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https://www.readbyqxmd.com/read/28917834/hexameric-assembly-of-membrane-fusion-protein-yknx-of-the-sporulation-delaying-efflux-pump-from-bacillus-amyloliquefaciens
#1
Yongbin Xu, Inseong Jo, Lulu Wang, Jinli Chen, Shengdi Fan, Yuesheng Dong, Chun-Shan Quan, Nam-Chul Ha
Membrane fusion proteins (MFPs) play an essential role in the action of the drug efflux pumps and protein secretion systems in bacteria. The sporulation delaying protein (SDP) efflux pump YknWXYZ has been identified in diverse Bacillus species. The MFP YknX requires the ATP-binding cassette (ABC) transporter YknYZ and the Yip1 family protein YknW to form a functional complex. To date, the crystal structure, molecular function and mechanism of action of YknX remain unknown. In this study, to characterize the structural and biochemical roles of YknX in the functional assembly of YknWXYZ from B...
September 13, 2017: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/28914316/negative-gaussian-curvature-induces-significant-suppression-of-thermal-conduction-in-carbon-crystals
#2
Zhongwei Zhang, Jie Chen, Baowen Li
From the mathematic category of surface Gaussian curvature, carbon allotropes can be classified into three types: zero curvature, positive curvature, and negative curvature. By performing Green-Kubo equilibrium molecular dynamics simulations, we found that surface curvature has a significant impact on the phonon vibration and thermal conductivity (κ) of carbon crystals. When curving from zero curvature to negative or positive curvature structures, κ is reduced by several orders of magnitude. Interestingly, we found that κ of negatively curved carbon crystals exhibits a monotonic dependence on curvature...
September 15, 2017: Nanoscale
https://www.readbyqxmd.com/read/28910388/structure-of-the-human-transcobalamin-beta-domain-in-four-distinct-states
#3
Joël S Bloch, Markus Ruetz, Bernhard Kräutler, Kaspar P Locher
Vitamin B12 (cyanocobalamin, CNCbl) is an essential cofactor-precursor for two biochemical reactions in humans. When ingested, cobalamins (Cbl) are transported via a multistep transport system into the bloodstream, where the soluble protein transcobalamin (TC) binds Cbl and the complex is taken up into the cells via receptor mediated endocytosis. Crystal structures of TC in complex with CNCbl have been solved previously. However, the initial steps of holo-TC assembly have remained elusive. Here, we present four crystal structures of the beta domain of human TC (TC-beta) in different substrate-bound states...
2017: PloS One
https://www.readbyqxmd.com/read/28905951/order-disorder-phase-transition-in-an-anhydrous-pyrazole-based-proton-conductor-the-enhancement-of-electrical-transport-properties
#4
M Widelicka, K Pogorzelec-Glaser, A Pietraszko, P Ławniczak, R Pankiewicz, A Łapiński
The crystal structure of 1H-pyrazol-2-ium hydrogen oxalate has been studied at 100 K. It consists of two-dimensional layers built with one-dimensional chains that contain pyrazolium and oxalate acids bonded by N-HO and O-HO hydrogen bonds. According to the X-ray data and the Quantum Theory of Atoms in Molecules, it was shown that weak and moderate hydrogen bonds are present in the crystal at room temperature. The thermal stability was studied with the DSC, TGA, and DTG methods: three endothermic peaks are observed at 384, 420, and 469 K...
September 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28901355/two-dimensional-metal-nacu6-3sb3-and-solid-state-transformations-of-sodium-copper-antimonides
#5
B Owens-Baird, S Lee, K Kovnir
A novel layered compound, NaCu6.3Sb3, has been successfully synthesized from elements. This unique structure crystallizes in the hexagonal space group P63/mmc and has lattice constants of a = 4.2166(2) Å and c = 24.041(1) Å. The structure consists of complex Cu/Sb 2D blocks separated by Na ions. These blocks contain graphene-like hexagonal layers of either Cu or CuSb. The solid-state transformations in the Na-Cu-Sb system between Cu2Sb-NaCu6.3Sb3-NaCu4Sb2 were explored using annealing at different partial vapor pressures of Na, differential scanning calorimetry, and in situ synchrotron powder X-ray diffraction...
