The Chemistry of Small-Molecule Fluorogenic Probes - Progress in Molecular Biology and Translational Science - page 10

0.84). 2,3
Hallmarks of these dyes are their insensitivity to environment and relatively
small Stokes shifts ( < 20 nm). The main utility of BODIPY dyes has been
as biomolecule labels. Unlike many other fluorophore classes, the
BODIPY core structure has no obvious points of attachment for enzyme-
or photolabile functionality. This limits the production of fluorogenic
molecules based on the BODIPY dyes. Still, there are a few examples of
fluorogenic molecules, especially as sensors based on PeT. Moreover, the
utility of BODIPY dyes continues to grow with the development of
advanced molecules, suggesting that this versatile dye scaffold is far from
fully explored. 45,46

10 4 M 1 cm 1 ,and

¼

e ¼ F ¼ ( l max / l 588/616 nm, 6.8 em

5.2. Enzyme substrates
Although it is difficult to install blocking groups on the BODIPY structure,
the small Stokes shift of these dyes makes them susceptible to quenching
by homo-FRET. As demonstrated in phospholipase substrate 3 ( Fig. 1.1B ,
Section 3 ), labeling a biomolecule with multiple BODIPY dyes yields a
quenched substrate; hydrolysis of this labeled molecule elicits a large increase
in fluorescence. 16 The environmental insensitivity of these dyes makes it
possible to prepare fluorogenic protease, glycosylase, and lipase substrates
based on this strategy. 3 For example, overlabeling of casein with BODIPYs
27 and 29 give conjugates 30 and 31 , which are useful fluorogenic substrates
for a variety of proteases. 48

5.3. Indicators
BODIPY dyes are modulated efficiently by PeT, allowing construction
of a variety of fluorogenic sensors based on this scaffold. 47 A prototypical
example is compound 32 , which incorporates a dimethylaniline moiety
into a red-shifted BODIPY (protonated form: l max / l ¼ 634/652 nm,

em

10 4 M 1 cm 1 , and

e ¼ F ¼

0.75) to give a fluorogenic pH sensor
with a p K a of 2.3. 49 Further elaboration by addition of various chelating
groups to the BODIPY core gives valuable fluorescent ion indicators useful
in biological applications. Compound 33 bears a N , N -bis(2-pyridylmethyl)
ethylenediamine chelation motif and shows an 20-fold increase in fluores-
cence upon binding to Zn 2 þ ion with

10.4

499/509 nm. 50
Compound 34 contains a BAPTA moiety to recognize calcium ion and
is an exciting calcium indicator exhibiting a large 250-fold increase in

l max / l ¼ em