Molecular Mobility in Keratin-Rich Materials Monitored by Nuclear Magnetic Resonance: A Tool for the Evaluation of Structure-Giving Properties

Keratins are structural proteins that are abundant inhuman skin,nails, and hair, where they provide mechanical strength. In the presentstudy, we investigate the molecular mobilities and structures of threekeratin-rich materials with clearly different mechanical properties:nails, stratum corneum (upper layer of epidermis), and keratinocytes(from lower layer of epidermis). We use solid-state NMR on natural-abundance C-13 to characterize small changes in molecular dynamics inthese biological materials with close to atomistic resolution. Onestrong advantage of this method is that it detects small fractionsof mobile components in a molecularly complex material while it simultaneouslygives information on the rigid components in the very same sample.The molecular mobility can be linked to mechanical material propertiesin different conditions, including hydration or exposure to osmolytesor organic solvents. Importantly, the study revealed that the responseto both hydration and addition of urea is clearly different for thenail keratin compared to the stratum corneum keratin. The comparativeexamination of these materials may provide a better understandingof skin diseases originating from keratin malfunction and contributesto the design and development of new materials.

Automated summary

The study investigates the molecular mobilities and structures of keratin-rich materials in the human body, such as skin, nails, and hair. The research reveals that different materials have different responses to hydration and addition of urea, which contributes to a better understanding of skin diseases and the development of new materials.