DETERMINATION OF NANOGRAMS OF NUCLEIC-ACIDS BY THEIR ENHANCEMENT EFFECT ON THE RESONANCE LIGHT-SCATTERING OF THE COBALT(II) 4-[(5-CHLORO-2-PYRIDYL)AZO]-1,3-DIAMINOBENZENE COMPLEX/

Using a common spectrofluorometer to measure the intensity of resonanc e light-scattering, a method for determination of nucleic acids in the nanogram range has been developed, In the pH range 11.5-12.0, the res onance light-scattering of the binary complex of II)/4-[(5-chloro-2-py ridyl)azo]-1,3-diaminobenzene (5-Cl-PADAB) is greatly enhanced by nucl eic acids, with the maximum scattering peak located at 547.0 nm, The e nhanced intensity of resonance light-scattering is in proportion to th e concentration of calf thymus DNA in the range 0-400 ng/mL and to tha t of fish sperm DNA and yeast RNA in the range 0-300 ng/mL. The limits of detection are 1.4 ng/mL for calf thymus DNA, 0.8 ng/mL for fish sp erm DNA, and 1.3 ng/mL for yeast RNA. Precision at 200 ng/mL for the t hree nucleic acids is 1.9%, 2.0% and 0.8%, respectively, Six synthetic samples were determined satisfactorily. Mechanism studies showed that the nature of the reaction is that the binary complex of Co(II)5-Cl-P ADAB reacts with single-stranded nucleic acid, and the enhancement eff ect of nucleic acids on the resonance light scattering of the binary c omplex is due to the stacking of the binary complex on nucleic acids, which act as a template.