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https://www.readbyqxmd.com/read/28102667/two-different-structures-of-the-oxygen-evolving-complex-in-the-same-polypeptide-frameworks-of-photosystem-ii
#1
Ayako Tanaka, Yoshimasa Fukushima, Nobuo Kamiya
The oxygen-evolving complex (OEC) forms the heart of photosystem II (PSII) in photosynthesis. The crystal structure of PSII from Thermosynechococcus vulcanus has been reported at a resolution of 1.9 Å and at an averaged X-ray dose of 0.43 MGy. The OEC structure is suggested to be partially reduced to Mn(II) by EXAFS and DFT compu-tational studies. Recently, the "radiation-damage-free" struc-tures have been published at 1.95 Å resolution using XFEL, but reports continued to appear that the OEC is reduced to the S0-state of the Kok cycle...
January 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28102523/the-effect-of-superparamagnetic-iron-oxide-nanoparticle-surface-charge-on-antigen-cross-presentation
#2
Yongbin Mou, Yun Xing, Hongyan Ren, Zhihua Cui, Yu Zhang, Guangjie Yu, Walter J Urba, Qingang Hu, Hongming Hu
Magnetic nanoparticles (NPs) of superparamagnetic iron oxide (SPIO) have been explored for different kinds of applications in biomedicine, mechanics, and information. Here, we explored the synthetic SPIO NPs as an adjuvant on antigen cross-presentation ability by enhancing the intracellular delivery of antigens into antigen presenting cells (APCs). Particles with different chemical modifications and surface charges were used to study the mechanism of action of antigen delivery. Specifically, two types of magnetic NPs, γFe2O3/APTS (3-aminopropyltrimethoxysilane) NPs and γFe2O3/DMSA (meso-2, 3-Dimercaptosuccinic acid) NPs, with the same crystal structure, magnetic properties, and size distribution were prepared...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28102411/defect-driven-shapes-in-nematic-droplets-analogies-with-cell-division
#3
Marco Leoni, Oksana V Manyuhina, Mark J Bowick, M Cristina Marchetti
Building on the striking similarity between the structure of the spindle during mitosis in living cells and nematic textures in confined liquid crystals, we use a continuum model of two-dimensional nematic liquid crystal droplets to examine the physical aspects of cell division. The model investigates the interplay between bulk elasticity of the microtubule assembly, described as a nematic liquid crystal, and surface elasticity of the cell cortex, modeled as a bounding flexible membrane, in controlling cell shape and division...
January 19, 2017: Soft Matter
https://www.readbyqxmd.com/read/28102388/crystal-structure-of-ba2-la0-727ba0-182m0-091-mo6-m-nb-sb-bi-symmetry-nuance-identified-in-photoluminescence-and-ir-spectroscopy-studies
#4
Rohan Phatak, Santosh K Gupta, Priya Maheshwari, Amitabh Das, Sanjay K Sali
A one-third lanthanum deficiency was created in Ba2LaM(5+)O6 compounds (LaM compounds) to form Ba2La2/3M(5+)O5.5 compounds (La2/3M compounds) for M = Nb, Sb, and Bi. The compounds were prepared by a gel-combustion method using citric acid as a fuel. All the compounds were characterized by powder X-ray diffraction (XRD). The XRD analysis showed that the space group of the La2/3M compounds remains the same for the Bi and Sb samples when compared to the reported LaM compounds, except for the Nb sample. La2/3Nb and La2/3Sb adopt a rhombohedral structure with the space group R3[combining macron], whereas La2/3Bi adopts a monoclinic structure with the space group I2/m...
January 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28102387/anion-dependent-self-assembly-of-sandwich-13-metal-ni-ln-nanoclusters-with-a-long-chain-schiff-base-ligand
#5
Shiqing Wang, Xiaoping Yang, Jinjie Qian, Qipeng Li, Zhongning Chen, Lijie Zhang, Shaoming Huang, Chengri Wang, Richard A Jones
Two classes of Ni-Ln clusters [Ln4Ni3L3(OAc)6(NO3)3(OH)3] (Ln = Gd (1) and Tb (2)) and [Ln6Ni7L6(OAc)12(OH)6](OH)2 (Ln = Gd (3) and Dy (4)) were prepared using a specifically designed Schiff base ligand built around a flexible (CH2)2O(CH2)2O(CH2)2 chain. 1 and 2 exhibit cone-like structures, while 3 and 4 have nanosized sandwich architectures. The structures were studied by single-crystal X-ray diffraction and TEM, and magnetic properties were investigated.
