O. Liivak et al., A MICROFABRICATED WET-SPINNING APPARATUS TO SPIN FIBERS OF SILK PROTEINS - STRUCTURE-PROPERTY CORRELATIONS, Macromolecules, 31(9), 1998, pp. 2947-2951
A microfabricated spinneret is described that is capable of spinning m
eters of fibers from solutions containing as little as 10 mg of purifi
ed protein. Using the spinneret, regenerated Bombyx mori fibers were m
ade using various processing parameters. A log-linear relationship was
found between the maximum stress sustained by the regenerated fibers
and their diameters. Solid state C-13 NMR was used to determine the ef
fects of spinneret diameter and postspinning draw ratio on the seconda
ry structure of the alanine residues in the silk protein. The relation
ship between the secondary structure of the alanine residues and the m
aximum stress of the silks was also examined. The results suggest that
a relatively high fraction of the alanine residues in the silks must
be in the beta-sheet conformation (>65%) in order to produce the highe
st stress fibers. However, the fraction of alanine residues in the bet
a-sheet conformation does not uniquely determine the maximum stress of
a fiber; it is suggested that orientation of these beta-sheets is als
o an important parameter.