Chain length effects on electrostatic interactions between hyaluronan fragments and albumin

We have shown that hyaluronan (HA) and bovine serum albumin (BSA) are able to form electrostatic HA-BSA complexes at pH 4, whatever the length of the HA chain over the very large domain ranging from 103 to 106 g mol−1. Only the solubility of the HA-BSA complex depends on the HA chain length. The complex formation is optimum for HA chains of 50,000 g mol−1. The stoichiometry is equal to 36 HA disaccharides per BSA molecule whatever the length of the HA chain may be. This suggests that the structure of the complex greatly depends on the HA chain length: a BSA molecule surrounded by several HA fragments for small HA chain length, and an HA molecule imprisoning several BSA molecules for high HA chain length. The HA chain length can thus control accessibility of the protein surface and eventually enzyme activity.