A Resonance Raman Spectroscopic Study of the Quadruplex Form of Polyriboinosinic Acid

Abstract

The four stranded form of polyriboinosinic acid, or poly(rl), formed under conditions of high ionic strength, has been studied principally by resonance Raman spectroscopy excited in the ultraviolet absorbent band of the hypoxanthine residues. UV Absorption and circular dichroism studies were made, principally in order to verify the presence of the quadruplex form at the low concentrations of poly(rl) used, and a trial experiment with the structural probe Tb³⁺was also performed. Experimental evidence is found for highly stacked metastable forms present at low concentrations of polynucleotide, which are destroyed by heating in favor of the two well known forms.