Schweizerische Gruppe für Massenspektrometrie
Gruppo svizzero di spettrometria di massa
| Swiss
Group for Mass Spectrometry Schweizerische Gruppe für Massenspektrometrie |
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Groupe
suisse de spectrométrie de masse Gruppo svizzero di spettrometria di massa |
| The 28th meeting
of the SGMS was held at the Dorint Resort Blüemlisalp Beatenberg, November 4-5, 2010, high above Lake Thun in the Bernese Oberland, with a scenic view of the Swiss Alps! |
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| Plenary Lectures | |
Mass spectrometry-based methodologies for investigations of N- and O-linked glycans and their effects on assembly and interactions of cells and organisms |
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Catherine
E Costello |
| The glycosylation status of cell surface proteins
and lipids influences interactions of individual cells and even whole organisms,
with one another and with the environment. For example, epithelial cellular
adhesion via adherens junctions is mediated by multi-protein complexes.
Similarly, cell-surface carbohydrates provide critical signals that govern
expansion of tumors and activation of growth factors. Assembly of multimers
of P0 protein, a major component in myelin is dependent on its glycosylation.
Furthermore, changes in cell surface glycosylation, either species-specific
or due to genetic mutations, cause changes in each system’s susceptibility
to microbial infection. We are developing new and improved methods, centered
on MS, for detailed structural determinations of glycans and glycoconjugates
present as components of these complex mixtures. We are investigating new
methods for glycan structural determinations and are utilizing glycomics
and proteomics-based approaches to define glycan-dependent interactions
and to correlate changes in the phenotypes of individual cells and whole
organisms with degrees of glycosylation and differences in glycans.
Acknowledgements: NIH National Center for Research Resources and National
Heart Lung and Blood Institute. |
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Orchids: models of biological complexity |
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Jyotsna
Sharma |
| Orchidaceae is one of the largest and most highly
evolved plant families. Although approximately 70% of the orchid species
are of tropical origins ranging in size from a few centimeters to several
meters, the rest are native to the temperate and even arctic regions of
the planet inhabiting most all natural ecosystems except for the driest
deserts. A majority of the tropical and subtropical orchids grow as epiphytes,
i.e., growing on top of other plants, whereas those in the temperate regions
tend to grow terrestrially and include several non-photosynthetic species.
There is at least one known subterranean orchid species. This wide diversity
and evolutionary success of orchids is a result of an array of very complex,
and often very specific, biological and ecological strategies employed by
these organisms. Their highly specialized floral and vegetative structures,
pollination mechanisms involving sophisticated chemistry, cryptic growth
habits, root morphology, and unique reliance on mycorrhizal fungi are just
some of the characteristics that make them outstanding, although challenging,
models for studying complex biological interactions and even motivated Darwin
to exclusively study their biology. Orchids continue to intrigue commercial
and biological explorers alike.
One of the highly distinctive features of orchids is their specialized interaction with mycorrhizal fungi. These interactions can range from complete dependence on fungi throughout the life of an orchid to heavy reliance only during certain life-stages or very little reliance on fungi beyond the fully heterotrophic, seed germination stage. Orchid fungus interactions also can either be highly specific or relatively general. Given that up to 30,000 species are estimated to belong to the Orchidaceae, a number of ecological strategies appear to exist among orchid mycorrhizae. However, all orchid fungi identified this far fall into select fungal taxonomic groups only. This presentation will highlight some examples of the intricate orchid-fungal interactions and their consequences for biodiversity. We seek to understand whether fungal distribution determines orchid distribution in natural habitats, and whether the associations of orchids and their fungi are specific or general. Overall, orchid mycorrhizae are relatively underexplored, and there is especially a need to understand their distribution, inter-dependence, and communication mechanisms. |
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Shotgun lipidomics for cell biology and molecular medicine |
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Andrej
Shevchenko |
Lipidomics, an emerging branch of the omics sciences, aims at cataloguing and quantifying the total lipid complement synthesized by a cell, tissue or organism. Shotgun analysis of the lipidome implies that total lipid extracts containing hundreds of molecules from different lipid classes, are directly infused into a tandem mass spectrometer and thousands of MS and MS/MS spectra are acquired in a single run. Individual molecular species are recognized and quantified using their accurately determined masses and characteristic structural fragments. Shotgun lipidomics approach is appealing: it is rapid, comprehensive
and easy to set up at any tandem mass spectrometer. Quantification of
lipid species does not involve time-integration because the same analyte
is infused into a mass spectrometer. There is ample time to achieve good
ion statistics even for minor peaks and the ionization conditions can
be tuned to enhance the sensitivity towards barely detectable lipid classes.
