Keratins molecular structure

Alpha farnesene, structure of, 207 Alpha helix (protein), 1038 Alpha-keratin, molecular model of, 1039... 

Astbury, W. T. Street, A., X-ray Studies of the Structure of Hair, Wool and Related Fibres. I. General. Trans. R. Soc. London 1931, A230,75 Astbury, W. T. Woods, H. J., II. The Molecular Structure and Elastic Properties of Hair Keratin. ibid. 1934, A232, 333 Astbury, W. T. Sisson, W. A., III. The Configuration of the Keratin Molecule and its Orientation in the Biological Cell, Proc. R. Soc. London 1935, A150, 533. 

Coupling of maeroseopie and molecular investigations of thermally induced alterations of hairless mouse stratum corneum provide insight into molecular structure and barrier functions of the stratum corneum. Enhanced permeabilities below 70°C have been associated with increased lipid fluidity. However, the keratinized protein component of stratum corneum experiences only minor tertiary structural alterations with thermal pretreatments above 70°C. 

Astbury WT, Woods HJ (1933) X-ray studies of the structure of hair, wool, and related fibres, II. Molecular structure and elastic properties of hair keratin. Items R Soc A232 333-394... 

Then, during a long visit to England in early 1948, Pauling heard about another approach. British researchers were saying that, instead of a kinked ribbon, keratin and other proteins might have a molecular structure more like a spiral or, as some called it, a helix. 

Characterization of the keratinized cells by classical histological and biochemical approaches has been difficult because of the intractable nature of the tissue. Yet it is precisely these properties of mechanical strength, insolubility, macromolecular character, and lack of metabolic activity along with its ease of isolation which makes stratum corneum amenable to analysis by physical methods. The extreme complexity of composition, molecular structure, and organization of stratum corneum make interpretation of these macroscopic properties in terms of molecular structure and events dependent heavily on analogous studies of model synthetic polymer systems and the more thoroughly characterized, keratin-containing wool. 

In the early 1930 s Astbury and his collaborators defined the principal features of the molecular structure of essentially all mammalian hard keratins (4, 6). This work introduced the concept of the regularly folded a-protein chain. Within this scheme of things the hard keratins of birds and reptiles stood out, for they gave highly characteristic diffraction patterns which could only be interpreted in terms of a special type of 0 or nonfolded chain (5). Nevertheless, much of the epidermal protein in birds and reptiles has the same a-type structure as is always found in the case of mammalian epidermal tissue. The special interest of these observations was to reveal a widespread common type of molecular structure in the principal fibrous proteins of vertebrate epidermis. This common type is not quite universal because of the seeming mutation in the hard keratins of birds and reptiles, which defines the unique relationship of these groups at the molecular level (5, 50). 

The primary core molecular structure is represented in terms of the a-helix of keratin, which is a major constituent of hair. Keratins are the most abundant proteins and are the main component of the horny layer of epidermis and the... 

Like all polymeric structures, keratin fibres consist of long, tightly bound molecular chains held together in many different ways from covalent bonds to weaker interactions such as hydrogen bonds, Coloumbic interactions, van der Walls interactions and, when water is present, hydrophobic bonds. Hair reactivity is complex and depends not only on the presence of reactive groups in the fibre, but also on their availability. The latter is significantly affected by fibre morphology and molecular structure [2]. Hair is mostly proteinaceous in nature, while structural hpids and other materials represent only a minor fraction of its constituents. 

Molecular structures of therapeutic agents now known to normalize disturbed keratinization in ichthyosis and other disorders of keratinization suggest that keratinization is normally modulated by certain a-hydroxy or a-keto acids. Evidence for this includes the demonstrated efficacy of topically applied a-hydroxy and a-keto acids in ichthyosis the presence of ichthyotic skin in Refsum s disease, a disorder associated with failure of an a-hydroxylase and preliminary findings that active forms of vitamin A acid may be hydroxylated derivatives. 

The Structure of the a-Keratins Was Determined with the Help of Molecular Models The fi-Keratins Form Sheetlike Structures with Extended Polypeptide Chains Collagen Forms a Unique Triple-Stranded Structure Globular Protein Structures Are Extremely Varied and Require a More Sophisticated Form of Analysis Folding of Globular Proteins Reveals a Hierarchy of Structural Organization... 

The Structure of the a-Keratins Was Determined with the Help of Molecular Models... 

Steinert, P. M., Marekov, L. N., Fraser, R. D. B., and Parry, D. A. D. (1993a). Keratin intermediate filament structure Crosslinking studies yield quantitative information on molecular dimensions and mechanism of assembly. /. Mol. Biol. 230, 436-452. 

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