Specific interaction of aniline blue with (1 → 3)-β- d-glucan

Abstract

Interaction between aniline blue and curdlan, a (1 → 3)-β- d-glucan, has been studied using absorption and fluorescence spectroscopy. The evidence suggests that a minor, weakly fluorescent component of commercial dyes forms a strongly fluorescent complex with curdlan, with an excitation maximum of 395 nm and an emission maximum of 495 nm. This component was partially purified by TLC on silica gel. Of many polysaccharides surveyed, a number showed weak interactions with the major component of aniline blue but only (1 → 3)-β- d-glucans such as pachyman, curdlan and laminaran induced fluorescence in the minor component. Fluorescence was less with laminaran than with curdlan and decreased with increasing alkali concentration suggesting conformational control of the dye-binding mechanism. As little as 5 μg/ml of curdlan induced easily detectable fluorescence increases in aniline blue, and this was used to demonstrate the presence of (1 → 3)-β- d-glucan in a fungal cell wall preparation. (1 → 3)-β- d-glucan in cereal grain sections was located as bright yellow-green fluorescent particles. In barley these stained particles, located in association with the sub-aleurone endosperm cell wall, showed a fluorescence excitation maximum at 395 nm and emission maximum of 495 nm.