Lars-Goran Ofverstedt

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Structures in situ of individual ribosomes in E. coli have been determined by computer-aided electron microscope tomography using a tilt series of positively stained embedded cellular sections. Amino acid starvation of a bacterial culture, causing a deficiency for aminoacyl-tRNA, induces a spatial separation between the ribosomal subunits compared with(More)
We have developed a least-squares refinement procedure that in an automated way performs three-dimensional alignment and averaging of objects from multiple reconstructions. The computer implementation aligns the three-dimensional structures by a two-step procedure that maximizes the density overlap for all objects. First, an initial average density is built(More)
In structural studies of proteins, the first task is to identify the different parts of the protein. We present a robust method using a fuzzy framework for delineating a protein and to identify its parts. The method is used in a study of the immunoglobulin G antibody, individually imaged using cryo electron tomography, with satisfactory results.
—Two-Dimensional (2D) Discrete Fourier Transform (DFT) is a basic and computationally intensive algorithm, with a vast variety of applications. 2D images are, in general, non-periodic, but are assumed to be periodic while calculating their DFTs. This leads to cross-shaped artifacts in the frequency domain due to spectral leakage. These artifacts can have(More)
Electron microscope tomography was used to reconstruct three-dimensionally the configuration of heavy metal staining in bovine intradural spinal root myelin. Samples were fixed with glutaraldehyde, exposed to osmium tetroxide, embedded, thin sectioned, and finally stained with uranyl-acetate and lead citrate. Reconstructions up to 4.2 nm resolution showed a(More)
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