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Kumar D, Gayen A, Chandra M. Membrane Permeability Dominates over Electrostatic Interactions in Dictating Drug Transport in Osmotically Shocked Escherichia coli. J Phys Chem B 2024; 128:4911-4921. [PMID: 38736363 DOI: 10.1021/acs.jpcb.3c08426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
To combat surging multidrug-resistant Gram-negative bacterial infections, better strategies to improve the efficacy of existing drugs are critical. Because the dual membrane cell envelope is the first line of defense for these bacteria, it is crucial to understand the permeation properties of the drugs through it. Our recent study shows that isosmotic conditions prevent drug permeation inside Gram-negative bacteria, Escherichia coli, while hypoosmotic stress enhances the process. Here, we unravel the reason behind such differential drug penetration. Specifically, we dissect the roles of electrostatic screening and low membrane permeability in the penetration failure of drugs under osmotically balanced conditions. We compare the transport of a quaternary ammonium compound malachite green in the presence of an electrolyte (NaCl) and a wide variety of commonly used organic osmolytes, e.g., sucrose, proline, glycerol, sorbitol, and urea. These osmolytes of different membrane permeability (i.e., nonpermeable sucrose and NaCl, freely permeable urea and glycerol, and partially permeable proline and sorbitol) clarify the role of osmotic stress in cell envelope permeability. The results showcase that under balanced osmotic conditions, drug molecules fail to penetrate inside E. coli cells because of low membrane permeabilities and not because of electrostatic screening imposed by the osmolytes. Contribution of the electrostatic interactions, however, cannot be completely overruled as at osmotically imbalanced conditions, drug transport across the bacterial subcellular compartments is found to be dependent on the osmolytes used.
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Affiliation(s)
- Deepak Kumar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India
| | - Anindita Gayen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India
| | - Manabendra Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India
- Center of Excellence: Tropical and Infectious Diseases, Gangwal School of Medical Sciences and Technology, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India
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2
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Effah F, Elzein A, Taiwo B, Baines D, Bailey A, Marczylo T. In Vitro high-throughput toxicological assessment of E-cigarette flavors on human bronchial epithelial cells and the potential involvement of TRPA1 in cinnamon flavor-induced toxicity. Toxicology 2023; 496:153617. [PMID: 37595738 DOI: 10.1016/j.tox.2023.153617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 08/06/2023] [Accepted: 08/15/2023] [Indexed: 08/20/2023]
Abstract
Electronic cigarettes (ECs) are considered a less hazardous alternative to tobacco smoking but are not harmless. Growing concerns about the safety profiles of flavors in e-liquids underpin the need for this study. Here, we screened 53 nicotine-free flavored e-liquids (across 15 flavor categories) across a 3-point concentration range (0.25%, 0.5%, and 1% v/v) in a high-throughput fashion in human bronchial epithelial (HBEC-3KT) submerged cell cultures to identify 'toxic hits' using in vitro endpoint assays comprising cell count, cell viability, and lactate dehydrogenase (LDH). We observed significant, dose-dependent adverse effects only with cinnamon, vanilla tobacco, and hazelnut e-liquids compared to media-only and PG/VG vehicle controls. Hence, we further analyzed these three flavors for their effects on HBEC-3KT proliferation, mitochondrial health, and oxidative stress. A significant decrease in cell proliferation after 36 h was observed for each e-liquid toxic hit compared to media-only and PG/VG controls. Hazelnut (at all concentrations) and vanilla tobacco (1%) increased cytoplasmic reactive oxygen species generation compared to media-only and PG/VG controls. Conversely, all three flavors at 0.5% and 1% significantly decreased mitochondrial membrane potential compared to PG/VG and media-only controls. Chemical analysis revealed that all three flavors contained volatile organic compounds. We hypothesized that the cytotoxicity of cinnamon might be mediated via TRPA1; however, TRPA1 antagonist AP-18 (10 μM) did not mitigate these effects, and cinnamon significantly increased TRPA1 transcript levels. Therefore, pathways mediating cinnamon's cytotoxicity warrant further investigations. This study could inform public health authorities on the relative health risks assessment following exposure to EC flavor ingredients.
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Affiliation(s)
- Felix Effah
- Pharmacology Section, St George's University of London, Cranmer Terrace, SW17 0RE London, UK; UK Health Security Agency, Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxfordshire OX11 ORQ, UK.
| | - Atallah Elzein
- UK Health Security Agency, Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxfordshire OX11 ORQ, UK
| | - Benjamin Taiwo
- Physiology Section, St George's University of London, Cranmer Terrace, SW17 0RE London, UK
| | - Deborah Baines
- Infection and Immunity Institute, St George's University of London, Cranmer Terrace, SW17 0RE London, UK
| | - Alexis Bailey
- Pharmacology Section, St George's University of London, Cranmer Terrace, SW17 0RE London, UK
| | - Tim Marczylo
- UK Health Security Agency, Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxfordshire OX11 ORQ, UK.
