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Zhengrong Yang, Qingxian Zhou, Leo Mok, Anukriti Singh, Douglas J Swartz, Ina L Urbatsch, Christie G Brouillette
Structural changes in mouse P-glycoprotein (Pgp) induced by thermal unfolding were studied by differential scanning calorimetry (DSC), circular dichroism and fluorescence spectroscopy to gain insight into the solution conformation(s) of this ABC transporter that may not be apparent from current crystal structures. DSC of reconstituted Pgp showed two thermal unfolding transitions in the absence of MgATP, suggesting that each transition involved the cooperative unfolding of two or more interacting structural domains...
October 23, 2016: Biochimica et Biophysica Acta
Sebastian Hasenstab-Riedel, Lisa Mann, Patrick Voßnacker, Carsten Müller
Tetramethylammonium tetraiodopentabromide [NMe4][I4Br5] was the first iodobromide synthesized and crystallized in an ionic liquid as well as in dichloromethane. The new iodobro-mides show different structure motives yet unknown from other nonahalides and can be better described as [(I2Br3)- · 2IBr]. The additional IBr units are connected by halogen-halogen interactions on the central V-shaped [I2Br3]-. The characterization was performed by Raman spectroscopy and single crystal X-ray structure determi-nation...
October 26, 2016: Chemistry: a European Journal
Shmuel Willensky, Hagit Bar-Rogovsky, Eduardo A Bignon, Nicole D Tischler, Yorgo Modis, Moshe Dessau
Hantaviruses are important emerging human pathogens and are the causative agents of serious diseases in humans with high mortality rates. Like other members in the Bunyaviridae family their M segment encodes two glycoproteins, GN and GC, which are responsible for the early events of infection. Hantaviruses deliver their tripartite genome into the cytoplasm by fusion of the viral and endosomal membranes in response to the reduced pH of the endosome. Unlike phleboviruses (e.g. Rift valley fever virus), that have an icosahedral glycoprotein envelope, hantaviruses display a pleomorphic virion morphology as GN and GC assemble into spikes with apparent four-fold symmetry organized in a grid-like pattern on the viral membrane...
October 2016: PLoS Pathogens
Tongtong Tian, Qiongzheng Hu, Yi Wang, Yanan Gao, Li Yu
A series of imidazolium-based surface active ionic liquids (IM-SAILs), viz. single-chained IM-SAILs, 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br, n=12, 14, 16), 1-dodecyl-3-methylimidazolium salicylate ([C12mim]Sal), 1-dodecyl-3-methylimidazolium 3-hydroxy-2-naphthoate ([C12mim]HNC), 1-dodecyl-3-methylimidazolium cinnamate ([C12mim]CA), 1-dodecyl-3-methylimidazolium para-hydroxy-cinnamate ([C12mim]PCA); gemini IM-SAIL, 1,2-bis(3-dodecylimidazolium-1-yl) ethane bromide ([C12-2-C12im]Br2), along with three short-chained ionic liquids (ILs), ethylammonium nitrate (EAN), propylammonium nitrate (PAN) and butylammonium nitrate (BAN), were synthesized and applied to nematic liquid crystal (LC)-fluid interfaces...
October 26, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Travis S Hughes, Jinsai Shang, Richard Brust, Ian Mitchelle S de Vera, Jakob Fuhrmann, Claudia Ruiz, Michael D Cameron, Theodore M Kamenecka, Douglas J Kojetin
In a previous study, a co-crystal structure of PPARγ bound to 2-chloro-N-(3-chloro-4-((5-chlorobenzo[d]thiazol-2-yl)thio)phenyl)-4-(trifluoromethyl)benzenesulfonamide (1, T2384) revealed two orthosteric pocket binding modes attributed to a concentration-dependent biochemical activity profile. However, 1 also bound an alternate/allosteric site that could alternatively account for the profile. Here, we show ligand aggregation afflicts the activity profile of 1 in biochemical assays. However, ligand-observed fluorine (19F) and protein-observed NMR confirms 1 binds PPARγ with two orthosteric binding modes and an allosteric site...
October 26, 2016: Journal of Medicinal Chemistry
Omer Kirshenboim, Sebastian Kozuch
Halogen bonds (XB) are no longer newcomers in the chemistry family. However, XB in hypervalent halogens has not been thoroughly studied. We provide a molecular orbital explanation of the shape and strength of XBs in hypervalent halogens and other species, focusing on the charge transfer and electrostatic aspects of these bonds. Our results show that σ-holes (and subsequently the XBs associated with them) can be easily divided and bent by the influence of equatorial substituents. Inductive effect of both the equatorial and axial groups can affect these distortions, but also the angle between the equatorial ligands has a large influence on the shape of the σ-holes and the molecular orbitals acting as electron acceptor...
October 26, 2016: Journal of Physical Chemistry. A
Eileen K Jaffe
Porphobilinogen synthase (PBGS), also known as 5-aminolevulinate dehydratase, is an essential enzyme in the biosynthesis of all tetrapyrroles, which function in respiration, photosynthesis, and methanogenesis. Throughout evolution, PBGS adapted to a diversity of cellular niches and evolved to use an unusual variety of metal ions both for catalytic function and to control protein multimerization. With regard to the active site, some PBGSs require Zn(2+); a subset of those, including human PBGS, contain a constellation of cysteine residues that acts as a sink for the environmental toxin Pb(2+)...
