Proton NMR characterization of isomeric sulfmyoglobins: preparation, interconversion, reactivity patterns, and structural features
The preparations of sulfmyoglobin (sulf-Mb) by standard procedures have been found heterogeneous by /sup 1/H NMR spectroscopy. Presented here are the results of a comprehensive study of the factors that influence the selection among the three dominant isomeric forms of sperm whale sulf-Mb and their resulting detailed optical and /sup 1/H NMR properties as related to their detectability and structural properties of the heme pocket. A single isomer is formed initially in the deoxy state; further treatment in any desired oxidation/ligation state can yield two other major isomers. Acid catalysis and chromatography facilitate formation of a second isomer, particularly in the high-spin state. At neutral pH, a third isomer is formed by a first-order process. The processes that alter oxidation/ligation state are found to be reversible and are judged to affect only the metal center, but the three isomeric sulf-Mbs are found to exhibit significantly different ligand affinity and chemical stability. The present results allow, for the first time, a rational approach for preparing a given isomeric sulf-Mb in an optimally pure state for subsequent characterization by other techniques. While optical spectroscopy can distinguish the alkaline forms, only /sup 1/H NMR clearly distinguishes all three ferric isomers. The hyperfine shift patterns in the various oxidation/spin states of sulf-Mbs indicate relatively small structural alteration, and the proximal and distal sides of the heme suggest that peripheral electronic effects are responsible for the differentially reduced ligand affinities for the three isomeric sulf-Mbs. The first /sup 1/H NMR spectra of sulfhemoglobins are presented, which indicate a structure similar to that of the initially formed sulf-Mb isomer but also suggest the presence of a similar molecular heterogeneity as found for sulf-Mb, albiet to a smaller extent.
- Research Organization:
- Univ. of California, Davis
- OSTI ID:
- 5599774
- Journal Information:
- Biochemistry; (United States), Vol. 26:22
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MYOGLOBIN
NUCLEAR MAGNETIC RESONANCE
STRUCTURAL CHEMICAL ANALYSIS
HEAVY WATER
HEME
PROTONS
SULFUR COMPOUNDS
BARYONS
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
FERMIONS
GLOBIN
HADRONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
RESONANCE
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550601* - Medicine- Unsealed Radionuclides in Diagnostics