RESUMO
A method for conjugation of ligands to the surface of exosomes was developed using click chemistry. Copper-catalyzed azide alkyne cycloaddition (click chemistry) is ideal for biocojugation of small molecules and macromolecules to the surface of exosomes, due to fast reaction times, high specificity, and compatibility in aqueous buffers. Exosomes cross-linked with alkyne groups using carbodiimide chemistry were conjugated to a model azide, azide-fluor 545. Conjugation had no effect on the size of exosomes, nor was there any change in the extent of exosome adherence/internalization with recipient cells, suggesting the reaction conditions were mild on exosome structure and function. We further investigated the extent of exosomal protein modification with alkyne groups. Using liposomes with surface alkyne groups of a similar size and concentration to exosomes, we estimated that approximately 1.5 alkyne groups were present for every 150 kDa of exosomal protein.
Assuntos
Alcinos/química , Azidas/química , Química Click , Exossomos/química , Animais , Linhagem Celular , Cobre/química , Reagentes de Ligações Cruzadas/química , Reação de Cicloadição , Camundongos , Propriedades de SuperfícieRESUMO
α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic ß-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center.
Assuntos
Compostos Alílicos/química , Carbonatos/química , Cetonas/química , Paládio/química , Alquilação , Catálise , Descarboxilação , Cetonas/síntese química , Ligantes , Estrutura Molecular , EstereoisomerismoRESUMO
The first Suzuki-Miyaura cross-couplings of carbamates, carbonates, and sulfamates is described. The method provides a powerful means of using simple derivatives of phenol as precursors to polysubstituted aromatic compounds, as exemplified by a concise synthesis of the anti-inflammatory drug flurbiprofen.
Assuntos
Carbamatos/síntese química , Carbonatos/síntese química , Flurbiprofeno/síntese química , Ácidos Sulfônicos/síntese química , Carbamatos/química , Carbonatos/química , Flurbiprofeno/química , Estrutura Molecular , Estereoisomerismo , Ácidos Sulfônicos/químicaRESUMO
The folding kinetics of R. palustris cytochrome c' (cyt c') have been monitored by heme absorption and native Trp72 fluorescence at pH 5. The Trp72 fluorescence burst signal suggests early compaction of the polypeptide ensemble. Analysis of heme transient absorption spectra reveals deviations from two-state behavior, including a prominent slow phase that is accelerated by the prolyl isomerase cyclophilin. A nonnative proline configuration (Pro21) likely interferes with the formation of the helical bundle surrounding the heme.
Assuntos
Citocromos c'/química , Dobramento de Proteína , Ciclofilinas/química , Citocromos c'/genética , Fluorescência , Humanos , Concentração de Íons de Hidrogênio , Cinética , Estrutura Secundária de Proteína , Rodopseudomonas/genética , Rodopseudomonas/metabolismo , TermodinâmicaRESUMO
An enantioselective total synthesis of (+)-cassiol is reported. The complex derived from Pd(2)(pmdba)(3) and enantiopure t-BuPHOX ligand catalyzes enantioconvergent decarboxylative alkylation to generate the quaternary carbon stereocenter at an early stage. The overall synthetic strategy involves a convergent late-stage coupling of two fragments. The synthesis features a longest linear sequence of eight steps.