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CALCIUM‐DEPENDENT FLUORESCENCE LIFETIMES OF INDO‐1 FOR ONE‐ AND TWO‐PHOTON EXCITATION OF FLUORESCENCE
Author(s) -
Szmacinski Henkyk,
Gryczynski Ignacy,
Lakowicz Joseph R.
Publication year - 1993
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1993.tb09571.x
Subject(s) - fluorescence , two photon excitation microscopy , excitation , chemistry , calcium , photochemistry , physics , optics , quantum mechanics , organic chemistry
— We characterized the fluorescence intensity decays of Indo‐1, which is commonly used as an emission wavelength‐ratiometric calcium probe. The apparent lifetime of the long‐wavelength side of the emission of Indo‐1 is dependent on Ca 2+ . This long‐wavelength emission displays the characteristics of an excited‐state reaction, that is, a negative preexponential component in thc multiexponential analysis. The emission spectra and lifetime of Indo‐1 appear to be identical for one‐photon and two‐photon excitation at 351 and 702 mn, respectively, suggesting that the relative one‐ and two‐photon cross sections are similar for the calcium‐free and calcium‐bound forms of Indo‐1. Also, the two‐photon cross section of Indo‐1 is relatively high, about 4 × 10 −49 cm 4 s/photon molecule at 690 nm for both the calcium‐free and calcium‐bound forms. Hence, Indo‐1 can be used for calcium imaging based on one‐ or two‐photon excitation, using either emission wavelength ratios or lifetime imaging methods.