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https://www.readbyqxmd.com/read/29352964/c24-hydroxylated-stigmastane-derivatives-as-liver-x-receptor-agonists
#1
Francisco Fermin Castro Navas, Gianluca Giorgi, Daniela Maggioni, Manuela Pacciarini, Vincenzo Russo, Maura Marinozzi
Phytosterols are stucturally correlated to the endogenous ligands of Liver X Receptor (LXR), a ligand-activated nuclear receptor that has emerged as an attractive drug target due to its ability to integrate metabolic and inflammatory signaling. Natural and semi-synthetic phytosterol derivatives characterized by the presence of side-chain oxygenated functions have shown to be able to modulate LXR activity. Here, we describe the efficient synthesis of four stigmastane derivatives, endowed with a hydroxyl group at C24 position, namely (24R)- and (24S)-stigmasta-5,28-diene-3β,24-ols (also referred to as saringosterols, 10a and 10b) and (24R)- and (24S)-stigmasta-5-ene-3β,24-ols (11a and 11b), starting from the readily available stigmasterol...
January 15, 2018: Chemistry and Physics of Lipids
https://www.readbyqxmd.com/read/29349888/distal-amyloid-%C3%AE-protein-fragments-template-amyloid-assembly
#2
Thanh D Do, Smriti Sangwan, Natália E C de Almeida, Alexandre I Ilitchev, Maxwell Giammona, Michael R Sawaya, Steven K Buratto, David S Eisenberg, Michael T Bowers
Amyloid formation is associated with devastating diseases such as Alzheimer's, Parkinson's and Type-2 diabetes. The large amyloid deposits found in patients suffering from these diseases have remained difficult to probe by structural means. Recent NMR models also predict heterotypic interactions from distinct peptide fragments but limited evidence of heterotypic packed sheets is observed in solution. Here we characterize two segments of the protein amyloid β (Aβ) known to form fibrils in Alzheimer's disease patients...
January 19, 2018: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/29349863/experimental-observation-of-thermally-excited-triplet-states-of-heavier-group-15-element-centered-diradical-dianions
#3
Yong Fang, Li Zhang, Cheng Cheng, Yue Zhao, Manabu Abe, Gengwen Tan, Xinping Wang
One-electron reductions of Mes*As=Fl* (1; Fl* = 2,7-di-tert-butylfluorenylidene, Mes* = 2,4,6-tBu3C6H2) and diarsaalkenes [1,2-b]-IF(=AsMes*)2 (2; IF = indenofluorene) with potassium led to the isolation of the arsenic-centered radical anion salts 1K and 2K, respectively. The diradical dianion salts 2K2 and 3K2 were afforded by the reduction of 2 and 2,8-tBu2-[2,1-b]-IF(=AsMes*)2 (3) with an excess amount of KC8. The radicals have been investigated by single-crystal X-ray crystallography, EPR and UV-Vis absorption spectroscopy, along with theoretical calculations...
January 18, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29345989/assembly-of-copi-and-copii-vesicular-coat-proteins-on-membranes
#4
Julien Béthune, Felix T Wieland
In eukaryotes, distinct transport vesicles functionally connect various intracellular compartments. These carriers mediate transport of membranes for the biogenesis and maintenance of organelles, secretion of cargo proteins and peptides, and uptake of cargo into the cell. Transport vesicles have distinct protein coats that assemble on a donor membrane where they can select cargo and curve the membrane to form a bud. A multitude of structural elements of coat proteins have been solved by X-ray crystallography...
January 18, 2018: Annual Review of Biophysics
https://www.readbyqxmd.com/read/29342978/host-guest-interaction-of-cucurbit-8-uril-with-n-3-aminopropyl-cyclohexylamine-cyclohexyl-encapsulation-triggered-ternary-complex
#5
Yu Xia, Chuan-Zeng Wang, Mengkui Tian, Zhu Tao, Xin-Long Ni, Timothy J Prior, Carl Redshaw
The host-guest interaction of a series of cyclohexyl-appended guests with cucurbit[8]uril (Q[8]) was studied by ¹H NMR spectroscopy, isothermal titration calorimetry (ITC), and X-ray crystallography. The X-ray structure revealed that two cycloalkane moieties can be simultaneously encapsulated in the hydrophobic cavity of the Q[8] host to form a ternary complex for the first time.
