Abstract
1. Conductivity and u.v. and visible spectroscopic techniques were used to investigate the solution structure of the prosthetic group of the ferric haemoproteins (ferrihaem) in dimethyl sulphoxide, NN-dimethylacetamide, NN-dimethylformamide and sulpholane, and certain of their aqueous mixtures. 2. In neutral or acid dimethyl sulphoxide, chlorohaemin is monomeric and completely dissociated into Cl−ion and a ferrihaem species with dimethyl sulphoxide molecules in the fifth and sixth co-ordination positions on iron. 3. In neutral NN-dimethylacetamide and NN-dimethylformamide chlorohaemin is monomeric but is largely undissociated, giving different spectra from that of chlorohaemin in dimethyl sulphoxide. On acidification, dissociation occurs and the dimethyl sulphoxide type of spectrum results. 4. Studies in a fourth solvent, sulpholane, indicate that solvent co-ordinating power (ligand strength) rather than bulk dielectric constant is responsible for dissociation of chlorohaemin. 5. In neutral dimethyl sulphoxide–water mixtures chlorohaemin remains monomeric and completely dissociated, and spectra are independent of mixture composition, except at high water concentrations, when precipitation occurs. In alkaline dimethyl sulphoxide–water mixtures, where the complete solvent mixture range is accessible, ferrihaem is polymeric (probably dimeric) and spectra are dependent on solvent composition. A quantitative analysis indicates that the spectral changes are due to replacement by water of one molecule of co-ordinated dimethyl sulphoxide per ferrihaem aggregate, and do not involve a two-molecule replacement as has been suggested for the alkaline pyridine–water system.
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Selected References
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- Brown S. B., Jones P., Lantzke I. R. Infrared evidence for an oxo-bridged (Fe-O-Fe) haemin dimer. Nature. 1969 Aug 30;223(5209):960–961. doi: 10.1038/223960a0. [DOI] [PubMed] [Google Scholar]
- Gallagher W. A., Elliott W. B. Alkaline haematin and nitrogenous ligands. Biochem J. 1968 Jun;108(1):131–136. doi: 10.1042/bj1080131. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jones P., Suggett A. The catalase-hydrogen peroxide system. A theoretical appraisal of the mechanism of catalase action. Biochem J. 1968 Dec;110(4):621–629. doi: 10.1042/bj1100621. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MacGregor W. S. The chemical and physical properties of DMSO. Ann N Y Acad Sci. 1967 Mar 15;141(1):3–12. doi: 10.1111/j.1749-6632.1967.tb34860.x. [DOI] [PubMed] [Google Scholar]
- Sund H., Weber K., Mölbert E. Dissoziation der Rinderleber-Katalase in ihre Untereinheiten. Eur J Biochem. 1967 Jun;1(4):400–410. doi: 10.1111/j.1432-1033.1967.tb00088.x. [DOI] [PubMed] [Google Scholar]
- Urry D. W. Model systems for interacting heme moieties. I. The heme undecapeptide of cytochrome c. J Am Chem Soc. 1967 Aug 2;89(16):4190–4196. doi: 10.1021/ja00992a601. [DOI] [PubMed] [Google Scholar]