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PubMed1996

Sub-species discrimination, using pyrolysis mass spectrometry and self-organising neural networks, of Propionibacterium acnes isolated from normal human skin.

Curie-point pyrolysis mass spectra were obtained from 30 Propionibacterium acnes strains isolated from the foreheads of six healthy humans. Multivariate analyses and Kohonen artificial neural networks (KANNs), employing unsupervised learning, were used successfully to discriminate between the P.acnes isolates from different individual hosts. The classification of the isolates by KANNs was compared with the more classical multivariate techniques of canonical variates analysis and hierarchical cluster analysis and found to give similar groupings. The combination of pyrolysis mass spectrometry with these numerical methods also showed that more than one strain of P.acnes had been isolated from three of the human hosts.

Adult↗

PubMed1996

Quantitative analysis of multivariate data using artificial neural networks: a tutorial review and applications to the deconvolution of pyrolysis mass spectra.

The implementation of artificial neural networks (ANNs) to the analysis of multivariate data is reviewed, with particular reference to the analysis of pyrolysis mass spectra. The need for and benefits of multivariate data analysis are explained followed by a discussion of ANNs and their optimisation. Finally, an example of the use of ANNs for the quantitative deconvolution of the pyrolysis mass spectra of Staphylococcus aureus mixed with Escherichia coli is demonstrated.

Escherichia coli↗

PubMed1997

Evaluation of Streptomyces species-groups by pyrolysis mass spectrometry.

Curie-point pyrolysis mass spectrometry was used to evaluate the taxonomic integrity of three subclusters, provisionally labelled S. albidoflavus, S. anulatus and S. halstedii, which formed a species-group in an extensive numerical phenetic survey of the genus Streptomyces. Excellent agreement was found between the results of the triplicate analyses of each strain while the duplicated strains clustered adjacent to one another. Sequential principal component-canonical variates analysis of the experimental data collected on the 32 representative organisms showed that the S. albidoflavus strains formed a distinct group. This result taken together with earlier chemical, molecular and numerical taxonomic data indicates that the S. albidoflavus subcluster corresponds to a distinct species. In contrast, the subclusters equated with S. anulatus and S. halstedii were found to be heterogeneous and hence in need of further study. However, it is evident from the present investigation that Curie-point pyrolysis mass spectrometry provides a rapid and reproducible way of evaluating the taxonomic integrity of Streptomyces species-groups.

Mass Spectrometry↗

PubMed1997

An investigation of the intra-generic structure of Rothia by pyrolysis mass spectrometry.

Previous studies of the genus Rothia have indicated that members of the only species, Rothia dentocariosa, are heterogeneous and may form more than one species. To study the intrageneric taxonomic structure of the Rothia taxon eighteen strains identified as R. dentocariosa, including reference organisms from culture collections (3 strains), isolates from healthy subjects (5 strains) and from clinical sources (10 strains) were examined using pyrolysis mass spectrometry. The ordination plots of the pyrolysis data indicated that all the strains clustered in a closely related group, with the exception of three strains which out-grouped. Phenotypic testing and fatty acid data indicated that the latter three strains are probably misclassified in the genus Rothia. Reanalysis of the PyMS data including only the fifteen authentic Rothia strains indicated that ten of these organisms formed a group which included the type strain, R. dentocariosa NCTC 10917. Four out of the remaining five organisms formed a diffuse group; the remaining strain was recovered as a single member cluster. These data indicate that R. dentocariosa is heterogeneous though at present there are no suitable criteria for assigning members of this taxon to more than one species.

Actinomycetales↗

PubMed1997

Typing of the fish pathogen Listonella (Vibrio) anguillara by pyrolysis mass spectrometry.

Twenty-eight representatives of Listonella (Vibrio) anguillara serovars O1, O2 and O3 were compared by Curie-point pyrolysis mass spectrometry (PyMS). The representatives of serovars O1 and O3 formed discrete, homogeneous groups in ordination plots of the PyMS data. Strains from serovar O2 were recovered in two groups, one of which encompassed six strains including the type strain of the species and the reference strain for serovar O2, and the other included two strains which showed cross-reactions between serovars O2 and O5. The almost complete agreement found between the PyMS and the serological data suggests that pyrolysis mass spectrometry will prove to be an effective method for interstrain comparison within the species Listonella anguillara.

Animals↗

PubMed1997

Application of neural networks to the analysis of pyrolysis mass spectra.

