I was looking for the gel type that is used for trypsin digestion. I did immunoprecipitation using anti-insulin and pro-insulin antibody IgG1 with milk sample. I have got two bands, the first one was IgG but the other one was unknown. It was higher than insulin size. I did western blot with the sample, I used a different anti-insulin antibody as it has been recommended by many researchers. I used positive control, which is Human insulin. Western blot IP sample result with unknown band was negative, positive bands have got with IgG band and the positive control.

I attached the pic for the Tris 12% gel (samples are not reduced) and the western blot membrane. I did mark the band next to positive control that i think it could be band but i'm not sure.