Background: Statistical comparison of peptide profiles in biomarker discovery requires fast, user-friendly software for high throughput data analysis. Important features are flexibility in changing input variables and statistical analysis of peptides that are differentially expressed between patient and control groups. In addition, integration the mass spectrometry data with the results of other experiments, such as microarray analysis, and information from other databases requires a central storage of the profile matrix, where protein id's can be added to peptide masses of interest.
Results: A new database application is presented, to detect and identify significantly differentially expressed peptides in peptide profiles obtained from body fluids of patient and control groups. The presented modular software is capable of central storage of mass spectra and results in fast analysis. The software architecture consists of 4 pillars, 1) a Graphical User Interface written in Java, 2) a MySQL database, which contains all metadata, such as experiment numbers and sample codes, 3) a FTP ( File Transport Protocol) server to store all raw mass spectrometry files and processed data, and 4) the software package R, which is used for modular statistical calculations, such as the Wilcoxon-Mann-Whitney rank sum test. Statistic analysis by the Wilcoxon-Mann-Whitney test in R demonstrates that peptide-profiles of two patient groups 1) breast cancer patients with leptomeningeal metastases and 2) prostate cancer patients in end stage disease can be distinguished from those of control groups.
Conclusion: The database application is capable to distinguish patient Matrix Assisted Laser Desorption Ionization (MALDI-TOF) peptide profiles from control groups using large size datasets. The modular architecture of the application makes it possible to adapt the application to handle also large sized data from MS/MS- and Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry experiments. It is expected that the higher resolution and mass accuracy of the FT-ICR mass spectrometry prevents the clustering of peaks of different peptides and allows the identification of differentially expressed proteins from the peptide profiles.
Publisher
14494Higher sensitivity secondary ion mass spectrometry of biological molecules for high resolution, chemically specific imaging
Liam A. McDonnell, Ron M.A. Heeren, Robert P.J. de Lange, Ian W. Fletcher
Journal of the American Society for Mass Spectrometry 17 (2006) 1195-1202
Published: 1-9-2006
To expand the role of high spatial resolution secondary ion mass spectrometry (SIMS) in biological studies, numerous developments have been reported in recent years for enhancing the molecular ion yield of high mass molecules. These include both surface modification, including matrix-enhanced SIMS and metal-assisted SIMS, and polyatomic primary ions. Using rat brain tissue sections and a bismuth primary ion gun able to produce atomic and polyatomic primary ions, we report here how the sensitivity enhancements provided by these developments are additive. Combined surface modification and polyatomic primary ions provided ≈15.8 times more signal than using atomic primary ions on the raw sample, whereas surface modification and polyatomic primary ions yield ≈3.8 and ≈8.4 times more signal. This higher sensitivity is used to generate chemically specific images of higher mass biomolecules using a single molecular ion peak.Publisher
14493The influence of the cholesterol microenvironment in tissue sections on molecular ionization efficiencies and distributions in ToF-SIMS
A.F. Maarten Altelaar, Jan van Minnen, Ron M.A. Heeren, Sander R. Piersma
Applied Surface Science 252 (2006) 6702-6705
Published: 30-7-2006
High-resolution images of cholesterol were obtained from Lymnaea stagnalis nervous tissue using metal-assisted (MetA) time-of-flight secondary ion mass spectrometry (ToF-SIMS). The spatial distributions of different pseudomolecular ions of cholesterol [M − H]+, [M − OH]+ and [2M + Au]+, illustrate the influence of the tissue microenvironment on the ionization efficiencies of these ions. These biological matrix effects result in differences in localizations of molecular ions derived from the same molecular species.Publisher
14492Why don't biologists use SIMS? : A critical evaluation of imaging MS
R.M.A. Heeren, L.A. McDonnell, E. Amstalden, S.L. Luxembourg, A.F.M. Altelaar, S.R. Piersma
Applied Surface Science 252 (2006) 6827-6835
Published: 30-7-2006
Secondary ion mass spectrometry is commonly used to study many different types of complex surfaces. Yet, compared with MALDI and ESI-MS, SIMS has not made a significant impact in biological or biomedical research. The key features of the technique, namely high spatial resolution, high detection efficiency of ions spanning a wide m/z range, surface sensitivity and the high scan rates seem to match ideally with several questions posed at the cellular level. To this date, SIMS has had only limited success in the biological arena. Why is this and what is needed to change this? This discussion paper will critically review the advances and the usefulness of SIMS in biomedical research and compare it to other approaches that offer spatially resolved molecular information available to a researcher with a biological interest. We will demonstrate that the type of information generated by the various incarnations of SIMS is strongly dependent on sample preparation and surface condition and these phenomena are only poorly understood. Modern approaches such as the cluster gun developments, ME-SIMS, gold coating and MALDI stigmatic imaging on a SIMS instrument might change the perception of SIMS being a tool for semiconductor manufacturers and physicists, and might persuade biologists to use these innovative mass spectrometric imaging tools.Publisher
14473Atypical behavior in the electron capture induced dissociation of biologically relevant transition metal ion complexes of the peptide hormone oxytocin
Anne J. Kleinnijenhuis, Romulus Mihalca, Ron M.A. Heeren, Albert J.R. Heck
International Journal of Mass Spectrometry 253 (2006) 217-224
Published: 1-7-2006
Doubly protonated ions of the disulfide bond containing nonapeptide hormone oxytocin and oxytocin complexes with different transition metal ions, that have biological relevance under physiological conditions, were subjected to electron capture dissociation (ECD) to probe their structural features in the gas phase. Although, all the ECD spectra were strikingly different, typical ECD behavior was observed for complexes of the nonapeptide hormone oxytocin with Ni2+, Co2+ and Zn2+, i.e., abundant c/zﾒ. and aﾒ./y backbone cleavages and ECD characteristic S–S and S–C bond cleavages were observed. We propose that, although in the oxytocin–transition metal ion complexes the metal ions serve as the main initial capture site, the captured electron is transferred to other sites in the complex to form a hydrogen radical, which drives the subsequent typical ECD fragmentations. The complex of oxytocin with Cu2+ displayed noticeably different ECD behavior. The fragment ions were similar to fragment ions typically observed with low-energy collision induced dissociation (CID). We propose that the electrons captured by the oxytocin–Cu2+ complex might be favorably involved in reducing the Cu2+ metal ion to Cu+. Subsequent energy redistribution would explain the observed low-energy CID-type fragmentations. Electron capture resulted also in quite different specific cleavage sites for the complexes of oxytocin with Ni2+, Co2+ and Zn2+. This is an indication for structural differences in these complexes possibly linked to their significantly different biological effects on oxytocin-receptor binding, and suggests that ECD may be used to study subtle structural differences in transition metal ion–peptide complexes. Publisher
14472Fragmentation at and above surfaces in SIMS : effects of biomolecular yield enhancing surface modifications
Stefan L. Luxembourg, Ron M.A. Heeren
International Journal of Mass Spectrometry 253 (2006) 181-192
Published: 1-7-2006
Matrix-enhanced SIMS and metal-assisted SIMS are successfully employed to increase the organic ion yield in SIMS. In this study we compare kinetic energy distributions obtained for the SIMS, ME-SIMS and MetA-SIMS sputtering of molecular ions. In comparison to the SIMS kinetic energy distributions, those obtained for ME-SIMS display larger energy deficits, indicative of entrainment of analyte ions by matrix molecules or collisions taking place above the sample surface. In the case of MetA-SIMS high energy broadening of the distributions is observed, resulting from the high stopping power of the gold used. A selection of substituted benzylpyridinium salts is used to investigate the effect of internal energy reduction in ME-SIMS. Kinetic energy distributions were used to separate the daughter ions formed in the sample region from those resulting from unimolecular decay on nanosecond timescales, in the first tens of micrometers above the sample surface. The longer-timescale decay was monitored by changing the energy acceptance window of the mass spectrometer used. From the decay rate constants internal energies of the precursor ions decaying on nanosecond timescales were determined using RRKM theory. Within the framework of the precursor model the results indicate an extension of the collision cascade over a wider area than in SIMS.Publisher
14463Massamicroscopie: moleculaire flitsfoto's van eiwitverdelingen
S. Luxembourg, M. Altelaar, L. McDonnell and R. Heeren
Nederlands Tijdschrift voor Natuurkunde 72 (2006) 188-192
Published: -6-2006
Het moleculaire landschap van een lichaamscel is dynamisch; de samenstelling is afhankelijk van de biochemische processen die zich binnen de cel en tussen cellen onderling afspelen. Eiwitten zijn bij bijna al deze cellulaire processen betrokken. Veel aandoeningen, zoals bijvoorbeeld kanker en de ziekte van Alzheimer, vinden hun oorsprong in een lokale abnormale expressie of modificatie van bepaalde eiwitten. Op het FOM-instituut voor Atoom- en Molecuulfysica (AMOLF) is een nieuwe massaspectrometrische methode ontwikkeld die gelijktijdig en met hoge plaatsresolutie de moleculaire massa en de ruimtelijke verdeling van biomoleculen in weefseloppervlakken in kaart brengen.
