Magnesium binding by terrestrial humic acids

2018 ◽  
Vol 15 (6) ◽  
pp. 317 ◽  
Author(s):  
Iso Christl
Keyword(s):  
Trace Elements ◽  
Ionic Strength ◽  
Functional Groups ◽  
Humic Acids ◽  
Specific Binding ◽  
Background Electrolyte ◽  
Essential Element ◽  
Cation Binding ◽  
Ion Hydration ◽  
Magnesium Binding

Environmental contextThe behaviour of magnesium, which is an essential element for all living organisms, in terrestrial environments is influenced by natural organic matter. This study shows that magnesium binding by terrestrial humic acids exhibits a pronounced ionic strength-dependence indicating a strong preference for electrostatic binding to humic acids. This interaction is expected to influence the mobility of humic substances and their associated trace elements. AbstractMagnesium binding by three terrestrial humic acids was investigated at pH 8 and 25 °C as a function of Mg2+ activity and ionic strength using NaCl as the background electrolyte. The Mg2+ activity in solution was directly measured with an Mg2+-selective electrode in the titration experiments. In addition, coagulation experiments using Ca2+ and Mg2+ as the coagulants were carried out at pH 8. For the titration data, the NICA–Donnan model was used to quantitatively describe Mg2+ binding to the humic acids considering electrostatic and specific Mg2+ binding. Mg2+ binding to humic acids was found to be strongly affected by ionic strength variations indicating that Mg2+ binding largely arose from electrostatic (nonspecific) interactions with negatively charged functional groups of the humic acids. Data modelling suggested that the relative contribution of specific binding increased with decreasing Mg2+ activity and was related to functional groups with low proton affinities. For all three humic acids studied, the fitted Mg2+ affinity constants for specific binding were lower than the respective Ca2+ affinities. Corresponding to the observed differences in cation binding and the known differences in ion hydration, Ca2+ was observed to be the stronger coagulant as compared with Mg2+. The results suggest that Mg2+ may influence the mobility of trace elements that are strongly bound to humic acids such as mercury, although Mg2+ is not expected to directly compete with strongly sorbing elements for specific binding.

Influence of extractant on quality and trace elements content of peat humic acids

Talanta ◽  
2007 ◽  
Vol 73 (5) ◽  
pp. 820-830 ◽  
Author(s):  
C ZACCONE ◽  
C COCOZZA ◽  
V DORAZIO ◽  
C PLAZA ◽  
A CHEBURKIN ◽  
...  
Keyword(s):  
Trace Elements ◽  
Humic Acids

scholarly journals Comparative Analysis on Dielectric Gold and Aluminium Triangular Junctions: Impact of Ionic Strength and Background Electrolyte by pH Variations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Iswary Letchumanan ◽  
M. K. Md Arshad ◽  
Subash C. B. Gopinath ◽  
R. D. A. A. Rajapaksha ◽  
S. R. Balakrishnan
Keyword(s):  
Comparative Analysis ◽  
Ionic Strength ◽  
Background Electrolyte ◽  
Ph Variations

scholarly journals Compositional and Temperature Effects on the Rheological Properties of Polyelectrolyte–Surfactant Hydrogels

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 927 ◽  
Author(s):  
Jiří Smilek ◽  
Sabína Jarábková ◽  
Tomáš Velcer ◽  
Miloslav Pekař
Keyword(s):  
Ionic Strength ◽  
Rheological Properties ◽  
Surfactant Concentration ◽  
Background Electrolyte ◽  
Effect Of Temperature ◽  
Physical Interactions ◽  
Chain Conformations ◽  
Oppositely Charged ◽  
Electrolyte Ph ◽  
Positively Charged

The rheological properties of hydrogels prepared by physical interactions between oppositely charged polyelectrolyte and surfactant in micellar form were studied. Specifically, hyaluronan was employed as a negatively charged polyelectrolyte and Septonex (carbethopendecinium bromide) as a cationic surfactant. Amino-modified dextran was used as a positively charged polyelectrolyte interacting with sodium dodecylsulphate as an anionic surfactant. The effects of the preparation method, surfactant concentration, ionic strength (the concentration of NaCl background electrolyte), pH (buffers), multivalent cations, and elevated temperature on the properties were investigated. The formation of gels required an optimum ionic strength (set by the NaCl solution), ranging from 0.15–0.3 M regardless of the type of hydrogel system and surfactant concentration. The other compositional effects and the effect of temperature were dependent on the polyelectrolyte type or its molecular weight. General differences between the behaviour of hyaluronan-based and cationized dextran-based materials were attributed to differences in the chain conformations of the two biopolymers and in the accessibility of their charged groups.

