Shizuo Watanabe

Fluorescence of magnesium-, calcium-, and zinc-8-quinolinol complexes☆

Abstract 1. 1. The study was made mainly in aqueous solutions of 0.1 M triethanolamine and tris (hydroxy) methylaminomethane on the fluorescence that was reported by Schacter in 1959 to be exhibited by an ethanolic solution of 8-quinolinol and metal ions (Mg2+, Ca2+, and Zn2+. The fluorescence was studied as a function of metal ion concentration, 8-quinolinol concentration, and also pH. 2. 2. The molar fluorescence and the apparent binding constant of these metal complexes and 8-quinolinol were then estimated. The apparent constants thus estimated were found to be in good agreement with those established by Nasanen and Pettinen (1952) using the light absorption method, the potentiometric method, and the method of solubility equilibrium. 3. 3. The sensitivity and specificity of the method for Mg2+ determination that was based on this fluorescence phenomenon were discussed in terms of the molar fluorescence and the binding constant.

A new kinetic property characteristic of the actomyosin-nucleoside-triphosphatase.

The nucleoside triphosphatase [EC 3.6.1.15] activity of actomysin and that of myosin are measured by varying the concentration of nucleoside triphosphate and that of CaCl2 or MgGl2. The results thus obtained are examined by asking a question of which is responsbile for the activity, the true substrate and the active enzyme in terms of the reaction scheme shown in p. 719. The answers found for the above question are summarized in Table I (see p. 720). It is emphasized that the summmary (Table I) corresponds very well to the fact that myosin alone does not superprecipitate in the presence of either calcium or magnesium ions, whereas actomyosin does superprecipitate in the presence of magnesium ions and not in the presence of calcium ions. Obviously, the true substrate type of reaction scheme represents a kinetic property characteristic of the superprecipitation-coupled nucleoside-triphosphatase. It is also noted of the summary (Table I) that actin is capable of not only activating Mg-nucleoside-triphosphatase but also switiching the reaction scheme from the active enzyme type to the true substrate type. It is known that trinitrophenylation of myosin results in activation of the Mg-ATPase activity of myosin. However, it is now found that trinitrophenylation is not capable of switiching the reaction scheme, that is to say that the Mg-ATPase reaction of trinitrophenyl-myosin stays with the active enzyme type of reaction scheme and that of acto-trinitrophenyl-myosin with the true substrate type of reaction scheme. Effect of actin on the function of myosin seems, therefore, very unique.