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Journal Article

Continuous wave two-photon scanning near-field optical microscopy

MPS-Authors
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Kirsch,  A. K.
Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society;

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Subramaniam,  V.
Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society;

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Striker,  G.
Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society;

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Schnetter,  C.
Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society;

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Arndt-Jovin,  D. J.
Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society;

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Jovin,  T. M.
Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society;

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600843.pdf
(Publisher version), 573KB

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Citation

Kirsch, A. K., Subramaniam, V., Striker, G., Schnetter, C., Arndt-Jovin, D. J., & Jovin, T. M. (1998). Continuous wave two-photon scanning near-field optical microscopy. Biophysical Journal, 75, 1513-1521.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0012-FD2B-F
Abstract
We have implemented continuous-wave two-photon excitation of near-UV absorbing fluorophores in a scanning near-field optical microscope (SNOM). The 647-nm emission of an Ar-Kr mixed gas laser was used to excite the UV-absorbing DNA dyes DAPI, the bisbenzimidazole Hoechst 33342, and ethidium bromide in a shared aperture SNOM with uncoated fiber tips. Polytene chromosomes of Drosophila melanogaster and the nuclei of 3T3 Balb/c cells labeled with these dyes were readily imaged. The fluorescence intensity showed the expected nonlinear (second order) dependence on the excitation power in the range of 8-180 mW. We measured the fluorescence intensity as a function of the tip-sample displacement in the direction normal to the sample surface in the single- and two-photon excitation modes (SPE, TPE). The fluorescence intensity decayed faster in TPE than in SPE.