14530Combined infrared multiphoton dissociation and electron capture dissociation using co-linear and overlapping beams in Fourier transform ion cyclotron resonance mass spectrometry
Romulus Mihalca, Yuri E.M. van der Burgt, Liam A. McDonnell, Marc Duursma, Iliya Cerjak, Albert J.R. Heck, R.M.A. Heeren
Rapid Communications in Mass Spectrometry 20 (2006) 1838-1844
Published: 16-5-2006
A novel set-up for Fourier transform ion cyclotron resonance mass spectrometry (FTICR) is reported for simultaneous infrared multiphoton dissociation (IRMPD) and electron-capture dissociation (ECD). An unmodified electron gun ensures complete, on-axis overlap between the electron and the photon beams. The instrumentation, design and implementation of this novel approach are described. In this configuration the IR beam is directed into the ICR cell using a pneumatically actuated mirror inserted into the ion-optical path. Concept validation was made using different combinations of IRMPD and ECD irradiation events on two standard peptides. The ability to perform efficient IRMPD, ECD and especially simultaneous IRMPD and ECD using lower irradiation times is demonstrated. The increase in primary sequence coverage, with the combined IRMPD and ECD set-up, also increases the confidence in peptide and protein assignments.Publisher
14460Tandem mass spectrometry of intact GroEL-substrate complexes reveals substrate-specific conformational changes in the trans ring
E. van Duijn, D.A. Simmons, R.H.H. van den Heuvel, P.J. Bakkes, H. van Heerikhuizen, R.M.A. Heeren, C.V. Robinson, S.M. van der Vies and A.J.R. Heck
Journal of the American Chemical Society 128 (2006) 4694-4702
Published: 12-4-2006
It has been suggested that the bacterial GroEL chaperonin accommodates only one substrate at any given time, due to conformational changes to both the cis and trans ring that are induced upon substrate binding. Using electrospray ionization mass spectrometry, we show that indeed GroEL binds only one molecule of the model substrate Rubisco. In contrast, the capsid protein of bacteriophage T4, a natural GroEL substrate, can occupy both rings simultaneously. As these substrates are of similar size, the data indicate that each substrate induces distinct conformational changes in the GroEL chaperonin. The distinctive binding behavior of Rubisco and the capsid protein was further investigated using tandem mass spectrometry on the intact 800-914 kDa GroEL-substrate complexes. Our data suggest that even in the gas phase the substrates remain bound inside the GroEL cavity. The analysis revealed further that binding of Rubisco to the GroEL oligomer stabilizes the chaperonin complex significantly, whereas binding of one capsid protein did not have the same effect. However, addition of a second capsid protein molecule to GroEL resulted in a similar stabilizing effect to that obtained after the binding of a single Rubisco. On the basis of the stoichiometry of the GroEL chaperonin-substrate complex and the dissociation behavior of the two different substrates, we hypothesize that the binding of a single capsid polypeptide does not induce significant conformational changes in the GroEL trans ring, and hence the unoccupied GroEL ring remains accessible for a second capsid molecule.
14423Gold-enhanced biomolecular surface imaging of cells and tissue by SIMS and MALDI mass spectrometry
A.F.M. Altelaar, I. Klinkert, K. Jalink, R.P.J. De Lange, R.A.H. Adan, R.M.A. Heeren and S.R. Piersma
Analytical Chemistry 78 (2006) 734-742
Published: 1-2-2006
Surface metallization by plasma coating enhances desorption/ionization of membrane components such as lipids and sterols in imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) of tissues and cells. High-resolution images of cholesterol and other membrane components were obtained for neuroblastoma cells and revealed subcellular details (resolving power 1.5 µm). Alternatively, in matrix-enhanced SIMS, 2,5-dihydroxybenzoic acid electrosprayed on neuroblastoma cells allowed intact molecular ion imaging of phosphatidylcholine and sphingomyelin at the cellular level. Gold deposition on top of matrix-coated rat brain tissue sections strongly enhanced image quality and signal intensity in stigmatic matrix-assisted laser desorption/ionization imaging mass spectrometry. High-quality total ion count images were acquired, and the neuropeptide vasopressin was localized in the rat brain tissue section at the hypothalamic area around the third ventricle. Although the mechanism of signal enhancement by gold deposition is under debate, the results we have obtained for cells and tissue sections illustrate the potential of this sample preparation technique for biomolecular surface imaging by mass spectrometry.Publisher
14392Comparing three PCA-based methods for the 3D visualization of imaging spectroscopy data
A. Broersen, R. van Liere and R.M.A. Heeren
Proceedings of the fifth International Conference Visualization, imaging, and image processing (VIIP 2005), Sept. 7-9, 2005, Benidorm, Spain / ed. J.J. Villanueva. - Calgary : Acta Press, 2005. - pp. 540-545
Published: --2005
In this paper we compare the quality of three different principle component analysis (PCA) based methods to generate transfer functions for the 3D visualization of imaging spectroscopy data. We discuss three criteria for judging the quality of features in these visualizations. These criteria are used to interpret visualizations of features in the brain of the snail Lymnaea Stagnalis. We show that the PCA method that uses model additional information, clearly results in superior visualizations. Publisher
14402Mass spectrometer identifies and localises biomarkers in cells
R.M.A. Heeren
NPC Highlights 1 (2005) 24-27
Published: --2005
Publisher
14403Examples of Fourier transform ion cyclotron resonance mass spectrometry developments: from ion physics to remote access biochemical mass spectrometry
A. Römpp, I.M. Taban, R. Mihalca, M.C. Duursma, T.H. Mize, L.A. McDonnell and R.M.A. Heeren
European Journal of Mass Spectrometry 11 (2005) 443-456
Published: --2005
The application of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) for high resolution biomolecular analysis has increased greatly after 30 years of innovation since its conception in 1974. FT-ICR-MS can now routinely be used for the analysis of complex organic mixtures such as biological or petrochemical samples. Many of these new possibilities have been the results of many different instrumental developments. This paper provides a mini review of selected instrumental developments that now allow these measurements. The development of soft ionization techniques such as Electrospray ionization (ESI) and Matrix Assisted Laser desorption and Ionisation (MALDI) was crucial for the analysis of biological macromolecules. Improved ion transport optics led to an increase in sensitivity. New ICR cell designs complement the capabilities of FT-ICR-MS by allowing a more thorough study of the mechanism and kinetics of ion reactions in the gas-phase. A selected example of electron capture dissociation (ECD) employs these developments to investigate the role of peptide conformation in ECD. Improved electronics and software allow faster and more flexible experiments. All these improvements led to an increase in speed and sensitivity that are necessary to couple FT-MS to fast separation techniques such as nano-HPLC. The modern FT-ICR-MS instruments can be incorporated in virtual organizations allowing remote access to unique infrastructure. This concept of remote experimentation opens new possibilities for scientific collaborations between expert scientists at different locations and allows the efficient use of this expensive instrumentation.Publisher
9271Mass microscopy: imaging biomolecules on surfaces
S.L. Luxembourg
University of Utrecht, 19-12-2005
Published: 19-12-2005
Publisher
14401Proteom imaging: a closer look at life's organization
R.M.A. Heeren
Proteomics 5 (2005) 4316-4326
Published: 17-11-2005
Imaging the proteome is a term that is used in many different contexts. The term implies that the entire cohort of proteins and their modifications are visualized. This unfortunately is not the case. In this mini-review, a concise overview is provided on different imaging technologies that are currently used to investigate the structure, function and dynamics of proteins and their organization. These techniques have been selected for review based on the unique insights they provide in subsets of the proteome. These techniques have been illustrated with practical examples of their merits. Mass spectrometry-based imaging technologies are playing a key role in proteome research and have been reviewed in more detail. They hold the promise of detailed molecular insight in the spatial organization of living system.Publisher
14385Does double electron capture lead to the formation of biradicals? An ECD-SORI-CID study on lacticin 481
A.J. Kleinnijenhuis, A.J.R. Heck, M.C. Duursma and R.M.A. Heeren
Journal of the American Society for Mass Spectrometry 16 (2005) 1595-1601
Published: -10-2005
We studied lacticin 481, a small lantibiotic with three lanthionine bridges, by electron capture dissociation (ECD) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Following electron capture, very little fragmentation was observed, but species formed by nondissociative single and multiple electron capture were abundant. Ions formed by double electron capture were subjected to sustained off resonance irradiation collision induced dissociation (SORI-CID) to determine whether stable biradicals were formed. In the SORI-CID spectra of the ions formed by double electron capture, some, but minor, H-. radical loss was observed, which was not observed at all for regularly protonated ions. A small part of the ions formed by double electron capture are thus long-lived biradicals. Apart from the observed H-. loss, the SORI-CID spectra of ions that captured two electrons was similar to that of regularly protonated ions and quite different from the SORI-CID spectra of radical ions formed by single electron capture. This implies that recombination of the two radical sites is the dominant process in biradical lacticin 481 ions, at least on the time scale of our SORI-CID experiments. Publisher
9269Structural analysis of sulfide containing peptides using electron capture dissociation
A.J. Kleinnijenhuis
University of Utrecht, 22-9-2005
Published: 22-9-2005
Publisher
14379FTIR studies of the effects of pigments on the aging of oil
J. van der Weerd, A. van Loon and J.J. Boon
Studies in Conservation 50 (2005) 1-33
Published: -8-2005
This study describes the changes in the infrared spectra of paint as a result of aging. The focus is on the influence of pigments on the long-term changes in the oil binding medium. Several naturally aged paints made with different pigments were analysed using Fourier-transform infrared spectroscopy (FTIR). One of the most pronounced effects observed in the infrared spectra of aging paint is the shifting and broadening of the carbonyl band due to the formation of carboxylic acids. Another effect of pigments on the oil binding medium is the catalysis of the hydrolysis of triglycerides, as indicated by the decreasing intensity of the ester absorption. Finally, the nature of the pigment included has a profound effect on the CH stretch absorptions. From these results it is clear that pigments can significantly alter the infrared spectra of drying oil, and should therefore be identified beforehand to ensure the correct assessment of the infrared spectra in drying oil paint.Publisher