There is no carry-over between samples and the entire process can be completely
automated. Shotgun lipidomics set up at the same instrumentation platform
supports both high- throughput clinical screens and targeted characterization
of molecular lipid species from a variety of model organisms from bacteria
to humans. However, two major bottlenecks of the shotgun approach are
in the limited dynamic range and possible ionization suppression of certain
species and in the consistent interpretation of exceedingly complex spectra
datasets. We argue that high resolution tandem mass spectrometers together
with the dedicated data interpretation software could overcome these hurdles
and support a broad scope of research efforts in cell biology, molecular
medicine and nutrition science. |
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Capillary electrophoresis and ultra high pressure liquid chromatography hyphenated with MS in pharmaceutical analysis |
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Jean-Luc
Veuthey |
| In the last ten years, a strong development has emerged in Capillary electrophoresis (CE) and in Liquid Chromatography (LC) to achieve fast, ultra-fast and highly efficient separations in the pharmaceutical field. In the same period of time, Mass Spectrometry (MS) with different analyzers became the best complementary tool to separation techniques, to further gain selectivity and/or sensitivity, when dealing with complex matrices (e.g. biological fluids and plant extracts). The use of large bio-molecules is increasing in pharmacy. Therefore, there is a need for efficient analytical techniques for determining these compounds (e.g. proteins). The on-line combination of capillary electrophoresis (CE) with mass spectrometry (MS) is an attractive option for intact protein analysis (i.e., no digestion, no derivatization). On the one hand, CE presents features such as high speed, great efficiency, and low solvent and sample consumptions. Moreover, CE allows working under aqueous conditions and without stationary phase. On the other hand, MS provides selectivity and ability to identification. TOF (time-of-flight) analyzer is particularly well suited to protein analysis, due to high mass range and mass accuracy. For small charged molecules, CE-MS with a simple quadrupole is also a powerful orthogonal analytical tool to LC-MS. Different examples will be given to illustrate the potential of CE-MS in the pharmaceutical domain. In LC, various analytical strategies have been reported for enhancing the chromatographic performance, such as the use of monolithic supports, high temperature, fused-core particles and sub-2µm particles working under very high pressure (UHPLC). Among the proposed approaches, it has been demonstrated that UHPLC and fused-core particles presented several advantages for the analysis of small molecules as well as large bio-molecules. Therefore, UHPLC-MS with different analyzers can be used to analyze very complex matrices with compounds present at low concentration. The possibilities offered by UHPLC at high temperature (i.e. HT-UHPLC) to further enhance chromatographic performance will be also discussed. Finally, UHPLC-MS/MS and UHPLC-TOF-MS can be attractive in ADME studies at an early stage of the drug discovery process. |
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| Short Communications | |
In-depth characterization of glycoproteins by ZIC-HILIC enrichment and mass spectrometryArnd Ingendoh1,
Arndt Asperger1, Anja Resemann1, Andrea Schneider1, N- and O-glycosylation of proteins are involved in many cellular processes and may play diverse roles at different sites within one protein. Therefore, the site-specific analysis of protein glycosylation has become an important issue in pharmaceutical and biotechnology applications for fundamental research as well as for quality control. A common technique for glycosylation analysis on the peptide level is LC/MS/MS. However, the analysis is difficult due to low abundance of glycopeptides in complex protein digests, micro heterogeneity at the same glycosylation site, ion suppression effects and competition for ionization by co-eluting (glyco-) peptides. The challenging requirement on mass spectrometric is the elucidation of both the peptide as well as the glycan moiety for a full structural assignment. Described here is a procedure for comprehensive glycosite analysis by specific and quantitative batch enrichment of N- and O-glycopeptides. Complementary 1D or 2D HILIC- and RP-LC setups are coupled to MS for the detection of low abundant glycoforms. Fetuin, alpha1-acidglycoprotein and Asialo-Fetuin were used to equally represent sialylated and non-sialylated glycosylic structures. In addition, monoclonal antibodies were analyzed as a dedicated example for pharmaceutical QC. Samples were digested with trypsin. The glycopeptides were enriched by a dedicated ZIC glycocapture resin in combination with an optimized buffer system. The intact glycoproteins and the digests were analyzed by various MS technologies (ion trap, MALDI-TOF/TOF or UHR-QTOF) for glycoprofiling and in depth characterization. Mascot searches of the glycopeptide MS/MS spectra provided for the peptide sequence and the localization of the glycosylation site. Searches in glycan databases on the same MS/MS spectra completed the characterization of N-linked glycopeptides. In the high resolution QTOF,