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3
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Sabo AN, Filaudeau E, Da Silva S, Becker G, Monassier L, Kemmel V. Flavoured and nicotine-containing e-liquids impair homeostatic properties of an alveolar-capillary cell model. Food Chem Toxicol 2023; 174:113650. [PMID: 36758787 DOI: 10.1016/j.fct.2023.113650] [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: 08/29/2022] [Revised: 01/26/2023] [Accepted: 02/01/2023] [Indexed: 02/11/2023]
Abstract
Most people consider that electronic cigarettes are safer than tobacco and are marketed as quit-smoking products. The e-liquid, which usually contains propylene glycol (PG) and vegetable glycerin (VG) in different ratios, nicotine and a wide variety of flavours, is heated by a coil and the aerosol droplets are primarily delivered to the alveolar area where nicotine and other molecules cross the alveolar-capillary barrier (ACB). However, e-cigarettes effects on the ACB are not yet established. In our study, a well-characterised in vitro model of the ACB was exposed to PG and VG and to five flavoured e-liquids with and without nicotine. The vehicles, due to their hypertonic properties, modulated the ACB integrity by modifying occludin expression. Below a 10% concentration, the vehicles did not trigger oxidative stress or cell death. Different results were observed between flavoured e-liquids: while red fruits and mint-eucalyptus disrupted ACB integrity, triggered oxidative stress and cell death, blond tobacco had no worse effect compared to the vehicles. However, the addition of nicotine in the latter e-liquid increased oxidative stress and cell death compared to the vehicles. Finally, mint-eucalyptus e-liquid increased some inflammation markers. Our results revealed that e-liquids alter ACB homeostasis, depending on flavour and nicotine presence.
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Affiliation(s)
- Amelia-Naomi Sabo
- Laboratoire de Pharmacologie et Toxicologie Neurocardiovasculaire, UR 7296, Faculté de Médecine de Maïeutique et des Métiers de la Santé, Centre de Recherche en Biomédecine de Strasbourg (CRBS), 67085, Strasbourg, France; Laboratoire de Biochimie et Biologie Moléculaire, Hôpitaux Universitaires de Strasbourg, 67200, Strasbourg, France.
| | - Emma Filaudeau
- Laboratoire de Pharmacologie et Toxicologie Neurocardiovasculaire, UR 7296, Faculté de Médecine de Maïeutique et des Métiers de la Santé, Centre de Recherche en Biomédecine de Strasbourg (CRBS), 67085, Strasbourg, France.
| | - Sylvia Da Silva
- Laboratoire de Pharmacologie et Toxicologie Neurocardiovasculaire, UR 7296, Faculté de Médecine de Maïeutique et des Métiers de la Santé, Centre de Recherche en Biomédecine de Strasbourg (CRBS), 67085, Strasbourg, France.
| | - Guillaume Becker
- Laboratoire de Pharmacologie et Toxicologie Neurocardiovasculaire, UR 7296, Faculté de Médecine de Maïeutique et des Métiers de la Santé, Centre de Recherche en Biomédecine de Strasbourg (CRBS), 67085, Strasbourg, France; Hôpitaux Universitaires de Strasbourg, Hôpital de Hautepierre, Pôle Pharmacie-Pharmacologie, 67200, France.
| | - Laurent Monassier
- Laboratoire de Pharmacologie et Toxicologie Neurocardiovasculaire, UR 7296, Faculté de Médecine de Maïeutique et des Métiers de la Santé, Centre de Recherche en Biomédecine de Strasbourg (CRBS), 67085, Strasbourg, France.
| | - Véronique Kemmel
- Laboratoire de Pharmacologie et Toxicologie Neurocardiovasculaire, UR 7296, Faculté de Médecine de Maïeutique et des Métiers de la Santé, Centre de Recherche en Biomédecine de Strasbourg (CRBS), 67085, Strasbourg, France; Laboratoire de Biochimie et Biologie Moléculaire, Hôpitaux Universitaires de Strasbourg, 67200, Strasbourg, France.
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Counil C, Abenojar E, Perera R, Exner AA. Extrusion: A New Method for Rapid Formulation of High-Yield, Monodisperse Nanobubbles. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2200810. [PMID: 35587613 PMCID: PMC9233137 DOI: 10.1002/smll.202200810] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/24/2022] [Indexed: 06/03/2023]
Abstract
Shell-stabilized gas microbubbles (MB) and nanobubbles (NB) are frequently used for biomedical ultrasound imaging and therapeutic applications. While it is widely recognized that monodisperse bubbles can be more effective in these applications, the efficient formulation of uniform bubbles at high concentrations is difficult to achieve. Here, it is demonstrated that a standard mini-extruder setup, commonly used to make vesicles or liposomes, can be used to quickly and efficiently generate monodisperse NBs with high yield. In this highly reproducible technique, the NBs obtained have an average diameter of 0.16 ± 0.05 µm and concentration of 6.2 ± 1.8 × 1010 NBs mL-1 compared to 0.32 ± 0.1 µm and 3.2 ± 0.7 × 1011 mL-1 for NBs made using mechanical agitation. Parameters affecting the extrusion and NB generation process including the temperature, concentration of the lipid solution, and the number of passages through the extruder are also examined. Moreover, it is demonstrated that extruded NBs show a strong acoustic response in vitro and a strong and persistent US signal enhancement under nonlinear contrast enhanced ultrasound imaging in mice. The extrusion process is a new, efficient, and scalable technique that can be used to easily produce high yield smaller monodispersed nanobubbles.
