Abstract
The exceptional strength and extensibility of spider dragline silk have been thought to be facilitated by two spidroins, major ampullate spidroin 1 (MaSp1) and major ampullate spidroin 2 (MaSp2), under the assumption that protein secondary structures are coupled with the expressed spidroins. We tested this assumption for the dragline silk of three co-existing Australian spiders, Argiope keyserlingi, Latrodectus hasselti and Nephila plumipes. We found that silk amino acid compositions did not differ among spiders collected in May. We extended these analyses temporally and found the amino acid compositions of A. keyserlingi silks to differ when collected in May compared to November, while those of L. hasselti did not. To ascertain whether their secondary structures were decoupled from spidroin expression, we performed solid-state nuclear magnetic resonance spectroscopy (NMR) analysis on the silks of all spiders collected in May. We found the distribution of alanine toward β-sheet and 3,10helix/random coil conformations differed between species, as did their relative crystallinities, with A. keyserlingi having the greatest 3,10helix/random coil composition and N. plumipes the greatest crystallinity. The protein secondary structures correlated with the mechanical properties for each of the silks better than the amino acid compositions. Our findings suggested that a differential distribution of alanine during spinning could decouple secondary structures from spidroin expression ensuring that silks of desirable mechanical properties are consistently produced. Alternative explanations include the possibility that other spidroins were incorporated into some silks.
Highlights
The exceptional strength, extensibility and toughness of spider dragline, or major ampullate (MA), silk make it a desirable material for multiple industrial uses [1]
We found that the dragline silk amino acid compositions did not differ between the three species examined in May (MANOVA: Wilk’s λ = 0.161; F = 2.387; df = 10, 16; p = 0.058) (Table 1a)
The amino acid composition of A. keyserlingi dragline silk collected in May differed from that collected in November (MANOVA: Wilk’s λ = 0.048; F = 15.99; df = 5,4; p = 0.009), with the silks from spiders collected in November having a greater percentage alanine (p = 0.038) and proline (p < 0.001) than those collected in May
Summary
The exceptional strength, extensibility and toughness of spider dragline, or major ampullate (MA), silk make it a desirable material for multiple industrial uses [1]. A possible reason why the mechanical properties of dragline silk sometimes vary independent of spidroin expression is that the silk spinning processes decouple spidroin expression from secondary structure formation through an “on-the-fly” redistribution of alanine or glycine residues [46] This explanation remains to be empirically tested in different spiders using multiple techniques. We determined the spidroin expression, protein secondary structure and mechanical properties of the dragline silks of three co-existing species of spider from Sydney, Australia: Argiope keyserlingi, Nephila plumipes and Latrodectus hasselti using high performance liquid chromatography (HPLC), ssNMR and tensile testing techniques. All of their silks were collected in May 2014. We regarded any similarities in amino acid composition between species at any particular time of year or any differences within species at different times of year as indicating that ecological circumstances or demographic factors influenced spidroin expressions
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
