Abstract: The present invention relates to an improved method for the identification and optionally the characterization of interacting molecules designed to detect positive clones from the rather large numbers of false positive clones isolated by two-hybrid systems. The method of the invention relies on a novel combination of selection steps used to detect clones that express interacting molecules from false positive clones. The present invention further relates to a kit useful for carrying out the method of the invention. The present invention provides for parallel, high-throughput or automated interaction screens for the reliable identification of interacting molecules.

Abstract: A combined objective and emission lens for a microbeam probe is described which is suitable for primary and secondary particles of the same charge sign, by which lens a bundle of primary rays of comparatively high energy can be focused on a very small spot of a plane sample surface and the secondary particles emitted by this spot can be collected into a collimated bundle of secondary rays which leaves the combined lens in a direction substantially opposite to the bundle of primary rays. In the present combined lens, the field strength between the sample surface and the lens electrode most closely adjacent to it is very high, in contrast to the known combined objective and emission lenses, so that a small emissivity of the secondary beam with a small diameter at the same time of the primary beam spot and an effective collection and collimation of the secondary particles are ensured.