Study on the interactions between CuL2 and Morin with DNA

Absorption, fluorescence spectral and viscometric studies have been carried out on the interaction of Morin (2',3,4',5,7-pentahydroxyflavone, Scheme 1) and its Cu complex, CuL2.2H(2) [L=Morin (2'-OH group deprotonated), Scheme 2] with calf thymus DNA. CuL2 shows different spectral characteristics from that of Morin in the presence of DNA. Increasing, fluorescence is seen for CuL2 with DNA addition whereas decreased fluorescence is observed for Morin. Quenching fluorescence is observed for the DNA-EB system when CuL2 is added whereas slightly quenched fluorescence is seen for the DNA-EB system with Morin addition, The relative viscosity of DNA and the DNA-EB system increases with the addition of CuL2 Hypochromism and a smaller shift are observed in the UV-visible spectra of CuL2 in the presence of DNA and the denatured temperature of DNA is decreased in the presence of CuL2. The above results suggested that Morin and CuL2 can both bind to DNA, but the binding mode is different. The complex binding to DNA mainly intercalation, while Morin binds in a nonintercalating mode. (C) 2002 Elsevier Science Inc. All rights reserved.