Binding properties of herbicide chlorpropham to DNA: spectroscopic, chemometrics and modeling investigations.

The binding properties of chlorpropham (CIPC) to calf thymus DNA (ctDNA) were investigated in vitro by UV-vis absorption, fluorescence, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy coupled with molecular modeling method. The results obtained from UV-vis absorption, fluorescence and CD spectroscopic methods as well as DNA viscosity and melting measurements indicated that the binding of CIPC to ctDNA was an intercalative mode. The FT-IR analysis and molecular modeling showed that CIPC mainly bound to guanine base of ctDNA. The association constant of the ctDNA-CIPC complex was determined to be in the order of 10(4) L mol(-1) by fluorescence titration. The calculated enthalpy change and entropy change suggested that hydrophobic forces and hydrogen bonds played prominent roles in the binding process. Furthermore, multivariate curve resolution-alternating least squares (MCR-ALS) approach was used to analyze the combined UV-vis absorption data matrix from the CIPC-ctDNA reaction system. The concentration profiles of the reaction components (CIPC, ctDNA and CIPC-ctDNA complex) and their pure spectra were successfully obtained to monitor the process of CIPC interaction with ctDNA. This study may contribute to the understanding of the CIPC-ctDNA interaction mechanism and toxicological effect of CIPC at the molecular level.