Which of the following is NOT a common use of GFP in research?

The correct answer highlights that using GFP as a food dye is not a common application in research. Green Fluorescent Protein is primarily valued in biological and medical research due to its fluorescent properties that allow scientists to visualize and track specific proteins within living organisms. Its applications include studying developmental biology, tracking protein localization, and investigating cellular signaling pathways. These uses leverage the ability of GFP to be expressed in various organisms and provide real-time imaging of biological processes.

In contrast, while GFP's fluorescent properties might theoretically allow for its use as a food dye, this is not a recognized or common application in the realm of scientific research, where the focus remains on its utility as a molecular marker in biological studies. Thus, the other options reflect established uses of GFP in research labs, which is not the case for the suggested use as a food dye.