Relative Fractional Exchange Comparability Plot

The following steps outline the approach taken in developing a relative fractional exchange 

The amount of deuterium that each peptide (i) exchanges as a function of time (t) is experimental determined from its change in mass (AAf.). This change in mass is used to calculate the corresponding y-coordinate values for each peptide used on both plots and is equal to the following AM., = M., —M. where corresponds to the mass of the nondeuterated 

values for the reference sample, (F., ) p can now be plotted (corresponding to SJ F.) in Houde et al. [22]). However, in order to plot the F values for the experimental sample, (F, ) (corresponding to (F,) in Houde et al. [22]), all (F i) values are multiplied by -1 in order to flip their values in the negative direction. For each peptide, the HX-MS data, as a function of time, are displayed as a series of vertical data points, which in the case of the reference sample run in the positive direction, while in the case of the experimental sample run in the negative direction. 

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Finally, the same time point data for each peptide for the reference sample are then connected with a specific colored line. This procedure is carried out for each time point, using a different color. This process is then repeated for the experimental sample using the same color scheme. The resulting plot is a relative fractional exchange comparability plot (which looks like a butterfly or mirror plot, as shown in Figure 13.5a), which allows for quick visual (qualitative) comparative assessments of all the data that is acquired in an HX-MS experiment. 

The associated dififa-ence plot that goes with each relative fractional exchange comparability plot is gena-ated by subtracting the change in mass data for peptide i) at time point (t) for the experimental sample from the change in mass data for the same peptide i) obtained at the same time point... 

Different types of cation exchange behaviour observed in zeolites. Isotherms represent equilibrium plots of the fractional concentration of extra-framework cations in the zeolite compared with the fractional concentration of cations in the solution in contact with the zeolite (see text for discussion). In case (a) cation M is taken in preference over a competing cation type for the entire relative concentration range, whereas the preference is inverted in case (c). The situation where there is no preference is represented by (b). Type (d) isotherms occur when only a certain fraction of the cations may be exchanged (experimentally, kinetic barriers may also result in this behaviour). Finally, isotherms of type (e) indicate that the selectivity changes as the relative concentration of the cations in solution changes. 

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