In this study, 1-naphthol has been used as a sensitive ESPT fluorescent molecular probe to investigate the interaction of submicellar concentrations of two physiologically important bile salts, sodium deoxycholate and sodium cholate, with dipalmitoylphosphatidylcholine small unilamellar vesicles in solid gel and liquid crystalline phases. Steady-state and time-resolved fluorescence of the two excited state prototropic forms of 1-naphthol indicate that the incorporation of monomeric bile salt molecules in the lipid bilayer membrane induces appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low (≤1 mM) concentrations of the bile salts. © 2010 American Chemical Society.

Ashok Kumar Mishra

Department Of Chemistry

Monalisa Mohapatra

Body fluids

Excited states

Fluorescence

Hydrocarbons

Lipid bilayers

Phenols

Probes

Surface active agents

1-NAPHTHOL

Bi-layer

Bilayer membranes

BILE SALTS

Dipalmitoyl phosphatidylcholine

HYDROCARBON CORES

LIPID BILAYER MEMBRANES

LIQUID-CRYSTALLINE PHASIS

Lung surfactants

Molecular Probes

Small unilamellar vesicle

Sodium Cholate

SODIUM DEOXYCHOLATE

Time-resolved fluorescence

Salts

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Physical Chemistry B

This study demonstrates that significant perturbation of tween20:cholesterol(1:1) niosome membrane takes place even at premicellar concentration of bile salts. Here, 1-naphthol (1-NpOH), a known and sensitive excited state proton transfer (ESPT) probe, was used to understand the nature of perturbation of the membrane in an unbuffered medium. The significant decrease in 1-NpOH fluorescence intensity in niosome-bile salt mixed system at both lower (10 °C) and higher (50 °C) temperatures indicates the bile salts [sodium cholate (NaC) and sodium deoxycholate (NaDC)] induce perturbation of niosome membranes. Variations in the fluorescence lifetime values of both the prototropic emissions (neutral and anionic species) along with the proton transfer rate of 1-NpOH confirm the bile salts perturb up to the hydrophobic core domain of the niosomal membranes. Bile salts induce size change of the niosomal membrane is confirmed through dynamic light scattering study. © 2019 Elsevier B.V.

Fulltext

Colloids and Surfaces B: Biointerfaces

Significant bile salt induced perturbation of niosome membrane: A molecular level interaction study using 1-Naphthol fluorescence

This study reports the utility of the hydrophobic probe Nile Red (NR) to understand the concentration induced microenvironmental changes of sodium deoxycholate (NaDC) bile salt from the premicellar to postmicellar range. The spectroscopic properties like absorbance value, fluorescence intensity and fluorescence lifetime of NR are significantly sensitive towards different states of aggregation of NaDC bile salt. The critical aggregation concentrations of different states (dimer to primary micellar aggregates (1.0 mM), secondary micellar aggregates (7.0 mM), and higher micellar aggregates (14 mM)) have been determined from the absorbance value and fluorescence intensity measurements. The ET(30) polarity parameter values suggest a considerable decrease in the micropolarity with an increase in NaDC concentrations. Furthermore, the spectroscopic properties of NR are also sensitive towards the NaCl induced gelation process of NaDC bile salt. Changes in the micropolarity and microviscosity of the NaDC + NaCl mixed system have been estimated using the emission maximum value (cm-1) and fluorescence lifetime values of NR with an increase in the NaCl concentration. Microviscosity of the medium increases from ∼19 mPa s to ∼26 mPa s from the sol phase to the gel phase. Temperature dependence of both size and phase changes of the NaDC + NaCl (30 mM + 1 M) gel network has been studied using differential scanning calorimetry and dynamic light scattering studies. Temperature induced polarity and microviscosity changes of the NaDC + NaCl (30 mM + 1 M) gel network have also been studied using the fluorescence properties of NR. This journal is © The Royal Society of Chemistry and Owner Societies.

Photochemical and Photobiological Sciences

Quantification of micropolarity and microviscosity of aggregation and salt-induced gelation of sodium deoxycholate (NaDC) using Nile red fluorescence

This work uses the dynamics of the excited state proton transfer of 1-naphthol to water as a basis for understanding the temperature-dependent changes in the water accessibility of the niosome membrane domain. The decrease in the neutral form fluorescence intensity of membrane bound 1-naphthol, the significant drop in the membrane-bound anion form fluorescence lifetime, and the changes in the fluorescence lifetime distribution plots of the two prototropic forms of 1-naphthol indicate a regular increase in the water penetration in the interfacial region of the niosome membrane domain, whereas the dry core regions appear unaffected with increasing temperature (10-60 °C). Unlike some liposomes and niosomes, these niosomes do not show thermotropic phase transition behavior. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

New Journal of Chemistry

Temperature-dependent water penetration in Tween20:cholesterol niosome membrane: A study using excited state prototropism of 1-naphthol

