Probing Gold: X-Ray Absorption Spectroscopy

  • Raphael Enoque Ferraz de PaivaEmail author
Part of the Springer Theses book series (Springer Theses)


Here, our focus shifts towards probing directly the metal. X-ray Absorption Spectroscopy (XAS) is appropriate for structural studies due to its capability to specifically probe the geometry around the metal absorber. Additionally, XAS spectra are sensitive to the electronic density on the mental center. As consequence, it represents an extremely powerful technique that is able to distinguish between oxidation states and coordination spheres of a metal complex, providing insights on the electronic and geometric structural details of the protein bound metal centers. In this chapter, the interaction of [AuCl(Et3P)] (I-1) and auranofin (I-3) with zinc finger peptides was investigated using Au L3-edge XAS measurements. To further support our conclusions, the data obtained for the reaction products were compared to the XAS spectra of selected model compounds and also to TD-DFT-calculated spectra. The viral NCp7 ZnF2 was compared to the human transcription factor Sp1 ZnF3. We examine the effects of the zinc coordination sphere in dictating reactivity and delineating the intimate mechanisms of metal ions substitution in a ZnF template. In the case of Au(I) compounds, we confirm the Lewis acid electrophilic attack of [AuCl(Et3P)] and auranofin after interaction with NCp7, resulting in a common final product with Cys-Au-PEt3 coordination sphere. In Chap. 1 , we demonstrated that the reaction product of [AuCl(Et3P)] with Sp1 had a remarkably clean mass spectrum. For that reason, we decided to purify and isolate the AuF obtained from that reaction and also study it using XAS. A Cys-Au-Cys coordination sphere is suggested for the the purified AuF studied here, as indicated by the electron rich gold center observed by XAS. As first discussed in Chap. 1 , we also demonstrate here that the reactivity of [AuCl(Et3P)] is also dependent on the ZnF core targeted.


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Authors and Affiliations

  1. 1.Institute of ChemistryUniversity of CampinasCampinasBrazil

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