posted on 2020-04-01, 12:05authored byMinh D. Phan, Olena I. Korotych, Nathan G. Brady, Madeline M. Davis, Sushil K. Satija, John F. Ankner, Barry D. Bruce
Styrene-maleic
acid (SMA) copolymers have recently gained attention for their ability
to facilitate the detergent-free solubilization of membrane protein
complexes and their native boundary lipids into polymer-encapsulated,
nanosized lipid particles, referred to as SMALPs. However, the interfacial
interactions between SMA and lipids, which dictate the mechanism,
efficiency, and selectivity of lipid and membrane protein extraction,
are barely understood. Our recent finding has shown that SMA 1440,
a chemical derivative of the SMA family with a functionalized butoxyethanol
group, was most active in galactolipid-rich membranes, as opposed
to phospholipid membranes. In the present work, we have performed
X-ray reflectometry (XRR) and neutron reflectometry (NR) on the lipid
monolayers at the liquid–air interface followed by the SMA
copolymer adsorption. XRR and Langmuir Π–A isotherms captured the fluidifying effect of galactolipids, which
allowed SMA copolymers to infiltrate easily into the lipid membranes.
NR results revealed the detailed structural arrangement of SMA 1440
copolymers within the membranes and highlighted the partition of butoxyethanol
group into the lipid tail region. This work allows us to propose a
possible mechanism for the membrane solubilization by SMA.