Analysis on Interaction between Human Serum Albumin and Zinc Ions by Circular Dichroism and Isothermal Titration Calorimetry / 世界科学技术-中医药现代化

ABSTRACT

This article was aimed to study the mechanism of interaction between human serum albumin (HSA) and zinc ions, in order to provide the information on the secondary structure modification of HSA and the thermodynamics parameters using circular dichroism (CD) and isothermal titration calorimetry (ITC). CD and ITC were applied in the study. The concentration of HSA were 0.025 mmol·L-1, 0.05 mmol·L-1, 0.1 mmol·L-1, and 0.2 mmol·L-1, respectively. The concentration of zinc ion was 5 mmol·L-1. The CD analysis revealed that the secondary structure modification of HSA differed depending on the concentration of HAS. And the content ofα-helix was inversely proportional to the concentration of HSA. When the concentration of HSA was 0.2 mmol·L-1, the content ofα-helix was special. A series of thermodynamics parameters including association constants (Kb), stoichiometry (N), entropy (ΔS) and enthalpy (ΔH) were investigated by ITC analysis. And two types of binding sites were observed when ZnSO4(mmol·L-1)?HSA (mmol·L-1)= 5?0.2. The secondary structure modification of HSA interacting with zinc ions depended on the concentration of HSA, a dramatic reduction ofα-helix was detected when the concentration of HSA attained 0.2 mmol·L-1. And the protein hydrophobicity reduction and peptide chains expansion were equally observed at this concentration. The ITC analysis also revealed endothermic and exothermic binding sites in the ZnSO4-HSA interaction when ZnSO4 (mmol·L-1)?HSA (mmol·L-1)= 5?0.2, indicating that the endothermic sites were specific but not preferential for zinc ions interactions. These results provided theoretical supports for the application of Zn2+ to open the endothermic sites of HSA.