Abstract
Spider silks are desirable biomaterials characterized by high tensile strength, elasticity, and biocompatibility. Spiders produce different types of silks for different uses, although dragline silks have been the predominant focus of previous studies. Spider wrapping silk, made of the aciniform protein (AcSp1), has high toughness because of its combination of high elasticity and tensile strength. AcSp1 in Argiope trifasciata contains a 200-aa sequence motif that is repeated at least 14 times. Here, we produced in E. coli recombinant proteins consisting of only one to four of the 200-aa AcSp1 repeats, designated W1 to W4. We observed that purified W2, W3 and W4 proteins could be induced to form silk-like fibers by shear forces in a physiological buffer. The fibers formed by W4 were ∼3.4 µm in diameter and up to 10 cm long. They showed an average tensile strength of 115 MPa, elasticity of 37%, and toughness of 34 J cm−3. The smaller W2 protein formed fewer fibers and required a higher protein concentration to form fibers, whereas the smallest W1 protein did not form silk-like fibers, indicating that a minimum of two of the 200-aa repeats was required for fiber formation. Microscopic examinations revealed structural features indicating an assembly of the proteins into spherical structures, fibrils, and silk-like fibers. CD and Raman spectral analysis of protein secondary structures suggested a transition from predominantly α-helical in solution to increasingly β-sheet in fibers.
Highlights
Spider silks are promising biomaterials with many potential uses in medicine, materials science and other fields, because of their exceptionally high tensile strength, elasticity, and toughness
Spider silk fibers have been described as being promising biomaterials for a biocompatible artificial nerve conduit [2] and for the enhancement of skin regeneration [3]. Before such potential uses can be fully realized, effective means of spider silk production and functional application are required, which may be achieved through better understanding of spider silk proteins and the mechanisms of silk fiber formation
Fibers Formed from Recombinant Proteins Derived from AcSp1
Summary
Spider silks are promising biomaterials with many potential uses in medicine, materials science and other fields, because of their exceptionally high tensile strength, elasticity, and toughness. Dragline silk can exhibit toughness surpassing even the strongest synthetic fibers, including nylon, Kevlar, and high-tensile steel [1] Spider silks, because they are made of protein, are biocompatible and biodegradable. Spider silk fibers have been described as being promising biomaterials for a biocompatible artificial nerve conduit [2] and for the enhancement of skin regeneration [3]. Before such potential uses can be fully realized, effective means of spider silk production and functional application are required, which may be achieved through better understanding of spider silk proteins and the mechanisms of silk fiber formation
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