Direct identification of trypanosomatids by matrix‐assisted laser desorption ionization–time of flight mass spectrometry (DIT MALDI‐TOF MS)

Accurate and rapid determination of trypanosomatids is essential in epidemiological surveillance and therapeutic studies. Matrix‐assisted laser desorption ionization/time of flight mass spectrometry (MALDI‐TOF MS) has been shown to be a useful and powerful technique to identify bacteria, fungi, metazoa and human intact cells with applications in clinical settings. Here, we developed and optimized a MALDI‐TOF MS method to profile trypanosomatids. trypanosomatid cells were deposited on a MALDI target plate followed by addition of matrix solution. The plate was then subjected to MALDI‐TOF MS measurement to create reference mass spectra library and unknown samples were identified by pattern matching using the BioTyper software tool. Several m/z peaks reproducibly and uniquely identified trypanosomatids species showing the potentials of direct identification of trypanosomatids by MALDI‐TOF MS. Moreover, this method discriminated different life stages of Trypanosoma cruzi, epimastigote and bloodstream trypomastigote and Trypanosoma brucei, procyclic and bloodstream. T. cruzi Discrete Typing Units (DTUs) were also discriminated in three clades. However, it was not possible to achieve enough resolution and software‐assisted identification at the strain level. Overall, this study shows the importance of MALDI‐TOF MS for the direct identification of trypanosomatids and opens new avenues for mass spectrometry‐based detection of parasites in biofluids. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry for the study of Helicobacter pylori

The characteristics of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry based investigation of extremely variable bacteria such as Helicobacter pylori were studied. H. pylori possesses a very high natural variability. Accurate tools for species identification and epidemiological characterization could help the scientific community to better understand the transmission pathways and virulence mechanisms of these bacteria. Seventeen clinical as well as two laboratory strains of H. pylori were analyzed by the MALDI Biotyper method for rapid species identification. Mass spectra collected were found containing 7–13 significant peaks per sample, and only six protein signals were identical for more than half of the strains. Four of them could be assigned to ribosomal proteins RL32, RL33, RL34, and RL36. The reproducible peak with m/z 6948 was identified as a histidine‐rich metal‐binding polypeptide by tandem mass spectrometry (MS/MS). In spite of the evident protein heterogeneity of H. pylori the mass spectra collected for a particular strain under several cultivations were highly reproducible. Moreover, all clinical strains were perfectly identified as H. pylori species through comparative analysis using the MALDI Biotyper software (Bruker Daltonics, Germany) by pattern matching against a database containing mass spectra from different microbial strains (n = 3287) including H. pylori 26695 and J99. The results of this study allow the conclusion that the MALDI‐TOF direct bacterial profiling is suited for H. pylori identification and could be supported by mass spectra fragmentation of the observed polypeptide if necessary. Copyright © 2010 John Wiley & Sons, Ltd.     

Detection of pathogenic Verticillium spp. using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Verticillium spp. have been listed by the European and Mediterranean Plant Protection Organization (EPPO) and China as plant quarantine pests. Although attempts have been made to develop a simple routine laboratory assay to detect these organisms, none are routinely used. We describe for the first time a robust assay for reliable identification of Verticillium spp. using protein fingerprinting data obtained by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry(MALDI‐TOF‐MS). Several sample preparation methods and matrices were investigated to improve mass spectra for the routine identification of six species of Verticillium spp.(Verticillium dahiliae, V. alboatrum, V. fungicola, V. nigrescens, and V. lecanii) by MALDI‐TOF‐MS. Using the optimized experimental method, we constructed a protein fingerprint database for six species of Verticillium and established a analysis criteria of log(Score). This MALDI‐TOF‐MS protocol should prove useful as a rapid and reliable assay for distinguishing different Verticillium spp. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of MALDI‐TOF mass spectra with microsatellite length polymorphisms in Candida albicans

