Is there a terahertz absorption peak in frozen aqueous solutions of DNA nucleosides?

In an attempt to reproduce a previously-reported absorption peak in the spectrum of a frozen aqueous solution of 5-methylcytidine (5-mc), we observed a resonant feature around 1.6 THz in all samples containing ice, including pure ice itself. Thus, simply fitting the left-hand side of a Gaussian function to the spectrum of ice does not fully describe it. The previously reported peak feature depends on the subtraction of the Gaussian fit from the 5-mc sample spectrum. Through direct subtraction of the ice spectrum from that of 5-mc, our data did not reveal any statistically distinct spectral features that would allow differentiation between 5-mc and ice, however, we observed a variation in the overall absorption over the entire frequency range measured. X-ray diffraction confirmed the formation of complex hydrates, the structure of which may have a strong influence on the overall absorption based on the theory of hydration shells. The difference in the overall absorption may allow for the detection of methylated cytidine at high concentrations.