Biologic duoflow quadtec 10 system

Plasma cholesterol (cat # TR13421), triglyceride (cat # TR22421), alanine aminotransferase (ALT; cat # TR71121), and aspartate aminotransferase (AST; cat # TR70121) levels were measured using Infinity reagents (ThermoFisher Scientific; Waltham, MA, USA). Plasma lipoproteins were separated by fast protein liquid chromatography (FPLC). In brief, more than 100 μL plasma was run at 0.5 mL/min in a buffer (0.15 mol/L NaCl, 0.01 mol/L Na2HPO4, 0.1 mmol/L EDTA, pH 7.5), and lipoproteins were separated on a Superose 6 10/300 GL column (GE Healthcare; Chicago, IL, USA) using BioLogic DuoFlow QuadTec 10 System (Bio-Rad; Hercules, CA, USA). The total cholesterol or triglyceride amount in each fraction (500 μL) was calculated after a small portion (50 μL) was used for quantification.

To increase purify of VLPs for VLP imaging, an additional 35% sucrose sedimentation was added to the extraction procedure as mentioned in Moon et al.^{32 (link)}. Gradients were fractionated by centrifugation at 90,000×g for 2 h. The final pellets were resuspended in sterile 50 mM potassium phosphate pH 7.0. To confirm self-assembled particle, the purified protein was analyzed by size exclusion chromatography using the BioLogic DuoFlow QuadTec 10 System (Bio-Rad) at the UNIST (Ulsan, Korea). Concentrated VLPs were subjected to negative staining and examination by transmission electron microscopy. Two microliters of each removed salt component suspensions were placed on 200-mesh copper grids (Electron Microscopy Sciences, Hatfield, PA, USA) and allowed to incubate at room temperature for 1 min in order for the particles to adhere. Two microliters of 1.5% uranyl acetate were added to the attached particles on the grid, grids were then analyzed by using a transmission electron microscope JEM-2100 (JEOL, Tokyo, Japan), and images were acquired through a CCD camera SIS veleta (Olympus, Munster, Germany) at the UNIST (Ulsan, Korea).