October 26, 2016: Accounts of Chemical Research
Ethan P McMoran, Douglas R Powell, Felio Perez, Gerard T Rowe, Lei Yang
A series of copper complexes supported by a simple dipyridylamide ligand (H2pcp) were isolated and characterized. Treatment of H2pcp with NaH and copper(I) salts led to the formation of [Cu2(2pcp)2] (1a) and {Na[(Cu2(2pcp)2)2]PF6}n (1b). The X-ray crystal structures of both complexes feature Cu(I)Cu(I) cores with close Cu···Cu interactions. Electrochemical studies of 1a showed a reversible one-electron oxidation wave in CH2Cl2. On the basis of the work on 1a, we began studying the mixed-valence copper species supported by this ligand...
October 26, 2016: Inorganic Chemistry
Prerak Gupta, Mimi Adhikary, Joseph Christakiran M, Manishekhar Kumar, Nandana Bhardwaj, Biman B Mandal
Composite biomaterials as artificial bone graft materials are pushing the present frontiers of bioengineering. In this study, a biomimetic, osteoconductive tricomposite scaffold made of hydroxyapatite (HA) embedded in non-mulberry Antheraea assama (A. assama) silk fibroin fibers and its fibroin solution is explored for osteogenic potential. Scaffolds were physico-chemically characterized for morphology, porosity, secondary structure conformation, water retention ability, biodegradability and mechanical property...
October 26, 2016: ACS Applied Materials & Interfaces
Morten Beck Trelle, Shona H Pedersen, Eva Christina Østerlund, Jeppe Buur Madsen, Søren Risom Kristensen, Thomas J D Jørgensen
Antithrombin deficiency is associated with increased risk of venous thrombosis. In certain families this condition is caused by pathogenic polymerization of mutated antithrombin in the blood. To facilitate future development of pharmaceuticals against antithrombin polymerization an improved understanding of the polymerogenic intermediates is crucial. However, X-ray crystallography of these intermediates is severely hampered by the difficulty in obtaining well-diffracting crystals of transient and heterogeneous noncovalent protein assemblies...
October 26, 2016: Analytical Chemistry
Sergey N Konchenko, Svetlana V Klementieva, Nina P Gritsan, Marat M Khusniyarov, Alexander Witt, Alexey A Dmitriev, Elizaveta A Suturina, Nathan D D Hill, Tracey L Roemmele, Michael T, René T Boeré, Peter W Roesky, Andrey V Zibarev
The first lanthanide complexes with a redox-active sulphur diimide ligand, [LnCp*2(Me3SiN=)2S] (Ln = Sm, Eu, Yb; Cp* = η5-C5Me5), are reported. The complexes were synthesized using [LnCp*2(THF)2] and (Me3SiN=)2S and have been thoroughly characterized by single-crystal X-ray diffraction, EPR spectroscopy, UV-Vis-NIR electronic absorption spectroscopy and SQUID magnetometry. The results, as interpreted by CASSCF/SOC-RASSI calculations providing a non-perturbative treatment of spin-orbit coupling, indicate that these paramagnetic complexes are best described as Ln3+ and [(Me3SiN=)2S]-* adducts...
October 26, 2016: Chemistry: a European Journal
Kerry Marie Goodman, Rotem Rubinstein, Chan Aye Thu, Seetha Mannepalli, Fabiana Bahna, Göran Ahlsén, Chelsea Rittenhouse, Tom Maniatis, Barry Honig, Lawrence Shapiro
Stochastic cell-surface expression of α-, β-, and γ-clustered protocadherins (Pcdhs) provides vertebrate neurons with single-cell identities that underlie neuronal self-recognition. Here we report crystal structures of ectodomain fragments comprising cell-cell recognition regions of mouse γ-Pcdhs γA1, γA8, γB2, and γB7 revealing trans-homodimers, and of C-terminal ectodomain fragments from γ-Pcdhs γA4 and γB2, which depict cis-interacting regions in monomeric form. Together these structures span the entire Pcdhγ ectodomain...
October 26, 2016: ELife
Dalei Wu, Xiaoyu Su, Nalini Potluri, Youngchang Kim, Fraydoon Rastinejad
The neuronal PAS domain proteins NPAS1 and NPAS3 are members of the basic helix-loop-helix-PER-ARNT-SIM (bHLH-PAS) family, and their genetic deficiencies are linked to a variety of human psychiatric disorders including schizophrenia, autism spectrum disorders and bipolar disease. NPAS1 and NPAS3 must each heterodimerize with the aryl hydrocarbon receptor nuclear translocator (ARNT), to form functional transcription complexes capable of DNA binding and gene regulation. Here we examined the crystal structures of multi-domain NPAS1-ARNT and NPAS3-ARNT-DNA complexes, discovering each to contain four putative ligand-binding pockets...
