Silken toolkits: biomechanics of silk fibers spun by the orb web spiderArgiope argentata(Fabricius 1775)

Abstract

SUMMARY Orb-weaving spiders spin five fibrous silks from differentiated glands that contain unique sets of proteins. Despite diverse ecological functions, the mechanical properties of most of these silks are not well characterized. Here,we quantify the mechanical performance of this toolkit of silks for the silver garden spider Argiope argentata. Four silks exhibit viscoelastic behaviour typical of polymers, but differ statistically from each other by up to 250% in performance, giving each silk a distinctive suite of material properties. Major ampullate silk is 50% stronger than other fibers, but also less extensible. Aciniform silk is almost twice as tough as other silks because of high strength and extensibility. Capture spiral silk, coated with aqueous glue, is an order of magnitude stretchier than other silks. Dynamic mechanical properties are qualitatively similar, but quantitatively vary by up to 300% among silks. Storage moduli are initially nearly constant and increase after fiber yield, whereas loss tangents reach maxima of 0.1–0.2 at the yield. The remarkable mechanical diversity of Argiope argentata silks probably results in part from the different molecular structures of fibers and can be related to the specific ecological role of each silk. Our study indicates substantial potential to customize the mechanics of bioengineered silks.

Structure of silk by raman spectromicroscopy: From the spinning glands to the fibers

“…This observation may contribute to the difference in the mechanical properties of the Mi silk, especially its higher extensibility, as compared with the Ma silk. 51 Apart from some residual native conformational elements, the Cyl silk has a very similar molecular structure than the Ma silk, having both almost identical b-sheet contents and levels of orientation. Thus, the differences found at a molecular level by Raman spectroscopy appear too small to explain the lower strength at rupture of the Cyl silk.…”

“…Thus, the differences found at a molecular level by Raman spectroscopy appear too small to explain the lower strength at rupture of the Cyl silk. 51 Specific micro-or macrostructural organizations may be part of the explanation and should require additional investigation using complementary characterization techniques.…”

“…57 The presence of a-helices in Ac silk and the moderate degree of molecular alignment seem to have a strong impact on the fiber's mechanical properties, particularly on its high toughness which results from a high extensibility and a reasonable tensile strength. 51 As a matter of fact, the deformation and extension of a-helices and unoriented chain FIGURE 5 Polarized spectra of the aciniform silk fiber of N. clavipes harvested from the net spun by a spider around its prey. The spectra presented are the average of 14 experimental spectra.…”

Evidence for antimicrobial activity associated with common house spider silk

“…Silks vary in their mechanical properties such as in the degree of extensibility and maximum strength [1][2]. The range of physical properties observed likely reflects differences amongst silk types in the relative proportions and combinations of particular amino acids such as alanine, glycine and proline [3]. …”

The role of terminal domains during storage and assembly of spider silk proteins

“…with different mechanical properties (for more details see Refs. [11][12][13][14] and other chapters of this special issue). The underlying proteins, also called spidroins, are named after the glands in which they are produced, e.g., major ampullate spidroin (MaSp), flagelliform spidroin (FlagSp), or aciniform spidroin (AcSp).…”