The electrostatic field of the component units of DNA and its relationship to hydration.

The electrostatic fields of the subunits of DNA are presented and compared with the corresponding electrostatic potentials. Differences are observed between these two properties, due to their different dependence on distance, which are of considerable interest since, whereas the potential may be used in studying the reactivity of molecules towards charged species, the field can be a similar guide to attack by neutral, dipolar molecules such as water. It is demonstrated, for the example of the purine and pyrimidine bases, that the field may indeed be used to detect preferential hydration sites.