Anomalous long- and short-scale behavior of DNA conformation on a highly charged monomolecular film at different ionic strength.

The conformation of a double-stranded DNA molecule is traditionally described by a wormlike chain (WLC) model with abnormally low flexibility. However, significant DNA bending (an increase in flexibility) is an important phenomenon that is crucial in numerous fundamental biological processes within a living cell and is used in biotechnology. It is still unknown how the linear density of sharp bends along a DNA molecule affects its overall conformation. To investigate this, we use a recently reported experimental model of DNA with numerous sharp bends, including extremely sharp ones with a mean radius of <3.5 nm (kinks) that form on a highly charged monomolecular film. We examine their effect on the long-scale DNA conformation at various ionic contents. We have observed a significant decrease in the linear density of DNA kinks as the ionic strength increases. The DNA conformation appeared to be more compact than a projected WLC conformation in monovalent electrolyte solutions. The behavior of kinked DNA molecules in an electrolyte solution could be explained by the competition of two factors: the "classical" polyelectrolyte behavior of the molecule in the solution and the regulation of the number of bends in the DNA by the ionic strength.

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