Two-photon absorption spectra of fluorescent isomorphic DNA base analogs

Alexander Mikhaylov; Sophie de Reguardati; Jüri Pahapill; Patrik R Callis; Bern Kohler; Aleksander Rebane

doi:10.1364/BOE.9.000447

Two-photon absorption spectra of fluorescent isomorphic DNA base analogs

Biomed Opt Express. 2018 Jan 5;9(2):447-452. doi: 10.1364/BOE.9.000447. eCollection 2018 Feb 1.

Authors

Alexander Mikhaylov¹, Sophie de Reguardati², Jüri Pahapill², Patrik R Callis³, Bern Kohler⁴, Aleksander Rebane^{1

2}

Affiliations

¹ Department of Physics, Montana State University, Bozeman, MT 59717, USA.
² National Institute of Chemical Physics and Biophysics, Tallinn 12618, Estonia.
³ Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
⁴ Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.

Abstract

Fluorescent DNA base analogs and intrinsic fluorophores are gaining importance for multiphoton microscopy and imaging, however, their quantitative nonlinear excitation properties have been poorly documented. Here we present the two-photon absorption (2PA) spectra of 2-aminopurine (2AP), 7-methyl guanosine (7MG), isoxanthopterin (IXP), 6-methyl isoxanthopterin (6MI), as well as L-tryptophan (L-trp) and 3-methylindole (3MI) in aqueous solution and some organic solvents measured in the wavelength range 550 - 810 nm using femtosecond two-photon excited fluorescence (2PEF) and nonlinear transmission (NLT) methods. The peak 2PA cross section values range from 0.1 GM (1 GM = 10^-50 cm⁴ s photon^-1) for 2AP to 2.0 GM for IXP and 7MG. Assuming typical excitation conditions for a scanning 2PEF microscope, we estimate a maximum image frame rate of ~175 frames per second (FPS).

Keywords: (190.0190) Nonlinear optics; (190.4180) Multiphoton processes; (190.4710) Optical nonlinearities in organic materials; (300.6410) Spectroscopy, multiphoton.