Low Molecular Weight Organic Compounds Research Articles

Controlling the toxicity of biomass-derived difunctional molecules as potential pharmaceutical ingredients for specific activity toward microorganisms and mammalian cells.

A biomass-derived difuran compound, denoted as HAH (HMF-Acetone-HMF), synthesized by aldol-condensation of 5-hydroxyfurfural (HMF) and acetone, can be partially hydrogenated to provide an electron-rich difuran compound (PHAH) for Diels-Alder reactions with maleimide derivatives. The nitrogen (N) site in the maleimide can be substituted by imidation with amine-containing compounds to control the hydrophobicity of the maleimide moiety in adducts of furans and maleimide by Diels-Alder reaction, denoted as norcantharimides (Diels-Alder adducts). The structural effects on the toxicity of various biomass-derived small molecules synthesized in this manner to regulate biological processes, defined as low molecular weight (≤ 1000 g/mol) organic compounds, were investigated against diverse microbial and mammalian cell types. The biological toxicity increased when hydrophobic N-substitutions and C=C bonds were introduced into the molecular structure. Among the synthesized norcantharamide derivatives, some compounds demonstrated pH-dependent toxicities against specific cell types. Reaction kinetics analyses of the norcantharimides in biological conditions suggest that this pH-dependent toxicity of norcantharimides could arise from retro Diels-Alder reactions in the presence of a Brϕnsted acid that catalyzes the release of an N-substituted maleimide, which has higher toxicity against fungal cells than the toxicity of the Diels-Alder adduct. These synthetic approaches can be used to design biologically-active small molecules that exhibit selective toxicity against various cell types (e.g., fungal, cancer cells) and provide a sustainable platform for production of prodrugs that could actively or passively affect the viability of infectious cells.

Histamine and Serotonin Levels in Bone Marrow Stem Cells Niche as Potential Biomarkers of Systemic Mastocytosis and Myeloproliferative Disorders

Bone marrow studies currently provide a lot of valuable information in the diagnostics of hematological diseases including hematopoietic stem cells disorders. Our studies on low-molecular weight organic compounds in bone marrow stem cell niche in various pathogenic conditions, revealed relatively high variability of histamine levels in different groups of hematological diseases. It was also found that serotonin levels were significantly lower than those typically measured in peripheral blood as well as many have the influence on stem cells proliferative potential. This paper presents findings from quantitative and statistical analyses of histamine and serotonin levels. Bone marrow collected from patients undergoing routine diagnostic procedures for hematological diseases and receiving inpatient treatment were analyzed. Histamine and serotonin levels were measured using hydrophilic interaction liquid chromatography (HILIC) coupled with tandem mass spectrometry. Obtained data were analyzed statistically and correlated with the diagnosed groups of hematological diseases and the parameters of complete blood counts. Histamine was found in all tested samples, including those from patients without malignancy, and the reported levels were comparable to the reference values in blood. This observation allows us to assume that bone marrow cells can produce and accumulate histamine. Moreover, the statistical analysis revealed a significant relationship between histamine levels and diagnosed mastocytosis, and between histamine levels and myeloproliferative neoplasms. Different results were obtained for serotonin, and its concentrations in most cases were below the limit of quantification of the method used (< 0.2 ng/mL), which can only be compared to peripheral blood plasma. In a few cases, significantly higher serotonin levels were observed and it concerned diseases associated with an increased number of megakaryocytes in the bone marrow.

