Transferable specific scaling factors for interpretation of infrared spectra of biomolecules from density functional theory

A set of transferable local scaling factors is established for assignment of infrared spectra of molecular systems of biological interest experimentally recorded under gas-phase conditions. Each scaling factor is specific for an experimentally observable vibrational mode chosen among those bringing significant structural information. Those factors are provided for harmonic calculations at the DFT B3LYP and DFT B3PW91 levels respectively with 7 and 2 different basis sets. The used training set of neutral molecules comprises nucleobases, aminoacids, peptides, sugars, and neurotransmitters. The proposed specific scaling factors usable for unambiguous conformer assignments lead to typical prediction errors ca. 10 cm(-1) for free and moderately hydrogen-bonded group frequencies with red-shifts up to 200 cm(-1).     

Controlled assembly of bacteria on chemical patterns using soft lithography

Highly ordered arrays of single living bacteria were obtained by selective adsorption of bacteria onto chemical patterns with micrometric resolution. The chemically engineered template surfaces were prepared with the combination of microcontact printing process and a simple incubation technique. This methodology can be used for fundamental studies of bacterium's inner mechanisms and sub-cellular organization as well as for interfacing living bacteria with artificial microsystems.     

Removal, recovery, and recycling of triarylphosphonium-supported tin reagents for various organic transformations

Phosphonium-supported tin reagents and catalysts were prepared and were shown to be effective in Stille couplings, radical dehalogenations, radical cyclizations, and carbonyl allylations. Not only could the tin residues be removed from the crude reaction mixture through a phase separation process but also they could be recovered and recycled.     

On the minimality of the p-harmonic ma p $$x/\|x\|$$ for weighted energy

In this paper, we study the minimality of the map for the weighted energy functional , where is a continuous function. We prove that for any integer and any non-negative, non-decreasing continuous function f, the map minimizes E _f,p among the maps in which coincide with on . The case p = 1 has been already studied in [Bourgoin J.-C. Calc. Var. (to appear)]. Then, we extend results of Hong (see Ann. Inst. Poincaré Anal. Non-linéaire 17: 35–46 (2000)). Indeed, under the same assumptions for the function f, we prove that in dimension n ≥  7 for any real with , the map minimizes E _f,p among the maps in which coincide with on .      

Probing amyloid fibril formation of the NFGAIL peptide by computer simulations

Amyloid fibril formation, as observed in Alzheimer's disease and type II diabetes, is currently described by a nucleation-condensation mechanism, but the details of the process preceding the formation of the nucleus are still lacking. In this study, using an activation-relaxation technique coupled to a generic energy model, we explore the aggregation pathways of 12 chains of the hexapeptide NFGAIL. The simulations show, starting from a preformed parallel dimer and ten disordered chains, that the peptides form essentially amorphous oligomers or more rarely ordered beta-sheet structures where the peptides adopt a parallel orientation within the sheets. Comparison between the simulations indicates that a dimer is not a sufficient seed for avoiding amorphous aggregates and that there is a critical threshold in the number of connections between the chains above which exploration of amorphous aggregates is preferred.     

Structure of a 4:1:4 supramolecular assembly of neutral TiiiiPO cavitands and tetrakis(N-methylpyridinium)porphyrin iodide

Four tetraphosphorylated TiiiiPO cavitands 1 encapsulate the pyridinium heads of a tetrakis(N-methylpyridinium)porphyrin iodide to form a 4:1:4 (host)4/guest4+/4I- complex. The single-crystal X-ray diffraction analysis shows the arrangement of the four cavities bound to the CH3N+ groups of the porphyrin moiety and the four iodide anions nested between the phenethyl substituents of the hosts. 1H NMR investigations show that the structure is preserved in chloroform solution and underscore the effect of the counteranions.     

Self-assembled nanocages for hydrophilic guest molecules

Reverse polymeric micelles are obtained following the association of polymeric amphiphiles in apolar media. To this date, reports of pharmaceutical applications for such micelles have been scarce, mainly because these systems have been studied in solvents that are not suitable for medical use. Here, alkylated star-shaped poly(glycerol methacrylate) polymers have been proposed in the design of oil-soluble reverse polymeric micelles. Micellar behavior was studied in various apolar solvents, including ethyl oleate, a pharmaceutically acceptable vehicle. The polymers were shown to assemble into spherical nanostructures (<40 nm) as determined by cryogenic transmission electron microscopy and atomic force microscopy studies. Interestingly, the reverse micelles were able to encapsulate various peptides/proteins (vasopressin, myoglobin, and albumin) in substantial amounts and facilitate their solubilization in oil. The nature of both the polymer used in micelle formation and the guest molecules was found to influence the ability of the micelle to interact with hydrophilic compounds.     

Numerical discrimination of intrachannel cross-phase modulation and intrachannel four-wave mixing and their respective effect on 40 Gbit/s transmissions

We propose a numerical method to accurately discriminate the influence of the different intrachannel nonlinear effects occurring in 40 Gbit/s optical transmissions, following an analogy with methods used to discriminate WDM interchannel effects. In contrast to other studies showing the predominance of intrachannel cross-phase modulation when low-dispersion fibers are used, in our study intrachannel four-wave mixing is the most penalizing effect in all investigated cases.