A vibrational spectroscopic study of the metastable form of associated polyinosinic acid

Abstract

We have studied by Raman and ir spectroscopy the metastable complex formed by the self‐association of polyinosinic acid in aqueous solution. The complex is easily prepared by quickly cooling to ca. 0°C a warm solution of the polyribonucleotide to which a small amount of rubidium salt has been added. Upon heating, this metastable form melts cooperatively near 13°C, well below the dissociation temperature of a stable four‐stranded complex, which occurs at 47°C in the same conditions. The presence of several components in the stretching‐mode region of the carbonyl groups in the vibrational spectra of the metastable complex suggests that it also has a parallel four‐stranded structure. The difference in structure between the two forms is believed to be caused by the presence of fewer metal ions in the central channel of the metastable complex, in agreement with conclusions reached in previous investigations. The Raman spectra further show that the ribose units in the metastable form have a C3′‐endo conformation, in contrast with the stable form, for which we have previously suggested a mixed C2′‐endo/C3′‐endo conformation. © 1996 John Wiley & Sons, Inc.

Crystal Structure of an RNA Quadruplex Containing Inosine Tetrad: Implications for the Roles of NH2 Group in Purine Tetrads

“…8 Further Raman IR spectroscopic measurements pointed out that the sugar pucker might be a mixture of C2′/C3′-endo conformations. 11,12 Recent biochemical research indicated that purinerich regions containing adenine bases play an important role in cellular processes. For instance, the fragile X mental retardation protein binds specifically to a purine-rich fragment containing both guanine and adenine in its mRNA.…”