COMPONENT COMPOSITION OF ESSENTIAL OIL AND ANTIOXIDANT ACTIVITY OF POTAMOGETON PERFO-LIATUS L. (POTAMOGETONACEAE) GROWING IN THE ASTRAKHAN REGION

For the first time, the component composition of the low-molecular-weight metabolome of perfoliate pondweed (Potamogeton perfoliatus L., family Potamogetonaceae), which grows in the Astrakhan region (lower zone of the Volga river delta), has been investigated. Low molecular weight organic compounds (LMWOCs) in the composition of essential oil were obtained from dried plants by steam hydrodistillation using the Clevenger apparatus. The qualitative and quantitative compositions of the LMWOCs were investigated using gas chromatography-mass spectrometry (GC/MS complex TRACE ISQ (Thermo Scientific) with a quadrupole mass analyzer). The low molecular weight metabolome of P. perfoliatus contained 164 components, of which 151 were identified. Major LMWOCs were carboxylic acids – tetradecanoic (69.7%) and hexadecanoic (10.1%), as well as phytol (3.4%) and phyton (1.4%), characterized by diverse biological activities. The antioxidant activity of an aqueous-alcoholic extract of P. perfoliatus was investigated by a photometric method based on the reaction of DPPH (2,2-diphenyl-1-picrylhydrazyl) dissolved in ethanol with an antioxidant sample. It has been shown that P. perfoliatus extract has more pronounced antioxidant properties than the tested drugs (ascorbic acid and emoxipine). P. perfoliatus from the lower zone of the Volga River delta can be considered as a naturally renewable resource for obtaining raw materials for creating effective composites of new generation algicides to combat cyanobacterial "bloom", as well as for obtaining valuable natural forms of LMWOCs of plant origin for various types of application in pharmacology, medicine, cosmetology, food industry, and other industries.

Effect of sludge retention time on the performance and sludge filtration characteristics of an aerobic membrane bioreactor treating textile wastewater

In this study, the impact of different sludge retention times (SRTs) on the wastewater treatment performance of an aerobic membrane bioreactor (MBR) was investigated using real textile industry wastewater. For this purpose, two laboratory-scale membrane bioreactors were operated in parallel. Under the same conditions, one of the systems was operated at an SRT of 30 d and, the other at SRTs of 20 d, and 10 d, respectively. The total chemical oxygen demand (COD), color and soluble total nitrogen (TN) of the wastewater averaged 927 ± 277 mg/L, 910 ± 287 PtCo and 39 ± 10 mg/L, respectively. COD removal efficiency remained above 90 % in all the tested SRTs. While the color removal efficiency was 55 % and 60 % at SRTs of 30 d and 20 d, respectively, it decreased to 50 % at SRT of 10 d. In addition, the impact of different SRTs on membrane filtration performance was studied. With the reduction of SRT to 10 d, an increase was observed in specific resistance to filtration (SRF) and supernatant filterability (SF) values, while viscosity decreased due to lower suspended solid (SS) concentration. According to gel permeation chromatography (GPC) analysis, the molecular weights of organic substances in the permeate distributed over a wide spectrum as SRT decreased. Also, signals given by the low molecular weight organic compounds were higher.

Acid Gas and Tar Removal from Syngas of Refuse Gasification by Catalytic Reforming

The existence of acid gas and tar in syngas of municipal solid waste gasification limits its downstream utilization as a clean energy source. Here, we investigated the catalytic removal of HCl and tar. The key parameters affecting the catalytic reaction, including space velocity, temperature, the amounts of active metals in the catalyst and the carrier material, were studied, targeting optimized operating conditions for enhanced syngas purification. The morphology, mineral phases, surface area and pore size before and after the reaction were investigated to understand the mechanism to dominate the reaction. The results showed that the removal rate of CaO adsorbent and HCl reached 96% at 400 °C. When the space velocity ratio was 1.0 and the temperature was 400 °C, HCl removal (97%) by NaAlO2 was even better. Nevertheless, clogging was observed for NaAlO2 via the BET test after reaction to jeopardize its durability. A level of 25% Ni doping on Zr1-x(Cex)O2 support provides high stability for tar removal. This is because the Zr1-x(Cex)O2 carrier has higher carbon deposition resistivity than the Al2O3 carrier. The EDX results confirmed that a large amount of C (79.3%) was accumulated on the commercial catalyst surface supported by Al2O3 (25% Ni-based). As for the temperature, a temperature higher than 800 °C could not enhance the efficiency of tar removal, likely due to catalyst deactivation. Carbon deposition and agglomeration are the two main causes of catalyst deactivation. At 800 °C, 25% Ni-based synthetic catalyst can convert 48.5 ± 19.4% tar to low molecular weight organic compounds. By contrast, such a conversion rate under the same temperature only accounted for 5.0 ± 6.8% based on a commercial catalyst. These insights point to the important role of catalyst support materials.

