ИСТИНА

Solubilization of membrane proteins by a styrene-maleic acid copolymer (SMA) has recently been reported as a promising tool for membrane protein extraction [1-4]. Such procedure results in structures termed lipodisks (or SMALPs) formation. Lipodisks allow extracting membrane proteins without the usage of detergents thus providing native lipid environment for membrane proteins. The simplicity of the method indicates it as an outstanding technique for membrane protein solubilization. However, the mechanism of lipodisk formation is still unknown on an atomic level. ¬In this work, we propose a stable full-atom lipodisk model prepared for long molecular dynamics simulations. The resulting lipodisk model contained 60 molecules of POPC (30 molecules in each membrane leaflet) and was around 9 nm in diameter. The lipodisk was built using 29 SMA molecules (around 36 monomers each) with 1:3 maleic acid/styrene ratio. Molecular models make it possible to evaluate the physicochemical properties of membranes (cooperativity parameter, the area per lipid, electron density profile) that are hard to measure in lipodisks and compare them with the characteristics of native membranes. Also, such models can be used to study the influence of lipodisk environment on the structure of the extracted proteins. This work was supported by the RFBR grant 18-504-12045 1. Bagrov, D. V. et al. Characterization of Lipodisc Nanoparticles Containing Sensory Rhodopsin II and Its Cognate Transducer from Natronomonas pharaonic (2016). Biophys, 61(6), 942–949. doi: 10.1134/S0006350916060063 2. Dörr, J. M. et al. The styrene–maleic acid copolymer: a versatile tool in membrane research (2016). Eur Biophys J, 45:3–21. doi: 10.1007/s00249-015-1093-y 3. Jamshad, M. et al. Structural analysis of a nanoparticle containing a lipid bilayer used for detergent-free extraction of membrane proteins (2014). Nano Research, 8(3), 774–789. doi: 10.1007/s12274-014-0560-6 4. Knowles, T. J. et al. Membrane proteins solubilized intact in lipid containing nanoparticles bounded by styrene maleic acid copolymer (2009). Journal of the American Chemical Society, 131(22), 7484–7485. doi: 10.1021/ja810046q