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1.
Food Chem ; 369: 130880, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34438344

RESUMO

Theoretical consideration about the impact of methyl groups on the structure and vibrational properties of ß-carotenoids, using medium size molecules of trans-butadiene and trans-isoprene, are reported. Density functional theory (DFT) calculations with correlation-consistent and polarization-consistent basis sets were applied to trans-1,3-butadiene and trans-isoprene as the smallest building bricks of ß-carotenoids. Their structure and harmonic vibrations were estimated in the complete basis set limit (CBS) using the non-linear least square fit. Optimized geometries and harmonic frequencies, obtained with B3LYP and BLYP density functionals and large basis sets, were favorably reproduced by a significantly faster approach, using a recently modified STO(1M)-3G Slater-type basis set. Selected density functionals with STO(1M)-3G and 6-311++G** basis sets were also successful in predicting ß-carotene structures and harmonic vibrations. This work demonstrates the potential applicability of the proposed level of theory for larger molecules, including ß-carotenoids, present in numerous natural food sources. The proposed scheme of molecular modeling, applied to biologically active compounds in food, could provide a deeper insight into their function in vivo, which is directly related to their structure and spectroscopic properties. It could also support the experimental qualitative analysis, based on peak assignment of ß-carotenoids in various food sources.


Assuntos
Butadienos , Vibração , Carotenoides , Hemiterpenos , Teoria Quântica , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman
2.
Environ Sci Technol ; 55(20): 14294-14304, 2021 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-34618435

RESUMO

1,2-Dihydroxy isoprene (1,2-DHI), a product of isoprene oxidation from multiple chemical pathways, is produced in the atmosphere in large quantities; however, its chemical fate has not been comprehensively studied. Here, we perform chamber experiments to investigate its gas-phase reactions. We find that the reactions of 1,2-DHI with OH radicals and ozone are rapid (kOH = 8.0 (±1.3) × 10-11 cm3 molecule-1 s-1; kO3 = 7.2 (±1.1) × 10-18 cm3 molecule-1 s-1). Reaction with OH, which dominates 1,2-DHI loss, leads primarily to fragmentation and radical recycling; major products under both high- and low-NO conditions include hydroxyacetone, glycolaldehyde, and 2,3-dihydroxy-2-methyl-propanal (DHMP). Radical-terminating hydroperoxide formation from the peroxy radical (RO2) reaction with HO2 and organonitrate formation from RO2 + NO are not observed in the gas phase, possibly due to low volatility; constraints for their branching ratios are instead derived by mass balance. We also measure secondary organic aerosol mass yields from 1,2-DHI (0-23%) and show that oxidation in the presence of aqueous particles leads to formic and acetic acid production. Finally, we incorporate results into GEOS-Chem, a global chemical transport model, to compute the global production (25.3 Tg a-1) and gas-phase loss (20.2 Tg a-1) of 1,2-DHI and show that its oxidation provides non-negligible contributions to the atmospheric budgets of hydroxyacetone, glycolaldehyde, hydroxymethyl hydroperoxide, formic acid, and DHMP.


Assuntos
Butadienos , Hemiterpenos , Aerossóis , Oxirredução
3.
Environ Sci Technol ; 55(20): 13728-13736, 2021 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-34587441