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Affiliation(s)
- Claire Counil
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-7207, USA
| | - Eric Abenojar
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-7207, USA
| | - Reshani Perera
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-7207, USA
| | - Agata A Exner
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-7207, USA
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5
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Woodall M, Jacob J, Kalsi KK, Schroeder V, Davis E, Kenyon B, Khan I, Garnett JP, Tarran R, Baines DL. E-cigarette constituents propylene glycol and vegetable glycerin decrease glucose uptake and its metabolism in airway epithelial cells in vitro. Am J Physiol Lung Cell Mol Physiol 2020; 319:L957-L967. [PMID: 32996783 PMCID: PMC7792687 DOI: 10.1152/ajplung.00123.2020] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 09/11/2020] [Accepted: 09/11/2020] [Indexed: 02/07/2023] Open
Abstract
Electronic nicotine delivery systems, or e-cigarettes, utilize a liquid solution that normally contains propylene glycol (PG) and vegetable glycerin (VG) to generate vapor and act as a carrier for nicotine and flavorings. Evidence indicated these "carriers" reduced growth and survival of epithelial cells including those of the airway. We hypothesized that 3% PG or PG mixed with VG (3% PG/VG, 55:45) inhibited glucose uptake in human airway epithelial cells as a first step to reducing airway cell survival. Exposure of H441 or human bronchiolar epithelial cells (HBECs) to PG and PG/VG (30-60 min) inhibited glucose uptake and mitochondrial ATP synthesis. PG/VG inhibited glycolysis. PG/VG and mannitol reduced cell volume and height of air-liquid interface cultures. Mannitol, but not PG/VG, increased phosphorylation of p38 MAPK. PG/VG reduced transepithelial electrical resistance, which was associated with increased transepithelial solute permeability. PG/VG decreased fluorescence recovery after photobleaching of green fluorescent protein-linked glucose transporters GLUT1 and GLUT10, indicating that glucose transport function was compromised. Puffing PG/VG vapor onto the apical surface of primary HBECs for 10 min to mimic the effect of e-cigarette smoking also reduced glucose transport. In conclusion, short-term exposure to PG/VG, key components of e-cigarettes, decreased glucose transport and metabolism in airway cells. We propose that this was a result of PG/VG reduced cell volume and membrane fluidity, with further consequences on epithelial barrier function. Taking these results together, we suggest these factors contribute to reduced defensive properties of the epithelium. We propose that repeated/chronic exposure to these agents are likely to contribute to airway damage in e-cigarette users.
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Affiliation(s)
- M. Woodall
- Institute for Infection and Immunity, St George’s, University of London, Tooting, London, United Kingdom
| | - J. Jacob
- Institute for Infection and Immunity, St George’s, University of London, Tooting, London, United Kingdom
| | - K. K. Kalsi
- Institute for Infection and Immunity, St George’s, University of London, Tooting, London, United Kingdom
| | - V. Schroeder
- Immunology and Respiratory Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - E. Davis
- Marsico Lung Institute and Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina
| | - B. Kenyon
- Marsico Lung Institute and Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina
| | - I. Khan
- Institute for Infection and Immunity, St George’s, University of London, Tooting, London, United Kingdom
| | - J. P. Garnett
- Immunology and Respiratory Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - R. Tarran
- Marsico Lung Institute and Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina
| | - D. L. Baines
- Institute for Infection and Immunity, St George’s, University of London, Tooting, London, United Kingdom
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6
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de Leon A, Perera R, Hernandez C, Cooley M, Jung O, Jeganathan S, Abenojar E, Fishbein G, Sojahrood AJ, Emerson CC, Stewart PL, Kolios MC, Exner AA. Contrast enhanced ultrasound imaging by nature-inspired ultrastable echogenic nanobubbles. NANOSCALE 2019; 11:15647-15658. [PMID: 31408083 PMCID: PMC6716144 DOI: 10.1039/c9nr04828f] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Advancement of ultrasound molecular imaging applications requires not only a reduction in size of the ultrasound contrast agents (UCAs) but also a significant improvement in the in vivo stability of the shell-stabilized gas bubble. The transition from first generation to second generation UCAs was marked by an advancement in stability as air was replaced by a hydrophobic gas, such as perfluoropropane and sulfur hexafluoride. Further improvement can be realized by focusing on how well the UCAs shell can retain the encapsulated gas under extreme mechanical deformations. Here we report the next generation of UCAs for which we engineered the shell structure to impart much better stability under repeated prolonged oscillation due to ultrasound, and large changes in shear and turbulence as it circulates within the body. By adapting an architecture with two layers of contrasting elastic properties similar to bacterial cell envelopes, our ultrastable nanobubbles (NBs) withstand continuous in vitro exposure to ultrasound with minimal signal decay and have a significant delay on the onset of in vivo signal decay in kidney, liver, and tumor. Development of ultrastable NBs can potentially expand the role of ultrasound in molecular imaging, theranostics, and drug delivery.
