I am interested in the photochemistry of fluorescent and photoactive molecules and biomolecules and its applications in quantitative biology.
Photochemist and spectroscopist by training, I am interested in the mechanisms and dynamics of light-induced reactions in different classes of photoactive proteins: fluorescent proteins of the GFP family, cryptochromes and DNA photolyases, the photoactive yellow protein (PYP). These reactions involve sequences of elementary steps (cis/trans isomerizations, electron or proton transfers, etc.) which can be very fast (femto-picosecond scale) and which I access through time-resolved spectroscopy techniques.
Beyond their fundamental interest, some of these photoactive proteins are used as fluorescent probes in advanced imaging or as photo-actuators in optogenetics. Better understanding their properties can make it possible to design more efficient variants or to exploit them for new applications. I thus contributed to the development of a cyan variant of GFP that has low pH sensitivity. More recently, I participated in the demonstration of a new multiplexed fluorescence imaging technique that exploits the kinetics of the elementary photo-switching steps of fluorescent proteins as discrimination parameters. Finally, I invented a new optical method to slow down the photobleaching of fluorescent proteins and reduce the associated phototoxicity.
“Method for enhancing the photoresistance of a fluorescent species and fluorescence microscopy system suitable for implementing said method”, K. Brettel, A. Espagne, L. Jullien, T. Le Saux, L. Ludvikova, P. Müller, L. Robert, PSL, CNRS, Sorbonne Univ., Univ. Paris-Saclay, INRAE, CEA & AgroParisTech, Patent application No.: EP21305834 (2021)
“Method and apparatus for detecting a photochemically active chemical species in a sample”, L. Jullien, R. Chouket, A. Espagne, A. Lemarchand, T. Le Saux, A. Pellissier-Tanon, CNRS, ENS & Sorbonne Université, Patent application No. : 19306120.7 (2019), International Pub. No.: WO 2021/052668 A1 (2021)
“Method for generating cyan fluorescent proteins which have a reduced pH sensitivity”, H. Pasquier, F. Mérola, M. Erard, A. Espagne, A. Fredj, CNRS & Université Paris-Sud, Patent Pub. No.: FR 1155227 (2011), International Extension Pub. No.: WO 2012172095 A1 (2012)
“Photoinduced chromophore hydration in the fluorescent protein Dreiklang is triggered by ultrafast excited-state proton transfer coupled to a low-frequency vibration”, F. Lacombat, P. Plaza, M.-A. Plamont, A. Espagne, J. Phys. Chem. Lett. 2017, 8, 1489-1495
“Real-time monitoring of chromophore isomerization and deprotonation during the photoactivation of the fluorescent protein Dronpa”, D. Yadav, F. Lacombat, N. Dozova, F. Rappaport, P. Plaza, A. Espagne, J. Phys. Chem. B 2015, 119, 2404-2414
“Ultrafast photoreduction dynamics of a new class of CPD photolyases”, F. Lacombat, A. Espagne, N. Dozova, P. Plaza, P. Müller, H.-J. Emmercih, M. Saft, L.-O. Essen, Photochem. Photobiol. Sci. 2021, 20, 733-746
“Ultrafast oxidation of a tyrosine by proton-coupled electron transfer promotes light activation of an animal-like cryptochrome”, F. Lacombat, A. Espagne, N. Dozova, P. Plaza, P. Müller, K. Brettel, S. Franz-Badur, L.-O. Essen, J. Am. Chem. Soc. 2019, 141, 13394-13409
“Investigations of the primary events in a bacterial photoreceptor for photomotility : the Photoactive Yellow Protein (PYP)”, P. Changenet-Barret, A. Espagne, P. Plaza, K.J. Hellingwerf, M.M. Martin, New J. Chem., 2005, 29, 527-534