Photo-effect in phospholipid liposome containing riboflavin (original) (raw)
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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.
Photochemistry and Photobiology, 1980
The fate of excitation energy and electron transfer to quinones within Chl-u-containing phosphatidyl choline liposomes has been investigated. The bilayer membrane of the liposome stabilizes the Chl triplet state, as evidenced by a threefold increase in the lifetime over that observed in ethanol solution. The relative triplet yield follows the relative fluorescence yield, indicative of quenching at the singlet level. Triplet state lifetimes are markedly shortened as the Chl concentration is increased. demonstrating that quenching occurs at the triplet level as well. This process is shown to be due to a collisional de-excitation. In the presence of quinones, the Chl triplet reduces the quinone resulting in production of long-lived electron transfer products. The percent conversion of Chl triplet to cation radical when benzoquinone is employed as acceptor is approximately 60 f lo?;, which is slightly less than in ethanol solution (70 f lo",). The lifetime of the radical, however, can be as much as 1900 times longer. With respect to potentially useful photochemical energy conversion. the magnitude of this increased lifetime is far more significant than is the decreased radical yield.
Photochemical & Photobiological Sciences, 2009
A detailed account of the photophysical behaviour of the phototautomer (PT) and the ground state anion (A-) of 3-hydroxyflavone in liposome membrane at various membrane conditions is presented. A quenching study with a hydrophilic quencher Ag + suggests that the phototautomeric emission generates from the fraction of 3HF that is located at the inner hydrophobic core, whereas the ground state anionic emission is from the fraction that resides near the water-accessible surface site. However, the biexponential nature of fluorescence decays of both the forms indicates that there is local heterogeneity in the distribution. Temperature dependence studies and experiments in the presence of ethanol reveal that, as the membrane becomes more fluid, redistribution of 3HF takes place between the two sites leading to increase in Apopulation. The temperature dependence of the fluorescence anisotropy change of PT shows good correlation with the phase change and shows a sharp drop at the transition temperature, whereas the corresponding change in the case of Ais gradual.
Photo-dynamics of roseoflavin and riboflavin in aqueous and organic solvents
Chemical Physics, 2009
a b s t r a c t and riboflavin in aqueous and organic solvents are studied by optical absorption spectroscopy, fluorescence spectroscopy, and fluorescence decay kinetics. Solvent polarity dependent absorption shifts are observed. The fluorescence quantum yields are solvent dependent. For roseoflavin the fluorescence decay shows a bi-exponential dependence (ps to sub-ps time constant, and 100 ps to a few ns time constant). The roseoflavin photo-dynamics is explained in terms of fast intra-molecular charge transfer (diabatic electron transfer) from the dimethylamino electron donor group to the pteridin carbonyl electron acceptor followed by intra-molecular charge recombination. The fast fluorescence component is due to direct locally-excited-state emission, and the slow fluorescence component is due to delayed locally-excited-state emission and charge transfer state emission. The fluorescence decay of riboflavin is mono-exponential. The S 1 -state potential energy surface is determined by vibronic relaxation and solvation dynamics due to excited-state dipole moment changes (adiabatic optical electron transfer).
The Journal of Physical Chemistry C, 2013
We show that Forster resonance energy transfer (FRET) between a conjugated oligoelectrolyte based on distyrylstilbene (DSSN+) and Nile red can enhance photocurrent generation when the photoagents are assembled vertically on gold electrodes. DSSN+ and Nile red intercalated into phospholipid membranes of unilamellar vesicles were found to form a useful FRET system because of the solvatochromic properties of DSSN +, and the accompanying photophysical properties were suitable for FRET with Nile red. As a result, a FRET efficiency of 93−94% was achieved, as shown by steady-state and time-resolved spectra in vesicle solutions. When Nile red was tethered in a selfassembled monolayer of 11-mercaptoundecanoic acid (MUA) on gold electrodes and phospholipid-assembled DSSN+ was sequentially organized on the MUA layer, the anodic photocurrent increased notably, reaching about 815 nA/cm 2 by virtue of FRET between the vertically aligned dyes.
