Open AccessX‐ray absorption spectroscopy and electrochemistry on biological samples
Author(s) -
Ascone I.,
Cognigni A.,
Giorgetti M.,
Berrettoni M.,
Zamponi S.,
Marassi R.
Publication year - 1999
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049599000047
Subject(s) - electrochemistry , spectroscopy , x ray absorption spectroscopy , absorption (acoustics) , absorption spectroscopy , materials science , analytical chemistry (journal) , x ray spectroscopy , chemistry , optics , physics , environmental chemistry , electrode , quantum mechanics , composite material
Nevertheless, there is an important increase of photon density on the sample and, consequently, a significant amount of free oxygen radicals is produced in solution. Oxygen radicals can photoreduce the metal center during sample X-ray irradiation. This effect is critical for the oxygen binding proteins in which the oxidation state have to be determined. Combination of electrochemical methods and XAS allows the study of the redox processes in situ without any chemical pollution. Therefore species otherwise unstable can be isolated. Moreover the electrode, under electrostatic control, acts as a scavenger avoiding damages to the protein structure. We have developed a three-electrode spectroelectrochemical cell (figure 1) based on the model proposed by Dewald et al. (1986). The main modification is that the total volume of the sample is considerably reduced (0.4 ml). The small amount of sample used permits also to minimize the whole faradic current, reducing the time to reach redox equilibrium.