Comparative analysis of sequences of protein D2 from photosystem 2 reaction center and various Ca 2+-binding proteins

The amino acid sequence of D2 protein was compared with those of calcium binding proteins and receptor for calcium channel blockers in connection with the data showing the participation of Ca2+ in photosystem 2 electron transport and the inhibition of this process by calmodulin antagonists, calcium channel blockers and local anesthetics. Protein D2 possesses a pattern analogous to the "EF-hand" sites of the calcium binding proteins. Comparison of the amino acid sequence of the calmodulin fragment binding the phenothiazine type calmodulin antagonists with the amino acid sequence of D2 protein and calcium channel protein revealed a high degree of sequence identity. Common structural features take place also between the membrane spanning segment III of D2 protein, which contains the tyrosine residue (161), responsible for ESR-signal IIS, and the membrane segment IVS5 of calcium channel protein. A model explaining the mechanism of calcium function in the oxygen-evolving system is proposed.     

Effect of cultivation conditions on the age structure of a yeast population

The work was aimed at studying the effect exerted by mineral components of the medium and a carbon source limiting the growth of Candida boidinii and Saccharomyces cerevisiae as well as by the dilution rate in the course of chemostat cultivation and by the temperature of growth on the age structure of a population, i.e. on the proportion of cells at different phases of the cell cycle. Nitrogen, phosphorus and magnesium deficiency delayed the growth of cells in the G1 phase and, if the growth rate was low, at the end of budding. The rise of the growth rate increased the proportion of budding cells. A temperature drop below 23 degrees C delayed the separation of the daughter and mother cells.     

Torsional flexibility of B-DNA as revealed by conformational analysis.

The thermal fluctuations of a regular double helix belonging to the B-family were studied by means of atom-atomic potentials method. The winding angle fluctuation was found to be 2.4 degrees for poly(dA):poly(dT) and 3.0 degrees for poly(dG):poly(dC). The reasonable agreement of these estimations with those obtained experimentally reveals the essential role of the small-amplitude torsional vibrations of atoms in the mechanism of the double helix flexibility. The calculated equilibrium winding angle, tau 0, essentially depends on the degree of neutralization of phosphate groups, being about 35.5 degrees for the full neutralization. The deoxyribose pucker is closely related to the tau angle: while tau proceeds from 30 degrees to 45 degrees the pseudorotation phase angle, P, increases from 126 degrees to 164 degrees. Fluctuations of the angles TL and TW, which specify inclination of the bases to the helix axis, were evaluated to be 5 degrees-10 degrees. Possible correlation between conformational changes in the adjacent nucleotides is discussed.     

On the mechanism of interaction of N-acetylphenylalanyl-tRNAPhe with ribosomes of Escherichia coli: effect of antibiotics and Tp psi pCpGp

The tetranucleotide Tp psi pCpGp acts as a specific inhibitor of the rate of AcPhe-tRNAPhe binding in the ribosomal P site. This effect is observed both in the presence and in the absence of poly(U). In the absence of poly(U) antibiotics tetracycline and puromycin also decrease the rate of AcPhe-tRNAPhe binding. Some inhibition by tetracycline is observed with poly(U). All these inhibitors are known to be ligands of the ribosomal A site, and their influence on the P site binding can be most naturally explained by the suggestion that AcPhe-tRNAPhe enters the ribosome via the A site, forms there an intermediate complex, and spontaneous translocation into the P site follows. In the presence of poly(U) arguments in favour of this hypothesis are much weaker, but the same sequence of events is possible.     

Role of paratypical factors in determining human multiple pregnancy. I. A comparative statistical analysis of the social biology characteristics of the mothers

Twelve social-biological characteristics were investigated in 400 mothers of monodizygotic twins and in 429 women in the control group. The mean age of mothers for dizygotic types of twins was, on the whole, authentically higher than that of the control women. The continuance of the working activity, the character of the work, inclination towards certain food have been reported to influence the manifestation of being a dizygotic twin. In addition to the above mentioned factors, the age of women at the beginning of their sexual life is of importance. Also, a woman's psychological attitude towards the possible pregnancy is reported to influence multiple pregnancy. The percentage of repeated marriages among twins mothers was higher than that in the control group. Conclusions are made on the use of the factors investigated for a probable estimation of manifestation of multiple pregnancy.     

Localization of embryonic aldolase isoenzyme in rat liver cells after a single injection of the carcinogen, 4-dimethylaminoazobenzene, and its noncarcinogenic analog

The localization of a fetal isoenzyme of aldolase (A) in rat liver cells early after a single injection of carcinogen 4-dimethylaminoazobenzene and its noncarcinogenic analog 4-diethylaminoazobenzene has been studied using the immunofluorescent method. Aldolase A was found in the cytoplasm of oval and "transition" cells. These cells appeared in rat liver as a result of treatment with carcinogen and its analog. In mature hepatocytes aldolase A was not found either in intact rat liver, after the treatment with carcinogen or its analog.     

Energy of adhesion of human T cells to adsorption layers of monoclonal antibodies measured by a film trapping technique.

A novel method for studying the interaction of biological cells with interfaces (e.g., adsorption monolayers of antibodies) is developed. The method is called the film trapping technique because the cell is trapped within an aqueous film of equilibrium thickness smaller than the cell diameter. A liquid film of uneven thickness is formed around the trapped cell. When observed in reflected monochromatic light, this film exhibits an interference pattern of concentric bright and dark fringes. From the radii of the fringes one can restore the shape of interfaces and the cell. Furthermore, one can calculate the adhesive energy between the cell membrane and the aqueous film surface (which is covered by a layer of adsorbed proteins and/or specific ligands), as well as the disjoining pressure, representing the force of interaction per unit area of the latter film. The method is applied to two human T cell lines: Jurkat and its T cell receptor negative (TCR-) derivative. The interaction of these cells with monolayers of three different monoclonal antibodies adsorbed at a water-air interface is studied. The results show that the adhesive energy is considerable (above 0.5 mJ/m2) when the adsorption monolayer contains antibodies acting as specific ligands for the receptors expressed on the cell surface. In contrast, the adhesive energy is close to zero in the absence of such a specific ligand-receptor interaction. In principle, the method can be applied to the study of the interaction of a variety of biological cells (B cells, natural killer cells, red blood cells, etc.) with adsorption monolayers of various biologically active molecules. In particular, film trapping provides a tool for the gentle micromanipulation of cells and for monitoring of processes (say the activation of a T lymphocyte) occurring at the single-cell level.