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Kankan Bhattacharyya - One of the best experts on this subject based on the ideXlab platform.
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Intramolecular Charge Transfer Processes in Confined Systems. Nile Red in Reverse Micelles
The Journal of Physical Chemistry B, 1997Co-Authors: Anindya Datta, Debabrata Mandal, Samir Kumar Pal, Kankan BhattacharyyaAbstract:Intramolecular charge transfer (ICT) processes of the neutral fluorescence probe, Nile Red, I, confined in the water pool of aerosol-OT (AOT) reverse micelle in n-heptane, is studied using picosecond emission spectroscopy. Utilizing the solvatochromism of Nile Red, only those probe molecules inside the reverse micelle are selectively excited. It is observed that while in aqueous solutions the lifetime (τf) of Nile Red is 650 ps, inside the reverse micelles τf increases to 3.73 ns in reverse micelle and to 2.06 ns at the highest water content of the microemulsion (wo = 32). With increase in the water-to-surfactant ratio, wo, as the water pool swells in size, the lifetime and quantum yield of emission decrease and the rate of the ICT process of Nile Red increases. However, the magnitude of the change (at most 8 times) in the rate of the ICT process of Nile Red compaRed to that of ordinary water is much smaller than the several thousandfold decrease observed in the solvation dynamics of water in the water po...
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twisted charge transfer processes of Nile Red in homogeneous solutions and in faujasite zeolite
Langmuir, 1994Co-Authors: Nilmoni Sarkar, K Das, Debnarayan Nath, Kankan BhattacharyyaAbstract:Steady-state and time-resolved emission studies on Nile Red, a biological fluorescent probe, in homogeneous solutions and in zeolite 13X and LZY are reported. It is shown that at moderately high polarity the main nonradiative pathway of Nile Red is twisted intramolecular charge transfer (TICT) process, the rate of which increases exponentially with increase in polarity (ET(30)) of the medium. Due to this polarity-dependent TICT process Nile Red is a sensitive indicator of the micropolarity of biological environments. From the comparison of the emission properties of Nile Red in zeolite X and Y with those in homogeneous solutions the ET(30) values of zeolite 13X and LZY are estimated to be 55.5 ± 1. This indicates the polarity of the zeolites is similar to that of an aqueous methanol solution.
Angela Maria Falchi - One of the best experts on this subject based on the ideXlab platform.
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hydrophobic characterization of intracellular lipids in situ by Nile Red Red yellow emission ratio
Micron, 2008Co-Authors: Giacomo Diaz, Marta Melis, Barbara Batetta, Fabrizio Angius, Angela Maria FalchiAbstract:Abstract Nile Red (9-diethylamino-5H-benzo [α] phenoxazine-5-one) is a fluorescent lipophilic dye characterized by a shift of emission from Red to yellow according to the degree of hydrophobicity of lipids. Polar lipids (i.e., phospholipids) which are mostly present in membranes, are stained in Red whereas neutral lipids (esterified cholesterol and triglycerides) which are present in lipid droplets, are stained in yellow. Besides this marked, qualitative contrast between polar and neutral lipids, small differences of the hydrophobic strength could be assessed by the quantitative ratio of Red and yellow emissions, in order to extend the discrimination of lipids within the groups of neutral and polar lipids. On the other hand, ratiometric data of Red and yellow emissions have not yet been evaluated in the numerous previous light microscopy investigations which used Nile Red. In this work we show that the Nile Red Red/yellow ratio enables discrimination of different lipids (monooleine > oleic acid > phosphatidylcholine > free cholesterol > trioleine > oleyl cholesteryl ester). We also show changes in the Nile Red Red/yellow emission ratio of lipid droplets of 3T3 mouse fibroblasts induced by drugs interfering with the cholesterol cycle.
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Hydrophobic characterization of intracellular lipids in situ by Nile Red Red/yellow emission ratio.
Micron (Oxford England : 1993), 2008Co-Authors: Giacomo Diaz, Marta Melis, Barbara Batetta, Fabrizio Angius, Angela Maria FalchiAbstract:Abstract Nile Red (9-diethylamino-5H-benzo [α] phenoxazine-5-one) is a fluorescent lipophilic dye characterized by a shift of emission from Red to yellow according to the degree of hydrophobicity of lipids. Polar lipids (i.e., phospholipids) which are mostly present in membranes, are stained in Red whereas neutral lipids (esterified cholesterol and triglycerides) which are present in lipid droplets, are stained in yellow. Besides this marked, qualitative contrast between polar and neutral lipids, small differences of the hydrophobic strength could be assessed by the quantitative ratio of Red and yellow emissions, in order to extend the discrimination of lipids within the groups of neutral and polar lipids. On the other hand, ratiometric data of Red and yellow emissions have not yet been evaluated in the numerous previous light microscopy investigations which used Nile Red. In this work we show that the Nile Red Red/yellow ratio enables discrimination of different lipids (monooleine > oleic acid > phosphatidylcholine > free cholesterol > trioleine > oleyl cholesteryl ester). We also show changes in the Nile Red Red/yellow emission ratio of lipid droplets of 3T3 mouse fibroblasts induced by drugs interfering with the cholesterol cycle.
