MOLECULAR RESOLUTION IMAGING OF MACROMOLECULAR CRYSTALS BY ATOMIC-FORCE MICROSCOPY

Atomic force microscopy (AFM) images at the molecular level have been obtained for a number of different protein and virus crystals. They ca n be utilized in some special cases to obtain information useful to cr ystal structure analyses by x-ray diffraction. In particular, question s of space group enantiomer, the packing of molecules within a unit ce ll, the number of molecules per asymmetric unit, and the dispositions of multiple molecules within the asymmetric unit may be resolved. In a ddition, because of the increasing sensitivity and resolution of the A FM technique, some molecular features of very large asymmetric units m ay be within reach. We describe here high-resolution studies, using AF M, to visualize individual molecules and viruses in their crystal latt ices. These investigations included fungal lipase, lysozyme, thaumatin , canavalin, and satellite tobacco mosaic virus (STMV).