Professeur des Universités, Sorbonne Université
Responsable du pôle de Chimie Physique et Biologique de la Matière Vivante
PASTEUR, Département de chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS
24 rue Lhomond, 75005 Paris, France
Email: Ludovic.Jullien@ens.psl.eu or Ludovic.Jullien@sorbonne-universite.fr
Phone: +33 144323333
Office: E142c
Home page: https://ludovicjullien.org/
Publications
2014 |
Photocontrolled ionization in the corona of rodlike assemblies of diblock copolymers Article de journal J Sun; L Jia; M Emond; M -H Li; E Marie; L Jullien; C Tribet Macromolecules, 47 (5), p. 1684–1692, 2014. @article{Sun:2014, title = {Photocontrolled ionization in the corona of rodlike assemblies of diblock copolymers}, author = {J Sun and L Jia and M Emond and M -H Li and E Marie and L Jullien and C Tribet}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900623616&doi=10.1021%2fma402591y&partnerID=40&md5=096eeaa435f309dc54c178b236d1de7c}, doi = {10.1021/ma402591y}, year = {2014}, date = {2014-01-01}, journal = {Macromolecules}, volume = {47}, number = {5}, pages = {1684--1692}, abstract = {To remotely control ionization of polymer assemblies, we tailored amphiphilic diblock polyacrylates with varying hydrophilic and hydrophobic block lengths and containing pendant 2-hydroxyazobenzene photoswitchable groups in the hydrophilic block. Formation in water of rodlike polymer micelles was obtained upon hydrophobic assembly of the pendant cholesterol groups present in the hydrophobic block. Phototriggered variation of both pH and UV-vis spectral properties confirmed that hydroxylazobenzene moieties, gathered in the hydrophilic corona, underwent both isomerization and ionization upon exposure to UV light. Dispersions of rods can accordingly be ionized on demand. © 2014 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } To remotely control ionization of polymer assemblies, we tailored amphiphilic diblock polyacrylates with varying hydrophilic and hydrophobic block lengths and containing pendant 2-hydroxyazobenzene photoswitchable groups in the hydrophilic block. Formation in water of rodlike polymer micelles was obtained upon hydrophobic assembly of the pendant cholesterol groups present in the hydrophobic block. Phototriggered variation of both pH and UV-vis spectral properties confirmed that hydroxylazobenzene moieties, gathered in the hydrophilic corona, underwent both isomerization and ionization upon exposure to UV light. Dispersions of rods can accordingly be ionized on demand. © 2014 American Chemical Society. |
Rapidly tunable and compact coherent Raman scattering light source for molecular spectroscopy Article de journal S Saint-Jalm; P Berto; L Jullien; E R Andresen; H Rigneault Journal of Raman Spectroscopy, 45 (7), p. 515–520, 2014. @article{Saint-Jalm:2014, title = {Rapidly tunable and compact coherent Raman scattering light source for molecular spectroscopy}, author = {S Saint-Jalm and P Berto and L Jullien and E R Andresen and H Rigneault}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904215402&doi=10.1002%2fjrs.4514&partnerID=40&md5=4cb0181caada13d4877cdcb5ab9d00f8}, doi = {10.1002/jrs.4514}, year = {2014}, date = {2014-01-01}, journal = {Journal of Raman Spectroscopy}, volume = {45}, number = {7}, pages = {515--520}, abstract = {We present a rapidly tunable (over 400 cm -1) and compact (0.7 m 2 footprint) coherent Raman scattering light source performing both coherent anti-Stokes Raman scattering and stimulated Raman scattering microspectroscopy. We use spectral focusing of a femtosecond Ti:Sapphire pulse and a redshifted soliton generated in a photonic crystal fiber to reach suitable spectral resolution and to rapidly acquire spectra by means of a delay line translation. The coherent Raman scattering light source is used to monitor the molecular equilibrium shift between hydrogen phosphate and dihydrogen phosphate ions under pH change. Copyright © 2014 John Wiley & Sons, Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a rapidly tunable (over 400 cm -1) and compact (0.7 m 2 footprint) coherent Raman scattering light source performing both coherent anti-Stokes Raman scattering and stimulated Raman scattering microspectroscopy. We use spectral focusing of a femtosecond Ti:Sapphire pulse and a redshifted soliton generated in a photonic crystal fiber to reach suitable spectral resolution and to rapidly acquire spectra by means of a delay line translation. The coherent Raman scattering light source is used to monitor the molecular equilibrium shift between hydrogen phosphate and dihydrogen phosphate ions under pH change. Copyright © 2014 John Wiley & Sons, Ltd. |
2013 |
