title: Cell-based and in vivo spectral analysis of fluorescent proteins for multiphoton microscopy.
abstract: Multiphoton microscopy of cells and subcellular structures labeled with fluorescent proteins is the state-of-the-art technology for longitudinal imaging studies in tissues and living animals. Successful analysis of separate cell populations or signaling events by intravital microscopy requires optimal pairing of multiphoton excitation wavelengths with spectrally distinct fluorescent proteins. While prior studies have analyzed two photon absorption properties of isolated fluorescent proteins, there is limited information about two photon excitation and fluorescence emission profiles of fluorescent proteins expressed in living cells and intact tissues. Multiphoton microscopy was used to analyze fluorescence outputs of multiple blue, green, and red fluorescent proteins in cultured cells and orthotopic tumor xenografts of human breast cancer cells. It is shown that commonly used orange and red fluorescent proteins are excited efficiently by 750 to 760 nm laser light in living cells, enabling dual color imaging studies with blue or cyan proteins without changing excitation wavelength. It is also shown that small incremental changes in excitation wavelength significantly affect emission intensities from fluorescent proteins, which can be used to optimize multi-color imaging using a single laser wavelength. These data will direct optimal selection of fluorescent proteins for multispectral two photon microscopy.
authors.affiliation: University of Michigan Medical School, Department of Radiology, 109 Zina Pitcher Place, A526 BSRB, Ann Arbor, Michigan 48109-2200, USA.
authors.forename: Emma
authors.initials: E
authors.lastname: Salomonnson
authors.forename: Laura Anne
authors.initials: LA
authors.lastname: Mihalko
authors.forename: Vladislav V
authors.initials: VV
authors.lastname: Verkhusha
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Luker
authors.forename: Gary D
authors.initials: GD
authors.lastname: Luker
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media; D006801:Humans; D008164:Luminescent Proteins / Q000737:chemistry*; D051379:Mice; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D009374:Neoplasms, Experimental / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D008164:Luminescent Proteins