Crystallization of Antimicrobial Pores in Membranes: Magainin and Protegrin

Membrane pores spontaneously formed by antimicrobial peptides in membranes were crystallized for the first time by manipulating the sample hydration and temperature. Neutron diffraction shows that magainins and protegrins form stable pores in fully hydrated fluid membranes. At lower hydration levels or low temperature, the membrane multilayers crystallize. In one crystalline phase, the pores in each bilayer arrange in a regular hexagonal array and the bilayers are stacked into a hexagonal ABC lattice, corresponding to the cubic close-packed structure of spheres. In another crystalline phase, the bilayers are modulated into the rippled multilamellae, corresponding to a 2D monoclinic lattice. The phase diagrams are described. Crystallization of the membrane pores provides possibilities for diffraction studies that might provide useful information on the pore structures.