An iterative approach to placing counterions around DNA.

An iterative approach, in which the effect of placing counter ions around DNA influences the electrostatic potential that the other subsequently approaching ions feel, has been used to place sodium ions around polynucleotides. The main focus of this report is to study the sequence and structure dependence on the distribution of ions around DNA, particularly that of tightly bound ions. The interesting results of the calculations are that there is significant sequence dependence on the electrostatic potentials in the B form of DNA, whereas relatively less difference in A form. In the case of Z form, the cations bridge the inter-stand phosphates along the minor groove.