Pyrolysis mass spectrometry is a data rich analysis technique now becoming widely applied in microbiology. Data analysis is a key step in the exploitation of the technique and the application of neural network analysis to pyrolysis mass spectrometric data offers new opportunities for classification, identification and inter-strain comparison of microorganisms in biotechnology and clinical microbiology. The use of a supervised neural network for the identification of members of a streptomycete species-group is described.

Mass Spectrometry↗

PubMed1997

Differentiation of Mycobacterium senegalense from related non-chromogenic mycobacteria using pyrolysis mass spectrometry.

Twenty-six representative strains of Mycobacterium chelonae, Mycobacterium fortuitum, Mycobacterium peregrinum and Mycobacterium senegalense were compared by Curie point pyrolysis mass spectrometry. The M. chelonae and M. senegalense strains formed distinct groups. A third, relatively diffuse group, contained the M. fortuitum and M. peregrinum strains. These results, together with those from corresponding analyses, suggest that pyrolysis mass spectrometry provides a rapid and reliable way of distinguishing between members of closely related mycobacterial species which are difficult to differentiate using conventional taxonomic procedures.

Mass Spectrometry↗

PubMed2002

Pyrolysis process for the treatment of scrap tyres: preliminary experimental results.

The aim of this work is the evaluation, on a pilot scale, of scrap tyre pyrolysis process performance and the characteristics of the products under different process parameters, such as temperature, residence time, pressure, etc. In this frame, a series of tests were carried out at varying process temperatures between 550 and 680 degrees C, other parameters being equal. Pyrolysis plant process data are collected by an acquisition system; scrap tyre samples used for the treatment, solid and liquid by-products and produced syngas were analysed through both on-line monitoring (for gas) and laboratory analyses. Results show that process temperature, in the explored range, does not seem to seriously influence the volatilisation reaction yield, at least from a quantitative point of view, while it observably influences the distribution of the volatile fraction (liquid and gas) and by-products characteristics.

Incineration↗

PubMed1996

Pyrolysis mass spectrometry and its applications in biotechnology.

Pyrolysis mass spectrometry is a rapid and high-resolution method for the analysis of otherwise non-volatile material and has been widely applied for discriminating between closely related microbial strains. Recent advances in statistical and neural network methods based on supervised learning have now permitted exploitation of pyrolysis mass spectrometry in the quantitative analysis of many diverse samples of biotechnological interest; the technique may thus be regarded as an 'anything-sensor'.

Journal Article↗

PubMed2001

Preparation of levoglucosan by pyrolysis of cellulose and its citric acid fermentation.

Levoglucosan (LG), 1,6-anhydro-beta-D-glucopyranose, was produced by pyrolysis of cellulose. A response surface method was used to optimize the reaction parameters: X1, temperature; X2, time required for heating cellulose from room temperature to the designed pyrolysis temperature; and X3, vacuum, and a Box-Behnken design was employed for this purpose. The optimal temperature and time were found to be 388 degrees C and 26.2 min by fixing the vacuum at 1 mm Hg. The levoglucosan prepared was fermented to citric acid by Aspergillus niger CBX-209, which was a mutant derived by gamma-ray mutagenesis of the parent strain CBX-2. The mutant could produce increasing citric acid with increasing LG purity and had a citric acid yield of 87.5% when using purified levoglucosan as the sole carbon source in a 5 day fermentation period.

Aspergillus niger↗

PubMed1999

Investigation of cell culture media infected with viruses by pyrolysis mass spectrometry: implications for bioaerosol detection.

Mass spectrometry coupled with a pyrolysis inlet system was used to investigate media from cell cultures infected with viruses. Cell culture media is an intricate mixture of numerous chemical constituents and cells that collectively produce complicated mass spectra. Cholesterol and free fatty acids were identified and attributed to lipid sources in the media (blood serum supplement and plasma membranes of host cells). These lipid moieties could be utilized as signature markers for rapidly detecting the cell culture media. Viruses are intracellular parasites and are dependent upon host cells in order to exist. Therefore, it is highly probable that significant quantities of media needed to grow and maintain viable host cells would be present if a viral agent were disseminated as an aerosol into the environment. Cholesterol was also detected from a purified virus sample, further substantiating its use as a target compound for detection. Implications of this research for detection of viral bioaerosols, using a field-portable pyrolysis mass spectrometer, is described.

Aerosols↗

PubMed1994

Pyrolysis-gas chromatography/mass spectrometry analyses of biological particulates collected during recent space shuttle missions.

