High-Resolution Imaging of the Nuclear Pore Complex by AC Scanning Force Microscopy

Abstract

The lateral resolution attained by scanning force microscopy, (SFM) on disordered membrane protein structures is often, limited. We have imaged one such structure – the nuclear pore complex, on chemically fixed nuclear envelopes isolated from Xenopus oocytes, optimizing procedures to maximize lateral resolution. The images, obtained in air using acoustic tapping, reveal NPC-associated nucleoplasmic and cytoplasmic features with a resolution approaching that of field emission in-lens scanning electron microscopy. Some of the features have hitherto evaded detection by SFM. We also demonstrate the usefulness of phase imaging and show that, with scanning parameters set appropriately, the contrast is dominated by surface topography. The results obtained confirm and substantiate previous EM and SFM data and illustrate the applicability of chemical fixation and oscillating force microscopy to image large disordered membrane protein structures at high spatial resolution.