Kevin Burgess - One of the best experts on this subject based on the ideXlab platform.
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Energy transfer dyads based on Nile Red.
Tetrahedron letters, 2009Co-Authors: Jiney Jose, Yuichiro Ueno, Juan C. Castro, Kevin BurgessAbstract:Through-bond energy transfer is possible in molecules containing two fluorophores connected in such a way that they would be electronically conjugated if they were planar.1–6 Our group is interested in the applications of such dyads in biotechnology,7,8 especially for multiplexing experiments in which several outputs are to be observed from a single excitation source.9,10 Nile Red is a solvatochromic dye with solvent dependent emissions. In polar media Nile Red derivatives have emissions in the 630 – 650 nm region. Outputs at such wavelengths, ie longer than cellular autofluorescence,11 are highly desirable for cellular probes, so dyads containing Nile Red are logical targets, but they have not been described in the literature. Here we report the syntheses and photophysical properties of dyads 1 – 5. Dyads 1 – 3 have fluorescein-based donors, while BODIPY derivatives perform this role in 4 and 5. Three of the donor fragments A – C were prepaRed via methods already developed in this laboratory (Figure 2).12–14 The other donor, the BODIPY derivative 6, was synthesized from the nitro compound D15 via Reduction with hydrazine.13 The amine product is unstable hence it was immediately diazotized then treated with azide anion (reaction 1). Water-solubilities are important since the long-term goals of this research are to prepare probes that can be used in biological environments. Consistent with this idea, donors A C are very hydrophilic. Nile Red acceptors that also tend to improve water solubilities were available from previous work by others16 and by us.17 Compounds in this series typically fluoresce with quantum yields around 0.4 in EtOH and 0.3 in pH 7.4 phosphate buffer.17,18 Thus, the sulfonate 7 was made via triflation {PhN(Tf)2, NEt3, THF, 25 °C, 24 h}19 of the corresponding 2-hydroxy Nile Red derivative,16 and a similar reaction followed by Sonogashira coupling20 (of trimethylsilylethyne, then TBAF deprotection) gave derivatives 8 and 9. Scheme 1 outlines syntheses of the alkyne-linked dyads 1 – 3. The coupling reactions proceeded only above 100 °C, and 130 °C was preferRed. The dichlorofluorescein alkyne B is not very stable at 130 °C hence the coupling reaction using this was low yielding. Throughout, Pd(PPh3)4 was an effective catalyst while Cl2Pd(PPh3)2 did not give any significant amount of product. Scheme 1 Syntheses of the alkyne linked dyads 1 – 3. Dyads 4 and 5 were synthesized via copper catalyzed 1,3-dipolar cycloadditions using tris(1 - benzyl - 1H - 1,2,3 - triazol - 4 - yl)methyl amine (TBTA) ligand21 as a copper stabilizer (Scheme 2) without which the yields were poor. Reaction of the water-soluble BODIPY-azide C with the Nile Red alkyne 9, followed by hydrolysis in aqueous methanolic K2CO3 afforded cassette 4 as a dark purple material. The low yields obtained for these two dyads are probably due to the apparent instability of BODIPY fragments in basic aqueous media. Scheme 2 Synthesis of dyads 4 and 5. Absorption and emission profiles of dyads 1 – 5 in EtOH are shown in Figure 1. As expected, two distinct absorption maxima were observed in each case corresponding to the donor and acceptor fragments. Their fluorescence spectra show efficient energy transfer without significant —leakage of emission from the donor fragment. The prominent emissions from all the dyads derive from the acceptor fragment with comparatively less emission from the donor parts. Their quantum efficiencies when excited at the donor absorption maxima, were determined to be in the range of 0.31 – 0.41. The energy transfer efficiency (ETE %, quantum yield of cassette when excited at the donor divided by that when excited at the acceptor)10 was calculated to be 77 – 97 % (Table 1). The later parameter is less informative, because it does not take into account energy lost in other processes. The apparent Stokes’ shifts for the dyads ranged from 120 to 150 nm. Much less efficient energy transfer was observed for the dyads in aqueous buffer, but the large Stokes’ shifts persisted (see supplementary). Figure 1 Normalized absorbance (a) and fluorescence (b) spectra of dyads 1 – 5 in EtOH (at 10−6 and 10−7 M for absorbance and fluorescence measurements, respectively). All dyads excited at their respective donor absorption maxima. Table 1 Photophysical properties of dyads 1 – 5 in EtOH. In conclusion we have prepaRed five dyads based on Nile Red acceptors and fluorescein or BODIPY fragments as donors. These show efficient energy transfer in ethanol and fluoresce with a quantum yield of 0.31–0.41. Their long wavelength emission and large Stokes’ shifts are useful for fluorescence studies in polar, hydrogen-bonding, organic solvents. Our current efforts are focused on making similar dyads with improved photophysical properties for use in biological media.
