title: Haematoporphyrin changes the mechanical properties of lipid bilayer membranes.
abstract: The interactions between haematoporphyrin (HP) and bilayer lipid membranes (BLM) were studied. A weak effect of HP on BLM conductivity was observed at HP concentrations ranging between 10(-6) and 3 x 10(-5) mol/l. Modulus of elasticity in the direction normal to the membrane plane (E perpendicular) and dynamic viscosity coefficient (eta) were measured, both exhibiting HP-induced decrease by 22-31% in the dark. In this case, membrane potential Vm became negative and reached a value close to -50 mV. Under illumination by low-intensity (1 mW) He-Ne laser (lambda = 632 nm) the values of parameters E perpendicular and eta of the HP-modified membranes increased by 41-66%, and Vm decreased to -20 mV. Upon removing HP from the solution by perfusion, irreversible changes in mechanical properties of the HP-modified membranes induced by the laser light were observed. The reason could be the formation of stable complexes of HP with the lipid molecules. HP binds to membrane noncooperatively, with a binding constant K approximately 10(5) l/mol.
authors.affiliation: Department of Biophysics and Chemical Physics, Faculty of Mathematics and Physics, Comenius University, Bratislava, Czechoslovakia.
authors.forename: T
authors.initials: T
authors.lastname: Hianik
authors.forename: D
authors.initials: D
authors.lastname: Masaryková
authors.forename: L V
authors.initials: LV
authors.lastname: Zhorina
authors.lastname: Poroshina MYu
authors.forename: E B
authors.initials: EB
authors.lastname: Chernyaeva
mesh_terms: D001665:Binding Sites; D001696:Biomechanical Phenomena; D004548:Elasticity; D006415:Hematoporphyrins / Q000737:chemistry*; D066298:In Vitro Techniques; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials; D014783:Viscosity
chemical_list: D006415:Hematoporphyrins; D008051:Lipid Bilayers