14357SIMION analysis of a high performance linear accumulation octopole with enhanced ejection capabilities
I.M. Taban, L.A. McDonnell, A. Römpp, I. Cerjak and R.M.A. Heeren
International Journal of Mass Spectrometry 244 (2005) 135-143
Published: 1-7-2005
Here, we present the results of extensive SIMION 7.0 modelling of a new linear octopole ion trap. The octopole was designed to increase the efficiency of an electrospray ion source coupled to a Fourier Transform Ion Cyclotron Resonance (FTICR) mass spectrometer. This improvement was achieved by applying a pulsed axial field to the octopole to eject the ion packet with a time and energy distribution that better match the acceptance criteria of the FTICR cell, thus increasing the trapping efficiency and sensitivity. The axial field was produced by applying a pulsed dc potential to the custom-designed ejection electrodes located between the octopole rods. The time and energy profiles of the ejected ion packets for several electrode shapes were calculated and are discussed in terms of their compatibility with efficient trapping of the ion packet in the FTICR cell. Preliminary experimental results show increased signal using the dc ejection electrodes of approximately 100%. Publisher
14307Monitoring macromolecular complexes involved in the chaperonin-assisted protein folding cycle by mass spectrometry
E. van Duijn, P.J. Bakkes, R.M.A. Heeren, R.H.H. van den Heuvel, H. van Heerikhuizen, S.M. van der Vries and A.J.R. Heck
Nature Methods 2 (2005) 371-376
Published: -5-2005
We have used native mass spectrometry to analyze macromolecular complexes involved in the chaperonin-assisted refolding of gp23, the major capsid protein of bacteriophage T4. Adapting the instrumental methods allowed us to monitor all intermediate complexes involved in the chaperonin folding cycle. We found that GroEL can bind up to two unfolded gp23 substrate molecules. Notably, when GroEL is in complex with the cochaperonin gp31, it binds exclusively one gp23. We also demonstrated that the folding and assembly of gp23 into 336-kDa hexamers by GroEL-gp31 can be monitored directly by electrospray ionization mass spectrometry (ESI-MS). These data reinforce the great potential of ESI-MS as a technique to investigate structure-function relationships of protein assemblies in general and the chaperonin-protein folding machinery in particular. A major advantage of native mass spectrometry is that, given sufficient resolution, it allows the analysis at the picomole level of sensitivity of heterogeneous protein complexes with molecular masses up to several million daltons.Publisher
14334Infrared mass spectrometric imaging below the diffraction limit
S.L. Luxembourg, L.A. McDonnell, T.H. Mize and R.M.A. Heeren
Journal of Proteome Research 4 (2005) 671-673
Published: 25-5-2005
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)(1) is an established technique for the analysis of biological macromolecules. Its relative insensitivity to pollutants makes MALDI-MS very suitable for the direct analysis of biological samples. As such, it has facilitated great advances in the field of biomolecular imaging mass spectrometry. Traditionally, MALDI-MS imaging is performed in a scanning microprobe methodology.(2-4) However, in a recent study we have demonstrated an alternative methodology; the so-called microscope mode,5 where the requirement for a highly focused ionization beam is removed. Spatial details from within the desorption area are conserved during the flight of the ions through the mass analyzer, and a magnified ion image is projected onto a 2D-detector. In this paper, we demonstrate how imaging mass spectrometry benefits from the microscope mode approach. For the first time, high-lateral resolution ion images were recorded using infrared MALDI at 2.94 mu m wavelength. The ion optical resolution achieved was well below the theoretical limit of (light-) diffraction for the setup used, which is impossible to achieve in the conventional scanning microprobe approach. Publisher
14297Subcellular imaging mass sectrometry of brain tissue
L.A. McDonnell, S.R. Piersma, M.A.F. Altelaar, T.H. Mize, S.L. Luxembourg, P.D.E.M. Verhaert, J. van Minnen and R.M.A. Heeren
Journal of Mass Spectrometry 40 (2005) 160-168
Published: -2-2005
Imaging mass spectrometry provides both chemical information and the spatial distribution of each analyte detected. Here it is demonstrated how imaging mass spectrometry of tissue at subcellular resolution can be achieved by combining the high spatial resolution of secondary ion mass spectrometry (SIMS) with the sample preparation protocols of matrix-assisted laser desorption/ionization (MALDI). Despite mechanistic differences and sampling 105 times less material, matrix-enhanced (ME)-SIMS of tissue samples yields similar results to MALDI (up to m/z 2500), in agreement with previous studies on standard compounds. In this regard ME-SIMS represents an attractive alternative to polyatomic primary ions for increasing the molecular ion yield. ME-SIMS of whole organs and thin sections of the cerebral ganglia of Lymnaea stagnalis demonstrate the advantages of ME-SIMS for chemical imaging mass spectrometry. Subcellular distributions of cellular analytes are clearly obtained, and the matrix provides an in situ height map of the tissue, allowing the user to identify rapidly regions prone to topographical artifacts and to deconvolute topographical losses in mass resolution and signal-to-noise ratio.Publisher
14261Direct molecular imaging of Lymnaea stagnalis nervous tissue at subcellular spatial resolution by mass spectrometry
A.F.M. Altelaar, J. van Minnen, C.R. Jiménez, R.M.A. Heeren and S.R. Piersma
Analytical Chemistry 77 (2005) 735-741
Published: -1-2005
The imaging capabilities of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and MALDI-MS sample preparation methods were combined. We used this method, named matrix-enhanced (ME) SIMS, for direct molecular imaging of nervous tissue at micrometer spatial resolution. Cryosections of the cerebral ganglia of the freshwater snail Lymnaea stagnalis were placed on indium-tin-oxide (ITO)-coated conductive glass slides and covered with a thin layer of 2,5-dihydroxybenzoic acid by electrospray deposition. High-resolution molecular ion maps of cholesterol and the neuropeptide APGWamide were constructed. APGWamide was predominantly localized in the cluster of neurons that regulate male copulation behavior of Lymnaea. ME-SIMS imaging allows direct molecule-specific imaging from tissue sections without labeling and opens a complementary mass window (<2500 Da) to MALDI imaging mass spectrometry at an order of magnitude higher spatial resolution (<3mm). Publisher
14266Zinc soap aggregate formation in 'falling leaves' (Les Alyscamps)' by Vincent van Gogh
J. van der Weerd, M. Geldof, L. Struik van der Loeff, R.M.A. Heeren and J.J. Boon
Zeitschrift für Kunsttechnologie und Konservierung 17 (2004) 407-416
Published: --2004
14230Preparation methods and accessories for the infrared spectroscopic analysis of multi-layer paint films
J. van der Weerd, R.M.A. Heeren and J.J. Boon
Studies in Conservation 49 (2004) 193-210
Published: --2004
14256Electron capture dissociation at low temperatures reveals selective dissociations
R. Mihalca, A. Kleinnijenhuis, L.A. McDonnell, M. Duursma, A.J.R. Heck and R.M.A. Heeren
Journal of the American Society for Mass Spectrometry 15 (2004) 1869-1873
Published: -12-2004
Electron capture dissociation at 86 K of the linear peptide Substance P produced just two backbone fragments, whereas at room temperature eight backbone fragments were formed. Similarly, with the cyclic peptide gramicidin S, just one backbone fragment was formed at 86 K but five at room temperature. The observation that some backbone scissions are active and others inactive, when all involve N-Cα cleavages and have a high rate constant, indicates that the more specific fragments at low temperatures reflects the reduced conformation heterogeneity at low temperatures. This is supported by reduced or inactive hydrogen loss, a channel that has previously been shown to be affected by conformation. The conclusion that the ECD fragments are a snapshot of the conformational (intramolecular solvation shell) heterogeneity helps explain how the relative intensities of ECD fragments can be different on different instrument and highlights the common theme in methodologies used to increase sequence coverage, namely an increase in the conformational heterogeneity of the precursor ion population.Publisher
14202High-spatial resolution mass spectrometric imaging of peptide and protein distributions on a surface
S.L. Luxembourg, T.H. Mize, L.A. McDonnell and R.M.A. Heeren
Analytical Chemistry 76 (2004) 5339-5344
Published: 15-9-2004
For the first time macromolecular ion microscope images have been recorded using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Single-shot, mass-resolved images of the spatial distributions of intact peptide and protein ions over an area of 200 mm in diameter were obtained in less than 1 ms at a repetition rate of 12 Hz. The magnifying ion optics of the ion microscope allowed ion images to be obtained with a lateral resolution of 4 mm. These results prove the concept of high-resolution MALDI-MS imaging in microscope mode without the need for a tight laser focus and the accompanying sensitivity losses. The ion microscopy approach offers an improvement of several orders of magnitude in speed of acquisition compared to the conventional (microprobe) approach to MALDI-MS imaging. Publisher
14200A modular data and control system to impove sensitivity, selectivity, speed of analysis, ease of use, and transient duration in an external source FTICR-MS
T.H. Mize, I. Taban, M. Duursma, M. Seynen, M. Konijnenburg, A. Vijftigschild, C. van Doornik, G. van Rooij and R.M.A. Heeren
International Journal of Mass Spectrometry 235 (2004) 243-253
Published: 15-7-2004
We present here a new Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) controller designed and constructed to meet the growing need for increased speed, memory, and ease of use. The system realizes these goals via the first published application of fast PXI bus technology and by employing a graphical user interface (GUI) for control of all aspects of ion production, delivery, containment, manipulation of internal and kinetic energies, and measurement in an external source instrument. Additionally, new hardware for monitoring and control of these aspects and for processing extended datasets both to and from the instrument have been implemented. The modular nature of the control hardware makes the instrument platform, in this case a modified external source 7T FTICR-MS, irrelevant. The GUI consists of two separate modules; one provides a temporal representation of the pulses, voltages (rf and dc), and dc heater currents that control all aspects of the experiment while the other provides complex data analysis capabilities and design of excitation waveforms. Real-time monitoring of the transient signal is available in this module as well as near real-time monitoring of the resulting mass spectrum (using a truncated dataset). A PXI bus with 40 digital to analog converters (DAC) and 64 digital (TTL) sources drive the source, optics, and trapping functions of the instrument as well as the other peripheral hardware. Acquisition is realized using a VME bus with a TTL triggered program resident on an embedded processor to minimize dead time. The acquisition system is equipped with 192 MB memory for both excitation and detection waveforms with FIFO buffering to provide full rate bandwidth of 10 MHz, and four digital down converters (DDCs) to enable mixing of heterodyne signals for narrow band measurements completes the ensemble.Publisher
