title: Development of new double-stranded phenylalanyl chelators using eta-chi diagrams and binding constants for chelators and lanthanide ions.
abstract: We examined the interaction between several ligands and alkaline (M(+)) or lanthanide (Ln(3+)) ions using eta-chi diagrams. eta and chi represent absolute hardness and absolute electronegativity, respectively. Based on the diagrams, new double-stranded amino acid chelators (1) conjugated to Cat (catechol) were synthesized. They had two cavities coordinating hard metal ions, such as Li(+) and K(+), and soft metal ions, such as Lu(3+) and Eu(3+). 1 formed a solvated molecular complex, 1-Ln(3+), with a molar ratio of 1 : 1 at a binding constant (K(b)) of 10(4)-10(6) with Y(3+), La(3+), Eu(3+), and Lu(3+), respectively. With a chemical hard ion, Li(+), we found that the K(b) of the 1-Eu(3+) complex increased. The optimized geometries of 1-Lu(3+) and 1-La(3+) complexes were obtained from B3LYP correlation functions using Stuttgart-Dresden-Bonn (SDD) Effective Core Potential (ECP) basis sets for Lu(3+) and La(3+) ions. The double-stranded chelator may prove useful for studying the selective separation of lanthanide ions, and the development of functional peptides.
authors.affiliation: Department of Analytical Chemistry of Medicines, Showa Pharmaceutical University, 3-3165 Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan. kobayasi@ac.shoyaku.ac.jp
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Chikuma
mesh_terms: D002396:Catechols / Q000737:chemistry*; D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry*; D007477:Ions; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D008672:Metals, Alkali / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D010649:Phenylalanine / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D002396:Catechols; D002614:Chelating Agents; D007477:Ions; D028581:Lanthanoid Series Elements; D008024:Ligands; D008672:Metals, Alkali; D009942:Organometallic Compounds; D010649:Phenylalanine; C034221:catechol