1
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Borsley S, Leigh DA, Roberts BMW. Molecular Ratchets and Kinetic Asymmetry: Giving Chemistry Direction. Angew Chem Int Ed Engl 2024; 63:e202400495. [PMID: 38568047 DOI: 10.1002/anie.202400495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Indexed: 05/03/2024]
Abstract
Over the last two decades ratchet mechanisms have transformed the understanding and design of stochastic molecular systems-biological, chemical and physical-in a move away from the mechanical macroscopic analogies that dominated thinking regarding molecular dynamics in the 1990s and early 2000s (e.g. pistons, springs, etc), to the more scale-relevant concepts that underpin out-of-equilibrium research in the molecular sciences today. Ratcheting has established molecular nanotechnology as a research frontier for energy transduction and metabolism, and has enabled the reverse engineering of biomolecular machinery, delivering insights into how molecules 'walk' and track-based synthesisers operate, how the acceleration of chemical reactions enables energy to be transduced by catalysts (both motor proteins and synthetic catalysts), and how dynamic systems can be driven away from equilibrium through catalysis. The recognition of molecular ratchet mechanisms in biology, and their invention in synthetic systems, is proving significant in areas as diverse as supramolecular chemistry, systems chemistry, dynamic covalent chemistry, DNA nanotechnology, polymer and materials science, molecular biology, heterogeneous catalysis, endergonic synthesis, the origin of life, and many other branches of chemical science. Put simply, ratchet mechanisms give chemistry direction. Kinetic asymmetry, the key feature of ratcheting, is the dynamic counterpart of structural asymmetry (i.e. chirality). Given the ubiquity of ratchet mechanisms in endergonic chemical processes in biology, and their significance for behaviour and function from systems to synthesis, it is surely just as fundamentally important. This Review charts the recognition, invention and development of molecular ratchets, focussing particularly on the role for which they were originally envisaged in chemistry, as design elements for molecular machinery. Different kinetically asymmetric systems are compared, and the consequences of their dynamic behaviour discussed. These archetypal examples demonstrate how chemical systems can be driven inexorably away from equilibrium, rather than relax towards it.
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Affiliation(s)
- Stefan Borsley
- Department of Chemistry, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
| | - David A Leigh
- Department of Chemistry, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
| | - Benjamin M W Roberts
- Department of Chemistry, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
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2
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Roy P, Sardjan AS, Browne WR, Feringa BL, Meech SR. Excited State Dynamics in Unidirectional Photochemical Molecular Motors. J Am Chem Soc 2024; 146:12255-12270. [PMID: 38656968 PMCID: PMC11082934 DOI: 10.1021/jacs.4c01019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 04/05/2024] [Accepted: 04/08/2024] [Indexed: 04/26/2024]
Abstract
Unidirectional photochemically driven molecular motors (PMMs) convert the energy of absorbed light into continuous rotational motion. As such they are key components in the design of molecular machines. The prototypical and most widely employed class of PMMs is the overcrowded alkenes, where rotational motion is driven by successive photoisomerization and thermal helix inversion steps. The efficiency of such PMMs depends upon the speed of rotation, determined by the rate of ground state thermal helix inversion, and the quantum yield of photoisomerization, which is dependent on the excited state energy landscape. The former has been optimized by synthetic modification across three generations of overcrowded alkene PMMs. These improvements have often been at the expense of photoisomerization yield, where there remains room for improvement. In this perspective we review the application of ultrafast spectroscopy to characterize the excited state dynamics in PMMs. These measurements lead to a general mechanism for all generations of PMMs, involving subpicosecond decay of a Franck-Condon excited state to populate a dark excited state which decays within picoseconds via conical intersections with the electronic ground state. The model is discussed in the context of excited state dynamics calculations. Studies of PMM photochemical dynamics as a function of solvent suggest exploitation of intramolecular charge transfer and solvent polarity as a route to controlling photoisomerization yield. A test of these ideas for a first generation motor reveals a high degree of solvent control over isomerization yield. These results suggest a pathway to fine control over the performance of future PMMs.
