LIFE ON BIOMEMBRANES VIEWED WITH THE ATOMIC-FORCE MICROSCOPE

Since its invention in 1986, the atomic force microscope (AFM) has bec ome one of the most widely used near-field microscopes. Surfaces of ha rd samples are imaged almost routinely with atomic resolution. Soft bi ological surfaces, however, are still challenging. In this brief revie w, the AFM technique is introduced to the experimental biologist. We d iscuss recent data on imaging molecular structures of biomembranes, an d give detailed information on the application of the AFM with three r epresentative examples. One is imaging plasma membrane turnover of tra nsformed renal epithelial cells during migration in vivo, another is v isualizing a cloned and isolated potassium channel usually located in kidney, and a third is imaging macromolecular pore complexes of the nu clear envelope of aldosterone-sensitive kidney cells and of Xenopus la evis oocytes. The review ends with the conclusion that nuclear pores c an serve as birthday candles on a Guglhupf.