Quantifying the Thresholds of the Phospholipid Surface Density for Nonspecific Protein Adsorption and Desorption at the Triacylglycerol/Water Interface

Quantitative investigation of protein adsorption and desorption at triacylglycerol/water interfaces is of great importance for understanding the properties and functions of intracellular lipid droplets. In this study, we investigated the adsorption and desorption of cytochrome c, lysozyme, and bovine serum albumin at the tricaprylin/water interface covered with 1,2-dioleoyl-<i>sn-glycero</i>-3-phosphocholine (DOPC) using a surface pressure measurement system and a pendant drop tensiometer. The aim of this study was to understand the quantitative relationships between the area per DOPC molecule and the protein adsorption and desorption. We found that the area per DOPC molecule required to preclude bovine serum albumin adsorption was much smaller than that required to preclude the adsorption of cytochrome <i>c</i> or lysozyme. However, the area per DOPC molecule required for all of the bound protein molecules to desorb from the interface was independent of the type of protein, and this threshold area per DOPC molecule was in good agreement with an area per lipid value previously reported for fully hydrated DOPC bilayers.