Production and purification of CGTase of alkalophylicBacillus isolated from Brazilian soil

Alkalophylic bacilli that produce cyclodextringlycosyltransferase (CGTase) were isolated from Brazilian soil, with a scheme of two plating steps. In the first step, the bacterial isolate forms a halo in the cultivation medium that contains γ-cyclodextrin (CD) complexing dyes. The CGTase of an isolate was purified 157-fold by biospecific affinity chromatography, with β-CD showing a mol wt of 77,580 Daltons. It produces a γ- to β-CD ratio of 0.156 and a small amount of α-CD, using maltodextrin 10% as substrate, at 50°C, pH 8.0 and 22 h reaction time, reaching 21.4% conversion of the substrate to cyclodextrins. In the second screening step, the isolates chosen give larger halos with β-CD complexing dyes, and smaller halos with β-CD complexing dyes, leading to a 30% improvement in γ-CD selectivity, although at lower total yield for cyclodextrins (11.5%).     

Dynamic light scattering of poly(n-laurylmethacrylate) in the melt and in concentrated ethyl acetate solutions

Dynamic light-scattering measurements have been made on the “soft” polymer: poly(n-laurylmethacrylate) (PLMA) in solution in ethyl acetate over the concentration range 0.1 < C < 0.9 g/mL as well as melt PLMA. With the concentrated solutions, the hydrodynamic screening length (ξ_h) scales with an exponent of −0.7 below C ≈ 0.3 g/mL. Importantly, ξ_h decreases above 0.3 g/mL, and the concentration dependence increases strongly above this concentration. The latter contrasts with the behavior in a variety of well-studied poly(styrene) solutions, which are inevitably investigated close to the glass point, and for which there is a pronounced increase of ξ_h over the same concentration range. In PLMA solutions, the decrease in ξ_h parallels the behavior of the static screening length (ξ_s) which has been observed in other flexible polymer systems. Dynamic “clusters” (also termed “long-range density fluctuations”) contribute a large part of the scattered intensity above the concentration 0.6 g/mL and also in melt PLMA which contrasts with poly(styrene) systems in which they are absent. In common with the clusters recently observed in another polymeric melt, poly(methyl-p-tolylsiloxane) (ref. 9) this component is diffusive. While, however, in the latter system the clusters “melt out” at 90°C, we find in the well-matured PLMA systems that the cluster amplitude is temperature-independent (within the temperature-time range studied) in the solutions up to at least 80°C and up to at least 150°C in the melt, which were the highest temperatures examined. The clusters in the PLMA systems have a correlation length of the magnitude 65 nm in the melt, whereas in the solutions this dimension varies between 73 nm at 0.9 g/mL to 126 nm at 0.7 g/mL. In PLMA the clusters are presumed to arise from local segregation owing to the large paraffinic side groups on the chain. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1013–1024, 1997     

A study of enhanced ion formation from metal‐semiconductor complexes in atmospheric pressure laser desorption/ionization mass spectrometry

The study of the key parameters impacted surface‐assisted laser desorption/ionization‐mass spectrometry is of broad interest. In previous studies, it has been shown that surface‐assisted laser desorption/ionization‐mass spectrometry is a complex process depending on multiple factors. In the presented study, we showed that neither porosity, light absorbance nor surface hydrophobicity alone influence the enhancement phenomena observed from the hybrid metal‐semiconductor complexes versus individual targets, but small changes in the analyte attaching to the target significantly affect laser desorption ionization‐efficiency. By means of Raman spectroscopy and scanning electron microscopy, it was revealed that the formation of an amorphous analyte layer after drying on a solid substrate was essential for the enhanced laser desorption ionization‐signal observed from the hybrid metal‐semiconductor targets, and the crystallization properties of the analyte appeared as a function of the substrate. Obtained results were used for the screening of regular and lactose‐free milk samples through the hybrid metal‐semiconductor target. Copyright © 2016 John Wiley & Sons, Ltd.     

Reliable screening of pesticide residues in maternal and umbilical cord sera by gas chromatography-quadrupole time of flight mass spectrometry

The widespread use of pesticides induces heavy adverse effects on human health,especially for the pregnant women and the newborns.In this study,a screening method has been developed for the determination of multi-pesticides in maternal and umbilical cord sera.All pesticides in sera were collected using solid phase extraction(SPE),and analyzed by gas chromatography-quadrupole time of flight mass spectrometry(GC-QTOF MS).To set up the quality criteria,a database of 50 pesticides was created and the accurate masses of 3 up to 5 representative ions with their intensity ratios were included for each pesticide.In addition,a novel"identification points"(IPs)system relying on the accurate MS1 and MS2 spectra was used to interpret the data for each suspected pesticide.The methodology was then applied to a pair of maternal and umbilical cord sera.A total of six pesticide residues were screened out successfully.In conclusion,GC-QTOF MS combined with an accurate mass database seemed to be one of the most efficient tools for systematic pesticide analysis.     

Shotgun lipidomics on a LTQ Orbitrap mass spectrometer by successive switching between acquisition polarity modes

Top–down shotgun lipidomics relies on direct infusion of total lipid extracts into a high‐resolution tandem mass spectrometer and implies that individual lipids are recognized by their accurately determined m/z. Lipid ionization efficiency and detection specificity strongly depend on the acquisition polarity, and therefore it is beneficial to analyze lipid mixtures in both positive and negative modes. Hybrid LTQ Orbitrap mass spectrometers are widely applied in top–down lipidomics; however, rapid polarity switching was previously unfeasible because of the severe and immediate degradation of mass accuracy. Here, we report on a method to rapidly acquire high‐resolution spectra in both polarity modes with sub‐ppm mass accuracy and demonstrate that it not only simplifies and accelerates shotgun lipidomics analyses but also improves the lipidome coverage because more lipid classes and more individual species within each class are recognized. In this way, shotgun analysis of total lipid extracts of human blood plasma enabled to quantify 222 species from 15 major lipid classes within 7 min acquisition cycle. Copyright © 2012 John Wiley & Sons, Ltd.     

双三元液相色谱-串联电喷雾检测器用于中药注射剂大分子物质筛查研究

A size exclusion chromatography method ( SEC) was established for the screening of macromolecules in traditional Chinese medicine (TCM) injections. In the experiment, TCM was collected through 0. 45μm ...