Molecular Organic Compounds Research Articles

Optimization of preparation conditions of sugarcane bagasse activated carbon via microwave-induced KOH activation for stabilized landfill leachate remediation

Adsorption via activated carbon has been testified as an effective way for removing high molecular weight refractory organic compounds from old landfill leachate which is hard to be treated biologically. The present work reveals the preparation and optimization of sugarcane bagasse-based activated carbon (SCAC) by microwave-induced KOH activation for the adsorptive treatment of organic and inorganic contaminants from the mature anaerobic landfill leachate using response surface methodology technique. The effects of variable parameters in SCAC preparation including activation power, activation time and KOH impregnation were studied. Based on the central composite design, the quadratic model was employed in order to correlate the effect of variable parameters in SCAC preparation on adsorptive removal of pollutants. The achieved removal efficiencies of color, COD and ammonia were 97.83, 88.14 and 47.25 %, based on optimum conditions of SCAC at 550 W of activation power, 7 min of activation time and 1.55 of impregnation ratios. The experimental results showed the capability of SCAC prepared via microwave-induced KOH activation in the treatment of stabilized landfill leachate.

Study on small molecular organic compounds pyrolysed from rubber seed oil and its sodium soap.

Rubber seed oil (RSO) and its sodium soap were pyrolysed in a batch reactor to obtain low molar mass organic substances. The pyrolitic oil of RSO was redistilled and the distillates were characterized by GC–MS and FTIR. Density, acid value, saponification value and ester values were also measured according to the ASTM standard methods. A similar analysis was done for samples taken out at different time intervals from the reaction mixture. Industrially important low molar mass alkanes, alkenes, aromatics, cyclic compounds and carboxylic acids were identified in the pyrolysis process of rubber seed oil. However, pyrolysis of the sodium soap of rubber seed oil gave a mixture of hydrocarbons in the range of C14–C17 and hence it has more applications as a fuel.

Metabolite profiling of the ripening ofMangoes Mangifera indica L. cv. 'Tommy Atkins' by real-time measurement of volatile organic compounds.

Real-time profiling of mango ripening based on proton transfer reaction-time of flight-mass spectrometry (PTR–ToF–MS) of small molecular weight volatile organic compounds (VOCs), is demonstrated using headspace measurements of ‘Tommy Atkins’ mangoes. VOC metabolites produced during the ripening process were sampled directly, which enabled simultaneous and rapid detection of a wide range of compounds. Headspace measurements of ‘Keitt’ mangoes were also conducted for comparison. A principle component analysis of the results indicated that several mass channels were not only key to the ripening process but could also be used to distinguish between mango cultivars. The identities of 22 of these channels, tentatively speciated using contemporaneous GC–MS measurements of sorbent tubes, are rationalized through examination of the biochemical pathways that produce volatile flavour components. Results are discussed with relevance to the potential of headspace analysers and electronic noses in future fruit ripening and quality studies.

Hydrothermal degradation of hemicelluloses from triploid poplar in hot compressed water at 180–340 °C

Hemicelluloses isolated from triploid poplar were subjected to hydrothermal degradation at 180–340 °C. The detailed physicochemical characteristics of hydrothermal degradation products including monosaccharide and XOS, molecular weight, inhibitory and organic compounds were detected by HPAEC, GPC, HPLC, and GC–MS, respectively. An increase in temperature led to a significant decrease in molecular weight and an increase in C2–C5 organic alcohols and acids. More importantly, besides two well-known routes that hemicelluloses are hydrolyzed to monosaccharide, followed by further degraded to furfural, a series of reaction routes was proposed to clarify and explain the mechanisms of the hydrothermal degradation of hemicelluloses from triploid poplar, which involved: (i) a predominant route of fragmentation; (ii) side reactions such as oxidation, dehydration, isomerization/rearrangement, and self-lactonization; (iii) larger molecular fragments from sugars by deoxydation or/and oxidation, followed by self-lactonization; and (iv) very few extensive re-polymerization including esterification and condensation among hemicelluloses and lignin fragments.

