Figure 1.

Schematic of the nuclear envelope. The outer nuclear membrane (ONM) and inner nuclear membrane (INM) form a double-membrane system that separates nuclear contents from the cytoplasm. Nuclear pore complexes bridge this system and regulate nucleo-cytoplasmic exchange of macromolecules. Further attachments to many other proteins make purification of individual compartments difficult.

Schirmer and Gerace Genome Biology 2002 3:reviews1008.1-reviews1008.4   doi:10.1186/gb-2002-3-4-reviews1008