Among several compounds protecting the outermost surface of mammalian hair, 18-methyl eicosanoic acid (18-MEA), a long chain fatty acid functionalised with a methyl branch at the antepenultimate carbon, is the most abundant. It is also the most intriguing as its precise function, and the role of the positioning of the methyl branch is still debated. A suggested reason for its structure is the decrease in melting temperature without the introduction of a double bond inherently prone to oxidation. In addition, a decreased packing density compared to the straight chain analogue has been proposed to better correspond to the limited number of binding sites on the underlayeing protein matrix.
The project aims to understand the intricacies of 3D domains formed by monolayers of branched fatty acids on the water surface. To probe the water-air interface, the Langmuir trough is used in combination with atomic force microscopy (AFM), neutron reflectivity (NR), and gracing incidence small angle neutron scattering (GISANS).