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https://www.readbyqxmd.com/read/28231454/zinc-complexes-of-diflunisal-synthesis-characterization-structure-antioxidant-activity-and-in-vitro-and-in-silico-study-of-the-interaction-with-dna-and-albumins
#1
Alketa Tarushi, Chrisoula Kakoulidou, Catherine P Raptopoulou, Vassilis Psycharis, Dimitris P Kessissoglou, Ioanna Zoi, Athanasios N Papadopoulos, George Psomas
From the reaction of ZnCl2 with the non-steroidal anti-inflammatory drug diflunisal (Hdifl), complex [Zn(difl-O)2(MeOH)4], 1 was formed, while in the presence of a N,N'-donor heterocyclic ligand 2,2'-bipyridylamine (bipyam), 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen) and 2,2'-dipyridylketone oxime (Hpko), the complexes [Zn(difl-O,O')2(bipyam)], 2, [Zn(difl-O,O')2(bipy)], 3, [Zn(difl-O,O')2(phen)], 4 and [Zn(difl-O)2(Hpko)2], 5 were isolated, respectively. The complexes were characterized by physicochemical and spectroscopic techniques and the crystal structures of complexes 2, 3 and 5 were determined by X-ray crystallography...
February 12, 2017: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/28230871/an-in-situ-tem-study-of-the-surface-oxidation-of-palladium-nanocrystals-assisted-by-electron-irradiation
#2
Dejiong Zhang, Chuanhong Jin, He Tian, Yalin Xiong, Hui Zhang, Peisheng Qiao, Jie Fan, Ze Zhang, Z Y Li, Jixue Li
The surface oxidation of palladium nanocrystals plays an important role in changing the active sites and subsequently influencing the catalytic reactivity. Such a microscopy study on surface oxidation, down to the atomic scale, is essential for understanding the structure-property correlations of palladium nanocrystal based catalysts. Herein, we present an in situ atomic scale study on the surface oxidation behavior of palladium nanocrystals, which is induced by electron beam irradiation under low oxygen partial pressure and at room temperature inside an environmental transmission electron microscope...
February 23, 2017: Nanoscale
https://www.readbyqxmd.com/read/28230363/inhibition-and-stabilization-cucurbituril-induced-distinct-effects-on-the-schiff-base-reaction
#3
Wanjun Gong, Jun Ma, Zhiyong Zhao, Fang Gao, Feng Liang, Haijun Zhang, Simin Liu
The different effects of cucurbit[7]uril (CB[7]) on the Schiff base reactions in aqueous solution were explored by 1H NMR spectroscopy and single X-ray crystallography. With CB[7] the condensation reaction of aldehyde and primary amine is dramatically inhibited. In contrast the presence of CB[7] does tremendously stabilize iminium cation in water through ion-dipole interactions. A single crystal structure of the complex of iminium ion 7 with CB[7] grown in water is reported.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28228927/computational-approaches-for-revealing-the-structure-of-membrane-transporters-case-study-on-bilitranslocase
#4
REVIEW
Katja Venko, A Roy Choudhury, Marjana Novič
The structural and functional details of transmembrane proteins are vastly underexplored, mostly due to experimental difficulties regarding their solubility and stability. Currently, the majority of transmembrane protein structures are still unknown and this present a huge experimental and computational challenge. Nowadays, thanks to X-ray crystallography or NMR spectroscopy over 3000 structures of membrane proteins have been solved, among them only a few hundred unique ones. Due to the vast biological and pharmaceutical interest in the elucidation of the structure and the functional mechanisms of transmembrane proteins, several computational methods have been developed to overcome the experimental gap...
