High Molar Research Articles

In vitro DIAAS of Swiss soybean cultivars using the INFOGEST model: Increase in protein quality from soybean to soymilk and tofu

To support the transition towards more sustainable and healthy diets, viable alternatives to foods of animal origin need to be identified. Many plant-based protein sources are currently marketed with claims of minimal environmental impact, but very limited consideration has been given to their protein quality and bioavailable mineral content considering the fact that animal-based foods are typically the primary source of both in Western diets. In this study, traditionally consumed soy foods (cooked soybeans, soymilk, tofu) from different Swiss soybean cultivars were nutritionally characterized and the in vitro digestibility of individual amino acids and total protein were assessed using an in vitro model based on the static INFOGEST protocol; the protein quality was evaluated using the in vitro digestible indispensable amino acid score (DIAAS). The results reveal an increase in total protein in vitro digestibility across the traditional soy food production value chain: 52.1–62.7% for cooked soybeans, 84.1–90.6% for soymilk, and 94.9–98.4% for tofu. Protein quality, determined using the recommended amino acid pattern for 0.5–3 years old, was “low” (no claim) for cooked soybeans (DIAAS < 60), while soymilk (DIAAS = 78–88) and tofu products (DIAAS = 79–91) were of similar “good” protein quality, with considerably higher DIAAS values than those of cooked soybeans (P < 0.001). The iron and zinc contents in soy foods were substantial, but high molar ratios of phytic acid (PA) to iron (PA/Fe; >8) and PA to zinc (PA/Zn; >15) indicate a possible strong inhibition of iron and zinc bioavailability. Based on the DIAAS results, soymilk and tofu would be suitable plant-based alternatives to animal-based foods, while future efforts should focus on optimizing soybean preparation to overcome the negative effects of the plant tissue matrix as well as processing steps to reduce mineral absorption inhibiting substances.

Effect of natural organic matter (NOM) on the removal efficiency of Hg(ii) by MoS2: dependence on the Hg/MoS2 ratio and NOM properties

In groundwater, the efficiency of MoS2 nanosheets for Hg(ii) removal is significantly hindered by natural organic matter (NOM) at high molar ratios of Hg/MoS2, whereas at low ratios, NOM has minimal impact on Hg(ii) removal.

Thiol-selective native grafting from polymerization for the generation of protein-polymer conjugates.

Protein-polymer conjugates combine properties of biopolymers and synthetic polymers, such as specific bioactivity and increased stability, with great benefits for various applications from catalysis to biomedicine. Furthermore, polymer conjugation can mimic important posttranslational modifications of proteins such as glycosylation. There are typically two approaches to create protein-polymer conjugates: the protein is functionalized in advance with an initiator for a grafting-from method or a previously produced polymer is conjugated to the protein via a grafting-to method. In this study, we present a new approach that uses native proteins and allows for direct grafting-from using a thiol-induced, light-activated controlled radical polymerization (TIRP) that is initiated at thiols from specific cysteine residues of the protein. This straightforward method is employed to introduce polymers onto proteins and enzymes without any prior protein modifications, it works in aqueous buffer and maintains the protein's native structure and activity. The resulting protein-polymer conjugates exhibit high molar masses and low dispersities. We demonstrate the versatility of this approach by introducing different types of polymers such as hydrophilic poly(2-hydroxyethyl acrylate) (pHEAA), temperature-responsive poly(N-isopropylacrylamide) (pNIPAM) as well as glycopolymers mimicking the natural protein glycosylation and enabling selective interactions. We present successful combinations of the protein and polymer functions e.g., temperature-induced aggregation leading to an increase in enzyme activity and the introduction of artificial glycosylation inducing specific protein-protein cluster formation and giving straightforward access to glycosurfaces. Based on this straightforward, potentially scalable yet highly controlled synthesis of protein-polymer conjugates, various areas of applications are envisioned ranging from biomedicine to material sciences.

Synthesis of 18F-labelled aryl trifluoromethyl ketones with improved molar activity.

