2-Naphthol-phosphatidylethanolamine: A fluorescent phospholipid analogue for excited-state proton transfer studies in membranes

Neyroz, Paolo; Franzoni, L.; Menna, Carolina; Spisni, Alberto; Masotti, Lanfranco

doi:10.1007/bf00732052

Cited by 9 publications

(7 citation statements)

References 45 publications

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“…7- Azaindole dimers, , 3-hydroxyflavone, hydroxyarenes (ROH) like naphthols, − phenols, hydroxyquinones, , pyranine, , and their derivatives exhibit interesting excited-state proton-transfer dynamics. Such excited-state dynamics are often governed by the properties of the microenvironment of the fluorophore and so these fluorophores can be used as probes in microheterogeneous media. , [2,2′-Bipyridyl]-3,3′-diol (BP(OH) 2 ) is one such fluorescent molecule which exhibits excited-state intramolecular double proton transfer (ESIDPT) (Scheme ). This molecule is reported to be planar with two strong intramolecular hydrogen bonds in its dienol tautomeric form (DE) by single-crystal X-ray analysis, and this form exists in all nonaqueous solvents .…”

Section: Introductionmentioning

confidence: 99%

Modulation of Ground- and Excited-State Dynamics of [2,2′-Bipyridyl]-3,3′-diol by Micelles

Datta

2011

J. Phys. Chem. B

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The binding of [2,2'-bipyridyl]-3,3'-diol (BP(OH)(2)) with ionic and neutral surfactants like cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Triton X-100 (TX-100) has been studied by steady-state and time-resolved fluorescence spectroscopy. The absorption as well as emission spectra of BP(OH)(2) are highly sensitive toward the variation of surfactant concentration and hydrophobicity of the environment. The fluorescent state of the diketo form gains stability in surfactant assemblies, leading to a red-shifted emission spectra. A sharp increase in the fluorescence quantum yield near critical micellar concentration (CMC) is encountered followed by saturation. This indicates a complete encapsulation of BP(OH)(2) in the micelles. The maximum fluorescence quantum yield in anionic SDS is rationalized by the formation of cationic fluorophore at the Stern layer. The increase in quantum yield in neutral TX-100 is attributed to higher microviscosity experienced by the fluorophore in the palisade layer. A direct support in favor of this argument in TX-100 is provided by the viscosity dependence exhibited by the probe in different concentrations of sucrose solutions. CTAB exhibiting only hydrophobic effect shows least increase in qunatum yield of BP(OH)(2) among all the surfactants. Time-resolved fluorescence study of BP(OH)(2) in micelles is used as a tool to monitor the extent of micellization in the lipophilic cavity. An increase in fluorescence quantum yield as well as lifetime of BP(OH)(2) upon micellization indicates an enhanced extent of ESIDPT in hydrophobic medium.

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Section: Introductionmentioning

confidence: 99%

Modulation of Ground- and Excited-State Dynamics of [2,2′-Bipyridyl]-3,3′-diol by Micelles

Datta

2011

J. Phys. Chem. B

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“…These molecules can be photoinduced to tautomerize in the excited state, and upon returning to the ground state, reverse tautomerization brings the molecule to its original structure. Due to their extreme sensitivity to solvent polarity and hydrogen bonding with protic solvents, some of these molecules have been suggested as probes for the study of protein conformation and binding sites. – We proposed one such molecule, which is 2,2′-bipyridine-3,3′-diol (BP(OH) 2 ), as a sensitive probe to report on its local environment change by examining its steady-state spectra in different environments. – …”

Section: Introductionmentioning

confidence: 99%

Steady-State and Time-Resolved Spectroscopy of 2,2′-Bipyridine-3,3′-diol in Solvents and Cyclodextrins: Polarity and Nanoconfinement Effects on Tautomerization

Abou‐Zied

2009

J. Phys. Chem. B

146

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The ground- and excited-state tautomerization of the 2,2'-bipyridine-3,3'-diol molecule (BP(OH)(2)) was studied in different solvents and in confined nanocavities of cyclodextrins (CDs) using steady-state and lifetime spectroscopic measurements. In all solvents, a dizwitterion (DZ) tautomer is produced in the excited state after intramolecular double-proton transfer. This tautomer is stabilized in the ground state in water only and produces two unique absorption peaks in the region of 400-450 nm. The DZ tautomer fluoresces in the green and as the solvent polarity increases, the fluorescence peak is blue-shifted (498 nm in cyclohexane versus 462 nm in water), and the fluorescence lifetime gets shorter (3.10 ns in cyclohexane versus 0.65 ns in water). The results indicate the sensitivity of this tautomer to solvent polarity, particularly the solvent's hydrogen-bonding capability. In water, another photoinduced tautomerization mechanism takes place via a water network solvating each of the two hydrogen-bonding centers of the molecule. The second tautomer is detected as a small shoulder in the blue side of the fluorescence peak and has a lifetime of 5.40 ns. Using BP(OH)(2) to probe the nanocavities of aqueous CDs reveals the degree of hydrophobicity of the cavities and the different mechanisms of probe encapsulation. As the cavity size decreases in the order gamma-CD to beta-CD to alpha-CD, the cavity is more hydrophobic, which is reflected in an intensity decrease of the absorbance of the DZ tautomer and a red shift in its fluorescence peak. The measured lifetimes show the same trend and reveal how the probe interacts with the CD moiety. In gamma-CD, the probe is located near the secondary rim of the CD annulus, whereas in alpha-CD, the probe is completely sequestered between two CDs, and the hydrophobicity is close to that observed in cyclohexane. In beta-CD and its derivatives, the spectral changes and the measured lifetimes indicate that the CD cavity gets more hydrophobic as a result of methyl substitution of the primary and secondary hydroxyls of the beta-CD rims. In the fully methylated 2,3,6-tri-O-methyl-beta-CD, the probe is exposed to water near the secondary rim due to the steric effect at the entrance rim that prevents the probe from full encapsulation.

