Silk fibers spectroscopy

The protein secondary structure of silk fibroin [60] was studied with near-lR spectroscopy, using silk fibers that had been very carefully selected from naturally generated fibers. The isolation of individual fibers allowed the trapping from Nature of a protein with a particular secondary structure. A spider is able to generate different fibers for different uses, with each fiber having its own secondary structural composition. In the case of silk, an individual fiber may well have a particular composition secondary structure, and in this case it is possible to use near-lR spectra to perform a characterization. This is quite remarkable because the use of a relatively prominent amide-1 band in the mid-lR represents a major challenge. 

T. Asakura, J.M. Yao, T. Yamane, K. Umemura, A.S. Ulrich, Heterogeneous structure of silk fibers from Bombyx mori resolved by C-13 solid-state NMR spectroscopy, J. Am. Chem. Soc. 124 (2002) 8794-8795. 

In order to use solid-state NMR for atomic coordinate determinations, the angle of the C H bond vector relative to the fiber axis was determined for [2,2- H2]Gly and [3,3,3- H3]Ala labeled silk fibroin fibers from B. mori with quadrupole echo NMR spectroscopy [65]. This structural information... 

There are only two important classes of natural fibers the carbohydrate fibers and the protein fibers. The carbohydrate fibers are primarily cellulosic fibers from plants, such as cotton, jute, flax, ramie, kapok, sisal, and coconut. The protein fibers are primarily animal furs, generically called wool or hair, and the insect-based secretions called silk, whether from a silkworm or a spider. Raman spectroscopy of these materials has recently been obtained and is described in Sections II.B and II.C. 

Clearly, Raman spectroscopy provides a wealth of information about the type and composition of polymeric fibers and films. In addition, it can determine the type and amount of additives or degradation in these fibers and films. However, the most important use of Raman spectroscopy of organic fibers and films is in the determination of their morphology, as already shown for silk and as discussed more fully in the next section. 

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