Valentina Caorsi

Until now, biological and medical research fluorescence imaging in multi-user facilities or institutes has been limited by the type or number of dyes that could be excited. The Leica TCS SP5 X supercontinuum confocal unites the broadband capabilities of the Leica TCS SP5 AOBS® and the freedom and flexibility to select any excitation line within the continuous range of 470 to 670 nm.

In the last decade, fluorescence resonance energy transfer (FRET) has become a useful technique for studying intermolecular interactions applied to the analysis of biological systems. Although FRET measurements may be very helpful in the comprehension of different cellular processes, it can be difficult to obtain quantitative results, hence the necessity of studying FRET on controllable systems.

We report about two-photon activation of a photoactivatable derivative of the Aequorea Victoria green fluorescent protein (pa-GFP). This special form of the molecule increases its fluorescence intensity when excited by 488 nm after irradiation with high intensity light at 413 nm. Two-photon photoactivation produces an effective real three-dimensional (3D) localization of the molecular switching of pa-GFP in the bright state.