Spider silk composition

Crystallinity. Generally, spider dragline and silkworm cocoon silks are considered semicrystalline materials having amorphous flexible chains reinforced by strong stiff crystals (3). The orb web fibers are composite materials (qv) in the sense that they are composed of crystalline regions immersed in less crystalline regions, which have estimates of 30—50% crystallinity (3,16). Eadier studies by x-ray diffraction analysis indicated 62—65% crystallinity in cocoon silk fibroin from the silkworm, 50—63% in wild-type silkworm cocoons, and lesser amounts in spider silk (17). 

The composition of lipids from the silk and cuticule has been reviewed by Schulz (1997a, 1999). These lipids consist primarily of alkanes, as found in other arthropods, with 2-methylalkanes with an even number of carbon atoms in the chain being most abundant, with lesser amounts of alcohols, acids, aldehydes, and wax esters. Recently, a thorough analysis of the silk lipids of N. clavipes (Schulz, 2001) revealed a unique class of lipids from spider silk and cuticle, consisting of straight-chain and branched methyl ethers (1-methoxyalkanes, Fig. 4.4) with chain lengths between 25 and 45 carbon atoms. 

Recently, Foo et al. (2006) produced some novel nanocomposites from spider silk-silica fusion (chimeric) proteins. The composite morphology and structure could be regulated by controlling processing conditions to produce films and fibers. Silk and biomineralization being natural inspiration sources will allow production of numerous new materials in various fields of application. 

Source From Denny, M.W. In Mechanical Properties of Biological Materials. Vincent, J.F.V. Currey, J.D. Eds., Cambridge University Press, Washington DC, 1980 Andersen, S.O. Amino acid composition of spider silks. Comp. Biochem. Physiol. 35 705-711, 1970. 

Andersen, S.O. Amino acid composition of spider silks. Comp. Biochem. Physiol. 35 705-711 (1970). 

Zhou, S., Peng, H., Yu, X. et al. (2008) Preparation and characterization of a novel electrospun spider silk fibroin/poly(D,L-lactide) composite fiber. Journal of Physical Chemistry B, 112, 11209-11216. 

Teuld F, Miao Y, Sohn BH, Kim YS, Hull JJ, Fraser MJ, Lewis RV and Jarvis DL. Silkworms transformed with chimeric silkworm/spider silk genes spin composite silk fibers with improved mechanical properties. Proc. Natl. Acad. Sci. USA. 109 923-928,2012. 

---