Chemical characterization of odorous emissions: A comparative performance study of different sampling methods

A comparison among different sampling methods (3 types of sorbent tubes and polymeric bags) commonly adopted in chemical analyses of odorous emissions was performed. To investigate the different performances, a lignocellulosic biomass storage plant was selected to obtain preliminary information about the chemical nature of odorous emissions. Samples of odorous emissions were collected at different biomass piles and analysed by dynamic olfactometry and TD-GC-MS. By comparing the two adopted sampling methods (tubes and bags), different performances are shown, depending on their specificity. By the comparison among the three types of sorbent tubes (Multi-sorbent bed (Carbotrap, Carbopack X and Carboxen 569), Tenax and Sulphur), Sulphur and Multi-sorbent bed present similar performance, while Tenax TA tubes show a different trend in terms of type and numerosity of detected compounds. In addition, from the comparison between tubes and polymeric bags, the number and types of compounds detected in bags are more comparable to those observed in the Multi-sorbent bed and Sulphur tubes. However, a difference between the two methods appears, especially in the detection of low-molecular weight organic compounds. In this study, it is possible to highlight that, due to the complexity of odorous emissions, the selection of the sampling material may affect the obtained chemical results. The detection of different classes of compounds, is a crucial point, to obtaining the most complete characterization of mixtures and comparing the chemical profile with olfactometric results: care must be taken in the choice of sampling material and procedure.

Chemoinformatics-driven classification of Angiosperms using sulfur-containing compounds and machine learning algorithm

BackgroundPhytochemicals or secondary metabolites are low molecular weight organic compounds with little function in plant growth and development. Nevertheless, the metabolite diversity govern not only the phenetics of an organism but may also inform the evolutionary pattern and adaptation of green plants to the changing environment. Plant chemoinformatics analyzes the chemical system of natural products using computational tools and robust mathematical algorithms. It has been a powerful approach for species-level differentiation and is widely employed for species classifications and reinforcement of previous classifications.ResultsThis study attempts to classify Angiosperms using plant sulfur-containing compound (SCC) or sulphated compound information. The SCC dataset of 692 plant species were collected from the comprehensive species-metabolite relationship family (KNApSAck) database. The structural similarity score of metabolite pairs under all possible combinations (plant species-metabolite) were determined and metabolite pairs with a Tanimoto coefficient value > 0.85 were selected for clustering using machine learning algorithm. Metabolite clustering showed association between the similar structural metabolite clusters and metabolite content among the plant species. Phylogenetic tree construction of Angiosperms displayed three major clades, of which, clade 1 and clade 2 represented the eudicots only, and clade 3, a mixture of both eudicots and monocots. The SCC-based construction of Angiosperm phylogeny is a subset of the existing monocot-dicot classification. The majority of eudicots present in clade 1 and 2 were represented by glucosinolate compounds. These clades with SCC may have been a mixture of ancestral species whilst the combinatorial presence of monocot-dicot in clade 3 suggests sulphated-chemical structure diversification in the event of adaptation during evolutionary change.ConclusionsSulphated chemoinformatics informs classification of Angiosperms via machine learning technique.

