The morphology of ultrathin cryosections

The morphology of ultrathin (ca. 100 nm thick) sections of glycerol-gelatine and yeast cell suspensions is studied in the frozen-hydrated and freeze-dried state by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). It is found that the quality of cryosections increases with decreasing ice crystal size in the specimen from which the sections are cut. However, linear deformations caused by sectioning cannot be avoided by varying the cutting temperature between 115 and 193 K or the cutting speed between 0.5 and 70 mm/s. A model idea describing the formation of periodic deformation lines in cryosections is proposed. Frozen-hydrated and freeze-dried cryosections are compared with respect to contrast, radiation damage and transfer requirements.