Evaluating the potential of fluorinated tyrosines as spectroscopic probes of local protein environments: A UV resonance Raman study

Ultraviolet resonance Raman (UVRR) studies designed to test the utility of fluorinated tyrosines as spectroscopic probes of the local environment are presented. Specifically, resonance Raman spectra of 2-fluoro-L-tyrosine and 3-fluoro-L-tyrosine (3-Y-f) obtained with 229 nm excitation are reported. In contrast to the modest environmental dependence of the tyrosine resonance Raman spectrum, the spectrum of 3-Yf is found to be extremely dependent on the hydrogen bonding strength of the surrounding environment. Preliminary ab initio studies suggest that this behavior is due to normal modes having dominant contributions from the C-OH and C-F internal coordinates. Hydrogen bonding to the solvent perturbs the internal coordinate energetics and/or couplings, thereby altering the character of the normal modes and the corresponding transition frequencies and/or intensities. In addition to the solvent studies, 3-Y-f is site specifically incorporated into the influenza hemagglutinin (HA) 100-107 peptide which binds to the Fv fragment of the 17/9 anti-HA(98-108) peptide antibody. These studies demonstrate that the spectrum of 3-Y-f can be monitored in the presence of native tyrosine. In summary, the studies presented here demonstrate that 3-Y-f holds exceptional promise as a probe of the protein environment.