1
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Peñalva DA, Monnappa AK, Natale P, López-Montero I. Mfn2-dependent fusion pathway of PE-enriched micron-sized vesicles. Proc Natl Acad Sci U S A 2024; 121:e2313609121. [PMID: 39012824 PMCID: PMC11287154 DOI: 10.1073/pnas.2313609121] [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: 08/07/2023] [Accepted: 06/17/2024] [Indexed: 07/18/2024] Open
Abstract
Mitofusins (Mfn1 and Mfn2) are the mitochondrial outer-membrane fusion proteins in mammals and belong to the dynamin superfamily of multidomain GTPases. Recent structural studies of truncated variants lacking alpha helical transmembrane domains suggested that Mfns dimerize to promote the approximation and the fusion of the mitochondrial outer membranes upon the hydrolysis of guanine 5'-triphosphate disodium salt (GTP). However, next to the presence of GTP, the fusion activity seems to require multiple regulatory factors that control the dynamics and kinetics of mitochondrial fusion through the formation of Mfn1-Mfn2 heterodimers. Here, we purified and reconstituted the full-length murine Mfn2 protein into giant unilamellar vesicles (GUVs) with different lipid compositions. The incubation with GTP resulted in the fusion of Mfn2-GUVs. High-speed video-microscopy showed that the Mfn2-dependent membrane fusion pathway progressed through a zipper mechanism where the formation and growth of an adhesion patch eventually led to the formation of a membrane opening at the rim of the septum. The presence of physiological concentration (up to 30 mol%) of dioleoyl-phosphatidylethanolamine (DOPE) was shown to be a requisite to observe GTP-induced Mfn2-dependent fusion. Our observations show that Mfn2 alone can promote the fusion of micron-sized DOPE-enriched vesicles without the requirement of regulatory cofactors, such as membrane curvature, or the assistance of other proteins.
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Affiliation(s)
- Daniel A. Peñalva
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Sur, Bahía BlancaB8000, Argentina
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía BlancaB8000, Argentina
| | - Ajay K. Monnappa
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid28041, Spain
| | - Paolo Natale
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid28041, Spain
- Departamento Química Física, Universidad Complutense de Madrid, Madrid28041, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid28041, Spain
| | - Iván López-Montero
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid28041, Spain
- Departamento Química Física, Universidad Complutense de Madrid, Madrid28041, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid28041, Spain
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2
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De Mel JU, Klisch S, Gupta S, Schneider GJ. Ion-Mediated Structural Discontinuities in Phospholipid Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:14990-15000. [PMID: 38978402 PMCID: PMC11270981 DOI: 10.1021/acs.langmuir.4c01219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 06/28/2024] [Accepted: 07/01/2024] [Indexed: 07/10/2024]
Abstract
Despite intense research, methods for controlling soft matter's spontaneous self-assembly into well-defined layers remain a significant challenge. We observed ion-induced structural discontinuities of phospholipid vesicles that can be exploited for controlled self-assembly of soft materials, using DOPC and NaCl as a model system. The observations were made for the 0.25 wt % lipid concentration. We used dynamic light scattering, zeta-potential measurement, cryo-electron microscopy, small-angle X-ray, and small-angle neutron scattering to understand the reason for the discontinuities. For salt concentrations below 8 mM, we observed a decrease in the liposome diameter with increased NaCl concentration. Above 8 mM, we measured a discontinuity; the radius increases within a very narrow salt concentration range within less than 0.1 mM and then decreases for values greater than 8 mM. At 75 mM, the radius becomes constant until it grows again at around 500 mM. Microscopy and scattering experiments show a transition from unilamellar to bilamellar at 8 mM and to trilamellar at 75 mM. At 500 mM, we found a heterogeneous liposome system with many different bilayer numbers. All the experimental observations indicate that declining solvent quality and increasing osmotic pressure direct lipids to expel preferentially to the inner compartment. Upon reaching a critical concentration, excess lipids can form a new bilayer. This spontaneous self-assembly process causes simultaneous shrinkage of the aqueous core and expansion of the vesicle. This approach opens an intriguing path for controlling the self-assembly of bioinspired colloids.
