The effects of sodium bicarbonate on conformational changes of natural actomyosin from Pacific white shrimp (Litopenaeus vannamei)

Changes in natural actomyosin (NAM) from Pacific white shrimp (Litopenaeus vannamei) treated with sodium bicarbonate (NaHCO3) at different concentrations (0–1 M) in the absence or the presence of 2.5% NaCl were studied. Turbidity of NAM solutions decreased with coincidental increase in solubility as the concentration of NaHCO3 increased. Surface hydrophobicity (SoANS) and total sulfhydryl content of NAM also increased when NaHCO3 concentration increased. Greater decreases in Ca2+- and Mg2+-ATPase activity were found in all NAM as NaHCO3 concentration increased, suggesting the denaturation of myosin head and the dissociation of actomyosin complex. The zeta potential (ζ) analysis suggested that the surface of NAM became more negatively charged (−12.12 to −26.98) as NaHCO3 concentration increased. Those changes were more intense in the presence of 2.5% NaCl. Transmission electron microscopy showed that the structure of actomyosin was more dissociated and lost the filamental structure when NaHCO3 at higher levels was used.