Molecular chain orientation in supercontracted and re-extended spider silk

111

117

Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Stretching of supercontracted fibers: a link between spinning and the variability of spider silk

Elices

Pérez‐Rigueiro

et al. 2005

111

117

“…Supercontraction is relatively well documented among orbweaving spiders such as Araneidae and Nephilidae (Grubb and Ji, 1999;Savage et al, 2004;van Beek et al, 2002;Work, 1981), and was also found in the Pisauridae (Shao and Vollrath, 1999) and Theridiidae (Shao and Vollrath, 1999;Work, 1981). Whether silk from other taxa supercontracts, in particular silk from 'basal' taxa such as tarantulas and haplogynes (e.g.…”

Section: Introductionmentioning

confidence: 98%

“…However, when the humidity rises, water disrupts these hydrogen bonds, allowing the non-crystalline regions to rearrange to lower energetic configurations, driving supercontraction (Eles and Michal, 2004;Savage and Gosline, 2008b;Yang et al, 2000). This rearrangement leads to the shrinking and thickening of the fiber and, at the molecular level, to an observed loss of orientation (Grubb and Ji, 1999;Parkhe et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Evolution of supercontraction in spider silk: structure–function relationship from tarantulas to orb-weavers

Boutry

Blackledge

2010

109

SUMMARYSpider silk is a promising biomaterial with impressive performance. However, some spider silks also 'supercontract' when exposed to water, shrinking by up to ~50% in length. Supercontraction may provide a critical mechanism to tailor silk properties, both for future synthetic silk production and by the spiders themselves. Several hypotheses are proposed for the mechanism and function of supercontraction, but they remain largely untested. In particular, supercontraction may result from a rearrangement of the GPGXX motif within the silk proteins, where G represents glycine, P proline and X is one of a small subset of amino acids. Supercontraction may prevent sagging in wet orb-webs or allow spiders to tailor silk properties for different ecological functions. Because both the molecular structures of silk proteins and how dragline is used in webs differ among species, we can test these hypotheses by comparing supercontraction of silk across diverse spider taxa. In this study we measured supercontraction in 28 spider taxa, ranging from tarantulas to orb-weaving spiders. We found that silk from all species supercontracted, except that of most tarantulas. This suggests that supercontraction evolved at least with the origin of the Araneomorphae, over 200 million years ago. We found differences in the pattern of evolution for two components of supercontraction. Stress generated during supercontraction of a restrained fiber is not associated with changes in silk structure and web architecture. By contrast, the shrink of unrestrained supercontracting fibers is higher for Orbiculariae spiders, whose silk contains high ratios of GPGXX motifs. These results support the hypothesis that supercontraction is caused by a rearrangement of GPGXX motifs in silk, and that it functions to tailor silk material properties.

“…Spider major ampullate (MA) silk is the main structural element in most prey capture webs and responds to humidity over 70% by supercontracting (Work, 1977). During supercontraction, water infiltrates the silk and disrupts the hydrogen bonding that maintains much of the ordered tertiary structure in the amorphous regions of silk proteins (Eles and Michal, 2004;Grubb and Ji, 1999;Parkhe et al, 1997;Termonia, 1994). Unrestrained MA silk fibers consequently shrink by up to half their length, while restrained fibers instead develop high tension (Bell et al, 2002;Boutry and Blackledge, 2010;Savage et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Wet webs work better: Humidity, supercontraction and the performance of spider orb webs

Boutry

Blackledge

2013

SUMMARYLike many biomaterials, spider silk responds to water through softening and swelling. Major ampullate silk, the main structural element of most prey capture webs, also shrinks dramatically if unrestrained or develops high tension if restrained, a phenomenon called 'supercontraction'. While supercontraction has been investigated for over 30years, its consequences for web performance remain controversial. Here, we measured prey capture performance of dry and wet (supercontracted) orb webs of Argiope and Nephila using small wood blocks as prey. Prey capture performance significantly increased at high humidity for Argiope while the improvement was less dramatic for Nephila. This difference is likely due to Argiope silk supercontracting more than Nephila silk. Web deflection, measured as the extension of the web upon prey impact, also increased at high humidity in Argiope, suggesting that silk softening upon supercontraction explains the improved performance of wet webs. These results strongly argue that supercontraction is not detrimental to web performance.