PubMed · 1939504
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D Lamy. 1991. A microcomputer program simulating rate zonal centrifugation.. https://doi.org/10.1016/0166-0934(91)90015-r
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The scanning tunnelling microscope has been used to image 16S ribosomal RNA molecules in water electrophoretically deposited on graphite surface. Two kinds of images have been obtained: images showing aggregates of 16S ribosomal RNA molecules similar to those obtained from DNA solutions and others showing individual 16S ribosomal RNA molecules. An interesting characteristic of these images, recorded in constant current mode, is that the 16S ribosomal RNA molecules appear to be located below the graphite surface. The morphology and several structural parameters of the molecules were consistent with the data obtained from electron microscopy.
PRD1 is a dsDNA virus that infects Escherichia coli and Salmonella typhimurium. The genome is a linear molecule with 5' covalently linked terminal protein. The virus has a lipid membrane inside the protein coat. We describe the large-scale purification of the virus using a zonal rotor and the yields and quality of the virus and its subviral assemblies for subsequent biophysical measurements.
Although peroxisomes are difficult to identify in Saccharomyces cerevisiae under ordinary growth conditions, they proliferate when cells are cultured on oleic acid. We used this finding to study the protein composition of these organelles in detail. Peroxisomes from oleic acid-grown cells were purified on a discontinuous sucrose gradient; they migrated to the 46 to 50% (wt/wt) sucrose interface. The peroxisomal fraction was identified morphologically and by the presence of all of the enzymes of the peroxisomal beta-oxidation pathway. These organelles also contained a significant but minor fraction of two enzymes of the glyoxylate pathway, malate synthase and malate dehydrogenase-2. The localization of malate synthase in peroxisomes was confirmed by immunoelectron microscopy. It is postulated that glyoxylate pathway enzymes are readily and preferentially released from peroxisomes upon cell lysis, accounting for their incomplete recovery from isolated organelles. Small uninduced peroxisomes from glycerol-grown cultures were detected on sucrose gradients by marker enzymes. Under these conditions, catalase, acyl-coenzyme A oxidase, and malate synthase cofractionated at equilibrium close to the mitochondrial peak, indicating smaller, less dense organelles than those from cells grown on oleic acid. Peroxisomal membranes from oleate cultures were purified by buoyant density centrifugation. Three abundant proteins of 24, 31, and 32 kilodaltons were observed.