A blue-absorbing photolabile protecting group for in vivo chromatically orthogonal photoactivation Article de journal L Fournier; C Gauron; L Xu; I Aujard; T Le Saux; N Gagey-Eilstein; S Maurin; S Dubruille; J -B Baudin; D Bensimon; M Volovitch; S Vriz; L Jullien ACS Chemical Biology, 8 (7), p. 1528–1536, 2013. @article{Fournier:2013a, title = {A blue-absorbing photolabile protecting group for in vivo chromatically orthogonal photoactivation}, author = {L Fournier and C Gauron and L Xu and I Aujard and T Le Saux and N Gagey-Eilstein and S Maurin and S Dubruille and J -B Baudin and D Bensimon and M Volovitch and S Vriz and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880534465&doi=10.1021%2fcb400178m&partnerID=40&md5=a6d82b0b12d74445d9235b43207903ed}, doi = {10.1021/cb400178m}, year = {2013}, date = {2013-01-01}, journal = {ACS Chemical Biology}, volume = {8}, number = {7}, pages = {1528--1536}, abstract = {The small and synthetically easily accessible 7-diethylamino-4- thiocoumarinylmethyl photolabile protecting group has been validated for uncaging with blue light. It exhibits a significant action cross-section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features have been implemented in living zebrafish embryos to perform chromatic orthogonal photoactivation of two biologically active species controlling biological development with UV and blue-cyan light sources, respectively. © 2013 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The small and synthetically easily accessible 7-diethylamino-4- thiocoumarinylmethyl photolabile protecting group has been validated for uncaging with blue light. It exhibits a significant action cross-section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features have been implemented in living zebrafish embryos to perform chromatic orthogonal photoactivation of two biologically active species controlling biological development with UV and blue-cyan light sources, respectively. © 2013 American Chemical Society. |
Coumarinylmethyl caging groups with redshifted absorption Article de journal L Fournier; I Aujard; T Le Saux; S Maurin; S Beaupierre; J -B Baudin; L Jullien Chemistry - A European Journal, 19 (51), p. 17494–17507, 2013. @article{Fournier:2013, title = {Coumarinylmethyl caging groups with redshifted absorption}, author = {L Fournier and I Aujard and T Le Saux and S Maurin and S Beaupierre and J -B Baudin and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890121904&doi=10.1002%2fchem.201302630&partnerID=40&md5=2dc2ad1b5ad79b030bc0b916107658cc}, doi = {10.1002/chem.201302630}, year = {2013}, date = {2013-01-01}, journal = {Chemistry - A European Journal}, volume = {19}, number = {51}, pages = {17494--17507}, abstract = {The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron-donating groups in the 7 position and electron-withdrawing groups in the 2-, and 2- and 3 positions. In particular, we showed that the diethylamino-thiocoumarylmethyl and the diethylamino-coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue-cyan light sources, respectively. Revealing protecting groups: The coumarinylmethyl backbone was used to generate a family of photolabile protecting groups with redshifted absorption (see scheme). Several members exhibit a significant action cross section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These features are favorable for chromatic orthogonal photoactivation with UV and blue-cyan light sources, respectively. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron-donating groups in the 7 position and electron-withdrawing groups in the 2-, and 2- and 3 positions. In particular, we showed that the diethylamino-thiocoumarylmethyl and the diethylamino-coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue-cyan light sources, respectively. Revealing protecting groups: The coumarinylmethyl backbone was used to generate a family of photolabile protecting groups with redshifted absorption (see scheme). Several members exhibit a significant action cross section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These features are favorable for chromatic orthogonal photoactivation with UV and blue-cyan light sources, respectively. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations Article de journal F Closa; C Gosse; L Jullien; A Lemarchand Journal of Chemical Physics, 138 (24), 2013. @article{Closa:2013, title = {Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations}, author = {F Closa and C Gosse and L Jullien and A Lemarchand}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879925744&doi=10.1063%2f1.4811288&partnerID=40&md5=cc245cf42ac7990ee3793cafb50dfdfd}, doi = {10.1063/1.4811288}, year = {2013}, date = {2013-01-01}, journal = {Journal of Chemical Physics}, volume = {138}, number = {24}, abstract = {Increased focus on kinetic signatures in biology, coupled with the lack of simple tools for chemical dynamics characterization, lead us to develop an efficient method for mechanism identification. A small thermal