2017: Computational and Structural Biotechnology Journal
https://www.readbyqxmd.com/read/28228478/an-engineered-tgf-%C3%AE-monomer-that-functions-as-a-dominant-negative-to-block-tgf-%C3%AE-signaling
#5
Sun Kyung Kim, Lindsey Barron, Cynthia S Hinck, Elyse M Petrunak, Kristin E Cano, Avinash Thangirala, Brian Iskra, Molly Brothers, Machell Vonberg, Belinda Leal, Blair Richter, Ravindra Kodali, Alex B Taylor, Shoucheng Du, Christopher O Barnes, Traian Sulea, Guillermo Calero, P John Hart, Matthew J Hart, Borries Demeler, Andrew P Hinck
The transforming growth factor beta isoforms, TGF-β1, -β2, and -β3 are small secreted homodimeric signaling proteins with essential roles in regulating the adaptive immune system and maintaining the extracellular matrix. However, dysregulation of the TGF-β pathway is responsible for promoting the progression of several human diseases, including cancer and fibrosis. In spite of the known importance of TGF-βs in promoting disease progression, no inhibitors have been approved for use in humans. Herein, we describe an engineered TGF-β monomer, lacking the heel helix, a structural motif essential for binding the TGF-β type I receptor, TβRI, but dispensible for binding the other receptor required for TGF-β signaling, the TGF-β type II receptor, TβRII, as an alternative therapeutic modality for blocking TGF-β signaling in humans...
February 22, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28228227/%C3%AE-butenolide-and-furanone-derivatives-from-the-soil-derived-fungus-aspergillus-sclerotiorum-psu-rspg178
#6
Patima Phainuphong, Vatcharin Rukachaisirikul, Kwanruthai Tadpetch, Yaowapa Sukpondma, Saowanit Saithong, Souwalak Phongpaichit, Sita Preedanon, Jariya Sakayaroj
Chromatographic separation of the broth extract of the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178 resulted in isolation of four γ-butenolide-furanone dimers, aspersclerotiorones A-D, a furanone derivative, aspersclerotiorone E, and two γ-butenolide derivatives, aspersclerotiorones F and G, together with six known compounds, penicillic acid, dihydropenicillic acid, 5,6-dihydro-6-hydroxypenicillic acid, 6-methoxy-5,6-dihydropenicillic acid, coculnol and (4R,5R)-4,5-dihydroxy-3-methoxy-5-methylcyclohex-2-en-1-one...
February 19, 2017: Phytochemistry
https://www.readbyqxmd.com/read/28228039/cell-quintupling-structural-phase-transition-in-a-molecular-crystal-bis-trans-4-butylcyclohexyl-methanol
#7
Kazuya Saito, Takaaki Ikeda, Yasuhisa Yamamura, Hideki Saitoh, Mafumi Hishida, Yutaro Kobayashi, Takeshi Fujita, Junji Ichikawa
A structural phase transition at 151.6 K of the title compound [bis(trans-4-butylcyclohexyl)methanol] is examined by X-ray diffraction crystallography, Fourier-transform infrared spectroscopy, and adiabatic calorimetry. A general consideration on possible superstructures indicates that a single modulation wave is sufficient to drive this cell-quintupling transition. The entropy of transition determined calorimetrically indicates that two conformations are dominant in the room-temperature phase in contrast to the fivefold disorder expected from the structure of the low-temperature phase...
February 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28224151/counterion-induced-crystallization-of-intermetalloid-matryoshka-clusters-sb-pd12-sb20-3-4
#8
Zhenyu Li, Huapeng Ruan, Lulu Wang, Caiping Liu, Li Xu
Two intermetalloid Matryoshka cluster anions [Sb@Pd12@Sb20](3-,4-) obtained from the reaction of KSb and Pd(PPh3)4 were isolated as [K(2,2,2-cryptand)](+) and [K(18-crown-6)](+) salt, respectively, and characterized by X-ray crystallography, EPR measurement and DFT theoretical calculations.
February 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28223522/conformational-dynamics-of-a-neurotransmitter-sodium-symporter-in-a-lipid-bilayer
#9
Suraj Adhikary, Daniel J Deredge, Anu Nagarajan, Lucy R Forrest, Patrick L Wintrode, Satinder K Singh
Neurotransmitter:sodium symporters (NSSs) are integral membrane proteins responsible for the sodium-dependent reuptake of small-molecule neurotransmitters from the synaptic cleft. The symporters for the biogenic amines serotonin (SERT), dopamine (DAT), and norepinephrine (NET) are targets of multiple psychoactive agents, and their dysfunction has been implicated in numerous neuropsychiatric ailments. LeuT, a thermostable eubacterial NSS homolog, has been exploited as a model protein for NSS members to canvass the conformational mechanism of transport with a combination of X-ray crystallography, cysteine accessibility, and solution spectroscopy...