January 15, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29342833/structural-determination-of-ruthenium-complexes-containing-bi-dentate-pyrrole-ketone-ligands
#6
Ya-Wen Tsai, Yun-Fan Chen, Yong-Jie Li, Kuan-Hung Chen, Chia-Her Lin, Jui-Hsien Huang
A series of ruthenium compounds containing a pyrrole-ketone bidentate ligand, 2-(2'-methoxybenzoyl)pyrrole (1), have been synthesized and characterized. Reacting 1 with [(η⁶-cymene)RuCl₂]₂ and RuHCl(CO)(PPh₃)₃ generated Ru(η⁶-cymene)[C₄H₃N-2-(CO-C₆H₄-2-OMe)]Cl (2) and {RuCl(CO)(PPh₃)₂[C₄H₃N-2-(COC₆H₄-2-OMe)]} (3), respectively, in moderate yields. Successively reacting 2 with sodium cyanate and sodium azide gave {Ru(η⁶-cymene)[C₄H₃N-2-(CO-C₆H₄-2-OMe)]X} (4, X=OCN; 5, X=N₃) with the elimination of sodium chloride...
January 13, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29341421/a-stable-room-temperature-luminescent-biphenylmethyl-radical
#7
Xin Ai, Yingxin Chen, Yuting Feng, Feng Li
There is only one family of room-temperature luminescent radicals, the triphenylmethyl radicals, to date. Herein, we synthesize a new stable room-temperature luminescent radical, (N-carbazolyl)bis(2,4,6-tirchlorophenyl)methyl radical (CzBTM), which has improved properties compared to the triphenylmethyl radicals. X-ray crystallography, electron paramagnetic resonance spectroscopy, and magnetic susceptibility measurements confirmed the radical structure. CzBTM shows room-temperature deep-red to near-infrared emission in various solutions...
January 17, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29341313/title-synthesis-of-%C3%AE-l-fucopyranoside-presenting-glycoclusters-and-investigation-of-their-interaction-with-recombinant-photorhabdus-asymbiotica-lectin-phl
#8
Jančaříková Gita, Mihály Herczeg, Eva Fujdiarová, Josef Houser, Katalin E Kövér, Anikó Borbás, Michaela Wimmerová, Magdolna Csávás
Photorhabdus asymbiotica is a gram-negative bacterium that is not only as effective an insect pathogen as other members of the genus, but it also causes serious diseases in humans. The recently identified lectin PHL from P. asymbiotica verifiably modulates an immune response of humans and insects, which supports the idea that the lectin might play an important role in the host-pathogen interaction. Dimeric PHL contains up to seven L-fucose specific binding sites per monomer, and in order to target multiple binding sites of PHL, α-L-fucoside-containing di-, tri- and tetravalent glycoclusters were synthesized...
January 17, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29340866/-in-silico-study-of-the-binding-of-two-novel-antagonists-to-the-nociceptin-receptor
#9
Stefano Della Longa, Alessandro Arcovito
Antagonists of the nociceptin receptor (NOP) are raising interest for their possible clinical use as antidepressant drugs. Recently, the structure of NOP in complex with some piperidine-based antagonists has been revealed by X-ray crystallography. In this study, a multi-flexible docking (MF-docking) procedure, i.e. docking to multiple receptor conformations extracted by preliminary molecular dynamics trajectories, together with hybrid quantum mechanics/molecular mechanics (QM/MM) simulations have been carried out to provide the binding mode of two novel NOP antagonists, one of them selective (BTRX-246040, formerly named LY-2940094) and one non selective (AT-076), i...
January 16, 2018: Journal of Computer-aided Molecular Design
https://www.readbyqxmd.com/read/29337573/cryoprotectants-severely-exacerbate-x-ray-induced-photoreduction
#10
Kurt H Nienaber, M Jake Pushie, Julien J H Cotelesage, Ingrid J Pickering, Graham N George
Approximately 11% of enzymes contain a transition metal ion that is essential for catalytic function. Such metalloenzymes catalyze much of the most chemically challenging and biologically essential chemistry carried out by life. X-ray based methods, predominantly macromolecular crystallography (MX) and also X-ray absorption spectroscopy (XAS), have proved essential for determining structures of transition metal ion-containing active sites in order to deduce enzyme catalytic mechanisms. However, X-ray irradiation can induce change in both oxidation state and structure of the metal, which is problematic in structure determination...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29336558/excited-state-processes-of-cyclometalated-platinum-ii-charge-transfer-dimers-bridged-by-hydroxypyridines
#11
Arnab Chakraborty, James E Yarnell, Roger D Sommer, Subhangi Roy, Felix N Castellano
A series of four anti-disposed dinuclear platinum(II) complexes featuring metal-metal-to-ligand charge-transfer (MMLCT) excited states, bridged by either 2-hydroxy-6-methylpyridine or 2-hydroxy-6-phenylpyridine and cyclometalated with 7,8-benzoquinoline or 2-phenylpyridine, are presented. The 2-hydroxypyridine bridging ligands control intramolecular d8-d8 metal-metal σ interactions, affecting the frontier orbitals' electronic structure, resulting in marked changes to the ground- and excited-state properties of these complexes...
