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Biomedical subjects

V V Filimonov

Publications and source records attributed to V V Filimonov.

At least 37 records · Page 2Linked to original sources
PubMed1986

Cooperativity of the alpha beta-protomer structure in Na+,K+-ATPase functioning. A scanning microcalorimetry study.

Heat denaturation of the free and ligand-bound forms of purified Na+,K+-ATPase from pig kidney is studied with the scanning microcalorimetry technique. A single two-state transition is observed during denaturation of the free enzyme, the molar concentration of the cooperatively melting units being equal to the concentration of alpha beta-protomers (Mr approximately equal to 140 000). Upon interaction of the enzyme with phosphate, Mg2+, and strophanthidin, but not with Na+, the cooperativity of the protomer unfolding is lost, and the protein stabilization enthalpy becomes approximately equal to 230 kJ/mol higher. The data suggest that in a functionally active enzyme form, the alpha beta-protomers possess a rigid structure with tight association of their subunits and domains, this structural rigidity is essential for the Na+,K+-ATPase functioning and there is a unique non-active conformation of the enzyme which may play an important role in its in vivo regulation.

Animals↗
PubMed1985

Conserved unpaired adenine residues are important for ordered structures of 5S ribosomal RNA. An infrared study of the secondary and tertiary structure of Thermus thermophilus 5S rRNA.

An improved set of infrared calibration spectra for the determination of G X C and A X U base pairs leads to 32 +/- 3 G X C (+ G X U) and 4 +/- 1 A X U base pairs for Thermus thermophilus 5S RNA in the presence and absence of Mg2+. These results give further support for the consensus secondary structure of 5S RNA recently proposed by several groups. T. thermophilus 5S RNA shows, in the presence of Mg2+, a distinct two-step thermal melting of its ordered structure. Based on new data about the stacking dependence of infrared intensities of unpaired ribonucleotides the spectral changes of the low-temperature transition should be explained by melting of stacked arrangements of unpaired bases and/or non-standard base pairs. Striking is the reduction in A stacking, which is not related to the melting of A X U base pairs, indicating the importance of the mostly conserved unpaired adenines for the Mg2+ stabilized higher-order structures especially within internal loops of 5S RNA.

Adenine↗
PubMed1981

A study of the structure of fibronectin.

The structure of a fibronectin molecule has been studied by circular dichroism, infrared spectroscopy, scanning microcalorimetry and electron microscopy. It has been shown that the secondary structure of fibronectin is formed exclusively by the antiparallel beta-form -- 35%; the fibronectin molecule consists of several domains; the protein has a compact structure, the length of the molecule is 15.5 +/- 1.3 nm, the width is 8.8 +/- 1.7 nm, the axial ratio is approximately 2:1.1.

Calorimetry↗
PubMed1979

Cleavage of elongation factor G into compact domains.

A limited trypsinolysis of native elongation factor G results in the formation of two large fragments resistant to further proteolysis. The fragments were isolated in homogeneous state in conditions when their native structure is retained. According to circular dichroism and scanning calorimetry data the formed fragments retain the stability and compact structure that they had in the whole protein.

Calorimetry, Differential Scanning↗
PubMed1978

A calorimetric investigation of melting of tRNAAsp from brewer's yeast.

The thermodynamics of tRNAAsp unfolding was studied using a precision scanning microcalorimeter. The overall heat of melting was found to be about 55 J/g irrespective of the ionic strength and magnesium activity. The analysis of complex melting curves obtained in the absence of Mg2+ reveals four successive two-state transitions. The first was identified as the cooperative melting of the tertiary structure and the D region and the others as the melting of individual helical arms.

Aspartic Acid↗
PubMed1978

Thermodynamic investigations of proteins. IV. Calcium binding protein parvalbumin.

The conformational transitions of calcium binding protein parvalbumin III from carp muscle were studied by scanning calorimetry, potentiometric titration and isothermal calorimetric titration. Changes of Gibbs energy, enthalpy and partial heat capacity were determined. The removal of calcium ions by EDTA is accompanied by 1) a heat absorption of 75 +/- 10 kJ per mole of the protein, 2) a decrease in the Gibbs energy of protein structure stabilisation of about 42 kJ mol-1 and 3) a decrease in thermostability by more than 50 K. The protonation of the acidic groups leads to a loss of calcium followed by denaturation, while the pH of the transition strongly depends on calcium activity. The enthalpy and heat capacity changes at denaturation are comparable with the values observed for other compact globular proteins.

