Adsorption of nucleic acid constituent uracil on copper(II)-loaded, solid peat and soil-derived humic acids

2001 ◽  
Vol 81 (3) ◽  
pp. 309-316
Author(s):  
E A Ghabbour ◽  
G. Davies ◽  
R L Dunfee ◽  
N A Smith ◽  
M E Vozzell
Keyword(s):  
Nucleic Acid ◽  
New Hampshire ◽  
Humic Acids ◽  
Metal Binding ◽  
Opposite Effect ◽  
Coordination Numbers ◽  
Enthalpy And Entropy Changes ◽  
Solute Interactions ◽  
Enthalpy And Entropy ◽  
Binding Enthalpy

Humic acids (HA) in compost, peats and soils sorb organic compounds selectively. This paper investigates the micro- and macroscopic properties of solid HAs isolated from a German peat (GHA) and a New Hampshire soil (NHA) using tightly bound copper(II) and nucleic acid constituent uracil adsorption as analytical probes. Isotherm measurements at 5.0–35.0°C show that tightly bound Cu(II) decreases the amount of uracil adsorbed by GHA at mM or lower uracil concentrations whereas previous work revealed the opposite effect for bound Hg(II). Site capacity comparisons are consistent with lower coordination numbers for HA-bound Hg(II) than for HA-bound Cu(II). Low coordination numbers leave Hg(II) sites open for uracil binding. Enthalpy and entropy changes for uracil adsorption on GHA, NHA, their Cu(II) and Hg(II)-loaded forms and on compost-derived HA are linearly correlated, indicating that HAs are free energy buffers. Water and bound metals evidently play major roles in HA-solute interactions and in HA aggregation/disaggregation. Key words: Humic acids, metal binding, nucleic acid constituents, uracil, adsorption, isotherms, thermodynamics

The effect of temperature on tight metal binding by peat and soil derived solid humic acids

2001 ◽  
Vol 81 (3) ◽  
pp. 331-336 ◽  
Author(s):  
Elham A Ghabbour ◽  
Geoffrey Davies ◽  
Nadeem K Ghali ◽  
Matthew D Mulligan
Keyword(s):  
Humic Acids ◽  
Conformational Changes ◽  
Metal Binding ◽  
Equilibrium Constants ◽  
Tight Binding ◽  
Metal Cations ◽  
Effect Of Temperature ◽  
Binding Isotherms ◽  
Different Temperatures ◽  
Binding Enthalpy

The brown biomaterials called humic acids (HA) in peats and soils retain water and bind metal cations and other solutes. Studies of the interactions of purified solid peat and soil-derived HA from different countries with metal cations in water probe HA microstructures and help to characterize the metal binding sites. Labile cations such as Caaq2+, Co aq2+, Cu aq2+, Fe aq3+, Mg aq2+ and Mn aq2+ tightly bind to solid HAs in sequential steps. The isotherms A vs. c are well fitted with the Langmuir model and plots of 1/A vs. 1/c are linear for each step. Here, A is mmol bound metal g–1 HA and c is the equilibrium cation concentration (M). This paper compares the stoichiometric site capacities vi and equilibrium constants Ki for tight binding of Ca aq2+, Co aq2+, Cu aq2+, Fe aq3+, Mg aq2+ and Mn aq2+ at different solid HA sites. Measurements at different temperatures give linearly correlated metal binding enthalpy and entropy changes, indicating that conformational changes and cation/HA hydration/dehydration are important factors in metal binding and release by solid HAs. Key words: Humic acids; metal binding; isotherms; thermodynamics

scholarly journals Direct measurement of enthalpy and entropy changes in NH3 promoted O2 activation over Cu‐CHA at low temperature

ChemCatChem ◽  
2021 ◽  
Author(s):  
Xueting Wang ◽  
Lin Chen ◽  
Peter N. R. Vennestrøm ◽  
Ton V. W. Janssens ◽  
Jonas Jansson ◽  
...  
Keyword(s):  
Low Temperature ◽  
Direct Measurement ◽  
O2 Activation ◽  
Entropy Changes ◽  
Enthalpy And Entropy Changes ◽  
Enthalpy And Entropy

Thermodynamics of Protonation and Sodium Binding of Sulfate in Concentrated NaCl and CsCl Solutions Studied by Raman Spectroscopy

2000 ◽  
Vol 53 (5) ◽  
pp. 363 ◽  
Author(s):  
Steven Kratsis ◽  
Glenn Hefter ◽  
Peter M. May ◽  
Pal Sipos
Keyword(s):  
Raman Spectroscopy ◽  
Excellent Agreement ◽  
Thermodynamic Data ◽  
Association Constant ◽  
Protonation Constant ◽  
Ion Pairing ◽  
Ion Pair ◽  
Enthalpy And Entropy Changes ◽  
Enthalpy And Entropy ◽  
Sodium Binding

The protonation constant (pKa) of SO42–(aq) has been determined at ionic strengths 0.5 M ≤I ≤4.0 M in NaCl and CsCl media at 25˚C by using Raman spectroscopy. These data were used to calculate the association constant of the NaSO4–(aq) ion pair in CsCl media. The results are in excellent agreement with previous values obtained by other techniques. The (pKa) was also measured at I = 4 M in both media at temperatures up to 85˚C and the associated enthalpy and entropy changes were calculated. However, reliable thermodynamic data for the ion-pairing reaction could not be obtained at higher temperatures probably because of competition from CsSO4–(aq).

