Figure 3. Photostability of red and green fluorescent proteins.

Yeast expressing fusions of each of the optimized fluorescent proteins to the TDH3 protein were imaged continuously until their intensity dropped below 50% of the initial intensity. The intensity of each cell integrated over the time until 50% bleaching occurred was then calculated, and the mean integrated intensity for each strain on each day was normalized to EGFP (for green proteins) or mCherry (red proteins) to compensate for day-to-day fluctuations in lamp brightness and detection efficiency. The measurement was repeated on at least two days and the mean and standard error for each strain is plotted. * indicates a protein with significantly larger integrated intensity than mCherry as determined by a one-sided t-test with 5% significance threshold.