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981.
The contribution of two components (pH and E) of the proton motive force to photosynthesis of C. reinhardtii was studied. Valinomycin, a photophosphorylation uncoupler, decreased significantly the fast phase (related mainly to the membrane electric potential) of millisecond delayed light emission (ms-DLE) of C. reinhardtii. Nigericin, another photophosphorylation uncoupler, decreased the slow phase (related mainly to the proton gradient) and partly also the fast phase of ms-DLE. Both valinomycin and nigericin decreased the net ATP content and photosynthetic rate of C. reinhardtii, but the inhibition by nigericin was stronger than that by valinomycin. Hence both components of the proton motive force contribute to photosynthesis and although the contribution of pH is larger than that of E, the latter is not negligible in photosynthesis of C. reinhardtii. 相似文献
982.
Huang Y Tang R Dai J Gu S Zhao W Cheng C Xu M Zhou Z Ying K Xi Y Mao Y 《Molecular biology reports》2001,28(4):185-191
We report the cloning and characterization of a novel human hydroxysteroid dehydrogenase like gene (HSDL1) located on human chromosome 16q24.2. The HSDL1 cDNA is 3407 base pair in length, encoding a 309 amino acid polypeptide related to human 17-HSD3. Northern blot reveals that the HSDL1 is highly expressed in testis and ovary. In situ hybridization indicates that the expression of HSDL1 is predominantly increased in the prostate cancer tissue compared with the normal prostate tissue, which suggests that the gene expression is important to the arising of prostate cancer. 相似文献
983.
984.
采用蒙古沙土双侧颈总动脉阻断前脑缺血模型,以放射自显影(反向磷酸化,back-phosphorylation)及免疫印迹(Western blotting)法体外测定缺血时纹状体DARPP-32磷酸化水平和蛋白含量的变化,结果表明,短暂性缺血纹状体DARPP-32的免疫学活性和蛋白含量地明显改变。在缺血10min内,随缺血时间的延长,体外DARPP-32的[^32P]的掺入量在缺血5min时升高,在缺血2,7,10min时均降低,而反向磷酸化的测定结果表明体内DARPP-32磷酸化水平增高,说明缺血可诱导DARPP-32磷酸化水平变化。 相似文献
985.
New chiral catalysts for reduction of ketones 总被引:2,自引:0,他引:2
The condensation of o-(diphenylphosphino)benzaldehyde and various chiral diamine gives a series of diimino-diphosphine tetradentate ligands, which are reduced with excess NaBH4 in refluxing ethanol to afford the corresponding diaminodiphosphine ligands in good yield. The reactivity of these ligands toward trans-RuCl2(DMSO)4 and [Rh(COD)Cl]2 had been investigated and a number of chiral Ru(II) and Rh(I) complexes with the PNNP-type ligands were synthesized and characterized by microanalysis and IR, NMR spectroscopic methods. The chiral Ru(II) and Rh(I) complexes have proved to be excellent catalyst precursors for the asymmetric transfer hydrogenation of aromatic ketones, leading to optically active alcohols in up to 97% ee. 相似文献
986.
987.
Tang L Okazawa A Fukusaki E Kobayashi A 《Zeitschrift für Naturforschung. C, Journal of biosciences》2000,55(11-12):923-926
Autumnal tints are one of the most manifest and fascinating natural phenomena, but the mechanism of chlorophyll (Chl)-breakdown in deciduous trees has not been fully elucidated. In this study, we analyzed the composition of Chl-related compounds and determined the activities of initial Chl-degrading enzymes in Ginkgo leaves at various stages in the process of autumnal coloring. Only pheophytin a (Pheo a, Mg-free Chl a) was detected in yellow leaves by HPLC analysis, and the activity of Mg-dechelatase in yellow leaves was found to be higher than in green leaves. These findings showed that the removal of magnesium from Chl a occurred in advance of dephytylation in the Ginkgo. 相似文献
988.
