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141.
鄂东南早白垩世灵乡群孢粉组合 总被引:1,自引:0,他引:1
张振来 《Acta Botanica Sinica》1984,(6)
本文根据从大冶灵乡-陈重山剖面的中部、灵乡狮子山东侧采坑和鄂城太和1孔的相当层位中所获得的孢粉组合(共67属120余种,其中新种9个,新联合2个),认为灵乡群孢粉组合属于 Classopollis、Psophosphaera-Cicatricosisporites、Schizaeoisporites-没有或极个别的出现被子植物花粉的组合类型,其地质时代应为早白垩世早期-中期(凡兰吟期-巴列姆期)。并推测鄂东南地区当时的气候属于偏干旱的热带-亚热带型。 相似文献
142.
应用植物学的研究动向 总被引:2,自引:0,他引:2
在一九八一年八月二十一日至二十九日于澳大利亚悉尼召开的“第十三届国际植物学会议”上,应用植物学作为一个学科组共有下列十三项中心议题:1.植物生产力的改进——生理学界线的探讨;2.植物育种的新领域;3.在植物生物学中的细胞培养和体细胞遗传;4.杂草的性质及其起源;5.有利于人类幸福的民族植物学;6.改善旱地作物的水分利用;7.生态系统中的氮素迁移;8.树木营养;9.人工气候室 相似文献
143.
The production of alpha-amylase by Bacillus amyloliquefaciens increased by a factor of 300 when glycine was added to a chemically defined simple medium at the early-logarithmic phase of growth. Glycine was not metabolized to a significant extent under the conditions used, but it considerably prevented the lowering of the pH of the culture. 相似文献
144.
足月分娩的新鲜胎盘组织制成匀浆后,经高速离心、超速离心,谷胱甘肽(GSH)Sepharose 6B亲合层析,Amicon pM-10膜超过滤及高效液相层析,最终经SDS-PAGE鉴定,结果呈现单一亚基区带,其亚基分子量为25000。 根据我们现有高效液相设备条件,用ODS柱代替RadulovicL等报道的特异阴离子柱,用磷酸盐洗脱液代替含谷胱甘肽、二硫苏糖醇及氯化钾的梯度洗脱液,从人胎盘组织成功地制备了谷胱甘肽硫转移酶(GST)纯酶,全过程在15min内完成,保留时间及主峰面积的重复性均较理想,7次实验结果的变异系数为0.2%,最终纯化578.9倍。本研究为各种形式GST的纯化制备提供了一个新的、重复性好、分辨率高及回收理想的简易方法。 相似文献
145.
本文介绍用二相分配法制备蚕豆叶片原生质膜上的Ca~(2+)·Mg~(2+)-ATPase,用以研究镧系,稀土离子对此酶活性的影响。初步证实Pr~(3+)、Nd~(3+)对依赖于CaM的以及不依赖于CaM的蚕豆叶片原生质膜上Ca~(2+)·Mg~(2+)-ATPase活性的抑制不是CaM专一的。 相似文献
146.
147.
Phosphorylation causes a conformational change in the carboxyl-terminal domain of the mouse RNA polymerase II largest subunit 总被引:12,自引:0,他引:12
The carboxyl-terminal domain (CTD) of the largest subunit of eukaryotic RNA polymerase II can be phosphorylated by a p34cdc2/CDC28-containing CTD kinase. Phosphorylated serine (or threonine) is located at positions 2 and 5 in the repetitive heptapeptide consensus sequence Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7. We show here that phosphorylation of the mouse CTD retards its electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels in a way similar to that observed for the II0 form of the largest subunit of RNA polymerase II phosphorylated in vivo. At the maximum level of phosphorylation by CTD kinase in vitro, there are 15-20 phosphates evenly distributed among the 52 heptapeptide repeats that comprise the mouse CTD. Gel filtration chromatography and sucrose gradient ultracentrifugation analyses indicate that phosphorylation induces a dramatic conformational change in the CTD with the phosphorylated form adopting a far more extended structure than the unphosphorylated CTD. 相似文献
148.
Dissociative inhibition of dimeric enzymes. Kinetic characterization of the inhibition of HIV-1 protease by its COOH-terminal tetrapeptide 总被引:7,自引:0,他引:7
Z Y Zhang R A Poorman L L Maggiora R L Heinrikson F J Kézdy 《The Journal of biological chemistry》1991,266(24):15591-15594
Human immunodeficiency virus 1 (HIV-1) protease is an aspartyl protease composed of two identical protomers linked by a four-stranded antiparallel beta-sheet consisting of the NH2- and COOH-terminal segments (Weber, I.T. (1990) J. Biol. Chem. 265, 10492-10496). Kinetic analysis of the HIV-1 protease-catalyzed hydrolysis of a fluorogenic substrate demonstrates that the enzyme is an obligatory dimer. At pH = 5.0, 0.1 M sodium acetate, 1 M NaCl, 1 mM EDTA buffer, 37 degrees C, the equilibrium dissociation constant, Kd = 3.6 +/- 1.9 nM. We found that the tetrapeptide Ac-Thr-Leu-Asn-Phe-COOH, corresponding to the COOH-terminal segment of the enzyme, is an excellent inhibitor of the enzyme. Kinetic analysis shows that the inhibitor binds to the inactive protomers and prevents their association into the active dimer (dissociative inhibition). The dissociative nature of this inhibition is consistent with the results obtained from sedimentation equilibrium experiments in which the apparent molecular weight of the enzyme was observed to be 20,800 +/- 1,500 and 12,100 +/- 300, in the absence and presence of the COOH-terminal tetrapeptide, respectively. The dissociation constant of the protomer-inhibitor complex is Ki = 45.1 +/- 1.8 microM. This is the first kinetic analysis and direct experimental demonstration of noncovalent dissociative inhibition. 相似文献
149.
