ABSTRACT
Biological structural adhesives may be defined as thermosetting resins that bond two rigid adherends to form a permanent load-bearing joint. Such polymeric resins must not only form strong bonds with the adherends but also must become an integral component of the structure and may influence the macroscopic properties of the resulting material (e.g., laminates). It is apparent that the properties of biopolymers conducive to good adhesion also improve the qualities of composite materials and varnishes. Although structural and chemical properties of adhesive biopolymers often differ in detail, there appears to be a family resemblance that, though not necessarily a result of evolutionary homology, may reflect common design pathways or optimized solutions to the problems faced. Protein bioadhesives often incorporate 3,4-dihydroxy phenylalanine and tyrosine residues into the sequence as cross-linking or surface bonding agents, and are (thus far) invariably arranged as extensive linear arrays of tandem motifs. Since the design of these protein polymer resins is undoubtedly constrained both by the tasks for which 108they evolved and by the genetic material available, it is striking that such a wide range of biological applications has resulted in what may be termed a “structural thematic consensus”.