January 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28102373/unprecedented-photochemical-rearrangement-of-an-open-cage-c60-derivative
#6
Tsukasa Futagoishi, Michihisa Murata, Atsushi Wakamiya, Yasujiro Murata
Upon irradiation of a sulfoxide C60 derivative with a 17-membered-ring opening, rearrangement of the carbon framework took place to give an unprecedented lactone C60 derivative with a 14-membered-ring opening, whose structure was unambiguously determined by single crystal X-ray analysis. This reaction is completely different from that of the previously reported sulfoxide C60 and C70 derivatives with a 13-membered-ring opening.
January 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28102312/correlations-of-charge-neutrality-level-with-electronic-structure-and-p-d-hybridization
#7
Arkaprava Das, Subodh K Gautam, D K Shukla, Fouran Singh
The formation of charge neutrality level (CNL) in highly conducting Cadmium oxide (CdO) thin films is demonstarted by the observed variation in the band gap upon annealing and doping. It may be explained by the observation that Tin (Sn) doping breaks the perfect periodicity of CdO cubic crystal structure and creates virtual gap states (ViGS). The level of local CNL resides at the branch point of ViGS, making the energy at which native defect's character changes from predominantly donor-like below CNL to predominantly acceptor-like above the CNL and a schematic band diagram is developed to substantiate the same...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28102285/non-destructive-study-of-bulk-crystallinity-and-elemental-composition-of-natural-gold-single-crystal-samples-by-energy-resolved-neutron-imaging
#8
Anton S Tremsin, John Rakovan, Takenao Shinohara, Winfried Kockelmann, Adrian S Losko, Sven C Vogel
Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5-10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28102198/shape-dependent-ordering-of-gold-nanocrystals-into-large-scale-superlattices
#9
Jianxiao Gong, Richmond S Newman, Michael Engel, Man Zhao, Fenggang Bian, Sharon C Glotzer, Zhiyong Tang
Self-assembly of individual building blocks into highly ordered structures, analogous to spontaneous growth of crystals from atoms, is a promising approach to realize the collective properties of nanocrystals. Yet the ability to reliably produce macroscopic assemblies is unavailable and key factors determining assembly quality/yield are not understood. Here we report the formation of highly ordered superlattice films, with single crystalline domains of up to half a millimetre in two dimensions and thickness of up to several microns from nanocrystals with tens of nanometres in diameter...
January 19, 2017: Nature Communications
https://www.readbyqxmd.com/read/28101956/aggregates-finding-structures-in-simulation-results-of-solutions
#10
Carlos E S Bernardes
Molecular Dynamic and Monte-Carlo simulations are widely used to investigate the structure and physical properties of solids and liquids at a molecular level. Tools to extract the most relevant information from the obtained results are, however, in considerable demand. One such tool, the program AGGREGATES, is described in this work. Based on distance criteria, the program searches trajectory files for the presence of molecular clusters and computes several statistical and shape properties for these structures...