September 13, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28898045/impact-of-hetero-interfaces-in-solar-cells-using-znsnp2-bulk-crystals
#6
Shigeru Nakatsuka, Shunsuke Akari, Jakapan Chantana, Takashi Minemoto, Yoshitaro Nose
We report on the optimization of interface structure in ZnSnP2 solar cells. The effects of back electrode materials and related interface on photovoltaic performance were investigated. It was clarified that a conventional structure Mo/ZnSnP2 showed a schottky-behaviour, while an ohmic-behaviour was observed in the Cu/ZnSnP2 structure annealed at 300 °C. STEM-EDX analysis suggested that Cu-Sn-P ternary compound was formed at the interface. This compound is considered to play an important role to obtain the ohmic contact between ZnSnP2 and Cu...
September 12, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28895746/growth-of-inas-wurtzite-nanocrosses-from-hexagonal-and-cubic-basis
#7
Filip Krizek, Thomas Kanne, Davydas Razmadze, Erik Johnson, Jesper Nygård, Charles M Marcus, Peter Krogstrup
Epitaxially connected nanowires allow for design of electron transport experiments and applications beyond the standard two terminal device geometries. In this letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the Vapor-Liquid-Solid mechanism. Two methods use conventional wurtzite nanowire arrays as a six-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the two-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc-blende in the center of the nanocrosses...
September 12, 2017: Nano Letters
https://www.readbyqxmd.com/read/28892051/a-map-of-high-mobility-molecular-semiconductors
#8
S Fratini, S Ciuchi, D Mayou, G Trambly de Laissardière, A Troisi
The charge mobility of molecular semiconductors is limited by the large fluctuation of intermolecular transfer integrals, often referred to as off-diagonal dynamic disorder, which causes transient localization of the carriers' eigenstates. Using a recently developed theoretical framework, we show here that the electronic structure of the molecular crystals determines its sensitivity to intermolecular fluctuations. We build a map of the transient localization lengths of high-mobility molecular semiconductors to identify what patterns of nearest-neighbour transfer integrals in the two-dimensional (2D) high-mobility plane protect the semiconductor from the effect of dynamic disorder and yield larger mobility...
September 11, 2017: Nature Materials
https://www.readbyqxmd.com/read/28889743/prediction-of-green-phosphorus-with-tunable-direct-band-gap-and-high-mobility
#9
Woo Hyun Han, Sunghyun Kim, In-Ho Lee, Kee Joo Chang
Black phosphorus is an emerging material in nanoelectronics and nanophotonics due to its high carrier mobility and anisotropic in-plane properties. In addition, the polymorphism of phosphorus leads to numerous searches for new allotropes that are more attractive than black phosphorus in a variety of applications. On the basis of ab initio evolutionary crystal structure search computation, we report the prediction of a phosphorus allotrope called green phosphorus (λ-P), which exhibits direct band gaps ranging from 0...
September 13, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28886706/can-randall-s-plug-composed-of-calcium-oxalate-form-via-the-free-particle-mechanism
#10
F Grases, O Söhnel
BACKGROUND: The likelihood of a Randall's plug composed of calcium oxalate monohydrate (COM) forming by the free particle mechanism in a model of kidney with a structure recently described by Robertson was examined at the most favourable conditions for the considered mechanism. METHODS: The Robertson model of the kidney is used in the following development. The classical theory of crystallization was used for calculations. RESULTS: Initial COM nuclei were assumed to form at the beginning of the ascending loop of Henle where the supersaturation with respect to COM has been shown to reach the threshold level for spontaneous nucleation...
