Guanine Raman spectra

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. 

Figure 17 shows the SERS spectra of native and methylated DNA. In the SERS spectrum of the native DNA (cf. Fig. 17a) the Raman bands at 736cm and 1332 cm corresponding to adenine residues are more intense than the bands in the SERS spectrum shown in Fig. 12. As has already been mentioned, the Raman intensity of the adenine vibration can vary somewhat depending on the electrochemical pretreatment of the silver electrode and the available quality of the DNA samples. Before discussing the specific changes in DNA SERS spectra, due to the methylation, it is necessary to know the SERS data of the methylated guanine bases. The observed frequencies and relative intensities of the SERS bands of guanine and its derivates are given in Table 4. The methylation of guanine leads to a specific...

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