I am using the antibody for western blot analysis of brain tissue homogenates on a 12% gel. Attached is the image of the blot. GAPDH is used as a loading control and is shown around 35 kDa. The staining for ferritin heavy chain is shown below around 21 kDa.

The doublet could be nonspecific binding of the antibody for ferritin light-chain. It could be a post-translation mod as well. I have ran the experiment with the antibody for the light chain ferritin and did not get a doublet (data not attached).

Is it simply nonspecific binding of my antibody for both of the ferritin chains?

ferritin light chain= 19 kDa

ferritin heavy chain= 21 kDa

Would they be that close?