Spectroscopic and binding properties of Berberine to DNA and its application to DNA detection

Berberine(BER) binds to the double helical DNA with a high affinity. There is only a much smaller hypochromism and no shifts in the absorption spectra when BER binds to calf thymus DNA(CT DNA). The fluorescence yields increase dramatically when BER binds to DNA, with no shifts in the emission maximum These spectral changes are in contrast to the behavior observed with many fluorescent intercalators Groove binding rather than intercalation was suggested to be the cause of these spectral changes, Consistent with groove binding, ferrocyanide anion quenching studies showed that the magnitude of K-sv of the bound BER was higher than that of the free BER. The addition of salt to the solution releases the DNA-bound drug cation from the groove and causes a decrease in the fluorescence yield. The results of all above studies proved the groove binding of BER to DNA, The large fluorescence enhancements observed when BER binds to DNA and the poor fluorescence yield of BER in the absence of DNA can be used for sensitive detection of DNA The linear concentration range was 0-20 mu g/ml. The limit of detection for CT DNA was 12 ng/ml.