posted on 2024-03-07, 10:43authored byFloriane Mangin, Vinay Chauhan, Pierre Guillet, Marjorie Damian, Marine Soulié, Jean-Louis Banères, Grégory Durand
We
have synthesized four acrylamide-based monomers whose
polar
headgroup consists of one or two glucose or one maltose moieties and
whose alkyl chain is made of a n-decyl or a n-octyl hydrophobic chain. These surface-active monomers,
called surfmers, were polymerized by free-radical telomerization in
the presence of a thiol-based transfer agent, leading to four new
nonionic polymers that belong to the class of amphipols. A very good
reproducibility and control of the polymerization was noted, leading
to average polymerization degrees in perfect agreement with the initial
ratio R0 and to quite a narrow polydispersity
index after purification. Surface tension (SFT) measurements indicate
that the four surfmers self-assemble at concentrations ranging from
∼0.5 to 4 mM. Dynamic light scattering (DLS) experiments suggest
the formation of rather small homogeneous aggregates of 5 nm diameter
for the monomers, while the size of the aggregates ranges from 5 to
16 nm diameter for the polymers. The ghrelin receptor GHSR, a typical
rhodopsin-like G protein-coupled receptor (GPCR), was used as a challenging
model because of its conformational instability in vitro. The surfmers
solubilized the receptor from membrane fractions more efficiently
than their polymeric counterparts. In contrast, the polymers were
significantly more efficient at stabilizing the functional fold of
the isolated protein in solution. This demonstrates the opposite effect
of surfmers and their polymer counterparts toward the solubilization
and stabilization of a fragile membrane protein.