Analytical IPG-Dalt

Immobilized pH ^† *adients (IPGs) for isoelectric focusing (IEF) were introduced in 1982 (1 ). After experiencing initial problems in handling IPGs, a basic protocol of two-dimensional electrophoresis (2-DE) with IPGs in the first dimension, followed by horizontal or vertical SDS electrophoresis (IPG-Dalt), was established in 1988 (2 ). Since that time, the protocol has not been changed essentially. Compared to classical 2-DE with carrier ampholytes (3 ,4 ), the employment of IPG-Dalt has produced significant improvements in 2-D electrophoretic separation, permitting higher resolution and reproducibility, which was also demonstrated by an interlaboratory comparison (5 ). Alkaline proteins, normally lost by the cathodic drift of carrier ampholyte focusing or separated by NEPHGE (6 ) with limited reproducibility, were perfectly separated under equilibrium conditions (7 ). These features together with the high loading capacity of IPG-Dalt for micropreparative runs (8 –10 ) have accelerated spot identification by microsequencing, amino acid composition analysis, and mass spectrometry.