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Journal articles on the topic 'Chemical lability'

Author: Grafiati
Published: 9 March 2023

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1

Frišták, Vladimír, Martin Pipíška, Tatiana Gablovičová, and Juraj Lesný. "Application of Isotopic Dilution and Single-Step Extractions for Labile Soil Zinc Determination." Nova Biotechnologica et Chimica 12, no. 1 (June 1, 2013): 46–55. http://dx.doi.org/10.2478/nbec-2013-0005.

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Abstract Concentration of available zinc from soils is the primary concern in assessment of its toxicity or essentiality for plants. This study evaluates the changes in chemical extractable Zn from three Slovak typical soils with simultaneous extractions as tools of zinc bioavailability. We found out that extractability of binding zinc decreased in order Na2EDTA, Mehlich 3, Mehlich 2, NH4NO3 and CaCl2 for all soil samples. Using flow-through stripping chronopotentiometry (SCP) and atomic absorption spectrometry (GFAAS) we found out that maximum of soil zinc was removed by organic ligands. Lability of Zn determined by isotopic dilution method using 65Zn and γ-spectrometry showed the significant decrease of isotopic exchangeable zinc fraction (E-value) with decrease of soil reaction. Obtained E-values of uppermost soil horizons showed the zinc lability ranged from 20 to 39%. Our research confirmed the effect of soil reaction, composition and physico-chemical characteristics to Zn lability. For further assessment of zinc bioavailability is needed to find the correlation and effects of structural changes and aging in studied soils
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2

Morris, Russell E., and Lee Brammer. "Coordination change, lability and hemilability in metal–organic frameworks." Chemical Society Reviews 46, no. 17 (2017): 5444–62. http://dx.doi.org/10.1039/c7cs00187h.

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Deformation or cleavage/reformation of metal–ligand bonds in MOFs lies at the heart of chemical/thermal stability and dynamic/flexible behaviour, provides avenues for post-synthetic modification, and can enable novel or improved performance for a variety of applications.
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3

Town, Raewyn M., and Herman P. van Leeuwen. "Dynamic Speciation Analysis of Heterogeneous Metal Complexes with Natural Ligands by Stripping Chronopotentiometry at Scanned Deposition Potential (SSCP)." Australian Journal of Chemistry 57, no. 10 (2004): 983. http://dx.doi.org/10.1071/ch04088.

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Stripping chronopotentiometry at scanned deposition potential (SSCP) allows chemical heterogeneity in metal speciation to be unambiguously identified. In the labile regime, use of the Freundlich binding isotherm allows straightforward determination of parameters to describe the apparent stability and heterogeneity of metal complexes with humic substances. The extent of heterogeneity of metal binding by several humic substances follows the order Cu(ii) >> Pb(ii) > Cd(ii). The lability of metal complexes decreases from the foot to the top of the wave, and the greater the degree of heterogeneity, the more readily lability is lost. In the kinetic current regime, the Koutecký–Koryta approximation allows an expression to be obtained for the SSCP wave that provides a good estimate of the experimental data for metal complexes with moderate degrees of heterogeneity.
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4

van Leeuwen, Herman P., and José-Paulo Pinheiro. "Lability criteria for metal complexes in micro-electrode voltammetry." Journal of Electroanalytical Chemistry 471, no. 1 (September 1999): 55–61. http://dx.doi.org/10.1016/s0022-0728(99)00249-1.

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5

Puy, Jaume, Joan Cecilia, Josep Galceran, Raewyn M. Town, and Herman P. van Leeuwen. "Voltammetric lability of multiligand complexes: the case of ML2." Journal of Electroanalytical Chemistry 571, no. 2 (October 2004): 121–32. http://dx.doi.org/10.1016/j.jelechem.2004.04.017.

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6

Salvador, José, Jaume Puy, Joan Cecília, and Josep Galceran. "Lability of complexes in steady-state finite planar diffusion." Journal of Electroanalytical Chemistry 588, no. 2 (March 2006): 303–13. http://dx.doi.org/10.1016/j.jelechem.2006.01.005.

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7

Hensgens, Geert, Oliver J. Lechtenfeld, François Guillemette, Hjalmar Laudon, and Martin Berggren. "Impacts of litter decay on organic leachate composition and reactivity." Biogeochemistry 154, no. 1 (May 2021): 99–117. http://dx.doi.org/10.1007/s10533-021-00799-3.

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AbstractLitter decomposition produces labile and recalcitrant forms of dissolved organic matter (DOM) that significantly affect soil carbon (C) sequestration. Chemical analysis of this DOM can provide important knowledge for understanding soil DOM dynamics, but detailed molecular analyses on litter derived DOM are scarce. Here we use ultrahigh resolution mass spectrometry (FT-ICR MS) to characterize the molecular composition of DOM from fresh and progressively decomposed litter samples. We compared high reactive (HR) and low reactive (LR) litter sources with regard to changes in the chemistry and bioavailability of leachates throughout the early phase of litter decay. We show that litter reactivity is a driver of chemical changes in the leached DOM of litter species. Birch, alder and Vaccinium (i.e. HR) litter initially produced more DOM with a higher lability than that of spruce, pine and wood (i.e. LR) litter. Labile oxidized phenolic compounds were abundant in leachates produced during the initial HR litter decay stages, indicating litter lignin degradation. However, the similarity in chemistry between HR and LR leachates increased during the litter decay process as highly leachable structures in HR litter were depleted. In contrast, chemistry of leachates from LR litter changed little during the litter decay process. The oxygenated phenolic compounds from HR litter were driving the lability of HR leachates and the changes in relative abundance of molecules during DOM incubation. This appeared to result in the creation of stable aliphatic secondary microbial compounds. In LR leachates, lability was driven by labile aliphatic compounds, while more resistant phenolic compounds were associated with recalcitrance. These results show how DOM dynamics follow different paths depending on litter reactivity, which has important implications for soil biogeochemistry and C sequestration.
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8

Schwab, A. P., K. Lewis, and M. K. Banks. "Biosolids-Amended Soils: Part II. Chemical Lability as a Measure of Contaminant Bioaccessability." Water Environment Research 78, no. 11 (November 2006): 2231–43. http://dx.doi.org/10.2175/106143005x73082.

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9

Nolan, Annette L., Enzo Lombi, and Mike J. McLaughlin. "Metal Bioaccumulation and Toxicity in Soils—Why Bother with Speciation?" Australian Journal of Chemistry 56, no. 3 (2003): 77. http://dx.doi.org/10.1071/ch02226.

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This review assesses metal speciation in soils, including analytical techniques used for measurement and the advantages and disadvantages of using chemical speciation information, in both the solid and aqueous phase, to predict adverse effects of metal contamination in soils and for use in soil protection policies. Other techniques used to assess metal lability and bioavailability in soil are also discussed.
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10

Stubbins, A., J. Niggemann, and T. Dittmar. "Photo-lability of deep ocean dissolved black carbon." Biogeosciences Discussions 9, no. 1 (January 16, 2012): 485–505. http://dx.doi.org/10.5194/bgd-9-485-2012.

