Search PubMed⌕ Search

Biomedical subjects

V N Orlov

Publications and source records attributed to V N Orlov.

At least 19 recordsLinked to original sources
PubMed1999

Two-state irreversible thermal denaturation of muscle creatine kinase.

Thermal denaturation of creatine kinase from rabbit skeletal muscle has been studied by differential scanning calorimetry. The excess heat capacity vs. temperature profiles were independent of protein concentration, but strongly temperature scanning rate-dependent. It has been shown that thermal denaturation of creatine kinase satisfies the previously proposed validity criteria for the two-state irreversible model [Kurganov et al., Biophys. Chem.70 (1997) 125]. The energy activation value has been calculated to be 461.0 +/- 0.7 kJ/mol.

Animals↗
PubMed1999

[Genetic differentiation of voles of the tribe Arvicolini (Cricetidae, Rodentia) using taxonprint analysis and polymerase chain reaction with random primers].

The variability of the genomes of ten vole species was analyzed by means of taxonomic DNA fingerprinting and polymerase chain reaction using random primers (RAPD-PCR). The dendrograms of genetic similarity between the representatives of the tribe Arvicolinae (Gray, 1821) were constructed, based on the data obtained by means of both methods. The topology of the genetic similarity dendrogram that is based on the RAPD-PCR data generally correlates with the genetic distances estimated from biochemical and karyological data. The results did not confirm the genus status of Terricola. On the other hand, the data from taxonprint analysis suggest the recognition of Lasiopodomys as a separate genus.

Animals↗
PubMed1998

Thermally induced chain exchange of smooth muscle tropomyosin dimers studied by differential scanning calorimetry.

The thermal unfolding of duck gizzard tropomyosin dimers, alphabeta, alphaalpha, and betabeta, and of a 1:1 mixture of alphaalpha and betabeta homodimers was studied by differential scanning calorimetry (DSC). Both alphaalpha and betabeta homodimers demonstrated a broad thermal transition with maxima at 37.4 degrees C and 44.6 degrees C, respectively. However, a sharp cooperative thermal transition at 41.5 degrees C characteristic for alphabeta heterodimer appeared on the thermogram of the mixture of homodimers. The appearance of this transition was prevented by disulfide cross-linking of polypeptide chains in the homodimers. Thus, DSC studies clearly demonstrate formation of tropomyosin heterodimers during heating of the mixture of homodimers and in agreement with earlier published reports indicate thermally induced chain exchange between tropomyosin dimers.

Animals↗
PubMed1998

A comparative differential scanning calorimetric study of tobacco mosaic virus and of its coat protein ts mutant.

The differential scanning calorimetry (DSC) 'melting curves' for virions and coat proteins (CP) of wild-type tobacco mosaic virus (strain U1) and for its CP ts mutant ts21-66 were measured. Strain U1 and ts21-66 mutant (two amino acid substitutions in CP: 121 --> T and D66 --> G) differ in the type of symptoms they induce on some host plants. It was observed that CP subunits of both U1 and ts21-66 at pH 8.0, in the form of small (3-4S) aggregates, possess much lower thermal stability than in the virions. Assembly into the virus particles resulted in a DSC melting temperature increase from 41 to 72 degrees C for U1 and from 38 to 72 degrees C for ts21-66 CP. In the RNA-free helical virus-like protein assemblies U1 and ts21-66 CP subunits had a thermal stability intermediate between those in 3-4S aggregates and in the virions. ts21-66 helical protein displayed a somewhat lower thermal stability than U1.

Amino Acid Substitution↗
PubMed1998

Irreversible thermal denaturation of uridine phosphorylase from Escherichia coli K-12.