Candida albicans is the most frequent yeast involved in human infections. Its population structure can be divided into several genetic clades, some of which have been associated with antifungal susceptibility. Therefore, detecting and monitoring fungal clones in a routine laboratory setting would be a major epidemiological advance. Matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra results are now widely used as bar codes to identify microorganisms in clinical microbiology laboratories. This study aimed at testing MALDI‐TOF mass spectra bar codes to identify clades among a set of C. albicans isolates. Accordingly, 102 clinical strains were genotyped using 10 microsatellite markers and analyzed via MALDI‐TOF mass spectrometry. The mass spectra were compared with a reference spectral library including 33 well‐characterized collection strains, using a Microflex^TM system and Biotyper^TM software, to test the capacity of the spectrum of a given isolate to match with the reference mass spectrum of an isolate from the same genetic clade. Despite high confidence species identification, the spectra failed to significantly match with the corresponding clade (p = 0.74). This was confirmed with the MALDI‐TOF spectra similarity dendrogram, in which the strains were dispersed irrespective of their genetic clade. Various attempts to improve intra‐clade spectra recognition were unsuccessful. In conclusion, MALDI‐TOF mass spectra bar code analysis failed to reliably recognize genetically related C. albicans isolates. Further studies are warranted to develop alternative MALDI‐TOF mass spectra analytical approaches to identify and monitor C. albicans clades in the routine clinical laboratory. Copyright © 2015 John Wiley & Sons, Ltd.     

Modern MALDI time‐of‐flight mass spectrometry

This paper focuses on development of time‐of‐flight (TOF) mass spectrometry in response to the invention of matrix‐assisted laser desorption/ionization (MALDI). Before this breakthrough ionization technique for nonvolatile molecules, TOF was generally considered as a useful tool for exotic studies of ion properties but was not widely applied to analytical problems. Improved TOF instruments and software that allow the full potential power of MALDI to be applied to difficult biological applications are described. A theoretical approach to the design and optimization of MALDI‐TOF instruments for particular applications is presented. Experimental data are provided that are in excellent agreement with theoretical predictions of resolving power and mass accuracy. Data on sensitivity and dynamic range using kilohertz laser rates are also summarized. These results indicate that combinations of high‐performance MALDI‐TOF and TOF‐TOF with off‐line high‐capacity separations may ultimately provide throughput and dynamic range several orders of magnitude greater than those currently available with electrospray LC‐MS and MS‐MS. Copyright © 2009 John Wiley & Sons, Ltd.     

Evaluation of matrix‐assisted laser desorption/ionization (MALDI) preparation techniques for surface characterization of intact Fusarium spores by MALDI linear time‐of‐flight mass spectrometry

Unambiguous identification of mycotoxin‐producing fungal species as Fusarium is of great relevance to agriculture and the food‐producing industry as well as in medicine. Protein profiles of intact fungal spores, such as Penicillium, Aspergillus and Trichoderma, derived from matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) were shown to provide a rapid and straightforward method for species identification and characterization. In this study, we applied this approach to five different Fusarium spp. strains which are known to affect the growth of different grain plants. To obtain a suitable MALDI matrix system and sample preparation method, thin‐layer, dried‐droplet and sandwich methods and several MALDI matrices, namely CHCA, DHB, FA, SA and THAP dissolved in various solvent mixtures (organic solvents such as ACN, MeOH, EtOH and iPrOH and for the aqueous phase water and 0.1% TFA), were evaluated in terms of mass spectrometric pattern and signal intensities. The most significant peptide/protein profiles were obtained with 10 mg ferulic acid (FA) in 1 mL ACN/0.1% TFA (7:3, v/v) used as matrix system. Mixing the spores with the matrix solution directly on the MALDI target (dried‐droplet technique) resulted in an evenly distributed spores/matrix crystal layer, yielding highly reproducible peptide/protein profiles from the spore surfaces. Numerous abundant ions throughout the investigated m/z range (m/z 1500–15 000) could be detected. Differences in the obtained mass spectral patterns allowed the differentiation of spores of various Fusarium species. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparative study of matrices for their use in the rapid screening of anabolic steroids by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry

