title: Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation.
abstract: This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb(+). Capillary affinity electrophoresis was employed for the experimental evaluation of the strength of the Val-Rb(+) complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb(+) cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb(+) cation concentration in the BGE (methanolic solution of 100 mM Tris, 50 mM acetic acid, 0-1 mM RbCl), the apparent binding (stability) constant (K(b)) of the Val-Rb(+) complex in methanol was evaluated as log K(b)=4.63+/-0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of Val-Rb(+) complex, Val is stabilized by strong non-covalent bond interactions of Rb(+) with six ester carbonyl oxygen atoms so that the position of the "central" Rb(+) cation in the Val cage is symmetric.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Sille
authors.initials: S
authors.lastname: Ehala
authors.forename: Jirí
authors.initials: J
authors.lastname: Dybal
authors.forename: Emanuel
authors.initials: E
authors.lastname: Makrlík
authors.forename: Václav
authors.initials: V
authors.lastname: Kasicka
mesh_terms: D002412:Cations / Q000737:chemistry; D003198:Computer Simulation; D004355:Drug Stability; D019075:Electrophoresis, Capillary; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D012413:Rubidium / Q000737:chemistry*; D013696:Temperature; D014634:Valinomycin / Q000737:chemistry*
chemical_list: D002412:Cations; D014634:Valinomycin; D012413:Rubidium