Modeling of breath methane concentration profiles during exercise on an ergometer

We develop a simple three compartment model based on mass balance equations which quantitatively describes the dynamics of breath methane concentration profiles during exercise on an ergometer. With the help of this model it is possible to estimate the endogenous production rate of methane in the large intestine by measuring breath gas concentrations of methane.Comment: 17 pages, 4 figure

Evaluation and application of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry for complex sample analysis.

An evaluation of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS) has been undertaken to assess its applicability for the determination of 32 volatile compounds (VCs). The key experimental variables of sample incubation time and temperature have been evaluated alongside the MCC-GC variables of column polarity, syringe temperature, injection temperature, injection volume, column temperature and carrier gas flow rate coupled with the IMS variables of temperature and drift gas flow rate. This evaluation resulted in six sets of experimental variables being required to separate the 32 VCs. The optimum experimental variables for SHS-MCC-GC-IMS, the retention time and drift time operating parameters were determined; to normalise the operating parameters, the relative drift time and normalised reduced ion mobility for each VC were determined. In addition, a full theoretical explanation is provided on the formation of the monomer, dimer and trimer of a VC. The optimum operating condition for each VC calibration data was obtained alongside limit of detection (LOD) and limit of quantitation (LOQ) values. Typical detection limits ranged from 0.1ng bis(methylthio)methane, ethylbutanoate and (E)-2-nonenal to 472ng isovaleric acid with correlation coefficient (R(2)) data ranging from 0.9793 (for the dimer of octanal) through to 0.9990 (for isobutyric acid). Finally, the developed protocols were applied to the analysis of malodour in sock samples. Initial work involved spiking an inert matrix and sock samples with appropriate concentrations of eight VCs. The average recovery from the inert matrix was 101±18% (n=8), while recoveries from the sock samples were lower, that is, 54±30% (n=8) for sock type 1 and 78±24% (n=6) for sock type 2. Finally, SHS-MCC-GC-IMS was applied to sock malodour in a field trial based on 11 volunteers (mixed gender) over a 3-week period. By applying the SHS-MCC-GC-IMS database, four VCs were identified and quantified: ammonia, dimethyl disulphide, dimethyl trisulphide and butyric acid. A link was identified between the presence of high ammonia and dimethyl disulphide concentrations and a high malodour odour grading, that is, ≥ 6. Statistical analysis did not find any correlation between the occurrence of dimethyl disulphide and participant gender

Monitoring the volatile language of fungi using gas chromatography-ion mobility spectrometry

Fusarium oxysporum is a plant pathogenic fungus leading to severe crop losses in agriculture every year. A sustainable way of combating this pathogen is the application of mycoparasites—fungi parasitizing other fungi. The filamentous fungus Trichoderma atroviride is such a mycoparasite that is able to antagonize phytopathogenic fungi. It is therefore frequently applied as a biological pest control agent in agriculture. Given that volatile metabolites play a crucial role in organismic interactions, the major aim of this study was to establish a method for on-line analysis of headspace microbial volatile organic compounds (MVOCs) during cultivation of different fungi. An ion mobility spectrometer with gas chromatographic pre-separation (GC-IMS) enables almost real-time information of volatile emissions with good selectivity. Here we illustrate the successful use of GC-IMS for monitoring the time- and light-dependent release of MVOCs by F. oxysporum and T. atroviride during axenic and co-cultivation. More than 50 spectral peaks were detected, which could be assigned to 14 volatile compounds with the help of parallel gas chromatography-mass spectrometric (GC-MS) measurements. The majority of identified compounds are alcohols, such as ethanol, 1-propanol, 2-methyl propanol, 2-methyl butanol, 3-methyl-1-butanol and 1-octen-3-ol. In addition to four ketones, namely acetone, 2-pentanone, 2-heptanone, 3-octanone, and 2-octanone; two esters, ethyl acetate and 1-butanol-3-methylacetate; and one aldehyde, 3-methyl butanal, showed characteristic profiles during cultivation depending on axenic or co-cultivation, exposure to light, and fungal species. Interestingly, 2-octanone was produced only in co-cultures of F. oxysporum and T. atroviride, but it was not detected in the headspace of their axenic cultures. The concentrations of the measured volatiles were predominantly in the low ppbv range; however, values above 100 ppbv were detected for several alcohols, including ethanol, 2-methylpropanol, 2-methyl butanol, 1- and 3-methyl butanol, and for the ketone 2-heptanone, depending on the cultivation conditions. Our results highlight that GC-IMS analysis can be used as a valuable analytical tool for identifying specific metabolite patterns for chemotaxonomic and metabolomic applications in near-to-real time and hence easily monitor temporal changes in volatile concentrations that take place in minutes

