In vitro characterization of selected NIR FPs

Absorbance, steady-state fluorescence spectra and two-photon cross-section spectra of the selected NIR FPs measured by Mikhail Drobizhev. <br> Recent progress in fluorescent protein development has generated a large diversity of near-infrared fluorescent proteins, which are rapidly becoming popular probes for a variety of imaging applications. To assist end-users with a selection of the right near-infrared fluorescent protein for a given application, we conducted a quantitative assessment of intracellular brightness, photostability, oligomeric state, and cytotoxicity of 22 near-infrared fluorescent proteins in cultured HEK cells and primary mouse neurons. The top-performing proteins were further validated for <em>in vivo</em> imaging of neurons in <em>C. elegans</em>, zebrafish, and mice as well as in liver of mice. We also assessed the applicability of the selected NIR FPs for multi-color imaging of fusions, expansion microscopy, and two-photon imaging.