February 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28221379/bridgehead-isomer-effects-in-bis-phosphido-bridged-diiron-hexacarbonyl-proton-reduction-electrocatalysts
#10
Ahibur Rahaman, Carolina Gimbert-Suriñach, Arne Ficks, Graham E Ball, Mohan Bhadbhade, Matti Haukka, Lee Higham, Ebbe Nordlander, Stephen B Colbran
The influence of the substitution, orientation and structure of the phosphido bridges in [Fe2(CO)6(μ-PR2)2] electrocatalysts of proton reduction has been studied. The isomers e,a-[Fe2(CO)6{μ-P(Ar)H}2] (1a(Ar): Ar = Ph, 2'-methoxy-1,1'-binaphthyl (bn')), e,e-[Fe2(CO)6{μ-P(Ar)H}2] (1b(Ar): Ar = Ph, bn') were isolated from reactions of iron pentacarbonyl and the corresponding primary phosphine, syntheses that also afforded the phosphinidene-capped tri-iron clusters, [Fe3(CO)9(μ-CO)(μ3-Pbn')] (2) and [Fe3(CO)9(μ3-PAr)2] (3(Ar), Ar = Ph, bn')...
February 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28221042/on-the-internal-dynamics-of-the-3-pyrroline-n-oxide-ring-in-spin-labeled-proteins
#11
Philipp Consentius, Bernhard Loll, Ulrich Gohlke, Claudia Alings, Carsten Mueller, Robert Müller, Christian Teutloff, Udo Heinemann, Martin Kaupp, Markus C Wahl, Thomas Risse
Site-directed spin labeling is a versatile tool to study structure as well as dynamics of proteins using EPR spectroscopy. Methanethiosulfonate (MTS)-spin labels tethered through a disulfide linkage to an engineered cysteine residue were used in a large number of studies to extract structural as well as dynamic information of the protein from the rotational dynamics of the nitroxide moiety. The ring itself was always considered to be a rigid body. In this contribution, we present a combination of high-resolution X-ray crystallography and EPR spectroscopy of spin-labeled protein single crystals demonstrating that the nitroxide ring inverts fast at ambient temperature, while being characterized by a bent conformation at low temperature...
February 21, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28221037/computational-investigation-of-ligand-binding-to-the-peripheral-site-in-cyp3a4-conformational-dynamics-and-inhibitor-discovery
#12
Hanwen Du, Junhao Li, Yingchun Cai, Hongxiao Zhang, Guixia Liu, Yun Tang, Weihua Li
Human cytochrome P450 3A4 (CYP3A4) is a major drug-metabolizing enzyme responsible for the metabolism of ~50% of clinically used drugs and is often involved in drug-drug interactions. It exhibits atypical binding and kinetic behavior towards many ligands. Binding of ligands to CYP3A4 is a complex process. Recent studies from both crystallography and biochemistry suggested the existence of a peripheral ligand-binding site at the enzyme surface. However, the stability of ligand bound at this peripheral site and the possibility of discovering new CYP3A4 ligands based on this site remain unclear...
