[Study of the recognition between alpinetin and calf thymus DNA]

The recognition between alpinetin and DNA under physiological condition (pH 7.4) was investigated by fluorescence and UV-visible spectrometry. The experiment demonstrated that the fluorescence of alpinetin could be quenched by DNA. A quenching mechanism was proved to be the single static quenching procedure according to the deescalating quenching constants Ksv (3.288 X 10(3) , 2.923 X 10(3) and 2.467 X 10(3) L x mol(-1), respectively) along with the escalating temperatures (25, 32 and 39 degrees C) and the quenching rate constant Kq was greater than the maximum scatter collision quenching rate constant of various quenchers with the biomolecule. From the UV-visible spectra of alpinetin and DNA, the result showed that the UV-visible spectra of alpinetin did not changed in the presence of DNA, i. e. neither the decrease in the maximum absorbance intensity nor the red shift of the maximum absorption wavelength changed. Both the fluorescence intensity and the maximum emission wavelength of ethidium bromide-DNA system remained unchanged in the presence of alpinetin, indicating that there is no direct competition for binding DNA between alpinetin and ethidium bromide. Furthermore, DNA thermal denaturation test indicated that the fluorescence quenching effect of alpinetin with unlinking DNA was stronger than that of alpinetin with natural DNA. It was concluded that there was not intercalation binding mode between alpinetin and DNA. At the same time, fluorescence quenching effect and salt effect on the binding of alpinetin with DNA were investigated. It was shown that the major mode of recognition was groove binding between alpinetin and DNA.