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Affiliation(s)
- Palas Roy
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
- School
of Basic Sciences, Indian Institute of Technology
Bhubaneswar, Bhubaneswar, Odisha 752050, India
| | - Andy S. Sardjan
- Molecular
Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747AG Groningen, The Netherlands
| | - Wesley R. Browne
- Molecular
Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747AG Groningen, The Netherlands
| | - Ben L. Feringa
- Centre
for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747AG Groningen, The Netherlands
| | - Stephen R. Meech
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
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3
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Roy P, Sardjan AS, Danowski W, Browne WR, Feringa BL, Meech SR. Control of Photoconversion Yield in Unidirectional Photomolecular Motors by Push-Pull Substituents. J Am Chem Soc 2023; 145:19849-19855. [PMID: 37646616 PMCID: PMC10510317 DOI: 10.1021/jacs.3c06070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Indexed: 09/01/2023]
Abstract
Molecular motors based on the overcrowded alkene motif convert light energy into unidirectional mechanical motion through an excited state isomerization reaction. The realization of experimental control over conversion efficiency in these molecular motors is an important goal. Here, we combine the synthesis of a novel "push-pull" overcrowded alkene motor with photophysical characterization by steady state and ultrafast time-resolved electronic spectroscopy. We show that tuning of the charge transfer character in the excited state has a dramatic effect on the photoisomerization yield, enhancing it to near unity in nonpolar solvents while largely suppressing it in polar solvents. This behavior is explained through reference to solvent- and substituent-dependent potential energy surfaces and their effect on conical intersections to the ground state. These observations offer new routes to the fine control of motor efficiency and introduce additional degrees of freedom in the synthesis and exploitation of light-driven molecular motors.
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Affiliation(s)
- Palas Roy
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
- School
of Basic Sciences, Indian Institute of Technology
Bhubaneswar, Bhubaneswar, Odisha 752050, India
| | - Andy S. Sardjan
- Molecular
Inorganic Chemistry, Stratingh Institute
for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Wojciech Danowski
- Centre
for Systems Chemistry, Stratingh Institute
for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
- University
of Strasbourg, CNRS, ISIS UMR 7006, 8 allée Gaspard Monge, F-67000 Strasbourg, France
| | - Wesley R. Browne
- Molecular
Inorganic Chemistry, Stratingh Institute
for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Ben L. Feringa
- Centre
for Systems Chemistry, Stratingh Institute
for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Stephen R. Meech
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
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4
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Roy P, Browne WR, Feringa BL, Meech SR. Ultrafast motion in a third generation photomolecular motor. Nat Commun 2023; 14:1253. [PMID: 36878920 PMCID: PMC9988961 DOI: 10.1038/s41467-023-36777-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 02/13/2023] [Indexed: 03/08/2023] Open
Abstract
Controlling molecular translation at the nanoscale is a key objective for development of synthetic molecular machines. Recently developed third generation photochemically driven molecular motors (3GMs), comprising pairs of overcrowded alkenes capable of cooperative unidirectional rotation offer the possibility of converting light energy into translational motion. Further development of 3GMs demands detailed understanding of their excited state dynamics. Here we use time-resolved absorption and emission to track population and coherence dynamics in a 3GM. Femtosecond stimulated Raman reveals real-time structural dynamics as the excited state evolves from a Franck-Condon bright-state through weakly-emissive dark-state to the metastable product, yielding new insight into the reaction coordinate. Solvent polarity modifies the photoconversion efficiency suggesting charge transfer character in the dark-state. The enhanced quantum yield correlates with suppression of a low-frequency flapping motion in the excited state. This detailed characterization facilitates development of 3GMs, suggesting exploitation of medium and substituent effects to modulate motor efficiency.
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Affiliation(s)
- Palas Roy
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom.,School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Argul, Odisha, 752050, India
| | - Wesley R Browne
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Ben L Feringa
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands.
| | - Stephen R Meech
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom.
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5
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Krueger TD, Tang L, Fang C. Delineating Ultrafast Structural Dynamics of a Green-Red Fluorescent Protein for Calcium Sensing. BIOSENSORS 2023; 13:bios13020218. [PMID: 36831983 PMCID: PMC9954042 DOI: 10.3390/bios13020218] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/27/2023] [Accepted: 01/30/2023] [Indexed: 05/14/2023]
Abstract
Fluorescent proteins (FPs) are indispensable tools for noninvasive bioimaging and sensing. Measuring the free cellular calcium (Ca2+) concentrations in vivo with genetically encodable FPs can be a relatively direct measure of neuronal activity due to the complex signaling role of these ions. REX-GECO1 is a recently developed red-green emission and excitation ratiometric FP-based biosensor that achieves a high dynamic range due to differences in the chromophore response to light excitation with and without calcium ions. Using steady-state electronic measurements (UV/Visible absorption and emission), along with time-resolved spectroscopic techniques including femtosecond transient absorption (fs-TA) and femtosecond stimulated Raman spectroscopy (FSRS), the potential energy surfaces of these unique biosensors are unveiled with vivid details. The ground-state structural characterization of the Ca2+-free biosensor via FSRS reveals a more spacious protein pocket that allows the chromophore to efficiently twist and reach a dark state. In contrast, the more compressed cavity within the Ca2+-bound biosensor results in a more heterogeneous distribution of chromophore populations that results in multi-step excited state proton transfer (ESPT) pathways on the sub-140 fs, 600 fs, and 3 ps timescales. These results enable rational design strategies to enlarge the spectral separation between the protonated/deprotonated forms and the Stokes shift leading to a larger dynamic range and potentially higher fluorescence quantum yield, which should be broadly applicable to the calcium imaging and biosensor communities.
