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A new class of coumarin photocaging groups modified with an electron-rich styryl moiety at the 3-position was constructed. The large π-conjugated structure and stabilization of the carbocation intermediates by electron donors endowed the new photocaging groups with excellent long-wavelength absorption, large two-photon absorption cross-sections, and high uncaging quantum yields. Moreover, the new photocaging groups displayed unique photobleaching properties after photocleavage as a result of the intramolecular cyclization rearrangement of a carbocation intermediate to form five-membered ring byproducts and block the styryl conjugation at the 3-position. These superior properties of the new photocaging groups are extremely beneficial for high-concentration samples and thick specimens, thus extending the application of photocaging groups in many fields.

affect the quality of life of patients. [2] Unlike the external cutaneous membrane, the lining of the oral cavity has a wet and highly dynamic environment, [3] with endogenous saliva and exogenous food and drink continuously bathing the oral mucosa. In addition, chewing, speech, swallowing, and even changes in facial expressions cause movement of the tongue and oral mucosa. These complex challenges typically render local treatment strategies for protective materials and therapeutic drugs ineffective, owing to their short retention on the mucosal surface. [4] Topical agents such as solutions, powders, ointments, polymer films, and hydrogels (e.g., Gengigel) commonly used in clinical settings are diluted or washed away by saliva within 1 h. This is far shorter than the optimal repair time for treating oral mucosal disorders, which require 12-24 h to heal. [4] In addition to meet the fundamental requirements of safety and usability, the ideal oral mucosal repair material should be thin, elastic, and have excellent wet-tissue adhesion to resist The wet and highly dynamic environment of the mouth makes local treatment of oral mucosal diseases challenging. To overcome this, a photo-crosslinking hydrogel adhesive is developed inspired by the success of light-curing techniques in dentistry. The adhesive operates on a fast (within 5 s) phototriggered S-nitrosylation coupling reaction and employs imine anchoring to connect to host tissues. Unlike other often-used clinical agents that adhere weakly and for short durations, this thin, elastic, adhesive, and degradable cyclic o-nitrobenzyl-modified hyaluronic acid gel protects mucosal wounds from disturbance by liquid rinsing, oral movement, and friction for more than 24 h. The results from both rat and pig oral mucosa repair models demonstrate that this new gel adhesive creates a favorable microenvironment for tissue repair and can shorten tissue healing time. This study thus illustrates a therapeutic strategy with the potential to advance the treatment of oral mucosal defects in the clinic.

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An ew class of coumarin photocaging groups modified with an electron-rich styryl moiety at the 3-position was constructed. The large p-conjugated structure and stabilization of the carbocation intermediates by electron donors endowed the new photocaging groups with excellent longwavelength absorption, large two-photon absorption crosssections,and high uncaging quantum yields.Moreover,the new photocaging groups displayed unique photobleaching properties after photocleavage as ar esult of the intramolecular cyclization rearrangement of ac arbocation intermediate to form five-membered ring byproducts and block the styryl conjugation at the 3-position. These superior properties of the new photocaging groups are extremely beneficial for highconcentration samples and thickspecimens,thus extending the application of photocaging groups in many fields.Photocaging groups,a lso termed photoremovable protecting groups (PPGs), are molecules capable of releasing active groups upon light activation at as pecific wavelength. [1,2] Because of the non-invasive,n on-contamination, and high spatiotemporal precision of light stimulus control, PPGs are widely used in various fields of chemistry,b iology,a nd materials science. [3][4][5] Thet raditional PPGs,s uch as o-nitrobenzyl, [6] benzoinyl(desyl), [7] 4-hydroxyphenacyl, [8] and coumarinyl [9] moieties,a re all absorptive in the UV-light region which suffers from low tissue penetration and causes unwanted photochemical side reactions. [10] In the development of new PPGs,t hey are expected to have long-wavelength absorption that leads to deeper tissue penetration and matches the common laser wavelengths. [3,11] Many efforts have been made to develop visible and near-IR light-induced uncaging groups based on o-nitrobenzyl, [12] coumarin, [13] BODIPY, [14] cyanine, [15] and quinone [16] derivatives either by one-or two-photon excitation. Among them, the coumarin-based photocaging groups attract much attention because of the rapid photolysis and large two-photon (TP) absorption cross-section. Ellis-Davies,J ullien and coworkers successfully extended the maximal absorption wavelength of coumarin-based photocaging groups to the bluelight region (450 nm) by either p-conjugation with an acrylamide moiety at the 3-position [17] or as ulfur atom at the 2-position. [18] However,f urther redshift absorption is accompanied by ad rop in the uncaging efficiency. [19] In addition, it is worth mentioning that besides the absorption wavelength and uncaging efficiency,t he competitive absorption by the photolysis byproducts also affects the application of PPGs,e specially for high-concentration or thick samples because of the inner filtering of light rapidly attenuates the valid light intensity, [20] which significantly prolongs the uncaging time and decreases the overall conversion. Hence, the development of PPGs with long-wavelength absorption and ah igh uncaging efficiency,a sw ell as photobleaching at the irradiation wavelength, is of great significance.Herein, we developed an ew class of coumar...

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Protein covalent labeling is dramatically useful for studying protein function in living cells and organisms. In this field, the chemical tag technique combined with fluorogenic probes has emerged as a powerful tool. Herein, a series of TMP tag fluorogenic probes have been developed to span the green to full blue spectral range. These probes feature an acrylamide unit that acts as a linker group to conjugate the fluorophore and the ligand as well as a quencher and a covalent reaction group. After the probes bind to eDHFR:L28C, the acrylamide unit specifically reacts with the thiol group of the L28C residue beside the ligand binding pocket, achieving protein-specific labeling without any liberation of leaving groups. With these probes, multicolor and specific protein labeling with a fast reaction rate (t 1/2 = 33 s) and dramatic fluorescence enhancement (4000-fold) were obtained. Furthermore, no-wash protein labeling in both living cells and zebrafish was successfully achieved. We expect it may provide a general and highly effective chemical tool for the study of protein function in living cells and organisms.