A method for the radiosynthesis of 18F-labelled aryl trifluoromethyl ketones starting from widely available Weinreb amides using [18F]fluoroform is presented. The method uses potassium hexamethyldisilazane as base and delivers products in high molar activity (up to 24 GBq μmol-1) and excellent radiochemical conversions. The applicability for PET tracer synthesis is demonstrated by the radiosynthesis of ten (hetero)aryl trifluoromethylketones, bearing electron-withdrawing and -donating substituents including a derivative of bioactive probenecid.

Determination of Molecular Dimensions of Carbohydrate Polymers (Polysaccharides) by Size Exclusion Chromatography (SEC).

Calibrated size exclusion chromatography (SEC) is a useful tool for the analysis of molecular dimensions of polysaccharides. The calibration takes place with a set of narrow distributed dextran standards and peak position technique. Adapted columns systems and dissolving processes enable for the adequate separation of carbohydrate polymers. Plant-extracted fructan (ahomopolymer with low molar mass and excellent water solubility) and mucilage (differently structured, high molar massheteropolysaccarides that includeexisting supramolecular structures, and require a long dissolving time) are presented as examples of the versatility of this technique. Since narrow standards similar to the samples (chemically and structurally) are often unavailable, it must be noted that the obtained molar mass values and distributions by this method are only apparent (relative) values, expressed as dextran equivalents.

Potentiating light-harvesting tactics through an A-D-A structure: repolarization of tumor-associated macrophages through phototherapy.

Aiming to decrease the recurrence of tumors and achieve patient satisfaction, the elicitation of immunotherapy and its integrated synergistic employment is a bright new direction in oncotherapy, yet an emergently challenging task. In particular, tumor-associated macrophage (TAM) regulation though light-induced photodynamic and photothermal therapy (PDT and PTT) is regarded as a powerful approach, which focuses on the systemic immune system instead of the tumor itself. Herein, this study reports an acceptor-donor-acceptor (A-D-A) aggregation-induced emission luminogen (AIEgen), named TPA-2CN, which was applied as a photosensitizer (PS) and photothermal agent (PTA). Attributed to its A-D-A structure and AIE properties, TPA-2CN exhibits a high molar absorption coefficient and acts as a perfect template in regulating radiative and nonradiative transitions, which mainly utilize excited energy. The generation of type I reactive oxygen promoted its application in hypoxic tumor sites and the combination of hyperpyrexia forcefully induces macrophages to polarize towards the immune response M1 phenotype. In in vitro and in vivo, the successful reversion and reprogramming of the immune microenvironment was impressively proved. This method optimally concentrated immune therapy, PDT and PTT as one and exhibited excellent synergistic therapeutic effects with good biosafety.

Controlled ring-opening (co)polymerization of macrolactones: a pursuit for efficient aluminum-based catalysts

This work reports on the search for highly efficient aluminum-based complexes for the synthesis of high molar mass polymacrolactones and their well-defined block copolymers with small ring lactones, ε-caprolactone and l-lactide.

Hydrogen Sulfide Adsorption from Natural Gas Using Silver-Modified 13X Molecular Sieve.

The removal of hydrogen sulfide from natural gas and other gases such as biogas, refinery gases, and coal gas is required because it is toxic and corrosive, even in traces. Zeolites are widely used in the removal of H2S from the abovementioned gases. In this work, we prepared an Ag-exchanged 13X molecular sieve by using different concentrations of AgNO3 to increase its adsorption properties. XRD, SEM, and BET techniques were used to characterize samples. To determine the adsorption properties of each of the samples, a laboratory setup with a fixed-bed adsorber was utilized. The adsorption capacity of modified 13X increased when the molar concentration of AgNO3 increased from 0.02 M to 0.05 M. However, the breakthrough time was attained quicker at a high molar concentration of 0.1 M AgNO3, indicating a low adsorption capacity. When compared to unmodified 13X, the adsorption capacity of AgII-13X increased by about 50 times. The results of this study suggest that the silver-modified 13X molecular sieve is highly effective at extracting H2S from natural gas.