Size-distribution of airborne polycyclic aromatic hydrocarbons and other organic source markers in the surroundings of a cement plant powered with alternative fuels

The distributions of polycyclic aromatic hydrocarbons (PAHs) and molecular tracer organic compounds for biomass combustion, traffic emissions, soil dust, and secondary aerosol processing have been studied in three fractions of ambient air particulate matter (PM10, 2.5, and 1) collected in the vicinity of a cement plant. PAH concentrations were used to estimate the carcinogenic risks in humans. Combustion related compounds, including PAHs, and those from secondary aerosol processing, predominated in the finest (PM<1) fraction, while saccharides related to organic soil dust predominated in the coarse fraction (2.5<PM<10). The molecular markers of biomass combustion were found in high concentrations, indicating the influence of biomass burning on PM. Most predominant PAHs were five and six rings species, related to a PAH profile characteristic of urban-industrial environments. The concentrations of benzo[a]pyrene varied between 0.2 and 1.0ng/m3, which is close but lower than the annual limit value of 1ng/m3 established by law. Exposure and inhalation carcinogenic risks from total PAHs were below the EPA threshold of acceptable risk (1·10−6).

Application of Microbial Culture and Rhamnolipid for Improving the Sedimentation of Oil Sand Tailings

Densification of oil sand tailings deposited in the tailing ponds and recovering water from them are two major challenges in the oil sands surface mining industry. A small increase in the tailings settlement rate (which normally is very slow) can improve the densification of tailings and significantly reduce water consumption and the volume of the tailing ponds. In this work, the objective was to evaluate the role of a mixed culture of two microbial strains isolated from weathered oil and rhamnolipid (JBR 425) together with these strains in the sedimentation of fine tailing particles. It has been found that a mixed culture of two microbial strains isolated from weathered oil increased the sedimentation. Rhamnolipid (0.5%) together with these two microbial strains at 15°C ± 2°C showed significant increases in sedimentation (by a factor of 5.1), the concentration of larger particles (by a factor of 2.63), the particle mean diameter (by a factor of 2.70) and flocculation in the tailings samples compared to the control while the zeta potential is still negative. This means that the mechanism of flocculation is probably due to increasing the hydrophobicity of the particles, interaction of biosurfactant and high molecular weight microbial organic compounds through a bridging mechanism with clay particles. This work shows the potential of using rhamnolipid and microbial culture in order to increase the oil sand sedimentation through flocculation and microbial activity in a more environmentally friendly densification process.

LOW-MOLECULAR WEIGHT METABOLITES IN SPIRODELA POLYRHIZA (L.) SCHEIDEN FROM NORTHWEST RUSSIA IN THE MIDDLE OF THE GROWING SEASON

Ponte Academic JournalOct 2016, Volume 72, Issue 10 LOW-MOLECULAR WEIGHT METABOLITES IN SPIRODELA POLYRHIZA (L.) SCHEIDEN FROM NORTHWEST RUSSIA IN THE MIDDLE OF THE GROWING SEASONAuthor(s): Evgeny A. Kurashov ,Galina G. Mitrukova, Julia V. Krylova, Dina G. Aleshina, Yulia V. Bataeva, Oxana V. AstafyevaJ. Ponte - Oct 2016 - Volume 72 - Issue 10 doi: 10.21506/j.ponte.2016.10.2 Abstract:Not much is known about the chemical composition of low-molecular weight secondary metabolites of Spirodela polyrhiza (L.) Scheiden. We aimed to investigate the composition of low molecular weight volatile organic compounds (VOCs) of S. polyrhiza in the middle of the growing season by GC-MS. A GC-MS analysis of the essential oil of fresh S. polyrhiza was undertaken for the first time. It was found that in the middle of the growing season (in July) the essential oil of S. polyrhiza from a hypertrophic pond (Northwest Russia) contains 89 VOCs, 83 of which were identified. The major low-molecular weight metabolites of S. polyrhiza were manool (25.11%), biformen (12.83%) and phytol (8.05%), which are valuable in practical terms and can play a very important role in aquatic ecosystems. Further study of the composition of VOCs of S. polyrhiza growing in different water bodies and in different conditions (different hydrobiological environments) is necessary to understand the role of this species in hydrobiocenoses. The production of valuable VOCs from S. polyrhiza may be combined with other uses of this plant, e.g., biomass production, the treatment of wastewater with high nutrient concentrations (municipal, industrial and livestock farm wastewater). Large amounts of Lemnaceae biomass and VOCs can be the result of the purification of numerous water bodies that are exposed to duckweed bloom. Download full text:Check if you have access through your login credentials or your institution Username Password

A Review on Bio-macromolecular Imprinted Sensors and Their Applications

Abstract Molecular imprinted technology has been maturely applied to analyze and detect small molecular organic compounds, also increasingly applied in biological macromolecules assay. This review addresses the perspective of bio-macromolecular imprinted sensors and their applications, including optical molecular imprinted sensors, electrochemical molecular imprinted sensors and mass-sensitive molecular imprinted sensors. In addition, the opportunities, challenges, and further research orientations of molecular imprinted sensors for bio-macromolecules detection were prospected.