February 21, 2017: Journal of Chemical Information and Modeling
https://www.readbyqxmd.com/read/28219079/light-induced-structural-changes-and-the-site-of-o-o-bond-formation-in-psii-caught-by-xfel
#13
Michihiro Suga, Fusamichi Akita, Michihiro Sugahara, Minoru Kubo, Yoshiki Nakajima, Takanori Nakane, Keitaro Yamashita, Yasufumi Umena, Makoto Nakabayashi, Takahiro Yamane, Takamitsu Nakano, Mamoru Suzuki, Tetsuya Masuda, Shigeyuki Inoue, Tetsunari Kimura, Takashi Nomura, Shinichiro Yonekura, Long-Jiang Yu, Tomohiro Sakamoto, Taiki Motomura, Jing-Hua Chen, Yuki Kato, Takumi Noguchi, Kensuke Tono, Yasumasa Joti, Takashi Kameshima, Takaki Hatsui, Eriko Nango, Rie Tanaka, Hisashi Naitow, Yoshinori Matsuura, Ayumi Yamashita, Masaki Yamamoto, Osamu Nureki, Makina Yabashi, Tetsuya Ishikawa, So Iwata, Jian-Ren Shen
Photosystem II (PSII) is a huge membrane-protein complex consisting of 20 different subunits with a total molecular mass of 350 kDa for a monomer. It catalyses light-driven water oxidation at its catalytic centre, the oxygen-evolving complex (OEC). The structure of PSII has been analysed at 1.9 Å resolution by synchrotron radiation X-rays, which revealed that the OEC is a Mn4CaO5 cluster organized in an asymmetric, 'distorted-chair' form. This structure was further analysed with femtosecond X-ray free electron lasers (XFEL), providing the 'radiation damage-free' structure...
February 20, 2017: Nature
https://www.readbyqxmd.com/read/28217896/detection-of-palladium-i-in-aerobic-oxidation-catalysis
#14
Jonathan N Jaworski, Scott D McCann, Ilia A Guzei, Shannon S Stahl
Palladium(II)-catalyzed oxidation reactions exhibit broad utility in organic synthesis; however, they often feature high catalyst loading and low turnover numbers relative to non-oxidative cross-coupling reactions. Insights into the fate of the Pd catalyst during turnover could help to address this limitation. Herein, we report the identification and characterization of a dimeric Pd(I) species in two prototypical Pd-catalyzed aerobic oxidation reactions: allylic C-H acetoxylation of terminal alkenes and intramolecular aza-Wacker cyclization...
February 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28217747/insights-into-photosystem-ii-from-isomorphous-difference-fourier-maps-of-femtosecond-x-ray-diffraction-data-and-quantum-mechanics-molecular-mechanics-structural-models
#15
REVIEW
Jimin Wang, Mikhail Askerka, Gary W Brudvig, Victor S Batista
Understanding structure-function relations in photosystem II (PSII) is important for the development of biomimetic photocatalytic systems. X-ray crystallography, computational modeling, and spectroscopy have played central roles in elucidating the structure and function of PSII. Recent breakthroughs in femtosecond X-ray crystallography offer the possibility of collecting diffraction data from the X-ray free electron laser (XFEL) before radiation damage of the sample, thereby overcoming the main challenge of conventional X-ray diffraction methods...
February 10, 2017: ACS Energy Lett
https://www.readbyqxmd.com/read/28217325/crystal-structures-of-a-novel-nnn-pincer-ligand-and-its-dinuclear-titanium-iv-alkoxide-pincer-complex
#16
Jakub Pedziwiatr, Ion Ghiviriga, Khalil A Abboud, Adam S Veige
This report describes a synthetic protocols and the crystal structures involving a novel pincer-type H3[NNN] ligand, namely di-μ-bromido-μ-{2-(2,2-di-methylpropanimido-yl)-N-[2-(2,2-di-methyl-propanimido-yl)-4-methyl-phen-yl]-4-methylaniline}-bis-[(diethyl ether)lithium], [Li2Br2(C24H33N3)(C4H10O)2] (1) and a dinuclear metal complex, namely di-μ-bromido-2:3κ(4)Br:Br-bis-{2-(2,2-di-methylpropanimido-yl)-N-[2-(2,2-di-methyl-propanimido-yl)-4-methyl-phen-yl]-4-methylaniline}-1κ(3)N,N',N'';4κ(3)N,N',N''-tetra-μ-iso-propano-lato-1:2κ(4)O:O;3:4κ(4)O:O-diiso-propano-lato-1κO,4κO-2,3-dilithium-1,4-dititanium, [Li2Ti2Br2(C24H32N3)2(C3H7O)6] or {[NHNNH]Ti(O (i) Pr)3(LiBr)2}2 (2)...