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Abstract. Dissolved black carbon (DBC), defined here as condensed aromatics isolated from seawater via PPL solid phase extraction and quantified as benzene polycarboxylic acid oxidation products, is a significant component of the oceanic dissolved organic carbon (DOC) pool. These condensed aromatics are widely distributed in the open ocean and appear to be tens of thousands of years old. As such DBC is regarded as highly refractory. In the current study, the photo-lability of DBC, DOC and coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance) were determined over the course of a 28 d irradiation of North Atlantic Deep Water under a solar simulator. During the irradiation DBC fell from 1044 ± 164 nM C to 55 ± 15 nM C, a 20-fold decrease in concentration. Dissolved black carbon photo-degradation was more rapid and more extensive than for bulk CDOM and DOC. Further, the photo-lability of components of the DBC pool increased with their degree of aromatic condensation. These trends indicate that a continuum of compounds of varying photo-lability exists within the marine DOC pool. In this continuum, photo-lability scales with aromatic character, specifically the degree of condensation. Scaling the rapid photo-degradation of DBC to rates of DOC photo-mineralisation for the global ocean leads to an estimated photo-chemical half-life for oceanic DBC of less than 800 yr. This is more than an order of magnitude shorter than the apparent age of DBC in the ocean. Photo-degradation is therefore posited as the primary sink for oceanic DBC and the survival of DBC molecules in the oceans for millennia appears to be facilitated not by their inherent inertness but by the rate at which they are cycled through the surface ocean's photic zone.
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11

Stubbins, A., J. Niggemann, and T. Dittmar. "Photo-lability of deep ocean dissolved black carbon." Biogeosciences 9, no. 5 (May 9, 2012): 1661–70. http://dx.doi.org/10.5194/bg-9-1661-2012.

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Abstract. Dissolved black carbon (DBC), defined here as condensed aromatics isolated from seawater via PPL solid phase extraction and quantified as benzenepolycarboxylic acid (BPCA) oxidation products, is a significant component of the oceanic dissolved organic carbon (DOC) pool. These condensed aromatics are widely distributed in the open ocean and appear to be tens of thousands of years old. As such DBC is regarded as highly refractory. In the current study, the photo-lability of DBC, DOC and coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance) were determined over the course of a 28 day irradiation of North Atlantic Deep Water under a solar simulator. During the irradiation DBC fell from 1044 ± 164 nM-C to 55 ± 15 nM-C, a 20-fold decrease in concentration. Dissolved black carbon photo-degradation was more rapid and more extensive than for bulk CDOM and DOC. The concentration of DBC correlated with CDOM absorbance and the quality of DBC indicated by the ratios of different BPCAs correlated with CDOM absorbance spectral slope, suggesting the optical properties of CDOM may provide a proxy for both DBC concentrations and quality in natural waters. Further, the photo-lability of components of the DBC pool increased with their degree of aromatic condensation. These trends indicate that a continuum of compounds of varying photo-lability exists within the marine DOC pool. In this continuum, photo-lability scales with aromatic character, specifically the degree of condensation. Scaling the rapid photo-degradation of DBC to rates of DOC photo-mineralisation for the global ocean leads to an estimated photo-chemical half-life for oceanic DBC of less than 800 years. This is more than an order of magnitude shorter than the apparent age of DBC in the ocean. Consequently, photo-degradation is posited as the primary sink for oceanic DBC and the apparent survival of DBC molecules in the oceans for millennia appears to be facilitated not by their inherent inertness but by the rate at which they are cycled through the surface ocean's photic zone.
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12

Kim, Ja-Myung, Oliver Baars, and François M. M. Morel. "The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2081 (November 28, 2016): 20150296. http://dx.doi.org/10.1098/rsta.2015.0296.

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A poorly studied but potentially important consequence of the CO 2 -induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis , demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’.
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13

House, D. A., and M. L. Tobe. "Effect of geometric restraints on lability of acidoamine cobalt(III) complexes." Pure and Applied Chemistry 60, no. 8 (January 1, 1988): 1197–200. http://dx.doi.org/10.1351/pac198860081197.

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14

Pinheiro, José Paulo, and Herman P. van Leeuwen. "Scanned stripping chronopotentiometry of metal complexes: lability diagnosis and stability computation." Journal of Electroanalytical Chemistry 570, no. 1 (August 2004): 69–75. http://dx.doi.org/10.1016/j.jelechem.2004.03.016.

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15

Pinheiro, José P., Marcel Minor, and Herman P. van Leeuwen. "Metal speciation dynamics in colloidal ligand dispersions. Part 2: Electrochemical lability." Journal of Electroanalytical Chemistry 587, no. 2 (February 2006): 284–92. http://dx.doi.org/10.1016/j.jelechem.2005.11.022.

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16

Huy, Trinh Quang, Satoshi Matsumoto, and Shin-Ichiro Wada. "Mineralogical and Chemical Properties and Lability of Cadmium in some Soils from Japan and Vietnam." Journal of the Faculty of Agriculture, Kyushu University 50, no. 2 (October 1, 2005): 851–60. http://dx.doi.org/10.5109/4693.

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17

Donner, Erica, Gianluca Brunetti, Bernie Zarcinas, Paul Harris, Ehsan Tavakkoli, Ravi Naidu, and Enzo Lombi. "Effects of Chemical Amendments on the Lability and Speciation of Metals in Anaerobically Digested Biosolids." Environmental Science & Technology 47, no. 19 (September 17, 2013): 11157–65. http://dx.doi.org/10.1021/es400805j.

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18

Ting, Keh-Chuh, Eddie Guangming Zhou, and Nirmal Saini. "Determination of Imidacloprid in Fruits and Vegetables by Liquid Chromatography with Diode Array and Nitrogen-Specific Chemiluminescence Detection." Journal of AOAC INTERNATIONAL 87, no. 4 (July 1, 2004): 997–1002. http://dx.doi.org/10.1093/jaoac/87.4.997.

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Abstract A national trend is focusing on expanding usage of environmentally friendly nitrogenous pesticides and herbicides. However, some of these chemicals are undetectable by any gas chromatographic method due to their thermal lability or nonvolatility. Using imidacloprid as a model compound, this laboratory has developed a simple, effective, and reliable liquid chromatography (LC) method to address the inherent difficulties of these chemicals. Focusing on nitro, nitrate, and/or nitrite chromophore groups and components contained in the chemical structure of most nitrogenous compounds, LC with diode array detector and a nitrogen-specific detector in tandem enabled determination and confirmation analyses in series. Furthermore, using 2 mixtures of solvents in conjunction with 2-stage solid-phase extraction cleanup on aminopropyl/Florisil cartridges to eliminate and/or minimize interferences resulting from free amino acids, peptides, proteins, pigments, and lipids in the plant tissues made the qualitative and quantitative analysis simple, fast, and cost effective. This method demonstrated the potential for becoming a viable analysis tool for many other types of nonvolatile nitrogenous chemicals.
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19

Lemon, Christopher M., and Penelope J. Brothers. "The synthesis, reactivity, and peripheral functionalization of corroles." Journal of Porphyrins and Phthalocyanines 15, no. 09n10 (September 2011): 809–34. http://dx.doi.org/10.1142/s1088424611003896.

