Some Physical-Chemical Properties of Smooth Muscle Smitin

摘要

Some physical-chemical properties of smitin were studied and the action of temperature on structural properties of smitin was investigated using the intrinsic fluorescence method. It is shown that amino acid residues of tryptophan and tyrosine play a key role in spectra intensity of the intrinsic fluorescence of smitin. It is shown that a rise in temperature from 40°C to 60°C results in a sharp change of fluorescence intensity. The calorimetry method was used to study thermal denaturation of smitin. Transition temperature is T_(max)=55.2~0 C. Melting temperature interval is T=30°C. Calorimetric enthalpy is equal ΔH = 6.4 cal/g. This value is rather low in comparison with the muscle proteins and probably reflects relatively low order of structural organization of smitin molecule. Circular dichroism spectrum of smitin shows strong negative bond at 226 nm, while molecular ellipsis of pure preparation is equal to - 2700. The secondary structures calculated from the circular dichroism spectrum of smitin shows: α-helix 2.59 %; β-sheet 22.24 %; random structure 75.17 %. The experimental data allow us to conclude that the molecule of smitin is mainly represented as random structure.