Cation concentrations, high-alkali

Activation studies were conducted at pH 7.5 at 30°C in 20 mL of 0.5% high methoxyl citrus pectin (Citrus Colloids, Hereford, U.K.). Final cation concentration in PE extracts used for activation studies was less than 2 mM as measured by potentiometry. Controls were conducted to correct for non-enzymic alkali consumption, with no polyamine/no PE and polyamine added/no PE. PE activity was normalized as a percentage of activity with no cation addition. 

In the area of cation analysis, the extremely selective method of postcolumn derivatization of alkaline-earth metals with Arsenazo I [o-(l,8-dihydroxy-3,6-disulfo-2-naphthylazo)-benzenearsonic acid] is particularly suited for the determination of these elements in the presence of high concentrations of alkali metals [51]. 

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. 

In a closer examination of the formation of oligomers, Ferris and co-workers found that the reaction is favoured by relatively high salt concentrations (e.g. 1M NaCl), while the presence of divalent cations is not necessary. The formation of RNA oligomers was found to be temperature sensitive the yields decrease when the temperature is raised from 4°C to 50° C. The addition of meteorite material (from 3 meteorites) does not catalyse the polymerisation reaction only galena (PbS) can do this. The authors thus assume that RNA oligomers could have been formed on the young Earth in solutions of alkali metal salts in the presence of montmorillonite and a pH value of 7-9 (Miyakawa et al., 2006). Ferris (2006) has provided a short but up-to-date survey of montmorillonite-catalysed RNA oligomerisation. 

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