October 26, 2016: ELife
Zhaodong Liu, Zhen Yao, Mingguang Yao, Jiayin Lv, Shuanglong Chen, Quanjun Li, Hang Lv, Tianyi Wang, Shuangchen Lu, Ran Liu, Bo Liu, Jing Liu, Zhiqiang Chen, Bo Zou, Tian Cui, Bingbing Liu
We present a joint experimental and theoretical study on the high-pressure behavior of bromine confined in the one-dimensional (1D) nanochannels of zeolite AlPO4-5 (AFI) single crystals. Raman scattering experiments indicate that loading bromine into AFI single crystals can lead to the formation of bromine molecular chains inside the nanochannels of the crystals. High-pressure Raman and X-ray diffraction studies demonstrate that high pressure can increase the length of the confined bromine molecular chains and modify the inter- and intramolecular interactions of the molecules...
September 28, 2016: Journal of Chemical Physics
Anuraag Gaddam, Lionel Montagne, José M F Ferreira
In this paper, we derive a new model to determine the distribution of silicate units in binary glasses (or liquids). The model is based on statistical mechanics and assumes grand canonical ensemble of silicate units which exchange energy and network modifiers from the reservoir. This model complements experimental techniques, which measure short range order in glasses such as nuclear magnetic resonance (NMR) spectroscopy. The model has potential in calculating the amounts of liquid-liquid phase segregation and crystal nucleation, and it can be easily extended to more complicated compositions...
September 28, 2016: Journal of Chemical Physics
Folarin Latinwo, Frank H Stillinger, Pablo G Debenedetti
Chirality is a hallmark feature for molecular recognition in biology and chemical physics. We present a three-dimensional continuum model for studying chirality phenomena in condensed phases using molecular simulations. Our model system is based upon a simple four-site molecule and incorporates non-trivial kinetic behavior, including the ability to switch chirality or racemize, as well as thermodynamics arising from an energetic preference for specific chiral interactions. In particular, we introduce a chiral renormalization parameter that can locally favor either homochiral or heterochiral configurations...
October 21, 2016: Journal of Chemical Physics
Minh D Nguyen, Huiyu Yuan, Evert P Houwman, Matthijn Dekkers, Gertjan Koster, Johan E Ten Elshof, Guus Rijnders
Ca2Nb3O10 (CNOns) and Ti0.87O2 (TiOns) metal oxide nanosheets (ns) are used as a buffer layer for epitaxial growth of piezoelectric capacitor stacks on Si and Pt/Ti/SiO2/Si (Pt/Si) substrates. Highly (001) and (110)-oriented Pb(Zr0.52Ti0.48)O3 (PZT) films are achieved by utilizing CNOns and TiOns, respectively. The piezoelectric capacitors are characterized by polarization and piezoelectric hysteresis loops and by fatigue measurements. The devices fabricated with SrRuO3 top and bottom electrodes directly on nanosheets/Si have ferroelectric and piezoelectric properties well comparable with devices using more conventional oxide buffer layers (stacks), such as YSZ, CeO2/YSZ or SrTiO3 on Si...
October 26, 2016: ACS Applied Materials & Interfaces
Neil Y C Lin, Itai Cohen
The mechanical properties of crystalline materials can be substantially modified under confinement. Such modified macroscopic properties are usually governed by the altered microstructures and internal stress fields. Here, we use a parallel plate geometry to apply a quasi-static squeeze flow crushing a colloidal polycrystal while simultaneously imaging it with confocal microscopy. The confocal images are used to quantify the local structure order and, in conjunction with Stress Assessment from Local Structural Anisotropy (SALSA), determine the stress at the single-particle scale...
October 26, 2016: Soft Matter
Zhendong Fu, Yinguo Xiao, Artem Feoktystov, Vitaliy Pipich, Marie-Sousai Appavou, Yixi Su, Erxi Feng, Wentao Jin, Thomas Brückel
The magnetic-field-induced assembly of magnetic nanoparticles (NPs) provides a unique and flexible strategy in the design and fabrication of functional nanostructures and devices. We have investigated the field-induced self-assembly of core-shell iron oxide NPs dispersed in toluene by means of small-angle neutron scattering (SANS). The form factor of the core-shell NPs was characterized and analyzed using SANS with polarized neutrons. Large-scale aggregates of iron oxide NPs formed above 0.02 T as indicated by very-small-angle neutron scattering measurements...
October 26, 2016: Nanoscale
Fengcang Ma, Ping Liu, Wei Li, Xinkuan Liu, Xiaohong Chen, Ke Zhang, Deng Pan, Weijie Lu
Low-cost TiB whiskers reinforced titanium matrix composite (TMCs) was fabricated with enhanced mechanical performances using in situ technologies and hot working. Morphologies observation indicates that needle-like TiB whiskers with a hexagonal transverse section grow along the [010] direction due to B27 crystal structure and its growth mechanism. Mechanical properties tests show that the mechanical behavior of the TiB whiskers reinforced TMCs is dependent on the deformation amplitudes applied in hot-working...
October 26, 2016: Scientific Reports
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