Investigation of the mechanisms for stark broadening and shift of the spectral lines in a nonideal plasma

Abstrac A method for calculating the Stark broadening and shift of the spectral lines was developed based on a combination of the ion plasma model and new theoretical and computational methods for taking the Stark effect into account. Theoretical results are compared with experimental data on the broadening and shift of the spectral lines in a strongly nonideal plasma. __________ Translated from Fizika Plazmy, Vol. 30, No. 10, 2004, pp. 944–947. Original Russian Text Copyright ? 2004 by Denisov, Orlov, Fortov, Kulish, Gryaznov, Mintsev.     

Use of biometric characteristics of major salivary glands as a base line to develop a formula for the quantitative estimation of posttraumatic regeneration of glandular tissue

In experiments conducted on 903 rats, we have studied biometric characteristics of the major salivary glands (parotid, submandibular, and sublingual glands) during ontogenesis. We have calculated the indices of non-directional fluctuation asymmetry for the submandibular and sublingual glands and determined correlation coefficients and coefficients of linear regression between salivary glands, rat body weight, and the weight of the femoral bone (the largest bone in the rat). The strongest correlation was found between the dry weight of the submandibular gland and the rat body weight. Mathematical analysis of the growth of the submandibular gland after sialotomy allowed us to derive a formula for the quantitative estimation of regeneration, taking into account the natural growth of the rat.     

Effect of taurine on the microvessel exchange function and adrenergic response of veins and arteries in the cat skeletal muscle

In cats anesthetized with Uretan and perfused with a constant blood volume, Taurine induced responses of neither arterial nor venous vessels of the skeletal muscle but increased the capillary filtration coefficient without any significant change of the capillary pressure in the skeletal muscle's microvessels. Taurine also increased both the constrictor and the dilatory responses of the arterial and venous vessels. The mechanism of the Taurine effects upon the smooth muscle elements of arteries and veins as well as upon proper mechanisms of capillary pressure control and capillary filtration coefficient, seems to be calcium-dependent.     

Hydration of denatured and molten globule proteins

The hydration of nonnative states is central to protein folding and stability but has been probed mainly by indirect methods. Here we use water 17O relaxation dispersion to monitor directly the internal and external hydration of alpha-lactalbumin, lysozyme, ribonuclease A, apomyoglobin and carbonic anhydrase in native and nonnative states. The results show that nonnative proteins are more structured and less solvent exposed than commonly believed. Molten globule proteins preserve most of the native internal hydration sites and have native-like surface hydration. Proteins denatured by guanidinium chloride are not fully solvent exposed but contain strongly perturbed occluded water. These findings shed new light on hydrophobic stabilization of proteins.     

The kinetics of the reaction between NO and O2 as studied by a novel approach

The kinetics of the reaction between NO and O2 was determined by measuring the time course of the decrease in the concentration of NO with a quench-flow technique. NO and O2 were mixed rapidly and reacted for periods of time varying from 10 to 50 s. A second rapid mixing with a solution containing an excess of deoxyhemoglobin and sodium hydrosulfite trapped free NO as nitrosylhemoglobin and reduced O2. The spectrum of the mixture of deoxy- and nitrosylhemoglobin was recorded within 30 s from the second mixing, before any appreciable dissociation of NO from the protein, by means of a flow-cell mounted on-line with the quench-flow apparatus. The amount of NO not consumed in the auto-oxidation reaction was calculated from the proportion of nitrosylhemoglobin in the mixture. As NO and O2 bind deoxyhemoglobin at comparable rates and NO is oxidized to nitrate by oxyhemoglobin, the ratio of hemoglobin/(NO + O2) had to be optimized to avoid the interference of this oxidation reaction. The kinetics was first and second order with respect to O2 and NO, respectively and third order overall with a rate constant k = 4 x kaq = 4 x 2.23 (+/- 0.26) x 10(6) M-2 s-1 at 20 degrees C, invariant in the pH range 7-9, in agreement with published values obtained by different methodologies.     

