CHAIN CONFORMATION OF DEACETYLATED BEIJERAN CALCIUM SALT

A well-defined X-ray fiber diffraction pattern was obtained from a str etched film of the calcium salt of a new uronic acid containing polysa ccharide designated as beijeran in the deacetylated form, poly[--> 3)- alpha-D-GalUA-(1 --> 3)-beta-L-Rham-(1 --> 3)-alpha-D-Glc-(1 --> ]. Th e oriented film showed no diffraction spots, indicating it to be amorp hous. However, when annealed at high temperature, the film exhibited h igh crystallinity. All the visible reflections could be indexed in ter ms of a monoclinic unit cell with the following dimensions: a = 1.297; b = 1.676; c (fiber axis)= 2.509 mn; and gamma = 106.50 degrees. The length of the fiber axis and the absence of meridional reflections at any odd layer line indicate that an extended two-fold helical conforma tion was made up of two trisaccharide residues.