The requirement of intact double helical structure for primary binding in quinacrine-nucleic acid complexes.

Exciton-like splitting is observed in the ultraviolet difference absorption spectra of complexes of quinacrine and polynucleotides with intact double helical structure but not in denatured DNA. These results indicate that an intact double helical structure of the polynucleotide is a prerequisite for exciton-like splitting and primary binding in quinacrine-nucleic acid complexes.