The name is absent

As can be seen in Figure 3.9, the counterion binding model produces a better fit to the
experimental data for the silicon nitride when compared with the fit produced by the
counterion binding model applied to the lipid case in Figure 3.8. This is not unexpected
since the analysis in Chapter 2 produced a fit to the GCS model in spite of that analysis
not explicitly accounting for the stem layers presence, suggesting that the stem layer has
little affect in the case of these particular experiments. This could be due to the large
differences in the association constants between the lipid and the silicon nitride surfaces.

3.3.3 Mobile lipid charge regulation

Another charge regulation mechanism is that due to the lateral mobility of the individual
lipids. Unlike most inorganic surfaces, the individual lipids and hence the charges in the
bilayer are highly mobile. This mobility has been found to be significant for cases such as
DNA binding to cationic lipids. Attempts have been made to include this mobility into
the GCS model of lipid electrostatics [26, 71, 85, 86]. Here, we will show that the
negatively charged silicon nitride AFM tip induces mobile lipid charge regulation in a
manner akin to that which is thought to occur when a charged macro-molecule such as
DNA or protein interacts with a charged lipid bilayer. We modeled the mobile lipid
charge regulation using a Boltzmann relaxation formula (Equation 3.6).

σ,,₊ι = σ_{n e}χp[-4-(<∕_n -^J]     (3.6)

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