Interaction between an 8-methoxypyrimido[4′,5′:4,5] thieno (2,3-b)quinoline-4(3H)one antitumour drug and deoxyribonucleic acid

Abstract

The interaction of 8-methoxypyrimido[4′,5′:4,5]thieno(2,3-b)quinoline-4(3H)one (MPTQ) with DNA was studied by UV-Vis and fluorescence spectrophotometry as well as by hydrodynamic methods. On binding to DNA, the absorption spectrum underwent bathochromic and hypochromic shifts and the fluorescence was quenched. Binding parameters, determined from spectrophotometric measurements by Scatchard analysis, indicated a binding constant of 3.56 × 106 M-1 for calf thymus DNA at ionic strength 0·01 M. Binding to the GC-rich DNA of Micrococcus lysodeikticus was stronger than the binding to calf thymus DNA at ionic strength 0·01 M. The MPTQ increased the viscosity of sonicated rod-like DNA fragments, producing a calculated length of 2·4 Å/bound MPTQ molecule. The binding of MPTQ to DNA increased the melting temperature by about 4°C. This research offers a new intercalation functional group to DNA targetted drug design.