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Affiliation(s)
- Judith U. De Mel
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Stefanie Klisch
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Sudipta Gupta
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Gerald J. Schneider
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Department
of Physics and Astronomy, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
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3
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Grad P, Edwards K, Gedda L, Agmo Hernández V. A closer look at calcium-induced interactions between phosphatidylserine-(PS) doped liposomes and the structural effects caused by inclusion of gangliosides or polyethylene glycol- (PEG) modified lipids. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184253. [PMID: 37979667 DOI: 10.1016/j.bbamem.2023.184253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 11/09/2023] [Accepted: 11/11/2023] [Indexed: 11/20/2023]
Abstract
The effects of polyethylene glycol- (PEG) modified lipids and gangliosides on the Ca2+ induced interaction between liposomes composed of palmitoyl-oleoyl phosphatidylethanolamine (POPE) and palmitoyl-oleoyl phosphatidylserine (POPS) was investigated at physiological ionic strength. Förster resonance energy transfer (FRET) studies complemented with dynamic light scattering (DLS) and cryo-transmission electron microscopy (Cryo-EM) show that naked liposomes tend to adhere, rupture, and collapse on each other's surfaces upon addition of Ca2+, eventually resulting in the formation of large multilamellar aggregates and bilayer sheets. Noteworthy, the presence of gangliosides or PEGylated lipids does not prevent the adhesion-rupture process, but leads to the formation of small, long-lived bilayer fragments/disks. PEGylated lipids seem to be more effective than gangliosides at stabilizing these structures. Attractive interactions arising from ion correlation are proposed to be a driving force for the liposome-liposome adhesion and rupture processes. The results suggest that, in contrast with the conclusions drawn from previous solely FRET-based studies, direct liposome-liposome fusion is not the dominating process triggered by Ca2+ in the systems studied.
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Affiliation(s)
- Philipp Grad
- Department of Chemistry-Ångström, Uppsala University, Box 573, 75123 Uppsala, Sweden
| | - Katarina Edwards
- Department of Chemistry-Ångström, Uppsala University, Box 573, 75123 Uppsala, Sweden.
| | - Lars Gedda
- Department of Chemistry-Ångström, Uppsala University, Box 573, 75123 Uppsala, Sweden.
| | - Víctor Agmo Hernández
- Department of Medicinal Chemistry, Uppsala University, Box 574, 75123 Uppsala, Sweden.
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4
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Heller WT. Small-Angle Neutron Scattering Study of a Phosphatidylcholine-Phosphatidylethanolamine Mixture. ACS OMEGA 2023; 8:33755-33762. [PMID: 37744859 PMCID: PMC10515593 DOI: 10.1021/acsomega.3c04164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 08/23/2023] [Indexed: 09/26/2023]
Abstract
The properties of single-component phospholipid lipid bilayers have been extensively characterized. Natural cell membranes are not so simple, consisting of a diverse mixture of lipids and proteins. While having detailed structural information on complex membranes would be useful for understanding their structure and function, experimentally characterizing such membranes at a level of detail applied to model phospholipid bilayers is challenging. Here, small-angle neutron scattering with selective deuteration was used to characterize a binary lipid mixture composed of 1,2-dimyristoyl-3-sn-glycero-phosphatidylcholine and 1,2-dimyristoyl-3-sn-glycero-phosphatidylethanolamine. The data analysis provided the area per lipid in each leaflet as well as the asymmetry of the composition of the inner and outer leaflets of the bilayer. The results provide new insight into the structure of the lipid bilayer when this lipid mixture is used to prepare vesicles.
