Quantitative determination of native proteins in individual human erythrocytes by capillary zone electrophoresis with laser-induced fluorescence detection.

Intracellular fluid within single human erythrocytes is analyzed by capillary electrophoresis with laser-excited native protein fluorescence. Good signal-to-noise is achieved, allowing even minor components to be quantified. Non-Gaussian distributions were found for total protein, fraction carbonic anhydrase, fraction hemoglobin A0, and an unidentified component. Variations among a group of 29 cells for each quantity are as much as 1 order of magnitude, even though erythrocytes are known to be fairly homogeneous in size distribution. Variations in fraction hemoglobin A0 reflect differences in in vitro oxidation rates to methemoglobin. A positive correlation was observed between carbonic anhydrase and hemoglobin A0 for individual cells. This is consistent with the presence of erythrocytes of different ages within the population, with the older cells being less capable of maintaining enzyme activity and preventing oxidative damage.