Proteins in wool

Keratinous proteins, in wool, 26 378-379 Kermesite, 3 41 Kemer equation, 11 309 Kemite (rasortie), 4 133t, 243t, 245 ... 

One common type of secondary structure resembles a spiral staircase. This spiral stmcture is called an a-helix (see Figure 21.3). A spiral-like secondary stmcture gives the protein elasticity (springiness) and is found in the fibrous proteins in wool, hair, and tendons. Another type of secondary structure involves joining several different protein chains in an arrangement called a pleated sheet, as shown below. 

By analogy with the effects of malnutrition and sulfur enrichment on the high-sulfur proteins of the keratin-associated proteins in wool fiber [44,45], these effects of a lower cystine content in hair are probably a result of a decreased synthesis of the sulfur-rich proteins because of malnutrition. Studies of the effects of diet in persons suffering malnutrition (i.e., protein deficiencies) show that diet supplementation can influence the protein composition of human hair. However, such effects have only been demonstrated among persons suffering from severe malnutrition and never among healthy persons on a normal diet see the section on the keratin-associated proteins of human hair later in this chapter. 

After acid hydrolysis of wool or proteins that have been treated with FDNB, the DNP derivatives of amino acids from the amino end of protein chains are soluble in ether, whereas amino acids whose side-chains have reacted only with FDNB together with unreacted amino acids are not soluble. Thus the amino acids from the amino ends of protein chains (amino-terminal amino acids) can be separated from other amino acids. The method is used to estimate the proportions of the different amino acids that occupy the amino-terminal positions of proteins in wool fibers and in proteins derived from wool. If peptide bond hydrolysis occurs... 

The types of monomers incorporated in a polymer strongly influence the flexibility and shape of the polymer. For example, polymers whose monomers contain aromatic rings are less flexible than those whose monomers are acychc. In some polymers, the chains are cross-hnked by covalent bonds. Cross-hnking creates larger macromolecules with more rigid structures. Cross-hnks are also important in naturally occurring polymers. For example, the proteins in wool fiber are cross-hnked by many disulfide bonds. 

Mechanically, the most important component of wool fibers is the cortex. Figure 5.15 shows the stmcture of the cortex in a wool fiber. The protein in wool fibers is called keratin. Three keratin chains in wool form helices with helix angles ranging from 30° to 35°. Three helix chains twist compactly together to form a protofibril with a diameter of aroimd 2 run. Eleven protofibrils assemble to form a microfibril with a diameter of 7-8 nm. Microfibrils also are called intermediate filaments and they helically wind together into a macrofibril with a diameter of... 

In addition to the restrictions on their mobiHty caused by steric and polar interactions between chemical groups, the protein molecules in wool fibers are covalentiy cross-linked by disulfide bonds. Permanent setting only occurs if these disulfide bonds are also rearranged to be in equiHbrium with the new shape of the fiber. Disulfide bond rearrangement occurs only at high temperature (>70° C) in wet wool and at even higher temperatures (above 100°C) in... 

In wool scouring, the contaminants on the wool, mainly grease, dirt, suint, and protein material, are washed off the fiber and remain in the wastewaters either in emulsions or suspension (grease, dirt, protein) or in solution (suint). Centrifugal extraction of the wastewaters produces a grease contaminated with detergent and suint. This product is called wool grease. 

The chloroisocyanurates can be used in the bleaching of cotton, synthetics, and their blends they do, however, attack proteinaceous fibers, such as silk or wool, presumably via active chlorine reaction with the peptide (amide) linkage. However, the chloroisocyanurates can be used as shrink-proofing agents in wool finishing (131), (see Textiles Wool). The same action of chlorine upon proteins contributes to the effectiveness of chloroisocyanurates in automatic dishwashers. 

The rubber polyisoprene is a natural polymer. So, too, are cellulose and lignin, the main components of wood and straw, and so are proteins like wool or silk. We use cellulose in vast quantities as paper and (by treating it with nitric acid) we make celluloid and cellophane out of it. But the vast surplus of lignin left from wood processing, or available in straw, cannot be processed to give a useful polymer. If it could, it... 

In addition to the natural protein fibres wool and silk, fibres have been produced commercially from other proteins. These materials were introduced as wool substitutes but today have little or no significance. Mention may, however, be made of ArdiP products from the groundnut protein and marketed for some years after World War II by ICI. Compared with wool it had inferior wet and dry strength and abrasion resistance. The inclusion of up to 20% ArdiP into wool, however, yielded a product with negligible loss in wearing properties. 

Plastics and fibers have been produced from regenerated proteins obtained from a number of sources [17]. The process involves dispersing the proteins in dilute sodium hydroxide followed by extrusion through a spinneret into an acid bath to form the fibers that are then crosslinked with formaldehyde to improve strength. The fibers are used along with silk and wool. 

WOOL, The natural, highly crimped fiber from sheep, wool is one of the oldest fibers from the standpoint of use in textiles. Minute scales on the surface of the fibers allow them to interlock and are responsible for the ability of the fiber to felt, a phenomenon responsible for felt cloth and mill-finished worsteds. Crimpiness in wool is due to the open formation of the scales. Fine merino wool has 24 crimps per inch ( " 10 per centimeter). Luster of the fiber depends upon the size and smoothness of the scales. The basic wool protein, keratin, comprises molecular chains that are linked with sulfur. When sulfur is fed to sheep in areas deficient of the element, the quality of the wool improves. Wool fibers that fall below 3 inches (7.5 centimeters) in length are known as clothing wool fibers 3-7 inches (7.5-17.8 centimeters) long are referred to as combing wools. The wool-liber diameter ranges from 0.0025 to 0.005 inch (0.06-0.13 millimeter). See also Fibers. 

Fibrous proteins in which the a helix is a major structural component are found in hair, scales, horns, hooves, wool, beaks, nails, and claws-—proteins referred to as a-... 

Swan153 demonstrated that sulfite or bisulfite ion reacts with sulfhydryl (SH) groups of cystine in wool protein, reducing the disulfide linkage and giving a protein fraction (P ) having one cysteine SH and a second protein (P ) on which a S-sulfo derivative of the cysteine moiety has been formed ... 

Also referred to as bippolyraers, they are synthesized in the cells of all organisms. It is interesting to note that two of the most prevalent types, polysaccharides and proteins, each contain diverse compounds with extremely different properties, structures, and uses. For example, the protein in egg white (albumin) serves a much different function (nutrition) from that in silk or wool (structural). Likewise, the properties of starch and cellulose could hardly be more different. Although each is made up of polymers based on the condensation of glucose, the final molecular structures differ dramatically. Both sustain life, but in completely different ways. We will discuss natural polymers in more detail in Chapter 3. 

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