Chemistry Reference
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k
1
Q
k
inc
θ
1
θ
1
θ
2
k
2
Substrate
Figure 4.16
Simplifi ed geometry of neutron refl ection from a supported lipid bilayer
system.
and recent studies have shown how LLC dispersion-supported lipid bilayer
interactions can be characterized using this technique (H.-H. Shen et al., 2011;
Vandoolaeghe et al., 2008, 2009a).
The basic theory of NR with respect to a lipid bilayer deposited on smooth
planar interface is illustrated in Figure 4.16. When a beam of neutrons is inci-
dent on a planar interface, it is both refl ected and refracted. Specular refl ection
is defi ned as refl ection with the angle of refl ection equal to the angle of inci-
dence (
θ
1
). At all other angles the signal is referred to as off-specular
refl ection.
The relative proportion of the refl ected and refracted waves depends on
the nature of the surface, in particular on the relative neutron interaction
potentials of the interfaces. The signal in neutron refl ection is determined by
the perpendicular variations in this potential through the surface, based on the
scattering length densities of the constituent materials, effectively their neutron
refractive indices.
Experimentally, the intensity of refl ected neutrons as a function of the total
momentum transfer perpendicular to the interface (
Q
) is determined in the
experiment, given by
4
πθ
λ
sin
Q
=
Detailed modeling of the measured refl ectivity profi le is used to extract
layer arrangement thicknesses, roughness, and scattering length densities for
different components within the layered system.
Vandoolaeghe et al. (2008, 2009b,c) have published several papers on cubo-
some interactions with a silica surface with and without supported bilayers
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