Electron microscopy surface labelling

The gold clusters appear to be ideal models for bulk metals, metal surfaces, and colloidal particles. The gold clusters are used for labelling in electron microscopy studies of biological materials. 

Electron microscopy was used to provide more details on the nature of the coke deposits as well as their location. HRSEM reveals the HS-FER crystallites to be platelets, typically 250 nm in size, with a mean thickness of only 20 nm. For a spent HS-FER containing 9.1 %w of coke TEM photographs are displayed in Fig. 7. Careful inspection of the FER platelets reveals that they are bordered by a layer of amorphous material (labelled) which is probably coke. Also at the edge of the platelets there are layers of similar width (picture corresponds to a view down the (100) surfaces as determined by a selected area diffraction study). This suggests that all the external surfaces, both porous and non-porous, contain a layer of coke. To confirm that the amorphous layers indeed consist of carbonaceous material, PEELS spectra were collected which closely resemble that of the amorphous carbon film supporting the sample crystallites. With samples containing less carbon (below 7 %w), TEM does not reveal a coke layer at the surface of the crystallites, but rather reveals discrete coke clusters of 1.0-1.5 run. 

Information about fluidity and viscosity of bilayers of artificial and natural membranes has been obtained from electron spin resonance studies in which the mobility of the spin-labelled species along the surface plane of the membrane is determined (17). However, the monolayer of either lipid, protein, or lipid-protein systems at the air-water interface, makes an ideal model because several parameters can be measured simultaneously. Surface tension, surface pressure, surface potential, surface viscosity, surface fluorescence and microviscosities, surface radioactivity, and spectroscopy may be determined on the same film. Moreover, the films can be picked up on grids from which they may be observed by electron microscopy, studied further for composition, and analyzed for structure by x-ray diffraction and spectroscopy. This approach can provide a clear understanding of the function and morphology of the lipid and lipid-protein surfaces of experimental membranes. However, the first objective is to obtain molecular correlations of surface tension, pressure, potential, and viscosity. 

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