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Phenylalkylamines of the general formula C6H5(CH2)nNH2 (n = 1-4) have been delivered to the gas phase as protonated species using electrospray ionization. The ions thus formed have been assayed by IRMPD spectroscopy in two different spectroscopic domains, namely, the 600-1800 and the 3000-3500 cm(-1) regions using either an IR free electron laser or a tabletop OPO/OPA laser source. The interpretation of the experimental spectra is aided by density functional theory calculations of candidate species and vibrational frequency analyses. Protonated benzylamine presents a relatively straightforward instance of a single stable conformer, providing a trial case for the adopted approach. Turning to the higher homologues, C6H5(CH2)nNH3(+) (n = 2-4), more conformations become accessible. For each C6H5(CH2)nNH3(+) ion (n = 2-4), the most stable geometry is characterized by cation-π interactions between the positively charged ammonium group and the aromatic π-electronic system, permitted by the folding of the polymethylene chain. The IRMPD spectra of the sampled ions confirm the presence of the folded structures by comparison with the calculated IR spectra of the various possible conformers. An inspection of the NH stretching region is helpful in this regard.

A comprehensive ab initio investigation has been performed on the structure and stability of the isomers of cycloserine and its protonated forms in the unsolvated state. Many conformers of cycloserine in the ketonic (K), enolic (E4 and E2 ), and zwitterionic (Z7 and Z2 ) forms have been characterized. Enols E2 are only a few kilocalories per mole less stable than the K isomers. Enols E4 , as well as Z7 and Z2 zwitterions, are several tens of kilocalories per mole less stable than K. All the above isomeric structures exhibit pronounced isoxazolidine ring puckering, which generates very rich conformeric landscapes. The relative stability of the conformers of K, E2 , and E4 responds essentially to a complex balance between the attractive and repulsive electrostatic interactions among their functional groups. The preferred site of protonation of cycloserine in the gas phase has been also investigated computationally and experimentally by IR multiphoton dissociation (IRMPD) spectroscopy. The most basic center of cycloserine is the N(7) nitrogen atom (proton affinity (PA)=215.3 kcal mol-1 ). Another important basic site is the O(6) oxygen atom (PA=213.0 kcal mol-1 ). Their most populated conformers have been identified by IRMPD spectroscopy. Their predominance responds to the electrostatic interactions among the functional groups of the protonated molecule.

Oxidative damage to DNA yields guanine radical cations. Their gas-phase IR spectroscopic signature and acidity have been modelled by the radical cation of 9-methylguanine. Comparisons with quantum chemistry calculations suggest that radical cation formation produces the ground-state keto tautomer, which has an N-H acidity enhanced by ~470 kJ mol(-1).

Owing to their ability to be genetically expressed in live cells, fluorescent proteins have become indispensable markers in cellular and biochemical studies. These proteins can undergo a number of covalent chemical modifications that may affect their photophysical properties. Among other mechanisms, such covalent modifications may be induced by reactive oxygen species (ROS), as generated along a variety of biological pathways or through the action of ionizing radiations. In a previous report [1], we showed that the exposure of cyan fluorescent protein (ECFP) to amounts of (•)OH that mimic the conditions of intracellular oxidative bursts (associated with intense ROS production) leads to observable changes in its photophysical properties in the absence of any direct oxidation of the ECFP chromophore. In the present work, we analyzed the associated structural modifications of the protein in depth. Following the quantified production of (•)OH, we devised a complete analytical workflow based on chromatography and mass spectrometry that allowed us to fully characterize the oxidation events. While methionine, tyrosine, and phenylalanine were the only amino acids that were found to be oxidized, semi-quantitative assessment of their oxidation levels showed that the protein is preferentially oxidized at eight residue positions. To account for the preferred oxidation of a few, poorly accessible methionine residues, we propose a multi-step reaction pathway supported by data from pulsed radiolysis experiments. The described experimental workflow is widely generalizable to other fluorescent proteins, and opens the door to the identification of crucial covalent modifications that affect their photophysics.

International audience; To probe the structural implications of the proline residue on its characteristic peptide fragmentation patterns, in particular its unusual cleavage at its C-terminus in formation of a b(2) ion in XxxProZzz sequences, the structures of a series of proline-containing b(2)(+) ions were studied by using action infrared multiphoton dissociation (IRMPD) spectroscopy and fragment ion hydrogen-deuterium exchange (HDX). Five different Xxx-Pro b(2)(+) ions were studied, with glycine, alanine, isoleucine, valine, or histidine in the N-terminal position. The residues selected feature different sizes, chain lengths, and gas phase basicities to explore whether the structure of the N-terminal residue influences the Xxx-Pro b(2)(+) ion structure. In proteins, the proline side chain-to-backbone attachment causes its peptide bonds to be in the cis conformation more than any other amino acid, although trans is still favored over cis. However, HP is the only b(2)(+) ion studied here that forms the diketopiperazine exclusively. The GP, AP, IP, and VP b(2)(+) ions formed from protonated tripeptide precursors predominantly featured oxazolone structures with small diketopiperazine contributions. In contrast to the b(2)(+) ions generated from tripeptides, synthetic cyclic dipeptides VP and HP were confirmed to have exclusive diketopiperazine structures.

The ESI-formed protonated 2′-deoxycytidine, cytidine, cytarabine, and gemcitabine have been probed using infrared multiphoton dissociation (IRMPD) spectroscopy performed in the 900–2000 cm−1 region at CLIO, the Orsay Free Electron Laser facility, and in the 2800–3800 cm−1 region using a YAG-laser coupled to a table-top optical parametric oscillator/amplifier (OPO/OPA). The IRMPD spectra are compared of the protonated nucleosides with the IR spectra of their B3LYP/6-311++G(d,p)-optimized isomeric forms. The stability at room temperature of some conformers has been investigated by means of ab initio molecular dynamics simulations. The IRMPD spectra are consistent with the formation in the ESI source of both the N3- and the O2-protonated nucleosides. The most favoured members of both families are characterized by the pyrimidine base oriented anti to the furanose moiety. Concerning the O2-protonated nucleosides, IRMPD spectra and thermochemical considerations support the predominant formation of the structures with the proton oriented up relative to the furanose moiety.

