SGMS Meeting 2002

This meeting of the SGMS was held on 14 and 15 November 2002 at the Hotel Dorint on the Beatenberg, high above Lake Thun in the Bernese Oberland, with a scenic view of the Swiss Alps.

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The Development of Quadrupole Field Mass Spectrometers

Michael S. Story, ThermoFinnigan, San José, USA

While the principles were thoroughly published in the early 50's, widespread availability of mass spectrometers utilizing these principles was not given until 20 years later. Linear and three dimensional quadrupole (ion trap) mass spectrometers represent the overwhelming majority of instruments operating in laboratories today.

As with any technology, there needed to be a driving force for the commercial development. Individuals and companies often do initiate this development, but without a significant market need to direct the technical development to a unique solution, there is most often failure. The success of quadrupole and ion trap mass spectrometry has relied on the environmental and biotechnology markets to provide the problems and support for academic, industrial, and commercial use and development.

This will be a retrospective description of these technical developments and the inter-play of instrumentation development, academia, and market needs.

IRM-GC-MS techniques to characterise sources and sinks of organic contaminants in ground water

Hans H. Richnow, UFZ Environmental Research Centre Leipzig Halle Ltd., Germany

In the past decade, stable isotope chemistry has received increasing attention in environmental science. The stable isotope signature of organic substances yield useful information to decipher source, distribution, and fate of organic substances in the ground water. The isotopic composition (D/H, ¹³C/¹²C, ¹⁵N/¹⁴N, ³⁷Cl/³⁷Cl) of organic contaminant can be used as fingerprints to trace their origin (Smallwood et al., 2002; Drenzek et al., 2002) which may have some potential in forensic approaches with respect to separate pollution sources. Isotope fractionation processes can be used to characterised in situ biodegradation.

Monitoring of ground water contamination has gained importance in the context of risk assessment, plume management strategies, and in the evaluation of remediation measures, in particular where natural attenuation concepts are applied. Thus, innovative approaches are needed to monitor processes governing the concentration of contaminants in the aquifer. A decrease of pollutants concentration in a contamination plume could have many reasons like dilution, sorption or biological degradation, but only the latter leads to sustainable contaminant reduction. Thus, the assessment and quantification of in situ biodegradation is essential to evaluate the risk of contaminated aquifers and is essential prove the success of monitored natural attenuation (MNA) or any other remedy.

To characterise in situ biodegradation, a concept based on the isotope fractionation of organic contaminants during biodegradation had been developed (Richnow and Meckenstock, 1999; Meckenstock et al., 1999; Richnow et al., 2002). Biodegradation of pollutants such as aromatic hydrocarbons and chlorinated ethenes l eads to an enrichment of 13C and 2H in the residual fraction (Meckenstock et al., 1999; Hunkeler et al.,1999; Bloom et al., 2000; Ward et. al., 2000; Morasch et al., 2001). This fractionation process can be described by the Rayleigh-Equation. The relation between concentration and isotopic composition of a compound is described by the kinetic isotope fractionation factor (a). In laboratory degradation experiments with batch cultures, the isotope fractionation factors have been determined for some typical BTEX, mineral oil and chlorinated groundwater contaminants. These factors were applied to quantify the biodegradation in several field studies and to evaluate the validity of the isotope fractionation concept.

Various test sites with distinct geochemical and hydrological characteristics were examined for isotopic fractionation to assess the in-situ biodegradation. Laboratory derived isotope fractionation factors were applied to calculate the extent of biodegradation (Vieth et al., 2002). Test site comprises variety of contaminants, such as (i) tar oils (BTEX and naphthalene), (ii) landfill leachate with BTEX, mineral oils (diesel fuel) and (iii) chlorinated solvents. Isotope fractionation may be well used to evaluate the biodegradation in contaminated aquifers independent of other concentration diminishing processes such as sorption and dilution. In the context of Natural Attenuation, this concept has a large potential to improve ground water monitoring and risk assessment strategies.

Modern IRM-GC-MS systems can be used in routine analysis and enable the exploitation of the large potential of isotope chemistry in ground water research. This paper discusses various aspects of IRM-GC-MS approaches in ground water analysis chemistry from a technical and scientific perspective.

