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ABSTRACT: 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, betaW15F Hb, betaW37S Hb, and betaY130F 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 approximately 1 ppm mean square deviation in shift from experiment, with the R2-like structure of HbCOA being in very close accord with experiment.
Biochemistry 04/1997; 36(12):3590-9. · 3.42 Impact Factor
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Journal of the American Chemical Society 01/1997; 119(49):11951-11958. · 9.91 Impact Factor
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Journal of the American Chemical Society 01/1995; 117(13):3800-3807. · 9.91 Impact Factor
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Journal of the American Chemical Society 01/1995; 117(37):9542-9546. · 9.91 Impact Factor
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ABSTRACT: An empirical correlation between the peptide 15N chemical shift, delta 15Ni, and the backbone torsion angles phi i, psi i-1 is reported. By using two-dimensional shielding surfaces delta (phi i, psi i-1), it is possible in many cases to make reasonably accurate predictions of 15N chemical shifts for a given structure. On average, the rms error between experiment and prediction is about 3.5 ppm. Results for threonine, valine and isoleucine are worse (approximately 4.8 ppm), due presumably to chi 1-distribution/gamma-gauche effects. The rms errors for the other amino acids are approximately 3 ppm, for a typical maximal chemical shift range of approximately 15-20 ppm. Thus, there is a significant correlation between 15N chemical shift and secondary structure.
Journal of Biomolecular NMR 06/1994; 4(3):341-8. · 3.61 Impact Factor
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ABSTRACT: We report the 470-MHz (11.7 T) 19F solution nuclear magnetic resonance (NMR) spectra of 2-, 3-, and 4-fluorophenylalanine incorporated into the egg white lysozymes (EC 3.2.1.17) of chicken, pheasant, and duck, as well as spectra of 4-fluorotryptophan incorporated into chicken, California valley quail, and Bob White quail and 5- and 6-fluorotryptophan-labeled chicken lysozyme. The 19F solution NMR spectrum of [4-F]Phe hen egg white lysozyme (HEWL) consists of three sharp resonances, which span a total chemical shift range of 4.8 ppm (at p2H = 6.1). For [3-F]Phe HEWL, the chemical shift range is much smaller, 1.0 ppm (at p2H = 5.9), due presumably to the occurrence of fast phenyl ring flips about the C beta-C gamma bond axis. For [2-F]Phe HEWL, six resonances are observed, spanning a chemical shift range of 7.4 ppm (at p2H = 5.8), due to slow C beta-C gamma ring flips, i.e., both ring-flip isomers appear to be "frozen in" because of steric hindrance. Rotation of the [2-F]Phe residues remains slow up to 55 degrees C (p2H = 4.7). With the [F]Trp-labeled proteins, we find a maximal 14.6-ppm shielding range for [4-F]Trp HEWL but only a 2.8- and 2.4-ppm range for [5- and 6-F]Trp HEWL, respectively, due presumably to increased solvent exposure in the latter cases. Guanidinium chloride denaturation causes loss of essentially all chemical shift nonequivalence, as does thermal denaturation. Spectra recorded as a function of pH show relatively small chemical shift changes (< 1.4 ppm) over the pH range of approximately 1.2-7.8.(ABSTRACT TRUNCATED AT 250 WORDS)
Biochemistry 05/1994; 33(17):5238-45. · 3.42 Impact Factor
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POLYMERIC MATERIALS SCIENCE AND ENGINEERING-WASHINGTON-. 01/1994; 71:263-263.
