T4 DNA condensation in water-alcohol media

TL;DR

This study investigates the compaction behavior of T4 DNA molecules in water-alcohol media using AFM imaging, revealing globule formation at high alcohol concentrations and toroidal structures at intermediate levels, with a proposed DNA packing model.

Contribution

It provides direct AFM evidence of DNA globule formation and proposes a new model of DNA packing in water-alcohol solutions.

Findings

Globules form at 80% isopropanol concentration.

Partially compacted toroidal structures appear at 40-50% isopropanol.

Globules contain only one DNA molecule.

Abstract

The process of compaction of high molecular weight DNA T4 is investigated directly in a AFM liquid cell. The AFM-images of globules formed by DNA molecules in the result of compaction in water-alcohol environments at high izopropanol concentration (80%) are received; it is found that at intermediate concentration of izopropanol (40-50%) the DNA molecules form partially compacted formations in which the separate coils of macromolecules twist in toroidal structures. It is shown using the technique of deconvolution of the AFM-images that the globule include only one closely packed DNA molecule. The model of DNA packing is proposed on the basis of AFM experiment.