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Affiliation(s)
- Al de Leon
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Reshani Perera
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Christopher Hernandez
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Michaela Cooley
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Olive Jung
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Selva Jeganathan
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Eric Abenojar
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Grace Fishbein
- Department of Physics, Ryerson University, Toronto, ON, Canada
| | | | - Corey C Emerson
- Department of Pharmacology and Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Phoebe L Stewart
- Department of Pharmacology and Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | | | - Agata A Exner
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106, USA. and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
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7
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Tsuji G, Sunami T, Ichihashi N. Production of giant unilamellar vesicles by the water-in-oil emulsion-transfer method without high internal concentrations of sugars. J Biosci Bioeng 2018; 126:540-545. [DOI: 10.1016/j.jbiosc.2018.04.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 04/24/2018] [Accepted: 04/26/2018] [Indexed: 10/16/2022]
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8
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Fushimi T, Uchino T, Miyazaki Y, Hatta I, Asano M, Fujino H, Suzuki R, Fujimori S, Kamiya D, Kagawa Y. Development of phospholipid nanoparticles encapsulating 3-O-cetyl ascorbic acid and tocopherol acetate (TA-Cassome) for improving their skin accumulation. Int J Pharm 2018; 548:192-205. [DOI: 10.1016/j.ijpharm.2018.06.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 05/29/2018] [Accepted: 06/11/2018] [Indexed: 10/28/2022]
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9
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Barker M, Kennedy A. Disruption of gel phase lipid packing efficiency by sucralose studied with merocyanine 540. Colloids Surf B Biointerfaces 2017; 152:214-219. [DOI: 10.1016/j.colsurfb.2017.01.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 12/23/2016] [Accepted: 01/14/2017] [Indexed: 11/30/2022]
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10
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Fernández-de-Alba C, Takahashi H, Richard A, Chenavier Y, Dubois L, Maurel V, Lee D, Hediger S, De Paëpe G. Matrix-free DNP-enhanced NMR spectroscopy of liposomes using a lipid-anchored biradical. Chemistry 2015; 21:4512-7. [PMID: 25663569 DOI: 10.1002/chem.201404588] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Indexed: 12/18/2022]
Abstract
Magic-angle spinning dynamic nuclear polarization (MAS-DNP) has been proven to be a powerful technique to enhance the sensitivity of solid-state NMR (SSNMR) in a wide range of systems. Here, we show that DNP can be used to polarize lipids using a lipid-anchored polarizing agent. More specifically, we introduce a C16-functionalized biradical, which allows localization of the polarizing agents in the lipid bilayer and DNP experiments to be performed in the absence of excess cryo-protectant molecules (glycerol, dimethyl sulfoxide, etc.). This constitutes another original example of the matrix-free DNP approach that we recently introduced.
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Affiliation(s)
- Carlos Fernández-de-Alba
- Université Grenoble Alpes, INAC, LCIB, 38000 Grenoble (France), Fax: (+33) 4-38-78-50-90; CEA, INAC, LCIB, 38054 Grenoble (France)
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11
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Wu FG, Wang NN, Tao LF, Yu ZW. Acetonitrile Induces Nonsynchronous Interdigitation and Dehydration of Dipalmitoylphosphatidylcholine Bilayers. J Phys Chem B 2010; 114:12685-91. [DOI: 10.1021/jp104190z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fu-Gen Wu
- Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China
| | - Nan-Nan Wang
- Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China
| | - Le-Fu Tao
- Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China
| | - Zhi-Wu Yu
- Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China
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12
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D'Errico G, De Lellis M, Mangiapia G, Tedeschi A, Ortona O, Fusco S, Borzacchiello A, Ambrosio L. Structural and mechanical properties of UV-photo-cross-linked poly(N-vinyl-2-pyrrolidone) hydrogels. Biomacromolecules 2007; 9:231-40. [PMID: 18163572 DOI: 10.1021/bm7008137] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biocompatible poly( N-vinyl-2-pyrrolidone) (PVP) hydrogels have been produced by UV irradiation of aqueous polymer mixtures, using a high-pressure mercury lamp. The resulting materials have been characterized by a combination of experimental techniques, including rheology, small-angle neutron scattering (SANS), electron paramagnetic resonance (EPR), and pulsed gradient spin-echo nuclear magnetic resonance (PGSE-NMR), to put in evidence the relationship between the microstructural properties and the macrofunctional behavior of the gels. Viscoelastic measurements showed that UV photo-cross-linked PVP hydrogels present a strong gel mechanical behavior and viscoelastic moduli values similar to those of biological gels. The average distance between the cross-linking points of the polymer network was estimated from the hydrogels elastic modulus. However, SANS measurements showed that the network microstructure is highly inhomogeneous, presenting polymer-rich regions more densely cross-linked, surrounded by a water-rich environment. EPR and PGSE-NMR data further support the existence of these water-rich domains. Inclusion of a third component, such as glycerol, in the PVP aqueous mixture to be irradiated has been also investigated. A small amount of glycerol (<3% w/w) can be added keeping satisfactory properties of the hydrogel, while higher amounts significantly affect the cross-linking process.
