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Benavides BS, Acharya R, Clark ER, Basak P, Maroney MJ, Nocek JM, Schanze KS, Kurtz DM. Structural, Photophysical, and Photochemical Characterization of Zinc Protoporphyrin IX in a Dimeric Variant of an Iron Storage Protein: Insights into the Mechanism of Photosensitized H 2 Generation. J Phys Chem B 2019; 123:6740-6749. [PMID: 31294990 DOI: 10.1021/acs.jpcb.9b04817] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Some of us have previously reported the preparation of a dimeric form of the iron storage protein, bacterioferritin (Bfr), in which the native heme b is substituted with the photosensitizer, Zn(II)-protoporphyrin IX (ZnPP-Bfr dimer). We further showed that the ZnPP-Bfr dimer can serve as a photosensitizer for platinum-catalyzed H2 generation in aqueous solution without the usually added electron relay between photosensitizer and platinum ( Clark , E. R. , Inorg. Chem. 2017 , 56 , 4584 - 4593 ). We proposed reductive or oxidative quenching pathways involving the ZnPP anion radical (ZnPP•-) or the ZnPP cation radical, (ZnPP•+), respectively. The present report describes structural, photophysical, and photochemical properties of the ZnPP in the ZnPP-Bfr dimer. X-ray absorption spectroscopic studies at 10 K showed a mixture of five- and six-coordinated Zn centers with axial coordination by one long Zn-SγMet distance of ∼2.8 Å and ∼40% having an additional shorter Zn-S distance of ∼2.4 Å, in addition to the expected 4 nitrogen atom coordination from the porphyrin. The ZnPP in ZnPP-Bfr dimer was prone to photosensitized oxidation to ZnPP•+. The ZnPP•+ was rapidly reduced by ascorbic acid, which we previously determined was essential for photosensitized H2 production in this system. These results are consistent with an oxidative quenching pathway involving electron transfer from 3ZnPP* to platinum, which may be assisted by a flexible ZnPP axial coordination sphere. However, the low quantum yield for H2 production (∼1%) in this system could make reductive quenching difficult to detect, and can, therefore, not be completely ruled out. The ZnPP-Bfr dimer provides a simple but versatile framework for mechanistic assessment and optimization of porphyrin-photosensitized H2 generation without an electron relay between porphyrin and the platinum catalyst.
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Affiliation(s)
- Brenda S Benavides
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Rajendra Acharya
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Emily R Clark
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Priyanka Basak
- Department of Chemistry , University of Massachusetts , Amherst , Massachusetts 01003 , United States
| | - Michael J Maroney
- Department of Chemistry , University of Massachusetts , Amherst , Massachusetts 01003 , United States
| | - Judith M Nocek
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - Kirk S Schanze
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Donald M Kurtz
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
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Conlan B, Messinger J. Thomas John Wydrzynski (8 July 1947-16 March 2018). PHOTOSYNTHESIS RESEARCH 2019; 140:253-261. [PMID: 30478710 PMCID: PMC6509086 DOI: 10.1007/s11120-018-0606-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 11/12/2018] [Indexed: 06/09/2023]
Abstract
With this Tribute, we remember and honor Thomas John (Tom) Wydrzynski. Tom was a highly innovative, independent and committed researcher, who had, early in his career, defined his life-long research goal. He was committed to understand how Photosystem II produces molecular oxygen from water, using the energy of sunlight, and to apply this knowledge towards making artificial systems. In this tribute, we summarize his research journey, which involved working on 'soft money' in several laboratories around the world for many years, as well as his research achievements. We also reflect upon his approach to life, science and student supervision, as we perceive it. Tom was not only a thoughtful scientist that inspired many to enter this field of research, but also a wonderful supervisor and friend, who is deeply missed (see footnote*).
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Affiliation(s)
- Brendon Conlan
- Research School of Biological Sciences, Australian Capital Territory, Australian National University, Acton, ACT, 0200, Australia
| | - Johannes Messinger
- Department of Chemistry - Ångström, Uppsala University, Lägerhyddsvägen 1, 75120, Uppsala, Sweden.
- Department of Chemistry, Umeå University, Linnaeus väg 6, 90187, Umeå, Sweden.
