Guanidinium, anion binding

Guanidinium group, ubiquitous in anion-binding enzymes, stabilizes oxoanions not only through electrostatic attraction but also by two parallel hydrogen bonds documented in numerous X-ray structures of the corresponding salts like 348 [13]. Simple guanidinium compounds like 349 form complexes of... 

Positively charged or neutral electron-deficient groups may serve as interaction sites for anion binding. Ammonium and guanidinium units, which form +N-H" X bonds, have mainly been used, but neutral polar hydrogen bonds (e.g., with -NHCO- or -COOH functions), electron-deficient centers (boron, tin, mercury, [3.6, 3.7] as well as perfluoro crown ethers and cryptands [3.8], etc.), or metal-ion centres in complexes also interact with anions. 

Key anion binding moieties are strong hydrogen bonding groups such as guanidinium, ureas, amides and pyrroles. 

Anion receptor molecules. Synthesis and some anion binding properties of macro-cyclic guanidinium salts, B. Dietrich, T. M. Fyles, J.-M. Fehn, F. G. Pease and D. F. Fyles, J. Chem. Soc., Chem. Commun., 1978, 934. 

The pyrophosphate moiety is bent over the fork of the side chain of Ile-269. The guanidinium group of Arg-47 provides a positive charge for an ionic interaction with the pyrophosphate. This site has been shown to be a general anion binding site in LADH (Section II,H,la). 

D.L. Anion receptor molecules. Synthesis and some anion binding properties of macrocyclic guanidinium salts. J. 

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