(2012). Proceedings of the National Academy of Sciences, 109(12) , 4455-4460. doi: 10.1073/pnas.1113770109. Article Pubmed
An attempt to find Dronpa variants with slower off-switching rate has led to the identification of PDM1-4. Unfortunately, PDM1-4 was prone to form tetramers and did not show improvement in photon output. In addition, PDM1-4 has worsened photostability and less contrast between on and off-states.