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Utschig LM, Mulfort KL. Photosynthetic biohybrid systems for solar fuels catalysis. Chem Commun (Camb) 2024. [PMID: 39229971 DOI: 10.1039/d4cc00774c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
Photosynthetic reaction center (RC) proteins are finely tuned molecular systems optimized for solar energy conversion. RCs effectively capture and convert sunlight with near unity quantum efficiency utilizing light-induced directional electron transfer through a series of molecular cofactors embedded within the protein core to generate a long-lived charge separated state with a useable electrochemical potential. Of current interest are new strategies that couple RC chemistry to the direct synthesis of energy-rich compounds. This Feature Article highlights recent work from our lab on RC and RC-inspired hybrid systems that capture the Sun's energy and convert it to chemical energy in the form of H2, a carbon-neutral energy source derived from water. Biohybrids made from the Photosystem I (PSI) RC are among the best photocatalytic H2-producing protein hybrids to date. Targeted self-assembly strategies that couple abiotic catalysts to PSI translate to catalyst incorporation at intrinsic PSI sites within thylakoid membranes to achieve complete solar water-splitting systems. RC-inspired biohybrids interface synthetic photosensitizers and molecular catalysts with small proteins to create photocatalytic systems and enable the spectroscopic discernment of the structural features and electron transfer processes that underpin solar-driven proton reduction. In total, these studies showcase the incredible scientific opportunities photosynthetic biohybrid research provides for harnessing the optimal qualities of both artificial and natural photosynthetic systems and developing materials that capture, convert, and store solar energy as a fuel.
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Affiliation(s)
- Lisa M Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA.
| | - Karen L Mulfort
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA.
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Utschig LM, Brahmachari U, Mulfort KL, Niklas J, Poluektov OG. Biohybrid photosynthetic charge accumulation detected by flavin semiquinone formation in ferredoxin-NADP + reductase. Chem Sci 2022; 13:6502-6511. [PMID: 35756516 PMCID: PMC9172293 DOI: 10.1039/d2sc01546c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022] Open
Abstract
Flavin chemistry is ubiquitous in biological systems with flavoproteins engaged in important redox reactions. In photosynthesis, flavin cofactors are used as electron donors/acceptors to facilitate charge transfer and accumulation for ultimate use in carbon fixation. Following light-induced charge separation in the photosynthetic transmembrane reaction center photosystem I (PSI), an electron is transferred to one of two small soluble shuttle proteins, a ferredoxin (Fd) or a flavodoxin (Fld) (the latter in the condition of Fe-deficiency), followed by electron transfer to the ferredoxin-NADP+ reductase (FNR) enzyme. FNR accepts two of these sequential one electron transfers, with its flavin adenine dinucleotide (FAD) cofactor becoming doubly reduced, forming a hydride which is then passed onto the substrate NADP+ to form NADPH. The two one-electron potentials (oxidized/semiquinone and semiquinone/hydroquinone) are similar to each other with the FNR protein stabilizing the hydroquinone, making spectroscopic detection of the intermediate semiquinone state difficult. We employed a new biohybrid-based strategy that involved truncating the native three-protein electron transfer cascade PSI → Fd → FNR to a two-protein cascade by replacing PSI with a molecular Ru(ii) photosensitizer (RuPS) which is covalently bound to Fd and Fld to form biohybrid complexes that successfully mimic PSI in light-driven NADPH formation. RuFd → FNR and RuFld → FNR electron transfer experiments revealed a notable distinction in photosynthetic charge accumulation that we attribute to the different protein cofactors [2Fe2S] and flavin. After freeze quenching the two-protein systems under illumination, an intermediate semiquinone state of FNR was readily observed with cw X-band EPR spectroscopy. The increased spectral resolution from selective deuteration allowed EPR detection of inter-flavoprotein electron transfer. This work establishes a biohybrid experimental approach for further studies of photosynthetic light-driven electron transfer chain that culminates at FNR and highlights nature's mechanisms that couple single electron transfer chemistry to charge accumulation, providing important insight for the development of photon-to-fuel schemes.
