COMPARATIVE STRUCTURAL CHARACTERIZATION OF NATURALLY-SPUN AND SYNTHETICALLY-SPUN FIBERS OF BOMBYX-MORI FIBROIN

This investigation describes the comparative structural characterizati on of naturally-and synthetically-spun fibers of Bombyx mori fibroin. Wet spinning from 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solutions w as used to spin fibroin fibers with varying degrees of postspinning dr aw. Quantitative Raman spectroscopy showed that the secondary structur e of fibroin changed dramatically from predominantly alpha-helical in HFIP solution to principally beta-sheet in the underdrawn syntheticall y-spun fiber. X-ray fiber diffraction showed that the underdrawn fiber s were highly crystalline (>50%) with little or no preferential crysta lline alignment. The addition of a postspinning draw caused the polype ptide backbone and beta-sheet crystals, which were formed largely by a methanol coagulation bath, to align with the fiber axis. The molecula r and crystalline structures most similar to those of naturally-spun f ibers were reproduced in synthetically-spun fibers with a minimum draw ratio of 2.5.