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Biomedical subjects

I A Bolotina

Publications and source records attributed to I A Bolotina.

At least 19 recordsLinked to original sources
PubMed1991

The number of cooperative regions (energetic domains) in a pepsin molecule depends on the pH of the medium.

The technique of scanning microcalorimetry was used to study the effect exerted by ethanol and by the pH of the medium on the number and size of cooperative regions in a pepsin molecule. Ethanol addition lowered the temperature of protein denaturation, but did not change the number of energetic domains. The number of thermodynamic cooperative units (determined as a delta Hcal to delta Heff ratio) was reduced from four to two when the pH changed from 6.7 to 2.0. As was demonstrated using the CD technique, this process involved no changes either in the secondary structure or in the local surroundings of aromatic amino acids. Therefore, variations in the cooperative properties of a pepsin globule at different pH values are associated with the electrostatic interactions of individual parts of the molecule.

Animals↗
PubMed1990

[A peptide, containing the universal antigenic determinant of tryptophanyl-tRNA-synthetase].

Among clostripain hydrolysate peptides of beef pancreas tryptophanyl-tRNA synthetase the peptide Ile-Ser-Phe-Pro-Ala-Ile-Asn-Gln-Phe-Ala-Ala-Pro-Ser-Gln-Phe-Ser-Ile-Arg was revealed which contains the continuous antigenic determinant for monoclonal antibody Am1. This antibody specifically cross-reacts with tryptophanyl-tRNA synthetases of procaryotes, eucaryotes and archebacteriae. The synthetic peptide with identical amino acid sequence plus N-terminal Arg residue (S-peptide), being immobilized on enzyme immunoassay (EIA) microtitration plate, also binds with Am1. Am1 affinity constant (M-1) measured by non-competitive EIA was (3.0 +/- 0.3).10(7) for S peptide and (1.4 +/- 0.3).10(9) for the native enzyme. The sequence of immunoreactive peptide adopts with high probability the secondary structure including beta-turn(s) and antiparallel beta-sheet composed of inverted repeats. At the same time, the analysis of circular dichroism spectrum (in the far UV) of the peptide dissolved in water comes closest to 16% beta-turn and only 8% beta-sheet. The binding of Am1 with peptide was not observed in aqueous solution.

Amino Acid Sequence↗
PubMed1985

Compact state of a protein molecule with pronounced small-scale mobility: bovine alpha-lactalbumin.

We describe a novel physical state of a protein molecule which is nearly as compact as the native state and has pronounced secondary structure, but differs from the native state by the large increase of thermal fluctuations (in particular, by the large mobility of side groups). This state has been characterized in detail for the acid form of bovine alpha-lactalbumin as a result of the study of physical properties of this state by a large variety of different methods (hydrodynamics, diffuse X-ray scattering, circular dichroism and infrared spectra, polarization of the luminescence, proton magnetic resonance, deuterium exchange and microcalorimetry). It has been shown that bovine alpha-lactalbumin can be transformed into a similar state by thermal denaturation. This process is thermodynamically two state (i.e. all-or-none transition), which means that this state differs from the native one by a phase transition of the first order.

Animals↗
PubMed1984

'Molten-globule' state accumulates in carbonic anhydrase folding.

Kinetics of folding and unfolding of bovine carbonic anhydrase B were monitored by circular dichroism, viscometry and esterase activity. It was shown that kinetic intermediate states accumulating in folding process reveal a native-like compactness and secondary structure but have a symmetrized average environment of aromatic side groups and no esterase activity. These properties allow one to consider these intermediate states as the 'molten-globule' state of a protein molecule previously described by us for several equilibrium forms of bovine and human alpha-lactalbumins and bovine carbonic anhydrase B.

Animals↗
PubMed1983

Studies of the structure of bacteriophage lambda cro protein in solution. Analysis of the circular dichroism data.

The secondary and tertiary structures of bacteriophage cro protein were studied by circular dichroism. The pH dependence of this structure was investigated: cro protein is stable over pH 4.5-10.5. At these pH-values cro protein contains approximately 35% alpha-helix, approximately 20% antiparallel beta-structure and approximately 15% beta-turn, while the remaining part of the protein molecule is in the irregular state. The secondary and tertiary structures of the protein are modified abruptly at more acid and more alkaline pH-values. The curves characterizing the secondary and tertiary structures of the protein are symbatic. The effect of Gu-HCl on the secondary and tertiary structures of cro protein at 22 degrees C and pH 7.2 was studied also. The conformational transition occurs within 0.6-1.9 M Gu-HCl. The changes in the secondary and tertiary structures of the protein have a symbatic character. Thermal denaturation of cro protein was examined. A possible mechanism of the protein denaturation is discussed.

