Microscopic and Molecular Insights into Heterogeneous Phase Degradation of Agars and Carrageenans by Marine Bacterial Galactanases

Agars and carrageenans are sulfated galactans and are the main matrix component of the cell wall of red algae. They form gels made of a 3D network of fibres built by the aggregation of polysaccharide double-helices. Agarases and carrageenase are enzymes produced by marine bacteria involved in the conversion of algal biomass. We have analyzed the structures and the modes of action of these enzymes adapted to the degradation of anionic polysaccharides in heterogeneous phase. We found that κ- and ι-carrageenases proceed via an endo-processive mode of action as it was already described for other enzymes active on neutral polysaccharides (cellulose, starch).     

Luminescence properties of ytterbium and erbium doped silica-zirconia nanostructured optical fiber under near infrared excitation

We present here the luminescence properties of erbium and ytterbium doped silica-zirconia nanostructured optical fibers prepared by the chemical sol-gel method. After describing the preparation process, their waveguiding properties as well as luminescence properties under continuous pumping in the near infrared domain (NIR) are reported; the effects of the zirconia nanocrystals that are dispersed in the core of the fibers on their optical properties are finally discussed.     

Advances in original fibres fabrication using innovative techniques

The development of original technologies to fabricate new kinds of fibres is presented here. First of all, the sol–gel process is developed to achieve fibres with original properties of waveguiding (new wavelength of emission of rare earths or transition metals, ultraviolet waveguiding): either a fibre composed of doped nanocrystals in a silica matrix or fibres composed of a one dimensional photonic bandgap structure. In this way, high refractive index dielectric oxides like ZrO₂, TiO₂ are studied. Secondly, the core suction technique associated with the stack and draw process is developed to fabricate fibres with various glasses and then, original profiles of refractive index to achieve multiwavelength lasers.     

Bromine is an endogenous component of a vanadium bromoperoxidase

On the basis of EXAFS and MS/MS experimental results and a reinterpretation of the electron density map obtained by X-ray crystallography, we describe a new post-translational modification, that is, a 3,5-dibromotyrosine residue that is incorporated in the polypeptide chain of a vanadium haloperoxidase.     

Electrical-field-induced structural change and charge transfer of lanthanide-salophen complexes assembled on carbon nanotube field effect transistor devices

The application of a negative gate voltage on a carbon nanotube field effect transistor decorated by a binuclear Tb(iii) complex leads to the generation of a negatively charged mononuclear one, presenting an electron density transfer to the nanotube and ambipolar behaviour.     

Charge transfer and tunable ambipolar effect induced by assembly of Cu(II) binuclear complexes on carbon nanotube field effect transistor devices

Assembly of paramagnetic Cu(2) complexes with a Schiff base scaffold possessing extended electron delocalization together with a quasi-planar structure onto carbon nanotubes induces a diameter-selective charge transfer from the complex to the nanotubes leading to an interestingly large and tunable ambipolar effect. We used complementary techniques such as electron paramagnetic resonance, absorption spectroscopy, and photoluminescence to ensure the success of the assembly process and the integrity of the complex in the nanohybrid. We carried out density functional theory type calculations to rationalize the experimental results, evidencing the selective enhanced interaction of the metal complexes with one type of nanotube.