Nuclear envelope permeability measured by fluorescence microphotolysis of single liver cell nuclei

Fluorescence microphotolysis ("photobleaching") has been widely used to measure translational diffusion coefficients of lipids and proteins in cell membranes. This communication shows that fluorescence microphotolysis can be also employed for measurement of membrane transport in single cells and organelles. The influx of fluorescently labeled dextrans of graded molecular size into leaky human erythrocyte ghosts and isolated rat liver cell nuclei has been measured. For the nuclear envelope, a functional pore radius of 56-59 A is derived.