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 evidenc showed two types of HSA–DNA complexes with strong binding of K ₁ = 4.5 × 10⁵ M⁻¹ and weak binding of K ₂ = 6.10 × 10⁴ M⁻¹. The two major binding sites were located on the G-C bases and the backbone PO₂ 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.