A kinetic fluorometric method for the determination of nucleic acids using a ternary equilibrium system of nucleic acids—iron (III) tetracarboxy phthalocyanine-poly-lysine coupled with the oxidation reaction between hydrogen peroxide and dl-tyrosine

Using the oxidation reaction between hydrogen peroxide and dl-tyrosine as fluorescence indication, the evident tuning effect of nucleic acids on catalytic activity of mimetic enzyme iron (III) tetracarboxy phthalocyanine (FeC₄Pc) in the presence of poly-lysine was observed and studied. The oxidation reaction between hydrogen peroxide and dl-tyrosine with FeC₄Pc as catalyst gave an intensively fluorescent compound, which has an excitation wavelength of 325 nm and an emission wavelength of 418 nm. The fluorescence was quenched by a proper concentration of poly-lysine due to its association with FeC₄Pc and consequently the descent of the catalytic activity of FeC₄Pc, but recovered by addition of nucleic acids. Under optimal conditions, the recovered fluorescence is proportional to the concentration of nucleic acids. Based on the fact, a kinetic fluorescent method was developed for the determination of nucleic acids. The calibration graphs are linear over the range 10-2000 ng/mL both for fish sperm DNA (FS DNA) and calf thymus DNA (CT DNA). The corresponding detection limits are 1.04 ng/mL for FS DNA and 1.18 ng/mL for CT DNA, respectively. Four synthetic and three real nucleic acid samples were determined with satisfactory results.