discrete changes in the glycosylation patterns even for molecules as large
as intact antibodies can be observed. After reduction and alkylation,
the molecular weights of the resulting light and heavy chains can be determined
with 0.2 ppm mass accuracy. In MALDI-TOF/TOF, the analysis of multi-sialylated
glycopeptides was performed. Linear positive ion mode spectra of sialylated
glycopeptides provided the respective precursor ion information. In reflector
mode, these precursors were selected for MS/MS even though they were not
detectable. Rich MS/MS spectra of the sialo-glycopeptides were obtained
providing both glycan and peptide fragments. A specific fragmentation
pattern allows identifying the MW of the peptide moiety and its proper
sequence assignment including the glycosylation site. Additionally, the
glycan heterogeneity can be elucidated. In Fetuin, tri-antennary glycan
structures with up to four sialic acids were elucidated using MALDI-TOF/TOF
and ion trap data. In comparison to direct MS analysis of glycoprotein
digests, the enriched samples resulted in MS/MS spectra of higher quality
and the detection of more glycopeptides. [back]
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Two-dimensional Fourier transform ion cyclotron resonance mass spectrometryMaria A van
Agthoven1, Marc-André Delsuc2, Christian Rolando1 In analytical chemistry, the
most interesting samples (biological, food, environmental or petroleum
samples) are often complex, containing hundreds or thousands different
compounds. The high resolving power and mass accuracy of FT-ICR/MS enables
the deduction of chemical formulae over a wide mass range and dynamic
range, and MS/MS yields more advanced structural information. However,
for complex samples this is time consuming, since it requires the fragmentation
of all the peaks in the MS spectrum and inaccurate since isolation windows
are rarely narrower than 0.1 Da. In 1988, Gäumann et al. [1] developed
a pulse sequence for 2D FT-ICR/MS that circumvents ion isolation and yields
data in one easily readable 2D mass spectrum. Until now, this method has
scarcely been used due to limitations both in acquisition and in data
analysis. [back]
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Phospholipidic fingerprinting by on-line desorption of dried spots and quadrupole-linear ion trap mass spectrometry: evaluation of atherosclerosis biomarkers in mouse plasmaAurélien Thomas1,2,
Julien Déglon1,2, Sébastien Lenglet3, François Mach3,
Patrice Mangin1, Jean-Luc Wolfender4, Sabine Steffens3 and Christian Staub1,2 Phospholipids play important
roles in the biochemistry of all living cells, either as the building
blocks of membranes or regulators of processes such as homeostasis, metabolism,
and signal transduction. This primordial physiological role is highlighted
by the numerous diseases in which phospholipids are implicated, such as
atherosclerosis, cancer, and Alzheimer’s disease. Atherosclerosis
is one of the major diseases in humans and is the most common cause of
death in western countries. It is induced by a chronic inflammatory response
in the subendothelial space resulting from the interaction of oxidized
low density lipoprotein (ox-LDL), monocyte-derived macrophages, T cells,
and normal cellular elements. In patients with hypercholesterolemia, excess
LDL infiltrates the artery at sites of hemodynamic strain. Oxidative and
enzymatic modifications of LDL then lead to the release of phospholipids
which are able to promote atherogenosis. This work presents a strategy
for the evaluation of differences in plasma phospholipid content between
atherosclerotic (ApoE-/-) and healthy mice from micro volumes (2 µL)
spotted on filter paper. Dried plasma spots (DPS) were directly desorbed
into a triple quadrupole linear ion trap mass spectrometer using a homemade
prototype, ensuring high-throughput analysis of dried spots without any
sample pretreatment. [back]
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Sites of metabolic substitution: Definitive metabolite structures deduced using ion mobility and molecular modelingRichard Lock As an analytical technique, mass spectrometry (MS) cannot separate isomeric species or provide conformational information. Structural information can be gained through tandem MS (MS/MS) techniques. There are classes of substituted molecules, such as hydroxylated metabolites which produce identical MS/MS spectra. This is problematic if the exact position of the hydroxylation is required. Ion mobility (IM) has the ability to separate isomeric species, such as hydroxylated metabolites, rapidly (msec) based on differences in their collision cross-section (O) in the gas-phase, thus providing specific