The role of sensitive bacteria in determining the count of phage negative colonies on solid growth media

The purpose of the work was to study how the number of phage negative colonies on a solid growth medium depended on the concentration of a sensitive bacterial strain. For the system of phage lambda and a sensitive E. coli cell, the number of negative colonies was maximal at a concentration of ca. 4 X 10(8) cells/ml.     

New developments in the synthesis of phosphopolyprenols and their glycosyl esters.

Efficient methods were developed in our group in recent years for chemical synthesis of polyprenyl phosphates, polyprenyl monophosphate sugars, and polyprenyl diphosphate sugars, which were known to serve as important intermediates in biosynthesis of complex carbohydrates. A simple procedure was developed involving the phosphorylation of aliphatic alcohols with tetra-n-butylammonium dihydrogen phosphate and trichloroacetonitrile. Monophosphates of various natural and modified dolichols and polyprenols, as well as the derivatives of retinol, cholesterol, and nonacosanol, were prepared in high yields. First syntheses of dolichyl thiophosphate and dolichyl hydrogen phosphonate were developed, and these derivatives were of interest as analogs of dolichyl phosphate. Polyprenyl monophosphate sugars, including derivatives of alpha- and beta-anomers of D-glucopyranose, D-galactopyranose, D-mannopyranose, and 2-acetamido-2-deoxy-D-glucopyranose, were obtained smoothly from moraprenyl trichloroacetimidate and acylated glycosyl phosphates after deprotection. A method for the synthesis of polyprenyl diphosphate sugars from polyprenyl phosphoroimidazolidate and unprotected glycosyl phosphates was shown to be applicable for a wide range of the monosaccharide derivatives including hexoses, deoxyhexoses, 2-acetamido-2-deoxyhexoses, and uronic acids. A series of the oligosaccharide derivatives was also prepared by this method.     

Phorbol ester modulation of integrin-mediated cell adhesion: a postreceptor event

Chinese hamster ovary (CHO) suspension culture cells adhere readily to substrata coated with extracellular matrix proteins such as fibronectin, vitronectin, or laminin. In the case of fibronectin, it is known that adhesion is mediated by an integrin-type, cell surface fibronectin receptor (FnR). We demonstrate here that treatment of CHO cells with submicromolar concentrations of phorbol ester produces a remarkable increase in the ability of these cells to adhere to fibronectin. Both the rate of adhesion and the efficiency of adhesion are enhanced about four- to fivefold. Further, phorbol ester treatment renders the fibronectin-mediated adhesion process less sensitive to inhibitors, including GRGDSP peptide and PB1, a monoclonal anti-FnR antibody. By contrast, nonspecific adhesion processes, for example cell attachment to substrata coated with polylysine or concanavalin A, are not affected by phorbol ester treatment. Thus integrin-mediated adhesion is modulated by phorbol esters, but nonspecific adhesion is not. Neither the number of cell surface FnRs nor the receptor affinity, as measured by 125I-fibronectin and 125I-anti-FnR antibody binding, is altered by phorbol ester treatment. Thus, the effect of phorbol ester on cell adhesion seems to occur at a step subsequent to initial ligand-receptor binding events. Since phorbol ester is a potent activator of protein kinase C, we examined phosphorylation patterns in control and phorbol-treated cells. In immunoprecipitates of lysates from suspension culture cells, there was no evidence of phorbol ester-stimulated phosphorylation of FnR or of talin, a protein thought to interact with FnR. These results suggest that phorbol ester effects on fibronectin-dependent adhesion are not due to phosphorylation of the FnR itself but rather may be due to postreceptor events, possibly the phosphorylation of cytoskeletal proteins involved in integrin-mediated adhesion.     

Sensitivity of biological objects to the effects of the geomagnetic field]

It is shown on the basis of calculations of energy sublevels of the hyperfine structure that the effect of the geomagnetic field upon the impurity atoms in the volume of living cells should be considered in relation to the value of geomagnetic field induction pulses delta B. When delta B > or = 10 pT and the dielectric constant epsilon > or = 10, magnetodipole transitions between sublevels of the hyperfine structure within one term are possible in impurity atoms in their 2P-state. During magnetic storms with delta B > or = 100 nT magnetodipole or magnetoquadrupole forced transitions from 2P1/2 and 2P3/2 states to 2S1/2 metastable state are possible in the resonant zones formed by intersection of hyperfine energy sublevels of the corresponding excited levels.     

