A technique is described for obtaining the spectra of biologic materials in aqueous media (H2O and D2O) over the frequency range 2000 cm-1 to 700 cm-1. It is now possible to use infrared spectroscopy not only for the identification of substances such as proteins and nucleic acids in their native states, but also to study their reactions and interactions with other materials. Examples are shown of the infrared spectra in aqueous solutions of proteins, nucleic acids, and nucleoproteins, as well as suspensions of living bacteria.
E. R. BLOUT and H. LENORMANT, "Infrared Spectroscopy of Biologic Materials in Aqueous Solutions," J. Opt. Soc. Am. 43, 1093-1095 (1953)