[Structural transitions of bovine serum albumin detected during scanning calorimetry]. / Proiavlenie strukturnykh perekhodov bych'ego syvorotochnogo al'bumina v skaniruiushchei kalorimetrii.

The calorimetry studies of temperature dependence of bovine serum albumin heat capacity for the temperature interval 20-150 degrees C and pH value varying from 4 to 9 were carried out. It is shown that in the pH range considered four types of denaturation curves differing in quantity and temperatures of endothermic pikes exist. The different types of the melting curves correspond to different types of protein domain structure. At 110-120 degrees C and pH greater than or equal to 5.6 the high temperature maximum is shown to exist. The later is supposed to be due not to BSA denaturation process but to cooperative destruction of postdenaturation remnants of the secondary protein structure.

[Calorimetric study of the formation and melting of thermotropic gel in solutions of globular proteins]. / Kalorimetricheskoe issledovanie obrazovaniia i plavleniia termotropnogo gelia v rastvorakh globuliarnogo belka.

Scanning calorimetry has been used for studying lysozyme water solutions of different buffer molarity (mu = 0.5 divided by 1.0) and concentrations (c = 1.5 divided by 25%) at pH 2.0. It is shown that an additional high temperature maximum (HTM) can be observed on the heating curves for lysozyme solutions during irreversible denaturation. Calorimetric and rheological studies under identical heating conditions have shown that aggregation of protein during denaturation leads to the formation of the thermotropic gel. Further increase of temperature brings up the melting of this gel which results in the appearance of HTM on thermograms. Slow cooling of lysozyme gel melt leads to its reconstruction which results in the appearance of exothermic maximum on the corresponding thermograms.

[Temperature and time stability of proteins in concentrated solutions]. / Temperaturno-vremennaia ustoichivost' belkov v kontsentrirovannykh rastvorakh.

A comparative calorimetric study of temperature stability of proteins in reversible and nonreversible denaturation has been carried out by means of continuous heating of its concentrated solutions. A wide range of heating rates (vh) was used. The dependence of denaturation temperature Td on the total heating time is quite different in cases of reversible (RNase, Ph 4) and nonreversible (catalase, PH 7) denaturation. At moderate heating rates (vh less than 5 deg/min) the temperature Td does not depend on vh for reversible denaturation in contrast to nonreversible denaturation where Td decreases with the decrease of vh. At high heating rates (vh greater than 10 deg/min) Td increases along with heating rate for both types of denaturation. It is assumed that the dependence of Td on the heating time for catalase at low and moderate heating rates is caused by the nonreversible nature of denaturation process. The increase of Td with vh at high heating rates is connected with superheating of native structure for td greater than 1 degree/vh.