Biomaterial Database

Stoichiometry of the reactions of calcium with the metallochromic indicator dyes antipyrylazo III and arsenazo III. 1981

E Ríos, and M F Schneider

A method for determining the stoichiometry of one-product reactions involving a metal ion and an organic ligand is presented and applied to the reactions of calcium and magnesium with the metallochromic dyes Antipyrylazo III and Arsenazo III. The method consists of fitting titration data, obtained in solutions buffered for the metal, with theoretical functions that include: (a) the dependence of product concentration on the concentration of both reactants, (b) the relationship between metal ion concentration and total amount added in the presence of the buffer, and (c) a correction for the amount of metal ion that binds to the organic ligand. It is shown that the products of the reactions of Antipyrylazo III with calcium and magnesium are CaD2 and MgD, respectively. The product formed between calcium and Arsenazo III at [Ca2+] over 20 microM is CaD2, other products accumulating at lower [Ca2+]. The kinetics of the Antipyrylazo III:Ca reaction are rapid under conditions in which this dye has been applied to measure calcium transients in skeletal muscle fibers. The present results provide a calibration for previous studies with Antipyrylazo III in muscle fibers.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D009282	Naphthalenesulfonates	A class of organic compounds that contains a naphthalene moiety linked to a sulfonic acid salt or ester.
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D004396	Coloring Agents	Chemicals and substances that impart color including soluble dyes and insoluble pigments. They are used in INKS; PAINTS; and as INDICATORS AND REAGENTS.	Coloring Agent,Dye,Dyes,Organic Pigment,Stain,Stains,Tissue Stain,Tissue Stains,Organic Pigments,Pigments, Inorganic,Agent, Coloring,Inorganic Pigments,Pigment, Organic,Pigments, Organic,Stain, Tissue,Stains, Tissue
D000042	Absorption	The physical or physiological processes by which substances, tissue, cells, etc. take up or take in other substances or energy.
D001150	Arsenazo III	Metallochrome indicator that changes color when complexed to the calcium ion under physiological conditions. It is used to measure local calcium ion concentrations in vivo.
D001391	Azo Compounds	Organic chemicals where aryl or alkyl groups are joined by two nitrogen atoms through a double bond (R-N	Azo Dye,Azo Dyes,Compounds, Azo,Dye, Azo,Dyes, Azo
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining