NUCLEAR MICROSCOPY OF BIOLOGICAL SPECIMENS

Recent developments in technology have enabled the scanning proton microprobe to scan at submicron spatial resolution on a routine basis. The use of the powerful combination of techniques PIXE (proton induced X-ray emission), nuclear (or Rutherford) backscattering (RBS), and secondary electron detection operating at this resolution will open up new areas in many scientific disciplines. This paper describes some of the work carried out in the biological sciences over the last year, using the Oxford SPM facility. Collaborations with biological scientists have drawn attention to the wealth of information that can be derived when these techniques are applied to micro-organisms, cells and plant tissue. Briefly described here are investigations into the uptake of heavy metals by the alga Pandorina morum, the structure of the diatom Stephanopyxis turris, the presence of various types of crystal structures within the cells of Spirogyra, the heavy metal uptake of a mycorrhizal fungus present in the bracken (Pteridium aquilinum) root, the role of sphagnum moss in the absorption of inorganic elements, the measurement of heavy metals in environmentally-adapted cells of the yeast Saccharomyces cerevisiae, and the elemental distribution in the growing tip of a spore from the plant Equisetum arvense, with special emphasis placed on the visual interpretation of the elemental and secondary-electron maps provided by the nuclear microscopical techniques.