113087-95-9Relevant academic research and scientific papers
Intrinsic Binding Properties of a Differentiated Iron Subsite in Analogues of Native [Fe4S4]2+ Clusters
Weigel, John A.,Holm
, p. 4184 - 4191 (2007/10/02)
The cubane-type clusters [Fe4S4LS3L′]z- (3; LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris-(p-tolylthio) benzene(3-)) contain [Fe4S4] core units whose iron subsites are differentiated in the ratio 3:1. In the first extensive study of its kind, the intrinsic binding affinities at the unique subsite toward a large variety of biological and abiological ligands have been examined in Me2SO solutions. The clusters [Fe4S4(LS3)Cl]2- (4) and [Fe4S4(LS3)(OC6H 4-p-Br)]2- (18), which have been isolated, undergo subsite-specific, usually stoichiometric, substitution reactions with free ligands and trimethylsilyl reagents, respectively. A set of some 30 clusters of type 3 with four-, five-, and six-coordinate subsites have been generated in situ from 4 and 18. These reactions can be monitored by 1H NMR owing to the extreme sensitivity of ligand isotropic shifts to the identity of ligand L′ at the unique subsite. The ligands RS-, ROand N3 afford four-coordinate subsites, while certain chelating ligands lead to five- and six-coordinate subsites. Among the clusters produced are those that simulate the binding of Tyr·O, Ser·O, Asp/Glu·CO2, one or two Cys·S, and three His·Im protein side chain groups and the solvated and deprotonated (hydroxide) forms of native clusters. Ligand binding reactions are accompanied by changes in [Fe4S4]/ redox potentials, which provide another means of detecting product clusters and convey the sign of the intrinsic potential shift upon variation of ligands at the unique subsite. These results are pertinent to the reaction chemistry of native subsite-differentiated clusters such as that in aconitase, which in the resting state exists with H2O/OH at the unique subsite.
