A vibrational spectroscopic study of the self-association of polyinosinic acid and polyguanylic acid in aqueous solution.
We have studied by Raman and ir spectroscopy the structure of self-associated polyinosinic acid and polyguanylic acid in aqueous solution. The results are consistent with the formation of a four-stranded complex, which melts cooperatively near 60 degrees C in the case of poly(I) in the presence of K+ ions. The conformation of the ribose in both systems is mixed C2'-endo/C3'-endo, giving a structure that is intermediate between the extremes proposed previously from x-ray diffraction studies. Characteristic Raman bands for the C2'-endo ribose conformation in polyribonucleotides are identified. The four-stranded structure of poly(I) appears to be very flexible, with approximately 15% of the tetrameric segments being disrupted and approximately 30% of the ribose units adopting a disordered conformation prior to melting. This disordering process increases to approximately 75% above the melting transition, with the remaining approximately 25% of the ribose units keeping an ordered C2'-endo or C3'-endo conformation.
Simard
C
C
Département de chimie, Université Laval, Québec, Canada.
Savoie
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R
D009690:Nucleic Acid Conformation; D011068:Poly G / Q000737:chemistry*; D011069:Poly I / Q000737:chemistry*; D012996:Solutions; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D014867:Water
D012996:Solutions; D014867:Water; D011068:Poly G; D011069:Poly I