Drum CL Yan SZ Sarac R Mabuchi Y Beckingham K Bohm A Grabarek Z Tang WJ 《The Journal of biological chemistry》2000,275(46):36334-36340
The edema factor exotoxin produced by Bacillus anthracis is an adenylyl cyclase that is activated by calmodulin (CaM) at resting state calcium concentrations in infected cells. A C-terminal 60-kDa fragment corresponding to the catalytic domain of edema factor (EF3) was cloned, overexpressed in Escherichia coli, and purified. The N-terminal 43-kDa domain (EF3-N) of EF3, the sole domain of edema factor homologous to adenylyl cyclases from Bordetella pertussis and Pseudomonas aeruginosa, is highly resistant to protease digestion. The C-terminal 160-amino acid domain (EF3-C) of EF3 is sensitive to proteolysis in the absence of CaM. The addition of CaM protects EF3-C from being digested by proteases. EF3-N and EF3-C were expressed separately, and both fragments were required to reconstitute full CaM-sensitive enzyme activity. Fluorescence resonance energy transfer experiments using a double-labeled CaM molecule were performed and indicated that CaM adopts an extended conformation upon binding to EF3. This contrasts sharply with the compact conformation adopted by CaM upon binding myosin light chain kinase and CaM-dependent protein kinase type II. Mutations in each of the four calcium binding sites of CaM were examined for their effect on EF3 activation. Sites 3 and 4 were found critical for the activation, and neither the N- nor the C-terminal domain of CaM alone was capable of activating EF3. A genetic screen probing loss-of-function mutations of EF3 and site-directed mutations based on the homology of the edema factor family revealed a conserved pair of aspartate residues and an arginine that are important for catalysis. Similar residues are essential for di-metal-mediated catalysis in mammalian adenylyl cyclases and a family of DNA polymerases and nucleotidyltransferases. This suggests that edema factor may utilize a similar catalytic mechanism. 相似文献
989.
Ding Z Yang X Pater A Tang SC 《Biochemical and biophysical research communications》2000,270(2):415-420
Recent studies have indicated that induction of apoptosis is the primary cytotoxic mechanism of most cancer chemotherapeutic agents, and abnormalities in the control of apoptosis can affect the sensitivity of malignant cells to multiple drugs. Here, we treated cells with cisplatin and other apoptotic stimuli and found that multidrug-resistant (MDR) endocervical HEN-16-2/CDDP cells, compared with drug-sensitive parental cells, were significantly more resistant to apoptosis and exhibited decreased proteolytic activation of caspase-3. The latter was further demonstrated by decreased cleavage of its substrate poly(ADP-ribose) polymerase (PARP). Further, Western blot analysis showed that MDR HEN-16-2/CDDP cells had significantly higher levels of the apoptosis-inhibiting proteins BAG-1 p50 and p33 isoforms and Bcl-X(L). This study provided the first evidence that overexpression of antiapoptotic BAG-1 p50 and p33 and Bcl-X(L) may cause resistance to apoptosis through reduction of caspase-3 activity in human cervical cells having an MDR phenotype. 相似文献
990.
Identification of neural progenitors in the adult mammalian eye 总被引:27,自引:0,他引:27
We have shown that the embryonic mammalian retina contains neural progenitors which display stem cell properties in vitro. Here we report the characterization of neural progenitors isolated from the adult mammalian eye. These quiescent cells, located in the pigmented ciliary bodies, proliferate in the presence of FGF2 and express the neuroectodermal marker nestin. The proliferating cells give rise to neural spheres and are multipotential; they express cell type-specific markers corresponding to neurons and glia. In addition, neural progenitors can generate secondary neural spheres, thus displaying potential to self-renew. The ciliary body-derived neural progenitors display retina-specific properties; the undifferentiated cells express Chx10, a retinal progenitor marker, and upon differentiation express markers corresponding to specific retinal cell types. Therefore, the pigmented ciliary body in the adult mammalian eye harbors neural progenitors that display stem cell properties and have the capacity to give rise to retinal neurons in vitro. 相似文献