Photophysics of a β-carboline based non-ionic probe in anionic and zwitterionic liposome membranes (original) (raw)
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Interaction of a cationic phenazinium dye, phenosafranin (PSF), with the anionic liposomal vesicle/bilayer of dimyristoyl-l-␣-phosphatidylglycerol (DMPG) has been demonstrated using steady state and time resolved fluorescence and fluorescence anisotropy techniques. The charge transfer emission spectrum of PSF shows a dramatic modification in terms of fluorescence yield together with an appreciable hypsochromic shift in the lipid environment. The blue shift indicates a lowering in polarity inside the vesicle as compared to that in bulk water. The fluorescence and fluorescence quenching studies and micropolarity determination reveal that the cationic fluorophore has a profound binding interaction with the anionic DMPG membrane. Anisotropy study indicates the imposition of a motional restriction on the probe inside the bilayer. The electrostatic interaction between the cationic dye and the anionic lipid membrane has been argued to be the reason behind all these observations. The results could be useful in analyzing membrane organization and heterogeneity in natural membranes exploiting PSF or alike compounds as fluorescent probes.
Fluorescence Behavior of the pH-Sensitive Probe Carboxy SNARF-1 in Suspension of Liposomes¶
When exposed to the intracellular environment fluorescent probes sensitive to pH exhibit changes of photophysical characteristics as a result of an interaction of the dye molecule with cell constituents such as proteins, lipids or nucleic acids. This effect is reflected in calibration curves different from those found with the same dye in pure buffer solutions. To study an interaction of the probe 5(and 6)-carboxy-10-dimethylamino-3-hydroxyspiro[7H-benzo[c]xanthene-7,1(3H)-isobenzofuran]-3one (carboxy SNARF-1) with membrane lipids, we measured its fluorescence in model systems of large unilamellar vesicles (LUV) prepared by extrusion. When the dye was removed from the bulk solution by gel filtration the relative fluorescence intensity of the lipid-bound dye form was enhanced, showing a strong interaction of the dye molecule with LUV membrane lipids. Surprisingly, the dye molecules seem to be bound predominantly to the outer surface of the lipid bilayer. The same situation was found with small unilamellar vesicles prepared by sonication. This effect makes it difficult to use carboxy SNARF-1 for measurements of the internal pH in suspensions of liposomes.
Imidazo[1,5-a]pyridine-Based Fluorescent Probes: A Photophysical Investigation in Liposome Models
Molecules
Imidazo[1,5-a]pyridine is a stable scaffold, widely used for the development of emissive compounds in many application fields (e.g., optoelectronics, coordination chemistry, sensors, chemical biology). Their compact shape along with remarkable photophysical properties make them suitable candidates as cell membrane probes. The study of the membrane dynamics, hydration, and fluidity is of importance to monitor the cellular health and to explore crucial biochemical pathways. In this context, five imidazo[1,5-a]pyridine-based fluorophores were synthesized according to a one-pot cyclization between an aromatic ketone and benzaldehyde in the presence of ammonium acetate and acetic acid. The photophysical features of prepared compounds were investigated in several organic solvents and probes 2–4 exhibited the greatest solvatochromic behavior, resulting in a higher suitability as membrane probes. Their interaction with liposomes as artificial membrane model was tested showing a successful i...
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
Biophysical Chemistry, 1985
Molecular relaxation fluorescence methods were applied to analyze the nature and characteristic times of motions of amphiphilic molecules absorbed in the polar region of a phospholipid bilayer. The fluorescence probes 2-toluidinonaphthalene-6-sulfonate and I-anilinonaphthalene-8-sulfonate in egg phosphatidylcholine vesicles were studied. The methods of edge excitation fluorescence red shifts, nanosecond time-resolved spectroscopy, fluorescence quenching by hydrophilic and hydrophobic quenchers and emission wavelength dependence of polarization were used. The structural (dipolar) relaxation is shown to be a very rapid (subnanosecond) process. The observed nanosecond phenomena are related to translational movement of the chromophore itself towards a more polar environment and its rotation. The polar surface area of the phospholipid membrane appears to be a highly mobile liquid-like system.
