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排序方式: 共有261条查询结果,搜索用时 31 毫秒
1.
Jesus Torres-Bacete Prem Kumar Sinha Motoaki Sato Gaurav Patki Mou-Chieh Kao Akemi Matsuno-Yagi Takao Yagi 《The Journal of biological chemistry》2012,287(51):42763-42772
The bacterial H+-translocating NADH:quinone oxidoreductase (NDH-1) catalyzes electron transfer from NADH to quinone coupled with proton pumping across the cytoplasmic membrane. The NuoK subunit (counterpart of the mitochondrial ND4L subunit) is one of the seven hydrophobic subunits in the membrane domain and bears three transmembrane segments (TM1–3). Two glutamic residues located in the adjacent transmembrane helices of NuoK are important for the energy coupled activity of NDH-1. In particular, mutation of the highly conserved carboxyl residue (KGlu-36 in TM2) to Ala led to a complete loss of the NDH-1 activities. Mutation of the second conserved carboxyl residue (KGlu-72 in TM3) moderately reduced the activities. To clarify the contribution of NuoK to the mechanism of proton translocation, we relocated these two conserved residues. When we shifted KGlu-36 along TM2 to positions 32, 38, 39, and 40, the mutants largely retained energy transducing NDH-1 activities. According to the recent structural information, these positions are located in the vicinity of KGlu-36, present in the same helix phase, in an immediately before and after helix turn. In an earlier study, a double mutation of two arginine residues located in a short cytoplasmic loop between TM1 and TM2 (loop-1) showed a drastic effect on energy transducing activities. Therefore, the importance of this cytosolic loop of NuoK (KArg-25, KArg-26, and KAsn-27) for the energy transducing activities was extensively studied. The probable roles of subunit NuoK in the energy transducing mechanism of NDH-1 are discussed. 相似文献
2.
Chemical modification of Rhodospirillum rubrum chromatophores by 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) results in inactivation of photophosphorylation, Mg2+-ATPase, oxidative phosphorylation and ATP-driven transhydrogenase, with apparent first-order kinetics. Other energy-linked reactions such as light-driven transhydrogenase and light-dependent proton uptake were insensitive to NBD-Cl. The Ca2+-ATPase activity of the soluble coupling factor from chromatophores (R. rubrum F1) was inactivated by NBD-Cl with kinetics resembling those described for Mg2+-ATPase and photophosphorylation activities of chromatophores. Both NBD-chromatophores and NBD-R. rubrum F1 fully recovered their activities when subjected to thiolysis by dithioerythritol. Phosphoryl transfer reactions of chromatophores and Ca2+-ATPase activity of R. rubrum F1 were fully protected by 5 mM Pi against modification by NBD-Cl. ADP or ATP afforded partial protection. Analysis of the protection of Ca2+-ATPase activity by Pi indicated that NBD-Cl and Pi are mutually exclusive ligands. Spectroscopic studies revealed that tyrosine and sulfhydryl residues in R. rubrum F1 underwent modification by NBD-Cl. However, the inactivation was only related to the modification of tyrosine groups. 相似文献
3.
Cerebral Blood Flow and Oxidative Metabolism in Conscious Fischer-344 Rats of Different Ages 总被引:1,自引:1,他引:0
Hidenori Takei Wendy R. Fredericks Edythe D. London Stanley I. Rapoport 《Journal of neurochemistry》1983,40(3):801-805
Abstract: The cerebral metabolic rates for O2 and for glucose were measured in conscious, fasted male Fischer-344 rats at the ages of 3, 12, and 24 months, and cerebral blood flow was determined with 14 C-iodoantipyrine. The metabolic rates for oxygen and glucose were obtained by multiplying blood flow by the O2 and glucose concentration differences, respectively, between blood in the femoral artery and in the superior sagittal sinus. Mean cerebral blood flow and the metabolic rates for oxygen and glucose did not differ significantly (p > 0.05) between 3 and 12 or between 12 and 24 months. Nor did the arteriovenous differences for O2 and for glucose change significantly with age. Because the superior sagittal sinus drains blood mainly from the cerebral cortex, the results indicate that average cerebral cortical oxidative metabolism, and the coupling ratios between the cerebral metabolic rate for oxygen and cerebral blood flow and between the cerebral metabolic rate for glucose and cerebral blood flow, do not change significantly with age in the Fischer-344 rat. 相似文献
4.
