Hannover 2010 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 2: Speicherringe und neue Entwicklungen

MS 2.5: Talk

Monday, March 8, 2010, 18:00–18:15, F 428

Marker bands for four-coordinate Fe(III)-heme proteins from absorption spectra of isolated chromophore ions in vacuo — •Jean Wyer — Department of Physics and Astronomy, Aarhus University

Heme proteins are ubiquitous in nature and are responsible for key biological. They are reddish-brown due to the presence of a heme group that is a porphyrin with an iron atom located in the centre. Electronic spectroscopy is used extensively to obtain detailed information on heme proteins such as conformation and dynamics. Importantly, spectral features depend on e.g. the iron oxidation state, axial ligands, and nearby amino acid residues. Often heme is located in hydrophobic protein pockets or crevices with minimal access to water. These pockets are in certain cases well simulated by a vacuum. It requires gas-phase experiments to establish the influence of a nearby environment, determined by the protein folding state. Conventional spectroscopic characterisations of Fe(III)-heme are hampered by the strong affinity of Fe(III) for water and anions. In this talk I will present the first unequivocal spectroscopic characterisation of isolated Fe(III)-heme ions and Fe(III)-heme-histidine complexes. Ions were generated by electrospray ionisation, stored in a pretrap, accelerated to keV energies and injected into the electrostatic ion storage ring in Aarhus, ELISA. Here they were irradiated by visible light. Based on the yield of photoproducts and the lifetimes with respect to dissociation, absorption spectra were obtained. The data are useful in bioanalytical chemistry and for benchmarking quantum mechanical calculations.