Chemistry & Biology, 2002
Gebze-Kocaeli 41470 applied probes for fluorescent labeling. In addition to high chemical and photochemical stability and high fluo-Turkey 2 Department of Chemistry rescence quantum yield, they should provide strong change of color in response to different membrane per-Kyiv National Shevchenko University 01033 Kiev turbations. In this sense the common polarity-sensitive [5] and electrochromic [6] dyes have very limited capa-3 A.V. Palladin Institute of Biochemistry 9 Leontovicha Street bilities, as these probes commonly provide the response by shifting one broad band that is present in emission, 01030 Kiev Ukraine and the magnitude of the shift is usually smaller than the bandwidth. In order to be sensitive to the two-band 4 Laboratoire de Pharmacologie et Physicochimie des Interactions Cellulaires et Molé culaires ratiometric probe, the dye is required to exhibit an excited-state reaction: isomerization, electronic charge UMR 7034 du CNRS Faculté de Pharmacie transfer, or proton transfer [7]
FEBS Letters, 2001
We report on dramatic differences in fluorescence spectra of 4P P-dimethylamino-3-hydroxyflavone (probe F) studied in phospholipid membranes of different charge (phosphatidyl glycerol, phosphatidylcholine (PC), their mixture and the mixture of PC with a cationic lipid). The effect consists in variations of relative intensities at two well-separated band maxima at 520 and 570 nm belonging to normal (N*) and tautomer (T*) excited states of flavone chromophore. Based on these studies we propose a new approach to measure electrostatic potential at the surface layer of phospholipid membranes, which is based on potential-dependent changes of bilayer hydration and involves very sensitive and convenient ratiometric measurements in fluorescence emission. ß 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.
Langmuir, 1998
Interaction of the coronary vasodilator dipyridamole (DIP) with vesicles of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG), and mixtures of them has been studied by fluorescence spectroscopy of the drug. Association constants were determined both below and above the phase transition temperature for the lipids, at different pHs (4.0 and 7.0). These constants at pH 7.0 were 633 M-1 (30°C) and 1.15 × 10 3 M-1 (50°C) for pure DPPC and 727 M-1 (30°C) and 1.48 × 10 3 M-1 (50°C) for pure DPPG. At pH 4.0 the association constants showed different behavior; Kb values decreased by a factor of 3 for DPPC but increased for DPPG due to the electrostatic interaction of the protonated drug with the phospholipid headgroup. In the mixed system formed by DPPC and DPPG (11% and 20%) the resulting variations in the mixture compositions have a marked effect on drug-vesicle interaction; a decrease of the association constants was observed consistent with a more tightly packed bilayer. Steady-state anisotropy binding data demonstrated the validity of the two-state binding model. Fluorescence quenching experiments with 5-doxylstearic acid (5-DSA) were also performed at pH 4 and pH 7 and with different compositions of lipids. The results support the interfacial location of the drug (close to the fifth carbon of the alkyl chain), suggesting also a strong dependence of binding on lipid packing and the presence of charges at the membrane interface. Fluorescence anisotropy decay experiments were also performed for dipyridamole (DIP) in pure DPPC and DPPG at different pHs and temperatures. The results show clearly that the initial anisotropy r0 of DIP in model systems (glycerol, sucrose) is quite high, above 0.3, attaining values of 0.20-0.24 in DPPG and being smaller in DPPC. These values are consistent with steady-state anisotropy values at saturating lipid concentrations. The anisotropy decays are best described as a single rotational correlation time which varies in the range 1.5-5.0 ns together with a limiting anisotropy value which also varies between 0.03 and 0.08. Data for anisotropy are in agreement with the binding data, also suggesting the location of the drug at the membrane interface.
Photochemical & Photobiological Sciences, 2012
The present work demonstrates the interaction of promising cancer cell photosensitizer, harmane (HM), with liposome membranes of varying surface charges, dimyristoyl-L-α-phosphatidylcholine (DMPC) and dimyristoyl-L-α-phosphatidylglycerol (DMPG). Electrostatic interaction of the cationic probe (HM) with the surface charges of the lipids is responsible for differential modulation of the spectral properties of the drug in different lipid environments. Estimation of partition coefficient (K p (±10%) = 5.58 × 10 4 in DMPC and 3.28 × 10 5 in DMPG) of HM between aqueous buffer and lipid phases reflect strong binding interaction of the drug with both the lipids. Evidence for greater degree of partitioning of HM into DMPG membrane compared to DMPC membrane has been deduced and further substantiated from experimental studies such as steady-state fluorescence anisotropy, micropolarity determination. The molecular modeling investigation by docking simulation coupled with fluorescence quenching experiment has been exploited to substantiate the location of drug at the lipid head-group region. Modulation of the dynamical properties of the drug within the lipid environments has also been addressed. Rotational relaxation dynamics studies unravel the impartation of a significant degree of motional restriction on the probe molecule within the lipids and reinforce the differential interactions of HM with the two lipid systems along the lines of other findings. Fluorescence kinetics studies reveal a faster association (in terms of apparent rate constants describing the process of interaction) of the drug with DMPG membrane compared to DMPC. This result is argued in connection with the electrostatic interaction between the drug and the liposome surface charges.