Use of the Low Voltage Transmission Electron Microscope with Biological Specimens: A Feasibility Study

Abstract Biological transmission electron microscopy (TEM) has evolved over the past 50 to 60 years in concert with the instrumentation available. As beam acceleration energies have increased to 100-200 keV, specimen preparation protocols have been modified and tailored to fit the capabilities and constraints of new TEMs. Higher voltage allows improved resolution, (Fig. 1) but as acceleration voltage increases, contrast decreases. Vacuum levels required for conventional TEM prevent specimen contamination which protects specimen details from being obscured, but lower contrast requires heavy metal post staining which may lead to specimen contamination. Specimen thickness can increase with higher voltage (up to lOOnm at 200keV) because penetration is much increased, however, the chance of specimen - electron interaction of the type that causes heat build-up and specimen damage increases rapidly with thickness. It seems that these limitations and others must be tolerated in order to enjoy the obvious advantages of TEM.