This paper introduces a novel method for creating caging-group-free photoactivatable fluorophores (PaX dyes) based on 3,6-diaminoxanthones. These dyes efficiently and cleanly convert into highly fluorescent pyronine dyes upon light irradiation, offering advantages over traditional methods that rely on photolabile protecting groups. The PaX strategy is versatile, applicable to various xanthone analogues, and produces fluorophores spanning the visible spectrum. The authors demonstrate PaX dyes' utility in various microscopy techniques (conventional, STED, PALM, MINFLUX) for both fixed and live-cell imaging.

Richard Lincoln, Mariano L. Bossi, Michael Remmel, Elisa D’Este, Alexey N. Butkevich, Stefan W. Hell