14106Design and performance of a new FT-ICR cell operating at a temperature range of 77-438 K
X. Guo, M. Duursma, A. Al-Khalili, L.A. McDonnell and R.M.A. Heeren
International Journal of Mass Spectrometry 231 (2004) 37-45
Published: -1-2004
A new ion cell for Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), which can be operated within the temperature range 77-438 K, has been designed and constructed. It has an elongated open-ended cylindrical configuration with capacitively coupled trapping electrodes. Fast and accurate thermal control of the cell is realized by embedding a heating element and a cooling pipe into the ceramic jacket holding the cell electrode plates. To determine the geometry factor, β, of the cell a novel empirical methodology has been developed that is applicable to any ICR cell. This was achieved by comparing breakdown diagrams of protonated leucine enkephalin obtained using the new cell with those obtained using a well characterized cell. Energy-resolved collision-activated dissociation (CAD) of protonated leucine enkephalin, performed using the new cell, was applied to probe the internal energy content of ions at different ICR cell temperatures. These experiments demonstrate that the trapped ion population reaches the preset temperature of the cell through thermal equilibration with the cell walls by blackbody infrared radiation. This has permitted FT-ICR-MS studies (dissociation or ion-molecule reactions, etc.) to be performed at a wide temperature range, including low temperatures.Publisher
14125A mini-review of mass spectrometry using high-performance FTICR-MS methods
R.M.A. Heeren, A.J. Kleinnijenhuis, L.A. McDonnell and T.H. Mize
Analytical and Bioanalytical Chemistry 378 (2004) 1048-1058
Published: 10-1-2004
Structural characterization of macromolecules is currently delivering new insights into the behavior of individual molecules or molecular ensembles. Technological advances have made it possible to examine smaller and smaller amounts (down to single molecules) of larger and larger molecular systems. Mass spectrometry in particular is capable of the detailed study of extremely small quantities (down to a single molecule) of very large (biological) molecules. The advent of new ionization techniques such as electrospray and matrix-assisted laser desorption are mainly responsible for these advances. As a result, mass spectrometry has evolved into an enabling discipline that plays an increasingly important role in combinatorial chemistry, polymer science, biochemistry, medicine, environmental and marine science, and archaeology and conservation science. This paper will review a selection of methodological developments in the field of high-performance Fourier transform ion cyclotron resonance mass spectrometry for structural analysis of these macromolecules.Publisher
9245Laser desorption mass spectrometric studies of artists' organic pigments
N. Wyplosz
Universiteit van Amsterdam, 20-11-2003
Published: 20-11-2003
Publisher
14068Using matrix peaks to map topography: increased mass resolution enhanced sensitivity and the rapid identifacation of artifacts in chemical images
L.A. McDonnell, T.H. Mize, S.L. Luxembourg, S. Koster, G.B. Eijkel, E. Verpoorte, N.F. de Rooij and R.M.A. Heeren
Analytical Chemistry 75 (2003) 4373-4381
Published: 17-9-2003
It is well known in secondary ion mass spectrometry (SIMS) that sample topography leads to decreased mass resolution. Specifically, the ion's time of flight is dependent on where it was generated. Here, using matrix-enhanced SIMS, it is demonstrated that, in addition to increasing the yield of intact pseudomolecular ions, the matrix allows the user to semiquantitatively record the topography of a sample. Through mapping the topography-related mass shifts of the matrix (which leads to decreased mass resolution), the analogous mass shifts of higher mass ions can be deconvoluted and higher resolution and greater sensitivity obtained. Furthermore, the semiquantitative topographical map obtained can be compared with any chemical images obtained, allowing the user to quickly ascertain whether local intensity maximums are due to topological features or represent genuine features of interest.Publisher
14054Evaluating the VLAM-G toolkit on the DAS-2
Z.W. Hendrikse, A.S.Z. Belloum, P.M.R. Jonkergouw, G.B. Eijkel, R.M.A. Heeren, B.L.O. Hertzberger, V. Korkhov, C.T.A.M. de Laat and D. Vasunin
Future Generation Computer Systems 19 (2003) 815-824
Published: -8-2003
The Grid-based Virtual Laboratory AMsterdam (VLAM-G) provides a science portal for distributed analysis in applied scientific research. DAS-2 is a wide-area distributed computer of 200 Dual Pentium-III nodes, distributed over five Dutch universities. During the iGrid conference, the current reference implementation of VLAM-G was evaluated with an application from the chemo-physical application domain on the DAS-2. It was shown how data flows are instantiated on DAS-2 resources, driven by an information management system that is designed to extract information from raw data sets. Both the information management system and data processing modules are provided by the middleware of the Virtual Laboratory (VL). This paper describes the software and hardware setup of this study, and evaluates the use and performance of the VLAM-G science portal.Publisher
14056Manipulating internal energy of protonated biomolecules in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
X. Guo, M.C. Duursma, P.G. Kistemaker, N.M.M. Nibbering, K. Vekey, L. Drahos and R.M.A. Heeren
Journal of Mass Spectrometry 38 (2003) 597-606
Published: 6-6-2003
The internal energy of protonated leucine enkephalin has been manipulated in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry with two newly designed pump-probe experiments. Blackbody infrared radiation was applied to pump an ion population into a well-defined internal energy distribution below the dissociation threshold. Following this pumping stage, the internal energy distribution was probed using on-resonance collisional activation to dissociate the ions. These pump-probe experiments were carried out in two different ways: (a) using on-resonance collisional activation with variable kinetic energies to dissociate the ions at a constant initial ion temperature (determining the precursor ion survival percentage as a function of kinetic energy) and (b) using on-resonance collisional activation with a constant kinetic energy to dissociate the ions at variable initial ion temperatures (to investigate the ion survival yield-initial ion temperature dependence). Using this approach, a detailed study of the effects of the initial ion temperature, the probing kinetic energy and the internal energy loss rate on the effective conversion efficiency of (laboratory-frame) kinetic energy to internal energy was conducted. This conversion efficiency was found to be dependent on the initial ion temperature. Depending on the experimental conditions the conversion efficiency (for collisions with argon) was estimated to be about 4.0 ± 1.7%, which agrees with that obtained from a theoretical modeling. Finally, the reconstructed curves of the ion survival yield versus the mode of the (final) total internal energy distribution of the activated ion population (after pump and probe events) at different pump-probe conditions reveal the internal energy content of the activated ions.Publisher
14053Localization of intramolecular monosulfide bridges in Iantibiotics determined with electron capture induced dissociation
A.J. Kleinnijenhuis, M.C. Duursma, E. Breukink, R.M.A. Heeren and A.J.R. Heck
Analytical Chemistry 75 (2003) 3219-3225
Published: 7-5-2003
Electron capture induced dissociation (ECD) and collisionally activated dissociation (CAD) experiments were performed on four lanthionine bridge-containing antibiotics. ECD of lantibiotics produced mainly c and z• ions, as has been observed previously with other peptides, but more interestingly, the less common c• and z ions were observed in abundance in the ECD spectra. These fragments specifically resulted from the cleavage of both a backbone amine bond and the thioether bond in a lanthionine bridge. ECD seemed to induce mainly cleavages near the lanthionine bridges. This fragmentation pattern indicates that lanthionine bridges play a key role in the selectivity of the ECD process. A new mechanism is postulated describing the formation of c. and z ions. Comparative low-energy CAD did not show such specificity. Nondissociative ECD products were quite abundant, suggesting that relatively stable double and triple radicals can be formed in the ECD process. Our results suggest that ECD can be used as a tool to identify the C-terminal attachment site of lanthionine bridges in newly discovered lantibiotics.Publisher
14017Electron capture and collisionally activated dissociation mass spectrometry of doubly charged hyperbranched polyesteramides
S. Koster, M.C. Duursma, J.J. Boon, R.M.A. Heeren, S. Ingemann, R.A.T.M. van Benthem and C.G. de Koster
Journal of the American Society for Mass Spectrometry 14 (2003) 332-341
Published: -4-2003
Electron capture dissociation (ECD) of doubly protonated hyperbranched polyesteramide oligomers (1100-1900 Da) was examined and compared with the structural information obtained by low energy collisionally activated dissociation (CAD). Both the ester and amide bonds of the protonated species were cleaved easily upon ECD with the formation of odd electron (OE+) or even electron (EE+) fragment ions. Several mechanistic schemes are proposed that describe the complex ECD fragmentation behavior of the multiply charged oligomers. In contrast to studies of biomolecules, the present results indicate that consecutive cleavages induced by intramolecular H-shifts are significant for ECD and of less importance for low energy CAD. The capture of an electron by the ionized species results in fragmentation associated with a redistribution of the excess internal energy over the products and the subsequent bond cleavage. Low energy, multiple collision CAD is found to be a more selective dissociation method than ECD in view of the observation that only amide bonds are cleaved for most of the hyperbranched polymers examined with CAD in this study. ECD appears not to provide complementary structural information compared to CAD in the study of hyperbranched polymers, even though a significantly more complex ECD fragmentation behavior is observed. ECD is shown to be of use for the structural characterization of large oligomers that may not dissociate upon low energy CAD. This is a direct result of the fact that ECD produces ionized hyperbranched oligomers with a relatively high internal energy.Publisher
