Low-Temperature Spectroscopy of Biological Compounds

It is well substantiated that the absorption spectra of complex molecules may be sharpened, and in many cases the vibrational and rotational details brought out, by refrigeration of the absorbing material to the temperature of liquid nitrogen or lower. This principle seems of great potential utility for the characterization and differentiation of compounds of biological interest heretofore indistinguishable by their absorption characteristics, and conceivably for the solution of cytochemical problems. However, the techniques that have been employed have only limited application to polar compounds. We have therefore developed new techniques with which we have undertaken a study of the absorption spectra of a number of purines, pyrimidines, amino acids, proteins, etc. at the temperature of liquid nitrogen (77° K).