Reductive Stress of Sulfur-Containing Amino Acids within Proteins and Implication of Tandem Protein–Lipid Damage

Reductive radical stress represents the other side of the redox spectrum, less studied but equally important compared to oxidative stress. The reactivity of hydrogen atoms (H•) and hydrated electrons (e–aq) connected with peptides/proteins is summarized, focusing on the chemical transformations of methionine (Met) and cystine (CysS–SCys) residues into α-aminobutyric acid and alanine, respectively. Chemical and mechanistic aspects of desulfurization processes with formation of diffusible sulfur-centered radicals, such as methanethiyl (CH3S•) and sulfhydryl (HS•) radicals, are discussed. These findings are further applied to biomimetic radical chemistry, modeling the occurrence of tandem protein–lipid damages in proteo-liposomes and demonstrating that generation of sulfur-centered radicals from a variety of proteins is coupled with the cis–trans isomerization of unsaturated lipids in membranes. Recent applications to pharmaceutical and pharmacological contexts are described, evidencing novel perspectives in the stability of formulations and mode of action of drugs, respectively.

Comparison of Performance of Flamelet Generated Manifold Model With That of Finite Rate Combustion Model for Hydrogen Blended Flames

International Air Transport Association (IATA) sets a 50% reduction in 2005 CO2 emissions levels by 2050, with no increase in net emissions after 2020 [1]. The association also expects the global aviation demand to double to 8.2 billion passengers per year by 2037. These issues have prompted the aviation industry to focus intensely on adopting sustainable aviation fuels (SAF). Further, reduction in CO2 emission is also an active area of research for land-based power generation gas turbine engines. And fuels with high hydrogen content or hydrogen blends are regarded as an essential part of future power plants. Therefore, clean hydrogen and other hydrogen-based fuels are expected to play a critical role in reducing greenhouse gas emissions in the future. However, the massive difference in hydrogen’s physical properties compared to hydrocarbon fuels, ignition, and flashback issues are some of the major concerns, and a detailed understanding of hydrogen combustion characteristics for the conditions at which gas turbines operate is needed. Numerical combustion analyses can play an essential role in exploring the combustion performance of hydrogen as an alternative gas turbine engine fuel. While several combustion models are available in the literature, two of the most preferred models in recent times are the flamelet generated manifold (FGM) model and finite-rate (FR) combustion model. FGM combustion model is computationally economical compared to the detailed/reduced chemistry modeling using a finite-rate combustion model. Therefore, this paper aims to understand the performance of the FGM model compared to detailed chemistry modeling of turbulent flames with different levels of hydrogen blended fuels. In this paper, a detailed comparison of different combustion characteristics like temperature, species, flow, and NOx distribution using FGM and finite rate combustion models is presented for three flame configurations, including the DLR Stuttgart jet flame [2], Bluff body stabilized Sydney HM1 flame [3] and dry-low-NOx hydrogen micro-mix combustion chamber [4]. One of the FGM model’s essential parameters is to select a suitable definition of the reaction progress variable. The reaction progress variable should monotonically increase from the unburnt region to the burnt region. The definition is first studied using a 1D premixed flame with different blend ratios and then used for the actual cases. 2D/3D simulations for the identified flames are performed using FGM and finite rate combustion models. Numerical results from both these models are compared with the available experimental data to understand FGM’s applicability. The results show that the FGM model performs reasonably well for pure hydrogen and hydrogen blended flames.

Digital Oil Model Development and Verification

Advances in digital technologies have the potential to enhance model predictive capability and redefine its boundaries at various scale. Digital oil with accurate representation of atomistic components is a powerful tool to analyze both macroscopic properties and microscopic phenomena of crude oil under any thermodynamic conditions. Digital oil model presented in this paper is the key input in molecular chemistry modeling for designing chemical enhanced oil recovery formulation. Hence, it is constructed based on a fit-for purpose strategy focusing in oil components that have large contribution to microemulsion stability. Complete crude oil composition could comprise over 100,000 components. Lengthy simulation time is required to simulate all crude oil components which is impratical, despite the challenges to identify all crude oil components experimentally. Therefore, we established a practical experimental strategy to identify key crude oil components and constructed the digital oil model based on surrogate components. The surrogate components are representative molecules of the volatiles, saturates, aromatics and resins. Two-dimensional digital oil model, with aromaticity on one axis, and the size of the molecules on the other axis was constructed. We developed algorithm to integrate nuclear magnetic resonance response with architecture of the molecular structure. A group contribution method was implemented to ensure reliable representation of the molecular structure. We constructed the digital oil models for a field in Malaysia Basin. We validated the physical properties of the digital oil model with properties measured from experiment, predicted from molecular dynamics simulation and calculated from quantitative property-property relationship method. Good agreement was obtained from the validation, with less than 5% and 13% variance in crude density and Equivalent Alkane Carbon Number respectively, indicating that the molecular characteristic of the digital oil model was captured correctly. We adopted the digital oil model in molecular chemistry modeling to gain insights into microemulsion formation in chemical enhanced oil recovery formulation design. Digital oil is a robust tool to make predictions when information cannot be extracted from experimental data alone. It can be extended for engineering applications involving processing, safety, hazard, and environmental considerations.

