Project description:The prevalence of 1,3-dipolar cycloadditions of azides and alkynes within both biology and chemistry highlights the utility of these reactions. However, the use of a copper catalyst can be prohibitive to some applications. Consequently, we have optimized a copper-free microwave-assisted reaction to alleviate the necessity for the copper catalyst. A small array of triazoles was prepared to examine the scope of this approach, and the methodology was translated to a protein context through the use of unnatural amino acids to demonstrate one of the first microwave-mediated bioconjugations involving a full length protein.
Project description:Since the seminal contribution of Rolf Huisgen to develop the [3+2] cycloaddition of 1,3-dipolar compounds, its azide-alkyne variant has established itself as the key step in numerous organic syntheses and bioorthogonal processes in materials science and chemical biology. In the present study, the copper(I)-catalyzed azide-alkyne cycloaddition was applied for the development of a modular molecular platform for medical imaging of the prostate-specific membrane antigen (PSMA), using positron emission tomography. This process is shown from molecular design, through synthesis automation and in vitro studies, all the way to pre-clinical in vivo evaluation of fluorine-18- labeled PSMA-targeting 'F-PSMA-MIC' radiotracers (t1/2 =109.7 min). Pre-clinical data indicate that the modular PSMA-scaffold has similar binding affinity and imaging properties to the clinically used [68 Ga]PSMA-11. Furthermore, we demonstrated that targeting the arene-binding in PSMA, facilitated through the [3+2]cycloaddition, can improve binding affinity, which was rationalized by molecular modeling. The here presented PSMA-binding scaffold potentially facilitates easy coupling to other medical imaging moieties, enabling future developments of new modular imaging agents.
Project description:Covalent organic frameworks (COFs) are porous materials formed through condensation reactions of organic molecules via the formation of dynamic covalent bonds. Among COFs, those based on imine and β-ketoenamine linkages offer an excellent platform for binding metallic species such as copper to design efficient heterogeneous catalysts. In this work, imine- and β-ketoenamine-based COF materials were modified with catalytic copper sites following a metallation method, which favored the formation of binding amine defects. The obtained copper-metallated COF materials were tested as heterogeneous catalysts for 1,3-dipolar cycloaddition reactions, resulting in high yields and recyclability.
Project description:Chemical reactions that enable selective biomolecule labeling in living organisms offer a means to probe biological processes in vivo. Very few reactions possess the requisite bioorthogonality, and, among these, only the Staudinger ligation between azides and triarylphosphines has been employed for direct covalent modification of biomolecules with probes in the mouse, an important model organism for studies of human disease. Here we explore an alternative bioorthogonal reaction, the 1,3-dipolar cycloaddition of azides and cyclooctynes, also known as "Cu-free click chemistry," for labeling biomolecules in live mice. Mice were administered peracetylated N-azidoacetylmannosamine (Ac(4)ManNAz) to metabolically label cell-surface sialic acids with azides. After subsequent injection with cyclooctyne reagents, glycoconjugate labeling was observed on isolated splenocytes and in a variety of tissues including the intestines, heart, and liver, with no apparent toxicity. The cyclooctynes tested displayed various labeling efficiencies that likely reflect the combined influence of intrinsic reactivity and bioavailability. These studies establish Cu-free click chemistry as a bioorthogonal reaction that can be executed in the physiologically relevant context of a mouse.
Project description:We present herein a straightforward and efficient pathway for the synthesis of pyrrolophthalazine cycloadducts via Huisgen [3 + 2] dipolar cycloaddition reactions of phthalazinium ylides to methyl propiolate or dimethyl acetylenedicarboxylate (DMAD). A thoroughly comparative study concerning the efficiency of synthesis, conventional thermal heating (TH) versus microwave (MW) and ultrasound (US) irradiation, has been performed. The cycloaddition reactions of phthalazinium ylides to methyl propiolate occur regiospecific, with a single regioisomer being obtained. Under conventional TH, the cycloaddition reaction of phthalazinium ylides with DMAD occurs to a mixture of inseparable partial and fully aromatized pyrrolophthalazine cycloadducts, while MW or US irradiation are leading only to fully aromatized compounds, with the reactions becoming selective. A feasible mechanism for formation of fully aromatized compounds is presented. Besides selectivity, it has to be noticed that the reaction setup under MW or US irradiation offer a number of other certain advantages: higher yields, decreasing of the amount of used solvent comparative with TH, decreasing of the reaction time from hours to minutes and decreasing of the consumed energy; consequently, these reactions could be considered environmentally friendly.
