CALCIUM‐DEPENDENT FLUORESCENCE LIFETIMES OF INDO‐1 FOR ONE‐ AND TWO‐PHOTON EXCITATION OF FLUORESCENCE

Henkyk Szmacinski, Ignacy Gryczynski, Joseph R. Lakowicz

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

Abstract— 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 Ca2+. 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 cm4 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.

Original languageEnglish
Pages (from-to)341-345
Number of pages5
JournalPhotochemistry and Photobiology
Volume58
Issue number3
DOIs
StatePublished - Sep 1993

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