Linear and circular dichroism of drug-nucleic acid complexes

Abstract

Publisher Summary Polarized light spectroscopy offers possibilities to quickly characterize nucleic acids and their complexes with bound proteins or drug molecules, using a relatively small amount of sample. Linear dichroism (LD) provides structure information in terms of relative orientation between the bound drug molecule and the DNA molecular long axis, and also about the effects of ligand binding on the host. Circular dichroism (CD) may contribute additional structural details about such complexes. LD and CD, like other optical techniques, offer possibilities for rapid characterization of nucleic acid complexes using relatively small amounts of sample. The information that may be gained varies with the level of sophistication at which the measurements are carried out and interpreted. The presence of detectable LD thus, means that the ligand is bound to the oriented DNA, while the sign and amplitude of the LD signal contain information about the nature of the predominant binding mode. Use of complementary techniques, such as CD and fluorescence spectroscopy, may allow further conclusions regarding the structure and dynamics of DNA-ligand complexes. Nonchiral drug molecules (molecules that lack handedness and thereby optical activity) have no CD signal.