Conjugated polyene fatty acids as fluorescent probes: synthetic phospholipid membrane studies

Abstract

The preparation of polyene fatty acid membrane probes cis- and trans-parinaric acid and parinaroylphosphatidylcholines and their use in studies of several one- and two- component lipid systems are described. The fluorescence quantum yield of trans-parinaric acid in dipalmitoylphosphatidylcholine at 20 degrees C is approximately 0.3; the quantum yield in aqueous solution is negligibly small. Thermal-phase transitions in single-component phospholipid dispersions are monitored with absorption and fluorescence excitation peak position, fluorescence intensity, lifetime, and polarization. The transition temperatures observed are consistent with previous determinations. Shifts in the absorption peak position are related to the bilayer expansion as it undergoes the gel to liquid-crystalline transition, while fluorescence depolarization provides semiquantitative information concerning molecular motion of the probe in the bilayer. A long fluorescence lifetime component is observed for parinaric acid in the solid phase (up to 50 ns), and a short lifetime component is observed (ca. 5 ns) in the fluid phase of dipalmitoylphosphatidylcholine; both lifetime components are observed in the transition region. In most phospholipids, cis-parinaric acid detects the melting transition at about 1 degree C lower than trans-parinaric acid. Partitioning experiments involving mixed populations of phospholipid vesicles show that trans-parinaric acid preferentially associates with solid-phase lipids, while cis-parinaric acid shows a more equal distribution between solid and fluid lipids. The binding of cis-parinaric acid to dipalmitoylphosphatidylcholine at 25 degrees C is described as partitioning of parinaric acid between lipid vesicles and the aqueous phase with a partition coefficient of 5 X 10(5). Several rates are observed in the binding process which are interpreted as rapid outer monolayer uptake and a much slower process of interlamellar exchange. The phase diagram of the binary lipid mixture dipalmitoylphosphatidylcholine-dipalmitoylphosphatidylethanolamine has also been examined and found to be essentially identical to the one constructed using a nitroxide probe.

Lipid Domains in Plasma Membrances from Rat Liver

“…The data presented here indicate that the binding properties of trans-parinaric and cis-parinaric acid to rat liver plasma membranes were similar to those for model phospholipid systems and rod outer segment membranes [33,39]. Briefly, the molar lipid to probe ratio at which cis-parinarate and trans-parinarate were equally distributed between aqueous and lipid phases was about 17/1 while in model phospholipids this ratio was 30/1 [33].…”

“…and X y are determined from multiple fluorescence lifetime analysis. The longer lifetime component, 72, has been correlated to the probe molecule in solid phase while the shorter lifetime component, tl was correlated to the probe molecule in fluid phase [39]. The parameters X Z and X I may be obtained rrom a phase diagram in simple model systems [39,40] but in the present work using rat liver plasma membrane this was The liver plasma membranes also undergo a phase alteration with beginning and end points near 18 "C and 31 "C [I I].…”

Parinaric acid as a sensitive fluorescent probe for the determination of lipid peroxidation

“…The fluorescent properties of parinaric acid, originating from the conjugated configuration of the four double bonds in the acyl chain, have made this molecule a very useful membrane probe [6,7]. The presence of the four double bonds, however, confers the acyl chain of parinaric acid.…”

“…The fluorescent polyunsaturated fatty acid, cis-parinaric acid, and its all-truns isomer are spectroscopically well defined membrane probes [5,6]. They have been used, as free acid or esterified in phospholipid analogues, to study lipid-lipid and lipid-protein interactions in lipid model systems as well as in biological membranes [7,8]. If exogenously administered, the free fatty acid incorporates readily into the membrane [9].…”

A comparative fluorescence polarization study of cis-parinaroyl-phosphatidylcholine and diphenylhexatriene in membranes containing different amounts of cholesterol

“…They have been used in lipid model systems and biological membranes to study lipid-lipid and lipid-protein interactions [2][3][4][5][6]. A number of different phospholipid analogues of parinaric acid have been synthesized recently and their partitioning behaviour between solid and fluid lipid phases in liposomes is known [7,8].…”