title: A new approach to dual-color two-photon microscopy with fluorescent proteins.
abstract: BACKGROUND
  Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs) is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA) efficiency.
  
  
  RESULTS
  Here we present a new method of dual-color two-photon microscopy that uses the simultaneous excitation of the lowest-energy electronic transition of a blue fluorescent protein and a higher-energy electronic transition of a red fluorescent protein.
  
  
  CONCLUSIONS
  Our method does not require large differences in Stokes shifts and can be extended to a variety of FP pairs with larger 2PA efficiency and more optimal imaging properties.
authors.affiliation: Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT 59717, USA.
authors.forename: Shane E
authors.initials: SE
authors.lastname: Tillo
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Hughes
authors.forename: Nikolay S
authors.initials: NS
authors.lastname: Makarov
authors.forename: Aleks
authors.initials: A
authors.lastname: Rebane
authors.forename: Mikhail
authors.initials: M
authors.lastname: Drobizhev
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry; D008164:Luminescent Proteins / Q000737:chemistry*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D000097573:Red Fluorescent Protein
chemical_list: D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein