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排序方式: 共有438条查询结果,搜索用时 15 毫秒
1.
Photoelectric signals from dried oriented purple membranes of Halobacterium halobium 总被引:9,自引:7,他引:2 下载免费PDF全文
In dried oriented samples of purple membrane isolated from Halobacterium halobium, the photoelectric activity decreases and the light adaptation vanishes when the water content of the sample is lowered. In the photocycle the first steps of the proton movement were accelerated with decreasing humidity, while the last steps of the photocycle could not be observed. From the analysis of the photoelectric signal we conclude that at low humidities the protons move forward in the L decay and return to their original place during M decay. 相似文献
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R Tóth-Boconádi S G Taneva A V Kiselev N G Abdulaev L Keszthelyi 《Archives of biochemistry and biophysics》1988,260(2):725-731
All six available lysine residues in bacteriorhodopsin were amidinated with dimethyl-3,3'-dithiobispropionimidate, which is a crosslinking agent. The photocycle was studied by measuring light absorption and electric signals. The data show an essential change in the photocycle: instead of single components, the rise of the signal due to the M intermediate can be decomposed into two components, and the decay into three. The life-times and the intensities of these components and in general the proton pumping activity of bacteriorhodopsin depend only negligibly upon pH. Changes upon removing the crosslinks are not significantly different from those in the crosslinked samples. The lysine residues therefore may not be considered of primary importance in proton translocation. 相似文献
4.
Summary A selection method has been developed for the isolation of recombinant strains of Trichoderma reesei QM 9414. The method is based on somatic hybridization via anastomosis or protoplast fusion, and on the difference in growth rate of the resulting heterokaryons and synkaryons. The more intensive growth of the synkaryons as due to allelic complementation of adenine-requiring auxotrophic strains mutated in the adenylosuccinate synthetase gene. The synkaryons appeared is energetically growing spots in the heterokaryotic background. Stable diploids could not be isolated, which points to the transient nature of the diploid state in this species. 相似文献
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Polyethylenimine selectivity precipitates a large fraction of the proteins present in a crude Drosophila embryonic extract. While the free catalytic subunit of the cAMP dependent protein kinase is quantitatively retained in the soluble fraction after polyethylenimine precipitation, the rest of the abundant and highly active protein kinases present in the embryo are quantitatively precipitated. The catalytic subunit of the cAMP dependent protein kinase was purified until apparent homogeneity from the soluble protein fraction after polyethylenimine precipitation. The pH optimum of the purified enzyme is 6.3. While magnesium is the preferred divalent cation for all the cAMP dependent protein kinases described previously, the Drosophila enzyme is three times more active if manganese is present as divalent cation compared with magnesium. The enzyme is tost active between 50–100 mM monovalent ion concentration. Heparin can selectively modulate the phosphorylation of different substrate proteins. 相似文献
7.
Electro-optical measurements on aqueous suspension of purple membrane from Halobacterium halobium 总被引:5,自引:5,他引:0 下载免费PDF全文
The permanent dipole moment, polarizability, and the retinal angle of Halobacterium halobium purple membranes were determined at different pH values. All of the parameters have a maximum between pH 5 and 6. There is a reversal in the direction of the permanent dipole moment near pH 5. The value of permanent dipole moment was determined to be 60 D/protein at pH 6.6, and the value obtained for polarizability was 3 X 10(-28) Fm2/membrane fragment. The retinal angle of all-trans retinal was 0.8 degrees smaller than that of the 13-cis conformation. 相似文献
8.
Bradykinin (BK) is a peptide hormone with sequence Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9 and has been implicated in a multitude of pathophysiological processes such as the ability to lower systemic blood pressure and stimulate pain. BK analogues having bulky, β-branched D -aliphatic residues at position 7 combined with bulky L -aliphatic residues at position 8 have now been observed to be strong antagonists. Conformational studies based on two-dimensional nmr experiments in methanol/water (80/20 v/v) were carried out on several such active antagonists in a polar solvent. Included in this study were the very active antagonists, [D -Arg0, Hyp3, Thi5, D -Cpg7, Cpg8]-BK [Cpg: α-cyclo-pentyl-glycine; Hyp: trans-4-hydroxy-L -proline; Thi: β-(2-thienyl)-L -alanine] ( I ), [D -Arg0, Hyp3, D -Cpg7, Cpg8] -BK ( II ), as well as its variant with D -Cpg7 replaced by Cpg7, namely [D -Arg0, Hyp3, Cpg7, Cpg8]-BK ( III ). A turn-like structure, which coexists with the extended conformation, was observed between residues 2 and 5 for the most active antagonists I and II , in direct correlation with the peptide activities. No turn-like structure was found for residues 6–9. In peptide III , a turn-like structure was not identified. The existence of a turn at the C-terminal end of bradykinin and its analogues has been predicted by empirical calculations and supported by nmr measurements. But the present nmr study on the most active antagonists ( I , II ) does not support this hypothesis. Instead, the data suggest that a turn-like structure between residues 2 and 5 could be important for antagonist activity. Finally, one weak inhibitor [D -Cpg7]-BK ( IV ) showed no defined secondary structure. © 1993 John Wiley & Sons, Inc. 相似文献
9.
Eszter Gács-Baitz Lajos Radics G.B. Oganessian Vilen A. Mnatsakanian 《Phytochemistry》1978,17(11):1967-1973
The structure and stereochemistry of teucrins H1, H2, H3 and H4, four novel diterpenes from Teucrium hyrcanicum have been established by detailed studies of the PMR and 13C NMR spectra, CD results and chemical transformations. Teucrin H4, a minor constituent is shown to possess a unique stereochemistry hitherto not reported for related diterpenoids. 相似文献
10.
Asymmetries of nature and the origin of biomolecular handedness 总被引:3,自引:0,他引:3
L Keszthelyi 《Bio Systems》1987,20(1):15-19
New developments in the problem of the origin of the asymmetry of the living systems are reviewed. The time of the appearance of the asymmetry was very probably during the chemical evolution. The asymmetry of weak interaction is still considered small to be the cause of chiral purity. New sources of asymmetry should also be considered, like the one proposed by Gilat. 相似文献