Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

21-POS Board 7 TRIGLYCERIDES STABILIZE ORGANIC-WATER INTERFACES OF CHANGING AREA VIA CONFORMATIONAL FLEXIBILITY

Thomas C Kinard 1 ; Steven P Wrenn 1 ; 1 Virginia Tech, Chemical Engineering, Blacksburg, VA, USA

The role of Triglycerides (TGs) in both natural and synthetic biological membranes has long been the subject of study, involving metabolism, disease, and colloidal synthesis. TGs have been found to be critical components for successful liposomal encapsulation via Water/Oil/Water double emulsion, which this work attempts to explain. TGs can occupy multiple positions in biological membranes. The glycerol backbone can sit at the water/organic interface, adjacent to phospholipid headgroups (“m” conformation), typically with relatively low (~3%) solubility. The glycerol backbone can also occupy hydrophobic regions, where it is isolated from water (“h” or “oil” conformation) in either mid-membrane positions or phospholipid-coated lipid droplets (LDs). These conformations can be distinguished using 13 C-Nuclear Magnetic Resonance Spectroscopy (NMR) to determine the degree of hydration of the TG backbone. Using this method, it was revealed that TGs transition from “m” to “h” conformation as the organic solvent is removed via evaporation. A new, transitional conformation has been identified. These results suggest that TGs are able to temporarily coat and stabilize the large water/organic interfaces present just after emulsification. As the organic solvent is removed and interfaces shrink, the TGs recede into mid-membrane spaces or bud off into phospholipid-coated Lipid Droplets (LDs), which are confirmed via Transmission Electron Microscopy (TEM) and can be removed via centrifugation. Encapsulation efficiency is found to be inversely related to both acyl chain saturation and length, indicating that membrane fluidization is a key property arising from the presence of TGs. Beyond clarification of a mechanism for high-efficiency liposomal encapsulation, these results implicate TGs as components that are able to stabilize biological membrane transitions involving changing interfacial area and curvature. This role for TGs may be of use in the formulation of drug delivery systems, as well as in the investigation of membrane transitions in life sciences.

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