to understand the lowering of ISF energy in terms of Al-Cu and Al-Al bond formation and braking during shearing along the direction. From the above we draw conclusions about the effects of Cu alloying on the mechanical properties of Al.

  3. Iron replacement therapy

    DEFF Research Database (Denmark)

    Nielsen, Ole Haagen; Coskun, Mehmet; Weiss, Günter

    2016-01-01

    PURPOSE OF REVIEW: Approximately, one-third of the world's population suffers from anemia, and at least half of these cases are because of iron deficiency. With the introduction of new intravenous iron preparations over the last decade, uncertainty has arisen when these compounds should...... be administered and under which circumstances oral therapy is still an appropriate and effective treatment. RECENT FINDINGS: Numerous guidelines are available, but none go into detail about therapeutic start and end points or how iron-deficiency anemia should be best treated depending on the underlying cause...... of iron deficiency or in regard to concomitant underlying or additional diseases. SUMMARY: The study points to major issues to be considered in revisions of future guidelines for the true optimal iron replacement therapy, including how to assess the need for treatment, when to start and when to stop...

  4. Total ankle joint replacement.

    Science.gov (United States)

    2016-02-01

    Ankle arthritis results in a stiff and painful ankle and can be a major cause of disability. For people with end-stage ankle arthritis, arthrodesis (ankle fusion) is effective at reducing pain in the shorter term, but results in a fixed joint, and over time the loss of mobility places stress on other joints in the foot that may lead to arthritis, pain and dysfunction. Another option is to perform a total ankle joint replacement, with the aim of giving the patient a mobile and pain-free ankle. In this article we review the efficacy of this procedure, including how it compares to ankle arthrodesis, and consider the indications and complications. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  5. Menopause and hormone replacement therapy

    Directory of Open Access Journals (Sweden)

    Ali Baziad

    2001-12-01

    Full Text Available The global population in the 21st century has reached 6.2 billion people, by the year 2025 it is to be around 8.3-8.5 billion, and will increase further. Elderly people are expected to grow rapidly than other groups. The fastest increase in the elderly population will take place in Asia. Life expectancy is increasing steadily throughout developed and developing countries. For many  menopausal women, increased life expectancy will accompanied by many health problems. The consequences of estrogen deficiency are the menopausal symptoms. The treatment of menopause related complaints and diseases became an  important socioeconomic and medical issue. Long term symptoms, such as the increase in osteoporosis fractures, cardio and cerebrovascular disesses and dementia, created a large financial burden on individuals and society. All these health problems can be lreated or prevented by hormone replacement therapy (HRT. Natural HRT is usually prefened. Synthetic  estrogen in oral contraceptives (oc are not recommended for HRT. Many contra-indications for oc, but now it is widely usedfor HRT. The main reasons for discontinuing HRT are unwanted bleeding, fear of cancer, and negative side effects. Until now there are sill debates about the rebrtonship between HRT and the incidence of breast cancer. Many data showed that there were no clear relationship between the use of HRT and breast cancer. ThereÎore, nwny experts advocate the use of HRTfrom the first sign of climacteric complaints until death. (Med J Indones 2001;10: 242-51Keywords: estrogen deficiency, climacteric phases, tibolone.

  6. HIV Medicines and Side Effects

    Science.gov (United States)

    ... medicines, talk to your health care provider about possible side effects. Tell your health care provider about your lifestyle and point out any possible side effects that would be especially hard for you to ...

  7. Probiotics: Safety and Side Effects

    Science.gov (United States)

    ... of this page please turn JavaScript on. Feature: Probiotics Safety and Side Effects Past Issues / Winter 2016 ... Says About the Safety and Side Effects of Probiotics Whether probiotics are likely to be safe for ...

  8. Photoorientation of a liquid crystalline polyester with azobenzene side groups

    DEFF Research Database (Denmark)

    Zebger, I; Rutloh, M; Hoffmann, U

    2002-01-01

    segments in the side- and main-chain. The very high values of the normalized linear dichroism up to 0.8 and the birefringence (above 0.3) are due to the interaction of photoorientation and thermotropic self-organization. The induction of anisotropy shows a pronounced dependence on the power density...

