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Biochim Biophys Acta. 2016 Nov;1858(11):2931-2939. doi: 10.1016/j.bbamem.2016.08.004. Epub 2016 Aug 15.

Tuning the size of styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) using RAFT polymerization for biophysical studies.

Author information

1
Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, United States.
2
Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, United States. Electronic address: gary.lorigan@miamioh.edu.

Abstract

Characterization of membrane proteins is challenging due to the difficulty in mimicking the native lipid bilayer with properly folded and functional membrane proteins. Recently, styrene-maleic acid (StMA) copolymers have been shown to facilitate the formation of disc-like lipid bilayer mimetics that maintain the structural and dynamic integrity of membrane proteins. Here we report the controlled synthesis and characterization of StMA containing block copolymers. StMA polymers with different compositions and molecular weights were synthesized and characterized by size exclusion chromatography (SEC). These polymers act as macromolecular surfactants for 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol (POPG) lipids, forming disc like structures of the lipids with the polymer wrapping around the hydrophobic lipid edge. A combination of dynamic light scattering (DLS), solid-state nuclear magnetic resonance (SSNMR) spectroscopy, and transmission electron microscopy (TEM) was used to characterize the size of the nanoparticles created using these StMA polymers. At a weight ratio of 1.25:1 StMA to lipid, the nanoparticle size created is 28+1nm for a 2:1 ratio, 10+1nm for a 3:1 StMA ratio and 32+1nm for a 4:1 StMA ratio independent of the molecular weight of the polymer. Due to the polymer acting as a surfactant that forms disc like nanoparticles, we term these StMA based block copolymers "RAFT SMALPs". RAFT SMALPs show promise as a new membrane mimetic with different nanoscale sizes, which can be used for a wide variety of biophysical studies of membrane proteins.

KEYWORDS:

2:1 StMA ratio; 3:1 StMA ratio; 4:1 StMA ratio; Dynamic light scattering; NOESY NMR; POPC/POPG vesicle; SSNMR spectroscopy; Styrene-maleic acid polymer

PMID:
27539205
DOI:
10.1016/j.bbamem.2016.08.004
[Indexed for MEDLINE]
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