:( Are you using the millipore 2a antibody? To my knowledge, there isn't one, especially because the unique region of the 2a peptide between F2A and T2A is around 5 or 6 amino acids, and everyone immunizes to the consensus GDVESNPG.

Is there a reason you must distinguish between the two that you cannot use pcr to test for?

Thank you for your answer Brian.

I transfected a multicistronic vector [Peptide 1+ F2A+Peptide2+ T2A+ Peptide 3] and I would like to check their expression by staining but there are no good antibodies against Peptide 1 and Peptide 2.

Ahhh, that's super unfortunate. I've made a similar one using tdtomato for peptides 2 and 3 so I was just able to quantify blots.

I will keep my eye out for a specific antibody, but as the 2a motifs haven't really been super popular, I wouldn't be surprised if it takes a long time before people really commercialize them. Please let me know if you end up finding a specific one, I would be interested in using it as well!

I'll let you know if I find something interesting. I will be in contact with you