INFLUENCE OF PROTEIN ON POLYSILOXANE POLYMER FORMATION - EVIDENCE FORINDUCTION OF COMPLEMENTARY PROTEIN-POLYMER INTERACTIONS

Results presented in the companion paper suggested that the protein it self might be actively involved in the polymerization process while be ing entrapped in polysiloxane polymers. It was speculated that the org ano-functional side chains on the silanol monomers (or small oligomers ) tended to associate with complementary residues on the protein surfa ce during the polymerization process. This phenomenon might lead to co mplementary binding pockets for the protein on the polymer. To investi gate this possibility, polysiloxane polymers were prepared from 3-amin opropyltriethoxysilane and tetraethylorthosilicate (1:3) in the presen ce of two proteins: urease and BSA. The entrapped proteins were remove d by pronase digestion and washing and the resulting polymers evaluate d for their ability to again bind the two proteins. It was found that urease preferentially bound to the polymer made in the presence of ure ase, and BSA preferentially bound to the polymer made in the presence of BSA. The absolute preferential binding excess was greater (30%) for urease binding relative to that observed for BSA (3%). However, in bo th cases the same relative binding ratio of 1.5 or 50% excess was foun d. A similar study using the closely related hemoglobin and myoglobin proteins failed to show comparable excess binding in the presence of t he predetermined protein. In the latter case, it was demonstrated that the rebound proteins did not equilibrate with labeled solution protei ns, indicating a very tight association with the polymer surface possi bly masking any specificity which existed. However, it was possible to show that urea release of rebound hemoglobin from the polymer made in the presence of hemoglobin was less than for myoglobin bound to the s ame polymer and visa versa, again suggesting induced properties unique to the polymer prepared with the predetermined protein. To the extent that this notion of induced complementary order is correct, it may ha ve implications in the development of protein specific adsorbants and in our understanding of polymer surface adhesion and the molding of te mplate fine structure.