A cyclic hexapeptide, cyclo(Pro-Gly-Pro-Gly-Pro-Gly), has been synthesized; its solution conformations were examined by 220-MHz nuclear magnetic resonance spectroscopy. The solution structures have been deduced, and shown to vary as a function of solvent polarity. In addition, it has been found that this cyclic peptide binds alkali metal cations. While the predominant conformation of this cycli...

An ab initio powder X-ray crystal structure analysis revealed that layered zinc 1,3,5-benzenetriphosphonates containing interlayer tetramethylammonium (ZBP-TMA) or 4,4'-bipyridinium cations (ZBP-bpy) are transformed to novel isomorphous 3D open-framework compounds ZBP-M (M: K, Rb, and Cs) by treatment in aqueous alkali metal chloride solutions. ZBP-Ms have a pillared layer-type of anionic frame...

When adsorbed (at a low temperature) on alkali-metal-exchanged zeolites, CO forms both M(CO) and M(OC) carbonyl species with the extra-framework alkali-metal cation of the zeolite. Both quantum chemical and experimental results show that C-bonded adducts are characterized by a C−O stretching IR band at a frequency higher than that of 2143 cm for free CO, while for O-bonded adducts this IR band ...

Calix[8]arenes of conformational rigid were isolated. The NMR parameters of the structure of calix[8]arenes have been compared. The study of organic structures to form nanoporous materials is well-known in chemistry phenomena to find the crystal form of calix[8]arene as supramolecule. Investigated and compared hydrogen bonding, oxygen and nitrogen atoms effect on calix[8]arene and its complexes...

Calix[8]arenes of conformational rigid were isolated. The NMR parameters of the structure of calix[8]arenes have been compared. The study of organic structures to form nanoporous materials is well-known in chemistry phenomena to find the crystal form of calix[8]arene as supramolecule. Investigated and compared hydrogen bonding, oxygen and nitrogen atoms effect on calix[8]arene and its complexes...

BACKGROUND Dibenzo-18-crown-6 (DB18C6) exhibits the binding selectivity for alkali metal cations in solution phase. In this study, we investigate the main forces that determine the binding selectivity of DB18C6 for the metal cations in aqueous solution using the density functional theory (DFT) and the conductor-like polarizable continuum model (CPCM). RESULTS The bond dissociation free energi...

The cation selectivity of the Na entry mechanism located in the outer membrane of the bullfrog (Rana catesbeiana) skin epithelium was studied. This selectivity was determined by measuring the short-circuit current when all of the external sodium was replaced by another cation and, also, by noting the relative degree of inhibition that the alkali metal cations produced on Na influx. The ability ...

A B S TRAC T The cation selectivity of the Na entry mechanism located in the outer membrane of the bullfrog (Rana catesbeiana) skin epithelium was studied. This selectivity was determined by measuring the short-circuit current when all of the external sodium was replaced by another cation and, also, by noting the relative degree of inhibition that the alkali metal cations produced on Na influx....

Guanine tetraplexes are biological non-covalent systems stabilized by alkali cations. Thus, self-clustering of guanine, xanthine and hypoxanthine with alkali cations (Na(+), K(+) and Li(+)) is investigated by electrospray ionization mass spectrometry (ESI-MS) in order to provide new insights into G-quartets, hydrogen-bonded complexes. ESI assays displayed magic numbers of tetramer adducts with ...

We developed a capillary zone electrophoresis method with indirect UV detection for determination of ammonium cations and alkali and alkaline earth metal cations in jellyfish. As the background electrolyte, a mixture of N-methylbenzylamine, citrate, and 18-crown-6 was used for the complete separation of all analyte cations. The limits of detection were 0.13 - 0.34 mg l(-1) at a signal-to-noise ...