title: Two mechanisms for supercontraction in Nephila spider dragline silk.
abstract: Supercontraction in dragline silk of Nephila edulis spider is shown to have two distinct components revealed by single fiber measurements using dynamic mechanical thermal analysis. The first component relies on a contraction of maximum 13% and seems to be associated with relaxation processed through the glass transition, T(g), as is induced by increasing temperature and/or humidity. The second component is induced by liquid water to the total contraction of 30%. The T(g)-induced contraction is linearly correlated with the restraining stress on the fiber, and the mechanical properties of the partially contracted silk have mechanical profiles that differ from both native and fully supercontracted fibers. Here we present novel supercontraction data and discuss their structural origins, examining the relaxation of stretched orientation in the different primary structure sequences.
authors.affiliation: Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
authors.forename: Juan
authors.initials: J
authors.lastname: Guan
authors.forename: Fritz
authors.initials: F
authors.lastname: Vollrath
authors.forename: David
authors.initials: D
authors.lastname: Porter
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D055119:Elastic Modulus; D005349:Fibroins / Q000737:chemistry*; D006813:Humidity; D020836:Protein Structure, Quaternary; D047011:Silk / Q000737:chemistry; D013112:Spiders; D013314:Stress, Mechanical; D013718:Tensile Strength; D044366:Transition Temperature
chemical_list: D047011:Silk; D005349:Fibroins