Monitoring
and early warning of spores germination is of great
significance in avoiding their potential pathogenicity. Thus, effective
monitoring of markers during spore germination is of great value.
A ratio-dependent fluorescent probe based on in situ incorporation
of fluorophores in a metal–organic framework (MOF) was designed
to monitor a main component of bacterial spores, 2,6-pyridinedicarboxylic
acid (DPA), with high sensitivity and specificity. The fluorescence
of CdS quantum dots loaded on zeolitic imidazolate framework-8 (ZIF-8)
nanocrystals is initially quenched by europium ions. The europium
ions, however, can be seized by DPA, leading to restoring the fluorescence
of quantum dots. Simultaneously, the fluorescence of another dye molecule,
rhodamine 6G, loaded on the ZIF-8 is not affected by DPA and can serve
as a stable internal fluorescence reference signal. On this basis,
a ratio-dependent fluorescence method for rapid detection of DPA was
established. The linear calibration ranged from 0.1 to 150 μM
with a detection limit of 67 nM, which is much lower than the amount
of DPA (60 μM) released by the contagious number of spores needed
to cause anthrax. This analysis platform exhibits good anti-interference
ability for monitoring spore germination. The practicable application
of the method was verified by monitoring and imaging the release of
DPA in the course of spore germination.
2-Amino-3-(arylthio)indoles were conveniently synthesized via the Rh(ii)-catalyzed C-S/N-C coupling reaction between 3-diazoindol-2-imines and thioesters. The products could be further oxidized to 2-amino-3-(arylsulfonyl)indoles by m-chloroperbenzoic acid and the N-sulfonyl group could be easily removed by reduction with SmI.
We report a facile and efficient synthesis of spiro[imidazolidine-4,3′-indolin]-2′-imines via a copper(i)-catalyzed cascade reaction of 3-diazoindolin-2-imines with 1,3,5-triazines.
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