Eukaryotic cells envelop their genetic material in the cell nucleus whose boundary contains numerous pores. Only small molecules can pass through these nuclear pores unhindered. For all larger ones, passage is highly selective and controlled. The control involves import and export proteins (transport receptors) that load and release cargo on the proper side of the nucleus upon interaction with signaling proteins. Researchers are presently solving the structure of the nuclear pore and its transport receptors with increasing resolution, and the first atomic level investigation into the mechanism of nuclear pore selectivity has recently been reported [paper]. The study inspected the interaction between the transport receptor importin-β with key nuclear pore proteins that appear disordered near the center of the pore and contain characteristic phenylalanine-glycine sequence repeats. Molecular dynamics simulations using NAMD and analyzed using VMD revealed a key insight into the selectivity mechanism. The simulations showed that the key sequences of the repeat proteins interact strongly with certain spots on the surface of importin-β. The study confirmed spots that had previously been identified experimentally and, moreover, found numerous binding spots not yet seen in experiment. Further experiments and simulations promise an understanding of the selectivity of entry and exit from the nucleus, a key element of the cell's genetic control. For more information see our nuclear pore complex webpage.