Assignment and analysis of fluorine nuclear magnetic resonance spectra of 4-fluorotryptophan myoglobins and hemoglobins

We have obtained the 470 MHz ¹⁹F NMR spectra of wild type [4-F]Trp- labeled myoglobins (MbCO, MbO₂, deoxyMb, metMb, and MbCN) and hemoglobins (HbCO, HbO₂, and deoxyHb), as well as those of several mutants (W7F Mb, βW 15F Hb, βW37S Hb, and βY 130F Hb, all as the carbonmonoxy adducts), prepared via site-directed mutagenesis. The maximum observed chemical shift range induced by folding is 6.4 ppm. Using a multipole shielding polarizability-local reaction field approach, we have computed the electrostatic field contributions to the fluorine shielding. For residues which do not have F atoms in contact with neighboring groups, we find an ~1 ppm mean square deviation in shift from experiment, with the R2-like structure of HbCOA being in very close accord with experiment.