Selenium substitution in [Fe4S4(SR)4]2-: synthesis and comparative properties of [Fe4X4(YC6H5)4]2- (X, Y = sulfur, selenium) and the structure of [(CH3)4N]2[Fe4Se4(SC6H5)4]

Abstract

Selenium Substitution in [Fe4S4(SR)4]2: Synthesis and Comparative Properties of [Fe4X4(YC6H5)4]2" (X, Y = S, Se) and the Structure of [(CH3)4N]2[Fe4Se4(SC6H5)4]

Characterization of [4Fe-4Se]2+/3+ high-potential iron-sulfur protein from Chromatium vinosum

“…The average g value of the EPR spectrum displayed by Se-HiPIP is higher than that of the native protein, and the corresponding tensor has more split mean values, as already observed with other Se-substituted Fe-S proteins [Gaillard et al (1986) and references cited therein]. The latter feature might result in part from the stronger strain applied by the polypeptide chain on the larger (Bobrik et al, 1978) [4Fe-4Se] cluster compared to its sulfur homologue.…”

“…Nevertheless, kinetic data available for HiPIP suggest that a large exposure of the prosthetic group to the environment lowers the energy barrier which has to be overcome prior to electron transfer . In this respect, the [4Fe-4Se] cluster of HiPIP, which is larger than the [4Fe-4S] center (Bobrik et al, 1978), might induce a small conformational change around the active site, hence a lower energy barrier to overcome before reaction with redox partners. This suggestion seems at variance with the observation that the redox potential of Cp Fd is insensitive toward the nature of its core chalcogenide (Moulis 8~ Meyer, 1982).…”

“…The substitution of inorganic sulfur by selenium in tetranuclear clusters has been used to assess the precise role played by the chalcogenide atoms in this complex structure (Bobrik et al, 1978;Meyer & Moulis, 1981). The overall properties of Clostridium pasteurianum Fd are not drastically affected by chalcogenide replacement (Moulis & Meyer, 1982), but all reduced selenium-containing clostridial Fd examined to date display unusual EPR and Mossbauer features which have been attributed to the Occurrence of high-spin ground states (Moulis et al, 1984a;Gaillard et al, 1986).…”

Direct electrochemical oxidation of Clostridium pasteurianum ferredoxin

“…Reduction potentials for [4Fe-4S]'+"+and [4Fe-4Se12+*'+ couples in native-and selenium-substituted C.pasteurianum ferredoxin differ by 6 mV [16]. In the case of the analog [4Fe-4S12+*'+ systems Fe4S4(SPh)$-'3-and FeASe4(SPh)i-'3-, measured reduction potentials differ by 29 mV [34]. Similarly for protein [2Fe-2S] systems and corresponding [2Fe-2Se] derivatives, variable sign perturbations in the range lo-38 mV are found [35][36][37].…”

[Fe6Se9(SR)2]4- Clusters (R = Me, CH2Ph): Synthesis and Characterization, and the X-Ray Structure of (PhCH2NEt3)4[Fe6Se9(SMe)2]

“…Core atom S/Se substitution occurs, for example, in [ 2~ (L = SPh, S-p-MeC 6 H 4 , 1/2 1,2-(SCH 2 ) 2 C 6 H 4 [3]; 1/2 2,2'-bis(thiophenolate), SePh [4]; Cl [5]; 1/2 Se 5 [6]; NO [7]), [Fe 2 Se 2 (CO) 6 ] 2 ' (in solution) [7], [Fe 2 4 Se 4 L 4 ]"-(n = 2: L = SPh [12,13]; S-r-Bu, SePh [13]; S-p-MeC 6 H 4 [14]; SCH 2 CH 2 OH [15]; 1/2 (SCH 2 CH 2 ) 2 S [16]; 0-2,6-Me 2 C 6 H 3 [10]; n = 3: L = S-p-MeC 6 H 4 [14]), [Fe 4 Se 4 (CO) 12 ] 0,+ [17], and [Fe 4 2 - [13], and [Fe 4 Se 4 (CO) 12 ] [17] have been described in detail.…”