Probing the binding of lomefloxacin to a calf thymus DNA-histone H1 complex by multi-spectroscopic and molecular modeling techniques

Abstract The interaction between lomefloxacin (LMF) and a ctDNA-H 1 complex was investigated by various spectroscopies, as well as viscometry and molecular modeling techniques. The RLS results pointed at different intensities of the ctDNA, H 1 and ctDNA-H 1 complex systems in the presence of LMF. The fluorescence intensity measurements of the ctDNA, H 1 and ctDNA-H 1 complex in the presence of LMF as binary and ternary systems at three temperatures exhibited regular quenching of the fluorescence emission curves signifying a static behavior of the binary and ternary systems. Stern-Volmer constant values of ctDNA-LMF complex formation were 7.94 × 10 7 , 4.94 × 10 7 and 3.54 × 10 7  M −1 at 298, 303 and 308 K respectively. In the presence of H1, the Stern-Volmer constant values had been changed to 1.41 × 10 8 , 0.84 × 10 8 and 0.21 × 10 8  M −1 at 298, 303 and 308 K respectively. The Stern-Volmer constant values of binary and ternary systems clearly revealed static quenching behavior of ctDNA upon interaction with LMF in absence and presence of H1. Thermodynamic parameters obtained from Van't Hoff plots revealed the different essence of interaction between LMF with ctDNA, H 1 and ctDNA complex systems. The interaction between LMF with ctDNA and the ctDNA-H 1 complex in the presence of ethidium bromide (EB) and acridine orange (AO) as intercalator probes showed that a competitive ness occurred between EB and AO with LMF, indicating that the LMF bound to ctDNA as an intercalator. Circular dichroism (CD) curves in far UV-CD were used to determine the enhancement of ellipticity in ctDNA upon interaction with LMF in the absence and presence of H 1 . The specific viscosity of ctDNA in the absence and presence of H 1 increased with an enhancement of the LMF concentration which was another reason for LMF binding to ctDNA as an intercalator. Molecular modeling data confirmed the experimental results pertaining to the interaction behavior in the ctDNA-LMF complex in the absence and presence of H 1 .