RESUMO

The hydroxyl radical (OH) oxidation of the most abundant nonmethane volatile organic compound emitted to the atmosphere, isoprene (C5H8), produces a number of chemical species that partition to the condensed phase via gas-particle partitioning or form condensed-phase compounds via multiphase/heterogeneous chemistry to generate secondary organic aerosols (SOA). The SOA species in aerosol water or cloud/fog droplets may oxidize further via aqueous reaction with OH radicals, among other fates. Rate coefficients for compounds in isoprene's photochemical cascade are well constrained in the gas phase; however, a gap of information exists for the aqueous OH rate coefficients of the condensed-phased products, precluding the atmospheric modeling of the oxidative fate of isoprene-derived SOA. This work investigated the OH-initiated oxidation kinetic rate coefficients (kOH) for six major SOA compounds formed from the high-NO and low-NO channels of isoprene's atmospheric oxidation and one analog, most of which were synthesized and purified for study: (k1) 2-methyltetrol [MT: 1.14 (±0.17) × 109 M-1 s-1], (k2) 2-methyl-1,2,3-trihydroxy-4-sulfate [MT-4-S: 1.52 (±0.25) × 109 M-1 s-1], (k3) 2-methyl-1,2-dihydroxy-3-sulfate [MD-3-S: 0.56 (±0.15) × 109 M-1 s-1], (k4) 2-methyl-1,2-dihydroxy-but-3-ene [MDE: 4.35 (±1.16) × 109 M-1 s-1], (k5) 2-methyl-2,3-dihydroxy-1,4-dinitrate [MD-1,4-DN: 0.24 (±0.04) × 109 M-1 s-1], (k6) 2-methyl-1,2,4-trihydroxy-3-nitrate [MT-3-N: 1.12 (±0.15) × 109 M-1 s-1], and (k7) 2-methylglyceric acid [MGA: pH 2:1.41 (±0.49) × 109 M-1 s-1; pH 5:0.97 (±0.42) × 109 M-1 s-1]. The second-order rate coefficients are determined against the known kOH of erythritol in pure water. The decays of each reagent were measured with nuclear magnetic resonance (NMR) and high-performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). The aqueous photooxidation fates of isoprene-derived SOA compounds are substantial and may impact the SOA budget when implemented into global models.


Assuntos
Radical Hidroxila , Compostos Orgânicos Voláteis , Aerossóis , Butadienos , Hemiterpenos , Oxirredução , Água
4.
J Plant Res ; 134(6): 1225-1242, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34505187

RESUMO

Despite its major role in global isoprene emission, information on the environmental control of isoprene emission from tropical trees has remained scarce. Thus, in this study, we examined the relationship between parameters of G-93 isoprene emission formula (CT1, CT2, and α), growth temperature and light intensity, photosynthesis (ɸ, Pmax), isoprene synthase (IspS) level, and 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway metabolites using sunlit and shaded leaves of four tropical trees. The results showed that the temperature dependence of isoprene emission from shaded leaves did not differ significantly from sunlit leaves. In contrast, there was a lower saturation irradiance in shaded leaves than in sunlit leaves, the same as temperate plants. The photosynthesis rate of shaded leaves showed lower saturation irradiance, similar to the light dependence of isoprene emission. In most cases, the concentration of MEP pathway metabolites was of lower tendency in shaded leaves versus in sunlit leaves, whereas no significant difference was noted in IspS level between sunlit and shaded leaves. Correlation analysis between these parameters found that CT1 of the G-93 parameter was positively correlated with the concentration of DXP and DMADP, whereas CT2 correlated with the concentration of MEP and the average air temperature for the past 48 h. Similarly, α closely associated with the initial slope (ɸ) of photosynthesis rate, and the basal emission factor is also linked to the photon flux of past days. These results suggest that growth conditions may control the temperature dependence of isoprene emission from tropical trees via the changes in the profiles of MEP pathway metabolites, causing alteration in the parameters of the isoprene emission formula.


Assuntos
Populus , Árvores , Butadienos , Hemiterpenos , Pentanos , Fotossíntese , Folhas de Planta
5.
Sci Rep ; 11(1): 16347, 2021 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-34381163

RESUMO

Gamma-delta (γδ) T cells express T cell receptors (TCR) that are preconfigured to recognize signs of pathogen infection. In primates, γδ T cells expressing the Vγ9Vδ2 TCR innately recognize (E)-4-hydroxy-3-methyl-but- 2-enyl pyrophosphate (HMBPP), a product of the 2-C-methyl-D-erythritol 4- phosphate (MEP) pathway in bacteria that is presented in infected cells via interaction with members of the B7 family of costimulatory molecules butyrophilin (BTN) 3A1 and BTN2A1. In humans, Listeria monocytogenes (Lm) vaccine platforms have the potential to generate potent Vγ9Vδ2 T cell recognition. To evaluate the activation of Vγ9Vδ2 T cells by Lm-infected human monocyte-derived dendritic cells (Mo-DC) we engineered Lm strains that lack components of the MEP pathway. Direct infection of Mo-DC with these bacteria were unchanged in their ability to activate CD107a expression in Vγ9Vδ2 T cells despite an inability to synthesize HMBPP. Importantly, functional BTN3A1 was essential for this activation. Unexpectedly, we found that cytoplasmic entry of Lm into human dendritic cells resulted in upregulation of cholesterol metabolism in these cells, and the effect of pathway regulatory drugs suggest this occurs via increased synthesis of the alternative endogenous Vγ9Vδ2 ligand isoprenyl pyrophosphate (IPP) and/or its isomer dimethylallyl pyrophosphate (DMAPP). Thus, following direct infection, host pathways regulated by cytoplasmic entry of Lm can trigger Vγ9Vδ2 T cell recognition of infected cells without production of the unique bacterial ligand HMBPP.