modulation is used to reveal chemical dynamics, which makes the technique compatible with in cellulo imaging. Then, the detection of concentration oscillations in an appropriate frequency range followed by a judicious analytical treatment of the data is sufficient to determine the number of chemical characteristic times, the reaction mechanism, and the full set of associated rate constants and enthalpies of reaction. To illustrate the scope of the method, dimeric protein folding is chosen as a biologically relevant example of nonlinear mechanism with one or two characteristic times. © 2013 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Increased focus on kinetic signatures in biology, coupled with the lack of simple tools for chemical dynamics characterization, lead us to develop an efficient method for mechanism identification. A small thermal modulation is used to reveal chemical dynamics, which makes the technique compatible with in cellulo imaging. Then, the detection of concentration oscillations in an appropriate frequency range followed by a judicious analytical treatment of the data is sufficient to determine the number of chemical characteristic times, the reaction mechanism, and the full set of associated rate constants and enthalpies of reaction. To illustrate the scope of the method, dimeric protein folding is chosen as a biologically relevant example of nonlinear mechanism with one or two characteristic times. © 2013 AIP Publishing LLC. |
Light activation for the versatile and accurate kinetic analysis of disassembly of self-immolative spacers Article de journal A Alouane; R Labruère; T Le Saux; I Aujard; S Dubruille; F Schmidt; L Jullien Chemistry - A European Journal, 19 (35), p. 11717–11724, 2013. @article{Alouane:2013, title = {Light activation for the versatile and accurate kinetic analysis of disassembly of self-immolative spacers}, author = {A Alouane and R Labru\`{e}re and T Le Saux and I Aujard and S Dubruille and F Schmidt and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882877857&doi=10.1002%2fchem.201301298&partnerID=40&md5=d2c00551ce1409fe58d0716e0cc747c8}, doi = {10.1002/chem.201301298}, year = {2013}, date = {2013-01-01}, journal = {Chemistry - A European Journal}, volume = {19}, number = {35}, pages = {11717--11724}, abstract = {Three procedures that rely on photoactivation are introduced to accurately analyze the disassembly kinetics of a collection of self-immolative spacer groups within the window 10-2-103 s. Our results are relevant for deriving quantitative structure-property relationships. In particular, we have been able to access 20 ms temporal resolution, which made possible the measurement of the shortest ever reported disassembly time for an activated self-immolative spacer. Quick as lightning! Accurate kinetic analysis of the disassembly of various self-immolative spacers in a 10 -2-103 s window was achieved. An epifluorescence setup allowed the measurement of the shortest time (20 ms) for a self-immolation event. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Three procedures that rely on photoactivation are introduced to accurately analyze the disassembly kinetics of a collection of self-immolative spacer groups within the window 10-2-103 s. Our results are relevant for deriving quantitative structure-property relationships. In particular, we have been able to access 20 ms temporal resolution, which made possible the measurement of the shortest ever reported disassembly time for an activated self-immolative spacer. Quick as lightning! Accurate kinetic analysis of the disassembly of various self-immolative spacers in a 10 -2-103 s window was achieved. An epifluorescence setup allowed the measurement of the shortest time (20 ms) for a self-immolation event. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Photochemical properties of Spinach and its use in selective imaging Article de journal P Wang; J Querard; S Maurin; S S Nath; T Le Saux; A Gautier; L Jullien Chemical Science, 4 (7), p. 2865–2873, 2013. @article{Wang:2013a, title = {Photochemical properties of Spinach and its use in selective imaging}, author = {P Wang and J Querard and S Maurin and S S Nath and T Le Saux and A Gautier and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878785970&doi=10.1039%2fc3sc50729g&partnerID=40&md5=1deeb79d383d404915eba832d5c4b9a6}, doi = {10.1039/c3sc50729g}, year = {2013}, date = {2013-01-01}, journal = {Chemical Science}, volume = {4}, number = {7}, pages = {2865--2873}, abstract = {The progress in imaging instrumentation and probes has revolutionized the way biologists look at living systems. Current tools enable both observation and quantification of biomolecules, allowing the measurement of their complex spatial organization and the dynamic processes in which they are involved. Here, we report