3xFLAG is 20 times as much as 1xFLAG

We  usually construct a interesting protein connecting with tags, which make us easy to detect the protein by using the specific antibody against the tag. I used to use Flag-tag to detect a protein in culture cells for several times. It is generally received that the affinity of antibodies against FLAG tag in 3xFLAG is 20 times as high as that in 1xFLAG. FLAG tag is hydrophilic and then mainly locates to the surface of the objective protein, which means that FLAG doesn't almost always affect the molecular structure and enzymatic activity of the interesting protein.