Abstract
Keratin extracts and hydrolysates from varying sources, their chemical modifications and compositions thereof have shown potential in the restoration of hair properties. Within this study on reactivity of thiol groups and the shielding effect of anionic charges the binding of keratin-associated proteins (KAP) and α-keratins (Ker) extracted from human hair to natural and permed hair fibers was evaluated. Selectively extracted KAP and Ker were preactivated with 6-mercaptonicotinamide in a quantity of 194 ± 21 μmol/g for KAP and 169 ± 27 μmol/g for Ker resulting in 1.9- and 1.4-fold enhanced binding to natural hair, respectively. The amount of accumulated Ker on hair fibers was furthermore increased by 1.7-fold in presence of 25 mM L-arginine. Perming of hair impaired binding characteristics of Ker with negligible effects for preactivation, whereas unmodified and preactivated KAP showed results comparable to natural hair. Strongly enhanced penetrability after perming was reflected by the mean penetration depth for fluorescein of 25 μm compared to 5 μm for natural fibers.
Highlights
Besides environmental influences like UV-light, cosmetic treatments of hair such as bleaching, dyeing, permanent waving, or grooming count to the main causes of hair damage associated with alterations in the surface architecture of the highly keratinized fibers [1]
Hard keratins in human hair can be distinguished in highly cross-linked α-keratins forming intermediate filaments that are further organized in micro- and macro-fibrils, β-keratin located in the cuticle as well as γ-keratins
As formation of aggregates and films on hair fiber surface was reported [7,12] these interactions between α-keratins and keratin-associated proteins (KAP) may affect the overall performance of keratin binding
Summary
Besides environmental influences like UV-light, cosmetic treatments of hair such as bleaching, dyeing, permanent waving, or grooming count to the main causes of hair damage associated with alterations in the surface architecture of the highly keratinized fibers [1]. Displaying the main proteinaceous constituent with about 80% of total hair mass, keratin gives the fiber its distinct mechanical strength, flexibility and durability due to its high cysteine content and pronounced ability to form inter- and intramolecular disulfide bridges [4,5]. Hard keratins in human hair can be distinguished in highly cross-linked α-keratins forming intermediate filaments that are further organized in micro- and macro-fibrils, β-keratin located in the cuticle as well as γ-keratins. The latter are known as matrix proteins or keratin-associated proteins (KAP) and form the non-filamentous matrix [6]
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