Aim To study the binding behavior between human serum albumin （HSA） and phosphorothioate oligodeoxynucleotide （PS- ODN） and the effects of bivalent cations on the interaction. Methods Surface plasma resonance, circular dichroism and fluorescence experiments were conducted. Results （ 1 ） the binding ability was decreased along with the increase of pH; （2） Zn^2＋and Ni^2＋ enhanced the interaction between PS-ODN and HSA; （3） Upon PS-ODN binding, the conformation of HSA was changed with an increase of β - sheet. Conclusion The results provide experimental evidences to the hypothesis that PS-ODN binds with HSA in the positive potential region, and histidine residues located in the region play a crucial rule in the interaction.
