Berlin 2005 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 30: POSTER: Chemical physics
CPP 30.25: Poster
Tuesday, March 8, 2005, 16:30–18:30, Poster TU D
X-ray Absorption Spectromicroscopy of the Copper-Oxygen Complex in the Respiratory Protein Haemocyanine — •A. Krasyuk1, A. Oelsner1, G. Schönhense1, M. Möller2, H. Decker2, M. Pohl3, U. Kleineberg3, and U. Heinzman3 — 1Institut für Physik, Johannes Gutenberg - Universität, 55099 Mainz — 2Institut für Biophysik, Johannes Gutenberg - Universität, 55099 Mainz — 3Fakultät für Physik, Universität Bielefeld, 33501 Bielefeld
We report on XANES investigations at the copper L2,3 edges and oxygen K-edge of haemocyanine molecules in aqueous TRIS buffer solution (or dehydrated) using photoemission electron microscope. The experiment [1] has been performed at the undulator beamline UE56/1 SGM at BESSY II. Although the investigated molecules (24-mere with a volume of 20 x 20 x 10nm3) contain only 48 Cu atoms, the Cu L2,3 absorption edges at 930 eV (L3) and 948 eV (L2) are clearly detectable. A spectromicroscopic analysis of different regions of a micrometer-size haemocyanine cluster reveals two different Cu species with the position of the L3 signal showing a chemical shift of about 1 eV. This is the size of shift expected for the difference between monovalent Cu (as present in the deoxy-state) and the divalent Cu (present in the oxy-state), as measured for copper oxides [2]. Measurements in the O K XANES region above 530 eV photon energy reveal strong differences in the oxygen XANES, again showing similarities with the corresponding spectra for Cu oxides. Financial support by BMBF (05 KS1 UMC-0) and DFG (SFB 625, project B5) is gratefully acknowledged. [1]M. Pohl et al., Ultramicroscopy (2004) in print, [2]M. Hävecker, Dissertation TU Berlin (2000).