Bacteriophage lambda↗
PubMedDate not supplied

[Number of cooperative regions (energy domains) in the pepsin molecule depends on the pH of the medium].

Ethanol and pH influence on the number and dimensions of cooperative regions in pepsin molecule was studied by scanning microcalorimetry. It is shown that ethanol solution causes a decrease of temperature of protein denaturation but does not influence the number of energetic domains. While changing pH from 6.7 to 2.0 the number of thermodynamic cooperative units (defined as the ratio delta Hcal/delta Heff) decreases from four to two. This process, as shown by CD technique, is followed by changes neither in the secondary structure, nor in the local environment of aromatic amino acids. A conclusion is made that the distinctions in cooperative characteristics of the protein globule at different pH are determined by electrostatic interactions of separate parts of the molecule.

Animals↗
PubMedDate not supplied

[Staged equilibrium of carbonic anhydrase unfolding in strong denaturants].

It has been shown by 1H-NMR, circular dichroism, fluorescence and viscometry techniques that equilibrium unfolding of carbonic anhydrase B (a one-domain globular protein) in urea guanidine hydrochloride consists of two sequential stages. The first stage is connected with a decrease of intramolecular interactions, stabilizing the rigid tertiary structure and with the increase of mobility of aliphatic side chain groups. At the second stage the decrease of protein secondary structure and hydrophobic interactions take place as well as the increase of mobility of massive aromatic side chain groups.

Carbonic Anhydrases↗
PubMedDate not supplied

[Localization of energy domains in Bacillus intermedius 7P ribonuclease].

Two independently melting regions (energetic domains) were localized in Bacillus intermedius 7P ribonuclease by methods of circular dichroism and high resolution X-ray analysis: the lov-temperature melting domain, containing C-terminal region of the molecule with five strands in antiparallel beta-structure and the high-temperature melting alpha-helical domain in the N-terminal region. The contact between these domains is stabilized mainly by ionic interaction Asp-22 - Lys+-48. At pH 2.4 and 30.5 0 C, when the low-temperature domain melts, half of the beta-structure content in binase is destroyed though the alpha-helical structure content is conserved. It has been shown that in pH interval 2.4-4.8 at 15 0 C no changes in secondary structure and local surrounding of aromatic amino acid residues could be identified. Thus, the changes in ionic interactions in the binase molecule due to protonation of Asp side chain groups does not effect the secondary or tertiary structure, though it changes the energetical state of the binase molecule, revealing a change of number and size of energetic domains.

Bacillus↗
PubMedDate not supplied

[Spatial structure of secretin molecule].

By conformational analysis and circular dichroism the structure of peptide hormone secretin and its shortened N-terminal fragments in different solvents (water, aqueous solutions of alpha-L-phosphatidic acid and sodium dodecyl sulfate) have been studied. The results obtained by the two methods are compared.

Circular Dichroism↗
PubMedDate not supplied

[Secondary structure of proteins from circular dichroism spectra. V. Secondary structure of proteins in a "molten globule" state].

A method that accounts for the contribution made by aromatic amino acid residues in circular dichroism spectra of proteins has been used in order to analyze the structure of bovine carboanhydrase B, bovine and human alpha-lactalbumin in the native state and when denatured with acid and temperature. At acid- and temperature-induced transitions of the secondary structure of these proteins has been shown not to change. However the rigidity of their tertiary structure decreases (the environment of aromatic amino acid residues is made more symmetrical).

Animals↗
PubMedDate not supplied

[Purification of homogeneous gamma-cystathionase and study of its structure by circular dichroism].

Rat liver gamma-cystathionase has been purified to homogeneity (verified by SDS electrophoresis and ultracentrifugation). The secondary and tertiary structures of the enzyme were studied by circular dichroism spectra. Our studies revealed that the holoenzyme molecule comprises approximately 22% of alpha-helices, 14% of beta-structure, 14% of beta-bends, and 50% of unordered structure. Conformational alterations of the enzyme molecule resulting from enzyme PLP elimination, reduction with sodium borohydride and irreversible inhibition by propargylglycine were examined. The enzyme's secondary structure was shown to be stable whereas the tertiary structure is labile. Saturation with PLP maintains the enzyme's optimal (catalytically active) tridimensional structure. Sodium dodecylsulfate alters its secondary (the amount of alpha-helix being raised to 34%) and tertiary structures.

Amino Acid Sequence↗