Selective modulation of band 4.1 binding to erythrocyte membranes by protein kinase C

We have studied the effects of band 4.1 phosphorylation on its association with red cell inside-out vesicles stripped of all peripheral proteins. Band 4.1 bound to these vesicles in a saturable manner, and binding was characterized by a linear Scatchard plot with an apparent Kd of 1-2 x 10(-7) M. Phosphorylation of band 4.1 by purified protein kinase C reduced its ability to bind to membranes, resulting in a reduction in the apparent binding capacity of the membrane by 60-70% but little or no change in the apparent Kd of binding. By contrast, phosphorylation of band 4.1 by cAMP-dependent kinase had no effect on membrane binding. Digestion of the stripped inside-out vesicles with trypsin cleaved 100% of the cytoplasmic domain of band 3 but had little or no effect on glycophorin. Binding of band 4.1 to these digested vesicles was reduced by 70%. Phosphorylation of band 4.1 by protein kinase C had no effect on its binding to the digested vesicles, suggesting that the cytoplasmic domain of band 3 contained the phosphorylation-sensitive binding sites. This was confirmed by direct measurement of band 4.1 binding to the purified cytoplasmic domain of band 3. Phosphorylation of band 4.1 by protein kinase C reduced its binding to the purified 43-kDa domain by as much as 90%, while phosphorylation by cAMP-dependent kinase was without effect. These results show a selective effect of protein kinase C phosphorylation on the binding of band 4.1 to one of its membrane receptors, band 3, and suggest a mechanism whereby one of the key red cell-skeletal membrane associations may be modulated.     

The effect of camphor on bacterial bioluminescence

Summary The inhibitory effect of camphor on bioluminescence of both bacteria and bacterial luciferase has been examined. The camphor has been shown to be a substrate of cytochrome P-450 of the luminous bacteria Photobacterium fischeri. The inhibition of the luminescence reaction provided evidence for the competitive nature of the interaction of camphor and aliphatic aldehyde at the binding site for luciferase. Camphor is also supposed to interact with P-450. The findings indicate that the hydroxylation process of camphor affects the kinetics of the luminescence.     

A Theoretical Study of the cis-syn Pyrimidine Dimers in the Gas Phase and Water Cluster and a Tautomer-Bypass Mechanism for the Origin of UV-induced Mutations

Abstract

A quantum mechanical study of all cis-syn cyclobutane pyrimidine photodimers including the normal and rare tautomeric forms of bases has been performed using the ab initio method at HF/6–31G(d,p), MP2(fc)//HF/6–31G(d,p) and MP2(fc)/6–31G(d,p) levels. A puckering angle of the cyclobutyl ring and twist angle of pyrimidine rings with respect to each other is well described by these calculations. It is predicted that in the gas phase all photodimers containing the rare imino form of cytosine are more stable than those containing its normal form. The Monte Carlo simulations show that the dimer containing the imino form of cytosine is more stabilized by water cluster than that containing its amino forms. The possible biological significance stems from the fact that the cytosine in the dimer directs the incorporation of adenine in the complementary strand during replicative bypass. Data obtained point to the cytosine tautomerism as a possible mechanism for the origin of UV-induced mutation.     

96 Study of the stacking of DNA homoassociates by the extended cluster approach

Metropolis Monte Carlo method based on the extended cluster approach (Danilov, Dailidonis, van Mourik, & Fruchtl, 2011a, 2011b; Dailidonis, Danilov, Früchtl, & van Mourik, 2011) is used to investigate adenine–adenine (AA), guanine–guanine (GG), thymine–thymine (TT), and cytosine–cytosine (CC) homoassociates in a cluster consisting of 400 water molecules. The starting structures taken were AA N(7) amino symmetric, TT N(3) – O(4) symmetric, GG N(1) – O(6) symmetric, and CC N(3) amino symmetric base pairs. A water spherical cluster with the density of water at room temperature and a radius sphere equal 13.9 Å was used, which corresponds to the most difficult conditions for the formation of stacks (see Abraham, 1982). In spite of such initial conditions, it is shown that during the simulation, each base pair is transformed into a more favorable stacked configuration. The results obtained allow to observe the whole process of convergence for the first time (for more information, visit the Website http://biophys.in.ua/).     

Genetic diversity of wild reindeer <Emphasis Type="Italic">Rangifer tarandus</Emphasis> L. from the eastern part of the Kola Peninsula: Polymorphism of the mtDNA control region

Based on the results of the analysis of nucleotide sequence polymorphism in the hypervariable fragment (left domain) of the mtDNA control region (D loop), the genetic diversity of wild reindeer from the eastern part of the Kola Peninsula (Murmansk oblast, Terskii region) was studied. Low values of the genetic diversity indices for Eurasian wild reindeer were detected. The effect of domestic reindeer breeding on the development of genetic diversity of the wild reindeer population in the studied region (indicating a low degree of hybridization of domesticated and wild reindeer) was estimated.