Chelation chemistry of manganese-52 for PET imaging applications

IntroductionDue to its decay and chemical properties, interest in manganese-52 has increased for development of long-lived PET radiopharmaceuticals. Its long half-life of 5.6 days, low average positron energy (242 keV), and sufficient positron decay branching ratio make it suitable for radiolabeling macromolecules for investigating slow biological processes. This work aims to establish suitable chelators for manganese-52 that can be radiolabeled at mild conditions through the evaluation of commercially available chelators. MethodsManganese-52 was produced through the nuclear reaction NatCr(p,n)52Mn by irradiation of natural chromium targets on a TR24 cyclotron followed by purification through ion exchange chromatography. The radiolabeling efficiencies of chelators: DOTA, DiAmsar, TETA, DO3A, NOTA, 4′-Formylbenzo-15-crown-5, Oxo-DO3A, and DFO, were assessed by investigating the impact of pH, buffer type, and temperature. In vitro stability of [52Mn]Mn(DO3A)−, [52Mn]Mn(Oxo-DO3A)−, and [52Mn]Mn(DOTA)2− were evaluated in mouse serum. The radiocomplexes were also evaluated in vivo in mice. Crystals of [Mn(Oxo-DO3A)]− were synthesized by reacting Oxo-DO3A with MnCl2 and characterized by single crystal X-ray diffraction. ResultsYields of 185 ± 19 MBq (5.0 ± 0.5 mCi) (n = 4) of manganese-52 were produced at the end of a 4 h, 15 μA, bombardment with 12.5 MeV protons. NOTA, DO3A, DOTA, and Oxo-DO3A chelators were readily radiolabeled with >96 % radiochemical purity at all conditions. Manganese radiocomplexes of Oxo-DO3A, DOTA, and DO3A remained stable in vitro up to 5 days and exhibited different biodistribution profiles compared to [52Mn]MnCl2. The solid-state structure of Mn-Oxo-DO3A complex was determined by single-crystal X-ray diffraction. ConclusionsDO3A and Oxo-DO3A are suitable chelators for manganese-52 which are readily radiolabeled at mild conditions with high molar activity, and demonstrate both in vitro and in vivo stability.

Fundamental Understanding of the Behavior Under Aging of Aqueous Magnesium-Based Concentrated Electrolytes

The concept of water-in-salt electrolytes (WISEs)1, implying highly concentrated aqueous solutions, has completely rejuvenated the aqueous systems. These electrolytes can be depicted as few water molecules surrounded by cations and anions forming ion pairs. This change of solvation structure compared to standard electrolytes increases the electrochemical stability window. For example, using 20 molal (molality: m, moles per kg) lithium (bistrifluoromethanesulfonyl(imide) (LiTFSI) aqueous solutions, a stability window of 3 V is reached.1 While WISEs open the way for sustainable systems, these solutions only use expensive and toxic lithium salts. To move towards more sustainable elements, one can envision magnesium and associated salts: safer, less expensive and more abundant than lithium. Yet, the state-of-the-art on water-in-salt aqueous Mg batteries is scarce,2,3 with potential windows reaching only 2-2.3 V. There is no clear understanding of the mechanisms at work but the low solubility of Mg salts could account for the narrow potential window. Rationalizing reactivity of water-in-salt solutions on a fundamental level is critical to design efficient strategies to increase the voltage window of concentrated aqueous Mg batteries. We investigated the Mg(TFSI)2/H2O system with radiolysis, a technique which provides a chemical approach4 to exacerbate in a short time the degradation mechanisms. The aging process with radiolysis is much shorter than the electrochemical one and mimics the products of salt and solvent degradation observed during long battery operation. We performed radiolysis to study and compare Mg(TFSI)2 and LiTFSI-based electrolytes with different molalities. Degradation products formed after irradiation were identified using Nuclear Magnetic Resonance spectroscopy (NMR) for the liquid phase, and with gas chromatography coupled to mass spectrometry (GC-MS) and micro-gas chromatography (μ-GC) for the gas phase. For example, the evolution of the amount of H2 and CO2 gases in the case of LiTFSI or Mg(TFSI)2/H2O electrolytes show large discrepancies, hinting at a preferential anion degradation in the Mg system. Overall, the nature of the degradation species strongly depends on the molality, with degradation routes driven by the water or the anion at low or high molalities. Finally, radiolysis allows to identify minor species, providing a view of the long-term (un)stability of these electrolytes.

