Infrared Spectra of Amino Acids and Simple Polypeptides

摘要

The infrared spectra of a number of amino acids and simple polypeptides have been studied over teh 4000-33/cm region at room temperature and at liquid nitrogen temperature. It was found that recording spectra at low temperature increases the band definition and sharpness for those compounds that exist in the zwitterion form. The spectra of the hydrochlorides of amino acid, which in general are well defined at room temperature, are not greatly improved in going to liquid nitrogen temperature. For materials in the zwitterion form, this observed improvement definitely aids in the identification of the compounds. Glycine, alanine, and leucine were studied in some detail. Sizable frequency shifts are noted in the absorption bands of vibrations assigned to torsions and skeletal deformations as the sample is cooled to lower temperatures. If this is found to be a general occurrence in other classes of compounds, this frequency shift may be useful for identifying the torsion and skeletal deformation bands for assignments of vibrational frequencies. (Author)