Enantioselective and regioselective indium(III)-catalyzed addition of pyrroles to isatins

The indium(III)-catalyzed enantioselective and regioselective addition of pyrroles to isatins is described. The effects of metal and solvent on the reactivity and selectivity are compared and discussed, demonstrating that the indium(III)-indapybox complex provides the most effective catalyst. A case of divergent reactivity between pyrroles and indoles is presented.     

Glycomics and glycoproteomics: Approaches to address isomeric separation of glycans and glycopeptides

Changes in the glycome of human proteins and cells are associated with the progression of multiple diseases such as Alzheimer's, diabetes mellitus, many types of cancer, and those caused by viruses. Consequently, several studies have shown essential modifications to the isomeric glycan moieties for diseases in different stages. However, the elucidation of extensive isomeric glycan profiles remains challenging because of the lack of analytical techniques with sufficient resolution power to separate all glycan and glycopeptide iso‐forms. Therefore, the development of sensitive and accurate approaches for the characterization of all the isomeric forms of glycans and glycopeptides is essential to tracking the progression of pathology in glycoprotein‐related diseases. This review describes the isomeric separation achievements reported in glycomics and glycoproteomics in the last decade. It focuses on the mass spectrometry–based analytical strategies, stationary phases, and derivatization techniques that have been developed to enhance the separation mechanisms in liquid chromatography systems and the detection capabilities of mass spectrometry systems.     

Time resolved fluorescence spectroscopy of quercetin and morin complexes with Al3+.

The association process of Al3+ with quercetin and morin in methanol was studied by electronic absorption and emission spectroscopies. The number of species in solution with different absorption spectra were determined by the method of Rank analysis of the absorbance matrix, and the stoichiometries of the complexes were evaluated using the Job method. The number of fluorescent species in solution were calculated from the Rank analysis method of the time resolved emission spectra (TRES), and compared with a global analysis of the decay surface using a proper multi-exponential decay model. The association of Al3+ with morin gives rise to two complexes with 1:1 and 2:1 (morin: Al3+) stoichiometries, but in both species the association of the cation involves the carbonyl and 3-hydroxyl groups of the pyrone ring. The fluorescence decay surface of this system is biexponential and the lifetimes of the 1:1 and 2:1 complexes are 4.3 and 2.0 ns, respectively. The association of Al3+ with quercetin forms preferentially two complexes with 1:1 and 1:2 (quercetin: Al3+) stoichiometries where the first cation binds to the site of the pyrone ring but the second one is bound to the cathecol group of the molecule. However, the multichelation character of the quercetin ligand allows larger aggregates to be formed, thereby the species Al2Q3 is also detected in methanol. The lifetime of the 1:1 complex is about 2.7 ns, while for 1:2 and 3:2 complexes the lifetimes measured are 3.5 and 1.8 ns, respectively.     

Nanotopography Engineering on Homopolymeric Surfaces Using Cold Plasma Generated Charges

Summary : Cold plasma as source for charged particles was used to induce nanotopographies on homopolymeric surfaces (nylon 12, PMMA, PMA, etc.). Hydrogen and helium plasmas were successfully used for surface nanoengineering of polymers using inductively coupled or atmospheric pressure non-equilibrium barrier discharge reactors. AFM analyses reveal the presence of nanotopographies on the treated surfaces. Physical factors control the process below the T_g and chemical factors dominate the process above T_g. Pyrolysis GC/MS analyses have been performed in order to obtain more information about the plasma processes. Cold plasma chemical processes, including charges effects are discussed as tools that open-up new ways for nanoengineering of the polymers' surfaces with specific functionalities and / or topography. Future nanomanufacturing techniques can generate anti-scratch, superhydrophobic or superhydrophilic properties on surface of every day use polymeric products by simple and convenient plasma enhanced processes.     

Manifestation of electrode surface states in molecular conduction

We present a conduction mechanism across molecular junctions which derives from conductance resonances that are not associated with particular molecular orbitals. Instead, the resonances are induced by states localized at the surface of the electrodes. To this end, we studied the conductance of a C₆₀ molecule bridging two carbon nanotubes. A simple tight-binding model is employed to investigate analytically the basic features of the effect.