SPECTROSCOPIC PROBE OF THE COMPETITIVE-BINDING OF ETHIDIUM-BROMIDE AND NEOMYCIN TO DNA

The three spectroscopic changes of ethidium bromide (EB) on its bindin g to DNA, namely red-shift of the v(max), enhancement of fluorescence and induced dichroism are utilized to study the competitive binding of neomycin (NMC) and EB to DNA. Reversion of v(max), decrease in fluore scence and reduction of dichroism of DNA-EB on addition of NMC shows t hat the binding of NMC and EB to DNA is competitive in nature, over a limited concentration of the polymer. The binding constant of EB-DNA f alls from 4.00 x 10(6) to 2.27 x 10(4) l mol(-1) in the presence of ad ded NMC.