Carboxylate groups metal binding

There are two cation-binding sites per subunit, classified nL and n2. The n, site is a structural site, which may involve the reorientation of a glutamate carboxyl group. Metals bind first at this site. The n2 site is the catalytic site and may bind metal or metal-nucleotide. Co111 and Cr111 can be incorporated into the nj metal-binding sites in un-adenylylated glutamine synthetase from E. co/i.318 Both derivatives were inactive, but were able to bind Mn2+ at the n2 site. Comparison of the quaternary enzyme-Crin-Mnn-ADP (which shows spin-spin interaction between the two metal centres) with enzyme-Com-Mnn-ADP leads to an estimate of the distance between n, and n2 sites of 7 2 A. 

Metal oxide colloids have been effectively coupled with multifunctional ligands containing carboxyl groups that bind to the surface of nanoparticles [46]. One can rationally design optimal photocatalysts by tailoring functional groups for selective adsorption of specific... 

These EPR studies have shown that the surface modifier must contain a carboxyl group to bind to the colloid surface and at the same time to bind to the metal ions. The surface modifier has to have a hole trap that enhances photogenerated charge pair separation distance. A mercapto group that is in an a position relative to a carboxyl group enhances adsorption of... 

Several enzymes bind both magnesium and zinc ions, using them for different purposes. For example, nucleotidyl transferases can use one metal ion, to which is coordinated a phosphate group and a carboxylate group, the latter serving to polarize the water nucleophile. When there are two metal ions present, the carboxylate group also binds the second metal ion which in turn activates the nucleophile. Therefore it appears that the second metal ion aids in the catalysis, replacing the action of an active-site side chain in those enzymes of that activity that only bind one metal ion. T vo enzymes will be described here—the alkaline phosphatase and the 3 -5 exonuclease from E. coli. 

About half of the dissolved organic carbon may appear in humic or fulvic acids. These are high-molecular weight organic compounds of a composition which is somewhat uncertain. They contain aromatic hydroxyl and carboxyl groups which have the ability to bind to metal ions. Rivers and estuaries typically contain 10 mg/liter of acid with an exchange capacity of 5-10 mmol/g, mainly due to carboxylic... 

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

---