Abstract: 

Lanthanide photocatalysis is a powerful tool to activate organic molecules under mild conditions. For instance, radical species can be formed using visible light and simple complexes of the earth-abundant lanthanide cerium. However, it remains a major challenge to control the fate of these reactive intermediates in subsequent reaction steps. To tackle this problem, we developed an artificial lanthanide-dependent photoenzyme (= PhotoLanZyme) enabling this chemistry inside a protein. We first equipped a de novo protein scaffold with a binding site for lanthanide ions and studied the interplay between protein dynamics and metal coordination in this system. Upon visible-light irradiation, the cerium-bound enzyme catalyses the radical C–C bond cleavage of 1,2-diols in aqueous solution. After characterising the molecular effects of photodamage, we used protein engineering to improve the enzyme’s photostability and metal binding properties. The photoenzyme cleaves a range of aromatic and aliphatic substrates, including lignin surrogates. Surface display of the protein scaffold on E. coli and subsequent treatment of the cells with CeCl₃ facilitates whole-cell photobiocatalysis. Furthermore, we found that also natural lanthanide-binding proteins have promiscuous enzymatic activity towards cerium photoredox chemistry.

Hosted by Ross Anderson