Chromatographic separation of silver-111 from neutron-irradiated palladium target: toward direct labeling of radiotracers

BackgroundSilver-111 is a promising β−-emitting radioisotope with ideal characteristics for targeted radionuclide therapy and associated single photon emission tomography imaging. Its decay properties closely resemble the clinically established lutetium-177, making it an attractive candidate for therapeutic applications. In addition, the clinical value of silver-111 is further enhanced by the existence of the positron-emitting counterpart silver-103, thus imparting a truly theranostic potential to this element. A so-fitting matching pair could potentially overcome the current limitations associated with the forced use of chemically different isotopes as imaging surrogates of lutetium-177, leading to more accurate and efficient diagnosis and treatment. However, the use of silver-111-based radiopharmaceuticals in vivo has faced obstacles due to the challenges related to its production and radiochemical separation from the target material. To address these issues, this study aims to implement a chromatographic separation methodology for the purification of reactor-produced silver-111. The ultimate goal is to achieve a ready-to-use formulation for the direct radiolabeling of tumour-seeking biomolecules.ResultsA two-step sequence chromatographic process was validated for cold Ag-Pd separation and then translated to the radioactive counterpart. Silver-111 was produced via the 110Pd(n,γ)111Pd nuclear reaction on a natural palladium target and the subsequent β−-decay of palladium-111. Silver-111 was chemically separated from the metallic target via the implemented chromatographic process by using commercially available LN and TK200 resins. The effectiveness of the separations was assessed by inductively coupled plasma optical emission spectroscopy and γ-spectrometry, respectively, and the Ag+ retrieval was afforded in pure water. Recovery of silver-111 was > 90% with a radionuclidic purity > 99% and a separation factor of around 4.21·10−4.ConclusionsThe developed separation method was suitable to obtain silver-111 with high molar activity in a ready-to-use water-based formulation that can be directly employed for the labeling of radiotracers. By successfully establishing a robust and efficient production and purification method for silver-111, this research paves the way for its wider application in targeted radionuclide therapy and precision imaging.

Exploration of Directing-Group-Assisted, Copper-Mediated Radiofluorination and Radiosynthesis of [18F]Olaparib.

Copper-mediated radiofluorination (CMRF) of organoboronic precursors is the method of choice for late-stage radiofluorination of aromatic compounds as positron emission tomography (PET) radiotracers. However, CMRF generally requires harsh reaction conditions, a large amount of substrates, and harsh solvents (e.g., DMA) to proceed, affording variable radiochemical yields (RCYs). Using [18F]tosyl fluoride as the source of [18F]fluoride, we have found a highly efficient CMRF of organoboronic precursors, assisted by a directing group (DG) at the ortho position. The reaction can be carried out under mild conditions (even at room temperature) in acetonitrile and results in high RCYs, providing a novel strategy for the radiofluorination of aromatic compounds. The exploration of this strategy also provided more information about side reactions in CMRF. Using this strategy, [18F]olaparib has been radiosynthesized in high RCYs, with high molar activity and high chemical and radiochemical purities, demonstrating the great potential of DG-assisted CMRF in the preparation of 18F-labeled PET radiotracers.

