The influence of inorganic phosphate and citrate anions on the effect of glycosaminoglycans during collagen fibril-formation.

Some anions like phosphate, sulfate and citrate delay the fibril-formation. The interaction of phosphate and citrate with chondroitin sulfate-A (CSA) in binding to collagen was investigated in different environmental conditions. By changing the concentration of phosphate from 5 to 50 mM/l and that of CSA from 0.5 to 16 mM/l some kind of competition of the anions was discovered. When different equilibration, systems were used the affinity of CSA to collagen was found to be 10 times greater than that of phosphate at pH 7.2 and I=0.15. As phosphate anions bind to collagen at physiological concentration. phosphate anions may be supposed to influence the biological fibril-formation. On the other hand the CSA exchanges phosphate for collagen. Therefore, glycosamino-glycans (GAG) in connective tissue ground substance in fibrillogenesis may regulate the ion binding and through this the tendency of aggregation of the collagen molecules. The binding of citrate to collagen and its effect and possible role in fibril-formation was also evaluated.