Mario Faretta

The comprehension of stem cell biology and its molecular basis is now acquiring paramount importance in cancer research. The need to look at a single, possibly living, cell makes fluorescence microscopy and confocal microscopy invaluable allies in the study of stem cells.

Sequencing of the human genome stimulated a radical change in the approach to biomedical research. The comprehension of the mechanisms regulating life gained a scale-up in throughput to speed up the retrieval of data for a global vision of a system of incomparable complexity.

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.

Multi-photon excitation (MPE) microscopy plays a growing role among microscopical techniques utilized for studying biological matter. In conjunction with confocal microscopy it can be considered the imaging workhorse of life science laboratories. Its roots can be found in a fundamental work written by Maria Goeppert Mayer more than 70 years ago. Nowadays, 2PE and MPE microscopes are expected to increase their impact in areas such biotechnology, neurobiology, embryology, tissue engineering, materials science where imaging can be coupled to the possibility of using the microscopes in an active way, too.