title: Can pyrene probes be used to measure lateral pressure profiles of lipid membranes? Perspective through atomistic simulations.
abstract: The lateral pressure profile of lipid bilayers has gained a lot of attention, since changes in the pressure profile have been suggested to shift the membrane protein conformational equilibrium. This relation has been mostly studied with theoretical methods, especially with molecular dynamics simulations, since established methods to measure the lateral pressure profile experimentally have not been available. The only experiments that have attempted to gauge the lateral pressure profile have been done by using di-pyrenyl-phosphatidylcholine (di-pyr-PC) probes. In these experiments, the excimer/monomer fluorescence ratio has been assumed to represent the lateral pressure in the location of the pyrene moieties. Here, we consider the validity of this assumption through atomistic molecular dynamics simulations in a DOPC (dioleoylphosphatidylcholine) membrane, which hosts di-pyr-PC probes with different acyl chain lengths. Based on the simulations, we calculate the pyrene dimerization rate and the lateral pressure at the location of the pyrenes. The dimerization rates are compared with the results of di-pyr-PC probes simulated in vacuum. The comparison indicates that the lateral pressure is not the dominant determinant of the excimer/monomer fluorescence ratio. Thus, the results do not support the usage of di-pyr-PC molecules to measure the shape of the lateral pressure profile. We yet discuss how the probes could potentially be exploited to gain qualitative insight of the changes in pressure profile when lipid composition is altered.
authors: Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague 2 CZ-12116, Czech Republic.
authors: Miroslava
authors: M
authors: Dékány Fraňová
authors: Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland; MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
authors: Ilpo
authors: I
authors: Vattulainen
authors: Helsinki Biophysics and Biomembrane Group, Department of Biomedical Engineering and Computational Science, Aalto University, Espoo, Finland. Electronic address: samuli.ollila@aalto.fi.
authors: O H
authors: OH
authors: Samuli Ollila
mesh_terms: D019281:Dimerization; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008566:Membranes / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D010713:Phosphatidylcholines / Q000737:chemistry; D011312:Pressure; D011721:Pyrenes / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D011721:Pyrenes; C030984:pyrene; C017251:1,2-oleoylphosphatidylcholine
keywords: Di-pyrenyl-phosphatidylcholine; Lateral pressure profile; Lipid bilayer; Molecular dynamics simulation