Solid-state NMR relaxation studies of Australian spider silks

Solid-state NMR techniques were used to study two different types of spider silk from two Australian orb-web spider species, Nephila edulis and Argiope keyserlingi. A comparison of ¹³C-T₁ and ¹H-T_1p solid-state NMR relaxation data of the Ala Cα, Ala Cβ, Gly Cα, and carbonyl resonances revealed subtle differences between dragline and cocoon silk. ¹³C-T_1p and ¹H-T₁ relaxation experiments showed significant differences between silks of the two species with possible structural variations. Comparison of our data to previous ¹³C-T₁ relaxation studies of silk from Nephila clavipes (A. Simmons et al., Macromolecules, 1994, Vol. 27, pp. 5235-5237) also supports the finding that differences in molecular mobility of dragline silk exist between species. Interspecies differences in silk structure may be due to different functional properties. Relaxation studies performed on wet (supercontracted) and dry silks showed that the degree of hydration affects relaxation properties, and hence changes in molecular mobility are correlated with functional properties of silk.