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Affiliation(s)
- William T. Heller
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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5
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Kano S, Takahashi H. Cholesterol's inhibition effect on entering of chlorzoxazone into phosphatidylethanolamine bilayer: Relevance to cytochrome P450 drug metabolism at endoplasmic reticulum membranes. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183954. [PMID: 35523303 DOI: 10.1016/j.bbamem.2022.183954] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 04/18/2022] [Accepted: 04/29/2022] [Indexed: 06/14/2023]
Abstract
Many drugs are metabolized by cytochrome P450 (CYP) in the endoplasmic reticulum (ER) membrane. Recent studies have shown that CYP-substrate drugs reach the CYP active site after entering the lipid hydrophobic part of the ER membrane. To clarify the role of cholesterol (Chol) in the CYP-related drug metabolic process, we investigated the lipid bilayer entry of CYP-substrate drugs using a model membrane system as follows. The model membrane system comprised palmitoyl-oleoyl-phosphatidylethanolamine (POPE) and Chol. Phosphatidylethanolamine is the second major phospholipid component of ER membranes. Chlorzoxazone (CZX) was used as the CYP-substrate drug. Calorimetric measurements showed that the addition of CZX to POPE bilayers decreased the gel-liquid crystal phase transition temperature; X-ray diffraction indicated that CZX distributes into the liquid crystal phase bilayers but not practically the gel phase POPE bilayers. In the presence of Chol, dialysis and X-ray structural analyses showed that Chol inhibited CZX entry into the bilayer with an increase in Chol concentration. The Chol concentration in the ER membrane (5-10 mol%) is much lower than that in the plasma membrane (approximately 30 mol%). This fact may allow CYP-substrate drugs to enter the hydrophobic portion of the ER membrane more easily than other organelle membranes, yielding efficient drug metabolism.
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Affiliation(s)
- Shosei Kano
- Division of Pure and Applied Science, Graduate School of Science and Technology, Gunma University, Maebashi, Gunma 371-8510, Japan
| | - Hiroshi Takahashi
- Division of Pure and Applied Science, Graduate School of Science and Technology, Gunma University, Maebashi, Gunma 371-8510, Japan.
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6
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Hornemann A, Eichert DM, Hoehl A, Tiersch B, Ulm G, Ryadnov MG, Beckhoff B. Investigating Membrane‐Mediated Antimicrobial Peptide Interactions with Synchrotron Radiation Far‐Infrared Spectroscopy. Chemphyschem 2022; 23:e202100815. [PMID: 35032089 PMCID: PMC9303692 DOI: 10.1002/cphc.202100815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/20/2021] [Indexed: 11/30/2022]
Abstract
Synchrotron radiation‐based Fourier transform infrared spectroscopy enables access to vibrational information from mid over far infrared to even terahertz domains. This information may prove critical for the elucidation of fundamental bio‐molecular phenomena including folding‐mediated innate host defence mechanisms. Antimicrobial peptides (AMPs) represent one of such phenomena. These are major effector molecules of the innate immune system, which favour attack on microbial membranes. AMPs recognise and bind to the membranes whereupon they assemble into pores or channels destabilising the membranes leading to cell death. However, specific molecular interactions responsible for antimicrobial activities have yet to be fully understood. Herein we probe such interactions by assessing molecular specific variations in the near‐THz 400–40 cm−1 range for defined helical AMP templates in reconstituted phospholipid membranes. In particular, we show that a temperature‐dependent spectroscopic analysis, supported by 2D correlative tools, provides direct evidence for the membrane‐induced and folding‐mediated activity of AMPs. The far‐FTIR study offers a direct and information‐rich probe of membrane‐related antimicrobial interactions.
