Antibodies are composed of four polypeptide chains: two heavy chains, each approximately 50 kDa and two light chains, each approximately 25 kDa. Thus, the quaternary structure of antibodies is approximately 150 kDa. Purified proteins were reduced and the samples were separated on SDS-PAGE.
The image above shows the coomassie-stained gel. Lane 1 contains a protein ladder with the molecular weights (in kDa) shown to the left. In lanes 2 through 10, individual protein samples are shown.
Which lane MOST likely contains the antibody sample?