Equilibrium exchange experiments

Equilibrium exchange experiments. In this situation, the unidirectional flux of isotopically labelled glucose across the membrane is measured as a function of the glucose concentration, which is kept equal on both sides of the membrane. Because the unidirectional influx and efflux at any particular concentration are necessarily equal, the equilibrium-exchange (ee) flux is characterized by a single V ax value, and a single Km value. A . 

In Eqn, 39 we have had to introduce new symbols over those in Eqn, 30 to account for the presence of two substrates S and P. There is now an intrinsic dissociation constant R for each substrate. Resistances terms R,2 and Rji, describing the zero trans situation, are defined for each substrate and also for the equilibrium exchange experiment R involving just a single substrate S or P. There are also defined cross-resistances R and for the situation where S is present only at one side of the membrane and P only at the other. These cross-resistances can be derived from the resistances obtainable by single substrate experiments (see Table 6 where these... 

In the isomerization reactions of cis- and trans-[Co en2 Cy+ in dimethylformamide and dimethylacetamide, the equilibrium isomer ratios depend upon the concentration of chloride. This has been interpreted in terms of ion association, and the equilibrium constants have been computed (31). The dependence of the isomerization rate upon the chloride concentration was interpreted in terms of the different reactivities of the free ion and the ion pair. Preliminary chloride exchange experi-... 

Keller (1964) reported that Ca is the dominant exchangeable cation on mont-morillonite in equilibrium with river water. In sea water Ca and also Na (Carroll and Starkey, 1960) tend to be replaced by Mg which becomes the dominant exchangeable cation. In many ancient clays, Na is the most abundant exchangeable cation therefore, this abundance of Na appears to be inconsistent with the above data. Recently Hanshaw (1964) conducted exchange experiments with compacted clays and found that the order of cation selectivity is dependent upon whether a clay is dispersed or compacted. He found that compacted montmorillonite preferred cations in the following order K+> Na+>H+>Ca2 +>Mg2 +. It may be that in dispersed marine mont-morillonites Mg is the predominant exchange cation, but as the mud is compacted by burial, Na replaces a portion of the Mg. This has been confirmed by Weaver and Beck (1971a). 

This section is not complete without mentioning the hydrogen-deuterium exchange experiment by Doehring and Hoffmann (12), which indicated an enhanced acidity of the hydrogens in a tetramethylstibonium salt. In the corresponding equilibrium, stibonium ylides play the role of strong bases ... 

Under experimental conditions in which the so-called EX2 regime is obeyed, the equilibrium constant for the following reaction is measured by hydrogen exchange experiments (see for example Bai et al., 1995) ... 

A variety of cation-exchange materials was tested in the laboratory using equilibrium-type experiments and small columns to determine the capability of these materials for removing cesium-137 and strontium-90 from the fuel storage basin water. 

How does the flow of protons drive the synthesis of ATP Isotopic-exchange experiments unexpectedly revealed that enzyme-bound ATP forms readily in the absence of a proton-motive force. When ADP and Pj were added to ATP synthase in H2 0, became incorporated into P, through the synthesis of ATP and its subsequent hydrolysis (Figure 18.27). The rate of incorporation of into P showed that about equal amounts of bound ATP and ADP are in equilibrium at the catalytic site, even in the absence of a proton gradient. However, ATP does not leave the catalytic site unless... 

The position of equilibrium, as would be expected, lies strongly towards the pyranose form ([/]/[p] = 0.057), " the furanose form being disfavoured by the cis interactions of hydroxyalkyl chain on C4, OH C2 and pyrophosphate on Cl. A positional isotope exchange experiment, monitored by the isotope effect... 

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