India ink staining of proteins on nylon and hydrophobic membranes.

India ink was found to be an acceptable stain for proteins blotted or dotted onto positively charged nylon or hydrophobic membranes. The hydrophobic membrane, Immobilon, was an outstanding matrix for binding proteins and displayed low levels of background staining. The least amount of protein detected by india ink staining was between 1.0 and 10 ng. India ink staining of proteins on nylon membranes is an easy, inexpensive, and quick method for the unequivocal detection of both standards and unknowns in the same blot. However, inks, ink concentrations, fixing conditions, staining times, pH, washing conditions, and membrane lots all need to be controlled to achieve maximum sensitivity for protein detection following india ink staining.