title: A steroid in a lipid bilayer: localization, orientation, and energetics.
abstract: Steroid hormones are known to freely partition into lipid bilayers. As a case study, we investigated the behavior of the steroid hormone cortisone in a model lipid bilayer. First, we looked at energy barriers involved in the partitioning of a single molecule into a bilayer using umbrella sampling molecular dynamics simulations. A rather wide well of -4.5 kcal/mol was observed in the interfacial region between the lipid headgroup and tailgroup. Next, using two unconstrained molecular dynamics simulations with cortisone initially positioned at distinct locations within a bilayer, we studied the preferred location and orientation of the molecule. Finally, we observed how cortisone molecules could spontaneously insert and localize in a bilayer from bulk solution. The three independent approaches produced a converged picture of how cortisone behaves in a model lipid bilayer.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Vijayan
authors.forename: Philip C
authors.initials: PC
authors.lastname: Biggin
mesh_terms: D003348:Cortisone / Q000737:chemistry* / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D003348:Cortisone