I Nakashima Y H Zhang S M Rahman T Yoshida K Isobe L N Ding T Iwamoto M Hamaguchi H Ikezawa R Taguchi 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(4):1153-1162
The potential role of Thy-1 in CD3/TCR complex-mediated signal delivery to murine thymocytes was studied. Ag-mimicking cross-linked anti-CD3 mAb stimulated suspension of thymocytes from adult (6 to 8 wk old) mice for a brisk free cytoplasmic calcium ion ([Ca2+]i) rise, low level of inositol phosphate production, and marginal increase in tyrosine-specific phosphorylation of 110/120-kDa and 40-kDa cellular proteins. Weak but sustained [Ca2+]i rise, low inositol phosphate production, and weak protein tyrosine phosphorylation were also induced by the cross-linked anti-Thy-1 mAb that mimicked the putative natural ligand. The signal delivered via either of these two pathways was however insufficient for definitively promoting cell death and DNA fragmentation in the adult thymocytes. Here we demonstrated that anti-Thy-1 mAb synergized with anti-CD3 mAb for inducing a long-lasting prominent [Ca2+]i rise, definite inositol 1,4,5-triphosphate and inositol 1,3,4,5-tetrakiphosphate production, and extensive tyrosine-specific phosphorylation of 110/120-, 92-, 75-, and 40-kDa proteins, which resulted in marked promotion of cell death and DNA fragmentation in the adult thymocytes. This unique anti-Thy-1 antibody activity was confirmed to be directed to glycosylphosphatidylinositol-anchored Thy-1, and was distinguished from the known anti-L3T4 activity that augmented the CD3-mediated signal transduction in a different manner. The synergistic actions of anti-CD3 and anti-Thy-1 mAb obligatorily required the cross-linking of the two mAb together. The anti-CD3 and anti-Thy-1 mAb cross-linked together acted on immature thymocytes from newborn (less than 24 h after birth) mice for rather more extensive promotion of protein tyrosine phosphorylation and cell death. In addition, they affected peripheral T lymphocytes for accelerating protein tyrosine phosphorylation but not cell death. These results suggest a novel function of glycosylphosphatidylinositol-anchored Thy-1 as a possible unique intrathymic intensifier of the CD3/TCR complex-delivered signal for negative thymocyte selection. 相似文献
150.
Delineation of type-specific regions on the envelope glycoproteins of human T cell leukemia viruses.
Y M Chen X Q Zhang C E Dahl K P Samuel R T Schooley M Essex T S Papas 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(7):2368-2376
Two different approaches were used to map the type-specific regions on human T cell leukemia virus (HTLV) envelope glycoproteins. 1) Antibody reactivities of polymerase chain reaction-confirmed HTLV-I or HTLV-II carriers' sera were analyzed by Western blot assay with seven recombinant proteins containing different regions of HTLV-I or HTLV-II envelope proteins. 2) Rabbit antibodies elicited by nine HTLV-I Env synthetic peptides were used to react with the native HTLV envelope glycoproteins in an antibody-dependent cellular cytotoxicity (ADCC) assay. The results of the Western blot analysis showed that RP-B2, which contains amino acid residues 166 to 213 from HTLV-II exterior glycoprotein, was specifically reactive with 90.6% (48 of 53) of the HTLV-II carriers' sera but not with any of the HTLV-I carriers' serum (0 of 71). In contrast, RP-B, which contains amino acid residues 166 to 229 from HTLV-I exterior glycoprotein, was reactive with 85.1% (114 of 134) of the HTLV-I carriers' sera but not with any HTLV-II carrier serum (0 of 62). Furthermore, anti-HTLV-I Env synthetic peptide antibody-mediated ADCC identified several distinguishing HTLV-I ADCC epitopes in the middle region (amino acid residues 177 to 257) of the HTLV-I exterior glycoprotein. Therefore, HTLV type-specific epitopes reside mainly in a 69-amino acid sequence bounded by two cysteine residues (amino acids 157 and 225 for HTLV-I and 153 and 221 for HTLV-II), in the middle region of the exterior envelope glycoproteins. 相似文献