Вітамінний статус як оцінка забезпеченості вітамінами А, Е, D в дітей з алергодерматозами

Vitamins are a group of biologically highly active, low molecular weight organic compounds of various chemical nature, which are practically not synthesized in the body or are synthesized in insufficient quantities, mainly income with food, and are vital to ensure for the flow and regulation of metabolic processes. Vitamins A, E, D play an important role in ensuring the normal functioning of the skin and mucous membranes, adequate immune response, maintaining the body’s resistance to various adverse external factors. Purpose - to study, evaluate and analyze the vitamin status, providing of vitamins A, E, D in children with allergic dermatoses. Materials and methods. 24 children with allergic dermatoses and 32 children of the control group aged 6 to 17 years were examined. General clinical, immunological, biochemical, questionnaires and statistical research methods were used. Results. Among the examined children with isolated allergopathology such as allergodermatoses were diagnosed 10 (41.7%) children, the remaining children were with combined allergic pathology such as allergodermatoses and bronchial asthma 14 (58.3%) children. The research of the providing of vitamins A, E, D in children with allergic dermatoses based on clinical symptoms showed the presence of hypovitaminosis manifestations of vitamin A in 9 (37.5%) children, vitamin E - 8 (33.3%) children, vitamin D - 14 (58.3%) children. Examination of vitamin status in children with allergodermatoses showed a marked decrease in blood levels of vitamin A, a moderate decrease in vitamin D levels, a slight decrease in vitamin E levels compared with children in the control group (p&lt;0.05). In general, all examined children with allergodermatoses and the control group had low levels of vitamin D, subnormal low levels of vitamin A, normal levels of vitamin E according to the recommended criteria of normal supply of vitamins A, E, D according to blood levels. Conclusions. Based on the results of the study, the need for personalized correction of the consumption of vitamins A, E, D, taking into account the composition of the diet in children with allergic dermatoses, who are on elimination hypoallergenic diets were established. The synergistic effect of three vitamins A, E, D at the level of the immune system allows to recommend such a vitamin formula both for prophylactic purposes and in the complex treatment of children with skin allergies. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

Methodical peculiarities of air sampling for detecting contents of low molecular weight organic compounds on the example of furan and methylfuran

Introduction. Variable analytical control methodologies are applied in monitoring over contents of low molecular weight organic compounds in ambient air. Their unification is a vital and serious challenge requiring valid substantiation and selection of optimal air sampling techniques. Our research goal was to substantiate and select an air sampling technique for chemical analysis of furan and methylfuran. Materials and methods. Our research concentrated on developing and optimizing the process of air samples preparation for chemical analysis of furan and methylfuran; examining effectiveness of furan and methylfuran sorption-desorption using various sorbents. Standard furan and methylfuran samples (≥99.0% Sigma-Aldrich), heptane solvents, sorbent tubes with Tenax, Sylochrom C-120, and coal as sorbents were used in the research. All experimental studies were aimed at testing effective procedures for taking and preparing air samples for further furan and methylfuran analysis in them. They were performed on “Kristall-5000” gas chromatographer with mass-selective detection (MSD) and 25-meter long PoraPlotQ-capillary column. Results. We comparatively analyzed the results produced by taking air samples for further detection of furan and methylfuran in them using different techniques. They included low temperature concentration; sorption on filters made of quartz microfiber and a sorbent tube with Nenax TA; sorption on a tube with Tenax TA at t=20-25 °C. The analysis enabled us to reveal an effective procedure for taking ambient air samples for further detection of furan and methylfuran in them. This procedure was low temperature concentration of low molecular weight organic compounds on a sorbent tube with Tenax TA. Limitations. The accomplished study had no limitations. Conclusion. The accomplished study allows us to recommend taking air samples during 10 minutes with consumption being 0.1 l/min for further detection of furan and methylfuran in them using low temperature concentration on a sorbent tube with Tenax TA. The achieved effectiveness is 99.2% for furan and 100% for methylfuran.

