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64.
Local deformation studies of chain molecules: differential conditions for changes of dihedral angles
W Braun 《Biopolymers》1987,26(10):1691-1704
New first and second-order differential equations for changes of dihedral angles characterizing local deformations of chain molecules with fixed bond lengths and bond angles are derived. Two methods for integrating the differential relations are given. The proposed method is used to generate a path of locally deformed conformations around a β-turn region of a small protein, bovine pancreatic trypsin inhibitor. The variable regions change their conformations by more than 3 Å root-mean-square distance value whereas the fixed regions stay within 0.02 Å. Possible applications of this method are in the field of computer graphics, Monte Carlo simulations, and energy minimization calculations of chain molecules. 相似文献
65.
The immobilization of penicillin G acylase on chitosan 总被引:3,自引:0,他引:3
66.
pH Dependence of Histidine Affinity for Blood-Brain Barrier Carrier Transport Systems for Neutral and Cationic Amino Acids 总被引:1,自引:1,他引:0
William H. Oldendorf Paul D. Crane† Leon D. Braun Eddy A. Gosschalk Jared M. Diamond† 《Journal of neurochemistry》1988,50(3):857-861
The effects of pH (3.5-7.5) on the brain uptake of histidine by the blood-brain barrier (BBB) carriers for neutral and cationic amino acids were tested, in competition with unlabeled histidine, arginine, or phenylalanine, with the single-pass carotid injection technique. Cationic amino acid ( [14C]arginine) uptake was increasingly inhibited by unlabeled histidine as the pH of the injection solution decreased. In contrast, the inhibitory effect of unlabeled histidine on neutral amino acid ( [14C]phenylalanine) uptake decreased with decreasing pH. Brain uptake indices with varying histidine concentrations indicated that the neutral form of histidine inhibited phenylalanine uptake whereas the cationic form competed with arginine uptake. Since phenylalanine decreased [14C]histidine uptake at all pH values whereas arginine did not, it was concluded that the cationic form of histidine had an affinity for the cationic carrier, but was not transported by it. We propose that the saturable entry of histidine into brain is, under normal physiological circumstances, mediated solely by the carrier for neutral amino acids. 相似文献
67.
The structural gene for the mitochondrial aldehyde dehydrogenase maps to human chromosome 12 总被引:1,自引:1,他引:0
T. Braun K. H. Grzeschik E. Bober S. Singh D. P. Agarwal H. W. Goedde 《Human genetics》1986,73(4):365-367
Summary A cloned 850 bp cDNA fragment corresponding to the 3-coding part of human ALDHI-mRNA was used as a probe for the chromosomal assignment of the ALDHI gene. Southern blot analysis of human-rodent somatic cell hybrids indicates that the human ALDHI gene resides on chromosome 12.Dedicated to Prof. Dr. H. Holzer on the occasion of his 65. birthday 相似文献
68.
The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K+, Ca2+ and Mg2+ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed. 相似文献
69.
N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus). 相似文献
70.
Demonstration of an “Excitation-Contraction Recoupling” Mechanism in Mammalian Ventricular Myocardium 总被引:1,自引:0,他引:1
A PROCESS called “excitation-contraction coupling” has been generally accepted to take place only in the direction of excitation to contraction. Through this mechanism a propagated action potential initiates an active state in skeletal or cardiac muscle and the muscle contracts. We propose that, in the mammalian ventricular myocardium at least, the process is not unidirectional and an important reverse coupling between the contractile system and the excitable plasma membrane has been overlooked. Through this feedback interaction the mode of contraction (that is, isotonic or isometric) not only determines the instantaneous electrical state of the plasma membrane, but also influences the mechanical events of the subsequent beats. Thus when Kaufmann et al.1 recorded intracellular action potentials from cat papillary muscle, the time course of the repolarization was altered depending on the mode of contraction. Some kind of contraction-excitation feedback has also been suggested by Stauch2 and Lab3,4. They showed a difference in the shape of the monophasic action potential, as recorded by a suction electrode, when comparing isotonic and isovolumic contraction of the intact ventricle. But their experimental conditions did not allow satisfactory analysis of the phenomenon. 相似文献