High resolution two‐dimensional polyacrylamide gel electrophoresis of basic myeloid polypeptides: Use of immobilized pH gradients in the first dimension

A two‐dimensional polyacrylamide gel electrophoresis approach for the separation of urea/detergent solubilized basic proteins is presented. An immobilized pH gradient (IPG) gel, pH range 7–10, containing 8 M urea, 2% Nonidet P‐40 and 10 mM dithioerythritol was used for the first‐dimensional isoelectric focusing separation. Approximately 400 to 500 basic polypeptides from myeloblasts or neutrophils were visualized with silver staining. The IPG gel in some cases included carrier ampholytes in the same pH range. The carrier ampholyte‐modified (“hybrid”) IPG gel exhibited improved resolution of some polypeptides, but at the expense of reproducibility in the focusing of other polypeptides. Transfer of sample into the IPG gel was facilitated by a combination of low initial voltage, presence of carrier ampholytes in the sample and application of the sample to the surface of the gel within a containment collar. 6 M urea was required in the SDS equilibration solution for the efficient transfer and high resolution separation of polypeptides in the second‐dimensional sodium dodecyl sulfate‐gel. Absolute spot position was highly reproducible among gels prepared simultaneously. Standard deviations of ± 0.84 mm for the focusing and ± 1.25 mm for the molecular weight dimensions of 70 randomly selected spots were obtained. Integrated spot intensities ranged from 0.17 to 80 O.D. × mm² with a median of 1.5 O.D. × mm².