Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Compost-Derived Humic Acid. 1. Naturally Occurring Pyrimidines

Khairy, Ahmed H.; Davies, Geoffrey; Ibrahim, and Hesham Z.; Ghabbour, Elham A.

doi:10.1021/jp9521565

Cited by 20 publications

(98 citation statements)

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“…Spectrometry. UV−visible and FTIR spectrometry was conducted with previously described instruments and procedures. , …”

Section: Methodsmentioning

confidence: 99%

“…This paper reports data for adsorption of uracil, uridine, and uridine-5‘-monophosphate on a humic acid isolated from German peat (GHA) and its tightly bound mercury(II) form (MGHA). The solutes were chosen because they all have the uracil nucleobase unit and CHA has unusually low capacity for uridine . This solute choice is important because other NACs such as adenine have the ability to free up (“create”) more sites after primary adsorption .…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Humic Acids. 3. Adsorption of Uracil, Uridine, and Uridine-5‘-Monophosphate on a German Peat-Derived Humic Acid and Its Tightly Bound Mercury(II) Form

et al. 1997

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Aqueous nucleic acid constituents uracil, uridine, and uridine-5‘-monophosphate are selectively adsorbed by a solid German peat-derived humic acid (GHA) and its tightly bound mercury(II) form (MGHA). Adsorption isotherms with GHA and MGHA adsorbents were obtained at 19 solute concentrations from 0 to 1.20 mM and seven fixed temperatures from 5.0 to 35.0 °C. Langmuir data analysis indicates that adsorption occurs in sequential steps A, B, and C, depending on the solute and experimental conditions. MGHA very strongly adsorbs low concentrations of uracil and site capacity vA for uracil adsorption on MGHA in step A increases with increasing temperature. The last steps of adsorption of relatively high concentrations of uridine, and uridine-5‘-monophosphate on MGHA are S-curves ascribed to increasing site capacity with increasing solute concentration. Comparison of the new data for adsorbents GHA and MGHA with data for adsorption of uracil, uridine, and uridine-5‘-monophosphate on compost-derived humic acid (CHA) from part 1 reveals similarities and differences. Nevertheless, linear plots of adsorption enthalpies vs entropies in all detected steps with CHA, GHA, and MGHA as adsorbents indicate that selective adsorption of nucleic acid constituents on different HAs is free energy buffered by similar mechanisms.

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“…Spectrometry. UV−visible and FTIR spectrometry was conducted with previously described instruments and procedures. , …”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Humic Acids. 3. Adsorption of Uracil, Uridine, and Uridine-5‘-Monophosphate on a German Peat-Derived Humic Acid and Its Tightly Bound Mercury(II) Form

et al. 1997

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“…Marschner & Bredow () and Khairy et al . (,b) have both observed that a rise in temperature moves the system toward a higher share of non‐sorbed reactants, and temperature has a progressively larger effect as more energy is needed to desorb reaction partners. Temperature also increases diffusion and dissolution, both of which increase substrate availability to soil microbes and leaching losses of soil carbon (Xu & Saiers, ).…”

Section: A Way Forward Through a New Conceptual Frameworkmentioning

confidence: 99%

Temperature and soil organic matter decomposition rates - synthesis of current knowledge and a way forward

et al. 2011

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The response of soil organic matter (OM) decomposition to increasing temperature is a critical aspect of ecosystem responses to global change. The impacts of climate warming on decomposition dynamics have not been resolved due to apparently contradictory results from field and lab experiments, most of which has focused on labile carbon with short turnover times. But the majority of total soil carbon stocks are comprised of organic carbon with turnover times of decades to centuries. Understanding the response of these carbon pools to climate change is essential for forecasting longer-term changes in soil carbon storage. Herein, we briefly synthesize information from recent studies that have been conducted using a wide variety of approaches. In our effort to understand research to-date, we derive a new conceptual model that explicitly identifies the processes controlling soil OM availability for decomposition and allows a more explicit description of the factors regulating OM decomposition under different circumstances. It explicitly defines resistance of soil OM to decomposition as being due either to its chemical conformation (quality) or its physico-chemical protection from decomposition. The former is embodied in the depolymerization process, the latter by adsorption/desorption and aggregate turnover. We hypothesize a strong role for variation in temperature sensitivity as a function of reaction rates for both. We conclude that important advances in understanding the temperature response of the processes that control substrate availability, depolymerization, microbial efficiency, and enzyme production will be needed to predict the fate of soil carbon stocks in a warmer world.