Enhancement of optical and radiation shielding properties in calcium–magnesium silicate bioactive glasses through Na2O and P2O5 additives

The present study investigates the influence of Na2O/MgO and P2O5/SiO2 substitutions on the structure and protective properties of bioactive glasses composed of 32CaO–19MgO–0.5P2O5–0.5CaF2–48SiO2 (mole %). The glass samples are prepared using the conventional melt-quenching method. Optical analyses, including refractive index (n), molar refraction (Rm), and cationic polarizability (αm), are calculated and discussed to examine structural modifications. Raman spectroscopy is employed for detailed structural analysis. The effects of compositional changes on the protective parameters are thoroughly investigated by theoretically determining mass attenuation using the newly developed Phy-X/PSD software and XCOM programs, which are then experimentally confirmed at three selected radioactive isotope energies. Experimental measurements of mass attenuation coefficient follow the sequence: MACG1 > MACG2 > MACG3 > MACG4. Raman spectroscopy results indicate that the glass network primarily consists of silicate and phosphate species as the main structural units. An increase in the molar ratio of Na2O and P2O5 improves the radiation shielding effectiveness of the samples. Among them, sample G5, with the lowest SiO2 and MgO content, exhibits the best shielding characteristics due to its high density and molar fraction of Na2O and P2O5. A correlation between microhardness and protective effectiveness is also established. The obtained results support the potential use of these glasses as dual agents for both radiation shielding and medical devices simultaneously.

In the presence of the other: How glyphosate and peptide molecules alter the dynamics of sorption on goethite

The interactions with soil mineral surfaces are among the factors that determine the mobility and bioavailability of organic contaminants and of nutrients present in dissolved organic matter (DOM) in soil and aquatic environments. While most studies focus on high molar mass organic matter fractions (e.g., humic and fulvic acids), very few studies investigate the impact of DOM constituents in competitive sorption. Here we assess the sorption behavior of a heavily used herbicide (i.e., glyphosate) and a component of DOM (i.e., a peptide) at the water/goethite interface, inclusive of potential glyphosate-peptide interactions. We used in-situ ATR-FTIR (attenuated total reflectance Fourier-transform infrared) spectroscopy to study sorption kinetics and mechanisms of interaction as well as conformational changes to the secondary structure of the peptide. NMR (nuclear magnetic resonance) spectroscopy was used to assess the level of interaction between glyphosate and the peptide and changes to the peptide' secondary structure in solution. For the first time, we illustrate competition for sorption sites results in co-sorption of glyphosate and peptide molecules that affects the extent, kinetics, and mechanism of interaction of each with the surface. In the presence of the peptide, the formation of outer-sphere glyphosate-goethite complexes is favored albeit inner-sphere glyphosate-goethite bonds (i.e., POFe) are still formed. The presence of glyphosate induces secondary structural shifts of the sorbed peptide that maximizes the formation of H-bonds with the goethite surface. However, glyphosate and the peptide do not seem to interact with one another in solution nor at the goethite surface upon sorption. The results of this work highlight potential consequences of competition for sorption sites, for example the transport of organic contaminants and nutrient-rich (i.e., nitrogen) DOM components in relevant environmental systems. Predicting the rate and extent with which organic pollutants are removed from solution by a given solid is also one of the most critical factors for the design of effective sorption systems in engineering applications.

Lipid species profiling of bronchoalveolar lavage fluid cells of horses housed on two different bedding materials

The lipidome of equine BALF cells has not been described. The objectives of this prospective repeated-measures study were to explore the BALF cells’ lipidome in horses and to identify lipids associated with progression or resolution of airway inflammation. BALF cells from 22 horses exposed to two bedding materials (Peat 1—Wood shavings [WS]—Peat 2) were studied by liquid chromatography-tandem mass spectrometry (LC–MS/MS). The effects of bedding on lipid class and species compositions were tested with rmANOVA. Correlations between lipids and cell counts were examined. The BALF cells’ lipidome showed bedding-related differences for molar percentage (mol%) of 60 species. Whole phosphatidylcholine (PC) class and its species PC 32:0 (main molecular species 16:0_16:0) had higher mol% after Peat 2 compared with WS. Phosphatidylinositol 38:4 (main molecular species 18:0_20:4) was higher after WS compared with both peat periods. BALF cell count correlated positively with mol% of the lipid classes phosphatidylserine, sphingomyelin, ceramide, hexosylceramide, and triacylglycerol but negatively with PC. BALF cell count correlated positively with phosphatidylinositol 38:4 mol%. In conclusion, equine BALF cells’ lipid profiles explored with MS-based lipidomics indicated subclinical inflammatory changes after WS. Inflammatory reactions in the cellular lipid species composition were detected although cytological responses indicating inflammation were weak.

