Secondary structure of glycosaminoglycans

It has been shown by X-ray diffraction and chiroptic spectroscopy that the glycosaminoglycans in connective tissue develop a helical structure; this induces the coordination of polycations and scleroproteins in their environment polycations and promotes or inhibites fibrillary aggregation. Analysis of the ORD and CD spectra of various glycosaminoglycans, as well as those of oversulphated and desulphated preparations allowed the following conclusions concerning the secondary structure. 1. For the helical structure of glycosaminoglycans a chain-length of 120 to 150 A and the presence of at least one sulphate group per two disaccharides are required. The helical structure is not influenced by binding to the protein skeleton, e.g. in proteoglycans. 2. Chiroptical properties of the glycosaminoglycan--either in themselves, or if their methylene blue complexes are studied--are determined by the degree of their sulphatation. 3. The degree of sulphatation determines the secondary structure of the molecule and thus also its biological properties. Fibrillogenesis in vitro and probably also in vivo are determined by the strength of the bond between collagen and glycosaminoglycans, in addition to the effect inducing the coordination. Structural analysis of the polysaccharides supports the coordinated fibrillary structure of GAG, as already assumed on the basis of polarization microscopic methods.