Precise mass measurement of a double-stranded 500 base-pair (309 kDa) polymerase chain reaction product by negative ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) has been used to determine the mass of a double-stranded 500 base-pair (bp) polymerase chain reaction (PCR) product with an average theoretical mass of the blunt-ended (i.e. unadenylated) species of 308 859.35 Da. The PCR product was generated from the linearized bacteriophage Lambda genome which is a double-stranded template. Utilization of ethanol precipitation in tandem with a rapid microdialysis step to purify and desalt the PCR product was crucial to obtain a precise mass measurement. The PCR product (0.8 pmol/μL) was electrosprayed from a solution containing 75% acetonitrile, 25 mM piperidine, and 25 mM imidazole and was infused at a rate of 200 nL/min. The average molecular mass and the corresponding precision were determined using the charge-states ranging from 172 to 235 net negative charges. The experimental mass and corresponding precision (reported as the 95% confidence interval of the mean) was 309 406 +/- 27 Da (87 ppm). The mass accuracy was compromised due to the fact that the PCR generates multiple products when using Taq polymerase due to the non-template directed 3'-adenylation. This results in a mixture of three PCR products with nearly identical mass (i.e. blunt-ended, mono-adenylated and di-adenylated) with unknown relative abundances that were not resolved in the spectrum. Thus, the experimental mass will be a weighted average of the three species which, under our experimental conditions, reflects a nearly equal concentration of the mono- and di-adenylated species. This report demonstrates that precise mass measurements of PCR products up to 309 kDa (500 bp) can be routinely obtained by ESI-FTICR requiring low femtomole amounts. Copyright 1999 John Wiley & Sons, Ltd.     

Inverse Cerenkov acceleration and inverse free-electron laserexperimental results for staged electron laser acceleration

The goal of the staged electron laser acceleration (STELLA) experiment is to demonstrate staging of the laser acceleration process whereby an inverse free electron laser (IFEL) will be used to prebunch the electrons, which are then accelerated in an inverse Cerenkov accelerator (ICA). As preparation for this experiment, a new permanent magnet wiggler for the IFEL was constructed and the ICA system was modified. Both systems have been tested on a new beamline specifically built for STELLA. The improved electron beam (e-beam) with its very low emittance (0.8 mm-mrad normalized) enabled focusing the e-beam to an average radius (1σ) of 65 μm, within the ICA interaction region. This small e-beam focus greatly enhanced the ICA process and resulted in electron energy spectra that have demonstrated the best agreement to date in both overall shape and magnitude with the model predictions. The electron energy spectrum using the new wiggler in the IFEL was also measured. These results will be described as well as future improvements to the STELLA experiment     

Contribution of polymeric supports to the development of tissue engineering

Tissue Engineering is an emerging discipline based on the concept of the rational design and fabrication of living tissues and organs for repair and replacement. The present article deals with the criteria for the selection of polymeric supports necessary for the growing and multiplication of cells responsible of the regenerative tissue. Criteria of biocompatibility, biodegradability and non toxic character of the degradation products are considered and the chemical structure and physical‐chemical properties and morphology of natural and synthetic polymeric systems are described. The experimental “in vivo” study of the regeneration of sciatic nerve in rats with a guided experimental device is presented. The activation of regeneration by the sustained release of growth hormone from a slow soluble vinyl pyrrolidone‐hydroxyethyl methacrylate copolymer hydrogel is shown on the basis of histopathological analysis.     

Symmetric Versus Asymmetric “Homologous” Vinylic Cross‐Linkers in Two‐Components Networks: Formation of Pseudo‐Conetworks or Pseudo‐IPNs

Radical copolymerizations of heterologous comonomers are compositionally heterogeneous, unless the reaction is performed in continuous conditions. A bicomponent network prepared from a heterogeneous reaction like the mentioned before is therefore a complex structure where chains with different compositions are linked through the cross‐linker molecules. It is theoretically shown here that the use of cross‐linkers with different structural homologies toward the two comonomers may lead to very different topologies. Thus, a mixture of symmetric cross‐linkers, each one homologous to each comonomer, tends to form interpenetrated networks (IPNs). However, the use of a single bihomologous asymmetric cross‐linker, where each of the functionalities is homologous toward each of the comonomers, tends to form conetworks. It is shown here that the higher the differential reactivity between the groups, the higher is the tendency toward these extreme structures.