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6
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Jiang Y, Danowski W, Feringa BL, Heinke L. Nanoporous Films with Oriented Arrays of Molecular Motors for Photoswitching the Guest Adsorption and Diffusion. Angew Chem Int Ed Engl 2023; 62:e202214202. [PMID: 36367076 PMCID: PMC10107543 DOI: 10.1002/anie.202214202] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 11/10/2022] [Accepted: 11/10/2022] [Indexed: 11/13/2022]
Abstract
Molecular motors are fascinating nanomachines. However, constructing smart materials from such functional molecules presents a severe challenge in material science. Here, we present a bottom-up layer-by-layer assembly of oriented overcrowded-alkene molecular motors forming a crystalline metal-organic framework thin film. While all stator parts of the overcrowded-alkene motors are oriented perpendicular to the substrate, the rotors point into the pores, which are large enough allowing for the light-induced molecular rotation. Taking advantage of the thin film's transparency, the motor rotation and its activation energy are determined by UV/Vis spectroscopy. As shown by gravimetric uptake experiments, molecular motors in crystalline porous materials are used, for the first time, to control the adsorption and diffusion properties of guest molecules in the pores, here, by switching with light between the (meta-)stable states. The work demonstrates the potential of designed materials with molecular motors and indicates a path for the future development of smart materials.
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Affiliation(s)
- Yunzhe Jiang
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), 76344, Eggenstein-Leopoldshafen, Germany
| | - Wojciech Danowski
- Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747, Nijenborgh 4, Groningen, AG, The Netherlands.,University of Strasbourg CNRS, ISIS UMR 7006, 8 Allée Gaspard Monge, 67000, Strasbourg, France
| | - Ben L Feringa
- Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747, Nijenborgh 4, Groningen, AG, The Netherlands
| | - Lars Heinke
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), 76344, Eggenstein-Leopoldshafen, Germany
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7
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Pooler DRS, Lubbe AS, Crespi S, Feringa BL. Designing light-driven rotary molecular motors. Chem Sci 2021; 12:14964-14986. [PMID: 34909140 PMCID: PMC8612399 DOI: 10.1039/d1sc04781g] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 10/14/2021] [Indexed: 01/04/2023] Open
Abstract
The ability to induce and amplify motion at the molecular scale has seen tremendous progress ranging from simple molecular rotors to responsive materials. In the two decades since the discovery of light-driven rotary molecular motors, the development of these molecules has been extensive; moving from the realm of molecular chemistry to integration into dynamic molecular systems. They have been identified as actuators holding great potential to precisely control the dynamics of nanoscale devices, but integrating molecular motors effectively into evermore complex artificial molecular machinery is not trivial. Maximising efficiency without compromising function requires conscious and judicious selection of the structures used. In this perspective, we focus on the key aspects of motor design and discuss how to manipulate these properties without impeding motor integrity. Herein, we describe these principles in the context of molecular rotary motors featuring a central double bond axle and emphasise the strengths and weaknesses of each design, providing a comprehensive evaluation of all artificial light-driven rotary motor scaffolds currently present in the literature. Based on this discussion, we will explore the trajectory of research into the field of molecular motors in the coming years, including challenges to be addressed, potential applications, and future prospects.
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Affiliation(s)
- Daisy R S Pooler
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Anouk S Lubbe
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Stefano Crespi
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Ben L Feringa
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
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8
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Pooler DRS, Pierron R, Crespi S, Costil R, Pfeifer L, Léonard J, Olivucci M, Feringa BL. Effect of charge-transfer enhancement on the efficiency and rotary mechanism of an oxindole-based molecular motor. Chem Sci 2021; 12:7486-7497. [PMID: 34163839 PMCID: PMC8171491 DOI: 10.1039/d1sc01105g] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 04/25/2021] [Indexed: 01/04/2023] Open
Abstract
Harvesting energy and converting it into mechanical motion forms the basis for both natural and artificial molecular motors. Overcrowded alkene-based light-driven rotary motors are powered through sequential photochemical and thermal steps. The thermal helix inversion steps are well characterised and can be manipulated through adjustment of the chemical structure, however, the insights into the photochemical isomerisation steps still remain elusive. Here we report a novel oxindole-based molecular motor featuring pronounced electronic push-pull character and a four-fold increase of the photoisomerization quantum yield in comparison to previous motors of its class. A multidisciplinary approach including synthesis, steady-state and transient absorption spectroscopies, and electronic structure modelling was implemented to elucidate the excited state dynamics and rotary mechanism. We conclude that the charge-transfer character of the excited state diminishes the degree of pyramidalisation at the alkene bond during isomerisation, such that the rotational properties of this oxindole-based motor stand in between the precessional motion of fluorene-based molecular motors and the axial motion of biomimetic photoswitches.
