|Title||X-ray magnetic circular dichroism of Pseudomonas aeruginosa nickel(II) azurin.|
|Publication Type||Journal Article|
|Year of Publication||2004|
|Authors||Funk, T, Kennepohl, P, Di Bilio, AJ, Wehbi, Wa, Young, AT, Friedrich, S, Arenholz, E, Gray, HB, Cramer, SP|
|Journal||J. Am. Chem. Soc.|
|Keywords||Azurin, Azurin: chemistry, circular dichroism, Circular Dichroism: methods, copper, Copper: chemistry, CRYSTALLOGRAPHY, LIGANDS, Magnetics, models, MOLECULAR, Molecular Conformation, NICKEL, Nickel: chemistry, PDF, Pseudomonas aeruginosa, Pseudomonas aeruginosa: chemistry, X-RAY, X-Rays|
We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L(3)-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character.