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Hingorani K, Pace R, Whitney S, Murray JW, Smith P, Cheah MH, Wydrzynski T, Hillier W. Photo-oxidation of tyrosine in a bio-engineered bacterioferritin 'reaction centre'-a protein model for artificial photosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1821-34. [PMID: 25107631 DOI: 10.1016/j.bbabio.2014.07.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 07/11/2014] [Accepted: 07/29/2014] [Indexed: 11/18/2022]
Abstract
The photosynthetic reaction centre (RC) is central to the conversion of solar energy into chemical energy and is a model for bio-mimetic engineering approaches to this end. We describe bio-engineering of a Photosystem II (PSII) RC inspired peptide model, building on our earlier studies. A non-photosynthetic haem containing bacterioferritin (BFR) from Escherichia coli that expresses as a homodimer was used as a protein scaffold, incorporating redox-active cofactors mimicking those of PSII. Desirable properties include: a di-nuclear metal binding site which provides ligands for bivalent metals, a hydrophobic pocket at the dimer interface which can bind a photosensitive porphyrin and presence of tyrosine residues proximal to the bound cofactors, which can be utilised as efficient electron-tunnelling intermediates. Light-induced electron transfer from proximal tyrosine residues to the photo-oxidised ZnCe6(•+), in the modified BFR reconstituted with both ZnCe6 and Mn(II), is presented. Three site-specific tyrosine variants (Y25F, Y58F and Y45F) were made to localise the redox-active tyrosine in the engineered system. The results indicate that: presence of bound Mn(II) is necessary to observe tyrosine oxidation in all BFR variants; Y45 the most important tyrosine as an immediate electron donor to the oxidised ZnCe6(•+) and that Y25 and Y58 are both redox-active in this system, but appear to function interchangebaly. High-resolution (2.1Å) crystal structures of the tyrosine variants show that there are no mutation-induced effects on the overall 3-D structure of the protein. Small effects are observed in the Y45F variant. Here, the BFR-RC represents a protein model for artificial photosynthesis.
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Affiliation(s)
- Kastoori Hingorani
- Building 134, Linnaeus Way, Research School of Biology, The Australian National University, ACT 0200, Australia.
| | - Ron Pace
- Building 137, Sullivans Creek Road, Research School of Chemistry, The Australian National University, ACT 0200, Australia.
| | - Spencer Whitney
- Building 134, Linnaeus Way, Research School of Biology, The Australian National University, ACT 0200, Australia
| | - James W Murray
- 724 Sir Ernst Chain Building, South Kensington Campus, Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Paul Smith
- Building 137, Sullivans Creek Road, Research School of Chemistry, The Australian National University, ACT 0200, Australia
| | - Mun Hon Cheah
- Building 134, Linnaeus Way, Research School of Biology, The Australian National University, ACT 0200, Australia
| | - Tom Wydrzynski
- Building 134, Linnaeus Way, Research School of Biology, The Australian National University, ACT 0200, Australia
| | - Warwick Hillier
- Building 134, Linnaeus Way, Research School of Biology, The Australian National University, ACT 0200, Australia
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Mahboob A, Vassiliev S, Poddutoori PK, van der Est A, Bruce D. Factors controlling the redox potential of ZnCe6 in an engineered bacterioferritin photochemical 'reaction centre'. PLoS One 2013; 8:e68421. [PMID: 23935866 PMCID: PMC3728335 DOI: 10.1371/journal.pone.0068421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 05/30/2013] [Indexed: 11/20/2022] Open
Abstract
Photosystem II (PSII) of photosynthesis has the unique ability to photochemically oxidize water. Recently an engineered bacterioferritin photochemical ‘reaction centre’ (BFR-RC) using a zinc chlorin pigment (ZnCe6) in place of its native heme has been shown to photo-oxidize bound manganese ions through a tyrosine residue, thus mimicking two of the key reactions on the electron donor side of PSII. To understand the mechanism of tyrosine oxidation in BFR-RCs, and explore the possibility of water oxidation in such a system we have built an atomic-level model of the BFR-RC using ONIOM methodology. We studied the influence of axial ligands and carboxyl groups on the oxidation potential of ZnCe6 using DFT theory, and finally calculated the shift of the redox potential of ZnCe6 in the BFR-RC protein using the multi-conformational molecular mechanics–Poisson-Boltzmann approach. According to our calculations, the redox potential for the first oxidation of ZnCe6 in the BRF-RC protein is only 0.57 V, too low to oxidize tyrosine. We suggest that the observed tyrosine oxidation in BRF-RC could be driven by the ZnCe6 di-cation. In order to increase the efficiency of tyrosine oxidation, and ultimately oxidize water, the first potential of ZnCe6 would have to attain a value in excess of 0.8 V. We discuss the possibilities for modifying the BFR-RC to achieve this goal.
