Directeur de recherche – CNRS
ENS – Département de chimie
24 rue Lhomond, 75005 Paris
Email: pascal.plaza@ens.psl.eu
Phone: 01 44 32 24 14
Office: E123
ORCID: 0000-0002-8021-4521
Research interests
Photoactives Proteins; Flavoproteins; Reversibly Switchable Fluorescent Proteins;
Ultrafast Time-Resolved Spectroscopy; Photophysics; Photochemical Processes;
Electron and Proton Transfer;
See more details here.
Teaching
Master of chemistry at Sorbonne Université: « Primary Photoreactivity of Molecular and Macromolecular Systems in Condensed Phase » module of UE 5C206 – Ultrafast Dynamics of Reactive Species.
Publications
2023 |
Multiscale Transient Absorption Study of the Fluorescent Protein Dreiklang and Two Point Variants Provides Insight into Photoswitching and Nonproductive Reaction Pathways Article de journal Emilie Renouard; Magdalena Nowinska; Fabien Lacombat; Pascal Plaza; Pavel Müller; Agathe Espagne The Journal of Physical Chemistry Letters, 14 (28), p. 6477-6485, 2023. @article{RN63c, title = {Multiscale Transient Absorption Study of the Fluorescent Protein Dreiklang and Two Point Variants Provides Insight into Photoswitching and Nonproductive Reaction Pathways}, author = {Emilie Renouard and Magdalena Nowinska and Fabien Lacombat and Pascal Plaza and Pavel M\"{u}ller and Agathe Espagne}, url = {https://doi.org/10.1021/acs.jpclett.3c00431}, doi = {10.1021/acs.jpclett.3c00431}, year = {2023}, date = {2023-01-01}, journal = {The Journal of Physical Chemistry Letters}, volume = {14}, number = {28}, pages = {6477-6485}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2021 |
Ultrafast Dynamics of Fully Reduced Flavin in Catalytic Structures of Thymidylate Synthase ThyX Article de journal Nadia Dozova; Fabien Lacombat; Murielle Lombard; Djemel Hamdane; Pascal Plaza Physical Chemistry Chemical Physics, 23 , p. 22692-22702, 2021, ISSN: 1463-9076. @article{RN123b, title = {Ultrafast Dynamics of Fully Reduced Flavin in Catalytic Structures of Thymidylate Synthase ThyX}, author = {Nadia Dozova and Fabien Lacombat and Murielle Lombard and Djemel Hamdane and Pascal Plaza}, url = {http://dx.doi.org/10.1039/D1CP03379D}, doi = {10.1039/D1CP03379D}, issn = {1463-9076}, year = {2021}, date = {2021-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {23}, pages = {22692-22702}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Ultrafast photoreduction dynamics of a new class of CPD photolyases Article de journal Fabien Lacombat; Agathe Espagne; Nadia Dozova; Pascal Plaza; Pavel Müller; Hans-Joachim Emmerich; Martin Saft; Lars-Oliver Essen Photochemical & Photobiological Sciences, 20 (6), p. 733-746, 2021, ISSN: 1474-9092. @article{RN632, title = {Ultrafast photoreduction dynamics of a new class of CPD photolyases}, author = {Fabien Lacombat and Agathe Espagne and Nadia Dozova and Pascal Plaza and Pavel M\"{u}ller and Hans-Joachim Emmerich and Martin Saft and Lars-Oliver Essen}, url = {https://doi.org/10.1007/s43630-021-00048-4}, doi = {10.1007/s43630-021-00048-4}, issn = {1474-9092}, year = {2021}, date = {2021-01-01}, journal = {Photochemical & Photobiological Sciences}, volume = {20}, number = {6}, pages = {733-746}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2019 |
Ultrafast Oxidation of a Tyrosine by Proton-Coupled Electron Transfer Promotes Light Activation of an Animal-like Cryptochrome Article de journal Fabien Lacombat; Agathe Espagne; Nadia Dozova; Pascal Plaza; Pavel Müller; Klaus Brettel; Sophie Franz-Badur; Lars-Oliver Essen Journal of the American Chemical Society, 141 (34), p. 13394-13409, 2019, ISSN: 0002-7863. @article{RN479, title = {Ultrafast Oxidation of a Tyrosine by Proton-Coupled Electron Transfer Promotes Light Activation of an Animal-like Cryptochrome}, author = {Fabien Lacombat and Agathe Espagne and Nadia Dozova and Pascal Plaza and Pavel M\"{u}ller and Klaus Brettel and Sophie Franz-Badur and Lars-Oliver Essen}, url = {https://doi.org/10.1021/jacs.9b03680}, doi = {10.1021/jacs.9b03680}, issn = {0002-7863}, year = {2019}, date = {2019-01-01}, journal = {Journal of the American Chemical Society}, volume = {141}, number = {34}, pages = {13394-13409}, abstract = {The animal-like cryptochrome of Chlamydomonas reinhardtii (CraCRY) is a recently discovered photoreceptor that controls the transcriptional profile and sexual life cycle of this alga by both blue and red light. CraCRY has