Thermal denaturation of uridine phosphorylase from Escherichia coli K-12 has been studied by differential scanning calorimetry. The excess heat capacity vs. temperature profiles were obtained at temperature scanning rates of 0.25, 0.5, and 1 K/min. These profiles were analysed using three models of irreversible denaturation which are approximations to the whole Lumry-Eyring model, namely, the one-step model of irreversible denaturation, the Lumry-Eyring model with the fast equilibrating first step, and the model involving two consecutive irreversible steps. In terms of statistics the latter model describes the kinetics of thermal denaturation of uridine phosphorylase more satisfactorily than the two other models. The values of energy activation for the first and second steps calculated for the model involving two consecutive irreversible steps are the following: Ea,1 = 609.3 +/- 1.8 kJ/mol and Ea,2 = 446.8 +/- 3.2 kJ/mol.

Calorimetry, Differential Scanning↗
PubMed1998

Differential scanning calorimetric studies on myosin and actin.

This review is concerned with the application of the method of differential scanning calorimetry (DSC) to structural and functional studies of myosin and actin--the main two proteins of muscles and many other systems of biological motility. The domain organization of these proteins as revealed by DSC is considered. Data are presented on the conformational changes which occur in the myosin head and in F-actin due to the formation of the ternary complexes with ADP and Pi analogs (such as orthovanadate, beryllium fluoride, or aluminum fluoride). Recent data on the application of DSC to studies on the interaction of F-actin with myosin heads and with tropomyosin are also considered. It is concluded that DSC offers a new and promising approach to probe the structural changes which occur in the myosin head and in F-actin during ATP hydrolysis and due to interaction of these proteins with each other.

Actins↗
PubMed1996

Differential scanning calorimetric study of the complexes of modified myosin subfragment 1 with ADP and vanadate or beryllium fluoride.

The effects of various modifications of rabbit skeletal myosin subfragment 1 on the thermal denaturation of subfragment 1 in ternary complexes with Mg-ADP and orthovanadate (V1) or beryllium fluoride (BeFx) have been studied by differential scanning calorimetry. It has been shown that specific modifications of SH1 group of Cys-707 by different sulfhydryl reagents, trinitrophenylation of Lys-83, and reductive methylation of lysine residues promote the decomposition of the S1.ADP.Vi complex and change the character of structural transitions of the subfragment 1 molecule induced by the formation of this complex, but they have much less or no influence on subfragment 1 thermal stability in the S1.ADP.BeFx complex. Thus, the differential scanning calorimetric studies on modified subfragment 1 preparations reveal a significant difference between S1.ADP.Vi and S1.ADP.BeFx complexes. It is suggested that S1.ADP.Vi and S1.ADP.BeFx complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1**.ADP.Pi and S1*.ATP, respectively. It is also proposed that during formation of the S1.ADP.Vi complex the region containing both Cys-707 and Lys-83 plays an important role in the spread of conformational changes from the active site of subfragment 1 ATPase throughout the structure of the entire subfragment 1 molecule. In such a case, the effects of reductive methylation of lysine residues on the subfragment 1 structure in the S1.ADP.Vi complex are related to the modification of Lys-83.

Adenosine Diphosphate↗
PubMed1996

Interaction of myosin subfragment 1 with F-actin studied by differential scanning calorimetry.

The thermal unfolding of the myosin subfragment 1 (S1) and of filamentous actin (F-actin) in their strong complex obtained in the presence of ADP was studied by differential scanning calorimetry (DSC). It is shown that in the acto-S1 complexes S1 and F-actin melt separately, and thermal transitions of each protein can be easily followed. Interaction of S1 with F-actin significantly increases S1 thermal stability and also affects the thermal stability of F-actin. Although S1 unfolds at much lower temperature than F-actin, the molecules of S1 remain bound to F-actin even after full denaturation. Under these conditions S1 may induce cross-linking between actin filaments. It is concluded that DSC studies on the acto-S1 complexes offer a new and promising approach to investigate the structural changes which occur in the myosin head and in F-actin due to their interaction.