High Kinetic Energy Ion Mobility Spectrometry- Mass Spectrometry investigations of four inhalation anaesthetics : isoflurane, enflurane, sevoflurane and desflurane

Here we report the first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometric (HiKE-IMSMS) investigations involving four fluranes; isoflurane, enflurane, sevoflurane and desflurane. Unlike standard (atmospheric pressure) IMS, HiKEIMS can detect these compounds in positive ion mode. This is because its low-pressure environment (similar to 14 mbar) and the associated short ion drift times in the HiKEIMS ensure the reagent ions O-2+(center dot) and H3O+ are present in the reaction region, and these can react with the fluranes by dissociative charge and proton transfer, respectively. However, their ion intensities are very dependent on the value of the reduced electric field (E/N) applied and the humidity of the air in the reaction region of the HiKE-IMS. In this paper we explore the potential use of HiKE-IMS for air quality control and breath analysis of fluranes. To help in the interpretation of the ion mobility spectra, and hence the ion-flurane chemistry occurring in reaction region, a HiKE-IMS was coupled to a Time-of-Flight Mass Spectrometer so that the m/z values of both the reagent and product ions that are contained within the various ion mobility peaks observed could be identified with a high level of confidence. The dependencies of the intensities of these ions as functions of E/N (30-115 Td) and humidity in the reaction region are reported. A number of product ions have been observed only under low humidity conditions (H2O volume-mixing ratio 100 ppm(v)), including CHF(2+)and CHFCl (+) for isoflurane and enflurane, CHF2(+), CF3(+) and C3H2F5O+ for desflurane, and CH3O+, CHF2+, C3H3F4O+, C4H3F6O+ and C4H3F6O+(H2O) for sevoflurane. It is interesting to note that CH3O+, CHF2+, CHFCl+ and CF3+ have shorter drift times than that measured for O-2(+center dot) This is explained by resonant charge transfer reaction processes occurring in the drift region: O-2(+center dot) + O-2 ? O-2+(center dot).O O-2 + O-2 +(center dot) (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

High kinetic energy-ion mobility spectrometry-mass spectrometry investigations of several volatiles and their fully deuterated analogues

The first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometry (HiKE-IMS-MS) studies involving six volatiles (acetone, acetonitrile, methanol, ethanol, 2-propanol, and 1-butanol) and their fully deuterated analogues are reported. The goal is to further our understanding of the ion-molecule chemistry occurring in the HiKE-IMS. This is needed for its full analytical potential to be reached. Product ions are identified as a function of the reduced electric field (30-115 Td) and the influence of sample air humidity in the reaction region on deuterium/hydrogen (D/H) exchange reactions is discussed. Reagent ions include H3O+(H2O)(m), (n = 0, 1, 2 or 3), NO+(H2O)(n) (m = 0 or 1) and O-2(+center dot). Reactions with H3O+(H2O)(m), lead to protonated monomers (through either proton transfer or ligand switching). Reactions with NO+ involve association with acetone and acetonitrile, hydride anion abstraction from ethanol, 2-propanol, and 1-butanol, and hydroxide abstraction from 2-propanol and 1-butanol. With the exception of acetonitrile, O-2(+center dot) predominantly reacts with the volatiles via dissociative charge transfer. A number of sequential secondary ion-volatile processes occur leading to the formation of dimer and trimer-containing ion species, whose intensities depend on a volatile's concentration and the reduced electric field in the reaction region. Deuterium/hydrogen (D/H) exchange does not occur for product ions from acetone-d(6) and acetonitrile-d(3), owing to their inert methyl functional groups. For the deuterated alcohols, rapid D/H-exchange reaction at the hydroxy group is observed, the amount of which increased with the increasing humidity of the sample air and/or lowering of the reduced electric field.Peer reviewe

A portable sensor system for the detection of human volatile compounds against transnational crime