the uncommon feature of efficient formation and longevity of the semireduced neutral form of its FAD cofactor upon blue light illumination. Tyrosine Y373 plays a crucial role by elongating , as fourth member, the electron transfer (ET) chain found in most other cryptochromes and DNA photolyases, which comprises a conserved tryptophan triad. Here, we report the full mechanism of light-induced FADH• formation in CraCRY using transient absorption spectroscopy from hundreds of femtoseconds to seconds. Electron transfer starts from ultrafast reduction of excited FAD to FAD•\textendash by the proximal tryptophan (0.4 ps) and is followed by delocalized migration of the produced WH•+ radical along the tryptophan triad (∼4 and ∼50 ps). Oxidation of Y373 by coupled ET to WH•+ and deprotonation then proceeds in ∼800 ps, without any significant kinetic isotope effect, nor a pH effect between pH 6.5 and 9.0. The FAD•\textendash/Y373• pair is formed with high quantum yield (∼60%); its intrinsic decay by recombination is slow (∼50 ms), favoring reduction of Y373• by extrinsic agents and protonation of FAD•\textendash to form the long-lived, red-light absorbing FADH• species. Possible mechanisms of tyrosine oxidation by ultrafast proton-coupled ET in CraCRY, a process about 40 times faster than the archetypal tyrosine-Z oxidation in photosystem II, are discussed in detail.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The animal-like cryptochrome of Chlamydomonas reinhardtii (CraCRY) is a recently discovered photoreceptor that controls the transcriptional profile and sexual life cycle of this alga by both blue and red light. CraCRY has the uncommon feature of efficient formation and longevity of the semireduced neutral form of its FAD cofactor upon blue light illumination. Tyrosine Y373 plays a crucial role by elongating , as fourth member, the electron transfer (ET) chain found in most other cryptochromes and DNA photolyases, which comprises a conserved tryptophan triad. Here, we report the full mechanism of light-induced FADH• formation in CraCRY using transient absorption spectroscopy from hundreds of femtoseconds to seconds. Electron transfer starts from ultrafast reduction of excited FAD to FAD•– by the proximal tryptophan (0.4 ps) and is followed by delocalized migration of the produced WH•+ radical along the tryptophan triad (∼4 and ∼50 ps). Oxidation of Y373 by coupled ET to WH•+ and deprotonation then proceeds in ∼800 ps, without any significant kinetic isotope effect, nor a pH effect between pH 6.5 and 9.0. The FAD•–/Y373• pair is formed with high quantum yield (∼60%); its intrinsic decay by recombination is slow (∼50 ms), favoring reduction of Y373• by extrinsic agents and protonation of FAD•– to form the long-lived, red-light absorbing FADH• species. Possible mechanisms of tyrosine oxidation by ultrafast proton-coupled ET in CraCRY, a process about 40 times faster than the archetypal tyrosine-Z oxidation in photosystem II, are discussed in detail. |
Ultrafast photoinduced flavin dynamics in the unusual active site of the tRNA methyltransferase TrmFO Article de journal N Dozova; F Lacombat; C Bou-Nader; D Hamdane; P Plaza Physical Chemistry Chemical Physics, 21 (17), p. 8743-8756, 2019, ISSN: 1463-9076. @article{RN115, title = {Ultrafast photoinduced flavin dynamics in the unusual active site of the tRNA methyltransferase TrmFO}, author = {N Dozova and F Lacombat and C Bou-Nader and D Hamdane and P Plaza}, doi = {10.1039/c8cp06072j}, issn = {1463-9076}, year = {2019}, date = {2019-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {21}, number = {17}, pages = {8743-8756}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2018 |
A novel diarylethene-based photoswitchable chelator for reversible release and capture of Ca2+ in aqueous media Article de journal N Dozova; G Pousse; B Barnych; J -M Mallet; J Cossy; B Valeur; P Plaza Journal of Photochemistry and Photobiology A: Chemistry, 360 , p. 181–187, 2018. @article{Dozova:2018, title = {A novel diarylethene-based photoswitchable chelator for reversible release and capture of Ca2+ in aqueous media}, author = {N Dozova and G Pousse and B Barnych and J -M Mallet and J Cossy and B Valeur and P Plaza}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046375200&doi=10.1016%2fj.jphotochem.2018.04.029&partnerID=40&md5=acfff9bc55e2d0bb41580e84374018fc}, doi = {10.1016/j.jphotochem.2018.04.029}, year = {2018}, date = {2018-01-01}, journal = {Journal of Photochemistry and Photobiology A: Chemistry}, volume = {360}, pages = {181--187}, abstract = {The synthesis and characterisation of a novel Reversibly Photoswitchable Chelator (RPC) of calcium ions, designed as a stepping stone towards producing pulses of calcium concentration in an aqueous environment, is reported. This RPC is constituted of a photochromic diarylethene core connected on one side to a BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid) calcium chelator and, on the other side, to an electron-withdrawing group. The operation principle consists in photoswitching on and off an intramolecular charge transfer between one nitrogen atom of the BAPTA moiety and the electron-withdrawing group, thereby modulating the chelating affinity of BAPTA for calcium ions. Solubility of the compound in a partially aqueous solvent was achieved by grafting a short PEG (polyethylene glycol) tail to the electron-withdrawing group. A reduction of the affinity for calcium ions upon photoswitching by a factor of 3\textendash4, in the hundred nM range of dissociation constant, is reported and constitutes a proof of concept of this type of RPC. © 2018 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The synthesis and characterisation of a novel Reversibly Photoswitchable Chelator (RPC) of calcium ions, designed as a stepping stone towards producing pulses of calcium concentration in an aqueous environment, is reported. This RPC is constituted of a photochromic diarylethene core connected on one side to a BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid) calcium chelator and, on the other side, to an electron-withdrawing group. The operation principle consists in photoswitching on and off an intramolecular charge transfer between one nitrogen atom of the BAPTA moiety and the electron-withdrawing group, thereby modulating the chelating affinity of BAPTA for calcium ions. Solubility of the compound in a partially aqueous solvent was achieved by grafting a short PEG (polyethylene glycol) tail to the electron-withdrawing group. A reduction of the affinity for calcium ions upon photoswitching by a factor of 3–4, in the hundred nM range of dissociation constant, is reported and constitutes a proof of concept of this type of RPC. © 2018 Elsevier B.V. |
Delocalized hole transport coupled to sub-ns tryptophanyl deprotonation promotes photoreduction of class II photolyases Article de journal F Lacombat; A Espagne; N Dozova; P Plaza; E Ignatz; S Kiontke; L O Essen Physical Chemistry Chemical Physics, 20 (39), p. 25446-25457, 2018, ISSN: 1463-9076. @article{RN114, title = {Delocalized hole transport coupled to sub-ns tryptophanyl deprotonation promotes photoreduction of class II photolyases}, author = {F Lacombat and A Espagne and N Dozova and P Plaza and E Ignatz and S Kiontke and L O Essen}, url = {<Go to ISI>://WOS:000448345400028}, doi = {10.1039/c8cp04548h}, issn = {1463-9076}, year = {2018}, date = {2018-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {20}, number = {39}, pages = {25446-25457}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2017 |
Loss of Fourth Electron-Transferring Tryptophan in Animal (6-4) Photolyase Impairs DNA Repair Activity in Bacterial Cells Article de journal J Yamamoto; K Shimizu; T Kanda; Y Hosokawa; S Iwai; P Plaza; P Müller Biochemistry, 56 (40), p. 5356–5364, 2017. @article{Yamamoto:2017, title = {Loss of Fourth Electron-Transferring Tryptophan in Animal (6-4) Photolyase Impairs DNA Repair Activity in Bacterial Cells}, author = {J Yamamoto and K Shimizu and T Kanda and Y Hosokawa and S Iwai and P Plaza and P M\"{u}ller}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031007482&doi=10.1021%2facs.biochem.7b00366&partnerID=40&md5=ec7f70f4b2e5c57ef35f65a223a0f0ed}, doi = {10.1021/acs.biochem.7b00366}, year = {2017}, date = {2017-01-01}, journal = {Biochemistry}, volume = {56}, number = {40}, pages = {5356--5364}, abstract = {(6-4) photolyases [(6-4)PLs] are flavoproteins that use blue light to repair the ultraviolet-induced pyrimidine(6-4)pyrimidone photoproduct in DNA. Their flavin adenine dinucleotide (FAD) cofactor can be reduced to its repair-active FADH- form by a photoinduced electron transfer reaction. In animal (6-4)PLs, a chain of four Trp residues was suggested