Spectral properties and binding study of DNA complexes with a rigid bisintercalator 1,4-bis((N-methylquinolinium-4-yl)vinyl)benzene

The DNA binding behavior of potentially bisintercalating ligand 1,4-bis((N-methyl quinolinium-4-yl)vinyl)benzene was studied by spectrophotometric titration, circular dichroism and matrix-assisted laser desorption-ionization-time-of-flight (MALDI-TOF) mass spectrometry. The formation of large DNA-ligand aggregates observed at low DNA concentration was ascribed to the interstrand cross-linking due to the bisintercalation and/or electrostatic interactions. On the other hand, a monointercalation was observed at higher DNA concentration and in the presence of higher content of NaCl. Intercalative DNA-ligand complex was featured by red shifted absorption band, modest hypochromicity and the presence of induced CD signal. MALDI-TOF mass spectra of short oligonucleotide-ligand systems revealed the formation of 1:1 complexes of the ligand with duplex and single-stranded oligonucleotides as well as a higher molecular weight species.