January 16, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29334167/cross-linking-mass-spectrometry-for-studying-protein-structures-and-protein-protein-interactions-where-are-we-now-and-where-should-we-go-from-here
#12
Andrea Sinz
Structural mass spectrometry (MS) is gaining increasing importance in deriving valuable three-dimensional structural information on proteins and protein complexes and complements existing techniques, such as NMR spectroscopy and X-ray crystallography. Structural MS unites different MS-based techniques, i.e, hydrogen-deuterium exchange, native MS, ion-mobility MS, protein footprinting, and chemical cross-linking/MS, and allows fundamental questions in structural biology to be addressed. In this article, I will focus on the cross-linking/MS strategy...
January 15, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29332565/beyond-the-lock-and-key-paradigm-targeting-lipid-rafts-to-induce-the-selective-apoptosis-of-cancer-cells
#13
Anna Carolina Schneider Alves, Reinaldo Antonio Dias, Luciano Porto Kagami, Gustavo Machado das Neves, Fernando Cidade Torres, Vera Lucia Eifler-Lima, Ivone Carvalho, Carolina de Miranda Silva, Daniel Fabio Kawano
For more than 40 years, the fluid mosaic model of cellular membranes have supported our vision of an inert lipid bilayer containing membrane protein receptors that are randomly hit by extracellular molecules to trigger intracellular signaling events. However, the notion that compartmentalized cholesterol- and sphingomyelin-rich membrane microdomains (known as lipid rafts) spatially arrange receptors and effectors to promote kinetically favorable interactions necessary for the signal transduction sounds much more realistic...
January 10, 2018: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/29329277/synthesis-structural-characterization-antimicrobial-activity-and-in-vitro-biocompatibility-of-new-unsaturated-carboxylate-complexes-with-2-2-bipyridine
#14
Gina Vasile Scăețeanu, Mariana Carmen Chifiriuc, Coralia Bleotu, Crina Kamerzan, Luminiţa Măruţescu, Constantin G Daniliuc, Cătălin Maxim, Larisa Calu, Rodica Olar, Mihaela Badea
The synthesis, structural characterization, cytotoxicity, and antimicrobial properties of four new complexes formed by employing acrylate anion and 2,2'-bipyridine are reported herein. X-ray crystallography revealed the trinuclear nature of [Mn₃(2,2'-bipy)₂(C₃H₃O₂)₆] (1), meanwhile complexes with general formula [M(2,2'-bipy)(C₃H₃O₂)₂(H₂O)x]∙yH₂O ((2) M: Ni, x = 1, y = 0; (3) M: Cu, x = 1, y = 0; (4) M: Zn, x = 0, y = 1; 2,2'-bipy: 2,2'-bipyridine; C₃H₃O₂: acrylate anion) were shown to be mononuclear...
January 12, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29329269/design-synthesis-and-safener-activity-of-novel-methyl-r-n-benzoyl-dichloroacetyl-thiazolidine-4-carboxylates
#15
Li-Xia Zhao, Hao Wu, Yue-Li Zou, Qing-Rui Wang, Ying Fu, Chun-Yan Li, Fei Ye
A series of novel methyl (R)-N-benzoyl/dichloroacetyl-thiazolidine-4-carboxylates were designed by active substructure combination. The title compounds were synthesized using a one-pot route from l-cysteine methyl ester hydrochloride, acyl chloride, and ketones. All compounds were characterized by IR, ¹H NMR, 13C NMR, and HRMS. The structure of 4q was determined by X-ray crystallography. The biological tests showed that the title compounds protected maize from chlorimuron-ethyl injury to some extent. The ALS activity assay showed that the title compounds increased the ALS activity of maize inhibited by chlorimuron-ethyl...