to be involved in a stepwise transfer of an oxidation hole from the flavin to the surface of the protein. Here, we investigated the effect of mutation of the fourth Trp on the DNA photorepair activity of Xenopus laevis (6-4)PL (Xl64) in bacterial cells. The photoreduction and photorepair properties of this mutant protein were independently characterized in vitro. Our results demonstrate that the mutation of the fourth Trp in Xl64 drastically impairs the DNA repair activity in cells and that this effect is due to the inhibition of the photoreduction process. We thereby show that the photoreductive formation of FADH- through the Trp tetrad is essential for the biological function of the animal (6-4)PL. The role of the Trp cascade, and of the fourth Trp in particular, is discussed. © 2017 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } (6-4) photolyases [(6-4)PLs] are flavoproteins that use blue light to repair the ultraviolet-induced pyrimidine(6-4)pyrimidone photoproduct in DNA. Their flavin adenine dinucleotide (FAD) cofactor can be reduced to its repair-active FADH- form by a photoinduced electron transfer reaction. In animal (6-4)PLs, a chain of four Trp residues was suggested to be involved in a stepwise transfer of an oxidation hole from the flavin to the surface of the protein. Here, we investigated the effect of mutation of the fourth Trp on the DNA photorepair activity of Xenopus laevis (6-4)PL (Xl64) in bacterial cells. The photoreduction and photorepair properties of this mutant protein were independently characterized in vitro. Our results demonstrate that the mutation of the fourth Trp in Xl64 drastically impairs the DNA repair activity in cells and that this effect is due to the inhibition of the photoreduction process. We thereby show that the photoreductive formation of FADH- through the Trp tetrad is essential for the biological function of the animal (6-4)PL. The role of the Trp cascade, and of the fourth Trp in particular, is discussed. © 2017 American Chemical Society. |
Photoinduced Chromophore Hydration in the Fluorescent Protein Dreiklang Is Triggered by Ultrafast Excited-State Proton Transfer Coupled to a Low-Frequency Vibration Article de journal F Lacombat; P Plaza; M -A Plamont; A Espagne Journal of Physical Chemistry Letters, 8 (7), p. 1489–1495, 2017. @article{Lacombat:2017, title = {Photoinduced Chromophore Hydration in the Fluorescent Protein Dreiklang Is Triggered by Ultrafast Excited-State Proton Transfer Coupled to a Low-Frequency Vibration}, author = {F Lacombat and P Plaza and M -A Plamont and A Espagne}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017130354&doi=10.1021%2facs.jpclett.7b00348&partnerID=40&md5=dba41290a37553caaabb354a87ad0ec6}, doi = {10.1021/acs.jpclett.7b00348}, year = {2017}, date = {2017-01-01}, journal = {Journal of Physical Chemistry Letters}, volume = {8}, number = {7}, pages = {1489--1495}, abstract = {Because of growing applications in advanced fluorescence imaging, the mechanisms and dynamics of photoinduced reactions in reversibly photoswitchable fluorescent proteins are currently attracting much interest. We report the first time-resolved study of the photoswitching of Dreiklang, so far the only fluorescent protein to undergo reversible photoinduced chromophore hydration. Using broadband femtosecond transient absorption spectroscopy, we show that the reaction is triggered by an ultrafast deprotonation of the chromophore phenol group in the excited state in 100 fs. This primary step is accompanied by coherent oscillations that we assign to its coupling with a low-frequency mode, possibly a deformation of the chromophore hydrogen bond network. A ground-state intermediate is formed in the picosecond-nanosecond regime that we tentatively assign to the deprotonated water adduct. We suggest that proton ejection from the phenol group leads to a charge transfer from the phenol to the imidazolinone ring, which triggers imidazolinone protonation by nearby Glu222 and catalyzes the addition of the water molecule. © 2017 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Because of growing applications in advanced fluorescence imaging, the mechanisms and dynamics of photoinduced reactions in reversibly photoswitchable fluorescent proteins are currently attracting much interest. We report the first time-resolved study of the photoswitching