title: Nonlinear Optical Properties of Fluorescent Dyes Allow for Accurate Determination of Their Molecular Orientations in Phospholipid Membranes.
abstract: Several methods based on single- and two-photon fluorescence detected linear dichroism have recently been used to determine the orientational distributions of fluorescent dyes in lipid membranes. However, these determinations relied on simplified descriptions of nonlinear anisotropic properties of the dye molecules, using a transition dipole-moment-like vector instead of an absorptivity tensor. To investigate the validity of the vector approximation, we have now carried out a combination of computer simulations and polarization microscopy experiments on two representative fluorescent dyes (DiI and F2N12S) embedded in aqueous phosphatidylcholine bilayers. Our results indicate that a simplified vector-like treatment of the two-photon transition tensor is applicable for molecular geometries sampled in the membrane at ambient conditions. Furthermore, our results allow evaluation of several distinct polarization microscopy techniques. In combination, our results point to a robust and accurate experimental and computational treatment of orientational distributions of DiI, F2N12S, and related dyes (including Cy3, Cy5, and others), with implications to monitoring physiologically relevant processes in cellular membranes in a novel way.
authors.affiliation: †Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic.
authors.forename: Štěpán
authors.initials: Š
authors.lastname: Timr
authors.affiliation: ‡Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS-50F-1650, Berkeley, California 94720 United States.
authors.forename: Jiří
authors.initials: J
authors.lastname: Brabec
authors.affiliation: §Institute of Nanobiology and Structural Biology GCRC, Academy of Sciences of the Czech Republic, v.v.i., Zámek 136, 37333 Nové Hrady, Czech Republic.|∥Faculty of Science, University of South Bohemia, Branišovská 31, 37005 České Budějovice, Czech Republic.
authors.forename: Alexey
authors.initials: A
authors.lastname: Bondar
authors.affiliation: ⊥Department of Cybernetics, Faculty of Applied Sciences, University of West Bohemia, Univerzitní 8, 30614 Plzeň, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Ryba
authors.affiliation: ⊥Department of Cybernetics, Faculty of Applied Sciences, University of West Bohemia, Univerzitní 8, 30614 Plzeň, Czech Republic.
authors.forename: Miloš
authors.initials: M
authors.lastname: Železný
authors.affiliation: †Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic.|§Institute of Nanobiology and Structural Biology GCRC, Academy of Sciences of the Czech Republic, v.v.i., Zámek 136, 37333 Nové Hrady, Czech Republic.|∥Faculty of Science, University of South Bohemia, Branišovská 31, 37005 České Budějovice, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Lazar
authors.affiliation: †Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic.|#Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
mesh_terms: D002462:Cell Membrane / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D017711:Nonlinear Dynamics; D055620:Optical Phenomena; D010743:Phospholipids
chemical_list: D005456:Fluorescent Dyes; D010743:Phospholipids