Hair, nails… just a couple of items on the beauty checklist. Whether it’s a long-awaited date or night out with the pals, hair and nails are often top priority! It’s strange to think that one essential molecule, keratin, is a key component to them both. And what makes it so important? We’ve got the low down to help you detangle the confusion around keratin.

The Molecular Stuff
Keratin is a fibrous protein found throughout the whole animal kingdom, leading a double life as α-keratin or β-keratin. Although they are created from the same basic string of amino acids, they are folded slightly differently to give them different traits. β-keratin (or beta keratin) found in beaks, hooves and feathers is in a sheet structure , but it is α–keratin (or alpha keratin) that is the most common form of keratin in the human body.

Alpha keratin gets its strength from its coiled-coil structure. This just means that the protein is not only wound into a helix, but is then wound round itself again. This is kind of like how a rope is made up (see the picture below!). This super strong structure is held together by disulphide bonds (bonds between two sulphur atoms). These special bridges form between cysteine amino acids (these contain sulphur), and cysteines actually make up a large proportion of keratin. We have this shape shifter of a protein to thank for making up a large portion of our hair, nails and the epidermis layer of our skin.

Keratins have been grouped in many different ways and are actually split into a further 80+ types named K1, K2, K3… you get the picture. Each is coded by a different gene and they have slightly different properties and are expressed in slightly different places in the body. Although it is relatively well known that keratin makes up a large component of hair, few people know that is it actually in the lining of our blood vessels, liver cells and cornea (the front of the eye). This is because, just like humans, cells have their own skeleton like structure called the ‘cytoskeleton’ which helps them keep their shape. Keratin makes up part of this cytoskeleton.

More Molecular Stuff – Soft and Hard Keratin
Just when you thought we had finished with the groupings, keratin can be sorted again into ‘soft’ keratin and ‘hard’ keratin. Soft keratin is found in the epidermis layer of the skin and is characterised by fewer disulphide bonds which increases the flexibility of the protein. Soft keratin is much more malleable and can flex back into shape when your skin is stretched.

Hard keratin is the type that makes up your hair and nails. These keratins have a higher density of cysteine amino acids, so more sulphurs to makedisulphide bonds, which make them very strong but unfortunately relatively brittle. Hair especially is very easily damaged by UV light, chemicals, heat or even mechanical damage from running your hands through it too often (you’ll have to tell prince charming to go easy on the luscious locks!). These things alter the disulphide bonds which give keratin its definitive strength so should be avoided or minimised wherever possible.

Nails might look completely different from hair but they are just lots and lots of layers of keratin. The only reason they are more durable than hair strands, is because they contain more keratin. Nails are protection for our fingertips and can be used as tools so they need to be stronger and more reliable than our hair.

The Cosmetic stuff – Hair Type
So if all hair is made up of the same protein then why does everyone have different hair? Keratin is not the only component of hair, just like it’s not the only component of skin. It works alongside other proteins. A lot about hair type is down to genetics altering the amount of melanin (pigment) present or the amount of hydrogen bonds. Hydrogen bonds between amino acids in keratin also contribute towards hair’s curl (and to frizz as well!).

The Cosmetic Stuff – Topical Keratin Application to Skin
Keratin is a huge molecule, too big to penetrate our skin, so for it to be effective in skincare or other cosmetic applications it must be hydrolysed. This means, the keratin must be broken down using water. Studies have shown that hydrolysed keratin can penetrate the skin and act as a moisturiser to help retain water hence the spongeyness of youthful skin. Wise Beauty Geeks will note that this keratin doesn’t magically integrate itself into the keratin in your skin to reinforce its structure, so don’t be led astray by claims of doing so!

The Cosmetic Stuff – Keratin Shampoos
Keratin is in the outer layer of the hair shaft, the hair cuticle, and hence is easily exposed to damaging factors which interfere with the cysteine amino acids that give keratin its resilient legacy. Keratin shampoos are meant to fill in any spaces in the cuticles to add more structure and strength to hair and to minimise entry of harmful chemicals which could interfere with the disulphide bonds, but we couldn’t find any evidence that these keratin molecules do help reinforce the hair’s structure itself. Whether or not keratin shampoos enhance hair growth is also uncertain – there is no concrete proof. If these shampoos do somehow strengthen the hair, reducing breakage and split ends may lead to a perceived hair length increase, but we’re certainly not sold on this science.

The Cosmetic Stuff – Keratin Hair treatments
Many people think keratin treatment is a permanent straightening treatment but the
Geeks are here to bust that myth. Keratin treatment is designed to fill in spaces in the hair cuticle to have a smoothing effect. The real results are often hair that is less frizzy and less curled, but often a slight wave still remains. There isn’t really any hardcore research on its mechanism, but one potential reason is that with the keratin less exposed fewer hydrogen bonds are made in the hair, meaning less curl. Keratin treatments works differently for different hair types and should be used with caution. Some formulas contain harmful formaldehyde and other chemicals so it is very important that you research further before considering this treatment.

‘The Structure of People’s Hair’ 2014
The human keratins: biology and pathology’
‘Cosmetic effectiveness of topically applied hydrolysed keratin peptides and lipids derived from wool’
‘Redox proteomic evaluation of bleaching and alkali damage in human hair’
‘Keratins – the hair’s shaft revealed’
‘Acidic and Basic Hair/Nail (“Hard”) Keratins: Their Colocalization in the Upper Cortical and Cutile Cells of the human hair follicle and their relationship to “Soft Keratins”
‘Keratins: Proteopedia Life in 3D’

Images: https://courses.candelalearning.com/apvccs/chapter/integumentary-levels-of-organization/, http://blogs.unimelb.edu.au/sciencecommunication/2013/10/21/chemistry-of-cosmetics-part-ii/