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Affiliation(s)
- Gerardino D'Errico
- Dipartimento di Chimica, Università di Napoli Federico II, Via Cintia, I-80126 Napoli, Italy
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13
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Bahri MA, Seret A, Hans P, Piette J, Deby-Dupont G, Hoebeke M. Does propofol alter membrane fluidity at clinically relevant concentrations? An ESR spin label study. Biophys Chem 2007; 129:82-91. [PMID: 17574724 DOI: 10.1016/j.bpc.2007.05.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 05/15/2007] [Accepted: 05/17/2007] [Indexed: 11/25/2022]
Abstract
General anesthetics have been shown to perturb the membrane properties of excitable tissues. Due to their lipid solubility, anesthetics dissolve in every membrane, penetrate into organelles and interact with numerous cellular structures in multiple ways. Several studies indicate that anesthetics alter membrane fluidity and decrease the phase-transition temperature. However, the required concentrations to induce such effects on the properties of membrane lipids are by far higher than clinically relevant concentrations. In the present study, the fluidizing effect of the anesthetic agent propofol (2,6-diisopropyl phenol: PPF), a general anesthetic extensively used in clinical practice, has been investigated on liposome dimyristoyl-L-alpha phosphatidylcholine (DMPC) and cell (erythrocyte, Neuro-2a) membranes using electron spin resonance spectroscopy (ESR) of nitroxide labeled fatty acid probes (5-, 16-doxyl stearic acid). A clear effect of PPF at concentrations higher than the clinically relevant ones was quantified both in liposome and cell membranes, while no evident fluidity effect was measured at the clinical PPF doses. However, absorption spectroscopy of merocyanine 540 (MC540) clearly indicates a PPF fluidizing capacity in liposome membrane even at these clinical concentrations. PPF may locally influence the structure and dynamics of membrane domains, through the formation of small-scale lipid domains, which would explain the lack of ESR information at low PPF concentrations.
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Affiliation(s)
- Mohamed A Bahri
- Laboratory of Experimental Medical Imaging, Department of Physics, Institute of Physics B5, University of Liège, Sart-Tilman, B-4000 Liège, Belgium.
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14
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Turina ADV, Nolan MV, Zygadlo JA, Perillo MA. Natural terpenes: Self-assembly and membrane partitioning. Biophys Chem 2006; 122:101-13. [PMID: 16563603 DOI: 10.1016/j.bpc.2006.02.007] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 02/15/2006] [Accepted: 02/16/2006] [Indexed: 11/30/2022]
Abstract
Monoterpenes (MTs) are highly hydrophobic substances present in essential oils. They cover a wide spectrum of biological effects with a membrane interaction as a common point. Here we studied the surface activity of camphor, cineole, thymol, menthol and geraniol, and their ability to reach and incorporate into model membranes affecting some features of their dynamic organization. All the MTs studied self-aggregated in water with critical micellar concentrations (CMC) between 3 and 8 microM. Their octanol-water and membrane-water partition coefficients were correlated with one another. They all penetrated in monomolecular layers of dipalmitoyl-phosphatildylcholine at the air-water interface, even at surface pressures (pi) above the equilibrium lateral pressure of bilayers; thymol exhibited the highest (61.3 mN/m) and camphor the lowest (37 mN/m) pi(cut-off) value. They affected the self-aggregation of Triton X-100, increasing its CMC from 0.16 mM in the absence of MTs up to 0.68 mM (e.g. for geraniol), and the topology of sPC vesicles, increasing its surface curvature, suggesting their location at the polar head group region of the membrane. The latter was supported by their ability to increase differentially the polarity of the membrane environment sensed by two electrochromic dyes. Dipole moment values (between 1.224 and 2.523 D) and solvation areas (between 80 and 97 A(2)) were calculated from their energy-minimized structures. The relative contribution of each experimental, theoretical and structural property to determine MTs' effects on membrane dynamics were evaluated by a principal component analysis.
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Affiliation(s)
- A del V Turina
- Biofísica-Química, Departamento de Química, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, 5016 Córdoba, Argentina
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15
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Bahri MA, Heyne BJ, Hans P, Seret AE, Mouithys-Mickalad AA, Hoebeke MD. Quantification of lipid bilayer effective microviscosity and fluidity effect induced by propofol. Biophys Chem 2004; 114:53-61. [PMID: 15792861 DOI: 10.1016/j.bpc.2004.11.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2004] [Revised: 11/03/2004] [Accepted: 11/03/2004] [Indexed: 10/26/2022]
Abstract
Electron spin resonance (ESR) spectroscopy with nitroxide spin probes was used as a method to probe the liposome microenvironments. The effective microviscosities have been determined from the calibration of the ESR spectra of the probes in solvent mixtures of known viscosities. In the first time, by measuring ESR order parameter (S) and correlation time (tau(c)) of stearic spin probes, we have been able to quantify the value of effective microviscosity at different depths inside the liposome membrane. At room temperature, local microviscosities measured in dimyristoyl-l-alpha phosphatidylcholine (DMPC) liposome membrane at the different depths of 7.8, 16.95, and 27.7 A were 222.53, 64.09, and 62.56 cP, respectively. In the gel state (10 degrees C), those microviscosity values increased to 472.56, 370.61, and 243.37 cP. In a second time, we have applied this technique to determine the modifications in membrane microviscosity induced by 2,6-diisopropyl phenol (propofol; PPF), an anaesthetic agent extensively used in clinical practice. Propofol is characterized by a unique phenolic structure, absent in the other conventional anaesthetics. Indeed, given its lipophilic property, propofol is presumed to penetrate into and interact with membrane lipids and hence to induce changes in membrane fluidity. Incorporation of propofol into dimyristoyl-l-alpha phosphatidylcholine liposomes above the phase-transition temperature (23.9 degrees C) did not change microviscosity. At 10 degrees C, an increase of propofol concentration from 0 to 1.0 x 10(-2) M for a constant lipid concentration mainly induced a decrease in microviscosity. This fluidity effect of propofol has been qualitatively confirmed using merocyanine 540 (MC540) as lipid packing probe. Above 10(-2) M propofol, no further decrease in microviscosity was observed, and the microviscosity at the studied depths (7.8, 16.95, and 27.7 A) amounted 260.21, 123.87, and 102.27 cP, respectively. The concentration 10(-2) M was identified as the saturation limit of propofol in dimyristoyl-l-alpha phosphatidylcholine liposomes.
