Sulfur electron donors

Table 2 Geometric parameters for halogen bonded complexes with phosphorus and sulfur electron donors... 

Horner-Wadsworth-Emmons procedures have been used to prepare a variety of compounds including chiral tetrahydrofuran- and tetrahydropyran-deriva-tives/ novel organo-sulfur electron donors containing dithiole and azulene... 

Iron-Sulfur Electron Donors Adrenodoxin, Putidaredoxin, and their Reductases... 

The heteroaromatic compounds can be divided into two broad groups, called n-excessive and n-deficient, depending on whether the heteroatom acts as an electron donor or an electron acceptor. Furan, pyrrole, thiophene, and other heterocyclics incorporating an oxygen, nitrogen, or sulfur atom that contributes two n electrons are in the rr-exeessive group. This classification is suggested by resonance structures and confirmed by various MO methods. ... 

Water-free nitric acid is amphoteric, ie, it acts both as an acid and a base, or better as an electron donor or electron acceptor. This view, already suggested in the early Hantzsch papers, was supported by Walden (Ref 14) and later by Dalmon (Ref 30). Then Usanovich (Ref 25) demonstrated that nitric acid acts as a base with sulfuric acid and as an acid with water. 

Y is a strongly pi electron donor group. As previously noted in the results section, examples of Y from Table VI include centers of high pi electron charge density at carbon, sulfur, nitrogen, and oxygen. Also included in Table VI are examples of nucleophilic substitution transition states (cf. reactions 21 and 22) of the type... 

Fig. 11. Active sites and reactions of the bifunctional CODH/ACS. For synthesis of acetyl-CoA, two electrons are transferred from external electron donors to Cluster B of the CODH subunit. Electrons are relayed to Cluster C which reduces CO2 to CO. The CO is proposed to be channeled to Cluster A of the ACS subunit to form a metal-CO adduct that combines with the methyl group of the CFeSP and CoA to form acetyl-CoA. For utilization of acetyl-CoA, these reactions are reversed. The abbreviations are CODH, CO dehydrogenase ACS, acetyl-CoA synthase CFeSP, the corrinoid iron-sulfur protein CoA, Coenzyme A.

It has always been assumed that these simple proteins act as electron-transfer proteins. This is also a fair conclusion if we take in account that different proteins were isolated in which the Fe(RS)4 center is in association with other non-heme, non-iron-sulfur centers. In these proteins the Fe(RS)4 center may serve as electron donor/ac-ceptor to the catalytic site, as in other iron-sulfur proteins where [2Fe-2S], [3Fe-4S], and [4Fe-4S] clusters are proposed to be involved in the intramolecular electron transfer pathway (see the following examples). 

Poly(2-methoxy, 5-(2 -ethylhexyloxy)-1,4-phenylene vinylene) MEH-PPV Emission peak = 605 nm p-type doping by sulfuric acid (H2SO4) -type doping by sodium (electron donor) Iodine (I2) = electron acceptor = > oxidizing agent... 

The reductase in Geobacter sulfurreducens is located in the outer membrane and a soluble Fe(III) reductase has been characterized from cells grown anaerobically with acetate as electron donor and Fe(III) citrate or fumarate as electron acceptor (Kaufmann and Lovley 2001). The enzyme contained Fe, acid-labile S, and FAD. An extracellular c-type cytochrome is distributed in the membranes, the periplasm, and the medium, and functions as a reductase for electron transfer to insoluble iron hydroxides, sulfur, or manganese dioxide (Seeliger et al. 1998). 

Breese K, G Fuchs (1998) 4-hydroxybenzoyl-CoA reductase (dehydroxylating) from the denitrifying bacterium Thauera aromatica prosthetic groups, electron donor, and genes of a member of the molybdenum-flavin-iron-sulfur proteins. Eur J Biochem 251 916-923. 

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