The helical structure of a β‐D‐1,3‐xylan

A structure determination is described of a naturally occurring non‐cellulosic polysaccharide which is found in the cell wall of some siphoneous green algae. The structure consists of three β‐1,3‐linked xylan polymer chains intertwining, each helical chain having exactly six residues in a pitch of 18.36 Å. The evidence is in favor of right‐handed helices with stoichiometrically bound water. There is a novel interchain hydrogen bond system at the center of the structure.