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Affiliation(s)
- Daisy R S Pooler
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Robin Pierron
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, UMR 7504 F-67034 Strasbourg France
| | - Stefano Crespi
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Romain Costil
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Lukas Pfeifer
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Jérémie Léonard
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, UMR 7504 F-67034 Strasbourg France
| | - Massimo Olivucci
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena 53100 Siena Italy
- Chemistry Department, Bowling Green State University Bowling Green Ohio 43403 USA
| | - Ben L Feringa
- Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
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9
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Roy P, Sardjan AS, Danowski W, Browne WR, Feringa BL, Meech SR. Photophysics of First-Generation Photomolecular Motors: Resolving Roles of Temperature, Friction, and Medium Polarity. J Phys Chem A 2021; 125:1711-1719. [PMID: 33606528 DOI: 10.1021/acs.jpca.0c11050] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Light-driven unidirectional molecular rotary motors have the potential to power molecular machines. Consequently, optimizing their speed and efficiency is an important objective. Here, we investigate factors controlling the photochemical yield of the prototypical unidirectional rotary motor, a sterically overcrowded alkene, through detailed investigation of its excited-state dynamics. An isoviscosity analysis of the ultrafast fluorescence decay data resolves friction from barrier effects and reveals a 3.4 ± 0.5 kJ mol-1 barrier to excited-state decay in nonpolar media. Extension of this analysis to polar solvents shows that this barrier height is a strong function of medium polarity and that the decay pathway becomes near barrierless in more polar media. Thus, the properties of the medium can be used as a route for controlling the motor's excited-state dynamics. The connection between these dynamics and the quantum yield of photochemical isomerization is probed. The photochemical quantum yield is shown to be a much weaker function of solvent polarity, and the most efficient excited-state decay pathway does not lead to a strongly enhanced quantum yield for isomerization. These results are discussed in terms of the solvent dependence of the complex multidimensional excited-state reaction coordinate.
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Affiliation(s)
- Palas Roy
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K
| | - Andy S Sardjan
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Wojciech Danowski
- Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Wesley R Browne
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Ben L Feringa
- Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Stephen R Meech
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K
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10
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Kolodzeiski E, Amirjalayer S. Elucidating the Impact of Molecular Motors on Their Solvation Environment. J Phys Chem B 2020; 124:10879-10888. [DOI: 10.1021/acs.jpcb.0c06343] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Elena Kolodzeiski
- Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, Münster 48149, Germany
- Center for Nanotechnology, Heisenbergstraße 11, Münster 48149, Germany
- Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, Münster 48149, Germany
| | - Saeed Amirjalayer
- Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, Münster 48149, Germany
- Center for Nanotechnology, Heisenbergstraße 11, Münster 48149, Germany
- Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, Münster 48149, Germany
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11
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Sardjan AS, Roy P, Danowski W, Bressan G, Nunes Dos Santos Comprido L, Browne WR, Feringa BL, Meech SR. Ultrafast Excited State Dynamics in a First Generation Photomolecular Motor. Chemphyschem 2020; 21:594-599. [PMID: 31975490 PMCID: PMC7187380 DOI: 10.1002/cphc.201901179] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/17/2020] [Indexed: 12/13/2022]
Abstract
Efficient photomolecular motors will be critical elements in the design and development of molecular machines. Optimisation of the quantum yield for photoisomerisation requires a detailed understanding of molecular dynamics in the excited electronic state. Here we probe the primary photophysical processes in the archetypal first generation photomolecular motor, with sub‐50 fs time resolved fluorescence spectroscopy. A bimodal relaxation is observed with a 100 fs relaxation of the Franck‐Condon state to populate a red‐shifted state with a reduced transition moment, which then undergoes multi‐exponential decay on a picosecond timescale. Oscillations due to the excitation of vibrational coherences in the S1 state are seen to survive the ultrafast structural relaxation. The picosecond relaxation reveals a strong solvent friction effect which is thus ascribed to torsion about the C−C axle. This behaviour is contrasted with second generation photomolecular motors; the principal differences are explained by the existence of a barrier on the excited state surface in the case of the first‐generation motors which is absent in the second generation. These results will help to provide a basis for designing more efficient molecular motors in the future.
