SUNY at Albany
June 19-23, 2001
Increased Binding Affinity of Caffeine to Denatured DNA and its Modulatory Effect on DNA-Binding Agents Cisplatin, Novontrone, and Ethidium Bromide
The mechanism of binding of caffeine (1,3,7-trimethyl xanthine) to DNA is actively being studied mainly because of its ability to modulate the binding of certain DNA damaging agents (1). We studied the binding of caffeine to calf thymus DNA under (a) denaturing conditions of temperature and pH ( 11.92 ± 0.015) (b) in the presence of DNA damaging agents such as cisplatin, novontrone, and Etbr, using UV absorption spectroscopy. Also the variations induced in double helical DNA structure due to binding of caffeine and the modulatory effect of caffeine on Etbr intercalation were monitored using DNA-dependent Etbr fluorescence spectroscopy. Caffeine was found to exhibit a dose dependent binding behaviour, with lower concentrations having a greater binding affinity to DNA. Interestingly, an increased DNA binding activity was observed for caffeine under alkaline pH and temperature of melting (an increase in the absorbance by 35% - 45% and 30% - 65% respectively in heat melted and alkaline treated DNA) and marked changes in the absorption spectra of DNA were observed in the presence of cisplatin, novontrone, and Etbr. An increase in the concentration of caffeine (P/D = 1, 5 & 10) resulted in the reduction of O.D values of DNA in the presence of the damaging agents which might possibly be due to the interaction of these drugs with caffeine. The analysis clearly indicate that caffeine can modulate the effect of DNA damaging agents and possibly reduce the DNA-directed toxicity. The UV absorbance and fluorescence spectra of DNA and caffeine in the presence of various DNA damaging agents at different concentrations, pH, temperature are presented.
References and Footnotes
*R.Malathi, S. G. Bhuvan Kumar and I. Maria Johnson
Dept. of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences,