Proteins keratin, feather

A Bird feathers are made largely of the protein keratin. 

Claws, beaks, horns, hooves, and baleen these materials may seem like strange companions, but they are all composed of basically the same material, the protein keratin. Hair and feathers are also keratin, but are addressed in detail in previous sections. All of these materials form on the outside of an animal s body, in the skin. 

Barone and Schmidt (2005) reported on the use of keratin feather fiber as a short-fiber reinforcement in LDPE composites and showed that protein fibers have good resiliency and elastic recovery. Besides protein fibers have higher moisture regain and warmthness than natural ceUulosic fibers properties, all related to its possible use in earth material. The keratin feather fiber for these tests was obtained from chicken feather waste generated by the U.S. poultry industry (Galan-Marm et al. 2010). Clearly, water can play a very important role in these materials that can be elucidated using NMR spectroscopy however, this aspect was poorly studied. 

The extraction of amino acids from protein is the oldest method for their manufacture. L-Cysteine is still obtained in this way, being isolated from an acid hydrolysate of the protein keratin, the principal component of hair and feathers. Chemical routes are successful where the racemate is a satisfactory product as it is with methionine (Figure 6.11), and there are several effective methods which link a chemical synthesis with a biochemical resolution of the... 

Wool is composed largely of the protein keratin, which is also found in feathers, hair, horn, nails and scales. The composition of the hydrolyzate of wool keratin is given in Table 9.3. It will be seen that this protein has a high content of cystine wool thus contains many disulphide cross-links which render the fibre insoluble. 

Production by Isolation. Natural cysteine and cystine have been manufactured by hydrolysis and isolation from keratin protein, eg, hair and feathers. Today the principal manufacturing of cysteine depends on enzymatic production that was developed in the 1970s (213). 

Wool belongs to a family of proteins, the keratins, that also includes hair and other types of animal protective tissues such as horn, nails, feathers, and the outer skin layers. The relative importance of wool as a textile fiber has declined over the decades as synthetic fibers have increa singly been used in textile consumption. Wool is still an important fiber in the middle and upper price ranges of the textile market. It is also an extremely important export for several nations, notably AustraUa, New Zealand, South Africa, and Argentina and commands a price premium over most other fibers because of its outstanding natural properties of soft handle (the feel of the fabric), moisture absorption abiUties (and hence comfort), and superior drape (the way the fabric hangs) (see Fibers Textiles). Table 2 shows wool production and sheep numbers in the world s principal wool-producing countries. 

Wool, as a keratin, is a highly cross-linked, insoluble proteinaceous fiber, and few animals have developed the specialized digestive systems that aUow them to derive nutrition from the potential protein resource. In nature, these few keratin-digesting animals, principally the larvae of clothes moths and carpet beetles, perform a useful function in scavenging the keratinous parts of dead animals and animal debris (fur, skin, beak, claw, feathers) that ate inaccessible to other animals. It is only when these keratin-digesting animals attack processed wool goods that they are classified as pests. Very often they enter domestic or industrial huildings from natural habitats such as birds nests. 

Alpha helices are sufficiently versatile to produce many very different classes of structures. In membrane-bound proteins, the regions inside the membranes are frequently a helices whose surfaces are covered by hydrophobic side chains suitable for the hydrophobic environment inside the membranes. Membrane-bound proteins are described in Chapter 12. Alpha helices are also frequently used to produce structural and motile proteins with various different properties and functions. These can be typical fibrous proteins such as keratin, which is present in skin, hair, and feathers, or parts of the cellular machinery such as fibrinogen or the muscle proteins myosin and dystrophin. These a-helical proteins will be discussed in Chapter 14. 

Z-Cystine has been obtained by the hydrolysis of a large number of proteins. However, the keratins are the only common proteins rich enough in cystine to serve as a source for this amino acid. Many investigators have devised methods for its isolation from the hydrolytic products of human hair,3 wool,2 horn,3 nail,3 feathers,3 and horse hair.4 The method of Folin5 is the basis for most of the others. The present method does not claim to give as high a yield as some of those reported in the literature, but is convenient and gives consistent results. 

Fibrous proteins - these have linear molecules, are insoluble in water and resistant to alkalis and acids. Collagen (in tendons and muscles), keratin (in nails, hair, horn and feathers) and elastin (in arteries) are all fibrous proteins. 

Proteins can be divided into two main types, based on their overall shape. Fibrous proteins, as their name implies, have fiberlike structures and are used for structure or support. They are found, for example, in collagen (skin, tendon cartilage, fish scales), elastin (connective tissue), and keratins (silk, feathers, horn, and hair). They are tough and insoluble macromolecules, often having several a-helical chains wound together into ropelike bundles. 

Keratins are insoluble proteins that make up such structures as hair, skin, nails, wool, and feathers and form the cytoskeleton structures in all cells of epithelial origin. Along with other fibrous proteins of the same dimensions (e.g., neurofilaments), keratin has been referred to as intermediary filament (IF). In the human being, keratin is one of the more abundant proteins. The basic keratin unit is a relatively small protein with a molecular weight of 40,000-70,000. About 20 different keratin polypeptides have been identified in human hair follicles, various epithelial cells, and tumor cells. They have been assigned numbers 1-20 and have been divided into two classes acidic (type 1) and neutral/base (type 2). A given tissue or cell line will have a characteristic keratin polypeptide distribution, as shown in Table 8.2. However, both types of peptides are always present in a given cell. 

Keratin is another group of fibrous proteins. These compounds are major components of hair, skin, wool, horns, hooves, fingernails, claws, and feather quills. These proteins contain a lot of cysteine, one of the few amino acids that has sulfur in it. 

Owing to the economic importance of wool most investigators have used this material as a convenient source of a-keratin. When parallel studies have been made on hairs from other animals and on nails, claws, hoofs, and quills it has been found that conclusions reached by studying wool proteins apply, with only minor qualifications, to other keratinized tissues. Feathers are only of slight economic value and correspondingly less attention has been devoted to their chemistry, despite the fact that feather proteins are more readily solubilized and purified and that feather rachis yields X-ray diffraction patterns of excellent quality. 

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