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Corroles are unusual macrocycles that often exhibit chemical reactivity that is distinct from their closely related porphyrin cousins. Standard organic transformations with corroles often result in the formation of unexpected products. A survey of synthetic methods for the preparation of both meso-substituted and β-substituted corroles will give an overview of the different synthetic strategies. This review provides a comprehensive description of the chemical reactivity and functionalization of corroles, focusing especially on reactions at the periphery of the macrocycle. Formylation, nitration, bromination and chlorosulfonation reactions will be explored in detail. In addition, demetalation processes, reactivity of the N-pyrrolic nitrogens and the lability of the macrocycle ring toward expansion and ring-opening reactions will be discussed. Finally, the synthesis of super-structured (picket-fence, capped, and strapped) corroles and isocorroles will be surveyed.
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20

Atkinson, N. R., E. H. Bailey, A. M. Tye, N. Breward, and S. D. Young. "Fractionation of lead in soil by isotopic dilution and sequential extraction." Environmental Chemistry 8, no. 5 (2011): 493. http://dx.doi.org/10.1071/en11020.

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Environmental contextThe chemical reactivity of lead in soil is difficult to assess and depends on both soil conditions and the origins of the lead. This paper tests the combined application of lead isotopic techniques and chemical extraction against our understanding of lead fractionation in soils. Possibly against expectation, it appears that the ‘reactivity’ of lead can be high and yet there is tentative evidence that the original source of the metal affects its fractionation in soil, even after long contact times. Abstract‘Reactivity’ or ‘lability’ of lead is difficult to measure using traditional methods. We investigated the use of isotopic dilution with 204Pb to determine metal reactivity in four soils historically contaminated with contrasting sources of Pb, including (i) petrol-derived Pb, (ii) Pb/Zn minespoil, (iii) long-term sewage sludge application and (iv) 19th century urban waste disposal; total soil Pb concentrations ranged from 217 to 13 600 mg kg–1. A post-spike equilibration period of 3 days and suspension in 5.0 × 10–4 M ethylenediaminetetraacetic acid provided reasonably robust conditions for measuring isotopically exchangeable Pb. However, in acidic organic soils a dilute Ca(NO3)2 electrolyte may be preferable to avoid mobilisation of ‘non-labile’ Pb. Results showed that the reactive pool of soil Pb can be a large proportion of the total soil lead content but varies with the original Pb source. A comparison of isotopic exchangeability with the results of a sequential extraction procedure showed that (isotopically) ‘non-labile’ Pb may be broadly equated with ‘residual’ Pb in organic soils. However, in mineral soils the ‘carbonate’ and ‘oxide-bound’ Pb fractions included non-labile forms of Pb. The individual isotopic signatures of labile and non-labile Pb pools suggested that, despite prolonged contact with soil, differences between the lability of the original contaminant and the native soil Pb may remain.
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21

Caprioglio, Diego, Daiana Mattoteia, Orazio Taglialatela-Scafati, Eduardo Muñoz, and Giovanni Appendino. "Cannabinoquinones: Synthesis and Biological Profile." Biomolecules 11, no. 7 (July 5, 2021): 991. http://dx.doi.org/10.3390/biom11070991.

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Neutral cannabinoids are oxidatively unstable and are converted into quinone derivatives by atmospheric- and/or chemical oxidative dearomatization. The study of cannabinoquinones has long been plagued by their lability toward additional oxidative degradation, but full substitution of the quinone ring, as well as the introduction of steric hindrance on the alkyl substituent, have provided sufficient stability for a systematic investigation of their bioactivity and for further clinical development. These studies culminated in the discovery of the aminocannabinoquinone VCE-004.8 (5), a compound under phase 2 clinical development with orphan drug status by EMA and FDA for the management of scleroderma. The synthesis and rich chemistry of these compounds will be described, summarizing their biological profile and clinical potential.
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22

Tyzack, Jonathan D., Peter A. Hunt, and Matthew D. Segall. "Predicting Regioselectivity and Lability of Cytochrome P450 Metabolism Using Quantum Mechanical Simulations." Journal of Chemical Information and Modeling 56, no. 11 (October 26, 2016): 2180–93. http://dx.doi.org/10.1021/acs.jcim.6b00233.

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23

Fontes, Maurício Paulo Ferreira, and Guilherme Cadinelli dos Santos. "Lability and sorption of heavy metals as related to chemical, physical, and mineralogical characteristics of highly weathered soils." Journal of Soils and Sediments 10, no. 4 (November 20, 2009): 774–86. http://dx.doi.org/10.1007/s11368-009-0157-y.

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24

Wells, M. L., and L. M. Mayer. "Variations in the chemical lability of iron in estuarine, coastal and shelf waters and its implications for phytoplankton." Marine Chemistry 32, no. 2-4 (March 1991): 195–210. http://dx.doi.org/10.1016/0304-4203(91)90038-x.

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25

Egorov, Yu P., V. V. Pen'kovskii, and I. E. Boldeskul. "Quantum-chemical evaluation of the lability of ?-electronic systems in n-benzoyl derivatives of phosphorus and sulfur imines." Theoretical and Experimental Chemistry 21, no. 4 (July 1985): 442–44. http://dx.doi.org/10.1007/bf01004516.

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26

Pinheiro, J. P., R. F. Domingos, M. Minor, and H. P. van Leeuwen. "Metal speciation dynamics in colloidal ligand dispersions. Part 3: Lability features of steady-state systems." Journal of Electroanalytical Chemistry 596, no. 1 (October 2006): 57–64. http://dx.doi.org/10.1016/j.jelechem.2006.07.004.

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27

Mukhopadhyay, Partha Pratim, Jean-Claude Chambron, and Roland Graff. "The [Pd(bipy)]2+ “merry-go-round”: Insights into the lability of the Pd–N bond." Comptes Rendus Chimie 12, no. 12 (December 2009): 1267–74. http://dx.doi.org/10.1016/j.crci.2009.03.002.

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28

Christophorov, L. N. "Indirect Evidences of Conformational Regulation in Protein Reactions: How Much Can Be Learnt?" Ukrainian Journal of Physics 57, no. 7 (July 30, 2012): 746. http://dx.doi.org/10.15407/ujpe57.7.746.

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Almost all reactions of proteins manifest deviations from the simple behaviour prescribed by standard (bio)chemical kinetics. This is caused by the extraordinary structural lability of protein macromolecules which is often not less important for the reaction efficiency than the properties of the active center. Unveiling the mechanisms of structural regulation encounters serious difficulties because of their hidden character, as either modern experiments or computational methods still fall short of monitoring simultaneously the reaction events and concomitant conformational changes, so that one has to decipher the reaction kinetics only. Nevertheless, it is possible to come to reliable conclusions on the mode of operation of proteins and the character of their structural relaxation with the help of a convenient and computationally accessible approach expounded in the present paper.
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29

Burd, Katheryn, Cristian Estop-Aragonés, Suzanne E. Tank, and David Olefeldt. "Lability of dissolved organic carbon from boreal peatlands: interactions between permafrost thaw, wildfire, and season." Canadian Journal of Soil Science 100, no. 4 (December 1, 2020): 503–15. http://dx.doi.org/10.1139/cjss-2019-0154.

