Effects of cations on the “salt in” of myofibrillar proteins

The solubilities of myofibrillar proteins (MPs) increased monotonically with increasing NaCl concentration at pH = pI (isoelectric point), but decreased monotonically with increasing NaCl concentration at pH < pI. At pH > pI, the solubilities decreased initially, but increased with increasing NaCl concentrations from 0.2 to 0.8 M. For chloride salts, the “salt in” effect of cations decreased in the order: Li+ > Na+ > K+ > Rb+. For sodium salts, the “salt in” effect of anions decreased in the sequence: Cl¯ > Br¯ > I¯ > SCN¯. The “salt in” effect of cations were stronger than that of anions. No evidence of increased electrostatic interaction was found during “salt in”. Presence of CH3COO¯ decreased the solubilization effect of Na+. These results indicate the “salt in” of MPs is more affected by the cations with higher degree of hydration, which may be interfered by the presence of highly hydrated anions.