Determination of nucleic acids on the basis of enhancement effect of resonance light scattering of toluidine blue

Based on a detailed study of the interaction of toluidine blue (TB) with nucleic acids, a novel resonance light scattering (RLS) method was developed for the determination of nucleic acids. The RLS intensity of TB at 400 nm was greatly enhanced in the presence of nucleic acids at pH 3.17. Linear relationships between the enhanced RLS intensity and the concentration of nucleic acids were observed in the range of 0.0-2.7 mug cm(-3) for calf thymus DNA (ctDNA), 0.0-2.2 mug cm(-3) for fish sperm DNA (fsDNA), and 0.0-0.5 mug cm(-3) for yeast RNA (yRNA), respectively. The limits of detection (3sigma) were determined to be 24.0 ng cm(-3) for ctDNA, 22.7 ng cm(-3) for fsDNA and 5.1 ng cm(-3) for yRNA. The binding constants were evaluated to be 1.1 x 10(4) dm(3) mol(-1) for ctDNA, 1.8 x 10(4) dm(3) mol(-1) for fsDNA, and 1.7 x 10(4) dm(3) mol(-1) for yRNA. The maximum binding numbers (n) were 2.7, 5.5, and 15.0 for ctDNA, fsDNA and yRNA, respectively. The proposed method was applied for determination of the nucleic acids in chicken blood. The analytical results obtained by the present method were in good with that from a UV method.