Stable ions 1064 INDEX

Sufficient stability of the hydrocarbon ions, as the salt or in the solution, is an obvious prerequisite for these procedures, and, in practice, selecting or designing the stable ions and choosing a proper solvent are tasks of primary importance. As an ordinary stability index for the ions, thermodynamic scales referred to the water molecule, i.e. p CR+ and pKa values, are chosen for the carbocation and carbanion, respectively. 

Ferrichrome iron transport in the enteric bacteria affords an experimentally feasible model for mechanistic studies. The ligand is rugged and can be labeled to high specific activity by microwave discharge activation of tritium gas. The labile ferric ion can be replaced with chromium to yield the kinetically stable isostructural chromic complex, chromichrome (61). Assuming this analog has the transport properties of the iron complex, its 3H counts would be an index of the behavior of... 

Cut points specify the beginning and end of the collection of a fraction. Cut points can be based on time, although in practice time is not the most stable parameter, due to possible fluctuations in the flow rate. They can be based on threshold values of the UV-detector signal or on volume of eluent through a mass flowmeter. Cut point locations can also be a combination of a characteristic feature on the chromatogram and volume. Cut point locations for valve switching may also be based on the response of less traditional detection instrumentation such as the on- line measurement of density, conductivity, temperature, spedflc ion detection, near infrared, or refractive index. 

In addition to the above mentioned research, the authors of [84] have also performed calculations for Li+, Na, K+, Be, Mg + and Ca + complexes of G-tetrads. Calculations showed that for an isolated quartet, the metal ion with the smallest ionic radius in their respective groups (lA and IIA) form more stable complexes. Other properties such as the HOMO-LUMO gap and polarizability have also been analyzed. The variation in the polarizability has been studied with respect to the movement of cations along the central cavity of the quartet to show that such movement leads to a large anisotropy of polarization and hence the refractive index (q) thereby creating optical birefringence which have potential apphcations in biomo-lecular imaging. 

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