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Affiliation(s)
- Mohamed A Bahri
- Laboratory of Experimental Medical Imaging, Liège, Belgium; Department of Physics, Institute of Physics, B5, University of Liege, Sart-Tilman, B-4000, Liège, Belgium
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16
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Beney L, Mille Y, Gervais P. Death of Escherichia coli during rapid and severe dehydration is related to lipid phase transition. Appl Microbiol Biotechnol 2004; 65:457-64. [PMID: 15095024 DOI: 10.1007/s00253-004-1574-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 01/12/2004] [Accepted: 01/16/2004] [Indexed: 10/26/2022]
Abstract
This study reports the effects of exposure to increasing osmotic pressure on the viability and membrane structure of Escherichia coli. Changes in membrane structure after osmotic stress were investigated by electron transmission microscopy, measurement of the anisotropy of the membrane fluorescent probe DPH (1,6-diphenyl-1,3,5-hexatriene) inserted in E. coli, and Fourier infrared spectroscopy (FTIR). The results show that, above a critical osmotic pressure of 35 MPa, the viability of the bacterium is drastically reduced (2 log decrease in survivors). Electron micrographs revealed a severe contraction of the cytoplasm and the formation of membrane vesicles at 40 MPa. Changes in DPH anisotropy showed that osmotic dehydration to 40 MPa promoted a decrease in the membrane fluidity of integral cells of E. coli. FTIR measurements showed that at 10-40 MPa a transition from lamellar liquid crystal to lamellar gel among the phospholipids extracted from E. coli occurred. Bacterial death resulting from dehydration can be attributed to the conjunction between membrane deformation, caused by the volumetric contraction, and structural changes of the membrane lipids. The influence of the latter on the formation of membrane vesicles and on membrane permeabilization at lethal osmotic pressure is discussed, since vesiculation is hypothetically responsible for cell death.
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Affiliation(s)
- L Beney
- Laboratoire de Génie des Procédés Alimentaires et Biotechnologiques, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, 21000, Dijon, France
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17
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Sánchez ME, Turina ADV, García DA, Nolan MV, Perillo MA. Surface activity of thymol: implications for an eventual pharmacological activity. Colloids Surf B Biointerfaces 2004; 34:77-86. [PMID: 15261077 DOI: 10.1016/j.colsurfb.2003.11.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2003] [Revised: 09/24/2003] [Accepted: 11/23/2003] [Indexed: 11/18/2022]
Abstract
In the present work, we studied the ability of thymol to affect the organization of model membranes and the activity of an intrinsic membrane protein, the GABA(A) receptor (GABA(A)-R). In this last aspect, we tried to elucidate if the action mechanism of this terpene at the molecular level, involves its binding to the receptor protein, changes in the organization of the receptor molecular environment, or both. The self-aggregation of thymol in water with a critical micellar concentration approximately = 4 microM and its ability to penetrate in monomolecular layers of soybean phosphatidylcholine (sPC) at the air-water interface, even at surface pressures above the equilibrium, lateral pressure of natural bilayers were demonstrated. Thymol affected the self-aggregation of Triton X-100 and the topology of sPC vesicles. It also increased the polarity of the membrane environment sensed by the electrochromic dye merocyanine. A dipolar moment of 1.341 Debye was calculated from its energy-minimized structure. Its effect on the binding of [3H]-flunitrazepam ([3H]-FNZ) to chick brain synaptosomal membranes changed qualitatively from a tendency to the inhibition to a clear activatory regime, up on changing the phase state of the terpene (from a monomeric to a self-aggregated state). Above its CMC, thymol increased the affinity of the binding of [3H]-FNZ (K(d-control)= 2.9, K(d-thymol)= 1.7 nM) without changing the receptor density (B(max-control)= 910, B(max-thymol)= 895 fmol/mg protein). The activatory effect of thymol on the binding of [ [3H]-FNZ was observed even in the presence of the allosteric activator gamma-aminobutyric acid (GABA) at a concentration of maximal activity, and was blocked by the GABA antagonist bicuculline. Changes in the dipolar arrangement and in the molecular packing of GABA(A)-R environment are discussed as possible mediators of the action mechanism of thymol.
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Affiliation(s)
- Mariela E Sánchez
- Biofísica-Química, Departamento de Química, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, Córdoba 5016, Argentina
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18
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Turina AV, del Turina AV, Perillo MA. Monoterpenes affect chlorodiazepoxide–micelle interaction through micellar dipole potential modifications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2003; 1616:112-20. [PMID: 14561468 DOI: 10.1016/s0005-2736(03)00236-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The ability of several natural terpenes to affect benzodiazepine (BZD)-micelle interaction through the membrane dipolar organization was investigated. The acid-base equilibrium of chlorodiazepoxide (CDX) and the spectroscopic behavior of the electrochromic dye merocyanine were tested in the presence and in the absence of Triton X-100 micelles (used to mimic a membrane environment) containing or not cineole, menthol, geraniol or camphor. CDX's apparent pK increased in the environment of terpene-containing micelles compared with pure Triton X-100 micelles. Decrements in electric potentials (between -111 and -128 mV with respect to pure detergent) were calculated from Boltzmann equation. This result suggested, that in the presence of terpenes, the tendency of CDXH(+) to remain in the membrane phase increased. The dielectric constant (D) of the microenvironment sensed by merocyanine within Triton X-100 micelles, determined from lambda(max,2) of merocyanine monomer, was D=9 and increased in the presence of all the terpenes assayed (D congruent with 11). The decrease in merocyanine partitioning (A(peak1)/A(peak2) increased) also reflected an increment in the negative dipole potential. The present results suggest that terpenes contributed to the whole dipolar arrangement of the micelle with a dipole moment vector which had an intense component oriented parallel to the intrinsic dipole of the Triton X-100 molecules in the micelles. This led to a more negative environment of the interface region where CDX was located, and increased the net polarity of the deepest micelle regions sensed by merocyanine.
