STRUCTURAL MODIFICATIONS IN THE AMINO-ACID LYSINE INDUCED BY SOFT-X-RAY IRRADIATION

The amino acid DL-lysine has been investigated using the surface-sensi tive probe XPS:(x-ray photoelectron spectroscopy). The XPS data confir m that solid-state lysine exists in the zwitterionic form. However, du ring the course of x;ray irradiation in the experiment, the molecule w as observed to decompose. A decomposition mechanism consistent with;th e data has been proposed which involves transformation of the zwitteri on to a free base, followed by decarboxylation, to produce 1,5-diamino pentane and CO2 gas. It would appear that caution should be exerted wh en studying amino acids using XPS if long x-ray irradiation times are employed.