Biomedical subjects

Stefan L Luxembourg

Publications and source records attributed to Stefan L Luxembourg.

6 recordsLinked to original sources

PubMed2006

The molecular scanner in microscope mode.

The combination of microscope mode matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) with protein identification methodology: the molecular scanner, was explored. The molecular scanner approach provides improvement of sensitivity of detection and identification of high-mass proteins in microscope mode IMS. The methodology was tested on protein distributions obtained after separation by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE). High-quality, high-spatial-resolution ion images were recorded on a TRIFT-II ion microscope after gold coating of the MALDI sample preparation on the poly(vinylidenedifluoride) capture membranes. The sensitivity of the combined method is estimated to be 5 pmol. The minimum amount of sample consumed, needed for identification, was estimated to be better than 100 fmol. Software tools were developed to analyze the spectral data and to generate broad mass range and single molecular component microscope mode ion images and single mass-to-charge ratio microprobe mode images.

Animals↗

PubMed2005

Subcellular imaging mass spectrometry of brain tissue.

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 10(5) 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.

Animals↗

PubMed2004

High-spatial resolution mass spectrometric imaging of peptide and protein distributions on a surface.

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 microm 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 microm. 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.

Image Processing, Computer-Assisted↗

PubMed2003

Using matrix peaks to map topography: increased mass resolution and enhanced sensitivity in chemical imaging.

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.

Journal Article↗

PubMed2003

Effect of local matrix crystal variations in matrix-assisted ionization techniques for mass spectrometry.

Intense intact molecular ion signals have been obtained from phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidyiinositol 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.

Crystallization↗

PubMedDate not supplied

Infrared mass spectrometric imaging below the diffraction limit.

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 microm 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.

Infrared Rays↗