Feather structure

Example 7.4. Effect of oil on aquatic birds. Aquatic birds keep their feathers hydrophobic with wax. For them it is essential that the feathers repel water. The air entrapped in and under the feathers provides a good heat insulation. It keeps the birds afloat and light so that they are able to fly. Due to low surface tension, oil has a strong tendency to wet all kinds of solid surfaces. It also wets the surfaces of feathers which then deprives the birds of all the essentials described. In addition, heavy oil is sticky, destroys the feather structure, and prevents the birds from moving freely. 

The feather structure is regularly interspersed with triangular windows (Figs 15.49 and 15.50) which fulfil four different functions ... 

Martinez-Hemandez AL, Velasco-Santos C (2012) Keratin fibers from chicken feathers structure and advances in polymer composites. Nova Publishers, New York, pp 149-211 Martinez-Hemandez AL, Velasco-Santos C, de-Icaza M, Castano VM (2007) D5mamical-mechanical and thermal analysis of polymeric composites reinforced with keratin biofibers from chicken feathers. Compos Part B Eng 38 405 10 Mathew AP, Dufresne A (2002) Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers. Biomacromolecules 3 609-617 Md. Islama S, Hamdana S, Talibb ZA, Ahmeda AS, Md. Rahmana R (2012) Tropical wood polymer nanocomposite (WPNC) The impact of nanoclay on dynamic mechanical thermal properties. Compos Sci Technol 72 1995-2001... 

Other hydrophobic example in nature is duck s feather. Both preen oil and feather structure have been regarded as important for the abiUty of adult plumage to shed water droplets and resist water penetration while swimming. Again a hierarchical structure barbs and barbules in the down coat makes the feather impermeable and prevents the skin of the duck to be in contact with water. This not only helps ducks floatabiUty, but also provides thermal insulation. 

Martinez-Hernandez AL, Velasco-Santos C [2011). Keratin fibers from chicken feathers Structure and advances in potymer composites, in Keratin Structure, Properties and Applications. Chapter 7 [Dullart R, Mousques )., eds.). Nova Science Publishers, Inc. Hauppauge, NY, USA, pp. 149-211. 

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. 

The use of thermal insulation dates back to ancient times, when primitive man used animal skins for clothing and built structures for protection from the elements. Primitive insulation included fibrous materials such as animal fur or wool, feathers, straw, or woven goods. Bricks and stone, while not highl y efficient thermal insulation, provided protection from the elements, reduced the loss of heat from fires, and provided large masses that moderate temperature changes and store heat. 

The spectral variations caused by the interference phenomena become relevant when a food contains tightly adjoining dense structures like feathers, fish scales, or the shells of crustaceans. 

Homologous Corresponding in structure, position, origin, etc., as (a) the feathers of a bird and the scales of a fish, (b) antigen and its specific antibody, (c) allelic chromosomes. [EU]... 

The beta-keratin structure is also foimd in the feathers and scales of birds and reptiles. 

In addition to their importance as essential amino acids for humans, the quantitative determination of cysteine and methionine seems to be growing in importance in the animal feed industry. The dietary requirements for the sulfur amino acids tend to be very high in many animals. This is presumably due to the magnitude of hair/feather growth and the fact that the structural proteins that comprise hair/feathers often have high cyst(e)ine content. 

While some of the Mississippian textiles are of similar structure to the Middle Woodland textiles, others are very complex materials and are lace-like in appearance. Many of the materials from Etowah are preserved by mineralization, and display green-colored deposits on their surfaces. Bast fiber, rabbit hair, and feathers have been identified (2, 11). The textiles from these two sites selected for analysis are representative of the complexity of structure and fineness of yarns seen in the materials they provide evidence of the sophisticated technology of prehistoric people in all phases of fiber collection, processing, yarn spinning, fabric manufacture and, when present, coloration. 

An example of a longer exact repeat is found in chick scale keratin. The sequence contains a fourfold tandem repeat, each IS residues long (G—Y-G—G-S-S-L-G—Y-G—G—L-Y Fig. 1). Interestingly, feather and scale keratin share a common microfibril structure with a 3.4 nm diameter. 

Gregg, K., Wilton, S. D., Parry, D. A. D., and Rogers, G. E. (1984). A comparison of genomic coding sequences for feather and scale keratins Structural and evolutionary implications. EMBO J. 3, 175-178. 

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