Future changes in isoprene-epoxydiol-derived secondary organic aerosol (IEPOX SOA) under the Shared Socioeconomic Pathways: the importance of physicochemical dependency

Secondary organic aerosol (SOA) is a dominant contributor of fine particulate matter in the atmosphere, but the complexity of SOA formation chemistry hinders the accurate representation of SOA in models. Volatility-based SOA parameterizations have been adopted in many recent chemistry modeling studies and have shown a reasonable performance compared to observations. However, assumptions made in these empirical parameterizations can lead to substantial errors when applied to future climatic conditions as they do not include the mechanistic understanding of processes but are rather fitted to laboratory studies of SOA formation. This is particularly the case for SOA derived from isoprene epoxydiols (IEPOX SOA), for which we have a higher level of understanding of the fundamental processes than is currently parameterized in most models. We predict future SOA concentrations using an explicit mechanism and compare the predictions with the empirical parameterization based on the volatility basis set (VBS) approach. We then use the Community Earth System Model 2 (CESM2.1.0) with detailed isoprene chemistry and reactive uptake processes for the middle and end of the 21st century under four Shared Socioeconomic Pathways (SSPs): SSP1–2.6, SSP2–4.5, SSP3–7.0, and SSP5–8.5. With the explicit chemical mechanism, we find that IEPOX SOA is predicted to increase on average under all future SSP scenarios but with some variability in the results depending on regions and the scenario chosen. Isoprene emissions are the main driver of IEPOX SOA changes in the future climate, but the IEPOX SOA yield from isoprene emissions also changes by up to 50 % depending on the SSP scenario, in particular due to different sulfur emissions. We conduct sensitivity simulations with and without CO2 inhibition of isoprene emissions that is highly uncertain, which results in factor of 2 differences in the predicted IEPOX SOA global burden, especially for the high-CO2 scenarios (SSP3–7.0 and SSP5–8.5). Aerosol pH also plays a critical role in the IEPOX SOA formation rate, requiring accurate calculation of aerosol pH in chemistry models. On the other hand, isoprene SOA calculated with the VBS scheme predicts a nearly constant SOA yield from isoprene emissions across all SSP scenarios; as a result, it mostly follows isoprene emissions regardless of region and scenario. This is because the VBS scheme does not consider heterogeneous chemistry; in other words, there is no dependency on aerosol properties. The discrepancy between the explicit mechanism and VBS parameterization in this study is likely to occur for other SOA components as well, which may also have dependencies that cannot be captured by VBS parameterizations. This study highlights the need for more explicit chemistry or for parameterizations that capture the dependence on key physicochemical drivers when predicting SOA concentrations for climate studies.

Recent updates to the atmospheric chemistry modeling of the ECMWF IFS in support to CAMS

<p>The Integrated Forecasting System (IFS) of ECMWF is the core of the Copernicus Atmosphere Monitoring Service (CAMS) which provides global analyses and forecasts of atmospheric composition, namely reactive gases, aerosol and greenhouse gases. With respect to the atmospheric chemistry component, the operational system currently relies on a modified version of the CB05 chemistry scheme for the troposphere, combined with the Cariolle scheme to describe stratospheric ozone. In an alternative, more recent configuration also stratospheric ozone chemistry is included based on the BASCOE chemistry module. Alternative atmospheric chemistry modules which can be employed are based on MOZART and MOCAGE chemistry. <br>Recently, further revisions to the modified CB05 tropospheric chemistry scheme have been developed, focusing both on inorganic and organic chemistry, with the aim of improving the quality of existing air-quality products, and the development of new products. On major update is a revision of the isoprene oxidation scheme based on those employed in existing chemistry transport models, as well as inclusion of the basic chemistry describing C8 and C9 aromatics degradation. <br>An example of a new product derived from these updates include a description of global distribution of glyoxal, while this also resulted in an improved modeling of OH recycling particularly over tropical forests. Also we support improved secondary organic aerosol formation due to gaseous anthropogenic, biogenic and biomass burning sources.<br>In this contribution we provide an overview of these revisions, and provide a first quantification of their uncertainties, by comparing products to observations and to those from alternative chemistry modules.</p>

Carbonate Replacement as the Principal Ore Formation Process in the Proterozoic McArthur River (HYC) Sediment-Hosted Zn-Pb Deposit, Australia

The McArthur River (HYC) Zn-Pb-Ag deposit in the Carpentaria Zn belt, northern Australia, is one of the world’s largest and most studied sediment-hosted base metal deposits, owing to its lack of deformation and preservation of sedimentary and ore textures. However, the ore formation process (syngenetic vs. epigenetic) is still a subject of controversy. In this paper we focus on key characteristics of the HYC deposit that remain unexplained: preservation of sedimentary carbonate (dolomite) and its association with Zn, and the role of thallium (Tl) and manganese (Mn) distribution in the orebody. Our findings demonstrate a sequence of events during ore formation: Tl is hosted almost exclusively within euhedral pyritic overgrowths around early diagenetic pyrite; sphalerite mineralization occurred after Tl-bearing pyrite overgrowths, in association with acid dissolution (replacement) of laminated and nodular dolomite across the subbasin; and outer rims are enriched in Mn on preserved dolomite at the dissolution reaction front in contact with sphalerite. New thermodynamic fluid chemistry modeling demonstrates the metal distribution and paragenesis can be explained by acidic, oxidized ore fluids entering the pyrite-dolomite host lithology, allowing reduction and pH buffering by acid carbonate dissolution, resulting in stepwise metal deposition in an evolving fluid. We argue this represents strong evidence for epigenetic ore formation at HYC. Furthermore, the primary control on ore deposition is not synsedimentary faulting in the subbasin; rather, the chemical potential of sedimentary carbonate within reduced, sulfidic lithologies appears to be of critical importance to precipitation of sphalerite.