title: Absolute two-photon absorption spectra and two-photon brightness of orange and red fluorescent proteins.
abstract: Fluorescent proteins with long emission wavelengths are particularly attractive for deep tissue two-photon microscopy. Surprisingly, little is known about their two-photon absorption (2PA) properties. We present absolute 2PA spectra of a number of orange and red fluorescent proteins, including DsRed2, mRFP, TagRFP, and several mFruit proteins, in a wide range of excitation wavelengths (640-1400 nm). To evaluate 2PA cross section (sigma(2)), we use a new method relying only on the optical properties of the intact mature chromophore. In the tuning range of a mode-locked Ti:sapphire laser, 700-1000 nm, TagRFP possesses the highest two-photon cross section, sigma(2) = 315 GM, and brightness, sigma(2)phi = 130 GM, where phi is the fluorescence quantum yield. At longer wavelengths, 1000-1100 nm, tdTomato has the largest values, sigma(2) = 216 GM and sigma(2)phi = 120 GM, per protein chain. Compared to the benchmark EGFP, these proteins present 3-4 times improvement in two-photon brightness.
authors.forename: M
authors.initials: M
authors.lastname: Drobizhev
authors.forename: S
authors.initials: S
authors.lastname: Tillo
authors.forename: N S
authors.initials: NS
authors.lastname: Makarov
authors.forename: T E
authors.initials: TE
authors.lastname: Hughes
authors.forename: A
authors.initials: A
authors.lastname: Rebane
mesh_terms: D003116:Color; D008164:Luminescent Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D017785:Photons; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
chemical_list: D008164:Luminescent Proteins