reversible photoconversion in the Spinach system, a recently described fluorescent probe for RNA imaging. Upon irradiation with blue light, the Spinach system undergoes photoconversion to a less fluorescent state and fully recovers its signal in the dark. Through thermodynamic titration, stopped-flow, and light-jump experiments, we propose a dynamic model that accounts for the photochemical behavior of the Spinach system. We exploit the dynamic fluorogen exchange and the unprecedented photoconversion properties in a non-covalent fluorescence turn-on system to significantly improve signal-to-background ratio during long-term microscopy imaging. © 2013 Royal Society of Chemistry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The progress in imaging instrumentation and probes has revolutionized the way biologists look at living systems. Current tools enable both observation and quantification of biomolecules, allowing the measurement of their complex spatial organization and the dynamic processes in which they are involved. Here, we report reversible photoconversion in the Spinach system, a recently described fluorescent probe for RNA imaging. Upon irradiation with blue light, the Spinach system undergoes photoconversion to a less fluorescent state and fully recovers its signal in the dark. Through thermodynamic titration, stopped-flow, and light-jump experiments, we propose a dynamic model that accounts for the photochemical behavior of the Spinach system. We exploit the dynamic fluorogen exchange and the unprecedented photoconversion properties in a non-covalent fluorescence turn-on system to significantly improve signal-to-background ratio during long-term microscopy imaging. © 2013 Royal Society of Chemistry. |
2012 |
"Self-immolative" spacer for uncaging with fluorescence reporting Article de journal R Labruère; A Alouane; T Le Saux; I Aujard; P Pelupessy; A Gautier; S Dubruille; F Schmidt; L Jullien Angewandte Chemie - International Edition, 51 (37), p. 9344–9347, 2012. @article{Labruere:2012, title = {"Self-immolative" spacer for uncaging with fluorescence reporting}, author = {R Labru\`{e}re and A Alouane and T Le Saux and I Aujard and P Pelupessy and A Gautier and S Dubruille and F Schmidt and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865847445&doi=10.1002%2fanie.201204032&partnerID=40&md5=b61369ac1effc61c29106c6a64c6cd44}, doi = {10.1002/anie.201204032}, year = {2012}, date = {2012-01-01}, journal = {Angewandte Chemie - International Edition}, volume = {51}, number = {37}, pages = {9344--9347}, abstract = {Dual photoliberation: A caged, branched, self-immolative spacer (see scheme, gray box) was designed to rapidly and simultaneously release a desired compound (green) and a fluorophore (red) upon photoactivation. Careful kinetic analysis of the disassembly of the spacer shows that it occurs on the shortest time scale reported to date. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dual photoliberation: A caged, branched, self-immolative spacer (see scheme, gray box) was designed to rapidly and simultaneously release a desired compound (green) and a fluorophore (red) upon photoactivation. Careful kinetic analysis of the disassembly of the spacer shows that it occurs on the shortest time scale reported to date. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Chemical mechanism identification from frequency response to small temperature modulation Article de journal A Lemarchand; H Berthoumieux; L Jullien; C Gosse Journal of Physical Chemistry A, 116 (33), p. 8455–8463, 2012. @article{Lemarchand:2012, title = {Chemical mechanism identification from frequency response to small temperature modulation}, author = {A Lemarchand and H Berthoumieux and L Jullien and C Gosse}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866372438&doi=10.1021%2fjp305737&partnerID=40&md5=69f2cc8fb4aa802f8af8abbf2e0a8d1d}, doi = {10.1021/jp305737}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry A}, volume = {116}, number = {33}, pages = {8455--8463}, abstract = {The description of interactions between biochemical species and the elucidation of the corresponding chemical mechanisms encounter an increasing interest both for the comprehension of biological pathways at the molecular scale and for the rationalization of drug design. Relying on powerful experimental tools such as thermal microfluidics and fluorescence detection, we propose a methodology to determine the chemical mechanism of a reaction without fitting parameters. A mechanism consistent with the accessible knowledge is assumed, and the assumption is checked through an iterative protocol. The test is based on the frequency analysis of the response of a targeted reactive species to temperature modulation. We build specific functions of the frequency that are constant for the assumed mechanism