Application of latex microspheres in the isolation of plasma membranes. Affinity density perturbation of erythrocyte membranes

Polymeric microspheres for immunoresearch

New microspheres having functional aldehyde groups have been prepared by radiation polymerization of acrolein solution containing hydroxyethyl methacrylate and glutalardehyde. The size distribution in the microspheres was narrow and average particle diameter was 1 - 2 micron. The binding ability of the microspheres to antigen increased by increasing the concentration of glutalardehyde. The preparation procedure of the microspheres is simple. The microspheres can be used for immunoresearch.

Subfractionation of liver membrane preparations by specific ligand-induced density perturbation

Immunofluorescence and immunoferritin staining with monospecific antibodies to dipeptidyl peptidase IV purified from rat liver plasma membrane showed that the antigenic sites of this glycoprotein was exposed only on the outer surface of the liver cell. In a vesiculated plasma membrane preparation the peptidase was located exclusively on right-side-out elements, which differed in their degrees of ferritin staining, and could be separated into subfractions of different buoyant densities corresponding to their concentration of dipeptidyl peptidase IV. The concomitant density perturbation of nucleotide pyrophosphatase was similar, but not identical, to that of the peptidase itself, indicating that these two marker enzymes are somewhat differently distributed in the plane of the liver plasma membrane. Since essentially all the galactosyl transferase in plasma membrane and none of that in Golgi membrane could be density-perturbed with the antipeptidase, the activity in the plasma membrane preparation could not be ascribed to contamination with discrete Golgi elements. On the other hand, the small amount of dipeptidyl peptidase IV found in the Golgi preparations was itself perturbed by the antipeptidase, indicating that it represented contaminating right-side-out plasma membrane vesicles. In preliminary experiments similar separations were also obtained with wheat germ agglutinin as the plasma membrane ligand. Density perturbation, mediated by the recognition of specific surface markers, should be a useful adjunct in the separation and characterization of subcellular components in other systems.

Plasma membrane: rapid isolation and exposure of the cytoplasmic surface by use of positively charged beads

Erythrocytes were ionically attached to polylysine-coated beads 30 micrometers in diameter. The binding of the cells was so tenacious that lysis or disruption of the attached cells left the beads covered by plasma membranes whose cytoplasmic surface was exposed and accessible for further analysis.

A scanning electron microscope study of concanavalin A receptors on retinal rod cells labeled with latex microspheres

Con A-methacrylate microsphere conjugates prepared by a two-step glutaraldehyde reaction were used to label Con A-binding sites on bovine rod photoreceptor cells for visualization by scanning electron microscopy. A dense distribution of markers was observed on the surface of the rod outer segment, the inner segment, and the synaptic region. Disk membranes also appear to be heavily labeled with the Con A-microsphere conjugates. The Con A inhibitor, alpha-methyl mannoside, inhibited the binding of the conjugate to the surface of these visual cells.