Project description:The strain-promoted click 1,3-dipolar cycloaddition reactions involving azides and cyclooctynes for the synthesis of triazoles offer the advantage of being able to be performed in biological settings via copper-free chemistries. While strained reagents conjugated to optical dyes and radiometal conjugates have been reported, cyclooctyne reagents labeled with fluorine-18 ((18)F) and radiochemically evaluated in a copper-free click reaction have yet to be explored. This report describes the conversion of a bifunctional azadibenzocyclooctyne (ADIBO) amine to the (18)F-labeled cyclooctyne 4, the subsequent fast copper-free 1,3-dipolar cycloaddition reaction with alkyl azides at 37 °C (>70% radiochemical conversion in 30 min), and biological evaluations (serum stability of >95% at 2 h). These findings demonstrate the excellent reactivity of the (18)F-labeled cyclooctyne 4 with readily available azides that will allow future work focusing on rapid copper-free in vitro and in vivo click chemistries for PET imaging using (18)F-labeled cyclooctyne derivatives of ADIBO.
Project description:In this work, low-cost lignin nanospheres were fabricated and further applied as an efficient and sustainable support for preparing cuprous oxide (Cu₂O) "green" catalyst by using electrospraying technology. The unalloyed lignin, a special three-dimensional molecular structure, was successfully processed into uniform nanospheres under an electrospraying condition. The synthesized lignin-supported Cu₂O catalyst had a well-defined nanosphere structure, and Cu₂O nanoparticles with sizes less than 30 nm were supported by exposed layers of lignin nanospheres. There were C⁻O⁻Cu bonds formed between the lignin nanospheres and the metallic nanoparticles. The lignin nanospheres and the lignin nanosphere-supported catalyst werfe characterized by utilizing XRD, SEM, TEM, XPS, EDS, and TGA. The immobilization of Cu₂O nanoparticles on the lignin nanospheres was beneficial for dispersion of the Cu₂O nanoparticles and preventing their aggregation, which could cause catalyst deactivation, which favored the Huisgen [3+2] cycloaddition reaction. The triazole synthesis results indicated that the lignin nanosphere-supported Cu₂O catalyst had a high catalytic performance with 99% yield under solvent-free conditions. Furthermore, the as-synthesized catalyst could be recycled for four times without significantly losing its catalytic activity.
Project description:We present the synthesis, properties, and biological applications of Ratio-Coppersensor-1 (RCS1), a new water-soluble fluorescent sensor for ratiometric imaging of copper in living cells. RCS1 combines an asymmetric BODIPY reporter and thioether-based ligand receptor to provide high selectivity and sensitivity for Cu(+) over other biologically relevant metal ions, including Cu(2+) and Zn(2+), a ca. 20-fold fluorescence ratio change upon Cu(+) binding, and visible excitation and emission profiles compatible with standard fluorescence microscopy filter sets. Live-cell confocal microscopy experiments show that RCS1 is membrane-permeable and can sense changes in the levels of labile Cu(+) pools within living cells by ratiometric imaging, including expansion of endogenous stores of exchangeable intracellular Cu(+) triggered by ascorbate stimulation in kidney and brain cells.
Project description:We present a full-field technique that allows label-free cytoskeletal network imaging inside living cells. This noninvasive technique allows monitoring of the cytoskeleton dynamics as well as interactions between the latter and organelles on any timescale. It is based on high-resolution quantitative phase imaging (modified Quadriwave lateral shearing interferometry) and can be directly implemented using any optical microscope without modification. We demonstrate the capability of our setup on fixed and living Chinese hamster ovary cells, showing the cytoskeleton dynamics in lamellipodia during protrusion and mitochondria displacement along the cytoskeletal network. In addition, using the quantitative function of the technique, along with simulation tools, we determined the refractive index of a single tubulin microtubule to be ntubu=2.36±0.6 at ?=527 nm.
Project description:To identity fast-acting, multistage antimalarial agents, a series of pyridylvinylquinoline-triazole analogues have been synthesized via CuAAC. Most of the compounds display significant inhibitory effect on the drug-resistant malarial Dd2 strain at low submicromolar concentrations. Among the tested analogues, compound 60 is the most potent molecule with an EC50 value of 0.04 ± 0.01 μM. Our current study indicates that compound 60 is a fast-acting antimalarial compound and it demonstrates stage specific action at the trophozoite phase in the P. falciparum asexual life cycle. In addition, compound 60 is active against both early and late stage P. falciparum gametocytes. From a mechanistic perspective, compound 60 shows good activity as an inhibitor of β-hematin formation. Collectively, our findings suggest that fast-acting agent 60 targets dual life stages of the malarial parasites and warrant further investigation of pyridylvinylquinoline hybrids as new antimalarials.