and show that the graph of these functions can be drawn from appropriate data analysis. The method is general and can be applied to any complex mechanism. It is here illustrated in detail in the case of single relaxation time mechanisms. © 2012 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The description of interactions between biochemical species and the elucidation of the corresponding chemical mechanisms encounter an increasing interest both for the comprehension of biological pathways at the molecular scale and for the rationalization of drug design. Relying on powerful experimental tools such as thermal microfluidics and fluorescence detection, we propose a methodology to determine the chemical mechanism of a reaction without fitting parameters. A mechanism consistent with the accessible knowledge is assumed, and the assumption is checked through an iterative protocol. The test is based on the frequency analysis of the response of a targeted reactive species to temperature modulation. We build specific functions of the frequency that are constant for the assumed mechanism and show that the graph of these functions can be drawn from appropriate data analysis. The method is general and can be applied to any complex mechanism. It is here illustrated in detail in the case of single relaxation time mechanisms. © 2012 American Chemical Society. |
Energy propagation through a protometabolism leading to the local emergence of singular stationary concentration profiles Article de journal M Emond; T Le Saux; J -F Allemand; P Pelupessy; R Plasson; L Jullien Chemistry - A European Journal, 18 (45), p. 14375–14383, 2012. @article{Emond:2012, title = {Energy propagation through a protometabolism leading to the local emergence of singular stationary concentration profiles}, author = {M Emond and T Le Saux and J -F Allemand and P Pelupessy and R Plasson and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868034869&doi=10.1002%2fchem.201201974&partnerID=40&md5=de25aef0cd9970e53e4c8d604267fd96}, doi = {10.1002/chem.201201974}, year = {2012}, date = {2012-01-01}, journal = {Chemistry - A European Journal}, volume = {18}, number = {45}, pages = {14375--14383}, abstract = {Living systems rely on chains of energy transfer from an energy source to maintain their metabolism. This task requires functionally identified components and organizations. However, propagation of a sustained energy flux through a cascade of reaction cycles has never been reproduced at a steady state in a simple chemical system. By using energy patterning and a diffusing hub reactant, we achieved the transfer of energy through an abiotic protometabolism. Patterned illumination was applied to a liquid solution of a reversible photoacid. It resulted in the local onset of a proton pump, which subsequently drove an extended reaction-diffusion cycle that involved pH-sensitive reactants. Thus, light has been used for locally setting out of chemical equilibrium a reaction involving "blind" reactants. The spontaneous onset of an energy-transfer chain notably drives the local generation of singular dissipative chemical structures; continuous matter fluxes are dynamically maintained at boundaries between spatially and chemically segregated zones, in the absence of any membrane or predetermined material structure. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Living systems rely on chains of energy transfer from an energy source to maintain their metabolism. This task requires functionally identified components and organizations. However, propagation of a sustained energy flux through a cascade of reaction cycles has never been reproduced at a steady state in a simple chemical system. By using energy patterning and a diffusing hub reactant, we achieved the transfer of energy through an abiotic protometabolism. Patterned illumination was applied to a liquid solution of a reversible photoacid. It resulted in the local onset of a proton pump, which subsequently drove an extended reaction-diffusion cycle that involved pH-sensitive reactants. Thus, light has been used for locally setting out of chemical equilibrium a reaction involving "blind" reactants. The spontaneous onset of an energy-transfer chain notably drives the local generation of singular dissipative chemical structures; continuous matter fluxes are dynamically maintained at boundaries between spatially and chemically segregated zones, in the absence of any membrane or predetermined material structure. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Unfolding of cytochrome c upon interaction with azobenzene-modified copolymers Article de journal J Sun; J Ruchmann; A Pallier; L Jullien; M Desmadril; C Tribet Biomacromolecules, 13 (11), p. 3736–3746, 2012. @article{Sun:2012, title = {Unfolding of cytochrome c upon interaction with azobenzene-modified copolymers}, author = {J Sun and J Ruchmann and A Pallier and L Jullien and M Desmadril and C Tribet}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869024546&doi=10.1021%2fbm301200p&partnerID=40&md5=6a3192fce387a1fce6cb3df6a36f2c5d}, doi = {10.1021/bm301200p}, year = {2012}, date = {2012-01-01}, journal = {Biomacromolecules}, volume = {13}, number = {11}, pages = {3736--3746}, abstract = {Hydrophilic or amphiphilic macromolecules are common organic matrices used to encapsulate and protect fragile drugs such as proteins. Polymer cargoes are in addition designed for remote control of protein delivery, upon imparting the macromolecules with stimuli-responsive properties, such as light-triggered polarity switches. The effect of interaction between polymers and proteins on the stability of the proteins is, however, rarely investigated. Here we studied the unfolding/folding equilibrium of cytochrome c (cyt c) under its oxidized or reduced forms, in the presence of various amphiphilic copolymers (by circular dichroism and intrinsic fluorescence measurements). As models of stimuli-responsive amphiphilic chains, we considered poly(acrylic acid) derivatives, modified to contain hydrophobic, light-responsive azobenzene moieties. These copolymers are, thus, capable to develop both ionic (under their sodium forms at pH > 8) and hydrophobic associations with the basic protein cyt c (isoelectric point of 10.0). In aqueous buffer upon increasing urea concentrations, cyt c underwent unfolding, at [urea] of 9-10 M, which was analyzed under the framework of the equilibrium between two states (native-unfolded). In the presence of polymers, the native folding of cyt c was preserved at low concentrations of urea (typically <4M). However, the presence of polymers facilitated unfolding, which occurred at urea concentrations lowered by 2-4 M as compared to unfolding in the absence of polymers (polymer/cyt c ratio of 1:1 g/g). The predominant contribution of coulombic interactions was shown by both the lack of significant impact of the amount of (neutral) azobenzene moieties in the copolymers and the disappearance of destabilization at ionic strength higher than 150 mM. In addition, stability was similar to that of an isolated cyt c, in the presence of a neutral chain bearing acryloyl(oligoethyleneoxide) units instead of the ionized sodium acrylate moieties. DSC measurements showed that in the presence of polymers, cyt c is thermally unfolded in aqueous buffer at temperatures lowered by >20 °C as compared to thermal unfolding in the absence of polymers. Upon exposure to UV light, properties of the polymers chains were perturbed in situ, upon cis/trans isomerization of the azobenzene groups. In polymers displaying a photoresponsive polarity and hydrophobicity switch (conventional azobenzene), the stability of cyt c was not affected by the exposure to light. In contrast, when photoionization occurred (using an hydroxyl-azobenzene whose pKa can be photoshifted), unfolding was initiated upon exposure to light. Altogether, these results show that coulombic binding is a predominant driving force that facilitates unfolding in water/urea solutions. In regard to the design of light-responsive systems for protein handling and control of folding, we conclude that remote control of the coulombic interaction upon photoionization of chromophores can be more efficient than the more conventional photomodulation of polarity. © 2012 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hydrophilic or amphiphilic macromolecules are common organic matrices used to encapsulate and protect fragile drugs such as proteins. Polymer cargoes are in addition designed for remote control of protein delivery, upon imparting the macromolecules with stimuli-responsive properties, such as light-triggered polarity switches. The effect of interaction between polymers and proteins on the stability of the proteins is, however, rarely investigated. Here we studied the unfolding/folding equilibrium of cytochrome c (cyt c) under its oxidized or reduced forms, in the presence of various amphiphilic copolymers (by circular dichroism and intrinsic fluorescence measurements). As models of stimuli-responsive amphiphilic chains, we considered poly(acrylic acid) derivatives, modified to contain hydrophobic, light-responsive azobenzene moieties. These copolymers are, thus, capable to develop both ionic (under their sodium forms at pH > 8) and hydrophobic associations with the basic protein cyt c (isoelectric point of 10.0). In aqueous buffer upon increasing urea concentrations, cyt c underwent unfolding, at [urea] of 9-10 M, which was analyzed under the framework of the equilibrium between two states (native-unfolded). In the presence of polymers, the native folding of cyt c was preserved at low concentrations of