of Dreiklang, so far the only fluorescent protein to undergo reversible photoinduced chromophore hydration. Using broadband femtosecond transient absorption spectroscopy, we show that the reaction is triggered by an ultrafast deprotonation of the chromophore phenol group in the excited state in 100 fs. This primary step is accompanied by coherent oscillations that we assign to its coupling with a low-frequency mode, possibly a deformation of the chromophore hydrogen bond network. A ground-state intermediate is formed in the picosecond-nanosecond regime that we tentatively assign to the deprotonated water adduct. We suggest that proton ejection from the phenol group leads to a charge transfer from the phenol to the imidazolinone ring, which triggers imidazolinone protonation by nearby Glu222 and catalyzes the addition of the water molecule. © 2017 American Chemical Society. |
Repair of (6-4) Lesions in DNA by (6-4) Photolyase: 20 Years of Quest for the Photoreaction Mechanism Article de journal J Yamamoto; P Plaza; K Brettel Photochemistry and Photobiology, 93 (1), p. 51–66, 2017. @article{Yamamoto:2017a, title = {Repair of (6-4) Lesions in DNA by (6-4) Photolyase: 20 Years of Quest for the Photoreaction Mechanism}, author = {J Yamamoto and P Plaza and K Brettel}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011581630&doi=10.1111%2fphp.12696&partnerID=40&md5=4127461fd365fb839dfef3ed244ba606}, doi = {10.1111/php.12696}, year = {2017}, date = {2017-01-01}, journal = {Photochemistry and Photobiology}, volume = {93}, number = {1}, pages = {51--66}, abstract = {Exposure of DNA to ultraviolet (UV) light from the Sun or from other sources causes the formation of harmful and carcinogenic crosslinks between adjacent pyrimidine nucleobases, namely cyclobutane pyrimidine dimers and pyrimidine(6\textendash4)pyrimidone photoproducts. Nature has developed unique flavoenzymes, called DNA photolyases, that utilize blue light, that is photons of lower energy than those of the damaging light, to repair these lesions. In this review, we focus on the chemically challenging repair of the (6\textendash4) photoproducts by (6\textendash4) photolyase and describe the major events along the quest for the reaction mechanisms, over the 20 years since the discovery of (6-4) photolyase. © 2016 The American Society of Photobiology}, keywords = {}, pubstate = {published}, tppubtype = {article} } Exposure of DNA to ultraviolet (UV) light from the Sun or from other sources causes the formation of harmful and carcinogenic crosslinks between adjacent pyrimidine nucleobases, namely cyclobutane pyrimidine dimers and pyrimidine(6–4)pyrimidone photoproducts. Nature has developed unique flavoenzymes, called DNA photolyases, that utilize blue light, that is photons of lower energy than those of the damaging light, to repair these lesions. In this review, we focus on the chemically challenging repair of the (6–4) photoproducts by (6–4) photolyase and describe the major events along the quest for the reaction mechanisms, over the 20 years since the discovery of (6-4) photolyase. © 2016 The American Society of Photobiology |
Ultrafast flavin photoreduction in an oxidized animal (6-4) photolyase through an unconventional tryptophan tetrad Article de journal P R Martin; F Lacombat; A Espagne; N Dozova; P Plaza; J Yamamoto; P Müller; K Brettel; A De La Lande Physical Chemistry Chemical Physics, 19 (36), p. 24493–24504, 2017. @article{Martin:2017a, title = {Ultrafast flavin photoreduction in an oxidized animal (6-4) photolyase through an unconventional tryptophan tetrad}, author = {P R Martin and F Lacombat and A Espagne and N Dozova and P Plaza and J Yamamoto and P M\"{u}ller and K Brettel and A De La Lande}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029817108&doi=10.1039%2fc7cp04555g&partnerID=40&md5=b5966e02f7c4f4fa9b385f15647311c3}, doi = {10.1039/c7cp04555g}, year = {2017}, date = {2017-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {19}, number = {36}, pages = {24493--24504}, abstract = {Photolyases are flavoenzymes repairing UV-induced lesions in DNA, which may be activated by a photoreduction of their FAD cofactor. In most photolyases, this photoreduction proceeds by electron transfer along a chain of three tryptophan (Trp) residues, connecting the flavin to the protein surface. Much less studied, animal (6-4) photolyases (repairing pyrimidine-pyrimidone (6-4) photoproducts) are particularly interesting as they were recently shown to have a longer electron transfer chain, counting four Trp residues. Using femtosecond polarized transient absorption spectroscopy, we performed a detailed analysis of the photoactivation reaction in the (6-4) photolyase of Xenopus laevis with oxidized FAD. We showed that the excited flavin is very quickly reduced (∼0.5 ps) by a nearby tryptophan residue, yielding FAD•- and WH•+ radicals. Subsequent kinetic steps in the picosecond regime were assigned to the migration of the positive charge along the Trp tetrad, in competition with charge recombination. We propose that the positive charge is actually delocalized over various Trp residues during most of the dynamics and that charge recombination essentially occurs through the proximal tryptophanyl radical. Oxidation of the fourth tryptophan is thought to be reached about as fast as that of the third one (∼40 ps), based on a comparison with a mutant protein lacking the distal Trp, implying ultrafast electron transfer between these two residues. This unusual mechanism sheds light on the rich diversity of electron transfer pathways found in various photolyases, and evolution-related cryptochromes alike. © the Owner Societies 2017.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Photolyases are flavoenzymes repairing UV-induced lesions in DNA, which may be activated by a photoreduction of their FAD cofactor. In most photolyases, this photoreduction proceeds by electron transfer along a chain of three tryptophan (Trp) residues, connecting the flavin to the protein surface. Much less studied, animal (6-4) photolyases (repairing pyrimidine-pyrimidone (6-4) photoproducts) are particularly interesting as they were recently shown to have a longer electron transfer chain, counting four Trp residues. Using femtosecond polarized transient absorption spectroscopy, we performed a detailed analysis of the photoactivation reaction in the (6-4) photolyase of Xenopus laevis with oxidized FAD. We showed that the excited flavin is very quickly reduced (∼0.5 ps) by a nearby tryptophan residue, yielding FAD•- and WH•+ radicals. Subsequent kinetic steps in the picosecond regime were assigned to the migration of the positive charge along the Trp tetrad, in competition with charge recombination. We propose that the positive charge is actually delocalized over various Trp residues during most of the dynamics and that charge recombination essentially occurs through the proximal tryptophanyl radical. Oxidation of the fourth tryptophan is thought to be reached about as fast as that of the third one (∼40 ps), based on a comparison with a mutant protein lacking the distal Trp, implying ultrafast electron transfer between these two residues. This unusual mechanism sheds light on the rich diversity of electron transfer pathways found in various photolyases, and evolution-related cryptochromes alike. © the Owner Societies 2017. |
2016 |
Excited-state symmetry breaking of linear quadrupolar chromophores: A transient absorption study Article de journal N Dozova; L Ventelon; G Clermont; M Blanchard-Desce; P Plaza Chemical Physics Letters, 664 , p. 56–62, 2016. @article{Dozova:2016, title = {Excited-state symmetry breaking of linear quadrupolar chromophores: A transient absorption study}, author = {N Dozova and L Ventelon and G Clermont and M Blanchard-Desce and P Plaza}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991648542&doi=10.1016%2fj.cplett.2016.10.020&partnerID=40&md5=93f48fbad7f0a0a40b036bef2e73147a}, doi = {10.1016/j.cplett.2016.10.020}, year = {2016}, date = {2016-01-01}, journal = {Chemical Physics Letters}, volume = {664}, pages = {56--62}, abstract = {The photophysical properties of two highly symmetrical quadrupolar chromophores were studied by both steady-state and transient absorption spectroscopy. Their excited-state behavior is dominated by the solvent-induced Stokes shift of the stimulated-emission band. The origin of this shift is attributed to symmetry breaking that confers a non-vanishing dipole moment to the excited state of both compounds. This dipole moment is large and constant in DMSO, whereas symmetry breaking appears significantly slower and leading to smaller excited-state dipole in toluene. Time-dependant increase of the excited-state dipole