Journal of Biomedical Optics, 2008
The time-resolved fluorescence of photosensitizers ͑PSs͒ of varying hydrophobicities, di-and tetrasulfonated Al phthalocyanines ͑Al-2 and Al-4͒, and Photochlor® ͑HPPH͒, was investigated in liposomes used as cell-mimetic models. Using frequency-and timedomain apparatus, the fluorescence lifetime, fluo , was compared for PSs free in aqueous solution and in a liposome-associated state at varied temperatures ͑25 to 78°C͒ and oxygen concentrations ͑0-190 M͒. The analysis of fluo revealed different decay behaviors for the free-solution and liposome-confined PSs, most significantly for the lipophilic HPPH. Hydrophilic PS drugs ͑Al-4, Al-2͒ were less affected by the liposomal confinement, depending on the relative hydrophilicity of the compound and the consequent localization in lipsomes. Changes in the emission decay due to confinement were detected as differences in the lifetime between the bulk solution and the liposome-localized PS in response to heating and deoxygenation. Specifically, hydrophilic Al-4 produced an identical lifetime trend as a function of temperature both in solu and in a liposome-confined state. Hydrophobic HPPH exhibited a fundamental transformation in its fluorescence decay kinetics, transitioning from a multiexponential ͑in free solution͒ to single-exponential ͑in liposome͒ decay. Deoxygenation resulted in a ubiquitous fluo increase for all PSs in free solution, while the opposite, a fluo decrease, occurred in all liposomal PSs.
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
Light-Triggered Liposomal Release: Membrane Permeabilization by Photodynamic Action
Langmuir, 2010
Photosensitized damage to liposome membranes was studied by using different dye-leakage assays based on fluorescence dequenching of a series of dyes upon their release from liposomes. Irradiation of liposomes with red light in the presence of a photosensitizer, trisulfonated aluminum phthalocyanine (AlPcS 3 ), resulted in the pronounced leakage of carboxyfluorescein, but rather weak leakage of sulforhodamine B and almost negligible leakage of calcein from the corresponding dye-loaded liposomes. The same series of selectivity of liposome leakage was obtained with chlorin e6 that appeared to be more potent than AlPcS 3 in bringing about the photosensitized liposome leakage. Electrically neutral zinc phthalocyanine tetrasubstituted with a glycerol moiety (ZnPcGlyc 4 ) was less effective than negatively charged AlPcS 3 in provoking the light-induced liposome permeabilization. On the contrary, both ZnPcGlyc 4 and AlPcS 3 were much more effective than chlorin e6 in sensitizing gramicidin channel inactivation in planar bilayer lipid membranes, thus showing that relative photodynamic efficacy of sensitizers can differ substantially for damaging different membrane targets. The photosensitized liposome permeabilization was apparently associated with oxidation of lipid double bonds by singlet oxygen as evidenced by the mandatory presence of unsaturated lipids in the membrane composition for the photosensitized liposome leakage to occur and the sensitivity of the latter to sodium azide. The fluorescence correlation spectroscopy measurements revealed marked permeability of photodynamically induced pores in liposome membranes for such photosensitizer as AlPcS 3 .
Functional reconstitution of photosynthetic cyclic electron transfer in liposomes
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1989
The interaction of solubilized reaction centers from the phototrophic bacterium, Rhodobacter sphaeroides, and the solubilized ubiquinol-cytochrome c oxidoreductase of Rhodobacter capsulatus was studied in solution and after coreconstitution in liposomes prepared from Escherichia coli phospholipids. Under both conditions, the ubiquinol-cytochrome c oxidoreductase increased the light-induced cyclic electron transfer, induced by reaction centers with 2,3-dimethoxy-5-methyl-6-(prenyl)z-l,4-benzoqumone and cytochrome c as redox mediators. This effect was more pronounced at acid pH values. The light-induced cyclic electron transfer in these liposomes resulted in the generation of a protonmotive force. Under conditions where the protonmotive force was composed of a membrane potential only, the highest membrane potential (approx.-200 mV) was generated when 2,3-dimethoxy-5-methyl-6-(prenyl)lo-l,4-benzoquinone was used as redox mediator and when both electron transfer proteins were co-reconstituted in a 2:1 molar ratio. At acid pH non-transitent membrane potentials could be generated only in liposomes containing both reaction centers and the ubiquinol-cytochrome c oxidoreductase. These observations show that the pH-dependent direct oxidation of cytochrome c by ubiquinol in the liposomes was indeed catalyzed by the ubiquinol-cytochrome c oxidoreductase and that this oxidoreductase participates in proton pumping. This could also be concluded from the stimulating effect of 2,3-dimethoxy-5-methyl-6-(prenyl)t0-1,4-benzoquinone on the membrane-potential-generating capacities in liposomes containing both electron transfer complexes. Such a stimulation was not observed in liposomes containing only reaction centers. The presence of cytochrome c in the co-reconstituted system was found to be essential for proton pumping.