Gert B. Eijkel

Curie-point pyrolysis-capillary gas chromatography-high-resolution mass spectrometry of microcrystalline cellulose

Abstract Microcrystalline cellulose was analysed by Curie-point pyrolysis-capillary gas chromatography-mass spectrometry (Py-GC-MS) under electron impact (70 eV) as well as chemical ionisation (isobutane) conditions. Almost all interpretations could be supported by high-resolution mass spectrometric data, obtained by Py-GC-high-resolution MS. The pyrolysis products identified can be classified into several main groups i.e. carbonyl compounds, acids and methyl esters, furans, pyrans, anhydrosugars and hydrocarbons. Altogether 96 compounds have been found, and structural assignments could be given to 94 of them. From these compounds 25 have not been identified earlier in pyrolysates of polysaccharides. Levoglucosan is the major GC amenable pyrolysis product detected. Several formation pathways are proposed to account for the formation of a number of pyrolysis products from levoglucosan and/or cellobiosan. An overview showing the thermal degradation pattern of cellulose through anhydrosaccharides to smaller pyrolysis products is also presented.

Hypertension Is Associated with Marked Alterations in Sphingolipid Biology: A Potential Role for Ceramide

Background Hypertension is, amongst others, characterized by endothelial dysfunction and vascular remodeling. As sphingolipids have been implicated in both the regulation of vascular contractility and growth, we investigated whether sphingolipid biology is altered in hypertension and whether this is reflected in altered vascular function. Methods and Findings In isolated carotid arteries from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, shifting the ceramide/S1P ratio towards ceramide dominance by administration of a sphingosine kinase inhibitor (dimethylsphingosine) or exogenous application of sphingomyelinase, induced marked endothelium-dependent contractions in SHR vessels (DMS: 1.4±0.4 and SMase: 2.1±0.1 mN/mm; n = 10), that were virtually absent in WKY vessels (DMS: 0.0±0.0 and SMase: 0.6±0.1 mN/mm; n = 9, p<0.05). Imaging mass spectrometry and immunohistochemistry indicated that these contractions were most likely mediated by ceramide and dependent on iPLA2, cyclooxygenase-1 and thromboxane synthase. Expression levels of these enzymes were higher in SHR vessels. In concurrence, infusion of dimethylsphingosine caused a marked rise in blood pressure in anesthetized SHR (42±4%; n = 7), but not in WKY (−12±10%; n = 6). Lipidomics analysis by mass spectrometry, revealed elevated levels of ceramide in arterial tissue of SHR compared to WKY (691±42 vs. 419±27 pmol, n = 3–5 respectively, p<0.05). These pronounced alterations in SHR sphingolipid biology are also reflected in increased plasma ceramide levels (513±19 pmol WKY vs. 645±25 pmol SHR, n = 6–12, p<0.05). Interestingly, we observed similar increases in ceramide levels (correlating with hypertension grade) in plasma from humans with essential hypertension (185±8 pmol vs. 252±23 pmol; n = 18 normotensive vs. n = 19 hypertensive patients, p<0.05). Conclusions Hypertension is associated with marked alterations in vascular sphingolipid biology such as elevated ceramide levels and signaling, that contribute to increased vascular tone.

Differences in relative growth rate in 11 grasses correlate with differences in chemical composition as determined by pyrolysis mass spectrometry

SummaryEleven grass species varying in potential relative growth rate (RGR) were investigated for differences in chemical composition by pyrolysis mass spectrometry. The spectral data revealed correlations between RGR and the relative composition of several biopolymers. Species with a low potential RGR contained relatively more cell wall material such as lignin, hemicellulose, cellulose, polysaccharide-bound ferulic acid and hydroxyproline-rich protein, whereas species with a high potential RGR showed relatively more cytoplasmic elements such as protein (other than those incorporated in cell walls) and sterols.

