Cations selectivity

Pyrolysis. Heating in the absence of oxygen releases moisture at low temperatures, carbon dioxide at temperatures >200° C, and a variety of gaseous products at very high temperatures. Acid washing of the raw coal is used to remove extractable cations, followed by treatment with selected cations. Yields of CO2, CO, CH, H2, and H2O depend on the amounts of inorganic species in the coal (42). 

Polyester Fiber Blends. Disperse dyeable and cationic dyeable polyester fibers are frequentiy combiaed ia apparel fabrics for styling purposes. Whereas the disperse dyes dye both fibers, but ia differeat depths, selected cationic dyes reserve the disperse dyeable fiber completely, resulting ia color/white effects. 

Table 10.6 Summarised procedures for EDTA titrations of some selected cations...

IP3 Receptor Ryanodine Receptor Non-selective Cations Channels TRP Channels... 

Cyclic Adenosine Monophosphate Table Appendix Membrane Transport Proteins Cyclic Guanosine Monophosphate Non-Selective Cation Channels... 

Nicotinic Receptors Voltage-dependent Na+ Channels Non-selective Cation Channels... 

Ionotropic Glutamate Receptors Nicotinic Receptors Non-selective Cation Channels K+ Channels... 

Non-selective cation channels are macromolecular pores in the cell membrane that form an aqueous pathway. These enable cations such as Na+, K+ or Ca++ to flow rapidly, as determined by their electrochemical driving force, at roughly equal rates (>107 cations per channel pore and per second). 

The open channel has in most cases a selective permeability, allowing a restricted class of ions to flow,for example Na+, K+, Ca++ or Cl- and, accordingly, these channels are called Na+-channels, K+-channels, Ca -channels and Cr-channels. In contrast, cation-permeable channels with little selectivity reject all anions but discriminate little among small cations. Little is known about the structures and functions of these non-selective cation channels [1], and so far only one of them, the nicotinic acetylcholine receptor (nAChR, see Nicotinic Receptors), has been characterized in depth [2, 3]. The nAChR is a ligand-gated channel (see below) that does not select well among cations the channel is even permeable to choline, glycine ethylester and tris buffer cations. A number of other plasma... 

Non-selective Cation Channels. Figure 1 The nicotinic acetylcholine receptor (nAChR) is localized within the cell membrane above the cell membrane is the synaptic cleft, below the cytoplasm. Drawing of the closed (left) and open (right) nAChR showing acetylcholine (ACh) binding and cation movement. Dimensions of the receptor were taken from references [2, 3]. 

Clay films cast from a pure aqueous colloid appear to form a regular array of microplatelets, thin films of which show selective cation exchange, e.g. segregation of Ru(bipy)i from Na" and methylviologen dication and even partial separation of the enantiomers of Co bipy)3 Thicker films (approx. 3 pm) can be supported by the addition of polyvinyl alcohol additive also aids swelling of the... 

As a further approach for novel electrolytes appropriate for selective cation transport, we have prepared poly(organoboron halide)-imidazole complexes.35 Even though boron-amine complexes are widely known materials reported by the early works of H. C. Brown et al.,52-54 they had not been investigated as solvents or electrolytes to the best of our knowledge. 

Eisch s work promoted investigation into the preparation of cationic metallocene complexes of Group 4 metals. Several preparative routes to cationic group 4 metallocene complexes are illustrated in Scheme II. Catalytic activities of some selected cationic metallocene complexes for the polymerization of a-olefins are summarized in Tables 5 and 6. The catalyst systems based on these cationic complexes are just as active as M AO-activated metallocene catalysts for the polymerization of a-olefins. 

Table 5. Catalytic activity of selected cationic metallocene complexes of Group 4 metals for the polymerization of ethylene... 

Hofmann, T. et al. TRPM5 is a voltage-modulated and Ca2+-activated monovalent selective cation channel. Curr. Biol. 13 1153-1158, 2003. 

Arnaudeau S, Lepretre N, Mironneau J 1994b Chloride and monovalent ion-selective cation currents activated by oxytocin in pregnant rat myometrial cells. Am J Obstet Gynecol 171 491-501... 

Helliwell RM, Large WA 1997 Alphal-adrenoceptor activation of a non-selective cation current in rabbit portal vein by 1,2-diacyl-sn-glycerol. J Physiol 499 417-428 Hofmann F, Lacinova L, Klugbauer N 1999 Voltage-dependent calcium channels from structure to function. Rev Physiol Biochem Pharmacol 139 33—87 Hofmann T, Schaefer M, Schultz G, Gundermann T 2000 Transient receptor potential channels as molecular substrates of receptor-mediated cation entry. J Mol Med 78 14—25 Inoue R, Okada T, Onoue H et al 2001 The transient receptor potential protein homologue TRP6 is the essential component of vascular aj-adrenoceptor-activated Ca2+-permeable cation channel. Circ Res 88 325—332... 

Parker KE 1998 Modulation of ATP-gated non-selective cation channel (P2X1 receptor) activation and desensitization by the actin cytoskeleton. J Physiol 510 19—25... 

The theoretical approach we have developed for determining the preferred conformation of uncharged molecules is also applicable to those cases where the molecule bears a net positive or negative charge. In this section we will examine the importance of nonbonded interactions in torsional isomerism of selected cations and anions. 

Several different types of serotonin receptor (for example, S-HTi / 5-HT2A/ 5-HT2C/ 5-HTib/id) have been associated with the motor side effects of the SSRIs which may arise should these drugs be administered in conjunction with a monoamine oxidase inhibitor. The 5-HT3 receptor is an example of a non-selective cation charmel receptor which is permeable to both sodium and potassium ions and, because both calcium and magnesium ions can modulate its activity, the 5-HT3 receptor resembles the glutamate-NMDA receptor. Antagonists of the 5-HT3 receptor, such as ondansetron, are effective antiemetics and are particularly useful when... 

Serotonin receptors. Based on biochemical and pharmacological criteria seven receptor classes can be distinguished. Of major pharmacotherapeutic importance are those designated 5-HTi, 5-HT2,5-HT4, and 5-HT7, all of which are G-protein-coupled, whereas the 5-HT3 subtype represents a ligand-gated non-selective cation channel. 

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