Growth of protein 2-d crystals on supported planar lipid bilayers imaged in situ by AFM

Theories of crystallization, both in 3-D and 2-D, are still very limited, mainly due to the scarcity of experimental approaches providing pertinent data on elementary phenomena. We present here a novel experimental approach for following, in real time and in situ, the process of 2-D crystallization of proteins on solid supports. Using annexin V as a model of a protein binding by affinity to a lipid matrix, we show that 2-D crystals of proteins can be formed on supported planar lipid bilayers (SPBs). Atomic Force Microscopy (AFM) enables the process of 2-D crystal growth to be visualized. The submolecular organization of the crystals was characterized at a resolution of similar to 2 nanometers, and defects, hitherto not observed in protein crystals, were resolved. These results have potential applications in basic and applied sciences. (C) 1998 Academic Press.