Electrochemistry as an Attractive and Effective Tool for the Synthesis and Immobilization of Porphyrins on an Electrode Surface

Magnesium(II) 10‐phenyl‐5,15‐p‐ditolylporphyrin is easily and cleanly transformed by electrolysis. A nitro group is first introduced at the free meso position by anodic substitution. Hydrogenation into the amine is then carried out electrocatalytically under ambient conditions with water as a hydrogen supplier. The synthesized porphyrin under the nickel(II) form can be covalently grafted onto a platinum electrode by electrochemical reduction of the diazonium cation, generated in situ by a reaction of the nickel(II) aminoporphyrin with sodium nitrite and trifluoroacetic acid. The electrosynthesized thin film gives an electrochemical response typical of a porphyrin material. Films grown under our conditions have a maximum surface coverage of approximately 5×10^?10 mol cm^?2. The modified electrode exhibits a reproducible electrochemical behavior and a good level of stability over potential cycling and exposition to air.     

Nonlinear friction dynamics on fibrous materials,application to the characterization of surface quality. Part I: global characterization of phase spaces

The diversity and the complexity of fibrous materials (woven fabrics, nonwovens or knitted fabrics) make the control of surface qualities very difficult. The control and the comprehension of the tribological phenomena generated by a dynamic friction are of major importance. Whereas the traditional investigations such as measurements of average parameters like roughness or friction coefficient quickly find their limits on such deformable, heterogeneous and flexible fibrous surfaces with very heterogeneous relief, this series of two publications proposes a new manner of observing the interactions of friction. Our laboratory has developed a patented method of measurements, called MODALSENS, which aims at rubbing a very fine and flexible blade on the analyzed surface. Dynamic friction with the contact generates nonlinear vibrations, and the response of the sensor is analyzed in its phase space using the tools of nonlinear analysis of time series. Then, when the evaluated surfaces change, this first part endeavors to characterize the portraits of phases related to the nonlinear vibrations of MODALSENS in a global way, by quantifying its invariants such as dimensions, Shannon entropies, diameters of attractors and largest Lyapunov exponents. From this first part, a classification of studied fibrous surfaces is built and is expected to give rise to new estimators for the surface quality analysis of fibrous media.     

Nonlinear friction dynamics on fibrous materials, application to the characterization of surface quality. Part?II: local characterization of phase space by recurrence plots

As has been shown in the first part of this series of papers, the global analysis of phase spaces does not allow one to access topographies of attractors, generated by the singular dynamic contacts between MODALSENS and our evaluated fibrous surfaces. By using the same time series from MODALSENS, this second paper presents a local exploration of the recurrences of the phase spaces. As a complement of the results from Part I, we propose, in this part of the work, a finer analysis of the vibrations of MODALSENS. Therefore, this part of the work aims at tracing friction dynamics cartographies of fibrous surfaces with the help of Recurrence Plots. This tool allows one to obtain images of recurrences in the space portraits. Hence, by regarding passages between strong and low magnitudes of vibrations, it is possible to take into account strong heterogeneities of relief and also the various mechanical and frictional behaviors of the asperities encountered during friction. Finally, Recurrence Quantification Analysis is performed in order to discuss the relationship between expected performances of the tested surfaces and their friction dynamics behaviors.     

Experimental observation of the transition between gas-phase and aqueous solution structures for acetylcholine, nicotine, and muscarine ions

Structural information on acetylcholine and its two agonists, nicotine, and muscarine has been obtained from the interpretation of infrared spectra recorded in the gas-phase or in low pH aqueous solutions. Simulated IR spectra have been obtained using explicit water molecules or a polarization continuum model. The conformational space of the very flexible acetylcholine ions is modified by the presence of the solvent. Distances between its pharmacophoric groups cover a lower range in hydrated species than in isolated species. A clear signature of the shift of protonation site in nicotine ions is provided by the striking change of their infrared spectrum induced by hydration. On the contrary, structures of muscarine ions are only slightly influenced by the presence of water.     

Towards the total synthesis of trichormamide A,a cyclic undecapeptide

Lipocyclopeptides isolated from marine sources hold great promise as new lead for therapeutics. Here, we propose the first attempt towards the total synthesis of Trichormamide A. This synthesis will help to confirm the proposed structure of the cyclic lipopeptide.