Isoprene is the most relevant volatile organic compound emitted during the biosynthesis of metabolism processes. The oxidation of isoprene by a hydroxy radical (OH) is one of the main consumption schemes that generate six isomers of isoprene hydroxy hydroperoxide radicals (ISOPOOs). In this study, the rate constants of ISOPOOs + sulphur dioxide (SO2) reactions that eventually generate sulphur trioxide (SO3), the precursor of sulphate aerosol (SO42-(p)), are determined using microcanonical kinetic theories coupled with molecular structures and energies estimated by quantum chemical calculations. The results show that the reaction rates range from 10-27 to 10-20 cm3 molecule-1 s-1, depending on the atmospheric temperature and structure of the six ISOPOO isomers. The effect of SO3 formation from SO2 oxidation by ISOPOOs on the atmosphere is evaluated by a global chemical transport model, along with the rate constants obtained from microcanonical kinetic theories. The results show that SO3 formation is enhanced in regions with high SO2 or low nitrogen oxide (NO), such as China, the Middle East, and Amazon rainforests. However, the production rates of SO3 formation by ISOPOOs + SO2 reactions are eight orders of magnitude lower than that from the OH + SO2 reaction. This is indicative of SO42-(p) formation from the direct oxidation of SO2 by ISOPOOs, which is almost negligible in the atmosphere. The results of this study entail a detailed analysis of SO3 formation from gas-phase reactions of isoprene-derived products.

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Metabolomics studies are becoming increasingly common for understanding how plant metabolism responds to changes in environmental conditions, genetic manipulations and treatments. Despite the recent advances in metabolomics workflow, the sample preparation process still limits the high-throughput analysis in large-scale studies. Here, we present a highly flexible robotic system that integrates liquid handling, sonication, centrifugation, solvent evaporation and sample transfer processed in 96-well plates to automatize the metabolite extraction from leaf samples. We transferred an established manual extraction protocol performed to a robotic system, and with this, we show the optimization steps required to improve reproducibility and obtain comparable results in terms of extraction efficiency and accuracy. We then tested the robotic system to analyze the metabolomes of wild-type and four transgenic silver birch (Betula pendula Roth) lines under unstressed conditions. Birch trees were engineered to overexpress the poplar (Populus × canescens) isoprene synthase and to emit various amounts of isoprene. By fitting the different isoprene emission capacities of the transgenic trees with their leaf metabolomes, we observed an isoprene-dependent upregulation of some flavonoids and other secondary metabolites as well as carbohydrates, amino acid and lipid metabolites. By contrast, the disaccharide sucrose was found to be strongly negatively correlated to isoprene emission. The presented study illustrates the power of integrating robotics to increase the sample throughput, reduce human errors and labor time, and to ensure a fully controlled, monitored and standardized sample preparation procedure. Due to its modular and flexible structure, the robotic system can be easily adapted to other extraction protocols for the analysis of various tissues or plant species to achieve high-throughput metabolomics in plant research.

Exhaled volatile organic compounds (VOCs) are of interest due to their minimally invasive sampling procedure. Previous studies have investigated the impact of exercise, with evidence suggesting that breath VOCs reflect exercise-induced metabolic activity. However, these studies have yet to investigate the impact of maximal exercise to exhaustion on breath VOCs, which was the main aim of this study. Two-litre breath samples were collected onto thermal desorption tubes using a portable breath collection unit. Samples were collected pre-exercise, and at 10 and 60 min following a maximal exercise test (VO2MAX). Breath VOCs were analysed by thermal desorption-gas chromatography-mass spectrometry using a non-targeted approach. Data showed a tendency for reduced isoprene in samples at 10 min post-exercise, with a return to baseline by 60 min. However, inter-individual variation meant differences between baseline and 10 min could not be confirmed, although the 10 and 60 min timepoints were different (p = 0.041). In addition, baseline samples showed a tendency for both acetone and isoprene to be reduced in those with higher absolute VO2MAX scores (mL(O2)/min), although with restricted statistical power. Baseline samples could not differentiate between relative VO2MAX scores (mL(O2)/kg/min). In conclusion, these data support that isoprene levels are dynamic in response to exercise.

Volatile organic compounds (VOCs) are important air pollution issues because of their potential health effects, and the contribution to ground ozone and secondary particulate matter. In this study, 53 VOC species near nine roads in Hanoi were monitored by sampling and analyzed by GC-FID four times per day on weekdays and in the morning on the weekend, from December 2014 to January 2015. In parallel with VOC sampling, vehicle number was counted, and meteorological conditions were recorded. A large share of motorbikes was found, accounted for 82% of overall for all period, and 88% in rush hours. The average TVOC concentration was 305.1 ppb; while those of BTEX were 12.8/27.4/4.8/15.9/6.0 ppb for benzene/toluene/ethylbenzene/m,p-xylenes/o-xylene, respectively. Isopentane was the most abundant species of VOCs. A significant carcinogenic risk of benzene species was found. Ozone formation potential (OFP) of VOCs was of 1752.7 ppb. Levels of VOC species reflected well the transportation volume. Strong correlations between motorbike number related parameters and ethylbenzene were found. High correlations were also found among ethylbenzene and almost all other VOC species. It implied that the majority of VOCs near road emitted from the same source, which is motorbikes. The calculation using emission factors from COPERT 5 model with conditions of fleets in Hanoi showed that VOCs from motorbikes contributed to more than 90% of the VOC level.

