Blue copper electron transfer proteins

Structure and electron transfer reactivity of the blue copper protein, plastocyanin. A. G. Sykes, Chem. Soc. Rev., 1985,14, 283 (117). 

Blue copper electron transfer proteins, 6,712-717 Blue copper oxidases, 6,699 Blue copper proteins, 2, 557 6, 649 Blue electron transfer proteins, 6,649,652 spectroscopy, 6, 651 Blue oxidases copper, 6,654,655 Blueprint process, 6,124 Blue proteins model studies, 6,653 Boleite... 

The many redox reactions that take place within a cell make use of metalloproteins with a wide range of electron transfer potentials. To name just a few of their functions, these proteins play key roles in respiration, photosynthesis, and nitrogen fixation. Some of them simply shuttle electrons to or from enzymes that require electron transfer as part of their catalytic activity. In many other cases, a complex enzyme may incorporate its own electron transfer centers. There are three general categories of transition metal redox centers cytochromes, blue copper proteins, and iron-sulfur proteins. 

C20-0102. Blue copper proteins are blue when they contain Cu but colorless as Cu compounds. The color comes from an interaction in which a photon causes an electron to transfer from a sulfur lone pair on a cysteine iigand to the copper center. Why does this charge transfer interaction occur for Cu but not Cu+ ... 

Copper, Cu+(d10), Cu2+ (d9) 4, tetrahedral N-Thiolate, thioether, AMmidazole Electron transfer in Type I blue copper proteins... 

C. Electron-Transfer Kinetics of Blue Copper Proteins... 

Electronic spectra of metalloproteins find their origins in (i) internal ligand absorption bands, such as n->n electronic transitions in porphyrins (ii) transitions associated entirely with metal orbitals (d-d transitions) (iii) charge-transfer bands between the ligand and the metal, such as the S ->Fe(II) and S ->Cu(II) charge-transfer bands seen in the optical spectra of Fe-S proteins and blue copper proteins, respectively. Figure 6.3a presents the characteristic spectrum of cytochrome c, one of the electron-transport haemoproteins of the mitochondrial... 

Simple thermodynamic considerations state that the reduction process is favoured (i.e. more positive cu(ii)/cu(p potential values are obtained) if the electron transfer is exothermic (AH° negative) and if the molecular disorder increases (AS° positive). It is therefore evident that the positive potential value for the reduction of azurin (as well as that of the most blue copper proteins) is favoured by the enthalpic factor. This means that the metal-to-ligand interactions inside the first coordination sphere (which favour the stability of the reduced form over the oxidized form) prevail over the metal complex-to-solvent interactions inside the second... 

Blue copper proteins, 36 323, 377-378, see also Azurin Plastocyanin active site protonations, 36 396-398 charge, 36 398-401 classification, 36 378-379 comparison with rubredoxin, 36 404 coordinated amino acid spacing, 36 399 cucumber basic protein, 36 390 electron transfer routes, 36 403-404 electron transport, 36 378 EXAFS studies, 36 390-391 functional role, 36 382-383 occurrence, 36 379-382 properties, 36 380 pseudoazurin, 36 389-390 reduction potentials, 36 393-396 self-exchange rate constants, 36 401-403 UV-VIS spectra, 36 391-393 Blue species... 

Electron-transferring subunit, nickel-containing hydrogenases, 38 409-410 Electron transport blue copper proteins, 36 378 NiFe hydrogenase, 47 16-17 Electron volt, 16 73... 

Blue copper proteins are a family of metalloproteins that have been found to play an important role in a number of electron-transfer reactions in nature. Solomon and coworkers have studied a range of blue copper enzymes in detail to produce a thorough description of how molecular and electronic structure interact to provide the function of these enzymes (26,158). 

The type-1 blue copper proteins act as electron carriers azurin, plastocyanin, stellacyanin, umecyanin e.g. They are characterized by a rather strong LMCT (ligand to metal charge transfer) band near 600 nm and by small hyperline coupling constants A in EPR. Copper is bound to two imidazole groups of histidine and to two... 

Pecht, I., Farver, O., Goldberg, M. Electron transfer pathways in blue copper proteins. In Bioinorganic Chemistry II. Advances in Chemistry Series, Vol. 162 (Raymond, K. N., ed.), Washington, Amer. Chem. Soc., 1977, pp. 179-206... 

The other way to study the "conductivity of protein molecules towards electron tunneling is to investigate the quenching of luminescence of electron-excited simple molecules by redox sites of proteins [95,96]. Experiments of this sort on reduced blue copper proteins have involved electron-excited Ru(II)(bpy)3, Cr(III)(phen)3, and Co(III)(phen)3 as oxidants. The kinetics of these reactions exhibit saturation at protein concentrations of 10 3 M, suggesting that, at high protein concentrations, the excited reagent is bound to reduced protein in an electron transfer precursor complex. Extensive data have been obtained for the reaction of reduced bean plastocyanin Pl(Cu(I)) with Cr(III)(phen)3. To analyze quenching experimental data, a mechanistic model that includes both 1 1 and 2 1 [Pl(Cu(I))/ Cr(III)(phen)3] complexes was considered [96]... 

Electron transfer rate constants, kt, free energy changes, - AG°, and stability constants, K1 and Kz, for the reactions of Cr(III)(phen)3 and Ru(II)(bpy)3 with reduced blue copper proteins at 295 K [96]... 

Cytochromes c, small blue-copper proteins, or an internal heme c group can function as natural electron acceptors for the dehydrogenases. Since these are soluble proteins and the genes have been cloned in most cases, they provide excellent possibilities to study electron transfer pathways in vitro and intermolecular as well as intramolecular pathways between a quinone and Cu or heme c in particular. 

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