Capillary electrophoretic study of the binding of zinc(II) ion to bacitracin A1 in water-2,2,2-trifluoroethanol

Binding of Zn(2+) to bacitracin A(1) was studied by capillary electrophoresis in water/2,2,2-trifluoroethanol (70/30 v/v) at different apparent pH values in order to estimate the association constant of metal, the acidic dissociation constants and the Stokes radii of both free and bounded peptide in apolar environment. The Stokes radii of the free peptide species were compared with those in aqueous solution, as obtained in a recent study performed by our group, indicating that apolar environment stabilizes bacitracin A(1) in a conformational structure with the lateral chain of apolar amino acids exposed on the external surface. This conformation of the macrocyclic dodecapeptide is ready to interact with Zn(2+) ion, as pointed out by the strong increase of the association constant measured in water/2,2,2-trifluoroethanol with respect to the value obtained in aqueous solution. In addition, whereas Zn(2+) ion binding in aqueous solution provides a sensible reduction of peptide Stokes radius, no sensible variations following to ion binding were observed in hydro-organic solution. The present results suggest that the apolar environment, rather than the metal ion binding, could be responsible for the conformational transition that brings bacitracin A(1) towards its biologically active structure.*     

Recycling of carbon fiber reinforced composite waste to close their life cycle in a cradle-to-cradle approach

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Size-selective template-assisted electrophoretic assembly of nanoparticles for biosensing applications

The precise, size-selective assembly of nanoparticles gives rise to many applications where the assembly of nano building blocks with different biological or chemical functionalizations is necessary. We introduce a simple, fast, reproducible-directed assembly technique that enables a complete sorting of nanoparticles with single-particle resolution. Nanoparticles are size-selectively assembled into prefabricated via arrays using a sequential template-directed electrophoretic assembly method. Polystyrene latex (PSL) nanoparticles with diameters ranging from 200 to 50 nm are selectively assembled into vias comparable to nanoparticle diameter. We investigate the effects of particle size and via size on the sorting efficiency. We show that complete sorting can be achieved when the size of the vias is close to the diameter of the nanoparticles and the size distribution of the chosen nanoparticles does not overlap. The results also show that it is necessary to keep the electric field on during the insertion and removal of the template. To elucidate the versatility and nil effects that the electrophoresis assembly technique has on the assembled nanoparticle characteristics, we have assembled cancer-specific monoclonal antibody-2C5-coated nanoparticles and have also shown that they can successfully measure low concentrations of the nucleosome (NS) antigen.     

A cyclodextrin-based nanoassembly with bimodal photodynamic action

We have developed a supramolecular nanoassembly capable of inducing remarkable levels of cancer cell mortality through a bimodal action based on the simultaneous photogeneration of nitric oxide (NO) and singlet oxygen ((1)O(2)). This was achieved through the appropriate incorporation of an anionic porphyrin (as (1)O(2) photosensitizer) and of a tailored NO photodonor in different compartments of biocompatible nanoparticles based on cationic amphiphilic cyclodextrins. The combination of steady-state and time-resolved spectroscopic techniques showed the absence of significant intra- and interchromophoric interaction between the two photoactive centers embedded in the nanoparticles, with consequent preservation of their photodynamic properties. Photodelivery of NO and (1)O(2) from the nanoassembly on visible light excitation was unambiguously demonstrated by direct and real-time monitoring of these transient species through amperometric and time-resolved infrared luminescence measurements, respectively. The typical red fluorescence of the porphyrin units was essentially unaffected in the bichromophoric nanoassembly, allowing its localization in living cells. The convergence of the dual therapeutic action and the imaging capacities in one single structure makes this supramolecular architecture an appealing, multifunctional candidate for applications in biomedical research.     

Magnetic field behavior of resonant current steps in one dimensional arrays of Josephson tunnel junctions

We study the magnetic field behavior of the resonant current steps appearing in one dimensional arrays of Josephson tunnel junctions. The analysis is carried out in the framework of the Kulik theory of resonances in small Josephson junctions, and the theoretical maximum current amplitude of the Fiske steps is computed as a function of the applied magnetic field. Preliminary measurements of the Fiske step current modulations induced by varying the magnetic field is also reported and discussed.     

Potential‐Driven Chirality Manifestations and Impressive Enantioselectivity by Inherently Chiral Electroactive Organic Films

The typical design of chiral electroactive materials involves attaching chiral pendants to an electroactive polyconjugated backbone and generally results in modest chirality manifestations. Discussed herein are electroactive chiral poly‐heterocycles, where chirality is not external to the electroactive backbone but inherent to it, and results from a torsion generated by the periodic presence of atropisomeric, conjugatively active biheteroaromatic scaffolds, (3,3′‐bithianaphthene). As the stereogenic element coincides with the electroactive one, films of impressive chiroptical activity and outstanding enantiodiscrimination properties are obtained. Moreover, chirality manifestations can be finely and reversibly tuned by the electric potential, as progressive injection of holes forces the two thianaphthene rings to co‐planarize to favor delocalization. Such deformations, revealed by CD spectroelectrochemistry, are elastic and reversible, thus suggesting a breathing system.