Addition Of Alkali Metal Cations Research Articles

Ion Pair Formation between Electro-generated 1,2-Naphtoquinone Anion Radicals and Alkali Metal Cations in Acetonitrile

Abstract Ion association of 1,2-naphthosemiquinone with the alkali metal cations in acetonitrile has been comprehensively studied by the use of ESR, absorption spectroscopy, polarography and with MO calculation. A continuous flow electrolysis system with a glassy carbon column electrode has been developed for the rapid quantitative preparation of organic free radicals, whose ESR spectrum or absorption spectrum was observed in situ. The formation constants of the ion pair with K+, Na+, and Li+ were estimated as 103.2, 104.5, and 108.0, respectively. By the addition of alkali metal cations, the half-wave potentials shifted to more positive potential in the order of K+<Na+<Li+. The proton hyperfine splitting constants in the ESR also varied in this order. This column electrolysis method is considered to be a powerful technique, particularly for the study of short lived free radicals, because the quantitative electrolysis is performed rapidly even in a solution of extremely diluted supporting electrolyte, such as 0.1 mM (mmol/dm3).

The pH dependence of the effects of Na + , K + and ouabain on the ATPase activity of NaI-treated brain microsomes with Mg 2+ , Mn 2+ , Ca 2+ and Zn 2+ as divalent metal activators.

1. 1. The influence of pH on the ATPase activities of NaI-treated microsomes from pig brain has been investigated with Mg2+, Mn2+, Ca2+ or Zn2+ as divalent metal cofactor. Some ouabain-inhibitable ATPase has been found with each of these cations even without addition of alkali metal cations. 2. 2. The pH profile of ouabain-sensitive Mg2+-ATPase varied in different preparations of NaI-microsomes. Some preparations had three pH optima at pH values 5.5, 7.4 and 9.0, corresponding to the pH optima for the K+-, (Na+-K+)- and Na+-ATPases of the same preparation. 30 mM K+ inhibited Mg2+-ATPase activity to an extent and with a pH dependence similar to ouabain. 3. 3. ATPase activities with Mn2+ were usually similar to those with Mg2+, except that at alkaline pH Mn2+ was inhibited by 100 mM Na+. Na+ also reduced ouabain-insensitive Mn2+-ATPase activity at high pH. 4. 4. Ca2+-ATPase was optimal at pH 9 and was slightly inhibited by ouabain. Low concentrations of Na+ stimulated Ca2+-ATPase at pH 7.5, while joint addition of 100 mM Na+ and 30 mM K+ stimulated ouabain-inhibitable ATPase activity with a pH optimum of 7.7. 100 mM Na+ alone inhibited Ca2+-ATPase but the ouabain-sensitivity of Ca2+-ATPase activity was increased in the presence of Na+. 5. 5. Zn2+-ATPase activity was greatest at pH 5.5 and was partially inhibited by ouabain. 30 mM K+ inhibited Zn2+-ATPase with a pH-dependence and extent very similar to ouabain at pH values up to 7. Both 4 mM Na+ and joint addition of 100 mM Na+ and 30 mM K+ stimulated ouabain-inhibitable Zn2+-ATPase activity with pH optima of 7.4 and 6–6.5 respectively. 6. 6. NaI-microsomes also had Mg2+- and Ca2+-ITPase activities, but Zn2+-ITPase was very low. Mg2+-ITPase was activated by Na+ but not by K+.

Stabilizing effectiveness of alkali metals toward ribonucleic acid from the bacterial virus R17

AbstractThe addition of alkali metal cations (0.10–1.00M) stabilizes the macromolecular structure of R17‐RNA as evidenced by a shift of the optical density–temperature profiles to higher temperature. This effectiveness is found to decrease in the order Li+ > Na+ > K+ > Rb+ > Cs+ and the midpoints of each profile (Tm) are found to increase linearly for each salt with the log of the salt concentration. The differences in effectiveness in this series can be best interpreted as a decreasing specific interaction of Li+, Na+, K+, and Rb+ with the phosphate groups of RNA as suggested by known binding constants to phosphate groups and the failure of adenine, adenosine, adenine monophosphoric acid, and uracil to show specific solubility differences in these salts. The importance of this feature is that the thermal stability of RNA in the presence of alkali metals shows specific ion requirements in addition to general electrostatic interactions. Furthermore, the more nonspecific, ionic strength‐dependent stabilization of native RNA also involves a decrease in adenine solubility (e.g., increased activity) and an increase in phosphate solubility in the aqueous salt solutions in addition to the well recognized Coulombic shielding of the negatively charged phosphates.