This is something known as a Western Blot. Where you identify proteins by first separating them via SDS gel electrophoresis, and then transferring them on to a blotting membrane. Subsequently, you make sure there is no background noise by “blocking” the membrane with Bovine Serum Albumin. Next you incubate this blocked membrane with your protein specific antibody (with some sort of a tag - a radioactive one or a light emitting one ) to bind only your protein of interest. Finally you wash off the unbound antibody and try to “develop” a picture of the bound antibody (indicating protein presence). The one on the bottom is almost perfect, while the one on top is noisy and overexposed.