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Synopsis15NN-labeled guanosines were synthesized and studied by Raman spectroscopy. The isotopic substitution was either on nitrogens 1,2, and 3 or on nitrogens 7 and 9. These substituted guanosines and their partially or totally deuterated derivatives were compared under a variety of experimental conditions: in aqueous solution in the presence of 0.1M KCI a t pH 7 a t 60 and 10°C, i.e., in solution and in gel form. The sensitivity to nitrogen isotopic substitution of some of the "hypochromic" bands was defined. These spectra were also compared with those in acidic and basic solution. The body of these data was compared with the results on poly(guany1ic acid) and on guanine-containing polynucleotides and nucleic acids.

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Acid and basic solutions of "N and D substituted guanines have been investigated by infrared and Ramanspectroscopy. Monoanion and dianion formation have been followed by spectra changes; N ' , N9H tautomery has also been studied by comparing with methylated derivatives. Assignment of the band frequencies have also been proposed. Analysing 15N results have permitted precise comparisons between the neutral form spectra and the anionic or cationic form spectra.$ ation of these molecules and the sensitivity of ring vibrations to these modifications; if these ionizations do not much perturb the fundamental vibrations of the molecule, it is possible to give them a specific character with their intensity and frequency variations.The attention of many workers is attracted by polyriboguanylic acid and its complex with polyribocytidilic acid

Isocytosine and isocytosine-d3 crystals have been investigated at 300 K, 90 K, and 10 K by infrared spectroscopy; the Raman spectra of crystals and solutions in H2O , D2O have also been studied. Using these data and the frequency group approximation we propose assignments of the fundamental molecular frequencies. Eleven lattice vibration frequencies have been observed in absorption and nine in diffusion.

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