February 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28215139/bridgehead-nitrogen-thiazolo-3-2-a-pyrimidine-a-privileged-structural-framework-in-drug-discovery
#17
Amit K Keshari, Ashok K Singh, Sudipta Saha
Thiazolopyrimidine derivatives containing bridgehead nitrogen atom are now-a-days attracting the attention of many medicinal chemists throughout the world to explore this framework for its potential. This biologically important scaffold is formed by the fusion of two aromatic rings, thiazole and pyrimidine, in such a way that one carbon atom at the ring junction is replaced by a nitrogen atom and is, therefore, being common for both the heterocyclic rings. One of the most common example of this type of fusion is thiazolo[3,2-a]pyrimidine which is being used perpetually with tremendous success in various field of therapeutic applications...
February 16, 2017: Mini Reviews in Medicinal Chemistry
https://www.readbyqxmd.com/read/28212012/-meyeniins-a-c-novel-hexahydroimidazo-1-5-c-thiazole-derivatives-from-the-tubers-of-lepidium-meyenii-complete-structural-elucidation-by-biomimetic-synthesis-and-racemic-crystallization
#18
Min Zhou, Hang-Ying Ma, Zhi-Hua Liu, Guang-Yu Yang, Gang Du, Yan-Qing Ye, Gan-Peng Li, Qiu-Fen Hu
(+)-Meyeniins A-C (1-3), a novel class of sulfur-containing hexahydroimidazo[1,5-c]thiazole derivatives, were isolated from the tubers of Lepidium meyenii (maca) cultivated in Lijiang, Yunnan province, China. Guided by their biosynthetic hypothesis, a stereocontrolled biomimetic synthesis of meyeniins A-C and their individual enantiomers was efficiently accomplished by a combination of a condensation reaction and Edman degradation. The formation of high-quality crystals for X-ray crystallography occurred much more readily from a racemic mixture of (±)-meyeniin A than with the single enantiomer alone in this case...
February 23, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28208266/link-between-affinity-and-cu-ii-binding-sites-to-amyloid-%C3%AE-peptides-evaluated-by-a-new-water-soluble-uv-visible-ratiometric-dye-with-a-moderate-cu-ii-affinity
#19
Amandine Conte-Daban, Valentina Borghesani, Stéphanie Sayen, Emmanuel Guillon, Yves Journaux, Geoffrey Gontard, Laurent Lisnard, Christelle Hureau
Being able to easily determine the Cu(II) affinity for biomolecules of moderate affinity is important. Such biomolecules include amyloidogenic peptides, such as the well-known amyloid-β peptide involved in Alzheimer's disease. Here, we report the synthesis of a new water-soluble ratiometric Cu(II) dye with a moderate affinity (10(9) M(-1) at pH 7.1) and the characterizations of the Cu(II) corresponding complex by X-ray crystallography, EPR, and XAS spectroscopic methods. UV-vis competition was performed on the Aβ peptide as well as on a wide series of modified peptides, leading to an affinity value of 1...
February 7, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28208018/pharmacophore-mapping-of-thienopyrimidine-based-monophosphonate-thp-mp-inhibitors-of-the-human-farnesyl-pyrophosphate-synthase
#20
Jaeok Park, Chun Yuen Leung, Alexios N Matralis, Cyrus M Lacbay, Michail Tsakos, Guillermo Fernandez De Troconiz, Albert M Berghuis, Youla S Tsantrizos
The human farnesyl pyrophosphate synthase (hFPPS), a key regulatory enzyme in the mevalonate pathway, catalyzes the biosynthesis of the C-15 isoprenoid farnesyl pyrophosphate (FPP). FPP plays a crucial role in the post-translational prenylation of small GTPases that perform a plethora of cellular functions. Although hFPPS is a well-established therapeutic target for lytic bone diseases, the currently available bisphosphonate drugs exhibit poor cellular uptake and distribution into non-skeletal tissues. Recent drug discovery efforts have focused primarily on allosteric inhibition of hFPPS and the discovery of non-bisphosphonate drugs for potentially treating non-skeletal diseases...
February 16, 2017: Journal of Medicinal Chemistry
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