A proton magnetic resonance study of the effects of polyamine and divalent metal ions on diadenosine 5′, 5‴-P 1, P 4-tetraphosphate base stacking

Abstract

Complexation of putrescine, spermidine, spermine, and Mg2+ with diadenosine 5',5'''-P1,P4-tetraphosphate induces an upfield shift in the signals for the H-2 and H-8 protons. The upfield shifts in H-2 indicate that cation complexation enhances intramolecular adenine stacking interactions. The resonances for H-2 and H-8 of neutral analogs of 5',5'-dinucleotides appear farther upfield relative to the appropriate monomeric models than those for the corresponding dinucleotide; reduction of intra-chain phosphate repulsion is the origin of cation induced enhancement of diadenosine 5H,5'''-P1,P4-tetraphosphate base stacking.