Electrokinetic Phenomena

Abstract

1. Although the isoelectric points of dissolved cystine, tyrosine, and aspartic acid molecules lie at widely differing pH values, the isoelectric points of the surfaces of these substances in the crystalline state are all near pH 2.3. This was found to be true in solutions of hydrochloric acid and in acetate buffers of approximately constant ionic strength. 2. When suspended in gelatin, tyrosine and cystine crystals adsorb the protein and attain a surface identical in behavior with gelatin-coated quartz or collodion particles. 3. Aluminum ions at low concentrations reduce the electric mobilities of tyrosine crystals to zero in a manner analogous to their effect on other surfaces. 4. Alkyl benzene droplets also have their electric mobility reduced to zero at low pH values but, unlike the amino acids, a change in sign was never noticed. 5. The mobility of tyrosine crystals is independent of crystal length between 2–100µ. Below this size the mobilities are decreased. 6. These results are discussed in connection with the concept of the general definition of the isoelectric point and the behavior of certain insoluble proteins such as wool and silk fibroin.

The Electrical Charge of Mammalian Red Blood Cells

“…By assuming that each effective electronic charge occupies an ionic area of, say, 1 × 10 -1~ cm3, the percentage of the surface occupied by these charges may be roughly estimated (Table I, Column 8). The values never rise far above 1 per cent, which agrees in magnitude with data obtained on other surfaces (2). The changes in the surface chemistry of the red cell due to alteration of the suspending medium may be investigated with profit by means of the method utilized to calculate the charge.…”

“…Since the electric mobility of red cells in salt solutions is independent of their orientation in the electric field (1) and since erythrocytes made spherical by traces of saponin have electric mobilities, within the limits of error, identical with the disc-shaped cells suspended in the same buffer, the electric mobilities of these microscopic particles can be treated by the theory derived for large particles (2). We can, with von Smoluchowski, calculate the f-potential from the electric mobility, %1…”

“…2 In any event, the measurements of v were carried out in the same medium so that any future corrections in the values of these constants would probably only change our results by a proportionality factor. From ~e, the net charge density, ~, on a surface may be calculated (2,5,6) 2. If the electric mobility of microscopically visible quartz particles covered with a film of adsorbed protein is studied in different concentrations of alcohol (4), it is possible to correlate the surface potential and surface charge calculated from these mobilities with the charge obtained by another (thermodynamic) method.…”

Quantitative Chemical Studies on Complement or Alexin

“…While these figures are not to be taken too literally they do at least indicate by roughly a power of ten that sensitization need not involve a coating of the entire red cell surface. The findings are therefore in accord with the "key spot" theory of Abramson (18).…”

Powdered Particle Interactions: Suspension Flocculation and Caking I

“…Abramson (8) has discussed the work of Burton, who used potassium sulfate to coagulate a copper sol. With other conditions held constant, Burton modified the zeta potential on the copper particles by the addition of electrolyte.…”