ABSTRACT
Since the commencement of biological studies using the transmission electron microscope (the TEM) in the late 1940s and early 1950s, scientists have sought to develop procedures for the preparation and investigation of thinly spread specimens of biological particulates. The word particulates will be used throughout in an extremely broad manner, to mean almost any finely dispersed biological material that can exist in an aqueous suspension. That is, material suspended in distilled water, low and increasing concentrations of buffer, through to a high salt or organic solute (e.g. sucrose, glycerol, urea) solution. Where appropriate, individual biological particulates will be named and discussed within the context of specimen preparations and electron microscopical applications. Thus, I refer here primarily to biological material in the form of isolated subcellular membranes and components such as ribosomes and nuclear pore complexes, nucleosomes, protein molecules (soluble and fibrous) and their higher oligomeric assemblies or complexes, bacteria and their appendages, viruses, liposomal vesicles and reconstituted membrane systems.
