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Recent discoveries suggest that cells of a clonal population often display multiple metabolic phenotypes at the same time. Motivated by the success of mass spectrometry (MS) in the investigation of population-level metabolomics, the analytical community has initiated efforts towards MS-based single cell metabolomics to investigate metabolic phenomena that are buried under the population average. Here, we review the current approaches and illustrate their advantages and disadvantages. Because of significant advances in the field, different technologies are now at the verge of generating data that are useful for exploring and investigating metabolic heterogeneity. [ABSTRACT FROM AUTHOR]

Mass spectrometry is becoming a more and more powerful tool for investigating protein complexes. Recent developments, based on different ionization techniques, electrospray, desorption/ionization and others are contributing to the usefulness of MS to describe the organization and structure of large non-covalent assemblies. [Copyright &y& Elsevier]

Presents information on a study which analyzed aromatic compounds on aerosols collected from a smoking lobby. Methodology of the study; Results and discussion; Conclusion.

Sleep is crucial to restore body functions and metabolism across nearly all tissues and cells, and sleep restriction is linked to various metabolic dysfunctions in humans. Using exhaled breath analysis by secondary electrospray ionization high-resolution mass spectrometry, we measured the human exhaled metabolome at 10-s resolution across a night of sleep in combination with conventional polysomnography. Our subsequent analysis of almost 2,000 metabolite features demonstrates rapid, reversible control of major metabolic pathways by the individual vigilance states. Within this framework, whereas a switch to wake reduces fatty acid oxidation, a switch to slow-wave sleep increases it, and the transition to rapid eye movement sleep results in elevation of tricarboxylic acid (TCA) cycle intermediates. Thus, in addition to daily regulation of metabolism, there exists a surprising and complex underlying orchestration across sleep and wake. Both likely play an important role in optimizing metabolic circuits for human performance and health. [Display omitted] • Sleep states regulate more than 50% of all metabolite features detected in human breath • Major pathways are up- or downregulated during wake, SWS, and REM sleep • Sleep-regulated pathways show stepwise logic across different sleep stages Measuring almost 2,000 metabolite features in breath every 10 s across a night of sleep, Nowak et al. demonstrate major pathways up- or downregulated during wake, slow-wave sleep, and rapid eye movement sleep. This control of metabolism by vigilance state is likely important in optimizing metabolic circuits for human health. [ABSTRACT FROM AUTHOR]

Over the past two decades, mass spectrometry (MS) has transformed the life sciences. The advances in understanding biomolecule structure and function by MS is progressing at an accelerated pace. MS has also largely been applied to study thermodynamic and kinetic structure of biomolecules. Herein, we highlight the recent discussions about native mass spectrometry and studies about determining stable gas phase structures, hydrogen/deuterium exchange studies about reaction kinetics and determination of binding constants of biomolecules with their ligands. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of volatile organic compounds in a commercially available non-thermal plasma based air purifying system was investigated. Several studies exist that interrogate the degradation of VOCs in closed air systems using a non-thermal plasma combined with a heterogeneous catalyst. For the first time, however, our study was performed under realistic conditions (normal indoor air, 297.5K and 12.5gm−3 water content) on an open system, in the absence of an auxiliary catalyst, and using standard operating air flow rates (up to 320Lmin−1). Cyclohexene, benzene, toluene, ethylbenzene and the xylene isomers were nebulized and guided through the plasma air purifier. The degradation products were trapped by activated charcoal tubes or silica gel tubes, and analyzed using gas chromatography mass spectrometry. Degradation efficiencies of 11±1.6% for cyclohexene, <2% for benzene, 11±2.4% for toluene, 3±1% for ethylbenzene, 1±1% for σ-xylene, and 3±0.4% for m-/ρ-xylene were found. A fairly wide range of degradation products could be identified. On both trapping media, various oxidized species such as alcohols, aldehydes, ketones and one epoxide were observed. The formation of adipaldehyde from nebulized cyclohexene clearly indicates an ozonolysis reaction. Other degradation products observed suggests reactions with OH radicals. We propose that mostly ozone and OH radicals are responsible for the degradation of organic molecules in the plasma air purifier. [Copyright &y& Elsevier]

We present a rapid and sensitive method based on secondary electrospray ionization mass spectrometry (SESI-MS) for profiling volatile emissions from the intact berries of non-Muscat grape cultivars (Pinot Noir, Chardonnay and Sauvignon Blanc). The method does not require sample preparation or concentration steps. Grape volatiles were tentatively identified based on accurate mass, the related elemental composition and literature. Approximately 300 peaks were detected in positive ion mode, and fewer (70–100) in negative ion mode. We monitored changes in grape berry volatile composition during ripening to screen for potential ripeness markers and observed ten [M+H] + peaks and two [M-H] - peaks that evolved in a significant linear trend (R 2 ≥ 0.80, p < 0.05) for the combined data across all cultivars either increasing or decreasing in the final four weeks of ripening. Peaks assigned to C 13 -norisoprenoids and benzenoid derivatives have shown similar trends in previous studies using offline gas chromatography (GC) approaches. Principal components analysis showed that negative ion mode clearly separated each stage of grape ripeness, whilst positive ion mode only separated berries in the final stage, pre-harvest. From this preliminary study, we conclude that SESI-MS holds promise as a tool for rapid screening of grape volatiles. Some marker ions had no interfering peaks within a 1-Da window, such that they could be monitored with simple unit-resolution instruments in future studies. This implies that SESI-MS in combination with portable MS instrumentation has potential for field analysis where real-time analysis is key. [ABSTRACT FROM AUTHOR]