September 8, 2017: BMC Urology
https://www.readbyqxmd.com/read/28884850/regioregular-phthalocyanines-substituted-with-bulky-donors-at-non-peripheral-positions
#11
Satoshi Yamamoto, Kengo Kuribayashi, Takuro N Murakami, Eunsang Kwon, Martin J Stillman, Nagao Kobayashi, Hiroshi Segawa, Mutsumi Kimura
Three regioregular phthalocyanines (1-3) were synthesized selectively by the cyclic tetramerization of phthalonitriles bearing a bulky diarylamine substituent at the next position of nitrile. The steric repulsion at the tetramerization of bulky phthalonitriles allowed for the selective formation of regioregular phthalocyanines as confirmed by NMR and single crystal X-ray structural analyses. The absorption spectrum of 1 substituted with di(4-tert-buthylphenyl)amine groups at the non-peripheral positions showed a non-split Q band at 764 nm, which was red-shifted by 83 nm compared with that of metal free phthalocyanine (H2Pc)...
September 8, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28883392/tunable-inverted-gap-in-monolayer-quasi-metallic-mos2-induced-by-strong-charge-lattice-coupling
#12
Xinmao Yin, Qixing Wang, Liang Cao, Chi Sin Tang, Xin Luo, Yujie Zheng, Lai Mun Wong, Shi Jie Wang, Su Ying Quek, Wenjing Zhang, Andrivo Rusydi, Andrew T S Wee
Polymorphism of two-dimensional transition metal dichalcogenides such as molybdenum disulfide (MoS2) exhibit fascinating optical and transport properties. Here, we observe a tunable inverted gap (~0.50 eV) and a fundamental gap (~0.10 eV) in quasimetallic monolayer MoS2. Using spectral-weight transfer analysis, we find that the inverted gap is attributed to the strong charge-lattice coupling in two-dimensional transition metal dichalcogenides (2D-TMDs). A comprehensive experimental study, supported by theoretical calculations, is conducted to understand the transition of monolayer MoS2 on gold film from trigonal semiconducting 1H phase to the distorted octahedral quasimetallic 1T' phase...
September 7, 2017: Nature Communications
https://www.readbyqxmd.com/read/28880952/large-scale-expression-and-purification-of-secreted-mouse-hephaestin
#13
Chandrika N Deshpande, Vicky Xin, Yan Lu, Tom Savage, Gregory J Anderson, Mika Jormakka
Hephaestin is a large membrane-anchored multicopper ferroxidase involved in mammalian iron metabolism. Newly absorbed dietary iron is exported across the enterocyte basolateral membrane by the ferrous iron transporter ferroportin, but hephaestin increases the efficiency of this process by oxidizing the transported iron to its ferric form and promoting its release from ferroportin. Deletion or mutation of the hephaestin gene leads to systemic anemia with iron accumulation in the intestinal epithelium. The crystal structure of human ceruloplasmin, another multicopper ferroxidase with 50% sequence identity to hephaestin, has provided a framework for comparative analysis and modelling...
2017: PloS One
https://www.readbyqxmd.com/read/28880547/probing-distance-dependent-charge-transfer-character-in-excimers-of-extended-viologen-cyclophanes-using-femtosecond-vibrational-spectroscopy
#14
Yilei Wu, Jiawang Zhou, Brian T Phelan, Catherine M Mauck, J Fraser Stoddart, Ryan M Young, Michael R Wasielewski
Facile exciton transport within ordered assemblies of π-stacked chromophores is essential for developing molecular photonic and electronic materials. Excimer states having variable charge transfer (CT) character are frequently implicated as promoting or inhibiting exciton mobility in such systems. However, determining the degree of CT character in excimers as a function of their structure has proven challenging. Herein, we report on a series of cyclophanes in which the interplanar distance between two phenyl-extended viologen (<b>ExV<sup>2+</b>) </sup>chromophores is varied systematically using a pair of o-, m-, or p-xylylene (<b>o-</b>, <b>m-</b>, or <b>p-Xy</b>) covalent linkers to produce <b>o-ExBox<sup>4+</sup></b> (3...
September 7, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28878082/lysine-242-within-helix-10-of-the-pseudorabies-virus-nuclear-egress-complex-pul31-component-is-critical-for-primary-envelopment-of-nucleocapsids
#15
Sebastian Rönfeldt, Barbara G Klupp, Kati Franzke, Thomas C Mettenleiter
Newly assembled herpesvirus nucleocapsids are translocated from the nucleus to the cytosol by a vesicle-mediated process engaging the nuclear membranes. This transport is governed by the conserved nuclear egress complex (NEC), consisting of the alphaherpesviral pUL34 and pUL31 homologs. The NEC is not only required for efficient nuclear egress but also sufficient for vesicle formation from the inner nuclear membrane (INM) as well as from synthetic lipid bilayers. The recently solved crystal structures for the NECs from different herpesviruses revealed molecular details of this membrane deformation and scission machinery uncovering the interfaces involved in complex and coat formation...
