Covalently Colored Marker Proteins

Protein molar mass standards covalently labeled with dyes are valuable when the electrophoresis is followed by a Western blot or when electrophoresis has to be monitored. Furthermore, procedures of gel staining alter the geometry, and assignment of bands on blot to marker bands within the gel is sometimes difficult. 

The electrophoretic mobility of the labeled proteins obtained by this protocol is practically not different from that of the unlabeled proteins. 

The respective marker proteins, single or mixed, are dissolved in Soln. A to a concentration of 20 mg/ml at RT. Then 0.5-1 vol. of Soln. B are added and the mixture is heated to 60 °C for 5 min. After cooling, the labeled proteins are lyophilized without further purification and dissolved again in Soln. C to a concentration of 20 mg/ml. If the assay was larger than 0.1 ml, the product is aliquoted and stored at -20 °C. 

The remaining dabsyl chloride is not removed, since it reacts with Tris of Soln. C to a dye acting as tracking dye like bromophenol blue. 

1 to 2 pg per lane of the obtained labeled marker proteins each are applied. 

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