Direct Evidence on the External Stimuli Induced Dissembly of DNA through Microscopic Techniques

Abstract

Calf thymus DNA exhibited a regular network-like structure on mica and copper surfaces, respectively, under atomic force (AFM) and scanning electron (SEM) microscopic techniques while oily streak cholesteric birefringent texture was observed on the glass surface under optical polarizing microscopy (OPM). In the presence of an external stimuli such as temperature, intercalating compounds such as the viologen-linked pyrene 1 and para-tolylacridinium iodide (2) and the minor groove binding spermine (4) prevented the DNA−DNA interactions and thereby perturbed the self-assembly of DNA. In contrast, the major groove binding bovine serum albumin (BSA) and the noninteracting ligand ortho-tolylacridinium iodide (3) did not affect the overall morphology of DNA, as characterized through the AFM, SEM, OPM, and circular dichroism (CD) techniques. As far as we know, this is the first report that presents direct evidence for the perturbation of supramolecular assembly of DNA under various conditions and that can be visualized through different microscopic techniques.