High-resolution atmospheric pressure infrared laser desorption/ionization mass spectrometry imaging of biological tissue

An atmospheric pressure laser desorption/ionization mass spectrometry imaging ion source has been developed that combines high spatial resolution and high mass resolution for the in situ analysis of biological tissue. The system is based on an infrared laser system working at 2.94 to 3.10 μm wavelength, employing a Nd:YAG laser-pumped optical parametrical oscillator. A Raman-shifted Nd:YAG laser system was also tested as an alternative irradiation source. A dedicated optical setup was used to focus the laser beam, coaxially with the ion optical axis and normal to the sample surface, to a spot size of 30 μm in diameter. No additional matrix was needed for laser desorption/ionization. A cooling stage was developed to reduce evaporation of physiological cell water. Ions were formed under atmospheric pressure and transferred by an extended heated capillary into the atmospheric pressure inlet of an orbital trapping mass spectrometer. Various phospholipid compounds were detected, identified, and imaged at a pixel resolution of up to 25 μm from mouse brain tissue sections. Mass accuracies of better than 2 ppm and a mass resolution of 30,000 at m/z?=?400 were achieved for these measurements.

The nature of Cu(II) species in ATRP: New insights via EPR

Identification of the paramagnetic species present in the Cu(I)Br‐catalyzed atom transfer radical polymerization (ATRP) of a model monomer (isobornyl acrylate) has been carried out by electron paramagnetic resonance (EPR) in the continuous wave mode at 90 K. Up to five different species—four copper‐based species and one organic radical—were detected with this technique. The EPR parameters of the copper‐based species are found to differ strongly, and originate from diverse isolated Cu(II) complexes, as well as dipolarly interacting and even exchange‐coupled Cu(II) species. The work highlights the complexity of the copper‐based EPR signal observed in copper‐mediated ATRP reactions. Analysis of the time evolution of the individual EPR contributions reveals the disadvantages of quantitative kinetics studies based on the summed EPR intensity of all copper‐based species, as is commonly used in literature for this type of reactions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1493–1501, 2010     

On Penicillin‐Binding Protein 1b Affinity‐Labeling Reagents

The synthesis of some 3‐aryl‐3‐(trifluoromethyl)3H‐diazirine and benzophenone‐based photoaffinity labels is reported. The photolabile group is bound to a scaffold that also accommodates functional groups to which an indicator unit (biotin) and the bioactive ligand can be attached orthogonally. To three of the labels, moenomycin was conjugated with the aim to provide tools for the identification of the moenomycin binding site within the transglycosylase domain of the enzyme PBP 1b. Some preliminary photoaffinity‐labeling experiments were carried out.     

The Use of Continuous Regularization in the Automated Analysis of MRS Time-Domain Data

In this paper, it is shown how the advantages of continuous regularization (CR) can be exploited to achieve an improved, fully automated LPSVD analysis of MRS time-domain data. The main advantage of CR is its ability to determine the number of spectral components even at low signal-to-noise ratios, which suggested its use forin vivospectroscopy. Estimation of the spectral parameters is possible. Two alternatives of automated data-analysis schemes are thoroughly investigated by means of Monte Carlo studies. The results suggest the combination of CR for model-order estimation with other methods for more-accurate parameter estimation. Several possible combinations, including those with an improved enhancement procedure and a total-least-squares method for quantitation, are discussed. Recommendations are given for spectral analysis, and a new data-analysis protocol which performs significantly better than previously used protocols of the same type is proposed.     

Ein Luftthermometer

Ohne Zusammenfassung     

Quantitative determination of heparinoid mimetics in human and rat plasma by micellar electrokinetic chromatography

The investigated new class of heparinoid mimetics are spaced persulfated carbohydrates designed to increase the success rate of angioplasty and bypass surgery by preventing restenosis without increasing the risk of bleeding. Due to the presence of sulfate groups, these compounds are highly charged and, for preclinical kinetic investigations only small sample volumes of rat plasma were available. Therefore, capillary electrophoresis (CE) was applied. A bioanalytical method based on micellar elektrokinetic chromatography (MEKC) with UV-detection was developed for the selective quantitation of heparinoid mimetics (e.g., Ro 48-0843, Ro 48-3151, Ro 47-6199 and Ro 48-8722) in plasma. Using this method, only small volumes of plasma were required, which could be introduced directly into the separation capillary after 1:1 dilution with 100 mM aqueous sodium dodecyl sulfate (SDS). For increased sample throughput, an additional ultrafiltration step was performed after SDS-dilution of the plasma sample, improving both reproducibility and robustness of the method considerably. The sensitivity of the new method (3 μg/ml) was sufficient to follow plasma levels in pharmacokinetic studies. The practicability of this easy and rapid assay was demonstrated by the analysis of more than 350 plasma samples from pharmacokinetic studies performed in rats.