Incoherent inelastic neutron-scattering studies of the structure of water associated with DNA and gelatin

Incoherent inelastic neutron-scattering spectra of DNA and gelatin samples with different hydration levels were measured with the TOSCA spectrometer at ISIS, Rutherford Appleton Laboratory. Comparison with the spectra of different ice phases shows that for water contents up to 0.75 g water/g DNA and 0.5 g water/g gelatin the optical region (20-50 meV) is almost featureless, similar to high-density amorphous ice (HDA). The librational band is shifted to lower energy transfers and its edge at 55 meV matches again the spectrum of HDA ice. For water contents of 1 g water/g DNA and 0.75 g water/g gelatin resemblance to spectra of ice Ih and low-density amorphous ice (LDA) is obvious.