     

Demonstration of α-helical structure of peptides tethered to gold surfaces using surface infrared and circular dichroic spectroscopies

Gold and quartz surfaces terminated in an alkane thiol self-assembled monolayer (SAM) that were partially terminated with azide were reacted with a helical peptide containing two alkyne groups in a Cu(I)-catalyzed Huisgen cycloaddition. Surface grazing incidence angle reflection-absorption infrared spectroscopy (GRAS-IR) was used to determine that when the Au surface was terminated with 25% of the monolayer containing azide groups, 92% of available azide groups reacted with the peptide. The majority of peptides reacted with both alkynes, resulting in peptides tethered to the surface through two covalent bonds. This was confirmed by comparison to a control peptide containing only one reactive alkyne group. Surface circular dichroic (CD) spectroscopy showed that while the helical structure of the peptide was distorted in the reaction solution, α-helical structure was induced when tethered on the SAM functionalized Au surface. Demonstration of the preservation of desired secondary structure of helical elements at a chemically functionalized surface is an important advance in preparing robust biologically mimetic surfaces to integrate functioning proteins into inorganic materials.     

Maghemite/poly(<Emphasis Type="SmallCaps">d,l</Emphasis>-lactide-<Emphasis Type="Italic">co</Emphasis>-glycolyde) composite nanoplatform for therapeutic applications

A reproducible methodology is described for the synthesis, by following the double emulsion/solvent evaporation technique, of magnetic nanocomposites (average diameter ≈ 135 nm) consisting of maghemite nuclei and a biodegradable poly(d,l-lactide-co-glycolide) matrix. The heterogeneous structure of the nanoparticles can confer them the responsiveness to magnetic gradients, giving both the possibility of their use as a drug delivery system and adequate heating characteristics for a hyperthermia effect. The physical chemistry of the nanocomposites was extensively characterized, this establishing that their surface properties were similar to that of pure poly(d,l-lactide-co-glycolide). From an electrokinetic point of view, zeta potential determinations (as a function of the ionic strength, and pH) pointed out that the nanocomposites were almost indistinguishable from the copolymer. The surface thermodynamic analysis agreed with the electrophoretic one in suggesting that the coverage of the magnetic nuclei was complete, since the hydrophilic nature of maghemite was modified and the nanoparticles turned into hydrophobic, just like the copolymer, when they were embedded into poly(d,l-lactide-co-glycolide). The magnetic behaviours of the composite nanoparticles were also checked. Their heating properties were studied in vitro in a high-frequency alternating gradient of magnetic field: a stable maximum temperature of 47 °C was satisfactorily achieved within 45 min. Blood compatibility of the nanocomposites was also defined in vitro. To our knowledge, this is the first time that such kind of magnetic-sensitive nanoformulation with very promising characteristics (e.g. blood compatibility, magnetic drug targeting capabilities, and hyperthermia) has been developed for therapeutic purposes.     

Food authentication of commercially-relevant shrimp and prawn species: From classical methods to Foodomics

Although seafood species identification has traditionally relied on morphological analysis, sometimes this is difficult to apply for the differentiation among penaeid shrimps owing to their phenotypic similarities and to the frequent removal of external carapace during processing. The objective of this review is to provide an updated and extensive overview on the molecular methods for shrimp and prawn species authentication, in which several omics approaches based on protein and DNA analysis are described. DNA-based methods include the amplification by PCR of different genes, commonly the mitochondrial 16S ribosomal RNA and cytochrome oxidase I genes. A recently described method based on RFLP coupled to PCR turned out to be particularly interesting for species differentiation and origin identification. Protein analysis methods for the characterization and detection of species-specific peptides are also summarized, emphasizing some novel proteomics-based approaches, such as phyloproteomics, peptide fragmentation, and species-specific peptide detection by HPLC coupled to multiple reaction monitoring (MRM) MS, the latter representing the fastest method described to date for species authentication in food.     

Classified Lines in the Spectra of Xe II and Xe III

The spectra of singly and doubly ionized xenon emitted by pulsed light sources have been studied. 35 lines of XeII and 69 lines of XeIII are classified in the range 112 - 676 nm.     

GPU computing for shallow water flow simulation based on finite volume schemes

This article is a review of the work that we are carrying out to efficiently simulate shallow water flows. In this paper, we focus on the efficient implementation of path-conservative Roe type high-order finite volume schemes to simulate shallow flows that are supposed to be governed by the one-layer or two-layer shallow water systems, formulated under the form of a conservation law with source terms. The implementation of the scheme is carried out on Graphics Processing Units (GPUs), thus achieving a substantial improvement of the speedup with respect to normal CPUs. Finally, some numerical experiments are presented.