I probed for mouse iNOS in brain homogenates for western blotting. I used monoclonal mouse antibody from Santacruz #SC7271. the predicted molecular weight based on the product datasheet and other published papers is 130 kDa. However, I have 2 bands at 60 and 30Kda, both of them have the expected pattern in positive and negative controls! Does anyone have any explanation for that?