Actins↗
PubMed1994

Combination of the electrogenic ionophores, valinomycin and CCCP, can lead to non-electrogenic K+/H+ exchange on bilayer lipid membranes.

The method of pH shift measuring by means of a pH microelectrode was applied to measure hydrogen ion fluxes across a planar bilayer lipid membrane (BLM) in the presence of the potassium ion ionophore, valinomycin, and a protonophore, carbonylcyanide m-chlorophenylhydrazone (CCCP), under conditions of the voltage clamp. The voltage dependence of the flux was determined to be in the range of +/- 150 mV under the conditions of both symmetrical KCl as well as a KCl gradient across the BLM. Surprisingly, at a clamped zero voltage on BLM a significant hydrogen ion flux was observed in the presence of a KCL gradient and both valinomycin and CCCP. This finding was interpreted as a result of induction of non-electrogenic K+/H+ exchange in the presence of valinomycin and CCCP, presumably through the formation of electrically neutral complexes of these two ionophores and K+ (H+) ions: valinomycin-K(+)-CCCP- and/or possibly valinomycin-CCCP(-)-H+.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1994

[Population-genetic variability of the house mouse Mus musculus L. 1758 S. stricto from the western, central, and southeastern area of species range].

Allozyme variation in nine populations of the house mouse Mus musculus L. s. str. was examined. Twenty-five out of 34 analyzed loci were shown to be polymorphic. Estimates of genetic variation were obtained for separate populations and for population groups classified according to their habitat. Populations from Moldova and Tadzhikistan displayed the lowest and highest amounts of allozyme variation, respectively. Variation in town populations was significantly greater than in rural ones. This can be explained by active human-induced migration of mice into towns. All Central Asian populations showed high levels of genic diversity, which is presumably related to their proximity to ancient centers of mice expansion. Allelic distributions in the populations were analyzed.

Animals↗
PubMed1994

[Allozyme variability of the European bean Castor fiber 1758 (Castoridae, Rodentia) from the Voronezh State Nature Reserve].

Electrophoretic methods were used to study protein products of 32 gene loci in the blood of European and Canadian beavers held in captivity at the Voronezh State Nature Reserve. In the studied samples, the levels of polymorphism and average heterozygosity exceeded the average values of corresponding indices determined for beavers that inhabit temperate zones. To what extent the studied samples represent the state of the gene pool of parental populations is discussed. A comparison between allozyme spectra of samples of European and Canadian beavers revealed many coinciding polymorphic loci, on the one hand, and pronounced genetic divergence of these species, on the other.

Animals↗
PubMed1993

[Behavior of pachytene chromosomes in male mice heterozygotic for various translocations (Rb(8,17), T(16,17)43H)].

The electron microscopic analysis of synaptonemal complexes of the Robertsonian translocation heterozygotes (Rb/T) and heterozygotes of the reciprocal translocation (Rb(8, 17)/T(16, 17) 43H revealed three types of translocation configurations (TC). The observed TC were subdivided into three types according to the manner of synapsis: 1) full synapsis of homologues forming trivalent with interstitial centromere in 15%; 2) the centromeric asynapsis (8 and 17-16 chromosomes forming trivalent with the extension region of asynapsis and breakpoint of the reciprocal translocation on chromosome 17 in 70%; 3) centromeric asynapsis (only single chromosome 17-16 of trivalent, when the break point of reciprocal translocation and the absence of centromeric asynapsis of another chromosome 8 formed trivalent in 15%). The frequency of association between trivalents and the XY bivalents is 20% and close proximity is 15% for heterozygotes Rb/T. Which are fertile, while in the sterile heterozygotes Rb(8, 17)/T(16, 17) 43H it is 45% for association and 15% close proximity (total 60%). These data show the significant differences in the contact of translocation configurations with the XY bivalents of fertile heterozygotes, in comparison with the sterile. Thus, it is shown that the chromosome pairing of fertile and sterile mice is clearly distinguished.

Animals↗