Axial ligation-induced structural changes in nickel hydrocorphinoids related to coenzyme F/sub 430/ detected by Raman difference spectroscopy
Raman difference spectroscopy provides a structural probe of the state of axial ligation of Ni(II) in nickel corphinoids of the type occurring in coenzyme F/sub 430/ of the methylreductase enzyme of methanogenic bacteria. The two model nickel corphinoids investigated, which have all of the structural features of the natural chromophore, were synthesized by A. Faessler, A. Pfaltz, and A. Eschenmoser. Raman lines analogues to the core-size marker lines of metalloporphyrins are identified for the Ni corphinoids, and, just as for the Ni porphyrins, the frequencies for the group of Raman marker lines characterize the 4-, 5-, and 6-coordinate complexes. Further, complexes with two strong nitrogenous bases (e.g., piperidine) can be distinguished from complexes with weak basic ligands (e.g., methanol) on the basis of the frequencies of these Raman lines. Finally, Raman spectra of polycrystalline samples of the Ni corphinoid and its monoisothiocyante complex show that the structures existing in solution differ markedly from the structures in the crystalline state. The Raman markers will be useful in elucidating the structure of coenzyme F/sub 430/ and its interaction with the nearby protein environment in component C of the methyl-S-coenzyme-M reductase system.
- Research Organization:
- Sandia National Labs., Albuquerque, NM
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5943546
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:14; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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