In the resulting slabs, each outward (surface) facing beta turn loop contains three candidate cysteine residues which can be covalently attached to an 18-MEA molecule via a thioester linkage (cf. Figure ). The number of 18-MEA bound to these cysteine sites therefore dictates the concentration of 18-MEA in the F-layer. At this point, the thickness of the protein-18-MEA layer model is of approximately 75 Å. Since the content of 18-MEA on the hair surface is directly linked to the level of damage in the hair fiber, we decided to test different 18-MEA/β-sheet connectivity configurations to evaluate the surface interactions of hair models under three different damage degrees. In the first configuration, termed 'virgin hair', the pristine conditions of a hair surface are modeled considering all three cysteine residues covalently bonded to 18-MEA molecules. In another configuration, named 'lightly damaged', a small degree of damage to the hair fiber is emulated by considering the bonding of two 18-MEA molecules onto the available cysteine sites and converting the third outermost cysteine site of each β-sheet to cysteic acid. The third surface configuration, named 'moderately damaged', contained one 18-MEA linkage and two cysteic acids per KAP5-1 beta sheet. Additionally, it is known that free 18-MEA is present among the covalently attached 18-MEA. Therefore, we added 9 free 18-MEA near each face of the protein slab.