Investigation of structural aspects and classification of plant sulfated polysaccharides on the basis of the optical properties of their complexes with metachromatic dyes

Optical properties of complexes of plant sulfated polysaccharides with basic dyes have been examined. Spectral shifts in the dye have been used as the basis for quantitative analysis of anionic sites in these compounds. The κ‐ and λ‐carrageenans have been shown to give characteristically different titration curves. Other, similar, plant extractives have been shown to fall into one or the other of these two classes. Cotton effects in the region of the absorption spectrum of the dye have been discovered, indicating the presence of long range order and asymmetry in the λ‐C2 carrageenan. The relation of the optical effects to each other and to the structure of the polymer is discussed briefly in terms of recent developments in the theory of metachromasy.