title: Spatial orientation and electric-field-driven transport of hypericin inside of bilayer lipid membranes.
abstract: Fluorescence experiments were carried out to investigate the interaction of hypericin (Hyp), a natural hydrophobic photosensitizer, with artificial bilayer lipid membranes. The spatial orientation of Hyp monomers incorporated in diphytanoyl phosphatidylcholine (DPhPC) membranes was determined by measuring the dependence of the Hyp fluorescence intensity on the angle of incidence of p- and s-polarized excitation laser beams. Inside of the membrane, Hyp monomers are preferentially located in the layers near the membrane/water interface and are oriented with the S(1) ← S(0) transition dipole moments perpendicular to the membrane surface. Transport of Hyp anions between the two opposite sides of the lipid bilayer was induced by applying rectangular electric field pulses to the membrane. The characteristic time for Hyp transport through the membrane center was evaluated by the analysis of the Hyp fluorescence signal during the voltage pulses. In the zero-voltage limit, the transport time approached 70 ms and gradually decreased with higher voltage applied to the membrane. In addition, our measurements indicated an apparent pK(a) constant of 8 for Hyp deprotonation in the membrane.
authors.affiliation: Department of Biophysics, Pavol Jozef Šafárik University, Jesenná 5, Košice 041 54, Slovak Republic.
authors.forename: Alena
authors.initials: A
authors.lastname: Strejčková
authors.forename: Jana
authors.initials: J
authors.lastname: Staničová
authors.forename: Daniel
authors.initials: D
authors.lastname: Jancura
authors.forename: Pavol
authors.initials: P
authors.lastname: Miškovský
authors.forename: Gregor
authors.initials: G
authors.lastname: Bánó
mesh_terms: D000873:Anthracenes; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D004586:Electrophoresis; D008051:Lipid Bilayers / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D000873:Anthracenes; D008051:Lipid Bilayers; D010569:Perylene; C004965:hypericin