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Sarkar P, Chattopadhyay A. Membrane Dipole Potential: An Emerging Approach to Explore Membrane Organization and Function. J Phys Chem B 2022; 126:4415-4430. [PMID: 35696090 DOI: 10.1021/acs.jpcb.2c02476] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biological membranes are complex organized molecular assemblies of lipids and proteins that provide cells and membrane-bound intracellular organelles their individual identities by morphological compartmentalization. Membrane dipole potential originates from the electrostatic potential difference within the membrane due to the nonrandom arrangement (orientation) of amphiphile and solvent (water) dipoles at the membrane interface. In this Feature Article, we will focus on the measurement of dipole potential using electrochromic fluorescent probes and highlight interesting applications. In addition, we will focus on ratiometric fluorescence microscopic imaging technique to measure dipole potential in cellular membranes, a technique that can be used to address novel problems in cell biology which are otherwise difficult to address using available approaches. We envision that membrane dipole potential could turn out to be a convenient tool in exploring the complex interplay between membrane lipids and proteins and could provide novel insights in membrane organization and function.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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Sahu AK, Das A, Ghosh A, Raj S. Understanding blue shift of the longitudinal surface plasmon resonance during growth of gold nanorods. NANO EXPRESS 2021. [DOI: 10.1088/2632-959x/abd966] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Abstract
We have investigated in detail the growth dynamics of gold nanorods with various aspect ratios in different surrounding environments. Surprisingly, a blue shift in the temporal evolution of colloidal gold nanorods in aqueous medium has been observed during the growth of nanorods by UV–visible absorption spectroscopy. The longitudinal surface plasmon resonance peak evolves as soon as the nanorods start to grow from spheres, and the system undergoes a blue shift in the absorption spectra. Although a red-shift is expected as a natural phenomenon during the growth process of all nano-systems, our blue shift observation is regarded as a consequence of competition between the parameters of growth solution and actual growth of nanorods. The growth of nanorods contributes to the red-shift which is hidden under the dominating contribution of the growth solution responsible for the observed massive blue shift.
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Garcia A, Lev B, Hossain KR, Gorman A, Diaz D, Pham THN, Cornelius F, Allen TW, Clarke RJ. Cholesterol depletion inhibits Na +,K +-ATPase activity in a near-native membrane environment. J Biol Chem 2019; 294:5956-5969. [PMID: 30770471 PMCID: PMC6463725 DOI: 10.1074/jbc.ra118.006223] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 02/08/2019] [Indexed: 12/28/2022] Open
Abstract
Cholesterol's effects on Na+,K+-ATPase reconstituted in phospholipid vesicles have been extensively studied. However, previous studies have reported both cholesterol-mediated stimulation and inhibition of Na+,K+-ATPase activity. Here, using partial reaction kinetics determined via stopped-flow experiments, we studied cholesterol's effect on Na+,K+-ATPase in a near-native environment in which purified membrane fragments were depleted of cholesterol with methyl-β-cyclodextrin (mβCD). The mβCD-treated Na+,K+-ATPase had significantly reduced overall activity and exhibited decreased observed rate constants for ATP phosphorylation (ENa3+ → E2P, i.e. phosphorylation by ATP and Na+ occlusion from the cytoplasm) and K+ deocclusion with subsequent intracellular Na+ binding (E2K2+ → E1Na3+). However, cholesterol depletion did not affect the observed rate constant for K+ occlusion by phosphorylated Na+,K+-ATPase on the extracellular face and subsequent dephosphorylation (E2P → E2K2+). Thus, partial reactions involving cation binding and release at the protein's intracellular side were most dependent on cholesterol. Fluorescence measurements with the probe eosin indicated that cholesterol depletion stabilizes the unphosphorylated E2 state relative to E1, and the cholesterol depletion-induced slowing of ATP phosphorylation kinetics was consistent with partial conversion of Na+,K+-ATPase into the E2 state, requiring a slow E2 → E1 transition before the phosphorylation. Molecular dynamics simulations of Na+,K+-ATPase in membranes with 40 mol % cholesterol revealed cholesterol interaction sites that differ markedly among protein conformations. They further indicated state-dependent effects on membrane shape, with the E2 state being likely disfavored in cholesterol-rich bilayers relative to the E1P state because of a greater hydrophobic mismatch. In summary, cholesterol extraction from membranes significantly decreases Na+,K+-ATPase steady-state activity.
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Affiliation(s)
- Alvaro Garcia
- From the School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, Sydney, NSW 2006, Australia
| | - Bogdan Lev
- the School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Khondker R Hossain
- From the School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Amy Gorman
- From the School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia; the Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Dil Diaz
- From the School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | | | - Flemming Cornelius
- the Department of Biomedicine, University of Aarhus, DK-8000 Aarhus C, Denmark
| | - Toby W Allen
- the School of Science, RMIT University, Melbourne, VIC 3001, Australia; the Department of Chemistry, University of California, Davis, California 95616
| | - Ronald J Clarke
- From the School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, Sydney, NSW 2006, Australia.