Nanofiber waveguides and photophysics of an organic dye

We present previously unreported properties of the organic molecular dye compound, 2,3,7,8-tetracyano-5,10-dimethyl-5,10-dihydrodipyrazino[2,3-b:2’,3’-e]pyrazine (DMTC-pyrazine) (CAS Reg. No. 150960-11-5), including photophysical properties with particular emphasis on optical waveguiding. We show that DMTC-pyrazine can self-assemble into monoclinic crystals that are thermally stable over 300°C. Through shape-engineering, optimized growth conditions produced high yields of nanofiber (aspect ratio >6) crystals. No photobleaching of this dye was observed in air even after hours of on-resonant illumination. Excitation of photoluminescence within the DMTC-pyrazine nanofibers propagates in tightly confined guided modes (up to 25 μm). The finesse, end-facet reflectance, and group refractive index of nanofiber DMTC-pyrazine Fabry-Perot cavities are reported.

A membrane introduction mass spectrometer utilizing ion-molecule reactions for the on-line speciation and quantitation of volatile organic molecules.

The ability of membrane introduction mass spectrometry to quantitatively resolve low molecular weight volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene and xylene (BTEX) using electron ionization (EI) can be compromised by isobaric interferences. This work focuses on reducing isobaric interferences with ion-molecule reactions in a portable quadrupole ion trap mass spectrometer for the analysis of VOCs. EI was used to produce reagent ions from precursors (chloroform, methyl iodide, trichloroethylene or chlorobenzene) that were continually infused into the helium acceptor phase upstream of the membrane introduction mass spectrometry (MIMS) sampling interface. The reagent ions were selectively stored in the ion trap, and then allowed to react with target VOC analytes in air samples via ion-molecule reactions within the trap storage volume. A variety of reaction times were examined (50-5000 ms), and the resulting product ions were analyzed in positive ion mode. The detection limits achieved were comparable with those obtained using EI (low ppbv), and in some cases better than for EI coupled with tandem mass spectrometry (MS/MS). For the VOCs studied, isobaric interferences were greatly reduced or eliminated using chloroform as a reagent gas. The predominant ionization mechanism was via adduct formation, although charge transfer and hydride abstractions were also observed. An internal standard was shown to be effective at correcting for signal changes due to consumption of reagent ions when complex mixtures were sampled. Ion-molecule reactions were exploited to eliminate isobaric interferences that are often encountered in direct, real-time analysis strategies for atmospheric VOC mixtures. The use of a continuously infused internal standard will improve quantitative results in field applications where analyte concentration and sample complexity may be wide ranging.

Peatland vascular plant functional types affect dissolved organic matter chemistry

Northern peatlands are large repositories of carbon. Peatland vascular plant community composition has been functionally associated to a set of biogeochemical processes such as carbon cycling. Yet, we do not fully understand to what extent vascular plant functional types (PFTs) affect the quality of dissolved organic matter, and if there is any feedback on soil microbial activity. Using a longer–term plant removal experiment in a boreo–nemoral peatland in Southern Sweden, we relate the dominance of different vascular plant functional types (i.e. ericoids and graminoids) to the chemistry of the dissolved organic matter (DOM) and microbial enzymatic activities (fluorescein diacetate hydrolysis, FDA). Our results show that PFTs modifies the composition of DOM moieties, with a decrease of low molecular weight organic compounds after vascular plant removal. The decrease of enzymatic activity by up to 68 % in the plant removal plots suggests a reduction in DOM mineralization in the absence of vascular plants. Our results show that plant–derived low molecular organic compounds enhance peatland microbial activity, and suggest that an increase of vascular plant cover in response to climate change can potentially destabilize the OM in peatlands, leading to increased carbon losses.

Vitreous State Characterization of Pharmaceutical Compounds Degrading upon Melting by Using Fast Scanning Calorimetry

Fast scanning calorimetry, a technique mainly devoted to polymer characterization, is applied here for the first time to low molecular mass organic compounds that degrade upon melting, such as ascorbic acid and prednisolone. Due to the fast scan rates upon heating and cooling, the substances can be obtained in the molten state without degradation and then quenched into the glassy state. The hydrated form and the polymorphic Form 1 of prednisolone were investigated. It is shown that once the sesquihydrate dehydrates, a molten product is obtained. Depending on the heating rate, this molten phase may recrystallize or not into Form 1.

