Non specific lipid transfer proteins are a family of basic, cysteine rich proteins found in a wide range of plant species. The biotechnological role of these proteins in beer and as allergens is well understood but their true role in plant biology is not. We propose to use neutron reflectometry to decipher whether lipid transport, antimicrobial activity or cutin formation best describe the activity of these proteins. To this end we plan to examine the interaction of these proteins with anionic phospholipid monolayers, to examine antimicrobial activity, with zwitterionic phospholipid monolayers, to examine lipid transport, and with fatty acid monolayers, to examine cutin formation by nsLTP's. The results obtained from this study will provide both strong evidence towards the true biological role of nsLTP's and show how neutron reflection can be used to answer complex biological questions.