Basic-neutral keratins

Twelve keratins with more acidic isoelectric points form type I (acidic) keratins, and eight keratins with more basic isoelectric points compose the type II (basic-neutral) keratins. " The keratins are products of two gene families Most genes for type II keratins are localized on chromosome 12, and the genes for type I keratins are localized on chromosome 17.H2-ii4 g ch... 

The wool fiber is composed of protein filaments and consists mainly of keratin with a very complex structure. The amino groups of keratin are of decisive importance for the dyeing process. The amount of basic groups titratable with acid is 850 1 mol per gram of wool fiber. In the acidic and neutral range, carboxyl groups are present largely in the undissociated state. 

The general mechanisms by which the NMF components influence SC functionality have been studied extensively. From a physical chemistry perspective the specific ionic interaction between keratin and NMF, accompanied by a decreased mobility of water, leads to a reduction of intermolecular forces between the keratin fibers and increased elastic behavior. Recent studies have emphasized that it is the neutral and basic FAA36 in particular that are important for helping keratin acquire and maintain its elastic properties. Consistent with these observations Sakai et al.37 reported that the ratio of acidic amino acids to total amino acids correlated to the resonant frequency a measure of skin stiffness. 

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. 

Cytokeratin Intermediate filament keratins found in epithelial tissue. There are two types of cytokeratins the acidic type 1 cytokeratins and the basic or neutral type 11 cytokeratins. Cytokeratins are thought to play a role in the activation of plasma prekallikrein and plasminogen. See Crewther, W.G., Fraser, R.D., Lennox, F.G., and Lindley, H., The chemistry of keratins, Adv. Protein Chem. 20, 191-346, 1965 Masri, M.S. and Friedman, M., Interactions of keratins with metal ions uptake profiles, mode of binding, and effects on the properties of wool, Arfv. Exp. Med. Biol. 48, 551-587,1974 Fuchs, E. and Green, H., Multiple keratins of cultured human epidermal cells are translated from different mRNA molecules. Cell 17, 573-582, 1979 ... 

Keratin filaments are formed by tetrameric heteropolymers of two different keratins, two from type I and two from type II, to maintain cellular electrical neutrality. The vast majority of keratins are paired together as acidic and basic types, with rare exception. The classification and numbering system of the keratins is based on the catalog of Moll and associates." ... 

The intermediate filament molecules in keratins are composed of two different types of polypeptides designated as Type I (acidic side chains) and Type II (neutral to basic side chains). These chains are coiled about each other forming a two-strand coiled-coil rope thus, each filament requires one acidic polypeptide that coils about a basic polypeptide partner or mate. In human hair, there are at least five of these low-sulfur proteins, two Type... 

Protein fibers are the most readily dyed fibers due to the numerous reactive functional groups present. They can be dyed with a wide range of dyes under acid, neutral, or slightly basic conditions. Since the keratin fibers are less crystalline and oriented than secreted fibers such as silk, they tend to dye more rapidly and more readily to deeper shades. 

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