Physical Chemistry

Cryo-transmission electron microscopy (cryo-TEM)

Amphiphilic molecules, such as lipids, surfactants and copolymers, may via self-assembly form a variety of complex structures in dilute aqueous solution. These delicate and dynamic structures are often very sensitive to changes in temperature, concentration, and ionic strength. Consequently fixation, drying, and staining protocols of conventional electron microscopy may induce serious structural artefacts. Cryo-transmission electron microscopy (cryo-TEM) has evolved as an excellent tool for the investigation of these labile structures.

Aggregate structure in monoolein / oleic acid dispersion.

Cryo-TEM is ideally suited for visualization of structures in the size range of 5-500 nm and during the last 15 years we have successfully employed the technique for structural investigations of systems containing micelles, liposomes, and various related lipid/surfactant aggregates.  In our experience the cryo-TEM method offers unique possibilities to retrieve detailed information on the aggregate level and constitutes a valuable complement to more indirect methods, such as light scattering, NMR, SAXS, and photophysical techniques.

Fibril-like aggregates formed upon incubation of Amyloid ß-peptide with the polyunsaturated fatty acid docosahexaenoic acid (DHA)

The equipment at our microscopy unit includes two transmission electron microscopes (Zeiss EM 902A and Zeiss LIBRA-120), environmental chambers for sample preparation, as well as equipment for preparation of freeze fractured specimens.

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