我们测定了鼠肝线粒体呼吸链不同偶联部位的质子系活性并通过荧光能量共振转移 法分析了鼠肝线粒体膜与脂质体(二油酰磷脂乙醇胺/心磷脂=8/2)的膜融合程度。根据测量呼吸链第一段及第二段偶联部位的H+/偶联部位的化学计量比值,观察到线粒体呼吸链质子泵的质子(H+)泵活性及 H+泵出量与膜融合程度呈现线性的定量相关性。这些实验结果进一步支持了我们提出的质子泵诱导膜融合的理论模型(刘树森等,1987、1989)。 相似文献
5.
An empirical projection method is described to predict the magnitudes and signs of two-bond 13C-13C spin-coupling constants (2JCC) in aldopyranosyl rings. The method has been applied primarily to the interpretation of 2JCCC values, although the behavior of 2JCOC has also been examined in light of the new approach, producing results which may prove useful in the conformational analysis of O-glycosidic linkages in oligosaccharides. High-level ab initio calculations of 2JCC values in model compounds were found to be in agreement with the predictions. 相似文献
6.
Marianna F. Asaroa Andreas Mayr Bart Kahra Donna Van Engen 《Inorganica chimica acta》1994,220(1-2):335-346
Reaction of the allylidene tungsten complex [W(CPhCHCHMe)Br2(CO)2(4-picoline)] (1) with the dithiocarbamates MS2CNR2 (a: M=Na, R=Et; b: M=Na, R=Me; c: M=Li, R=Ph) in THF at 50 °C affords the vinylketene tungsten complexes [W(S2CNR2)2(OCCPhCHCHMe)(CO)] (2a–c). At lower temperatures, four reaction intermediates (3–6) may be discerned. Spectroscopic studies indicate that these compounds contain η4-allyldithiocarbamate ligands which are generated by addition of dithiocarbamate across the metal-carbon double bond of the allylidene-tungsten unit in 1. The structures of [W(S2CNEt2)2(OCCPhCHCHMe)(CO)] (2a) and of one intermediate, [W(η4-Et2NCS2CPhCHCHMe)(S2CNEt2)(CO)2] (5a) were elucidated by X-ray crystallography. 相似文献
7.
Iman Abdelmoty Fernando Albericio Louis A. Carpino Bruce M. Foxman Steven A. Kates 《Letters in Peptide Science》1994,1(2):57-67
Summary X-ray structure determinations of HBTU and HATU, well-known reagents for peptide bond formation, show that the solid-state structures of these compounds differ markedly from those commonly presented in the literature. The solid-state structures are isomers of the N,N,N',N'-tetramethyluronium salt formulation commonly written for HBTU and HATU. HBTU and HATU, obtained either directly from synthesis or from CH3CN solution, crystallize as the guanidinium N-oxide isomers. Both compounds crystallize in nearly identical conformations, despite marked differences in crystal packing. 相似文献
8.
Summary The multiplet structure of cross peaks in double-quantum-filtered COSY NMR spectra is analysed for those resonances that include passive heteronuclear couplings. Interestingly, the cross peak involving the sugar-ring protons H2 and H3 in nucleic acids display an E.COSY-type appearance exclusively when the backbone torsion angle (C4-C3-O3-P) adopts a gauche(-) conformation. This observation allows an unambiguous analysis of the conformation around , without the knowledge of 3Jcp coupling constants. 相似文献
9.
Oxalis regnellii Mig. is a trifoliate plant, and the three leaflets usually show synchronized up and down movements with a circadian period of 26–27 h. The three leaflets can also perform desynchronized ultradian oscillations, and we report on such rhythms under different conditions. A study of the occurrence of ultradian leaf movement rhythms as a function of irradiance is presented. At an irradiance of approximately 1 μW cm−2 , the occurrence was maximal and ca 30%. The periods varied from 5 to 15 h. Four other cases of ultradian rhythms in different conditions are also presented. In one case spontaneous ultradian rhythms occurred, and in another, two of the leaflets showed ultradian rhythms when the third leaflet had received a light pulse. In two more cases, the three leaflets on a leaf were separated by physical cuts along the petiole between the pulvini; in both cases the period was approximately 5 h. Possible mechanisms to explain the ultradian rhythms in Oxalis regnelli are discussed. 相似文献
10.
Jens Chr. Madsen Ole Winneche Sørensen Poul Sørensen Flemming M. Poulsen 《Journal of biomolecular NMR》1993,3(2):239-244
Summary NMR pulse sequences for measuring coupling constants in 13C, 15N-labeled proteins are presented. These pulse sequences represent improvements over earlier experiments with respect to resolution and number of radiofrequency pulses. The experiments are useful for measuring JNH
, JNCO, JNC
, JH
N
CO and JH
N
H
. Applications to chymotrypsin inhibitor 2 (CI-2) are shown. 相似文献