Calorimetric and Structural Investigation of the Interaction between Bovine Serum Albumin and High Molecular Weight Dextran in Water

This work studies specific interactions between a small globular protein and a highly flexible, branched polysaccharide using differential scanning calorimetry (DSC), circular dichroism (CD), fluorescence, and turbidimetry measurements. It uses the system water/bovine serum albumin (BSA)/dextran (D 2000) as a model. Dextran molecules are able to form interpolymeric complexes with BSA in water at both low and high temperatures if the polysaccharide is in excess and if the protein exists in its associated state. It leads to a partial destabilization of the secondary and tertiary structures of the protein and an additional exposure of the hydrophobic tryptophan residues to the surface of globule. If the total concentration of biopolymers in the mixture is high enough, the stability of the protein molecules with respect to unfolding and thermoaggregation is significantly decreased as a result of an increase in the protein hydrophobicity.