If, ten years ago, one had been asked to comment on the prospects of peering into the fmest details of biomolecular organization, most electron microscopists would, I suppose at least, have been quite en­ thusiastic. When, during the early seventies, several groups were success­ ful in visualizing single heavy atoms, which undoubtedly was a techni­ cal triumph, this prompted the most sanguine expectations among bi­ ologists. In the following years, however, it began to transpire that radiation damage might impose limitations preventing us from taking full advantage of these exciting instrumental feasibilities. Fortunately, the radiation damage nightmare did no paralyze further activities, and it was in particular the work on the purple membrane which, brilliant­ ly exploiting the redundancy stratagem, revealed exhilarating new perspectives. Now, almost five years later, it seemed timely and appro­ priate to organize an international symposium to discuss and weight recent activities and current trends in "molecular microscopy". In planning this symposium, we selected topics according to our view of what is important or will deserve more attention in the near future. Taking into consideration suggestions made by the invited participants, some supplementary aspects were included; as a conse­ quence, the program developed somewhat beyond the scope as adum­ brated by the original title of this meeting (Regular 2-D Arrays of Biomacromolecules: Structure Determination and Assembly). As the meeting was organized, we had three morning sessions aimed at reflecting the "State ofthe Art".

Inhalt

State of the Art.- Matrix Porin: a Periodically Arranged Pore Protein in the Outer Membrane of Escherichia coli.- Structure of the HPI-Layer of Micrococcus radiodurans.- Morphological Model of the Surface-Layer Array in Spririllum serpens.- The 2-d Crystalline Cell Wall of Sulfolobus acidolarius: Structure, Solubilization, and Reassembly.- The Dynamic Process of Assembly of Two-Dimensional Arrays of Macromolecules on Bacterial Cell Walls.- The Two-Dimensional Lattice of the Photosynthetic Membrane of Rhodopseudomonas viridis.- Diffraction Studies of Modified Purple Membrane.- Formation of a New 2-D-Crystalline Form of Purple Membrane with Orthorhombic Lattice.- Ultrahigh Vacuum Freeze-Fracturing at -196°C and Decoration of Specific Sites of Paracrystalline Membranes.- The Structure of Cytochrome c Oxidase: Immuno-Electron Mircroscopy and Image Analysis of Two-Dimensional Crystals.- Structure of Cytochrome Oxidase Vesicle Crystals.- Membrane Crystals of Ubiquinone: Cytochrome C. Reductase from Neurospora Mitochondria.- Structural Analysis of Stained und Unstained Two-Dimensional Ribosome Crystals.- Subunit Structure and Conformations of Tubulin Protofilaments.- The Role of a Scaffolding Core in the Assembly of the Bacteriophage T4 Head Shell Lattice.- Electron Diffraction Study of Crotoxin Complex at 1,6 Å.- High Resolution Electron Microscopy on Peptidoglycan.- Low-Dose Electron Microscopy of Individual Biological Macromolecules.- Image Averaging of Membrane-Bound Acetylcholine Receptor from Torpedo marmorata.- Image Recording.- Current State of Biological Scanning Transmission Electron Microscopy.- The Electron Utilization Efficiency in STEM.- Low-Dose Image Recording by TV Techniques.- Evaluation of Photographic Emulsions for Low-Exposure Imaging.- Properties of Commercial Films for Electron Microscopy.- Low Temperature Microscopy.- Electron Microscopy at Liquid Helium Temperature.- Use of Low Temperatures for Electron Diffraction and Imaging of Biological Macromolecular Arrays.- Reduction of Radiation Damage by Imaging with a Superconducting Lens System.- Image Processing.- Matching and Averaging over Fragmented Lattices.- On the Stretching of Distorted Images of Two-Dimensional Crystals.- Methods for Averaging of Single Molecules and Lattice Fragments.- The Reconstruction of Structure from Electron Micrographs of Randomly Oriented Particles.- Comments on Three-Dimensional Reconstructions and Averaging.- Some Unsolved Problems and Promising Methods in Electron Image Processing.- Chairman's Account of the Discussion During the Session on Image Processing.- Artificial Assembly of 2-D Arrays.- Crystallization Processes of Biological Macromolecules.- Self-Assembly and Nucleation of a Two-Dimensional Array of Protein Subunits.- A. Simple Way of Making a 2-D Array.- The Principles of Governing Particles Aggregation im Membranes.- Assembling of Proteins at Lipid-Monolayers.