TOWARD MODEL COMPOUNDS FOR THE ACTIVE SITE STRUCTURE OF CYTOCHROME C OXIDASE: SULFUR-BRIDGED HETEROBIMETALLIC COMPOUNDS OF COPPER(II) WITH IRON(III), COBALT(II) AND MANGANESE(II) TETRAPHENYLPORPHYRIN CENTERS

[摘要] In order to further examine the geometric and electronic properties associated with active sites in copper proteins, four new pentacoordinate model compounds, Zn(;;II)(imidH)(S)DAP (SO(,3)CF(,3)), Cu(;;II)(imidR)(S)DAP (SO(,3)CF(,3)), Zn(;;II)(imidR)(S)DAP (SO(,3)CF(,3)), and Cu(;;II)(imidR)(S)DAP (SO(,3)CF(,3)) containing M-N(imidazole) and M-S (thiolate) bonds have been synthesized and characterized. Through comparative spectroscopic and electrochemical studies with ;;Blue;; cuproprotein centers, the new mononuclear copper(II) compounds have been found to not well mimic the electronic properties of the copper(II) active sites in the proteins. The mononuclear copper(II) compounds (and their zinc(II) counterparts) have also been reacted with ;;axially-starved;; iron(III), cobalt(II), and manganese(II) Tetra- phenylporphyrin compounds to yield a new class of twelve (mu)-thiolato bimetallic complexes as model compounds for the proposed thiolate-bridged cyt. a(,3)(;;3+)-S-Cu(,U)(;;2+) active site structure of resting cyto- chrome c oxidase. The model compounds have been derived from LFe(;;III)(TPP) (TPP(;;2-) = tetraphenylporphyrinato and L = SO(,3)CF(,3)(;;-)) and M;;(;;II)(imidH)(S)DAP (SO(,3)CF(,3)) or M;;(;;II)(imidR)(S)DAP (SO(,3)CF(,3)) (M;;(;;II) = Zn or Cu) to yield species containing LFe(;;III)-S-Zn(;;II)(imidH)- DAP (;;+), LFe(;;III)-SCu(;;II)(imidH)DAP (;;+), LFe(;;III)-S-Zn(;;II)(imidR)DAP (;;+), and LFe(;;III)-S-Cu(;;II)(imidR)DAP (;;+) cores. Furthermore, reaction of M(;;II)(TPP) (M(;;II) = Co or Mn) with M;;(;;II)(imidH)(S)DAP (SO(,3)CF(,3)) or M;;(;;II)(imidR)(S)DAP (SO(,3)CF(,3)) (M;;(;;II) = Zn or Cu) has produced new model compounds containing Co(;;II)-S-Zn(;;II)(imidH)DAP (;;+), Co(;;II)-S-Cu(;;II)(imidH)DAP (;;+), Co(;;II)-S-Zn(;;II)(imidR)DAP (;;+), Co(;;II)-S-Cu(;;II)(imidR)- DAP (;;+), Mn(;;II)-S-Zn(;;II)(imidH)DAP (;;+), Mn(;;II)-S-Cu(;;II)(imidH)DAP (;;+), Mn(;;II)-S-Zn(;;II)(imidR)DAP (;;+), and Mn(;;II)-S-Cu(;;II)(imidR)DAP (;;+) centers as (SO(,3)CF(,3)(;;-)) salts. Through comparative magnetochemical and spectroscopic investigations of these novel heterobinuclear com- pounds with parallel studies on the enzyme active site, a cyt. a(,3)(;;3+)- S-Cu(,U)(;;2+) active site structure for the resting enzyme has been sys- tematically tested, for the first time, by a model compound approach.

[发布机构] Rice University