Solubilizing Benzodifuranone-Based Conjugated Copolymers with Single-Oxygen-Containing Branched Side Chains.

Single-oxygen-containing branched side chains are designed and used to solubilize n-type copolymers consisting of BDF (benzodifuranone), isatin, and thiophene-based units. We present a simple synthetic approach to side chains with varying linker distances between the backbone and the branching point. The synthetic pathway is straightforward and modular and starts with commercially available reagents. The side chains give rise to excellent solubilities of BDF-thiophene copolymers of up to 90 mg/mL, while still being moderate in size (26-34 atoms large). The excellent solubility furthermore allows high molar mass materials. BDF-thiophene copolymers are characterized in terms of optoelectronic and thermoelectric properties. The electrical conductivity of chemically doped polymers is found to scale with molar mass, reaching ∼1 S/cm for the highest molar mass and longest backbone-branching point distance.

Synthesis and Fabrication of Betulin-Derived Polysulfide and Polysulfoxide Electrospun Fibers for Fruit Preservation.

Plant-derived biocompounds play a crucial role in the field of renewable materials due to their sustainability as they can be converted into monomers for polymerization, comparable to numerous monomers obtained from petroleum. In this work, betulin, a triterpene derivative with antibacterial properties obtained from birch tree bark, was esterified to produce two varieties of α,ω-diene derivatives with different lengths of methylene spacers. These derivatives were then copolymerized with 2,2'-(ethylenedioxy)diethanethiol using thiol-ene photopolymerization. We optimized and confirmed the polymerization parameters such as solvents, catalysts, and monomer concentrations. These analyses allowed for the obtainment of polysulfides with a high molar mass of up to 38.9 kg/mol under the optimized conditions. Furthermore, the polysulfides were converted into polysulfoxides by using a dilute hydrogen peroxide solution. Thermal analysis of the obtained polymers revealed excellent thermal stability (up to 300 °C) and tunable glass transition temperatures depending on their molar mass and composition. We successfully produced fibers with a diameter of approximately 3.9 μm by using the electrospinning technique. The morphology and hydrophobicity of the fibers were analyzed by using scanning electron microscopy and water contact angle analysis. Plant-derived polymeric fibers exhibited good cellular biocompatibility and broad-spectrum antibacterial activity, making them promising candidates for applications in fruit preservation.

Effects of metal acetate addition on the gas separation properties of polymers of intrinsic microporosity PIM-1 and PIM-Py

Gas separation properties are reported for self-standing polymer of intrinsic microporosity (PIM) films after addition of palladium (II) acetate or iron (II) acetate by solid state or liquid state mixing. Membranes, with thicknesses in the range 35–55 μm, were prepared from three high molar mass PIMs, two different branched versions of the much-reported PIM-1 (PIM-1a and PIM-1b) and of PIM-Py. Addition of either Fe(OAc)2 or Pd(OAc)2 to all three PIMs led to a reduction in permeability and increase in selectivity, but the permeability reduction was much greater for Pd(OAc)2, which is able to interact with branch points in the PIM and crosslink the polymer. CO2/CH4 selectivity of membranes containing Pd(OAc)2 was poor upon aging, especially after solid state addition to the PIM-1 polymers, for which CO2 permeabilities dropped to below 200 Barrer after 85 days. Hydrogen permeability and H2/N2 selectivity of membranes containing Pd(OAc)2 did more closely follow conventional permeability/selectivity trade off upon aging. This illustrates the profound differences that can arise in gas permeation properties and aging behaviour from variations in chemical structure and macromolecular characteristics, and from the addition of metal acetates that interact with the polymer in different ways.