14040Effect of local matrix crystal variations in matrix-assisted ionization techniques for mass spectrometry
S.L. Luxembourg, L.A. McDonnell, M.C. Duursma, X. Guo and R.M.A. Heeren
Analytical Chemistry 75 (2003) 2333-2341
Published: 12-4-2003
Intense intact molecular ion signals have been obtained from phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylinositol using matrix-enhanced secondary ion mass spectrometry (ME-SIMS). It was found that the high-mass (m/z >500) regions of the ME-SIMS spectra closely resembled those obtained using matrix-assisted laser desorption/ionization (MALDI). Using high spatial resolution SIMS, a detailed investigation of dried-droplet samples was performed. Based on the detected Na+ and 2,5-DHB matrix signal intensities, different crystal types were distinguished, in addition to different sizes of crystals. Spatially mapping the pseudomolecular and fragment ions of the phospholipids revealed that the nature of the pseudomolecular ions formed, as well as the ratio of intact molecular to fragment ion, was dependent on the type and surface composition of the crystal. The observed chemical bias effects due to crystal heterogeneity and the resulting variation in desorption/ionization efficiency will complicate the interpretation of data obtained from matrix-assisted mass spectrometric (imaging) techniques and is an important factor in the "hot spot" phenomenon frequently encountered in MALDI experiments. In this respect, imaging SIMS was found to be a versatile tool to investigate the effects of the local physicochemical conditions on the detected molecular species.Publisher
13969Experimental calibration of SORI-CID internal energy scale: energy uptake and loss
X. Guo, M.C. Duursma, A. Al-Khalili and R.M.A. Heeren
International Journal of Mass Spectrometry 225 (2003) 71-82
Published: -2-2003
This paper describes a novel method to experimentally determine the net amount of internal energy deposited into biomolecules during sustained off-resonance irradiation collision-induced dissociation (SORI-CID). The method of calibration is based on a controlled manipulation of the initial internal energy of a trapped ion population prior to dissociation. A decrease in the initial internal energy will lead to an increase of the amount of internal energy needed to reach the same degree of dissociation. The number of SORI cycles needed to reach 50% dissociation for different initial internal energies has been determined for leucine enkephalin. The number of SORI cycles is proportional to the amount of the internal energy accumulated. The ratio between the change in internal energy and the change in the number of SORI cycles (needed to reach 50% dissociation) hence yields the net amount of internal energy deposited per SORI cycle. This methodology was applied to ion populations at room temperature and at temperatures down to 143 K. The latter temperatures were reached in a novel liquid nitrogen cooled ICR cell. The calibration of the SORI internal energy scale also revealed that at low environmental temperatures the amount of internal energy loss from an activated ion population is strongly increased. With this novel methodology the net internal energy loss during SORI was quantified, and it is argued that the main loss mechanism is the emission of IR photons.Publisher
13992Identification of pigments in paint cross sections by reflection visible light imaging microspectroscopy
J. van der Weerd, M.K. van Veen, R.M.A. Heeren and J.J. Boon
Analytical Chemistry 75 (2003) 716-722
Published: 15-2-2003
A setup for reflection visible light imaging microspectros-copy (VIS-imaging) as well as its evaluation and applica-tion is described and tested. The spatial resolution of the system is ∼1 μm at a spectral resolution of 4 nm. The optical contrast between different colored particles in the surface of a sample is optimized with a new image processing method for mapping of the distribution of the identified pigment particles. The potential of VIS-imaging in the study of paint cross sections obtained from paint-ings is explored. Spectra obtained from pigment particles in these cross sections result in classification or identi-fication of several pigments. The investigated paint samples are challenging test cases, as they contain several colored materials with a very fine distribution. VIS-imaging can identify and map the most common traditional blue pigments, i.e., smalt, azurite, ultramarine, and indigo in 17th century oil paintings. Smalt can be identified even after complete discoloration. VIS-imaging analysis assisted in the identification and mapping of modern synthetic red and yellow pigments in a 20th century painting.Publisher
14026Evaluation of the chemical and physical changes induced by KrF laser irradiation of tempera paints
M. Castillejo, M. Martín, M. Oujja, J. Santamaría, D. Silva, R. Torres, A. Manousaki, V. Zafiropulos, O.F. van den Brink, R.M.A. Heeren, R. Teule and A. Silva
Journal of Cultural Heritage 4 (2003) 257s-263s
Published: -1-2003
A systematic study of the chemical and physical changes induced by exposure to UV (248 nm) excimer laser light of unvarnished tempera paint samples has been undertaken as a part of the research activities included in the European project "Advanced workstation for controlled laser cleaning of artworks". The direct exposure of the paint to the UV laser configures the worst case scenario of laser cleaning, as a thin protective layer of varnish is normally left to minimize the dose of UV radiation that reaches the paint surface. However, in the practice of laser cleaning, there is a need to characterize and quantify the possible effects of direct UV laser irradiation of unvarnished paints. To this purpose, a broad range of techniques have been used including profilometry, colorimetry, optical and vibrational spectroscopic techniques, such as laser-induced fluorescence (LIF), laser-induced breakdown spectroscopy (LIBS), Fourier transform Raman (FTR) and infrared (FTIR), and analytical mass spectrometric techniques, like direct-temperature-resolved mass spectrometry (DTMS) and laser desorption and ionization time of flight mass spectrometry (LDI-TOF). Integration of the results obtained by these techniques allowed the investigation of the nature and degree of change of the irradiated paint systems. These were observed to strongly depend on the type of paint system.Publisher
14025Controlled UV laser cleaning of painted artworks: a systematic effect study on egg tempera paint samples
R. Teule, H. Scholten, O.F. van den Brink, R.M.A. Heeren, V. Zafiropulos, R. Hesterman, M. Castillejo, M. Martin, U. Ullenius, I. Larsson, F. Guerra-Librero, A. Silva, H. Gouveia and M.-B. Albuquerque
Journal of Cultural Heritage 4 (2003) 209s-215s
Published: -1-2003
The Cooperative Research project "Advanced workstation for controlled laser cleaning of artworks" (ENV4-CT98-0787) has yielded important information on the application of UV laser cleaning to paint materials. In the project, in which conservators, researchers and engineers participated, the viability of the laser technique as an additional tool in present conservation practice was investigated. The research was pointed at the definition of the boundary conditions in which laser cleaning can be safely applied. It included a systematic effect study of tempera paint systems. Physical and chemical changes, induced by exposure to UV (248 nm) excimer laser light under various conditions, were evaluated. In parallel, an innovative laser cleaning tool was developed, allowing accurate and controlled removal of superficial layers from paint materials. Both aspects of the project are presented. The presentation of the research focuses on the integration of the results from various analytical techniques, yielding valuable information on the immediate and long-term effects of UV laser radiation on the paint materials. The analytical techniques include colorimetry, spectroscopic techniques, mass spectrometry and profilometry, as well as thermographic and UV transmission measurements. Furthermore, the application of the laser workstation on various painted artworks is shown. This includes the gradual removal of varnish layers and the recovery of original paint colour in fire-damaged paintings.Publisher
13951Chemical changes in old master paintings: dissolution, metal soap formation and remineralization processes in lead pigmented paint layers of 17th century paintings
J. van der Weerd, J.J. Boon, M. Geldof, R.M.A. Heeren and P. Noble
Zeitschrift für Kunsttechnologie und Konservierung 16 (2002) 36-51
Published: --2002
13944Probing mass discriminations and mass shifts in the ITMS mass spectra of externally generated MALDI ions with synthetic polymers
G.J. van Rooij, J.J. Boon, M.C. Duursma and R.M.A. Heeren
International Journal of Mass Spectrometry 221 (2002) 191-207
Published: --2002
Synthetic polymers are demonstrated to be very useful probes for the characterization of a newly constructed external ion source matrix-assisted laser desorption and ionization quadrupole ion trap mass spectrometer (MALDI-ITMS). Mass discrimination effects and space-charge-induced mass shifts can readily be identified and quantified with these synthetic polymer probes. Mass dependencies in the trapping efficiency were evaluated by comparison of measurements of poly(methyl methacrylate) (PMMA) standards in the mass range m/z 400-3400 with MALDI-TOF-MS measurements of the same samples. This established the optimal experimental conditions for the analysis of mass ranges smaller than 1000 u with negligible mass discrimination. This is demonstrated on the basis of measurements on a tri-block copolymer of poly(ethylene oxide) poly(propylene oxide). As expected, mass measurements were highly influenced by the magnitude of the trapped ion population. Using poly(ethylene glycol) standards we were able to quantify these mass shifts as a function of the total ion load. Consequently, reproducible results can only be obtained by reproducing the total space-charge in the trap. In MALDI experiments, this can be achieved by tuning the laser power just above threshold. This approach allowed the mass determination of three different end groups in a complex Jeffamine D2000 sample with an accuracy of better than 0.1 u.Publisher
13922Analytical study of the chemical and physical changes induced by KrF laser cleaning of tempera paints
M. Castillejo, M. Martin, M. Oujja, D. Silva, R. Torres, A. Manousaki, V. Zafiropulos, O.F. van den Brink and R.M.A. Heeren
Analytical Chemistry 74 (2002) 4662-4671
Published: --2002
