Electron Crystallography of Organic Molecules

Maximum Entropy (ME) techniques have found widespread applicability in the reconstruction of incomplete or noisy data. These techniques have been applied in many areas of data analysis including imaging, spectroscopy, and scattering [Gull and Skilling, 1984]. The techniques have proven particularly useful in astronomy [Narayan and Nityanada, 1984]. In many of these applications the goal of the reconstruction is the detection of point objects against a noisy background. In this work we investigate the applicability of ME techniques to data sets which have strong components which are periodic in space or time. The specific interest in our laboratory is High Resolution Electron Micrographs of beam sensitive materials. However, ME techniques are of general interest for all types of data. These data mayor may not have a spatial or temporal character. Figure 1 shows an HREM image of the rigid-rod polymer poly(paraphenylene benzobisoxazole) (PBZO). The 0.55 nm spacings in the image correspond to the lateral close-packing between the extended polymer molecules. Near the center of this crystallite there is evidence for an edge dislocation. In HREM images both the frequency and position of the infonnation is important for a proper interpretation. Therefore, it is necessary to consider how image processing affects the fidelity of this information in both real and Fourier space.

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Presented lectures.- Electron diffraction structure analysis of organic crystals..- Crystal structures by electron diffraction: diacetylene monomers and polymers in Langmuir-Blodgett films and single crystals..- Observation of hexatic behaviour in liquid crystals In Situ electron diffraction..- A priori crystal structure modeling of polymeric materials..- Specimen orientation and environment..- Electron diffraction of polymer single crystals..- The prediction of the crystal packing of organic molecules: geometry and intermolecular potentials..- A theoretical technique for layer structure prediction..- Electron microscopy and molecular modelling of some Langmuir-Blodgett films..- Maximum entropy reconstruction of low dose, high-resolution electron microscope images..- The achievement and limitation of high resolution-high voltage electron microscopy..- Crystal structures from high-resolution electron microscopy..- Electron crystallography of radiation-sensitive polymer crystals..- High resolution electron microscopy on VH amylase crystals..- High resolution electron microscopy on liquid crystaline polymers..- Scanning tunnelling microscopy of surface structures..- Polymer decoration:recent developments..- Epitaxial growth of octacyanometalphthalocyanine-metal complex crystals..- Epitaxial crystal growth on organic and polymeric substrates..- Solving difficult structures including those from powder and electron diffraction data. (Lecture in joint session with Direct Methods meeting)..- Direct phase determination in the electron crystallography of organic compounds. (Lecture in joint session with Direct Methods meeting)..- Structure determination at atomic resolution by electron crystallography..- Electron crystallography of bacterial surface proteins..- Structure of hydrogenase from Thiocapsa Roseopersicina..- Cryoelectron microscopy of protein crystals.Some remarks on the methodology..- Electron crystallographic analysis of reconstituted PhoE porin..- Concerning the surface lattice of microtubules..- Correlation averaging and filtering of electron micrographs..- Electron crystallography in an industrial laboratory..- The structure analysis of an organo-azo-calcium salt by high resolution electron microscopy and image processing..- Radiation damage in electron crystallography..- Electron beam damage in polyethylene(PE) single crystals..- An analysis of the broadening induced by beam damage in transmission electron diffraction spots from an oriented aliphatic monolayer..- Discussion session..