Nopadiene: A Pinene-Derived Cyclic Diene as a Styrene Substitute for Fully Biobased Thermoplastic Elastomers.

The bicyclic 1,2-substituted, 1,3-diene monomer nopadiene (1R,5S)-2-ethenyl-6,6-dimethylbicyclo[3.1.1]hept-2-ene was successfully polymerized by anionic and catalytic polymerization. Nopadiene is produced either through a facile one-step synthesis from myrtenal via Wittig-olefination or via a scalable two-step reaction from nopol (10-hydroxymethylene-2-pinene). Both terpenoids originate from the renewable β-pinene. The living anionic polymerization of nopadiene in apolar and polar solvents at 25 °C using organolithium initiators resulted in homopolymers with well-controlled molar masses in the range of 5.6-103.4 kg·mol-1 (SEC, PS calibration) and low dispersities (Đ) between 1.06 and 1.18. By means of catalytic polymerization with Me4CpSi(Me)2NtBuTiCl2 and (Flu)(Pyr)CH2Lu(CH2TMS)2(THF), the 1,4 and 3,4- microstructures of nopadiene are accessible in excellent selectivity. In pronounced contrast to other 1,3-dienes, the rigid polymers of the sterically demanding nopadiene showed an elevated glass temperature, Tg,∞ = 160 °C (in the limit of very high molar mass, Mn). ABA triblock copolymers with a central polymyrcene block and myrcene content of 60-75 mol %, with molar masses of 100-200 kg/mol were prepared by living anionic polymerization of the pinene-derivable monomers nopadiene and myrcene. This diene copolymerization resulted in thermoplastic elastomers displaying nanophase separation at different molar ratios (DSC, SAXS) and an upper service temperature about 30 K higher than that for traditional petroleum-derived styrenic thermoplastic elastomers due to the high glass temperature of polynopadiene. The materials showed good thermal stability at elevated temperatures under nitrogen (TGA), promising tensile strength and ultimate elongation of up to 1600%.

Ecosystem-specific patterns and drivers of global reactive iron mineral-associated organic carbon

Abstract. Reactive iron (Fe) oxides are vital for long-term soil or sediment organic carbon (SOC) storage. However, the patterns and drivers of Fe-associated organic carbon (Fe-OC) over global geographic scales under various ecosystem types remain controversial. Here, we provided a systematic assessment of the distribution patterns and determinants of Fe-OC content and its contribution to SOC (fFe-OC) by assembling a global dataset comprising 862 observations from 325 sites in distinct ecosystems. We found that Fe-OC content across global ecosystems ranged from 0 to 83.3 g kg−1 (fFe-OC ranged from 0 % to 82.4 %), reflecting the high variability of the Fe-OC pool. Fe-OC contents varied with ecosystem type being greater in wetlands with a high molar ratio of Fe-OC / dithionite-extractable Fe (Fed) compared with marine and terrestrial ecosystems. Furthermore, fFe-OC in wetlands was significantly lower than that in other ecosystems due to rich organic carbon (OC). In contrast with climate variables and soil pH, the random forest modeling and multivariate analysis showed that the Fe-OC : Fed and SOC were the predominant predictors of Fe-OC content and fFe-OC in wetlands and terrestrial ecosystems, whereas Fed content was a primary driver in marine ecosystems. Based on upper estimates of global SOC storage in various ecosystem types, we further estimated that 83.84 ± 3.8, 172.45 ± 8.74, and 24.48 ± 0.87 Pg of SOC were preserved by association with Fe oxides in wetland, terrestrial, and marine ecosystems, respectively. Taken together, our findings highlighted the importance of reactive Fe oxides in global SOC preservation, and their controlling factors were ecosystem specific.