Rapid mass spectrometric identification of human genomic polymorphisms using multiplexed photocleavable mass-tagged probes and solid phase capture

A mass spectrometric approach for rapid and simultaneous detection of several single nucleotide polymorphisms (SNPs) is reported. Oligonucleotide single base extension (SBE) primers, labelled at the 5'-end with photocleavable, quaternised and brominated peptidic mass tags, are extended by a mixture of the four dideoxynucleotides of which one is biotinylated. The 3'-biotinylated extension products are captured by streptavidin-coated solid phase magnetic beads, whilst non-biotinylated extension products and unreacted primers are washed away. Quaternised and brominated mass tags, cleaved from captured extension products during analysis by matrix-assisted laser desorption/ionisation-time-of-flight (MALDI-TOF) MS, are detected at pmol levels. This method is applied to the analysis of mitochondrial DNA polymorphisms for the purpose of human identification.     

Probing nanoscale solids at thermal extremes

We report a novel nanoscale thermal platform compatible with extreme temperature operation and real-time high-resolution transmission electron microscopy. Applied to multiwall carbon nanotubes, we find atomic-scale stability to 3200 K, demonstrating that carbon nanotubes are more robust than graphite or diamond. Even at these thermal extremes, nanotubes maintain 10% of their peak thermal conductivity and support electrical current densities approximately 2 x 10{8} A/cm{2}. We also apply this platform to determine the diameter dependence of the melting temperature of gold nanocrystals down to three nanometers.     

A micro procedure for the estimation of the protein content of mucus glycoproteins

A sensitive automated procedure for the estimation of the protein content of glycoproteins has been developed using 0.5-mg samples (10–250 μg of protein). The method employs a modification of the conventional amino acid analysis using the unresolved neutral and acidic amino acid peak to estimate the total protein content. Hexosamines, sialic acid, and amide amino acids do not interfere.     

Two similar dibenzo cyclic ethers with dissimilar conformations

Two dibenzo cyclic ether compounds, 6,12‐dibromodibenzo[d,i]‐1,2,3,6,7,8‐hexahydro‐1,3‐dioxecin (systematic name: 8,16‐dibromo‐2,4‐dioxatricyclo[12.4.0.0^5,10]octadeca‐5,7,9,14,16,18‐hexaene), C₁₆H₁₄Br₂O₂, (II), and 8,14‐dibromodibenzo[f,k]‐1,5‐dioxa‐1,2,3,4,5,8,9,10‐octahydrocyclododecene (systematic name: 7,19‐dibromo‐11,15‐dioxatricyclo[14.4.0.0^5,10]icosa‐5,7,9,16,18,20‐hexaene), C₁₈H₁₈Br₂O₂, (III), were prepared as scaffolding for phosphate‐anion receptors. In both compounds, the two aromatic rings are linked by three methylene units ortho to the oxygen substituent of each ring. The only difference between the two compounds is the number of methylene units linking the two ether O atoms. The dibenzo cyclic ether with an ether linkage of one methylene unit adopts a chair‐like conformation, where the two aromatic rings are parallel to each other. On the other hand, the dibenzo cyclic ether with an oxygen linkage of three methylene units adopts a bowl‐like conformation. The latter scaffold configuration is the only structure of the two that would allow for the placement of convergent functional groups necessary for the establishment of an anion‐selective binding pocket.     

Projective semimodules over semirings with valuations in nonnegative integers

We introduce semirings with valuations in nonnegative integers and prove that all projective semimodules over them are free.     

Identification of intra‐grain and grain boundary defects in polycrystalline Si thin films by electron paramagnetic resonance

We investigate the characteristics of intra‐grain and grain boundary defects in polycrystalline Si films, by employing quantitative electron paramagnetic resonance measurements on liquid phase crystallized layers with an average grain size of 200 µm and tailored solid phase crystallized Si layers with similar intra‐grain morphology but systematically varied grain sizes between 0.25 µm and 1 µm. The defect characteristics are found to be composed of two distinctive g ‐values of g = 2.0055 and 2.0032, which are attributed to grain boundary defects and intra‐grain defects, respectively. Additional hydrogenation leads to a reduction of the overall defect concentration, while a rapid thermal annealing process primarily heals intra‐grain defects.

     

Evaluation and single laboratory validation of an on-line turbulent flow extraction tandem mass spectrometry method for melamine in infant formula

This report presents the single-laboratory validation of a method for the determination of melamine in dairy-based products using on-line turbulent flow extraction-tandem mass spectrometry. Liquid or powder test portions were dissolved in water, enriched with (13)C(3)(15)N(3)-Melamine internal standard, followed by protein precipitation and withdrawal of an aliquot for analysis. The turbulent flow method was validated by analyses of liquid and powdered proficiency test portions containing up to 10mg/kg melamine. Accuracy of results ranged from 96 to 106% of the assigned values for the 6 proficiency test portions tested with relative standard deviations of 4-8%. Apparent recoveries based on addition of amino-(15)N(3)-Melamine to prepared test portions were between 98 and 114%. Based on the repeat analysis of a known blank sample the limit of detection and limit of quantification were determined to be 27 and 87 μg/kg, respectively. Additionally, this report demonstrates that turbulent flow chromatography is significantly faster than traditional LC-MS, with sample analysis times of less than 2 min.