An electron microscopic and X-ray diffraction study of osmium localization in membrane structures after fixation with OsO4 introduced to native and freeze-dried specimens.

Ultrathin sections of the sciatic nerve myelin fibres of the frog Rana temporaria and liquid crystals of egg lecithin fixed in OsO4 have been treated by 4% or 30% acetic acid. Following uranyl acetate contrasting of thus treated sections the myelin structure and that of lecithin crystals completely recover. However, in the case of preliminary treatment of the sections with lead tetraacetate the subsequent contrasting fails to recover lamellar structures. The data obtained how that during the fixation of myelin sheath and lecithin crystals with osmium tetroxide, the whole amount of osmium locates in charged regions. The data on the X-ray analysis of myelin with OsO4 introduced before or after freeze-drying are in agreement with these results. It is assumed that the stabilization of fatty acid tails of the membrane lipid molecules is accomplished via formation of hydrogen links induced by glycol hydroxyl groups.