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991.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Bataineh H Alexander J Al-Jamel A Aoki K Aphecetche L Armendariz R Aronson SH Asai J Atomssa ET Averbeck R Awes TC Azmoun B Babintsev V Baksay G Baksay L Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bennett R Berdnikov Y Bickley AA Bjorndal MT Boissevain JG Borel H Boyle K Brooks ML Brown DS Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Campbell S Chai JS Chang BS 《Physical review letters》2007,98(16):162301
Differential measurements of elliptic flow (v2) for Au+Au and Cu+Cu collisions at sqrt[sNN]=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v2 with eccentricity, system size, and transverse kinetic energy (KE T). For KE T identical with mT-m up to approximately 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KE T mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v2 for both mesons and baryons over the full KE T range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KE T, rather than transverse momentum. 相似文献
992.
Tatiana Vasilevskaya Maria G. Khrenova Alexander V. Nemukhin Walter Thiel 《Journal of computational chemistry》2015,36(21):1621-1630
The mechanism of enzymatic peptide hydrolysis in matrix metalloproteinase‐2 (MMP‐2) was studied at atomic resolution through quantum mechanics/molecular mechanics (QM/MM) simulations. An all‐atom three‐dimensional molecular model was constructed on the basis of a crystal structure from the Protein Data Bank (ID: 1QIB), and the oligopeptide Ace‐Gln‐Gly~Ile‐Ala‐Gly‐Nme was considered as the substrate. Two QM/MM software packages and several computational protocols were employed to calculate QM/MM energy profiles for a four‐step mechanism involving an initial nucleophilic attack followed by hydrogen bond rearrangement, proton transfer, and C? N bond cleavage. These QM/MM calculations consistently yield rather low overall barriers for the chemical steps, in the range of 5–10 kcal/mol, for diverse QM treatments (PBE0, B3LYP, and BB1K density functionals as well as local coupled cluster treatments) and two MM force fields (CHARMM and AMBER). It, thus, seems likely that product release is the rate‐limiting step in MMP‐2 catalysis. This is supported by an exploration of various release channels through QM/MM reaction path calculations and steered molecular dynamics simulations. © 2015 Wiley Periodicals, Inc. 相似文献
993.
The resonance Raman spectrum of Sepia eumelanin is discussed by analogy to model compounds containing catechol (CAT)‐like structural units. These data are then compared with the analogous data on Fe(III)‐enriched Sepia eumelanin. In contrast to the natural eumelanin, the Fe(III)‐enriched samples exhibit absorption features in the visible and near‐IR spectral regions, which are attributed to ligand‐to‐metal charge‐transfer (LMCT) bands. Resonance Raman spectra collected by exciting these LMCT bands reveal bands at 580 and 1470 cm?1; the intensity of these features increases wioth increasing Fe(III) content. The 580 and 1470 cm?1 bands are assigned to Fe‐OR stretching and ring deformation modes, respectively. These data further substantiate that the Fe(III)‐ melanin‐binding site in melanin is composed of CAT‐like structural units. 相似文献
994.
