The molecular structure of wool
As described above, a protein macromolecule is a polypeptide formed by a large number of a-amino acids connected end to end in a certain order. Although the research on amino acid arrangement order in skin chain has made great progress, it is far from clear.
The spatial conformation of the self-quality molecular chains of wool fibers is relatively complicated. According to the analytical data, it can be confirmed that there is a helical conformation in the wool protein's molecular chain, as shown in Fig. 4-4.
The skin chains in the a-helical conformation are helically wound along the surface of the cylinder. The skin chain strands were wound in a circle and separated by 3.6 amino acid residues. The vertical distance of each amino acid residue in the axial direction was 0. 15 nm.
Further studies have found that not all wool proteins have a helical conformation in the molecular chain. It exists only in the skin chain of about 50% of low-sulfur proteins, and the skin chain of high-sulfur proteins is randomly curled.
Wool stretches in the presence of moisture. When the elongation reaches more than 20%, the helical conformation of the skin chain begins to change; when the elongation reaches 35%, the helical conformation of the skin chain changes significantly; when the elongation reaches 70 At %, the helical conformation of the skin chain is completely converted to the le conformation (stretched state conformation of the skin chain).
After relaxation, the conformation of the belly chain changes reversibly and finally returns to the a-conformation. In the pull-second state, if a new stable cross-linking bond can be established between the polypeptide chains, there is an effect of preventing the conformation recovery of the skin chain, so that the wool fibers are maintained in the elongated state for a longer period of time.