The transport systems for a-AIB and neutral, acid, and basic amino acids into lens were found to comprise a ~N a*-dependent and a Na-independent component. Na ions, required for 60 to 70 per cent of C-a-AlB transported into rabbit lens, were combined with a-AIB molecules in a 1:1 ratio while transported by a common "carrier" system. However, Na ions did not affect the diffusion constant nor the...

Na/K-ATPase pumps expel three Na ions and import two K ions for each ATP hydrolyzed, generating the ion gradients across the membrane that are essential to the life of all animal cells. Each transport cycle comprises a sequence of conformational transitions that permit extracellular K ions to access the binding sites in phosphorylated pumps (E2P conformations; Fig. 1) and cytoplasmic Na ions to...

We have recently isolated a mutant (aK220R, aV264E, aI278N) of the Na+-translocating Escherichia coli/Propionigenium modestum ATPase hybrid with a Na+-inhibited growth phenotype on succinate. ATP hydrolysis by the reconstituted mutant ATPase was inhibited by external (N side) NaCl but not by internal (P side) NaCl. In contrast, LiCl activated the ATPase from the N side and inhibited it from the...

A B S TR ACT Ionic fluxes in Na channels of myelinated axons show ionic competition, block, and deviations from simple flux independence. These phenomena are particularly evident when external Na + ions are replaced by other permeant or impermeant ions. The observed currents require new flux equations not based on the concepts of free diffusion. A specific permeability model for the Na channel ...

A series of molecular dynamics simulations have been conducted in order to study the structural and interfacial properties of dodecyl sulfate (DS−) monolayers with Li+, Na+, Cs+ and NH4 cations. Varying the counterion has no significant effect on the structural properties of the surfactant molecules within the different monolayers. However, the different counterions have a significant effect on...

The influence of Mn2+ ions on the structure of natural calf thymus DNA was studied by Raman spectroscopy. Measurements were done at room temperature and pH 6.2± 0.2, in the presence of the physiological concentration of 150 mM Na ions, and in the presence of Mn2+ concentrations that varied between 0 and 600 mM. No condensation of DNA was observed at any of the Mn2+ concentrations. At 5 mM Mn2+ ...

Ionic fluxes in Na channels of myelinated axons show ionic competition, block, and deviations from simple flux independence. These phenomena are particularly evident when external Na+ ions are replaced by other permeant or impermeant ions. The observed currents require new flux equations not based on the concepts of free diffusion. A specific permeability model for the Na channel is developed f...

Geopolymer paste is an innovative construction material which shall be produced by chemical action of inorganic molecules. It is a more environmentally friendly alternative to conventional Portland cement which is abundantly available worldwide. In this study, the influence of different alkaline activators (Na and K) on the mechanical and thermal behaviors of metakaolin-based geopolymer was inv...

Sequence-dependent coordination of alkali ions to the nucleotide bases in the minor groove of AT-tract B-DNA has recently been inferred from X-ray crystallography, solution NMR and computer simulations. Here, we present new (23)Na and (87)Rb magnetic relaxation dispersion (MRD) data that demonstrate competitive and long-lived binding of Na(+) and Rb(+) ions in the minor groove of the B-DNA dupl...

Transition metals are essential for many metabolic processes, and their homeostasis is crucial for life. Metal-ion transporters play a major role in maintaining the correct concentrations of the various metal ions in living cells. Little is known about the transport mechanism of metal ions by eukaryotic cells. Some insight has been gained from studies of the mammalian transporter DCT1 and the y...