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951.
Regulation of p34CDC28 tyrosine phosphorylation is not required for entry into mitosis in S. cerevisiae. 总被引:40,自引:0,他引:40
Progression from G2 to M phase in eukaryotes requires activation of a protein kinase composed of p34cdc2/CDC28 associated with G1-specific cyclins. In some organisms the activation of the kinase at the G2/M boundary is due to dephosphorylation of a highly conserved tyrosine residue at position 15 (Y15) of the cdc2 protein. Here we report that in the budding yeast Saccharomyces cerevisiae, p34CDC28 also undergoes cell-cycle regulated dephosphorylation on an equivalent tyrosine residue (Y19). However, in contrast to previous observations in S. pombe, Xenopus and mammalian cells, dephosphorylation of Y19 is not required for the activation of the CDC28/cyclin kinase. Furthermore, mutation of this tyrosine residue does not affect dependence of mitosis on DNA synthesis nor does it abolish G2 arrest induced by DNA damage. Our data imply that regulated phosphorylation of this tyrosine residue is not the 'universal' means by which the onset of mitosis is determined. We propose that there are other unidentified controls that regulate entry into mitosis. 相似文献
952.
G. Wegener U. Krause E. A. Newsholme 《Cellular and molecular life sciences : CMLS》1996,52(5):391-395
953.
FMS建模和形式化验证 总被引:1,自引:1,他引:0
提出了一种FMS的建模方法,此方法是基于时间自动机模型。运用模型检查工具UPPAAL来进行建模,仿真和验证。由于时间的因素被考虑到建模方法中,因此FMS的调度和控制问题可以被集成到这个模型中。在系统的行为被控制的同时,可以保证系统的性能指标。从而最优调度和最优控制可以得到检查和验证。 相似文献
954.
The explanation and simulation of the natural and artificial intelligence are the central goals of the studies of Neuroscience, Psychology, Artificial Intelligence and Cognitive Science. This paper first gives an introduction to the core topics and approaches in the study. Then, GAF--a general adaptive framework for neural system is proposed. Interdisciplinary discussions around the adaptation of the human nervous system are presented. Rules describing the theory of adaptation of the nervous system are provided. 相似文献
955.
Hsp90 chaperones protein folding in vitro. 总被引:31,自引:0,他引:31
The heat-shock protein Hsp90 is the most abundant constitutively expressed stress protein in the cytosol of eukaryotic cells, where it participates in the maturation of other proteins, modulation of protein activity in the case of hormone-free steroid receptors, and intracellular transport of some newly synthesized kinases. A feature of all these processes could be their dependence on the formation of protein structure. If Hsp90 is a molecular chaperone involved in maintaining a certain subset of cellular proteins in an inactive form, it should also be able to recognize and bind non-native proteins, thereby influencing their folding to the native state. Here we investigate whether Hsp90 can influence protein folding in vitro and show that Hsp90 suppresses the formation of protein aggregates by binding to the target proteins at a stoichiometry of one Hsp90 dimer to one or two substrate molecule(s). Furthermore, the yield of correctly folded and functional protein is increased significantly. The action of Hsp90 does not depend on the presence of nucleoside triphosphates, so it may be that Hsp90 uses a novel molecular mechanism to assist protein folding in vivo. 相似文献
956.
Paternal inheritance of mitochondrial DNA in mice. 总被引:46,自引:0,他引:46
For nearly 20 years it has been assumed on the basis of low-resolution experiments that mitochondrial (mt)DNA, in contrast to the genes in the nucleus, has an exclusively maternal mode of inheritance in animals. Using the polymerase chain reaction, paternally inherited mtDNA molecules have now been detected in mice at a frequency of 10(-4), relative to the maternal contributions. These mice were hybrids between two inbred strains (C57BL/6J and Mus spretus) whose mtDNAs can be distinguished easily. This new mode of inheritance provides a mechanism for generating heteroplasmy and may explain mitochondrial disorders exhibiting biparental transmission. 相似文献
957.
在一维布朗运动生成算法的基础上,构成一种二维生成算法,并在计算机上得到实现。在构造二维生成算法时,充分利用一维生成算法,将二维生成算法分解成多个一维生成算法,这样极大地减少了运算量和存储量,有利于计算机实现,因此该方法具有普遍意义。 相似文献
958.
在超声波复合振动机理的基础上,分别对纵向振动和两种横向振动组成的Ⅰ型、Ⅱ型超声波复合振动的加工特性进行了较系统的试验研究.研究结果表明:Ⅰ型超声波复合振动可以对未烧结陶瓷等非导电限性材料的异型孔穴、窄槽进行高效加工,而Ⅱ型超声波复合振动适用于对上述材料进行精细加工. 相似文献
959.
在非均匀的SzekersClass-Ⅱ时空中引入一个无质量的标量场,得到了精确的非均匀各向异性的暴涨解。在长时间近似下,度规的时间部分趋向于deSitter解。选取适当坐标,度规可以写成一个精确的Robertson-Walker度规形式。 相似文献
960.