Non-Magnetic Stainless Steels Reinvestigated – a Small Effective Field Component in External Magnetic Fields

Hyperfine Interactions - Three standard non-magnetic stainless steels of composition (wt%) Fe70Cr19Ni11, Fe70Cr17Ni13 and Fe69Cr18.5Ni10.3Mn1.8Ti0.4 have been investigated by Mössbauer...     

Solid phase organic synthesis of piperazinone containing enkephalin mimetics: a readily derivatized, traceless scaffold

The solid phase synthesis of a series of piperazinone-derived Leu-enkephalin analogues is presented. The initial step in the synthesis involved the N-alkylation of Wang resin bound N-(4-tert-butyloxy-phenethyl)-glycine with D or L Boc-serine-beta-lactone (the Vederas lactone). The resulting carboxylic acid was then coupled to a variety of monosubstituted benzylamine derivatives using benzotriazol-1-yloxy-tris(dimethyl-amino)phosphonium hexafluorophosphate (the BOP reagent) to yield a series of resin bound tertiary amides. Treatment with 5% H2O in TFA resulted in the facile cleavage, deprotection, and cyclization of this linear precursor to yield a series of piperazinones (compounds 1-8).     

Microarray-based resequencing by apyrase-mediated allele-specific extension

We have developed an array-based resequencing method to determine genetic alterations in putative cancer genes. The method relies on that the specificity of DNA polymerase in allele-specific extensions can be enhanced by terminating the extension reactions with apyrase and that a tiling set of primers are synthesized covering the investigated gene sequence. We report on such apyrase-mediated allele-specific primer extension (AMASE) assay as a method suitable for high-throughout resequencing and mutation detection in tumor suppressor genes and oncogenes. In the experimental setup, primers complementary to codons 12, 13 and codon 61 of the N-ras proto-oncogene were spotted onto glass slides. Overlapping sense and anti-sense primers were designed so that complementary primers for all possible mutations in each base position were investigated. The extension reactions were performed in a single step following hybridization of target DNA to the immobilized primers on the array surface. Mutation detection limits and the possibility of quantifying the mutations were investigated using synthetic oligonucleotides. In addition, 64 clinical samples were sequenced and 16 of these showed mutations in the N-ras gene.     

Ion-pair high-performance liquid chromatographic determination of isoniazid and acetylisoniazid in plasma and urine. Application for acetylator phenotyping

Isotachophoresis seems a likely candidate for a reference method, as it is more accurate and precise than common routine methods. The response is highly linear and depends on a well defined transport number of the leading ion, stability of the driving current, mobility of the separand, which is well controlled by the leading electrolyte and the use of a high-resolution detector. The suitability of isotachophoresis as a reference method was investigated for the determination of sodium in human serum. The operational conditions were 0.01 M K+/citrate (leading electrolyte) at pH 5.5 and 0.01 M creatinine X HCl (terminating electrolyte). Both n-butylamine and ammediol could be used as internal standards. The calibration graph constructed from standard solutions, diluted by weight with the internal standard, yielded a correlation coefficient of 0.99994 (n = 50) in the working range. The method seems especially useful for the determination of any ionic solute in, e.g., clinical samples (lithium, calcium, creatinine or drugs).     

Applications of thin-layer chromatography to process control in the pulp and paper field

A thin-layer chromatographic method for analytical separation and detection of the main component groups in extracts of wood, pulp and paper was designed. The method separates fatty acids from resin acids, which has not been reported in earlier studies. Neutral extractives were separated into sterols, triglycerides and steryl esters. The method proved to be useful for troubleshooting and production control and a number of applications are given.     

Separation of peptides on a polystyrene resin column

A high-performance liquid chromatographic column of porous spherical polystyrene--divinylbenzene copolymer (Hamilton PRP-1) was found to be useful for reversed-phase resolution of a wide range of peptides. Recoveries and resolution were comparable with those from more widely used alkyl silica-based columns. Tests involving more than 40 peptides, ranging from 2 to 34 residues, and 3 proteins, indicated wide applicability of this column. The retention times of peptides of known composition are predicted. The stability of the resin at high pH permits protocols of separation involving successive chromatograms at widely different pH values, and offers a second dimension to the resolving power of a single column.     

Aggregate morphology and flow behaviour of micellar alkylglycoside solutions

Solutions of n-nonyl-β-D-glucoside (C₉G₁), n-decyl-β-D-glucoside (C₁₀G₁), n-dodecyl-β-D-maltoside (C₁₂G₂), n-tetradecyl-β-D-maltoside (C₁₄G₂) and C₉G₁/C₁₀G₁ mixtures have been characterised by capillary viscometry and rheology in H₂O and D₂O, in order to map the influence of surfactant characteristics on micellisation over a wide concentration range. For the maltosides, the micellar solutions are shear thinning with a zero-shear viscosity that scales with concentration according to a power law with an exponent of about 5.8. In contrast, solutions of the glucosides C₉G₁, C₁₀G₁ and their mixtures show Newtonian flow behaviour and a much lower scaling exponent (<2.4). In C₉G₁/C₁₀G₁ mixtures, the scaling exponent decreases monotonously with increasing C₁₀G₁ content. The flow behaviour correlates with the packing requirements of the various surfactants, and are compatible with the idea that the maltosides form worm-like micelles, whereas the glucosides form branched, interconnected micelles (C₉G₁) and space-filling micellar networks (C₁₀G₁).     

Dynamic microwave-assisted extraction

An apparatus for extraction of solid matrices has been constructed which utilizes a microwave technique for heating in a dynamic mode. During the extraction, fresh solvent is continuously pumped through the extraction cell, which is maintained at a slight overpressure in order to keep the solvent in a liquid state. The extraction efficiency, which can be easily monitored, has been investigated in a factorial design and validated for polycyclic aromatic hydrocarbons in a reference sediment sample (EC-1). Important parameters were found to be temperature and duration of extraction. Flow-rate had no significant first-order effect on the recovery, but interaction effects with flow-rate were found to be significant. The dynamic microwave-assisted extraction apparatus was demonstrated to yield recoveries equivalent to Soxhlet extraction, but in a much shorter time. Each extraction of EC-1 typically takes 40 min.     

Vacancy ordering in Fe7Se8-Fe7S8 solid solutions studied by Mössbauer,X-ray and magnetization techniques

Superstructures, due to cation vacancy ordering, form in the NiAs-related pseudobinary solid solution Fe₇Se₈-Fe₇S₈ close to both end compositions (Fe₇(S_xSe_1–x)₈ withx0.15 andx0.85) during rapid cooling of quartz ampoules from 600 °C, according to X-ray diffractometry (XRD) and magnetization (SQUID) measurements. Mössbauer spectroscopy indicates local vacancy ordering in the whole interval, but XRD and SQUID data exclude long-range vacancy ordering when the anion proportion of sulphur is between 15% and 85%.