Metal Ion Binding by Humic Acid:  Application of the NICA-Donnan Model

1996 ◽  
Vol 30 (5) ◽  
pp. 1687-1698 ◽  
Author(s):  
David G. Kinniburgh ◽  
Christopher J. Milne ◽  
Marc F. Benedetti ◽  
Jose P. Pinheiro ◽  
Jeroen Filius ◽  
...  
Keyword(s):  
Humic Acid ◽  
Metal Ion ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Donnan Model

Analysis of Metal-Ion Binding by a Peat Humic Acid Using a Simple Electrostatic Model

1995 ◽  
Vol 175 (2) ◽  
pp. 448-460 ◽  
Author(s):  
Christopher J. Milne ◽  
David G. Kinniburgh ◽  
Johannes C.M. de Wit ◽  
Willem H. van Riemsdijk ◽  
Luuk K. Koopal
Keyword(s):  
Humic Acid ◽  
Metal Ion ◽  
Ion Binding ◽  
Electrostatic Model ◽  
Metal Ion Binding

scholarly journals Humic matter and contaminants. General aspects and modeling metal ion binding

2001 ◽  
Vol 73 (12) ◽  
pp. 2005-2016 ◽  
Author(s):  
Luuk K. Koopal ◽  
Willem H. van Riemsdijk ◽  
David G. Kinniburgh
Keyword(s):  
Heavy Metal ◽  
Humic Substances ◽  
Fresh Water ◽  
Metal Ion ◽  
Heavy Metal Ions ◽  
Ion Binding ◽  
Inorganic Contaminants ◽  
Metal Ion Binding ◽  
Mineral Particles ◽  
Donnan Model

Humic substances are soil and fresh-water components that play an important role in the binding and transport of both organic and inorganic contaminants. Transport of the contaminants due to ground- and fresh-water dynamics is directly related to the risks associated with contaminations. The mobility of soluble humic substances is related to their interaction with soil mineral particles. Some key references for the binding of organic and inorganic contaminants and for the binding of humics to mineral particles are presented. Humic substances also play a role in the analysis of the contaminants in natural waters and with remediation of water or soil polluted with pesticides, heavy metal ions, and radionuclides. These aspects are illustrated with some examples. The problems that are encountered with the modeling of the binding of contaminants to humics and of heavy metal ions in particular are illustrated by considering the nonideal competitive adsorption model (NICA) extended with electrostatic interactions. The NICA-Donnan model gives quite good results for the description of metal ion binding, as is illustrated for metal ion binding to purified peat humic acid (PPHA). Finally, some remarks are made with respect to the use of the NICA-Donnan model in general purpose speciation programs and of simplified versions of the model for predictions under restricted environmental conditions.

Generic NICA−Donnan Model Parameters for Metal-Ion Binding by Humic Substances

2003 ◽  
Vol 37 (5) ◽  
pp. 958-971 ◽  
Author(s):  
Christopher J. Milne ◽  
David G. Kinniburgh ◽  
Willem H. van Riemsdijk ◽  
Edward Tipping
Keyword(s):  
Humic Substances ◽  
Metal Ion ◽  
Model Parameters ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Donnan Model

Photophysical Characterisation, Metal Ion Binding and Enantiomeric Recognition of Chiral Ligands Containing Phenazine Fluorophore

2004 ◽  
Vol 69 (4) ◽  
pp. 885-896 ◽  
Author(s):  
Luisa Stella Dolci ◽  
Péter Huszthy ◽  
Erika Samu ◽  
Marco Montalti ◽  
Luca Prodi ◽  
...  
Keyword(s):  
Metal Ion ◽  
Photophysical Properties ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Ammonium Ions ◽  
Enantiomerically Pure ◽  
Binding Process ◽  
High Affinity ◽  
Enantiomeric Recognition ◽  
Chiral Species

Enantiomerically pure dimethyl- and diisobutyl-substituted phenazino-18-crown-6 ligands bind metal and ammonium ions and also primary aralkylammonium perchlorates in acetonitrile with high affinity, causing pronounced changes in their luminescence properties. In addition, they show enantioselectivity towards chiral primary aralkylammonium perchlorates. The possibility to monitor the binding process by photoluminescence spectroscopy can gain ground for the design of very efficient enantioselective chemosensors for chiral species. The observed changes in the photophysical properties are also an important tool for understanding the interactions present in the adduct.

scholarly journals Snapshots of a Non-Canonical RdRP in Action

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1260
Author(s):  
Diego S. Ferrero ◽  
Michela Falqui ◽  
Nuria Verdaguer
Keyword(s):  
Metal Ion ◽  
Rna Viruses ◽  
Ion Binding ◽  
Genome Replication ◽  
Metal Ion Binding ◽  
Insect Virus ◽  
X Ray ◽  
Template Strand ◽  
Nucleotide Incorporation ◽  
Elongation Process

RNA viruses typically encode their own RNA-dependent RNA polymerase (RdRP) to ensure genome replication and transcription. The closed “right hand” architecture of RdRPs encircles seven conserved structural motifs (A to G) that regulate the polymerization activity. The four palm motifs, arranged in the sequential order A to D, are common to all known template dependent polynucleotide polymerases, with motifs A and C containing the catalytic aspartic acid residues. Exceptions to this design have been reported in members of the Permutotetraviridae and Birnaviridae families of positive single stranded (+ss) and double-stranded (ds) RNA viruses, respectively. In these enzymes, motif C is located upstream of motif A, displaying a permuted C–A–B–D connectivity. Here we study the details of the replication elongation process in the non-canonical RdRP of the Thosea asigna virus (TaV), an insect virus from the Permutatetraviridae family. We report the X-ray structures of three replicative complexes of the TaV polymerase obtained with an RNA template-primer in the absence and in the presence of incoming rNTPs. The structures captured different replication events and allowed to define the critical interactions involved in: (i) the positioning of the acceptor base of the template strand, (ii) the positioning of the 3’-OH group of the primer nucleotide during RNA replication and (iii) the recognition and positioning of the incoming nucleotide. Structural comparisons unveiled a closure of the active site on the RNA template-primer binding, before rNTP entry. This conformational rearrangement that also includes the repositioning of the motif A aspartate for the catalytic reaction to take place is maintained on rNTP and metal ion binding and after nucleotide incorporation, before translocation.

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