scholarly journals Multiple interactions between pituitary hormones and the mannose receptor

1999 ◽  
Vol 343 (2) ◽  
pp. 403-411 ◽  
Author(s):  
Daniel Z. SIMPSON ◽  
Paul G. HITCHEN ◽  
Elizabeth L. ELMHIRST ◽  
Maureen E. TAYLOR
Keyword(s):  
Ionic Strength ◽  
Binding Site ◽  
Specific Binding ◽  
Mannose Receptor ◽  
Pituitary Hormones ◽  
Pituitary Hormone ◽  
Truncated Form ◽  
Additional Function ◽  
Rich Domain ◽  
Cysteine Rich Domain

The macrophage mannose receptor, which has a well-documented role in the innate immune system, has an additional function in the clearance of pituitary hormones. Clearance is mediated by the recognition of sulphated terminal N-acetylgalactosamine residues (SO4-4GalNAc) on the hormones. Previous studies with an SO4-4GalNAc-containing neoglycoprotein suggest that the SO4-4GalNAc-binding site is localized to the N-terminal cysteine-rich domain of the receptor, distinct from the mannose/N-acetylglucosamine/fucose-specific C-type carbohydrate-recognition domains (CRDs). The present study characterizes the binding of natural pituitary hormone ligands to a soluble portion of the mannose receptor consisting of the whole extracellular domain and to a truncated form containing the eight CRDs but lacking the N-terminal cysteine-rich domain and the fibronectin type II repeat. Both forms of the receptor show high-affinity saturable binding of lutropin and thyrotropin. Binding to the full-length receptor is dependent on pH and ionic strength and is inhibited effectively by SO4-4GalNAc but only partly by mannose. In contrast, binding to the truncated form of the receptor, which is also dependent on pH and ionic strength, is inhibited by mannose but not by SO4-4GalNAc. The results are consistent with the presence of an SO4-4GalNAc-specific binding site in the cysteine-rich domain of the mannose receptor but indicate that interactions between other sugars on the hormones and the CRDs are also important in hormone binding.

The impact of selenium on an Archaea-dominated, methanogenic granular sludge consortium

2020 ◽  
Author(s):  
Lucian Staicu ◽  
Mikolaj Dziurzynski ◽  
Adrian Gorecki ◽  
Gavin Collins ◽  
Simon Mills ◽  
...  
Keyword(s):  
Trace Elements ◽  
Essential Element ◽  
Granular Sludge ◽  
Microbial Metabolism ◽  
High Energy ◽  
Dairy Wastewater ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Terminal Electron Acceptor ◽  
The Impact

<p>Selenium (Se) is one of the latest chemical elements identified as a terminal electron acceptor in anaerobic respiration. Before this important discovery, Se was mainly known for its toxicity and its limited use as an essential element for microbial metabolism (Staicu et al., 2019). This study screened the presence of selenium respiratory genes/operons and the impact of selenium on the microbial community from a methanogenic anaerobic granular sludge. The inoculum was collected from a full-scale bioreactor treating dairy wastewater (Ireland). To identify the presence of selenium respiration, the following primers were designed: for selenate, SeO<sub>4</sub><sup>2-</sup> (Thauera selenatis, Bacillus selenatarsenatis SF-1) and for selenite, SeO<sub>3</sub><sup>2-</sup> (Bacillus selenitireducens MLS10). The primers were designed based on the available sequences and refined using the UniPriVal algorithm developed by our group at University of Warsaw. Apart from Se respiration, the study also investigated the change in bacterial diversity using 16S rRNA genes as a function of incubation time and exposure to selenate (with acetate as electron donor) and selenite (with lactate as e-donor). An additional focus of the study attempted to shed light into the biomineralization of elemental Se, Se<sup>0</sup>, since this process is still not fully understood (e.g. intracellular vs extracellular nucleation, growth of the particles by an Ostwald-like ripening process) (Staicu and Barton, 2017). The results indicate the high contribution of Archaea (22% - 37%) to the community of the granular sludge. The addition of 10 mM selenate/selenite did not have an impact on the Archaean community, nor did it trigger the reduction of selenate/selenite to Se<sup>0</sup> via a known respiratory pathway. On the other hand, selenium addition did not particularly affect the community structure. There was a shift towards Bacteroidetes during the 7-day incubation period, with a high and consistent contribution of Firmicutes over Bacilli, which are putative host of selenate and selenite reductases. Furthermore, no significant Betaproteobacteria (Thauera selenatis) were identified, other putative host of selenate reductase. The biogenic Se<sup>0</sup> particles were localized both outside and at the intracellular level, displaying polydisperse size distribution (<100-500 nm), indicative of different biomineralization mechanisms involved. Overall, this dataset indicates the reduction of selenium might be a purely detoxification process in methanogenic Archaea-dominated microbial communities, which brings into question the use of high energy-dense selenium oxyanions for respiratory purposes in certain biogeochemical conditions. Alternatively, this might emphasize the uncharted respiratory potential of selenium, since the process was reported to have diverse ecosystem distribution (Steinberg and Oremland, 1990).</p> <p><strong>Reference</strong></p> <p>Staicu LC, Barton LL (2017) Microbial metabolism of selenium – for survival or profit. In: Bioremediation of selenium contaminated wastewaters, van Hullebusch ED (Ed.), Springer, 1-31.</p> <p>Staicu LC, Simon S, Guibaud G et al. (2019) Biogeochemistry of trace elements in anaerobic digesters. In: Trace elements in anaerobic biotechnologies, Fermoso FF et al. (Eds.), IWA, 23-50.</p> <p>Steinberg NA, Oremland RS (1990) Dissimilatory selenate reduction potentials in a diversity of sediment types. Appl Environ Microbiol 56, 3550-57.</p>

