Fractionation of the fibroin of Bombyx mori with alkali

Abstract

not at present much information concerning the effect of limited attack by alkali upon fibroin, or indeed upon proteins in general, and it seemed worthwhile to investigate the situation more fully. MATERIALS AND METHODS Bombyx mori silk fibroin. Japanese B. mori silk was purchased from H. T. Gaddum and Co. Ltd., Manchester, and was degummed as described by Drucker, Hainsworth & Smith (1953). Solutions were prepared by dissolving the fibroin in aq. 60% (w/v) LiSCN (1 g. in 5 ml.), diluting with water to 50 ml. and dialysing the solution in Visking II in. cellophan dialysis tubing against a stream of water until free from SCNions. Chemicals. 6,9-Diamino-2-ethoxyacridine lactate was a commercial sample purporting to be of not less than 97 % purity, purchased from the Aldrich Chemical Co. Inc., Milwaukee 10, Wis., U.S.A. I-Fluoro-2,4-dinitrobenzene was also a commercial preparation, obtained from L. Light and Co. Ltd., Colnbrook, Bucks. Other chemicals were of analytical reagent grade. Alkali-treatment. Solutions of fibroin containing about 2 % (w/v) of protein were diluted with N-NaOH and with water so that they were 1 % in protein and 0-1 N in NaOH. The pH of such solutions was found to be 12-8. In most of the experiments described in this paper the solutions were kept at 30 in a refrigerator, and were then brought to pH 6-2 by the addition of N-phosphoric acid. Such a preparation resulting from an alkali-treatment lasting 48 hr. is subsequently referred to as a solution of A-fibroin (Gk. Au'etv, to loose). Similar experiments were performed in which the solution at pH 12-8 was maintained at 250. Solutions at pH 110, 11-5, 12-0 and 12-5 were also prepared from 2 % solutions of fibroin in water by the addition of equal volumes of an appropriate sodium borate buffer, 0-2M in Na+ ions: the pH values were finally adjusted by the addition of a few drops of N-NaOH or m-boric acid. The solution at pH 13-0 was obtained by the cautious addition of N-NaOH to the standard pH 12-8 solution described above.

Studies on Indian silk. I. Macrocharacterization and analysis of amino acid composition

“…Shaw [12][13][14] investigated the amino acid composition of the residues obtained by treatment of various silk fibroins with acid, alkali, and hydrogen peroxide by column chromatography, discussed in relation to the structure and the effect of amino acid composition and the residues derived from them on the structure. The above studies also included the analysis of the amino acid composition of Japanese Bombyx mori fibroins treated with enzymes such as trypsin using paper chromatography.…”