  9. Using demand-side management to decrease transformer ageing

    NARCIS (Netherlands)

    van der Klauw, Thijs; Gerards, Marco Egbertus Theodorus; Hurink, Johann L.

    2016-01-01

    The introduction of local, often uncontrollable, generation units as well as larger loads such as electric vehicles (EVs) causes an increasing amount of stress on our energy supply chain, specifically on the distribution grids. Demand-side management (DSM) is often seen as a potential technology to

  10. Salivary cortisol day curves in assessing glucocorticoid replacement therapy in Addison's disease

    NARCIS (Netherlands)

    Smans, L.; Lentjes, E.G.W.M.; Hermus, A.R.; Zelissen, P.M.J.

    2013-01-01

    OBJECTIVE: Patients with Addison's disease require lifelong treatment with glucocorticoids. At present, no glucocorticoid replacement therapy (GRT) can exactly mimic normal physiology. As a consequence, under- and especially overtreatment can occur. Suboptimal GRT may lead to various side effects.

  11. Side-View Face Recognition

    NARCIS (Netherlands)

    Santemiz, P.; Spreeuwers, Lieuwe Jan; Veldhuis, Raymond N.J.

    2010-01-01

    Side-view face recognition is a challenging problem with many applications. Especially in real-life scenarios where the environment is uncontrolled, coping with pose variations up to side-view positions is an important task for face recognition. In this paper we discuss the use of side view face

  12. CHAINS-PC, Decay Chain Atomic Densities

    International Nuclear Information System (INIS)

    1994-01-01

    1 - Description of program or function: CHAINS computes the atom density of members of a single radioactive decay chain. The linearity of the Bateman equations allows tracing of interconnecting chains by manually accumulating results from separate calculations of single chains. Re-entrant loops can be treated as extensions of a single chain. Losses from the chain are also tallied. 2 - Method of solution: The Bateman equations are solved analytically using double-precision arithmetic. Poles are avoided by small alterations of the loss terms. Multigroup fluxes, cross sections, and self-shielding factors entered as input are used to compute the effective specific reaction rates. The atom densities are computed at any specified times. 3 - Restrictions on the complexity of the problem: Maxima of 100 energy groups, 100 time values, 50 members in a chain

  13. Multi-stage type replacing method of iodine filter

    International Nuclear Information System (INIS)

    Kitamura, Masao; Kamiya, Kunio.

    1976-01-01

    Object: To effectively replace a filter into a removing device of radioactive impurities used in ventilation and air conditioning system or the like in an atomic power plant. Structure: A plurality of elements of a filter are arranged in series relative to fluid. In the first replacement, an ante-filter-element on inlet side of fluid is removed, and a post-filter-element is repositioned to that position of the ante-element. Then, a fresh element is newly mounted on that position of the post-element. Replacement after the second time may be effected by repeating the operation noted above. With this arrangement, the minimal value of collection efficiency at replacement of filter may be increased. (Ikeda, J.)

  14. Antenna Controller Replacement Software

    Science.gov (United States)

    Chao, Roger Y.; Morgan, Scott C.; Strain, Martha M.; Rockwell, Stephen T.; Shimizu, Kenneth J.; Tehrani, Barzia J.; Kwok, Jaclyn H.; Tuazon-Wong, Michelle; Valtier, Henry; Nalbandi, Reza; hide

