Figure 2.

Example of a typical import measurement. At zero time, a microchamber containing an isolated and purified nucleus was loaded with a transport medium containing the green fluorescent NLS protein P4K (480 kDa) as transport substrate, the red fluorescent control substrate Texas red-labeled dextran of 70 kDa (TRD70) as well as karyopherins α2 and β1, an energy mix, and, for osmotic balancing, BSA. It can be seen that the transport substrate rapidly accumulated at the nuclear periphery. At initial stages of import, a concentration gradient between nuclear periphery and center existed that dissipated within approximately 30 min. The control substrate was excluded from the nucleus, indicating that NPC and nuclear membranes had remained intact.