Bacterial and fungal infections of cereal crops pose a considerable risk to global food security. Typically plant pathogens are controlled through the use of chemical agents including fungicides and pesticides, to which resistance is becoming widespread. Increasingly attention is now being turned to the role that naturally occurring antimicrobial proteins can play in defence against disease-causing agents. We are studying one such protein, called puroindoline, which is found in wheat. We wish to use neutron reflectivity to understand better how it penetrates the surface of microbial and fungal cells and what controls how it does this in terms of the structure of the protein and of different types of cell surfaces.