This work focuses on the study of aqueous phase aggregation of the recently FDA approved oral drug molecule FTY720 (fingolimod hydrochloride) and its effect on dimyristoylphosphatidylcholine (DMPC) liposomes using different fluorescent molecular probes and fluorescence parameters. The variation of the steady state fluorescence intensity of 8-anilino-1-naphthalene sulfonic acid (ANS) with FTY720 in water shows an efficient micellar aggregation with the critical micellar concentration (CMC) at ∼75 μM. The aggregation number calculation from steady state fluorescence quenching of pyrene shows the formation of small micellar aggregates in aqueous solution having an aggregation number of 42 ± 3 with the free energy of micellization ∼-23 kJ mol-1. Fluorescence intensity and lifetime decay analysis of the molecular probe 1-naphthol indicate that the interaction of FTY720 with the DMPC lipid bilayer membrane prevents partitioning of small molecules such as 1-naphthol to the membrane in both solid gel (SG) and liquid crystalline (LC) phases. Temperature dependent fluorescence intensity studies of 1-naphthol and fluorescence anisotropy measurements of 1,6-diphenyl-1,3,5-hexatriene (DPH) have shown that above the CMC of FTY720, the SG to LC main phase transition temperature (TM) of the lipid bilayer membrane decreases from 23°C to 21°C in the aqueous medium. © 2013 the Owner Societies.

Physical Chemistry Chemical Physics

Study of aqueous phase aggregation of FTY720 (fingolimod hydrochloride) and its effect on DMPC liposomes using fluorescent molecular probes

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 from the bilayer to the aqueous bulk phase. 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 DPPC bilayer and modification in the membrane fluidity. In presence of sodium deoxycholate (NaDC) and sodium cholate (NaC) in DPPC vesicles, ANS experiences restriction in rotational mobility which is evident from the variation in steady-state fluorescence anisotropy and fluorescence anisotropy decay parameters. © 2013 American Chemical Society.

Langmuir

Photophysical behavior of 8-anilino-1-naphthalenesulfonate in vesicles of pulmonary surfactant dipalmitoylphosphatidylcholine (DPPC) and its sensitivity toward the bile salt-vesicle interaction

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. © The Royal Society of Chemistry and Owner Societies 2009.

Photophysical behaviour of ground state anion and phototautomer of 3-hydroxyflavone in liposome membrane

Effects of two bile salts, namely sodium deoxycholate (NaDC) and sodium cholate (NaC), on DPPC small unilamellar vesicles have been investigated using the steady-state fluorescence anisotropy (rss) of diphenylhexatriene (DPH) as a tool. It was found that the variation of rss is sensitive enough to monitor different stages of interaction of bile salts with DPPC vesicles. NaDC induced significant changes in the membrane well below its CMC (6 mM). Even at 4 mM, which is still lower than the CMC, the phospholipids were completely solubilised by the NaDC micelles. The effect of NaC on DPPC vesicles, however, was much less significant, especially in the sub-micellar concentration regime. Being more hydrophilic NaC does not interact with the membrane efficiently. Complete solubilisation of phospholipids took place only when the concentration of NaC was above its CMC (16 mM). The experiments also showed that the bile salt-induced changes of vesicle structure were strongly dependent on the concentration of the bile salt and not on the molar ratio of lipid and bile salt. © Indian Academy of Sciences.

Journal of Chemical Sciences

Effect of sodium deoxycholate and sodium cholate on DPPC vesicles: A fluorescence anisotropy study with diphenylhexatriene

In this work we have tried to evaluate the usefulness of 1-naphthol as an excited state proton transfer fluorescent probe for studying the ethanol-induced interdigitation in lipid bilayer membranes. When ethanol concentration in lipisome is progressively increased, the neutral form fluorescence of 1-naphthol is found to decrease with corresponding increase in the anionic form intensity. This behavior is in contrast to that observed in the absence of lipid where a reverse effect is noticed. Modification of lipid bilayer is known to occur in the presence of ethanol, which increases the packing density of the membrane. Due to this induction of interdigitated gel phase, redistribution of naphthol between the inner core and interfacial region of the lipid bilayer takes places, accounting for the reduction in neutral form fluorescence intensity. The partition coefficient values and the quenching studies also support the redistribution of 1-naphthol in the liposome membrane. The neutral form fluorescence of 1-naphthol successfully monitors the shift in phase transition temperature due to ethanol-induced interdigitation. It also explains the prevention of interdigitation in lipid bilayer at high cholesterol concentration.

Photochemistry and Photobiology

Evaluation of 1-naphthol as a convenient fluorescent probe for monitoring ethanol-induced interdigitation in lipid bilayer membrane

They Wished They Were Honest

12. Waverly Logan

Photochemical & Photobiological Sciences

Preface

1-naphthol as a sensitive fluorescent molecular probe for monitoring the interaction of submicellar concentration of bile salt with a bilayer membrane of DPPC, a lung surfactant

Journal	Data powered by TypesetJournal of Physical Chemistry B
Publisher	Data powered by TypesetAmerican Chemical Society
ISSN	15206106
Open Access	No