Humic acid induced indirect photolysis of polybrominated diphenyl ethers under visible light irradiation

Polybrominated diphenyl ethers (PBDEs), as typical persistent organic pollutants (POPs) have been world widely detected in environmental media and biological tissues. Compared with the extensive study on direct photolysis of PBDEs in the ultraviolet region (UV), indirect photodegradation of PBDEs under visible light triggered by the co-existing substances in the environment has been largely ignored. Herein, the indirect photolysis and debromination of organic brominated pollutants decabromodiphenyl ether (BDE209) induced by humic acid (HA) have achieved both in homogeneous and heterogeneous system under visible light irradiation. It shows a new transformation pathway of PBDEs in environment that plays an important role on their ultimate environmental fate. Different from direct photolysis of PBDEs in UV light, the indirect photolysis of PBDEs by HA under visible light irradiation experiences the electrons transfer from HA to PBDEs induced by a halogen-bond between HA and PBDEs. HA contributes to the activation of C-Br bond via formation of halogen bond, and promotes electron transfer under visible light irradiation, leading to meta-C-Br cleavage preferentially. To evaluate the effects of various functional groups in HA, eleven low-molecular-weight organic compounds (LMWOs) containing reactive oxygen terminal are selected to study the indirect photolysis of BDE209. Combined with the density functional theory (DFT) calculation results, it is shown that carboxyl group is proposed to be the key functional group capable of providing oxygen terminals to form halogen bonds. This work provides novel and valuable insights into the photolysis and debromination of PBDEs with co-existing HA in the environment under sunlight.

Migration of terephthalate from scraps of poly(ethylene terephthalate) (PET) in water and artificial seawater

We report the migration of terephthalate and some low molecular weight organic compounds from poly(ethylene terephthalate) (PET) scraps in Milli-Q water and artificial seawater (ASW). The photochemical processes and the subsequent dark reactions were investigated using PET scraps obtained from postconsumer bottles of commercial non‑carbonated mineral water. Concentrations of terephthalate exponentially increased with irradiation time, reaching approximately 6–8 μmol L−1 in ASW after 80 h irradiation. The photochemical migrations of compounds related to terephthalate were also observed. Concentrations of terephthalate and related compounds reached higher concentrations in ASW than in Milli-Q water. After 80 h irradiation, two dark experiments were conducted: one on the solutions after irradiation without PET scraps, and the other on photochemically damaged PET scraps. In ASW in the dark without PET scraps, the terephthalate concentration increased, and concentrations of other compounds related to terephthalate also changed. The results suggested that terephthalate was generated by hydrolytic reaction in dark ASW from the scission products of PET which were generated during the irradiation of PET scraps. Photochemically damaged PET scraps released terephthalate and related compounds in the dark. The half-life of the photo-irradiated PET scraps in the dark is approximately 205 years. Our results show that PET bottles in marine environments can continuously release terephthalate and other low molecular weight organic compounds during the day at the sunny surface, at the dark ocean floor, and during the night.

Evolution of low molecular weight organic compounds during ultrapure water production process: A pilot-scale study

This study evaluated the evolution of low molecular weight organic compounds in ultrapure water (UPW) production using a pilot-scale UPW production system and an ultrafiltration–reverse osmosis (UF–RO) system. During UPW production, a dissolved organic carbon (DOC) removal efficiency of 99.4% was achieved with a feedwater DOC level of 1.42 mg/L. The pretreatment, make-up, and polishing stages accounted for 85.3%, 13.7%, and 0.4% of DOC removal, respectively. Urea, trichloromethane, and dibromochloromethane persisted throughout UPW production process, contributing 24.7%, 9.2%, and 22.6%, respectively, to the final effluent DOC level of 8.1 μg/L. The pretreatment and make-up stages of the UPW production process could remove N-nitrosodimethylamine, chloral hydrate, dichloroacetonitrile, and tribromomethane. The UF–RO system could remove approximately 90% of DOC. However, the proportion of halogenated disinfection by-products (DBPs) in the DOC increased by 1.4–4.5 times in the RO effluents. RO could completely reject haloacetaldehydes. However, RO could not completely remove trichloromethane, tribromomethane, bromodichloromethane, and dibromoacetonitrile, which remained the main halogenated DBPs in the RO effluents.

Removal of Organic Compounds with an Amino Group during the Nanofiltration Process.