information on ionic configuration and therefore, the position of the hydroxyl moiety. Experiments were performed using a hybrid quadrupole/ion mobility/orthogonal acceleration time-of-flight Synapt G2 HDMS instrument. Ion mobility separation was performed at a pressure of 3.2 mbar nitrogen with a wave velocity of 1100 m/sec and a travelling wave amplitude of 40 V was used. Theoretical O values were calculated using MOBCAL and compared to the travelling wave derived O values. Ion mobility calibration was undertaken using five singly charged polyalanine ions. Three-dimensional metabolite conformations were explored with the "Systematic Search" protocol in MOE. Ten thousand combinations of possible values for variables were explored. All conformations were minimised with the MMFF94 forcefield. Conformations with energies below 2 kcal/mol were selected for each metabolite. All three hydroxylated metabolites
showed different UPLC chromatographic elution times. However, the MS and
MS/MS spectra are all identical, thus hampering identification. The O
value of the parent compound ondansetron and the three hydroxylated metabolites
GR60661, GR63418 and GR90315 were measured by UPLC-IMS-MS. Theoretically
derived O values for hydroxylated metabolites GR60661, GR63418 and GR90315
are 110.9 Å2, 110.4 Å2 and 109.5 Å2 respectively. Travelling
wave ion mobility derived ? values are in very close agreements with the
theoretically derived values, thus allowing accurate identification of
the hydroxylated metabolites, even those with a ? difference of less than
1 Å2. No additional structural characterization techniques, such
as NMR or X-ray crystallography were required for metabolite structural
determination. This is a very time efficient and effective means of identifying
drug metabolites directly from biological matrices. Additionally this
method can be utilised in a situation where chemically synthesised standards
may not be available. [back]
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Stable isotope-labeled metabolomes — a tool for systems level analysisMichaël Méret Metabolomics aims to study
the chemical content of a wide range of organisms, fingerprint of dynamic
processes and consequences of specific development conditions. At first
introduced for diseases diagnostics until nowadays for system biology
understanding. [back]
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Electrochemistry/MS a powerful analytical technique to mimic drug metabolism and other redox reactions in life sciencesJean-Pierre Chervet1, Martin
Eysberg1, Agnieszka Kraj1, Daniel Vetter2 Traditional methods to investigate
oxidative drug metabolism are based on in-vitro (e.g. microsomes) or in-vivo
(urine, plasma, etc.) methods, which are both cumbersome and time consuming.
Therefore, mimicking oxidative metabolism using Electrochemistry (EC)
is of great interest as a fast and inexpensive alternative. [back]
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Online breath analysis by mass spectrometry, a possible tool for anesthesia monitoring?Berchtold Christian A big challenge in anesthesiology is the dynamic control of drug dosage used to anesthetize a person during surgery. Today, sophisticated patient monitoring is used to control the health status, as well as the level of consciousness of a patient. During surgery, a patient is usually connected to a breathing machine that allows monitoring of his breath. Currently, a patient’s breath is monitored for CO2 saturation as well as isoflurane levels by spectroscopic methods. Unfortunately, no commercial tool is available for the monitoring of metabolites or other drugs in breath such as morphine or fentanyl. Recent developments in ambient ionization technologies suggest using mass spectrometry as a system for the detection of metabolites in breath, such as the narcotics used in anesthesia. Technologies like atmospheric pressure chemical ionization mass spectrometry (APCI-MS), selected ion flow tube mass spectrometry (SIFT-MS), proton transfer reaction mass spectrometry (PTR-MS) or extractive electronspray ionization mass spectrometry (EESI) show very sensitive detection limits and enable direct analysis of compounds in exhaled breath. Recent investigations using offline methods suggest a sensitivity of low ppt(V) is needed to detect narcotics in breath if they are present. At the moment, no technology reaches this sensitivity for online detection of narcotics. In our ambitious research project we try to overcome this problem. The sensitivity of mass spectrometric methods is an issue of sample preparation, ionization method and mass spectrometer used. If a method is supposed to be considered as online, sample preparation has to be very limited. This means the sensitivity has to be reached by both the ionization method as well as the mass analyzer used. Our investigations on different
mass analyzers, such as quadrupole time of flight, 3D and linear ion traps
indicate that most commercial system are at the same level of sensitivity