Cooperativity in cytochrome P450 3A4: linkages in substrate binding, spin state, uncoupling, and product formation

Understanding the detailed metabolic mechanisms of membrane-associated cytochromes P450 is often hampered by heterogeneity, ill-defined oligomeric state of the enzyme, and variation in the stoichiometry of the functional P450.reductase complexes in various reconstituted systems. Here, we describe the detailed characterization of a functionally homogeneous 1:1 complex of cytochrome P450 3A4 (CYP3A4) and cytochrome P450 reductase solubilized via self-assembly in a nanoscale phospholipid bilayer. CYP3A4 in this complex showed a nearly complete conversion from the low- to high-spin state when saturated with testosterone (TS) and no noticeable modulation due to the presence of cytochrome P450 reductase. Global analysis of equilibrium substrate binding and steady-state NADPH consumption kinetics provided precise resolution of the fractional contributions to turnover of CYP3A4 intermediates with one, two, or three TS molecules bound. The first binding event accelerates NADPH consumption but does not result in significant product formation due to essentially complete uncoupling. Binding of the second substrate molecule is critically important for catalysis, as the product formation rate reaches a maximum value with two TS molecules bound, whereas the third binding event significantly improves the coupling efficiency of redox equivalent usage with no further increase in product formation rate. The resolution of the fractional contributions of binding intermediates of CYP3A4 into experimentally observed overall spin shift and the rates of steady-state NADPH oxidation and product formation provide new detailed insight into the mechanisms of cooperativity and allosteric regulation in this human cytochrome P450.     

The one-electron autoxidation of human cytochrome P450 3A4

Monomeric cytochrome P450 3A4 (CYP3A4), the most prevalent cytochrome P450 in human liver, can simultaneously bind one, two, or three molecules of substrates and effectors. The difference in the functional properties of such binding intermediates gives rise to homotropic and heterotropic cooperative kinetics of this enzyme. To understand the overall kinetic processes operating in CYP3A4, we documented the kinetics of autoxidation of the oxy-ferrous intermediate of CYP3A4 as a function of testosterone concentration. The rate of autoxidation in the presence of testosterone was significantly lower than that observed with no substrate present. Stability of the oxy-ferrous complex in CYP3A4 and the amplitude of the geminate CO rebinding increased significantly as a result of binding of just one testosterone molecule. In contrast, the slow phase in the kinetics of cyanide binding to the ferric CYP3A4 correlated with a shift of the heme iron spin state, which is only caused by the association of a second molecule of testosterone. Our results show that the first substrate binding event prevents the escape of diatomic ligands from the distal heme binding pocket, stabilizes the oxy-ferrous complex, and thus serves as an important modulator of the uncoupling channel in the cytochromes P450.     

Dispersal of the flea Ctenophyllus hirticrus and spreading of plague epizooties in Gorny Altai

Gradual dispersion of an abundant flea species Ctenophyllus hirticrus specific to the Pallas's pika (the main plague carrier), is revealed in the Gorno-Altai natural plague focus on the territory, occupied by two populations of this lagomorph. Spreading of Yersinia pestis in these areas took place a short time later the rise of this ectoparasite's abundance. It is supposed that the colonization of these areas by C. hirticrus was one of the factors determined epizooties spreading within the focus and formation of new sites of stable Y. pestis preservation.     

The diploid genome sequence of an individual human

Presented here is a genome sequence of an individual human. It was produced from ∼32 million random DNA fragments, sequenced by Sanger dideoxy technology and assembled into 4,528 scaffolds, comprising 2,810 million bases (Mb) of contiguous sequence with approximately 7.5-fold coverage for any given region. We developed a modified version of the Celera assembler to facilitate the identification and comparison of alternate alleles within this individual diploid genome. Comparison of this genome and the National Center for Biotechnology Information human reference assembly revealed more than 4.1 million DNA variants, encompassing 12.3 Mb. These variants (of which 1,288,319 were novel) included 3,213,401 single nucleotide polymorphisms (SNPs), 53,823 block substitutions (2–206 bp), 292,102 heterozygous insertion/deletion events (indels)(1–571 bp), 559,473 homozygous indels (1–82,711 bp), 90 inversions, as well as numerous segmental duplications and copy number variation regions. Non-SNP DNA variation accounts for 22% of all events identified in the donor, however they involve 74% of all variant bases. This suggests an important role for non-SNP genetic alterations in defining the diploid genome structure. Moreover, 44% of genes were heterozygous for one or more variants. Using a novel haplotype assembly strategy, we were able to span 1.5 Gb of genome sequence in segments >200 kb, providing further precision to the diploid nature of the genome. These data depict a definitive molecular portrait of a diploid human genome that provides a starting point for future genome comparisons and enables an era of individualized genomic information.