title: Probing Microscopic Orientation in Membranes by Linear Dichroism.
abstract: The cell membrane is an ordered environment, which anisotropically affects the structure and interactions of all of its molecules. Monitoring membrane orientation at a local level is rather challenging but could reward crucial information on protein conformation and interactions in the lipid bilayer. We monitored local lipid ordering changes upon varying the cholesterol concentration using polarized light spectroscopy and pyrene as a membrane probe. Pyrene, with a shape intermediate between a disc and a rod, can detect microscopic orientation variations at the level of its size. The global membrane orientation was determined using curcumin, a probe with nonoverlapping absorption relative to that of pyrene. While the macroscopic orientation of a liquid-phase bilayer decreases with increasing cholesterol concentration, the local orientation is improved. Pyrene is found to be sensitive to the local effects induced by cholesterol and temperature on the bilayer. Disentangling local and global orientation effects in membranes could provide new insights into functionally significant interactions of membrane proteins.
authors.affiliation: Chemistry and Chemical Engineering, Chalmers University of Technology , SE-41296 Gothenburg, Sweden.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rocha
authors.affiliation: Chemistry and Chemical Engineering, Chalmers University of Technology , SE-41296 Gothenburg, Sweden.
authors.forename: Maxim
authors.initials: M
authors.lastname: Kogan
authors.affiliation: Chemistry and Chemical Engineering, Chalmers University of Technology , SE-41296 Gothenburg, Sweden.|Research Centre for Natural Sciences, Hungarian Academy of Sciences , H-1125 Budapest, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Beke-Somfai
authors.affiliation: Chemistry and Chemical Engineering, Chalmers University of Technology , SE-41296 Gothenburg, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Nordén
mesh_terms: D002784:Cholesterol / Q000737:chemistry; D003474:Curcumin / Q000737:chemistry; D008027:Light; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D011721:Pyrenes / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D015335:Molecular Probes; D010713:Phosphatidylcholines; D011721:Pyrenes; D002784:Cholesterol; C030984:pyrene; C017251:1,2-oleoylphosphatidylcholine; D003474:Curcumin