    2010-01-01

    The Antenna Controller Replacement (ACR) software accurately points and monitors the Deep Space Network (DSN) 70-m and 34-m high-efficiency (HEF) ground-based antennas that are used to track primarily spacecraft and, periodically, celestial targets. To track a spacecraft, or other targets, the antenna must be accurately pointed at the spacecraft, which can be very far away with very weak signals. ACR s conical scanning capability collects the signal in a circular pattern around the target, calculates the location of the strongest signal, and adjusts the antenna pointing to point directly at the spacecraft. A real-time, closed-loop servo control algorithm performed every 0.02 second allows accurate positioning of the antenna in order to track these distant spacecraft. Additionally, this advanced servo control algorithm provides better antenna pointing performance in windy conditions. The ACR software provides high-level commands that provide a very easy user interface for the DSN operator. The operator only needs to enter two commands to start the antenna and subreflector, and Master Equatorial tracking. The most accurate antenna pointing is accomplished by aligning the antenna to the Master Equatorial, which because of its small size and sheltered location, has the most stable pointing. The antenna has hundreds of digital and analog monitor points. The ACR software provides compact displays to summarize the status of the antenna, subreflector, and the Master Equatorial. The ACR software has two major functions. First, it performs all of the steps required to accurately point the antenna (and subreflector and Master Equatorial) at the spacecraft (or celestial target). This involves controlling the antenna/ subreflector/Master-Equatorial hardware, initiating and monitoring the correct sequence of operations, calculating the position of the spacecraft relative to the antenna, executing the real-time servo control algorithm to maintain the correct position, and

  15. Temperature control feedback loops for the linac upgrade side coupled cavities at Fermilab

    International Nuclear Information System (INIS)

    Crisp, J.

    1990-01-01

    The linac upgrade project at Fermilab will replace the last 4 drift-tube linac tanks with seven side coupled cavity strings. This will increase the beam energy from 200 to 400 MeV at injection into the Booster accelerator. The main objective of the temperature loop is to control the resonant frequency of the cavity strings. A cavity string will constant of 4 sections connected with bridge couplers driven with a 12 MW klystron at 805 MHz. Each section is a side coupled cavity chain consisting of 16 accelerating cells and 15 side coupling cells. For the linac upgrade, 7 full cavity strings will be used. A separate temperature control system is planned for each of the 28 accelerating sections, the two transition sections, and the debuncher section. The cavity strings will be tuned to resonance for full power beam loaded conditions. A separate frequency loop is planned that will sample the phase difference between a monitor placed in the end cell of each section and the rf drive. The frequency loop will control the set point for the temperature loop which will be able to maintain the resonant frequency through periods within beam or rf power. The frequency loop will need the intelligence required to determine under what conditions the phase error information is valid and the temperature set point should be adjusted. This paper will discuss some of the reason for temperature control, the implementation, and some of the problems encountered. An appendix contains some useful constants and descriptions of some of the sensor and control elements used. 13 figs

  16. Logistic chain modelling

    NARCIS (Netherlands)

    Slats, P.A.; Bhola, B.; Evers, J.J.M.; Dijkhuizen, G.

    1995-01-01

    Logistic chain modelling is very important in improving the overall performance of the total logistic chain. Logistic models provide support for a large range of applications, such as analysing bottlenecks, improving customer service, configuring new logistic chains and adapting existing chains to

  17. Hip Replacement: MedlinePlus Health Topic

    Science.gov (United States)

    ... invasive hip replacement (Medical Encyclopedia) Also in Spanish Topic Image MedlinePlus Email Updates Get Hip Replacement updates ... replacement - precautions Minimally invasive hip replacement Related Health Topics Hip Injuries and Disorders National Institutes of Health ...

  18. Educating My Replacement

    Science.gov (United States)

    Tarter, Jill

    , in partnership with the dedicated teachers out there, I think I can help promote the critical thinking skills and scientific literacy of the next generation of voters. Hopefully, I can also help train my replacement to be a better scientist, capable of seizing all the opportunities generated by advances in technology and our improved understanding of the universe to craft search strategies with greater probability of success than those I have initiated.

