Chelerythrine, a new benzo[c]phenanthridine based converter of alternate DNA structure into conventional one: A spectroscopic exploration

Abstract

Association of different polymprphic forms of DNA having alternating G-C sequences with the alkaloid Chelerythrine Chloride (CHL) was probed by using UV absorption and circular dichroism (CD) spectrometry. Spectrophotometric titration revealed that the association of CHL with right handed B-form was non-cooperative in nature with higher binding affinity (∼106 M−1) in contrast to the cooperative binding with left handed Z-form and HL-form where the intrinsic binding constants were of the order of ∼104 M−1. Further, conversion of the left-handed Z-form and the HL-form of the polymer back to the bound right-handed form by CHL has been evidenced from CD spectroscopy and under our experimental condition, the number of base pairs of Z-form and HL-form that switched to right-handed conformation by each bound CHL molecule was found to be 2–3. Moreover, kinetic measurements showed that in presence of increasing concentration of CHL, both the rate and the extent of B-form to Z-form transition were reduced.