Molecular mitosis

Although it is generally accepted that the f-butylcalix[8]arene is the kinetically and the -calix[4]arene the thermodynamically controlled product while the formation of the -calix[6]arene seems to be due to a template effect, not much is really known about the mechanism of calixarene formation. The hypothesis that 2a is formed from 2e by an intramolecular step ( molecular mitosis ) could not be confirmed by isotopic labelling, which proves a more or less statistical fragmentation and recombination. ... 

Figure 2.1 Test for molecular mitosis pathway filled circles, deuterated residues open circles, proteated residues)...

Since nucleic acids and enzymes play such a large role in chromosome replication during mitosis, a considerable amount of research has been conducted in this area to control viruses. On the molecular level, analogues of nucleic acids are capable of forming complexes with adenine, cytosine, uracil, thymine, and guanine. Through complexation, these nucleic acid analogues are potential inhibitors of biosyntheses that require nucleic acids as templates. 

Unfortunately, this field is made difficult for a student by the terminology used by biochemists. For example, there is a protein kinase that regulates the cycle between G2 and M, i.e. the second restriction point. This protein is known as maturation (or mitosis) promoting factor, since it promotes entry into mitosis. It phosphorylates a protein, probably a transcription factor, in the nucleus. The kinase has a molecular mass of 34kDa. Hence it is known as p34 cell division kinase, abbreviated to p34-cdc and, since it is regulated at restriction point 2, it is known as p34-cdc-2 protein, which is sometimes written as p34°. This kinase is normally inactive until it binds a cyclin. Hence the active maturation-promoting factor is, in fact, a protein kinase-cyclin complex, which is referred to as p34° °-cyclin complex. It is hoped that this piece of information may help a student (or lecturer from another field) to understand one part of a review article that contains the abbreviation p34° -cyclin complex, without explanation, or other similar pieces of biochemical shorthand. 

The two chromatids in Fig. 26-13G are said to be coiled with opposite handedness. Can you draw this conclusion from Fig. 26 alone What are the biological implications for mitosis 280 Does the DNA have a differing chirality at the molecular level Compare this observation with the existence of snail shells or flowers497 with both right and left handedness within the same species. 

Thus, they prevent an arrangement of the spindle apparatus. The tubuline-benzimidazole-interactions have been studied in detail (.6). It is known that carbendazim, for example, after entering the nucleus, specifically binds to the 3 -subunit of tubuline and by this inhibits the dimerization of the a and 3 -subunits to a functional tubuline unit. Resistant strains possess altered 0 -subunits with a decreased affinity for benzimidazoles (7). The modes of action of other inhibitors of mitosis, like dicarboximides, aromatic hydrocarbons, or dithiocarbamates, have not yet been precisely described on a molecular basis. 

The centrioles migrate to opposite poles of the cell and the mitotic spindle is formed, apparently joining the cell membrane through the centrioles to the centromere of each chromosome. Spindle fibres consist of one type of protein, tubulin, of molecular weight 60,000. It is the organisation of these molecules to form the mitotic spindle which is blocked by the drugs colchicine, colcemide, nocodazole, vincristine and vinblastine (Fig. 10.3) with the consequence that mitosis is arrested in metaphase. 

M MCDB mitosis media developed at the Department of Molecular, Cellular and Developmental Biology, University of Colorado... 

There are several self-assembling macromolecules that are of interest to us in this text. They include (1) collagen, the primary structural material found in the extracellular matrix (2) actin, a component of the cell cytoskeleton that is involved in cell locomotion and in formation of the thin filaments of muscle (3) microtubules, which are involved in cell mitosis, movement, and organelle movement and finally (4) fibrinogen, which forms fibrin networks that minimize bleeding from cut vessels. Self-assembly is important in these systems because the function of these macromolecules can be modified via processes that increase the molecular axial ratio and hence decrease the solubility. 

Following the S phase is the G2 phase, in which the cell prepares for mitosis and cytokinesis. Although few of the molecular events that occur in G2 phase have been identified, it is known that some proteins synthesized during this period are essential for cell division. It is believed that contractile proteins necessary for chromosome separation and cytokinesis accumulate and are accompanied by modifications in the structure of chromosomal proteins. The phosphorylation of histone HI, known to be involved in the packaging of nucleosomes, could cause the initiation of chromosome condensation that directs the cell into mitosis. 

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