VIBRATIONAL STUDY OF PHOSPHATE MODES IN GDP AND GTP AND THEIR INTERACTION WITH MAGNESIUM IN AQUEOUS-SOLUTION

Raman and infrared spectra were examined for guanosine 5'-diphosphate (GDP) and guanosine 5'-triphosphate (GTP) in aqueous solution. The vib rational modes were assigned on the basis of isotopic frequency shifts and relative intensities in the Raman and infrared spectra. The obser ved frequency shifts on O-18 isotope labeling made it possible to iden tify the bands from each phosphate group (alpha, beta, gamma). Frequen cy shifts were observed as Mg2+ complexes with GDP and GTP. The result s suggested that Mg2+ binds to GDP in a bidentate manner to the alpha, beta P chemical anion O bonds and in a tridentate manner to the alpha , beta and gamma P chemical anion O bonds of Mg . GTP. The results ind icate that structure of Mg2+ coordinated to GTP in aqueous solution di ffers somewhat to that found for Mg . ATP. (C) 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 219-227, 1998.