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Effect of Cholesterol on the Dipole Potential of Lipid Membranes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:135-154. [DOI: 10.1007/978-3-030-04278-3_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Solubilization of the serotonin 1A receptor monitored utilizing membrane dipole potential. Chem Phys Lipids 2017; 209:54-60. [DOI: 10.1016/j.chemphyslip.2017.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 10/02/2017] [Accepted: 10/02/2017] [Indexed: 12/31/2022]
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Davis BM, Brenton J, Davis S, Shamsher E, Sisa C, Grgic L, Cordeiro MF. Assessing anesthetic activity through modulation of the membrane dipole potential. J Lipid Res 2017; 58:1962-1976. [PMID: 28818873 PMCID: PMC5625120 DOI: 10.1194/jlr.m073932] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 08/09/2017] [Indexed: 12/21/2022] Open
Abstract
There is great individual variation in response to general anesthetics (GAs) leading to difficulties in optimal dosing and sometimes even accidental awareness during general anesthesia (AAGA). AAGA is a rare, but potentially devastating, complication affecting between 0.1% and 2% of patients undergoing surgery. The development of novel personalized screening techniques to accurately predict a patient’s response to GAs and the risk of AAGA remains an unmet clinical need. In the present study, we demonstrate the principle of using a fluorescent reporter of the membrane dipole potential, di-8-ANEPPs, as a novel method to monitor anesthetic activity using a well-described inducer/noninducer pair. The membrane dipole potential has previously been suggested to contribute a novel mechanism of anesthetic action. We show that the fluorescence ratio of di-8-ANEPPs changed in response to physiological concentrations of the anesthetic, 1-chloro-1,2,2-trifluorocyclobutane (F3), but not the structurally similar noninducer, 1,2-dichlorohexafluorocyclobutane (F6), to artificial membranes and in vitro retinal cell systems. Modulation of the membrane dipole provides an explanation to overcome the limitations associated with the alternative membrane-mediated mechanisms of GA action. Furthermore, by combining this technique with noninvasive retinal imaging technologies, we propose that this technique could provide a novel and noninvasive technique to monitor GA susceptibility and identify patients at risk of AAGA.
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Affiliation(s)
| | - Jonathan Brenton
- University College London Institute of Ophthalmology, London EC1V 9EL, United Kingdom
| | - Sterenn Davis
- University College London Institute of Ophthalmology, London EC1V 9EL, United Kingdom
| | - Ehtesham Shamsher
- University College London Institute of Ophthalmology, London EC1V 9EL, United Kingdom
| | - Claudia Sisa
- University College London Institute of Ophthalmology, London EC1V 9EL, United Kingdom
| | - Ljuban Grgic
- University College London Institute of Ophthalmology, London EC1V 9EL, United Kingdom
| | - M Francesca Cordeiro
- University College London Institute of Ophthalmology, London EC1V 9EL, United Kingdom .,Western Eye Hospital, Imperial College Healthcare National Health Service Trust, and Imperial College Ophthalmic Research Group, Imperial College London, London NW1 5QH, United Kingdom
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Differential Membrane Dipolar Orientation Induced by Acute and Chronic Cholesterol Depletion. Sci Rep 2017; 7:4484. [PMID: 28667339 PMCID: PMC5493612 DOI: 10.1038/s41598-017-04769-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 05/22/2017] [Indexed: 02/02/2023] Open
Abstract
Cholesterol plays a crucial role in cell membrane organization, dynamics and function. Depletion of cholesterol represents a popular approach to explore cholesterol-sensitivity of membrane proteins. An emerging body of literature shows that the consequence of membrane cholesterol depletion often depends on the actual process (acute or chronic), although the molecular mechanism underlying the difference is not clear. Acute depletion, using cyclodextrin-type carriers, is faster relative to chronic depletion, in which inhibitors of cholesterol biosynthesis are used. With the overall goal of addressing molecular differences underlying these processes, we monitored membrane dipole potential under conditions of acute and chronic cholesterol depletion in CHO-K1 cells, using a voltage-sensitive fluorescent dye in dual wavelength ratiometric mode. Our results show that the observed membrane dipole potential exhibits difference under acute and chronic cholesterol depletion conditions, even when cholesterol content was identical. To the best of our knowledge, these results provide, for the first time, molecular insight highlighting differences in dipolar reorganization in these processes. A comprehensive understanding of processes in which membrane cholesterol gets modulated would provide novel insight in its interaction with membrane proteins and receptors, thereby allowing us to understand the role of cholesterol in cellular physiology associated with health and disease.
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Sethy D, Chakraborty H. Micellar dipolar rearrangement is sensitive to hydrophobic chain length: Implication for structural switchover of piroxicam. Chem Phys Lipids 2016; 200:120-125. [PMID: 27680423 DOI: 10.1016/j.chemphyslip.2016.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 09/06/2016] [Accepted: 09/21/2016] [Indexed: 10/21/2022]
Abstract
The interfacial properties of the membrane are exceptionally vital in drug-membrane interaction. They not only select out a particular prototropic form of the drug molecule for incorporation, but are also potent enough to induce structural switchover of these drugs in several cases. In this work, we quantitatively monitored the change in dipolar rearrangement of the micellar interface (as a simplified membrane mimic) by measuring the dielectric constant and dipole potential with the micellization of SDS at pH 3.6. The dielectric constant and dipole potential were measured utilizing the fluorescence of polarity sensitive probe, pyrene and potential-sensitive probe, di-8-ANEPPS, respectively. Our study demonstrates that the change in dipolar rearrangement directly influences the switchover equilibrium between the anionic and neutral from of piroxicam. We have further extended our work to evaluate the effect of hydrophobic chain length of the surfactants on the dipolar rearrangement and its effect on the structural switchover of piroxicam. It is interesting that the extent of switchover of piroxicam is directly correlated with the dipolar rearrangement induced bythe varying hydrophobic chain length of the surfactants. To the best of our knowledge, our results constitute the first report to show the dependence of dipole potential on the hydrophobic chain length of the surfactant and demonstrate that the dipolar rearrangement directly tunes the extent of structural switchover of piroxicam, which was so far only intuitive. We consider that this new finding would have promising implication in drug distribution and drug efficacy.
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Affiliation(s)
- Dasaratha Sethy
- School of Chemistry, Sambalpur University, Burla, Odisha 768 019, India
| | - Hirak Chakraborty
- School of Chemistry, Sambalpur University, Burla, Odisha 768 019, India.
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