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1.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
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R. Salomon 《Zeitschrift für Physik B Condensed Matter》1989,73(4):519-527
The diffusion constant and the diagonal conductivity for non-interacting electrons in a two-dimensional, disordered system are studied. A homogeneous magnetic field perpendicular to the electron system is assumed. For weak short-range random potentials and high fields the Landau quantum numbern can be used as expansion parameter. In the limit of high Landau levels the system shows metallic behaviour. Corrections for finiten decrease the conductivity and indicate localized states in the whole energy band. A breakdown of the expansion and stronger localization are observed only for the lowest Landau levels if the typical experimental length scale of the quantized Hall effect is used. 相似文献
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Marcel Oliver 《Theoretical and Computational Fluid Dynamics》1997,9(3-4):311-324
The so-called lake equations arise as the shallow-water limit of the rigid-lid equations—three-dimensional Euler equations
with a rigid-lid upper boundary condition—in a horizontally periodic basin with bottom topography. We prove an a priori estimate in the Sobolev space H
m
for m≥ 3 which shows that a solution to the rigid-lid equations can be approximated by a solution of the lake equations for an
interval of time which can be estimated in terms of the initial deviation from a columnar configuration and the magnitude
of the initial data in H
m
, the gradient of the bottom topography in H
m+1
, and the aspect ratio of the basin. In particular, any solution to the lake equations remains close to some solution of the
rigid-lid equations for an interval of time that can be made arbitrarily large by choosing the aspect ratio of the basin small.
Received 10 October 1996 and accepted 15 May 1997 相似文献
6.
The consecutive reactions of (CH3)2Si(OC2H5)2 and CH3Si(OC2H5)3 with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C2H5O? + CH3OH ? C2H5OH + CH3O?. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH3)2Si(OC2H5)2 + 2CH3O? → (CH3)2Si(OCH3)2 + 2C2H5O?. The two consecutive rate constants were established as 1.93 ± 0.12M?1s?1 and 1.00 ± 0.12M?1s?1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH3Si(OC2H5)3 + 3CH3O? → CH3Si(OCH3)3 + 3C2H5O?. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M?1s?1, 0.82 ± 0.10 M?1s?1, and 0.51 ± 0.06 M?1s?1, respectively. © 1995 John Wiley & Sons, Inc. 相似文献
7.
A PULSED LASER AND PULSE RADIOLYSIS STUDY OF AMPHIPHILIC CHLOROPHYLL DERIVATIVES WITH PDT ACTIVITY TOWARD MALIGNANT MELANOMA 总被引:1,自引:0,他引:1
L. Fiedor A. A. Gorman I. Hamblett V. Rosenbach-Belkin Y. Salomon A. Scherz I. Tregub 《Photochemistry and photobiology》1993,58(4):506-511
Two amphiphilic derivatives of chlorophyll, which have high potential as photodynamic therapy sensitizers for malignant melanoma have been investigated by a combination of laser flash photolysis and pulse radiolysis. It is shown that direct excitation of monomeric forms of these molecules in both hydrophilic and hydrophobic environments produces significant yields of the corresponding triplet states, which have been characterized in terms of spectral and kinetic parameters. In both environments, scavenging of the triplets by oxygen produces singlet oxygen, O2 (l Δ8 ), with essentially unit efficiency as evidenced by time-resolved IR luminescence measurements. 相似文献
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