Fig. 5. Adjacent nuclear pore complexes are connected by branching filaments that exhibit a right-handed periodicity. (A,B) Filaments of 40 nm diameter are seen to interconnect groups of neighboring nuclear pore complexes (circled). (C) Higher magnification view of a pore-linked filament with pronounced periodicity (arrows indicate repeat elements). (D) Filaments attached to the nuclear envelope extend deep into the nucleus, branching and forming junctions (arrows).