PARAMAGNETIC SHIFTS IN THE PROTON MAGNETIC RESONANCE SPECTRA OF HEME PROTEINS

Author Institution: Biophysics Research Department, Bell Telephone Laboratories, Inc..The proton NMR spectra of sperm whale myoglobin and human hemoglobin (KW), studied at 220 Mc with a Varian Spectrometer, will be presented. In these spectra one observes strong resonances in the 0 to - 10 ppm range (internal standard: 2,2-dimethyl-2-sila-pentane-5-sulfonate, ``DSS''), which correspond to ca. 1000 protons per molecule of myoglobin, and 4000 protons per molecule of hemoglobin. In addition, well resolved resonances of groups of 1 to 3 protons per heme are found in the regions upfield from DSS, and downfield from - 10 ppm. The temperature dependence in the range $5-35^{\circ} C$ of the chemical shifts, and a comparison of the paramagnetic and diamagnetic states of the proteins, indicate that most of these latter resonances are shifted upfield or downfield by scalar hyperfine interactions with the paramagnetic metal ion. Some of the high field resonances have temperature independent chemical shifts and cannot be caused by hyperfine interactions; they are most likely due to ring current shifts