To quantify the effects of the presence of water on each surface, the distribution of water density in each system was measured. Overlapping densities of water and the KAP5-1 layer indicate water penetration through the substrate following rearrangement of the fatty acid layer (Supplementary Figure ). For the virgin hair system, density plots showed a transition from a near flat 18-MEA layer to a clustered, cylinder-like structure (Figure ). Visual inspection of the hair model surface in the presence of water showed reorganization of the 18-MEA layer, exposing the KAP5-1 layer beneath (Figure ). This behavior was also seen in the lightly and moderately damaged models. Covalently attached 18-MEA, in the presence of water, is no longer able to remain disordered due to the hydrophobic effect. Formation of nanodomains of 18-MEA minimizes surface area exposure for each lipid through favorable Van der Waals interactions, but at the expense of increasing exposure of the protein layer to water. Previous simulations noted water penetration but not beyond the graphene sheet . An advantage of our model is that water penetration can be studied within the protein layer. Given the large number of hydrophilic residues in KAP5-1, water permeation is energetically favorable and slightly increases as a function of damage (Figure ). This is corroborated by a study of moisture isotherms of virgin and partially deaminated wool fibers, where the authors concluded reduction of amino and guanidino groups was responsible for water adsorption on the surface .