Potassium (K(+)) channels are tetrameric membrane-spanning proteins that provide a selective pore for the conductance of K(+) across the cell membranes. These channels are most remarkable in their ability to discriminate K(+) from Na(+) by more than a thousandfold and conduct at a throughput rate near diffusion limit. The recent progress in the structural characterization of K(+) channel provid...

2014 The spin-lattice relaxation of the Fe3+ ion in cubic ZnS has been studied between 1.3 and 300 K by pulse saturation, progressive saturation and broadening of the E.P.R. line. In ZnS, the Fe3+ ion is more strongly coupled to the lattice than the isoelectronic ion Mn2+. For T > 50 K, the optical phonons contribute to the relaxation, and are responsible for a strong line broadening at 30...

Although the benefits of decreased sample temperature for the molecular profiling of organic materials with time-of-flight secondary ion mass spectrometry (TOF-SIMS) have been established, the mechanism behind spectral changes observed at low temperature, particularly increased protonated molecular ion (M + H)(+) yields, have not been examined in detail. We have developed a procedure to investi...

We have examined the voltage dependence of external TEA block of Shaker K(+) channels over a range of internal K(+) concentrations from 2 to 135 mM. We found that the concentration dependence of external TEA block in low internal K(+) solutions could not be described by a single TEA binding affinity. The deviation from a single TEA binding isotherm was increased at more depolarized membrane vol...

K+ channels conduct and regulate K+ flux across the cell membrane. Several crystal structures and biophysical studies of tetrameric ion channels have revealed many of the structural details of ion selectivity and gating. A narrow pore lined with four arrays of carbonyl groups is responsible for ion selectivity, whereas a conformational change of the four inner transmembrane helices (TM2) is inv...

Ion association of the ionic liquid [bmim][Cl] in acetonitrile and in water was studied by dielectric spectroscopy for salt concentrations c ≤ 1.3 M at 298.15 K and by measurement of molar electrical conductivities, Λ, of dilute solutions (c ≤ 0.006 M) in the temperature range 273.15 ≲ T/K ≤ 313.15. Whilst acetonitrile solutions of [bmim][Cl] exhibit moderate ion pairing, with an association co...

Ouabain (from 8 x to 3.26 x lo-' M) caused a decrease in the steady level of K+ion concentration in a dose-dependent manner. This effect was reversed by removing ouabain or by raising the external K+-ion concentration. K+ ion lost by the cells was seen to be replaced by ~ a ' . ~ a + ion accumulated in response to the drug treatment was shown by nuclear magnetic resonance spectroscopy t o be pr...

The density (d), speed of sound (u) and electrolytic conductivity (Λ) for systems containing acetaminophen, ionic liquid {1-octyl-3-methyl imidazolium bromide, [OMIm] Br} and water have been measured at T = 293.15-308.15 K. The measured data have been applied to calculate, standard partial molar volume ( ), Hepler’s constant , apparent molar isentropic compressibility...

Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K(+) channels discriminate K(+) over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of ...