Multimodal Mass Spectrometric Imaging of Small Molecules Reveals Distinct Spatio-Molecular Signatures in Differentially Metastatic Breast Tumor Models

Phosphocholine (PC) and total choline (tCho) are increased in malignant breast tumors. In this study, we combined magnetic resonance spectroscopic imaging (MRSI), mass spectrometry (MS) imaging, and pathologic assessment of corresponding tumor sections to investigate the localization of choline metabolites and cations in viable versus necrotic tumor regions in the nonmetastatic MCF-7 and the highly metastatic MDA-MB-231 breast cancer xenograft models. In vivo three-dimensional MRSI showed that high tCho levels, consisting of free choline (Cho), PC, and glycerophosphocholine (GPC), displayed a heterogeneous spatial distribution in the tumor. MS imaging performed on tumor sections detected the spatial distributions of individual PC, Cho, and GPC, as well as sodium (Na+) and potassium (K+), among many others. PC and Cho intensity were increased in viable compared with necrotic regions of MDA-MB-231 tumors, but relatively homogeneously distributed in MCF-7 tumors. Such behavior may be related to the role of PC and PC-related enzymes, such as choline kinase, choline transporters, and others, in malignant tumor growth. Na+ and K+ colocalized in the necrotic tumor areas of MDA-MB-231 tumors, whereas in MCF-7 tumors, Na+ was detected in necrotic and K+ in viable tumor regions. This may be attributed to differential Na+/K+ pump functions and K+ channel expressions. Principal component analysis of the MS imaging data clearly identified different tumor microenvironmental regions by their distinct molecular signatures. This molecular information allowed us to differentiate between distinct tumor regions and tumor types, which may, in the future, prove clinically useful in the pathologic assessment of breast cancers.

Thermal Degradation Characteristics of High Impact Polystyrene/Decabromodiphenylether/Antimony Oxide Studied by Derivative Thermogravimetry and Temperature Resolved Pyrolysis-Mass Spectrometry. Formation of Polybrominated Dibenzofurans, Antimony (oxy) Bromides and Brominated Styrene Oligomers

Abstract The thermal stability and the thermal degradation products of high impact polystyrene / decabromodiphenylether / antimony oxide (HIPS FR) have been studied in situ with derivative thermogravimetry (DTG), temperature resolved pyrolysis—mass spectrometry (Py-MS) and pyrolysis—gas chromatography / mass spectrometry (Py-GC /MS). With in-source temperature resolved Py-MS (negative ions) the thermal degradation processes of HIPS FR have been studied dynamically and antimony (oxy)bromides and brominated higher styrene oligomers upto n = 15 have been detected. During degradation of the HIPS FR polymer matrix several processes take place, such as debromination of the flame retardant decabromodiphenylether to form less brominated diphenylethers, bromination of polystyrene and formation of antimony bromides and antimony oxybromides. The formation of toxic polybrominated dibenzofurans (PBDFs) has been shown to occur in the temperature range in which the HIPS FR polymer matrix degrades (350–400°C). This is explained by debromination of decabromodiphenylether to form less brominated diphenylethers which are much more reactive towards formation of PBDFs.

Evidence for oligomers in pyrolysates of microcrystalline cellulose

Abstract Microcrystalline cellulose was analysed by platinum filament pyrolysis desorption chemical ionisation mass spectrometry (DCI-MS) under ammonia chemical ionisation conditions. This polysaccharide was also pyrolysed on a preparative scale as well as by off-line Curie-point pyrolysis and subsequently analysed by ammonia DCI-MS. The DCI-MS data of the native polysaccharide show ion series corresponding to ammonium adduct ions of anhydrocello-oligosaccharides up to anhydrocello-hexaose. In the preparative-scale and the off-line Curie-point pyrolysates up to the pentamer could be detected. Related ion series corresponding to the ammonia adducts of ring fragments left on the saccharide chain were also seen. It is uncertain whether these compounds are formed during pyrolysis directly from the native polymer or arise from the corresponding anhydro-oligosaccharides during the ionisation process. The three pyrolysis methods tested yield comparable results with respect to the pyrolysis products formed, which indicates that the mechanism of formation of anhydrocello-oligosaccharides from cellulose is a generally significant process. Curie-point pyrolysis-gas chromatography data should be interpreted with caution since the oligomeric part of the pyrolysate is not monitored by this method.

Time-of-flight secondary ion mass spectrometry-based molecular distribution distinguishing healthy and osteoarthritic human cartilage.

