Application of Scanning Probe Microscopy for DNA Topology Imaging

Abstract

Scanning probe microscopy (SPM) provides new possibilities for the biological objects investigation [1]. It is a near field technique which is based on the interaction between a sharp microtip and the surface while scanning a portion of a sample surface area. The resolution up to several nanometers in the scanned plane can be realised with a sharp enough probing tip while the relief height resolution may be as high as several Angstroms. Earlier we reported on SPM study of some biological objects [1, 2]. In this paper we report on SPM study of DNA plasmid’s molecules. The modification of a DNA supercoiling might play a key role in the control of genetic processes in the cell. It is well-known that changes in DNA structure can be induced by enzymes. Topoisomerase I is an example of an intranuclear enzyme which effects topological changes of DNA by transiently cleaving one its strand at a time to allow the passage of another. Topoisomerase I is now being actively studied in pharmacology and clinical medicine for anticancer drug testing. We applied atomic force microscopy for imaging of plasmids and their modification after interaction with topoisomerase I.