Measurement of thickness and phase transitions in supported lipid bilayers using quantitative differential interference contrast microscopy
2019
Supported lipid bilayers are one of the most commonly used model membrane systems,
studied with a wide variety of different techniques. One family of microscopy
techniques is quantitative phase imaging, which measures the phase shift of light
passing through a sample. This phase shift is determined by a sample’s thickness
and refractive index, and so the phase information provides meaningful structural
information about the sample. Here, we seek to investigate how a relatively new
form of quantitative phase imaging, quantitative differential interference contrast
(qDIC), can be used to further the study of supported lipid bilayers.
Of particular interest is the thickness of the supported bilayer, since this is
an important parameter which can affect protein-membrane interactions. Given a
known refractive index of the bilayer, the thickness can be extracted from the phase
information. Using literature values for the refractive index of lipids we obtain
thickness values which are in good agreement with those in the literature obtained
using other techniques. We show that qDIC can detect differences in the thicknesses
of supported bilayers of less than one nanometre, revealing that the hydrophilicity
of the glass support causes significant reductions in the thickness of the supported
bilayer in closest contact with it, and that this effect is modulated by the choice of
fluorophore and the degree of coverage at the surface.
Another application of qDIC is in the study of the supported bilayer phase
behaviour. We use qDIC to study the main phase transition during cooling from
the solid-ordered to liquid-disordered phase, and measure thickness changes which
take place during the transition. We also show that qDIC can be used to image
liquid-liquid phase coexistence, with the liquid-ordered phase distinguished from
the liquid-disordered by its greater optical thickness, and we measure the difference
in thickness between these phases.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
0
References
0
Citations
NaN
KQI