An approach to the evaluation of RNA solution structure and metal coordination chemistry by titration calorimetry

Abstract

 Binding of divalent magnesium to RNA homopolymers was evaluated by titration calorimetry and analyzed in terms of the McGhee and von Hippel model of a one-dimensional infinite lattice. Examination of Mg²⁺ binding data for ds poly(A)×poly(U), ss poly(A), and ss poly(U) revealed that the sign of the enthalpy term relates to the mode of metal binding (inner or outer sphere), which in turn is directly related to the structural ordering of the polynucleotide in solution. This approach provides details of the thermodynamics of metal binding, stoichiometry, and coordination chemistry that underlie the structural and catalytic chemistry of RNA and offers a potential new probe of the solution structure of nucleic acids.