Ora M Lönnberg T Florea-Wang D Zinnen S Karpeisky A Lönnberg H 《The Journal of organic chemistry》2008,73(11):4123-4130
Kinetics of the hydrolytic reactions of four bisphosphonate derivatives of nucleoside antimetabolites, viz., 5-fluorouridine 5'-beta,gamma-(1-hydroxyethylidene) triphosphate ( 4), 5-fluorouridine 5'-beta,gamma-methylene triphosphate ( 5), ara-cytidine 5'-beta,gamma-(1-hydroxyethylidene) triphosphate ( 6), and ara-cytidine 5'-beta,gamma-methylene triphosphate ( 7), have been studied over a wide pH range (pH 1.0-8.5) at 90 degrees C. With each compound, the disappearance of the starting material was accompanied by formation of the corresponding nucleoside 5'-monophosphate, the reaction being up to 2 orders of magnitude faster with the beta,gamma-(1-hydroxyethylidene) derivatives ( 4, 6) than with their beta,gamma-methylene counterparts ( 5, 7). With compound 7, deamination of the cytosine base competed with the phosphate hydrolysis at pH 3-6. The measurements at 37 degrees C (pH 7.4) in the absence and presence of divalent alkaline earth metal ions (Mg (2+) and Ca (2+)) showed no sign of metal ion catalysis. Under these conditions, the initial product, nucleoside 5'-monophosphate, underwent rapid dephosphorylation to the corresponding nucleoside. Hydrolysis of the beta,gamma-methylene derivatives ( 5, 7) to the corresponding nucleoside 5'-monophosphates was markedly faster in mouse serum than in aqueous buffer (pH 7.4), the rate-acceleration being 5600- and 3150-fold with 5 and 7, respectively. In human serum, the accelerations were 800- and 450-fold compared to buffer. In striking contrast, the beta,gamma-(1-hydroxyethylidene) derivatives did not experience a similar decrease in hydrolytic stability. The stability in human serum was comparable to that in aqueous buffer (tau 1/2 = 17 and 33 h with 4 and 6, respectively), and on going to mouse serum, a 2- to 4-fold acceleration was observed. To elucidate the mineral-binding properties of 4- 7, their retention on a hydroxyapatite column was studied and compared to that of zoledronate ( 1a) and nucleoside mono-, di-, and triphosphates. 相似文献
995.
Ryabukhin SV Plaskon AS Volochnyuk DM Shivanyuk AN Tolmachev AA 《The Journal of organic chemistry》2007,72(19):7417-7419
A convenient one-pot method for the synthesis of 2,3-dihydro-1H-benzimidazoles has been elaborated. A set of 2,3-dihydro-1H-benzimidazoles was prepared from various ortho-dialkylaminoanilines and aldehydes using Me3SiCl as a condensation agent and pyridine as a basic medium. 相似文献
996.
Dr. Eva‐Maria Rummel Prof. Dr. Piero Mastrorilli Dr. Stefano Todisco Prof. Mario Latronico Dr. Gábor Balázs Dr. Alexander V. Virovets Prof. Dr. Manfred Scheer 《Angewandte Chemie (International ed. in English)》2016,55(42):13301-13305
By employing silver salts with a weakly coordinating anion Ag[A] ([A]=[FAl{OC12F15}3], [Al{OC(CF3)3}4]), two phosphaalkynes could be coordinated side‐on to a bare silver(I) center to form the unprecedented homoleptic complexes [Ag(η2‐P≡CtBu)2][FAl{OC12F15}3] ( 1 ) and [Ag(η2‐P≡CtBu)2][Al{OC(CF3)3}4] ( 2 ). DFT calculations show that the perpendicular arrangement in 1 is the minimum energy structure of the coordination of the two phosphaalkynes to a silver atom, whereas for 2 a unique square‐planar coordination mode of the phosphaalkynes at Ag+ was found. Reactions with donor molecules yield the trigonally planar coordinated silver salts [((CH3)2CO)Ag(η2‐P≡CtBu)2][FAl{OC12F15}3] ( 3 ) and [(C7H8)2Ag(η2‐P≡CtBu)][FAl{OC12F15}3] ( 4 ). All of the compounds were comprehensively characterized in solution and in the solid state. 相似文献
997.
