Abstract: The study focused on the function of plasma protein by analyzing the purified plasma protein in five taxonomic representative bivalves(Crassostrea gigas, Mytilus coruscus, Meretrix meretrix, Sinonovacula constricta, and Scapharca broughtonii). The existence and morphological characteristics of plasma protein particles were proved by transmission electron microscope observation. The result showed that the plasma proteins of the four bivalves formed similar particle morphology with different particle sizes, except Sinonovacula constricta. Then, the constituent of the plasma protein particles and total plasma proteins were identified by PAGE. The results of PAGE showed the plasma protein particles of Crassostrea gigas and Mytilus coruscus were mainly consisted of one or two high-density protein bands, while the plasma protein particles of Meretrix meretrix and Scapharca broughtonii consisted of many low-density protein bands. In addition, we analyzed the metal ion dissociation and binding activity of the purified plasma protein particles of the Pacific oyster. The result showed that Ca2+ carried by natural plasma particles of Crassostrea gigas could be separated by dialysis. The particles could absorb more metal ion in the 50 mg/L group than the 5 mg/L group. Under the same metal ion mass concentration, the binding capacity of protein particles between different metal ions showed diversity (Cd2+> Pb2+>Ca2+> Zn2+). The plasma particles might function as the transporting and storing buffer of metal participate in the metal metabolism process of bivalve mollusks.

Key words: bivalves, plasma protein particle, metal binding, molecular sieve chromatography, metal-ions transportation