In the pH 1.9～2.1 Britton-Robinson (B-R) buffer solution, rifamycin drugs such as Rifamycin SV (RFSV), Rifapentine (RFPT) and Rifampicin (RFP) could react with ct-DNA. These rifamycin drugs themselves had slight resonance Rayleigh scattering (RRS) spectral peaks and analogical spectral characteristics with RRS peaks at around 290 and 370 nm; meanwhile, ctDNA had a faint peak at 310 nm. The RRS intensity was enhanced obviously after the drugs and DNA reacting with each other, which indicated the formation of new products for the maximum peak appeared at around 375 nm with slight red shift. Then the Cu(II) ion was added into the system to form a ternary system, and the RRS intensity was enhanced significantly, when the enhanced spectral value was directly proportional to the concentration of the DNA. Thus a highly sensitive method could be obtained for determining DNA and the detection limit of the experiment reached 9.7 ng/mL for the RFSV system. In this work, the optimum reaction conditions and influencing factors were investigated and a new method for the determination of DNA has been developed by the RRS spectral technology.

Key words: resonance Rayleigh scattering, nucleic acid, rifamycin drugs, copper dichloride