Gamma-radiation induced agglomeration of chicken muscle myosin and actin

Radiolytic behaviour of the major vertebrate muscle proteins: fibrillar myosin (molar mass, Mm = 520,000 g/mol) and filament forming actin (Mm = 42,050 g/mol) was studied using a SDS-polyacrylamide gel electrophoresis and quantified by high precision laser-densitometry. In order to study the OH radical contribution to the radiation damage, purified chicken myosin and actin (4 mM) were prepared in N2O saturated solution and irradiated with 13 kGy at 60Co gamma source. With respect to changes in the molecular mass, the only observed myosin and actin damage was dose dependent agglomeration of proteins. The corresponding radiation chemical yields of 5×10-8 mol J-1 and 6.3×10-8 mol J-1 were obtained for myosin and actin, respectively. This result confirmed that only the radiation-induced agglomeration is initiated with the reaction of the OH radical even in the situation where the OH radical concentration produced exceeds the protein concentration 500 times, thus enabling the multi-radical attack to occur.