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1.
THERMODYNAMICS OF PORPHYRIN BINDING TO SERUM ALBUMIN: EFFECTS OF TEMPERATURE, OF PORPHYRIN SPECIES and OF ALBUMIN-CARRIED FATTY ACIDS 总被引:1,自引:0,他引:1
Abstract Porphyrin binding to serum albumin was studied at the molecular level probing the effects of: porphyrin self-aggregation, porphyrin species, temperature and protein-bound fatty acids. Human serum albumin was found to have a single high-affinity site for porphyrin monomers, with binding constants of 2 x 106 , 5 x 107 and 3 x 108 (37o C, neutral pH, M −1 ), for hemato-, deutero- and protoporphyrins, respectively. Three equilibria models for the dimer binding were developed and tested. The data were found to fit best with a model proposing a single high-affinity binding site for the dimer, independent of and different than the monomer site. The binding constants of the hematoporphyrin and deuteroporphyrin dimers to human serum albumin (37o C, neutral pH, M−l ) being 4 x 10* and 5 x 108 respectively. The temperature dependence (Dp and HSA, 22-37o C) of the monomer binding showed the process to be entropy-driven (δGo = -45 kJ mol−1 ; δSo =+146 kJ mol−1 ; δHo = 0 kJ mol−1 ). For the dimer binding, the enthalpy change was found to be highly temperature-dependent implying continuous changes in the heat capacity of the system over the entire temperature range, the trend at the 37o C region fitting an entropy-driven process. The monomer vs dimer differences in temperature dependence strongly support separate and independent binding sites for these species. Similar thermodynamics were determined for fatty-acid carrying as well as for fatty-acid free HSA, with mild quantitative (but not qualitative) shifts. 相似文献
2.
We demonstrate the ability to control the magnetic phase diagram of Cr1-x Vx(110) thin films grown on a W(110) substrate. Using angle-resolved photoemission, we have mapped paramagnetic and commensurate and incommensurate antiferromagnetic phases as a function of temperature, film thickness, and composition. We show that surface-localized electron states play a key role in the observed phase behaviors and suggest from this that it might be possible to control the magnetic phase by applying an external electric field. 相似文献
3.
Conclusions The O--D-galactopyranosides of some serine-containing dipeptides were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2092–2094, September, 1971. 相似文献
4.
Rotenberg B Cadéne A Dufrêche JF Durand-Vidal S Badot JC Turq P 《The journal of physical chemistry. B》2005,109(32):15548-15557
A simple two-state model is proposed to explicitly derive the ionic contribution to the frequency-dependent dielectric permittivity of clay. This model is based on a separation of time scales and accounts for two possible solvation modes (inner/outer-sphere complexes) for ions in the interlayer spacing and a possible chemical exchange between both forms. The influence on the permittivity of thermodynamic (distribution constant K(d)) and dynamic (diffusion coefficient, chemical relaxation rate) parameters is discussed. In turn, this model is used to analyze experimental data obtained with Na-montmorillonite for two relative humidities. The values of the parameters extracted from these measurements, and their variation with water content, show that the proposed model is at least reasonable. 相似文献
5.
Weber T Czasch A Jagutzki O Müller A Mergel V Kheifets A Feagin J Rotenberg E Meigs G Prior MH Daveau S Landers AL Cocke CL Osipov T Schmidt-Böcking H Dörner R 《Physical review letters》2004,92(16):163001
We report the first kinematically complete study of the four-body fragmentation of the D2 molecule following absorption of a single photon. For equal energy sharing of the two electrons and a photon energy of 75.5 eV, we observed the relaxation of one of the selection rules valid for He photo-double-ionization and a strong dependence of the electron angular distribution on the orientation of the molecular axis. This effect is reproduced by a model in which a pair of photoionization amplitudes is introduced for the light polarization parallel and perpendicular to the molecular axis. 相似文献
6.
Schäfer J Schrupp D Rotenberg E Rossnagel K Koh H Blaha P Claessen R 《Physical review letters》2004,92(9):097205
High-resolution photoemission data of the (110) iron surface reveal the existence of well-defined metallic surface resonances in good correspondence to band calculations. Close to the Fermi level, their dispersion and momentum broadening display anomalies characteristic of quasiparticle renormalization due to coupling to bosonic excitations. Its energy scale exceeds that of phonons by far, and is in striking coincidence with that of the spin wave spectrum in iron. The self-energy behavior thus gives spectroscopic evidence of a quasiparticle mass enhancement due to electron-magnon coupling. 相似文献
7.
Z. A. Rotenberg N. V. Lukovtseva V. P. Lukovtsev 《Russian Journal of Electrochemistry》2004,40(9):987-989
Migration factors Y are determined for an [Fe(CN)6]3–/4– reversible system at a platinum microelectrode 10 m in radius by measuring anodic and cathodic limiting currents at different concentrations of the redox forms in solution, from which Y
a and Y
c are calculated. The obtained results agree with theory. The experimental error for the Y
a/Y
c ratio is smaller than for each factor taken separately. 相似文献
8.
Here we report on high-resolution photoemission of iron layers grown on a W(1 1 0) substrate. The evolution of the substrate states upon sub-monolayer adsorption of Fe atoms leads to a shift in surface state binding energy. For thicker (1 1 0) films, sharp metallic surface states are obtained. Their dispersion displays the signature of quasiparticle renormalization due to dressing with excitations. The energy scale is characteristic for the spin wave spectrum in iron, thereby giving evidence of electron-magnon coupling. Furthermore, it is found that quantum well states occur as a function of layer thickness. These modify the spin density of states at the Fermi level in the ferromagnetic film. 相似文献
9.
We present a new model to analyze dielectric spectroscopy measurements on charged lamellar systems, with the following improvements with respect to the hitherto available models: (i) it does not rely on the hypothesis of local electro-neutrality, and allows to treat the salt-free case; (ii) the chemical exchange governing the partition between free and bound ions is properly taken into account; (iii) a fully analytical solution is provided. The variation of the frequency-dependent dielectric permittivity with both thermodynamic and kinetic characteristics of the free-bound ion equilibrium is presented. In particular, the relative weights of both relaxation modes (exchange and transport), and their characteristic frequencies are discussed. This study opens the way to the analysis of systems for which the usual models are irrelevant, such as salt-free clay gels or membranes. 相似文献
10.
V.?P.?LukovtsevEmail author Z.?A.?Rotenberg A.?V.?Dribinskii E.?M.?Maksimov V.?N.?Ur'ev 《Russian Journal of Electrochemistry》2005,41(10):1097-1100
The depth of discharge of lithium-thionyl chloride batteries is estimated from their impedance characteristics. It is shown that, in principle, it can be determined when using as an informative parameter indicating the phase value at the extreme point in impedance spectra of lithium batteries. 相似文献