New data on sample preparation and matrix selection for the fast screening of androgenic anabolic steroids (AAS) by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) is presented. The rapid screening of 15 steroids included in the World Anti‐Doping Agency (WADA) prohibited list using MALDI was evaluated. Nine organic and two inorganic matrices were assessed in order to determine the best matrix for steroid identification in terms of ionisation yield and interference by characteristic matrix ions. The best results were achieved for the organic matrices 2‐(4‐hydroxyphenylazo)benzoic acid (HABA) and trans‐3‐indoleacrylic acid (IAA). Good signals for all the steroids studied were obtained for concentrations as low as 0.010 and 0.050 µg/mL on the MALDI sample plate for the HABA and IAA matrices, respectively. For these two matrices, the sensitivity achieved by MALDI is comparable with the sensitivity achieved by gas chromatography/mass spectrometry (GC/MS), which is the conventional technique used for AAS detection. Furthermore, the accuracy and precision obtained with MALDI are very good, since an internal mass calibration is performed with the matrix ions. For the inorganic matrices, laser fluences higher than those used with organic matrices are required to obtain good MALDI signals. When inorganic matrices were used in combination with glycerol as a dispersing agent, an important reduction of the background noise was observed. Urine samples spiked with the study compounds were processed by solid‐phase extraction (SPE) and the screening was consistently positive. Copyright © 2009 John Wiley & Sons, Ltd.     

MALDI‐based intact spore mass spectrometry of downy and powdery mildews

Fast and easy identification of fungal phytopathogens is of great importance in agriculture. In this context, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has emerged as a powerful tool for analyzing microorganisms. This study deals with a methodology for MALDI‐TOF MS‐based identification of downy and powdery mildews representing obligate biotrophic parasites of crop plants. Experimental approaches for the MS analyses were optimized using Bremia lactucae, cause of lettuce downy mildew, and Oidium neolycopersici, cause of tomato powdery mildew. This involved determining a suitable concentration of spores in the sample, selection of a proper MALDI matrix, looking for the optimal solvent composition, and evaluation of different sample preparation methods. Furthermore, using different MALDI target materials and surfaces (stainless steel vs polymer‐based) and applying various conditions for sample exposure to the acidic MALDI matrix system were investigated. The dried droplet method involving solvent evaporation at room temperature was found to be the most suitable for the deposition of spores and MALDI matrix on the target and the subsequent crystallization. The concentration of spore suspension was optimal between 2 and 5 × 10⁹ spores per ml. The best peptide/protein profiles (in terms of signal‐to‐noise ratio and number of peaks) were obtained by combining ferulic and sinapinic acids as a mixed MALDI matrix. A pretreatment of the spore cell wall with hydrolases was successfully introduced prior to MS measurements to obtain more pronounced signals. Finally, a novel procedure was developed for direct mass spectra acquisition from infected plant leaves. Copyright © 2012 John Wiley & Sons, Ltd.     

Identification and classification of seafood‐borne pathogenic and spoilage bacteria: 16S rRNA sequencing versus MALDI‐TOF MS fingerprinting

The present study aims to compare two molecular technologies, 16S rRNA sequencing and MALDI‐TOF MS, for bacterial species identification in seafood. With this aim, 70 reference strains from culture collections, including important seafood‐borne pathogenic and spoilage bacterial species, and 50 strains isolated from commercial seafood products, were analysed by both techniques. Genomic analysis only identified the species of 50% of the isolated strains, proving to be particularly poor at identifying members of the Pseudomonas and Bacillus genera. In contrast, MALDI‐TOF MS fingerprinting identified 76% of the strains at the species level. The mass spectral data were submitted to the SpectraBank database ( http://www.spectrabank.org ), making this information available to other researchers. Furthermore, cluster analysis of the peak mass lists was carried out with the web application SPECLUST and the calculated groupings were consistent with results determined by a phylogenetic approach that is based on the 16S rRNA sequences. However, the MALDI‐TOF MS analysis demonstrated more discriminating potential that allowed for better classification, especially for the Pseudomonas and Bacillus genera. This is of importance with respect to the varying pathogenic and spoilage character at the intragenus and intraspecies level. In this sense, MALDI‐TOF MS demonstrated to be a competent bacterial typing tool that extends phenotypic and genotypic approaches, allowing a more ample classification of bacterial strains.     

