Guido F. Verbeck

ABA Is Required for Plant Acclimation to a Combination of Salt and Heat Stress

Abiotic stresses such as drought, heat or salinity are a major cause of yield loss worldwide. Recent studies revealed that the acclimation of plants to a combination of different environmental stresses is unique and cannot be directly deduced from studying the response of plants to each of the different stresses applied individually. Here we report on the response of Arabidopsis thaliana to a combination of salt and heat stress using transcriptome analysis, physiological measurements and mutants deficient in abscisic acid, salicylic acid, jasmonic acid or ethylene signaling. Arabidopsis plants were found to be more susceptible to a combination of salt and heat stress compared to each of the different stresses applied individually. The stress combination resulted in a higher ratio of Na+/K+ in leaves and caused the enhanced expression of 699 transcripts unique to the stress combination. Interestingly, many of the transcripts that specifically accumulated in plants in response to the salt and heat stress combination were associated with the plant hormone abscisic acid. In accordance with this finding, mutants deficient in abscisic acid metabolism and signaling were found to be more susceptible to a combination of salt and heat stress than wild type plants. Our study highlights the important role abscisic acid plays in the acclimation of plants to a combination of two different abiotic stresses.

Visualization of Lipid Droplet Composition by Direct Organelle Mass Spectrometry

An expanding appreciation for the varied functions of neutral lipids in cellular organisms relies on a more detailed understanding of the mechanisms of lipid production and packaging into cytosolic lipid droplets (LDs). Conventional lipid profiling procedures involve the analysis of tissue extracts and consequently lack cellular or subcellular resolution. Here, we report an approach that combines the visualization of individual LDs, microphase extraction of lipid components from droplets, and the direct identification of lipid composition by nanospray mass spectrometry, even to the level of a single LD. The triacylglycerol (TAG) composition of LDs from several plant sources (mature cotton (Gossypium hirsutum) embryos, roots of cotton seedlings, and Arabidopsis thaliana seeds and leaves) were examined by direct organelle mass spectrometry and revealed the heterogeneity of LDs derived from different plant tissue sources. The analysis of individual LDs makes possible organellar resolution of molecular compositions and will facilitate new studies of LD biogenesis and functions, especially in combination with analysis of morphological and metabolic mutants. Furthermore, direct organelle mass spectrometry could be applied to the molecular analysis of other subcellular compartments and macromolecules.

Temporal variation in groundwater quality in the Permian Basin of Texas, a region of increasing unconventional oil and gas development.

The recent expansion of natural gas and oil extraction using unconventional oil and gas development (UD) practices such as horizontal drilling and hydraulic fracturing has raised questions about the potential for environmental impacts. Prior research has focused on evaluations of air and water quality in particular regions without explicitly considering temporal variation; thus, little is known about the potential effects of UD activity on the environment over longer periods of time. Here, we present an assessment of private well water quality in an area of increasing UD activity over a period of 13months. We analyzed samples from 42 private water wells located in three contiguous counties on the Eastern Shelf of the Permian Basin in Texas. This area has experienced a rise in UD activity in the last few years, and we analyzed samples in four separate time points to assess variation in groundwater quality over time as UD activities increased. We monitored general water quality parameters as well as several compounds used in UD activities. We found that some constituents remained stable over time, but others experienced significant variation over the period of study. Notable findings include significant changes in total organic carbon and pH along with ephemeral detections of ethanol, bromide, and dichloromethane after the initial sampling phase. These data provide insight into the potentially transient nature of compounds associated with groundwater contamination in areas experiencing UD activity.

Soft-landing ion mobility of silver clusters for small-molecule matrix-assisted laser desorption ionization mass spectrometry and imaging of latent fingerprints.

Matrix-assisted laser desorption ionization (MALDI) imaging is gaining popularity, but matrix effects such as mass spectral interference and damage to the sample limit its applications. Replacing traditional matrices with silver particles capable of equivalent or increased photon energy absorption from the incoming laser has proven to be beneficial for low mass analysis. Not only can silver clusters be advantageous for low mass compound detection, but they can be used for imaging as well. Conventional matrix application methods can obstruct samples, such as fingerprints, rendering them useless after mass analysis. The ability to image latent fingerprints without causing damage to the ridge pattern is important as it allows for further characterization of the print. The application of silver clusters by soft-landing ion mobility allows for enhanced MALDI and preservation of fingerprint integrity.

Vehicle-Mounted Portable Mass Spectrometry System for the Covert Detection via Spatial Analysis of Clandestine Methamphetamine Laboratories.

The ability to detect atmospheric effluent from clandestine methamphetamine manufacture is a useful tool for law enforcement. A membrane inlet mass spectrometer is mounted onto an all-electric drive capable hybrid vehicle that samples the atmosphere while in motion. Attributing a latitude and longitude to each spectrum collected, unique chemical fingerprints from clandestine manufacture are then mapped. This location-based mass spectrum data provides a localization to an area of interest. The synthesis of methamphetamine precursors was performed, and the impurities from such reactions were observed. A mock manufacture was setup, and the impurities were introduced into the atmosphere via heating. The detection of products and impurities using this mobile platform has shown the effectiveness of locating and localizing the manufacture of methamphetamine.

