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171.
本文报道流行性出血热病毒(汉坦病毒)H-114株的电镜形态。发现形态发生以内质网膜和胞浆膜芽生为主。病毒颗粒为圆形或卵圆形。具有双层膜结构,大小为90~120nm。提出了汉坦病毒形态发生的理论观点。 相似文献
172.
1985年我们采用间接免疫荧光法(IF法)检测出甲肝患者外周血白细胞中有甲肝抗原(HAAg)存在,继而又将HAAg阳性白细胞直接种入PLC/PRF/5细胞,分离到两株甲肝病毒(HAV)NJ—3株和H—1株。为了弄清白细胞所携带的病毒究竟仅为吸附吞饮,抑或能在其中复制增殖,我们将分离到的HAV用正常人血白细胞进行体外增殖试验,现将结果报告如下。 相似文献
173.
Membrane interactions of tetradecapeptide toxin mastoparan (MP) and analogues (MP-3, MP-X and polistes MP), as indicated by inhibition of various enzymatic and cellular activities, were investigated. MP-3 was found to be the least active in inhibiting protein kinase C (PKC; activated by phosphatidylserine vesicles, synaptosomal membranes or phorbol ester), synaptosomal membrane Na,K-ATPase and proliferation and viability of leukemia HL60 cells. MP-3, however, was as active as others in inhibiting PKC activated by arachidonate monomers and phorbol ester binding. The unique properties of MP-3, the [des-Ile1-Asn2]-analogue of MP, might be related to its low functional amphiphilicity compared to others and useful in further delineating biological activities associated with or regulated by membranes. 相似文献
174.
S Pattanakitsakul J H Zheng S Natsuume-Sakai M Takahashi M Nonaka 《The Journal of biological chemistry》1992,267(11):7814-7820
The serum level of the fourth component of complement (C4) in mice bearing the H-2k haplotype is only 1/10 to 1/20 of that of non-H-2k mice. We have analyzed C4 cDNA clones from B10.BR(H-2k) mouse liver and found aberrant C4 cDNA which contained a 200-base pair (bp) insertion between the exon 13 and exon 14 encoded sequences in addition to the normal C4 cDNA. The 5' 148 bp and the 3' 52 bp of this insert were derived from the B2 sequence, the short interspersed repeats of mouse genome, and the central part of intron 13, respectively. Sequence analysis of intron 13 of the C4k gene showed the presence of a complete copy of a B2 consensus sequence. The structure of aberrant C4 mRNA indicated that the possible 3' splice site in the B2 sequence and the cryptic 5' splice site in intron 13 were used. Both the insertion of the B2 sequence into intron 13 and the presence of aberrant mRNA in the liver were specific to H-2k-bearing mice, suggesting that the aberrant splicing due to the B2 insertion is the basis for low C4 expression in H-2k mice. 相似文献
175.
Based on CHARMM potential (Brooks et al., 1983) an energetic analysis has been carried out for four typical 4-alpha-helix bundle proteins, i.e., methemerythrin, cytochrome b-562, cytochrome c', and bovine somatotropin. The bovine somatotropin possesses long loops, but all the other three proteins have short loops. It was found that in all these four 4-alpha-helix bundle motif structures the interaction between loops and helices was much stronger than the interaction among the four helices themselves. Particularly for the electrostatic interaction energy, the loop-helix interaction is overwhelmingly stronger than the interhelix interaction although the latter involves the favorable helix dipole interaction due to the antiparallel arrangement of neighboring alpha-helices. The present study indicates that such a conclusion holds true regardless of what loops, long or short, are in the 4-alpha-helix bundle protein, and also regardless of which empirical potential, ECEPP or CHARMM, is used for calculations although in CHARMM the electrostatic energy is much more heavily emphasized than in ECEPP. Therefore, no appropriate conclusion can be drawn in arguing whether the dipole interaction among the four alpha-helices play a stabilizing role or destabilizing role for a 4-alpha-helix bundle protein without taking into consideration the effect of interaction between helices and loops. The calculated results reported here provide, from a different point of view, insights that might be useful for revealing the essence of the driving forces during the folding of proteins. 相似文献
176.
Two concentrations of glycerol in a freezing diluent were tested with respect to the in vitro fertilizing capacity of frozen-thawed boar spermatozoa which, before exposure to oocytes, were subjected to 3 methods of fractionation. These were 1) the upper fraction, 2) the swim-up and 3) percoll gradinet-centrifugation. The highest proportions of motile spermatozoa were obtained by the swim-up procedure, while acrosomal integrity was best preserved by the upper fraction procedure. Raising the glycerol concentration from 2 to 6% (v/v) during freezing decreased the proportion of spermatozoa with a normal apical ridge. Spermatozoa separated by the upper fraction method showed the greatest penetration of oocytes and produced the highest indidence of polyspermy. The glycerol level affected penetration and polyspermy only with spermatozoa separated in a percoll gradient, where the higher level of glycerol increased oocytes penetration and polyspermy. Pronuclei formation was influenced by the separation procedure and by the glycerol concentration in the freezing diluent. The results indicate that frozen boar semen can be used for in vitro fertilization more successfully than fresh semen since penetration by frozen upper fraction spermatozoa was similar to, the degree of polyspermy was lower, and the formation of two pronuclei was greater (P<0.01) than in oocytes exposed to fresh semen. 相似文献
177.
178.
179.
Sensitive Raman difference spectroscopy was used to monitor the protonation and deprotonation of histidine residues in apo-transferrin. We have shown previously that the behavior of small molecules and/or small molecular groups bound to proteins or other large macromolecules can be studied by Raman difference spectroscopy (Yue, K.T. et al. (1989) J. Raman Spectrosc. 20, 541-545). Using this method, we have measured the Raman difference spectra of human transferrin at different pH values with respect to pH 8.9, titrating its various histidine residues. About 12 +/- 2 of the 19 residues were titrated. The pH difference spectrum of transferrin obtained is very similar to that of histidine in solution, but with clear differences in the 1200-1400 cm-1 region. A titration curve with pKa of 6.08 +/- 0.01 fit the data of histidine in solution and a value of 6.56 +/- 0.02 was found for the average value of the 12 histidine residues inside transferrin. The technique has enough sensitivity at present to monitor a single histidine residue in a 130 kDa molecule and to determine the titration curve of one residue in a 40 kDa protein. 相似文献
180.
多效唑连用其它植物激素对水稻试管苗生长的影响 总被引:3,自引:0,他引:3
本实验采用继代多年的花培体细胞无性系Hu18再生绿芽(0.5mm)为起始材料,研究多效唑(MET)与其它激素配合使用对试管苗的调控作用,结果指出:(1)单独使用MET对绿芽生长有毒害作用,除2,4-D、GA,外,MET与适宜浓度的其它激素配合使用才能发挥增苗、壮苗作用,其中以MET与BA配合使用的培养效果最好,MET与NAA,C_2H_4配合使用的效果次之;(2)MET与其他激素配合使用不但能降低植株高度,促进根系发育,而且可以延长试管苗的保存时间;(3)MET与乙烯利配合使用能加速绿芽成苗速度,而与其他激素配合使则延缓绿芽成苗速度,如与2,4-D配合使用则延缓2,4-D对绿芽的脱分化进程;(4)在本实验条件下,以MET 2.5mg/L+BA 2mg/L+NAA 0.2mg/L配合使用有利根芽的协调生长。本文还从植株干物质累积,叶细胞结构,细胞活力等方面进行了探讨。 相似文献