The puroindoline (PIN) and purothionin (PTH) families of polypeptides both occur in wheat and are implicated in antipathogenic defence mechanisms, and of interest for potential uses for increasing the pathogenic resistance of transgenic crops and as topical antibiotics. PINs and PTHs are co-localised in the wheat seed, which raises the possibility of cooperative activity against pathogens. It is our hypothesis that different numbers of Trp residues in PIN isoforms and mutants alters their effectiveness as lipid binding proteins in the presence of PTHs. Neutron reflectometry measurements will enable the quantitative observation of the level of penetration of proteins into air/liquid lipid monolayer models. This will enable us to determine the inhibitive or cooperative effects of co-adsorption and sequential adsorption of these proteins.