Poster Presentation HUPO 2019 - 18th Human Proteome Organization World Congress

Triglyceride-Based Nanodroplets and Their Interaction with Lipid-Specific Proteins (#899)

Valerija Vezočnik 1 , Vesna Hodnik 1 , Halil I. Okur 2 , Simona Sitar 3 , Magda Tušek-Žnidarič 4 , Ksenija Kogej 1 , Kristina Sepcic 1 , Sylvie Roke 2 , Ema Žagar 3 , Peter Maček 1
  1. University of Ljubljana, Ljubljana, Slovenia
  2. École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
  3. National Institute of Chemistry, Ljubljana, Slovenia
  4. National Institute of Biology, Ljubljana, Slovenia

Understanding of the interactions between proteins and natural and artificially prepared lipid membrane surfaces and embedded nonpolar cores is important in studies of physiological processes and their pathologies and is applicable to nanotechnologies. In particular, rapidly growing interest in cellular droplets defines the need for simplified biomimetic lipid model systems to overcome in vivo complexity and variability. In this study, we present a protocol for the preparation of kinetically stable nanoemulsions with nanodroplets composed of sphingomyelin (SM) and cholesterol (Chol), as amphiphilic surfactants, and trioleoylglycerol (TOG), at various molar ratios. To prepare stable SM/Chol-coated monodisperse lipid nanodroplets (LDs), we modified a reverse phase evaporation method and combined it with ultrasonication. Lipid composition, ζ-potential, gyration and hydrodynamic radius, shape, and temporal stability of the LDs were characterized and compared to extruded SM/Chol large unilamellar vesicles (LUVs). LDs and LUVs with theoretical SM/Chol/TOG molar ratios of 1/ 1/4.7 and 4/1/11.7 were further investigated for the orientational order of their interfacial water molecules using a second harmonic scattering technique, and for interactions with the SM-binding and Chol-binding pore-forming toxins equinatoxin II and perfringolysin O, respectively. The surface characteristics and binding of these proteins to the LDs SM/Chol monolayers were similar to those for the SM/Chol bilayers of the LUVs and SM/Chol Langmuir monolayers, in terms of their surface structures. We propose that such SM/ Chol/TOG nanoparticles with the required lipid compositions can serve as experimental models for monolayer membrane to provide a system that imitates the natural lipid droplets.