Electron spin resonance of an irradiated single crystal of L-tyrosine-HC.

Analysis of the electron spin resonance (ESR) of a gamma-irradiated single crystal of L-tyrosine-HCl reveals a free radical formed by loss of an H from the hydroxyl group attached to the ring. Principal g values of the radical are g(x) = 2.0023 +/- 0.0005, g(y) = 2.0067 +/- 0.0005, and g(z) = 2.0045 +/- 0.0005, with g(x) perpendicular to the plane of the ring and g(y) along the CO bond to the ring. Analysis of the hyperfine structure of the spectra shows electron spin density on C((2)) and C((6)) to be 0.24 and on C((4)) to be 0.32. Corresponding spin densities calculated from molecular orbital theory are 0.26 and 0.31, respectively.