Guanine, deuterated

At higher temperatures, ionic radicals are not expected to be stable, but rather these species protonate or deprotonate to form neutral, secondary radical products. As mentioned, the first of these products, T(C6H), was identified as evolving from the thymine anion in early ESR studies. Later, the decay of the guanine cation was predicted to be related to the growth of G(N1) [73,74]. T(CH2) has also been observed in highly hydrated DNA samples [73]. Evidence exists that the cytosine anion is stabilized by protonation at N3 at 77 K [75]. Additionally, in thymine deuterated DNA samples, a deuteron has been determined to add to the C6 position of the cytosine anion [73]. Despite the fact that the types of products observed are diverse, these products were each observed in different samples. 

Z. Dhaouadi, M. Ghomi, C. Coulombeau, Ce. Coulombeau, H. Jobic, P. Mojzes, L. Chinsky P.Y. Turpin (1993). Eur. Biophys. J., 22, 225-236. The molecular force field of guanine and its deuterated species as determined from neutron inelastic scattering and resonance Raman measurements. 

The observation of the H—D exchange in the spectral range near the laser excitation frequency by means of SERS spectroscopy is illustrated in Fig. 22. This SERS spectrum of guanine dissolved in DjO shows a remarkable increase of intensity of new bands and a decrease of intensity of other bands. A detailed analysis of this isotopic exchange from C—H to C—D is given elsewhere In the deuterated guanine... 

Bradbury et al. (1967) have studied partial nucleoproteins produced by removal of histone fractions from nucleohistone. Figure 12.6 shows a polarized infrared spectrum of one of the nucleoproteins oriented by shearing. The spectrum is that of a film deuterated by D2O vapor. The bands of the in-plane vibrations of cytosine and guanine moieties are highly polarized when the electric vector is placed perpendicular to the fiber axis. The 1452 cm absorption is that of the amide IF band (Miyazawa et al., 1956 Miyazawa, 1962) for the readily deuterated fraction of the partial nucleoprotein. As seen in Fig. 12.6, the 1452 cm band is polarized considerably in the direction parallel to the fiber axis, giving evidence that the extended polypeptide chain is situated so that its axis lies between the angle of the groove in the DNA double helix and the axis of the DNA helices (Bradbury et al., 1967). 

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