RAPID COMMUNICATION |
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| Authors: | Ignacy Gryczynski Henryk Szmacinski Joseph R Lakowicz |
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| Institution: | Center for Fluorescence Spectroscopy and Medical Biotechnology Center, Department of Biological Chemistry, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, MD 21201, USA |
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| Abstract: | Abstract— We show that the calcium fiuorophore Indo-1 can be excited by simultaneous absorption of three-photons at 885 nra, a wavelength readily available from Ti:sapphire lasers. Three-photon excitation was demonstrated by the emission intensity of Indo-1 which depended on the cube of the laser power, and by a higher anisotropy than was observed for two-photon excitation. Excitation of Indo-1 becomes a two-photon process when the wavelength is decreased to 820 nm. Three-photon excitation was accomplished at a low 17μ concentration of Indo-1. Examination of the spatial profile of the excited Indo-1 showed a smaller volume for three- versus two-photon excitation. These results suggest that three-photon excitation may be useful in fluorescence microscopy using the long wavelength output of Tksapphire lasers, and may provide higher spatial resolution than available using two-photon excitation. |
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