Enhanced Photoinduced Electron Transfer Through a Tyrosine Relay in a De Novo Designed Protein Scaffold Bearing a Photoredox Unit and a FeIIS4 Site

Electron transfer (ET) processes in biology over long distances often proceed via a series of hops, which reduces the distance dependence of the rate of ET. The protein matrix itself can be involved in mediating ET directly through the participation of redox-active amino acids. We have designed an electron transfer chain incorporated into a de novo protein scaffold, which is capable of photoinduced intramolecular electron transfer between a photoredox unit and a (FeS4)-S-II site through a tyrosine amino acid relay. The kinetics were characterized by nanosecond laser pulse photolysis and revealed that electron transfer from [Ru(III)bpymal](3+) proceeds most efficiently via a tyrosine located similar to 16 angstrom from Rubpymal (bpymal=1-((1-([2,2 '-bipyridin]-4-yl)-1H-1,2,3-triazol-4-yl)methyl)-1H-pyrrole-2,5-dione). Removal of the tyrosine as the electron relay station results in a 20-fold decrease in the apparent rate constant for the electron transfer.

Automated summary

Electron transfer in biology often involves a series of hops, reducing the distance dependence of the rate of ET. The protein matrix can mediate ET directly through redox-active amino acids. A designed electron transfer chain incorporated into a de novo protein scaffold successfully achieved photoinduced intramolecular electron transfer via a tyrosine relay station.