Dansyl‐peptides matrix‐assisted laser desorption/ionization mass spectrometric (MALDI‐MS) and tandem mass spectrometric (MS/MS) features improve the liquid chromatography/MALDI‐MS/MS analysis of the proteome

Peptide tagging is a useful tool to improve matrix‐assisted laser desorption/ionization tandem mass spectrometric (MALDI‐MS/MS) analysis. We present a new application of the use of the dansyl chloride (DNS‐Cl). DNS‐Cl is a specific primary amine reagent widely used in protein biochemistry. It adds a fluorescent dimethylaminonaphthalene moiety to the molecule. The evaluation of MALDI‐MS and MS/MS analyses of dansylated peptides shows that dansylation raises the ionization efficiency of the most hydrophilic species compared with the most hydrophobic ones. Consequently, higher Mascot scores and protein sequence coverage are obtained by combining MS and MS/MS data of native and tagged samples. The N‐terminal DNS‐Cl sulfonation improves the peptide fragmentation and promotes the generation of b‐fragments allowing better peptide sequencing. In addition, we set up a labeling protocol based on the microwave chemistry. Peptide dansylation proved to be a rapid and cheap method to improve the performance of liquid chromatography (LC)/MALDI‐MS/MS analysis at the proteomic scale in terms of peptide detection and sequence coverage. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of poly(methylmethacrylate)/silica nanocomposites: Study of the interphase by solid‐state NMR and structure/properties relationships

Organic/inorganic nanocomposites were synthesized from poly(methylmethacrylate) (PMMA) and properly modified silica nanoparticles by in situ polymerization. Methacryloylpropyltrimethoxysilane was selected as nanoparticle surface modifier because it is characterized by unsaturated end groups available to radical reactions, making possible to suppose their participation in the acrylic monomer polymerization. As a result of the above hypothesized reactions, a phase constituted by polyacrylic chains grafted onto modified silica surface was isolated. ²⁹Si and ¹³C solid‐state nuclear magnetic resonance experiments permitted to analyze this phase in terms of composition and chain mobility as well as to highlight interaction mechanisms occurring between growing PMMA oligoradicals and functional groups onto silica surface. It was demonstrated that this PMMA grafted onto silica surface acts as an effective coupling agent and assures a good dispersion of nanoparticles as well as a strong nanoparticle/matrix interfacial adhesion. As a result of strong interactions occurring between phases, a significant increase of the glass transition temperature was recorded. Finally, the abrasion resistance of PMMA in the hybrids was significantly improved as a result of a different abrasion propagation mechanism induced by silica particles thus overcoming one of the most serious PMMA drawback. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and chiroptical properties of (naphthyl)ethylidene ketals of carbohydrates in solution and solid state

1,3-Dioxolane- and dioxane-type (1- and 2-naphthyl)ethylidene ketals of p-methoxyphenyl α-l-rhamnopyranoside and β-d-glucopyranoside were prepared and their stereochemistry studied by solution and solid-state circular dichroism, X-ray diffraction, and coupled-oscillator CD calculations on the solid-state and MMFF-calculated geometries. Intermolecular exciton-coupled interactions between the nearby aromatic chromophores in the solid state and different conformers in solution and solid state could be identified as the main reason for the difference between solution and solid-state CDs.     

Determination of perfluorochemicals in biological, environmental and food samples by an automated on-line solid phase extraction ultra high performance liquid chromatography tandem mass spectrometry method

A rapid on-line solid phase extraction ultra high performance liquid chromatography tandem mass spectrometry method was developed for the identification and quantitation of nine perfluorinated compounds in matrices of environmental, biological and food interest. Pre-treatment, solid phase extraction, chromatographic and mass detection conditions were optimised, in order to apply the whole methodology to the analysis of different matrices. Particular attention was devoted to the evaluation of matrix effect and the correlated phenomena of ion enhancement or suppression in mass spectrometry detection. LOD and LOQ range from 3 to 15ngL(-1) and from 10 to 50ngL(-1), respectively. Method detection limits (MDLs) were also calculated for each kind of matrix. The recovery, evaluated for each analyte, does not depend on analyte concentration in the explored concentration range: average Rˉ% values are always greater than 82.9%. In the whole, the results obtained for samples of river waters, blood serum, blood plasma, and fish confirm the ubiquitous presence of perfluorinated compounds, as recently denounced by many sources.     

Capillary electrophoresis-mass spectrometry methods for tryptic peptide mapping of therapeutic antibodies

Tryptic peptide mapping is routinely used in the biotech industry to confirm primary sequence, cell line stability, and to analyze posttranslational modifications. Peptide analysis is generally done by reverse phase liquid chromatography with UV or mass spectrometric detection. This method provides excellent resolution and sequence coverage. However, traditional methods are slow, and generally cannot detect small, hydrophilic peptides due to coelution with the column void volume. In this work, complementary CE-MS peptide analysis methods have been developed. The analyses are performed on a traditional CE-MS instrument with a sheath interface, and also on a novel sheathless interface that promises improved resolution and limit of detection. The methods were performed on a tryptic digest of a therapeutic monoclonal antibody for which LC-MS detects 97% sequence coverage. The 3% not covered consists of 11 peptides containing three amino acids or fewer, including two in the critical complementarity binding domain. Without further processing, the same tryptic digest was analyzed by CE-MS. Separation and detection of the 11 small peptides was achieved on CE-MS systems with both interfaces. The sheathless system produced better peak capacity and gave mass spectra with significantly less noise, while the sheath system proved to have better repeatability.     

Annoyance due to railway vibration at different times of the day

The time of day when vibration occurs is considered as a factor influencing the human response to vibration. The aim of the present paper is to identify the times of day during which railway vibration causes the greatest annoyance, to measure the differences between annoyance responses for different time periods and to obtain estimates of the time of day penalties. This was achieved using data from case studies comprised of face-to-face interviews and internal vibration measurements (N=755). Results indicate that vibration annoyance differs with time of day and that separate time of day weights can be applied when considering exposure-response relationships from railway vibration in residential environments.     

Interband absorption edge shift in dilute α-phase Cu-Zn and Cu-Al alloys

Recent compositional modulation spectra of dilute α-phase Cu-Zn and Cu-Al alloys have been re-analyzed. Kramers-Kronig analysis of Andrews and Hummel's modulated reflectivity data has been used to obtain the variation of the imaginary part of the dielectric constant. This in turn has been fitted with a recently developed phenomenological model. The procedure has allowed the determination of the interband absorption edge shifts induced by the solute.