Abstract: Fluorescence spectroscopy, circular dichroism and electrophoresis were used to study the interaction between myosin and rosmarinic acid (RA) in an aqueous buffer solution and the effect of RA addition on the conformation and physicochemical properties of myosin at different NaCl concentrations. The results showed that RA exhibited a strong static quenching effect on the endogenous fluorescence of myosin and they combined mainly by hydrophobic interaction without covalent cross-linking. RA could promote the unfolding of myosin, resulting in a reduction in α-helix content, exposure of more active groups and an increase in surface hydrophobicity. At each NaCl concentration, the addition of RA reduced the absolute value of the Zeta potential, resulting in decreased solubility as well as increased turbidity and particle size of myosin. The emulsifying properties of myosin was reduced by RA addition at low salt concentration (0.2–0.4 mol/L NaCl), but was little affected at moderate and high salt concentrations (0.6–1.0 mol/L NaCl).

Key words: myosin, rosmarinic acid, interaction, physical and chemical properties