Quenching effect of nucleic acids on resonance light scattering of colloidal silver chloride and its application

A novel quantitative method, based on the quenching of resonance light scattering (RLS) of colloidal silver chloride by nucleic acids, has been developed for the determination of nucleic acids in aqueous solutions. Under optimal conditions, the quenched intensity of RLS is proportional to the concentrations of calf thymus DNA, herring DNA and yeast RNA in the ranges of 0 ∼ 20 × 10^-9 g/mL, 0 ∼ 60 × 10^-9 g/mL and 0 ∼ 80 × 10^-9 μg/L, respectively. The limits of detection for the three nucleic acids are 0.65 × 10^-9 μg/L, 1.1 × 10^-9 g/mL and 1.9 × 10^-9 g/mL, respectively. Six synthetic samples were analyzed with satisfactory results, mechanism studies showed the quenching effect of nucleic acids on RLS of collidal silver chloride was possibly due to the equilibrium shift of Ag⁺ + Cl^- = AgCl (existed in colloid formation) when nucleic acids whose bases, especially purines, having power to bind silver ions were added.