FOURIER-TRANSFORM RAMAN-STUDY OF ACID-BASE INTERACTIONS VIA GUANOSINEN-7 IN SOLID COMPLEXES AND IN STRONGLY ACIDIC SOLUTIONS

Among the nucleosides, guanosine shows an anomalous behaviour which ha s been related to various factors (conformation, H-bonding, self-assoc iation, etc.), which characterize this nucleoside in relation to the o thers. It also easily forms a gel, the structure of which is well know n. This work concerns the Raman vibrational spectroscopic characteriza tion of the reactivity of guanosine N-7, which is one of the main fact ors responsible for the anomalous behaviour of guanosine. For this pur pose, some of its acid-base solid complexes and strongly acidic aqueou s solutions were studied. In particular, this study considers the two Raman bands at about 1480 and 1540 cm-1, attributable to vibration mod es with prevailing imidazolic character, N-7 of free guanosine or bond ed guanosine, respectively. In addition, the acid-base interaction via the H-bond of N-7 and the proton transfer in relation to the DELTApK( a) of the interacting group were studied.