Planar Optical Nanoantennas Resolve Cholesterol-Dependent Nanoscale Heterogeneities in the Plasma Membrane of Living Cells

Optical nanoantennas can efficiently confine light into nanoscopic hotspots, enabling single-molecule detection sensitivity at biological relevant conditions. This innovative approach to breach the diffraction limit offers a versatile platform to investigate the dynamics of individual biomolecules in living cell membranes and their partitioning into cholesterol-dependent lipid nanodomains. Here, we present optical nanoantenna arrays with accessible surface hotspots to study the characteristic diffusion dynamics of phosphoethanolamine (PE) and sphingomyelin (SM) in the plasma membrane of living cells at the nanoscale. Fluorescence burst analysis and fluorescence correlation spectroscopy performed on nanoantennas of different gap sizes show that, unlike PE, SM is transiently trapped in cholesterol-enriched nanodomains of 10 nm diameter with short characteristic times around 100 μs. The removal of cholesterol led to the free diffusion of SM, consistent with the dispersion of nanodomains. Our results are consistent with the existence of highly transient and fluctuating nanoscale assemblies enriched by cholesterol and sphingolipids in living cell membranes, also known as lipid rafts. Quantitative data on sphingolipids partitioning into lipid rafts is crucial to understand the spatiotemporal heterogeneous organization of transient molecular complexes on the membrane of living cells at the nanoscale. The proposed technique is fully biocompatible and thus provides various opportunities for biophysics and live cell research to reveal details that remain hidden in confocal diffraction-limited measurements.Peer ReviewedPostprint (author's final draft

Ceres2d: a Numerical Prototype for Hc Potential Evaluation in Complex Area

Abstract-Ceres2D: A Numerical Prototype for HC Potential Evaluation in Complex Area-This paper deals with the Ceres prototype which is a basin model able to account for porous medium compaction, heat transfer, and hydrocarbon generation and migration. Furthermore, Ceres was designed to handle changing geometry through time as results of sedimentation, erosion, salt or mud creeping and block displacement along fault. The classical flow chart to perform a case study is composed of three main steps. The first step is the building of the present day section. This is generally done with data coming from the seismic interpretation, well data, field data and core data. The second step is the restoration of the section. Thus from the section at present day, the section is restored back in the past for each of the defined layer, and until the substratum is reached. The last step is the forward simulation. And, in order to solve the coupled equations that are generally used in basin models, we had to develop original numerical methods based on domain decomposition techniques. The Ceres prototype has now been used to study petroleum systems. It has been used to perform sensitivity studies on fault permeability in the Bolivian foothills and the Congo offshore. In the Gulf of Mexico, it allowed to study the impact of the salt tectonics on the hydrocarbon migration. More recently, the Ceres prototype has been tested, within the frame of the SubTrap consortium, in thrust areas such as the Canadian foothills and the Eastern Venezuelan foothills. For these last case studies, it has been beneficial that structural geologists were involved at all stages of the process