Understanding functions of biological membranes requires detailed knowledge of their structural and dynamics properties. Over the last decade the questions about the lateral organization and dynamics of biomembranes have received an increasing attention due to the introduction of the lipid-raft hypothesis. This hypothesis postulates the existence of detergent-resistant domains, which are also known as lipid rafts, with an enhanced concentration of cholesterol, sphingolipids and certain types of proteins. This work demonstrates the feasibility of non-invasive studies of diffusion on a sub-micrometer length scale in lipid membranes using pulsed field gradient (PFG) NMR with ultra-high (up to 35 T/m) gradient strength. Application of such gradients allows using sufficiently small diffusion times. As a result, monitoring anomalous or restricted diffusion in lipid membranes on the length scale in the range of 100 nm becomes possible. An ability to study diffusion in lipid membranes on this length scale is very important because it is comparable with the size of biologically-relevant domains (i.e. rafts). Application of PFG NMR with high gradients for studies of diffusion in lipid membranes presents an attractive alternative to well-established optical techniques such as fluorescence correlation spectroscopy, fluorescence recovery after photobleaching and single particle tracking using optical or fluorescence microscopy. In comparison to the latter techniques, PFG NMR does not require any perturbing labelling of diffusing species.

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