Part I. Magnetochemical Studies of Bovine Cytochrome c Oxidase. The variable-temperature (20-200 K) magnetic susceptibility properties of bovine cytochrome c oxidase in its fully-oxidized or resting state (Hartzell-Beinert and Yonetani preparations), its fully-reduced state (Hartzell-Beinert) and its resting(.)CN('-) state (Hartzell-Beinert and Yonetani) have been examined. In general, the magnetochemical results for the Hartzell-Beinert (g(,12) and g(,12)-less) and Yonetani resting enzyme forms are nearly Curie in nature and identical to those of Tweedle. All three sets of data are consistent with a strong antiferromagnetic exchange-coupled pair at the active site with -J (GREATERTHEQ) 200cm('-1) to give a epr inactive S = 2 ground state. The Hartzell-Beinert reduced enzyme displays magnetochemical behavior like that previously reported by Tweedle, where only cyt.a(,3)('2+) (S = 2) is a paramagnetic center. Finally, the magnetochemistry of the Hartzell-Beinert and Yonetani resting(.)CN('-) derivatives were also found to be nearly identical to that of Tweedle, in that the data are non-Curie in nature and can be interpreted in terms of a weak antiferromagnetic exchange-coupled pair at the active site.
Part II. A Synthetic Model Compound Approach to the Active Site Structure of Cytochrome c Oxidase. Twelve new (mu)-imidazolato heterobinuclear metal complexes have been synthesized to model the proposed imidazolate-bridged cyt.a(,3)('3+)(imid)Cu(,U)('2+) active site structure of resting cytochrome c oxidase where -J(,(Fe('III)-Cu('II))) (GREATERTHEQ) 200 cm('-1) may be the case. The model compounds have been derived from LFe('III)(TPP) (TPP('2-) = tetraphenylporphyrinato and L = OSO(,2)CF(,3)('-)) and M'('II)(2-meimidH)(,2)DAP ('2+) or M'('II)(imidH)(,2)DAP ('2+) (M'('II) = Zn and Cu) to yield 12 species. The variable-temperature (ca. 20-200 K) magnetochemical and epr (10 K) data obtained indicate that the Fe(III) and Cu(II) centers in compound 2 and Co(II) and Cu(II) centers in compounds 6 and 8 are electronically isolated from one another with -J (TURN) 0 cm('-1). Compound 4 exhibits magnetochemcial and epr spectral properties consistent with strong antiferromagnetic coupling between Fe(III) (S = 5/2, 1/2) and Cu(II) (S = 1/2) where -J(,(Fe('III)-Cu('II))) (GREATERTHEQ) 200 cm('-1). Compounds 10 and 12 also display variable-temperature magnetochemical and epr spectral behavior consistent with a strong antiferromagnetic exchange-coupled Mn('II)(S = 5/2)(imid)Cu('II)(S = 1/2) ('+) pair with -J (GREATERTHEQ) 200 cm('-1) to give a resultant epr inactive S = 2 ground state. As such, these model compounds may be considered to be good spin mimics of the cyt.a(,3)('3+)(S = 5/2)- Cu(,U)('2+)(S = 1/2) active site of cytochrome c oxidase in its resting state. (Abstract shortened with permission of author.)
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/15888 |
| Date | January 1985 |
| Creators | CHUNPLANG, VINAI |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | application/pdf |
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