The structure and environment of redox active tyrosines present in several metalloenzymes can be studied by resonance Raman spectroscopy or Fourier transform infrared difference spectroscopy. Assignments of the vibrational modes in vivo often requires in vitro studies on model compounds. This approach is briefly reviewed. New results are shown on the influence of isotope-labeling on the infrared spectra of tyrosine, p-methylphenol and phenol radicals obtained in vitro by UV-irradiation. The infrared spectra of the radicals are dominated by the ν(CO) mode at 1515-1504 cm-1. The frequency shifts induced on this mode by 13C- 2H-, and 18O-labeling are reported.
Berthomieu, C., Boullais, C., Neumann, J. M., & Boussac, A. (1998). Effect of 13C-, 18O- and 2H-labeling on the infrared modes of UV- induced phenoxyl radicals. In Biochimica et Biophysica Acta - Bioenergetics (Vol. 1365, pp. 112–116). https://doi.org/10.1016/S0005-2728(98)00056-5