bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple, consecutive, fully‐extended 2.05‐helix peptide conformation
Authors: Peggion Cristina , Moretto Alessandro , Formaggio Fernando , Crisma Marco , Toniolo Claudio 
Published: July 2013

ABSTRACTThe peptide 2.05‐helix does exist. It has been experimentally authenticated both in the crystalline state (by X‐ray diffraction) and in solution (by several spectroscopic techniques). It is the most common conformation for Cα‐tetrasubstituted α‐amino acids with at least two atoms in each side chain, provided that cyclization on the Cα‐atom is absent. X‐Ray diffraction has allowed a detailed description of its geometrical and three‐dimensional (3D)‐structural features. The infrared absorption and the nuclear magnetic resonance parameters characteristics of this multiple, consecutive, fully‐extended structure have been described. Conformational energy calculations are in agreement with the experimental findings. As the contribution per amino acid residue to the length of this helix is the longest possible, its exploitation as a molecular spacer is quite promising. However, it is a rather fragile 3D‐structure and particularly sensitive to solvent polarity. Interestingly, in such a case, it may reversibly convert to the much shorter 310‐helix, thus generating an attractive molecular spring. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 621–636, 2013.
Effects of lysine methylation on gramicidin A channel folding in lipid membranes
Authors: Wang Fang , Qin Luoheng , Wong Patrick , Gao Jianmin 
Published: July 2013

ABSTRACTProtein‐membrane interactions underlie numerous biological processes including folding of ion channels and signal transduction across lipid membranes. A detailed understanding of protein–lipid interactions is critical for designing membrane‐active peptides as potential antibiotics, as well. Using gramicidin A (gA) as a model system, we investigated the effects of lysine methylation on peptide folding into transmembrane channels. The results are discussed in terms of the peptides' binding affinity to, translocation across, and structure formation in lipid membranes. The results show that gA mutants with Nɛ‐trimethylated d‐lysines (dMe3K) are capable of folding into wild type‐like channels that are selective for monovalent cations. Surprisingly, Nɛ‐trimethylation in general reduces the peptide's binding affinity to lipid membranes despite the increased hydrophobicity. Further investigation reveals the critical contribution of the hydrogen bonding potential of lysine side chains to peptide‐membrane association, which has previously been underappreciated. Importantly, methylation does give improved therapeutic indices for certain combinations of gA variant and bacterium, indicating that methylation can be an effective strategy to fine tune the performance of peptide antibiotics. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 656–661, 2013.
Dual system for the central nervous system targeting and blood‐brain barrier transport of a selective prolyl oligopeptidase inhibitor
Authors: Teixidó Meritxell , Zurita Esther , Mendieta Laura , Oller‐Salvia Benjamí , Prades Roger , Tarragó Teresa , Giralt Ernest 
Published: July 2013

ABSTRACTLess than 2% of all potential neurotherapeutics cross the blood‐brain barrier (BBB). Here, we sought to build a construct with the capacity to cross this barrier, to behave as a chemical delivery system, and, once inside the central nervous system, to be transformed and then act as an enzyme inhibitor. With all this in mind, here, we describe the entire process to obtain such a compound, from the initial candidate selection to preparation of the compound library and posterior evaluation and final selection of the most promising candidates in terms of selectivity, serum stability, and BBB‐transport. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 662–674, 2013.
Synthesis of temperature‐dependent elastin‐like peptide‐modified dendrimer for drug delivery
Authors: Kojima Chie , Irie Kotaro 
Published: July 2013

ABSTRACTDendrimers are synthetic macromolecules with a unique structure that are potential unimolecular drug carriers and potential scaffolds for peptides. Elastin is one of the main components of the extracellular matrix, as well as a temperature‐sensitive biomacromolecule. Val‐Pro‐Gly‐Val‐Gly repeats, an elastin‐like peptide, have been used for designing artificial elastin molecules. In this study, we have synthesized a novel type of temperature‐dependent drug carrier by conjugating Ac‐Val‐Pro‐Gly‐Val‐Gly to a dendrimer, named elastin‐mimetic dendrimer. The elastin‐mimetic dendrimer formed β‐turn structure by heating. The elastin‐mimetic dendrimer exhibited the inverse phase transition, depending on pH and NaCl concentration in addition to temperature. The elastin‐mimetic dendrimer could encapsulate a model drug, rose bengal, even though the complex stability was similar to the dendrimer without elastin‐like peptide. Therefore, the elastin‐mimetic dendrimer is a potential drug carrier with temperature‐ and pH‐dependent properties. (134 words) © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 714–721, 2013.
Toward the de novo design of antimicrobial peptides: Lack of correlation between peptide permeabilization of lipid vesicles and antimicrobial, cytolytic, or cytotoxic activity in living cells
Authors: He Jing , Krauson Aram J. , Wimley William C. 
Published: July 2013

