Multi-color electron microscopy by element-guided identification of cells, organelles and molecules.

Cellular complexity is unraveled at nanometer resolution using electron microscopy (EM), but interpretation of macromolecular functionality is hampered by the difficulty in interpreting grey-scale images and the unidentified molecular content. We perform large-scale EM on mammalian tissue complemented with energy-dispersive X-ray analysis (EDX) to allow EM-data analysis based on elemental composition. Endogenous elements, labels (gold and cadmium-based nanoparticles) as well as stains are analyzed at ultrastructural resolution. This provides a wide palette of colors to paint the traditional grey-scale EM images for composition-based interpretation. Our proof-of-principle application of EM-EDX reveals that endocrine and exocrine vesicles exist in single cells in Islets of Langerhans. This highlights how elemental mapping reveals unbiased biomedical relevant information. Broad application of EM-EDX will further allow experimental analysis on large-scale tissue using endogenous elements, multiple stains, and multiple markers and thus brings nanometer-scale 'color-EM' as a promising tool to unravel molecular (de)regulation in biomedicine.

Improving the energy spread and brightness of thermal-field (Schottky) emitters with PHAST--PHoto Assisted Schottky Tip.

Using a relatively simple model of photoemission we derive an expression for the reduced on axis brightness of a thermal-photofield emitter. We then show that it is theoretically possible to reduce the energy spread of a Schottky (thermal field) emitter whilst increasing the reduced brightness. This can be achieved by the illumination of the tip with a high intensity laser light. We call the source PHAST-PHoto Assisted Schottky Tip. We find that due to the strong E-fields applied PHAST may operate at photon energies below the (Schottky reduced) work function. Thus removing the need for UV lasers, we will show that it is in fact preferable to work in the red, or in the green. The necessary laser intensities probably limit the application to pulsed operation.