Asparagine-linked glycosylation is a post-translational protein modification that is conserved in all domains of life. The initial transfer of a lipid-linked oligosaccharide (LLO) onto acceptor asparagines is catalyzed by the integralmembrane protein oligosaccharyltransferase (OST). The previously reported structure of a single-subunit OST enzyme, the Campylobacter lari protein PgIB, revealed a partially disordered external loop (EL5), whose role in catalysis was unclear. We identified a new and functionally important sequence motif in EL5 containing a conserved tyrosine residue (Tyr293)whose aromatic side chain is essential for catalysis. A synthetic peptide containing the conserved motif can partially but specifically rescue in vitro activity of mutated PgIB lacking Tyr293. Using site-directed disulfide cross-linking, we show that disengagement of the structurally ordered part of EL5 is an essential step of the glycosylation reaction, probably by allowing sequon binding or glyco-product release. Our findings define two distinct mechanistic roles of EL5 in OST-catalyzed glycosylation. These functions, exerted by the two halves of EL5, are independent, because the loop can be cleaved by specific proteolysis with only slight reduction in activity. [ABSTRACT FROM AUTHOR]

Abstract: Atmospheric particulate matter (PM) is an air-suspended mixture of solid and liquid particles that vary in size, shape, and chemical composition. Long-term exposure to elevated concentrations of fine atmospheric particles is considered to pose a health threat to humans and animals. In this context, it has been hypothesized that toxic chemicals such as polycyclic aromatic hydrocarbons (PAHs) play an important role. Some PAHs are known to be carcinogenic and it has been shown that carcinogenic effects of PAHs are mediated by the aryl hydrocarbon receptor (AhR). In this study, PM1 was collected at a rural and an urban traffic site during an intense winter smog period, in which concentration of PM1 often exceeded 50 μg m−3. We applied an in vitro reporter gene assay (DR-CALUX) to detect and quantify PM1-associated chemicals that induce AhR-mediated gene expression. This activity was expressed as CALUX equivalents of 2,3,7,8-tetrachlorodibenzodioxin (PM-TCDD-CEQs). In addition, concentrations of PAHs in the PM1 extracts were determined using gas chromatography/high-resolution mass spectrometry. Concentrations of PM-TCDD-CEQs ranged from 10 to 85 pg m−3 and from 19 to 87 pg m−3 at the urban and rural site, respectively. By the use of known relative potency factors, the measured concentration of a PAH was converted into a PAH-TCDD-CEQ concentration. ΣPAH-TCDD-CEQ and PM-TCDD-CEQ were highly correlated at both sites (r 2 = 0.90 and 0.69). The calculated ΣPAH-TCDD-CEQs explain between 2% and 20% of the measured PM-TCDD-CEQs. Benzo[k]fluoranthene was the most important PAH causing approximately 60% of the total ΣPAH-TCDD-CEQ activity. In contrast to NO, CO, PM10, and PM1, the concentration of PM-TCDD-CEQs showed no significant difference between the two sites. No indications were found that road traffic emissions caused elevated concentrations of PM-TCDD-CEQs at the urban traffic site. [Copyright &y& Elsevier]

Abstract: High-mass matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with chemical cross-linking has the ability to monitor the ligand-dependent dimerization of the human estrogen receptor α ligand binding domain (hERα LBD) in solution. Because only ER ligands enhance the homodimer abundance, we evaluated the ability of this label-free approach for identifying endocrine disrupting compounds (EDCs) in a high-throughput manner. This was achieved by combining an automated liquid handler with an automated MS acquisition procedure, which allowed a five-fold gain in operator time compared to a fully manual approach. To detect ligand binding with enough confidence, the receptor has to be incubated with at least a 10μM concentration of the test compound. Based on the increase of the measured homodimer intensity, eight compounds with a relative binding affinity (RBA, relative to the natural hormone estradiol) >7% were identified as ER ligands among the 28 chemicals tested. Two other compounds, quercetin and 4-tert-amylphenol, were also identified as ER ligands, although their RBAs have been reported to be only 0.01% and 0.000055%, respectively. This suggests that these two ligands have a higher affinity for hERα LBD than reported in the literature. The high-mass MALDI approach thus allows identifying high affinity EDCs in an efficient way. [Copyright &y& Elsevier]