Nucleic acid derivatives studied by preresonance and resonance Raman spectroscopy in the ultraviolet region

Abstract

SynopsisRaman spectra of AMP, UTP, GMP, and CMP, and of their bromo-derivatives , are reported. They are obtained using excitation wavelengths of 457.9 nm (ionized continuous argon laser) and of 300 nm (tunable pulsed dye laser). Comparison of spectra leads to the following observations: (1) preresonance Raman effects on nucleotides spectra a t 300 nm; (2) resonance Raman effects on bromoderivatives spectra a t 300 nm; (3) in dilute solution (10-4M), shifts and enhancements of Raman lines of the bromo-derivatives with respect to the corresponding lines of nucleotides. On the basis of these comparisons, the assignments of the Raman lines are discussed. This provides the necessary background for the understanding of the properties of selected groups in DNA in dilute solution. The new experimental set-up for measurements of Raman spectra using excitation in the uv region is described. It is specially designed to incorporate the pulsed feature of the excitation laser and for correcting of the instabilities of the source.

An FT-ir study of cis study of trans-dichlorodiammineplatinum(II) bound to inosine-5′-monophosphate

“…The other absorption bands at about 1380, 1346, 1333, 1260, and 1217 cm-' have been attributed mainly to the purine ring vibrational frequencies (27,41). They showed marked spectral changes (intensity changes and shifting) upon N7-metalation (Table 3).…”

A Fourier transform infrared study of the electrophilic attack at the N7-site of guanosine-5′-monophosphate

“…The shift observed for that absorption frequency is most likely due to the different hydrogen binding system of the pyrimidinic ring upon N7-protonation than to any inductive effects caused by N7-binding, since the effect of electrophilic attack at the N7-site hardly goes beyond the purine ring system (24). The other absorption bands at 1330 (sh), 1255 (m), 1234 (m), and 1175 cm-' (m) in the spectra of 5'-GMPNa2 are attributed mainly to Cx-N9, C5-N7, Cx-N7, stretchings and to the bending mode of Cx-H (25,30). The bands showed considerable changes in the spectra upon N7-protonation.…”

“…The absorption bands at 1330, 1255, 1234, and 1175 cm-' with medium intensities in the spectrum of the free base show considerable changes (shifting and splitting), in the spectra of the N7-metal complexes. These absorption bands have been primarily assigned (25,30) to the purine ring vibrational freq"encies, involving C8-N7, C5-N7 stretching and N7-C,-N, and Cx-H bending vibrations. It seems, therefore, that the distortion of the molecular geometry (12-16) of the ring system caused by N7-metalation (Table 2) brings a large perturbation to the purine ring electronic distribution and alters the imidazol ring vibrational frequencies the most.…”

Platinum(II) and magnesium(II) nucleotide complexes. Synthesis, FT-ir spectra, and structural properties

“…In the spectrum of the free 5'-GMP there are five absorption bands at 1692 cm-' (bs), 1662 cm-' (sh), 1597 cm-' (s), 1575 cm-I (sh), and 1535 cm-' (m) assignable mainly to the stretching of C6=0, the scissoring mode of NH,, C,-N,, CJ-Cs, and the C,-N, stretching vibrations, respectively (28)(29)(30)(31)(32)(33). These absorption bands showed considerable changes upon N7-coordination in the structurally known metal complexes ( Fig.…”

“…They show large perturbations upon phosphate coortlination. Due to the skeletal and the breathing modes of the pyrimidine and purine vibrational frequencies together with the NH, outof-plane wagging (30) vibrations in the region 700-400 cm-' of'the spectra of the nucleotide complexes, it is very difficult to distinguish any changes which occurred for the syni. def.…”