Osteoarthritis (OA) is a pathology that ultimately causes joint destruction. The cartilage is one of the principal affected tissues. Alterations in the lipid mediators and an imbalance in the metabolism of cells that form the cartilage (chondrocytes) have been described as contributors to the OA development. In this study, we have studied the distribution of lipids and chemical elements in healthy and OA human cartilage. Time of flight-secondary ion mass spectrometry (TOF-SIMS) allows us to study the spatial distribution of molecules at a high resolution on a tissue section. TOF-SIMS revealed a specific peak profile that distinguishes healthy from OA cartilages. The spatial distribution of cholesterol-related peaks exhibited a remarkable difference between healthy and OA cartilages. A distinctive colocalization of cholesterol and other lipids in the superficial area of the cartilage was found. A higher intensity of oleic acid and other fatty acids in the OA cartilages exhibited a similar localization. On the other hand, CN(-) was observed with a higher intensity in the healthy samples. Finally, we observed an accumulation of calcium and phosphate ions exclusively in areas surrounding the chondrocyte in OA tissues. To our knowledge, this is the first time that TOF-SIMS revealed combined changes in the molecular distribution in the OA human cartilage.

Matrix-assisted laser desorption ionization-imaging mass spectrometry: a new methodology to study human osteoarthritic cartilage.

OBJECTIVE Information about the distribution of proteins and the modulation that they undergo in the different phases of rheumatic pathologies is essential to understanding the development of these diseases. We undertook this study to demonstrate the utility of mass spectrometry (MS)-based molecular imaging for studying the spatial distribution of different components in human articular cartilage sections. METHODS We compared the distribution of peptides and proteins in human control and osteoarthritic (OA) cartilage. Human control and OA cartilage slices were cut and deposited on conductive slides. After tryptic digestion, we performed matrix-assisted laser desorption ionization-imaging MS (MALDI-IMS) experiments in a MALDI-quadrupole time-of-flight mass spectrometer. Protein identification was undertaken with a combination of multivariate statistical methods and Mascot protein database queries. Hematoxylin and eosin staining and immunohistochemistry were performed to validate the results. RESULTS We created maps of peptide distributions at 150-μm raster size from control and OA human cartilage. Proteins such as biglycan, prolargin, decorin, and aggrecan core protein were identified and localized. Specific protein markers for cartilage oligomeric matrix protein and fibronectin were found exclusively in OA cartilage samples. Their distribution displayed a stronger intensity in the deep area than in the superficial area. New tentative OA markers were found in the deep area of the OA cartilage. CONCLUSION MALDI-IMS identifies and localizes disease-specific peptides and proteins in cartilage. All the OA-related peptides and proteins detected display a stronger intensity in the deep cartilage. MS-based molecular imaging is demonstrated to be an innovative method for studying OA pathology.

Chemical imaging of lipid droplets in muscle tissues using hyperspectral coherent Raman microscopy.

The accumulation of lipids in non-adipose tissues is attracting increasing attention due to its correlation with obesity. In muscle tissue, ectopic deposition of specific lipids is further correlated with pathogenic development of insulin resistance and type 2 diabetes. Most intramyocellular lipids are organized into lipid droplets (LDs), which are metabolically active organelles. In order to better understand the putative role of LDs in pathogenesis, insight into both the location of LDs and nearby chemistry of muscle tissue is very useful. Here, we demonstrate the use of label-free coherent anti-Stokes Raman scattering (CARS) microscopy in combination with multivariate, chemometric analysis to visualize intracellular lipid accumulations in ex vivo muscle tissue. Consistent with our previous results, hyperspectral CARS microscopy showed an increase in LDs in tissues where LD proteins were overexpressed, and further chemometric analysis showed additional features morphologically (and chemically) similar to mitochondria that colocalized with LDs. CARS imaging is shown to be a very useful method for label-free stratification of ectopic fat deposition and cellular organelles in fresh tissue sections with virtually no sample preparation.

Dosimetry of paintings : determination of the degree of chemical change in museum-exposed test paintings by mass spectrometry

Abstract Painted works of art are constantly exposed to and affected by their environment. The chemical, mechanical and visual characteristics of paintings are subject to changes. The paintings themselves can be seen as dosimeters that integrate the effect of their environment. In the present research, mock paintings are used as dosimeters to integrate the overall effect of the museum environment on the paint in a given time span. Direct temperature resolved mass spectrometry (DTMS) and the multivariate technique of discriminant analysis are used to compare the chemical composition of mock paintings exposed in five different museums in Europe. Changes observed on laboratory-exposed (light, temperature and a mixture of nitrogen oxides and sulphur dioxide) dosimeters serve as the calibration set. The methodology applied to derive chemical information from the dosimeters is presented here. The results obtained on the exposed mock paintings show that the principle of paint-based dosimetry works. Other factors than light alone are found to play an important role in environment-induced deterioration.