Hair is an important biomaterial primarily consisting of protein, notably keratin. It grows on most areas of the body except for the palms and soles of the feet, but is most noticeable on parts of the head, neck, arms and legs. It can be straight, wavy or curly and can vary in colour. It also goes through many changes as we age, including turning grey or losing colour. Generally, shiny, smooth, well-maintained hair is perceived as healthy.
However, it is not only the appearance that we care about; hair plays an important role in our lives. It can be an indicator of biological sex, age or ethnic ancestry, as well as have cultural significance, for example in the form of a headscarf or turban. Unfortunately, it is also often used as a source of stereotypes about a person and this can be damaging to those who are subjected to such stereotypes.
As such, it is important for scientists to understand how this important biological material works in order to be able to assess the impact of genetic, environmental and other factors that may have an effect on its structure. For this, X-ray diffraction has been shown to be a useful tool for analysing the molecular composition of hair.
Using this technique, the keratin of hair samples from different individuals has been studied in detail. It was found that there is a significant variation in the molecular structure of hair, even within the same individual. This is due to the fact that hair contains a coiled-coil phase, which results in differences in the diffraction pattern observed.
In addition, the lipids present in the cell membrane complex also exhibit a wide range of scattering patterns, ranging from lamellar structures at spacings of around 45 A to rings at q-values of about 4.3 A, corresponding to the order in which they are arranged within the layers.
In the study, hair samples were collected from 12 healthy individuals of various characteristics and compared to each other. It was found that, despite this variation in the molecular structure, there is a good correlation between the optical appearance of the hair and its genetic relation to the other samples analysed. This makes it possible to identify a number of features relating to a specific hair type or to its condition, such as the presence of dandruff. These features could potentially be used to identify individuals with conditions that might cause them to suffer from hair loss or other cosmetic problems such as brittleness or thinning of the hair. They might also be used to diagnose certain diseases affecting the hair shaft such as alopecia areata or lupus. This information can be useful for determining which treatments might work best for each individual in order to achieve the most desirable results. These include a reduction in shedding, and an improvement in the texture of the hair, thereby making it softer or more resilient. This might help reduce the risk of damage during daily wear and tear, such as in hair brushes or in hair dyes.