Retracted Article: On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre

Abstract

Catalase and methaemoglobin have very similar haem groups, which are both ferric, yet catalase decomposes hydrogen peroxide to water and oxygen very efficiently, while methaemoglobin does not. Structural studies have attributed this behaviour to their different distal environments. Here we present Fe L 2,3 -edge X-ray absorption spectra of these proteins in physiological solutions, which reveal clear differences in their electronic structures, in that p back-donation of the Fe atom occurs in catalase, which confers on it a partial ferryl (Fe 4+ ) character, while this is not the case in methaemoglobin. The origin of the Fe 4+ character stems from the proximal tyrosine residue. We also find that both systems are in a high spin state. Temperature effects influence the spectra of catalase only weakly, in agreement with previous studies of its chemical activity. We conclude that the high activity of catalase is not only determined by its distal environment but also by its partial ferryl character.

Ultrafast photoelectron spectroscopy of solutions: space-charge effect

“…The study of electronic and structural dynamics in solutions and at interfaces received much attention during the past years [1][2][3][4][5][6][7][8][9]. The interest and the importance of these studies arise from the fact that solutions represent a natural environment for most biochemical complexes [10][11][12][13]. Various non-radiative electronic transitions can be initiated by light in biochemical complexes.…”

Probing the electronic and geometric structure of ferric and ferrous myoglobins in physiological solutions by Fe K-edge absorption spectroscopy

“…39,[43][44][45][46][47][48][49][50][51] Despite the fact that the physiological environment is the most relevant to the biological function, XAS studies of heme proteins under physiological conditions (pH 7 solution, room temperature and pressure) are almost completely lacking, except for the recent soft X-ray studies carried out at the Fe L 2/3 -edges. 40,42,52 Low temperature frozen solutions of heme proteins have generally been used as they reduce the thermal vibration of the atoms and, in the case of photolysed samples, trap intermediates so that their structures could be determined. However, aside from being far from the conditions in which proteins function, these samples are prone to radiation damage and lysis.…”

Insights into the Induced Ultrafast Electron Delocalization in Fe(CO)5 Using Dark Channel Fluorescence Yield X‐Ray Absorption

“…Experimental details for soft X-ray spectroscopy of liquid solutions have been described previously. [22,25] During acquisition of the L 3 -edge spectra, the sample was circulating in direct contact behind the entrance window of the cell, which was a 150 nm thick Si 3 N 4 membrane. The cell was placed inside a highvacuum chamber.…”

“…The experimental setup is described in detail in previous reports, [22][23][24][25] as well as in the Supporting Information (S1 for sample preparation and S2.a for the experiment). Figure 1 shows the L 2,3 -edge spectra of Fe(CO) 5 in n-hexane versus THF.…”

“…New developments allow the application of L-edge XAS to high vapour pressure samples at synchrotron light facilities. [22][23][24][25] In general, there are three methods that can be used for Ledge XAS. Transmission measurements are known to directly probe the absorption cross section.…”