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Boreal peatlands are major sources of dissolved organic carbon (DOC) to downstream aquatic ecosystems, where it influences carbon cycling and food web structure. Wildfire and permafrost thaw alter peatland vegetation and hydrology and may affect the quantity and chemical composition of exported DOC. We studied the influence of wildfire and thaw on microbial and photochemical lability of near-surface porewater DOC, assessed through 7 d incubations. We carried out these incubations in spring, summer, and fall but only found differences in spring when DOC biodegradability (% loss during dark incubations) increased with lower DOC aromaticity and C/N ratios. During spring, the most labile DOC was found in recently formed thermokarst bogs along collapsing peat plateau edges (25% loss), which was greater than in mature sections of thermokarst bogs (3%), and peat plateaus with intact permafrost (9%). Increased DOC lability following thaw was likely linked to high DOC production and turnover associated with productive hydrophilic Sphagnum mosses and sedges, rather than thawed permafrost peat. A wildfire (3 yr prior) reduced DOC biodegradability in both peat plateaus (4%) and rapidly collapsing peat plateau edges (14%). Biodegradability of DOC in summer and fall was low across all sites; 2% and 4%, respectively. Photodegradation was shown to potentially contribute significantly to downstream DOC degradation but did not vary across peatland sites. We show that disturbances such as permafrost thaw and wildfire have the potential to affect downstream carbon cycling, particularly as the largest influences were found in spring when peatlands are well connected to downstream aquatic ecosystems.
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Tebbe, Jonas, Emily Humble, Martin Adam Stoffel, Lisa Johanna Tewes, Caroline Müller, Jaume Forcada, Barbara Caspers, and Joseph Ivan Hoffman. "Chemical patterns of colony membership and mother-offspring similarity in Antarctic fur seals are reproducible." PeerJ 8 (October 19, 2020): e10131. http://dx.doi.org/10.7717/peerj.10131.

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Replication studies are essential for evaluating the validity of previous research findings. However, it has proven challenging to reproduce the results of ecological and evolutionary studies, partly because of the complexity and lability of many of the phenomena being investigated, but also due to small sample sizes, low statistical power and publication bias. Additionally, replication is often considered too difficult in field settings where many factors are beyond the investigator’s control and where spatial and temporal dependencies may be strong. We investigated the feasibility of reproducing original research findings in the field of chemical ecology by performing an exact replication of a previous study of Antarctic fur seals (Arctocephalus gazella). In the original study, skin swabs from 41 mother-offspring pairs from two adjacent breeding colonies on Bird Island, South Georgia, were analyzed using gas chromatography-mass spectrometry. Seals from the two colonies differed significantly in their chemical fingerprints, suggesting that colony membership may be chemically encoded, and mothers were also chemically similar to their pups, hinting at the possible involvement of phenotype matching in mother-offspring recognition. In the current study, we generated and analyzed chemical data from a non-overlapping sample of 50 mother-offspring pairs from the same two colonies 5 years later. The original results were corroborated in both hypothesis testing and estimation contexts, with p-values remaining highly significant and effect sizes, standardized between studies by bootstrapping the chemical data over individuals, being of comparable magnitude. However, exact replication studies are only capable of showing whether a given effect can be replicated in a specific setting. We therefore investigated whether chemical signatures are colony-specific in general by expanding the geographic coverage of our study to include pups from a total of six colonies around Bird Island. We detected significant chemical differences in all but a handful of pairwise comparisons between colonies. This finding adds weight to our original conclusion that colony membership is chemically encoded, and suggests that chemical patterns of colony membership not only persist over time but can also be generalized over space. Our study systematically confirms and extends our previous findings, while also implying more broadly that spatial and temporal heterogeneity need not necessarily negate the reproduction and generalization of ecological research findings.
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Shang, Chao, and Holm Tiessen. "ORGANIC MATTER LABILITY IN A TROPICAL OXISOL: EVIDENCE FROM SHIFTING CULTIVATION, CHEMICAL OXIDATION, PARTICLE SIZE, DENSITY, AND MAGNETIC FRACTIONATIONS." Soil Science 162, no. 11 (November 1997): 795–807. http://dx.doi.org/10.1097/00010694-199711000-00004.

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32

Hayes, Sarah M., Scott A. White, Thomas L. Thompson, Raina M. Maier, and Jon Chorover. "Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses." Applied Geochemistry 24, no. 12 (December 2009): 2234–45. http://dx.doi.org/10.1016/j.apgeochem.2009.09.010.

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33

Percipalle, Mathias, Yamanappa Hunashal, Jan Steyaert, Federico Fogolari, and Gennaro Esposito. "Structure of Nanobody Nb23." Molecules 26, no. 12 (June 11, 2021): 3567. http://dx.doi.org/10.3390/molecules26123567.

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Background: Nanobodies, or VHHs, are derived from heavy chain-only antibodies (hcAbs) found in camelids. They overcome some of the inherent limitations of monoclonal antibodies (mAbs) and derivatives thereof, due to their smaller molecular size and higher stability, and thus present an alternative to mAbs for therapeutic use. Two nanobodies, Nb23 and Nb24, have been shown to similarly inhibit the self-aggregation of very amyloidogenic variants of β2-microglobulin. Here, the structure of Nb23 was modeled with the Chemical-Shift (CS)-Rosetta server using chemical shift assignments from nuclear magnetic resonance (NMR) spectroscopy experiments, and used as prior knowledge in PONDEROSA restrained modeling based on experimentally assessed internuclear distances. Further validation was comparatively obtained with the results of molecular dynamics trajectories calculated from the resulting best energy-minimized Nb23 conformers. Methods: 2D and 3D NMR spectroscopy experiments were carried out to determine the assignment of the backbone and side chain hydrogen, nitrogen and carbon resonances to extract chemical shifts and interproton separations for restrained modeling. Results: The solution structure of isolated Nb23 nanobody was determined. Conclusions: The structural analysis indicated that isolated Nb23 has a dynamic CDR3 loop distributed over different orientations with respect to Nb24, which could determine differences in target antigen affinity or complex lability.
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Gates, Paul J. "Atmospheric pressure chemical ionisation mass spectrometry for the routine analysis of low molecular weight analytes." European Journal of Mass Spectrometry 27, no. 1 (February 2021): 13–28. http://dx.doi.org/10.1177/14690667211005055.

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The routine analysis of low molecular weight analytes by mass spectrometry is often complicated by the lability of the analyte’s functional groups and/or the lack of moieties that can be easily charged. If a molecule is too labile this precludes analysis by techniques such as electron ionisation or chemical ionisation as the analyte will undergo thermal decomposition prior to ionisation as well as spontaneous fragmentation during the ionisation process. If the analyte has a low propensity to form ions in electrospray ionisation (i.e., lacks acidic or basic sites) then often no analyte related ions are observed. In this paper, the robustness and versatility of the established method of atmospheric pressure chemical ionisation is demonstrated for the analysis of low molecular weight analytes. The utility of the technique is demonstrated through the analysis of 30 reference standards of varying functionality, and further by the analysis of 75 synthetic samples which were problematic when analysed by electron or electrospray ionisation. The resulting spectra are dominated by intact molecular species ([M+H]+ and M+ in positive ion mode and [M − H]− and [M + Cl]− in negative ion mode) along with logical neutral losses reminiscent of what you might expect from the analyte’s structure (losses of H2O from alcohols or CO from aldehydes etc). This paper presents atmospheric pressure chemical ionisation as an essential tool for broadening the chemical space of successful analyses for any routine mass spectrometry service laboratory of facility.
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DAVE, PARESH C., and D. SRINIVAS. "Effect of substitution on the redox behaviour and EPR spectra of zinc(II) substituted tetraphenylporphyrin cation radicals." Journal of Porphyrins and Phthalocyanines 04, no. 02 (March 2000): 192–201. http://dx.doi.org/10.1002/(sici)1099-1409(200003)4:2<192::aid-jpp193>3.0.co;2-5.

