[Changes in structure and functional properties of cytoskeletal elastic protein titin in dilated cardiomyopathy].

To elucidate the role of titin in the onset and development of dilated cardiomyopathy, the structure and functional properties of this protein from pathological myocardium (human left ventricle) were studied. By the use of SDS gel electrophoresis, a decrease in molecular weight of titin in dilated cardiomyopathy compared with norm (pig left ventricle) was revealed. The decrease correlated with the stage of the disease.

[Correlation between Ca2+-dependent movement of crosslinks in myosin filaments and Ca2+-sensitive actin-activated ATPase of skeletal muscle myosin].

The dependence of actin-activated ATPase activity and myosin filament structure have been studied on Ca(2+)-concentration in the range between pCa 7.5 and pCa 4.6.

[Features of the effect of ammonium ion on the enzymatic activity of myosin and subfragment-1].

The kinetic isotope effect of hydrolysis of ATP by myosin subfragment-I in the presence of K+, NH4+, Rb+ was measured. VH/VD was found to be 1.8; 1.

[Changes in mechanical characteristics of immobilized crystals and films of globular proteins during substitution of D2O for H2O].

The influence of substitution of the isotopic composition of the medium on the mechanical properties of immobilized crystals and films from bovine pancreatic ribonuclease and hen egg white lysozyme was investigated. The order of magnitude of the observed effects indicates that the contribution of the electrostatic interaction to the observed isotopic effect may be considered inessential. The absence of aggregation in the H2O and D2O medium under experimental conditions is demonstrated by the method of the low angle dispersion of X-rays.

[Analysis of kinetic isotope effects in H2O-D2O mixtures in enzymatic catalysis: detection of conformation-dynamic processes].

An analysis was carried out of Gross-Butler type equations describing relationship between deuterium isotope effect in reactions with proton transfer and deuterium concentration in the medium. It has been shown that with all possible coefficient values of isotopic fractionation of enzyme functional group protons the shape of indicated relationships qualitatively differs from the experimentally observed one for myosin hydrolysis of ATP. This discrepancy as well as uniform nonlinear change of myosin denaturation temperature and of kinetic isotope effect in myosin hydrolysis of ATP on deuterium fraction in solution give evidence of D2O effect as a solvent and point to an essential role of conformational - dynamic processes in the course of enzymic catalysis with myosin.