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Natural Materials – Composition and Combinations
Published in Graham A. Ormondroyd, Angela F. Morris, Designing with Natural Materials, 2018
Beta-keratin is arranged in a pleated structure, with antiparallel chains (McKittrick et al. 2012). The so-called β-sheet has a crimp of 0.70 nm in length. Hydrogen bonding holds the molecules within the sheet in lateral relationship to each other. It has been shown that if the α-form is stretched, it will transform to a β-form (Frazer et al. 1971). The β-form of keratin is unique to reptiles and birds, and is found in their claws, feathers, beaks and scales, while they also produce α-keratin in other tissues, e.g. skin. Evolutionary genetics studies have shown that β-keratinogenesis has been important in the evolution of feathers and adaptation to ecological niches (Greenwold et al. 2014).
Evaluating the antioxidant effects of human hair protein extracts
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Hui Ying Lai, Shuai Wang, Vaishali Singh, Luong T. H. Nguyen, Kee Woei Ng
With increasing interests in human hair extracts as functional materials, other intrinsic properties and potential applications are being studied. Various studies on chicken feather keratin hydrolysates have demonstrated antioxidant and antibacterial activities [11,12]. A recent work conducted by Wan et al. identified a novel antioxidant peptide from chicken feather keratin which exhibited free radical scavenging and Fe2+ chelation properties [13]. However, there have been no reports about the antioxidant activity of keratin extracts obtained from human hair thus far. The antioxidizing capability of a protein is usually derived from rich amounts of reductive or free radical scavenging amino acid side chains [14]. Amino acid analysis of extracted human hair proteins revealed that these generally contain 9–10% cysteine residues, which are the highest among known human proteins [5,15]. When extraction is done using a reductive method, the oxidized dimers of cysteines are reduced to their monomers containing active free thiol (–SH) groups [8,16,17], conferring keratin monomers and KAPs antioxidizing potential. Although the cysteine amount (14 mol %) present in chicken feather is similar to that in human hair, the keratin composition of chicken feather mainly consists of low molecular weight fractions of around 20 kDa [18]. In addition, feather keratin is reported to contain more beta-keratin, which is similar to the hard keratin which can only be found in the cuticle of human hair. Due to such differences, the antioxidant capacity of human hair extracted keratins is therefore worthy of exploration.