Principles of Fluorescence Spectroscopy

650 FLUORESCENCE SENSING
Figure 19.52. Chemical structures of the calcium probe of Indo-1 and
the magnesium probe Mag-Indo-1. Data from [181].
Indo-1, and the analogous magnesium probe Mag-Indo-1
(Figure 19.52).
19.8.5. Probes for Intracellular Zinc
In recent years there has been increased interest in zinc. It
is well known that zinc if bound to a number of enzymes
and plays a structural role in zinc finger proteins. At present
there is interest in the possible rate of zinc in plaque formation
in Alzheimer's disease, post-ischemic toxicity, and as a
neurotransmitter. 185 A number of zinc-sensitive fluorophores
are now available. 186–189 Most of these probes contain
the chelating group shown for Zinpry-1 (Figure 19.53).
These probes show increases in fluorescence in the presence
of zinc, which is probably due to a decrease in the
amount of PET quenching in the zinc-bound form. The dissociation
constants of these probes are near 1 to 3 nM. The
Figure 19.53. Chemical structure and emission spectra of Zinpyr-1.
Reprinted with permission from [186]. Copyright © 2000, American
Chemical Society.
levels of free zinc in cells may be in the picomolar range, so
that zinc probes with higher affinity are needed. 190–191
19.9. GLUCOSE-SENSITIVE FLUOROPHORES
The principles of analyte recognition have been used to
develop fluorophores that are sensitive to glucose. There is
Figure 19.54. Glucose sensor based on photoinduced electron transfer. Revised from [194].