Molecular Interactions behind the Self-Assembly and Microstructure of Mixed Sterol Organogels

George Dalkas, Andrew Matheson, Hugh Vass, Andrey Gromov, Gareth Lloyd, Vasileios Koutsos, Paul Clegg, Steve Euston

Research output: Contribution to journalArticlepeer-review

Abstract

In this work, we have employed docking and atomistic molecular dynamics (MD) simulations supported by complementary experiments using atomic force microscopy, rheology, and spectroscopy to investigate the self-assembled structure of β-sitosterol and γ-oryzanol molecules into cylindrical tubules in a nonaqueous solvent. Docking models of several phytosterols, including sitosterol, with oryzanol and other sterol esters demonstrate that for systems to form tubules, the phytosterol sterane group must be stacked in a wedge shape with the ester sterane group and a hydrogen bond must form between the hydroxyl group of the phytosterol and the carbonyl group of the ester. MD of the self-assembled structure were initiated with the molecules in a roughly cylindrical configuration, as suggested from previous experimental studies, and the configurations were found to be stable during 50 ns simulations. We performed MD simulations of two tubules in proximity to better understand the aggregation of these fibrils and how the fibrils interact in order to stick together. We found that an interfibril network of noncovalent bonds, in particular van der Waals and π–π contacts, which is formed between the ferulic acid groups of oryzanol through the hydroxyl, methoxy, and aromatic groups, is responsible for the surface-to-surface interactions between fibrils; an observation supported by molecular spectroscopy. We believe that these interactions are of primary importance in creating a strong organogel network.
Original languageEnglish
Pages (from-to)8629-8638
Number of pages10
JournalLangmuir
Volume34
Early online date2 Jul 2018
DOIs
Publication statusE-pub ahead of print - 2 Jul 2018

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