C.A. Price

A membrane method for determination of total protein in dilute algal suspensions

Abstract We have adapted the Lowry method to the determination of algal proteins collected on membrane filters. When cells of Euglena gracilis were analyzed the yield of protein was linear with cell amounts to 400 μg. The error of repeatability was 3 μg, and the recovery > 98%.

Equivolumetric gradients for zonal rotors: separation of ribosomes.

Abstract We have described a gradient shape for zonal rotors in which the volume through which a particle migrates is proportional to time and to the sedimentation coefficient of the particle. Such gradients are the sectorial analogs of the isokinetic gradients of swinging-bucket rotors. We propose to call these equivolumetric gradients. We have tested resolution in these gradients with Euglena ribosomal subunits and polysomes, and found it superior to that of comparable isometric or linear gradients. Broadening of particle zones is independent of particle size and the volumetric distance migrated, but depends on the time of centrifugation and on the concentration of particles above certain limiting values.

Resolution in zonal rotors

Abstract We have studied “static” factors affecting resolution in zonal rotors, that is, factors that are independent of diffusion or sedimentation of the sample. For most zonal rotors under the recommended conditions, there is proportionately very little zone broadening of sample volumes larger than 10 cc. There appears to be a correlation between the height of the rotor and resolution. We show that step gradients surrounding the sample can result in zone broadening in the case of slowly sedimenting particles. We did not detect any deleterious effects from increasing the initial sample radius.

Isolation of intact spinach chloroplasts in the CF-6 continuous-flow zonal rotor; Implications for membrane-bound organelles☆

Abstract Intact chloroplasts were separated from large volumes of spinach brei by continuous-flow zonal centrifugation in the CF-6 rotor in gradients of colloidal silica. Tests with the Z-15/Mark 10 rotor showed that the external membranes of chloroplasts were sensitive to high rotor speeds and especially to the bore of the fluid seal. Enlargement of the CF-6 seal channel diameter to 4 mm resulted in almost complete recovery of the intact chloroplasts.

Multiple Alternate Channel Selection (MACS): New versatility for zonal centrifuge rotors

Abstract We describe a system of Multiple Alternate Channel Selection (MACS) for zonal rotors in which conical adapters, which attach to the dynamic seal, connect at different vertical heights to any pair of channels in the core. In this way one can pump fluids to and from different positions or compartments in the same rotor during a single run. The specific applications described in this paper include edge-unloading of sensitive particles through the center channel of the dynamic seal and direct insertion of samples at a predetermined radius. Other applications are outlined.