SPECIES SPECIFICITY OF CONFORMATION OF SILK FIBROIN IN SOLUTION

The conformation of silk fibroins in aqueous solution is determined by optical rotatory dispersion and infrared absorption. 1. 1. Silk fibroins of subfamilies Bombycinae and Thaumetopoeinae, whose main primary structures are alternating glycine and alanine (or serine in the former sequences), essentially exist in a disordered conformation. 2. 2. Bombycinae fibroins are slightly β when taken straight from the posterior silkgland and Thaumetopoeinae fibroin is slightly α-helical in a certain species. 3. 3. Saturniinae fibroins, whose main primary structures are sequences of consecutive alanines, contain 15-20% α-helix. 4. 4. In all the fibroins tested, however, a cross β-form appears, regardless of the subfamily, when more than 30% (v/v) dioxane or methanol is added to solution. The α-helix which is primarily present in Saturniinae fibroins remains unchanged while in Thaumetopoeinae fibroins it is newly formed. © 1968.