and any reasonable enhancement is not easily realized. As a next step
in this development we used EESI and APCI to detect compounds like fentanyl,
morphine, caffeine and nicotine and determine the limit of detection in
the gas phase. Our first evaluation showed that reasonable detection limits
in breath (low ppb(V) levels, online detection) is possible for the more
volatile narcotics like fentanyl or nicotine. For less volatile compounds,
such as morphine or caffeine, detection by online methods seems to be
more challenging. Offline experiments with morphine show that the estimated
online concentration is at the level of low ppt(V), which cannot be reached
at the moment. Further optimization and enhancement of the ionization
methods is needed. Online breath analysis for anesthesia in breath is
a challenging topic and is directly related to the development of ionization
systems. We are still investigating feasible tools for the sensitive and
fast ionization of breath. [back]
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Dried blood spots – a revolution in drug development?Katja Heinig, Almudena Gajate-Perez,
Berthold Lausecker Dried blood spots (DBS) is
a technique where blood is sampled on filter paper-based cards, dried,
discs punched out, extracted and the compounds of interest contained in
the blood are analyzed. It is widely applied in neonatal screening of
inborn errors of metabolism and in therapeutic drug monitoring for many
years. Recently, it has been expanded into the DMPK field within drug
development [1], as an alternative to measure plasma concentrations to
obtain pharmacokinetic data. This became feasible since analytical techniques
have advanced, and LC-MS/MS is now state of the art in drug analysis,
with mass spectrometers getting more and more sensitive. Only small sample
volumes are needed which provides benefits for toxicology (i.e. reduction
of animal numbers), pharmacokinetics (i.e. serial sampling from small
animals) and clinics (i.e. enabling of pediatric studies). Transport and
storage costs for study samples are significantly reduced. Furthermore,
improved stability of otherwise instable compounds could be demonstrated
in some cases. [1] Barfield M, Spooner N,
Lad R, Parry S, Fowles S. Application of Dried Blood Spots combined with
HPLC-MS/MS for the quantification of acetaminophen in toxicokinetic studies.
J. Chromatogr. B 870, 32-37 (2008). [back]
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Probing the architecture of protein complexes by chemical cross-linking and mass spectrometryFranz Herzog, Thomas Walzthöni,
Alexander Leitner, Martin Beck, Ruedi Aebersold Introduction: Structural biology techniques like X-ray crystallography and NMR spectroscopy have solved structures of individual proteins and subcomplexes , however, failed to reveal a comprehensive picture of the architecture of marcromolecular protein assemblies . Our strategy aims at integrating spatial constraints identified by mass spectrometry and structural information obtained by conventional methods. We apply chemical agents to cross-link different amino acid side chains within a single polypeptide chain or two polypeptides in a complex and identify the covalently linked peptides by mass spectrometry. The length of the cross-linker provides a measure for the maximum distance spanned between the two connected residues. Method: Protein samples are cross-linked with an equimolar mixture of isotopically light and heavy labeled cross-linkers facilitating the identification of all modified peptides by a characteristic isotope pattern. Following enzymatic digestion, cross-linked peptides are enriched over the vast majority of the non-cross-linked species by size exclusion chromatography and analyzed by LC-MS/MS on a LTQ-Orbitrap hybrid instrument. Pairs of isotope-coded peptides are identified by the precursor ion mass shift and the corresponding tandem mass spectra are submitted to the dedicated search engine, xQuest. The experimental product ion spectrum is matched to all possible theoretical candidate spectra derived from a database. The general feasibility of the concept is indicated by the identification of inter- and intra-protein cross-links within purified recombinant protein complexes. Preliminary Data: Based on
the analysis of a mixture of eight model proteins we estimate a false
discovery rate of our cross-linking strategy of ~4%. Cross-linking of
multi-protein complexes like proteasome or RNA polymerase I at high purity
and concentration yielded about 100 – 150 non-redundant distance
constraints. Novel Aspect: Cross-linking
of native human protein complexes may facilitate the analysis of protein-protein
interactions and complex topologies on a routine basis. [back]
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Towards label free protein quantification of the plasma membranomeNiurka Meneses Moreno3, Natasha
