High binding yet accelerated guest rotation within a cucurbit[7]uril complex. Toward paramagnetic gyroscopes and rolling nanomachines †

International audienceThe (15-oxo-3,7,11-triazadispiro[5.1.5.3]hexadec-7-yl)oxidanyl, a bis-spiropiperidinium nitroxide derived from TEMPONE, can be included in cucurbit[7]uril to form a strong (K a ∼ 2 × 10 5 M −1) CB[7]@bPTO complex. EPR and MS spectra, DFT calculations, and unparalleled increased resistance (a factor of ∼10 3) toward ascorbic acid reduction show evidence of deep inclusion of bPTO inside CB[7]. The unusual shape of the CB[7]@bPTO EPR spectrum can be explained by an anisotropic Brownian rotational diffusion, the global tumbling of the complex being slower than rotation of bPTO around its " long molecular axis " inside CB[7]. The CB[7] (stator) with the encapsulated bPTO (rotator) behaves as a supramolecular para-magnetic rotor with increased rotational speed of the rotator that has great potential for advanced nano-scale machines requiring wheels such as cucurbiturils with virtually no friction between the wheel and the axle for optimum wheel rotation (i.e. nanopulleys and nanocars)

New organogelators based on cyclotriveratrylene platforms bearing 2-dimethylacetal-5-carbonylpyridine fragments

International audienc

L’électron : une sonde fantastique

International audienceLe TEMPO (2,2,6,6-tétraméthyl-1-piperidinyloxy), et les nitroxydes en général, constituent une classe particulière de radicaux libres. Leur stabilité en ont fait des outils précieux et efficaces dans de nombreux domaines de la chimie, notamment comme agents d’oxydation en synthèse organique, comme aimants moléculaires ou bien encore comme sondes pour l’étude structurale et dynamique de systèmes complexes, organismes vivants inclus.La présence concomitante de spécificités chimiques, électrochimiques et magnétiques au sein d’une si petite molécule organique a conduit à une large variété d’applications en recherche mais aussi dans l’industrie, et les perspectives inspirantes et excitantes sont nombreuses.En outre, le signal RPE des nitroxydes encode une somme d’informations phénoménale qui est rendue plus accessible avec les récents développements méthodologiques et technologiques de la RPE

Antibiotic spider silk: site-specific functionalisation of recombinant spider silk using ‘click’- chemistry

The use of functionalised recombinant spider silk as a sustainable advanced biomaterial is currently an area of intense interest owing to spider silk’s intrinsic strength, toughness, biocompatibility and biodegradability. This paper demonstrates, for the first time, the site-specific chemical conjugation of different organic ligands that confer either antibiotic or fluorescent properties to spider silk. This has been achieved by the incorporation of the non-natural methionine analogue L-azidohomoalanine (L-Aha) using an E. coli methionine auxotroph and subsequent copper catalysed azide-alkyne cycloaddition (CuAAC) or ‘click chemistry’ functionalisation of 4RepCT3Aha. The 4RepCT3Aha protein can be modified either prior to, or post fibre formation increasing the versatility of this approach as demonstrated here by the formation of silk fibres bearing a defined ratio of two different fluorophores uniformly distributed along the fibres. Silk decorated with the fluoroquinone family broad spectrum antibiotic levofloxacin via a labile linker is shown to have significant antibiotic activity over a period of at least 5 days. The inherent low immunogenicity and pyrogenicity of spider silk should allow a diverse range of functionalised silks to be produced using these approaches that are tailored to applications including wound dressings and as tissue regeneration scaffolds

L’électron : une sonde fantastique

International audienceLe TEMPO (2,2,6,6-tétraméthyl-1-piperidinyloxy), et les nitroxydes en général, constituent une classe particulière de radicaux libres. Leur stabilité en ont fait des outils précieux et efficaces dans de nombreux domaines de la chimie, notamment comme agents d’oxydation en synthèse organique, comme aimants moléculaires ou bien encore comme sondes pour l’étude structurale et dynamique de systèmes complexes, organismes vivants inclus.La présence concomitante de spécificités chimiques, électrochimiques et magnétiques au sein d’une si petite molécule organique a conduit à une large variété d’applications en recherche mais aussi dans l’industrie, et les perspectives inspirantes et excitantes sont nombreuses.En outre, le signal RPE des nitroxydes encode une somme d’informations phénoménale qui est rendue plus accessible avec les récents développements méthodologiques et technologiques de la RPE

Sodium chains as core nanowires for gelation of organic solvents from a functionalized nicotijnic acid and its sodium salt

A new metallo-organic gelator formed from an admixture of a substituted nicotinic acid and its sodium salt is described. The nicotinic acid is substituted in the 6-position by an acetal functionality. The crystal structure of the 1:1 mixture revealed that the sodium atoms are aligned in infinite chains with the two organic units hydrogen bonded together to create potentially trinucleating ligands that encase the metal core, which leads to tube-like structures. These one-dimensional crystals were found to spontaneously gelify dichloromethane and provide pyridine gels with high thermal resistance. Gel formation was investigated by several analytical techniques, which included differential scanning calorimetry, TEM, freeze fracture electron microscopy (FFEM), IR spectroscopy and X-ray diffraction, and was found to be induced by the swelling of the one-dimensional material. FFEM and powder X-ray diffraction have revealed that the sodium chains are associated in a highly compacted state into a layered structure inside the gel. Doping these robust gels with dyes by diffusion, such as xylene cyanol, methyl yellow and bromo thymol blue, is feasible without destruction of the gels