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Affiliation(s)
- Andrea Hornemann
- Department 7.1 Radiometry with Synchrotron Radiation and Department 7.2 X-Ray Metrology with Synchrotron Radiation Physikalisch-Technische Bundesanstalt (PTB) Abbestr. 2–12 10587 Berlin Germany
| | - Diane M. Eichert
- ELETTRA – Sincrotrone Trieste S.S.14 Km 163.5 in Area Science Park 34149 Basovizza Trieste Italy
| | - Arne Hoehl
- Department 7.1 Radiometry with Synchrotron Radiation and Department 7.2 X-Ray Metrology with Synchrotron Radiation Physikalisch-Technische Bundesanstalt (PTB) Abbestr. 2–12 10587 Berlin Germany
| | - Brigitte Tiersch
- Universität Potsdam Karl-Liebknecht-Str. 24–25 14476 Potsdam Germany
| | - Gerhard Ulm
- Department 7.1 Radiometry with Synchrotron Radiation and Department 7.2 X-Ray Metrology with Synchrotron Radiation Physikalisch-Technische Bundesanstalt (PTB) Abbestr. 2–12 10587 Berlin Germany
| | - Maxim G. Ryadnov
- National Physical Laboratory Hampton Rd Teddington Middlesex TW11 0LW UK
| | - Burkhard Beckhoff
- Department 7.1 Radiometry with Synchrotron Radiation and Department 7.2 X-Ray Metrology with Synchrotron Radiation Physikalisch-Technische Bundesanstalt (PTB) Abbestr. 2–12 10587 Berlin Germany
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7
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Mahmoudzadeh M, Magarkar A, Koivuniemi A, Róg T, Bunker A. Mechanistic Insight into How PEGylation Reduces the Efficacy of pH-Sensitive Liposomes from Molecular Dynamics Simulations. Mol Pharm 2021; 18:2612-2621. [PMID: 34096310 PMCID: PMC8289284 DOI: 10.1021/acs.molpharmaceut.1c00122] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Liposome-based drug
delivery systems composed of DOPE stabilized
with cholesteryl hemisuccinate (CHMS) have been proposed as a drug
delivery mechanism with pH-triggered release as the anionic form (CHSa)
is protonated (CHS) at reduced pH; PEGylation is known to decrease
this pH sensitivity. In this manuscript, we set out to use molecular
dynamics (MD) simulations with a model with all-atom resolution to
provide insight into why incorporation of poly(ethyleneglycol) (PEG)
into DOPE–CHMS liposomes reduces their pH sensitivity; we also
address two additional questions: (1) How CHSa stabilizes DOPE bilayers
into a lamellar conformation at a physiological pH of 7.4? and (2)
how the change from CHSa to CHS at acidic pH triggers the destabilization
of DOPE bilayers? We found that (A) CHSa stabilizes the DOPE lipid
membrane by increasing the hydrophilicity of the bilayer surface,
(B) when CHSa changes to CHS by pH reduction, DOPE bilayers are destabilized
due to a reduction in bilayer hydrophilicity and a reduction in the
area per lipid, and (C) PEG stabilizes DOPE bilayers into the lamellar
phase, thus reducing the pH sensitivity of the liposomes by increasing
the area per lipid through penetration into the bilayer, which is
our main focus.
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Affiliation(s)
- Mohammad Mahmoudzadeh
- Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, 00100 Helsinki, Finland
| | - Aniket Magarkar
- Medicinal Chemistry, Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, D-88397 Biberach a.d. Riss, Germany
| | - Artturi Koivuniemi
- Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, 00100 Helsinki, Finland
| | - Tomasz Róg
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56, Viikinkaarie 5 E, FI-00014 Helsinki, Finland
| | - Alex Bunker
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56, Viikinkaarie 5 E, FI-00014 Helsinki, Finland
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8
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Yee SM, Gillams RJ, McLain SE, Lorenz CD. Effects of lipid heterogeneity on model human brain lipid membranes. SOFT MATTER 2021; 17:126-135. [PMID: 33155582 DOI: 10.1039/d0sm01766c] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cell membranes naturally contain a heterogeneous lipid distribution. However, homogeneous bilayers are commonly preferred and utilised in computer simulations due to their relative simplicity, and the availability of lipid force field parameters. Recently, experimental lipidomics data for the human brain cell membranes under healthy and Alzheimer's disease (AD) conditions were investigated, since disruption to the lipid composition has been implicated in neurodegenerative disorders, including AD [R. B. Chan et al., J. Biol. Chem., 2012, 287, 2678-2688]. In order to observe the effects of lipid complexity on the various bilayer properties, molecular dynamics simulations were used to study four membranes with increasing heterogeneity: a pure POPC membrane, a POPC and cholesterol membrane in a 1 : 1 ratio (POPC-CHOL), and to our knowledge, the first realistic models of a healthy brain membrane and an Alzheimer's diseased brain membrane. Numerous structural, interfacial, and dynamical properties, including the area per lipid, interdigitation, dipole potential, and lateral diffusion of the two simple models, POPC and POPC-CHOL, were analysed and compared to those of the complex brain models consisting of 27 lipid components. As the membranes gain heterogeneity, a number of alterations were found in the structural and dynamical properties, and more significant differences were observed in the lateral diffusion. Additionally, we observed snorkeling behaviour of the lipid tails that may play a role in the permeation of small molecules across biological membranes. In this work, atomistic description of realistic brain membrane models is provided, which can add insight towards the permeability and transport pathways of small molecules across these membrane barriers.
