In N-salicylideneaniline derivatives, photochromism occurs by a two-step isomerization mechanism. Photochromism has been reported to be closely related to the molecular conformation of the N-salicylideneanilines (described by the dihedral angle Φ) and to the free available space (V free ) in the crystal. In this contribution, we focus on cocrystals of isomeric Nsalicylideneaminopyridines with perfluorinated halogen bond donors as coformers. The advantage of working with isomers is that they have a similar (if not equal) molecular volume. This aspect means that the evaluation and comparison of the free available spaces within cocrystals is not affected by the differences in the molecular volumes of their constituents. Cocrystals were synthesized by a one-pot procedure, which allowed concomitant formation of covalent (imine) and noncovalent (halogen) bonds. Each cocrystal was characterized by X-ray diffraction, and its photochromism was assessed by UV−vis diffuse reflectance. Our results suggest that the Φ/V free model grossly oversimplifies the complexity of the dynamic phenomenon behind the photoisomerization of N-salicylideneanilines. For the above-mentioned reasons, careful examination of intermolecular interactions and crystals packing (localization of voids, evaluation of intermolecular interactions and stacking modes) should be taken into account and used to supplement the current proposed model based on Φ and V free .

Brucellosis is one of the most widespread bacterial zoonoses worldwide. Here, our aim was to identify the effector mechanisms controlling the early stages of intranasal infection with Brucella in C57BL/6 mice. During the first 48 hours of infection, alveolar macrophages (AMs) are the main cells infected in the lungs. Using RNA sequencing, we identified the aconitate decarboxylase 1 gene (Acod1; also known as Immune responsive gene 1), as one of the genes most upregulated in murine AMs in response to B. melitensis infection at 24 hours post-infection. Upregulation of Acod1 was confirmed by RT-qPCR in lungs infected with B. melitensis and B. abortus. We observed that Acod1-/- C57BL/6 mice display a higher bacterial load in their lungs than wild-type (wt) mice following B. melitensis or B. abortus infection, demonstrating that Acod1 participates in the control of pulmonary Brucella infection. The ACOD1 enzyme is mostly produced in mitochondria of macrophages, and converts cis-aconitate, a metabolite in the Krebs cycle, into itaconate. Dimethyl itaconate (DMI), a chemically-modified membrane permeable form of itaconate, has a dose-dependent inhibitory effect on Brucella growth in vitro. Interestingly, structural analysis suggests the binding of itaconate into the binding site of B. abortus isocitrate lyase. DMI does not inhibit multiplication of the isocitrate lyase deletion mutant ΔaceA B. abortus in vitro. Finally, we observed that, unlike the wt strain, the ΔaceA B. abortus strain multiplies similarly in wt and Acod1-/- C57BL/6 mice. These data suggest that bacterial isocitrate lyase might be a target of itaconate in AMs.

Direct access to the protonated merocyanine forms of two substituted spiropyrans by mechanosynthesis or sonochemistry was explored. The compounds were formed by the condensation reaction of the methyleneindolium iodide salt with salicylaldehyde derivatives. X‐ray crystallography, 1H NMR spectroscopy, ab initio geometry optimization, and absorption spectroscopy were combined to provide a better understanding of the four‐state molecular switch system in which the newly synthesized protonated merocyanines were found to play a central role. The results of this study suggest that the stability of the protonated merocyanines requires acidic conditions, as treatment with base led to the corresponding unprotonated merocyanines, which in turn spontaneously converted into photochromic closed spiropyrans.

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ObjectivesThe spread of antibiotic resistant bacteria is an important threat for human health. Acinetobacter baumannii bacteria impose such a major issue, as multidrug- to pandrug-resistant strains have been isolated, rendering some infections untreatable. In this context, carbapenem-resistant A. baumannii bacteria were ranked as top priority by both WHO and CDC. In addition, A. baumannii bacteria survive in harsh environments, being capable of resisting to disinfectants and to persist prolonged periods of desiccation. Due to the high degree of variability found in A. baumannii isolates, the search for new antibacterials is very challenging because of the requirement of drug target conservation amongst the different strains. Here, we screened a chemical library to identify compounds active against several reference strains and carbapenem-resistant A. baumannii bacteria.MethodsA repurposing drug screen was undertaken to identify A. baumannii growth inhibitors. One hit was further characterized by determining the IC50 and testing the activity on 43 modern clinical A. baumannii isolates, amongst which 40 are carbapenem-resistant.ResultsThe repurposing screen led to the identification of a harmine-derived compound, called HDC1, which proves to have bactericidal activity on the multidrug-resistant AB5075-VUB reference strain with an IC50 of 48.23 µM. In addition, HDC1 impairs growth of 43 clinical A. baumannii isolates.ConclusionsWe identified a compound with inhibitory activity on all tested strains, including carbapenem-resistant clinical A. baumannii isolates.