DNA interaction studies of an anticancer plant alkaloid, vincristine, using Fourier transform infrared spectroscopy.

The binding of vincristine with DNA has been investigated using Fourier transform infrared spectroscopy. Various changes in the double helical structure of DNA after addition of vincristine have been examined. It is evident from Fourier transform infrared results that vincristine-DNA interaction occurs through guanine and cytosine base pairs. External binding of vincristine with phosphate backbone of the DNA is also observed. Vincristine perturbs guanine band at 1714 cm(-1), cytosine band at 1488 cm(-1), and the phosphate vibrations at 1225 and 1086 cm(-1). The UV-visible spectra of vincristine-DNA complex show hypochromic and bathochromic shifts, indicating the intercalation of vincristine into the double helical structure of DNA. Both intercalative and external binding modes are observed for vincristine binding with DNA, with an estimated binding constant K = 1.0 × 10(3) M(-1).