Organization and Dynamics of Membrane Probes and Proteins Utilizing the Red Edge Excitation Shift

Haldar, Sourav; Chaudhuri, Arunima; Chattopadhyay, Amitabha

doi:10.1021/jp200255e

Cited by 90 publications

(113 citation statements)

References 128 publications

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Section: Resultsmentioning

confidence: 82%

“…1b). These results suggest that the BODIPY moiety of the probe is localized at the interfacial region of the membrane, a region characterized by unique dynamics and dielectric properties (Haldar et al, 2011).We have previously shown that cholesterol content in hippocampal membranes can be efficiently modulated using MβCD as it forms a selective inclusion complex with cholesterol by including it in the central nonpolar cavity (Pucadyil and Chattopadhyay, 2004). Fig.…”

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confidence: 77%

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Molecular rheology of neuronal membranes explored using a molecular rotor: Implications for receptor function

Pal

Chakraborty

Bandari

et al. 2016

Chemistry and Physics of Lipids

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The role of membrane cholesterol as a crucial regulator in the structure and function of membrane proteins and receptors is well documented. However, there is a lack of consensus on the mechanism for such regulation. We have previously shown that the function of an important neuronal receptor, the serotonin1A receptor, is modulated by cholesterol in hippocampal membranes. With an overall objective of addressing the role of 3 membrane physical properties in receptor function, we measured the viscosity of hippocampal membranes of varying cholesterol content using a meso-substituted fluorophore (BODIPY-C12) based on the BODIPY probe. BODIPY-C12 acts as a fluorescent molecular rotor and allows measurement of hippocampal membrane viscosity through its characteristic viscosity-sensitive fluorescence depolarization. A striking feature of our results is that specific agonist binding by the serotonin1A receptor exhibits close correlation with hippocampal membrane viscosity, implying the importance of global membrane properties in receptor function. We envision that our results are important in understanding GPCR regulation by the membrane environment, and is relevant in the context of diseases in which GPCR signaling plays a major role and are characterized by altered membrane fluidity.Abbreviations: 2-AS, 2-(9-anthroyloxy)stearic acid; 12-AS, 12-(9-anthroyloxy)stearic acid; BODIPY, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; GPCR, G protein-coupled receptor; 8-12-PC, 1-palmitoyl-2-(12-doxyl)stearoyl-sn-glycero-3-phosphocholine; DMPC, 1,2-dimyristoyl-sn-glycero-3-phosphocholine; DOPC, 1,2-dioleoylsn-glycero-3-phosphocholine; MβCD, methyl-β-cyclodextrin; Tempo-PC, 1,2-dioleoyl-snglycero-3-phosphotempocholine Keywords: Molecular rotor; hippocampal membrane; viscosity; cholesterol; neuronal receptor IntroductionBiological membranes are complex, highly organized, two-dimensional, supramolecular assemblies of a diverse variety of lipids and proteins. The function of membranes is to allow cellular compartmentalization, and impart an identity to individual cells and organelles, besides providing an appropriate environment for proper functioning of membrane proteins. Interestingly, cellular membranes in the nervous system are characterized by very high concentration and remarkable diversity of lipids, and these are correlated with increased complexity in the function of the nervous system (Sastry, 1985;Wenk, 2005). In this context, cholesterol represents an important lipid since brain cholesterol has been implicated in a number of neurological disorders (Chattopadhyay and Paila, 2007;Martín et al., 2014), some of which share a common etiology of defective cholesterol 4 metabolism in the brain (Porter and Herman, 2011). More importantly, the function of neuronal receptors depends on cholesterol (Pucadyil and Chattopadhyay, 2006;Allen et al., 2007;Paila and Chattopadhyay, 2010;Jafurulla and Chattopadhyay, 2013), which affects neurotransmission, resulting in mood and anxiety disorders (Papakostas et al., 2004). In spite of ...