Biological particulates collected on air filters during shuttle missions (STS-40 and STS-42) were identified using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). A method was developed for identifying the atmospheric particles and their sources through the analysis of standard materials and the selection of "marker" compounds specific to the particle type. Pyrolysis spectra of biological standards were compared with those of airborne particles collected during two space shuttle missions; marker compounds present in the shuttle particle spectra were matched with those of the standards to identify the source of particles. Particles of 0,5--1-mm diameter and weighing as little as 40 micrograms could be identified using this technique. The Py-GC/MS method identified rat food and soilless plant-growth media as two sources of particles collected from the shuttle atmosphere during flight.

Air Pollutants↗

PubMed1990

Direct analysis of bacterial fatty acids by Curie-point pyrolysis tandem mass spectrometry.

Although pyrolysis-mass spectrometry (Py-MS) has been used for bacterial taxonomy, many of the mass spectral peaks used for discrimination of organisms have not been correlated to known biomolecules. This work presents the discrimination of five bacterial species based on Py-MS patterns containing only peaks that can be correlated to fatty acids and fatty acid derivatives. These correlations were confirmed by pyrolysis-tandem mass spectrometry of authentic standards and the organisms. The pattern recognition procedures used gave better results when only the fatty acid peaks were used in the analysis than when full spectra were used.

Bacillus↗

PubMed1990

Characterization of underivatized lipid biomarkers from microorganisms with pyrolysis short-column gas chromatography/ion trap mass spectrometry.

A microvolume Curie-point pyrolysis short-column (5 m) gas chromatography/mass spectrometry (Py-GC/MS) procedure was developed for the characterization of various lipid moieties in microorganisms. High linear flow rates (approximately 175 cm/s) characterized the GC conditions in order to effect an efficient chromatographic transfer and elution of the underivatized diglycerides and monoglycerides, and small modifications were necessary to the ion trap MS system in order for it to accommodate the relatively high gas load. During a typical analysis run anhydrodiacylglycerides eluted within a 5-6-min time frame. Gram-positive bacilli and Gram-negative species were differentiated from each other by the pyrolysis patterns of their lipid components. In spite of the complexity of the analyte, a straightforward visual analysis was achieved with the aid of simple computerized data display procedures. These procedures included examination of (1) total ion current (TIC) profiles of the lipid region of the reconstructed chromatogram, (2) the integrated mass spectrum of this region, (3) selected reconstructed ion chromatograms (RICs), (4) RIC intensity distributions, and (5) corresponding mass spectra. An appealing aspect of the lipid data reduction procedure is that most of it can be accomplished visually without requiring computerized pattern recognition techniques.

Bacteria↗

PubMed2001

Quantitative analysis of detailed lignin monomer composition by pyrolysis-gas chromatography combined with preliminary acetylation of the samples.

Detailed quantitative analysis of lignin monomer composition comprising p-coumaryl, coniferyl, and sinapyl alcohol and p-coumaraldehyde, coniferaldehyde, and sinapaldehyde in plant has not been studied from every point mainly because of artifact formation during the lignin isolation procedure, partial loss of the lignin components inherent in the chemical degradative methods, and difficulty in the explanation of the complex spectra generally observed for the lignin components. Here we propose a new method to quantify lignin monomer composition in detail by pyrolysis-gas chromatography (Py-GC) using acetylated lignin samples. The lignin acetylation procedure would contribute to prevent secondary formation of cinnamaldehydes from the corresponding alcohol forms during pyrolysis, which are otherwise unavoidable in conventional Py-GC process to some extent. On the basis of the characteristic peaks on the pyrograms of the acetylated sample, lignin monomer compositions in various dehydrogenative polymers (DHP) as lignin model compounds were determined, taking even minor components such as cinnamaldehydes into consideration. The observed compositions by Py-GC were in good agreement with the supplied lignin monomer contents on DHP synthesis. The new Py-GC method combined with sample preacetylation allowed us an accurate quantitative analysis of detailed lignin monomer composition using a microgram order of extractive-free plant samples.

Acetylation↗

PubMed2003

Resonance-enhanced multiphoton ionization and VUV-single photon ionization as soft and selective laser ionization methods for on-line time-of-flight mass spectrometry: investigation of the pyrolysis of typical organic contaminants in the steel recycling process.

