The role of proline in the elastic mechanism of hydrated spider silks
Open Access
- 15 June 2008
- journal article
- Published by The Company of Biologists in Journal Of Experimental Biology
- Vol. 211 (12), 1948-1957
- https://doi.org/10.1242/jeb.014225
Abstract
SUMMARY This study used thermoelastic measurements to investigate the role of proline in the elastic mechanism of hydrated, spider major ampullate (MA) and flagelliform (FL) silks. Experiments on hydrated MA silk from Araneus diadematus (proline content 16%) reveal that conformational entropy elasticity accounts for about 90% of the elastic force at small extensions,but entropy elasticity drops to about half by 50% extension. The decrease in the entropic component with extension is due to the presence of relatively short and conformationally restricted network chains in Araneus MA silk. Experiments on hydrated Araneus FL silk (proline content 16%)indicate that entropy elasticity dominates the elastic mechanism up to extensions of 100% and beyond, which likely reflects the fact that the glycine-rich network chains in FL silk are longer and less conformationally restricted than those in the MA silk. Thus, the rubber-like, entropic elasticity of these two proline-rich silks is consistent with networks of amorphous chains that become mobile when hydrated. By contrast, the elastic mechanism of hydrated Nephila clavipes MA silk (proline content 3.5%)shows a small contribution from entropic elasticity for extensions of 5% or less, and by 10% extension the elastic force is due entirely to bond-energy elasticity, probably associated with the deformation of stable secondary structures. These results indicate that there are major differences in the structural organization of the glycine-rich network chains and the mechanism of elasticity in proline-rich and proline-deficient fibroins.Keywords
This publication has 17 references indexed in Scilit:
- The effect of proline on the network structure of major ampullate silks as inferred from their mechanical and optical propertiesJournal Of Experimental Biology, 2008
- Proline and Glycine Control Protein Self-Organization into Elastomeric or Amyloid FibrilsStructure, 2006
- A DECODER NMR Study of Backbone Orientation in Nephila clavipes Dragline Silk under Varying Strain and Draw RateBiomacromolecules, 2004
- Strain Dependent Local Phase Transitions Observed during Controlled Supercontraction Reveal Mechanisms in Spider SilkMacromolecules, 2004
- The Mechanical Properties of Hydrated Intermediate Filaments: Insights from Hagfish Slime ThreadsBiophysical Journal, 2003
- Extreme Diversity, Conservation, and Convergence of Spider Silk Fibroin SequencesScience, 2001
- Silk Properties Determined by Gland-Specific Expression of a Spider Fibroin Gene FamilyScience, 1996
- Local Structure in Spider Dragline Silk Investigated by Two-Dimensional Spin-Diffusion Nuclear Magnetic ResonanceMacromolecules, 1996
- Spider silk as rubberNature, 1984
- Elastin as a rubberPeptide Science, 1977