SPECTROSCOPIC EVIDENCE FOR AN INTRAMOLECULAR RNA TRIPLE-HELIX

A 29-base RNA oligomer has been chemically synthesized and shown to fo rm an intramolecular triple helix in solution at acidic pH. Assignment of the majority of the exchangeable proton NMR resonances demonstrate d the Watson-Crick and Hoogsteen base pairings consistent with folding to form pyrimidine-purine-pyrimidine base triplets. FTIR spectroscopy provided independent evidence of base triplet formation, and indicate d a predominately C3'-endo sugar pucker. UV absorption as a function o f temperature suggested monophasic melting behaviour, which was confir med by NMR of the imino protons.