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Section: Resultsmentioning

confidence: 82%

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confidence: 77%

Molecular rheology of neuronal membranes explored using a molecular rotor: Implications for receptor function

Pal

Chakraborty

Bandari

et al. 2016

Chemistry and Physics of Lipids

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“…Under such a condition, solvent relaxation slows down dramatically, making the membrane/water interface the most "REES-prone" region of the lipid bilayer. 48,49 Figure 2a shows the emission wavelengths (λ em ) of oligocholates 2 and 3 as a function of the excitation wavelength (λ ex ) at [oligocholate]/[phospholipids] = 0.05% (Figure 2a). Glucose transport at this level of the oligocholates (cyclic or linear) was negligible.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Effects of Amphiphile Topology on the Aggregation of Oligocholates in Lipid Membranes: Macrocyclic versus Linear Amphiphiles

Widanapathirana

Zhao

2012

Langmuir

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A macrocyclic and a linear trimer of a facially amphiphilic cholate building block were labeled with a fluorescent dansyl group. The environmentally sensitive fluorophore enabled the aggregation of the two oligocholates in lipid membranes to be studied by fluorescence spectroscopy. Concentration-dependent emission wavelength and intensity revealed a higher concentration of water for the cyclic compound. Both compounds were shown by the red-edge excitation shift (REES) to be located near the membrane/water interface at low concentrations, but the cyclic trimer was better able to migrate into the hydrophobic core of the membrane than the linear trimer. Fluorescent quenching by a water-soluble (NaI) and a lipid-soluble (TEMPO) quencher indicated that the cyclic trimer penetrated into the hydrophobic region of the membrane more readily than the linear trimer, which preferred to stay close to the membrane surface. The fluorescent data corroborated with the previous leakage assays that suggested the stacking of the macrocyclic cholate trimer into transmembrane nanopores, driven by the strong associative interactions of water molecules inside the macrocycles in a nonpolar environment. Disciplines Chemistry CommentsReprinted (adapted) with permission from Langmuir 28 (2012) ABSTRACT: A macrocyclic and a linear trimer of a facially amphiphilic cholate building block were labeled with a fluorescent dansyl group. The environmentally sensitive fluorophore enabled the aggregation of the two oligocholates in lipid membranes to be studied by fluorescence spectroscopy. Concentration-dependent emission wavelength and intensity revealed a higher concentration of water for the cyclic compound. Both compounds were shown by the red-edge excitation shift (REES) to be located near the membrane/water interface at low concentrations, but the cyclic trimer was better able to migrate into the hydrophobic core of the membrane than the linear trimer. Fluorescent quenching by a water-soluble (NaI) and a lipid-soluble (TEMPO) quencher indicated that the cyclic trimer penetrated into the hydrophobic region of the membrane more readily than the linear trimer, which preferred to stay close to the membrane surface. The fluorescent data corroborated with the previous leakage assays that suggested the stacking of the macrocyclic cholate trimer into transmembrane nanopores, driven by the strong associative interactions of water molecules inside the macrocycles in a nonpolar environment.

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“…The dipolar relaxation time of the solvent shell around a polar fluorophore becomes comparable to or longer than its fluorescence lifetime in motionally restricted environment and this gives rise to photoselection of differentially relaxed population of fluorophores upon excitation toward the red edge [39][40][41][42][43][44]. The fact that the fluorophore in REES measurements merely acts as a reporter group and allows to monitor the mobility parameters of the environment itself (represented by the relaxing solvent molecules) adds to its uniqueness.…”

Section: Red Edge Excitation Shift Of Brain Spectrin In Native and Urmentioning

confidence: 99%

Organization and Dynamics of Tryptophan Residues in Brain Spectrin: Novel Insight into Conformational Flexibility

et al. 2015

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Brain spectrin enjoys overall structural and sequence similarity with erythroid spectrin, but less is known about its function. We utilized the fluorescence properties of tryptophan residues to monitor their organization and dynamics in brain spectrin. Keeping in mind the functional relevance of hydrophobic binding sites in brain spectrin, we monitored the organization and dynamics of brain spectrin bound to PRODAN. Results from red edge excitation shift (REES) indicate that the organization of tryptophans in brain spectrin is maintained to a considerable extent even after denaturation. These results are supported by acrylamide quenching experiments. To the best of our knowledge, these results constitute the first report of the presence of residual structure in urea-denatured brain spectrin. We further show from REES and time-resolved emission spectra that PRODAN bound to brain spectrin is characterized by motional restriction. These results provide useful information on the differences between erythroid spectrin and brain spectrin.

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Organization and Dynamics of Membrane Probes and Proteins Utilizing the Red Edge Excitation Shift

Cited by 90 publications

References 128 publications

Molecular rheology of neuronal membranes explored using a molecular rotor: Implications for receptor function

Molecular rheology of neuronal membranes explored using a molecular rotor: Implications for receptor function

Effects of Amphiphile Topology on the Aggregation of Oligocholates in Lipid Membranes: Macrocyclic versus Linear Amphiphiles

Organization and Dynamics of Tryptophan Residues in Brain Spectrin: Novel Insight into Conformational Flexibility

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