Rubidium transport

Kresca, L., Cotlier, E. Invest. Ophthalmol 13 (4), 310 (1974). Valinomycin-stimulated 86 -rubidium transport and efflux from lens... 

Fukui HN, Epstein DL and Kinoshita JH (1973) Ascorbic acid effects on lens rubidium transport. Exp Eye Res 15 249-253. 

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. 

Sodium azide (see above, p. 189 and Table 36) can be decomposed on heating but it is of low sensitiveness to impact or friction and is not listed as an explosive in transport regulations. According to Gunther et al. [138] rubidium azide is much more sensitive to impact and friction than sodium azide. Gunther believes this to be due to the fact that the radius of the orbit of nitrogen atoms in rubidium azide is much shorter than that in sodium azide. 

Norden, A., and A. Lodding Self-Transport, Electro Convection and Effective Self-Diffusion in Liquid Rubidium Metal. Z. Naturforsch. 22 a, 215 (1967). 

Rubidium uptake via the transport system was measured in depleted cells of Methanospirillum hungatei [272]. At low external Rb concentration the accumulation gradient was significantly larger (2300-fold) than could be explained by the existing membrane potential ( —120 mV). The driving force for Rb" uptake has not been elucidated. 

Lithium also enters the chloride-dependent sodium-potassium cotransport system, inhibited by furosemide (129). Lithium and rubidium in the external medium can be simultaneously transported, and it is thought that they can replace sodium and potassium, respectively... 

Absorption, Transportation, and Distribution Rubidium is very well absorbed from the alimentary tract of animals (Schafer and Forth 1983), with absorption in humans exceeding 60% in both sexes (Table 1.4-5). Rubidium resembles potassium in its pattern of absorption (channels). On the basis of studies with brush border membrane vesicles isolated from the jejuna of rabbits, potassium and rubidium apparently share a transport system. All plant and animal cells are apparently permeable to rubidium ions at rates comparable with those of potassium (Nielsen 1986). It seems that rubidium uses the potassium channels for entering the cell (Clay and Shlesinger 1983, Gallacher et al. 1984). All soft tissues of the body have rubidium concentrations that are high compared with trace elements, with a typical... 

Flora, Essentiality, and Toxicity It appears that rubidium is easily taken up by plants, and may partly substitute for potassium sites, though not in a metabolic role. At high concentrations, therefore, rubidium is rather toxic to plants. The essentiality of rubidium in plant physiology has not yet been fully defined, and in spite of chemical similarities between rubidium and potassium, the uptake and transportation... 

The phytotoxic actions of rubidium mostly affect the transportation of substances in the xylan (Zornoza and Carpona 1996). In order to prevent excessive amounts of rubidium in plant tissues, these authors proposed an increase in the content of potassium, manganese and boron in the soil solution, because of the known antagonism of these elements towards rubidium. Young, growing plants or parts of plants are extremely rubidium-rich and accumulate this element like most other macro, trace and ultratrace elements (Angelow 1994, Wyttenbach et al. 1995). The toxicity of rubidium in plants is low, and essentially unknown. 

Zoenoza P and Carpena O (1996) Influence of potassium rubidium ratios on the xylematic transport of solutes in cucumber plants grown with nitrate plus ammonium. J Plant Nutr 19,3 - 4 469 -480. 

Fig. 1. Comparison of the current noise due to a carrier with that due to a pore. (A) Current fluctuations in the presence of valinomycin with lithium (which is poorly transported) and the rubidium (which is well transported) as the cation. Noise increases at high frequencies because the empty carrier must return after carrying one ion across the membrane. (From [8].) (B) Current fluctuations in the presence of alamethicin. Noise decreases at high frequencies because the channels open and close at a limited rate. (From [7].)...

The solid solution KCl-RbCl differs basically from the solid solution NiO-MgO in two ways. Firstly, the system KCl-RbCl exhibits purely ionic conduction. The transport numbers of electronic charge carriers are negligibly small. Secondly, a finite transport of anions occurs. Because of these facts, the atomic mechanism of the solid state reaction between KCl and RbCl is essentially of a different sort than that between NiO and MgO. Once again, the diffusion profile exhibits an asymmetry (see Fig. 6-1). However, in this case the asymmetry arises not so much because of the variation of the defect concentration with composition, but rather because of the different mobilities of the ions at given concentration. Were the transport number of the chloride ions negligible, then the diffusion potential (which would be set up because of the different diffusion velocities of potassium and rubidium) would ensure that the motion of the two cations is coupled. If, on the contrary, the transference number of the chloride ions is one, then there is no diffusion potential, and the motion of the two cations is decoupled. 

Additional studies (Collins et al., 1987) have, on the whole, confirmed the results mentioned above. According to these experimental investigations (which were performed in the ORNL heating device), tellurium is transported from the fuel pellet to the pellet - cladding gap most probably as the tellurides of cesium and rubidium... 

This little story is mainly about my associations with potassium and rubidium, two elements in the alkali metal series of the periodic table. My Ph.D. thesis at the University of California in Berkeley (1934-1937) was concerned with potassium metabolism in the rat during pregnancy and lactation. In those days nutrition research was the major activity in biochemistry in the United States. In the course of my work I found among other things that the essential element, potassium, could be replaced by rubidium for growth of the rat, although after a time nervous disturbances and other toxic manifestations resulted. Rubidium is, in fact, transported by the same system which tissues use to take up potassium, so that nowadays one often measures potassium uptake activity with the radioactive isotope, Rb. The rubidium isotope happens to have a longer half-life and is more convenient to use than... 

Transport rates for the five alkali metal perchlorates across bulk chloroform membranes by lariat ether amides 17-28 are presented in Table 3. In all cases, transport of li um, rubidium and cesium perchlorates was undetectable. The Na /K" transport selectivities calculated from the single species transport rates are also given in Table 3. 

Table m records the transport yields of eleven main elements (out of thirty-four present in very high-level radioactive liquid wastes, s ch as fission products solutions) fi-om nitric acid feed solutions (3 M in HNO3 and 10 M in the element) to deionized water. Metal cation concentrations were determined by atomic absorption spectrometry of aliquots sampled in the receiving solutions after 24 hours of permeation. Except for rubidium, whose chemical behavior is similar to that of cesium among the other alkali cations, the high selectivity of the tested l,3-cahx[4]-A/5-crowns toward cesium is maintained in the presence of the other 9 elements. 

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