The cleaning of paintings using UV lasers is a growing field of interest in the practice of conservation. In this work, we have studied the chemical and physical changes induced by KrF excimer laser at 248 nm of tempera paint dosimeter systems. The changes have been evaluated by using a range of analytical techniques. These include profilometry; colorimetry; optical and vibrational spectroscopies, such as laser-induced fluorescence (LIF), laser-induced breakdown spectroscopy (LIBS), Fourier transform Raman (FTR), and infrared (FT-IR); and analytical mass spectrometric techniques, such as direct-temperature-resolved mass spectrometry (DTMS) and matrix-assisted laser desorption and ionization mass spectrometry (MALDI-MS). Integration of the results obtained by these techniques allowed the investigation of the nature and degree of change of the irradiated paint systems. Direct laser irradiation induces various degrees of discoloration that depend strongly on the nature of the pigment. This effect takes place mainly on the surface layer of the sample. Degradation of the binding medium occurs in the presence of inorganic pigments, and in some cases, evidence of alterations in the molecular composition of the pigment has been obtained. Varnished systems do not display this discoloration when a thin protective layer is left on the paint. A laser cleaning strategy for varnished paintings should be based on the partial removal of the varnish, leaving a residual layer that shields the underlying pigments from direct laser exposure.Publisher
13907Isomer seperation of hyperbranched polyesteramides with gas-phase H/D exchange and a novel MSn approach: DoDIP
S. Koster, M.C. Duursma, X. Guo, R.A.T.M. Van Benthem, C.G. de Koster, J.J. Boon and R.M.A. Heeren
Journal of Mass Spectrometry 37 (2002) 792-802
Published: --2002
Two approaches are introduced that provide information about the isomeric composition of hyperbranched polyesteramides. The first approach is based on a novel tandem mass spectrometric (MSn) approach that allows the study of different types of isomeric structures by a separation based on their difference in appearance energy. The method is called DoDIP: dissociation of depleted ion populations. A first MS/MS step is used to fragment isomers with relatively low appearance energy. The isomers with higher appearance energy are fragmented in a second MS/MS step of higher energy. The second approach is based on gas-phase H/D exchange experiments that result in a bimodal isotopic distribution for oligomers XnDn+1 of which one distribution corresponds to a type of isomeric structure that exhibits H/D exchange behaviour and the other to an isomeric structure that does not exhibit H/D exchange behaviour. X is a difunctional anhydride of phthalic acid (P), 1,2-cyclohexanedicarboxylic acid (C), succinic acid (S) or glutaric acid (G). D in XnDn+1 is a trifunctional diisopropanolamine and n the degree of polymerization. The type of isomeric structure that does not exhibit H/D exchange behaviour has a non-alternating monomer sequence that contains an amine bond with a relatively high proton affinity. The other isomeric structure that does exhibit H/D exchange behaviour has an alternating monomer sequence containing only amide and ester bonds with relatively low proton affinity. Oligomer structures were confirmed with additional MS2 experiments after H/D exchange. H/D exchange experiments on the fragments obtained after MS2 of the parent ion show that next to previously postulated mechanisms for the cleavage of the ester and amide bond another reaction pathway must be operational. A new mechanism is introduced to explain the H/D exchange behaviour of the fragments that requires a cleavage of the amide bonds only. Two types of fragments are formed by this mechanism. One type is protonated due to the cleavage of the amide bond whereas the other type has an oxazolonium ion structure due to the loss of an additional H2O.Publisher
13895Quantitative analysis of copolymers: influence of the structure of the monomer on the ionization efficiency in electrospray ionization FTMS
S. Koster, B. Mulder, M.C. Duursma, J.J. Boon, H.J.A. Philipsen, J.W. van Velde, M.W.F. Nielen, C.G. de Koster and R.M.A. Heeren
Macromolecules 35 (2002) 4919-4928
Published: --2002
The influence of the ionization efficiency on the measured copolymer sequence distribution is presented. Large differences in ionization efficiency were observed for mixtures of homopolyesters containing dipropoxylated bisphenol A/adipic acid and dipropoxylated bisphenol A/isophthalic acid and the corresponding copolyester dipropoxylated bisphenol A/isophthalic acid/adipic acid. The adipic acid structure has a higher affinity for the sodium cation, which results in more intense peaks for adipic acid containing oligomers. Relative sodium affinities of the oligomers were found to increase with an increasing number of acid end groups in favor of adipic acid containing oligomers. The ESI response of the oligomers depends on the polymer concentration in the sprayed mixture. This makes it impossible to correct for the ionization efficiency necessary for copolymer analysis. If differences in ionization efficiency are not corrected, the ion intensities in the copolymer mass spectra will show large deviations from the real composition and no conclusion can be drawn about the chemical (in)homogeneity of the MWD nor the random or block structure of the copolymer. This will also be valid for other cationization techniques like MALDI and FAB.Publisher
13884Water-conducting properties of lipids during pollen hydration
M. Wolters-Arts, L. van der Weerd, A.C. van Aelst, J. van der Weerd, H. van As and C. Mariani
Plant, Cell and Environment 25 (2002) 513-519
Published: --2002
Based on the authors' previous work an attempt has been made to study water flow in the lipid matirx during pollen hydration. The present study has demonstrated that in the presence of small amounts of water, the type of lipids used defined the time of hydration of pollen in vivo on the stigma and in vitro. Several approaches were used including cryo-scanning electron microscopy, magnetic resonance imaging and Fourier transform infrared microspectroscopic imaging, with the purpose of detecting very small amounts of water. The results show that no water is detectable in the lipid matrix. It was observed and concluded that the water for pollen hydration accumulates as a thin layer at the contact side between pollen and stigma, during the normal process of pollination in plant species with a wet stigma. However, using the same species deprived of the stigma by cell ablation, it was shown that the layer of water observed in wild-type plants is not necessary for pollen hydration.
13882Fourier Transform Infrared microscopic imaging of an embedded paint cross-section
J. van der Weerd, H. Brammer, J.J. Boon and R.M.A. Heeren
Applied Spectroscopy 56 (2002) 275-283
Published: --2002
Fourier transform infrared imaging is presented as a new analytical approach in the study of paint cross-sect ions. Analytical FT-IR reflection imaging provides the spatially resolved acquisition of infrared spectra with a resolution of about 7 µm. The technique reveals detailed information on the organic functional group distribution in the individual layers of embedded paint cross-sections and is used complementary to visual microscopy and scanning electron microscopy/energy dispersed X-ray spectroscopy (SEM-EDX). This method was applied to a paint cross-section of Rembrandt's Portrait of a Standing Man (1639). FT-IR imaging of this cross-section identified and localized different compounds present in the layers of this sample. Identification of these compounds based on their infrared spectra is confirmed by results from art historical and conservation literature. Special attention was given to a discoloration that was observed in large parts of the described painting. This discoloration was clearly visible in the paint cross-section. A hypothesis on the nature of the discolored paint layer is formulated based on the FTIR imaging results.
13970VLAM-G: a grid-based virtual laboratory
H. Afsarmanesh, R.G. Belleman, A.S.Z. Belloum, A. Benabdelkader, J.F.J. van den Brand, G.B. Eijkel, A. Frenkel, C. Garita, D.L. Groep, R.M.A. Heeren, Z.W. Hendrikse, L.O. Hertzberger, J.A. Kaandorp, E.C. Kaletas, V. Korkhov, C.T.A.M. de Laat, P.M.A. Sloot, D. Vasunin, A. Visser and H.H. Yakali
Scientific Programming 10 (2002) 173-181
Published: --2002
The Grid-based Virtual Laboratory AMsterdam (VLAM-G), provides a science portal for distributed analysis in applied scientific research. It offers scientists remote experiment control, data management facilities and access to distributed resources by providing cross-institutional integration of information and resources in a familiar environment. The main goal is to provide a unique integration of existing standards and software packages. This paper describes the design and prototype implementation of the VLAM-G platform. In this testbed we applied several recent technologies such as the Globus toolkit, enhanced federated database systems, and visualization and simulation techniques. Several domain specific case studies are described in some detail. Information management will be discussed separately in a forthcoming paper.
13975A REMPI investigation of the minimum energy conformations of diphenyl ether
A.C.S. Paiva, P.G. Kistemaker and T.L. Weeding
International Journal of Mass Spectrometry 221 (2002) 107-115
Published: --2002
The structure and low-frequency vibrations of jet-cooled molecules of diphenyl ether are studied with the resonance-enhanced two-photon ionization technique. The origin for the S1 S0 transition is assigned at 35,873 cm-1 and, within 400 cm-1, the vibrational progressions suggest the existence of different conformations proposed for this molecule. A potential energy surface for the ground state, obtained with the use of group theory, is checked against the conformational energy surface given by molecular mechanics simulations.Publisher
9241Microspectroscopic analysis of traditional oil paint
J. van der Weerd
Universiteit Amsterdam, 6-12-2002
Published: 6-12-2002
Publisher
13861Localizaton of intramolecular monosulfide bridges in Nisin with bond selective tandem mass spectrometry
A.J. Kleinnijenhuis, A.J.R. Heck, R.M.A. Heeren and M.C. Duursma
Proceedings of the 49th ASMS conference on Mass Spectrometry and Allied Topics, Chicago, Illinois, May 27-31, 2001 [published on CD-ROM only].
Published: --2001
13862Probing changes in the lipid composition on the surface of laser treated artist paints bij MALDI-MS
O. van den Brink, M. Duursma, S. Oonk, G.B. Eijkel, J.J. Boon and R.M.A. Heeren
Proceedings of the 49th ASMS conference on Mass Spectrometry and Allied Topics, Chicago, Illinois, May 27-31, 2001 [published on CD-ROM only].
Published: --2001
13858On the origin of: Structural characterisation of hyperbranched polyesteramides with ESI FTMS
S. Koster, C.G. de Koster, B.R. A.T.M., M.C. Duursma, J.J. Boon and R.M.A. Heeren
Proceedings of the 49th ASMS conference on Mass Spectrometry and Allied Topics, Chicago, Illinois, May 27-31, 2001 [published on CD-ROM only].
Published: --2001
Four hyperbranched synthetic polyesteramides were synthesized by the polycondensation of the trifunctional diisopropanolamine (D) and difunctional anhydrides (X) of succinic acid, glutaric acid, 1,2-cyclohexane dicarboxylic acid and phthalic acid. The polymers were analysed with Electrospray Ionisation Fourier Transform Ion Cyclotron Resonace Mass Spectrometry. MSn studies, on resonance excitation with Argon as collision gas, confirmed that a polymerisation terminating oligomer series was present in the reaction mixture and not a result of nozzle skimmer dissociation.