Assuntos
Células Dendríticas/imunologia , Listeria monocytogenes/imunologia , Monócitos/imunologia , Organofosfatos/imunologia , Receptores de Antígenos de Linfócitos T gama-delta/imunologia , Linfócitos T/imunologia , Butirofilinas/imunologia , Células Cultivadas , Hemiterpenos/imunologia , Humanos , Ativação Linfocitária/imunologia , Proteína 1 de Membrana Associada ao Lisossomo/imunologia , Compostos Organofosforados/imunologia , Ligação Proteica/imunologia
6.
Sci Total Environ ; 775: 145592, 2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34380608

RESUMO

Recently, we identified seven novel hydroxy-carboxylic acids resulting from gas-phase reactions of isoprene in the presence of nitrogen oxides (NOx), ozone (O3), and/or hydroxyl radicals (OH). In the present study, we provide evidence that hydroxy-carboxylic acids, namely methyltartaric acids (MTA) are: (1) reliable isoprene tracers, (2) likely produced via rapid peroxy radical hydrogen atom (H) shift reactions (autoxidation mechanism) and analogous alkoxy radical H shifts in low and high NOx environments respectively and (3) representative of aged ambient aerosol in the low NOx regime. Firstly, MTA are reliable tracers of isoprene aerosol because they have been identified in numerous chamber experiments involving isoprene conducted under a wide range of conditions and are absent in the oxidation of mono- and sesquiterpenes. They are also present in numerous samples of ambient aerosol collected during the past 20 years at several locations in the U.S. and Europe. Furthermore, MTA concentrations measured during a year-long field study in Research Triangle Park (RTP), NC in 2003 show a seasonal trend consistent with isoprene emissions and photochemical activity. Secondly, an analysis of chemical ionization mass spectrometer (CIMS) data of several chamber experiments in low and high NOx environments show that highly oxidized molecules (HOMs) derived from isoprene that lead to MTAs may be produced rapidly and considered as early generation isoprene oxidation products in the gas phase. Density functional theory calculations show that rapid intramolecular H shifts involving peroxy and alkoxy radicals possess low barriers for methyl-hydroxy-butenals (MHBs) that may represent precursors for MTA. From these results, a viable rapid H shift mechanism is proposed to occur that produces isoprene derived HOMs like MTA. Finally, an analysis of the mechanism shows that autoxidation-like pathways in low and high NOx may produce HOMs in a few OH oxidation steps like commonly detected methyl tetrol (MT) isoprene tracers. The ratio of MTA/MT in isoprene aerosol is also shown to be significantly greater in field versus chamber samples indicating the importance of such pathways in the atmosphere even for smaller hydrocarbons like isoprene.


Assuntos
Laboratórios , Aerossóis , Álcoois , Butadienos , Hemiterpenos , Isomerismo
7.
Sci Total Environ ; 801: 149768, 2021 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-34438153

RESUMO

Isoprene is the most abundant non-methane VOC and a significant SOA contributor. The atmospheric oxidation initiated by atomic chlorine is an important sink for isoprene, especially in certain regions with high Cl concentration, while its detailed oxidation mechanism remains unclear. In this work, we comprehensively investigated the reaction mechanism of isoprene with Cl using quantum chemistry calculation, and first elaborated the specific reaction mechanisms of chloroalkenyl peroxy radicals with HO2/NO and the formation of 2-methylbut-3-enal, highlighting their important roles in the SOA formation. For the initial reactions, Cl additions to terminal carbons and H abstraction from CH3 moiety of isoprene are the predominant reactions, which is consistent with previous research. Following the initial reactions, their subsequent reactions with O2 and HO2 (or NO) under different atmospheric conditions could lead to the formation of 17 highly oxidized molecules (HOMs), of which P10, P12, P16, P17, P19 and P33 generated by the subsequent reactions of the major first-generation products (MVK, CMBO, CMBA and MBO) have been detected in the reaction process of isoprene with Cl in the chamber experiment. In addition to auto-oxidation process, the reaction of chloroalkenyl peroxy radicals with HO2/NO and their subsequent reactions are all easy to occur under atmospheric conditions, which could be crucial contributors to the formation of HOMs and SOA arising from the Cl initiated oxidation of isoprene. This study would be conducive to clarifying the atmospheric oxidation process of isoprene initiated by Cl and providing a new understanding of its SOA formation.


