High sensitive determination of DNA by use of molecular"light switch" complex of Ru(phen)2(dppx)2+

A novel fluorimetric method is developed for selective determination of DNA with the molecular "light switch" complex of Ru(phen)2(dppx)2+. The maximal fluorescence intensity is produced in the pH range of 9.3-11.5, with the maximum excitation and emission wavelength of 464 and 594nm, respectively. Under the optimum conditions, the fluorescence intensity was in proportion to the concentration of DNA. The linear range for calfthymus DNA, salmon sperm DNA and herring sperm DNA is 0-0.2µg/ml. The limits of detection for calfthymus DNA, salmon sperm DNA and herring sperm DNA are 0.3, 0.24 and 0.74ng/ml, respectively. And the proposed method was successfully used to determine DNA contents in real sample, which was dealt with RNase before the determination. The mechanism of the fluorescence sensitization is also studied. We also found that Ru(phen)2(dppx)2+ preferalls intercalates into AT base pairs to GC base pairs.