X-ray diffraction shows that chondroitin 6-sulfate, and some further rulfated derivatives, can occur in two ordered structures in stretched films. Both structures contain single helices with similar projected disaccharide lengths (9.6 and 9.8 angstroms) but with very different turn angles between successive disaccharides (120 and 45 degrees). In contrast, coaxial double helices of hyaluronates and t-carrageenates have shorter projected disaccharide lengths (8.5 and 8.9 angstroms).

Carrageenan↗

PubMed1973

Hyaluronic acid: a novel, double helical molecule.

Films prepared from a deformable gel (or putty) of hyaluronic acid show high crystallinity and orientation in their x-ray diffraction patterns. We have derived a probable structure for the molecules in these films. This is a double helix in which two identical, left-handed strands are antiparallel to one another. Each strand has four disaccharide residues per pitch length. Although the putty is prepared at pH 2.5, at which dilute solutions of hyaluronic have exaggerated rheological properties, the double helical form can also exist at physiological pH and therefore may be a biologically important form.

Circular Dichroism↗

PubMedDate not supplied

A structural analysis of human renin.

A three-dimensional model of human renin has been used to define amino acid residues involved in interaction with substrate. The structure revealed proteolytic cleavage sites on the surface of the molecule that may help explain numerous experimental observations concerning prorenin and its activation and forms of renin differing in size.

Binding Sites↗