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Affiliation(s)
- Andy S Sardjan
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Palas Roy
- School of Chemistry, University of East Anglia Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Wojciech Danowski
- Synthetic Organic Chemistry Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Giovanni Bressan
- School of Chemistry, University of East Anglia Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Laura Nunes Dos Santos Comprido
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Wesley R Browne
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Ben L Feringa
- Synthetic Organic Chemistry Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Stephen R Meech
- School of Chemistry, University of East Anglia Norwich Research Park, Norwich, NR4 7TJ, UK
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12
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Fang C, Tang L, Chen C. Unveiling coupled electronic and vibrational motions of chromophores in condensed phases. J Chem Phys 2019; 151:200901. [PMID: 31779327 DOI: 10.1063/1.5128388] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The quest for capturing molecular movies of functional systems has motivated scientists and engineers for decades. A fundamental understanding of electronic and nuclear motions, two principal components of the molecular Schrödinger equation, has the potential to enable the de novo rational design for targeted functionalities of molecular machines. We discuss the development and application of a relatively new structural dynamics technique, femtosecond stimulated Raman spectroscopy with broadly tunable laser pulses from the UV to near-IR region, in tracking the coupled electronic and vibrational motions of organic chromophores in solution and protein environments. Such light-sensitive moieties hold broad interest and significance in gaining fundamental knowledge about the intramolecular and intermolecular Hamiltonian and developing effective strategies to control macroscopic properties. Inspired by recent experimental and theoretical advances, we focus on the in situ characterization and spectroscopy-guided tuning of photoacidity, excited state proton transfer pathways, emission color, and internal conversion via a conical intersection.
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Affiliation(s)
- Chong Fang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Longteng Tang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Cheng Chen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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13
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Abstract
Directed motion at the nanoscale is a central attribute of life, and chemically driven motor proteins are nature's choice to accomplish it. Motivated and inspired by such bionanodevices, in the past few decades chemists have developed artificial prototypes of molecular motors, namely, multicomponent synthetic species that exhibit directionally controlled, stimuli-induced movements of their parts. In this context, photonic and redox stimuli represent highly appealing modes of activation, particularly from a technological viewpoint. Here we describe the evolution of the field of photo- and redox-driven artificial molecular motors, and we provide a comprehensive review of the work published in the past 5 years. After an analysis of the general principles that govern controlled and directed movement at the molecular scale, we describe the fundamental photochemical and redox processes that can enable its realization. The main classes of light- and redox-driven molecular motors are illustrated, with a particular focus on recent designs, and a thorough description of the functions performed by these kinds of devices according to literature reports is presented. Limitations, challenges, and future perspectives of the field are critically discussed.
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Affiliation(s)
- Massimo Baroncini
- CLAN-Center for Light Activated Nanostructures , Istituto ISOF-CNR , via Gobetti 101 , 40129 Bologna , Italy.,Dipartimento di Scienze e Tecnologie Agro-alimentari , Università di Bologna , viale Fanin 44 , 40127 Bologna , Italy
| | - Serena Silvi
- CLAN-Center for Light Activated Nanostructures , Istituto ISOF-CNR , via Gobetti 101 , 40129 Bologna , Italy.,Dipartimento di Chimica "G. Ciamician" , Università di Bologna , via Selmi 2 , 40126 Bologna , Italy
| | - Alberto Credi
- CLAN-Center for Light Activated Nanostructures , Istituto ISOF-CNR , via Gobetti 101 , 40129 Bologna , Italy.,Dipartimento di Scienze e Tecnologie Agro-alimentari , Università di Bologna , viale Fanin 44 , 40127 Bologna , Italy
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14
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New Members and Foreign Associates of the National Academy of Sciences 2019. Angew Chem Int Ed Engl 2019; 58:8625-8626. [PMID: 31148356 DOI: 10.1002/anie.201905912] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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15
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16
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Tang L, Fang C. Nitration of Tyrosine Channels Photoenergy through a Conical Intersection in Water. J Phys Chem B 2019; 123:4915-4928. [PMID: 31094198 DOI: 10.1021/acs.jpcb.9b03464] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Nitration of tyrosine occurs under oxidative stress in vivo. The product, 3-nitrotyrosine (3NY), has a dramatically decreased quantum yield and can be used as a molecular ruler. In this study, femtosecond transient absorption spectroscopy and quantum calculations were implemented to elucidate the photoinduced relaxation processes of anionic 3NY in water. Upon 400 nm excitation into an excited electronic state with notable charge-transfer (CT) character, a barrierless nitro-twisting motion rapidly (<100 fs) guides the chromophore into an adjacent twisted intramolecular CT state, therein reaching a sloped S1/S0 conical intersection on the ∼100 fs time scale. Once in the hot ground state, excess energy is further released through vibrational cooling with biexponential time constants of ∼140 and 680 fs in water. Nitro back-twisting occurs on longer time scales (∼1.1 and 9 ps in water), returning the system to original ground state. Systematic evaluations of excited-state potential energies of anionic 3NY were performed by density functional theory (DFT) and time-dependent DFT calculations, showing that intersystem crossing (ISC) from the first singlet state (S1) to the first or second triplet state (T1 or T2) is unlikely. Inclusion of an explicit water molecule in calculations leads to improved mapping of the excited-state energy ordering of the second singlet state (S2) and T2, further diminishing ISC probability from S1 and favoring an ultrafast internal conversion to S0. These results provide deep insights into the highly efficient nonradiative decay of anionic 3NY in aqueous solution, with nitro-site-specific information that can help infer the characterization and potential optogenetic control of 3NY in protein environment.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331-4003 , United States
