LASER SPECTROSCOPY OF MOLECULAR ASSEMBLIES WITH BIOMOLECULES

Work package:
Biological systems are gouverned by non-covalent molecular interactions (Hydrogen bonding (HB), Van der Waals bonding) that can be probed by gas phase laser spectroscopy techniques experiments, in combination of theoretical molecular modeling methods at the quantum and classical levels. These interactions have physical origins: electrostatics, induction, dispersion, and repulsion. Characterizing the interactions between peptides and carbohydrates (CBH) is of prime importance in biology, as CBH play a major role in molecular recognition processes and peptides are models for sugar receptor proteins (lectins). Conformational effects, of importance in such flexible molecules, also have a strong influence on the HB donating and accepting capacity of a specific CBH OH. The internship will consist in the study of the structural preferences of fluorinated CBH and their complexes with few water molecules. These studies will reveal the individual contributions of key carbohydrate characteristics such as the anomeric effect, relative stereochemistry, and of important features of glycomimetic design, such as deoxygenation and deoxyfluorination, on their conformational and HB properties. Vibrational spectroscopy is a tool of choice for probing the non-covalent molecular interactions that are at the center of interactions between biological molecules. In our laboratory, we have developed an expertise in the infrared (IR) spectroscopy of the elongation modes of the O-H, NH and O-D modes, in the gas phase. These modes, which absorb in the infrared region of 2.5 to 4 um, are very important since they are at the center of the non-covalent interactions to interrogate. The intern will be introduced to several experimental techniques used in many fields of experimental physical chemistry: lasers and optics, IR and UV spectroscopy, laser desorption of biomolecules, supersonic expansions to cool down the molecules and stabilize the complexes, mass spectrometry detection, vacuum techniques. In parallel, quantum chemistry methods will be employed to explore the conformational landscapes of the systems under study and the simulation of the spectra to interpret the data. The internship can be adapted to student with background in physics and chemistry. The internship could be followed by a PhD project, depending on funding opportunities.