The influence of crystal structure on radical formation in x-irradiated amino acids

ESR spectra from the L and DL optical isomers of thirteen amino acids have been observed after x-irradiation at 77 K. For most of the acids, spectra from the L and DL isomers are different at corresponding temperatures in a range from 77 to 250 K. These differences are attributed to differences in crystal structure, and specifically to the conformation of the amino group with respect to the adjacent carboxyl group. The temperature at which deamination occurs is described by the equation T=13+137 sin2ϑ, where ϑ is the dihedral angle between the C–N bond and the pz orbital occupied by the unpaired electron.