Premium
Raman studies of nucleic acids. IX: A salt‐induced structural transition in poly(rG)
Author(s) -
Rice J.,
Lafleur L.,
Medeiros G. C.,
Thomas G. J.
Publication year - 1973
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250010208
Subject(s) - raman spectroscopy , chemistry , tautomer , phosphodiester bond , salt (chemistry) , hydrogen bond , ionic bonding , aqueous solution , crystallography , guanine , counterion , nucleic acid , stereochemistry , nucleotide , ion , molecule , organic chemistry , rna , biochemistry , physics , optics , gene
Raman spectra of poly(rG), obtained from neutral aqueous solutions containing excess sodium counterions, are qualitatively different than spectra obtained from salt‐free solutions. In the presence of a two‐fold molar excess of Na + (per phosphate group) the Raman spectrum of poly(iG) closely resembles that of the gel of Guo‐5′‐P and is characteristic of an ordered helical structure in which guanine residues are hydrogen bonded to one another. In the absence of added salt the spectrum of poly(rG) is characterized by unusual guanine ring frequencies which suggests a tautomeric or ionic modification of the ordinary (keto‐amino) ring structure. Both the high‐salt and no‐salt forms of poly(rG) represent stable secondary structures as evidenced by the conformationally sensitive phosphodiester frequencies and by the absence of significant spectral changes on heating the solutions.