Data from: Examining the thermotropic properties of large, circularized nanodiscs

Nanodiscs, soluble membrane mimetics composed of an amphipathic membrane
scaffold protein encircling a lipid bilayer, are widely used in
biophysical and structural studies of membrane proteins. Because many
membrane proteins are responsive to their membrane environment, through
specific protein–lipid interactions and bulk membrane shape and structure,
it is important to understand the properties of lipid bilayers contained
within nanodiscs in order to interpret studies using this technology.
Nanodiscs are known to alter lipid properties, such as membrane thickness
and melting temperature, and interactions with the nanodisc rim have been
hypothesized to produce local perturbations in lipid structure and
dynamics. Larger nanodiscs should compensate for this effect with a larger
unperturbed area. To test this hypothesis, we examined the lipid bilayer
properties of several lipids (DMPC, DPPC, POPC, DSPC) and soy polar lipid
in circularized nanodiscs of 11 nm to 50 nm diameter using the
environmentally-sensitive fluorophore, Laurdan. In nanodiscs containing a
single lipid type, as nanodisc size increased, lipid packing, melting
temperature, and cooperativity better approximated the properties of that
lipid in large unilamellar vesicles (LUVs). In spNW50 (50 nm nanodisc),
the lipid packing and melting temperature were indistinguishable from
LUVs. However, nanodiscs containing soy polar lipids did not follow this
trend, suggesting that complex lipid mixtures may produce preferential
incorporation of lipids into the nanodisc or nonhomogeneous distribution
of lipids within the nanodisc.