Lipid Phase Behavior and Protein-Lipid Interactions within Nanolipoprotein Particles upon Sol-Gel Derived Encapsulation

Abstract

Nanolipoprotein Particles (NLPs) and liposomes were entrapped within transparent, mesoporous silica derived from Tetramethylorthosilicate (TMOS). NLPs are discoidal patches of lipid bilayer that are belted by amphiphilic scaffold proteins. NLPs possess an average thickness of 5 nm, with a diameter that ranges from 10-15 nm. The phase behavior of lipids within liposomes and NLPs was examined, as well as the scaffold protein conformational changes within NLPs. Liposomes have previously been examined inside of silica gels and been shown to be exhibit instability. This is attributed by their size (∼150 nm) and altered structure and lipid dynamics upon entrapment within the nanometer scale pores (5-50 nm) of the silica gel. Using various spectroscopic techniques, we have demonstrated that NLPs are much more compatible with the nanometer scale size of the porous environment than liposomes. In addition, we utilized fluorescence quenching of tryptophan to find that the scaffold proteins in NLPs were minimally altered upon entrapment, thus suggesting that the NLPs remained stable. NLPs are capable of solubilizing a wide variety of Integral Membrane Proteins (IMPs). Successful NLP immobilization allows for the development of of biohybrid nanomaterials that exploit the functionality of IMPs. Areas of application of this work include high-throughput drug screening, chromatography, and biosensors.