Jie Zhang

Monoamine oxidase A (MAO‐A) plays a crucial role in neurotransmitter metabolism and oxidative stress regulation and is implicated in various neurological disorders and cancer progression. However, its detection is hindered by high structural similarity to its isoform MAO‐B and limitations of conventional methods, which exhibit poor specificity, low sensitivity, and spectral crosstalk. To overcome these challenges, Cyma , a water‐soluble near‐infrared ratiometric probe engineered on a cyanine platform, is developed. Cyma integrates a sulfonated cyanine core for improved water solubility, a clorgyline‐derived recognition unit to confer MAO‐A selectivity, and a propylamine moiety to enable enzymatic activation. Upon interaction with MAO‐A, Cyma undergoes a specific 1,6‐elimination and Smiles rearrangement, yielding a distinct fluorescence shift from 805 nm to 740 nm. Cyma demonstrates excellent selectivity for MAO‐A over MAO‐B and exhibits high sensitivity (detection limit: 0.0035 μg mL ⁻¹ ), with a strong linear correlation between ratiometric fluorescence intensity and MAO‐A concentration. Furthermore, excellent biocompatibility and MAO‐A detection ability of Cyma are demonstrated in SH‐SY5Y cells. These findings establish Cyma as a powerful tool for selectively detecting MAO‐A activity, offering significant potential for disease diagnosis, therapeutic monitoring, and intraoperative imaging.

A unique class of bioorthogonal fluorogenic probes, based on difluoroboronated tetrazine ( Tz-BFs ), has been developed. These probes are the smallest tetrazine-based fluorescent structures and exhibit a high fluorescence turn-on ratio (up to 582-fold) following the inverse electron-demand Diels-Alder reaction. By engineering π-conjugated systems and using push-pull groups, their fluorescence emission can be tuned across blue to yellow (440 to 570 nanometers). They offer no-wash fluorogenic behavior, excellent cell permeability, rapid reaction kinetics, and high photostability, ideal for real-time biomolecule tracking, suborganelle bioorthogonal imaging, and metabolic labeling. In addition, they enable stimulated emission depletion (STED) microscopy for subdiffraction resolution imaging and have click-to-release functionality for simultaneous fluorescence activation and therapeutic agent release, such as TCO ( trans -cyclooctene)–DOX (doxorubicin). These probes provide broad potential for advanced imaging and drug delivery applications.

The dynamics of excited‐state charge transfer (CT) in second near‐infrared (NIR‐II) fluorophore proceeds with conformational change that govern fluorescence. Unveiling the relationship between CT dynamics and conformational change in excited state is of great fundamental significance in optimizing NIR‐II fluorescence but remains less explored. This study unveils the pivotal role of large conformational change in promoting the evolution of emissive CT state into nonemissive CT state in NIR‐II fluorophore (CA‐BBT). Spectroscopic and computational results reveal that large conformational rotation/twisting leads to a pronounced increase in the CT character in excited state. This heightened CT character in CA‐BBT enables a rapid evolution of emissive CT state into a nonemissive CT state within 1.4 ps, as observed by ultrafast spectroscopy. Subsequently, this nonemissive state dominates nonradiative decay, resulting in very low NIR‐II fluorescence. Preventing such detrimental evolution by constraining the conformational dynamics of CA‐BBT results in a 10‐fold enhancement of NIR‐II fluorescence, enabling high‐resolution dynamic visualization of vasculature within osteosarcoma. This study offers a profound understanding of the relationship between CT dynamics and conformational changes in NIR‐II fluorescence, presenting innovative perspectives to develop bright NIR‐II fluorophores.

Photoaffinity labeling is a powerful technique to interrogate drug‐protein interactions in native cellular environments. Photo‐cross‐linkers are instrumental for this technique. However, the introduction of unnatural photo‐cross‐linkers may significantly reduce the bioactivity of the drug, thus impairing the chemoproteomic outcomes. Herein, we developed a common pharmacophore, isoxazole, into a natively embedded photo‐cross‐linker for chemoproteomics, which minimally perturbs the drug structure. The photo‐cross‐linking reactions of the isoxazole were thoroughly investigated for the first time. Functionalized isoxazoles were then designed and applied to protein labeling, demonstrating the superior photo‐cross‐linking efficiency. Subsequently, two isoxazole‐based drugs, Danazol and Luminespib, were employed in chemoproteomic studies, revealing their potential cellular targets. These results provide valuable strategies for future chemoproteomic study and drug development.