Assuntos
Cloro , Hemiterpenos , Aerossóis , Butadienos , Oxirredução
8.
Sheng Wu Gong Cheng Xue Bao ; 37(6): 2039-2049, 2021 Jun 25.
Artigo em Chinês | MEDLINE | ID: mdl-34227293

RESUMO

Triptolide has wide clinical applications due to its anti-inflammatory, anti-tumor and immunosuppressive activities. In this study, we investigated the effect of blocking isopentenyl pyrophosphate (IPP) translocation on the biosynthesis of triptolide by exogenously adding D,L-glyceraldehyde (DLG) to the suspension cells of Ttripterygium wilfordii at different stages (7 d, 14 d). Subsequently, the cell viability, biomass accumulation, triptolide contents, as well as the profiles of the key enzyme genes involved in the upstream pathway of triptolide biosynthesis, were analyzed. The results showed that IPP translocation is involved in the biosynthesis of triptolide. IPP is mainly translocated from the plastid (containing the MEP pathway) to the cytoplasm (containing the MVA pathway) in the early stage of the culture, but reversed in the late stage. Blocking the translocation of IPP affected the expression of key enzyme genes involved in the upstream pathway of triptolide, which in turn affected the accumulation of triptolide. Understanding the characteristics and mechanism of IPP translocation provides a theoretical basis for further promoting triptolide biosynthesis through synthetic biology.


Assuntos
Diterpenos , Fenantrenos , Compostos de Epóxi , Hemiterpenos , Compostos Organofosforados
9.
Bioresour Technol ; 340: 125634, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34325393

RESUMO

The bacterial degradation of isoprene is important for maintaining its atmospheric concentration in unpolluted environment. It may be possible to use natural isoprene degrading bacteria in engineered systems to eliminate or limit isoprene emissions from various sources. Biodegradation of isoprene by Arthrobacter sp. strain BHU FT2 was investigated. The genome was found to contain 4151545 bp long chromosome having 3747 coding genes, and coded potential isoprene degrading enzymes. The molecular docking of monooxygenases with isoprene displayed a higher binding energy (-4.59 kcal/mol) for WP_015938387.1 monooxygenase. Analysis of the identified monooxygenases with the known isoprene monooxygenases revealed 67% sequence identity of WP_015938387.1 (Locus tag JHV56_10705) monooxygenase of the considered strain with the OPX16961.1 monooxygenase of Gordonia sp. i37 isoprene degrading starin. These results provided a strong evidence for the high isoprene degrading potential of the Arthrobacter sp. BHU FT2 which could be efficiently exploited for isoprene degradation in large scale bio-filtration units.


Assuntos
Arthrobacter , Arthrobacter/genética , Biodegradação Ambiental , Butadienos , Genômica , Hemiterpenos , Simulação de Acoplamento Molecular , Proteômica
10.
mBio ; 12(3): e0076021, 2021 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-34182772

RESUMO

During its complex life cycle, the malaria parasite survives dramatic environmental stresses, including large temperature shifts. Protein prenylation is required during asexual replication of Plasmodium falciparum, and the canonical heat shock protein 40 protein (HSP40; PF3D7_1437900) is posttranslationally modified with a 15-carbon farnesyl isoprenyl group. In other organisms, farnesylation of Hsp40 orthologs controls their localization and function in resisting environmental stress. In this work, we find that plastidial isopentenyl pyrophosphate (IPP) synthesis and protein farnesylation are required for malaria parasite survival after cold and heat shock. Furthermore, loss of HSP40 farnesylation alters its membrane attachment and interaction with proteins in essential pathways in the parasite. Together, this work reveals that farnesylation is essential for parasite survival during temperature stress. Farnesylation of HSP40 may promote thermotolerance by guiding distinct chaperone-client protein interactions.


