Measurements of s-p coordinates during the development of Euglena chloroplasts

Studies on the isolation and purification of chloroplasts from Euglena gracilis

A method has been developed for the isolation of chloroplasts from Euglena gracilis grown under mixotrophic conditions. This method utilizes sucrose density-gradient centrifugation in the AXII zonal rotor and allows the rapid preparation of large amounts of chloroplasts free from contaminating whole cells and other cytoplasmic materials. The majority of the isolated chloroplasts appear intact in phase contrast and electron micrographs. The purified chloroplast fraction contains DNA, the major species of which has a density of 1.682 g/cm(3). The species of DNA having a density of 1.707 g/cm(3) seemed to result from the presence of contaminating nuclear fragments which could be removed by isopycnic flotation.

Size-separation of yeast mitochondria in the zonal centrifuge

Mitochondria, released from yeast spheroplasts and subjected to rate separation through sorbitol gradients in the zonal centrifuge, migrated in a wide symmetrical zone. Electron micrographs showed that the mitochondria had been resolved within the zone according to size. The mean mitochondrial diameter at the leading edge was approximately twice that at the trailing edge of the particle zone. Activities of the enzymes cytochrome oxidase, malate dehydrogenase, and reduced nicotinamide adenine dinucleotide- and d-lactate cytochrome c reductases were essentially uniform throughout the mitochondrial zone. Mitochondria from a vegetative-petite mutant had almost the same size distribution as the isogenic wild type, but with somewhat larger mean diameter and either absent or markedly reduced enzyme activities. Mixtures of wild-type and petite mitochondria produced sedimentation profiles showing overlap of particle populations with respect to mean sedimentation rates and mitochondrial diameters, as well as intermediate levels of enzyme activities. Both cristate and noncristate organelles were present throughout the mitochondrial zone from these mixtures. Mitochondria centrifuged in sorbitol density gradients were well-preserved and yielded consistent sedimentation profiles, whereas particles in sucrose density gradients migrated more slowly, produced varied sedimentation profiles, and often showed spurious peaks, presumably due to particle aggregations.