ABSTRACTWe previously performed a lipid vesicle‐based, high‐throughput screen on a 26‐residue combinatorial peptide library that was designed de novo to yield membrane‐permeabilizing peptides that fold into β‐sheets. The most active and soluble library members that were identified permeabilized lipid vesicles detectably, but not with high potency. Nonetheless, they were broad‐spectrum, membrane‐permeabilizing antibiotics with minimum sterilizing activity at low µM concentrations. In an expansion of that work, we recently performed an iterative screen in which an active consensus sequence from that first‐generation library was used as a template to design a second‐generation library which was then screened against lipid vesicles at very high stringency. Compared to the consensus sequence from the first library, the most active second‐generation peptides are highly potent, equilibrium pore‐formers in synthetic lipid vesicles. Here, we use these first‐ and second‐generation families of peptides to test the hypothesis that a large increase in potency in bacteria‐like lipid vesicles will correlate with a large improvement in antimicrobial activity. The results do not support the hypothesis. Despite a 20‐fold increase in potency against bacteria‐like lipid vesicles, the second‐generation peptides are only slightly more active against bacteria, and at the same time, are also more toxic against mammalian cells. The results suggest that a “pipeline” strategy toward the optimization of antimicrobial peptides could begin with a vesicle‐based screen for identifying families with broad‐spectrum activity, but will also need to include screening or optimization steps that are done under conditions that are more directly relevant to possible therapeutic applications. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 102: 1–6, 2014.
Cell attachment and spreading activity of mixed laminin peptide–chitosan membranes
Authors: Otagiri Dai , Yamada Yuji , Hozumi Kentaro , Katagiri Fumihiko , Kikkawa Yamato , Nomizu Motoyoshi 
Published: July 2013

ABSTRACTLaminins are a multifunctional molecule with numerous active sites that have been identified in short peptide sequences. Mixed peptide‐conjugated chitosan membranes using laminin‐derived active peptides have been previously demonstrated to be useful as a biomaterial for tissue engineering. In this study, two syndecan‐binding peptides, AG73 (RKRLQVQLSIRT) and C16 (KAFDITYVRLKF), and three integrin‐binding peptides, EF1zz (ATLQLQEGRLHFXFDLGKGR, X: Nle, binding to integrin α2β1), A99a (ALRGDN, binding to integrin αvβ3), and A2G10 (SYWYRIEASRTG, binding to integrin α6β1), were mixed in various combinations, conjugated to chitosan membranes, and evaluated for their cell attachment and spreading activities. The cell attachment and spreading activity of EF1zz, A99a, and A2G10 were enhanced by AG73. In contrast, C16 enhanced only the cell attachment and spreading activity of A99a and did not influence the activity of EF1zz and A2G10. As well as previous study, the AG73–chitosan membrane bound to only syndecan. On the other hand, the C16–chitosan membrane interacted with both syndecan and β1 integrin. These data suggest that interaction of different receptors can cause synergistic effects. Therefore, AG73 is widely applicable as a synergistic agent for mixed peptide–matrices using several types of integrin‐binding peptides. Additionally, the A2G10/AG73–chitosan membrane may be useful to investigate detailed biological functions of α6β1 integrin, which is a major laminin‐binding receptor. Using a combination of tissue‐appropriate laminin‐derived peptides, the mixed peptide–chitosan membranes may serve as functional biomaterials for tissue engineering. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 751–759, 2013.
Self‐assembling peptide nanofibers promoting cell adhesion and differentiation
Authors: Fukunaga Kazuto , Tsutsumi Hiroshi , Mihara Hisakazu 
Published: July 2013

