The interplay between silk fibroin's structure and its adhesive properties.

Bombyx mori-derived silk fibroin (SF) is a well-characterized protein employed in numerous biomedical applications. Structurally, SF consists of a heavy chain (HC) and a light chain (LC), connected via a single disulfide bond. The HC sequence is organized into 12 crystalline domains interspersed with amorphous regions that can transition between random coil/alpha helix and beta-sheet configurations, giving silk its hallmark properties. SF has been reported to have adhesive properties and shows promise for development of medical adhesives; however, the mechanism of these interactions and the interplay between SF's structure and adhesion is not understood. In this context, the effects of physical parameters (i.e., concentration, temperature, pH, ionic strength) and protein structural changes on adhesion were investigated in this study. Our results suggest that amino acid side chains that have functionalities capable of coordinate (dative) bond or hydrogen bond formation (such as those of serine and tyrosine), might be important determinants in SF's adhesion to a given substrate. Additionally, the data suggest that fibroin amino acids involved in beta-sheet formation are also important in the protein's adhesion to substrates.