Films That Wet Without Glow Discharge

Abstract

Mass measurements with the Scanning Transmission Electron Microscope (STEM) provide a direct link between biochemistry and the information in the dark field STEM image of an unstained biological specimen. Total mass of a complex mass of individual components, mass per unit length, mass per unit area, or change in mass distribution following biochemical treatment, are easily determined. Accuracy and preparation requirements have been described elsewhere. In the past year, we have made significant progress in specimen preparation, developing a “wet film” technique which eliminates the need for glow discharge treatment of grids. The method is similar to the Valentine technique but uses minute quantities of specimen. A thin carbon film is evaporated under UHV conditions onto freshly cleaved rock salt. The thin carbon is floated off the rock salt onto distilled water and a titanium grid with a thick, holey carbon film laid on top of it. After a few minutes, the grid is picked up from above by grasping its edge with a tweezer and turned over so that the adhering drop of water is facing upward.