How does pH affect the fluorescence of GFP?

The correct answer highlights the relationship between pH and the fluorescence of GFP. Fluorescence in GFP is sensitive to the environmental conditions, including pH levels. At extreme acidic or alkaline pH values, the structure of the chromophore, which is responsible for the fluorescent properties of GFP, can be altered. This structural change often leads to a decrease in fluorescence intensity or even a complete loss of fluorescence.

When the pH deviates significantly from the optimal range, the protonation state of the amino acids surrounding the chromophore is affected. These changes can disrupt the electronic environment necessary for the chromophore to absorb light and emit fluorescence efficiently.

In contrast, under conditions where the pH remains stable and within a moderate range, GFP retains its characteristic fluorescence. Understanding this relationship is crucial for applications that utilize GFP as a reporter, as maintaining an appropriate pH is essential for optimal fluorescence output.