Genetic code expansion (GCE) technology allows the specific incorporation of functionalized noncanonical amino acids (ncAAs) into proteins. Here, we investigated the Diels-Alder reaction between trans-cyclooct-2-ene (TCO)-modified ncAAs, and 22 known and novel 1,2,4,5-tetrazine-dye conjugates spanning the entire visible wavelength range. A hallmark of this reaction is its fluorogenicity - the tetrazine moiety can elicit substantial quenching of the dye. We discovered that photoinduced electron transfer (PET) from the excited dye to tetrazine is the main quenching mechanism in red-absorbing oxazine and rhodamine derivatives. Upon reaction with dienophiles quenching interactions are reduced resulting in a considerable increase in fluorescence intensity. Efficient and specific labeling of all tetrazine-dyes investigated permits super-resolution microscopy with high signal-to-noise ratio even at the single-molecule level. The different cell permeability of tetrazine-dyes can be used advantageously for specific intra- and extracellular labeling of proteins and highly sensitive fluorescence imaging experiments in fixed and living cells.
{Ag2 (12-C≡C-closo-1-CB11 H11 )}n and selected pyridine ligands have been used for the synthesis of photostable Ag(I) clusters that, with one exception, exhibit for Ag(I) compounds unusual room-temperature phosphorescence. Extraordinarily intense phosphorescence was observed for a distorted pentagonal bipyramidal Ag(I) 7 cluster that shows an unprecedented quantum yield of Φ=0.76 for Ag(I) clusters. The luminescence properties correlate with the structures of the central Ag(I) n motifs as shown by comparison of the emission properties of the clusters with different numbers of Ag(I) ions, different charges, and electronically different pyridine ligands.
Genetic code expansion (GCE) technology allows the specific incorporation of functionalized noncanonical amino acids (ncAAs) into proteins. Here, we investigated the Diels-Alder reaction between trans-cyclooct-2-ene (TCO)-modified ncAAs, and 22 known and novel 1,2,4,5tetrazine-dye conjugates spanning the entire visible wavelength range. A hallmark of this reaction is its fluorogenicity -the tetrazine moiety can elicit substantial quenching of the dye.We discovered that photoinduced electron transfer (PET) from the excited dye to tetrazine as the main quenching mechanism in red-absorbing oxazine and rhodamine derivatives. Upon reaction with dienophiles quenching interactions are reduced resulting in a considerable increase in fluorescence intensity. Efficient and specific labeling of all tetrazine-dyes investigated permits super-resolution microscopy with high signal-to-noise ratio even at the single-molecule level. The different cell permeability of tetrazine-dyes can be used advantageously for specific intra-and extracellular labeling of proteins and highly sensitive fluorescence imaging experiments in fixed and living cells.
A simple and efficient microwave-assisted synthesis of asymmetric pentamethine cyanine dyes with various functional groups was developed, which allows high-yielding results. The synthesized dyes are modifiable and suitable for single-molecule imaging in biological and medical sciences by application of click chemistry or classic esterification and amidation.
Salts of anionic silver(I) clusters with the carba-closo-dodecaboranylethynyl ligand were obtained from {Ag (12-C≡C-closo-1-CB H )} , selected pyridines, and [Et N]Cl or [Ph P]Br. Salts of octahedral silver(I) clusters [Et N] [Ag (12-C≡C-closo-1-CB H ) (4-X-C H N) ] were formed with pyridine (X=H, x=8), 4-methylpyridine (X=Me, x=8), and 4-cyanopyridine (X=CN, x=10). In contrast, 3,5-lutidine (3,5-Me Py) did not result in salts of dianionic clusters, even in the presence of excess of [Et N]Cl or [Ph P]Br; instead salts of monoanionic Ag clusters, [Et N][Ag (12-C≡C-closo-1-CB H ) (3,5-Me Py) ] and [Ph P][Ag (12-C≡C-closo-1-CB H ) (3,5-Me Py) ] were obtained. The Ag cluster is pentagonal bipyramidal in the former, but is an edge-capped octahedron in the latter. The 4-methylpyridine and 3,5-lutidine complexes show green phosphorescence at room temperature. Although argentophilic interactions give rise to sufficient spin-orbit coupling for intersystem crossing S →T and moderate-to-high radiative rate constants, time-resolved measurements indicate that the quantum yields are greatly influenced by the pyridine ligands, which mainly determine the non-radiative rate constants. In addition, the crystal structures of [Ag (12-C≡C-closo-1-CB H ) (Py) (CH CN) (CH Cl ) ]⋅CH Cl , [Ag (12-C≡C-closo-1-CB H ) (Py) ], [Ag (12-C≡C-closo-1-CB H ) (4-MePy) Br ], [Ag (12-C≡C-closo-1-CB H ) (4-tBuPy) Cl]⋅(4-tBuPy), and [Ag (12-C≡C-closo-1-CB H ) (3,5-Me Py) Cl] were elucidated.
Metabolic glycoengineering enables a directed modification of cell surfaces by introducing target molecules to surface proteins displaying new features. Biochemical pathways involving glycans differ in dependence on the cell type; therefore, this technique should be tailored for the best results. We characterized metabolic glycoengineering in telomerase-immortalized human mesenchymal stromal cells (hMSC‑TERT) as a model for primary hMSC, to investigate its applicability in TERT-modified cell lines. The metabolic incorporation of N‑azidoacetylmannosamine (Ac4ManNAz) and N‑alkyneacetylmannosamine (Ac4ManNAl) into the glycocalyx as a first step in the glycoengineering process revealed no adverse effects on cell viability or gene expression, and the in vitro multipotency (osteogenic and adipogenic differentiation potential) was maintained under these adapted culture conditions. In the second step, glycoengineered cells were modified with fluorescent dyes using Cu-mediated click chemistry. In these analyses, the two mannose derivatives showed superior incorporation efficiencies compared to glucose and galactose isomers. In time-dependent experiments, the incorporation of Ac4ManNAz was detectable for up to six days while Ac4ManNAl-derived metabolites were absent after two days. Taken together, these findings demonstrate the successful metabolic glycoengineering of immortalized hMSC resulting in transient cell surface modifications, and thus present a useful model to address different scientific questions regarding glycosylation processes in skeletal precursors.
Ausgehend von {Ag 2 (12-CC-closo-1-CB 11 H 11 )} n und ausgewählten Pyridinliganden wurden photostabile Ag ICluster synthetisiert, die,m it einer Ausnahme,e ine für Ag IVerbindungen ungewçhnliche Raumtemperaturphosphoreszenzz eigen. Eine besonders intensive Phosphoreszenz wurde für einen verzerrt pentagonal-bipyramidalen Ag
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.