January 19, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/28101862/crystallographic-studies-of-intermediate-filament-proteins
#11
Dmytro Guzenko, Anastasia A Chernyatina, Sergei V Strelkov
Intermediate filaments (IFs), together with microtubules and actin microfilaments, are the three main cytoskeletal components in metazoan cells. IFs are formed by a distinct protein family, which is made up of 70 members in humans. Most IF proteins are tissue- or organelle-specific, which includes lamins, the IF proteins of the nucleus. The building block of IFs is an elongated dimer, which consists of a central α-helical 'rod' domain flanked by flexible N- and C-terminal domains. The conserved rod domain is the 'signature feature' of the IF family...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28101797/ni-ii-and-zn-ii-complexes-containing-alkynyl-functionalized-salicylaldimine-ligand-and-heterocyclic-coligand-synthesis-characterization-and-luminescence-properties
#12
M S More, S S Devkule, S S Chavan
Some nickel(II) and zinc(II) complexes of the type [Ni(L)(phen/bipy)]X (1a-6a) and [Zn(L) (phen/bipy)]X (1b-6b) (where L = 2-{(E)-[(4-trimethylsilylethynylphenyl)imino]methyl}-4-(4-nitro phenylethynyl)phenol; phen = 1, 10-phenanthroline, bipy = 2, 2´-bipyridine; X = ClO4(-), BF4(-), PF6(-)) have been prepared and characterized on the basis of elemental analyses, FTIR, (1)H NMR and mass spectral studies. The molecular structure of L was determined by single crystal X-ray diffraction studies. The electrochemical behaviour of the Ni(II) complexes indicate that the phen complexes appears at more positive potential as compared to those for bipy complexes, as a consequence of its strong π-acidic character...
January 18, 2017: Journal of Fluorescence
https://www.readbyqxmd.com/read/28101544/tetrathienyl-functionalized-red-and-nir-absorbing-bodipy-dyes-appending-various-peripheral-substituents
#13
Ping Liu, Feng Gao, Lina Zhou, Yu Chen, Zhijian Chen
A series of boron-dipyrromethene dyes (BODIPYs) 4a-g with different thienyl moieties at 2,3,5,6-positions of the BODIPY core were synthesized by the Stille cross-coupling reaction. The new compounds were characterized by (1)H NMR, (13)C NMR, HRMS, and IR spectroscopy. The single crystal structure of compound 4e was obtained by X-ray crystallography. The optical and electrochemical properties of these dyes were studied by UV/Vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. The DFT calculation of the frontier molecular orbitals of these dyes corroborates the observed effects of peripheral substituents on the optical and redox properties...
January 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28100693/viral-genome-packaging-terminase-cleaves-dna-using-the-canonical-ruvc-like-two-metal-catalysis-mechanism
#14
Rui-Gang Xu, Huw T Jenkins, Maria Chechik, Elena V Blagova, Anna Lopatina, Evgeny Klimuk, Leonid Minakhin, Konstantin Severinov, Sandra J Greive, Alfred A Antson
Bacteriophages and large dsDNA viruses encode sophisticated machinery to translocate their DNA into a preformed empty capsid. An essential part of this machine, the large terminase protein, processes viral DNA into constituent units utilizing its nuclease activity. Crystal structures of the large terminase nuclease from the thermophilic bacteriophage G20c show that it is most similar to the RuvC family of the RNase H-like endonucleases. Like RuvC proteins, the nuclease requires either Mn(2+), Mg(2+) or Co(2+) ions for activity, but is inactive with Zn(2+) and Ca(2+) High resolution crystal structures of complexes with different metals reveal that in the absence of DNA, only one catalytic metal ion is accommodated in the active site...
January 18, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28100692/insights-into-the-recq-helicase-mechanism-revealed-by-the-structure-of-the-helicase-domain-of-human-recql5
#15
Joseph A Newman, Hazel Aitkenhead, Pavel Savitsky, Opher Gileadi
RecQ helicases are important maintainers of genome integrity with distinct roles in almost every cellular process requiring access to DNA. RECQL5 is one of five human RecQ proteins and is particularly versatile in this regard, forming protein complexes with a diverse set of cellular partners in order to coordinate its helicase activity to various processes including replication, recombination and DNA repair. In this study, we have determined crystal structures of the core helicase domain of RECQL5 both with and without the nucleotide ADP in two distinctly different ('Open' and 'Closed') conformations...
January 18, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28100079/a-novel-proton-transfer-salt-of-2-amino-6-sulfamoylbenzothiazole-and-its-metal-complexes-the-evaluation-of-their-inhibition-effects-on-human-cytosolic-carbonic-anhydrases
#16
Zeynep Alkan Alkaya, Halil İlkimen, Cengiz Yenikaya, Yasemin Kaygısız, Metin Bülbül, Tuncay Tunç, Musa Sarı
A novel proton transfer compound (SMHABT)(+)(HDPC)(-) (1) obtained from 2-amino-6-sulfamoylbenzothiazole (SMABT) and 2,6-pyridinedicarboxylic acid (H2DPC) and its Fe(III), Co(II), Ni(II) complexes (2-4), and Fe(II) complex of SMABT (5) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to complexes (2-4). All complexes (2-4) have distorted octahedral conformations and the structure of 5 might be proposed as octahedral according to spectral and analytical results...
