NAS Workshop on the Industrialization of Biology

Transcription

1 High throughput chemical characterization using mass spectrometry NAS Workshop on the Industrialization of Biology Jonathan V. Sweedler University of Illinois Urbana, IL USA May 2014 Funding: DOE, NSF and NIH

2 Measuring a cell via mass spectrometry: the information we gain depends on the instrument platform Capillary Electrophoresis electrospray MS Matrix Assisted Laser Desorption Ionization Mass Spectrometry (MALDI MS) Secondary Ion Mass Spectrometry (SIMS) Sweedler group, UIUC

3 An example of high information from carefully selected cells: electrophysiology, structure and metabolomics from the same cell... Separate the cell s contents and then detect the purified bands; we obtain 100 or so identifications from each cell. Anal. Chem., 2014, 86 (6), pp 3203

4 Relative Intensity To increase throughput, remove the separation and profile the sample via MS 100 µm Prohormone mrna expression in neurons Relative Intensity 1-9 ELH AP 9-27 AP 8-27 ELH AP ELH ELH 1-14 AP ELH p pelh m/z 1-29 p 100 µm [88-101] SEM microphotograph of neurons; the arrow points to where a single neuron was removed for MS Mass spectrum acquired from a neuron FMRFa [39-52] [22-35] Neuropsychopharmacology 36, 2014, m/z

5 Sweedler group, UIUC Perhaps the highest throughput MS approach: imaging with mass spectrometry (sampling at 100 Hz)

6 MS for volume-limited surface-deposited peptides... zeptomole detection limits Sweedler group, UIUC Matrix-assisted laser desorption / ionization MS imaging experiment to determine the detection limits using a chemical printer to print solutions of angiotensin I followed by printing of the matrix. Angiotensin I levels ranged from 340 zmol to 67 fmol. Signal was observed consistently at all levels including 340 zmol. At the 95% confidence limit, LOD is about 100 zmol. Thus, sampling and not LOD is often the key for volume limited samples

7 One approach for thousands of samples: the stretched bead array approach from Monroe, Anal. Chem. Oct 1, 2006

8 MSI-based profiling of cells with beads Section of the Aplysia abdominal ganglion Adapted from Monroe, Anal. Chem. Oct 1, 2006

9 Direct imaging of dissociated cells and fibers with mass spectrometry imaging Enzymatic dissociation of DRG cells and fibers allows MS measurements of many cells We disassociate the cells onto a glass slide, locate them and profile each cell with mass spectrometry, here shown using neurons from a rat dorsal root ganglion. Sweedler group, UIUC, unpublished

10 Intense and unusual signals are found in individual cells from pain-treated animals When cell populations are heterogeneous, examining cells provides information on the subpopulations that have interesting characteristics, here shown as several that have a large change in a few metabolites related to a painful stimulus. Sweedler group, UIUC, unpublished

11 PC3 Relative intensity PCA analysis of MS data received from populations of dissociated DRG neurons and fibers indicates increasing response of individual structures to level of nociceptive stimuli PCA analysis of unrestricted data set in molecular mass region Anticipated strength of injection influence on DRG s biochemistry Distribution of m/z signal intensities Control for water injection Water injection Control for formalin injection PC1 Animal 1 Animal 2 Formalin injection Control for formalin injection Control for water injection Water injection Formalin injection Sweedler group unpublished

12 Measuring the content of an individual neuron using CE-MS after we have profiled it via MALDI MS Intens. x Arginine Histidine Ornithine Urocanic acid Serine Valine Tryptophan Phenylalanine Glutamate Proline Glutamine Citrulline Acetylcarnitine Aspartic acid 2 Threonine Tyrosine Choline Carnitine Creatine Alanine Glycine 1 Asparagine Time [min] Extracted ion electropherogram, 21nL injection, 20kV separation potential, separation buffer: 26mM formic acid ph 1.9, Sheath liquid: 2.6mM formic acid, 50% methanol, 0.750uL/min Sweedler group, UIUC, unpublished

13 Increasing efficiency by not measuring from empty space: only look at cells Cell Sweedler group, UIUC, unpublished

14 Automate cell localization and MS acquisition Brightfield Darkfield + Autofluorescence Brightfield image taken after MSI overlayed with darkfield and autofluorescence image. A 3x3 raster is done around each cell. There is good registry between cell locations and MALDI laser marks. Sweedler group, UIUC, unpublished

15 Profiling ~10000 cells and finding the rare cells via principal component analyses Sweedler group, UIUC, unpublished

16 Multi-scale MSI of bacterial biofilms low level compounds may be at high levels in specific cells, even with so-called homogeneous bacterial biofilms Optical SIMS Survey Detail LDI TOF MS Rhamnolipid (Rha-Rha-C10-C10) m/z TOF-SIMS TIC 1 mm 1 mm 1 mm m/z m/z m/z m/z m/z µm Sweedler (UIUC), Bohn and Shrout (Notre Dame) laboratories, submitted to The Analyst, 2014

17 Approaches work on any heterogeneous sample, here shown to follow processing of lignocellulosic materials with combined LDI, SIMS and Raman Negative Total Ion Lignin, cm -1 Positive Total Ion Anal Chem , Cellulose, cm -1 All organic components cm -1 Color-coded image Scale bar 100 mm

18 Molecular Portrait of a Complex Cell: We can perform direct single-cell analysis from RNAs to proteins : is it enough? RNAs Proteins With current technologies, many compounds cannot be assayed from a single cell sample, and cellular subcompartments remain beyond our measurement capabilities. Metabolites, Lipids, Signaling molecules Image from Leonid Moroz, University of Florida