The research covered the process of nanofiltration of low molecular weight organic compounds in aqueous solution. The article presents the results of experiments on membrane filtration of compounds containing amino groups in the aromatic ring and comparing them with the results for compounds without amino groups. The research was carried out for several commercial polymer membranes: HL, TS40, TS80, DL from various manufacturers. It has been shown that the presence of the amino group and its position in relation to the carboxyl group in the molecule affects the retention in the nanofiltration process. The research also included the oxidation products of selected pharmaceuticals. It has been shown that 4-Amino-3,5-dichlorophenol—a oxidation product of diclofenac and 4-ethylbenzaldehyde—a oxidation product of IBU, show poor separation efficiency on the selected commercial membranes, regardless of the pH value and the presence of natural organic matter (NOM). It has been shown that pre-ozonation of natural river water can improve the retention of pollutants removed.

Plasmonically-enhanced competitive assay for ultrasensitive and multiplexed detection of small molecules

Novel methods that enable facile, ultrasensitive and multiplexed detection of low molecular weight organic compounds such as metabolites, drugs, additives, and organic pollutants are valuable in biomedical research, clinical diagnosis, food safety and environmental monitoring. Here, we demonstrate a simple, rapid, and ultrasensitive method for detection and quantification of small molecules by implementing a competitive immunoassay with an ultrabright fluorescent nanolabel, plasmonic fluor. Plasmonic-fluor is comprised of a polymer-coated gold nanorod and bovine serum albumin conjugated with molecular fluorophores and biotin. The synthesis steps and fluorescence emission of plasmonic-fluor was characterized by UV–vis spectroscopy, transmission electron microscopy, and fluorescence microscopy. Plasmon-enhanced competitive assay can be completed within 20 min and exhibited more than 30-fold lower limit-of-detection for cortisol compared to conventional competitive ELISA. The plasmon-enhanced competitive immunoassay when implemented as partition-free digital assay enabled further improvement in sensitivity. Further, spatially multiplexed plasmon-enhanced competitive assay enabled the simultaneous detection of two analytes (cortisol and fluorescein). This simple, rapid, and ultrasensitive method can be broadly employed for multiplexed detection of various small molecules in research, in-field and clinical settings.

Development of the Composition, Technology and Study of the Effectiveness of Drops for Oral Administration "Ascorbicdrop"

For normal life, many different substances are needed, among which vitamins play an important role. Everyone knows that the word "vitamin" comes from the Latin "vita" - life. This name is not accidental at all [1].&#x0D; Vitamins are low molecular weight organic compounds, very small amounts of which are required for the implementation of various metabolic processes in the body. Most vitamins are indispensable because are not synthesized in the human body. In their natural state, they can be found in very small quantities in all foods of organic origin [1,2].&#x0D; Insufficient intake of vitamins from food is a global problem, and not seasonal, as it is mistakenly believed. For a number of reasons, a modern person cannot get them in the right amount with food. Inadequate nutrition, physical inactivity lead to metabolic disorders in the body and increase the risk of developing serious diseases [3,4,5,6].&#x0D; One of the main problems faced by drug manufacturers is sometimes a short shelf life. In order to preserve the pharmacological properties of drugs, they add preservatives to them or place them in a vacuum package. To date, the most effective way to solve this problem is to use a modified atmosphere with nitrogen.&#x0D; The stability of solutions of easily oxidizable substances increases significantly if they are filled in an inert gas environment, for example, carbon dioxide, nitrogen or argon. This filling allows you to remove oxygen, this oxidizing agent that destroys unstable substances. The following factors influence the reduction of shelf life:&#x0D; &#x0D; oxidative processes,&#x0D; development of molds,&#x0D; reproduction of microorganisms.&#x0D; &#x0D; All oxidative processes in the packaging of a medicinal product occur under the influence of oxygen. As a result of this reaction, medications deteriorate. With the help of a pure nitrogen environment, it is possible to reduce the O2 content to a minimum level [7].