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Substituted tetraphenylporphyrinatozinc(II) complexes have been synthesized and characterized by various physicochemical techniques. The effects of substitution and counterions on the redox behaviour and EPR spectra have been examined. The EPR spectra revealed that chemical oxidation with bromine yields ZnT ( X - P ) P + Br - (species I) and a brominated tetraphenylporphyrin cation radical (species II). The former exhibits a labile electronic ground state (with 2 A 2 u ground state transforming into 2 A 1 u at 175 K), while the latter is characterized by a 2 A 1 u state. The lability in the electronic ground state for species I is discussed in terms of the change in molecular geometry as the temperature is lowered. The EPR spectra also revealed for the first time the formation of dimeric agglomerates of TPP cation radicals in low concentration below the electronic transition (i.e. near 170 K) wherein the paramagnetic sites are antiferromagnetically coupled.
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36

Del Ciampo, Luiz Antonio, and Ieda Regina Lopes Del Ciampo. "Adolescent brain and nicotine." Journal of Drug Delivery and Therapeutics 10, no. 4-s (August 15, 2020): 232–34. http://dx.doi.org/10.22270/jddt.v10i4-s.4237.

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Adolescence is a period of transition between childhood and adulthood that involves major changes in development in the physical, psychological, social and neurobiological domains. During this phase of life, multiple physical and emotional events occur throughout the body, markedly in the central nervous system, regulated by neurohormones, which are fundamental for human development, responsible for changes in thoughts, attitudes and behaviors that culminate in complete maturity for a laborious and reproductive life. Due to the lability of the neurological tissue in this period, external aggressions by means of chemical substances can cause serious and lasting effects. Nicotine is one of the substances considered legal and that more easily the adolescent comes into contact early, and can cause many harm to current and future health. This article presents some characteristics of the development of the adolescent's nervous system and the deleterious actions that can be caused by nicotine in its various forms of social presentation. Keywords: Adolescence – nicotine – smoking – nicotine addiction
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37

Kitagawa, Hakuba, Hiroyoshi Ohtsu, Aurora J. Cruz-Cabeza, and Masaki Kawano. "Isolation and evolution of labile sulfur allotropesviakinetic encapsulation in interactive porous networks." IUCrJ 3, no. 4 (June 8, 2016): 232–36. http://dx.doi.org/10.1107/s2052252516008423.

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The isolation and characterization of small sulfur allotropes have long remained unachievable because of their extreme lability. This study reports the first direct observation of disulfur (S2) with X-ray crystallography. Sulfur gas was kinetically trapped and frozen into the pores of two Cu-based porous coordination networks containing interactive iodide sites. Stabilization of S2was achieved either through physisorption or chemisorption on iodide anions. One of the networks displayed shape selectivity for linear molecules only, therefore S2was trapped and remained stable within the material at room temperature and higher. In the second network, however, the S2molecules reacted further to produce bent-S3species as the temperature was increased. Following the thermal evolution of the S2species in this network using X-ray diffraction and Raman spectroscopy unveiled the generation of a new reaction intermediate never observed before, thecyclo-trisulfur dication (cyclo-S32+). It is envisaged that kinetic guest trapping in interactive crystalline porous networks will be a promising method to investigate transient chemical species.
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38

Magalhaes, Sulamirtes S. de A., Fabricio T. Ramos, and Oscarlina L. dos S. Weber. "Carbon stocks of an Oxisol after thirty-eight years under different tillage systems." Revista Brasileira de Engenharia Agrícola e Ambiental 20, no. 1 (January 2016): 85–91. http://dx.doi.org/10.1590/1807-1929/agriambi.v20n1p85-91.

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ABSTRACT Soil carbon (C) stock determination can subsidize discussions on the continuity of an agricultural management. This study aimed to evaluate the stocks of total organic C (STOC) and labile C (SLC), and the indices of C lability (CLI), C compartment (CCI) and C management (CMI), and correlate them with chemical and physical attributes of a Red Yellow Latosol (Oxisol) managed for 38 years with different tillage systems in a Cerrado region of Mato Grosso, Brazil. Disturbed and undisturbed soil samples were collected in three layers (0-0.05, 0.05-0.10 and 0.10-0.20 m). The CMI (CLI x CCI) showed higher STOC possibly as the tillage depth decreased, because none of the tillage systems conserved STOC and SLC in the layers of 0-0.05 and 0.05-0.10 m, compared with the Native Cerrado, i.e., soil C conservation only occurred in the layer of 0.10-0.20 m. Although the percentage of SLC in STOC was lower, only SLC was correlated with soil chemical and physical attributes and, based on the multiple linear regression analysis, SLC was explained in 54% (R2) by the cation exchange capacity and soil micropores. Therefore, for monitoring purposes, the SLCestimated can be useful to evaluate soil C storage.
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Šimon, Tomáš, and Mikuláš Madaras. "Chemical and Spectroscopic Parameters Are Equally Sensitive in Describing Soil Organic Matter Changes After Decades of Different Fertilization." Agriculture 10, no. 9 (September 22, 2020): 422. http://dx.doi.org/10.3390/agriculture10090422.

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The composition and dynamics of soil organic matter (SOM) are decisive factors in soil quality. In this work, total organic C (Ctot), hot water extractable C (Chwl), and aliphatic and aromatic SOM components detected by Fourier transform infrared (FTIR) spectroscopy were determined to evaluate SOM quantity and quality in soil samples taken between 2004 and 2017 from 13 field experiments established in different soil and climatic conditions of the Czech Republic. In addition, the C pool index (CPI), lability index (LI), C management index (CMI), and SOM decomposition index (DI) were assessed. Treatments were selected as follows: Unfertilized control (Nil), mineral fertilized treatment (NPK), farmyard manured treatment (FYM), and organic and mineral fertilized treatment (FYM+NPK). Both organic and combined fertilization significantly increased soil Ctot, Chwl, CPI, LI, CMI, and labile aliphatic SOM components (FTIRaliph) in most of the experiments compared to unfertilized treatments (p ≤ 0.05). In contrast, the highest content of recalcitrant aromatic SOM components (FTIRarom) and increased DI were determined in majority of unfertilized soils. Our results show that: (1) fertilization regimes increased both labile and total C pools; the highest increase was nearly uniformly observed for NPK+FYM treatment; (2) SOM chemical and FTIR spectral detection had equal sensitivity to the changes; and (3) none of the parameters or indices tested can be used as a stand-alone SOM quality descriptor.
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40

Anisimov, Vyacheslav Sergeevich, Lydia Nikolaevna Anisimova, and Andrey Ivanovich Sanzharov. "Zinc Plant Uptake as Result of Edaphic Factors Acting." Plants 10, no. 11 (November 18, 2021): 2496. http://dx.doi.org/10.3390/plants10112496.

