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1.
Snyder DA Chen Y Denissova NG Acton T Aramini JM Ciano M Karlin R Liu J Manor P Rajan PA Rossi P Swapna GV Xiao R Rost B Hunt J Montelione GT 《Journal of the American Chemical Society》2005,127(47):16505-16511
X-ray crystallography and NMR spectroscopy provide the only sources of experimental data from which protein structures can be analyzed at high or even atomic resolution. The degree to which these methods complement each other as sources of structural knowledge is a matter of debate; it is often proposed that small proteins yielding high quality, readily analyzed NMR spectra are a subset of those that readily yield strongly diffracting crystals. We have examined the correlation between NMR spectral quality and success in structure determination by X-ray crystallography for 159 prokaryotic and eukaryotic proteins, prescreened to avoid proteins providing polydisperse and/or aggregated samples. This study demonstrates that, across this protein sample set, the quality of a protein's [15N-1H]-heteronuclear correlation (HSQC) spectrum recorded under conditions generally suitable for 3D structure determination by NMR, a key predictor of the ability to determine a structure by NMR, is not correlated with successful crystallization and structure determination by X-ray crystallography. These results, together with similar results of an independent study presented in the accompanying paper (Yee, et al., J. Am. Chem. Soc., accompanying paper), demonstrate that X-ray crystallography and NMR often provide complementary sources of structural data and that both methods are required in order to optimize success for as many targets as possible in large-scale structural proteomics efforts. 相似文献
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Shearer J Zhang CX Zakharov LN Rheingold AL Karlin KD 《Journal of the American Chemical Society》2005,127(15):5469-5483
A series of copper-dioxygen adducts [{Cu(II)(MePY2)(R)}(2)(O(2))](B(C(6)F(5))(4))(2) (1(R)()), systematically varying in their electronic properties via ligand pyridyl donor substituents (R = H, MeO, and Me(2)N), oxidize a variety of substrates with varying C-H or O-H bond dissociation enthalpies. Detailed mechanistic studies have been carried out, including investigation of 1(R)() thermodynamic redox properties, 1(R)() tetrahydrofuran (THF) and N,N'-dimethylaniline (DMA) oxidation kinetics (including analyses of substrate dicopper binding equilibria), and application of mechanistic probes (N-cyclopropyl-N-methylaniline (CMA) and (p-methoxyphenyl)-2,2-dimethylpropanol (MDP)), which can distinguish if proton-coupled electron-transfer (PCET) processes proceed through concerted electron-transfer proton-transfer (ETPT) or consecutive electron-transfer proton-transfer (ET/PT) pathways. The results are consistent with those of previous complementary studies; at low thermodynamic driving force for substrate oxidation, an ET/PT is operable, but once ET (i.e., substrate one-electron oxidation) becomes prohibitively uphill, the ETPT pathway occurs. Possible differences in coordination structures about 1(Me)()()2(N)()/1(MeO)() compared to those of 1(H)() are also used to rationalize some of the observations. 相似文献
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Fry HC Scaltrito DV Karlin KD Meyer GJ 《Journal of the American Chemical Society》2003,125(39):11866-11871
The observation and fast time-scale kinetic determination of a primary dioxygen-copper interaction have been studied. The ability to photorelease carbon monoxide from [Cu(I)(tmpa)(CO)](+) in mixtures of CO and O(2) in tetrahydrofuran (THF) between 188 and 218 K results in the observable formation of a copper-superoxide species, [Cu(II)(tmpa)(O(2)(-))](+) lambda(max) = 425 nm. Via this "flash-and-trap" technique, temperature-dependent kinetic studies on the forward reaction between dioxygen and [Cu(I)(tmpa)(thf)](+) afford activation parameters DeltaH = 7.62 kJ/mol and DeltaS = -45.1 J/mol K. The corresponding reverse reaction proceeds with DeltaH = 58.0 kJ/mol and DeltaS = 105 J/mol K. Overall thermodynamic parameters are DeltaH degrees = -48.5 kJ/mol and DeltaS degrees = -140 J/mol K. The temperature-dependent data allowed us to determine the room-temperature second-order rate constant, k(O2) = 1.3 x 10(9) M(-1) s(-1). Comparisons to copper and heme proteins and synthetic complexes are discussed. 相似文献
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Laxman Singh Ravikant Sharma Narayan Singh Atendra Kumar Dev K Mahato Youngil Lee Mikhael Bechelany KD Mandal 《Progress in Crystal Growth and Characterization of Materials》2021,67(4):100542
This review paper covers the low temperature wet growth of nano-engineered particles of ZnO-based mixed metal oxides, their growth mechanism, and characterization using X-ray diffraction, SEM, TEM and IR, UV–visible, and XPS spectral techniques. Main focus of this article is centered on low temperature semi-wet methods of synthesis that are suitable for large scale production of zinc oxide-based systems mixed with iron oxide, copper oxide, nickel oxide and cobalt oxide. These mixed metal oxides have broad industrial applications as catalyst, semiconductors, adsorbents, superconductors, electro-ceramics, and antifungal agents in addition to extensive applications in medicines. This paper discusses the low-cost and environment friendly synthesis of these mixed metal oxides, measurement of properties and applicability of these materials systems. 相似文献
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Kenneth D. Karlin B. F. G. Johnson J. Lewis 《Journal of organometallic chemistry》1978,160(2):C21-C23
IR studies show that in solution aluminum trihalides form Lewis acid adducts at the iron atom in polyolefin tricarbonyliron complexes. A ketonic organometallic compound also forms a 2/1 adduct. 相似文献
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Probability Theory and Related Fields - 相似文献