ABSTRACTThere is an increasing need for the development of functional artificial extracellular matrices (ECMs) for tissue engineering. Recently, we have successfully designed a self‐assembling peptide, named E1Y9, to construct functional ECMs. We describe here an enhancement of abilities of E1Y9 materials to promote cell adhesion and differentiation, using functional peptide sequences derived from natural extracellular matrix proteins. We designed functionalized self‐assembling peptides, RGDS‐conjugated E1Y9 (E1Y9‐RGDS) and IKVAV‐conjugated E1Y9 (E1Y9‐IKVAV). E1Y9‐RGDS and E1Y9‐IKVAV formed peptide nanofibers in a similar manner to E1Y9, with β‐sheet secondary structures. Surfaces coated with peptide nanofibers displayed the higher bioactivities of E1Y9‐RGDS for cell adhesion and E1Y9‐IKVAV for cell differentiation than those of E1Y9, with the activities being dependent on the concentrations of the functional peptides. These functionalized peptides will be useful for the construction of functional ECMs in cell and tissue engineering. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 731–737, 2013.
Multinuclear Solid‐State Magnetic Resonance as a Sensitive Probe of Structural Changes upon the Occurrence of Halogen Bonding in Co‐crystals
Authors: Widdifield Cory M. , Cavallo Gabriella , Facey Glenn A. , Pilati Tullio , Lin Jingxiang , Metrangolo Pierangelo , Resnati Giuseppe , Bryce David L. 
Published: July 2013

AbstractAlthough the understanding of intermolecular interactions, such as hydrogen bonding, is relatively well‐developed, many additional weak interactions work both in tandem and competitively to stabilize a given crystal structure. Due to a wide array of potential applications, a substantial effort has been invested in understanding the halogen bond. Here, we explore the utility of multinuclear (13C, 14/15N, 19F, and 127I) solid‐state magnetic resonance experiments in characterizing the electronic and structural changes which take place upon the formation of five halogen‐bonded co‐crystalline product materials. Single‐crystal X‐ray diffraction (XRD) structures of three novel co‐crystals which exhibit a 1:1 stoichiometry between decamethonium diiodide (i.e., [(CH3)3N+(CH2)10N+(CH3)3][2 I−]) and different para‐dihalogen‐substituted benzene moieties (i.e., p‐C6X2Y4, X=Br, I; Y=H, F) are presented. 13C and 15N NMR experiments carried out on these and related systems validate sample purity, but also serve as indirect probes of the formation of a halogen bond in the co‐crystal complexes in the solid state. Long‐range changes in the electronic environment, which manifest through changes in the electric field gradient (EFG) tensor, are quantitatively measured using 14N NMR spectroscopy, with a systematic decrease in the 14N quadrupolar coupling constant (CQ) observed upon halogen bond formation. Attempts at 127I solid‐state NMR spectroscopy experiments are presented and variable‐temperature 19F NMR experiments are used to distinguish between dynamic and static disorder in selected product materials, which could not be conclusively established using solely XRD. Quantum chemical calculations using the gauge‐including projector augmented‐wave (GIPAW) or relativistic zeroth‐order regular approximation (ZORA) density functional theory (DFT) approaches complement the experimental NMR measurements and provide theoretical corroboration for the changes in NMR parameters observed upon the formation of a halogen bond.
Computational Analysis of 47/49Ti NMR Shifts and Electric Field Gradient Tensors of Half‐Titanocene Complexes: Structure–Bonding–Property Relationships
Authors: Srebro Monika , Autschbach Jochen 
Published: July 2013

AbstractMetal NMR shielding and electric‐field gradient (EFG) tensors are examined by quantum‐chemical calculations for a set of 14 titanium(IV) complexes. Benchmarks are performed for titanocene chlorides that have been characterized recently by solid‐state NMR experiments, focusing on the dependence of TiIV NMR parameters on the computational model in terms of the choice of the density functional, and considering molecular clusters versus infinite‐periodic solid. Nearest‐neighbor and long‐range effects in the solid state are found to influence NMR parameters in systems without spatially extended ligands. Bulky ligands increase the fraction of local structure and bonding information encoded in the EFG tensors by reducing intermolecular interactions. Next, Ti shielding constants and EFG tensors for a variety of olefin (co)polymerization catalysts are analyzed in terms of contributions from localized molecular orbitals representing Lewis bonds and lone pairs. Direct links between the observed theoretical trends and the local bonding environment around the Ti metal center are found. A specific dependence of the Ti EFG tensors on the exact arrangement and type of surrounding bonds is demonstrated, providing a basis for further studies on solid‐supported titanium catalytic systems.
Pacman and Hangman Metal Tetraazamacrocycles
Authors: Lee Chang Hoon , Villágran Dino , Cook Timothy R. , Peters Jonas C. , Nocera Daniel G. 
Published: July 2013

