Pulse-chase analysis

In biochemistry and molecular biology, a pulse-chase analysis is a method for examining a cellular process occurring over time by successively exposing the cells to a radioactive compound (pulse) and then to the same compound in nonradioactive form (chase).

Mechanism
A selected cell or group of cells is first exposed to a radioactively labeled compound (the pulse) that is to be incorporated into a molecule or system that is studied. The compound then goes through the metabolic pathways and is used in the synthesis of the product studied. For example a radioactively labeled form of leucine (3H-leucine) can be supplied to a group of pancreatic B cells, which then use this amino acid in insulin synthesis.

Shortly after introduction of the labeled compound (usually about 5 minutes, however time is dependent on the actual object studied) excess of the same but unlabeled substance (the chase) is introduced into the environment. Following the previous example, the production of insulin would continue, however it would no longer contain the radioactive leucine and would not be visible using radioactive detection methods. However, the movement of the labeled insulin produced during the pulse period could still be tracked within the cell.

Uses
This method is useful for determining the activity of certain cells over a prolonged period of time. The method has been used to study protein kinase C, ubiquitin, and many other proteins.