Synthesis and Characterization of the Rubidium Thiophosphate Rb6(PS5)(P2S10) and the Rubidium Silver Thiophosphates Rb2AgPS4, RbAg5(PS4)2 and Rb3Ag9(PS4)4
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Fatimah Alahmari Bambar Davaasuren Jayaprakash Khanderi Alexander Rothenberger 《无机化学与普通化学杂志》2016,642(5):361-367
The metal thiophosphates Rb2AgPS4 ( 2 ), RbAg5(PS4)2 ( 3 ), and Rb3Ag9(PS4)4 ( 4 ) were synthesized by stoichiometric reactions, whereas Rb6(PS5)(P2S10) ( 1 ) was prepared with excess amount of sulfur. The compounds crystallize as follows: 1 monoclinic, P21/c (no. 14), a = 17.0123(7) Å, b = 6.9102(2) Å, c = 23.179(1) Å, β = 94.399(4)°; 2 triclinic, P$\bar{1}$ (no. 2), a = 6.600(1) Å, b = 6.856(1) Å, c = 10.943(3) Å, α = 95.150(2)°, β = 107.338(2)°, γ = 111.383(2)°; 3 orthorhombic, Pbca (no. 61), a = 12.607(1) Å, b = 12.612(1) Å, c = 17.759(2) Å; 4 orthorhombic, Pbcm (no. 57), a = 6.3481(2) Å, b = 12.5782(4) Å, c = 35.975(1) Å. The crystal structures contain discrete units, chains, and 3D polyanionic frameworks composed of PS4 tetrahedral units arranged and connected in different manner. Compounds 1 – 3 melt congruently, whereas incongruent melting behavior was observed for compound 4 . 1 – 4 are semiconductors with bandgaps between 2.3 and 2.6 eV and thermally stable up to 450 °C in an inert atmosphere. 相似文献
998.
Vadim?B.?Fetisov Alexander?N.?Ermakov Galina?M.?Belysheva Andrey?V.?Fetisov Valentin?M.?Kamyshov Khiena?Z.?BraininaEmail author 《Journal of Solid State Electrochemistry》2004,8(8):565-571
The present paper deals with the electrochemical behavior of magnetite microcrystals in an acid medium. A voltammetric method employing a carbon-paste electroactive electrode (CPEE) with an organic binder was used. It was found that the cathodic voltammograms, which were recorded at different scan rates, formed a set bounded in the space of i–E parameters by a generalizing voltammetric curve corresponding to the effective potential scan rate eff. In other words, all curves are situated under one enveloping curve, just as the smaller dolls sit in the largest doll of a Russian doll. Reverse currents (a cathodic current in the anodic direction of the potential scan) were observed on the cyclic voltammogram. Forward and reverse currents obey the same laws and have one and the same generalizing curve, which could be taken as the magnetite characteristic. 相似文献
999.
Alexander Bendikov Patrick Maheux 《Transactions of the American Mathematical Society》2007,359(7):3085-3097
Assuming that a Nash type inequality is satisfied by a non-negative self-adjoint operator , we prove a Nash type inequality for the fractional powers of . Under some assumptions, we give ultracontractivity bounds for the semigroup generated by .
1000.
Ansa‐Complexes of [Mn(η5‐C5H5)(η6‐C6H6)]: Preparation,Characterization, and Reactivity of [n]Manganoarenophanes (n=1, 2, 3)
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Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Klaus Dück Dr. Marco Fuß Dr. Christian Hörl Dr. Thomas Kramer Dr. Ivo Krummenacher Dr. Thomas Kupfer Valerie Paprocki Christoph Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14797-14803
We report the synthesis of [n]manganoarenophanes (n=1, 2) featuring boron, silicon, germanium, and tin as ansa‐bridging elements. Their preparation was achieved by salt‐elimination reactions of the dilithiated precursor [Mn(η5‐C5H4Li)(η6‐C6H5Li)]?pmdta (pmdta=N,N,N′,N′,N′′‐pentamethyldiethylenetriamine) with corresponding element dichlorides. Besides characterization by multinuclear NMR spectroscopy and elemental analysis, the identity of two single‐atom‐bridged derivatives, [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] and [Mn(η5‐C5H4)(η6‐C6H5)SiPh2], could also be determined by X‐ray structural analysis. We investigated for the first time the reactivity of these ansa‐cyclopentadienyl–benzene manganese compounds. The reaction of the distannyl‐bridged complex [Mn(η5‐C5H4)(η6‐C6H5)Sn2tBu4] with elemental sulfur was shown to proceed through the expected oxidative addition of the Sn?Sn bond to give a triatomic ansa‐bridge. The investigation of the ring‐opening polymerization (ROP) capability of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] with [Pt(PEt3)3] showed that an unexpected, unselective insertion into the Cipso?Sn bonds of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] had occurred. 相似文献