Conformational Space of a Polyphilic Molecule with a Fluorophilic Side Chain Integrated in a DPPC Bilayer.

Abstract

We investigate the conformational space of a polyphilic molecule with hydrophilic, lipophilic and fluorophilic parts inserted as a transmembrane agent into a dipalmitoylphosphatidylcholine bilayer by means of all-atom molecular dynamics simulations. Special focus is put on the competing structural driving forces arising from the hydrophilic, lipophilic and fluorophilic side chains and the aromatic backbone of the polyphile. We observe a significant difference between the lipophilic and the fluorophilic side chains regarding their intramembrane distribution. While the lipophilic groups remain membrane-centered, the fluorophilic parts tend to orient toward the phosphate headgroups. This trend is important for understanding the influence of polyphile agents on the properties of phospholipid membranes. From a fundamental point of view, our computed distribution functions of the side chains are related to the interplay of sterical, enthalpic and entropic driving forces. Our findings illustrate the potential of rationally designed membrane additives which can be exploited to tune the properties of phospholipid membranes. © 2017 Wiley Periodicals, Inc.