Photoaffinity labeling is a powerful technique to interrogate drug‐protein interactions in native cellular environments. Photo‐cross‐linkers are instrumental for this technique. However, the introduction of unnatural photo‐cross‐linkers may significantly reduce the bioactivity of the drug, thus impairing the chemoproteomic outcomes. Herein, we developed a common pharmacophore, isoxazole, into a natively embedded photo‐cross‐linker for chemoproteomics, which minimally perturbs the drug structure. The photo‐cross‐linking reactions of the isoxazole were thoroughly investigated for the first time. Functionalized isoxazoles were then designed and applied to protein labeling, demonstrating the superior photo‐cross‐linking efficiency. Subsequently, two isoxazole‐based drugs, Danazol and Luminespib, were employed in chemoproteomic studies, revealing their potential cellular targets. These results provide valuable strategies for future chemoproteomic study and drug development.

Background and Purpose: Endothelium‐derived hyperpolarizing factor (EDHF) has been suggested as a therapeutic target for vascular protection against ischaemic brain injury. However, the molecular entity of EDHF and its action on neurons remains unclear. This study was undertaken to demonstrate whether the hydrogen sulfide (H₂S) acts as EDHF and exerts neuroprotective effect via large‐conductance Ca²⁺‐activated K⁺ (BK_Ca/K_Ca1.1) channels.Experimental Approach: The whole‐cell patch‐clamp technology was used to record the changes of BK_Ca currents in rat neurons induced by EDHF. The cerebral ischaemia/reperfusion model of mice and oxygen–glucose deprivation/reoxygenation (OGD/R) model of neurons were used to explore the neuroprotection of EDHF by activating BK_Ca channels in these neurons.Key Results: Increases of BK_Ca currents and membrane hyperpolarization in hippocampal neurons induced by EDHF could be markedly inhibited by BK_Ca channel inhibitor iberiotoxin or endothelial H₂S synthase inhibitor propargylglycine. The H₂S donor, NaHS‐induced BK_Ca current and membrane hyperpolarization in neurons were also inhibited by iberiotoxin, suggesting that H₂S acts as EDHF and activates the neuronal BK_Ca channels. Besides, we found that the protective effect of endothelium‐derived H₂S against mice cerebral ischaemia/reperfusion injury was disrupted by iberiotoxin. Importantly, the inhibitory effect of NaHS or BK_Ca channel opener on OGD/R‐induced neuron injury and the increment of intracellular Ca²⁺ level could be inhibited by iberiotoxin but enhanced by co‐application with L‐type but not T‐type calcium channel inhibitor.Conclusion and Implications: Endothelium‐derived H₂S acts as EDHF and exerts neuroprotective effects via activating the BK_Ca channels and then inhibiting the T‐type calcium channels in hippocampal neurons.

A rotor-based fluorescent probe to label exosomes in living cells.

Hydrogen sulfide (H₂S) has been recognized to influence a wide range of physiological and pathological processes. Its underlying molecular events, however, are still poorly understood. An activatable H₂S probe for photoacoustic (PA) imaging is desirable to further explore the role of H₂S in vivo. Nevertheless, only a few activatable PA probes for H₂S detection have been reported. In particular, examples of dual-modal H₂S probes with the combined advantages of fluorescence (high sensitivity and resolution) and PA imaging (deep penetration) are very rare. Herein the controllable cleavage of the C–N bond in nitrobenzoxadiazole (NBD) amine derivatives by H₂S is presented for the first time. The cleavage reactivity was found to be accelerated by the introduction of an electron-withdrawing group. Through this strategy, a series of fluorescent and PA dual-modal probes (1–3) were developed for H₂S detection. Among them, probe 3 shows a high fluorescence on–off response rate (k₂ = 4.04 M^–1 s^–1) and excellent selectivity for H₂S over other biothiols. Moreover, probe 3 can also work as an activatable PA H₂S probe because of the significant shift of its absorption peak from 468 to 532 nm in the H₂S reaction. Importantly, probe 3 demonstrates its capability for fluorescence and PA imaging of H₂S in living cells and mice. These results indicate that the controllable cleavage of the C–N bond can serve as an efficient strategy for designing fluorescent and PA dual-modal H₂S probes.