Asymmetry of protein peaks in capillary zone electrophoresis: effect of starting zone length and presence of polymer.
The asymmetry of R-phycoerythrin (M(r) = 240,000) peaks in capillary zone electrophoresis measured as In[(tm-t1)/(t2-tm)], where tm, t1 and t2 are migration times of the peak mode and at the intersection of the peak width at half-height with the ascending and descending limbs, respectively, was found to undergo a transition from negative to positive values with increasing starting zone length. The transition is compatible with a mathematical model of peak dispersion which assumes that an interaction of protein with the capillary walls governs the evolution of the peak during capillary zone electrophoresis. Models assuming a final peak shape defined solely by longitudinal diffusion, or by a heterogeneity with regard to mobility or by a conductivity difference between analyte zone and background electrolyte, have failed to give rise to a change in the sign of peak asymmetry when the starting zone length is varied. The presence of polyethylene glycol in the buffer within a concentration range up to 4% does not appreciably affect the peak asymmetry regardless of whether the concentration regime is dilute or semi-dilute. Above 4% of polyethylene glycol, the asymmetry becomes nearly independent of starting zone length, and progressively negative with increasing polymer concentration. The concentration range at which the transition from negative to positive asymmetry disappears coincides with that at which the average mesh size of the polymer network falls below the size of the protein.
Section on Macromolecular Analysis, National Institute of Child Health and Development, National Institutes of Health, Bethesda, MD 20892-1580, USA.
S P
SP
Radko
A
A
Chrambach
G H
GH
Weiss
D019075:Electrophoresis, Capillary / Q000379:methods*; D011108:Polymers; D011506:Proteins / Q000302:isolation & purification*
D011108:Polymers; D011506:Proteins