No abstract

A correlated human red blood cell membrane fluctuation dependent on d-glucose concentration was found with dual time resolved membrane fluctuation spectroscopy (D-TRMFS). This new technique is a modified version of the dual optical tweezers method that has been adapted to measure the mechanical properties of red blood cells (RBCs) at distant membrane points simultaneously, enabling correlation analysis. Mechanical parameters under different d-glucose concentrations were obtained from direct membrane flickering measurements, complemented with membrane fluidity measurements using Laurdan Generalized Polarization (GP) Microscopy. Our results show an increase in the fluctuation amplitude of the lipid bilayer, and a decline in tension value, bending modulus and fluidity as d-glucose concentration increases. Metabolic mechanisms are proposed as explanations for the results.

Nanoscale organization of the membranes of living cells plays crucial roles in numerous vital processes, including during the activation of T-cells and their formation of the immunological synapse. However, the exact nature and function of reorganization of lipids during this key initiating event remain unclear. To gain further insight into this process, we employed two techniques that probe complementary properties of the membranes at the molecular level: 1) super-resolution STED-FCS to reveal detailed picture of the diffusion of the lipids, with additional information on spatial heterogeneity provided by the scanning mode; and 2) spectral (super-resolution STED) imaging with environment-sensitive membrane probes, i.e. fluorescence microspectroscopy, to map differences in local molecular order within the lipid bilayer. Using these methods, we monitored diffusion properties of lipids and molecular order of the plasma membrane of (Jurkat) T-cells over space and time upon their activation, revealing marked differences in lipid diffusion and molecular order. For the most informative and robust description of the latter, we systematically analyzed the benefits and pitfalls of the established representations, i.e. phasors, generalized polarization, and lineshape description.