Figure 3.4 32
(Left) The finite element model is solved with a constant charge density boundary
condition from D = 40 nm to D = 11 nm as in Chapter 2. Note that these values of D
are for the data shown in Figure 3.2. For other data sets, the D values will be different.
For D=Il nm and less, we vary the lipids surface charge density according to the law
governing the phenomenon being addressed (i.e. whether it is counterion binding or
mobile lipid charge regulation).
Figure 3.5 32
Do is chosen as the point where the AFM data starts deviating significantly from
the electrostatic simulation of Chapter 2. For the above sample, Do = 11 nm. The
AFM data and the electrostatic simulation shown here is the same as in Figure 3.2.
Figure 3.6 33
Schematic of how the tip-induced charge regulation finite element model is
implemented. Here, ψ is the surface potential σ is the surface charge density of the
lipid bilayer and F is the electrostatic force on the tip. The functional form of g
will depend on the form of charge regulation being considered (e.g. charge regulation
due to counterion binding).
Figure 3.7 35
Comparison of the AFM data with the van der Waals computational model.
The AFM data and the electrostatic simulation shown here are the same as in
Figure 3.2.
Figure 3.8 37
Comparison of the AFM data with the van der Waals and stem layer
inclusive computational model. The AFM data and the electrostatic simulation
shown here is the same as in Figure 3.2.
Figure 3.9 38
AFM data for a Si3N4 sample fit with a model that includes charge regulation
due to cation binding via a Langmuir isotherm. (Black, solid curve) - AFM data,
(Red, dashed curve) - constant surface charge electrostatic model,
(Blue, solid curve) - cation binding model.
Figure 3.10 40
Data fit with the Boltzmann relaxation model of mobile lipid charge regulation.
The AFM data and the electrostatic simulation shown here is the same as in Figure 3.2.
Figure3.il 42
(Top) DOPC-neutral at pH 7, (Bottom) DOPS-anionic. A mixture of these lipids
will be in fluid phase at room temperature.
IX