title: Towards an alignment of the actin molecule within the actin filament.
abstract: Electron micrographs of negatively stained actin filament paracrystals and single-layered filament rafts showing different interfilament spacings have been studied and three-dimensional reconstructions have been computed from them. Lateral ordering of the filaments in rafts was lost when interfilament spacings exceeded 8.5 nm, suggesting this distance as an upper limit for the filament diameter. Further, all reconstructions showed the same structural features at the 3 nm resolution level, except that the filaments from ordered single-layered rafts appeared 10-20% wider than those from multi-layered paracrystals. A comparison between electron microscopical and X-ray filament data, and synthetic filaments generated using different tentative molecular models and/or orientations for actin did not allow a single best model to be selected.
mesh_terms: D000199:Actins; D000656:Amoeba / Q000648:ultrastructure; D000818:Animals; D003461:Crystallography / Q000379:methods; D003599:Cytoskeleton / Q000648:ultrastructure*; D046911:Macromolecular Substances; D008854:Microscopy, Electron / Q000379:methods; D008954:Models, Biological; D009132:Muscles / Q000648:ultrastructure; D011817:Rabbits
chemical_list: D000199:Actins; D046911:Macromolecular Substances