MALDI‐TOF mass spectrometry of hordeins: rapid approach for identification of malting barley varieties

A procedure for identification of malting barley varieties using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) of ethanol‐soluble barley proteins (hordeins) is described. The hordeins were first extracted from milled barley grains by several extraction protocols (using different extraction agents and conditions). Hordein extracts were then analyzed directly via MALDI‐TOF MS without any preliminary purification or separation step, and the protein profiles of analyzed hordein extracts were compared in order to find out the most suitable extraction procedure for mass spectrometric analysis. The optimized procedure was successfully applied to identification of 13 malting barley varieties. Our results revealed that the proposed mass spectrometry‐based approach provides characteristic mass patterns of extracted hordeins, which can be advantageously used for barley variety identification. Copyright © 2009 John Wiley & Sons, Ltd.     

Glycation sites in neoglycoglycoconjugates from the terminal monosaccharide antigen of the O‐PS of Vibrio cholerae O1, serotype Ogawa,and BSA revealed by matrix‐assisted laser desorption–ionization tandem mass spectrometry

We present the MALDI‐TOF/TOF‐MS analyses of various hapten–bovine serum albumin (BSA) neoglycoconjugates obtained by squaric acid chemistry coupling of the spacer‐equipped, terminal monosaccharide of the O‐specific polysaccharide of Vibrio cholerae O1, serotype Ogawa, to BSA. These analyses allowed not only to calculate the molecular masses of the hapten–BSA neoglycoconjugates with different hapten–BSA ratios (4.3, 6.6 and 13.2) but, more importantly, also to localize the covalent linkages (conjugation sites) between the hapten and the carrier protein. Determination of the site of glycation was based on comparison of the MALDI‐TOF/TOF‐MS analysis of the peptides resulting from the digestion of BSA with similar data resulting from the digestion of BSA glycoconjugates, followed by sequencing by MALDI‐TOF/TOF‐MS/MS of the glycated peptides. The product‐ion scans of the protonated molecules were carried out with a MALDI‐TOF/TOF‐MS/MS tandem mass spectrometer equipped with a high‐collision energy cell. The high‐energy collision‐induced dissociation (CID) spectra afforded product ions formed by fragmentation of the carbohydrate hapten and amino acid sequences conjugated with fragments of the carbohydrate hapten. We were able to identify three conjugation sites on lysine residues (Lys235, Lys437 and Lys455). It was shown that these lysine residues are very reactive and bind lysine specific reagents. We presume that these Lys residues belong to those that are considered to be sterically more accessible on the surface of the tridimensional structure. The identification of the y‐series product ions was very useful for the sequencing of various peptides. The series of a‐ and b‐product ions confirmed the sequence of the conjugated peptides. Copyright © 2010 John Wiley & Sons, Ltd.     

Mass spectrum analysis of serum biomarker proteins from patients with schizophrenia

Diagnosis of schizophrenia does not have a clear objective test at present, so we aimed to identify the potential biomarkers for the diagnosis of schizophrenia by comparison of serum protein profiling between first‐episode schizophrenia patients and healthy controls. The combination of a magnetic bead separation system with matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry (MALDI‐TOF/TOF‐MS) was used to analyze the serum protein spectra of 286 first‐episode patients with schizophrenia, 41 chronic disease patients and 304 healthy controls. FlexAnlysis 3.0 and ClinProTools^TM 2.1 software was used to establish a diagnostic model for schizophrenia. The results demonstrated that 10 fragmented peptides demonstrated an optimal discriminatory performance. Among these fragmented peptides, the peptide with m/z 1206.58 was identified as a fragment of fibrinopeptide A. Receiver operating characteristic analysis for m/z 1206.58 showed that the area under the curve was 0.981 for schizophrenia vs healthy controls, and 0.999 for schizophrenia vs other chronic disease controls. From our result, we consider that the analysis of serum protein spectrum using the magnetic bead separation system and MALDI‐TOF/TOF‐MS is an objective diagnostic tool. We conclude that fibrinopeptide A has the potential to be a biomarker for diagnosis of schizophrenia. This protein may also help to elucidate schizophrenia disease pathogenesis. Copyright © 2013 John Wiley & Sons, Ltd.     

