In order to study metalloproteins, which change the metal oxidation states during the catalytic cycle, we have developed an electrochemical cell for in situ XAS measurement on biological samples. To be able to use proteins and mutants that are usually available in small quantities the cell was designed to minimise: a) cavity of RVC working electrode and b) cavities for electric contact between RVC working electrode and the other electrodes (counter and reference). The sample volume of 0.4 ml is sufficient for measurements at several applied potentials. We have investigated the reduction of (a) the hydroxocobalamin (from Co(III) to Co(I)) and (b) microperoxidase (from Fe(III) to Fe(II)). We have then determined the correct energy shift of XANES in the two systems. In the case of hydroxocobalamin, reduction from Co(III) to Co(II) produces the most significant structural changes (Giorgetti et al. 1997) The reduction from Co(II) to Co(I) produces mainly electronic effects with no apparent change of the coordination number. Microperoxidase XANES spectrum shifts by 1 eV ±0.5 eV upon oxidation.
X-ray absorption spectroscopy and electrochemistry on biological samples / Ascone I.; Cognigni A.; Giorgetti M.; Berrettoni M.; Zamponi S.; Marassi R.. - In: JOURNAL OF SYNCHROTRON RADIATION. - ISSN 0909-0495. - STAMPA. - 6:3(1999), pp. 384-386. [10.1107/S0909049599000047]
X-ray absorption spectroscopy and electrochemistry on biological samples
Giorgetti M.;
1999
Abstract
In order to study metalloproteins, which change the metal oxidation states during the catalytic cycle, we have developed an electrochemical cell for in situ XAS measurement on biological samples. To be able to use proteins and mutants that are usually available in small quantities the cell was designed to minimise: a) cavity of RVC working electrode and b) cavities for electric contact between RVC working electrode and the other electrodes (counter and reference). The sample volume of 0.4 ml is sufficient for measurements at several applied potentials. We have investigated the reduction of (a) the hydroxocobalamin (from Co(III) to Co(I)) and (b) microperoxidase (from Fe(III) to Fe(II)). We have then determined the correct energy shift of XANES in the two systems. In the case of hydroxocobalamin, reduction from Co(III) to Co(II) produces the most significant structural changes (Giorgetti et al. 1997) The reduction from Co(II) to Co(I) produces mainly electronic effects with no apparent change of the coordination number. Microperoxidase XANES spectrum shifts by 1 eV ±0.5 eV upon oxidation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