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The influence of soil characteristics on the lability and bioavailability of zinc at both background and phytotoxic concentrations in Albic Retisol soil (Loamic, Ochric) was studied using various methods. Ranges of insufficient, non-phytotoxic, and phytotoxic zinc concentrations in soil solutions were established in an experiment with an aqueous barley culture. It was experimentally revealed that for a wide range of non-toxic concentrations of Zn in the soil corresponding to the indicative type of plant response, there was constancy of the concentration ratio (CR) and concentration factor (CF) migration parameters. As a result, a new method for assessing the buffer capacity of soils with respect to Zn (PBCZn) is proposed. The transformation processes of the chemical forms and root uptake of native (natural) zinc contained in the Albic Retisol (Loamic, Ochric) through the aqueous culture of barley were studied using a cyclic lysimetric installation and radioactive 65Zn tracer. The distribution patterns of Zn(65Zn) between different forms (chemical fractions) in the soil were established using the sequential fractionation scheme of BCR. The coefficients of distribution and concentration factors of natural Zn and 65Zn, as well as accumulation and removal of the metal by plants were estimated. The values of the enrichment factor of natural (stable) Zn contained in sequentially extracted chemical fractions with the 65Zn radioisotope were determined and the amount of the pool of labile zinc compounds in the studied soil was calculated.
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41

Li, Wanqing, Marcos D. Battistel, Hannah Reeves, Lisa Oh, Hai Yu, Xi Chen, Lee-Ping Wang, and Darón I. Freedberg. "A combined NMR, MD and DFT conformational analysis of 9-O-acetyl sialic acid-containing GM3 ganglioside glycan and its 9-N-acetyl mimic." Glycobiology 30, no. 10 (April 29, 2020): 787–801. http://dx.doi.org/10.1093/glycob/cwaa040.

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Abstract O-Acetylation of carbohydrates such as sialic acids is common in nature, but its role is not clearly understood due to the lability of O-acetyl groups. We demonstrated previously that 9-acetamido-9-deoxy-N-acetylneuraminic acid (Neu5Ac9NAc) is a chemically and biologically stable mimic of the 9-O-acetyl-N-acetylneuraminic acid (Neu5,9Ac2) of the corresponding sialoglycans. Here, a systematic nuclear magnetic resonance (NMR) spectroscopic and molecular dynamics (MD) simulation study was undertaken for Neu5,9Ac2-containing GM3 ganglioside glycan (GM3-glycan) and its Neu5Ac9NAc analog. GM3-glycan with Neu5Ac as the non-O-acetyl form of Neu5,9Ac2 was used as a control. Complete 1H and 13C NMR chemical shift assignments, three-bond 1H-13C trans-glycosidic coupling constants (3JCH), accurate 1H-1H coupling constants (3JHH), nuclear Overhauser effects and hydrogen bonding detection were carried out. Results show that structural modification (O- or N-acetylation) on the C-9 of Neu5Ac in GM3 glycan does not cause significant conformational changes on either its glycosidic dihedral angles or its secondary structure. All structural differences are confined to the Neu5Ac glycerol chain, and minor temperature-dependent changes are seen in the aglycone portion. We also used Density Functional Theory (DFT) quantum mechanical calculations to improve currently used 3JHH Karplus relations. Furthermore, OH chemical shifts were assigned at −10°C and no evidence of an intramolecular hydrogen bond was observed. The results provide additional evidence regarding structural similarities between sialosides containing 9-N-acetylated and 9-O-acetylated Neu5Ac and support the opportunity of using 9-N-acetylated Neu5Ac as a stable mimic to study the biochemical role of 9-O-acetylated Neu5Ac.
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42

Varghese, Shery, Yue Tang, and James A. Imlay. "Contrasting Sensitivities of Escherichia coli Aconitases A and B to Oxidation and Iron Depletion." Journal of Bacteriology 185, no. 1 (January 1, 2003): 221–30. http://dx.doi.org/10.1128/jb.185.1.221-230.2003.

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ABSTRACT Superoxide damages dehydratases that contain catalytic [4Fe-4S]2+ clusters. Aconitases are members of that enzyme family, and previous work showed that most aconitase activity is lost when Escherichia coli is exposed to superoxide stress. More recently it was determined that E. coli synthesizes at least two isozymes of aconitase, AcnA and AcnB. Synthesis of AcnA, the less-abundant enzyme, is positively controlled by SoxS, a protein that is activated in the presence of superoxide-generating chemicals. We have determined that this arrangement exists because AcnA is resistant to superoxide in vivo. Surprisingly, purified AcnA is extremely sensitive to superoxide and other chemical oxidants unless it is combined with an uncharacterized factor that is present in cell extracts. In contrast, AcnB is highly sensitive to a variety of chemical oxidants in vivo, in extracts, and in its purified form. Thus, the induction of AcnA during oxidative stress provides a mechanism to circumvent a block in the tricarboxylic acid cycle. AcnA appears to be as catalytically competent as AcnB, so the retention of the latter as the primary housekeeping enzyme must provide some other advantage. We observed that the [4Fe-4S] cluster of AcnB is in dynamic equilibrium with the surrounding iron pool, so that AcnB is rapidly demetallated when intracellular iron pools drop. AcnA and other dehydratases do not show this trait. Demetallated AcnB is known to bind its cognate mRNA. The absence of AcnB activity also causes the accumulation and excretion of citrate, an iron chelator for which E. coli synthesizes a transport system. Thus, AcnB may be retained as the primary aconitase because the lability of its exposed cluster allows E. coli to sense and respond to iron depletion.
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43

Mossa, Abdul-Wahab, Dawd Gashu, Martin R. Broadley, Sarah J. Dunham, Steve P. McGrath, Elizabeth H. Bailey, and Scott D. Young. "The effect of soil properties on zinc lability and solubility in soils of Ethiopia – an isotopic dilution study." SOIL 7, no. 1 (June 21, 2021): 255–68. http://dx.doi.org/10.5194/soil-7-255-2021.

