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Nefedova A, Svensson FG, Vanetsev AS, Agback P, Agback T, Gohil S, Kloo L, Tätte T, Ivask A, Seisenbaeva GA, Kessler VG. Molecular Mechanisms in Metal Oxide Nanoparticle-Tryptophan Interactions. Inorg Chem 2024; 63:8556-8566. [PMID: 38684718 PMCID: PMC11094791 DOI: 10.1021/acs.inorgchem.3c03674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 04/10/2024] [Accepted: 04/15/2024] [Indexed: 05/02/2024]
Abstract
One of the crucial metabolic processes for both plant and animal kingdoms is the oxidation of the amino acid tryptophan (TRP) that regulates plant growth and controls hunger and sleeping patterns in animals. Here, we report revolutionary insights into how this process can be crucially affected by interactions with metal oxide nanoparticles (NPs), creating a toolbox for a plethora of important biomedical and agricultural applications. Molecular mechanisms in TRP-NP interactions were revealed by NMR and optical spectroscopy for ceria and titania and by X-ray single-crystal study and a computational study of model TRP-polyoxometalate complexes, which permitted the visualization of the oxidation mechanism at an atomic level. Nanozyme activity, involving concerted proton and electron transfer to the NP surface for oxides with a high oxidative potential, like CeO2 or WO3, converted TRP in the first step into a tricyclic organic acid belonging to the family of natural plant hormones, auxins. TiO2, a much poorer oxidant, was strongly binding TRP without concurrent oxidation in the dark but oxidized it nonspecifically via the release of reactive oxygen species (ROS) in daylight.
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Affiliation(s)
- Alexandra Nefedova
- Institute
of Physics, University of Tartu, W.Ostwaldi 1, 50411 Tartu, Estonia
| | - Fredric G. Svensson
- Department
of Solid State Physics, Ångström Laboratory, Uppsala University, Box 35, SE-75103 Uppsala, Sweden
| | | | - Peter Agback
- Department
of Molecular Science, BioCenter, Swedish
University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden
| | - Tatiana Agback
- Department
of Molecular Science, BioCenter, Swedish
University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden
| | - Suresh Gohil
- Department
of Molecular Science, BioCenter, Swedish
University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden
| | - Lars Kloo
- Applied
Physical Chemistry, KTH Royal Institute
of Technology, Teknikringen 30, SE-100 44 Stockholm, Sweden
| | - Tanel Tätte
- Institute
of Physics, University of Tartu, W.Ostwaldi 1, 50411 Tartu, Estonia
| | - Angela Ivask
- Institute
of Molecular and Cell Biology, University
of Tartu, Riia 23, 51010 Tartu, Estonia
| | - Gulaim A. Seisenbaeva
- Department
of Molecular Science, BioCenter, Swedish
University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden
| | - Vadim G. Kessler
- Department
of Molecular Science, BioCenter, Swedish
University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden
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Kessinger MC, Xu J, Cui K, Loague Q, Soudackov AV, Hammes-Schiffer S, Meyer GJ. Direct Evidence for a Sequential Electron Transfer-Proton Transfer Mechanism in the PCET Reduction of a Metal Hydroxide Catalyst. J Am Chem Soc 2024; 146:1742-1747. [PMID: 38193695 DOI: 10.1021/jacs.3c10742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
The proton-coupled electron transfer (PCET) mechanism for the reaction Mox-OH + e- + H+ → Mred-OH2 was determined through the kinetic resolution of the independent electron transfer (ET) and proton transfer (PT) steps. The reaction of interest was triggered by visible light excitation of [RuII(tpy)(bpy')H2O]2+, RuII-OH2, where tpy is 2,2':6',2″-terpyridine and bpy' is 4,4'-diaminopropylsilatrane-2,2'-bipyridine, anchored to In2O3:Sn (ITO) thin films in aqueous solutions. Interfacial kinetics for the PCET reduction reaction were quantified by nanosecond transient absorption spectroscopy as a function of solution pH and applied potential. Data acquired at pH = 5-10 revealed a stepwise electron transfer-proton transfer (ET-PT) mechanism, while kinetic measurements made below pKa(RuIII-OH/OH2) = 1.3 were used to study the analogous interfacial reaction, where electron transfer was the only mechanistic step. Analysis of this data with a recently reported multichannel kinetic model was used to construct a PCET zone diagram and supported the assignment of an ET-PT mechanism at pH = 5-10. Ultimately, this study represents a unique example among Mox-OH/Mred-OH2 reactivity where the protonation and oxidation states of the intermediate were kinetically and spectrally resolved to firmly establish the PCET mechanism.
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Affiliation(s)
- Matthew C Kessinger
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Jeremiah Xu
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Kai Cui
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Quentin Loague
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Alexander V Soudackov
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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