Human smuggling accounts for a significant part of transnational organized crime, creating a growing threat to national and international security and putting at risk the health and lives of the people being smuggled. Early detection and interception of human beings hidden in containers or trucks are therefore of considerable importance, especially at key transportation hubs, such as at international borders and harbors. The major challenge is to provide fast inspection procedures without needing to open sealed trucks and containers. The detection of trace key volatile organic compounds, which includes aldehydes and ketones, emitted by humans can be used to rapidly determine human presence, requiring only several ml of air to be taken from inside a container. In this paper, we describe a prototype portable device for the rapid detection of hidden or entrapped people, employing a combined ion mobility spectrometer and sensor array system for obtaining a volatile signature of human presence. The detection limits of this combined analytical device are sufficiently low for use in sensing ketones and aldehydes being emitted by humans in closed containers. For easy handling by security personnel, a classification algorithm is applied that provides a simple YES or NO decision. With a training dataset of more than 1000 measurements, the algorithm achieved an area under curve of 0.9 for untrained scenarios. The field measurements show that two people need to stay in a car for between 20 and 30 minutes in order for the emitted trace volatile organic compounds to reach concentrations high enough for reliable detection with our analytical device

Precursors for cytochrome P450 profiling breath tests from an in silico screening approach

The family of cytochrome P450 enzymes (CYPs) is a major player in the metabolism of drugs and xenobiotics. Genetic polymorphisms and transcriptional regulation give a complex patient-individual CYP activity profile for each human being. Therefore, personalized medicine demands easy and non-invasive measurement of the CYP phenotype. Breath tests detect volatile organic compounds (VOCs) in the patients’ exhaled air after administration of a precursor molecule. CYP breath tests established for individual CYP isoforms are based on the detection of 13CO2 or 14CO2 originating from CYP-catalyzed oxidative degradation reactions of isotopically labeled precursors. We present an in silico work-flow aiming at the identification of novel precursor molecules, likely to result in VOCs other than CO2 upon oxidative degradation as we aim at label-free precursor molecules. The ligand-based work-flow comprises five parts: (1) CYP profiling was encoded as a decision tree based on 2D molecular descriptors derived from established models in the literature and validated against publicly available data extracted from the DrugBank. (2) Likely sites of metabolism were identified by reactivity and accessibility estimation for abstractable hydrogen radical. (3) Oxidative degradation reactions (O- and N-dealkylations) were found to be most promising in the release of VOCs. Thus, the CYP-catalyzed oxidative degradation reaction was encoded as SMIRKS (a programming language style to implement reactions based on the SMARTS description) to enumerate possible reaction products. (4) A quantitative structure property relation (QSPR) model aiming to predict the Henry constant H was derived from data for 488 organic compounds and identifies potentially VOCs amongst CYP reaction products. (5) A blacklist of naturally occurring breath components was implemented to identify marker molecules allowing straightforward detection within the exhaled air.peer-reviewe

Monitoring of selected skin- and breath-borne volatile organic compounds emitted from the human body using gas chromatography ion mobility spectrometry (GC-IMS)

ISSN:1873-376XISSN:1570-0232ISSN:1572-6495ISSN:1387-227

The Lipoxygenase Lox1 Is Involved in Light‐ and Injury-Response, Conidiation, and Volatile Organic Compound Biosynthesis in the Mycoparasitic Fungus Trichoderma atroviride

18 páginas, 10 figuras. -- The first publication by Frontiers Media is avalilable at https://www.frontiersin.org/articles/10.3389/fmicb.2020.02004/fullThe necrotrophic mycoparasite Trichoderma atroviride is a biological pest control agent frequently applied in agriculture for the protection of plants against fungal phytopathogens. One of the main secondary metabolites produced by this fungus is 6-pentyl-α-pyrone (6-PP). 6-PP is an organic compound with antifungal and plant growth-promoting activities, whose biosynthesis was previously proposed to involve a lipoxygenase (Lox). In this study, we investigated the role of the single lipoxygenase-encoding gene lox1 encoded in the T. atroviride genome by targeted gene deletion. We found that light inhibits 6-PP biosynthesis but lox1 is dispensable for 6-PP production as well as for the ability of T. atroviride to parasitize and antagonize host fungi. However, we found Lox1 to be involved in T. atroviride conidiation in darkness, in injury-response, in the production of several metabolites, including oxylipins and volatile organic compounds, as well as in the induction of systemic resistance against the plant-pathogenic fungus Botrytis cinerea in Arabidopsis thaliana plants. Our findings give novel insights into the roles of a fungal Ile-group lipoxygenase and expand the understanding of a light-dependent role of these enzymes.This research was supported by the Austrian Science Fund (FWF; grant P32179-B), Tyrolean Science Fund (TWF; grant number AP718021) and the doctoral program BioApp from the University of InnsbruckPeer reviewe