Impact of updating the MALDI‐TOF MS database on the identification of nontuberculous mycobacteria

Conventional identification of mycobacteria species is slow, laborious and has low discriminatory power. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has proved highly effective for identifying conventional bacteria, and it may also be useful for identifying mycobacteria. The aim of this study was to evaluate and compare MALDI‐TOF MS with currently recommended molecular methods for the identification of nontuberculous mycobacteria (NTM), applying Mycobacteria Libraries v3.0 (ML3.0) and v2.0 (ML2.0). A total of 240 clinical isolates of 41 NTM species grown on solid media were analysed: 132 isolates of slow‐growing mycobacteria and 108 of rapid‐growing mycobacteria. MALDI‐TOF MS, using ML3.0, identified 192 (80%) NTM isolates with a score ≥1.7, encompassing 35 (85.4%) different species, that is, 17 (7.1%; p  = 0.0863) isolates and 15 (36.6%; p  = 0.0339) species more than currently recommended molecular techniques (polymerase chain reaction reverse hybridization). All these isolates were correctly identified according to molecular identification methods. The application of ML3.0 also identified 15 (6.2%) NTM isolates more than ML2.0 (p  < 0.01). The scores obtained with MALDI‐TOF MS using ML3.0 (mean score: 1.960) were higher in 147 (61.2%) isolates than when using ML2.0 (mean score: 1.797; p  < 0.01). Three of the species analysed were not included in either database, so they were not recognized by this system. In conclusion, MALDI‐TOF MS identified more isolates and species than the recommended polymerase chain reaction reverse hybridization assays. Although the new ML3.0 is not the definitive database, it yielded better results than ML2.0. This shows that the updating of the MALDI‐TOF MS database plays an essential role in mycobacterial identification. Copyright © 2017 John Wiley & Sons, Ltd.     

Correlative mass spectrometry imaging,applying time‐of‐flight secondary ion mass spectrometry and atmospheric pressure matrix‐assisted laser desorption/ionization to a single tissue section

Rationale

Mass spectrometry imaging (MSI) is a powerful tool for mapping the surface of a sample. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) and atmospheric pressure matrix‐assisted laser desorption/ionization (AP‐MALDI) offer complementary capabilities. Here, we present a workflow to apply both techniques to a single tissue section and combine the resulting data for the example of human colon cancer tissue.

Methods

Following cryo‐sectioning, images were acquired using the high spatial resolution (1 μm pixel size) provided by TOF‐SIMS. The same section was then coated with a para‐nitroaniline matrix and images were acquired using AP‐MALDI coupled to an Orbitrap mass spectrometer, offering high mass resolution, high mass accuracy and tandem mass spectrometry (MS/MS) capabilities. Datasets provided by both mass spectrometers were converted into the open and vendor‐independent imzML file format and processed with the open‐source software MSiReader.

Results

The TOF‐SIMS and AP‐MALDI mass spectra show strong signals of fatty acids, cholesterol, phosphatidylcholine and sphingomyelin. We showed a high correlation between the fatty acid ions detected with TOF‐SIMS in negative ion mode and the phosphatidylcholine ions detected with AP‐MALDI in positive ion mode using a similar setting for visualization. Histological staining on the same section allowed the identification of the anatomical structures and their correlation with the ion images.

