Reorganization Energy of the CuA Center in Purple Azurin: Impact of the Mixed Valence-to-Trapped Valence State Transition
Citations Over TimeTop 21% of 2007 papers
Abstract
Mixed valence (MV) coordination compounds play important roles in redox reactions in chemistry and biology. Details of the contribution of a mixed valence state to protein electron transfer (ET) reactivity such as reorganization energy, however, have not been experimentally defined. Herein we report measurements of reorganization energies of a binuclear CuA center engineered into Pseudomonas aeruginosa azurin that exhibits a reversible transition between a totally delocalized MV state at pH 8.0 and a trapped valence (TV) state at pH 4.0. The reorganization energy of a His120Ala variant of CuA azurin that displays a TV state at both the above pH values has also been determined. We found that the MV-to-TV state transition increases the reorganization energy by 0.18 eV, providing evidence that the MV state of the CuA center has lower reorganization energy than its TV counterpart. We have also shown that lowering the pH from 8.0 to 4.0 results in a similar (approximately 0.4 eV) decrease in reorganization energy for both blue (type 1) and purple (CuA) azurins, even though the reorganization energies of the two different copper centers are different at a given pH. These results suggest that the MV state plays only a secondary role in modulation of the ET reactivity via the reorganization energy, as compared to that of the driving force.
Related Papers
- → The kinetics of a weakly electron-coupled proton transfer in azurin(2002)27 cited
- → Valence‐Delocalized and Valence‐Trapped FeIIFeIII Complexes: Drastic Influence of the Ligands(1997)72 cited
- → Surface Immobilized His-tagged Azurin as a Model Interface for the Investigation of Vectorial Electron Transfer in Biological Systems(2015)7 cited
- → Electron transfer between azurin and cytochrone c-551 from Pseudomonas aeruginosa(1975)56 cited
- → Electron Transfer Reactions(2000)1 cited