Sites of Cu

Klapper, I., Hagstrom, R., Fine, R., Sharp, K., Honig, B. Focusing of electric fields in the active site of cu,zn superoxide dismutase. Proteins Struct. Pune. Genet. 1 (1986) 47-79. 

Fig. 15. The optical spectrum of Cu Ar = 1 10 at 10-12 K, (A) showing isolated Cu atoms and Cuj molecules (B), (C) photoaggregation as the result of two 30-min irradiations in the resonance lines of Cu atoms at 302 nm, (D) photodissociation of Cu, resulting from a 30-min irradiation at the 370-nm band of Cu,. The features marked "a are thought to arise from secondary trapping sites of Cu,. Note the scale change between 325 and 400 nm (150).

Nachtigallova, D., Nachtigall, P., Sierka, M. et al. (1999) Coordination and siting of Cu+ ions in ZSM-5 A combined quantum mechanics/interatomic potential function study, Phys. Chem. Chem. Phys., 1, 2019. 

Klapper I, Hagstrom R, Fine R, Sharp K, Honig B (1986) Focusing of Electric Fields in the Active Site of Cu-Zn Superoxide Dismutase Effects of Ionic Strength and Amino-Acid Modification. Proteins 1 47-59. 

Imidazoles are of interest as bridging ligands particularly with regard to mimics of the active site of Cu-Zn superoxide dismutase (SOD). Structures with imidazolate bridges have been... 

The carbonyl complex formed on Cu(P8/T4)-K(P8/Tl) dual cation site is depicted in Figure 2. Both cations are localized in the FER cage Cu+ is in the P8/T4 site (that is the most stable Cu+ site when framework A1 is in T4, see Ref. [7] for details) and K+ is in the P8/T1 site (the most stable K+ site in the vicinity of framework A1 in Tl, see Ref. [2] for details). The vibrational frequency calculated for this complex is 2133 cm 1 in a very reasonable agreement with the experimental value for low-energy band (Figure 1). The stability of CO adsorption complex is -107 kj/mol, 4 kJ/mol less than the corresponding complex on the isolated P8/T4 site of Cu+ [7],... 

Addition of NaN02 (50 pM) had no effect on the reaction profile with NO present, and no reaction was observed (on the time scale of the stopped-flow experiment) when NO was absent. However, at higher concentrations, anions, including the conjugate bases of various buffers (B ), slowed down the reaction. This was attributed to the competition between water and the anions for the labile 5th coordination site of Cu(dmp)2(H20)2+. 

Fig. 31 a, b. Proton ENDOR spectrum of two overlapping sites of Cu(sal)2. a) Arrow indicates the choice of the B0 field position in the EPR spectrum, b) Differentiation of ENDOR signals of overlapping sites by means of the phases of their signals. (Adapted from Ref. 62)... 

The chelate effect in proteins is also important, since the three-dimensional (3-D) structure of the protein can impose particular coordination geometry on the metal ion. This determines the ligands available for coordination, their stereochemistry and the local environment, through local hydrophobicity/hydrophilicity, hydrogen bonding by nearby residues with bound and non-bound residues in the metal ion s coordination sphere, etc. A good example is illustrated by the Zn2+-binding site of Cu/Zn superoxide dismutase, which has an affinity for Zn2+, such that the non-metallated protein can extract Zn2+ from solution into the site and can displace Cu2+ from the Zn2+ site when the di-Cu2+ protein is treated with excess Zn2+. 

Section 6.1 Minimizations of an Ag adatom on hollow and bridge sites of Cu(100) were performed with the parameters described above and 4x4x1 k points. 

FIGURE 12. The active site of Cu,Zn SOD. Adapted with permission from Reference 50. Copyright (2003) Wiley Sons... 

A Cu(II)-induced perturbation of pyrene fluorescence has been utilized to create a sensor for glutamate [388], A 2 2 1 Cu2+ 3-CD pyrene complex is formed by the noncovalent assembly of the constituents the site of Cu(II) binding is unknown. The pyrene emission resulting from complexation of the lu-mophore to 3-CD is effectively quenched by the addition of Cu(II). A 500-fold enhancement in pyrene intensity is observed upon the addition of 1.87 M glutamate, which is presumed to extract Cu(II) from the 2 2 1 complex. The precise nature of the quenching and restoration mechanisms is currently unknown. 

Uchida K. Kawakishi S. Identification of oxidized histidine generated at the active site of Cu, Zn-superoxide dismutase exposed to H202. J. Biol. Chem. 1994, 269, 2405-2410. 

Focusing of Electric Fields in the Active Site of Cu-Zn Superoxide Dismutase Effects of Ionic Strength and Amino-Acid Modification. 

The significance of axial coordination sites of Cu(II) in poly(L-histidine)-Cu(II) complex for oxidation and reduction reaction is pointed out (106,107). A loosely axial coordinated Cu(II) ion gives a high activity. 

The question as to what is the active site of Cu-based catalysts in MSR is still unclear and debated in the literature. Similar to the methanol synthesis reaction, either metallic Cu° sites, oxidized Cu+ sites dispersed on the oxide component or at the Cu-oxide interface, or a combination of both kinds of sites are thought to contribute to the active ensembles at the Cu surface. Furthermore, the oxidic surface of the refractory component may take part in the catalytic reaction and provide adsorption sites for the oxygenate-bonded species [126], whereas hydrogen is probably adsorbed at the metallic Cu surface. Similar to methanol synthesis, factors intrinsic to the Cu phase also contribute to the MSR activity in addition to SACu- There are two major views discussed in the literature relating these intrinsic factors either to the variable oxidation state of Cu, in particular to the in situ adjustment of the Cu°/Cu+ ratio at the catalyst s surface [102, 107, 127 132], or to the defect structure and varying... 

Fig. 17. Perspective view showing the siting of Cu(III) cations at the pore entrance to the supercage (Cu2 +-exchanged faujasite, dehydrated at I50°C, butadiene adsorbed). The occupancy factors are such that there is approximately one Cu(III) cation per two pore entrances.

Figure 3 Examples of metal cofactors in proteins (a) the zinc center of carbonic anhydrase, (b) the blue-copper center of plastocyanin, (c) the iron center in 2,3-dihydroxybiphenil dioxygenase, (d) the iron binding site of transferrin, and (e) the dinuclear copper site of Cu/ in cytochrome c oxidase.

Fig, 3. The approximately trigonal-bypyramid active site of Cu(II) azurin, with long axial bonds to the polypeptide carbonyl 0 atom of Gly 45 and S atom of Met 121. 

The most widely used technique to get information on the electronic structure of clean surfaces, nanostructures on surfaces, or even molecules adsorbed on surfaces is ultraviolet photoelectron spectroscopy (UPS). The difficulty of this method, when applying it to clusters on surfaces, is to obtain sufficient spectral contrast between the low number of adsorbed clusters and the substrate [45]. Thus, electron energy loss spectroscopy (EELS) is more successfully used as a tool for the investigation of the electronic structure of supported clusters. An interesting test case for its suitability is the characterization of supported monomers, i.e., single Cu atoms on an MgO support material [200], as this system has been studied in detail before with various surface science techniques [201-204]. The adsorption site of Cu on MgO(lOO) is predicted... 

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