Red-shifted fluorescence from polyguanylic acid in aqueous solution at room temperature

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The absorption, fluorescence emission, fluorescence excitation and fluorescence polarization spectra of polyriboguanylic acid (poly(G)) were studied in aqueous solution at room temperature. Greatly red-shifted fluorescence from poly(G) in water was attributed to a small amount of the bases protonated on the N(7) atom. This was supported by the following points: (1) the fluorescence emission spectrum of guanosine 5'-monophosphate in acid pH conditions was very close to that of poly(G) in water, and their fluorescence excitation spectra were coincident, and (2) the red-shifted fluorescence band disappeared on increasing pH with the addition of tris(hydroxymethyl) amino methane. The fluorescence titration curve exhibited a maximum at pH 4.8 that was assigned to the four-stranded form of poly(G), with part of the bases being protonated. The protonation degree was found to depend on the ionic strength of the solution.

Original languageEnglish
Pages (from-to)211-216
Number of pages6
JournalJournal of Photochemistry and Photobiology B: Biology
Issue number2-3
Publication statusPublished - 1 Jan 1996


Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging

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