References:

Bloom Y, Aravena R, Hunkeler D, Edward E, Frape SK (2000): Environ. Sci. Technol. 34, 2768-2772
Drenzek NJ, Tarr CH, Eglinto TI, Heraty LJ, Sturchio NC, Shinner VJ Reedy CM (2002) Org.Geochem. 33, 437-444.
Hunkeler D, Aravena R, Butler BJ (1999): Environ. Sci. Technol. 33, 2733-2738
Meckenstock RU, Morasch B, Warthmann R, Schink B, Annweiler E, Michaelis W, Richnow HH (1999): Environ. Microbiol. 1, 409-414;
Morasch B., Richnow H.H., Schink B., Meckenstock R.U. (2001): Appl. Envinonm. Microbiol. 67, 4842-4849.
Richnow HH, Annweiler E, Michaelis W, Meckenstock RU (2002): J. Contam. Hydrol. (in revision)
Richnow HH, Meckenstock RU (1999): TerraTech 5, 38-41;
Smallwood BJ, Philp RP, Allem JD (2002) Org. Geochem. 22, 149-159.
Vieth A., Kästner M., Morasch B., Meckenstock R. U., Richnow H. H.(2001): TerraTech 5, 37-41.
Ward JA, Ahad JME, Lacrampe-Couloume G, Slater GF, Edwards EA, Sherwood Lollar B (2000): Environ. Sci. Technol. 34, 4577-4581.

Can we cover the metabolome only by means of mass spectrometry?

*Fiehn O., #Costisella, B. & *Tolstikov VV
*Max-Planck-Institute of Molecular Plant Physiology, 14424 Potsdam (Germany)
# University of Dortmund, Dept. of Chemistry, Dortmund (Germany)
Corresponding author: fiehn at mpimp-golm.mpg.de

Analogous to the transcriptome and the proteome, an organism's metabolome is defined as the complete set of its metabolites present in a certain tissue under defined conditions. Plant metabolomes are comprised by thousands of individual compounds. Is it possible to identify and quantitate all metabolites in a biological system by means of mass spectrometry?

Currently, the answer is a clear 'no'. However, in the context of functional genomics, there is the need to analyse as detailed as possible the response of an organism to genetic, environmental or developmental perturbation. We have therefore started to analyse parts of the metabolome in an unbiased way by combining GC-TOF with mass spectral deconvolution, and RP and HILIC-ion trap-MS^3 at positive and negative ESI for assessing the relative abundance of all detectable peaks, with currently some 1,000 peaks to be found in a plant sample. This strategy leads to a high number of unidentified compounds, and de novo identification is an essential part of truly metabolomic approaches. Using the example of a novel amino-callose found in cucurbit phloem we demonstrate, how ion trap mass spectrometry alone may be misleading in structural elucidation, and that accurate mass MS is required by necessity. We compared the use of GC-Quadrupole MS (!), QTOF and FT-MS for that purpose, and concluded that without the additional help of 2D µNMR, metabolites cannot be elucidated, even with the help of software like MassFrontier or databases like KEGG and Beilstein. After de novo identification of several metabolites we later found to be already published, we concluded that it would be a great help to have a comprehensive biological LC/MS library, despite the fact that standardisation between different instruments is hardly possible.

As a biological application example, the comparison of a silent SuSy antisense potato line and its corresponding Desirée cultivar is shown. Using the peak areas of identified and unidentified compounds, we normalized each individual plant sample to the total metabolome content. Metabolic distances as well as shifts in biochemical networks could be computed. Network generation was performed by correlation analysis and 3D visualization. By investigating these networks, novel hypotheses on hexose transformations and sugar alcohol metabolism could be generated.

MALDI MS Imaging of Biological Tissue: A Powerful Tool in the Drug Discovery Process

Markus Stoeckli, Analytical and Imaging Sciences, Novartis Pharama AG, Basel

The detailed analysis of biological tissues for their molecular contents is a key element in the search for cures for diseases. A wide variety of techniques is available for this challenging task, but there is a continuous need for tools that enable the collection of large amounts of data with higher spatial resolution in a short time.

Expression profiling by mass spectrometry is a powerful technique that can quickly provide information on a wide range of molecular contents in tissues, but its spatial resolution is only as good as the tissue portion used for the experiment. The goal of our work was to identify molecular entities in tissues and to localize them within small, defined cell populations.

A method is presented for direct spatial analysis of biological tissue sections for their molecular distribution. The technique takes advantage of the very sensitive matrix-assisted laser desorption/ionization mass spectrometry technology and employs a commercial instrument with modifications only to a few components and the software. With this setup, hundreds of molecular images can be generated simultaneously and within just a few minutes. The current features are a spatial resolution of 50 µm and a sensitivity in the attomol range.

In this presentation, the basic principle of this technology is demonstrated, covering the complete process from tissue preparation to image analysis. Improvements developed in our lab will be shown, which allow fast data acquisition and processing. The potential of this method for the drug development process is shown in examples of protein and drug imaging.

Ref: Stoeckli et al., A new technology for the analysis of protein expression in mammalian tissues. Nat. Med., 2001 7(4), 493-496

The detailed programme of the meeting, including all abstracts, can be found in the SGMS Newsletter 20_2 (October 2002). This document is available for download (PDF).

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