Fluorescence Polarization Study on the Dynamics and Location of Peroxidized Fluorescent Phospholipids in Liposomes (original) (raw)

1996, Archives of Biochemistry and Biophysics

gested to have a chemical structure in which the angle between the absorption and emission dipole moments Motional properties of fluorescent substances prois very large. On the basis of these observations, the duced by lipid peroxidation by a time-resolved fluoproduction pathway of fluorophores in oxidized memrescence polarization technique were studied. When branes is discussed. ᭧ 1996 Academic Press, Inc. liposomes containing phosphatidylethanolamine (PE) Key Words: amino phospholipid; anisotropy; fluoand linoleic hydrocarbon chain were incubated at rescence; liposome, peroxidation. 37ЊC, fluorophores absorbing maximally at 360 nm and emitting near 430 nm were produced. Their fluorescence anisotropy decay measured at 23ЊC was fitted well with a sum of a fast relaxation and a time-inde-Lipid peroxidation alters several physical properties pendent residual term. With the increase of oxidation of biomembranes. For example, membrane proteins are degree, the time constant of the relaxation term incrosslinked, and their rotational and translateral mocreased. This may be explained by alteration in the bility is decreased (1). In the lipid domain, lipid peroximembrane structure or by modification of the fluoresdation causes an enhancement of flip-flop movements cent products themselves. Information on the location of phospholipids (2, 3), influences polymorphic phase of the fluorescent products was obtained when their behavior of lipids (4), and alters the membrane fluidity motional property was compared with those of various (5, 6). In addition, peroxidation can inactivate enzymes extrinsic probes that were incorporated at different and cause structural abnormalities of biomembranes. positions of the lipid bilayer. It was found that the Some of the abnormalities are concomitant with formamotional property of the fluorescent oxidation prodtion of fluorescent substances, which are produced ucts is similar to that of 1-(4-trimethylammoniummostly by the reaction of lipid oxidation products with phenyl)-6-phenyl-1,3,5-hexatriene, a rod-shaped hyprimary amino compounds. This reaction has been drophobic probe with a charged terminal. Other shown to be responsible for the accumulation of fluoprobes sensing the polar region or the hydrophobic rescent pigments in aged cells (7, 8). region of the membrane were characterized by a lower So far, three types of model reactions have been proorder parameter. It is suggested that the fluorescent posed to describe production of fluorescent substances oxidation products have a polar moiety located at the by peroxidation in the presence of amino compounds: membrane surface and attached to the amino group of PE while the tail part being buried in the hydrophobic (1) malondialdehyde (MDA), 2 one of the major products region of the membrane. This picture is supported by fluorescence quenching experiments with the aqueous