December 2017: Journal of Enzyme Inhibition and Medicinal Chemistry
https://www.readbyqxmd.com/read/28099021/location-of-methanol-on-the-s2-state-mn-cluster-in-photosystem-ii-studied-by-proton-matrix-electron-nuclear-double-resonance
#17
Hiroki Nagashima, Hiroyuki Mino
Proton matrix electron nuclear double resonance (ENDOR) spectroscopy was performed in order to specify the location of the methanol molecule near the manganese cluster in photosystem II. Comparison of the ENDOR spectra in the presence of CH3OH and CD3OH revealed two pairs of hyperfine couplings, 1.15 MHz for A⊥ and 2.32 MHz for A∥, arising from the methyl group in methanol. Based on the crystal structure, the possible location of methanol close to the manganese cluster was discussed.
January 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28099001/conformational-dynamics-in-penicillin-binding-protein-2a-of-methicillin-resistant-staphylococcus-aureus-allosteric-communication-network-and-enablement-of-catalysis
#18
Kiran V Mahasenan, Rafael Molina, Renee Bouley, Maria T Batuecas, Jed F Fisher, Juan A Hermoso, Mayland Chang, Shahriar Mobashery
The mechanism of the β-lactam antibacterials is the functionally irreversible acylation of the enzymes that catalyze the cross-linking steps in the biosynthesis of their peptidoglycan cell wall. The Gram-positive pathogen Staphylococcus aureus uses one primary resistance mechanism. An enzyme, called penicillin-binding protein 2a (PBP2a), is brought into this biosynthetic pathway to complete the cross-linking. PBP2a effectively discriminates against the β-lactam antibiotics as potential inhibitors, and in favor of the peptidoglycan substrate...
January 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28098999/dna-deformation-coupled-recognition-of-8-oxoguanine-conformational-kinetic-gating-in-human-dna-glycosylase
#19
Haoquan Li, Anton V Endutkin, Christina Bergonzo, Fu Lin, Arthur P Grollman, Dmitry O Zharkov, Carlos Simmerling
8-Oxoguanine (8-oxoG), a mutagenic DNA lesion generated under oxidative stress, differs from its precursor guanine by only two substitutions (O8 and H7). Human 8-oxoguanine glycosylase 1 (OGG1) can locate and remove 8-oxoG through extrusion and excision. To date, it remains unclear how OGG1 efficiently distinguishes 8-oxoG from a large excess of undamaged DNA bases. We recently showed that formamidopyrimidine-DNA glycosylase (Fpg), a bacterial functional analog of OGG1, can selectively facilitate eversion of oxoG by stabilizing several intermediate states, and it is intriguing whether OGG1 also employs a similar mechanism in lesion recognition...
January 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28098986/investigation-of-the-energy-transfer-mechanism-in-ho-3-and-yb-3-codoped-lu2o3-phosphor-with-efficient-near-infrared-downconversion
#20
Guotao Xiang, Yan Ma, Xianju Zhou, Sha Jiang, Li Li, Xiaobing Luo, Zhendong Hao, Xia Zhang, Guo-Hui Pan, Yongshi Luo, Jiahua Zhang
A high-temperature solid-state method was used to synthesize the Ho(3+)- and Yb(3+)-codoped cubic Lu2O3 powders. The crystal structures of the as-prepared powders were characterized by X-ray diffraction. The energy-transfer (ET) phenomenon between Ho(3+) ions and Yb(3+) ions was verified by the steady-state spectra including visible and near-infrared (NIR) regions. Beyond that, the decay curves were also measured to certify the existence of the ET process. The downconversion phenomena appeared when the samples were excited by 446 nm wavelength corresponding to the transition of Ho(3+): (5)I8→(5)G6/(5)F1...
January 18, 2017: Inorganic Chemistry
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