Ultraviolet and laser Raman investigation of the buried tyrosines in fd phage.

The tyrosines of the filamentous phage fd have been found to be inaccessible to solvent by pH titration while monitoring the ultraviolet spectrum or the laser Raman spectrum. The uv spectra suggest that the tyrosines do not become deprotonated unless the phage becomes disrupted. One possible explanation of the Raman spectra is that the tyrosine OH groups are the recipients of hydrogen-bonded protons arising from fairly acidic donors, yet these acidic donors do not become titrated over the pH 7 to 12 range.