Ultrahigh-resolution scanning electron microscopy of biological materials.

The age of ultrahigh-resolution scanning electron microscopy (SEM) began in 1985, when the UHS-T1, with a resolution of 0.5 nm, was developed. Commercial instruments of the same or similar types followed rapidly. As instrumental resolution progressed, conventional specimen preparation methods became inadequate, and a number of new techniques were devised. In this paper, detailed procedures for these preparation methods such as the CC plate method and heavy metal impregnation are described, together with precautions recommended for achieving ultrahigh-resolution. Some applications of the method to biological specimens are also reported. Morphological identification of immunoglobulins prepared from human blood was attempted, and although the identification was not completely successful this technique may yet come to be of use in the clinical examination of allergic or infectious diseases. SEM images of complement, Clq, proteoglycan and the helical structure of double stranded DNA are shown, as also is the visualization of immunolabelled cell-surface receptors.