AUTOMATION OF SPECIMEN SELECTION AND DATA-ACQUISITION FOR PROTEIN ELECTRON CRYSTALLOGRAPHY

A system is presented for semi-automatic specimen selection and data a cquisition for protein electron crystallography, based on a slow-scan CCD camera connected to a transmission electron microscope and control from an external computer. Areas of interest on the specimen are loca lised at low magnification and subsequently imaged on the CCD camera, using a dose which is small compared to the dose used in the exposure mode. The crystalline quality of the area is evaluated from the appear ance of diffraction peaks in the calculated image Fourier transform. I f the quality is considered good, images can then be recorded in diffe rent modes, both on film and using the CCD camera. Using this system a significant gain, both quantitatively and qualitatively, can be obtai ned in acquiring data for electron crystallography of beam-sensitive m aterials. (C) 1998 Elsevier Science B.V. All rights reserved.