Cation and sequence effects on stability of intermolecular pyrimidine-purine-purine triplex.

A differential effect is found of various bivalent cations (Ba2+, Ca2+, Mg2+, Cd2+, Co2+, Mn2+, Ni2+, Zn2+ and Hg2+) on stability of intermolecular Py-Pu-Pu triplex with different sequence of base triads. Ca2+, Mg2+, Cd2+, Co2+, Mn2+, Ni2+ and Zn2+ do stabilize the d(C)n d(G)n d(G)n triplex whereas Ba2+ and Hg2+ do not. Ba2+, Ca2+, Mg2+ and Hg2+ destabilize the d(TC)n d(GA)n d(AG)n triplex whereas Cd2+, Co2+, Mn2+, Ni2+ and Zn2+ stabilize it. The complexes we observe are rather stable because they do not dissociate during time of gel electrophoresis in the co-migration experiments. Chemical probing experiments with dimethyl sulfate as a probe indicate that an arbitrary homopurine-homopyrimidine sequence forms triplex with corresponding purine oligonucleotide in the presence of Mn2+ or Zn2+, but not Mg2+. In the complex the purine oligonucleotide has antiparallel orientation with respect to the purine strand of the duplex. Specifically, we have shown the formation of the Py-Pu-Pu triplex in a fragment of human papilloma virus HPV-16 in the presence of Mn2+.     

Organometallic flavonoid derivatives as spectroscopic probes

Derivatives of naringenin have been synthesized with organometalcarbonyl reporting groups for IR spectroscopy attached at C-2, C-3′, or C-6, and the products have been tested for the induction of nod gene expression using a Rhizobium leguminosarum strain which contains the Escherichia coli lacZ (β-galactosidase) gene fused to nodABC. Derivatives with an OMe substituent within the reporting group moiety showed residual gene induction activity.     

Synthesis of novel 5-aryl-2-thio-1,3,4-oxadiazoles and the study of their structure-anti-mycobacterial activities

The preparation of novel 5-aryl-2-thio-1,3,4-oxadiazoles 4a-41 and the computer-aided study of their in vitro anti-tubercular activity against Mycobacterium tuberculosis H37Rv (ATCC 27294) are reported. The average accuracy of the electronic-topological method and neural network methods applied to the activity prediction in leave-one-out cross validation is 80%.     

A Reexamination of Correlations of Amino Acids with Particular Secondary Structures

Using the data from Protein Data Bank the correlations of primary and secondary structures of proteins were analyzed. The correlation values of the amino acids and the eight secondary structure types were calculated, where the position of the amino acid and the position in sequence with the particular secondary structure differ at most 25. The diagrams describing these results indicate that correlations are significant at distances between −9 and 10. The results show that the substituents on Cβ or Cγ atoms of amino acid play major role in their preference for particular secondary structure at the same position in the sequence, while the polarity of amino acid has significant influence on α-helices and strands at some distance in the sequence. The diagrams corresponding to polar amino acids are noticeably asymmetric. The diagrams point out the exchangeability of residues in the proteins; the amino acids with similar diagrams have similar local folding requirements. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Features of the summer distribution of birds in Central Altai

The results of bird route surveys over the territory of the Central Altai during the summer seasons in 1968–2001 were analyzed. Hierarchic classifications of species by the similarities of residence and distribution were compiled on the basis of a multivariate factor analysis. The basic environmental factors that determine the non-uniformity of bird distribution were revealed. It was demonstrated that the classifications of bird species in the central Altai province and in the Altai physiogeographic mountainous region are, in general, similar in structure. The provincial specificity of distribution intensifies with an increase in the altitude of the territory.     

The crucial role of roots in increased cadmium-tolerance and Cd-accumulation in the pea mutant <Emphasis Type="Italic">SGECd</Emphasis><Superscript><Emphasis Type="Italic">t</Emphasis></Superscript>

Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECd^t (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECd^t/SGECd^t, SGE/SGECd^t, and SGECd^t/SGE. They were grown in hydroponics in the presence of 1 μM CdCl₂ for 30 d. The SGE and SGECd^t scions on the SGECd^t rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECd^t rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECd^t root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECd^t in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECd^t mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.     

Influence of the intensity of oxygen mass transfer on the biosynthesis of amphotericin B

Influence of oxygen mass transfer intensity characterized by the rate of oxygen dissolution (S) and the agitation rate (n), as well as influence of dissolved oxygen concentration on the process of amphotericin B biosynthesis was studied. It was shown that S = 40 and 110 mg/l. min and n = 450 and 800 min-1 were respectively the lower and the upper levels of the optimal conditions by oxygen mass transfer during amphotericin B biosynthesis. When biosynthesis of amphotericin B was conducted under conditions of the optimal oxygen mass transfer, the dissolved oxygen concentration of about 12 to 15 per cent of the saturation level was critical for the culture respiration. Inhibition of the culture respiration and antibiotic synthesis was induced under conditions of increased oxygen mass transfer intensity (S greater than 110 mg/l. min and n greater than 800 min-1) by high intensity mechanical agitation of the fermentation broth. Under conditions of decreased oxygen mass transfer (S less than 40 mg/l. min and n = less than 450 min-1) it was induced by insufficient supply of oxygen to the culture. On the basis of the results it was shown possible to control the aeration and agitation conditions by the rate of oxygen uptake and dissolved oxygen concentration. The data should be considered in optimization of aeration and agitation conditions in biosynthesis of amphotericin B in large fermenters.     

Effect of carbon and nitrogen source additions on the development of a productive strain of P. nigricans Thom and on the level of adenylates in its mycelium]

Growth of the cultured strain og P. nigricans and dynamics of the adenylate levels in its mycelium on mineral media with 2 per cent of glucose were studied in relation to the means and time of addition of glucose, NaNO3 or their mixture to the medium. It was shown that the maximum yield of the mycelium could be obtained with addition of glucose once at the moment of inoculation. The mixture of glucose with NaNO3 provided even higher yields of the biomass but only with its fractional addition. Introduction of additional amounts of NaNO3 at the moment of inoculation and during the growth phase (5 days) inhibited the subsequent development of the culture providing stable levels of ATP and ADP, while introduction of NaNO3 on the 7th day stimulated the culture growth and the antibiotic yield. The use of NaNO3 in the mixture with glucose eliminated inhibition and increased the ratio of ATP to ADP and the antibiotic yield.     

Fluorescence analysis study of the lability of biomembranes and their components. III. Kinetics of complex formation between bovine serum albumin molecules and higher saturated fatty acids]

Kinetic peculiarities of the sorption of natural limited fatty acids on the molecules of bovine serum albumine (BSA) were studied by investigating fluorescent parameters of ionic (1-anilinonaphtalin-8-sulphonate-ANS) and neutral (N-phenyl-1-naphtylamine-PNA) probes. The following regularities were found: 1. The parameters which characterize the microsurroundings of both probes (quantum yield of fluorescence, the binding constant) did not change significantly during the sorption of the fattyn acids (laurinic, palmitinic and methyl ether of the stearinic acid). An exponential character of BSA fluorescent titration with fatty acids points to a competitive character of the relationship dye -- fatty acid for the binding sites in hydrophobic sacks of BSA. 2. The study of the character of the effect of solution ionic strength on the sorption of fatty acids showed that along with hydrophobic interactions the electrostatic interaction between carboxyl residues of fatty acids and charged protein groups also significantly contributed to this process. 3. Temperature relationship of AMS and PNA fluorescence intensity in the complex BSA -- laurinic acid correlates well with temperature relationship obtained from a pure protein system.