What is the purpose of using a protease inhibitor during GFP purification?

The use of a protease inhibitor during GFP purification is primarily aimed at preventing the degradation of the target protein, GFP. Proteases are enzymes that break down proteins into smaller peptides or amino acids. During the purification process, cells are often lysed to release the proteins, which can inadvertently expose them to intrinsic proteases that can degrade proteins, including GFP. By adding a protease inhibitor, the activity of these enzymes is halted, ensuring that the GFP remains intact throughout the purification process. This is crucial for maintaining the integrity and functionality of GFP for later analysis or applications, as any degradation could lead to a loss of signal or activity and adversely affect experimental results.