The time evolution of silica nanoparticles in solutions of tetrapropylammonium (TPA) has been studied using a combination of small-angle scattering, conductivity, and pH measurements to provide the first comprehensive analysis of nanoparticle structural and compositional changes at elevated temperatures. We have found that silica-TPA nanoparticles subjected to hydrothermal treatment (70-90 degr...

Current models of the Na(+)-K(+)-ATPase reaction cycle have ATP binding with low affinity to the K(+)-occluded form and accelerating K(+) deocclusion, presumably by opening the inside gate. Implicit in this situation is that ATP binds after closing the extracellular gate and thus predicts that ATP binding and extracellular cation binding to be mutually exclusive. We tested this hypothesis. Acco...

The transient receptor potential vanilloid 1 (TRPV1) nonselective cationic channel is a polymodal receptor that activates in response to a wide variety of stimuli. To date, little structural information about this channel is available. Here, we used quaternary ammonium ions (QAs) of different sizes in an effort to gain some insight into the nature and dimensions of the pore of TRPV1. We found t...

We studied block of the internal pore of the ROMK1 inward-rectifier K+ channel by Mg2+ and five quaternary ammoniums (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrapentylammonium). The apparent affinity of these blockers varied as a function of membrane voltage. As a consequence, the channel conducted K+ current more efficiently in the inward than th...

Using whole-cell patch-clamp techniques, we studied the interaction of open NMDA channels with tetraalkylammonium compounds: tetraethylammonium (TEA), tetrapropylammonium (TPA), tetrabutylammonium (TBA), and tetrapentylammonium (TPentA). Analysis of the blocking kinetics, concentration, and agonist dependencies using a set of kinetic models allowed us to create the criteria distinguishing the e...

Arrays of microscale interfaces between two immiscible electrolyte solutions (μITIES) were formed using glass membranes perforated with microscale pores by laser ablation. Square arrays of 100 micropores in 130 μm thick borosilicate glass coverslips were functionalized with trichloro(1H,1H,2H,2H-perfluorooctyl)silane on one side, to render the surface hydrophobic and support the formation of aq...