title: Kinetic scheme for Ca2+-arsenazo III interactions.
abstract: Temperature-jump relaxation kinetic studies show that the complex formation between Ca2+ and the metallochromic dye arsenazo III (Ar) is associated with a rapid mode (less than or equal to 10 mus-range) involving both Ca2+ and Na+ of the Na-salt of Ar and a slower mode (approximately 10 ms range) which can be attributed to structural rearrangements in the 1:2 complex CaAr2. The kinetic data suggest the scheme: Ca+2Ar = CaAr+Ar = CaAr2 = CaAr2. The relatively slow rate-limiting step sets a limit for the use of arsenazo III to study the kinetics of Ca2+ processes in cell biology.
mesh_terms: D001150:Arsenazo III; D001391:Azo Compounds; D002118:Calcium / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D008956:Models, Chemical; D012964:Sodium / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics
chemical_list: D001391:Azo Compounds; D001150:Arsenazo III; D012964:Sodium; D002118:Calcium