It is generally assumed that isoprene-derived secondary organic aerosol (SOA) precursors are mainly formed from the secondary reactions of intermediate products with OH radicals in the gas phase and multiphase oxidation in particles. In this paper, we predicted a theoretical mechanism for the primary formation of highly oxygenated molecules (HOM) in the gas phase through successive intramolecular H-shifts and O2 addition in the specific Z-δ isomer of hydroxyl-peroxy radicals and alkoxy radicals. The position of O2 addition is different from that in forming hydroperoxy aldehydes. The prediction was further supported experimentally by successfully identifying a few highly oxidized peroxy radicals and closed-shell products such as C5H9O7,9, C5H10O6,7,8, and C4H8O5 in a flow reactor by chemical ionization mass spectrometry at air pressure. These HOM products could serve as important precursors to isoprene-derived SOA. Further modeling studies on the effect of NO concentration suggested that HOM formation could account for up to ∼11% of the branching ratio (∼9% from the 4-OH channel and ∼2% from the 1-OH channel) in the reaction of isoprene with OH when the lifetimes of peroxy radicals due to bimolecular reactions are ∼100 s, which is typical in forest regions.

Separation of branched chain hydrocarbons and straight chain hydrocarbons is very important in the isomerization process. Grand canonical ensemble Monte Carlo simulations were used to investigate the adsorption and separation of iso-pentane and n-pentane in four types of zeolites: MWW, BOG, MFI, and LTA. The computation of the pure components indicates that the adsorption capacity is affected by physical properties of zeolite, like pore size and structures, and isosteric heat. In BOG, MFI and LTA, the amount of adsorption of n-pentane is higher than iso-pentane, while the phenomenon is contrary in MWW. For a given zeolite, a stronger adsorption heat corresponds to a higher loading. In the binary mixture simulations, the separation capacity of n-and iso-pentane increases with the elevated pressure and the increasing iso-pentane composition. The adsorption mechanism and competition process have been examined. Preferential adsorption contributions prevail at low pressure, however, the size effect becomes important with the increasing pressure, and the relatively smaller n-pentane gradually competes successfully in binary adsorption. Among these zeolites, MFI has the best separation performance due to its high shape selectivity. This work helps to better understand the adsorption and separation performance of n- and iso-pentane in different zeolites and explain the relationship between zeolite structures and adsorption performance.

The potential role of isoprene oxidative processes, as well as the possible impact of air pollution on isoprene emissions, are more important in tropical cities, surrounded by rainforests. In this study, the contribution of isoprene to ozone formation was determined considering different scenarios, mainly volatile organic compounds/NO x (VOC/NO x ) ratios, and typical atmospheric conditions for the city of Rio de Janeiro, where more than 36% of the urbanized area is covered by vegetation. Ozone isopleths and incremental reactivity coefficients (IR) were evaluated to understand the direct contribution of isoprene to ground-level ozone formation and the negative impact of anthropogenic NO x emissions on the natural atmospheric balance. Although isoprene accounted for only 2.7% of the total VOC mass, excluding the isoprene concentration from the model reduced the maximum ozone value by 14.1%. The calculated IR coefficient (grams of O3 formed per gram of added isoprene) was 2.2 for a VOC/NO x ratio of 8.86.

In the efforts at controlling automobile emissions, it is important to know in what extent air pollutants from on-road vehicles could be truly reduced. In 2014 we conducted tests in a heavily trafficked tunnel in south China to characterize emissions of volatile organic compounds (VOC) from on-road vehicle fleet and compared our results with those obtained in the same tunnel in 2004. Alkanes, aromatics, and alkenes had average emission factors (EFs) of 338, 63, and 42 mg km-1 in 2014 against that of 194, 129, and 160 mg km-1 in 2004, respectively. In 2014, LPG-related propane, n-butane and i-butane were the top three non-methane hydrocarbons (NMHCs) with EFs of 184 ± 21, 53 ± 6 and 31 ± 3 mg km-1; the gasoline evaporation marker i-pentane had an average EF of 17 ± 3 mg km-1; ethylene and propene were the top two alkenes with average EFs of 16 ± 1 and 9.7 ± 0.9 mg km-1, respectively; isoprene had no direct emission from vehicles; toluene showed the highest EF of 11 ± 2 mg km-1 among the aromatics; and acetylene had an average EF of 7 ± 1 mg km-1. While EFs of total NMHCs decreased only 9% from 493 ± 120 mg km-1 in 2004 to 449 ± 40 mg km-1 in 2014, their total ozone formation potential (OFP) decreased by 57% from 2.50 × 103 mg km-1 in 2004 to 1.10 × 103 mg km-1 in 2014, and their total secondary organic aerosol formation potential (SOAFP) decreased by 50% from 50 mg km-1 in 2004 to 25 mg km-1 in 2014. The large drop in ozone and SOA formation potentials could be explained by reduced emissions of reactive alkenes and aromatics, due largely to fuel transition from gasoline/diesel to LPG for taxis/buses and upgraded vehicle emission standards.

Cathepsin B is a lysosomal cysteine protease involved in many diseases. The present research demonstrates that derivatives of epoxysuccinyl-peptide are effective and selective cathepsin B inhibitors. We synthesized a series of epoxysuccinyl-peptide derivatives based on the well-known cathepsin B inhibitor E64d. Specifically, we substituted the 2-methylpropane group at the R1 position of E64d with a sulfane, such as ethyl(methyl) sulfane or benzyl(methyl) sulfane. We also designed and synthesized a library of molecules with various substituents at the R2 position of E64d to replace 2-methylbutane. By studying the structure-activity relationships of these newly synthesized molecules as cathepsin B inhibitors, we demonstrated that substituting ethyl(methyl) sulfane for 2-methylbutane (R2) of E64d improves the inhibitory activity and selectivity for cathepsin B inhibition. Our new cathepsin B inhibitors were highly effective and selective.