Probing local lipid dynamics at the picosecond timescale with the Bicout model
Résumé
Lipid membranes are at the basis of cell organization. Understanding their functionality, in the light of their structure and dynamics is then crucial. Using quasi-elastic neutron scattering (QENS), it is possi- ble to access picosecond timescale dynamics. However, since years, only few models addressed the question of local lipid dynamics, whereas the increase of the neutron flux and data quality called for novel general models. Based on a timescale separation approach from Wanderlingh et al (2014), the Bicout model re-introduces the main local motions presented in the 80s by Pfeiffer et al, but writes them all in a unique framework that requires few hypotheses. Among others are described motions of the whole lipid, like its rotation, diffusion within the membrane, or in-out-of-the- plane dynamics. In addition, it makes a distinction between the head and the tail dynamics. Here, we would like to present a quantitative and complete study of local lipid dynamics on standard DMPC mem- branes. We probed the effects of known features such as the main phase transition, membrane geometry, or direction of motions, and proved the application of this new model.