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Affinity Capillary Electrophoresis 311
A 200 nm
A 200 nm
0.030
0.025
0.020
0.015
0.010
0.005
0.000
-0.005
0.030
0.025
0.020
0.015
0.010
0.005
0.000
-0.005
Current (µ A)
140
120
100
80
60
40
20
0
0.2 0.7 1 2
Time (min.)
4 5 6 7 8 9 10
140
120
100
80
60
40
20
0
0.2 0.7 1 2
Time (min.)
4 5 6 7 8 9 10
Time (min.)
Current (µ A)
Fig. 2. Sample zone temperature influences the peak profile of 2 -microglobulin
( 2 m). This protein displays conformational heterogeneity at elevated temperatures
(45). 2 m diluted from 9.4 mg/ml in phosphate-buffered saline (PBS) to 0.5 mg/ml
by water was injected for 4 s. Capillary electrophoresis (CE) was performed in 0.1 M
phosphate, pH 7.4, using stepwise constant current profiles as indicated by the inserted
graphs. The capillary was liquid thermostated at 18°C. Under CE conditions with a
rapid current ramping after sample injection (upper graph), 2 m separates into two
peaks representing different conformations, while a slow ramping, even with a higher
final current, (lower graph) results in a single peak with no signs of conformational
heterogeneity.
containing electrophoresis buffer is in practice easily prevented by introducing
a 1s injection step, of water. This step is programmed to occur before injection
of sample and after rinsing the capillary with ligand-containing electrophoresis
buffer. It is then possible to perform tests with multiple ligands using the same