The mechanism of the interaction between mercaptopurine (MP) metal (Me) complexes and calf thymus (CT) DNA has been studied by using ethidium bromide (EB) as a fluorescence probe. The results from varied experiments such as ultraviolet and fluorescence spectra, fluorescence quenching curve and Scatchard equation and circular dichroism, etc., confirm that intercalation and electrostatic binding are the two major modes for interaction between MP-Me complexs and CT DNA. The absence of the intercalation binding between the MP and CT DNA has been proved. The binding constant of MP-Me complexs with CT DNA has been determined.

Key words: MERCAPTOPURINE, ethidium bromide, CALF, THYMUS GLAND, COMPLEX COMPOUNDS