> Composition of the team
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Structural characterization of biomolecules
C. Desfrançois, F. Lecomte, N. Nieuwjaer and B. Manil
In the last years, the BMS team has been involved in fruitful collaborations with other experimental groups, in order to extend our research activity to the study of model biomolecules through a combined laser-spectroscopy and mass-spectrometry approach. To that end, we perform IR spectroscopy of neutral isomer-selected or ionic mass-selected systems (nucleic acid bases, amino acids, peptides, drugs) and their non-covalent complexes in the gas-phase for which structural assignment is done through comparison with high-level quantum chemistry calculations. Recently, we performed an experiment with the group of G. Grégoire (ISMO-Orsay) to study the vibronic spectra of protonated hydroxypyridines (HPH), whose derivatives are endogenous or synthetic photosensitizers which could contribute to solar radiation damages. The study of their excited states could lead to a better understanding of their action mechanisms. We obtained the ultraviolet (UV) spectra of the protonated 2-, 3- and 4-hydroxypyridine. They display well-resolved vibrational structures, with a clear influence of the position of the OH group. These results are interpreted with excited states calculations at the coupled cluster CC2 level.
We aims also to study liganded nano-clusters (see figure), after mass-selection in the gas phase, using IRMPD laser spectroscopy at CLIO facility (IR Free Elecron Laser in Orsay). The advantage of the mass-selection is to avoid all contribution from the solvent or from multiple cluster sizes and to simplify the comparison with quantum chemical calculations. The IR spectra (performed in a wide range of IR wavelengths: 3 to 100 µm) will hopefully give an unambiguous signature for the structural assignments. The goal is to get a better understanding of the nature of the metal-ligand interactions connected with some physical and chemical processes, which are involved in various biological applications (grafting, functionalization, phototherapy, radiosensitizers …) of nanoparticles.
Calculated structure of a liganded gold nanocluster (Au11(((PC6H4-CONH-CH3)3)7Cl3)
T.N. Le, J-C. Poully, F. Lecomte, N. Nieuwjaer, B. Manil, C. Desfrançois, F. Chirot, J. Lemoine, P. Dugourd, G. van der Rest, G. Grégoire,
Journal of the American Society for Mass Spectrometry, 24, 1937, (2013).