Animals↗
PubMed1977

Calorimetric studies on melting of tRNA Phe (yeast).

The heat effects involved in thermal unfolding of tRNAPhe from yeast have been determined in various buffer systems by direct differential scanning calorimetry. Perfect reversibility of the melting process has been demonstrated for measurements in the absence of Mg2+ ions. The overall molar transition enthalpy, delta Ht = 298 +/- 15 kcal mol-1 (1247 +/- 63 kJ mol-1), has been shown to be independent of the NaCl concentration and the nature of the buffers used in this study. Delta Ht is identical in the presence and in the absence of Mg2+ ions within the margin of experimental error. This experimental result implies a vanishing or very small heat capacity change to be associated with melting. Decomposition of the calorimetrically determined complex transition curves, on the assumption that the experimental melting profile represents the sum of independent two-state transitions, results in five transitions which have been assigned to melting of different structural domains of the tRNA.

Calorimetry↗
PubMed1976

Calorimetric investigations on thermal stability of tRNAIle (yeast) and tRNASer (yeast).

Variation with temperature of the partial heat capacities of tRNAIle (yeast) and tRNASer (yeast) has been determined in two buffers at various salt conditions by scanning microcalorimetry. The overall molar transition enthalpy, deltaHt = 320 +/- 20 kcal mol-1 (1339 +/- 84 kJ mol-1) is identical for the two tRNA species within the limits of experimental error. deltaHt does not show any dependence on the nature of the buffer, nor does it vary on addition of 1 mM MgCl2 or 150 mM NaCl. Thermal unfolding of the native structure to the random coil cannot adequately be described by a two-state, concerted transition under the experimental conditions applied in this study, but exhibits a multistep mechanism characterized by sequential unfolding of separable cooperative domains.

Calorimetry↗
PubMedDate not supplied

[Calorimetric study of the polyG-polyC complex].

Heat effects of polyG-polyC melting in neutral aqueous solutions have been measured using differential scanning microcalorimeter with an extended temperature range. The limiting value of melting enthalpy is 53 +/- 4 kJ per mole of base pairs and melting temperature dependence on the sodium concentration can be expressed by the empiric relation Tm = 13.2 log(Na+) + 420 K.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

[Thermodynamics of stacking-interactions in polyA and polyC].

Thermodynamics of stacking-contacts breakdown in single chains of polyA and polyC was studied by scanning microcalorimetry. Temperature relationships of partial heat capacities of polymers within 5 divided by 130 degrees C were measured for the first time and contributions to heat capacity of corresponding nucleosidemonophosphates were taken into account. As a result of the data analysis on the basis of Ising linear model entalpies and entropies of stacking-interactions were determined, as well as the values of the cooperativity factor, which in the scale of mole contacts equaled: delta Hm = 14.5 +/- 8 kJ/mole, delta Sm = 46.3 +/- 3 J/K.mole, delta Cp,m = 110 J/K.mole, delta = 0.18 and delta Hm = 13.8 +/- 0.8 kJ/mole, delta Sm = 41.6 +/- 3 J/K.mole, delta Cp,m = 80 J/K.mole, sigma = 0.13 for polyA and polyC respectively in solution with 0.12 M NaCl and pH 7.0.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

[A thermodynamic approach to the study of the structural organization of 5S RNA from Escherichia coli ribosomes. 1. Analysis of scanned microcalorimetry data].

Melting of the 5S RNA from E. coli ribosomes has been studied by differential scanning microcalorimetry. It has been shown that: (1) heat capacity temperature functions of the "native" and A-forms of the 5S RNA coincide in all the conditions studied; (2) heat capacity temperature functions of the B-form of the 5S RNA differ in a low-temperature region from the heat capacity functions of the A-form, the complete melting enthalpy of the A-form being higher by 125 +/- 30 kJ X M-1; (3) the teritary structure of the 5S RNA does not unite secondary structure elements into a single cooperative unit even in the presence of 10 mM MgCl2; (4) the results of the analysis of the "equilibrium" part of heat capacity temperature functions and the A- and B-forms of the 5S RNA can be explained by melting of four cooperative blocks which interact with each other.

Calorimetry, Differential Scanning↗