Rubidium ion

As an example we may mention an aqueous solution of thallous chloride, T1C1. The radius ascribed to the ion T1+ is a little larger than that of K+, and about equal to that of the rubidium ion Rb+. The electrical conductivity of a dilute solution of T1C1 is not very different from that of KC1 or RbCl, but its variation with the concentration of T1C1 is... 

Rb, as the rubidium ion (Rb+), is a potassium ion mimic and can be used to image viable myocardium. The development of an infusion generator makes this very-short-half-life (76 s) positron-emitting radionuclide useful.20,21... 

The KTP chips are individually immersed in a molten bath of a mixture of RbNOs and Ba(N03)2. Within this bath, the Rb ions diffuse into the unmasked portions of the KTP chip, while the K ions diffuse out of the substrate and into the bath, shown in the illustration in figure 6. In the diffused regions, the rubidium ions increase the index of refraction relative to the undiffused KTP and thus form the optical waveguide. Note that due to the presence of barium, there is an increase in the index of refraction and the ferroelectric domain in the diffused region is reversed and hence the term chemical poling is used for this process. 

Korolev, S., et al. (2001). Using surface-bound rubidium ions for protein phasing. Acta Crystallogr. D 57, 1008-1012. 

A quite new type of antibiotic and one of the few naturally-occurring boron compounds is boromycin (86). Hydrolytic cleavage of D-valine with the M(7) hydroxides gave caesium and rubidium salts of this antibiotic, and crystal structure analysis established the formula as (XIIT). The rubidium ion is irregularly coordinated by eight oxygen atoms. Experiments with models showed that the cation site would be the natural place for the—NH3+ end of the D-valine residue, and the whole structure raises the possibility that transport of larger alkali metals is related to the N-ends of peptides and proteins. 

Similarly, the reaction of metallic rubidium with another metal in ammonia led to the appropriate heterobimetallic amides, as in the reaction of Rb with Ca in supercritical ammonia at 573 K yielding RbCa(NH2)3. " " which consists of one-dimensional infinite face-sharing anion-octahedra occupied by calcium and connected into a three-dimensional network by the rubidium ions (Rb N contacts between 3.11 and 3.92 A). 

Unlike the results calculated for degrees of ionization from the depressions of the f.p., the values of Ostwald s constant computed from the electric conductivities of soln. of rubidium nitrate show marked deviations from constancy and they are thus constant with results with other strong electrolytes—the rubidium ion Rb and the N0V4on are among those with the greatest electro-affinities. The electrical conductivity of lithium nitrate is greater in methyl alcohdl than in water, but in... 

The following table lists some standard electrode potentials (in V) in various solvents. The rubidium ion, which possesses a large radius and shows a low deformability, has a rather low and constant solvation energy in all solvents.1 As a result, the rubidium electrode is taken as a standard reference electrode in all solvents. 

The effect of other electrolytes is also of interest. Addition of divalent cations, e.g., in the form of calcium and magnesium chloride salts, results in precipitation of the anionic vesicles, which is also observed for micelles in water. There is, however, a significant trend within the alkali metal cations, e.g., from Na+ to Rb+. The larger rubidium ion has a promotional effect on the formation of vesicles, and indeed with Cs+, vesicles are already formed on the addition of trace amounts of salt. The relevant data are shown in Fig. 19.8. 

The ability of experimental agents to pass across the blood-brain barrier, log P, was determined according to the method of Hansch (2), inhibition constants, Kiy calculated using the method of Chang (3), and dopamine and rubidium ion release obtained calculated according to the method of Dull (4). Inhibition constants, dopamine and rubidium ion release testing results are provided in Table 2. 

Table 2 Test results of selected experimental agents indicating the ability of these materials to pass across the blood-brain barrier and impact on dopamine and rubidium ion release...

Entry Capacity to Pass Blood-Brain Barrier Dopamine Release Rubidium Ion Release ... 

Spruce, A. E., Standen, N. B., and Stanfield, P. R. (1989). Rubidium ions and the gating of delayed rectifier potassium channels of frog skeletal-muscle. J. Physiol. (London) 411, 597-610. 

Other compounds of the selenophene series such as potassium tetra(a-selenienyl)borate (23), obtained by interaction of a-selenienyl-magnesium iodide with potassium tetrafluoroborate, precipitate rubidium ions and, more completely, cesium and quaternary ammonium ions from water solutions and can be used as analytical reactants for those ions.81... 

The ammonium ion NH4+ has a tetrahedral structure and is slightly acidic (p/fa = 9.25). If no strong hydrogen bonds are present, like in NH4F, the properties of ammonium salts, for example, the solubility and the structure, are similar to the corresponding potassium and rubidium salts. The reasons are similar ionic radii of the aimnonium (143 pm), potassium (137 pm), and rubidium ions (148 pm). The oxonium salts H30+X , which have lower melting points, are also similar to the ammonium salts. The similar properties of element-hydrogen compounds have been rationalized by the hydride displacement law shown in Table 12. 

Finally, consider the crystal structure of the rubidium salt of 5,5-dimethyl-l,3-cyclohexanedione-2-sulfonic acid. This species exists as the ketoenol wherein the rubidium ion is surrounded by seven oxygen atoms in pentagonal bipyramidal coordination. We know of no ketoenolate (and hence dianionic) salt of this sulfo-dione with any cation. Perhaps some more highly charged cation would allow for this—note the significantly enhanced stability of rare earth complexes of 2-acetyl-5,5-dimethyl-l,3-cyclohexanedione over the parent diketone . 

The majority of PET research involves (ti/2 = 110 min) and (ti/2 = 20 min). With considerable effort, these isotopes can be incorporated into organic molecules such as hormones or drugs. The benefit is that the tracer does not alter the pharmacokinetics of the molecule being labeled in the same way that the conjugation of a metal complex wiU. Nevertheless, applications of metallic PET tracers exist. Rubidium-82 (ti/2 = 1.27 min) has a very short half-hfe but is easily obtained from a strontium-82 generator. The rubidium ion is a potassium analog, and Rb+ is used in myocardial perfusion studies. 

The stmcture of the sodium-potassium pump was solved in 2007 to a resolution of 3.5 A (Fig. lb), in complex with two bound rubidium ions (13). Structures were also solved for other members of the P-type ATPase family (18, 19) around the same time revealing the structural similarity between family members as well as the conformational changes that occur during function. 

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