September 6, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28878024/molecular-mechanism-of-substrate-recognition-and-transport-by-the-atsweet13-sugar-transporter
#16
Lei Han, Yongping Zhu, Min Liu, Ye Zhou, Guangyuan Lu, Lan Lan, Xianping Wang, Yongfang Zhao, Xuejun C Zhang
Sugar Will Eventually be Exported Transporters (SWEETs) are recently identified sugar transporters that can discriminate and transport di- or monosaccharides across a membrane following the concentration gradient. SWEETs play key roles in plant biological processes, such as pollen nutrition, nectar secretion, seed filling, and phloem loading. SWEET13 from Arabidopsis thaliana (AtSWEET13) is an important sucrose transporter in pollen development. Here, we report the 2.8-Å resolution crystal structure of AtSWEET13 in the inward-facing conformation with a substrate analog, 2'-deoxycytidine 5'-monophosphate, bound in the central cavity...
September 6, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28877507/crystal-structure-of-a-plant-multidrug-and-toxic-compound-extrusion-family-protein
#17
Yoshiki Tanaka, Shigehiro Iwaki, Tomoya Tsukazaki
The multidrug and toxic compound extrusion (MATE) family of proteins consists of transporters responsible for multidrug resistance in prokaryotes. In plants, a number of MATE proteins were identified by recent genomic and functional studies, which imply that the proteins have substrate-specific transport functions instead of multidrug extrusion. The three-dimensional structure of eukaryotic MATE proteins, including those of plants, has not been reported, preventing a better understanding of the molecular mechanism of these proteins...
September 5, 2017: Structure
https://www.readbyqxmd.com/read/28875161/crystal-structures-of-a-zip-zinc-transporter-reveal-a-binuclear-metal-center-in-the-transport-pathway
#18
Tuo Zhang, Jian Liu, Matthias Fellner, Chi Zhang, Dexin Sui, Jian Hu
Zrt/Irt-like proteins (ZIPs) play fundamental roles in metal metabolism/homeostasis and are broadly involved in numerous physiological and pathological processes. The lack of high-resolution structure of the ZIPs hinders understanding of the metal transport mechanism. We report two crystal structures of a prokaryotic ZIP in lipidic cubic phase with bound metal substrates (Cd(2+) at 2.7 Å and Zn(2+) at 2.4 Å). The structures revealed a novel 3+2+3TM architecture and an inward-open conformation occluded at the extracellular side...
August 2017: Science Advances
https://www.readbyqxmd.com/read/28871493/plant-and-animal-aquaporins-crosstalk-what-can-be-revealed-from-distinct-perspectives
#19
REVIEW
Moira Sutka, Gabriela Amodeo, Marcelo Ozu
Aquaporins (AQPs) can be revisited from a distinct and complementary perspective: the outcome from analyzing them from both plant and animal studies. (1) The approach in the study. Diversity found in both kingdoms contrasts with the limited number of crystal structures determined within each group. While the structure of almost half of mammal AQPs was resolved, only a few were resolved in plants. Strikingly, the animal structures resolved are mainly derived from the AQP2-lineage, due to their important roles in water homeostasis regulation in humans...
September 4, 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/28867210/membrane-transporter-research-in-times-of-countless-structures
#20
REVIEW
Markus A Seeger
Structural biology has advanced our understanding of membrane proteins like no other scientific discipline in the past two decades and the number of high resolution membrane transporter structures solved by X-ray crystallography has increased exponentially over this time period. Currently, single particle cryo-EM is in full swing due to a recent resolution revolution and permits for structural insights of proteins that were refractory to crystallization. It is foreseeable that multiple structures of many human transporters will be solved in the coming five years...
August 31, 2017: Biochimica et Biophysica Acta
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