Conclusions

This multimodal approach using two MSI platforms shows an excellent complementarity for the localization and identification of lipids. The spatial resolution of both systems is at or close to cellular dimensions, and thus spatial correlation can only be obtained if the same tissue section is analyzed sequentially. Data processing based on imzML allows a real correlation of the imaging datasets provided by these two technologies and opens the way for a more complete molecular view of the anatomical structures of biological tissues.

     

MSQ: a tool for quantification of proteomics data generated by a liquid chromatography/matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry based targeted quantitative proteomics platform

Mass spectrometry (MS)‐based quantitative proteomics has become a critical component of biological and clinical research for identification of biomarkers that can be used for early detection of diseases. In particular, MS‐based targeted quantitative proteomics has been recently developed for the detection and validation of biomarker candidates in complex biological samples. In such approaches, synthetic reference peptides that are the stable isotope labeled version of proteotypic peptides of proteins to be quantitated are used as internal standards enabling specific identification and absolute quantification of targeted peptides. The quantification of targeted peptides is achieved using the intensity ratio of a native peptide to the corresponding reference peptide whose spike‐in amount is known. However, a manual calculation of the ratios can be time‐consuming and labor‐intensive, especially when the number of peptides to be tested is large. To establish a liquid chromatography/matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry (LC/MALDI TOF/TOF)‐based targeted quantitative proteomics pipeline, we have developed a software named Mass Spectrometry based Quantification (MSQ). This software can be used to automate the quantification and identification of targeted peptides/proteins by the MALDI TOF/TOF platform. MSQ was applied to the detection of a selected group of targeted peptides in pooled human cerebrospinal spinal fluid (CSF) from patients with Alzheimer's disease (AD) in comparison with age‐matched control (OC). The results for the automated quantification and identification of targeted peptides/proteins in CSF were in good agreement with results calculated manually. Copyright © 2010 John Wiley & Sons, Ltd.     

Mass spectrometric characterization of the zein protein composition in maize flour extracts upon protein separation by SDS‐PAGE and 2D gel electrophoresis

Highly homogenous α zein protein was isolated from maize kernels in an environment‐friendly process using 95% ethanol as solvent. Due to the polyploidy and genetic polymorphism of the plant source, the application of high resolution separation methods in conjunction with precise analytical methods, such as MALDI‐TOF‐MS, is required to accurately estimate homogeneity of products that contain natural zein protein. The α zein protein product revealed two main bands in SDS‐PAGE analysis, one at 25 kDa and other at 20 kDa apparent molecular mass. Yet, high resolution 2DE revealed approximately five protein spot groups in each row, the first at ca. 25 kDa and the second at ca. 20 kDa. Peptide mass fingerprinting data of the proteins in the two dominant SDS‐PAGE bands matched to 30 amino acid sequence entries out of 102 non‐redundant data base entries. MALDI‐TOF‐MS peptide mapping of the proteins from all spots indicated the presence of only α zein proteins. The most prominent ion signals in the MALDI mass spectra of the protein mixture of the 25 kDa SDS gel band after in‐gel digestion were found at m/z 1272.6 and m/z 2009.1, and the most prominent ion signals of the protein mixture of the 20 kDa band after in‐gel digestion were recorded at m/z 1083.5 and m/z 1691.8. These ion signals have been found typical for α zein proteins and may serve as marker ion signals which upon chymotryptic digestion reliably indicate the presence of α zein protein in two hybrid corn products.     

Heterobifunctional isotope‐labeled amine‐reactive photo‐cross‐linker for structural investigation of proteins by matrix‐assisted laser desorption/ionization tandem time‐of‐flight and electrospray ionization LTQ‐Orbitrap mass spectrometry

