Page 171 - Handbook of Properties of Textile and Technical Fibres

148 Handbook of Properties of Textile and Technical Fibres

142
393–398

328
250 300 240 387
Raman intensity Wavenumber / cm –1 307 369
100
200
111
378

100 200 300 400 500
Position along the fibre / μm
Figure 5.5 Plot of the intensity of the c.142 cm 1 Raman peak (see inset) measured along a
Bombyx mori degummed single fiber. This narrow peak is characteristic of “crystalline” silk.
After Wojcieszak M, Percot A, Noinville S, Gouadec G, Colomban P: Origin of the variability of
the mechanical properties of silk fibres: 4. Order/cristallinity along silkworm and spider fibres,
J Raman Spectrosc 45(10):895e902, 2014. https://doi.org/10.1002/jrs.4579.

Table 5.3 Unit-cell parameters of representative spider and
silkworm silk
Nephila clavipes Bombyx mori
Parameter/nm (Parkhe et al., 1997) (Takahashi et al., 1999)
Intersheet distance 0.936 0.936
Interchain distance 1.077 0.949
Macromolecule axis 0.695 0.698

Silk sericin is a gluelike protein that covers the double strands of fibroin of silk
cocoons (wild silk and B. mori), contributing about 20% to 30% of the total weight
of the silk cocoons. In contrast, no coating is present on spider draglines. Raman
spectroscopy easily probes the absence of sericin traces as sericin is detected from
the Raman resonance spectrum of carotene species coloring the sericin (Percot
et al., 2014). The sericin material is composed of different proteins with a molecular
weight between 65 and 400 kDa (Gareletal.,1997). Sericin proteins are rich in
serine and consist of 18 types of amino acids including up to 32% of the essential
amino acids (serine, glycine, aspartic acid, glutamic acid, threonine, and tyrosine)