The vibrational spectra of ciprofloxacin complexes with monovalent (Li +, Na+, K+, Ag+) and polyvalent (Mg2+, Al3+) metal ions are recorded in the range 1000-1900 cm-1 by means of infrared multiple-photon dissociation (IRMPD) spectroscopy. The IRMPD spectra are analyzed and interpreted in the light of density functional theory (DFT)-based quantum chemical calculations in order to identify the possible structures present under our experimental conditions. For each metal-ciprofloxacin complex, four isomers are predicted, considering different chelation patterns. A good agreement is found between the measured IRMPD spectrum and the calculated absorption spectrum of the most stable isomer for each complex. Metal ion size and charge are found to drive the competition among the different coordination motifs: small size and high charge density metal ions prefer to coordinate the quinolone between the two carbonyl oxygen atoms, whereas large-size metal ions prefer the carboxylate group as a coordination site. In the latter case, an intramolecular hydrogen bond compensates the weaker interaction established by these cations. The role of the metal cation on the stabilization of ionic and nonionic structures of ciprofloxacin is also investigated. It is found that large-size metal ions preferentially stabilize charge separated motifs and that the increase of metal ion charge has a stabilizing effect on the zwitterionic form of ciprofloxacin. © 2012 American Chemical Society.

The bare deprotonated 2,4-dinitrotoluene [DNT-H](-) anion, formed by electrospray ionization and trapped in a Paul ion-trap, has been investigated by IR multiple photon dissociation (IRMPD) spectroscopy and quantum chemical calculations at the B3LYP∕6-311++G** level. IRMPD spectra were recorded in the 950-1800 cm(-1) fingerprint range and interpreted by comparison with the calculated IR absorption spectra for different low-lying isomers. The sampled [DNT-H](-) species is found to involve deprotonation at the methyl group, yielding a benzyl carbanion 1', previously described as an amine complex in solution and here characterized by vibrational spectroscopy as an unperturbed gaseous species. Anion 1' is the most stable species among [DNT-H](-) isomers.

Gas-phase infrared photodissociation spectroscopy is reported for the microsolvated [Mn(ClO(4))(H(2)O)(n)](+) and [Mn(2)(ClO(4))(3)(H(2)O)(n)](+) complexes from n = 2 to 5. Electrosprayed ions are isolated in an ion-trap where they are photodissociated. The 2600-3800 cm(-1) spectral region associated with the OH stretching mode is scanned with a relatively low-power infrared table-top laser, which is used in combination with a CO(2) laser to enhance the photofragmentation yield of these strongly bound ions. Hydrogen bonding is evidenced by a relatively broad band red-shifted from the free OH region. Band assignment based on quantum chemical calculations suggest that there is formation of water-perchlorate hydrogen bond within the first coordination shell of high-spin Mn(II). Although the observed spectral features are also compatible with the formation of structures with double-acceptor water in the second shell, these structures are found relatively high in energy compared with structures with all water directly bound to manganese. Using the highly intense IR beam of the free electron laser CLIO in the 800-1700 cm(-1), we were also able to characterize the coordination mode (eta(2)) of perchlorate for two clusters. The comparison of experimental and calculated spectra suggests that the perchlorate Cl-O stretches are unexpectedly underestimated at the B3LYP level, while they are correctly described at the MP2 level allowing for spectral assignment.

A novel type of hemispherical cage was synthesized in a one-pot procedure, which displayed good binding properties towards nickel(II).

In this paper, some terms of Artificial Intelligence are defined. Some present and potential applications of knowledge based systems are presented in the field of wine-making. Areas of concern were: multi sensor fusion, prediction by model cooperation, and diagnosis. Artificial intelligence techniques can indeed be applied for aiding the wine-maker in his choices. They facilitate the combination between experience and recent progress in technology. When associated with statistical processing, they allow knowledge sources to be used more effectively. Beyond wine-making, the prospects of artificial intelligence are promising for research and food industry, especially for improving the robustness of measurement systems (multi-sensors, sensors interpreted or validated by models), and for process diagnosis (risk prediction, action proposal)., Certains termes d'Intelligence Artificielle (IA) sont définis dans cette publication. Quelques applications en cours ou potentielles de systèmes fondés sur la connaissance sont présentés dans le domaine de la vinification. Les domaines d'étude sont : la fusion multi-capteurs, la prédiction par coopération de modèles, et le diagnostic. Les techniques IA peuvent aider le vinificateur dans ses choix par une symbiose entre expérience et progrès technologiques. En association avec des traitements statistiques, ces techniques permettent une utilisation plus efficace des sources de connaissances. Au-delà de la vinification, les perspectives de l'intelligence artificielle sont prometteuses en industrie alimentaire, en particulier pour améliorer la robustesse d'un système de mesure (fusion de capteurs, validation d'un capteur par un modèle) ou pour élaborer un diagnostic sur l'évolution d'un procédé (prédiction de risques, proposition d'intervention).

A machine vision system was developed to inspect roses, and assign grades similar to those used by human graders. Illumination and image processing techniques were developed to extract the main features used by human vision. These features were identified as stem length, diameter and straightness, and bud color and maturity (i.e., openness). Illumination techniques include the design of an inspection chamber and the choice of proper light source. Image analysis includes the development of algorithms for image understanding. Supervised learning was used to classify roses.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.