Assuntos
Proteínas de Choque Térmico HSP40/metabolismo , Plasmodium falciparum/metabolismo , Prenilação de Proteína , Termotolerância , Eritrócitos/parasitologia , Proteínas de Choque Térmico HSP40/genética , Resposta ao Choque Térmico , Hemiterpenos/metabolismo , Interações Hospedeiro-Parasita , Humanos , Estágios do Ciclo de Vida , Compostos Organofosforados/metabolismo , Plasmodium falciparum/genética , Proteínas de Protozoários/genética
11.
Chemosphere ; 283: 131184, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34146869

RESUMO

The north-west Indo-Gangetic Plain is the agricultural cereal-basket of India owing to its prolific wheat and rice production. Surface ozone pollution is of growing concern over it, yet no detailed year-round in-situ measurements of its most reactive precursors, particularly the volatile organic compounds (VOCs) are available from this region. Here, using the first year-long continuous measurements of 23 major VOCs, ozone, NOx, CO and their atmospheric oxidation products from a regionally representative site in north-west India, we evaluated speciated OH reactivities (OHR), ozone formation potential (OFP) and ozone production regimes (OPR) across all seasons. The average seasonal OHR ranged from 14 s-1 (winter) to 21.5 s-1 (summer). We provide the first estimate of OH radical mixing ratios varying between 0.06 and 0.37 ppt in different seasons for the peak daytime hours in this region. Recycling via HO2+NO was the most important pathway contributing to >85% of the OH production throughout the year. Contrary to satellite derived proxies and chemical transport models which predict NOx sensitive OPR, we show it to be strongly sensitive to both VOCs and NOx (>90% days in a year). Remarkably for densely populated regions, isoprene and acetaldehyde collectively accounted for ~30-50% of the total OFP in all seasons. Biogenic emissions of isoprene (reaching 12.9 mg/m2/h) and high acetaldehyde from anthropogenic and photochemical sources were observed for all seasons. Monitoring and control of isoprene and acetaldehyde are therefore urgently required for efforts focused on mitigating surface ozone pollution in this demographically important region of the world.


Assuntos
Poluentes Atmosféricos , Ozônio , Compostos Orgânicos Voláteis , Acetaldeído , Poluentes Atmosféricos/análise , Butadienos , Monitoramento Ambiental , Hemiterpenos , Radical Hidroxila , Índia , Ozônio/análise , Compostos Orgânicos Voláteis/análise
12.
Microbiologyopen ; 10(2): e1174, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33970541

RESUMO

Human body malodour is a complex phenomenon. Several types of sweat glands produce odorless secretions that are metabolized by a consortium of skin-resident microorganisms to a diverse set of malodorous substances. Isovaleric acid, a sweaty-smelling compound, is one major malodorous component produced by staphylococci with the skin-derived amino acid L-leucine as a substrate. During wearing, fabrics are contaminated with sweat and microorganisms and high humidity propagates growth and microbial malodour production. Incomplete removal of sweat residues and microorganisms from fabrics during laundry with bleach-free detergents and at low temperatures elevate the problem of textile malodour. This study aimed to analyze the inhibitory effect of the antimicrobial 4,4' dichloro 2-hydroxydiphenyl ether (DCPP) on the formation of isovaleric acid on fabrics. Therefore, GC-FID- and GC-MS-based methods for the analysis of isovaleric acid in an artificial human sweat-mimicking medium and in textile extracts were established. Here, we show that antimicrobials capable to deposit on fabrics during laundry, such as DCPP, are effective in growth inhibition of typical malodour-generating bacteria and prevent the staphylococcal formation of isovaleric acid on fabrics in a simple experimental setup. This can contribute to increased hygiene for mild laundry care approaches, where bacterial contamination and malodour production represent a considerable consumer problem.


