Streptavidin as a Scaffold for Light‐Induced Long‐Lived Charge Separation

Abstract

Long-lived photo-driven charge separation is demonstrated by assembling a triad on a protein scaffold. For this purpose, a biotinylated triarylamine was added to a Ru -streptavidin conjugate bearing a methyl viologen electron acceptor covalently linked to the N-terminus of streptavidin. To improve the rate and lifetime of the electron transfer, a negative patch consisting of up to three additional negatively charged amino acids was engineered through mutagenesis close to the biotin-binding pocket of streptavidin. Time-resolved laser spectroscopy revealed that the covalent attachment and the negative patch were beneficial for charge separation within the streptavidin hosted triad; the charge separated state was generated within the duration of the excitation laser pulse, and lifetimes up to 3120 ns could be achieved with the optimized supramolecular triad.

Controlling the optical and catalytic properties of artificial metalloenzyme photocatalysts using chemogenetic engineering

“…methyl viologen in streptavidin). 29 Non-covalent binding in POP Neut and POP Neg increases substantially, and K d values approaching the nM regime are observed for Ru(Bpy) 3…”

“…cytochrome f in photosystem I) [70][71][72] and synthetic systems (e.g. methyl viologen in streptavidin) 29 . Non-covalent binding in POP Neut and POP Neg increases substantially, and K d values approaching the nM regime are observed for Ru(Bpy) 3 2+ binding.…”

“…Importantly, in these cases, the metal polypyridine complexes were solvent exposed, often residing in shallow clefts with limited capacity to interact with the cofactor. While changes in the photophysical or redox properties of the protein-linked complexes were reported in these examples [20][21][22][23][24][25][26][27][28][29] and others [30][31][32][33] , none of these systems were used as photocatalysts for direct transformations of organic substrates.…”

“…[22][23][24] Cheruzel later developed related systems to enable light-driven P450 hydroxylation catalysis 25 and to modulate the photophysical and catalytic properties of these systems through pyridyl ligand substitution. 26 Ward linked Ru(II)-polypyridyl complexes to (strept)avidin via non-covalent biotin binding 27 or covalent cysteine bioconjugation 28,29 and explored SET in donorphotosensitizer-acceptor triads involving these systems. Importantly, in these cases, the metal polypyridine complexes were solvent exposed, oen residing in shallow cles with limited capacity to interact with the cofactor.…”

Controlling the Optical and Catalytic Properties of Artificial Metalloenzyme Photocatalysts Using Chemogenetic Engineering

“…Importantly, in these cases, the metal polypyridine complexes were solvent exposed, oen residing in shallow cles with limited capacity to interact with the cofactor. While changes in the photophysical or redox properties of the protein-linked complexes were reported in these examples [20][21][22][23][24][25][26][27][28][29] and others, [30][31][32][33] none of these systems were used as photocatalysts for direct transformations of organic substrates.…”