Electron microscope specimen preparation of rat liver chromatin by a modified Miller spreading technique

We describe a modification of the spreading method of Miller and Bakken [17]. Prior to mounting the samples, the carbon supports used for electron microscopy are coated with Alcian blue. By this method the chromatin fibres stick firmly to the supporting film such that the shape of the fibres is independent of the washing and drying procedures used during specimen preparation. Using this technique we show an ionic strength-dependent condensation of rat liver chromatin protruding from lysed nuclei which is fully compatible with that reported previously [34] for soluble chromatin.