Fluorescent molecular probes based on excited state prototropism in lipid bilayer membrane
02 Feb 2012-Proceedings of SPIE (International Society for Optics and Photonics)-Vol. 8233, pp 823309
TL;DR: The recent work using 1-naphthol as an ESPT fluorescent molecular probe has shown that the incorporation of monomeric bile salt molecules into lipid bilayer membranes composed from dipalmitoylphosphatidylcholine and dimyristoy lphosph atidyl choline induce appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low concentrations of the bile salts.
Abstract: Excited state prototropism (ESPT) is observed in molecules having one or more ionizable protons, whose proton
transfer efficiency is different in ground and excited states. The interaction of various ESPT molecules like naphthols
and intramolecular ESPT (ESIPT) molecules like hydroxyflavones etc. with different microheterogeneous media have
been studied in detail and excited state prototropism as a probe concept has been gaining ground. The fluorescence of
different prototropic forms of such molecules, on partitioning to an organized medium like lipid bilayer membrane,
often show sensitive response to the local environment with respect to the local structure, physical properties and
dynamics. Our recent work using 1-naphthol as an ESPT fluorescent molecular probe has shown that the incorporation
of monomeric bile salt molecules into lipid bilayer membranes composed from dipalmitoylphosphatidylcholine (DPPC,
a lung surfactant) and dimyristoylphosphatidylcholine (DMPC), in solid gel and liquid crystalline phases, induce
appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low (≤ 1 mM) concentrations of the
bile salts. The incorporation and location of fisetin, an ESIPT molecule having antioxidant properties, in lipid bilayer
membrane has been sensitively monitored from its intrinsic fluorescence behaviour.
Citations
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TL;DR: Lower-temperature shift in the phase transition of DPPC bilayer indicates that fluorescence anisotropy of ANS is sensitive enough to the bile salt induced perturbation in the packed acyl chains of DP PC bilayer and modification in the membrane fluidity.
Abstract: The photophysical behavior of 8-anilino-1-naphthalenesulphonate (ANS) in vesicles of dipalmitoylphosphatidylcholine (DPPC), a pulmonary surfactant, has been carried out in a detailed manner. ANS shows notable variations in fluorescence intensity, lifetime, and anisotropy parameters as it gets into the vesicle. It was found that ANS partitions well into the DPPC bilayer membrane with an estimated partition coefficient of ∼2.0 × 105. Among the various fluorescence parameters of ANS, fluorescence anisotropy was found to be most responsive to the temperature induced phase change of the bilayer membrane. These interesting fluorescence parameters of ANS were then used to study the hydration of lipid bilayer membrane by submicellar concentration of bile salts. From the steady-state fluorescence intensity and dynamic fluorescence lifetime analyses it is clear that ANS is able to probe the submicellar concentration (≤1 mM) of bile salt induced hydration of lipid bilayer membrane that accompanies expulsion of ANS f...
36 citations
References
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TL;DR: The kinetics of intervesicular P-C12-NBD-PC transfer in the presence of cholate were found to be consistent with a mass action kinetic model based on the premise that bile salts bind to the vesicles, alter the dissociation and/or association rate constants for phospholipid monomer-vesicle interaction, and increase the rate of phospholIPid transfer via the diffusion of soluble monomers through the aqueous phase.
Abstract: The rate of 1-palmitoyl-2-[12-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino] dodecanoyl] phosphatidylcholine (P-C12-NBD-PC) transfer between dioleoylphosphatidylcholine vesicles was measured by a technique based on resonance energy transfer between P-C12-NBD-PC and N-(lissamine rhodamine B sulfonyl)dioleoylphosphatidylethanolamine [Nichols, J. W., & Pagano, R. E. (1982) Biochemistry 21, 1720-1726]. Addition of bile salts at concentrations below their critical micelle concentrations increased the rate of spontaneous P-C12-NBD-PC transfer without disrupting the vesicles. The effectiveness in increasing the transfer rate was dependent on the structure of the bile salt. In general, conjugated bile salts were more effective than unconjugated, and mono- and dihydroxy bile salts were more effective than trihydroxy. The kinetics of intervesicular P-C12-NBD-PC transfer in the presence of cholate were found to be consistent with a mass action kinetic model based on the premise that bile salts bind to the vesicles, alter the dissociation and/or association rate constants for phospholipid monomer-vesicle interaction, and increase the rate of phospholipid transfer via the diffusion of soluble monomers through the aqueous phase. Temperature dependence studies indicated that cholate binding to vesicles is an entropy-driven process and that cholate binding lowers the free energy of activation for phospholipid monomer-vesicle dissociation by producing compensatory decreases in both the enthalpy and entropy of activation.
