Biotechnological Applications
Fuchsin acid has very many applications in biological microtechnique. Gray (1954) describes around two hundred of these.
It was discovered some years ago (MacConaill and Gurr, 1960; Gurr, 1962) that fuchsin acid forms complexes with light green SF (yellowish), conjugation taking place apparently between the amino groups of the first and the sulphonic groups of the second dye. These interactions were first discovered by Professor M .Conaill of University College, Cork, in 1958. About two years later one of these complexes (a blue dye which was given the name of Trifalgic acid; synonyms: MG blue, Falg blue) was synthesized in the solid state by the writer and found useful application in clinical pathology as a differential stain for proteins in electrophoresis (Bodman, 1960).
MacConailPs discovery was made during the course of an investigation into the chemical and physical nature of certain substances present in mammalian tissues and cells. Histological sections were stained first with the red anionic dye, fuchsin acid, then counterstained with the anionic dye, light green SF (yellowish). It was naturally expected that these dyes would impart a dichrome picture, in red and green. However, when he came to examine the sections under the microscope the picture seen was not in red and green but scarlet, various shades of violet and pure blue. The blue coloration excited his interest in particular. Although he considered at first that its presence was probably due to physical causes, subsequent tests carried out by him appeared to suggest that chemical interactions between the red and the green dye had taken place with the formation of at least three new dyes, one of which was blue. Cumulative and circumstantial evidence resulting from histological, physical and chemical experiments, since carried out over a period of years, leave no room for doubt that fuchsin acid and similar anionic dyes which have basic colligators (e.g. primary amino groups), can and do, under appropriate conditions, interact both in vitro and in tissues with other anionic dyes to form compounds which are polyanionic dyes.
