ChemInform Abstract: Coumaryl Crown Ether Based Chemosensors: Selective Detection of Saxitoxin in the Presence of Sodium and Potassium Ions.

ChemInform ◽  
2010 ◽  
Vol 33 (36) ◽  
pp. no-no
Author(s):  
Peter Kele ◽  
Jhony Orbulescu ◽  
Tiffany L. Calhoun ◽  
Robert E. Gawley ◽  
Roger M. Leblanc
Keyword(s):  
Crown Ether ◽  
Potassium Ions ◽  
Selective Detection ◽  
Sodium And Potassium

Coumaryl crown ether based chemosensors: selective detection of saxitoxin in the presence of sodium and potassium ions

2002 ◽  
Vol 43 (25) ◽  
pp. 4413-4416 ◽  
Author(s):  
Péter Kele ◽  
Jhony Orbulescu ◽  
Tiffany L Calhoun ◽  
Robert E Gawley ◽  
Roger M Leblanc
Keyword(s):  
Crown Ether ◽  
Potassium Ions ◽  
Selective Detection ◽  
Sodium And Potassium

A novel crowned porphyrin derived from meso-tetrakis(penta-fluorophenyl)porphyrin

2003 ◽  
Vol 07 (06) ◽  
pp. 399-404 ◽  
Author(s):  
Maria Carolina A. F. Gotardo ◽  
Hérica C. Sacco ◽  
Juvenal C. S. Filho ◽  
Antônio G. Ferreira ◽  
Antônio Claudio Tedesco ◽  
...  
Keyword(s):  
Crown Ether ◽  
Ionic Radius ◽  
Potassium Ions ◽  
Aggregation Process ◽  
Sodium Ions ◽  
Dimerization Constant ◽  
Chloroform Methanol ◽  
Sodium And Potassium ◽  
Spectroscopic Behavior ◽  
Absorption Measurements

The porphyrin 5,10,15,20-tetrakis[4-(1,4,7,10,13-pentaoxacyclopentadecane-2-aminomethyl)2,3,5,6-tetrafluorophenyl]porphyrin,T15C5P, was synthesized by the reaction of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin with the crown ether 2-aminomethyl-(15-crown-5). The crowned porphyrin showed a distinct spectroscopic behavior in the presence of sodium and potassium ions. Dimerization studies based on absorption measurements clearly indicate that T15C5P aggregates in the presence of potassium ions in chloroform/methanol medium (1.0 × 10−5 mol.L −1 or 1.0 × 10−4 mol.L −1), with a dimerization constant ( K D ) of 2.14 × 10−5 and 2.23 × 10−5, respectively. The same formalism applied to the T15C5P in the presence of sodium ions indicated absence of the aggregation process. The ionic radius of Na + is suitable to fit well into the cavity of 15-crown-5 moieties, leading to intramolecular complexes only. Potassium ion is too large to lie in the hole of the crown ether entities and is probably located between two porphyrin molecules, promoting 2:1 aggregated complexes through it's sandwiching, as is observed for phthalocyanines.

Sodium and Potassium Fluxes in the Abdominal Nerve Cord of the Cockroach, Periplaneta Americana L

1961 ◽  
Vol 38 (2) ◽  
pp. 315-322
Author(s):  
J. E. TREHERNE
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nerve Cord ◽  
Periplaneta Americana ◽  
Unit Area ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Nerve Sheath ◽  
The Central Nervous System ◽  
Sodium And Potassium

1. The influx of sodium and potassium ions into the central nervous system of Periplaneta americana has been studied by measuring the increase in radioactivity within the abdominal nerve cord following the injection of 24NA and 42K. into the haemolymph. 2. The calculated influx of sodium ions was approximately 320 mM./l. of nerve cord water/hr. and of potassium ions was 312 mM./l. of nerve cord water/hr. These values are very approximately equivalent to an influx per unit area of nerve cord surface of 13.9 x 10-2 M cm. -2 sec.-1 for sodium and 13.5 x 10-12 M cm. -2 sec.-1 for potassium ions. 3. The relatively rapid influxes of these ions are discussed in relation to the postulated function of the nerve sheath as a diffusion barrier. It is suggested that a dynamic steady state rather than a static impermeability must exist across the sheath surrounding the central nervous system in this insect.

Tetanic hyperpolarization of single medullated nerve fibers in sodium and lithium

1976 ◽  
Vol 231 (4) ◽  
pp. 1033-1038 ◽  
Author(s):  
GM Schoepfle
Keyword(s):  
Steady State ◽  
Interspike Interval ◽  
Nerve Fibers ◽  
Repetitive Stimulation ◽  
Time Dependent ◽  
Potassium Ions ◽  
Current Densities ◽  
Medullated Nerve Fiber ◽  
Sodium And Potassium ◽  
Stimulation Of

Repetitive stimulation of a single medullated nerve fiber of Xenopus yields a succession of postspike voltage-time curves which are nearly coincident until attainment of a voltage that corresponds to that of the maximum attained by the normal postspike undershoot. Initially the interspike potential returns toward a resting level after this brief phase of hyperpolarization. However, as tetanization proceeds, a pattern of hyperpolarization develops with the result that, in the tetanic steady state, there exists a progressive hyperpolarization throughout each interspike interval. Extent of postspike hyperpolarization in terms of a deviation deltaVm from the resting level of membrane potential is approximated by the variation deltaVm = delta[MNa + MK]/[GNa + GK] where MNa and MK are current densities associated with active pumping of sodium and potassium ions and GNa and GK are corresponding time-dependent leak conductances. Tetanic hyperpolarization is reversibly abolished by cyanide and by exposure to lithium Ringer. Eventual reappearance of tetanic hyperpolarization in the presence of lithium Ringer suggests lithium pumping.

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