  19. Transforming Normal Programs by Replacement

    NARCIS (Netherlands)

    Bossi, Annalisa; Pettorossi, A.; Cocco, Nicoletta; Etalle, Sandro

    1992-01-01

    The replacement transformation operation, already defined in [28], is studied wrt normal programs. We give applicability conditions able to ensure the correctness of the operation wrt Fitting's and Kunen's semantics. We show how replacement can mimic other transformation operations such as thinning,

  20. Minimally invasive aortic valve replacement

    DEFF Research Database (Denmark)

    Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

    2009-01-01

    In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy...... operations were completed as mini-sternotomies, 4 died later of noncardiac causes. The aortic cross-clamp and perfusion times were significantly different across all groups (P replacement...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

  1. Excitation of bond-alternating spin-1/2 Heisenberg chains by tunnelling electrons

    International Nuclear Information System (INIS)

    Gauyacq, J-P; Lorente, N

    2014-01-01

    Inelastic electron tunneling spectra (IETS) are evaluated for spin-1/2 Heisenberg chains showing different phases of their spin ordering. The spin ordering is controlled by the value of the two different Heisenberg couplings on the two sides of each of the chain's atoms (bond-alternating chains). The perfect anti-ferromagnetic phase, i.e. a unique exchange coupling, marks a topological quantum phase transition (TQPT) of the bond-alternating chain. Our calculations show that the TQPT is recognizable in the excited states of the chain and hence that IETS is in principle capable of discriminating the phases. We show that perfectly symmetric chains, such as closed rings mimicking infinite chains, yield the same spectra on both sides of the TQPT and IETS cannot reveal the nature of the spin phase. However, for finite size open chains, both sides of the TQPT are associated with different IETS spectra, especially on the edge atoms, thus outlining the transition. (paper)

  2. Ethamsylate and blood loss in total hip replacement.

    Science.gov (United States)

    Keith, I

    1979-01-01

    Nineteen consecutive patients undergoing total hip replacement under epidural anaesthesia were randomly divided into two groups. The treatment group received 1000 mg of ethamsylate intravenously before induction of anaesthesia. Blood lost during surgery was measured by a colorimetric technique. Closed suction drains were used and all blood lost after operation collected for measurement. Ethamsylate did not decrease the average volumes of blood lost during or after the operation. Neither did it reduce the requirements for blood transfusion. Although there were no side-effects attributable to ethamyslate, there seems to be no indication for its use in total hip replacement under epidural anaesthesia.

  3. Sustainable Supply Chain Design

    DEFF Research Database (Denmark)

    Bals, Lydia; Tate, Wendy

    A significant conceptual and practical challenge is how to integrate triple bottom line (TBL; including economic, social and environmental) sustainability into global supply chains. Although this integration is necessary to slow down global resource depletion, understanding is limited of how...... to implement TBL goals across the supply chain. In supply chain design, the classic economic perspective still dominates, although the idea of the TBL is more widely disseminated. The purpose of this research is to add to the sustainable supply chain management literature (SSCM) research agenda...... by incorporating the physical chain, and the (information and financial) support chains into supply chain design. This manuscript tackles issues of what the chains are designed for and how they are designed structurally. Four sustainable businesses are used as illustrative case examples of innovative supply chain...

  4. Segmental blood pressure after total hip replacement

    DEFF Research Database (Denmark)

    Gebuhr, Peter Henrik; Soelberg, M; Henriksen, Jens Henrik Sahl

    1992-01-01

    Twenty-nine patients due to have a total hip replacement had their systemic systolic and segmental blood pressures measured prior to operation and 1 and 6 weeks postoperatively. No patients had signs of ischemia. The segmental blood pressure was measured at the ankle and at the toes. A significant...... drop was found in all pressures 1 week postoperatively. The decrease followed the systemic pressure and was restored to normal after 6 weeks. In a group of six patients with preoperatively decreased ankle pressure, a significant transient further decrease in the ankle-toe gradient pressure was found...... on the operated side. None of the patients had symptoms from the lowered pressure. We conclude that in patients without signs of ischemia, the postoperative segmental pressure decrease is reversible and therefore not dangerous....

  5. Patients Unicondylar Knee Replacement vs. Total Knee Replacement

    OpenAIRE

    Hedra Eskander

    2017-01-01

    The aim of this review article is to analyse the clinical effectiveness of total knee replacement (TKR) compared to unicondylar knee replacement (UKR) on patients. In terms of survival rates, revision rates and postoperative complications. The keywords used were: knee arthroplasty. Nearly three thousand articles were found on 25 August 2016. Of those, only twenty-five were selected and reviewed because they were strictly focused on the topic of this article. Compared with those who have TKR, ...