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Abstract. Zinc (Zn) deficiency is a widespread nutritional problem in human populations, especially in sub-Saharan Africa (SSA). The Zn concentration of crops consumed depends in part on the Zn status of the soil. Improved understanding of factors controlling the phyto-availability of Zn in soils can contribute to potential agronomic interventions to tackle Zn deficiency, but many soil types in SSA are poorly studied. Soil samples (n=475) were collected from a large part of the Amhara Region of Ethiopia, where there is widespread Zn deficiency. Zinc status was quantified by measuring several fractions, including the pseudo-total (aqua regia digestion; ZnTot), available (DTPA (diethylenetriamine pentaacetate) extractable; ZnDTPA), soluble (dissolved in 0.01 M Ca(NO3); ZnSoln) and isotopically exchangeable Zn, using the enriched stable Zn isotope 70Zn (ZnE). Soil geochemical properties were assessed for their influence on Zn lability and solubility. A parameterized geochemical assemblage model (Windermere Humic Aqueous Model – WHAM) was also employed to predict the solid phase fractionation of Zn in tropical soils rather than using sequential chemical extractions. ZnTot ranged from 14.1 to 291 mg kg−1 (median = 100 mg kg−1), whereas ZnDTPA in the majority of soil samples was less than 0.5 mg kg−1, indicating widespread phyto-available Zn deficiency in these soils. The labile fraction of Zn in soil (ZnE as % ZnTot) was low, with median and mean values of 4.7 % and 8.0 %, respectively. Labile Zn partitioning between the solid and the solution phases of soil was highly pH dependent, where 94 % of the variation in the partitioning coefficient of 70Zn was explained by soil pH. Similarly, 86 % of the variation in ZnSoln was explained by soil pH. Zinc distribution between adsorbed ZnE and ZnSoln was controlled by pH. Notably, Zn isotopic exchangeability increased with soil pH. This contrasts with literature on contaminated and urban soils and may arise from covarying factors, such as contrasting soil clay mineralogy across the pH range of the soils used in the current study. These results could be used to improve agronomic interventions to tackle Zn deficiency in SSA.
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44

Bastidas, David. "(Corrosion Division Rusty Award for Mid-Career Excellence) Rust At a Glance: Electrochemical Thermodynamics and Kinetics of Porous Corroding Interfaces." ECS Meeting Abstracts MA2022-02, no. 13 (October 9, 2022): 800. http://dx.doi.org/10.1149/ma2022-0213800mtgabs.

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The development of a rust layer is governed by physico-chemical processes at the electrode/electrolyte porous interface, including electrochemical thermodynamics and kinetics, as well as transport and reaction processes. While rust can be protective under passive and inert regions found on the Pourbaix diagram, it becomes interesting to see whether its stability is compromised under harsh conditions that lead to active dissolution of this porous interface. Thermodynamics calculations can predict phase transformation, which nucleation and growth is governed by the chemical activity of the porous interfaces as well as by the saturation of the electrolyte solution. Understanding the electrochemical interface is a major challenge to unravel the corrosion mechanism of porous systems. The heterogeneous nature of the oxide structure as well as the development of amorphous gel regions influences the formation of active sites and point defects with a high lability for reacting with gas phases dissolved, entrapped, or occluded within interfacial substructures. The stabilization and corrosion protection of the rust interface requires to understand the adsorption of corrosion inhibitors on the surface of the active site on the electrode ‒ creating a stable protective passive film. Enthalpy and entropy of the dissolution process can explain the spontaneous formation of a rust layer as well as the displacement of water molecules, which ultimately will result in the effective physico-chemical adsorption of the inhibitor molecules. In summary, this communication is aimed to present the role of rust at a glance, and its implications on the electrochemical corrosion mechanisms on porous interfaces. The application of electrochemical fundamentals and first principles combined with state of the art electrochemical, chemical and surface characterization techniques provides a comprehensive vision and mission on current trends in corrosion and protection of steel in porous media.
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45

Portola, V. A., A. A. Bobrovnikova, S. I. Protasov, E. A. Seregin, and A. A. Eremenko. "Assessment of Spontaneous Ignition Lability and Gas Evolution of Coal-Bearing Rocks of Dumps and Sludges of the Coal Enterprises." Occupational Safety in Industry, no. 3 (March 2021): 74–80. http://dx.doi.org/10.24000/0409-2961-2021-3-74-80.

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Rock dumps of coal mining and coal processing enterprises contain coal, which is capable to absorbing oxygen to generate heat. Under favorable conditions, the heat generated is sufficient to increase the rock temperature and to form spontaneous fire seats. At the same time, coal-bearing rocks emit combustible and toxic gases generated during the coal decay and the oxidation of combustible elements. To assess the possibility of the development of spontaneous ignition processes in the coal-bearing rock agglomerates that were exposed to air for a long time, the samples were taken, the constant oxygen sorption rate and the duration of the spontaneous ignition incubation period were determined. Sampling was carried out on the surface of two dumps of the open pits, as well as at different depths of the slimepit of the processing plant, which were not in operation for decades. The experiment allowed to determine the concentration and intensity of the evolution of various gases from the coal-bearing rocks at natural ambient temperature. The uneven sorption activity of the rocks on the surface of dumps contributes to forming spontaneous fire seats in the areas that are most liable to this. In addition, rock dumps for decades continue to emit methane and carbon monoxide into the atmosphere at the natural temperature of the rocks, which negatively affects the surrounding nature. In the sludge settling tank, not operated for about 60 years, the sorption activity of the sludge in relation to oxygen changes not only on the surface, but also at different depths of the settling tank. The revealed features of long-term storage of coal-bearing rocks in the dumps and slimepits should be taken into account when choosing the technologies for coal mining and processing, as well as storage of the overburden rocks and processing wastes.
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46

Dubenko, Anastasiia V., Mykola V. Nikolenko, Eugene V. Aksenenko, Andrii Kostyniuk, and Blaž Likozar. "Mechanism, Thermodynamics and Kinetics of Rutile Leaching Process by Sulfuric Acid Reactions." Processes 8, no. 6 (May 27, 2020): 640. http://dx.doi.org/10.3390/pr8060640.

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Rutile decomposition by sulfuric acid, including the formation of two salts, Ti(SO4)2/TiOSO4, is thermodynamically modelled. It is shown that TiO2 can spontaneously dissolve in H2SO4 solutions. However, titania is considered as an inert (ballast) phase component of titanium-containing raw materials due to the decelerated separate nature of such chemical transformations. It is concluded that the hampered related kinetics of dissolution can be attributed to the lability of Ti(IV) cations/the specific engineered features of the hierarchical crystalline structure. It is suggested that the breaking of Ti–O–Ti bonds without additional mechanical strains in crystal lattice geometry becomes more advantageous when smaller negative anions/fluoride ions can be used. The analysis of sulfate-fluoride extraction leaching of titanium confirmed that a decrease in the Gibbs energy in the presence of F occurs. It is indicated by kinetic research studies that the addition of corrosive sodium reagent (NaF) reduces the activation by 45 kJ/mol, which results in intensification. A mechanism is proposed for the interactions involving the Ti–O–Ti cleavage on the surface/the H2SO4-induced Ti dioxide degradation on the sites of defects. Moreover, F acts as a homogeneous/heterogeneous bifunctional catalyst.
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47

Ong, Voon, Grayson Hough, Michael Schlosser, Ken Bartizal, James M. Balkovec, Kenneth D. James, and B. Radha Krishnan. "Preclinical Evaluation of the Stability, Safety, and Efficacy of CD101, a Novel Echinocandin." Antimicrobial Agents and Chemotherapy 60, no. 11 (September 12, 2016): 6872–79. http://dx.doi.org/10.1128/aac.00701-16.

