Attenuated total reflectance Fourier transform infrared (ATR/FT-IR) spectroscopy is a powerful and widely used technique for obtaining molecular structural information from thin films of material. The ability of the method to provide orientational information from partially ordered samples such as lipid multibilayers (possibly with incorporated peptides) has resulted in several recent applications of the method to biophysical problems. In most ATR studies, the material under investigation is deposited as a dry film on an appropriate crystal, Ge or ZnSe being widely used for this purpose. Obviously, the biological relevance of dry films is questionable, as water often forms an integral part of the in vivo macromolecular assembly. It is evidently desirable to study biological samples under conditions of full hydration, where the effects of variation in pH and ionic strength and composition can be explored. Commercial ATR cells with water jackets are available, but these are expensive and fragile and have fairly large jacket volumes.
J. W. Brauner and R. Mendelsohn, "A Simple, Inexpensive, Hydration Chamber for Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy," Appl. Spectrosc. 42, 188-190 (1988)