N.G.Brady et al. SAXS Data of SMA Copolymers in Solution
Description
Over the past decade, Styrene Maleic Acid Alternating Copolymers (SMA) have gained interest as an alternative to detergent solubilization for the isolation of membrane bound proteins. During the canonical method of membrane solubilization via surfactant-lipid exchange, detergents have been shown to replace membrane lipids peripheral and interior to membrane bound proteins [1]. For both the investigation of the proteolipid interface and the retention of native activity in vitro, the formation of SMA lipid particles (SMALPs) presents a novel opportunity to isolate the proximal membrane environment, encompassing and throughout membrane proteins in vitro. The mechanism by which SMA associates with the membrane resulting in SMALPs is unknown, leading to SMAs of differing physicochemical properties (styrene:maleic acid ratio and length of copolymer fragments) being reported as optimum for extraction of various membrane proteins. The coordinated supramolecular assembly of SMA amphiphilic copolymers free in solution has yet to be elucidated over a range of environmental conditions, which may be pertinent to the underlying mechanism of protein extraction by this method. This study investigates the shape and size of diverse SMA aggregates in solution at various pH, ionic strength, concentration and temperature, analyzed by small angle X-ray scattering. The SMA supramolecular aggregates exhibit similar prolate ellipsoidal geometry of varying size, dependent on the degree of hydrophobicity of the SMA copolymer. At elevated pH and temperature, particles composed of SMAs enriched in styrene undergo elongation at the poles, increasing in maximum particle diameter. The magnitude of this effect increases proportional to increasing length of the SMA copolymer fragments. Included here is all raw data for SAXS curves, Guinier approximation and distance distribution analyses.