Synthesis and characterization of a photoaffinity labelling probe based on the structure of the cystic fibrosis drug ivacaftor

Cystic Fibrosis (CF) is a genetic disorder caused by loss-of-function mutations to the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Ivacaftor (1) was the first therapeutic approved for the treatment of CF that is able to restore gating activity to certain CFTR variants although the mechanism of action is poorly understood. Herein we describe the synthesis of a photoaffinity labelling (PAL) probe (2) based on the structure of ivacaftor incorporating a photoreactive diazirine moiety for use in labelling studies designed to identify the binding site for ivacaftor on mutant CFTR. The PAL probe 2 retained potentiation activity, with a potency similar to 1, using a Fluorescent Imaging Plate Reader (FLIPR^®) assay measuring ion conductance potentiation of wild type (Wt)-CFTR. Photolabelling experiments with human serum albumin (HSA) as a model protein have shown that probe 2 can label HSA in a manner consistent with observed and predicted binding.     

Determination of the photolytic decomposition pathways of benzylchlorodiazirine by C60 probe technique

By employing C₆₀ as a chemical probe, the photolysis of benzylchlorodiazirine has been proposed to form carbene and the rearranged products via the excited state.     

Synthesis of nucleoside units possessing photoreactive diazirine groups on the major and minor groove faces

In this work, we developed and examined photoreactive nucleoside units, which are chemical probes to investigate the interaction between nucleic acids and proteins. Starting with 6-chloro-7-iodo-7-deazapurine derivative 5, 7-(3-oxobutyl)-7-deazaadenosine derivative 8 was prepared via a palladium-catalyzed reaction with 3-buten-2-ol. Then, the carbonyl group of 8 was converted into a diazirinyl group to provide the desired Dia⁷C⁷A 3. In a similar manner, Dia²A 4 was prepared from 2 to iodoadenosine derivative 11. The resulting 3 and 4 were confirmed to form chemically active carbene species via photo-irradiation.     

Preparation of novel 3H-trifluoromethyldiazirine-based photoactivatable potassium channel antagonists

The preparation of a series of photoactivatable precursors for use in photoaffinity labelling of potassium channels is described. 3H-Diazirine functionalities were incorporated into the previously described potassium channel antagonists 1-3. The ability to perform enantioselective reductions and Wittig reactions in the presence of 3H-diazirines was central to this work.     

Diazirine‐functionalized Nanostructured Platform for Enzymes Photografting and Electrochemical Biosensing

A simple technique for the construction of a versatile diazirine‐functionalized nanostructured platform for enzymes photografting and electrochemical biosensing was proposed in this work. The feasibility of the approach was proved by photo crosslinking of an enzyme, tyrosinase, to diazirine‐activated aminated carbon nanotubes coated glassy carbon electrode. The analytical performances of the realized biosensor were evaluated employing catechol as analyte. Then the sensor based on the diazirine‐functionalized nanostructured platform with photografted tyrosinase was applied together with the high resolution technique Differential Alternative Pulses Voltammetry for dopamine determination in the linear concentration range of 5–25 μmol L^?1 in the presence of interfering agents as uric acid up to its 100‐fold excess.     

An improved synthesis of 3-[3-(trifluoromethyl)-3H-1,2-diazirin-3-yl]aniline: A key intermediate in the synthesis of photoaffinity probes

An improved synthesis of 3-[3-(trifluoromethyl)-3H-1,2-diazirin-3-yl]aniline, achieving an overall yield of 38% over seven steps is reported. Only three chromatographic separations were needed and the preparation of ～0.7 g of the target compound was demonstrated. The stability of the diazirine in solution at room temperature while exposed to ambient light was studied. No significant degradation of the compound was observed over the course of five weeks in a 130 mM sample and only minor degradation was observed in weaker samples (10, 5, and 2.5 mM), as demonstrated by ¹H and ¹⁹F NMR.     

Diazirines as Potential Molecular Imaging Tags: Probing the Requirements for Efficient and Long‐Lived SABRE‐Induced Hyperpolarization

Diazirines are an attractive class of potential molecular tags for magnetic resonance imaging owing to their biocompatibility and ease of incorporation into a large variety of molecules. As recently reported, ¹⁵N₂‐diazirine can be hyperpolarized by the SABRE‐SHEATH method, sustaining both singlet and magnetization states, thus offering a path to long‐lived polarization storage. Herein, we show the generality of this approach by illustrating that the diazirine tag alone is sufficient for achieving excellent signal enhancements with long‐lasting polarization. Our investigations reveal the critical role of Lewis basic additives, including water, on achieving SABRE‐promoted hyperpolarization. The application of this strategy to a ¹⁵N₂‐diazirine‐containing choline derivative demonstrates the potential of ¹⁵N₂‐diazirines as molecular imaging tags for biomedical applications.     

Effects of Pressure, Solvent, and Substituent on the Thermal Isomerization of 2-Oxo- spiro[diazirine-3,3''''-indoline]

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Synthesis of an electronically-tuned minimally interfering alkynyl photo-affinity label to measure small molecule–protein interactions

We report the synthesis of an electronically-tuned minimally interfering photo-affinity label (MI-PAL), a compact five-carbon tag functionalized with an alkyl diazirine and alkyne handle. MI-PAL is compatible with protein photo-conjugation, click chemistry and mass spectrometry and readily installed to complex molecules for biological target identification.