title: Three-photon excitation of N-acetyl-L-tyrosinamide.
abstract: We observed emission from the tyrosine derivative N-acetyl-L-tyrosinamide (NATyrA) when excited with the fundamental output of a femtosecond Ti:Sapphire laser from 780 to 855 nm. The dependence on incident laser power indicates a three-photon process. The emission spectra and intensity decay in glycerol-water (30:70) at 5 degrees C were found to be identical for one- and three-photon excitation. Also the excitation spectrum of three-photon-induced fluorescence of NATyrA corresponds to the one-photon excitation spectrum. The time-zero or fundamental anisotropy spectrum was reconstructed from the frequency-domain anisotropy decays. The three-photon anisotropies are similar or larger than the one-photon anisotropies. These three-photon anisotropies are surprising given the near zero values known for tyrosine with two-photon excitation. The observations indicate that one- and three-photon excitation directly populates the same singlet excited states(s). However, the origin of the anisotropies with multi-photon excitation of tyrosine remain unclear and unpredictable.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland at Baltimore 21201, USA.
authors.forename: I
authors.initials: I
authors.lastname: Gryczynski
authors.forename: H
authors.initials: H
authors.lastname: Malak
authors.forename: J R
authors.initials: JR
authors.lastname: Lakowicz
mesh_terms: D005454:Fluorescence Polarization; D066298:In Vitro Techniques; D007834:Lasers; D010777:Photochemistry; D017785:Photons; D013050:Spectrometry, Fluorescence; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects
chemical_list: C019142:N-acetyltyrosylamide; D014443:Tyrosine