Infrared multiple-photon dissociation (IRMPD) spectroscopy is employed to obtain detailed binding information on singly charged silver and alkali metal-ion/tryptophan complexes in the gas phase. For these complexes the presence of the salt bridge (i.e. zwitterionic) tautomer can be virtually excluded, except for perhaps a few percent in the case of Li+. Two low-energy structures having the char...

Infrared multiple-photon dissociation (IRMPD) spectroscopy is employed to obtain detailed binding information on singly charged silver and alkali metal-ion/tryptophan complexes in the gas phase. For these complexes the presence of the salt bridge (i.e. zwitterionic) tautomer can be virtually excluded, except for perhaps a few percent in the case of Li. Two low-energy structures having the charg...

The effect of increasing the number of monocyclic six-membered rings or bicyclic rings of bicyclo[2.1.1]hexenyl fused to benzene on cation-π interactions involving alkali metal ions (Li(+), Na(+), and K(+)) has been investigated. The binding energy data at the B3LYP/6-311+G(2d,2p) level clearly indicate that the binding affinity of the metal ion with benzene is enhanced by increasing the number...

Formation constants for complexion between alkali metal cations and the crown ether 18C6 in the solvent 2-cyanopyridine at 3OoC were determined from conductance measurements. The method allows for precise determination of these formation constants up to values of K around 10" mol-' dm3. The method also f. permits accurate evaluation of association equilibrium constants between the complex speci...

The binding affinity and selectivity of a new ionophore, [1(8)]starand (1), toward alkali metal cations in methanol were examined through NMR titration experiments and free energy perturbation (FEP) and molecular dynamics simulations. The preference was determined to be K(+) > Rb(+) > Cs(+) > Na(+) >> Li(+) in both FEP simulations and NMR experiments. The FEP simulation results were able to pre...

A physical model of selective "ion binding" in the L-type calcium channel is constructed, and consequences of the model are compared with experimental data. This reduced model treats only ions and the carboxylate oxygens of the EEEE locus explicitly and restricts interactions to hard-core repulsion and ion-ion and ion-dielectric electrostatic forces. The structural atoms provide a flexible envi...

Electrode potential measurements have been applied to study electrical characteristics like transport numbers, permselectivity & fixed charge density of ion-exchange membranes. Membrane potential measurements were made across zirconium phosphotungstate cation-exchange membrane maintained at 27◦C, using halide salts of alkali & alkaline earth metals as electrolytes. The effect of concentration o...

The alkali-metal ions, Li+, Na+ and K+, exhibit complex pH-dependent effects on sucrase that seem to involve at least three separate types of mechanism and, perhaps, an equal number of specific metal-binding sites. In metal-free buffers, the alkali metals give mixed activating effects below pH 7 that involve: 1) Affinitytype (K-type) activation kinetics, where the apparent K,,, decreases as the...