Analysis of spider silk in native and supercontracted states using Raman spectroscopy

Well-defined, fluorescence-free Raman spectra were obtained from native as well as treated (supercontracted) major ampullate dragline silks reeled fro m four very different spiders: Araneus diadematus, Nephila edulis, Latrodec tus mactans and Euprosthenops sp. Conformational sensitive regions were ass igned in the spectra. Compared to the silk of the silkworm Bombyx mori, all spider silks showed less beta-sheet and more random coil and/or alpha-heli x material. Polarized spectra suggested that the molecular chains of the sp ider silk were aligned parallel to the axis of the fibre. The differences i n the mechanical properties between the native and supercontracted silks we re attributed to variations in beta-sheet content. The mechanism of contrac tion of spider silks in solvents was correlated to conformational changes i n the supermolecular structure. (C) 1999 Elsevier Science Ltd. All rights r eserved.