Selectivity reversible anion binding

Dickins, R. S. Gunnlaugsson, T. Parker, D. Peacock, R. D. Reversible anion binding in aqueous solution at a cationic heptacoordinate lanthanide centre selective bicarbonate sensing by time-delayed luminescence. Chem. Commun. 1998, 16, 1643-1644. 

Carboxymethylation. It was found by Vallee and Li that one cysteine residue per subunit may be selectively carboxymethylated with iodoacetate.1405 Since this reaction causes deactivation of the enzyme, this cysteine residue, later identified as Cys-46,1406 was suggested to be at the active site. The deactivated carboxymethylated enzyme still binds NAD+. The carboxymethylation of this residue is preceded by a reversible binding of iodoacetate to the enzyme.1407 This observation has helped to identify an anion-binding site in the coenzymebinding domain, where the pyrophosphate group of the coenzyme binds. 

Anion binding is reversible and the precise interactions between receptor and anionic guest can be finely controlled by synthetic development of subtlety modified hydrogen-bond functional anion-binding cavities. This methodology for easy functionalization means these receptors have been modified to show unusual anion selectivities. They therefore have a great potential for incorporation into anion sensory, switchable, and functional devices. 

Bruce JI, Dickins RS, Govenlock LJ, Gimnlaugsson T, Lopinski S, Lowe MP, Parker D, Peacock RD, Perry JJB, Aime S, Botta M. 2000. The selectivity of reversible oxy-anion binding in aqueous solution at a chiral europium and terbium center signaling of carbonate chelation by changes in the form and circular polarization of luminescence emission. J Am Chem Soc 122 9674-9684. 

Receptor-binding of glycine induces the opening of an intrinsic anion channel highly selective for chloride and bicarbonate [2 4-]. Depending on the low reversal... 

Also for the anion library two selectivity experiments for the binding of HS(V, N03- and AcCT were conducted with T3. In both experiments, first 10 M N(>3" was added to a T3 layer, showing no response as expected. Then, two separate experiments were performed reversing subsequent additions of solutions of HS04 and AcCT, ranging from 10-6 M to 10-3 M. In each case, the addition of AcCT caused 70% fluorescence quenching, but only when the HSC>4- was added first did the HSCV result in a fluorescence intensity in-... 

There has been some development of optical biosensors. Nitrate reductase was immobilised within a sol-gel matrix, with binding of nitrate ion (down to a limit of 10"6 M) causing a characteristic change in the optical absorption [132]. It is notable that this sensor was reversible, allowed selective nitrate detection over other physiologically significant anions and did not lose activity even over six months. Phosphate-binding protein was immobilised on a fibre-optic detector and could be used to measure phosphate with a detection limit of about 10 6 M [133]. 

Heteroditopic ruthenium(n) and rhenium(l) bipyridyl bis(benzo-15-crown-5) ion-pair receptors 19 and 20 display, upon K+ complexation, a remarkable switch in anion selectivity <1998CC825>. In the absence of K+, receptors 19 and 20 exhibit a selectivity preference for II2PO4 over CP. However, addition of KPF6 caused in both cases, the formation of a sandwich K+ complex, which shows a reversed CP over H2POP binding selectivity because of a more favorable electrostatic attraction between K+- and CP-bound ions (positive binding cooperativity). 

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