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Affiliation(s)
- Sze May Yee
- Department of Physics, King's College London, London WC2R 2LS, UK.
| | - Richard J Gillams
- School of Electronics and Computer Science, and Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Sylvia E McLain
- Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN1 9RH, UK
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9
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Horne JE, Brockwell DJ, Radford SE. Role of the lipid bilayer in outer membrane protein folding in Gram-negative bacteria. J Biol Chem 2020; 295:10340-10367. [PMID: 32499369 PMCID: PMC7383365 DOI: 10.1074/jbc.rev120.011473] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
β-Barrel outer membrane proteins (OMPs) represent the major proteinaceous component of the outer membrane (OM) of Gram-negative bacteria. These proteins perform key roles in cell structure and morphology, nutrient acquisition, colonization and invasion, and protection against external toxic threats such as antibiotics. To become functional, OMPs must fold and insert into a crowded and asymmetric OM that lacks much freely accessible lipid. This feat is accomplished in the absence of an external energy source and is thought to be driven by the high thermodynamic stability of folded OMPs in the OM. With such a stable fold, the challenge that bacteria face in assembling OMPs into the OM is how to overcome the initial energy barrier of membrane insertion. In this review, we highlight the roles of the lipid environment and the OM in modulating the OMP-folding landscape and discuss the factors that guide folding in vitro and in vivo We particularly focus on the composition, architecture, and physical properties of the OM and how an understanding of the folding properties of OMPs in vitro can help explain the challenges they encounter during folding in vivo Current models of OMP biogenesis in the cellular environment are still in flux, but the stakes for improving the accuracy of these models are high. OMP folding is an essential process in all Gram-negative bacteria, and considering the looming crisis of widespread microbial drug resistance it is an attractive target. To bring down this vital OMP-supported barrier to antibiotics, we must first understand how bacterial cells build it.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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10
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Shahane G, Ding W, Palaiokostas M, Azevedo HS, Orsi M. Interaction of Antimicrobial Lipopeptides with Bacterial Lipid Bilayers. J Membr Biol 2019; 252:317-329. [PMID: 31098677 PMCID: PMC6790193 DOI: 10.1007/s00232-019-00068-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/03/2019] [Indexed: 02/07/2023]
Abstract
The resistance of pathogens to traditional antibiotics is currently a global issue of enormous concern. As the discovery and development of new antibiotics become increasingly challenging, synthetic antimicrobial lipopeptides (AMLPs) are now receiving renewed attention as a new class of antimicrobial agents. In contrast to traditional antibiotics, AMLPs act by physically disrupting the cell membrane (rather than targeting specific proteins), thus reducing the risk of inducing bacterial resistance. In this study, we use microsecond-timescale atomistic molecular dynamics simulations to quantify the interaction of a short AMLP (C16-KKK) with model bacterial lipid bilayers. In particular, we investigate how fundamental transmembrane properties change in relation to a range of lipopeptide concentrations. A number of structural, mechanical, and dynamical features are found to be significantly altered in a non-linear fashion. At 10 mol% concentration, lipopeptides have a condensing effect on bacterial bilayers, characterized by a decrease in the area per lipid and an increase in the bilayer order. Higher AMLP concentrations of 25 and 40 mol% destabilize the membrane by disrupting the bilayer core structure, inducing membrane thinning and water leakage. Important transmembrane properties such as the lateral pressure and dipole potential profiles are also affected. Potential implications on membrane function and associated proteins are discussed.
