SALT NUCLEIC-ACID INTERACTIONS

Coulombic interactions of salt ions with polymeric and oligomeric nucl eic acids in solution have large and distinctive effects on ion distri butions, on thermodynamic coefficients, and hence on equilibrium proce sses involving nucleic acids, such as their conformational transitions and binding interactions. In experimental or theoretical studies wher e an oligonucleotide is taken to represent the corresponding polynucle otide, the impact of coulombic end effects on molecular and thermodyna mic properties must be taken into account. Observable consequences of coulombic interactions in nucleic acid solutions have been calculated by using models with varying degrees of detail and methods formulated at varying levels of rigor. From comparisons of experimental results w ith predictions of the prevalent theoretical approaches, this review c oncludes that the more rigorous methods have proved capable of account ing for thermodynamic (and some molecular) consequences of coulombic i nteractions with a minimal number of preaveraged parameters that repre sent the most important structural features of the nucleic acid soluti on.