Der Einfluß von D-Penicillamin auf den Gehalt einiger Organe an Spurenelementen sowie auf die mechanischen Eigenschaften von Kollagen / Trace Elements in Several Organs and Mechanical Properties of Collagen under the Influence of D-Penicillamin

1978 ◽  
Vol 33 (5-6) ◽  
pp. 346-358 ◽  
Author(s):  
H. Wesch ◽  
R. Jonak ◽  
H. Nemetschek-Gansler ◽  
H. Riedl ◽  
Th. Nemetschek
Keyword(s):  
Mechanical Properties ◽  
Trace Elements ◽  
Schiff Base ◽  
Connective Tissue ◽  
Functional Groups ◽  
Schiff Bases ◽  
Collagen Fibrils ◽  
Principal Effect ◽  
Tail Tendon ◽  
Cu Ions

Abstract The content of trace elements in several organs of rats under the influence of D-penicillamine (D-PA) was investigated by the neutronactivation-analysis. It could be shown an diminution of Cu, and Co under D-PA-treatment, the content of Fe, Mn, Rb and Zn was not influenced. The investigat­ ed organs didn’t show any submicroscopic alterations under D-PA. On isolated collagen fibrils of tail tendon was seen a significantly diminuition of E-moduls. In accordance with Siegel the principal effect of D-PA is thought to block the synthesis of functional groups from Schiff-base crosslink precursors but not to inhibit lysyloxidase by loss of Cu-ions of connective tissue. The thermostability of D-PA influenced fibrils is changed in stretched state only and will be due to the lack of crosslink Schiff-bases; where as the shrinking point of not stretched fibrils shows only aging dependent changes.

Ionic strength- and pH-dependence of calcium binding by terrestrial humic acids

2012 ◽  
Vol 9 (1) ◽  
pp. 89 ◽  
Author(s):  
Iso Christl
Keyword(s):  
Experimental Data ◽  
Ionic Strength ◽  
Humic Acids ◽  
Calcium Binding ◽  
Good Description ◽  
Ph Dependence ◽  
Wide Range ◽  
Electrostatic Binding ◽  
Carboxylic Groups ◽  
Terrestrial Environments

Environmental contextIn terrestrial environments, humic substances act as major sorbents for calcium, which is an essential nutrient for organisms. This study shows that calcium binding by terrestrial humic acids is strongly dependent on pH and ionic strength. The results indicate that calcium binding by humic acids is primarily controlled by electrostatic forces and specific binding to carboxylic groups. AbstractCalcium binding by two terrestrial humic acids was investigated at 25 °C as a function of pH, ionic strength and Ca2+ activity with calcium titration experiments. A Ca2+-selective electrode was used for Ca2+ measurements to cover a wide range of Ca2+ activities (10–8.5–10–2.5). Experimental data were quantitatively described with the NICA–Donnan model accounting for electrostatic and specific calcium binding. The results showed that calcium binding as a function of Ca2+ activity was strongly affected by variations of pH and ionic strength indicating that electrostatic binding is an important mechanism for calcium binding by humic acids. Data modelling providing a good description of experimental data for both humic acids suggested that electrostatic binding was the dominant calcium binding mechanisms at high Ca2+ activities often observed in terrestrial environments. Specific calcium binding being quantitatively predominant only at low Ca2+ activities was exclusively attributed to binding sites exhibiting a weak affinity for protons considered to represent mainly carboxylic groups. Since the negative charge of the humic acids being prerequisite for electrostatic calcium binding was found to be mainly due to deprotonation of carboxylic groups except under alkaline conditions, carboxylic groups were identified to primarily control calcium binding of humic acids.

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