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“…23 for adsorption of 14 nucleic acid constituents (NACs) on a solid compost-derived HA and on solid HA particles from different soil sources without or with added Hg II 24 show that HAs can be purified to the point where they become understandable. The data fit the Langmuir model for reversible solute adsorption in sequential steps labelled i = A, B and C. 14,[22][23][24] Analysis gives the stoichiometric site capacity ν i and the equilibrium constant K i for each solute and step. The ν i data indicate interaction of the HA surface with the nucleobase units of NAC solutes.…”

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confidence: 89%

Tight metal binding by humic acids and its role in biomineralization †

Davies¹,

Fataftah²,

Cherkasskiy³

et al. 1997

J. Chem. Soc., Dalton Trans.

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Analytical and thermodynamic data, EPR, FTIR, solution 1 H and solid-state 13 C cross polarization magic angle spinning NMR and solid-state extended X-ray absorption fine structure (EXAFS) and X-ray absorption nearedge structure (XANES) spectra have been recorded for purified humic acids (HAs) isolated from a German peat (GHA), an Irish peat (IHA), an unpolluted New Hampshire bog soil (NHA) and their tightly bound copper(), iron() and manganese() forms. Brief water washing of partly or fully metal-loaded HAs leaves 'tightly' bound metal in the isolated freeze-dried solids. Most of this metal is removed by washing with 0.1  HCl, indicating acidic HA functional groups as principal metal binding sites. The number of nearest-neighbour atoms coordinated to tightly bound Cu II (four), Fe III (six, probably with distorted geometry) and Mn II (six, undistorted) in solid GHA, IHA and NHA were determined by XANES and EXAFS spectroscopy with reference standards. Isotherms measured at 20.0 ЊC and pH 2.4-3.2 with [M] total = 0.18-25.8 m for tight, reversible Cu 2ϩ (aq), Fe 3ϩ (aq), and Mn 2ϩ (aq) binding by solid IHA and NHA fit the Langmuir model and give the pH-independent stoichiometric site capacities ν i and equilibrium constants K i for metal binding at specific HA sites i = A, B and C. Tight binding sites A, B and C of IHA are occupied by Cu II , sites A and B by Fe III and site A by Mn II , while only identical metal binding site A in NHA is tight enough to resist metal removal by brief water washing. A new helical HA molecular model based on the empirical formula C 36 H 30 N 2 O 15 ؒxH 2 O visualizes metal binding and the likely roles of HAs in biomineralization. Site A is suggested to be carboxylate, mixed ligands probably constitute site B, and site C is tentatively assigned as the interior of the HA helix. Binding free energies and EPR evidence suggest that Cu 2ϩ (aq), Fe 3ϩ (aq) and Mn 2ϩ (aq) rapidly transfer between specific HA binding sites. This affects rates of metal release and transfer to minerals.

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Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Compost-Derived Humic Acid. 1. Naturally Occurring Pyrimidines

Cited by 20 publications

References 21 publications

Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Humic Acids. 3. Adsorption of Uracil, Uridine, and Uridine-5‘-Monophosphate on a German Peat-Derived Humic Acid and Its Tightly Bound Mercury(II) Form

Adsorption of Aqueous Nucleobases, Nucleosides, and Nucleotides on Humic Acids. 3. Adsorption of Uracil, Uridine, and Uridine-5‘-Monophosphate on a German Peat-Derived Humic Acid and Its Tightly Bound Mercury(II) Form

Temperature and soil organic matter decomposition rates - synthesis of current knowledge and a way forward

Tight metal binding by humic acids and its role in biomineralization †

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