报告主题：Effect of structure on digestion of proteins
主讲人：François Boué 教授（Laboratoire Léon Brillouin）
Although the biochemical processes of protein digestion are widely studied, the biophysical ones, like conformational changes, are more neglected, especially when resolving both time and space scales. Synchrotron radiation Small-Angle X-ray Scattering (SAXS) offers quick measurements at the resolution of tens of Å, with narrow beams. Here we present a method for efficiently monitoring the protein digestion canola proteins in a gel matrix, as a model solid-like plant protein food. Rapid scan of a capillary, allowed tracking digestion under diffusion of the enzymatic juice, for several tenth of hours. We distinguish compact, unfolded or aggregated states of proteins under different pH and enzymatic conditions. Data for compactness and size at different times and distances from the initial level of the digestive liquid fall on a master curve, evidencing the complex behavior of proteins, involving forth and back unfolding and re-compaction. This can give precious information for food and nutritional science.
At the scale of large aggregates, we mainly observe for both gels the decreasing of the size and/or number of these aggregates during digestion and the alteration of their interfaces, partly due to the loosening of the local protein network (protein unfolding and cutting).
These studies were completed by imaging experiments, allowing to explore micron scale, i.e. structure of the gels and sizes of protein aggregates (confocal and neutron imaging), and the in situ digestion processes of the gels (UV fluorescence microscopy).
After education for research and teaching (French Ecole Normale), François Boué got a full time research position (CNRS), while keeping a teaching, training and research evaluation activity. A large part of his career ran at LLB, a large neutron scattering facility at Saclay south of Paris, where he managed a group in charge of 5 beam lines, hosting a hundred of research groups per year. He thus worked in many different fields of physics and chemistry. Simultaneously, he developed personal research (255 publications). Using SANS, SAXS, rheology, microscopies, he studied, including the sample chemical synthesis:
- polymer solutions, melts, rubbers, gels, nanocomposites in particular under deformation, for which he tackled problems such as chain stretching, reptation, heterogeneities of deformation, entangled solutions under shear, relation between reinforcement and nanoparticles dispersion (e.g. in rubbers for tyres).
- polyelectrolytes solutions, he studied chain conformation (persistence length, pearlnecklace for hydrophobic chains) and interactions (counterions condensation), and electrostatic complexation.
He later on extended this work on biopolymers and their complexation with nanoparticles and proteins. He moved to Institut National de Recherche pour l’Agriculture et l’environnement (INRAe) for four years, where he applied these approaches to digestion of model systems such as starch, dairy gels, and plant protein gels, at different scales from the body one down to nanometers, his today’s talk.