“…The exceptional performance is thanks to its distinctive protein structure, especially the repetitive domain [17], which usually has long repetitive units, i.e., mostly longer than 200 amino acids with motifs like (A)2, (S)2-5 [9] and high Gly, Ala, and Ser contents [7,14], while lacking short repetitive motifs, such as polyGA, GGX, GPGGX, and polyA [18]. In the previous attempts to synthesize new, high performance and sustainable recombinant spidroin materials, researchers produced many recombinant spidroins, including multiple repetitive motifs [19,20] fused with or without nonrepetitive regions [21][22][23][24][25][26][27][28]. However, the yield of these spidroins were usually too low to meet the needs of large scale application, and only rarely could they reach a level of solubility that was comparable to the storage concentration of natural spidroin in the spider gland, most likely resulting in inferior mechanical properties [3].…”