Increased specificity of colloidal silver staining by means of chemical attenuation

A modification of the silver staining procedure of Howell and Black (1980) is reported which makes use of teleostean gelatin as protective colloid and renders a high signal-to-noise ratio. We demonstrate that this ratio can be further increased by subsequent attenuation with a chemical reducer consisting of a mixture of potassium ferricyanide (III) and sodium thiosulphate. It is shown that slight changes of the concentration of the reactive compounds of the chemical reducer make the protocol applicable to human, plant (Aliium cepa, Rhinanthus minor) as well as meiotic insect (Acheta domesticus) chromosome preparations. Due to its broad applicability, the method could find utilization in studies on chromatin and chromosome functions in many species.