Relationship between Physical Parameters of Various Metal Ions and Binding Affinity for Alginate

• Published in: Biological & pharmaceutical bulletin Vol. 39; no. 11; pp. 1893 - 1896
• Main Authors: Idota, Yoko, Kogure, Yumi, Kato, Takako, Yano, Kentaro, Arakawa, Hiroshi, Miyajima, Chihiro, Kasahara, Fumiyoshi, Ogihara, Takuo
• Format: Journal Article
• Language: English
• Published: Japan The Pharmaceutical Society of Japan 2016; Pharmaceutical Society of Japan; Japan Science and Technology Agency
• Subjects: Affinity; alginate; Alginates - chemistry; Alginic acid; Aluminum; binding mechanism; Binding Sites; Cadmium; Calcium; Carbon dioxide; Copper; Excretion; Glucuronic Acid - chemistry; Hexuronic Acids - chemistry; Ions; Iron; Lead; Magnesium; Metal ions; Metals - chemistry; Potassium; Sequestering Agents - chemistry; Sorption; toxic metal
• ISSN: 0918-6158; 1347-5215
• DOI: 10.1248/bpb.b16-00127

We investigated the relationship between the physical parameters of various metal ions, including toxic metal ions, and the binding affinity of these metal ions for alginate (Alg). The binding constant, K, of Sr2+ was the highest among all tested metal ions. The order of K values was: Sr2+>Pb2+>Tb3+>Dy3+>Ca2+>Cd2+>Mg2+>Fe2+>Fe3+>Co2+>Al3+>Ni2+>Cs+>Cu2+>Ag+>Li+>K+. The metal ions showing the highest K values had ionic radii within the range of about 90–120 pm. Moreover, the K values of divalent or trivalent metal ions tended to be higher than those of monovalent ions. The number of binding sites per 1 mg of Alg (n) was highest for K+, followed by Pb2+ and Cs+. The order of affinity (calculated as the product of n and K) was Pb2+>Dy3+>Tb3+>Sr2+>Ca2+>Mg2+>Cd2+>Fe2+, Fe3+>Cs+>Al3+>Co2+>Ni2+>Cu2+>Ag+>K+>Li+. Our results support the idea that Alg would be effective as an excretion accelerator and/or absorption inhibitor for various toxic metal ions.