A newly conceived compact and mobile time-of flight mass spectrometer (TOFMS) for real-time monitoring of highly complex gas mixtures is presented. The device utilizes two selective and sensitive soft ionization techniques, viz., resonance-enhanced multiphoton ionization (REMPI) and single-photon ionization (SPI) in a (quasi)-simultaneous mode. Both methods allow a fragmentationless ionization. The REMPI method selectively addresses aromatic species, while with SPI applying vacuum ultaviolet light (118 nm) in principle all compounds with an ionization potential below 10.5 eV are accessible. This provides comprehensive information of the chemical composition of complex matrixes. The combustion and pyrolysis behavior of five organic materials typically used in steel processing in China was studied. The trace amounts of organic compounds in the gas phase during combustion and pyrolysis were monitored selectively and sensitively by real-time SPI/REMPI-TOFMS. The measurements were carried out at several constant temperatures in the range from 300 to 1190 degrees C in both synthetic air and nitrogen. Timely resolved mass spectra reveal the formation and subsequent growth of aromatic molecules. At lower temperatures, highly alkylated PAHs predominate, while at temperatures above 800 degrees C, the more stable benzene and PAHs without side chains prevail. Potential hyphenation of SPI/REMPI-TOFMS to methods of thermal analysis is discussed.

Journal Article↗

PubMed2004

Correlation of mass spectrometry identified bacterial biomarkers from a fielded pyrolysis-gas chromatography-ion mobility spectrometry biodetector with the microbiological gram stain classification scheme.

A pyrolysis-gas chromatography-ion mobility spectrometry (Py-GC-IMS) briefcase system has been shown to detect and classify deliberately released bioaerosols in outdoor field scenarios. The bioaerosols included Gram-positive and Gram-negative bacteria, MS-2 coliphage virus, and ovalbumin protein species. However, the origin and structural identities of the pyrolysate peaks in the GC-IMS data space, their microbiological information content, and taxonomic importance with respect to biodetection have not been determined. The present work interrogates the identities of the peaks by inserting a time-of-flight mass spectrometry system in parallel with the IMS detector through a Tee connection in the GC module. Biological substances producing ion mobility peaks from the pyrolysis of microorganisms were identified by their GC retention time, matching of their electron ionization mass spectra with authentic standards, and the National Institutes for Standards and Technology mass spectral database. Strong signals from 2-pyridinecarboxamide were identified in Bacillus samples including Bacillus anthracis, and its origin was traced to the cell wall peptidoglycan macromolecule. 3-Hydroxymyristic acid is a component of lipopolysaccharides in the cell walls of Gram-negative organisms. The Gram-negative Escherichia coli organism showed significant amounts of 3-hydroxymyristic acid derivatives and degradation products in Py-GC-MS analyses. Some of the fatty acid derivatives were observed in very low abundance in the ion mobility spectra, and the higher boiling lipid species were absent. Evidence is presented that the Py-GC-ambient temperature and pressure-IMS system generates and detects bacterial biochemical information that can serve as components of a biological classification scheme directly correlated to the Gram stain reaction in microorganism taxonomy.

Biomarkers↗

PubMed2006

Fabrication of optically transparent carbon electrodes by the pyrolysis of photoresist films: approach to single-molecule spectroelectrochemistry.

This paper describes the preparation, physical and chemical characterization, and performance of carbon-based optically transparent electrodes (C-OTEs) fabricated by the pyrolysis of thin films of photoresist. The electrodes are prepared by spin coating dilute solutions of the positive photoresist AZ 4330 onto quartz substrates. Pyrolysis of these samples at 1000 degrees C in a reducing atmosphere yields optically transparent carbon films that have thicknesses ranging between 10 and 80 nm. Sheet resistance measurements, X-ray photoelectron spectroscopy, Raman spectroscopy, and atomic force microscopy were used to determine the physical and chemical properties of the films, and cyclic voltammetry and chronoabsorptometry were employed to delineate the electrochemical and conventional spectroelectrochemical performance of the C-OTEs. These findings showed that the transparency of this material improves as film thickness decreases, but at the expense of an increase in film resistance. At a wavelength of 500 nm, for example, 13- and 79-nm-thick films have transparencies of 47 and 10% and sheet resistances of 1100 and 210 Omega/ square, respectively. Importantly, adjusting the dilution factor allows the facile and reproducible variation of thickness and transparency. Preliminary results using these C-OTEs for single-molecule spectroelectrochemistry, which represents a new development in the merger of optical and electrochemical techniques, by probing the potential dependence of the adsorption of individual YOYO-I-labeled lambda-DNA are also presented.

Journal Article↗