Chlorophyll a and chlorophyllide a inside liposomes made of saturated and unsaturated lipids: A possible impact of the lipids microenvironment (original) (raw)
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Absorption and emission spectral shifts of rose bengal associated with DMPC liposomes
Dyes and Pigments, 2008
Rose bengal is a water-soluble xanthene dye that is currently used in ophthalmology for the diagnosis of dry eyes. Although the dye is also a potential photosensitizer for photodynamic therapy of tumors, owing to insufficient lipophilicity and tumor accumulation, the clinical application of rose bengal in photodynamic therapy has been hampered. Liposomal encapsulation was seen as a promising approach to overcome these disadvantages, to which end, the spectral properties of the dye in the presence of materials for liposome preparation were studied. The presence of phospholipid influenced the spectral properties of the dye, probably due to the establishment of an equilibrium between monomeric and dimeric forms of the dye, since the photophysical properties of rose bengal depend strongly on its environment. The liposomal encapsulation of the dye generates stronger emission than the free form of the colorant; increased lipid:dye ratio further enhances this emission.
Carotenoids in Liposomes: Photodegradation, Excited State Lifetimes, and Energy Transfer
The Journal of Physical Chemistry B, 2000
DMPC (dimyristoyl-L-R-phosphatidylcholine) liposomes are used as artificial photosynthetic media to study the behavior of carotenoids. 8′-Apo--caroten-8′-al (I) and -carotene (II) degrade faster under irradiation in DMPC liposomes than in organic solvents, which is possibly because vibrational deactivation of carotenoid excited states is less efficient in rigid lipid membranes. The lifetime of the first excited singlet state (S 1 ) of I in DMPC liposomes is 27.2 ps, very close to that in 3-methylpentane (26.4 ps), but longer than its lifetime in EtOH (17.1 ps) or CH 2 Cl 2 (14.1 ps). The lifetime of the S 1 state of I in DMPC liposomes is as expected for an alkane environment. The lifetime of the S 1 state of II in DMPC liposomes is 10.3 ps, very close to its lifetimes in 3-methylpentane (8.1 ps), EtOH (9.2 ps), and CH 2 Cl 2 (8.5 ps). This independence of the S 1 state lifetime of II from the matrix agrees with earlier conclusions. Carotenoid I can suppress the photodegradation of chlorophyll a (Chl a) in liposomes, which shows the protection role of I on Chl a under strong irradiation. In liposomes, Chl a fluorescence quenching by I is observed when using either the Q y band or the Soret band of Chl a as the excitation line.
Archives of Biochemistry and Biophysics, 1996
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
Aggregation/disaggregation of chlorophyll a in model phospholipid–detergent vesicles and micelles
Photochemical & Photobiological Sciences, 2014
The photosynthetic pigments of higher plants exist in complex oligomeric states, which are difficult to study in vivo. To investigate aggregation processes of chlorophyll a (Chl a), we used an in vitro reconstitution procedure, with this pigment incorporated into liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), micelles and pre-micelle media of the detergent n-dodecyltrimethylammonium chloride (DTAC), and mixed, spontaneous, DMPC-DTAC vesicles and micelles. Chl a oligomers were characterized by UV-visible absorption, steady-state and time-resolved fluorescence, and fluorescence lifetime imaging microscopy. Equivalent diameters of the colloidal structures were obtained by fluorescence correlation spectroscopy. In DMPC liposomes and DMPC-DTAC vesicles and micelles, three fluorescence lifetimes indicated the coexistence of Chl a monomers (≈5 ns) and oligomers (≈1-2 to ≈0.1 ns). The increase in DTAC amount, in the mixed system, induces a progressive solubilization of DMPC liposomes (from vesicles to micelles) and simultaneous disruption of Chl a aggregates; in pure DTAC micelles, mostly monomers were found. The present work aims for a better understanding of chlorophyll-chlorophyll (Chl-Chl), Chl-lipid, and Chl-detergent interactions in spontaneous colloidal micro-and nanostructures. † Electronic supplementary information (ESI) available: (1) Turbidity correction of electronic absorption spectra of chlorophyll a in DMPC-DTAC media; (2) parameters of electronic absorption spectra of chlorophyll a in DMPC-DTAC media;
Journal of Luminescence, 2011
The association and photobehavior of Rose Bengal (RB) in the presence of dipalmitoylphosphatidyl choline (DPPC) small unilamellar liposomes is determined by the temperature. At temperatures above the main phase transition of the bilayer, the incorporation of the dye is ca. 2.5 times more efficient than that taking place when the bilayer is in the gel state. In both temperature ranges, adsorption isotherms show a noticeable anti-cooperativity that can be related to electrostatic repulsion between bound molecules. The photophysics and the photochemistry of the bound dye molecules also depend on the bilayer status. In particular, in the liquid crystalline state the surrounding of the dye is more polar and production of singlet oxygen is less efficient (F $ 0.1). This reduced singlet oxygen production is partially due to a low triplet yield (F T ¼0.35) and triplet self-quenching due to a high local RB concentration. In spite of these, tryptophan is efficiently photobleached when RB is associated to liposomes in the liquid crystalline state, probably due to a Type I mechanism favored by its high local concentration in the sensitized surroundings.