13857Analysis of natural organic pigments by laser desorption mass spectrometry (ldms): a preliminary study to spatially resolved mass spectrometry
N. Wyplosz, R.M.A. Heeren, G. van Rooij and J. Boon
Dyes in History and Archaelogy 16-17 (2001) 187-198
Published: --2001
Laser desorption mass spectrometry (LDMS) was used for the analysis of organic pigments and dyes. Use of a laser for desorption and ionisation provides the means to perform spatially resolved surface mass spectrometry. Analyses were performed with an ion trap mass spectrometer (ITMS) or a time-of-flight mass spectrometer (TOF-MS). The use of an ITMS makes multistage mass spectrometry possible. Preliminary results demonstrate the viability of LDMS in the analysis of flavonoids and indigo.
13856Fragmentation of suberin and composition of aliphatic monomers released bij methanolysis of cork from quercus
M.F. Bento, H. Pereira, A.M.C. Moutinho, K.J. van den Berg, J.J. Boon, O. van den Brink and R. Heeren
Holzforschung 55 (2001) 487-493
Published: --2001
Suberin from extractive-free cork from Quercus suber L. was depolymerised by methanolysis using different sodium methanolate (NaOMe) concentrations. 1 % and 3 % NaOMe completely removed suberin from cork (54 %-56 % of extractive-free cork), but for lower concentrations there was incomplete solubilisation; with 0.05 % NaOMe, only approximately 80 % of total suberin was removed. The monomeric composition of the extracts differed significantly: for the 0.05 % NaOMe, only alkanoic acids and diacids were found; the yield of co-hydroxy acids increased with reactant concentration, as well as alkanols and ferulic acid.Publisher
13855A European 640 x 486 PtSi camera for infrared reflectography
J. van der Weerd, R.M.A. Heeren and J.R.J. van Asperen de Boer
La peinture et le laboratoire: procédés. méthodologie. applications / ed. R. van Schouten, H. Verougstraete. - Leuven: Peeters, 2001. - pp. 231-243
Published: --2001
In this contribution we describe and evaluate the AIM 640P camera for Infrared reflectography. It is demonstrated that infrared reflectograms with high resolution and low geometric distortion can be acquired with this 640 x 486 pixel computer controlled Platinum Silicide camera system. The on-board 14 bit Analogue-to-Digital converter captures IR images in 16,384 grey-scales, compared to 256 with normal 8 bit AD-converters. This accuracy makes it possible to utilise the complete dynamic range, without the influence of gain and offset parameters during the examination. An internal Stirling cooler cools the detector to 85K thus avoiding the use of liquid nitrogen. This new European digital IRR system was evaluated and compared to a conventional vidicon system. The image quality of both systems was quantified through the experimental determination of the Modulation Transfer Function (MTF) for which a new experimental method was developed. In addition several paintings were reexamined with teh PtSi system for comparative purposes. Results from thes comparative studies demonstrate that the AIM 640P provides sharper (higher resolution) digital reflectograms with substantially decreased image distortion and a higher dynamic range.
13843Sequencing of synthetic copolyesters by ESI FTMS
S. Koster, M.C. Duursma, J.J. Boon, M.W.F. Nielen, C.G. de Koster and R.M.A. Heeren
Advances in Mass Spectrometry; Vol. 15 / ed. E. Gelpi. - Chichester: Wiley, 2001. - pp. 917-918
Published: --2001
13842An ESI-FTMSMS study of the structure of photo-oxidised egg glycerolipids
O.F. van den Brink, M.C. Duursma, J.J. Boon and R.M.A. Heeren
Advances in Mass Spectrometry; Vol. 15 / ed. E. Gelpi. - Chichester: Wiley, 2001. - pp. 889-890
Published: --2001
13841Spatially-resolved TOF-MS analysis of paint materials and easel paintings samples
N. Wyplosz, M.C. Duursma, J.J. Boon and R.M.A. Heeren
Advances in Mass Spectrometry; Vol. 15 / ed. E. Gelpi. - Chichester: Wiley, 2001. - pp. 883-884
Published: --2001
13859Internal energy control in (activated) ion dissociation experiments
R.M.A. Heeren, S. Koster, M. Duursma, X. Guo, N. Nibbering, L. Dharos and K. Vekey
Proceedings of the 49th ASMS conference on Mass Spectrometry and Allied Topics, Chicago, Illinois, May 27-31, 2001 [published on CD-ROM only].
Published: --2001
13838A novel surface induced dissociation tandem mass spectrometry set-up
R.M.A. Heeren, M.C. Duursma, A. de Snaijer, P.G. Kistemaker and J.J. Boon
Advances in Mass Spectrometry; Vol. 15 / ed. E. Gelpi. - Chichester: Wiley, 2001. - pp. 469-470
Published: --2001
13757Matrix-assisted laser desorption/ionization Fourier transform mass spectrometric analysis of oxygenated triglycerides and phosphatidylcholines in egg tempera paint dosimeters used for environmental monitoring of museum display conditions
O.F. van den Brink, J.J. Boon, P.B. O'Connor, M.C. Duursma and R.M.A. Heeren
Journal of Mass Spectrometry 36 (2001) 479-492
Published: --2001
Oxidative changes in triacylglycerols and diacylphosphatidylcholines in egg tempera paint strips are used for chemical dosimetry of the quality of the museum environment. High-resolution matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) was used as a rapid method for the determination of the exact elemental composition of the alteration products from diacylphosphatidylcholines and triacylglycerols, Light exposure of the egg tempera paints yields oxygenated diacylphosphatidylcholines and triacylglycerols. In the latter multiple incorporation of oxygen was observed as a recurring mass difference of 15.995, the exact atomic mass of oxygen. Owing to the high resolution of the FTMS data (routinely 20 000 at m/z 1000 in broadband mode), oxidation products with different elemental compositions but identical nominal mass could be distinguished. Products of oxidative cleavage of triacylglycerols were observed in samples exposed for longer times. The relative intensities of the peaks of singly and multiply oxygenated triacylglycerols were used to derive the degree of oxygenation of the egg lipids in the tempera paint dosimeters. The degree of oxygenation was found to be directly related to the light exposure time. Exposure to elevated temperature (60°C) for a period of 21 days did not lead to oxygenation of the triacylglycerols and diacylphosphatidylcholines. Exposure to NOx and SO2 in the dark greatly increased the degree of oxygenation. Addition of lead- or copper-containing pigments to the egg binding medium (and subsequent storage for 6 months in the dark) led to accelerated conversion of egg lipids to oxidised products.Publisher
13819Structural characterization of hyperbranched polyesteramides: MSn and the origin of species
S. Koster, C.G. de Koster, R.A.T.M. Van Benthem, M.C. Duursma, J.J. Boon and R.M.A. Heeren
International Journal of Mass Spectrometry 210-211 (2001) 591-602
Published: --2001
Four hyperbranched synthetic polyesteramides were synthesized by the polycondensation of the trifunctional diisopropanolamine (D) and difunctional anhydrides (X) of succinic acid, glutaric acid, 1,2-cyclohexane dicarboxylic acid, and phthalic acid. The polymers were analyzed with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The most intense oligomer series observed was XnDn+1 containing diisopropanolamine end groups as expected from the polycondensation conditions. A series of oligomers n - H2O is observed as well, which can have its origin in the polymerization process or alternatively could result from in-source fragmentation of n. Breakdown diagrams of the protonated parent ions X3D4 and additional MSn (n = 1, 2, 3) measurements gave insight in the fragmentation behavior of the polymers. Three main fragmentation pathways have been observed for all polymers of which the loss of H2O to oxazolonium ions has the lowest onset energy followed by the rearrangement of the amide and ester bonds also leading to oxazolonium ions. The loss of a second H2O to allylic or morpholine end groups has highest onset energy. MS3 experiments demonstrated that the presence of a series of oligomer XnDn+1 -H2O can be attributed to the polymerization process. Most probably an allylic end group has formed from one of the alcohol end groups. The formation of allylic end groups partly terminates the polymerization reaction and results in a change of the composition of the molecular weight distribution and decrease of the number average molecular weight.Publisher
13820Escherichia coli minicell membranes are enriched in cardiolipin
C.-M. Koppelman, T. den Blaauwen, M.C. Duursma, R.M.A. Heeren and N. Nanninga
Journal of Bacteriology 183 (2001) 6144-6147
Published: --2001
The phospholipid composition of Escherichia coli minicells has been studied as a model for the cell division site. Minicells appeared to be enriched in cardiolipin at the expense of phosphatidylglycerol. Mass spectrometry showed no differences between the gross acyl chain compositions of minicells and wild-type cells.Publisher
13835Imaging microspectroscopic, secondary ion mass spectrometric and electron microscopic studies on discoloured and partially discoloured smalt in crosssections of 16th century paintings
J.J. Boon, K. Keune, J. van der Weerd, M. Geldof and J.R.J. van Asperen de Boer
Chimia 55 (2001) 952-960
Published: --2001
Paint cross-sections of five 16th century paintings with areas of discoloured smalt oil paint were investigated. Semi-quantitative SEM-EDX analysis revealed that potassium was relatively low in all discoloured smalts, while cobalt remained at an approximately steady level. Reflection light microscopy demonstrated the presence of partially discoloured smalt particles with a remaining blue core. Imaging SIMS demonstrated that cobalt has a uniform distribution in the glass particles. Potassium however shows relatively high levels in the oil paint matrix around the discoloured glass particles and an uneven distribution in smalt particles with a blue core. These blue cores always have a higher K level compared to the discoloured rim of the particles. The loss of potassium from smalt in oil paint is interpreted as a leaching process which lowers the basicity of the glass below a critical level for colour maintenance. The colour change of the smalt is thus an indicator of a change in alkalinity inside the glass. The critical level appears to be near a K:Co of about 1:1 in 16th century potash glass on the basis of semi-quantitative SEM-EDX data. The migrated K is thought to be accommodated on the many fatty acid groups of the mature oil network ionomer in the aged oil paint. Ca was observed in a number of blue remaining smalts which suggest a role in preservation of the blue glass or retardation of the leaching process. It is estimated that the colour change is an early phenomenon possibly related to the early stages of oxidation and hydrolysis of the cross-linking oil paint. The differences in potassium levels in the remaining blue part of the smalt articles point to variability in the quality of the base potash glass in the 16th century. Analysis of partially discoloured smalt from two panels of a triptych by Dirck Barendsz (1534-1592) demonstrated that he had access to two chemically different smalts.