Fuchsiella ferrireducens sp. nov., a novel haloalkaliphilic, lithoautotrophic homoacetogen capable of iron reduction, and emendation of the description of the genus Fuchsiella.

Two strains of haloalkaliphilic homoacetogenic bacteria capable of iron reduction, Z-7101T and Z-7102, were isolated from soda lake Tanatar III (Altai, Russia). Cells of both strains were flexible, motile, Gram-negative, spore-forming rods. The strains were mesophilic and obligately alkaliphilic: the pH range for growth was 8.5-10.2 (pHopt 9.8). Growth depended on carbonate and chloride ions. The strains were able to grow chemolithoautotrophically on H2+CO2, producing acetate as the only metabolic product. In medium with carbonates as the only potential electron acceptor, the following substrates were utilized for chemo-organotrophic growth: pyruvate, lactate, ethanol, 1-propanol, ethylene glycol and 1-butanol. Strain Z-7101T was able to reduce nitrate, selenate, thiosulfate and anthraquinone 2,6-disulfonate with ethanol as an electron donor. It was also able to reduce synthesized ferrihydrite to siderite with molecular hydrogen or organic compounds, including acetate and formate, as electron donors. It was able to reduce S0 with acetate or formate as electron donors. The DNA G+C content of strain Z-7101T was 34.6 mol%. 16S rRNA gene sequence analysis showed that strains Z-7101T and Z-7102 were members of the order Halanaerobiales and family Halobacteroidaceae, clustering with Fuchsiella alkaliacetigena Z-7100T (98.9-98.4% similarity). DNA-DNA hybridization was 63.0% between strain Z-7101T and F. alkaliacetigena Z-7100T. Based on morphological and physiological differences from F. alkaliacetigena Z-7100T and the results of phylogenetic analysis and DNA-DNA hybridization, it is proposed to assign strains Z-7101T and Z-7102 ( = DSM 26052 = VKM B-2790) to the novel species Fuchsiellaferrireducens sp. nov. The type strain is strain Z-7101T ( = DSM 26031T = VKM B-2766T).

Polyacrylonitrile membranes modified with carbon nanotubes: characterization and micropollutants removal analysis

The phase inversion method was used to prepare polyacrylonitrile membranes modified with single-walled carbon nanotubes. The influence of the amount and the kind of carbon nanotubes (CNTs) (pristine and functionalized with carboxyl groups) were determined analysing the structure of membranes, hydrophobic–hydrophilic characteristics, zeta potential, and transport-separation properties. Based on the microscopic analysis, it was established that their structure changed depending on the amount of nanotubes added. The membranes with the highest content of CNTs were characterized by the highest membrane capacity. Those membranes were used in low pressure filtration in order to remove micropollutants from synthetic wastewater. The effectiveness of micropollutants removal was dependant on the kind of membrane—in the range 15–65% for bisphenol A, and 25–87% for nonylphenol. The key mechanism in separation of low molecular organic compounds was the sorption phenomenon intensified by the presence of CNTs.

Natural low molecular mass organic compound shows catalytic activity

Organocatalysts are catalysts being low molecular mass organic compounds derived from non‐metal elements. However, there is no report that organocatalysts of biological origins function in vivo. Here we report that the “natural” product, actinorhodin (ACT), produced by Streptomyces coelicolor A3(2) acts as a biocatalyst.&#x0D; During the screening of a new oxidase from streptomycetes, we found that supernatant of S. coelicolor A3(2) showed catalytic activity to oxidize l‐ascorbic acid (l‐ASC). The oxidase could not be purified, but, a correlation between the depth of color and the oxidase activity was obtained. We discovered that the addition of purified ACT to the reaction mixture containing l‐ASC as a substrate led to a decrease in the O2 concentration. We characterized ACT from enzymological standpoints. As a result, (i) oxidation reactions producing H2O2 proceeded on the addition of ACT to the reaction mixture; (ii) ACT was not consumed during the reactions; and (iii) a small amount of ACT consumed an excess amount of the substrates. Even under room temperature, atmospheric pressure and neutral pH, ACT showed catalytic activity in aqueous solution. ACT exhibited substrate specificity in the oxidation reactions. These findings reveal that ACT is discovered as a new member of organocatalyst. ACT is known as an antibiotic toward some microorganisms, but the action mechanism remains unknown. We also propose that bacterial death by ACT is caused by the toxicity of H2O2 produced.

