What process is used to detect proteins on a membrane after gel electrophoresis?

The detection of proteins on a membrane after gel electrophoresis is effectively accomplished through Western blotting. This technique involves transferring proteins separated by gel electrophoresis onto a membrane, typically made of nitrocellulose or PVDF, and then probing that membrane with antibodies specific to the target proteins.

After the proteins are immobilized on the membrane, the antibodies bind to their respective antigens, allowing researchers to identify and quantify specific proteins within a complex mixture. The signal from the bound antibodies can then be detected using various methods, including enzyme-linked detection systems, leading to visualization of the proteins of interest. This process is critical in various applications, including diagnostics, research, and assessing protein expression levels.

The other options listed do not pertain to the detection of proteins on a membrane following gel electrophoresis. For instance, polymerase chain reaction (PCR) is primarily used for amplifying DNA, not proteins. Immune sedimentation involves the precipitation of antigens from solution using antibodies and is not a method for detection on membranes. Affinity chromatography is a technique for purifying proteins based on their interactions with specific ligands and also does not involve the detection on a membrane. Thus, Western blotting is the appropriate choice for this scenario.