Mono-valent cation

Williamson, J. R., Raghuraman, M. K., Cecil, T. R., Mono valent cation induced structure of telomeric DNA - the G-quartet model. Ceil 1989, 59, 871-880. 

For convenience and simplicity, some assumptions are made. The solid electrolyte (E) is assumed to be an exclusive ionic conductor of mono-valent cation (A+). Two porous electroiuc conducting electrodes (C) and (W) are attached to the solid electrolyte (E) from the source and sink side, respectively. An external electric circuit with a dc source is coimected to the solid electrochemical cell via both electrodes. 

The cooperativity of cation-it and n-n interactions has also been demonstrated taking a series of mono-valent cationic species such as, Li+, Na" ", K+, NH4+,PH4+, OH3+ and SH3+ where systematic quantum chemical studies were performed to estimate the effects of cation-n and n-n interaction on each other in cation-Tt-7T systems (Fig. 18.6b) [123]. In this study all possible orientations of onium ions to form cation-jt complexes have been explored and the most stable conformation has been taken further to evaluate its effect on k-k interaction. The results from this study indicate a notable increase of 2-5 kcal/mol in the n-n interaction energy in the presence of the cations. The cation-jt interaction energy is also enhanced in the presence of n-n interaction albeit to a smaller extent. The wide varieties of cations (which include both metal and inorganic ions) employed here underline the generality of the results. 

TX-100. Mono-valent cations depressed the cloud point more than di- or tri-valent cations. On a weight percent basis, the cloud point was nearly the same in the presence of calcium or aluminum chloride. Sodium ion caused the steepest drop in the cloud point among the three mono-valent cations examined. The relationship between the cloud point and salt concentration was linear for the five salts. It is interesting to note that the effect of salt type on the cloud point was similar to that observed with nonionic surfactants at neutral pH conditions [95]. 

Eisenberg M, Gresalfi T, Riccio T, McLaughlin S (1979) Adsorption of mono-valent cations to bilayer membranes containing negative phospholipids. Biochemistry 18 5213-5223... 

In summary, electromembrane processes, especially when used as part of hybrid treatment schemes, can provide an efficient removal of toxic metal ions from water. When a target metal exists in water as a mono-valent species, the use of mono-valent (cation- and/or anion-permselective membranes) is especially attractive. Situations, in which ED appears to be less applicable are for waters of very low salinity (conductivity of less than 0.5 mS cm ), for which EDI or DD can be better choices, and, in cases when besides ions, removal of low molecular mass non-charged compounds from the water is desired. In the latter case, pressure-driven membrane processes such as RO or NF may be preferable. 

Surfactant molecules can be considered as building blocks for certain forms of geometry in colloidal chemistry. Various forms of association molecules can be obtained as the concentration of surfactant in water is increased and/or physicochemical conditions are changed (e.g. CMC, Craft-point, etc.). Figure 2 schematically shows the most likely structural configurations and assemblages of surfactants association in an aqueous system (26). Upon addition of oil and a short-chain alcohol, for example, one can convert the oil-in-water micelles into water-in-oil microemulsions. It is therefore possible to induce a transition from one structure to another by changing the physicochemical conditions such as temperature, pH and addition of mono or di-valent cations to the surfactant solution. It should be also noted that the sur-... 

Table 7.6 cites a few sample values of y as a function of concentration. Note how multi-valent anions and cations cause y to vary more greatly than do mono-valent ions. The implications are vast if an indium electrode were to be immersed in a solution of In2(S04)3 of concentration 0.1 mol dm-3, for example, then a value of y = 0.035 means that the activity (the perceived concentration) would be about 30 times smaller ... 

Competition between mono- and di-valent cations has an important role in biological processes. Furthermore, the lipophilicity of a ligand and its complex plays an important role in deciding whether a species is soluble in organic media of low polarity. This has important consequences in areas such as phase-transfer catalysis, the use of crown ethers as anion activators, and in cation transport through lipid membranes. Many crown ethers have now been synthesized with incorporation of long alkyl side chains and enhanced lipophilicity and used successfully in the above areas. 

ID metals based on the [Pt(C204)2] anions are all of the cation-deficient type. Unlike the tcps they are found with either mono- or di-valent cations. A comprehensive review of the literature up to 1979 has been published and is a source of earlier references.63 Details of well-characterized compounds are given in Table 2. 

As the electrolytes, alkali metal sulfates(M=Li, Na, and K)(l-ll), 3-Alumina(12), and NASIC0N(13, 14) have been examined. Alkali metal sulfates are cation conductors at elevated temperature(>700 C). However, they have several disadvantages. One is the phase transformation of the sulfates(15-18). By this transformation, cracks occur in the electrolyte body and result in the permeation of the ambient gases. The other disadvantage is their low electrical conductivity. Mono, di, or tri-valent cations(19-24) have been doped so as to enhance their conductivity. Furthermore, they become ductile at a tem-... 

Here, R is the average resistance and A the area of a cell pair, Cfd and C<1 are the salt concentrations of the diluate at the inlet and outlet of the cell, Cfc and C are the salt concentrations of the concentrate cell at the inlet and outlet, F1" and rcm are the area resistances of the anion- and cation-exchange membranes. The membrane area required for a certain plant capacity as a function of the feed and product concentration of a single mono-valent salt is obtained by combination of Equations 5.22-5.26 and rearranging ... 

One of the best studied enzymes involving phosphoryl group transfer is pyruvate kinase, which catalyzes the transfer of a phosphoryl group from phosphoenolpyruvate to ADP. Pyruvate kinase requires a mono- and a di-valent cation for activation, and will be discussed in more detail in Section 62.1.3. It is well known that is the most effective monovalent activator. Figure 7 shows how the activity of the enzyme varies with the ionic radius of the monovalent cation. It is clear that NH4 (1.43 A), Rb (1.47 A) and Tl (1.47 A) are able to replace (1.33 A), while (0.68 A), Na" (0.97 A) and Cs" (1.67 A) are ineffective. Studies in which has been replaced by Tl have been most informative. Tl has an affinity some 50 times greater than for the potassium site, and so its binding could be detected more readily by equilibrium dialysis techniques. This showed that four TT cations were bound per molecule of enzyme, which has four subunits. 

It is easily shown that for this pupose the absolute values of Q for tri, quadri and even hexa valent cations need not be known, but that the gross reversal of charge concentrations obtained at only one definite sol concentration may serve as well as in the case of mono and diavalent cations, as a basis for discussion. 

If it were possible to use in Table 2 (p. 270) only ideal 6, 5, 4, and 3 valent mono-atomic cations (La and Ce being the only ideal cases of 3 valent cations, A1 and Th already behaving as large complex ions, see p. 291, and the still higher valent cations not existing at all) then the sulphate colloids would behave totally otherwise than the phosphate and carboxyl colloids (horizontal rows consisting presumably only in minus signs). 

A quality feature of all cation exchangers suitable for simultaneous analysis of mono- and di-valent cations is the maximal concentration ratio between sodium and ammonium that allows a separation of both components. Under isocratic conditions with 10 mmol/L methanesulfonic acid at 2 mL/min, the lonPac CS12 separates ammonium in the presence of a 250-fold to 500-fold amount of sodium. Higher concentration differences are only applicable when using a step gradient or a continuous concentration gradient (see Section 4.7). 

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