Scanning force microscopical studies of the Na⁺/K⁺-ATPase

Abstract

Scanning Force Microscopy (SFM) is an imaging technique, that can resolve features on a nanometer scale on both conducting and non-conducting surfaces. This advantage was almost immediately used to scan organic surfaces like crystals of amino acids (1) or organic monolayers (2). To extend the method onto biological material was close at hand and first examples have been blood cells and bacteria (3). Especially the purple membrane which consists of crystalline arrays formed by a single proton pumping protein, bacteriorhodopsin, was investigated extensively. Its crystalline arrangement has been characterized by various techniques and it was known how the structure “looks like”. Therefore, these preparations are crucial to get information about the capabilities of SFM. Bacteriorhodopsin has been scanned in dried form on lysine-coated glass and on mica (3, 4) and in buffer solutions (5). The observed lattice constant was in agreement with results of electron diffraction experiments. A recent review of the application of the SFM technique is provided in Ref. 6. A second integral membrane protein, investigated by SFM, was the Na⁺/K⁺-ATPase (7). In this paper, results are presented which were obtained from membrane fragments with two-dimensional crystalline arrays of Na⁺/K⁺-ATPase molecules.