For immunoprecipitation the smller the molecular is the harder to detetion. Usually, when tansfecting, the protein may be go throgh the PVDF membrane. Non-protein was detected in western blotting. We suggest that the transfer membrane time shoud be shorten. Besides, voltage must be setted lower than midium molecular. The best method is to test your experiment conditions by gradient reducing.
When the concentration of the small protein is low, you also can enrich the protein by dialysis or other method. Equally，you also can use more IP immunomagnetic beads for capture the antigen,then detected the target with western blotting. The western blotting antibody should be incubated overnight,for better results.
The small molecular proteins were very important for cells' function, research the small protein uncover the secret of small proteins, will help us understand life. Sino Biological immunoprecipitation kit will give you a tool discover the secrets.