Fluorophore Release from a Polymethinic Photoremovable Protecting Group Through a Nonlinear Optical Process

Triggering the release of chemical species through the use of light is crucial for modern microscopy applications, such as single-molecule localization and, in general, in the regulation of molecular effectors. Herein, we demonstrate a nonlinear-optical scheme for the control of photorelease. Our system consists of a two-photon-absorbing photoremovable protecting group (PPG) bonded to a second chromophore which undergoes photo-induced detachment and activation upon excitation with lambda=850nm femtosecond pulses. The two-photon PPG section consists of a cyanine-type dye, and the releasable section is a highly fluorescent derivatized anthracene chromophore bonded to the cyanine through a photolabile etheric-meso-carbon bond. This method allows for the release of a fluorophore following a spatially localized two-photon excitation event. Both the excitation energy and the long lifetime of the upper excited states of the PPG chromophore are thought to be involved in the release process.