Normal coordinate analysis of 5?-dGMP and its deuterated derivatives

By calculations based on the Wilson GF-method and using a valence force field, the vibration modes of 5′-dGMP have been assigned. Good agreement was obtained between the calculated and experimental results corresponding to the Raman and infrared spectra of 5′-dGMP. The calculations can also predict the displacement of infrared bands observed upon selective deuteration on C8 and simultaneously on the C8, N1 and N2 atoms of the guanine ring. In order to preserve the harmonic approximation of the potential field, the redundancy between the internal coordinates is entirely removed using a \(B \cdot \tilde B\) matrix-product diagonalization procedure. In this treatment the local symmetry of different constituents of the molecule is taken into consideration, thus avoiding extensive linear combinations of internal coordinates. The extension of these calculations to the guanosine-moiety involved in the double helix structures of DNAs allowed us to reproduce a certain number of the characteristic guanine vibration modes altered by the B→Z transitions of poly(dG-dC)·poly(dG-dC) and d(CG)₃·d(CG)₃.