AbstractMetal complexes of derivatized 2,12‐dimethyl‐3,7,11,17‐tetraazabicyclo[11.3.1]heptadeca‐1(17),2,11,13,15‐pentane (bapa) ligands were prepared from 4‐substituted diacetylpyridine derivatives by templated condensation with 3,3′‐diaminodipropylamine in the presence of a metal halide or nitrate. The diacetylpyridine derivatives with Pacman and Hangman scaffolds are delivered from borylation of the 4‐postion of diacetylpyridine and subsequent Suzuki coupling with the appropriate Hangman or Pacman backbone. Electrochemical examination of the parent [Co(bapa)]2+ scaffold reveals it to be a catalyst for the hydrogen evolution reaction (HER) in acetonitrile. Similar studies of the Hangman complex appear to be obscured by trace amounts of residual palladium remaining from the Suzuki coupling reaction to provide a cautionary note for the use of such cross‐coupling methodologies in the preparation of HER catalysts.
Genetic structure, spatial organization, and dispersal in two populations of bat‐eared foxes
Authors: Kamler Jan F. , Gray Melissa M. , Oh Annie , Macdonald David W. 
Published: July 2013

AbstractWe incorporated radio‐telemetry data with genetic analysis of bat‐eared foxes (Otocyon megalotis) from individuals in 32 different groups to examine relatedness and spatial organization in two populations in South Africa that differed in density, home‐range sizes, and group sizes. Kin clustering occurred only for female dyads in the high‐density population. Relatedness was negatively correlated with distance only for female dyads in the high‐density population, and for male and mixed‐sex dyads in the low‐density population. Home‐range overlap of neighboring female dyads was significantly greater in the high compared to low‐density population, whereas overlap within other dyads was similar between populations. Amount of home‐range overlap between neighbors was positively correlated with genetic relatedness for all dyad‐site combinations, except for female and male dyads in the low‐density population. Foxes from all age and sex classes dispersed, although females (mostly adults) dispersed farther than males. Yearlings dispersed later in the high‐density population, and overall exhibited a male‐biased dispersal pattern. Our results indicated that genetic structure within populations of bat‐eared foxes was sex‐biased, and was interrelated to density and group sizes, as well as sex‐biases in philopatry and dispersal distances. We conclude that a combination of male‐biased dispersal rates, adult dispersals, and sex‐biased dispersal distances likely helped to facilitate inbreeding avoidance in this evolutionarily unique species of Canidae.
Catalysis of Hydrogen Evolution by Polylysine, Polyarginine and Polyhistidine at Mercury Electrodes
Authors: Vargová Veronika , Zivanović Marko , Dorčák Vlastimil , Paleček Emil , Ostatná Veronika 
Published: July 2013

AbstractProtein catalyzed hydrogen evolution reaction at mercury‐containing electrodes controlled by constant‐current chronopotentiometric stripping (CPS) is representing a new tool useful in protein research. The resulting CPS peak H is sensitive to changes in the protein structure and its amino acid composition. Besides CPS, cyclic voltammetry appears to be useful for study of poly(amino acids) as an intermediate model system between peptides and macromolecular proteins. Here we show that similarly as arginine in polyarginine and lysine in polylysine also histidine residues in polyhistidine contribute to the catalysis of hydrogen evolution under the given conditions. Peak potentials of individual poly(amino acids) are different and depend on the type of amino acid residues.
Durability and Performance of High Performance Infiltration Cathodes
Authors: Samson A. J. , Søgaard M. , Hjalmarsson P. , Hjelm J. , Bonanos N. , Foghmoes S. P. V. , Ramos T. 
Published: July 2013

