Crystallinity of Calcium Chondroitin Sulphate

Abstract

WELL-DEFINED macroscopic shapes containing symmetry elements are generally regarded as a sign of crystalline arrangement of molecules. Recently, Kargin¹ demonstrated that polymer molecules might have a regular geometrical aggregate as viewed in the electron microscope without being crystalline so far as X-ray diffraction measurement is concerned and vice versa. In our work with calcium chondroitin sulphate A we encountered apparently a similar phenomenon. Einbinder and Schubert² reported that calcium chondroitin sulphate (their so-called mid and tail fraction) showed crystalline shapes under the microscope when precipitated with ethanol from aqueous solution. These same fractions, however, proved to be amorphous in our X-ray diffraction experiments. Further investigation also revealed that the ‘head’ fraction of calcium chondroitin sulphate which Einbinder and Schubert² reported as amorphous under the microscope was highly crystalline in X-ray diffraction studies. Detailed analysis of these results will be reported elsewhere.