Potassium binding

For the above reasons, the IFCC recommendations on activity coefficients [19] and the measurement of and conventions for reporting sodium and potassium [21] and chlorides [25] by ISEs were developed. At the core of these recommendations is the concept of the adjusted active substance concentration (mmol/L), as well as a traceable way to remove the discrepancy between direct and indirect determinations of these electrolytes in normal sera. Extensive studies of sodium and potassium binding to inorganic ligands and proteins, water binding to proteins, liquid-junction effects and the influence of ionic strength have demonstrated that the bias between sodium and potassium reports obtained from an average ISE-based commercial... 

Bitartrate Stabilization. Potassium and tartaric acid are natural constituents of the grape. Wine content of these constituents depends on a number of variables, not all well understood variety, vintage, and weather pattern degree of skin contact alcohol level bitartrate holding capacity of phenolic compounds and potassium binding capacity of the wine (30, 35). Most wines after fermentation are supersaturated solutions of potassium bitartrate. This compound is less soluble at lower temperatures, and, thus, lower temperatures will cause precipitation of bitartrate crystals. This lowering of temperature and subsequent removal of crystals by filtration is called cold stabilization. 

Potassium-binding benzofuran isophthalate (PBFI) 273 is a comparable fluorescer that incorporates a larger aza crown for complexing potassium ions. The tetraammonium salt of PBFI was used to examine the influence of potassium nutrition on apoplastic in situ by fluorescence imaging of the leaves of Yicia faba (a broad bean) <1997MI1609>. 

The final step of acid secretion is mediated by H /K -ATPase (E.C. 3.6.1.3.), the so-called gastric proton pump. Shull and Lindgrel reported that this enzyme consists of 1,033 amino acids with a combined molecular weight of 114,012 [9]. It shows about 62% homology of the amino acid sequence of NaVK -ATPase. Both enzymes are phosphorylated by ATP and potassium binding causes dephosphorylation and a conformational change in the protein. In contrast to Na /K -ATPase, which is widely distributed in all mammalian cells, HVK -ATPase is predominantly located at the apical membrane of the parietal cell, although a similar enzyme has... 

Cesium, on the other hand, is toxic to plants in anything but trace amounts, whereas indications are that Cs+ ions impair the activity of potassium-binding sites in proteins. Excess cesium can be found in the air and in soils as a by-product of nuclear testing and spent nuclear fuels. Radioactive cesium 137, which results from the fission of uranium 235, decays by emission of a... 

V.M. Marathias and P.H. Bolton, Determinants of DNA quadruplex structural type sequence and potassium binding. Biochemistry, 1999, 38(14), 4355-4364. 

Figure 5.5. A crystal contact at the potassium binding site may influence the dynamics of active-site moieties, particularly Tyr96, and thus indirectly, camphor.

Valinomvcln. To observe the effect of the potassium binding polypeptide valinomycin on lipid bilayer resistance, a phospholipid bilayer membrane was formed under PBS containing 1 mM KCl, and valinomycin was added with stirring to the front chamber. While lipid bilayers are normally highly impermeable to charged species, K" " ions bound to the lipophilic valinomycin diffuse freely through the hydrophobic core of a bilayer (11,12). Valinomycin... 

The two ends of the bipyridyl-bis-crown ether ligand LI 154 can be clipped together by K+. Reaction of [Cu(MeCN)4]+ with two equivalents of LI 154 gave the precursor [Cu(Ll 154)2]+, which with an excess of KPFe gave the novel alkali-metallated catenate [Cu(KL1154)2](PF6)3. The potassium binds the benzo-15-crown-5 units sufficiently tightly for demetallation, with potassium or tetramethy-lammonium cyanide, to be feasible, giving the [2]-catenane (KL 1154)2 as its hexafluorophosphate salt [299] (Scheme 4-32),... 

Additional studies showed that ion pair binding has its own influence on the intercomponent dynamics of rotaxane 20. In polar solvents such as dg-acetone and dg-DMSO, the broad H NMR spectrum revealed dynamic co-conformational behavior between the axle and macrocycle components, most likely pirouetting and shuttling motions. Upon potassium binding, however, only one co-conformation existed in solution, with one of the axle carbonyl groups thought to coordinate to the bound alkali metal, halting the dynamic motion. 

MQAE Ar-Ethoxycarbonylmethyl-6-methoxyquinolinium bromide NADH Reduced nicotinamide dinucleotide PBFI Potassium-binding fluorescence indicator PI-TP Phosphatidylinositol-transfer protein PKC Protein kinase C... 

Zhang, J. Dyachova, E. Ha, T.-K. Knochenmuss, R. Zenobi, R. Gas-phase potassium binding energies of MALDI matrices, an experimental and theoretical study. J. Phys. Chem. A 2003, 107, 6891. 

We now concentrate on ion-pairing in more biologically relevant systems. Simulation work on proteins, oligopeptides, and amino acid residues has shown that sodium and potassium bind differently to biomolecules. 

Van den Brenk, A.L, Fairhe, D.P., Gahan, L.R., Hanson, G.R., and Hambley, TW. (1996) A novel potassium-binding hydrolysis product of ascidiacyclamide a cyclic octapeptide isolated from the ascidian Lissoclinum patella. Inorg. Chem., 35,1095—1100. 

For ameliorating ion exchange, montmorillonites (smectites) are especially useful. With respect to potassium binding, kaolinites bind the least, and, e.g., mica and illite, bind the most K" " (Low, 1975). 

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