39 citations
TL;DR: Experimental results give evidence of two localization sites of naphthols in the microphase of micellar solutions and phospholipid vesicles by fluorescence spectra and kinetics.
Abstract: Protolytic photodissociation of some hydroxyaromatic compounds, ArOH (1- and 2-naphthol, chlorosubstituted naphthols), was studied in micellar solutions and phospholipid vesicles by fluorescence spectra and kinetics. Experimental results give evidence of two localization sites of naphthols in the microphase of these systems. In lipid bilayer membranes of vesicles there are two comparable fractions of ArOH molecules, one of which undergoes photodissociation but the other does not dissociate. In micelles, a minor fraction (few percent) of ArOH molecules, which are located probably in the core of the micelle, do not take part in excited-state proton-transfer reaction. These phenomena reflect heterogeneous structure and dynamic properties of lipid bilayer membranes and micelles.
33 citations
TL;DR: There is NaC-induced nanoscale aggregation of PNIPAM in its sol state and the lower critical solution temperature corresponding to sol-gel transition shifts to a lower temperature by about 2 °C.
Abstract: The effect of sodium cholate (NaC; concentration 1-16 mM), a biological surfactant, on the aggregation behavior of 1% (w/v, 2.2 × 10(-3) M) poly(N-isopropylacrylamide) (PNIPAM) aqueous solutions was studied as a function of temperature. From turbidity, dynamic light scattering, viscosity, and fluorescence measurements, it was observed that (i) there is NaC-induced nanoscale aggregation of PNIPAM in its sol state and (ii) the lower critical solution temperature corresponding to sol-gel transition shifts to a lower temperature by about 2 °C.
26 citations
"Fluorescent molecular probes based ..." refers background in this paper
...water, but becomes highly fluorescent with a blue shift in emission maximum in lesser polar solvents or on binding to hydrophobic systems.(19) The fluorescence properties of ANS are sensitive to the polarity of the microenvironment....
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TL;DR: A detailed account of the photophysical behaviour of PT and ground state anion (A−) of 3-hydroxyflavone in liposome membrane at various membrane conditions is presented in this paper.
Abstract: 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 A− population 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 A− is gradual
21 citations
"Fluorescent molecular probes based ..." refers background in this paper
...Previous studies on photophysical behaviour of 3-hydroxyflavone in DMPC liposome membrane suggests that the fluorescence of phototautomer form originates from the 3-hydroxyflavone molecules present at the hydrocarbon core of the bilayer membrane.(21) However, the fluorescence of fisetin phototautomer form comes from the membrane bound fisetin molecule, which is suggested to be near the bilayer interface....
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21 Aug 2001
TL;DR: In this article, the authors describe the photochemical behaviour of coumarins and related systems in the crystalline state of cyclodextrin materials, including assembly of ions, molecules, metal complexes, and proteins.
Abstract: Ortho photocycoladdition of alkenes and alkynes to the Benzene ring photocycloaddition and photoaddition reactions of aromatic compounds singlet oxygen ene sensitised photooxygenations - stereochemistry and mechanisms singlet oxygen reactions - solvent and compartmentalization effects microreactor-controlled product selectivity in organic photochemical reactions enantioselective photoreactions in the solid state observations on the photochemical behaviour of coumarins and related systems in the crystalline state supramolecular photochemistry of cyclodextrin materials photoactive layered materials - assembly of ions, molecules, metal complexes, and proteins fluorescence of excited singlet state acids in certain organized media - applications as molecular probes.
21 citations
"Fluorescent molecular probes based ..." refers background in this paper
...with different microheterogeneous media have been studied in detail and excited state prototropism as a probe concept has been gaining ground.(1) The fluorescence of different prototropic forms of such molecules, on partitioning to an organized medium like lipid bilayer membrane, often show sensitive response to the local environment with respect to the local structure, physical properties and dynamics....
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