Which of the following methods uses antibodies to identify target proteins?

Western blotting is a method specifically designed to detect and identify target proteins within a sample using antibodies. It involves the separation of proteins based on size using gel electrophoresis (often SDS-PAGE), followed by the transfer of these proteins to a membrane where specific antibodies can bind to the target proteins. This binding allows for the visualization of the target proteins through techniques such as enzyme-linked detection or fluorescent tagging, confirming their presence and providing information about their size and abundance.

In contrast, gel filtration chromatography separates proteins based on size, without the use of antibodies. SDS-PAGE also separates proteins by size through denaturing gel electrophoresis, but it does not involve the use of antibodies to identify specific proteins. Ion exchange chromatography separates proteins based on their charge and also does not utilize antibodies for protein identification.

Thus, Western blotting stands out as the method that directly employs antibodies to identify and characterize specific proteins, making it the correct choice.