Interaction of neutral polysaccharides with human erythrocyte membrane: involvement of phospholipid bilayer

The erythrocyte aggregating activity of different neutral polysacharides depends on the polymer - membrane affinity and its molecular length. Extended proteolytic and neuraminidase treatments of red blood cell membrane did not reduce aggregation induced by polysaccharides. Fluo=rescent dextran studies showed that polymer adsorption on red blood cells was measurable only for a dextran mole=cular weight above 40,000 as for cell aggregation. Identical dextran adsorption behaviour was observed for all liposomes composed of various purified phospholipids, suggesting the involvement of the phospholipid bilayer in dextran-membrane interaction. All aggregations induced by neutral polysaccha=rides were inhibited by D-and L-tryptophan. Compounds very similar to tryptophan were less active or completely inactive inhibitors. Equilibrium dialysis, gel filtration and tryptophan fluorescence studies clearly showed that there was no com=plex formation between tryptophan and neutral polysaccha=rides. Therefore tryptophan does not result an haptenic inhi=bitor, but reduces the adsorption of polysaccharides on cell membrane.