The electrostatic origin of low-hydration polymorphism in DNA.

In recent years, significant progress has been made towards uncovering the physical mechanisms of low-hydration polymorphism in double-helical DNA. The effect appears to be mechanistically similar in different biological systems, and it is due to the ability of water to form spanning H-bonded networks around biomacromolecules via a quasi-two-dimensional percolation transition. In the case of DNA, disintegration of the spanning H-bonded network leads to electrostatic condensation of DNA strands because, below the percolation threshold, water loses its high dielectric permittivity, whereas the concentration of neutralizing counterions becomes high. In this Concept article arguments propose that this simple electrostatic mechanism represents the universal origin of low-hydration polymorphism in DNA.