Rybergmanning9722

Ultrahigh molecular weight (UHMW) poly(ethylene oxide) (PEO) is a synthetic hydrophilic polymer with wide dispersity which shows considerable promise as a hemostatic agent in the treatment of gastrointestinal bleeding. Currently there is no analytical method for the determination of highly disperse UHMW PEO in biological samples that would allow its characterization in vivo and support its clinical development. Although liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a powerful bioanalytical tool, it faces major challenges when applied to UHMW PEO. In this work, we report a novel bioanalytical method for the determination of UHMW PEO involving microsolid phase extraction (μ-SPE), chromatography on a PLRP-S 1000 Å reversed phase column and detection by positive ion Q-Q-TOF MS using the MSALL technique. In this mode, dissociation of all precursor ions in Q2 generated a series of product ions at m/z 89.0715, 133.0854, 177.1047, and 221.1475 of which the product ion at m/z 133.0854 was common to all precursor ions and enabled quantitation of all polymers in UHMW PEO. The method was successfully applied to the determination of UHMW PEO polymers in rat plasma, urine, and feces after oral administration of 1700 kDa PEO. The results show that UHMW PEO is not absorbed into the blood and is largely eliminated unchanged in feces over 48 h. We maintain the method is sufficiently robust to be used in routine bioanalysis of polymers with UHMW and wide dispersity.Studies of the topology, functioning, and regulation of metabolic systems are based on two main types of information that can be measured by mass spectrometry the (absolute or relative) concentration of metabolites and their isotope incorporation in 13C-labeling experiments. These data are currently obtained from two independent experiments because the 13C-labeled internal standard (IS) used to determine the concentration of a given metabolite overlaps the 13C-mass fractions from which its 13C-isotopologue distribution (CID) is quantified. Here, we developed a generic method with a dedicated processing workflow to obtain these two sets of information simultaneously in a unique sample collected from a single cultivation, thereby reducing by a factor of 2 both the number of cultivations to perform and the number of samples to collect, prepare, and analyze. The proposed approach is based on an IS labeled with other isotope(s) that can be resolved from the 13C-mass fractions of interest. PLX4032 As proof-of-principle, we analyzed amino acids using a doubly labeled 15N13C-cell extract as IS. Extensive evaluation of the proposed approach shows a similar accuracy and precision compared to state-of-the-art approaches. We demonstrate the value of this approach by investigating the dynamic response of amino acids metabolism in mammalian cells upon activation of the protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), a key component of the unfolded protein response. Integration of metabolite concentrations and isotopic profiles reveals a reduced de novo biosynthesis of amino acids upon PERK activation. The proposed approach is generic and can be applied to other (micro)organisms, analytical platforms, isotopic tracers, or classes of metabolites.Co-substituted LaFeO3 was electrodeposited on the surface of BiVO4 as a co-catalyst to enhance the water splitting performance. Compared to bare BiVO4, the BiVO4/Co-LaFeO3 composite photoanode shows a water oxidation photocurrent of 3.4 mA/cm2 at 1.23 V versus reverse hydrogen electrode, accompanied by a notable cathodic shift in the onset potential for 300 mV. Combined optical and electrochemical characterizations show that the solid/electrolyte charge transfer efficiency of BiVO4 are dramatically improved by the incorporation of Co-substituted LaFeO3. From the surface kinetic study of charge carriers by intensity-modulated photocurrent spectroscopy, a suppressed surface recombination rate constant is observed and the enhanced photoelectrochemical water splitting performance observed in the BiVO4/Co-LaFeO3 photoanode is attributed to the surface passivation effect of Co-substituted LaFeO3.Mobility isolated spectra were obtained for protonated monomers of 42 volatile oxygen containing organic compounds at ambient pressure using a tandem ion mobility spectrometer with a reactive stage between drift regions. Fragment ions of protonated monomers of alcohols, acetates, aldehydes, ketones, and ethers were produced in the reactive stage using a 3.3 MHz symmetrical sinusoidal waveform with an amplitude of 1.4 kV and mobility analyzed in a 19 mm long drift region. The resultant field induced fragmentation (FIF) spectra included residual intensities for protonated monomers and fragment ions with characteristic drift times and peak intensities, associated with ion mass and chemical class. High efficiency of fragmentation was observed with single bond cleavage of alcohols and in six-member ring rearrangements of acetates. Fragmentation was not observed, or seen weakly, with aldehydes, ethers, and ketones due to their strained four-member ring transition states. Neural networks were trained to categorize spectra by chemical class and tested with FIF spectra of both familiar and unfamiliar compounds. Rates of categorization were class dependent with best performance for alcohols and acetates, moderate performance for ketones, and worst performance for ethers and aldehydes. Trends in the rates of categorization within a chemical family can be understood as steric influences on the energy of activation for ion fragmentation. Electric fields greater than 129 Td or new designs of reactive stages with improved efficiency of fragmentation will be needed to extend the practice of reactive stage tandem IMS to an expanded selection of volatile organic compounds.A wide range of collision cross section (CCS) databases for different families of compounds have recently been established from ion mobility mass spectrometry (IM-MS) measurements. Nevertheless, the need to validate these new data sets to provide the necessary confidence about the use of this parameter is increasingly expressed by the scientific community. If such a validation requires that complementary mass spectrometry experiments are conducted, it also appears that alternative strategies can contribute to the validation of such empirical data. In particular, in silico approaches are relevant to compute theoretical CCS values, to be compared to experimental ones. A recently published CCS database for 300 steroids allowed one to observe experimentally significant deviations of the expected CCS versus m/z correlations for some compounds. The present work attempts to rationalize such deviations with Density Functional Theory (DFT) calculations. MN15/6-311++G(d,p) investigations have been carried out, starting with a conformational analysis of a sample of 20 selected steroids and the determination of their preferred gas-phase ionization site.