Donnerstag, 16. November 2017, 13:30 - 14:45 iCal

Prof. Antonin Vlcek

Queen Mary University of London, UK


"Tryptophan-Acceleration of Photoinduced Electron Transfer in Rhenium-Labeled Proteins"

Seminarraum, 4. Stock
Währinger Straße 17, 1090 Wien


„Tryptophan-Acceleration of Photoinduced Electron Transfer in Rhenium-Labeled Proteins”


Acceleration and control of electron transfer (ET) through proteins and across protein-protein interfaces are necessary prerequisites for designing protein-based light-harvesting systems and photocatalysts. Herein, we will demonstrate that long-range electron transfer in azurins labeled with a Re(CO)3(4,7-Me2-1,10-phenanthroline)+ chromophore (Re) is strongly accelerated by introducing a tryptophan (Trp) residue in the label vicinity. Initial steps of Re photoreduction are ultrafast (fs-ps), accompanied by structural relaxation of the binding site. Theoretical studies revealed an electronic delocalization in the *Re---Trp unit that enables very fast formation of a Re–---Trp?+ charge separated state, followed by a ~30 ns CuI?Trp?+ ET over 11 Å. Moving the Re chromophore two amino acid residues away from the active tryptophan shuts the direct intramolecular Re---W interaction, but the CuI?*Re ET still occurs on the same ns timescale, again involving ultrafast initial ET steps at the Re site, this time enabled by interfacial electron hopping across a hydrophobic protein-protein boundary. Fast ET kinetics and ultrafast initial steps were also found in a "tryptophan wire" azurin mutant, where ET occurs in 30 ns over a remarkably long distance of 23 Å through two tryptophans. Ultrafast charge separation in Trp-containing proteins seems to be characteristic of systems where the protein environment properly orients the chromophore and the Trp indole group. This is the case of the Re-azurins, as well as, e.g., the enzyme photolyase.


Fakultät für Chemie, Institut für Theoretische Chemie


Brigitte Schwarz
Fakultät für Chemie der Universität Wien