ELECTROPHORETIC MOBILITY OF WORMLIKE CHAINS .1. EXPERIMENT - HYALURONATE AND CHONDROITIN 4-SULFATE

As measured by the free-zone technique of Hjerten, the reduced electrophoretic mobility u' of tryptophan-labeled polymers decreased with increasing ionic strength I in Tris acetate buffers (pH ca. 8.2). For hyaluronate values of u' were proportional to the slope DELTA-pK/DELTA-alpha of plots of apparent pK against degree of ionization-alpha (COOH groups) from potentiometric titration. The proportionality constant was about 50% larger than that predicted by the uniformly charged cylinder model having the radius (1 nm) required to fit potentiometric titration data. Labeling with tryptophan did not significantly affect the mobility. Hyaluronate polyions containing a small number (no more than 140) of disaccharide subunits gave values of u' 10-20% lower than a sample having several thousand such subunits. In buffers of constant ionic strength and varying pH u' increased with alpha for these polyions in satisfactory agreement with theoretical predictions of the wormlike cylinder model.