The thiolysis of NBD piperazinyl amine (NBD-PZ) is highly selective for H2S over GSH and has been widely used for the development of many H2S fluorescent probes. Whether the NBD amine in H2S-specific probes could be a fluorescent quencher should be further clarified, because NBD amines have been used as environment-sensitive fluorophores for many years. Here, we compared the properties of NBD-based secondary and tertiary amines under the same conditions. For example, the emission of NBD-N(Et)2 is much smaller in water and less responsive to changes in polarity than that of NBD-NHEt. The emission of NBD-PZ-TPP is also smaller than that of NBD-NH-TPP both in aqueous buffer and in live cells. In addition, confocal bioimaging signals of NBD-PZ-TPP with excitation at 405 nm and 454 nm are much weaker than that at 488 nm. Based on these results as well as the previous work on NBD-based probes, we discuss and summarize the design strategies and sensing mechanisms for different NBD-based H2S probes. Moreover, NBD-PZ-TPP may be a useful tool for reaction with and imaging of mitochondrial H2S in live cells. This work should be useful for clarification of the roles of NBD in H2S-specific fluorescent probes as well as for facilitating the development of future NBD-based probes.

An NBD tertiary amine is a fluorescent quencher and/or a weak green-light fluorophore in H2S-specific probes.

H2S has acquired great attention in plant research because it has signaling functions under physiological and stress conditions. However, the direct detection of endogenous H2S and its potential emission is still a challenge in higher plants. In order to achieve a comparative analysis of the content of H2S among different plants with agronomical and nutritional interest including pepper fruits, broccoli, ginger, and different members of the genus Allium such as garlic, leek, Welsh and purple onion, the endogenous H2S and its emission was determined using an ion-selective microelectrode and a specific gas detector, respectively. The data show that endogenous H2S content range from pmol to μmol H2S · g−1 fresh weight whereas the H2S emission of fresh-cut vegetables was only detected in the different species of the genus Allium with a maximum of 9 ppm in garlic cloves. Additionally, the activity and isozymes of the L-cysteine desulfhydrase (LCD) were analyzed, which is one of the main enzymatic sources of H2S, where the different species of the genus Allium showed the highest activities. Using non-denaturing gel electrophoresis, the data indicated the presence of up to nine different LCD isozymes from one in ginger to four in onion, leek, and broccoli. In summary, the data indicate a correlation between higher LCD activity with the endogenous H2S content and its emission in the analyzed horticultural species. Furthermore, the high content of endogenous H2S in the Allium species supports the recognized benefits for human health, which are associated with its consumption.

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H2S in Horticultural Plants: Endogenous Detection by an Electrochemical Sensor, Emission by a Gas Detector, and Its Correlation with L-Cysteine Desulfhydrase (LCD) Activity

The endogenous level of biological H2S (submicromolar) is much lower than that of GSH (millimolar), leading to the requirement of exploring highly selective chemical tools for differentiation of intracellular H2S...

Clarification of the roles of the NBD tertiary amine in H2S-specific probes as a fluorescent quencher and/or a weak fluorophore

Development of Bi-oligo (ethylene glycol)-Functionalized fluorescent probe for two-photon and noninvasive imaging in Arabidopsis thaliana

Hydrogen sulfide (H2S) has comprehensive contributions to maintaining the normal operation and stability of organisms, and it also occurs in the wastewater environment and is related to the deterioration of foodstuffs. Therefore, developing high-sensitive detection techniques for tracing H2S is promising and meaningful. Inspired by this, a novel nopinone-based fluorescent probe NPS for the recognition of H2S was designed and synthesized with excellent sensitivity, low limit of detection (79 nM), good selectivity, and wide pH range (5-9). NPS could emit strong yellow fluorescence and its emission intensity showed a remarkable augmentation at 520 nm upon the supplement of H2S. Furthermore, the recognition mechanism of NPS for H2S was verified by the HRMS analysis, 1H NMR spectra titration, and DFT computation. What is more, NPS also had broad applications in the monitoring of real water samples, red wine, beer, and eggs samples, which showed its development prospect and value in environmental pollution, foodstuffs quality analysis fields. NPS also was applied to monitor trace exogenous H2S and bioimaging in living cells and zebrafish.

Novel 2-Benzo[d]thiazolyl-4-quinolinylphenol Skeleton-Based Turn-on Fluorescent Probe for H2S Detection and its Multiple Applications in Water Environment, Foodstuffs, and Living Organisms.

Hydrogen sulfide (H2S) is one of the typical reactive sulfur species, which exhibits an important role in regulating both physiological and pathological processes. Recent studies indicate that H2S also serves as a key signaling molecule in a broad range of regulatory processes in plants. However, in situ imaging and detection of the levels of H2S in plant tissues remains a challenge. In this work, a NIR fluorescent probe (HBTP-H2S) was synthesized to achieve H2S imaging in living plant tissues. HBTP-H2S exhibited high sensitivity toward H2S with a large Stokes shift (250 nm). HBTP-H2S could be applied to HeLa cells to detect the fluctuation of endogenous H2S levels in response to physiological stimulations. Importantly, HBTP-H2S was utilized for direct H2S imaging of rice roots and revealed the upregulation of H2S signaling in response to aluminum ions and flooding stresses. Our work thus provides a new tool to investigate H2S-involved signal interaction and protective resistance of crops under environmental stresses.

Rong Wang

Papers

NIR Fluorescent Probe for In Situ Bioimaging of Endogenous H2S in Rice Roots under Al3+ and Flooding Stresses.