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“…These changes generally are observed by monitoring the variation of photophysical properties, such as fluorescence anisotropy and lifetime, spectral position, and fluorescence quantum yield of the dye within the bilayers (1)(2)(3)(4). Recently, molecules showing excited-state protontransfer (ESPT) reactions have been suggested as probes for the study of protein conformation and binding-sites (5)(6)(7)(8). ESPT reactions are very fast elementary processes (9)(10)(11) involved in various area of physics, chemistry, and biology (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18).…”

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confidence: 99%

A coupled proton-transfer and twisting-motion fluorescence probe for lipid bilayers

Mateo

Douhal²

1998

Proc. Natl. Acad. Sci. U.S.A.

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A new and sensitive molecular probe, 2-(2-hydroxyphenyl)imidazo[1,2-a]pyridine (HPIP), for monitoring structural changes in lipid bilayers is presented. Migration of HPIP from water into vesicles involves rupture of hydrogen (H) bonds with water and formation of an internal H bond once the probe is inside the vesicle. These structural changes of the dye allow the occurrence of a photoinduced intramolecular proton-transfer reaction and a subsequent twisting͞rotational process upon electronic excitation of the probe. The resulting large Stokes-shifted f luorescence band depends on the twisting motion of the zwitterionic phototautomer and is characterized in vesicles of dimyristoylphosphatidylcholine and in dipalmitoyl-phosphatidylcholine at the temperature range of interest and in the presence of cholesterol. Because the f luorescence of aqueous HPIP does not interfere in the emission of the probe within the vesicles, HPIP proton-transfer͞twisting motion f luorescence directly allows us to monitor and quantify structural changes within bilayers. The static and dynamic f luorescence parameters are sensitive enough to such changes to suggest this photostable dye as a potential molecular probe of the physical properties of lipid bilayers.Several fluorescent organic molecules have been described as molecular probes of structural and dynamical changes in lipid bilayers (1-3). These changes generally are observed by monitoring the variation of photophysical properties, such as fluorescence anisotropy and lifetime, spectral position, and fluorescence quantum yield of the dye within the bilayers (1-4). Recently, molecules showing excited-state protontransfer (ESPT) reactions have been suggested as probes for the study of protein conformation and binding-sites (5-8). ESPT reactions are very fast elementary processes (9-11) involved in various area of physics, chemistry, and biology (6-18). Because of the observed large Stokes-shifted fluorescence of the proton-transfer band in these systems, such molecules might show some advantages with respect to others having a normal Stokes-shifted emission band.Very recently, we have shown that the ESPT cycle can be coupled to a cis-trans isomerization reaction resulting in the formation of a rotamer of the phototautomer and opening a possible way to store information at a molecular level (15). We also reported on the photophysics and cyclodextrin inclusion of a dye, 2-(2Ј-hydroxyphenyl)imidazo[1,2-a]pyridine (HPIP, Fig. 1). HPIP shows ESPT in fluid (16) and restricted media (cyclodextrins, CDx) (17). More specifically, we showed that the proton motion within the internal H bond of this dye in the first electronically excited state generates a zwitterionic phototautomer emitting a large Stokes-shifted fluorescence band. In rigid media [poly(methyl methacrylate) films or in CDx] the yellow-green fluorescence comes from the tautomer 2 or one of its close rotamers (17). In fluid media 2 gives rise to the red-emitting species 3 through a rotational process around the C 2 OC 1Ј si...

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2-Naphthol-phosphatidylethanolamine: A fluorescent phospholipid analogue for excited-state proton transfer studies in membranes

Cited by 9 publications

References 45 publications

Modulation of Ground- and Excited-State Dynamics of [2,2′-Bipyridyl]-3,3′-diol by Micelles

Modulation of Ground- and Excited-State Dynamics of [2,2′-Bipyridyl]-3,3′-diol by Micelles

Steady-State and Time-Resolved Spectroscopy of 2,2′-Bipyridine-3,3′-diol in Solvents and Cyclodextrins: Polarity and Nanoconfinement Effects on Tautomerization

A coupled proton-transfer and twisting-motion fluorescence probe for lipid bilayers

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