Improving the detection of proteins after transfer to polyvinylidene difluoride membranes.

N-Terminal sequence analysis of proteins separated by two-dimensional polyacrylamide gel electrophoresis and transferred onto polyvinylidene difluoride (PVDF) membranes has become the method for molecular characterization of proteins contained in biological samples. However, the proteins of lower abundance cannot be sequenced directly, without improving the technique. We have studied a drying method on several PVDF membranes including Trans-Blott, Immobilon P and Problott. Using Amido Black, Coomassie Brilliant Blue R-250 and Ponceau S, we have obtained, in comparison with the non-dried membranes, an enormous increase in the number of detectable proteins.