Chemical cross‐linking combined with a subsequent enzymatic digestion and mass spectrometric analysis of the created cross‐linked products presents an alternative approach to assess low‐resolution protein structures. By covalently connecting pairs of functional groups within a protein or a protein complex a set of structurally defined interactions is built up. We synthesized the heterobifunctional amine‐reactive photo‐cross‐linker N‐succinimidyl p‐benzoyldihydrocinnamate as a non‐deuterated (SBC) and doubly deuterated derivative (SBDC). Applying a 1:1 mixture of SBC and SBDC for cross‐linking experiments aided the identification of cross‐linked amino acids in the mass spectra based on the characteristic isotope patterns of fragment ions. The cross‐linker was applied to the calcium‐binding protein calmodulin with a subsequent analysis of cross‐linked products by nano‐high‐performance liquid chromatography matrix‐assisted laser desorption/ionization tandem time‐of‐flight mass spectrometry (nano‐HPLC/MALDI‐TOF/TOF‐MS) and nano‐HPLC/nano‐electrospray ionization (ESI)‐LTQ‐Orbitrap‐MS. Copyright © 2009 John Wiley & Sons, Ltd.     

Cyclic and telechelic ladder polymers derived from tetrahydroxytetramethylspirobisindane and 1,4‐dicyanotetrafluorobenzene

5,5′,6,6′‐Tetrahydroxy‐3,3,3′,3′‐tetramethylspirobisindane was polycondensed with 1,4‐dicyanotetrafluorobenzene in four different solvents at 70 °C. In dimethylformamide, N‐methylpyrrolidone, and sulfolane exclusively, cyclic polymers were detectable by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry up to masses around 13,000 Da. In dimethyl sulfoxide, linear byproducts were also found. Higher temperatures caused degradation reactions catalyzed by potassium carbonate. Polycondensations performed with the addition of 4‐tert‐butyl catechol or 2,2′‐dihydroxy binaphthyl yielded linear telechelic oligomers. Equimolar mixtures of linear and cyclic ladder polymers were examined by MALDI‐TOF mass spectra to determine how the end groups and the cyclic structure influenced the signal‐to‐noise ratio. The results suggested a preferential detection of the linear chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5344–5352, 2006     

MALDI‐TOF‐Massenspektrometrie: Risikoanalyse im Flug

The high accuracy, molecular resolution and sensitivity of matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) make it an efficient method for analysing all kinds of biomolecules including nucleic acids, proteins/peptides, carbohydrates and lipids. MALDI‐TOF‐MS based high‐throughput genotyping of genetic heterogeneities possesses the potential of becoming a routine method. MAL‐DI‐TOF‐MS can be used for the identification of proteins and posttranslational modifications. Taken together, MALDI‐TOF‐MS represents a integrated platform technology in bioanalytics and molecular medicine.     

Deciphering key proteins of oil palm (Elaeis guineensis Jacq.) fruit mesocarp development by proteomics and chemometrics

Palm oil is an edible vegetable oil derived from lipid‐rich fleshy mesocarp tissue of oil palm (Elaeis guineensis Jacq.) fruit and is of global economic and nutritional relevance. While the understanding of oil biosynthesis in plants is improving, the fundamentals of oil biosynthesis in oil palm still require further investigations. To gain insight into the systemic mechanisms that govern oil synthesis during oil palm fruit ripening, the proteomics approach combining gel‐based electrophoresis and mass spectrometry was used to profile protein changes and classify the patterns of protein accumulation during these complex physiological processes. Protein profiles from different stages of fruit ripening at 10, 12, 14, 15, 16, 18 and 20 weeks after anthesis (WAA) were analysed by two‐dimensional gel electrophoresis (2DE). The proteome data were then visualised using a multivariate statistical analysis of principal component analysis (PCA) to get an overview of the proteome changes during the development of oil palm mesocarp. A total of 68 differentially expressed protein spots were successfully identified by matrix‐assisted laser desorption/ionisation‐time of flight (MALDI‐TOF/TOF) and functionally classified using ontology analysis. Proteins related to lipid production, energy, secondary metabolites and amino acid metabolism are the most significantly changed proteins during fruit development representing potential candidates for oil yield improvement endeavors. Data are available via ProteomeXchange with identifier PXD009579. This study provides important proteome information for protein regulation during oil palm fruit ripening and oil synthesis.