urea (typically <4M). However, the presence of polymers facilitated unfolding, which occurred at urea concentrations lowered by 2-4 M as compared to unfolding in the absence of polymers (polymer/cyt c ratio of 1:1 g/g). The predominant contribution of coulombic interactions was shown by both the lack of significant impact of the amount of (neutral) azobenzene moieties in the copolymers and the disappearance of destabilization at ionic strength higher than 150 mM. In addition, stability was similar to that of an isolated cyt c, in the presence of a neutral chain bearing acryloyl(oligoethyleneoxide) units instead of the ionized sodium acrylate moieties. DSC measurements showed that in the presence of polymers, cyt c is thermally unfolded in aqueous buffer at temperatures lowered by >20 °C as compared to thermal unfolding in the absence of polymers. Upon exposure to UV light, properties of the polymers chains were perturbed in situ, upon cis/trans isomerization of the azobenzene groups. In polymers displaying a photoresponsive polarity and hydrophobicity switch (conventional azobenzene), the stability of cyt c was not affected by the exposure to light. In contrast, when photoionization occurred (using an hydroxyl-azobenzene whose pKa can be photoshifted), unfolding was initiated upon exposure to light. Altogether, these results show that coulombic binding is a predominant driving force that facilitates unfolding in water/urea solutions. In regard to the design of light-responsive systems for protein handling and control of folding, we conclude that remote control of the coulombic interaction upon photoionization of chromophores can be more efficient than the more conventional photomodulation of polarity. © 2012 American Chemical Society. |
2011 |
Autocatalyses Article de journal R Plasson; A Brandenburg; L Jullien; H Bersini Journal of Physical Chemistry A, 115 (28), p. 8073–8085, 2011. @article{Plasson:2011a, title = {Autocatalyses}, author = {R Plasson and A Brandenburg and L Jullien and H Bersini}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960350219&doi=10.1021%2fjp110079p&partnerID=40&md5=5d640b81be3368a9b4b87f7a16fd5119}, doi = {10.1021/jp110079p}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry A}, volume = {115}, number = {28}, pages = {8073--8085}, abstract = {Autocatalysis is a fundamental concept, used in a wide range of domains. From the most general definition of autocatalysis, that is, a process in which a chemical compound is able to catalyze its own formation, several different systems can be described. We detail the different categories of autocatalyses and compare them on the basis of their mechanistic, kinetic, and dynamic properties. It is shown how autocatalytic patterns can be generated by different systems of chemical reactions. With the notion of autocatalysis covering a large variety of mechanistic realizations with very similar behaviors, it is proposed that the key signature of autocatalysis is its kinetic pattern expressed in a mathematical form. © 2011 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Autocatalysis is a fundamental concept, used in a wide range of domains. From the most general definition of autocatalysis, that is, a process in which a chemical compound is able to catalyze its own formation, several different systems can be described. We detail the different categories of autocatalyses and compare them on the basis of their mechanistic, kinetic, and dynamic properties. It is shown how autocatalytic patterns can be generated by different systems of chemical reactions. With the notion of autocatalysis covering a large variety of mechanistic realizations with very similar behaviors, it is proposed that the key signature of autocatalysis is its kinetic pattern expressed in a mathematical form. © 2011 American Chemical Society. |
Autocatalysis: At the root of self-replication Article de journal R Plasson; A Brandenburg; L Jullien; H Bersini Artificial Life, 17 (3), p. 219–236, 2011. @article{Plasson:2011, title = {Autocatalysis: At the root of self-replication}, author = {R Plasson and A Brandenburg and L Jullien and H Bersini}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960494353&doi=10.1162%2fartl_a_00033&partnerID=40&md5=42a275d57ed71a4825c0fab5de24dd7a}, doi = {10.1162/artl_a_00033}, year = {2011}, date = {2011-01-01}, journal = {Artificial Life}, volume = {17}, number = {3}, pages = {219--236}, abstract = {Autocatalysis is a fundamental concept, used in a wide range of domains. From its most general definition, that is, a process in which a chemical compound is able to catalyze its own formation, several different systems can be described. We detail the different categories of autocatalyses, and compare them on the basis of their mechanistic, kinetic, and dynamic properties. It is shown how autocatalytic patterns can be generated by different systems of chemical reactions. The notion of autocatalysis covers a large variety of mechanistic realizations with very similar behaviors; it is proposed that its key signature is its kinetic pattern expressed in a mathematical form. This notion, while describing dynamic behaviors at the most fundamental level, is at the basis for developing higher-level concepts towards life: autocatalytic sets and autopoietic systems. © 2011 Massachusetts Institute of Technology.