Puroindolines are basic cystiene rich proteins which possess unique Trp rich domains which are fully conserved in the predominant isoform Pin-a and partially in Pin-b. This family of proteins has gained considerable interest due to their role in wheat endosperm texture and plant antimicrobial defence. Previously we studied the interaction of Pin-a with floating anionic phospholipid bilayers of DPPG, finding that the protein is able to penetrate in these membrane models causing an incease in hydration across the film. This suggests that the antimicrobial acitivty of Pin-a is related to channel formation. Here we intend to examine the interaction of Pin-b with floating lipid bilayers of DPPG, attempting to compare and contrast the behaviour of Pin-a and Pin-b to better understand the antimicrobial activity of this functionally important protein family.