Fracturing of melamine-embedded cells and tissues: a new technique for studying cell membranes

A new technique is presented for studying cell membranes by scanning electron microscopy. It is based on the observation that cells and tissues, embedded in a water-compatible melamine resin, are as hard as glass and consequently can be fractured with ease. Fracture faces so exposed are either sputter-coated for studying the surface topography or re-embedded for thin-sectioning, or both. Scanning electron microscopy shows that the fracture faces of a variety of tissues reveal cell membranes and associated structures with remarkable detail. Re-embedding and thin-sectioning of fractured frog retina, mycoplasma and red blood cells indicate that membranes become divided into their exo- and protoplasmic leaflets during fracturing. In this respect, the results reported here must be compared with conventional freeze-fracture techniques.