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Autocatalysis is a fundamental concept, used in a wide range of domains. From its most general definition, that is, a process in which a chemical compound is able to catalyze its own formation, several different systems can be described. We detail the different categories of autocatalyses, and compare them on the basis of their mechanistic, kinetic, and dynamic properties. It is shown how autocatalytic patterns can be generated by different systems of chemical reactions. The notion of autocatalysis covers a large variety of mechanistic realizations with very similar behaviors; it is proposed that its key signature is its kinetic pattern expressed in a mathematical form. This notion, while describing dynamic behaviors at the most fundamental level, is at the basis for developing higher-level concepts towards life: autocatalytic sets and autopoietic systems. © 2011 Massachusetts Institute of Technology. |
Kinetic and thermodynamic characterisation by heating in a microfluidic cell Article de journal K Zrelli; T Barilero; H Berthoumieux; T Le Saux; C Gosse; A Lemarchand; L Jullien Sensor Letters, 9 (6), p. 2332–2335, 2011. @article{Zrelli:2011, title = {Kinetic and thermodynamic characterisation by heating in a microfluidic cell}, author = {K Zrelli and T Barilero and H Berthoumieux and T Le Saux and C Gosse and A Lemarchand and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862014294&doi=10.1166%2fsl.2011.1819&partnerID=40&md5=faecf5d436b7a9e626512b71f0f19249}, doi = {10.1166/sl.2011.1819}, year = {2011}, date = {2011-01-01}, journal = {Sensor Letters}, volume = {9}, number = {6}, pages = {2332--2335}, abstract = {We describe a technique that allows characterisation of both thermodynamic and kinetic parameters associated to DNA hybridization. This is achieved by means of a microdevice capable of modulating the interaction of the probe with the specific compound in the mixture. Copyright © 2011 American Scientific Publishers All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We describe a technique that allows characterisation of both thermodynamic and kinetic parameters associated to DNA hybridization. This is achieved by means of a microdevice capable of modulating the interaction of the probe with the specific compound in the mixture. Copyright © 2011 American Scientific Publishers All rights reserved. |
Photoinduced pH drops in water Article de journal M Emond; J Sun; J Grégoire; S Maurin; C Tribet; L Jullien Physical Chemistry Chemical Physics, 13 (14), p. 6493–6499, 2011. @article{Emond:2011, title = {Photoinduced pH drops in water}, author = {M Emond and J Sun and J Gr\'{e}goire and S Maurin and C Tribet and L Jullien}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952973660&doi=10.1039%2fc0cp02464c&partnerID=40&md5=34514ef4944c4bfa7ef5ebac9963af48}, doi = {10.1039/c0cp02464c}, year = {2011}, date = {2011-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {14}, pages = {6493--6499}, abstract = {A 2-hydroxyazobenzene platform has been evaluated to photorelease protons in aqueous solutions. Three different systems relying on molecular, supramolecular and polymeric strategies have been investigated in order to tune the water solubility and the thermodynamic and kinetic properties. This paper first reports on the syntheses and the physico chemical analyses for each system. Subsequently, we show that the three strategies are appropriate to reversibly photo-generate tunable pH drops in water up to one pH unit amplitude and at the 10-100 s timescale, upon transient illumination at 365 nm. © 2011 the Owner Societies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A 2-hydroxyazobenzene platform has been evaluated to photorelease protons in aqueous solutions. Three different systems relying on molecular, supramolecular and polymeric strategies have been investigated in order to tune the water solubility and the thermodynamic and kinetic properties. This paper first reports on the syntheses and the physico chemical analyses for each system. Subsequently, we show that the three strategies are appropriate to reversibly photo-generate tunable pH drops in water up to one pH unit amplitude and at the 10-100 s timescale, upon transient illumination at 365 nm. © 2011 the Owner Societies. |