moment induced by weak solvation is proposed to explain the results in toluene. © 2016 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The photophysical properties of two highly symmetrical quadrupolar chromophores were studied by both steady-state and transient absorption spectroscopy. Their excited-state behavior is dominated by the solvent-induced Stokes shift of the stimulated-emission band. The origin of this shift is attributed to symmetry breaking that confers a non-vanishing dipole moment to the excited state of both compounds. This dipole moment is large and constant in DMSO, whereas symmetry breaking appears significantly slower and leading to smaller excited-state dipole in toluene. Time-dependant increase of the excited-state dipole moment induced by weak solvation is proposed to explain the results in toluene. © 2016 Elsevier B.V. |
Ultrafast Dynamics of a Green Fluorescent Protein Chromophore Analogue: Competition between Excited-State Proton Transfer and Torsional Relaxation Article de journal T Chatterjee; F Lacombat; D Yadav; M Mandal; P Plaza; A Espagne; P K Mandal Journal of Physical Chemistry B, 120 (36), p. 9716–9722, 2016. @article{Chatterjee:2016, title = {Ultrafast Dynamics of a Green Fluorescent Protein Chromophore Analogue: Competition between Excited-State Proton Transfer and Torsional Relaxation}, author = {T Chatterjee and F Lacombat and D Yadav and M Mandal and P Plaza and A Espagne and P K Mandal}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987847663&doi=10.1021%2facs.jpcb.6b05795&partnerID=40&md5=dbc7a71ee9d3e1a62872f19c1f0c7204}, doi = {10.1021/acs.jpcb.6b05795}, year = {2016}, date = {2016-01-01}, journal = {Journal of Physical Chemistry B}, volume = {120}, number = {36}, pages = {9716--9722}, abstract = {The competition between excited-state proton transfer (ESPT) and torsion plays a central role in the photophysics of fluorescent proteins of the green fluorescent protein (GFP) family and their chromophores. Here, it was investigated in a single GFP chromophore analogue bearing o-hydroxy and p-diethylamino substituents, OHIM. The light-induced dynamics of OHIM was studied by femtosecond transient absorption spectroscopy, at different pH. We found that the photophysics of OHIM is determined by the electron-donating character of the diethylamino group: torsional relaxation dominates when the diethylamino group is neutral, whereas ultrafast ESPT followed by cis/trans isomerization and ground-state reprotonation are observed when the diethylamino group is protonated and therefore inactive as an electron donor. © 2016 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The competition between excited-state proton transfer (ESPT) and torsion plays a central role in the photophysics of fluorescent proteins of the green fluorescent protein (GFP) family and their chromophores. Here, it was investigated in a single GFP chromophore analogue bearing o-hydroxy and p-diethylamino substituents, OHIM. The light-induced dynamics of OHIM was studied by femtosecond transient absorption spectroscopy, at different pH. We found that the photophysics of OHIM is determined by the electron-donating character of the diethylamino group: torsional relaxation dominates when the diethylamino group is neutral, whereas ultrafast ESPT followed by cis/trans isomerization and ground-state reprotonation are observed when the diethylamino group is protonated and therefore inactive as an electron donor. © 2016 American Chemical Society. |
2015 |
Photo-induced cation translocation in a molecular shuttle based on a calix[4]-biscrown including DCM and DMABN chromophores Article de journal N Dozova; R Kumar; T Pradhan; F Lacombat; B Valeur; J S Kim; P Plaza Chemical Communications, 51 (80), p. 14859–14861, 2015. @article{Dozova:2015, title = {Photo-induced cation translocation in a molecular shuttle based on a calix[4]-biscrown including DCM and DMABN chromophores}, author = {N Dozova and R Kumar and T Pradhan and F Lacombat and B Valeur and J S Kim and P Plaza}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942474410&doi=10.1039%2fc5cc06054k&partnerID=40&md5=857b5558380ed42e21e82790184d89cb}, doi = {10.1039/c5cc06054k}, year = {2015}, date = {2015-01-01}, journal = {Chemical Communications}, volume = {51}, number = {80}, pages = {14859--14861}, abstract = {We present a new molecular shuttle, consisting of a calixarene core attached to two different photoactive centers, DCM and DMABN. We show that a K+ ion bound to the DCM-grafted crown is translocated towards the other site of the molecule upon photoexcitation, but not released to the bulk. © The Royal Society of Chemistry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a new molecular shuttle, consisting of a calixarene core attached to two different photoactive centers, DCM and DMABN. We show that a K+ ion bound to the DCM-grafted crown is translocated towards the other site of the molecule upon photoexcitation, but not released to the bulk. © The Royal Society of Chemistry. |
