Figure 1.
Comparison of one-photon and two-photon absorption spectra of fluorescent proteins with different chromophores. Two-photon absorption spectra (red symbols, left axis) are presented versus laser wavelength, used for excitation. For comparison purposes, in one-photon absorption spectra (blue lines, right axis) the actual excitation wavelength is multiplied by a factor of two. All spectra are presented in absolute values determined per mature chromophore. Reproduced in part from Ref.11. Copyright 2009 American Chemical Society.