Determination of yeast DNA based on its quenching the fluorescence emission of norfloxacin

The interaction between norfloxacin and yeast double-stranded DNA (dsDNA) was studied using UV spectrometry and fluorescence spectrometry. Norfloxacin exhibited a fluorescence excitation at 272 nm and a fluorescence emission at 415 nm in pH 7.0 phosphate buffer solution.. The addition of yeast dsDNA to the norfloxacin solution resulted in a strong static fluorescence quenching due to the binding of the norfloxacin by yeast dsDNA. The binding constant was (2.90 +/- 0.03) x 10(4) M-1 (15degreesC). Based on the fluorescence quenching, a novel method for sensitive determination of yeast dsDNA concentration ranging from 77 nM to 43.2 muM was developed. The relative standard deviation for eleven detections of 28.8 muM dsDNA was 3.0%. The fluorescence spectrum of the norfloxacin bound covalently to single-stranded DNA (ssDNA) showed an obvious change after the ssDNA hybridized with its complementary DNA, producing a qualitative detection method for DNA sequence.