Composition of the silk lipids of the spider Nephila clavipes

A detailed analysis of the lipids of spider silk is given for the first tim e. Extracts of the silk from the golden orb weaver, Nephila clavipes, were studied by gas chromatography, mass spectrometry, and chemical derivatizati ons. The major group of the lipids consisted of methyl-branched 1-methoxyal kanes (methyl ethers) with up to four methyl groups in the chain (chain len gth between C-28 and C-34), which are unique to spiders. The position of th e methyl branches was determined by conversion into cyanides, which allowed easy location of methyl branches. The second-largest group included alkane s with a wide structural variety; 2-methyl-branched, even-numbered hydrocar bons predominated. A general numerical method for the estimation of retenti on indices of alkanes and their derivatives is presented. Further component s of the web included alkanols and alkanediols, fatty acids, and glyceryl e thers. Some comments on the biosynthesis of these compounds are also given.