Relating Ion Binding by Fulvic and Humic Acids to Chemical Composition and Molecular Size. 2. Metal Binding

2001 ◽  
Vol 35 (12) ◽  
pp. 2512-2517 ◽  
Author(s):  
Iso Christl ◽  
Chris J. Milne ◽  
David G. Kinniburgh ◽  
Ruben Kretzschmar
Keyword(s):  
Chemical Composition ◽  
Humic Acids ◽  
Metal Binding ◽  
Molecular Size ◽  
Ion Binding

scholarly journals Isolation of humic acid from oxidized lignite and complexation with metal cations

2017 ◽  
Vol 71 (4) ◽  
pp. 319-327
Author(s):  
Benjamin Catovic ◽  
Minela Sisic ◽  
Majda Srabovic ◽  
Melita Huremovic
Keyword(s):  
Humic Acid ◽  
Metal Ions ◽  
Humic Acids ◽  
Metal Binding ◽  
Base Material ◽  
Metal Cations ◽  
Biological Properties ◽  
Metal Nitrate ◽  
Chemical Difference ◽  
The Difference

Lignite is brown coal, which in its composition contains humic acids. Humic acids are produced by coal combustion, which leads to the enrichment of coal humic acids. Lignite, from the opet pit mine Sikulje, lignite ore ?Kreka?, Bosnia and Herzegovina, was fragmented and sieved to the appropriate size and used as a base material. The isolation of humic acid was carried out from pre-oxidized and dried lignite after which it was refined. Identification thus obtained humic acids was carried out by FTIR spectroscopy and its characterization of UV analysis which is determined by optical density of isolated humic acid and its complexation with metal cations. Data obtained by FTIR spectroscopic analysis of isolated humic acids show no significant structural and chemical difference in relation to the spectrum obtained for standard humic acids (Sigma Aldrich). UV analysis showed that isolated and standard humic acid have E4/E6 ratio in an appropriate range of 3?5, which indicates the presence of a large number of aliphatic structure. Based on the degree of humification was found that the isolated humic acids belong to the type B standard while humic acids belong to type A. The most important property of the humic substances is the ability to interact with the metal ions forming soluble or insoluble complexes which possess different chemical and biological properties and stability. The nature of the complex between humic acid and metal cation derived from the heterogeneous, polyelectric and polydispersive character humic acids that occurs due to the presence of a large number of functional groups. Complexation of humic acid is carried out with different concentrations of metal nitrate solutions and at different pH values. Different amounts of humic acids were used for the complexation. The amount of the free metal ions was measured with the ICP-OES methode. The data were also statistically analyzed with ANOVA. The results showed that increasing the pH reduces the concentration of metal ions adsorbed on humic acid and by increasing the concentrations and amounts of metal humic acid that power increases. On the basis of the difference in absorbance between metals and humic acids can be said that there is an interaction between the metal and the ligand and is based on absorbance values obtained can be determine the next set of metal binding to humic acids Pb>Zn>Ni>Cu.

scholarly journals A THERMODYNAMIC ANALYSIS OF MITOTIC SPINDLE EQUILIBRIUM AT ACTIVE METAPHASE

1973 ◽  
Vol 57 (1) ◽  
pp. 133-147 ◽  
Author(s):  
R. E. Stephens
Keyword(s):  
Growth Conditions ◽  
Pool Size ◽  
Polarization Microscopy ◽  
Dissociation Kinetics ◽  
Mitotic Apparatus ◽  
Enthalpy And Entropy Changes ◽  
Enthalpy And Entropy ◽  
Best Fit ◽  
Two Temperature ◽  
Direct Immersion

The mitotic apparatus of first-division metaphase eggs of the sea urchin Strongylocentrotus drobachiensis was observed by means of polarization microscopy under controlled temperature conditions. Eggs were fertilized and grown at two temperature extremes in order to produce two different sizes of available spindle pool. Slow division time allowed successive samples of such cells to be observed at the same point in metaphase but at different equilibrium temperatures, yielding curves of metaphase equilibrium birefringence vs. observational temperature. Using the plateau value of birefringence at higher temperatures as a measure of total available spindle pool and the observed birefringence at lower temperatures as a measure of polymerized material at equilibrium, the spindle protein association was evaluated according to the method of Inoué. Both pool conditions produced linear van't Hoff functions. Analysis of these functions yielded enthalpy and entropy changes of +55–65 kcal/mol and +197–233 entropy units (eu), respectively. These values for active mitotic metaphase are quite comparable to those obtained by Inoué and co-workers for arrested meiotic metaphase cells. When other equilibrium treatments were considered, the best fit to the experimental data was still that of Inoué, a treatment which theoretically involves first-order polymerization and dissociation kinetics. Treatment of metaphase cells with D2O by direct immersion drove the equilibrium to completion regardless of temperature, attaining or exceeding a birefringence value equal to the cell's characteristic pool size; perfusion with D2O appeared to erase the original temperature-determined pool size differences for the two growth conditions, attaining a maximum value characteristic of the larger pool condition. These data confirm Inoué's earlier contention that D2O treatment can modify the available spindle pool.

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