Photochemical and Photobiological Sciences
The photosynthetic pigments of higher plants exist in complex oligomeric states, which are difficult to study in vivo. To investigate aggregation processes of chlorophyll a (Chl a), we used an in vitro reconstitution procedure, with this pigment incorporated into liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), micelles and pre-micelle media of the detergent n-dodecyltrimethylammonium chloride (DTAC), and mixed, spontaneous, DMPC–DTAC vesicles and micelles. Chl a oligomers were characterized by UV-visible absorption, steady-state and time-resolved fluorescence, and fluorescence lifetime imaging microscopy. Equivalent diameters of the colloidal structures were obtained by fluorescence correlation spectroscopy. In DMPC liposomes and DMPC–DTAC vesicles and micelles, three fluorescence lifetimes indicated the coexistence of Chl a monomers (≈5 ns) and oligomers (≈1–2 to ≈0.1 ns). The increase in DTAC amount, in the mixed system, induces a progressive solubilization of DMP...
Chemistry and Physics of Lipids, 1984
The steady state fluorescence anisotropy (r s) of l-acyl-2-cis parinaroyl phosphatidylcholine (PnPC) was compared with that of diphenylhexatriene (DPH) in a variety of model-and biological membrane systems. The fluorescence anisotropy of both probes responded similarly to temperature changes and variations in the acyl chain composition in phosphatidylcholine (PC) liposomes. The presence of proteins and cholesterol increased r s for both DPH and PnPC in the biological membranes as compared to the isolated polar membrane lipids. Comparison of DPH and PnPC in dipalmitoyl-PC-liposomes with and without 50 mol% cholesterol, showed at temperatures above the phase transition of pure dipalmitoyl-PC the presence of cholesterol increased the rs-value for DPH strongly, whereas the rs-value for PnPC was much less affected. In the cholesterol-rich erythrocyte membrane as well as in microsomes from Morris hepatoma 7787, which have an increased cholesterol content as compared to normal rat liver microsomes, the r s of DPH was higher than that of PnPC. No large differences between the rs-values of both probes were evident in the normal cholesterol-poor rat liver microsomes. These effects are discussed in terms of structural differences between the probes and variation of cholesterol content. Alterations in the fatty acid composition of PC present in human erythrocyte membranes were introduced with the aid of a PC-specific transfer protein. Fluorescence anisotropy values of both probes hardly changed upon enrichment of the red cell membrane with either dipalmitoyl PC or 1-paimitoyl-2-arachidonyl PC.
Biophysical Journal, 1991
The sensitivity of Laurdan (6-dodecanoyl-2-dimethylaminonaphthalene) excitation and emission spectra to the physical state of the membrane arises from dipolar relaxation processes in the membrane region surrounding the Laurdan molecule. Experiments performed using phospholipid vesicles composed of phospholipids with different polar head groups show that this part of the molecule is not responsible for the observed effects. Also, pH titration in the range from pH 4 to 10 shows that the spectral variations are independent of the charge of the polar head. A two-state model of dipolar relaxation is used to qualitatively explain the behavior of Laurdan. It is concluded that the presence of water molecules in the phospholipid matrix are responsible for the spectral properties of Laurdan in the gel phase. In the liquid crystalline phase there is a relaxation process that we attribute to water molecules that can reorientate during the few nanoseconds of the excited state lifetime. The quantitation of lipid phases is obtained using generalized polarization which, after proper choice of excitation and emission wavelengths, satisfies a simple addition rule.
Journal of Photochemistry and Photobiology A-chemistry, 2006
Liposomes composed of cationic lipids and neutral phospholipids have been used as vehicles for cellular delivery of DNA and drug delivery. The aim of this study is to get a better understanding of phospholipid-cationic lipid interactions that is essential for the development of this potential. We have studied the interaction between cationic lipid liposomes primarily composed of dioctadecyldimethylammonium bromide (DODAB) with two different phospholipids, dioleoyl phosphatidylethanolamine (DOPE) and soybean phosphatidylcholine (PC), as well as with cholesterol. The effect of these components on the liposome's physical properties (microviscosity and polarity) was accessed by studying, both the steady-state and time-resolved, fluorescence anisotropy of the dye Nile Red. This information combined with analysis of the steady-state emission and fluorescence lifetime of Nile Red using the different lipids and cholesterol provided information concerning the polarity and hydration level changes in these vesicle systems along with organisational information.