On the binding of Mg2+ and Mn2+ to tRNA

In this paper previous binding studies of Mg2+ and Mn2+ ions to tRNA's are reconsidered. Binding data of some representative examples are interpreted including interactions between charges located on the macroion. Both curved and bell-shaped Scatchard plots can be accounted for quantitatively if corrections are made for electrostatic interactions and, if necessary, for the effect of conformational changes on these interactions. It appears that there is no need to invoke more than one class of binding sites on tRNA's, meaning that the experimental binding data can be described using the same intrinsic pK value for all phosphate groups.