Conformationally tunable calix[4]pyrrole-based nanofilms for efficient molecular separation

Preparation of nanofilms which are able to reject water-soluble low molecular weight organic compounds in nanofiltration remains to be a challenge. Herein, we report a new kind of self-standing, defect-free, robust, centimeter-sized and thickness controllable calix[4]pyrrole (C[4]P)-based nanofilms with excellent molecular sieving performance in nanofiltration. The nanofilms were prepared via confined dynamic condensation of the tetra-benzoyl-hydrazine derivative of calix[4]pyrrole (CPTBH) with 1,3,5-benzenetricarboxaldehyde (BTC) at the air/dimethyl sulfoxide (DMSO) interface. Nanofiltration tests under 2 bar pressure with porous polyethylene terephthalate (PET) as the support and a CsF treated CPTBH-BTC nanofilm (∼100 nm) as the selective layer depicted a water permeance of 15 L m-2h−1 bar−1 and a methanol permeance of 45 L m-2h−1 bar−1. High rejection rates (>95%) were found in aqueous solution for most of the tested dyes and pharmaceuticals. Remarkably, the composite membrane also demonstrated good separation performance in aqueous phase to some amino acids and organic dyes with molecular weights around 200 g/mol. High-performance nanofiltration in methanol was also realized. In this case, the molecular weight cutoff value is ∼ 800 g/mol. These findings showed that introduction of macrocyclic hosts is an effective way to develop nanofilms with high solvent permeance but low molecular weight cutoff value.

Hydrogen/deuterium exchange mass spectrometry in the world of small molecules.

The combined use of hydrogen/deuterium exchange (HDX) and mass spectrometry (MS), referred to as HDX-MS, is a powerful tool for exploring molecular edifices and has been used for over 60 years. Initially for structural and mechanistic investigation of low-molecular weight organic compounds, then to study protein structure and dynamics, then, the craze to study small molecules by HDX-MS accelerated and has not stopped yet. The purpose of this review is to present its different facets with particular emphasis on recent developments and applications. Reversible H/D exchanges of mobilizable protons as well as stable exchanges of non-labile hydrogen are considered whether they are taking place in solution or in the gas phase, or enzymatically in a biological media. Some fundamental principles are restated, especially for gas-phase processes, and an overview of recent applications, ranging from identification to quantification through the study of metabolic pathways, is given.

Hydroxyl radicals induced mineralization of organic carbon during oxygenation of ferrous mineral-organic matter associations: Adsorption versus coprecipitation

The iron (Fe) phases have been widely proposed to preserve organic carbon (OC) via adsorption or coprecipitation pathways, however, such role of Fe phases might be largely reversed under redox-fluctuation conditions, especially for Fe(II) minerals-protected OC. In this study, we synthesized the Fe(II)-OC associations via adsorption and coprecipitation using FeCO3 and three types of low-molecular-weight organic compounds (LMWOCs) at different C/Fe molar ratios, and investigated the OC mineralization induced by hydroxyl radicals (OH) during oxygenation processes. Abundant OH can be produced upon oxygenation of FeCO3-LMWOCs associations within 96 h, giving values of 28.49‐151.36 μM in adsorption and 12.63–76.41 μM in coprecipitation treatments depended on types of LMWOCs and C/Fe molar ratios. Fe(II) species in coprecipitates with hydroquinone (HQ) mainly transformed into Goethite-like phases after oxygenation, while adsorption samples induced more formation of lower-crystalline Fe phase (e.g., ferrihydrite). The surface-Fe(II) was the primary electron donors to O2, which further induced hydrogen peroxide (H2O2) formation via one- and two-electron transfer pathways. Finally, the produced OH removed 0.55-9.65 and 0.16–85.54 mg L−1 total OC in adsorption and coprecipitation treatments after oxygenation. Collectively, this study highlights that OC associated with Fe(II) minerals might be labile due to the oxidation of formed OH, and the role of Fe phases in OC sequestration may be further re-evaluated under redox fluctuation conditions.