  6. An innovative strategy for secondary side system lay-up using film-forming amines

    International Nuclear Information System (INIS)

    Ramminger, U.; Drexler, A.; Fandrich, J.

    2012-01-01

    The major safety function of steam generators (SG) in pressurized reactors is well known as acting as a barrier between the radioactive primary side and the non-radioactive secondary side. The main reason for SG tube failure is known to be the accumulation of deposits contributing to formation of local aggressive conditions. Consequently the SG has to be kept as clean as possible and the corrosion product transport into the SG has to be minimized. In order to reach this target, plant operators are making worldwide huge efforts to protect plant systems against corrosion during standstill and outages. Especially in case of large component replacements campaigns like steam generator or fuel channel replacements which are linked to prolonged outages lay-up strategies become important. The use of surface active agents like film-forming amines (FFA) has become very popular in the fossil power plant sector, showing a decrease of corrosion product generation by improving the surface conditions. The adherent non wettable film built by FFA acts as a shield that limits the access of water and hydrated species to the metal or metal oxide surface. This barrier lowers the corrosion rate by inhibiting the mass transfer between surface and solution. The hydrocarbon chain imparts a hydrophobic character while the amine group bounds to the metal. Advantages of the FFA application for lay-up: Significant reduction of lay-up efforts; Long-term stability of the protective film even in aggressive environmental conditions; No influence on existing oxide layers; No negative influence on plant operation and performance; No environmental hazards of the waste water after system lay-up. Nevertheless application of film-forming amines are applied in fossil fired power plants, the requirement of nuclear power reactors are more ambitious. This paper deals with a possible lay-up application scenario in pressurized heavy water reactors. The proposed lay-up strategy will consider AREVA

  7. Sweet proteins – Potential replacement for artificial low calorie sweeteners

    Directory of Open Access Journals (Sweden)

    Kant Ravi

    2005-02-01

    Full Text Available Abstract Exponential growth in the number of patients suffering from diseases caused by the consumption of sugar has become a threat to mankind's health. Artificial low calorie sweeteners available in the market may have severe side effects. It takes time to figure out the long term side effects and by the time these are established, they are replaced by a new low calorie sweetener. Saccharine has been used for centuries to sweeten foods and beverages without calories or carbohydrate. It was also used on a large scale during the sugar shortage of the two world wars but was abandoned as soon as it was linked with development of bladder cancer. Naturally occurring sweet and taste modifying proteins are being seen as potential replacements for the currently available artificial low calorie sweeteners. Interaction aspects of sweet proteins and the human sweet taste receptor are being investigated.

  8. Nuclear reactor fuel replacement system

    International Nuclear Information System (INIS)

    Kayano, Hiroyuki; Joge, Toshio.

    1976-01-01

    Object: To permit the direction in which a fuel replacement unit is moving to be monitored by the operator. Structure: When a fuel replacement unit approaches an intermediate goal position preset in the path of movement, renewal of data display on a goal position indicator is made every time the goal position is changed. With this renewal, the prevailing direction of movement of the fuel replacement unit can be monitored by the operator. When the control of movement is initiated, the co-ordinates of the intermediate goal point A are displayed on a goal position indicator. When the replacement unit reaches point A, the co-ordinates of the next intermediate point B are displayed, and upon reaching point B the co-ordinates of the (last) goal point C are displayed. (Nakamura, S.)

  9. Slab replacement maturity guidelines : [summary].

    Science.gov (United States)

    2014-04-01

    Concrete sets in hours at moderate temperatures, : but the bonds that make concrete strong continue : to mature over days to years. However, for : replacement concrete slabs on highways, it is : crucial that concrete develop enough strength : within ...

