What is Keratin in Chemistry?

From numerous television commercials of hair oils and shampoos, it has become quite well known that keratin is found in the hair. It can be concluded that keratin is an essential protein for hair growth and development. Scientifically speaking, keratin protein is one of the families of fibrous structural proteins known as the scleroproteins. 

In vertebrates like human beings, the variant of keratin protein available is the 𝛼-Keratin. This keratin is an essential structural protein not only for the growth and development of hair but also for making up the scalp, nails, feathers, horns, hooves, calluses, claws, and outer layer of the skin. The keratin protein is also responsible for the protection of epithelial cells from stress or damage. 

Keratin Characteristics

Keratin is a structural protein which is extremely insoluble in water and organic solvents. The monomers of keratin protein come together to form bundles of intermediate filaments that are strong and tough. In reptiles, birds, amphibians, and some mammals they create a strong and unmineralized form of epidermal appendages such as hair follicles and sebaceous glands, etc. 

Usually keratin in two types: soft and hard. The softer keratin is a primitive form found in all the vertebrates whereas the harder keratin is found in the epidermis of reptiles and birds. Keratin is strong and resists digestion from digestive juices. Owing to this reason, cats regurgitate hairballs as they are unable to digest the hair keratin.  

Keratin is subdivided, based on its secondary structure, into two types of keratin: the 𝛼-Keratin and the β-Keratin. They are explained briefly as follows:

• 𝛼-Keratin: From the given introduction, it is known that 𝛼-Keratin is present in all the vertebrates and is responsible for the formation of hair, nails, feathers, horns, etc. The polypeptide chains under the influence of hydrogen-bonding are helical in this type of keratin.

• β-Keratin: On the other hand, another type of keratin, the β-Keratin is found in the nails, claws, and scales of reptiles and in the feathers, claws, and beaks of birds due to its characteristic property of being hard. Sometimes this β-Keratin is also found in the shells of reptiles such as some species of tortoise. In this type of keratin, the polypeptide chains are arranged as parallel sheets. 

Another characteristic of the structure of keratin is the composition of amino acids. Depending upon the localization of the keratin molecules in the body, the content of amino acids that make up keratin varies. Especially the cysteine residue is found to vary amongst the different structures of keratin as it is mainly responsible for the stability of the protein. An important part of the keratin structure is the formation of disulfide bridges amongst these cysteine residues. The degree of the disulfide bridge formation varies depending on the region where the keratin is present. For instance, the number of disulfide bridges in hair keratin is less than the number of disulfide bridges in the keratin present in the nails.  In many of the keratin treatment of hair keratin the main focus are these disulfide bridges. An example of this includes the chemical-based treatment in which the disulfide bonds are broken in order to provide a straight strand of hair. 

Keratin has a filamentous structure formed from the intermediate filaments. The fibers of keratin undergo a series of steps beginning with dimerization, and then further assembling into the tetramers and octamers eventually forming the filaments of unit length. These unit-length filaments are capable of annealing end-to-end into long filaments.

The length of the pure keratin fibers is dependent on the water content in it. Complete hydration of the keratin fibers increases their length by 10% to 12%. This is the reason for the growth of hair keratin and nail keratin. 

Keratin Treatment of Hair

Keratin is the building block of the filaments of strands of hair. The amount of hair keratin is indicative of the health of the hair. A decent amount of keratin shows that the hair is healthy. But owing to certain lifestyle habits such as exposure to chlorinated water in swimming pools and other places and certain unavoidable circumstances such as harmful rays from the sun, the health of the hair diminishes with the decrease in the amount of keratin. Because of this many people prefer keratin treatment to keep their hair healthy. 

Another reason for the preference of keratin treatment is stylizing of hair according to the needs, and interests of the person. For example, straightening of hair, a very common practice since the 1950s, is one of the most common uses of keratin treatment. There are many commercial products available for helping the consumers for use at home or at the salon. These products include keratin oil, shampoos, and conditioners containing keratin. One of the most common and famous products in this category is the loreal keratin products which are widely used amongst customers. As already disclosed above there are also many chemical keratin treatment techniques also available in the market that are used and applied by the consumers. Another evolving of such treatment techniques is the keratin hair spa which is some of the exclusive centers for keratin treatment. Although the opinions on the best keratin treatment vary from home remedies to professional salon techniques, the consumers are cautioned against repeated utilization in order to avoid hair damage as these can be harmful on regular use.