Anionic copper complex fragmentations from enkephalins under low-energy collision-induced dissociation in an ion trap mass spectrometer

Peptide metallation with Cu2+ was explored in the negative ESI mode using an ion trap mass spectrometer. Under these conditions, the [(M-3H) + CuII]- species formed were investigated under low-energy collision-induced dissociation conditions. MS2 experiments indicate a very different behavior of CuII metallated complexes compared with [M-H]- species. CuII induces an easy loss of CO2 and specific side-chain cleavages (by radical losses) at the C-terminal residue, as observed previously by prompt 'in source' dissociation experiments. The loss of CO2 yields an unstable carbylide that leads to further dissociations involving the migration of a proton or a hydrogen radical (through the reduction of CuII). Multistage MS3 experiments were carried out to rationalize this behavior. Fragmentation pathways are proposed in order to explain the product ions observed. The side-chain radical loss at the C-terminus was demonstrated to be a consecutive process. Finally, evidence is provided that the specific side-chain cleavages can be used for the differentiation of Leu/Ile and Gln/Lys residues when they are located at the C-terminus. The existence of a zwitterionic form in the case of the anionic YGGFK-CuII complex is proposed.     

Laser-induced periodic surface structures on different poly-carbonate films

Laser-induced periodic surface structures (LIPSS) were generated on oriented and amorphous thick, as well as on spin-coated thin, poly-carbonate films by polarized ArF excimer laser light. The influence of the film structure and thickness on the LIPSS formation was demonstrated. Below a critical thickness of the spin-coated films the line-shaped structures transformed into droplets. This droplet formation was explained by the laser-induced melting across the whole film thickness and subsequent de-wetting on the substrate. The thickness of the layer melted by laser illumination was computed by a heat-conduction model. Very good agreement with the critical thickness for spin-coated films was found. The original polymer film structure influences the index of refraction of the thin upper layer modified by the laser treatment, as was proven by the dependence of the structure’s period on the angle of incidence both for ‘s’- and ‘p’-polarized beams. The effect of the original surface roughness – grains in thick films or holes in thin films – was studied using atomic force microscopy. It was shown that the oblique incidence of ‘s’-polarized beams results in an intensity confinement in the direction of the forward scattering and in asymmetrical interference pattern formation around these irregularities. A new, two-dimensional grating-like structure was generated on spin-coated films. These gratings might be used as a special kind of mask. Received: 10 July 2001 / Accepted: 23 July 2001 / Published online: 30 August 2001     

Novel chemico-mechanical approach towards long-term implantable glucose sensing

The proof of concept of a continuously sensing affinity device based on the glucose-dependent viscosity of a sensitive solution containing dextran and Concanavalin A has been successfully demonstrated. The biosensor incorporates a piezoelectric diaphragm and a flow-resisting microchannel for viscosity detection, and a free-standing Anodic Alumina Oxide (AAO) porous nano-membrane as glucose selective interface. Extensive in vitro glucose measurements between two physiologically relevant glucose concentrations, 2 mM and 9 mM (respectively hypo- and hyperglycemia), were successfully performed during 4 days. To the best of our knowledge, such reversibility and stability of glucose measurement over time had not been reported yet.     

Lefschetz pencil structures for 2-calibrated manifolds

We prove that for closed 2-calibrated manifolds there always exist Lefschetz pencil structures. This generalizes similar results for symplectic and contact manifolds. To cite this article: A. Ibort, D. Marti´nez Torres, C. R. Acad. Sci. Paris, Ser. I 339 (2004).