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Affiliation(s)
- Ganesh Shahane
- Institute of Bioengineering, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Wei Ding
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Michail Palaiokostas
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Helena S Azevedo
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Mario Orsi
- Department of Applied Sciences, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
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11
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Marzuoli I, Margreitter C, Fraternali F. Lipid Head Group Parameterization for GROMOS 54A8: A Consistent Approach with Protein Force Field Description. J Chem Theory Comput 2019; 15:5175-5193. [PMID: 31433640 PMCID: PMC7377650 DOI: 10.1021/acs.jctc.9b00509] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
![]()
Membranes
are a crucial component of both bacterial and mammalian
cells, being involved in signaling, transport, and compartmentalization.
This versatility requires a variety of lipid species to tailor the
membrane’s behavior as needed, increasing the complexity of
the system. Molecular dynamics simulations have been successfully
applied to study model membranes and their interactions with proteins,
elucidating some crucial mechanisms at the atomistic detail and thus
complementing experimental techniques. An accurate description of
the functional interplay of the diverse membrane components crucially
depends on the selected parameters that define the adopted force field.
A coherent parameterization for lipids and proteins is therefore needed.
In this work, we propose and validate new lipid head group parameters
for the GROMOS 54A8 force field, making use of recently published
parametrizations for key chemical moieties present in lipids. We make
use additionally of a new canonical set of partial charges for lipids,
chosen to be consistent with the parameterization of soluble molecules
such as proteins. We test the derived parameters on five phosphocholine
model bilayers, composed of lipid patches four times larger than the
ones used in previous studies, and run 500 ns long simulations of
each system. Reproduction of experimental data like area per lipid
and deuterium order parameters is good and comparable with previous
parameterizations, as well as the description of liquid crystal to
gel-phase transition. On the other hand, the orientational behavior
of the head groups is more realistic for this new parameter set, and
this can be crucial in the description of interactions with other
polar molecules. For that reason, we tested the interaction of the
antimicrobial peptide lactoferricin with two model membranes showing
that the new parameters lead to a weaker peptide–membrane binding
and give a more realistic outcome in comparing binding to antimicrobial
versus mammal membranes.
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Affiliation(s)
- Irene Marzuoli
- Randall Centre for Cell and Molecular Biology , King's College London , London SE1 1UL , U.K
| | - Christian Margreitter
- Randall Centre for Cell and Molecular Biology , King's College London , London SE1 1UL , U.K
| | - Franca Fraternali
- Randall Centre for Cell and Molecular Biology , King's College London , London SE1 1UL , U.K
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12
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Rosa AS, Cejas JP, Disalvo EA, Frías MA. Correlation between the hydration of acyl chains and phosphate groups in lipid bilayers: Effect of phase state, head group, chain length, double bonds and carbonyl groups. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1197-1203. [PMID: 30926364 DOI: 10.1016/j.bbamem.2019.03.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 03/24/2019] [Accepted: 03/25/2019] [Indexed: 01/17/2023]
Abstract
This paper demonstrates by means of FTIR/ATR analysis that water molecules intercalate at different extents in the acyl chain region of lipid membranes in correlation with the hydration of the phosphate groups. This correlation is sensible to the chain length, the presence of double bonds and the phase state of the lipid membrane. The presence of carbonyl groups CO modifies the profile of hydration of the two regions as observed from the comparison of DMPC and 14:0 Diether PC. The different water populations in lipid interphases would give arrangements with different free energy states that could drive the interaction of biological effectors with membranes.
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Affiliation(s)
- Antonio S Rosa
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL), National University of Santiago del Estero and CONICET, RN 9 - Km 1125, 4206 Santiago del Estero, Argentina
| | - Jimena P Cejas
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL), National University of Santiago del Estero and CONICET, RN 9 - Km 1125, 4206 Santiago del Estero, Argentina
| | - Edgardo A Disalvo
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL), National University of Santiago del Estero and CONICET, RN 9 - Km 1125, 4206 Santiago del Estero, Argentina
| | - María A Frías
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL), National University of Santiago del Estero and CONICET, RN 9 - Km 1125, 4206 Santiago del Estero, Argentina.
