Cerium-mediated free radicals in contractile proteins - EPR and DSC study

The effect of free radicals obtained in hydroxyl and cerium(IV)-nitrilotria cetic acid free radical generating systems on contractile proteins (actin, myosin and their complexes in glycerinated muscle fibres) was studied using differential scanning calorimetry and spin trapping electron paramagnetic resonance technique. The analysis of spectra showed that selective attack o f thiol groups - Cys-257 and Cys-374 residues of actin, and among others Cy s-707 residue of myosin - and random attack of sidechains of the main prote ins of muscle tissue produced structural and functional changes, which affe cted the ATP hydrolysis cycle and very likely the dynamics of actin. The me lting curves obtained on protein systems support the view that global confo rmational changes accompany the local damage of free radicals.