Isoprene function in two contrasting poplars under salt and sunflecks.

In the present study, biogenic volatile organic compound (BVOC) emissions and photosynthetic gas exchange of salt-sensitive (Populus x canescens (Aiton) Sm.) and salt-tolerant (Populus euphratica Oliv.) isoprene-emitting and non-isoprene-emitting poplars were examined under controlled high-salinity and high-temperature and -light episode ('sunfleck') treatments. Combined treatment with salt and sunflecks led to an increased isoprene emission capacity in both poplar species, although the photosynthetic performance of P. × canescens was reduced. Indeed, different allocations of isoprene precursors between the cytosol and the chloroplast in the two species were uncovered by means of (13)CO2 labeling. Populus × canescens leaves, moreover, increased their use of 'alternative' carbon (C) sources in comparison with recently fixed C for isoprene biosynthesis under salinity. Our studies show, however, that isoprene itself does not have a function in poplar survival under salt stress: the non-isoprene-emitting leaves showed only a slightly decreased photosynthetic performance compared with wild type under salt treatment. Lipid composition analysis revealed differences in the double bond index between the isoprene-emitting and non-isoprene-emitting poplars. Four clear metabolomics patterns were recognized, reflecting systemic changes in flavonoids, sterols and C fixation metabolites due to the lack/presence of isoprene and the absence/presence of salt stress. The studies were complemented by long-term temperature stress experiments, which revealed the thermotolerance role of isoprene as the non-isoprene-emitting leaves collapsed under high temperature, releasing a burst of BVOCs. Engineered plants with a low isoprene emission potential might therefore not be capable of resisting high-temperature episodes.

Manganese speciation in paired serum and CSF samples using SEC-DRC-ICP-MS and CE-ICP-DRC-MS.

Occupational manganese (Mn) overexposure leads to accumulation in the brain and has been shown to cause progressive, permanent, neuro-degenerative damage with syndromes similar to idiopathic Parkinsonism. Mn is transported by an active mechanism across neural barriers (NB) finally into the brain; but to date, modes of Mn neurotoxic action are poorly understood. This paper investigates the relevant Mn-carrier species which are responsible for widely uncontrolled transport across NB. Mn speciation in paired serum/cerebrospinal fluid (CSF) samples was performed by size exclusion chromatography-inductively coupled plasma-dynamic reaction cell-mass spectrometry (SEC-ICP-DRC-MS) and capillary zone electrophoresis coupled to ICP-DRC-MS in a 2D approach for clear identification. For additional species verification, electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry was used after SEC-ICP-DRC-MS (second 2D approach). The Mn species from the different sample types were interrelated and correlation coefficients were calculated. In serum protein-bound Mn species like Mn-transferrin/albumin (Mn-Tf/HSA) were dominant, which had the main influence on total Mn in serum if Mn(total) was <1.5 µg/L. Above serum Mn(total) concentration of 1.6 µg/L the serum Mn(total) concentration was correlated with increasing Mn-citrate (Mn-Cit) concentration. In parallel Mn(total) and Mn species in CSF were determined. It turned out that Mn(total) from CSF was about half of Mn(total) in serum; Mn-Tf/HSA was only about 10% compared to serum. It turned out that above 1.6 µg/L Mn(total) in serum Mn-Cit was not only the leading Mn species in serum but also was the main influencing factor of both Mn(total) and Mn-Cit concentration in CSF. These results were further investigated using two statistical models (orthogonal partial least squares discriminant analysis, canonical discriminant analysis). Both models discriminated the samples in two groups where CSF samples were either correlated to Mn(total) and Mn-Cit (samples with serum Mn(total) > 1,550 ng/L) or correlated to Mn-Tf/HSA (samples with serum Mn(total) < 1,550 ng/L). We conclude that elevated Mn-Cit(serum) could be a valuable marker for increased total Mn in CSF (and brain), i.e., it could be a marker for elevated risk of Mn-dependent neurological disorders such as manganism in occupational health.

The gas-phase ozonolysis of beta-caryophyllene (C(15)H(24)). Part II: A theoretical study.

The O(3)-initiated oxidation of beta-caryophyllene, a sesquiterpene emitted in forested areas, was theoretically characterized for the first time using DFT quantum chemical calculations combined with statistical kinetic RRKM/master equation analysis and variational transition state theory. O(3)-Addition occurs primarily, >95%, on the endocyclic double bond without a barrier, leading to a total rate coefficient of 8.3 x 10(-24) T(3.05) exp(1028 K/T) cm(3) molecule(-1) s(-1), with a slight negative T-dependence. Thermal and chemically activated unimolecular reactions following this addition, including the so-called ester and hydroperoxide channels, and internal formation of the secondary ozonide, where characterized and quantified; a newly discovered reaction pathway through intersystem crossing from a dioxirane to a triplet bis(oxy) biradical intermediate is incorporated in the mechanism. The first generation product distribution at 298 K is predicted as 74% stabilized Criegee intermediates (CI), 8% OH radicals together with vinoxy-type 2-oxo alkyl radical co-products, 8% acids, 0.3% esters, and 9% CO(2) with two alkyl radical co-products. The thermalized CI can convert to the secondary ozonide in many reaction conditions, in particular the atmosphere; secondary ozonides are thus expected as dominant products of the beta-caryophyllene ozonolysis. These results are consistent with the experimental data presented in the accompanying paper (Part I). The temperature dependence and uncertainties of the product distribution are discussed. The high molecular weight oxygenated products, including beta-caryophyllonic acid and secondary ozonides, are expected to contribute to secondary organic aerosol formation.

Characterization of a new open cylindrical ion cyclotron resonance cell with unusual geometry.

A new cylindrical ion cyclotron resonance cell with electrodes of different diameters is characterized. It consists of a central segmented electrode for ion trapping and detection and two planar trapping electrodes with a center bore, to which two small tube electrodes are fitted. The cell can trap either positive or negative ions or both ion polarities in the center region. For trapping both ion polarities, an unsymmetrical double well potential can be generated. Ions generated from SF(6) by electron impact or electron attachment are investigated. In depth analysis of radial excitation patterns of positive and negative ions trapped simultaneously in different stability regions reveals sharp discrimination in the extent of radial acceleration. SIMION simulations of the radial excitation show different trajectories of positive and negative ions. Axial component of radial dipolar excitation field exists in the terminal stability regions.