These results also confirm that MAOs recognize probe 1a
as a substrate and thus produce IminoPOS, a two-photon
fluorophore, through the enzymatic oxidation followed by the
hydrolysis and cyclization processes. The cellular fluorescent
imaging experiments also indicate that probe 1a penetrates the
cells readily. As probes 1 have good cell-viability (Fig. S10,
ESIw), they can be potentially useful for imaging MAOs’
activity in living systems.
In summary, we have developed reactive fluorescent probes
for MAOs based on a novel two-photon absorbing material,
IminoPOS. The probes, precursors of IminoPOS, showed
turn-on fluorescence changes upon reaction with the enzymes
owing to the IminoPOS produced through the enzymatic
process. The enzymatic activity in cells was also fluorescently
imaged in the presence and absence of inhibitors, using one of
the probes by OPM as well as TPM for the first time.
This work was supported by grants from the EPB
center (R11-2008-052-01001) through the National Research
Foundation, Korea. K. H. Kim thanks financial support
by the Bio & Medical Technology Development Program
(2011-0019619, 2011-0019632).
Fig. 2 (a) Enzyme inhibition assays. Fluorescence response of probe
1a (70 mM) toward (a) MAO A or (b) MAO B (the final concentration:
10 mg mLÀ1) in the absence and presence of inhibitors, moclobemide
or pargyline (70 mM for each). Fluorescence intensity was measured
during 0–180 min at 10 min intervals and 37 1C.
Notes and references
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Fig. 3 Representative two-photon fluorescence images of C6 glioma
cells and chromaffin cells that were treated with (a) IminoPOS (control),
(b) probe 1a, (c) IminoPOS (control), (d) probe 1a, (e) moclobemide
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with moclobemide and pargyline, respectively, for 2 h at 37 1C,
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c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 6833–6835 6835