Assuntos
Corynebacterium/efeitos dos fármacos , Corynebacterium/metabolismo , Hemiterpenos/análise , Ácidos Pentanoicos/análise , Prolina/análogos & derivados , Piridinas/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/metabolismo , Anti-Infecciosos/farmacologia , Hemiterpenos/biossíntese , Humanos , Lavanderia , Leucina/metabolismo , Odorantes , Oligopeptídeos , Prolina/farmacologia , Pele/microbiologia , Têxteis/microbiologia
13.
Environ Sci Pollut Res Int ; 28(31): 42562-42569, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33813697

RESUMO

Isoprene can react with sulfoxy radicals (SO4•- and SO3•-) to form organosulfur compounds in aqueous phase, and the organosulfur compounds are important compositions of secondary organic aerosols (SOAs). To make sure the specific configurations of the products and the role of SO4•- and SO3•- in the formation of organosulfur compounds, the reaction mechanisms are studied by theoretical calculations. The lowest Gibbs free energy barrier of addition of SO3•- onto isoprene is 24.06 kcal mol-1 at C4 site, and its rate constant is 1.30 × 10-11 M-1 s-1 at 298 K and 1 atm. And the Gibbs free energy barriers of addition of SO4•- onto isoprene at C1 and C4 sites are barrierless and 0.92 kcal mol-1; the rate constants of these two addition processes are 6.85 × 109 and 1.17 × 105 M-1 s-1 at 298 K and 1 atm. It elucidates that organosulfates are easier to be formed. As for the products P1 (with alcohol group) and P2 (with aldehyde group), the lowest Gibbs free energy barrier of the formation of P1 is 3.17 kcal mol-1, and that of the formation of P2 is 15.84 kcal mol-1, which means that the product with alcohol group is easier to be formed than that with aldehyde group. This work provides a reference for the formation of organosulfur compounds in aqueous phase, and it may help to understand the SOA formation.


Assuntos
Butadienos , Hemiterpenos , Aerossóis , Água
14.
Astrobiology ; 21(7): 765-792, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33798392

RESUMO

The search for possible biosignature gases in habitable exoplanet atmospheres is accelerating, although actual observations are likely years away. This work adds isoprene, C5H8, to the roster of biosignature gases. We found that isoprene geochemical formation is highly thermodynamically disfavored and has no known abiotic false positives. The isoprene production rate on Earth rivals that of methane (CH4; ∼500 Tg/year). Unlike methane, on Earth isoprene is rapidly destroyed by oxygen-containing radicals. Although isoprene is predominantly produced by deciduous trees, isoprene production is ubiquitous to a diverse array of evolutionary distant organisms, from bacteria to plants and animals-few, if any, volatile secondary metabolites have a larger evolutionary reach. Although non-photochemical sinks of isoprene may exist, such as degradation of isoprene by life or other high deposition rates, destruction of isoprene in an anoxic atmosphere is mainly driven by photochemistry. Motivated by the concept that isoprene might accumulate in anoxic environments, we model the photochemistry and spectroscopic detection of isoprene in habitable temperature, rocky exoplanet anoxic atmospheres with a variety of atmosphere compositions under different host star ultraviolet fluxes. Limited by an assumed 10 ppm instrument noise floor, habitable atmosphere characterization when using James Webb Space Telescope (JWST) is only achievable with a transit signal similar or larger than that for a super-Earth-sized exoplanet transiting an M dwarf star with an H2-dominated atmosphere. Unfortunately, isoprene cannot accumulate to detectable abundance without entering a run-away phase, which occurs at a very high production rate, ∼100 times the Earth's production rate. In this run-away scenario, isoprene will accumulate to >100 ppm, and its spectral features are detectable with ∼20 JWST transits. One caveat is that some isoprene spectral features are hard to distinguish from those of methane and also from other hydrocarbons containing the isoprene substructure. Despite these challenges, isoprene is worth adding to the menu of potential biosignature gases.


