Understanding the interactions between sebum triglycerides and water: a molecular dynamics simulation study

Abstract

In recent years, sebum oil has been found to play a key role in the regulation of the hydration of the outermost layer of the skin, the stratum corneum. Understanding how a major component of the sebum oil, the triglyceride tri-cis-6-hexadecenoin (TG), interacts with water is an important step in gaining insight into the water regulation function of the sebum oil. Here we use molecular dynamics simulations to investigate the structural and interfacial properties of TG in bulk and at the air and water interface. Our model performs very well in reproducing experimental results, such as density, surface tensions and surface pressure area isotherms. We show that triglyceride molecules in the liquid phase assemble together, through the glycerol group, forming a single percolating network. TG-air interfaces orient the lipids with the interface enriched with the hydrophobic tails and the glycerol groups buried inside. When in contact with water, the TG molecules at the interface orient the glycerol group towards the water phase and adopt a characteristic trident conformation. Water is shown to penetrate the TG layer thanks to the interaction with the oxygen atoms of the TG molecules, which acts as a pathway for water diffusion. The activation energy for the passage of water is found to be ≈9.5kT at 310 K, showing that the layer is permeable to water diffusion.

On the Structure of Solid Lipid Nanoparticles

“…The SLN would then have the chance to develop into one of the crystalline polymorphs. Experimental and computational studies of bulk triglycerides have shown that the tuning fork and chair conformations are the most common in bulk lipid, which is also reflected in our SLN lipid core . Additional simulation work confirms the preference of lipids to adopt the trident conformation at the lipid/water interface and experimental evidence has shown that lipids at the air/water interface are also in the trident conformation …”

“…The angle criteria used to classify a triglyceride molecule is summarized in the Supporting Information. It is the same as used in a previous study however this work defines the vectors from the central carbon (C18) as opposed to the first oxygen in each chain . Determining the length of each vector also provided with an understanding of lipid extension, as shown in the Supporting Information.…”

“…Although there has been significant experimental research dedicated to determining the physicochemical properties (including stability) of SLNs, there is currently little understanding of the detailed molecular structure of these nanoparticles. Furthermore, while molecular dynamics (MD) simulations have been used to investigate the molecular scale structure and nucleation processes of bulk crystalline lipids, there are few simulation studies of lipid nanoparticles. The few that have been conducted have studied liquid, not solid, nanoparticles.…”

Molecular Dynamics Simulation for Mechanism Elucidation of Food Processing and Safety: State of the Art

“…This observation displayed how environment factors may affect the dynamic organization of phospholipid molecules. Apart from the interactions between lipid and water (Tascini, Noro, Chen, Seddon, & Bresme, ), there are other investigations concerning lipids, such as lipid aggregating into vesicles and bunches (Marrink & Mark, ; Wassall et al., ) and phase transition in lipid systems (Gai et al., ; Marrink, Risselada, & Mark, ).…”

“…[ Figure 2 and Table 2 were updated. Chen et al (2018) was corrected to Chen et al (2018a) and Chen et al (2018b) in the reference list after initial online publication.] that define the atoms, residues, and their masses, charges, types, and so on involved in a system under study (Cheng et al, 2018;Couallier, Riaublanc, David, & Rousseau, 2018;Foley, Tessier, & Woods, 2012;Watts, Gregory, Frisbie, & Lovas, 2018).…”