Real-time monitoring of chromophore isomerization and deprotonation during the photoactivation of the fluorescent protein Dronpa Article de journal D Yadav; F Lacombat; N Dozova; F Rappaport; P Plaza; A Espagne Journal of Physical Chemistry B, 119 (6), p. 2404–2414, 2015. @article{Yadav:2015, title = {Real-time monitoring of chromophore isomerization and deprotonation during the photoactivation of the fluorescent protein Dronpa}, author = {D Yadav and F Lacombat and N Dozova and F Rappaport and P Plaza and A Espagne}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922794115&doi=10.1021%2fjp507094f&partnerID=40&md5=6618718bf1ba6e1f5e5f2194c9480d5b}, doi = {10.1021/jp507094f}, year = {2015}, date = {2015-01-01}, journal = {Journal of Physical Chemistry B}, volume = {119}, number = {6}, pages = {2404--2414}, abstract = {Dronpa is a photochromic green fluorescent protein (GFP) homologue used as a probe in super-resolution microscopy. It is known that the photochromic reaction involves cis/trans isomerization of the chromophore and protonation/deprotonation of its phenol group, but the sequence in time of the two steps and their characteristic time scales are still the subject of much debate. We report here a comprehensive UV-visible transient absorption spectroscopy study of the photoactivation mechanism of Dronpa, covering all relevant time scales from ∼100 fs to milliseconds. The Dronpa-2 variant was also studied and showed the same behavior. By carefully controlling the excitation energy to avoid multiphoton processes, we could measure both the spectrum and the anisotropy of the first photoactivation intermediate. We show that the observed few nanometer blue-shift of this intermediate is characteristic for a neutral cis chromophore, and that its anisotropy of ∼0.2 is in good agreement with the reorientation of the transition dipole moment expected upon isomerization. These data constitute the first clear evidence that trans → cis isomerization of the chromophore precedes its deprotonation and occurs on the picosecond time scale, concomitantly to the excited-state decay. We found the deprotonation step to follow in ∼10 μs and lead directly from the neutral cis intermediate to the final state. © 2014 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dronpa is a photochromic green fluorescent protein (GFP) homologue used as a probe in super-resolution microscopy. It is known that the photochromic reaction involves cis/trans isomerization of the chromophore and protonation/deprotonation of its phenol group, but the sequence in time of the two steps and their characteristic time scales are still the subject of much debate. We report here a comprehensive UV-visible transient absorption spectroscopy study of the photoactivation mechanism of Dronpa, covering all relevant time scales from ∼100 fs to milliseconds. The Dronpa-2 variant was also studied and showed the same behavior. By carefully controlling the excitation energy to avoid multiphoton processes, we could measure both the spectrum and the anisotropy of the first photoactivation intermediate. We show that the observed few nanometer blue-shift of this intermediate is characteristic for a neutral cis chromophore, and that its anisotropy of ∼0.2 is in good agreement with the reorientation of the transition dipole moment expected upon isomerization. These data constitute the first clear evidence that trans → cis isomerization of the chromophore precedes its deprotonation and occurs on the picosecond time scale, concomitantly to the excited-state decay. We found the deprotonation step to follow in ∼10 μs and lead directly from the neutral cis intermediate to the final state. © 2014 American Chemical Society. |