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.

Border control for homeland security faces major challenges worldwide due to chemical threats from national and/or international terrorism as well as organized crime. A wide range of technologies and systems with threat detection and monitoring capabilities has emerged to identify the chemical footprint associated with these illegal activities. This review paper investigates artificial sniffing technologies used as chemical sensors for point-of-use chemical analysis, especially during border security applications. This article presents an overview of (a) the existing available technologies reported in the scientific literature for threat screening, (b) commercially available, portable (hand-held and stand-off) chemical detection systems, and (c) their underlying functional and operational principles. Emphasis is given to technologies that have been developed for in-field security operations, but laboratory developed techniques are also summarized as emerging technologies. The chemical analytes of interest in this review are (a) volatile organic compounds (VOCs) associated with security applications (e.g., illegal, hazardous, and terrorist events), (b) chemical "signatures" associated with human presence, and

Mass spectrometry has become an indispensable tool in identifying post-translationally modified proteins, but multiple peptide mass-mapping/peptide-sequencing experiments are required to answer questions involving the site and type of modification present. Here, we apply ion mobility-mass spectrometry (IM-MS), a high-throughput analysis method having high selectivity and sensitivity, to the challenge of identifying phosphorylated peptides. Ion mobility separation is based on the collision cross-section of the ion. Phosphorylation can result in a conformational change in gas-phase peptide ions, which can be detected by IM. To demonstrate this point, a peptide mixture containing a variety of peptide sequences is examined with IM-MS and molecular dynamics calculations. During the course of these studies, two classes of phosphopeptide were identified: (i) phosphorylated peptide ions that have conformers that differ from the nonphosphorylated ion and (ii) phosphorylated peptide ions that have conformations that are very similar to the nonphosphorylated peptide. The utility of IM-MS peptide mass mapping for identifying both types of phosphorylated peptides is discussed.

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Results from ion mobility studies of tryptic peptides suggest that, in some cases, the gas-phase structures can be related to the solution-phase structure of the parent protein. The interpretation of ion mobility measurements is supported by results from molecular modeling and H/D exchange experiments on the same peptides. This study clearly illustrates the utility of IM-MS for screening complex mixtures for peptides having intrinsically stable secondary/tertiary structures, and/or posttranslational modification.