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Affiliation(s)
- Anahí V Turina
- Cátedra de Biofísica Química, Depto. de Química, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Velez Sarsfield 1611, X5016CAG Córdoba, Argentina
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19
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Pan Z, Chen J. A mechanism underlying stimulation and inhibition of protein kinase C by lyso-PC: A role of membrane physical state. SCIENCE IN CHINA. SERIES C, LIFE SCIENCES 1998; 41:584-591. [PMID: 18726213 DOI: 10.1007/bf02882899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/1998] [Indexed: 05/26/2023]
Abstract
Lysophosphatidylcholine (lyso-PC) biphasically regulates the diacylglycerol-induced activation of protein kinase C (PKC). In common parlance, lyso-PC stimulates PKC at low concentrations, but, conversely, inhibits it at high concentrations. The activity of purified PKC from rat brains was measured in the vesicles made up of dipalmitoylphosphatidylserine (DPPS), 1, 2-sn-diolein (DOG) and different molar ratios of 1-palmitoyl-sn-glycerol-3-phosphoryl-choline (C16:0 lyso-PC). The effect, i. e. stimulation or inhibition on PKC by C16:0 lyso-PC, depends on DPPS and DOG concentrations as well as its own concentration. When the concentration of DOG is stable, this C16:0 lyso-PC action depends on C16:0 lyso-PCIDPPS molar ratio. Differential scanning calorimetry (DSC), two fluorescence probes and light scattering were used to analyze the physical characteristics of membrane, including thermotropic phase behavior, the turbidity, the lipid molecular acyl chains packing and the head group spacing. The more adulteration of C16:0 lyso-PC in liposome bilayer membrane, the looser acyl chains pack, and the broader head group spacing. DSC results show that there are two immiscible lipid areas in the membrane: C16:0 lyso-PC-rich area and C16: 0 lyso-PC-poor area. When C16:0 lyso-PC/DPPS molar ratio was 0.234, the two areas had the broadest boundary and the activation of PKC was the highest. When the ratio was over 0.434, the phase transition of DPPS disappeared; micelle tended to substitute the structure of bilayer; the activity of PKC was inhibited completely. DOG can stabilize the bilayer structure of membrane, so the C16:0 lyso-PC/DPPS molar ratios to inhibit PKC in lipid mixture with DOG are higher than that without DOG. The ability of C16:0 lyso-PC to change the physical properties and the structure of membrane plays an important role in its effect on PKC activation.
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Affiliation(s)
- Z Pan
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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20
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Effect of a linear (1-octanol) and a branched (2,6-dimethyl-4-heptanol) alkanol upon the properties of dipalmitoylphosphatidylcholine large unilamellar vesicles. Colloids Surf A Physicochem Eng Asp 1995. [DOI: 10.1016/0927-7757(95)03160-f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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21
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Arias HR, Alonso-Romanowski S, Disalvo EA, Barrantes FJ. Interaction of merocyanine 540 with nicotinic acetylcholine receptor membranes from Discopyge tschudii electric organ. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1190:393-401. [PMID: 8142441 DOI: 10.1016/0005-2736(94)90099-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Interactions between merocyanine 540 (MC540) and nicotinic acetylcholine receptor (AChR) have been studied by visible absorption spectroscopy using native receptor-rich membranes from Discopyge tschudii electric tissue and liposomes obtained by aqueous dispersion of endogenous lipids extracted from the same tissue. The fact that merocyanine partitions into the membrane when this is in the liquid-crystalline state, exhibiting a characteristic peak at 567 nm, was exploited to obtain quantitative information about the physical state of the AChR-rich membrane. Spectra of MC540 revealed that this molecule was preferentially incorporated into AChR-rich membranes, with an affinity (Kdapp 30 microM) 10-fold higher than that in liposomes (Kdapp 290 microM). Changes were observed in the equilibrium dissociation constant of MC540 at different temperatures: the two-fold higher affinity at 8 degrees C than at 23 degrees C can be rationalized in terms of a higher value of the overall dimerization constant (Kdim) at the lower temperature. The local anaesthetic benzocaine competed for MC540 binding sites with higher potency in AChR-rich native membranes than in liposomes made with endogenous lipids. This competition was found to be AChR concentration-dependent, whereas in liposomes the displacement was constant at different lipid/MC540 molar ratios. Titration experiments yielded an apparent dissociation constant for benzocaine of 0.6 mM and 0.7 mM for liposomes and AChR-rich membranes, respectively. The possible location of the benzocaine binding site is deduced from the competition experiments to be at the lipid annulus surrounding the nicotinic AChR protein.
