The distance of manganese to phosphorus atoms of polynucleotides, and dynamics of binding.

The structure of manganese - polynucleotide complexes is studied by phosphorous NMR. An average value for the phosphorus-manganese distance is derived from the longitudinal relaxation rate. It is larger than the distance for direct coordination and decreases as a function of temperature. An inner-sphere/outer sphere equilibrium is proposed. The outer-sphere dominates in the doublestranded polynucleotides, whereas the inner-sphere contribution is important in single-stranded species. The kinetic parameters of the model are derived from the transverse relaxation time. The similar properties of DNA fragments and tRNA argue strongly against entrapment of of manganese in special sites of tRNA.