Keratin protein in nail plate

Keratin proteins in the nail plate are highly cross-linked fibrous proteins forming the toughest and most visible part of the nail, with high sulfur (cystine) content and organized intermediate filaments[1][4][7]. They are polymers formed from type I and II keratin heterodimers, assembled into coiled-coil structures and then into intermediate filaments (about 70 Å in diameter) that confer mechanical strength and chemical resilience to the nail plate[1][4][7]. Keratin provides the nail with its distinctive hardness, translucency, and resistance to environmental and mechanical insults[2][3][8]. While not a conventional therapeutic target, understanding nail keratin’s structure is critical for designing transungual drug delivery systems, studying nail disorders, and forensic analysis[1][4][9]. Changes in keratin composition or structure are seen in a variety of nail pathologies but are not routinely targeted by pharmacological agents.

Other names

Nail plate keratinAlpha-keratin (specifically the hard keratin type forming intermediate filaments in nails)[2][4][7]Onychin keratin (sometimes used to differentiate nail keratin from other forms, but not widely standard)[3]

Proteolytic digestion (keratinase): breaks peptide bonds in keratin structure[1]. Chemical softening (urea, salicylic acid): disrupts hydrogen and disulfide bonds, alters hydration to reduce keratin rigidity. Mechanical disruption/barrier penetration (for transungual drug delivery).