Spider silk dragline

Secondary Structure. The silkworm cocoon and spider dragline silks are characterized as an antiparaHel P-pleated sheet wherein the polymer chain axis is parallel to the fiber axis. Other silks are known to form a-hehcal (bees, wasps, ants) or cross- P-sheet (many insects) stmctures. The cross-P-sheets are characterized by a polymer chain axis perpendicular to the fiber axis and a higher serine content. Most silks assume a range of different secondary stmctures during processing from soluble protein in the glands to insoluble spun fibers. 

Thermal Properties. Spider dragline silk was thermally stable to about 230°C based on thermal gravimetric analysis (tga) (33). Two thermal transitions were observed by dynamic mechanical analysis (dma), one at —75° C, presumed to represent localized mobiUty in the noncrystalline regions of the silk fiber, and the other at 210°C, indicative of a partial melt or a glass transition. Data from thermal studies on B. mori silkworm cocoon silk indicate a glass-transition temperature, T, of 175°C and stability to around 250°C (37). The T for wild silkworm cocoon silks were slightly higher, from 160 to 210°C. 

Simmons, A.H., Michal, C.A., Jelinski, L.W. Molecular orientation and two-component nature of the crystalline fraction of spider dragline silk. Science 271 84-87, 1996. 

Xu, M., Lewis, R.V. Structure of a protein superfiber spider dragline silk. Proc. Natl. Acad. Sci. USA 87 7120-7124, 1990. 

Charlotte s Web Revisited Helix-Sheet Composites in Spider Dragline Silk... 

Beek, J. D.v., Kummerlen, J., Vollrath, F., and Meier, B. H. (1999). Supercontracted spider dragline silk A solid-state NMR study of the local structure. Ini. J. Biol. Macromol. 24, 173-178. 

Dicko, C., Knight, D., Kenney, J., and Vollrath, F. (2005). Conformational polymorphism, stability and aggregation in spider dragline silks proteins. Int. J. Biol. Macromol. 36, 215-224. 

Oroudjev, E., Soares, J., Arcdiacono, S., Thompson, J. B., Fossey, S. A., and Hansma, H. G. (2002). Segmented nanofibres of spider dragline silk Atomic force microscopy and single-molecule force spectroscopy. Proc. Natl. Acad. Sci. USA 99, 6460-6465. 

Sapede, D., Seydel, T., Forsyth, V. T., Koza, M. A., Schweins, R., Vollrath, F., and Riekel, C. (2005). Nanofibrillar structure and molecular mobility in spider dragline silk. Macromolecules 38, 8447-8453. 

Oroudjev E, Soares J, Arcdiacono S, Thompson JB, Fossey SA, Hansma HG. Segmented nanofibers of spider dragline silk atomic force microscopy and single-molecule force spectroscopy. Proc Natl Acad Sci USA 2002 99 6460-6465. 

Super-contraction, the chaperonage of the special structure of spidroin, is indeed an obstacle to the use of native spider dragline silk, especially in bioapplication (usually wet condition). Recently, it was found that the intrinsic properties of silk fibroin are much better than the data listed in Table 2. The inferior properties are generated by the spinning habit of... 

As to fibers, it was reported that the inferior mechanical properties of silk from cocoons compared to spider silk result from the silkworm spinning process. If silkworm silk is processed at a constant pulling speed rather than constant force pulling, it possesses excellent properties, approaching the spider dragline silk (Shao and Vollrath, 2002). This suggests that the silkworm silk has the potential to produce better fibers, and the regenerated fibroin, which is easy to harvest, has the possibility to be fabricated into a reconstituted super-fiber. 

Huemmerich, D., Helsen, C.W., Quedzuweit, S., Oschmann, J., Rudolph, R., and Scheibel, T. "Primary structure elements of spider dragline silks and their contribution to protein solubility". Biochemistry 43(42), 13604—13612 (2004). 

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