Lipid membrane dynamics and micromechanics are vital for many cellular processes including mediating protein activity, signalling and apoptosis. Pressure can play a key role in the study of these fundamental membrane properties and the biology they support.
Pressure is directly relevant to deep sea habitats but can also be used to induce a wide range of membrane structural changes1,2 (increasing pressure is qualitatively similar to reducing temperature). Critically, pressure can be changed extremely quickly (in around 5 ms) allowing fast structural responses to be probed effectively. In contrast, temperature jumps may take several seconds to stabilise.
We have recently employed high-pressure microscopy and pressure-jump small angle X-ray diffraction (SAXS) to probe bilayer restructuring and lateral phase separation in phosphatidycholine and sphingomyelin containing model membranes: Using fluorescence microscopy, we have imaged the formation and evolution of microdomains in giant unilameller vesicles (GUVs) triggered by rapid application of pressures up to 100 MPa. In tandem, synchrotron SAXS has shown that pressure causes significant changes in the overall structure of these membranes1 and mismatch in bilayer height between ordered and disordered membrane domains. These experiments may offer a vital insight into the parameters that control membrane microdomain formation and structure. Additionally, we have made the first measurements of lipid membrane bending rigidity under pressure using high speed video microscopy to image thermal fluctuations in GUV model membranes.
These exciting experiments have been facilitated by our recent development of complementary high pressure SAXS and microscopy platforms tailored for experiments on soft-matter and biological systems.3