Scanning Electron Microscopy


Complementary freeze-fracture replicas have been prepared of ultra-rapidly cooled specimens in the absence of chemical pretreatments. The grid-sized replicas were stabilized by open mesh gold grids during the cleaning process and, after cleaning, were supported on thin Formvar films. The complementary replicas were valuable for describing artifacts, for interpreting the nature of fracture planes and for evaluating the resolution of replicas. Complementary images demonstrated that heat emitted from resistance electrodes or electron guns during evaporation can seriously distort fracture surfaces even for samples held at -150°C. Complementary images of crystalline membranous cytochrome c oxidase helped establish that fracturing reveals hydrophilic surfaces. Complementary images of proteoliposomes showed that intramembrane particles produced by an integral 140kdal protein generated complementary pits whereas intramembrane particles produced by a smaller integral 46.5kdal protein did not. The inability to observe the small pits is in part a limitation of the resolution of conventionally prepared platinum/carbon replicas.

Included in

Biology Commons