Laser Ablation ICP-MS Co-Localization of Mercury and Immune Response in Fish

Mercury (Hg) contamination is a global issue with implications for both ecosystem and human health. In this study, we use a new approach to link Hg exposure to health effects in spotted gar (Lepisosteus oculatus) from Caddo Lake (TX/LA). Previous field studies have reported elevated incidences of macrophage centers in liver, kidney, and spleen of fish with high concentrations of Hg. Macrophage centers are aggregates of specialized white blood cells that form as an immune response to tissue damage, and are considered a general biomarker of contaminant toxicity. We found elevated incidences of macrophage centers in liver of spotted gar and used a new technology for ecotoxicology studies, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), to colocalize aggregates and Hg deposits within the tissue architecture. We conclude that Hg compromises the health of spotted gar in our study and, perhaps, other fish exposed to elevated concentrations of Hg.

Trace analysis of energetic materials via direct analyte-probed nanoextraction coupled to direct analysis in real time mass spectrometry

Direct analysis in real time mass spectrometry (DART-MS) has proven to be a useful forensic tool for the trace analysis of energetic materials. While other techniques for detecting trace amounts of explosives involve extraction, derivatization, solvent exchange, or sample clean-up, DART-MS requires none of these. Typical DART-MS analyses directly from a solid sample or from a swab have been quite successful; however, these methods may not always be an optimal sampling technique in a forensic setting. For example, if the sample were only located in an area which included a latent fingerprint of interest, direct DART-MS analysis or the use of a swab would almost certainly destroy the print. To avoid ruining such potentially invaluable evidence, another method has been developed which will leave the fingerprint virtually untouched. Direct analyte-probed nanoextraction coupled to nanospray ionization-mass spectrometry (DAPNe-NSI-MS) has demonstrated excellent sensitivity and repeatability in forensic analyses of trace amounts of illicit drugs from various types of surfaces. This technique employs a nanomanipulator in conjunction with bright-field microscopy to extract single particles from a surface of interest and has provided a limit of detection of 300 attograms for caffeine. Combining DAPNe with DART-MS provides another level of flexibility in forensic analysis, and has proven to be a sufficient detection method for trinitrotoluene (TNT), RDX, and 1-methylaminoanthraquinone (MAAQ).

On the mechanism for plasma hydrogenation of graphene

We report that hydrogenation of mono-, bi-, and trilayer graphene samples via exposure to H2 plasma occurs as a result of electron irradiation of H2O adsorbates on the samples, rather than H species in the plasma as reported by [Elias et al., Science 323, 610 (2009)]. We propose that the hydrogenation mechanism is electron-impact fragmentation of H2O adsorbates into H+ ions. At incident electron energies >60 eV, we observe hydrogenation that is significantly more stable at temperatures >200 °C than previously reported.

One-bead, one-compound peptide library sequencing via high-pressure ammonia cleavage coupled to nanomanipulation/nanoelectrospray ionization mass spectrometry.

Biological screening of one-bead, one-compound (OBOC) combinatorial peptide libraries is routinely carried out with the peptide remaining bound to the resin bead during screening. After a hit is identified, the bead is isolated, the peptide is cleaved from the bead, and its sequence is determined. We have developed a new technique for cleavage of peptides from resin beads whereby exposure of a 4-hydroxymethyl benzoic acid (HMBA)-linked peptide to high-pressure ammonia gas led to efficient cleavage in as little as 5min. Here we also report a new method of extracting peptide from individual library beads for its introduction into a mass spectrometer that uses nanomanipulation combined with nanoelectrospray ionization mass spectrometry (NSI MS). Single beads analyzed by nanomanipulation/NSI MS were found to give identical MS results to those of bulk samples. Detection of 18 unique cleaved peptides 1 to 8 amino acids in length, and sequencing of 14 different peptide sequences 4 to 8 amino acids in length, was demonstrated on a combination of bulk samples and ones from individual beads of an OBOC library. The method was highly reproducible, with 100% of attempts to extract peptide resulting in high-quality MS data. This new collection of techniques allows rapid, reliable, environmentally responsible sequencing of hit beads from combinatorial peptide libraries.

Microelectromechanical system assembled ion optics: An advance to miniaturization and assembly of electron and ion optics

Deep-reactive ion etching of n-doped silicon-on-insulator is utilized to make ion optical components to aid in the miniaturization of mass analyzers. The microelectromechanical system components are bound to aluminum nitride substrates and employed three-dimensional assembly. The assembly methods are tested for breakdown (V(b)), durability, and alignment. Demonstration of ion manipulation is shown with a 1 mm Bradbury-Nielsen gate, 500 mum Einzel lens, 500 mum coaxial ring ion trap, and reflectron optics. Data are presented showing the resolution, attenuation, and performance of each of these devices. We demonstrate advantages and disadvantages of this technology and its applications to mass analysis.