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13
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Shahane G, Ding W, Palaiokostas M, Orsi M. Physical properties of model biological lipid bilayers: insights from all-atom molecular dynamics simulations. J Mol Model 2019; 25:76. [PMID: 30806797 DOI: 10.1007/s00894-019-3964-0] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 02/07/2019] [Indexed: 02/04/2023]
Abstract
The physical properties of lipid bilayers are sensitive to the specific type and composition of the lipids that make up the many different types of cell membranes. Studying model bilayers of representative heterogeneous compositions can provide key insights into membrane functionality. In this work, we use atomistic molecular dynamics simulations to characterize key properties in a number of bilayer membranes of varying composition. We first examine basic properties, such as lipid area, volume, and bilayer thickness, of simple, homogeneous bilayers comprising several lipid types, which are prevalent in biological membranes. Such lipids are then used in simulations of heterogeneous systems representative of bacterial, mammalian, and cancer membranes. Our analysis is especially focused on depth-dependent, transmembrane profiles; in particular, we calculate lateral pressure and dipole potential profiles, two fundamental properties which play key roles in a large number of biological functions.
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Affiliation(s)
- Ganesh Shahane
- Institute of Bioengineering, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Wei Ding
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Michail Palaiokostas
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Mario Orsi
- Department of Applied Sciences, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
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Kimble-Hill AC, Petrache HI, Seifert S, Firestone MA. Reorganization of Ternary Lipid Mixtures of Nonphosphorylated Phosphatidylinositol Interacting with Angiomotin. J Phys Chem B 2018; 122:8404-8415. [PMID: 29877706 PMCID: PMC6351316 DOI: 10.1021/acs.jpcb.7b12641] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Phosphatidylinositol (PI) lipids are necessary for many cellular signaling pathways of membrane associated proteins, such as angiomotin (Amot). The Amot family regulates cellular polarity, growth, and migration. Given the low concentration of PI lipids in these membranes, it is likely that such protein-membrane interactions are stabilized by lipid domains or small lipid clusters. By small-angle X-ray scattering, we show that nonphosphorylated PI lipids induce lipid demixing in ternary mixtures of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), likely because of preferential interactions between the head groups of PE and PI. These results were obtained in the presence of buffer containing tris(hydroxymethyl)aminomethane, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, NaCl, ethylenediaminetetraacetic acid, dithiothreitol, and benzamidine at pH 8.0 that in previous work showed an ability to cause PC to phase separate but are necessary to stabilize Amot for in vitro experimentation. Collectively, this provided a framework for determining the effect of Amot on lipid organization. Using fluorescence spectroscopy, we were able to show that the association of Amot with this lipid platform causes significant reorganization of the lipid into a more homogenous structure. This reorganization mechanism could be the basis for Amot membrane association and fusogenic activity previously described in the literature and should be taken into consideration in future protein-membrane interaction studies.
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Affiliation(s)
- Ann C. Kimble-Hill
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, MS 4053, 635 Barnhill Dr., Indianapolis, Indiana 46202, United States
| | - Horia I. Petrache
- Department of Physics, Indiana University Purdue University Indianapolis, LD 154, 402 N. Blackford Street, Indianapolis, Indiana 46202, United States
| | - Soenke Seifert
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Millicent A. Firestone
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, MPA-CINT, MS K771, Los Alamos, New Mexico 87545, United States
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15
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Caruso B, Martini MF, Pickholz M, Perillo MA. V-Shaped Molecular Configuration of Wax Esters of Jojoba Oil in a Langmuir Film Model. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:7887-7898. [PMID: 29852738 DOI: 10.1021/acs.langmuir.8b00693] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The aim of the present work was to understand the interfacial properties of a complex mixture of wax esters (WEs) obtained from Jojoba oil (JO). Previously, on the basis of molecular area measurements, a hairpin structure was proposed as the hypothetical configuration of WEs, allowing their organization as compressible monolayers at the air-water interface. In the present work, we contributed with further experimental evidence by combining surface pressure (π), surface potential (Δ V), and PM-IRRAS measurements of JO monolayers and molecular dynamic simulations (MD) on a modified JO model. WEs were self-assembled in Langmuir films. Compression isotherms exhibited πlift-off at 100 Å2/molecule mean molecular area ( Alift-off) and a collapse point at πc ≈ 2.2 mN/m and Ac ≈ 77 Å2/molecule. The Δ V profile reflected two dipolar reorganizations, with one of them at A > Alift-off due to the release of loosely bound water molecules and another one at Ac < A < Alift-off possibly due to reorientations of a more tightly bound water population. This was consistent with the maximal SP value that was calculated according to a model that considered two populations of oriented water and was very close to the experimental value. The orientation of the ester group that was assumed in that calculation was coherent with the PM-IRRAS behavior of the carbonyl group with the C═O oriented toward the water and the C-O oriented parallel to the surface and was in accordance with their orientational angles (∼45 and ∼90°, respectively) determined by MD simulations. Taken together, the present results confirm a V shape rather than a hairpin configuration of WEs at the air-water interface.
