Interaction of morin-cetyltrimethylammonium bromide with nucleic acids anddetermination of nucleic acids at nanograms per milliliter levels based onthe enhancement of preresonance light scattering

A new preresonance light scattering (PRLS) assay of nucleic acids is presen ted. At pH 7.30, the weak PRLS of morin-cetyltrimethylammonium bromide (CTM AB) can be greatly enhanced by the addition of nucleic acids, owing to the interaction between the nucleic acid and morin-CTMAB. After the addition of morin and CTMAB to DNA, the zeta potential of DNA decreases and changes fr om negative to positive. which is due to the formation of an associate, the aggregation of morin on nucleic acids and the electric neutralization betw een DNA and the cationic surfactant CTMAB. Mechanism studies showed that th e enhanced PRLS comes from the aggregation of morin in the presence of nucl eic acids and CTMAB. The enhanced intensity of PRLS is in proportion to the concentration of nucleic acids in the range 7.5 x 10(-9)-1.0 x 10(-5) g ml (-1) for calf thymus DNA, 7.5 x 10(-9)-1.0 x 10(-6) g ml(-1) for salmon spe rm DNA and 1.0 x 10(-8)-1.0 x 10(-6) g ml(-1) for yeast RNA. The detection limits are 3.4, 6.2 and 4.1 ng ml(-1) for calf thymus DNA, salmon sperm DNA and yeast RNA, respectively. Synthetic samples were analyzed satisfactoril y.