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Scientists have long wondered why spider silk is so incredibly strong—and whether they can make similar materials themselves. In a new study, researchers investigated two key proteins in the silk from a spider called Nephila Clavipes, initially using computer models to predict the three-dimensional structure of the proteins from their amino acid sequence; then they modeled how these structures behaved when stretched, and compared the outcomes with lab measurements. Their findings, published online by the Journal of the Royal Society Interface, suggest that one of the proteins, MaSp1, consists mostly of so-called beta-sheets, which, thanks to hydrogen bonds, stack together like egg cartons (yellow, above); they give the silk its muscle. The other protein, MaSp2, contains many beta-turns (blue and white), molecular structures resembling coiled springs that provide elasticity.