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Syntheses and properties of water-soluble Nile Red derivatives.
The Journal of organic chemistry, 2006Co-Authors: Jiney Jose, Kevin BurgessAbstract:Nile Red (compound A) fluoresces at about 530 nm with good quantum yields in apolar solvents. In more polar ones its fluorescence emission shows a dramatic, and potentially useful, shift to about 640 nm, but its quantum yield is significantly Reduced. Further, Nile Red has a very poor solubility in aqueous media. The hypothesis tested in this paper is that Nile Red derivatives that incorporate water-solubilizing groups will tend to fluoresce with good quantum yields in aqueous media, and in the more useful wavelength range around 640 nm. Thus three Nile Red derivatives, 1-3, were prepaRed. Compound 1 had three hydroxyl groups more than Nile Red, but was surprisingly insoluble in aqueous media. However, the dicarboxylic acid 2 and carboxylic/sulfonic acid derivative 3 showed excellent water solubilities. Spectral data for 2 and 3 showed that they do indeed fluoresce with good quantum yields in the 640 nm region in aqueous media. These properties of compounds 2 and 3 might be useful in the development of fluorescent probes for biotechnology.
Jan B. F. N. Engberts - One of the best experts on this subject based on the ideXlab platform.
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the use of Nile Red to monitor the aggregation behavior in ternary surfactant water organic solvent systems
Journal of Physical Organic Chemistry, 2005Co-Authors: Marc C. A. Stuart, John C. Van De Pas, Jan B. F. N. EngbertsAbstract:Ternary systems of surfactants, water and organic solvents were studied by monitoring the steady-state fluorescence of the versatile solvatochromic probe Nile Red. We found not only that Nile Red can be used throughout the whole isotropic regions in the phase diagram, but also that subtle changes in the aggregation state of the surfactant can be monitoRed. The formation of inverted micelles in n-hexane could be followed upon the addition of small amounts of water, in addition to the formation of normal micelles in water and water-organic solvent mixtures. In aqueous C12EO4 solutions the temperature-dependent micelle-to-vesicle-to-inverted micelle transition was visualized by Nile Red fluorescence. Finally, the incorporation of solvent into the micellar interior could also be monitoRed using Nile Red as the probe. Copyright (c) 2005 John Wiley & Sons, Ltd.
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The use of Nile Red to monitor the aggregation behavior in ternary surfactant–water–organic solvent systems
Journal of Physical Organic Chemistry, 2005Co-Authors: Marc C. A. Stuart, John C. Van De Pas, Jan B. F. N. EngbertsAbstract:Ternary systems of surfactants, water and organic solvents were studied by monitoring the steady-state fluorescence of the versatile solvatochromic probe Nile Red. We found not only that Nile Red can be used throughout the whole isotropic regions in the phase diagram, but also that subtle changes in the aggregation state of the surfactant can be monitoRed. The formation of inverted micelles in n-hexane could be followed upon the addition of small amounts of water, in addition to the formation of normal micelles in water and water-organic solvent mixtures. In aqueous C12EO4 solutions the temperature-dependent micelle-to-vesicle-to-inverted micelle transition was visualized by Nile Red fluorescence. Finally, the incorporation of solvent into the micellar interior could also be monitoRed using Nile Red as the probe. Copyright (c) 2005 John Wiley & Sons, Ltd.
Anna Synak - One of the best experts on this subject based on the ideXlab platform.
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Concentration - dependent fluorescence properties of Nile Red in TiO2 based thin films
Journal of Molecular Liquids, 2020Co-Authors: Anna Synak, Beata Grobelna, Piotr Bojarski, Leszek Kułak, Elżbieta Szczepańska, Michał MońkaAbstract:Abstract Thin films of Nile Red in TiO2 matrix were prepaRed with the sol–gel method for different dye concentrations. It was found that at high dye concentration fluorescence and absorption spectra as well as fluorescence intensity decay and time-resolved fluorescence spectra exhibit strong changes. In particular, fluorescence spectra profiles are strongly shifted to the Red in a way typical of aggregate formation. Fluorescence intensity decays much faster with increase in concentration in the monomer band due to Nile Red aggregate formation and excitation energy trapping. Time-resolved fluorescence spectra exhibit strong evolution. Clear formation of aggregate band at the Red part of time-resolved emission spectra was observed.
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Enhanced emission of Nile Red on plasmonic platforms
Optical Materials, 2018Co-Authors: Anna Synak, Rafał Fudala, Beata Grobelna, Piotr Bojarski, Ignacy Gryczynski, Michal MońkaAbstract:Strongly enhanced fluorescence of Nile Red deposited in the vicinity of silver nanoparticles and gold semitransparent mirror was observed. The properties of three different plasmonic platforms based on TiO2, TiO2-GLYMO (1:1) and SiO2matrices were studied with spectroscopic and microscopic techniques. Significant differences of Nile Red spectroscopic properties in both matrices were observed. In particular, the sensitivity of Nile Red fluorescence enhancement and its peak location to the polarity of local surrounding was found.