Spectroscopic study on the interaction of eugenol with salmon sperm DNA in vitro

Fluorescence spectra, absorption spectra, melting temperature, ionic strength effect, and viscosity experiments were described that characterize the interaction of eugenol with salmon sperm DNA in vitro. Eugenol was found to bind but weakly to DNA, with binding constants of 4.23×103, 3.62×103 and 2.47×103 L mol−1 at 18, 28 and 38 °C respectively. The Stern–Volmer plots at different temperatures suggested that the quenching type of fluorescence of eugenol by DNA was a static quenching. Both the relative viscosity and the melting temperature of DNA were increased by the addition of eugenol. The changes of ionic strength had no affect on the binding. In addition, the binding constant of eugenol with single stranded DNA (ssDNA) was larger than that of eugenol with double stranded DNA (dsDNA). These results revealed that the binding mode of eugenol to DNA was intercalative binding. The thermodynamic parameters ΔH, ΔG and ΔS were also obtained according to the Vanʹt Hoff equations, which suggested that hydrogen bond or van der Waals force might play an important role in a binding of eugenol to DNA. Based on the theory of the Förster energy transference, the binding distance between DNA and eugenol was determined as 4.40 nm, indicating that the static fluorescence quenching of eugenol by DNA was also a non-radiation energy transfer process.