DNA interaction with human serum albumin studied by affinity capillary electrophoresis and FTIR spectroscopy

The question addressed in this study is how does the protein-DNA complexation affect the structure and dynamics of DNA and protein in aqueous solution. We examined the interaction of calf-thymus DNA with human serum albumin (HSA) in aqueous solution at physiological conditions, using constant DNA concentration of 12.5 mM (phosphate) and various HSA contents 0.25 to 2% or 0.04 to 0.3 mM. Affinity capillary electrophoresis and FTIR spectroscopic methods were used to determine the protein binding mode, the association constant, sequence preference, and the biopolymer secondary structural changes in the HSA-DNA complexes. Spectroscopic evidence showed two types of HSA-DNA complexes with strong binding of K(1) = 4.5 x 10(5) M(-1) and weak binding of K(2) = 6.10 x 10(4) M(-1). The two major binding sites were located on the G-C bases and the backbone PO(2) group. The protein-DNA interaction stabilizes the HSA secondary structure. A minor alteration of B-DNA structure was observed, while no major protein conformational changes occurred.