Vinblastine sulfate, a clinical agent for the treatment of leukemia and its simpler structural analogs were studied for the DNA binding by fluorescence, NMR and molecular modeling.



It was demonstrated that the mode of binding is non-specific. It was neither intercalation nor minor groove binding. By these studies it was found that the molecules remain anchored in the minor groove through carboxylic acid terminus and indole ring is stacking in and out between the DNA base pairs on a time scale faster than the fluorescence. The methylene linker between indole ring and carboxylic acid terminus facilitates the better binding mode as compared to short linker with one or no methylene group. The NMR studies of Vinblastine and DNA duplex also suggest that the drug is binding between the GC base pairs as evidenced by their ³¹P chemical shifts. A complete ¹H-NMR assignment of the representative DNA decamer has also been furnished using 2D-NMR techniques.