Proton-transfer reaction dynamics and energetics in calcification and decalcification.

CaCO3 -saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca(2+) +HCO3 (-) ⇌CaCO3 +H(+) ; and reversible static physical precipitation/dissolution, Ca(2+) +CO3 (2-) ⇌CaCO3 . The former reversible reaction was determined using a strong base and acid titration.

Buffering dissociation/formation reaction of biogenic calcium carbonate.

The oscillating stability of coral reef seawater pH has been maintained at around physiological pH values over the past 300 years (Pelejero et al., 2005). The stability mechanism of its pH has been interpreted in terms of the buffering dissolution/formation reaction of CaCO(3) as well as the proton consumption/generation reaction in CaCO(3)-saturated water.

Nucleophilic reaction by carbonic anhydrase model zinc compound: characterization of intermediates for CO2 hydration and phosphoester hydrolysis.

The partially hydrophilic and hydrophobic tripodal ligands, tris(hydroxy-2-benzimidazolylmethyl)amine L1h and tris(2-benzimidazolyl)amine L1 were used for the preparation of biomimetic complex of carbonic anhydrase. The CO(2) hydration using [L1hZn(OH)]ClO(4).1.

Control of calcium carbonate polymorphism and morphology through biomimetic mineralization by means of nanotechnology.

In vitro biomimetic mineralization by means of nanotechnology allows the formation of calcium carbonate polymorphs at low temperatures (<25 degrees C) under a CO(2) atmosphere of 500-1500 ppm. A two-dimensional zinc-ion ordered array (zinc array), which acts as an active-site mimic of carbonic anhydrase, has been prepared by immersing the self-organized monolayer of 3-(2-imidazolin-1-y)propyltriethosilane on mica (ImSi substrate) into aqueous zinc solution. The zinc array mounted on the ImSi substrate catalyzed the conversion from CO(2) to HCO(3) (-), and accelerated the formation of calcium carbonate.

Hydrolysis of natural and artificial phosphoesters using zinc model compound with a histidine-containing pseudopeptide.

Zinc(II) complex with histidine-containing pseudopeptide derived from N,N'-bis(benzylhistidyl) diethylenetriamine L was examined as catalyst for the hydrolysis of bis(p-nitrophenyl) phosphate (BNPP), p-nitrophenyl phosphate (NPP), adenylyl-(3'-5')adenosine (ApA), thymidylyl-(3'-5') thymidine (TpT) and PBR 322 supercoiled DNA. The stepwise protonation constants of the ligand, stability constants for its zinc(II) complex LZn have been determined potentiometrically in aqueous solution. LZn efficiently hydrolyzed BNPP and NPP and their pseudo-first-order rate constants k(obs) are 1.

Kinetic study of catalytic CO(2) hydration by water-soluble model compound of carbonic anhydrase and anion inhibition effect on CO(2) hydration.

A kinetic study of CO(2) hydration was carried out using the water-soluble zinc model complex with water-soluble nitrilotris(2-benzimidazolylmethyl-6-sulfonate) L1S, [L1SZn(OH(2))](-), mimicking the active site of carbonic anhydrase, in the presence and absence of anion inhibitors NCS(-) and Cl(-). The obtained rate constants k(cat) for CO(2) hydration were 5.9x10(2), 1.

Hydroxyl radical as a strong electrophilic species.

In order to clarify an index which could be used as proof of the presence of hydroxyl radical, a new standard isomer distribution ratio of phenols formed from aromatic hydroxylation with [(4-bromophenyl)diazenyl](phenyl)methyl hydroperoxide 4, which is a stable source of hydroxyl radical, under a new appropriate photolysis condition in the presence or absence of benzoquinones is reported. We also demonstrated the strong electrophilic properties of hydroxyl radical in reference to earlier results of electron density calculations.