  10. Prolonged Intermittent Renal Replacement Therapy.

    Science.gov (United States)

    Edrees, Fahad; Li, Tingting; Vijayan, Anitha

    2016-05-01

    Prolonged intermittent renal replacement therapy (PIRRT) is becoming an increasingly popular alternative to continuous renal replacement therapy in critically ill patients with acute kidney injury. There are significant practice variations in the provision of PIRRT across institutions, with respect to prescription, technology, and delivery of therapy. Clinical trials have generally demonstrated that PIRRT is non-inferior to continuous renal replacement therapy regarding patient outcomes. PIRRT offers cost-effective renal replacement therapy along with other advantages such as early patient mobilization and decreased nursing time. However, due to lack of standardization of the procedure, PIRRT still poses significant challenges, especially pertaining to appropriate drug dosing. Future guidelines and clinical trials should work toward developing consensus definitions for PIRRT and ensure optimal delivery of therapy. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  11. Clinical study on postoperative steroid hormon replacement for preclinical Cushing's syndrome

    International Nuclear Information System (INIS)

    Furuta, Nozomu; Koide, Haruhisa; Sasaki, Hiroshi; Miki, Jun; Kimura, Takahiro; Egawa, Shin

    2009-01-01

    Diagnostic criteria for preclinical Cushing's syndrome (PCS) were reported in 1996. However, requirement of postoperative steroid hormone replacement is still controversial issue. In this study, we observed recent surgical cases retrospectively and evaluate the use of postoperative steroid hormone replacement. Eighteen patients with PCS underwent surgery from 1997 to 2007 in Jikei University Hospital. Thirteen of them received postoperative steroid hormone replacement. We investigated preoperative hormone activity by 131 I-adosterol scintigraphy and suppression of adrenocorticotropic hormone (ACTH) and evaluated the requirement of postoperative steroid hormone replacement. Preoperative serum cortisol was normal range in all patients. Serum ACTH was suppressed in 10 of them (56%). In 131 I-adosterol scintigraphy, accumulation in ipsilateral side was observed in all patients. Accumulation in contralateral side was observed in 13 patients whose serum ACTH had tendency to be suppressed. Mean period of steroid hormone replacement was 19.8 weeks. Patients with lower preoperative ACTH tended to require longer period until withdrawal of steroid hormone replacement. In addition, patients received steroid hormone replacement with higher starting dose significantly required longer period. Three of them had complications during tapering of steroid hormone. Postoperative adrenal insufficiency is important issue as postoperative management of PCS patients whose function of contralateral adrenal or pituitary gland is suppressed. 131 I-adosterol scintigraphy and preoperative serum ACTH were important factors to evaluate the requirement of postoperative steroid hormone replacement. Especially, patients with low preoperative serum ACTH tended to require long duration of postoperative steroid hormone replacement. On the other hand, patients with accumulation of contralateral side in 131 I-adosterol scintigraphy and without suppression of serum ACTH may not require steroid hormone

  12. Replacement of sub-systems

    International Nuclear Information System (INIS)

    Rosen, S.E.

    1992-01-01

    This paper describes a number of quality aspects related to replacement of important systems or components in a nuclear power station. Reference is given to the steam generator replacement and power uprating performed at Ringhals 2 in Sweden in 1989. Since quality is a wide concept there has been put special emphasis in this paper to the important aspects that traditionally are not connected to quality. (author) 1 fig

  13. Feeder replacement tooling and processes

    International Nuclear Information System (INIS)

    Mallozzi, R.; Goslin, R.; Pink, D.; Askari, A.

    2008-01-01

    Primary heat transport system feeder integrity has become a concern at some CANDU nuclear plants as a result of thinning caused by flow accelerated corrosion (FAC). Feeder inspections are indicating that life-limiting wall thinning can occur in the region between the Grayloc hub weld and second elbow of some outlet feeders. In some cases it has become necessary to replace thinned sections of affected feeders to restore feeder integrity to planned end of life. Atomic Energy of Canada Limited (AECL) and Babcock and Wilcox Canada Ltd. (B and W) have developed a new capability for replacement of single feeders at any location on the reactor face without impacting or interrupting operation of neighbouring feeders. This new capability consists of deploying trained crews with specialized tools and procedures for feeder replacements during planned outages. As may be expected, performing single feeder replacement in the congested working environment of an operational CANDU reactor face involves overcoming many challenges with respect to access to feeders, available clearances for tooling, and tooling operation and performance. This paper describes some of the challenges encountered during single feeder replacements and actions being taken by AECL and B and W to promote continuous improvement of feeder replacement tooling and processes and ensure well-executed outages. (author)

