Conjugated polyene fatty acids as fluorescent probes: spectroscopic characterization

Abstract

This paper is the first in a series which extends introductory studies of parinaric acid and its phospholipid derivatives as membrane probes (Sklar, L.A., Hudson, B., and Simoni, R.D. (1975), Proc. Natl. Acad. Sci. after U.S.A. 72, 1649; (1976), J. Supramol. Struct. 4, 449). Parinaric acid has a conjugated tetraene chromophore and exhibits many spectroscopic properties common to linear polyenes. Its absorption spectrum is characterized by a strong near-ultraviolet transition with vibronic structure, which is strongly affected by solvent polarizability. The fluorescence emission occurs at considerably lower energy than the absorption and the wavelength of the emission is nearly independent of the solvent. The fluorescence quantum yield and lifetime are strongly affected by temperature and solvent. These spectral features are interpreted in terms of an excited electronic-state order such that a weak transition occurs at longer wavelengths than the strongly allowed transition which dominates the absorption. The sensitivity of the fluorescence quantum yield an lifetime to environment is shown to be due primarily to variations in the nonradiative rate, although changes in the radiative rate constant are also observed and interpreted. The absorption spectrum (epsilon max greater than 65 000) is in the 300-320-nm range, a region relatively free of absorption due to intrinsic biological chromophores. Shifts of several nanometers are characteristic of different environments. These shifts are compared to similar effects observed for a series of diphenylpolyenes for which new data are given and are correlated using a simple but adequate theory of solvent shifts. The intrinsic (or radiative) fluorescence lifetime is near 100 ns in a wide variety of environments. This is much longer than the intrinsic lifetime calculated from the absorption spectrum and strongly supports the proposed excited-state order.

Binding of phospholipids to the phosphatidylinositol transfer protein from bovine brain as studied by steady-state and time-resolved fluorescence spectroscopy

“…The average lifetime is probably related to the polarity of the binding site for the 2-acyl chain, which has a large influence on the actual lifetime value [32,33]. The complete immobilization of the 2-acyl chain in both phospholipids, evidenced by a long-lived anisotropy decay, indicates an efficient binding to a hydrophobic pocket on the protein.…”

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

“…The equilibrium of incorporation in the membrane is reached within l-2 min, as is indicated by the rate of increase of fluorescence intensity. In the membrane, the quantum yield of parinaric acid depends on the physical properties of the membrane itself as well as on the concentration of the probe [5,6]. In Fig.…”

“…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.…”

“…and (iii) loss of lipid substrate, more specifically, the loss of polyunsaturated fatty acyl chains. 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].…”

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

“…The fluorescent fatty acid cis-parinaric acid (9,11,13,15-cis, trans, trans, cisoctadecatetraenoic acid) and its all-trans isomer are spectroscopically well-characterized probes [1]. They have been used in lipid model systems and biological membranes to study lipid-lipid and lipid-protein interactions [2][3][4][5][6].…”