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Affiliation(s)
- Abdullah Mahboob
- Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada.
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Abstract
This paper presents an overview of the prospects for bio-solar energy conversion. The Global Artificial Photosynthesis meeting at Lord Howe Island (14–18 August 2011) underscored the dependence that the world has placed on non-renewable energy supplies, particularly for transport fuels, and highlighted the potential of solar energy. Biology has used solar energy for free energy gain to drive chemical reactions for billions of years. The principal conduits for energy conversion on earth are photosynthetic reaction centres – but can they be harnessed, copied and emulated? In this communication, we initially discuss algal-based biofuels before investigating bio-inspired solar energy conversion in artificial and engineered systems. We show that the basic design and engineering principles for assembling photocatalytic proteins can be used to assemble nanocatalysts for solar fuel production.
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Vassiliev S, Mahboob A, Bruce D. Calculation of chromophore excited state energy shifts in response to molecular dynamics of pigment-protein complexes. PHOTOSYNTHESIS RESEARCH 2011; 110:25-38. [PMID: 21964859 DOI: 10.1007/s11120-011-9689-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 09/15/2011] [Indexed: 05/26/2023]
Abstract
The absorption and energy transfer properties of photosynthetic pigments are strongly influenced by their local environment or "site." Local electrostatic fields vary in time with protein and chromophore molecular movement and thus transiently influence the excited state transition properties of individual chromophores. Site-specific information is experimentally inaccessible in many light-harvesting pigment-proteins due to multiple chromophores with overlapping spectra. Full quantum mechanical calculations of each chromophores excited state properties are too computationally demanding to efficiently calculate the changing excitation energies along a molecular dynamics trajectory in a pigment-protein complex. A simplified calculation of electrostatic interactions with each chromophores ground to excited state transition, the so-called charge density coupling (CDC) for site energy, CDC, has previously been developed to address this problem. We compared CDC to more rigorous quantum chemical calculations to determine its accuracy in computing excited state energy shifts and their fluctuations within a molecular dynamics simulation of the bacteriochlorophyll containing light-harvesting Fenna-Mathews-Olson (FMO) protein. In most cases CDC calculations differed from quantum mechanical (QM) calculations in predicting both excited state energy and its fluctuations. The discrepancies arose from the inability of CDC to account for the differing effects of charge on ground and excited state electron orbitals. Results of our study show that QM calculations are indispensible for site energy computations and the quantification of contributions from different parts of the system to the overall site energy shift. We suggest an extension of QM/MM methodology of site energy shift calculations capable of accounting for long-range electrostatic potential contributions from the whole system, including solvent and ions.
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Affiliation(s)
- Serguei Vassiliev
- Department of Biology, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada.
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Williamson A, Conlan B, Hillier W, Wydrzynski T. The evolution of Photosystem II: insights into the past and future. PHOTOSYNTHESIS RESEARCH 2011; 107:71-86. [PMID: 20512415 DOI: 10.1007/s11120-010-9559-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 05/07/2010] [Indexed: 05/29/2023]
Abstract
This article attempts to address the molecular origin of Photosystem II (PSII), the central component in oxygenic photosynthesis. It discusses the possible evolution of the relevant cofactors needed for splitting water into molecular O2 with respect to the following functional domains in PSII: the reaction center (RC), the oxygen evolving complex (OEC), and the manganese stabilizing protein (MSP). Possible ancestral sources of the relevant cofactors are considered, as are scenarios of how these components may have been brought together to produce the intermediate steps in the evolution of PSII. Most importantly, the driving forces that maintained these intermediates for continued adaptation are considered. We then apply our understanding of the evolution of PSII to the bioengineering of a water oxidizing catalyst for utilization of solar energy.
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Affiliation(s)
- Adele Williamson
- Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, ACT, 0200, Australia
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Thordarson P, Payne RJ. The Inaugural Australian Workshop on Bioconjugate Chemistry, UNSW 2008. Aust J Chem 2009. [DOI: 10.1071/ch09412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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