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941.
942.
Trung Le Hao Nguyen Lisa M. Perez Donald J. Darensbourg Marcetta Y. Darensbourg 《Angewandte Chemie (International ed. in English)》2020,59(9):3645-3649
With the goal of generating anionic analogues to MN2S2 ? Mn(CO)3Br we introduced metallodithiolate ligands, MN2S22? prepared from the Cys‐X‐Cys biomimetic, ema4? ligand (ema=N,N′‐ethylenebis(mercaptoacetamide); M=NiII, [VIV≡O]2+ and FeIII) to Mn(CO)5Br. An unexpected, remarkably stable dimanganese product, (H2N2(CH2C=O(μ‐S))2)[Mn(CO)3]2 resulted from loss of M originally residing in the N2S24? pocket, replaced by protonation at the amido nitrogens, generating H2ema2?. Accordingly, the ema ligand has switched its coordination mode from an N2S24? cavity holding a single metal, to a binucleating H2ema2? with bridging sulfurs and carboxamide oxygens within Mn‐μ‐S‐CH2‐C‐O, 5‐membered rings. In situ metal‐templating by zinc ions gives quantitative yields of the Mn2 product. By computational studies we compared the conformations of “linear” ema4? to ema4? frozen in the “tight‐loop” around single metals, and to the “looser” fold possible for H2ema2? that is the optimal arrangement for binucleation. XRD molecular structures show extensive H‐bonding at the amido‐nitrogen protons in the solid state. 相似文献
943.
Although oxidative folding of disulfide-rich proteins is often sluggish, this process can be significantly enhanced by targeted replacement of cysteines with selenocysteines. In this study, we examined the effects of a selenosulfide and native versus nonnative diselenides on the folding rates and mechanism of bovine pancreatic trypsin inhibitor. Our results show that such sulfur-to-selenium substitutions alter the distribution of key folding intermediates and enhance their rates of interconversion in a context-dependent manner. 相似文献
944.
945.
A variety of functionalised β-iodoacetals have been prepared, and their elimination reaction to give ketene acetals conducted under mild conditions. 相似文献
946.
Donald R. Hogg Mohammad A.M. Rashid 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract The coloured solutions of 2-nitrobenzenesulphenyl derivatives in 98% sulphuric acid have previously been suggested to contain either the conjugate acid of the sulphenyl derivative1 or the sulphenium ion in equilibrium with the starting material. 19F n.m.r. studies on solutions of 4-trifluoromethyl-2-nitrobenzenesulphenyl derivatives show that these compounds react in sulphuric acid to give the corresponding 2-amino- and 2-nitro-benzenesulphonic acids together with other products. 相似文献
947.
948.
Donald G. Miller 《Journal of solution chemistry》2007,36(11-12):1469-1477
We consider the properties of Ω graphs (Ω versus f(z)) obtained from Gouy interferometry on multicomponent systems with constant diffusion coefficients. We show that they must have (a) either a maximum or else a minimum between f(z)=0 and f(z)=1 and (b) an inflection point between the f(z) value at the extremum and f(z)=1. Consequently, an Ω graph cannot have both positive and negative Ω values. 相似文献
949.
950.
Robert G.K. Donald Stephen Skwish R. Allyn Forsyth Jennifer W. Anderson Tanya Zhong Colleen Burns Suzy Lee Xin Meng Lynn LoCastro Lisa Wang Jarantow Jesus Martin Sang Ho Lee Ian Taylor David Robbins Cheryl Malone Liangsu Wang Carlos S. Zamudio Philip J. Youngman John W. Phillips 《Chemistry & biology》2009,16(8):826-836