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Affiliation(s)
- H R Arias
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, CONICET/Universidad Nac. del Sur, Argentina
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22
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Bernik DL, Disalvo EA. Gel state surface properties of phosphatidylcholine liposomes as measured with merocyanine 540. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1146:169-77. [PMID: 7680899 DOI: 10.1016/0005-2736(93)90352-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The surface properties of liposomes composed by saturated phosphatidylcholines and their mixtures with cholesterol in the gel state have been studied using merocyanine 540 as a fluorescent and optical probe. A new absorption peak at 450 nm and a new fluorescent band at 630 nm were observed when the dye was added to suspensions of DMPC multilamellar liposomes in the gel state. These peaks were also observed in membranes with different lipid compositions in conditions in which the P beta' and the L beta' phases were present. The increase of temperature above the main transition temperature of DMPC or the incorporation of 35% cholesterol into DMPC bilayers at 13 degrees C caused the disappearance of these peaks. The changes in the absorption and fluorescent spectra upon addition of cholesterol resembles very well the phase diagrams reported by Mortensen et al. ((1988) Biochim. Biophys. Acta 945, 221-245) indicating that the corrugated structures characteristic of the L beta' and the P beta' phases have different surface properties related to the partitioning of amphiphilic dies.
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Affiliation(s)
- D L Bernik
- Area de Biomembranas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, Argentina
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23
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Viera LI, Alonso-Romanowski S, Borovyagin V, Feliz MR, Disalvo EA. Properties of gel phase lipid-trehalose bilayers upon rehydration. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1145:157-67. [PMID: 8422407 DOI: 10.1016/0005-2736(93)90393-e] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
When dipalmitoylphosphatidylcholine bilayers dried under vacuum in different concentrations of trehalose are rehydrated in buffer without the sugar they show different physicochemical properties in the gel state in comparison to the normal gel state. Dry DPPC/trehalose mixtures are readily dispersed in buffer below the phase transition showing by electron microscopy a morphology similar to liposomes prepared by dispersing the lipids in buffer above the phase transition temperature. In these conditions, an increase in the peak at 570 nm of merocyanine after the dehydration-rehydration process in the presence of the sugar is observed and the water permeation increases to values comparable to those found in the fluid state as indicated by the activation energy values and the osmotic volume. The trehalose-dried liposomes rehydrated in buffer show a similar osmotic response to hypertonic gradient as DPPC liposomes without sugar near the phase transition temperature. In accordance with this behavior the trehalose-dried liposomes are lysed below the phase transition temperature by lysoderivatives. These modifications of the gel state of hydrated phospholipids by trehalose can only be achieved if a drastic dehydration is performed in the presence of the sugar. After rehydration the changes in the gel state can be detected after dyalizing the rehydrated membranes in media without trehalose during at least 24 h. These results suggest that trehalose is still intercalated between the phospholipids after restoring water to the dried liposomes either at temperatures below or above the phase transition.
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Affiliation(s)
- L I Viera
- Area de Biomembranas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, INIFTA, Facultad de Ciencias Exactas, UNLP, La Plata, Argentina
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24
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Biondi AC, Senisterra GA, Disalvo EA. Permeability of lipid membranes revised in relation to freeze-thaw processes. Cryobiology 1992; 29:323-31. [PMID: 1499317 DOI: 10.1016/0011-2240(92)90033-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Water and solute activity gradients created during freeze-thaw processes produce water and solute fluxes across the cell membrane resulting in volume changes. Under these conditions, osmotic and thermal stresses affect the curvature, the phase behavior, and the surface properties of the lipid bilayer. These structural changes are not considered by the classical formalisms describing permeability of lipid membranes to water and nonelectrolytes such as the Nernst-Planck equation, Eyring's absolute rate theory, and Kedem-Katchalsky's thermodynamic of irreversible processes approach. In this paper, the influence of such changes on the glycerol permeation kinetics are reported. The results indicate that osmotic and chemical effects of the cryoprotectant on the membrane properties affect the rate of volume swelling depending on whether the membrane is in the gel or in the liquid crystalline state.
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Affiliation(s)
- A C Biondi
- Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA) Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Argentina
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Biondi AC, Féliz MR, Disalvo EA. Surface changes induced by osmotic stress and its influence on the glycerol permeability in lipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1069:5-13. [PMID: 1932049 DOI: 10.1016/0005-2736(91)90097-r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The penetration rate of glycerol across lipid bilayers can be assayed dispersing liposomes filled with a 0.1 M glucose solution in an isotonic or a hypertonic solution of glycerol. The kinetic of glycerol permeation is found to be different in each of those cases. Liposomes dispersed above the phase transition temperature in hypertonic solutions show an increase in the surface polarization as measured by means of merocyanine 540. Under this condition, the permeation of glycerol shows a two-step kinetic which is indicative of a non-fickean diffusion process. In contrast, liposomes dispersed in isotonic solutions of the permeant show a fickean behavior. The changes in polarization of the membrane interface are ascribed to variations in the surface potential due to the osmotic collapse and the glycerol concentration in contact with the outer surface. The permeability of polar molecules can, in consequence, be considered as a function of the surface potential of the liposome which is congruent with previous data in literature reporting that water permeability increases as a function of the zeta potential of liposomes shrunken in hypertonic solutions.
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Affiliation(s)
- A C Biondi
- Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de Tucumán, Argentina
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26
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