Assuntos
Exobiologia , Meio Ambiente Extraterreno , Atmosfera , Butadienos , Gases , Hemiterpenos , Planetas
15.
Environ Sci Technol ; 55(8): 4399-4409, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33769798

RESUMO

The atmospheric chemistry of isoprene has broad implications for regional air quality and the global climate. Allylic radicals, taking 13-17% yield in the isoprene oxidation by •Cl, can contribute as much as 3.6-4.9% to all possible formed intermediates in local regions at daytime. Considering the large quantity of isoprene emission, the chemistry of the allylic radicals is therefore highly desirable. Here, we investigated the atmospheric oxidation mechanism of the allylic radicals using quantum chemical calculations and kinetics modeling. The results indicate that the allylic radicals can barrierlessly combine with O2 to form peroxy radicals (RO2•). Under ≤100 ppt NO and ≤50 ppt HO2• conditions, the formed RO2• mainly undergo two times "successive cyclization and O2 addition" to finally form the product fragments 2-alkoxy-acetaldehyde (C2H3O2•) and 3-hydroperoxy-2-oxopropanal (C3H4O4). The presented reaction illustrates a novel successive cyclization-driven autoxidation mechanism. The formed 3-hydroperoxy-2-oxopropanal product is a new isomer of the atmospheric C3H4O4 family and a potential aqueous-phase secondary organic aerosol precursor. Under >100 ppt NO condition, NO can mediate the cyclization-driven autoxidation process to form C5H7NO3, C5H7NO7, and alkoxy radical-related products. The proposed novel autoxidation mechanism advances our current understanding of the atmospheric chemistry of both isoprene and RO2•.


Assuntos
Butadienos , Hemiterpenos , Aerossóis , Ciclização
16.
J Agric Food Chem ; 69(12): 3712-3719, 2021 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-33734707

RESUMO

3-Hydroxy-3-methylbutyrate (HMB) is an important compound that can be used for the synthesis of a variety of chemicals in the food and pharmaceutical fields. Here, a biocatalytic method using l-leucine as a substrate was designed and constructed by expressing l-amino acid deaminase (l-AAD) and 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) in Escherichia coli. To reduce the influence of the rate-limiting step on the cascade reaction, two 4-HPPD mutants were screened by rational design and both showed improved catalytic activity. Under optimal reaction conditions, the maximum conversion rate and production rate were 80% and 0.257 g/L·h, respectively. HMB production could be realized with high efficiency without an additional supply of adenosine triphosphate (ATP), which successfully overcomes the shortcomings of chemical production and fermentation methods. This design-based strategy of constructing a whole-cell catalyst system from l-leucine might serve as an alternative route to HMB synthesis.


Assuntos
Hemiterpenos , Ácidos Pentanoicos , Biocatálise , Leucina/metabolismo , Valeratos
17.
J Agric Food Chem ; 69(13): 3797-3821, 2021 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-33761246

RESUMO

As the second natural rubber resource, Eucommia ulmoides rubber (EUR) from Eucommia ulmoides Oliver is mainly composed of trans-1,4-polyisoprene, which is the isomer of natural rubber cis-1,4-polyisoprene from Hevea brasiliensis. In the past few years, the great potential application of EUR has received increasing attention, and there is a growing awareness that the natural polymer EUR could become an emerging research topic in field of the novel materials due to its unique and excellent duality of both rubber and plastic. To gain insight into its further development, in this review, the extraction, structure, physicochemical properties, and modification of EUR are discussed in detail. More emphasis on the potential applications in the fields of the environment, agriculture, engineering, and biomedical engineering is summarized. Finally, some insights into the challenges and perspectives of EUR are also suggested.


Assuntos
Eucommiaceae , Hevea , Hemiterpenos , Polímeros , Borracha
18.
J Neuroimaging ; 31(3): 517-523, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33783911

RESUMO

BACKGROUND AND PURPOSE: The role of the cerebellum in olfactory function is not fully understood. In this study, we tried to combine resting state and task functional MRI (fMRI) to improve the understanding of the cerebellum during olfactory processing. METHODS: A resting state and a block paradigm of olfactory stimulation fMRI were scanned in 50 subjects. The olfactory stimuli, including phenylethyl alcohol and isovaleric acid, were alternately delivered to the subject using a custom-built olfactometer through air flow. The cerebellar activations elicited by isovaleric acid were subsequently used in the seed-based resting-state functional connectivity study. RESULTS: Phenylethyl alcohol did not induce any cerebellum activation, while isovaleric acid with a more unpleasant smell elicited significant cerebellum activations, primarily in the bilateral posterior lateral hemispheres (bilateral lobule crus I and right lobule VI). Seed-based functional connectivity analysis revealed significant within-cerebellum and corticocerebellar connections. CONCLUSIONS: The results imply that the cerebellum is probably involved in olfactory-related responses caused by unpleasant odor but does not directly participate in olfactory perception. Our results may further improve the understanding of the cerebellum in olfactory function.