The Effect of Microwave-Assisted Alkali and Xanthomonas t ranslucens ICBB 9762 for Rice Straw Pretreatment on Electricity Generation of Microbial Fuel Cell Inoculated by Staphylococcus saprophyticus ICBB 9554

Rice straw can be utilized as an organic substrate in Microbial Fuel Cell (MFC) to generate electricity by microbes as a biocatalyst. This research was aimed to observe the effect of Xanthomonas translucens ICBB 9762 inoculation pretreatment on microwave-assisted alkali treated rice straw on the lignocellulosic structure change of rice straw and to observe the performance of MFC system fed by treated rice straw. The stages of research included: (1) pretreatment of rice straw through microwave-assisted alkali and Xanthomonas translucens ICBB 9762 inoculation, (2) observation of MFC performance including electrical voltage; electrical current; power density; and Coulombic efficiency, and (3) anolite analysis including COD removal, pH and Eh. The result showed that rice straw was successfully decomposed by inoculation of Xanthomonas translucens ICBB 9762 on microwave-assisted alkali pretreatment which the highest cellulose yield about 29.36 %. Treated rice straw produced better performance than rice straw without pretreatment which the best performance resulted by the combination of Xanthomonas translucens ICBB 9762 inoculation and microwave-assisted alkali pretreatment which produce electrical voltage, electrical current, and power density value of 337.90 mV, 0.39 mA, and 26.20 mW/m2, respectively. The utilization of solid substrate such as rice straw need more attention due to there was COD enhancement while in COD reduction reach COD removal efficiency and coulombic efficiency ranged 5.15 - 54.08 % and 0.25 - 7.83 %, respectively. HIGHLIGHTS Microbial Fuel Cell fueled by lignocellulose substrate, which is rice straw Lignocellulose structure deconstruction through microwave-assisted alkali pretreatment A combination of microwave-assisted alkali and cellulose-degrading bacteria inoculation pretreatment for rice straw generate the highest electricity Electricity generation improvement in microbial fuel cell through mix culture between cellulose-degrading bacteria and exoelectrogen bacteria Cellulose degrading bacteria increase Chemical Oxygen Demand (COD) due to the solubility of low molecular weight organic compounds increasing during microbial fuel cell incubation

Molecular characterization and spatial distribution of dicarboxylic acids and related compounds in fresh snow in China

Low molecular weight organic compounds are ubiquitous in the atmosphere. However, knowledge on their concentrations and molecular distribution in fresh snow remains limited. Here, twelve fresh snow samples collected at eight sites in China were investigated for dicarboxylic acids and related compounds (DCRCs) including oxocarboxylic acids and α-dicarbonyls. Dissolved organic carbon (DOC) concentrations in the snow samples ranged from 0.99 to 14.6 mg C L−1. Concentrations of total dicarboxylic acids were from 225 to 1970 μg L−1 (av. 650 μg L−1), while oxoacids (28.3–173, av. 68.1 μg L−1) and dicarbonyls (12.6–69.2, av. 31.3 μg L−1) were less abundant, accounting for 4.6–8.5% (6.2%), 0.45–1.4% (0.73%), and 0.12–0.88% (0.46%) of DOC, respectively. Molecular patterns of dicarboxylic acids are characterized by a predominance of oxalic acid (C2) (95.0–1030, av. 310 μg L−1), followed by phthalic (Ph) (9.69–244, av. 69.9 μg L−1) or succinic (C4) (23.8–163, av. 63.7 μg L−1) acid. Higher concentrations of Ph in snow from Beijing and Tianjin than other urban and rural regions suggest significant emissions from vehicular exhausts and other fossil fuel combustion sources in megacities. C2 constituted 40–54% of total diacids, corresponding to 1.5–2.6% of snow DOC. The total measured DCRCs represent 5.5–10% of snow DOC, which suggests that there are large amounts of unknown organics requiring further investigations. The spatial distributions of diacids exhibited higher loadings in megacities than rural and island sites. Molecular distributions of diacids indicated that the photochemical modification was restrained under the weak solar radiation during the snow events, while anthropogenic primary sources had a more significant influence in megacities than rural areas and islands.