Modulating Aryl Azide Photolysis: Synthesis of a Room-Temperature Phosphorescent Carboline in Cucurbit[7]uril Host.

Cucurbit[7]uril (CB7), a supramolecular host, is employed to control the pathway of photolysis of an aryl azide in an aqueous medium. Normally, photolysis of aryl azides in bulk water culminates predominantly in the formation of azepine derivatives via intramolecular rearrangement. Remarkably, however, when this process unfolds within the protective confinement of the CB7 cavity, it results in a carboline derivative, as a consequence of a C─H amination reaction. The resulting carboline caged by CB7 reveals long-lived room temperature phosphorescence (RTP) in the solid state, with lifetimes extending up to 2.1 s. These findings underscore the potential of supramolecular hosts to modulate the photolysis of aryl azides and to facilitate novel phosphorescent materials.

Fluorescent labeling of plasmid DNA for gene delivery: Implications of dye hydrophobicity on labeling efficiencies and nanoparticle size.

Covalent fluorescent labels are important tools for monitoring the in vitro and in vivo localization of plasmid DNA nanoparticles, but must meet several criteria including high DNA labeling efficiencies and minimal impact on nanoparticle size. We developed a novel fluorescent labeling strategy utilizing an aryl azide photolabel conjugated to a short cationic peptide to label plasmid DNA with Cyanine 5 and sulfo-Cyanine 5. Using a simple camera flash apparatus, photolabel-peptide-dyes can be conjugated to DNA in minutes with preservation of DNA structure and minimal dye photobleaching. The addition of two anionic sulfonates to the Cyanine 5 core greatly improved labeling efficiencies from ~13 to ~53% and mitigated PEGylated polyacridine peptide-DNA nanoparticle size increases over a range of labeling densities. Comparison of our sulfo-Cyanine 5 peptide label to the Mirus Bio Label IT-Cy5 kit revealed that while both did not affect nanoparticle sizes appreciably, labeling efficiencies with our conjugate were higher, possibly due to the higher positive charge density on the peptide linker. The results from this work provide important considerations for choosing fluorophore tags to track DNA nanoparticles.

Photo-affinity labeling (PAL) in chemical proteomics: a handy tool to investigate protein-protein interactions (PPIs).

Protein-protein interactions (PPIs) trigger a wide range of biological signaling pathways that are crucial for biomedical research and drug discovery. Various techniques have been used to study specific proteins, including affinity chromatography, activity-based probes, affinity-based probes and photo-affinity labeling (PAL). PAL has become one of the most powerful strategies to study PPIs. Traditional photocrosslinkers are used in PAL, including benzophenone, aryl azide, and diazirine. Upon photoirradiation, these photocrosslinkers (Pls) generate highly reactive species that react with adjacent molecules, resulting in a direct covalent modification. This review introduces recent examples of chemical proteomics study using PAL for PPIs.

Proximity Labeling and Proteomics: Get to Know Neighbors.

Protein-protein interactions are essential in biological reactions and fundamental to cell-cell communication (e.g., the binding of secreted proteins, such as hormones, to cell membrane receptors) and the subsequent intracellular signal transduction cascade. Several studies have been extensively carried out on protein-protein interactions because they have the potential to resolve various problems in molecular biology. Biochemical methods, such as chemical cross-linking and immunoprecipitation, have long been used to analyze which proteins interact with each other. However, there are some problems, such as unphysiological states and non-specific binding, that require the development of more useful experimental methods. This chapter discusses the "proximity labeling (Proteomics)" analysis technique, which has been attracting attention in protein-protein interaction analysis in recent years and is used in many biological studies. "Membrane proximity labeling (proteomics)," which analyzes the interaction of cell membrane proteins, and "intracellular proximity labeling (proteomics)" will be explained in-depth.

Multifluorinated Aryl Azides for the Development of Improved H2 S Probes, and Fast Strain-promoted Azide-Alkyne Cycloaddition and Staudinger Reactions.

The development of advanced bioorthogonal reactions for detection and labeling of biomolecules is significant in chemical biology. Recently, researchers have found that multifluorinated aryl azides hold great potential for the development of improved bioorthogonal reactions. The fluorine atom can be a perfect substituent group because of its properties of excellent electronegativity and small steric hindrance. In this Minireview, we discuss recent developments of improved hydrogen sulfide (H2 S) fluorescence probes, fast strain-promoted azide-alkyne cycloaddition (SPAAC) and nonhydrolysis Staudinger reactions based on the use of multifluorinated aryl azides. Additionally, kinetic studies and biological applications of these reactions are also presented.

Synergistic anti-fouling and bactericidal poly(ether ether ketone) surfaces via a one-step photomodification.

Implants of poly(ether ether ketone) (PEEK) are gaining importance in surgical bone reconstruction of the skull. As with any implant material, PEEK is susceptible to bacterial contamination and occasionally PEEK implants were removed from patients because of infection. To address this problem, a combination of anti-fouling and bactericidal polymers is grafted onto PEEK. The originality is that anti-fouling (modified poly(ethylene glycol)) and bactericidal (quaternized poly(dimethylaminoethyl acrylate)) moieties are simultaneously and covalently grafted onto PEEK via UV photoinsertion. The functionalized PEEK surfaces are evaluated by water contact angle measurements, FTIR, XPS and AFM. Grafting of anti-fouling and bactericidal polymers significantly reduces Staphylococcus aureus adhesion on PEEK surfaces without exhibiting cytotoxicity in vitro. This study demonstrates that grafting combinations of anti-fouling and bactericidal polymers synergistically prevents bacterial adhesion on PEEK implants. This approach shows clinical relevance as grafting is rapid, does not modify PEEK properties and can be conducted on pre-formed implants.

Generation of cellular micropatterns on a single-layered graphene film.

Micropatterns of fibroblast and hippocampal neurons are generated on a single-layered graphene substrate. A large-area (1 cm × 1 cm) graphene film on Si/SiO2 is functionalized by surface-initiated ATRP of non-biofouling oligo(ethylene glycol) methacrylate, after grafting of the polymerization initiator bearing α-bromoisobutylate via photoreaction of the perfluorophenyl azide group. The microcontact printing-assisted spatio-selective reaction, after chemical activation of the terminal hydroxyl group of oligo(ethylene glycol) in the polymeric film, is utilized to generate the patterns of fibroblast and hippocampal neurons.

Structure-Activity Relationship of Semicarbazone EGA Furnishes Photoaffinity Inhibitors of Anthrax Toxin Cellular Entry.

EGA, 1, prevents the entry of multiple viruses and bacterial toxins into mammalian cells by inhibiting vesicular trafficking. The cellular target of 1 is unknown, and a structure-activity relationship study was conducted in order to develop a strategy for target identification. A compound with midnanomolar potency was identified (2), and three photoaffinity labels were synthesized (3-5). For this series, the expected photochemistry of the phenyl azide moiety is a more important factor than the IC50 of the photoprobe in obtaining a successful photolabeling event. While 3 was the most effective reversible inhibitor of the series, it provided no protection to cells against anthrax lethal toxin (LT) following UV irradiation. Conversely, 5, which possessed weak bioactivity in the standard assay, conferred robust irreversible protection vs LT to cells upon UV photolysis.