MACROMOLECULAR SUBSTRUCTURE IN NUCLEAR-PORE COMPLEXES BY IN-LENS FIELD-EMISSION SCANNING ELECTRON-MICROSCOPY

Scanning electron microscopy (SEM) has produced a wealth of novel imag es that have significantly complemented our perception of biological s tructure and function, derived initially from transmission electron mi croscopy (TEM) information. SEM is a surface imaging technology, and i ts impact at the subcellular level has been restricted by reduced reso lution in comparison with TEM. Recently, SEM resolution has been consi derably improved by the advent of high-brightness sources used in fiel d-emission instruments (FEISEM) which have produced resolution of arou nd 1 nm, virtually equivalent to TEM ''working resolution.'' Here we r eview our findings in the use of FEISEM in the imaging of nuclear enve lopes and their associated structures, such as nuclear pore complexes, and the relationships of structure and function. FEISEM allows the st ructurally orientated cell biologist to visualise, directly and in thr ee dimensions, subcellular structure and its modulation with a view to understanding its functional significance.