Tetkovic1, Dimitrios J Fotiadis2, Manfred Heller1 Background: A major proportion (~30%) of the human genes code for membrane proteins. This class of protein fulfills a variety of important cellular functions, such as metabolite or macro-molecule trafficking through a lipid bilayer, homeostasis of membrane potential, energy production, cellular signaling, and last but not least, cell to environment communication at the plasma membrane. Despite their importance, membrane proteins in general, and plasma membrane proteins in particular, are hugely underrepresented in proteome study results. Reasons for this are manifold, e.g. solubility, low abundance, or inaccessibility for proteolysis. Our research focuses on the molecular processes at the surface of endothelial cells exposed to different shear stress qualities. In order to make quantitative prediction of plasma membrane protein changes, there is a clear need to improve plasma membrane enrichment and protein digestion efficiencies. Methods: Tests for increasing the digestion efficiency of membrane proteins were carried out with a purified urea transporter protein, using trypsin and proteinase K and acid labile detergent. Primary human umbilical endothelial cells and an immortal lymphocyte cell line were used to test plasma membrane enrichment strategies based on affinity capture, e.g. ConA binding, cell surface protein biotinylation, or centrifugation techniques. Proteins were separated by SDS-PAGE and identified by in-gel digestion and LC-MS/MS on an orbitrap system. Gene ontology analyses were used for cellular location prediction of the identified proteins. Results: The urea transporter
(MW ~36 kDa) has nine predicted transmembrane helices. While trypsin digestion
resulted in a sequence coverage of only 29%, a short proteinase K digestion
covered 67%, including many hydrophobic stretches. Many expensive kits
with elaborate affinity methods for the enrichment of plasma membrane
proteins are propagated by commercial companies. We have compared the
efficiency of some with a very simple two-step centrifugation protocol
after microsomal aggregation induced by addition of Ca2+ ions [Lin et
al. (1987) Biochemistry, 26, 731]. With this latter, low tech protocol
we were able to find many more potential plasma membrane proteins than
with any other protocol. The combined trypsin and proteinase K digests
increased the sequence coverage of membrane associated proteins. [back]
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Tissue transglutaminase-induced deamidation and transamidation of neuropeptides revealed by electron capture dissociation mass spectrometryLuca Fornelli1, Luigino Grasso2,
Horst Vogel2, Adrien W Schmid3, Yury O Tsybin1 Upon interaction with peptides and proteins, the ubiquitously expressed enzyme tissue transglutaminase (tTGase) catalyzes glutamine (Gln) deamidation and, in presence of a peptidyl-lysine (Lys), transamidation, which results in the formation of a protease-resistant isopeptide bond. Particularly, recent in vitro studies indicate that tTGase might be involved in the deamidation and covalent cross-linking of neuropeptides and proteins, e.g., amyloid beta and alpha-synuclein, which seem to be related with the onset of neurodegenerative disorders. In the present study we first used the neuropeptide substance P (SP, RPKPQQFFGLM-NH2) as a model to determine the catalytic activity of tTGase. We applied reversed-phase liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry for the reaction products analysis, see Figure.
Electron capture dissociation (ECD) was used to elucidate the sequential deamidation of Gln5 and Gln6 residues in SP and get an insight into the structure of transamidated SP dimers. Three different dimer populations were detected, distinguished by the number of deamidated Gln residues. Upon all the tested reaction conditions the most abundant reaction product was always the singly-deamidated Glu5-SP. Therefore, we carried out an in vitro assay to compare its agonist potency toward the natural NK1 receptor with the one of unmodified SP. Based on the results obtained
with tTGase-induced modification of SP, the ECD-based methodology is being
applied to the study of deamidation and transamidation of amyloid beta
peptides, e.g., the full-length amyloid beta 1-40 and its truncated forms,
to unambiguously clarify their deamidation and cross-linking sites. [back]
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MALDI-TOF mass spectrometry: Applications in food microbiological identification and food safety researchRené Brunisholz1, Britta
Stoop2, Simone Wüthrich1, Frank Hesford2, Ralph Schlapbach1, David
Drissner2 MALDI-TOF mass spectrometry
for the characterization and classification of fungi and bacteria is based
on the detection of mainly ribosomal proteins which are constantly expressed
as high-abundant proteins. Resulting protein fingerprints are unique,
highly reproducible and mostly independent of culture medium, incubation
temperature and growth state. The objective of this study is to efficiently
identify undesired and human pathogenic microorganisms in food products
of plant origin by this rapidly emerging technology. [back]
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