AbstractThe performance and durability of solid oxide fuel cell (SOFC) cathodes consisting of a porous Ce0.9Gd0.1O1.95 (CGO) infiltrated with nitrates corresponding to the nominal compositions La0.6Sr0.4Co1.05O3–δ (LSC), LaCoO3–δ (LC), and Co3O4 are discussed. At 600 °C, the polarization resistance, Rp, varied as: LSC (0.062 Ω cm2) < LC (0.079 Ω cm2) < Co3O4 (0.27 Ω cm2). High temperature X‐ray diffraction revealed a number of different phases in LSC and LC. The electrochemical performance of the LSC‐infiltrated CGO cathode was found to depend on the infiltrate firing temperature and is suggested to originate from a complex interplay between the formation, percolation, and surface area of electronically conducting and catalytically active phases. Simplified models that predict the Rp of LSC‐infiltrated CGO were applied and showed that the performance is not only characterized by the nanoscale size of the infiltrate but also from a better surface exchange property. A 450 h test of an LSC‐infiltrated CGO cathode showed an Rp with final degradation rate of only 11 mΩ cm2 kh–1. An SOFC with an LSC‐infiltrated CGO cathode tested for 1,500 h at 700 °C and 0.5 A cm–2 (60% fuel, 20% air utilization) revealed no measurable degradation.
The Interdependence of Macro‐ and Microstructure on Internal‐Reforming Performance in Ni‐YSZ SOFC Anode Supports
Authors: Richards A. E. , Sullivan N. P. 
Published: July 2013

AbstractThis paper presents an analysis of the gas‐transport and methane internal‐reforming characteristics of two commercially developed solid‐oxide fuel cell (SOFC) anode supports. The anode supports are fabricated by CoorsTek, Inc. (Golden, CO, USA) and Risø‐DTU (Lyngby, Denmark). While both supports are ceramic‐metallic composites of yttria‐stabilized zirconia and nickel (Ni‐YSZ), their morphological structures and thicknesses are quite different. The CoorsTek support is thick and displays an open microstructure, while the Risø‐DTU support is fairly thin with a tighter morphology. These micro‐ and macrostructural differences lead to significant variations in gas transport and methane internal‐reforming chemistry within the porous support structures that directly affect cell performance. In this study, anode‐support performance is analyzed using the separated anode experiment, a unique tool that decouples anode‐support thermal‐chemistry processes from electrochemical processes typically underway during SOFC operation. Experimental results are interpreted using a detailed computational model. Gas transport is higher in the CoorsTek support despite being nearly five times thicker than the Risø‐DTU support. The methane internal‐reforming performance of the Risø‐DTU anode, however, speaks to its tighter microstructure and resulting higher catalytic surface area. These results highlight the dependence of support performance on macro‐ and microstructure in terms of gas transport and internal‐reforming chemistry.
Concordance of white matter and gray matter abnormalities in autism spectrum disorders: A voxel‐based meta‐analysis study
Authors: Cauda Franco , Costa Tommaso , Palermo Sara , D'Agata Federico , Diano Matteo , Bianco Francesca , Duca Sergio , Keller Roberto 
Published: July 2013

AbstractThere are at least two fundamental unanswered questions in the literature on autism spectrum disorders (ASD): Are abnormalities in white (WM) and gray matter (GM) consistent with one another? Are WM morphometric alterations consistent with alterations in the GM of regions connected by these abnormal WM bundles and vice versa? The aim of this work is to bridge this gap. After selecting voxel‐based morphometry and diffusion tensor imaging studies comparing autistic and normally developing groups of subjects, we conducted an activation likelihood estimation (ALE) meta‐analysis to estimate consistent brain alterations in ASD. Multidimensional scaling was used to test the similarity of the results. The ALE results were then analyzed to identify the regions of concordance between GM and WM areas. We found statistically significant topological relationships between GM and WM abnormalities in ASD. The most numerous were negative concordances, found bilaterally but with a higher prevalence in the right hemisphere. Positive concordances were found in the left hemisphere. Discordances reflected the spatial distribution of negative concordances. Thus, a different hemispheric contribution emerged, possibly related to pathogenetic factors affecting the right hemisphere during early developmental stages. Besides, WM fiber tracts linking the brain structures involved in social cognition showed abnormalities, and most of them had a negative concordance with the connected GM regions. We interpreted the results in terms of altered brain networks and their role in the pervasive symptoms dramatically impairing communication and social skills in ASD patients. Hum Brain Mapp 35:2073–2098, 2014. © 2013 Wiley Periodicals, Inc.