| | - Chong Fang
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331-4003 , United States
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17
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Amirjalayer S, Buma WJ. Light on the Structural Evolution of Photoresponsive Molecular Switches in Electronically Excited States. Chemistry 2019; 25:6252-6258. [PMID: 30576061 DOI: 10.1002/chem.201805810] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 12/21/2018] [Indexed: 11/08/2022]
Abstract
Stimuli-responsive materials are attracting extensive interest as they offer the opportunity to transform external inputs such as light into a functionality by control at the molecular level. As a result, a large number of molecular building units have been developed that enable switching between two or more states. Since the trajectory describing the transition between the various states defines the efficiency of the usually immobilized unit and the resulting functionality, it does not suffice to merely consider the initial and final states of the switching process. A key challenge is in fact to decipher at the atomic scale the actual motion that takes place after photoexcitation. Understanding and being able to manipulate this trajectory is crucial for an efficient implementation of photoactive molecular switches into functional materials, as well as to rationally develop novel tailor-made materials. In this Concept article, we highlight the potential to characterize in detail photoinitiated switching mechanisms by combining quantum chemical calculations with advanced laser spectroscopic techniques that probe the vibrational manifold of electronically excited states and its evolution.
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Affiliation(s)
- Saeed Amirjalayer
- Physikalisches Institut and Center for Multiscale Theory &, Computation (CMTC), Westfälische Wilhelms-Universität Münster, Willhelm-Klemm-Strasse 10, 48149, Münster, Germany.,Center for Nanotechnology (CeNTech), Heisenbergstrasse 11, 48149, Münster, Germany
| | - Wybren Jan Buma
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098, XH, Amsterdam, The Netherlands
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18
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Pagano K, Paolino M, Fusi S, Zanirato V, Trapella C, Giuliani G, Cappelli A, Zanzoni S, Molinari H, Ragona L, Olivucci M. Bile Acid Binding Protein Functionalization Leads to a Fully Synthetic Rhodopsin Mimic. J Phys Chem Lett 2019; 10:2235-2243. [PMID: 30995409 DOI: 10.1021/acs.jpclett.9b00210] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Rhodopsins are photoreceptive proteins using light to drive a plethora of biological functions such as vision, proton and ion pumping, cation and anion channeling, and gene and enzyme regulation. Here we combine organic synthesis, NMR structural studies, and photochemical characterization to show that it is possible to prepare a fully synthetic mimic of rhodopsin photoreceptors. More specifically, we conjugate a bile acid binding protein with a synthetic mimic of the rhodopsin protonated Schiff base chromophore to achieve a covalent complex featuring an unnatural protein host, photoswitch, and photoswitch-protein linkage with a reverse orientation. We show that, in spite of its molecular-level diversity, light irradiation of the prepared mimic fuels a photochromic cycle driven by sequential photochemical and thermal Z/E isomerizations reminiscent of the photocycles of microbial rhodopsins.
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Affiliation(s)
- Katiuscia Pagano
- Istituto per lo Studio delle Macromolecole, CNR , Via A. Corti 12 , 20133 Milano , Italy
| | - Marco Paolino
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022) , Università degli Studi di Siena , Via Aldo Moro 2 , 53100 Siena , Italy
| | - Stefania Fusi
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022) , Università degli Studi di Siena , Via Aldo Moro 2 , 53100 Siena , Italy
| | | | | | - Germano Giuliani
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022) , Università degli Studi di Siena , Via Aldo Moro 2 , 53100 Siena , Italy
| | - Andrea Cappelli
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022) , Università degli Studi di Siena , Via Aldo Moro 2 , 53100 Siena , Italy
| | - Serena Zanzoni
- Centro Piattaforme Tecnologiche , Università di Verona , Strada Le Grazie , 37134 Verona , Italy
| | - Henriette Molinari
- Istituto per lo Studio delle Macromolecole, CNR , Via A. Corti 12 , 20133 Milano , Italy
| | - Laura Ragona
- Istituto per lo Studio delle Macromolecole, CNR , Via A. Corti 12 , 20133 Milano , Italy
| | - Massimo Olivucci
- Dipartimento di Biotecnologie, Chimica e Farmacia (Dipartimento di Eccellenza 2018-2022) , Università degli Studi di Siena , Via Aldo Moro 2 , 53100 Siena , Italy
- Chemistry Department , Bowling Green State University , Bowling Green , Ohio 43403 , United States
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19
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António JPM, Russo R, Carvalho CP, Cal PMSD, Gois PMP. Boronic acids as building blocks for the construction of therapeutically useful bioconjugates. Chem Soc Rev 2019; 48:3513-3536. [DOI: 10.1039/c9cs00184k] [Citation(s) in RCA: 124] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This review summarizes boronic acid's contribution to the development of bioconjugates with a particular focus on the molecular mechanisms underlying its role in the construction and function of the bioconjugate, namely as a bioconjugation warhead, as a payload and as part of a bioconjugate linker.
