Abstract
It is a fundamental question in cell biology and biophysics whether sphingomyelin (SM)- and cholesterol (Chol)- driven nanodomains exist in living cells and in model membranes. Biophysical studies on model membranes revealed SM and Chol driven micrometer-sized liquid-ordered domains. Although the existence of such microdomains has not been proven for the plasma membrane, such lipid mixtures have been often used as a model system for ‘rafts’. On the other hand, recent super resolution and single molecule results indicate that the plasma membrane might organize into nanocompartments. However, due to the limited resolution of those techniques their unambiguous characterization is still missing. In this work, a novel combination of Förster resonance energy transfer and Monte Carlo simulations (MC-FRET) identifies directly 10 nm large nanodomains in liquid-disordered model membranes composed of lipid mixtures containing SM and Chol. Combining MC-FRET with solid-state wide-line and high resolution magic angle spinning NMR as well as with fluorescence correlation spectroscopy we demonstrate that these nanodomains containing hundreds of lipid molecules are fluid and disordered. In terms of their size, fluidity, order and lifetime these nanodomains may represent a relevant model system for cellular membranes and are closely related to nanocompartments suggested to exist in cellular membranes.
Highlights
We discovered and characterized nanodomains in binary DOPC/SM and ternary DOPC/Chol/SM bilayers of compositions that should result in homogeneous bilayers according to published phase diagrams
In the ternary lipid mixtures containing Chol, nanodomains were revealed at DOPC/Chol/SM (70–65/25/5–10)
All lipid mixtures were made from stock solutions in chloroform
Summary
Alena Koukalová[1], Mariana Amaro 1, Gokcan Aydogan[1], Gerhard Gröbner[2], Philip T. Combining MC-FRET with solidstate wide-line and high resolution magic angle spinning NMR as well as with fluorescence correlation spectroscopy we demonstrate that these nanodomains containing hundreds of lipid molecules are fluid and disordered In terms of their size, fluidity, order and lifetime these nanodomains may represent a relevant model system for cellular membranes and are closely related to nanocompartments suggested to exist in cellular membranes. The postulation of such heterogeneities found support in experiments where detergent resistant membranes biochemically isolated from cells were shown to be enriched in SM and Chol[1, 2] This was supported by biophysical studies on model membranes (i.e. giant unilamellar vesicles; GUVs) composed of SM, Chol and phosphatidylcholine which revealed micrometer-sized liquid-ordered (Lo) domains.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have