N-Alkylnicotinium halides: A class of cationic matrix additives for enhancing the sensitivity in negative ion Fast-Atom bombardment mass spectrometry of polyanionic analytes

The addition of some surfactants to the fast-atom bombardment (FAB) matrix previously has been demonstrated to enhance analyte signals in fast-atom bombardment mass spectrometry. In particular, cationic surfactants appear to enhance the negative ion FAB detectability of analytes that exist as anionic species in the matrix solution. It has been proposed that the charged surfactant concentrates the oppositely charged analyte near the surface, which results in larger signals for the analyte. Cationic surfactants that contain a fixed positive charge and an additional basic site were prepared with different hydrophobic moieties and were evaluated for their effectiveness as FAB matrix additives. The compound N-octylnico-tinium bromide (ONBr) is shown to improve greatly the analyte-related signals in negative ion fast-atom bombardment mass spectrometry for a variety of polyanionic analytes, relative to other surfactants (e.g., cetylpyridinium salts). This surfactant not only enhances detectability, but also simplifies the pseudomolecular ion region of the resulting spectra by reducing or eliminating metal cation adduct peaks. The simple mechanism of enhancement via surface activity is evaluated, and alternative mechanisms are considered. It is clearly shown that ONBr, as a FAB matrix additive, will allow mass spectrometry to be used for the analysis of anionic compounds that normally exhibit very low responses.     

Hydroxylated polychlorinated biphenyls selectively bind transthyretin in blood and inhibit amyloidogenesis: rationalizing rodent PCB toxicity

Polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) are known to bind to transthyretin (TTR) in vitro, possibly explaining their bioaccumulation, rodent toxicity, and presumed human toxicity. Herein, we show that several OH-PCBs bind selectively to TTR in blood plasma; however, only one of the PCBs tested binds TTR in plasma. Some of the OH-PCBs displace thyroid hormone (T4) from TTR, rationalizing the toxicity observed in rodents, where TTR is the major T4 transporter. Thyroid binding globulin and albumin are the major T4 carriers in humans, making it unlikely that enough T4 could be displaced from TTR to be toxic. OH-PCBs are excellent TTR amyloidogenesis inhibitors in vitro because they bind to the TTR tetramer, imparting kinetic stability under amyloidogenic denaturing conditions. Four OH-PCB/TTR cocrystal structures provide further insight into inhibitor binding interactions.     

Microwave-assisted synthesis utilizing supported reagents: a rapid and efficient acylation procedure

[reaction: see text] The application of microwave heating to a polymer-assisted solution-phase (PASP) synthesis technique has been utilized to develop a rapid and efficient protocol for the solution-phase synthesis of amides from either amine or carboxylic acid cores.     

New type of dry substances content meter using microwaves for application in biogas plants

Dry substances (DS) are an important index for monitoring and controlling anaerobic co-digestion in biogas plants. We have developed and tested an online meter that measures suspended solids by means of the reflection coefficient of an exiting microwave signal, which is dependent on the dielectric properties of the suspensions. Intelligent models based on partial least squares regression (PLSR) and artificial neural network (ANN) for calibration allow exact and reproducible measurements under different circumstances. This measuring method is appropriate for contactless and online measurements of dry substance contents in biogas plants in a large range from 2–14%.     

The Synthesis of II-VI Binary Alloys and Organometallic Compounds via Me3SiOR Elimination Reactions

Trimethylsilyl chloride elimination reactions have been well documented. We now report the use of trimethylsilyl acetate elimination reaction in the preparation of binary alloys, HgTe and CdTe. The new compound, (MeHg)₃P, and the known compound (MeHg)₂S have been prepared by the trimethylsilyl acetate elimination reaction and characterized by NMR spectroscopy, electron ionization mass spectroscopy, and elemental analysis.     

Synthesis and Evaluation of 2-Deoxy-2-amino-β-cellobiosides as Cellulase Inhibitors

The cellulase mixture of Hypocrea jecorina (formerly Trichoderma reesei) contains a variety of exo- and endoglucanases that belong to different structural families. As such, these enzymes form an interesting model system to study the enzyme-ligand interactions in glycoside hydrolases. The nucleophilic carboxylate of retaining β-glycosidases is believed to form a hydrogen bond with the 2-hydroxyl group of their substrate. Consequently, replacing this hydroxyl group with an amino group should result in a stronger electrostatic interaction and thus an increased affinity for the ligand. In this study, several modified cellobiosides were synthesized and evaluated as cellulase inhibitors. The introduction of an amino group was found to have an unpredictable effect on the inhibitory power of the ligands. However, the enzymes display a very high affinity for the corresponding 2-azido compounds, precursors in the synthetic route. The new ligand m-iodobenzyl 2-deoxy-2-azido-β-cellobioside even is the strongest inhibitor of cellobiohydrolase I known to date (K_I = 1 μM).     

Certification of total arsenic in blood and urine standard reference materials by radiochemical neutron activation analysis and inductively coupled plasma-mass spectrometry

Radiochemical neutron activation analysis (RNAA) was used to measure arsenic at four levels in standard reference material (SRM) 955c Toxic Elements in Caprine Blood and at two levels in SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing mass concentration values for certification. Samples were freeze-dried prior to analysis followed by neutron irradiation for 3 h at a fluence rate of 1 × 10¹⁴ cm^?2 s^?1. After sample dissolution in perchloric and nitric acids, arsenic was separated from the matrix either by retention on hydrated manganese dioxide (urine) or by extraction into zinc diethyldithiocarbamate in chloroform (blood). ⁷⁶As was quantified by gamma-ray spectroscopy. Differences in chemical yield and counting geometry between samples and standards were monitored by measuring the count rate of a ⁷⁷As tracer added before sample dissolution. RNAA results were combined with inductively coupled plasma-mass spectrometry values from National Institute of Standards and Technology and collaborating laboratories to provide certified values of 10.81 ± 0.54 and 213.1 ± 0.73 μg/L for SRM 2668 Levels I and II, and certified values of 21.66 ± 0.73, 52.7 ± 1.1, and 78.8 ± 4.9 μg/L for SRM 955c Levels II–IV, respectively. Because of discrepancies between values obtained by different methods for SRM 955c Level I, an information value of <5 μg/L was assigned for this material.