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ABSTRACTFungal infections pose a significant public health burden with high morbidity and mortality. CD101 is a novel echinocandin under development for the treatment and prevention of systemicCandidainfections. Preclinical studies were conducted to evaluate the metabolic stability, plasma protein binding, pharmacokinetics, toxicity, and efficacy of CD101 at various dose levels. CD101 was stable to biotransformation in rat, monkey, and human liver microsomes and rat, monkey, dog, and human hepatocytes.In vitrostudies suggest minimal interaction with recombinant cytochrome P450 enzymes (50% inhibitory concentrations [IC50s] of >10 μM). Similar to anidulafungin, CD101 bound avidly (>98%) to human, mouse, rat, and primate plasma proteins. In a 2-week repeat-dose comparison study, CD101 was well tolerated in rats (no effects on body weight, hematology, coagulation, or urinalysis). In contrast, administration of anidulafungin (at comparable exposure levels) resulted in reduced body weight, decreases in red blood cell, hemoglobin, hematocrit, mean cell volume, mean corpuscular hemoglobin, platelet, and reticulocyte counts, increases in neutrophil and eosinophil counts, polychromasia, and decreased activated partial thromboplastin time. Elevated plasma transaminases, total bilirubin, cholesterol, and globulin, dark and enlarged spleens, and single-cell hepatocyte necrosis were also observed for anidulafungin but not CD101. Hepatotoxicity may be due to the inherent chemical lability of anidulafungin generating potentially reactive intermediates. A glutathione trapping experiment confirmed the formation of a reactive species from anidulafungin, whereas CD101 did not exhibit instability or reactive intermediates. CD101 showed antifungal activity againstCandidaandAspergillusinfections in neutropenic mice. These preclinical studies demonstrated that CD101 is chemically and metabolically stable, well tolerated with no hepatotoxicity, and efficacious as an antifungal agent.
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48

Lebedev, Anton S., and Vladimir Yu Orlov. "IDENTIFICATION OF TRANSFORMATION FUNCTIONALIZED ARENES DIRECTIONS IN NATURAL ENVIRONMENT CONDITIONS." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, no. 7 (May 21, 2020): 15–19. http://dx.doi.org/10.6060/ivkkt.20206307.6193.

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The article discusses the evaluation of the aromatic compounds pathways transformations – widespread xenobiotics of aqueous systems. This issue has both theoretical (chemical lability in complex reaction systems) and applied (target designation for the development analytical methods) meaning. Benzoic, 4-hydroxybenzoic, 2-hydroxybenzoic, 2-chlorobenzoic acids, 4-hyd-roxybenzoic acid methyl ester, and salicylic ester of acetic acid were chosen as objects of investigation. They have been used in food, pharmaceutical, cosmetic industries as preservatives, in chemical industry and laboratory practice as starting materials for the synthesis of new organic compounds, in analytical chemistry as reagents, chromophores, and standards in calorimetric analysis. We used quantum chemical modeling mechanisms of abiotic and biodegradation of functionalized arenes as a research method. It has been shown that for the transformation of benzoic acid, including oxidative breaking of cycle, the most probable is the path through 2,3-di-hydroxybenzoic acid to 1,3-butadiene-1,1,4-tricarboxylic acid (the product of the intradiol oxidative breaking of the cycle). There is transformation path through 2,3-dihydroxybenzoic acid to 1,3-butadiene-1,1,4-tricarboxylic acid (product intradiol oxidative rupture of the cycle) realized for 2-hydroxybenzoic acid (compound itself and the products of the conversion of salicylic ester of acetic acid, 2-chlorobenzoic acid). Pathway is observed through 3,4-dihydroxybenzoic acid to 1,3-butadiene-1,2,4-tricarboxylic acid (the product of the intradiol oxidative break cycle) for 4-hydroxybenzoic acid (compound itself and the product of the conversion of 4-hydroxybenzoic acid methyl ester). As it follows from the above, the intraradiol path of the oxidative cycle breaking seems to be the most preferable. Accordingly, a preferential accumulation of the following substances should be expected as results of the samples transformation: 2- and 4-hydroxybenzoic acids, 2,3- and 3,4-dihydroxybenzoic acids, products of the radical oxidative breaking of the cycle and the results of their further transformation.
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49

Liu, Hongfei, Sha Xue, Guoliang Wang, and Guobin Liu. "Corrigendum to: Effects of nitrogen addition on soil oxidisable organic carbon fractions in the rhizospheric and bulk soils of Chinese pines in north-western China." Soil Research 56, no. 4 (2018): 441. http://dx.doi.org/10.1071/sr16358_co.

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Increased atmospheric nitrogen (N) deposition caused by human activities has potentially important effects on ecosystem carbon (C) dynamics and different effects on C fractions with different stabilities and chemical compositions. A better understanding of the responses of different C fractions to N addition is vital for maintaining soil quality and protecting vegetation. In order to investigate the differential effects of N addition on total soil organic carbon (SOC) and four SOC fractions with increasing degrees of oxidisability in Pinus tabuliformis rhizospheric and bulk soils, a 6-year pot experiment was performed testing the effects of the addition of N at rates of 2.8, 5.6, 11.2, 22.4 and 44.8g m–2 year–1 compared with a control (CK) group (no N addition). Addition of N addition had significant (P–2 year–1. Low rates (N2.8–N5.6) of N addition considerably increased C4 and the ratio of C4 to TOC in the rhizosphere, whereas addition of high rates (N11.2–N44.8) of N decreased these parameters. The responses of C1 and C4 in the bulk soil to N addition were opposite. The SOC fraction was significantly higher in the rhizosphere than in the bulk soil, indicating large rhizospheric effects. However, increased N addition weakened these effects. These findings suggest that low rates (N2.8–N5.6) of N addition stabilise SOC against chemical and biological degradation, whereas increased rates of N addition increase the lability of SOC in the bulk soil. Thus, the rhizosphere plays a vital role in soil carbon stability and sequestration in response to N addition.
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50

Aghnatios, C., R. Losno, and F. Dulac. "A fine fraction of soil used as an aerosol analogue during the DUNE experiment: sequential solubility in water, decreasing pH step-by-step." Biogeosciences 11, no. 17 (September 2, 2014): 4627–33. http://dx.doi.org/10.5194/bg-11-4627-2014.

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Abstract. A soil sample collected in a desert aerosol source area near Douz (southern Tunisia) was dry-sieved at 20 μm in order to extract the fraction similar to a wind-generated aerosol, and was used to seed mesocosms during the DUNE experiment (a DUst experiment in a low Nutrient, low chlorophyll Ecosystem). In this work, said "aerosol-like" fine dust was sequentially leached by short contacts with water at initial pHs, decreasing from seven to one, representing various wet environmental conditions. For each step, the solubility of a given element is calculated as the amount of its dissolved fraction, relative to its total amount. The evolution of this fractional solubility from the highest to lowest pHs provides information on the chemical strength needed to solubilise a given element and its lability. The behaviour of the elemental solubility was sorted into two groups: (1) Ca, Sr, Ba, Mn, and P, with a solubility between 23% and 70%, and a maximum sequential solubility at pH 3; (2) Al and Fe, with a solubility of less than 2% and the highest release at pH 1. Similar solubility patterns in group 1 for Ca, P, and Mn suggest a possible association of the elements in the same minerals, most probably carbonates.
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