Tryptophan fluorescence intensity and anisotropy decays of human serum albumin resulting from one-photon and two-photon excitation.
We measured the emission spectra, intensity decays and anisotropy decays of the single tryptophan residue of human serum albumin (HSA) resulting from one-photon (295-298 nm) and two-photon (590-596) excitation. The emission spectra and intensity decays were independent of the mode of excitation. The anisotropy decays were superficially similar for one- and two-photon excitation. However, upon consideration of the different orientation photoselection for one- and two-photon excitation, the anisotropy data reveal different angles between the absorption and emission oscillators for one-photon and two-photon excitation. This result suggests different relative one-photon and two-photon cross-sections for the 1La and 1Lb transitions of the indole residue. This first report of the time-resolved anisotropy decay of a protein resulting from two-photon excitation suggests that such measurement will yield insights into the complex photophysical properties of tryptophan residues in proteins.
Lakowicz
J R
JR
Department of Biological Chemistry, University of Maryland, School of Medicine, Baltimore 21201.
Gryczynski
I
I
D005454:Fluorescence Polarization / Q000379:methods; D006801:Humans; D008433:Mathematics; D011827:Radiation; D012709:Serum Albumin / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D014364:Tryptophan / Q000032:analysis*
D012709:Serum Albumin; D014364:Tryptophan