Iodine stain for detection of peptides after isoelectric focusing.

Iodine stain is used for the detection of peptides after isoelectric focusing has been developed. Ultrathin gels (240-360 micrometer) are cast and, after focusing, dried at 110 degrees C on a filter paper sheet. The paper-pasted gel is then exposed to iodine vapors for a few seconds to a few minutes, depending on the peptide load. White peptide zones are visible on a brown, uniform background. The reaction is fully reversible and can be used also for small-scale preparative purification of peptides. Better than 80% recoveries of peptide from the gel can be obtained by elution in 80% acetic acid.