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排序方式: 共有124条查询结果,搜索用时 93 毫秒
1.
Jung SY Lim SM Albertorio F Kim G Gurau MC Yang RD Holden MA Cremer PS 《Journal of the American Chemical Society》2003,125(42):12782-12786
The molecular level details of the displacement of surface adsorbed fibrinogen from silica substrates were studied by atomic force microscopy, immunochemical assays, fluorescence microscopy, and vibrational sum frequency spectroscopy. The results showed that human plasma fibrinogen (HPF) can be readily displaced from the interface by other plasma proteins near neutral pH because the positively charged alpha C domains on HPF sit between the rest of the macromolecule and the underlying surface. The alpha C domains make weak electrostatic contact with the substrate, which is manifest by a high degree of alignment of Lys and Arg residues. Upon cycling through acidic pH, however, the alpha C domains are irreversibly removed from this position and the rest of the macromolecule is free to engage in stronger hydrogen bonding, van der Waals, and hydrophobic interactions with the surface. This results in a 170-fold decrease in the rate at which HPF can be displaced from the interface by other proteins in human plasma. 相似文献
2.
Dr. Andrey Y. Khalimon Prof. Dr. Stanislav K. Ignatov Andrey I. Okhapkin Dipl.‐Ing. Razvan Simionescu Prof. Dr. Lyudmila G. Kuzmina Prof. Dr. Judith A. K. Howard Dr. Georgii I. Nikonov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8573-8590
The reactions of bis(borohydride) complexes [(RN?)Mo(BH4)2(PMe3)2] ( 4 : R=2,6‐Me2C6H3; 5 : R=2,6‐iPr2C6H3) with hydrosilanes afford new silyl hydride derivatives [(RN?)Mo(H)(SiR′3)(PMe3)3] ( 3 : R=Ar, R′3=H2Ph; 8 : R=Ar′, R′3=H2Ph; 9 : R=Ar, R′3=(OEt)3; 10 : R=Ar, R′3=HMePh). These compounds can also be conveniently prepared by reacting [(RN?)Mo(H)(Cl)(PMe3)3] with one equivalent of LiBH4 in the presence of a silane. Complex 3 undergoes intramolecular and intermolecular phosphine exchange, as well as exchange between the silyl ligand and the free silane. Kinetic and DFT studies show that the intermolecular phosphine exchange occurs through the predissociation of a PMe3 group, which, surprisingly, is facilitated by the silane. The intramolecular exchange proceeds through a new non‐Bailar‐twist pathway. The silyl/silane exchange proceeds through an unusual MoVI intermediate, [(ArN?)Mo(H)2(SiH2Ph)2(PMe3)2] ( 19 ). Complex 3 was found to be the catalyst of a variety of hydrosilylation reactions of carbonyl compounds (aldehydes and ketones) and nitriles, as well as of silane alcoholysis. Stoichiometric mechanistic studies of the hydrosilylation of acetone, supported by DFT calculations, suggest the operation of an unexpected mechanism, in that the silyl ligand of compound 3 plays an unusual role as a spectator ligand. The addition of acetone to compound 3 leads to the formation of [trans‐(ArN)Mo(OiPr)(SiH2Ph)(PMe3)2] ( 18 ). This latter species does not undergo the elimination of a Si? O group (which corresponds to the conventional Ojima′s mechanism of hydrosilylation). Rather, complex 18 undergoes unusual reversible β‐CH activation of the isopropoxy ligand. In the hydrosilylation of benzaldehyde, the reaction proceeds through the formation of a new intermediate bis(benzaldehyde) adduct, [(ArN?)Mo(η2‐PhC(O)H)2(PMe3)], which reacts further with hydrosilane through a η1‐silane complex, as studied by DFT calculations. 相似文献
3.
Razvan Gurau 《Communications in Mathematical Physics》2011,304(1):69-93
Random matrix models generalize to Group Field Theories (GFT) whose Feynman graphs are dual to higher dimensional topological
spaces. The perturbative development of the usual GFT’s is rather involved combinatorially and plagued by topological singularities
(which we discuss in great detail in this paper), thus very difficult to control and unsatisfactory. 相似文献
4.
In this article we continue with the study of smooth Gauss–Weierstrass singular integral operators over the real line regarding their simultaneous global smoothness preservation property with respect to the Lp norm, 1≤p≤∞, by involving higher order moduli of smoothness. Also we study their simultaneous approximation to the unit operator with rates involving the modulus of continuity with respect to the uniform norm. The produced Jackson type inequalities are almost sharp containing elegant constants, and they reflect the high order of differentiability of the engaged function. 相似文献
5.
Razvan Gabriel Iagar Ariel Sánchez Juan Luis Vázquez 《Journal de Mathématiques Pures et Appliquées》2008,89(1):1-24
In this paper we prove that there exists an explicit correspondence between the radially symmetric solutions of two well-known models of nonlinear diffusion, the porous medium equation and the p-Laplacian equation. We establish exact correspondence formulas between these solutions. We also study in detail the application of the results in the important case of self-similar solutions. In particular, we derive the existence of new self-similar solutions for the evolution p-Laplacian equation. 相似文献
6.
7.
We derive high-order corrections to a modulation theory for the propagation of internal gravity waves in a density-stratified fluid with coupling to the mean flow. The methodology we use allows for strong modulations of wavenumber and mean flow, extending previous approaches developed for the quasi-monochromatic regime. The wave mean flow modulation equations consist of a system of nonlinear conservation laws that may be hyperbolic, elliptic or of mixed type. We investigate the regularizing properties of the asymptotic correction terms in the case when the system becomes unstable and ill-posed due to a change of type (loss of hyperbolicity). A linear analysis reveals that the regularization by the added correction terms does so by introducing a short-wave cut-off of the unstable wavenumbers. We perform various numerical experiments that confirm the regularizing properties of the correction terms, and show that the growth of unstable modes is tempered by nonlinearity. We also find an excellent agreement between the solution of the corrected modulation system and the modulation variables extracted from the numerical solution of the nonlinear Boussinesq equations. 相似文献
8.
In this paper, we employ a technique combining the Euler Maclaurin formula with the saddle point approximation method to obtain
the asymptotic behavior (in the limit of large representation index J) of generic Wigner matrix elements DJMM¢(g){D^{J}_{MM'}(g)} . We use this result to derive asymptotic formulae for the character χ
J
(g) of an SU(2) group element and for Wigner’s 3j symbol. Surprisingly, given that we perform five successive layers of approximations, the asymptotic formula we obtain for
χ
J
(g) is in fact exact. The result hints at a “Duistermaat-Heckman like” localization property for discrete sums. 相似文献
9.
10.
Lu Q Keskar G Ciocan R Rao R Mathur RB Rao AM Larcom LL 《The journal of physical chemistry. B》2006,110(48):24371-24376
Density gradient centrifugation is a high-resolution technique for the separation and characterization of large molecules and stable complexes. We have analyzed various nanotube structures by preparative centrifugation in sodium metatungstate-water solutions. Bundled, isolated and acid-treated single-walled nanotubes (SWNTs) and multiwall nanotubes (MWNTs) formed sharp bands at well-defined densities. The structure of the material in each band was confirmed by transmission electron microscopy and Raman spectroscopy. Our data suggest respective densities of 1.87, 2.13, 1.74, and 2.1 g/cm(3) for bundled, isolated, and acid-treated SWNTs and MWNTs. These measured results compare well with their calculated densities. 相似文献