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13837ESI-FTICR tandem mass spectrometry in the determination of internal energy relaxation rates of macromolecules
R.M.A. Heeren, M.C. Duursma, L. Drahos and K. Vékey
Advances in Mass Spectrometry; Vol. 15 / ed. E. Gelpi. - Chichester: Wiley, 2001. - pp. 354-355
Published: --2001
13840Monitoring the effects of traditional 19th century ADDITIVES on the chemical drying of OIL PAINT by mass spectrometry
G.M. Languri, J. van der Horst, W.J. Muizebelt, R.M.A. Heeren and J.J. Boon
Advances in Mass Spectrometry; Vol. 15 / ed. E. Gelpi. - Chichester: Wiley, 2001. - pp. 831-832
Published: 1-1-2001
13636Lysozyme distribution and conformation in a biodegradable polymer matrix as determined by FTIR techniques
M. van de Weert, R. van 't Hof, J. van der Weerd, R.M.A. Heeren, G. Posthuma, W.E. Hennink and D.J.A. Crommelin
Journal of Controlled Release 68 (2000) 31-40
Published: --2000
Lysozyme distribution and conformation in poly(lactic-co-glycolic acid)(PLGA) microspheres was determined using various infrared spectroscopic techniques. Infrared microscopy and confocal laser scanning microscopy indicated that the protein was homogeneously distributed inside the microspheres in small cavities resulting from the water-in-oil emulsification step. Part of the protein was observed at or near the cavity walls, while the rest was located within these cavities. Attenuated total reflectance (ATR) and photoacoustic spectroscopy (PAS) also showed that there is hardly any protein at the surface of the microspheres. Since this microsphere formulation gave a large burst release (ca. 50%), this burst release can not be caused by protein at the surface of the particles. Probably, the protein is rapidly released through pores in the PLGA matrix. Conformational analysis of lysozyme in the PLGA microspheres by KBr pellet transmission suffered from band shape distortion and baseline slope. Despite incomplete subtraction of the PLGA background, a characteristic band of 21 non-covalent aggregates at 1625 cm was observed in the second derivative spectrum of the protein Amide I region. The other Fourier-transform infrared (FTIR) methods yielded similar results, indicating that the sample preparation procedure did not introduce artifacts. The observed aggregation signal may correspond to the protein adsorbed to the cavity walls inside the microspheres.Publisher
13624Structural analysis of synthetic homo- and copolyesters by electrospray ionization on a Fourier transform ion cyclotron resonance mass spectrometer
S. Koster, M.C. Duursma, J.J. Boon, M.W.F. Nielen, C.G. de Koster and R.M.A. Heeren
Journal of Mass Spectrometry 35 (2000) 739-748
Published: --2000
The molecular structure of a series of homo- and copolyesters was studied using sustained off-resonance irradiation collisionally activation dissociation on a Fourier transform ion cyclotron resonance mass spectrometer. Electrospray ionization was used as an ionization technique. The most important fragmentation pathways of the homopolyesters poly(dipropoxylated bisphenol-A/adipic acid) and poly(dipropoxylated bisphenol-A/isophthalic acid) were studied. Six different dissociation mechanisms were observed which are very similar to the mechanisms found to occur during pyrolysis of these compounds. Four of these mechanisms are a result of cleavages of the ester bond and the others are due to cleavages of the ether bond or bisphenol-A unit. Some of the fragments expected are not present in the spectrum, indicating that each fragment has a specific sodium affinity. Sequence-specific fragments of two of the three copolyester sequences that theoretically can exist were experimentally observed. Fragments that originate from the third sequence are not unique and can also be formed from other sequences. Therefore, it was not possible to determine the presence of the third sequence.Publisher
13686Controlled laser cleaning of painted artworks using accurate beam manipulation and on-line LIBS-detection
J.H. Scholten, J.M. Teule, V. Zafiropulos and R.M.A. Heeren
Journal of Cultural Heritage 1 (2000) S215-S220
Published: --2000
An innovative laser restoration tool for non-contact cleaning of painted artworks is developed. Accurate beam manipulation techniques in combination with on-line detection make the system suitable for selective cleaning of delicate surfaces. The utilisation of lasers obviates the use of various chemicals, and provides a method to remove layers that are untreatable using conventional methods. The first professional laser cleaning station for paintings is equipped with a modern mechatronic engineering tool for accurate beam manipulation ('optical arm'). An intelligent combination of software and hardware enables accurate control, necessary to deal with the variable properties of the artworks to be treated. An on-line monitoring system is incorporated, using laser-induced breakdown spectroscopy. The user interface plays an important role in simulating the 'hands-on' treatment. In January 1999, the 2-year European co-operative research project 'Advanced workstations for controlled laser cleaning of artworks' started. The research objective is to define the boundary conditions in which laser cleaning with the present technology can be safely applied.
13605Endgroup determination of synthetic polymers by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
S. Koster, M.C. Duursma, J.J. Boon and R.M.A. Heeren
Journal of the American Society for Mass Spectrometry 11 (2000) 536-543
Published: --2000
Electrospray ionization (ESI) was performed on a Fourier transform ion cyclotron resonance mass spectrometer for the endgroup and monomer mass determination of three poly(oxyalkylene)s in the mass range of 400-8000 Da. A combined use of the multiple charge states observed with ESI, leads to a threefold increase in accuracy of the endgroup and monomer determination. The improvement is attributed to the increased number of datapoints used for the regression procedure, yielding more accurate results. Endgroup masses are determined with a mass error better than 5 and 75 millimass units for the molecular weight range of 400-4200 and 6200-8000 Da, respectively. A mass error of better than 1 millimass unit was observed for all monomer mass determinations. With ESI, endgroup and monomer masses have been determined for poly(ethylene glycol) oligomers with a mass higher than 8000 Da. This is almost two times higher than observed with matrix-assisted laser desorption/ ionization on the same instrument.
13611Advanced workstation for controlled laser cleaning of paintings
J.H. Scholten, J.M. Teule, V. Zafiropulos and R.M.A. Heeren
Optics and Lasers in Biomedicine and Culture: Contributions to the 5th Internat. Conference on Optics Within Life Sciences OWLS V, Crete, 13-16 October 1998 / ed. C. Fotakis, T.G. Papazoglou and C. Kalpouzos. - Berlin: Springer, 2000. - pp.183-187
Published: --2000
Any artwork conservation procedure relies on effective diagnostic techniques and controlled cleaning methods. Traditional methods for the removal of unwanted layers from an artwork comprise mechanical or chemical techniques, which often cause (unknown) damage to the object. New technologies can offer valuable tools to support conservators and restorers.
13618Improvements in surface preparation of paint cross-sections necessary for advanced imaging techniques
N. Wyplosz, R. Koper, J. van der Weerd, R. Heeren and J. Boon
Art et Chimie, la Couleur: Actes du congrès / ed. J. Goupy, J.-P. Mohen. - Paris: CNRS Éditions, 2000. - pp. 65-68
Published: --2000
A new polishing procedure is presented for the preparation of paint cross-sections with enhanced surface quality. As a result, chemical surface analysis by Fourier Transform Infrared (FTM) imaging spectroscopy and Laser Desorption lon Trap Mass Spectrometry (LDMS) is now possible. Surface quality is demonstrated by FTIR-imaging, Differential Interference Contrast (DIC) microscopy and Interferometric Profiling.
13620Aspects of 17th century binding medium: inclusions in Rembrandt's Anatomy Lesson of Dr Nicolaes Tulp
P. Noble, J. Wadum, K. Groen, R. Heeren and K.J. van den Berg
Art et Chimie, la Couleur: Actes du congrès / ed. J. Goupy, J.-P. Mohen. - Paris: CNRS Éditions, 2000. - pp. 126-129
Published: --2000
During the recent restoration of Rembrandt's Anatomy Lesson of Dr. Nicolaes Tulp minuscule crater-like holes, which cover the surface of the painting, were studied. Whitish material within the holes was identified as lead chloride hydroxide and a variety of lead soaps. These inclusions, which in many cases protrude through the paint, are thought to have formed as a result of the agglomeration of lead compounds and saponification of the linseed oil within the ground layer. Possible scenarios for the origin of the chloride are discussed.
13610FTIR imaging spectroscopy for organic surface analysis of embedded paint cross-sections
R.M.A. Heeren, J. van der Weerd and J.J. Boon
Optics and Lasers in Biomedicine and Culture: Contributions to the Fifth International Conference om Optics Within Life Sciences OWLS V, Crete, 13-16 October 1998 / ed. C. Fotakis, T.G. Papazoglou and C. Kalpouzos. - Berlin: Springer, 2000. - pp. 179-182
Published: 1-1-2000
A description of the microscopic analysis of an embedded paint cross section with a novel FTIR imaging technique will be provided. Sample preparation turns out to be crucial for the success of the method used and some of its practical aspects for organic surface analytical techniques will be discussed. FTIR imaging analysis carried out with this novel technique is successfully employed to determine the binding medium type in individual paint layers.