Guanine SERS spectroscopy

In order to confirm and study in situ the respective conformational changes of DNA in the adsorbed state, the SERS spectroscopy was applied later Native DNA exhibits some 30-40 normal solution Raman scattering bands in the spectral range of 200-1800 cm iss.ise) jj g more intense bands are caused by vibrations of the base residues adenine (A), guanine (G), cytosine (C) and thymine (T). 

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... 

To illustrate the high sensitivity of SERS spectroscopy we have selected the guanine molecule, because this molecule has a very low solubility in H2O (5 x 10 g in 100 g H2O). Therefore, under these conditions it is impossible to obtain a normal Raman spectrum of this important molecule in biochemical research. But by means of electrode SERS-spectroscopy such a very insoluble molecule shows a very strong vibration spectrum (cf. Figure 1). Thus, SERS spectroscopy opened up a new field of vibration spectroscopy for very low solubility molecules in water. 

Alkylation of nucleic acid components and nucleic acids has been of considerable interest in recent years. SERS spectroscopy on Ag electrode is a useful technique for the identification of methyl derivatives of nucleic acids. The methylation of guanine leads to a specific change in the SERS spectrum. 

Surface Enhanced Raman Scattering (SERS) Spectroscopy of Guanine Derivatives E. Koglin and J.-M. Sequaris... 

---