[FeFe]-hydrogenases are known for their high rates of hydrogen turnover, and are intensively studied in the context of biotechnological applications. Evolution has generated a plethora of different subclasses with widely...
Artificial
photosynthesis is seen as a path to convert and store
solar energy into chemical energy for our society. In this work, highly
fluorescent aspartic acid-based carbon dots (CDs) are synthesized
and employed as a photosensitizer to drive photocatalytic hydrogen
evolution with an [FeFe] hydrogenase (CrHydA1). The direct interaction
in CDs from l-aspartic acid (AspCDs)/CrHydA1 self-assembly
systems, which is visualized from native gel electrophoresis, has
been systematically investigated to understand the electron-transfer
dynamics and its impact on photocatalytic efficiency. The study discloses
the significant influence of the electrostatic surrounding generated
by sacrificial electron donors on the intimate interplay within the
oppositely charged subunits of the biohybrid assembly as well as the
overall photocatalytic performance. The system reaches an external
quantum efficiency of 1.7% at 420 nm and an initial activity of 1.73
μmol(H2) mg–1(hydrogenase) min–1 under favorable electrostatic conditions. Owing to
the ability of the synthesized AspCDs to operate efficiently under
visible light, in contrast to other materials that require UV illumination,
the stability of the biohybrid assembly in the presence of a redox
mediator extends beyond 1 week.
EPR spectroscopy reveals the formation of two different semi‐synthetic hydrogenases in vivo. [FeFe] hydrogenases are metalloenzymes that catalyze the interconversion of molecular hydrogen and protons. The reaction is catalyzed by the H‐cluster, consisting of a canonical iron–sulfur cluster and an organometallic [2Fe] subsite. It was recently shown that the enzyme can be reconstituted with synthetic cofactors mimicking the composition of the [2Fe] subsite, resulting in semi‐synthetic hydrogenases. Herein, we employ EPR spectroscopy to monitor the formation of two such semi‐synthetic enzymes in whole cells. The study provides the first spectroscopic characterization of semi‐synthetic hydrogenases in vivo, and the observation of two different oxidized states of the H‐cluster under intracellular conditions. Moreover, these findings underscore how synthetic chemistry can be a powerful tool for manipulation and examination of the hydrogenase enzyme under in vivo conditions.
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