Proton magnetic resonance melting studies of CCGGp, CCGGAp, ACCGGp, CCGGUp, and ACCGGUp

Proton magnetic resonance melting curves are reported for the base and ribose 1' nonexchangeable protons of CCGGp, CCGGAp, ACCGGp, CCGGUp, and ACCGGUp. In general, the double helices melt in a cooperative two-state transition. For CCGGp, CCGGAp, CCGGUp, and ACCGGUp, the 3' ribose exhibits conformational flexibility at lower temperatures than the other ribose residues. For ACCGGp, the 5'-C ribose is the first to exhibit flexibility. The conformations of the 3' terminal bases in CCGGAp and CCGGUp change cooperatively with the double- to single-strand transition, whereas the 5' A of ACCGGp appears to have more conformational freedom.