One of the toughest protein fibers: The N‐terminal domain (NTD) of spider dragline silk shows a pH‐dependent monomer–dimer equilibrium: The N‐terminal domain silk protein is stored as a stabilized monomer at neutral pH and high salt concentration, whereas during fiber assembly at a lower pH value this domain is able to form antiparallel dimers. Multivalent linking results in endless and highly stable fibers (see picture).

Fibrous proteins in nature fulfill a wide variety of functions in different structures ranging from cellular scaffolds to very resilient structures like tendons and even extra‐corporal fibers such as silks in spider webs or silkworm cocoons. Despite their different origins and sequence varieties many of these fibrous proteins share a common building principle: they consist of a large repetitive core domain flanked by relatively small non‐repetitive terminal domains. Amongst protein fibers, spider dragline silk shows prominent mechanical properties that exceed those of man‐made fibers like Kevlar. Spider silk fibers assemble in a spinning process allowing the transformation from an aqueous solution into a solid fiber within milliseconds. Here, we highlight the role of the non‐repetitive terminal domains of spider dragline silk proteins during storage in the gland and initiation of the fiber assembly process. © 2011 Wiley Periodicals, Inc. Biopolymers 97: 355–361, 2012.

Spider dragline silk exhibits an extraordinary toughness and is typically composed of two types of major ampullate spidroins (MaSp1 and MaSp2), differing in their proline content and hydrophobicity. In this paper, we recombinantly produced an unusual but naturally occurring short major ampullate spidroin (MaSp1s) as a fusion construct between established Latrodectus hesperus terminal domains and the novel Cyrtophora moluccensis core domain. The sequence of the recombinant spidroin was engineered to guarantee high yields upon recombinant production and was named eMaSp1s. Its solution structure as well as the mechanical properties of wet-spun eMaSp1s fibers were examined. Structural characterization using CD- and FTIR spectroscopy showed a predominantly α-helical solution structure and a high ß-sheet content within fibers. Surprisingly, eMaSp1s fibers show similar mechanical properties as wet-spun fibers of other engineered spider silk proteins, albeit eMaSp1s has a lower molecular weight and not the typical sequence repeats in its core domain. Therefore, the findings provide insights into the molecular interplay necessary to obtain the typical silk fiber mechanics.

No abstract

Recombinantly produced spider silk proteins have high potential for bioengineering and various biomedical applications because of their biocompatibility, biodegradability, and low immunogenicity. Here, the recently described small spider silk protein eMaSp1s is assembled into hydrogels, which can be 3D printed into scaffolds. Further, blending with a recombinantly produced MaSp2 derivative eADF4(C16) alters the mechanical properties of the resulting hydrogels. Different spider silk hydrogels also show a distinct recovery after a high shear stress deformation, exhibiting the tunability of their features for selected applications.