Abstract: By using the method of fixing the concentration of paramagnetic metal ion and gradually changing the concentration of α-globulin, the proton relaxation time of solvent was determined, the complexation of a-globulin with gadoliniun (Ⅲ) was studied. The results show that there are three binding sites of Gd(Ⅲ) in a-globulin molecule and the dissociation constant is 2. 5× 10^-4mol/L.

Key words: α-Globulin, Gd(Ⅲ) ion, Dissociation constant