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Affiliation(s)
- Lisa M Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Udita Brahmachari
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Karen L Mulfort
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
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Marzolf DR, McKenzie AM, O’Malley MC, Ponomarenko NS, Swaim CM, Brittain TJ, Simmons NL, Pokkuluri PR, Mulfort KL, Tiede DM, Kokhan O. Mimicking Natural Photosynthesis: Designing Ultrafast Photosensitized Electron Transfer into Multiheme Cytochrome Protein Nanowires. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2143. [PMID: 33126541 PMCID: PMC7693585 DOI: 10.3390/nano10112143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/23/2020] [Accepted: 10/26/2020] [Indexed: 05/02/2023]
Abstract
Efficient nanomaterials for artificial photosynthesis require fast and robust unidirectional electron transfer (ET) from photosensitizers through charge-separation and accumulation units to redox-active catalytic sites. We explored the ultrafast time-scale limits of photo-induced charge transfer between a Ru(II)tris(bipyridine) derivative photosensitizer and PpcA, a 3-heme c-type cytochrome serving as a nanoscale biological wire. Four covalent attachment sites (K28C, K29C, K52C, and G53C) were engineered in PpcA enabling site-specific covalent labeling with expected donor-acceptor (DA) distances of 4-8 Å. X-ray scattering results demonstrated that mutations and chemical labeling did not disrupt the structure of the proteins. Time-resolved spectroscopy revealed three orders of magnitude difference in charge transfer rates for the systems with otherwise similar DA distances and the same number of covalent bonds separating donors and acceptors. All-atom molecular dynamics simulations provided additional insight into the structure-function requirements for ultrafast charge transfer and the requirement of van der Waals contact between aromatic atoms of photosensitizers and hemes in order to observe sub-nanosecond ET. This work demonstrates opportunities to utilize multi-heme c-cytochromes as frameworks for designing ultrafast light-driven ET into charge-accumulating biohybrid model systems, and ultimately for mimicking the photosynthetic paradigm of efficiently coupling ultrafast, light-driven electron transfer chemistry to multi-step catalysis within small, experimentally versatile photosynthetic biohybrid assemblies.
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Affiliation(s)
- Daniel R. Marzolf
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Aidan M. McKenzie
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Matthew C. O’Malley
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Nina S. Ponomarenko
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA; (N.S.P.); (K.L.M.); (D.M.T.)
| | - Coleman M. Swaim
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Tyler J. Brittain
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Natalie L. Simmons
- Department of Biology, James Madison University, Harrisonburg, VA 22807, USA;
| | | | - Karen L. Mulfort
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA; (N.S.P.); (K.L.M.); (D.M.T.)
| | - David M. Tiede
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA; (N.S.P.); (K.L.M.); (D.M.T.)
| | - Oleksandr Kokhan
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
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Edwards EH, Bren KL. Light-driven catalysis with engineered enzymes and biomimetic systems. Biotechnol Appl Biochem 2020; 67:463-483. [PMID: 32588914 DOI: 10.1002/bab.1976] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 06/21/2020] [Indexed: 01/01/2023]
Abstract
Efforts to drive catalytic reactions with light, inspired by natural processes like photosynthesis, have a long history and have seen significant recent growth. Successfully engineering systems using biomolecular and bioinspired catalysts to carry out light-driven chemical reactions capitalizes on advantages offered from the fields of biocatalysis and photocatalysis. In particular, driving reactions under mild conditions and in water, in which enzymes are operative, using sunlight as a renewable energy source yield environmentally friendly systems. Furthermore, using enzymes and bioinspired systems can take advantage of the high efficiency and specificity of biocatalysts. There are many challenges to overcome to fully capitalize on the potential of light-driven biocatalysis. In this mini-review, we discuss examples of enzymes and engineered biomolecular catalysts that are activated via electron transfer from a photosensitizer in a photocatalytic system. We place an emphasis on selected forefront chemical reactions of high interest, including CH oxidation, proton reduction, water oxidation, CO2 reduction, and N2 reduction.
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Affiliation(s)
- Emily H Edwards
- Department of Chemistry, University of Rochester, Rochester, NY, USA
| | - Kara L Bren
- Department of Chemistry, University of Rochester, Rochester, NY, USA
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