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Na+ Solution (na+ + solution)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Response properties of isolated mouse olfactory receptor cells

THE JOURNAL OF PHYSIOLOGY, Issue 1 2001
Johannes Reisert
1Response properties of isolated mouse olfactory receptor cells were investigated using the suction pipette technique. Cells were exposed to the odour cineole or to solutions of modified ionic content by rapidly changing the solution superfusing the cilia. All experiments were performed at 37°C. 2Mouse olfactory receptor cells displayed a steep dependence of action potential frequency on stimulus concentration, a 3-fold increase in stimulus concentration often saturating the firing frequency at 200-300 Hz. The receptor current increased more gradually with increasing cineole concentration and did not saturate within the 100-fold range of cineole concentrations applied. 3When stimulated for 30 s with a low odour concentration, cells responded with sporadic spike firing. Higher concentrations led to the generation of a large receptor current at the onset of stimulation which returned to baseline levels within a few seconds, accompanied during its rising phase by a short burst of action potentials. Thereafter an oscillating response pattern was observed during the remainder of the stimulus, consisting of repetitive increases in receptor current of around 1 s duration accompanied by short bursts of action potentials. 4Olfactory adaptation was studied by comparing the responses to two closely spaced odour stimuli. The response to the second odour stimulus recovered to 80% of its original magnitude when the cell was superfused with Ringer solution during the 5 s interval between odour exposures. In contrast, exposure to a choline-substituted low Na+ solution between odour stimuli had two effects. First, the receptor current response to the first odour stimulus did not terminate as quickly as in the presence of Na+, suggesting the presence of a Na+ -Ca2+ exchanger. Second, the response to the second stimulus only recovered to 55% of its original magnitude, demonstrating the involvement of Na+ -Ca2+ exchange in the recovery of sensitivity in mouse olfactory receptor cells following stimulation. [source]

Structure of a d(TGGGGT) quadruplex crystallized in the presence of Li+ ions

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2007
Christophe Creze
A parallel 5,-d(TGGGGT)-3, quadruplex was formed in Na+ solution and crystallized using lithium sulfate as the main precipitating agent. The X-ray structure was determined to 1.5,Å resolution in space group P21 by molecular replacement. The asymmetric unit consists of a characteristic motif of two quadruplexes stacked at their 5, ends. All nucleotides are clearly defined in the density and could be positioned. A single bound Li+ ion is observed at the surface of the column formed by the two joined molecules. Thus, this small alkali metal ion appears to be unsuitable as a replacement for the Na+ ion in the central channel of G-quartets, unlike K+ or Tl+ ions. A well conserved constellation of water molecules is observed in the grooves of the dimeric structure. [source]

Quadruplexes of human telomere DNA analogs designed to contain G:A:G:A, G:G:A:A, and A:A:A:A tetrads,

BIOPOLYMERS, Issue 10 2010
Janos Sagi
Abstract Replacement of two to four guanines by adenines in the human telomere DNA repeat dG3(TTAG3)3 did not hinder the formation of quadruplexes if the substitutions took place in the terminal tetrad bridged by the diagonal loop of the intramolecular antiparallel three-tetrad scaffold, as proved by CD and PAGE in both Na+ and K+ solutions. Thermodynamic data showed that, in Na+ solution, the dG3(TTAG3)3 quadruplex was destabilized, the least by the two G:A:G:A tetrads, the most by the G:G:A:A tetrad in which the adenosines replaced syn -guanosines. In physiological K+ solution, the highest destabilization was caused by the 4A tetrad. In K+, only the unmodified dG3(TTAG3)3 quadruplex rearranged into a K+ -dependent quadruplex form, none of the multiple adenine-modified structures did so. This may imply biological consequences for nonrepaired A-for-G mutations. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 880,886, 2010. [source]

Guanine quadruplex formation by RNA/DNA hybrid analogs of Oxytricha telomere G4T4G4 fragment

BIOPOLYMERS, Issue 10 2008
Jitka Vondru
Abstract Using circular dichroism spectroscopy, gel electrophoresis, and ultraviolet absorption spectroscopy, we have studied quadruplex folding of RNA/DNA analogs of the Oxytricha telomere fragment, G4T4G4, which forms the well-known basket-type, antiparallel quadruplex. We have substituted riboguanines (g) for deoxyriboguanines (G) in the positions G1, G9, G4, and G12; these positions form the terminal tetrads of the G4T4G4 quadruplex and adopt syn, syn, anti, and anti glycosidic geometries, respectively. We show that substitution of a single sugar was able to change the quadruplex topology. With the exception of G4T4G3g, which adopted an antiparallel structure, all the RNA/DNA hybrid analogs formed parallel, bimolecular quadruplexes in concentrated solution at low salt. In dilute solutions (,0.1 mM nucleoside), the RNA/DNA hybrids substituted at positions 4 or 12 adopted antiparallel quadruplexes, which were especially stable in Na+ solutions. The hybrids substituted at positions 1 and 9 preferably formed parallel quadruplexes, which were more stable than the nonmodified G4T4G4 quadruplex in K+ solutions. Substitutions near the 3,end of the molecule affected folding more than substitutions near the 5,end. The ability to control quadruplex folding will allow further studies of biophysical and biological properties of the various folding topologies. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 797,806, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]