Dragline silk

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... 

Figure 10 shows polarized spectra of two types of silks recorded by Raman spectromicroscopy the dragline silk (the lifeline) of the spider Nephila edulis and the cocoon silk of a wild silkworm Sarnia cynthia ricini. The position of the amide I band at 1,668-1,669 cm-1 for both threads is characteristic of the /i-sheet... 

Figure 10 Polarized spectra obtained by Raman microspectroscopy of (A) the dragline silk of the spider Nephila edulis and (B) the cocoon silk of the silkworm Sarnia cynthia ricini. Adapted with permission from Rousseau et al. [63]. Copyright 2004 American Chemical Society.

The dragline silk is composed of the two spidroins MaSpI and MaSpII. A 2.4-kb segment from the 3 end of the original MoSpl-mRNA and a 2-kb segment from the... 

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. 

Sponner, A., Schlott, B., Vollrath, F., Unger, E., Grosse, F., and Weisshart, K. (2005a). Characterization of the protein components of Nephila clavipes dragline silk. Biochemistry 44, 4727—1736. 

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. 

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