Phase separation and mechanical properties of an elastomeric biomaterial from spider wrapping silk and elastin block copolymers

Abstract

Elastin and silk spidroins are fibrous, structural proteins with elastomeric properties of extension and recoil. While elastin is highly extensible and has excellent recovery of elastic energy, silks are particularly strong and tough. This study describes the biophysical characterization of recombinant polypeptides designed by combining spider wrapping silk and elastin-like sequences as a strategy to rationally increase the strength of elastin-based materials while maintaining extensibility. We demonstrate a thermo-responsive phase separation and spontaneous colloid-like droplet formation from silk-elastin block copolymers, and from a 34 residue disordered region of Argiope trifasciata wrapping silk alone, and measure a comprehensive suite of tensile mechanical properties from cross-linked materials. Silk-elastin materials exhibited significantly increased strength, toughness, and stiffness compared to an elastin-only material, while retaining high failure strains and low energy loss upon recoil. These data demonstrate the mechanical tunability of protein polymer biomaterials through modular, chimeric recombination, and provide structural insights into mechanical design. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 693-703, 2016.

Beta turn propensity and a model polymer scaling exponent identify intrinsically disordered phase-separating proteins

“…The silk-wrapping protein, spidroin-1 ( Fig. 4 , G and H ), consists of a repeat folded region ( 82 ) with intervening, short IDRs that mediate phase separation via hydrophobic amino acids ( 83 ). The N terminus (residues 1–236) of DDX4 ( Fig.…”

Self-Assembly of Silk-like Protein into Nanoscale Bicontinuous Networks under Phase-Separation Conditions

“…mussel feet adhesive proteins, [16][17][18] squid beak protein components, or nacre protein biomineralization. 19 In polymer technology, the condensate phase is referred to as coacervate phase and it is a key assembly phase to, for example, the superior mechanical characteristics, [20][21][22] superhydrophobic, 23 or responsive materials 24 rising from hydrated polyelectrolyte assemblies, in particular layer-by-layer polyelectrolyte multilayers (PEMs) and polyelectrolyte complexes (PECs). Hydrated polyelectrolyte assemblies rising from LLPS have a wide set of technological applications in e.g.…”

Biomechanical Design of Elastic Protein Biomaterials: A Balance of Protein Structure and Conformational Disorder

“…Tensile strength was extracted from raw stress-strain data from studies referenced above. Modulus and strength were converted to MPa as described previously. , Resilience was measured using the fourth cycle of loading/unloading to 50% strain. Stress relaxation was measured after 500 s at 50% strain.…”

“…Fibers have been produced from recombinant wrapping silk polypeptides corresponding to between one and four tandem ensemble repeats. , Increasing the polypeptide length proportionately increases strength, stiffness, and toughness of fibers (Table ). Adding just the last 34 disordered residues of the wrapping silk ensemble repeat to an ELP increases the strength and toughness of the material, potentially on the basis of increased β-turn formation and stability within the silk domain …”