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Affiliation(s)
- João P. M. António
- Research Institute for Medicines (iMed.ULisboa)
- Faculty of Pharmacy
- Universidade de Lisboa
- Lisbon
- Portugal
| | - Roberto Russo
- Research Institute for Medicines (iMed.ULisboa)
- Faculty of Pharmacy
- Universidade de Lisboa
- Lisbon
- Portugal
| | - Cátia Parente Carvalho
- Research Institute for Medicines (iMed.ULisboa)
- Faculty of Pharmacy
- Universidade de Lisboa
- Lisbon
- Portugal
| | - Pedro M. S. D. Cal
- Instituto de Medicina Molecular
- Faculty of Medicine
- Universidade de Lisboa
- Lisbon
- Portugal
| | - Pedro M. P. Gois
- Research Institute for Medicines (iMed.ULisboa)
- Faculty of Pharmacy
- Universidade de Lisboa
- Lisbon
- Portugal
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20
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Schönegger S, Jantz SG, Saxer A, Bayarjargal L, Winkler B, Pielnhofer F, Höppe HA, Huppertz H. Synthesis and Characterization of the First Tin Fluoride Borate Sn 3 [B 3 O 7 ]F with Second Harmonic Generation Response. Chemistry 2018; 24:16036-16043. [PMID: 30079577 PMCID: PMC6221176 DOI: 10.1002/chem.201803478] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Indexed: 11/11/2022]
Abstract
The new non-centrosymmetric tin fluoride borate Sn3 [B3 O7 ]F was synthesized hydrothermally, and was characterized by single-crystal and powder X-ray diffraction, vibrational spectroscopy, DFT calculations, second harmonic generation (SHG) measurements, thermogravimetry, and differential scanning calorimetry. Its SHG response is about 12 times that of quartz. The compound crystallizes in the non-centrosymmetric orthorhombic space group Pna21 with lattice parameters a=922.4(2), b=769.8(4), and c=1221.9(6) pm (Z=4). Characteristic for the structure are isolated B3 O7 moieties, consisting of two corner-sharing BO3 units and one BO4 tetrahedron. These occupy half of the octahedral voids of a slightly distorted hexagonal closest packing of Sn2+ atoms, with [SnF]+ units in the other half of the octahedral voids. Sn3 [B3 O7 ]F is transparent over a wide spectral range with a UV cut-off edge at about 263 nm.
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Affiliation(s)
- Sandra Schönegger
- Institut für Allgemeine, Anorganische und Theoretische ChemieLeopold-Franzens-Universität InnsbruckInnrain 80–826020InnsbruckAustria
| | - Stephan G. Jantz
- Institut für PhysikUniversität AugsburgUniversitätstr. 186159AugsburgGermany
| | - Andreas Saxer
- Institut für Konstruktion und MaterialwissenschaftenLeopold-Franzens-Universität InnsbruckTechnikerstraße 136020InnsbruckAustria
| | - Lkhamsuren Bayarjargal
- Institut für GeowissenschaftenUniversität FrankfurtAltenhöferallee 160438Frankfurt/MainGermany
| | - Björn Winkler
- Institut für GeowissenschaftenUniversität FrankfurtAltenhöferallee 160438Frankfurt/MainGermany
| | - Florian Pielnhofer
- Institut für Anorganische ChemieUniversität RegensburgUniversitätsstraße 3193053RegensburgGermany
| | - Henning A. Höppe
- Institut für PhysikUniversität AugsburgUniversitätstr. 186159AugsburgGermany
| | - Hubert Huppertz
- Institut für Allgemeine, Anorganische und Theoretische ChemieLeopold-Franzens-Universität InnsbruckInnrain 80–826020InnsbruckAustria
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21
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Hall CR, Romanov AS, Bochmann M, Meech SR. Ultrafast Structure and Dynamics in the Thermally Activated Delayed Fluorescence of a Carbene-Metal-Amide. J Phys Chem Lett 2018; 9:5873-5876. [PMID: 30230847 DOI: 10.1021/acs.jpclett.8b02797] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Thermally activated delayed fluorescence has enormous potential for the development of efficient light emitting diodes. A recently discovered class of molecules (the carbene-metal-amides, CMAs) are exceptionally promising as they combine the small singlet-triplet energy gap required for thermal activation with a large transition moment for emission. Calculations suggest excited state structural dynamics modulate the critical coupling between singlet and triplet, but they disagree on the nature of those dynamics. Here we report ultrafast time-resolved transient absorption and Raman studies of CMA photodynamics. The measurements reveal complex structural evolution following intersystem crossing on the tens to hundreds of picoseconds time scale, and a change in the low-frequency vibrational spectrum between singlet and triplet states. The latter is assigned to changes in Raman active modes localized on the metal center.
