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Thermodynamic Extent Of Counterion Release Upon Binding Oligolysines To Single-Stranded Nucleic Acids., David Mascotti, Timothy Lohman

David P. Mascotti

A major contribution to the binding free energy associated with most protein-nucleic acid complexes is the increase in entropy due to counterion release from the nucleic acid that results from electrostatic interactions. To examine this quantitatively, we have measured the thermodynamic extent of counterion release that results from the interaction between single-stranded homopolynucleotides and a series of oligolysines, possessing net charges z = 2-6, 8, and 10. This was accomplished by measuring the salt dependence of the intrinsic equilibrium binding constants--i.e., (delta log Kobs/delta log[K+])--over the range from 6 mM to 0.5 M potassium acetate. These data provide a rigorous …