Optical absorptions of aliphatic amino acids in the far ultraviolet

The far ultraviolet absorptions of aliphatic amino acids such as glycine, alanine, aminobutyric acid, valine, and leucine were measured with their solid thin films down to 120 nm. Four absorption bands arising from the carboxyl group were observed in the 200–140 nm region. It was found that the band positions and intensities vary systematically according to the number of carbon atoms in the aliphatic side chain. This result may be interpreted as a phenomenon similar to the hyper‐and hypochromisms of aliphatic homopolypeptides in far ultraviolet region.