January 12, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29327921/the-nature-and-reactivity-of-ferryl-heme-in-compounds-i-and-ii
#16
Peter C E Moody, Emma L Raven
Aerobic organisms have evolved to activate oxygen from the atmosphere, which allows them to catalyze the oxidation of different kinds of substrates. This activation of oxygen is achieved by a metal center (usually iron or copper) buried within a metalloprotein. In the case of iron-containing heme enzymes, the activation of oxygen is achieved by formation of transient iron-oxo (ferryl) intermediates; these intermediates are called Compound I and Compound II. The Compound I and II intermediates were first discovered in the 1930s in horseradish peroxidase, and it is now known that these same species are used across the family of heme enzymes, which include all of the peroxidases, the heme catalases, the P450s, cytochrome c oxidase, and NO synthase...
January 12, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29323880/photoactivated-in-vitro-anticancer-activity-of-rhenium-i-tricarbonyl-complexes-bearing-water-soluble-phosphines
#17
Sierra C Marker, Samantha N MacMillan, Warren R Zipfel, Zhi Li, Peter C Ford, Justin J Wilson
Fifteen water-soluble rhenium compounds of the general formula [Re(CO)3(NN)(PR3)]+, where NN is a diimine ligand and PR3 is 1,3,5-triaza-7-phosphaadamantane (PTA), tris(hydroxymethyl)phosphine (THP), or 1,4-diacetyl-1,3,7-triaza-5-phosphabicylco[3.3.1]nonane (DAPTA), were synthesized and characterized by multinuclear NMR spectroscopy, IR spectroscopy, and X-ray crystallography. The complexes bearing the THP and DAPTA ligands exhibit triplet-based luminescence in air-equilibrated aqueous solutions with quantum yields ranging from 3...
January 11, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29323171/new-anti-inflammatory-guaianes-from-the-atlantic-hydrotherm-derived-fungus-graphostroma-sp-mccc-3a00421
#18
Siwen Niu, Chun-Lan Xie, Jin-Mei Xia, Zhu-Hua Luo, Zongze Shao, Xian-Wen Yang
Nine new guaianes (graphostromanes A-I, 1-9) were isolated from the deep-sea-derived fungus Graphostroma sp. MCCC 3A00421, along with four known ones (10-13). The relative configurations were established mainly by detailed analysis of the NMR and HRESIMS data, while the absolute configurations were assigned using the X-ray crystallography and modified Mosher's method. All isolates were evaluated for their inhibitory effects against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages...
January 11, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29323112/signaling-ammonium-across-membranes-through-an-ammonium-sensor-histidine-kinase
#19
Tobias Pflüger, Camila F Hernández, Philipp Lewe, Fabian Frank, Haydyn Mertens, Dmitri Svergun, Manfred W Baumstark, Vladimir Y Lunin, Mike S M Jetten, Susana L A Andrade
Sensing and uptake of external ammonium is essential for anaerobic ammonium-oxidizing (anammox) bacteria, and is typically the domain of the ubiquitous Amt/Rh ammonium transporters. Here, we report on the structure and function of an ammonium sensor/transducer from the anammox bacterium "Candidatus Kuenenia stuttgartiensis" that combines a membrane-integral ammonium transporter domain with a fused histidine kinase. It contains a high-affinity ammonium binding site not present in assimilatory Amt proteins. The levels of phosphorylated histidine in the kinase are coupled to the presence of ammonium, as conformational changes during signal recognition by the Amt module are transduced internally to modulate the kinase activity...
January 11, 2018: Nature Communications
https://www.readbyqxmd.com/read/29319704/multiply-trapped-3-trans-pt-pr3-2-c-triple-bond-length-as-m-dash-cc6h4x-2-conformers-in-rigid-media
#20
Gabriel Marineau-Plante, Frank Juvenal, Adam Langlois, Daniel Fortin, Armand Soldera, Pierre D Harvey
The complexes (R = Me, Et, Bu; X = H, SMe) exhibit well-defined multi-exponential emissions (2-4 components) in the solid state at 77 and 298 K and in 2MeTHF glasses at 77 K due to multiple frozen conformers exhibiting variable dihedral angles formed by the PtP2C2 and C6H4 planes. The demonstration was made using X-ray crystallography at various temperatures where different sites are present in the samples, and using geometry optimization (DFT computations) where various stable conformers are noted.
January 10, 2018: Chemical Communications: Chem Comm
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