Nanosecond heme-to-heme electron transfer rates in a multiheme cytochrome nanowire reported by a spectrally unique His/Met-ligated heme
Jessica H. van Wonderen, Katrin Adamczyk, Xiaojing Wu, Xiuyun Jiang, Samuel E. H. Piper, Christopher R. Hall, Marcus J. Edwards, Thomas A. Clarke, Huijie Zhang, Lars J. C. Jeuken, Igor V. Sazanovich, Michael Towrie, Jochen Blumberger, Stephen R. Meech, Julea N. Butt
Abstract
(3.7 to 4.3 Å edge-to-edge distance), in good agreement with predictions based on density functional and molecular dynamics calculations. These rates are among the highest reported for ground-state electron transfer in biology. Yet, some fall 2 to 3 orders of magnitude below the Moser-Dutton ruler because electron transfer at these short distances is through space and therefore associated with a higher tunneling barrier than the through-protein tunneling scenario that is usual at longer distances. Moreover, we show that the His/Met-ligated heme creates an electron sink that stabilizes the charge separated state on the 100-μs time scale. This feature could be exploited in future designs of multiheme cytochromes as components of versatile photosynthetic biohybrid assemblies.