Which blot technique is used to detect proteins?

• A. Western blot
• B. Northern blot
• C. Southern blot
• D. Eastern blot

Answer: (A)

Proteins are detected on blot membranes by using antibodies that specifically bind the target protein. After separating proteins by size on an SDS-PAGE gel, they’re transferred to a membrane, covered to prevent nonspecific binding, and then exposed to a primary antibody that recognizes the protein, followed by a labeled secondary antibody. The signal reveals whether the protein is present and, often, gives an idea of its size and relative abundance. This approach is the Western blot, the standard method for protein detection.

Northern blot, by contrast, uses nucleic-acid probes to detect RNA; Southern blot detects DNA. Eastern blot is not a routine, widely used method for protein detection and is associated with specialized post-translational modification analyses.