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Keratin: Nature’s remarkable protein

Read time: 2 mins

What is the one thing that is common among the colourful feathers of birds, the long claws of a tiger, the prized horn of a rhinoceros, the antlers of a feer, the scales of the pangolin, the fine wool of the cashmere goat, or Rapunzel’s super long hair? Did this question get you to scratch your head or bite your nails? It’s there too! It’s the ubiquitous protein keratin found in the skin or epithelial cells of vertebrates. Keratin is one of the strongest materials in nature. The only other tissue that resembles the toughness of keratin is chitin, the material found in the exoskeleton of insects and the outer shell of shellfish.

Structurally, keratin is fibrous and has a very high concentration of cysteine, a sulphur-containing amino acid. When you burn hair, the pungent smell that you sense is of this sulphur. The sulphur bonds present within and between the molecules provide the strength and elasticity we see in human hair or wool. Keratin is present in two forms—α-keratin and β-keratin. The former is found in soft tissues like skin, hair and sheep wool, while the latter is present in hard tissues like horns, feathers, claws or hooves. Keratin is also resistant to digestive acids in the stomach, and hence, carnivores that eat fur or hair throw it out as hairballs. Rhino horn, which is also just keratin but is claimed to have medicinal values in traditional Chinese medicine, will also be excreted as is!

Since keratin is a natural protein that is compatible with our body and enzymes do not degrade it, scientists are exploring its applications as biomaterials. They use keratin from human hair to build three-dimensional scaffolds for growing cells and regenerating tissues in a lab and as wound-healing agents used in topical creams and cosmetic uses. The elasticity and strength of keratinous structures like wool and hair are used to make super-strong fibres and ‘smart’ fabrics that retain their shape and form. Analysis of keratin in the hair also reveals ancient diets of humans and animals and is used in forensic sciences to determine causes of death. Who knew the protein in our treasured tresses was capable of so many wonders!