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Affiliation(s)
| | | | - Manfred Bochmann
- School of Chemistry , University of East Anglia , Norwich NR4 7TJ , U.K
| | - Stephen R Meech
- School of Chemistry , University of East Anglia , Norwich NR4 7TJ , U.K
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22
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Wiley TE, Konar A, Miller NA, Spears KG, Sension RJ. Primed for Efficient Motion: Ultrafast Excited State Dynamics and Optical Manipulation of a Four Stage Rotary Molecular Motor. J Phys Chem A 2018; 122:7548-7558. [DOI: 10.1021/acs.jpca.8b06472] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Theodore E. Wiley
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Nicholas A. Miller
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Kenneth G. Spears
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Roseanne J. Sension
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
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23
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Tang L, Zhu L, Wang Y, Fang C. Uncovering the Hidden Excited State toward Fluorescence of an Intracellular pH Indicator. J Phys Chem Lett 2018; 9:4969-4975. [PMID: 30111103 DOI: 10.1021/acs.jpclett.8b02281] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Intracellular pH (pHi) imaging is of paramount importance for life sciences. In this work, we implement the ultrafast electronic and stimulated Raman spectroscopies to unravel the fluorescence mechanism of an excitation-ratiometric pHi indicator in basic aqueous solution. After photoexcitation of the pHi indicator HPTS, a hidden charge-transfer (CT) state following the locally excited (LE) state is uncovered as an essential step prior to fluorescence and this LE → CT transition is gated by ultrafast solvation dynamics. A 835 cm-1 intermolecular vibrational mode is identified to potentially facilitate the CT-state formation on the 700 fs time scale. Dynamic correlation with the other excited-state Raman marker bands suggests that the transition between transient electronic states is aided by solvation events mostly in the molecular plane of HPTS. These vivid structural dynamics insights can enable the rational design of more efficient and bright pHi indicators in an H-bonding environment with controllable properties.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Liangdong Zhu
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Yanli Wang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Chong Fang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
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24
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Excited State Structural Evolution of a GFP Single-Site Mutant Tracked by Tunable Femtosecond-Stimulated Raman Spectroscopy. Molecules 2018; 23:molecules23092226. [PMID: 30200474 PMCID: PMC6225354 DOI: 10.3390/molecules23092226] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/29/2018] [Accepted: 08/31/2018] [Indexed: 12/31/2022] Open
Abstract
Tracking vibrational motions during a photochemical or photophysical process has gained momentum, due to its sensitivity to the progression of reaction and change of environment. In this work, we implemented an advanced ultrafast vibrational technique, femtosecond-stimulated Raman spectroscopy (FSRS), to monitor the excited state structural evolution of an engineered green fluorescent protein (GFP) single-site mutant S205V. This mutation alters the original excited state proton transfer (ESPT) chain. By strategically tuning the Raman pump to different wavelengths (i.e., 801, 539, and 504 nm) to achieve pre-resonance with transient excited state electronic bands, the characteristic Raman modes of the excited protonated (A*) chromophore species and intermediate deprotonated (I*) species can be selectively monitored. The inhomogeneous distribution/population of A* species go through ESPT with a similar ~300 ps time constant, confirming that bridging a water molecule to protein residue T203 in the ESPT chain is the rate-limiting step. Some A* species undergo vibrational cooling through high-frequency motions on the ~190 ps time scale. At early times, a portion of the largely protonated A* species could also undergo vibrational cooling or return to the ground state with a ~80 ps time constant. On the photoproduct side, a ~1330 cm−1 delocalized motion is observed, with dispersive line shapes in both the Stokes and anti-Stokes FSRS with a pre-resonance Raman pump, which indicates strong vibronic coupling, as the mode could facilitate the I* species to reach a relatively stable state (e.g., the main fluorescent state) after conversion from A*. Our findings disentangle the contributions of various vibrational motions active during the ESPT reaction, and offer new structural dynamics insights into the fluorescence mechanisms of engineered GFPs and other analogous autofluorescent proteins.
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