Using microwave heating to improve the desorption efficiency of high molecular weight VOC from beaded activated carbon.

Incomplete regeneration of activated carbon loaded with organic compounds results in heel build-up that reduces the useful life of the adsorbent. In this study, microwave heating was tested as a regeneration method for beaded activated carbon (BAC) loaded with n-dodecane, a high molecular weight volatile organic compound. Energy consumption and desorption efficiency for microwave-heating regeneration were compared with conductive-heating regeneration. The minimum energy needed to completely regenerate the adsorbent (100% desorption efficiency) using microwave regeneration was 6% of that needed with conductive heating regeneration, owing to more rapid heating rates and lower heat loss. Analyses of adsorbent pore size distribution and surface chemistry confirmed that neither heating method altered the physical/chemical properties of the BAC. Additionally, gas chromatography (with flame ionization detector) confirmed that neither regeneration method detectably altered the adsorbate composition during desorption. By demonstrating improvements in energy consumption and desorption efficiency and showing stable adsorbate and adsorbent properties, this paper suggests that microwave heating is an attractive method for activated carbon regeneration particularly when high-affinity VOC adsorbates are present.

Superspace crystallography: a key to the chemistry and properties.

An overview is given of the recent advances in the field of modulated molecular and inorganic crystals with an emphasis on the links between incommensurability, intermolecular and interatomic interactions and, wherever possible, the properties of the materials. The importance of detailed knowledge on the modulated structure for understanding the crystal chemistry and the functional properties of modulated phases is shown using selected examples of incommensurate modulations in organic molecular compounds and inorganic complex oxides.

What Animal Models of Parkinsonism Tell us About the Distinct Nicotinic Acetylcholine Receptors Involved in Pathogenesis?

A prominent degeneration of dopaminergic (DA-ergic) neurons in basal ganglia (striatum and substantia nigra) and a profound loss of dopamine resulting in patient motor dysfunctions are the main characteristics of Parkinson's disease (PD). The data available indicate a substantial role of nicotinic acetylcholine receptors (nAChR) in molecular mechanisms underlying PD. nAChRs belong to the superfamily of ligand-gated ion channels, their pharmacological profile being determined by an array of subunits forming a distinct receptor subtype. Acetylcholine modulates dopamine release via an interaction with multiple nAChRs subtypes present on the nigrosriatal neurons. This suggests nAChRs as possible targets in the treatment of PD, however the knowledge of subunit composition is necessary for effective drug design. As studies in humans are quite limited, animal models are broadly used for these purposes. For creating experimental Parkinsonism models, low molecular weight toxic organic compounds are commonly used. 1-Methyl-4- phenyl-1,2,3,6-tetrahydropyridine (MPTP), 6-hydroxydopamine (6-OHDA), 1,1'-Dimethyl-4-4'-bypiridinium dichloride (paraquat), pesticide rotenone and ubiquitin proteasome system inhibitors, such as lactacystin and epoxomicin, can be mentioned as applied more often. Both mammalian and non-mammalian animals are used as model organisms, rodent and non-human primates being used mainly as mammalian models. This review summarizes the data obtained on toxic animal models about the involvement of different nAChR subtypes in PD at different stages. The present data suggest that degeneration of nigrostriatal DA-ergic neurons in the animal PD models is accompanied by alterations in the expression level and functional activity of different nAChR subtypes. Both heterooligomeric α6- and/or α4-containing and α7 homooligomeric subtypes are affected and can be regarded as possible targets for intervention.

Potassium fluoride as a selective moisture trapping agent for SPE-TD-GC-FID determination of volatile organic compounds in air

Anhydrous potassium fluoride has been proposed as a novel selective moisture trapping agent for gas chromatography to remove water vapor during adsorption concentration of low molecular weight volatile organic compounds (VOCs) from moist air.

Haldane phase in the Hubbard model at 2/3-filling for the organic molecular compound Mo3S7(dmit)3.

We report the discovery of a correlated insulator with a bulk gap at 2/3 filling in a geometrically frustrated Hubbard model that describes the low-energy physics of Mo3S7(dmit)3. This is very different from the Mott insulator expected at half-filling. We show that the insulating phase, which persists even for very weak electron-electron interactions (U), is adiabatically connected to the Haldane phase and is consistent with experiments on Mo3S7(dmit)3.