Assuntos
Mapeamento Encefálico/métodos , Cerebelo/diagnóstico por imagem , Cerebelo/fisiologia , Neuroimagem Funcional/métodos , Imageamento por Ressonância Magnética/métodos , Olfato/fisiologia , Adulto , Feminino , Hemiterpenos/química , Humanos , Masculino , Ácidos Pentanoicos/química , Álcool Feniletílico/química
19.
Bioorg Med Chem Lett ; 40: 127967, 2021 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-33753259

RESUMO

An ethanolic extract of Derris scandens flowers showed potent preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrient-deprived condition, with a PC50 value of 0.7 µg/mL. Phytochemical investigation of this active extract led to the isolation of four prenylated isoflavones (1-4) including a new compound named 4'-O-methylgrynullarin (1). The structure elucidation of the new compound was achieved by HRFABMS and NMR spectroscopic analysis. The isolated compounds exhibited potent anti-austerity activity against four different human pancreatic cancer cell lines under nutrient-deprived conditions. The new compound 4'-O-methylgrynullarin (1) was also found to inhibit PANC-1 cell migration and colony formation under nutrient-rich condition. Mechanistically, compound 1 inhibited key survival proteins in the Akt/mTOR signaling pathway. Therefore, 4'-O-methylgrynullarin (1) can be considered as a potential lead compound for the anticancer drug development based on the anti-austerity strategy.


Assuntos
Antineoplásicos Fitogênicos/farmacologia , Morte Celular/efeitos dos fármacos , Hemiterpenos/farmacologia , Isoflavonas/farmacologia , Neoplasias Pancreáticas/tratamento farmacológico , Transdução de Sinais/efeitos dos fármacos , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/isolamento & purificação , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Derris/química , Ensaios de Seleção de Medicamentos Antitumorais , Flores/química , Hemiterpenos/síntese química , Hemiterpenos/isolamento & purificação , Humanos , Isoflavonas/química , Isoflavonas/isolamento & purificação , Proteínas Proto-Oncogênicas c-akt/metabolismo , Serina-Treonina Quinases TOR/metabolismo
20.
J Cell Mol Med ; 25(9): 4287-4297, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33768674

RESUMO

Osteoclasts (OCs) play important roles in bone remodelling and contribute to bone loss by increasing bone resorption activity. Excessively activated OCs cause diverse bone disorders including osteoporosis. Isovaleric acid (IVA), also known as 3-methylbutanoic acid is a 5-carbon branched-chain fatty acid (BCFA), which can be generated by bacterial fermentation of a leucine-rich diet. Here, we find that IVA suppresses differentiation of bone marrow-derived macrophages into OCs by RANKL. IVA inhibited the expression of OC-related genes. IVA-induced inhibitory effects on OC generation were attenuated by pertussis toxin but not by H89, suggesting a Gi -coupled receptor-dependent but protein kinase A-independent response. Moreover, IVA stimulates AMPK phosphorylation, and treatment with an AMPK inhibitor blocks IVA-induced inhibition of OC generation. In an ovariectomized mouse model, addition of IVA to the drinking water resulted in significant decrease of body weight gain and inhibited the expression of not only OC-related genes but also fusogenic genes in the bone tissue. IVA exposure also blocked bone destruction and OC generation in the bone tissue of ovariectomized mice. Collectively, the results demonstrate that IVA is a novel bioactive BCFA that inhibits OC differentiation, suggesting that IVA can be considered a useful material to control osteoclast-associated bone disorders, including osteoporosis.


Assuntos
Reabsorção Óssea/prevenção & controle , Diferenciação Celular , Hemiterpenos/farmacologia , Osteoclastos/citologia , Osteoporose/prevenção & controle , Ovariectomia/efeitos adversos , Ácidos Pentanoicos/farmacologia , Animais , Remodelação Óssea , Reabsorção Óssea/etiologia , Reabsorção Óssea/patologia , Feminino , Macrófagos/citologia , Macrófagos/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Osteoclastos/efeitos dos fármacos , Osteoporose/patologia , Osteoporose/cirurgia , Transdução de Sinais
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