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A one- and two-photon activated photoremovable protecting group (PRPG) was designed based on a carbazole fused o-hydroxycinnamate platform for the dual (same or different) release of alcohols. The mechanism for the dual release proceeds through a stepwise pathway and also monitors the first and second photorelease in real time by an increase in fluorescence intensity and color change, respectively. Further, its application in staining live neurons and ex vivo imaging with two-photon excitation is shown. [ABSTRACT FROM AUTHOR]

An ESIPT based light activated hydrogen sulfide (H2S) donor using a p-hydroxyphenacyl phototrigger has been developed. The unique feature of our H2S donor system is that it provides real-time monitoring of H2S release by a non-invasive fluorescence colour change approach. [ABSTRACT FROM AUTHOR]

In this paper, we present fluorescent photoremovable protecting groups (FPRPG) based on bis-acetyl carbazole for the release of two different functional groups such as carboxylic acids, alcohols, thiols, and amines in a sequential fashion. Dualarm caged bis-acetyl carbazoles with different combinations of two unlike functional groups were synthesized. Photophysical studies showed that caged bis-acetyl carbazoles are blue fluorescent and their emission properties are sensitive to the environment. Sequential photorelease of two different functional groups by bis-acetyl carbazole was analyzed by HPLC, UV and emission spectroscopy. The mechanism of the dual release by bis-acetyl carbazole was investigated and supported by TD-DFT calculations. To demonstrate the applicability of the dual release ability of bis-acetyl carbazole FPRPG, we synthesized a drug delivery system (DDS) in which one arm of bis-acetyl carbazole is linked to the carboxylic functional group of chlorambucil (CBL) and the other arm is attached to the hydroxyl group of ferulic acid ethyl ester (FAEE). In vitro studies showed that our DDS presents excellent properties such as photoregulated dual drug delivery, cellular uptake, and biocompatibility. [ABSTRACT FROM AUTHOR]

A series of ester conjugates of carboxylic and amino acids were synthesized based on bimane fluorescent photoremovable protecting group (FPRPG). The photorelease of single and dual (same as well as different) carboxylic and amino acids is demonstrated from a single bimane molecule on irradiation with visible light (λ ≥ 410 nm). The detailed mechanistic study of photorelease revealed that the release of two caged acids is simultaneous but in a stepwise pathway. [ABSTRACT FROM AUTHOR]

The design, synthesis, and in vitro biological studies of a biotin-carbazole-dicyanovinyl-chlorambucil conjugate (Bio-CBZ-DCV-CBL; 6) are reported. This conjugate ( 6) is a multifunctional single-molecule appliance composed of a thiol-sensor DCV functionality, a CBZ-derived phototrigger as well as fluorescent reporter, and CBL as the anticancer drug, and Bio as the cancer-targeting ligand. In conjugate 6, the DCV bond undergoes a thiol-ene click reaction at pH<7 with intracellular thiols, thereby shutting down internal charge transfer between the donor CBZ and acceptor DCV units, resulting in a change of the fluorescence color from green to blue, and thereby, sensing the tumor microenvironment. Subsequent photoirradiation results in release of the anticancer drug CBL in a controlled manner. [ABSTRACT FROM AUTHOR]

A new fluorescent photoremovable protecting group (FPRPG) based on acetylcarbazole framework has been explored for the first time release of single and dual (similar or different) substrates from single chromophore. Mechanistic studies of the photorelease process revealed that photorelease of two (similar or different) substrates from acetyl carbazole proceeds via a stepwise pathway. Further, we constructed photoresponsive dual drug delivery system (DDS) to release two different anticancer drugs (caffeic acid and chlorambucil, 1 equiv each). In vitro study reveals that our DDS exhibit excellent properties like biocompatibility, cellular uptake, and photoregulated dual drug release. [ABSTRACT FROM AUTHOR]

The anti-tumor activity of Cu complexes is well established in cancer research. We developed a biotin-tagged Cu-chelating prodrug that is activated by one-photon and two-photon irradiation for the target-specific and spatio-temporally controlled in situ generation of a Cu complex. In this way, we transform copper from a "cancer-promoting" agent to an anticancer agent. [ABSTRACT FROM AUTHOR]

The combination of an organic photocatalyst [4CzIPN (1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6 dicyanobenzene) or 5MeOCzBN (2,3,4,5,6‐pentakis(3,6‐dimethoxy‐9 H‐carbazol‐9‐yl)benzonitrile)], quinuclidine, and tetra‐n‐butylammonium phosphate (hydrogen‐bonding catalyst) was employed for amide bond formations. The hydrogen‐bonded OH group activated the adjacent C−H bond of alcohols towards hydrogen atom transfer (HAT) by a radical species. The quinuclidinium radical cation, generated through single‐electron oxidation of quinuclidine by the photocatalyst, employed to abstract a hydrogen atom from the α‐C−H bond of alcohols selectively due to a polarity effect‐produced α‐hydroxyalkyl radical, which subsequently converted to the corresponding aldehyde under aerobic conditions. Then the coupling of the aldehyde and an amine formed a hemiaminal intermediate that upon photocatalytic oxidation produced the amide. [ABSTRACT FROM AUTHOR]

We report a new strategy, viz. cascade photocaging, for protecting diethylamine diazeniumdiolate (O2-position), a light sensitive molecule. Upon photolysis, the cascade photocage at first releases the light activatable linker (latent fluorophore) O2-caged diazeniumdiolate, which undergoes spontaneous 1,8-elimination, triggering the release of the diazeniumdiolate anion and the fluorophore. [ABSTRACT FROM AUTHOR]

With the recent explosion in high-resolution protein structures, one of the next frontiers in biology is elucidating the mechanisms by which conformational rearrangements in proteins are regulated to meet the needs of cells under changing conditions. Rigorously measuring protein energetics and dynamics requires the development of new methods that can resolve structural heterogeneity and conformational distributions. We have previously developed steady-state transition metal ion fluorescence resonance energy transfer (tmFRET) approaches using a fluorescent noncanonical amino acid donor (Anap) and transition metal ion acceptor to probe conformational rearrangements in soluble and membrane proteins. Here, we show that the fluorescent noncanonical amino acid Acd has superior photophysical properties that extend its utility as a donor for tmFRET. Using maltose-binding protein (MBP) expressed in mammalian cells as a model system, we show that Acd is comparable to Anap in steady-state tmFRET experiments and that its long, single-exponential lifetime is better suited for probing conformational distributions using time-resolved FRET. These experiments reveal differences in heterogeneity in the apo and holo conformational states of MBP and produce accurate quantification of the distributions among apo and holo conformational states at subsaturating maltose concentrations. Our new approach using Acd for time-resolved tmFRET sets the stage for measuring the energetics of conformational rearrangements in soluble and membrane proteins in near-native conditions. [ABSTRACT FROM AUTHOR]

A FRET donor–acceptor xanthene–coumarin conjugate has been designed for redox-regulated synergic treatment of photodynamic therapy and chemotherapy with real-time monitoring. The “locked” FRET pair was selectively “unlocked” by biological reducing thiols via rupture of a sacrificial disulfide linker. A distinct change in fluorescence color and selective cancer cell toxicity were observed in vitro. [ABSTRACT FROM AUTHOR]