  14. The Global Value Chain

    DEFF Research Database (Denmark)

    Sørensen, Olav Jull

    The conference paper aims to develop the global value chain concept by including corporate internal value adding activities and competition to the basic framework in order to turn the global value chain into a strategic management tool......The conference paper aims to develop the global value chain concept by including corporate internal value adding activities and competition to the basic framework in order to turn the global value chain into a strategic management tool...

  15. Systematic replacement of lysine with glutamine and alanine in Escherichia coli malate synthase G: effect on crystallization

    International Nuclear Information System (INIS)

    Anstrom, David M.; Colip, Leslie; Moshofsky, Brian; Hatcher, Eric; Remington, S. James

    2005-01-01

    Alanine and glutamine mutations were made to the same 15 lysine positions on the surface of E. coli malate synthase G and the impact on crystallization observed. The results support lysine replacement for improvement of crystallization and provide insight into site selection and type of amino-acid replacement. Two proposals recommend substitution of surface lysine residues as a means to improve the quality of protein crystals. In proposal I, substitution of lysine by alanine has been suggested to improve crystallization by reducing the entropic cost of ordering flexible side chains at crystal contacts. In proposal II, substitution of lysine by residues more commonly found in crystal contacts, such as glutamine, has been proposed to improve crystallization. 15 lysine residues on the surface of Escherichia coli malate synthase G, distributed over a variety of secondary structures, were individually mutated to both alanine and glutamine. For 28 variants, detailed studies of the effect on enzymatic activity and crystallization were conducted. This has permitted direct comparison of the relative effects of the two types of mutations. While none of the variants produced crystals suitable for X-ray structural determination, small crystals were obtained in a wide variety of conditions, in support of the general approach. Glutamine substitutions were found to be more effective than alanine in producing crystals, in support of proposal II. Secondary structure at the site of mutation does not appear to play a major role in determining the rate of success

  16. Risks and benefits of citrate anticoagulation for continuous renal replacement therapy.

    Science.gov (United States)

    Shum, H P; Yan, W W; Chan, T M

    2015-04-01

    Heparin, despite its significant side-effects, is the most commonly used anticoagulant for continuous renal replacement therapy in critical care setting. In recent years, citrate has gained much popularity by improving continuous renal replacement therapy circuit survival and decreasing blood transfusion requirements. However, its complex metabolic consequences warrant modification in the design of the citrate-based continuous renal replacement therapy protocol. With thorough understanding of the therapeutic mechanism of citrate, a simple and practicable protocol can be devised. Citrate-based continuous renal replacement therapy can be safely and widely used in the clinical setting with appropriate clinical staff training.

  17. Side Effects and Their Management

    Science.gov (United States)

    ... tumors. Donate Now Subscribe for e-updates Please leave this field empty ... tumors and their treatments bring an array of possible side effects in to a patient’s life. Fatigue, cognitive changes, and mood changes are ...

  18. Side Effects: Hair Loss (Alopecia)

    Science.gov (United States)

    Hair loss, also called alopecia, is a side effect of cancer treatments, such as chemotherapy and radiation therapy. Learn how to cope with and manage hair loss. Listen to tips from others who have experienced hair loss.

  19. Coping – Late Side Effects

    Science.gov (United States)

    Cancer treatment can cause late side effects that may not show up for months or years after treatment. These late effects may include heart and lung problems, bone loss, eye and hearing changes, lymphedema, and other problems

  20. Side Effects: Nausea and Vomiting

    Science.gov (United States)

    Types of nausea and vomiting caused by cancer treatment include: anticipatory, acute, and delayed. Controlling these side effects will help to prevent serious problems such as malnutrition and dehydration in people with cancer.