Stoichiometries of arsenazo III-Ca complexes (original) (raw)
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Biophysical Journal, 1987
The equilibrium reactions of the metallochromic indicator dye Antipyrylazo III with calcium at physiological ionic strength have been investigated spectrophotometrically. Dye absorbance as a function of wavelength was measured at various total dye and calcium concentrations. Analysis of the absorbance spectra indicated that at pH 6.9 at least three calcium:dye complexes form, with 1: 1, 1:2, and possibly 2:2 stoichiometries. The dissociation constant and the changes in dye extinction coefficients on formation of the 1:2 complex, the main complex which forms when Antipyrylazo III is used to study cytoplasmic calcium transients, have been characterized. BIOPHYS. J.
Biophysical Journal, 1981
ABSTRACr Equilibrium binding properties of the metallochromic indicator Arsenazo III (AIII) were characterized by Ca2" and acid/base titration. Free calcium was measured directly with Ca2" ion-sensitive electrodes. Absorbance changes were measured by both a conventional scanning spectrophotometer and a dual wavelength spectrophotometer. Acid/ base titration of AIII in conjunction with Ca2" ion-sensitive electrode measurement and absorbance changes indicate that pH can change AIII absorbance through a change of the KD for Ca-AIII formation, and, in addition, that there is a pH-speciflic component that is not dependent on Ca-AIII formation. The dissociation constant (KD) of AIII varied not only with pH, but with ionic strength and AIII concentration. Studies conducted to examine AIII-Ca stoichiometry resulted in different initial conclusions, depending on the method of analysis. Log AA-log AIII relations were in accord with previously published results, which indicates that more than one AIII binds to one Ca2" ion. But Job plots, Scatchard analysis, and Hill plots all indicated 1:1 binding. The method of absorbance measurement, i.e., scanning or dual wavelength did not influence the results. These findings were reconciled on the basis of changes in KD with AIII concentration and ionic strength. In 200 mM KCI, KD of AIII-Ca varies by a factor of 7 between 10-4 and 10-3 M AIII. Thus, a disproportionately large amount of Ca-AIII is formed as AIII concentration is increased, which results in slopes greater than unity for log AA-log AIII relations.
Colorimetry Based Calcium Measurement
2014
Abstract:- Calcium Analysis is one of the significant parameter for the clinical diagnosis. Calcium controls osmosis and diffusion through the cell membranes, and also the passing of information within the cell. Normal range of Calcium in human serum is around 8.5mg/dl-10.5mg/dl. The paper is focused on the Colorimetric Sensing technique for measurement of calcium. Colorimetry is a useful analytical tool for determining concentration of colored material in the solution. This sensing technique consists of LED as a light source of 650nm and a high speed photodiode BPW34 as a detector. Calcium reacts with ArsenazoIII and forms a colored complex. Concentration of calcium is measured by measuring the absorbance using Beer Lambert’s law. The paper describes the test preparation and measurement procedures. The designed colorimetric sensing system is maintenance free and is cost effective. Keywords:- Absorbance, Calcium, Concentration, Cuvette. I.
Arsenazo III and antipyrylazo III calcium transients in single skeletal muscle fibers
The Journal of General Physiology, 1982
The metallochrome calcium indicators arsenazo III and antipyrylazo III have been introduced individually into cut single frog skeletal muscle fibers from which calcium transients have been elicited either by action potential stimulation or by voltage-clamp pulses of up to 50 ms in duration. Calcium transients recorded with both dyes at selected wavelengths have similar characteristics when elicited by action potentials. Longer voltage-clamp pulse stimulation reveals differences in the late phases of the optical signals obtained with the two dyes. The effects of different tension blocking methods on Ca transients were compared experimentally. Internal application of EGTA at concentrations up to 3 mM was demonstrated to be efficient in blocking movement artifacts without affecting Ca transients. Higher EGTA concentrations affect the Ca signals' characteristics. Differential effects of internally applied EGTA on tension development as opposed to calcium transients suggest that diff...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1983
If arsenazo III is present during homogenization of brain this metallochromic indicator is entrapped within subsequently isolated synaptosomes. A large proportion of the entrapped indicator is released upon addition of digitonin to disrupt the synaptosomal plasma membrane. A similar proportion of [3H]sucrose is also trapped within synaptosomes if present in the homogenization medium, suggesting that homogenization causes a transient opening of the nerve ending as it is chopped off from the axon. Addition of the ionophore A23187 or depolarization of the plasma membrane by adding veratridine, gramicidin or increasing external K ÷ changes the absorbance of the entrapped dye, with peaks of absorbance around 600 and 650 nm, typical of the arsenazo lll-Ca 2+ complex. The response to veratridine is inhibited by the Ca2+-channel antagonist, verapamil, while that of A23187 is unaffected. The present method provides a sensitive technique for measurements of changes in cytosolic calcium ion concentrations within nerve endings.
Some observations on screened indicators for the direct chelatometric titration of calcium
Microchemical Journal, 1990
The screening of five common metallochromic indicators used in the complexometric determination of Ca was studied using tristimulus chromaticity theory. Calcon-tartrazine-Orange II (6.8 + 1 + 4.6, w/w), thymolphthalein complexone-Orange II-tartrazine (14.22 + 1.22 + 1), Arsenazo III-Remazol Brilliant Blue-tartrazine (25.2 + 8.9 + 1), phthalein complexonetartrazine-Remazol Brilliant Blue (2.47 + 1 + 1.0, and methylthymol Blue-Orange II-tartrazine (13 + 2.9 + 1) are proposed for the titration of calcium against Na, EDTA. The clarity and accuracy of titration are improved. o WJO Academic PESS, IN.
Green approaches to colorimetric monitoring of calcium in water
Pure and Applied Chemistry, 2009
Simple, ecologically harmless chemical reactions have always been a point of interest for chemists and analysts as fit to be applied to work in or out of laboratories. A new concept of chemical analysis is exemplified in the article by means of selective determination of calcium ions with the organic reagent arsenazo III (2,2'-[1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo]-bisbenzenearsonic acid disodium salt) with no application of toxic solvents during the seasonal analysis of water in the Yauza River (the city of Moscow).
Membrane perturbation: studies employing a calcium-sensitive dye, arsenazo III, in liposomes
Proceedings of the National Academy of Sciences, 1976
A metallochromic dye, arsenazo III [2,7-bis-(2-arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid], has been incorporated into the aqueous interspaces of multilamellar liposomes. Addition of Ca produced no shift in the absorbance spectrum of dye captured by liposomes, whereas disruption of liposomes by Triton X-100, followed by Ca, produced the spectrum characteristic of the dye-Ca complex: evidence of latency. Addition of excess ethylenegly-