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Affiliation(s)
- Benjamín Caruso
- Universidad Nacional de Córdoba , Facultad de Ciencias Exactas, Fı́sicas y Naturales, Departamento de Quı́mica, Cátedra de Quı́mica Biológica. , Av. Velez Sarsfield 1611 , 5016 Córdoba , Argentina
- CONICET-Universidad Nacional de Córdoba , Instituto de Investigaciones Biológicas y Tecnológicas (IIByT) , Córdoba , Argentina
| | - M Florencia Martini
- Universidad de Buenos Aires , Facultad de Farmacia y Bioquı́mica, Cátedra de Quı́mica Medicinal , Junı́n 956 SS , 1113 Buenos Aires , Argentina
- CONICET-Universidad de Buenos Aires , Instituto de la Quı́mica y Metabolismo del Fármaco (IQUIMEFA) , Buenos Aires , Argentina
| | - Mónica Pickholz
- Universidad de Buenos Aires , Facultad de Ciencias Exactas y Naturales, Departamento de Fı́sica , Intendente Güiraldes 2160, Pabellon 1, Ciudad Universitaria , C1428BFA CABA , Buenos Aires , Argentina
- CONICET - Universidad de Buenos Aires , Instituto de Fı́sica de Buenos Aires (IFIBA) , Buenos Aires , Argentina
| | - María A Perillo
- Universidad Nacional de Córdoba , Facultad de Ciencias Exactas, Fı́sicas y Naturales, Departamento de Quı́mica, Cátedra de Quı́mica Biológica. , Av. Velez Sarsfield 1611 , 5016 Córdoba , Argentina
- CONICET-Universidad Nacional de Córdoba , Instituto de Investigaciones Biológicas y Tecnológicas (IIByT) , Córdoba , Argentina
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16
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Rabinovich AL, Lyubartsev AP, Zhurkin DV. Unperturbed hydrocarbon chains and liquid phase bilayer lipid chains: a computer simulation study. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2017; 47:109-130. [PMID: 28698919 PMCID: PMC5834621 DOI: 10.1007/s00249-017-1231-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/13/2017] [Accepted: 06/07/2017] [Indexed: 11/24/2022]
Abstract
In this work, the properties of saturated and unsaturated fatty acid acyl chains 16:0, 18:0, 18:1(n-9)cis, 18:2(n-6)cis, 18:3(n-3)cis, 18:4(n-3)cis, 18:5(n-3)cis, 20:4(n-6)cis, 20:5(n-3)cis and 22:6(n-3)cis in a bilayer liquid crystalline state and similar hydrocarbon chains (with CH[Formula: see text] terminal groups instead of C=O groups) in the unperturbed state characterised by a lack of long-range interaction were investigated. The unperturbed hydrocarbon chains were modelled by Monte Carlo simulations at temperature [Formula: see text] K; sixteen fully hydrated homogeneous liquid crystalline phosphatidylcholine bilayers containing these chains were studied by molecular dynamics simulations at the same temperature. To eliminate effects of the simulation parameters, the molecular dynamics and Monte Carlo simulations were carried out using the same structural data and force field coefficients. From these computer simulations, the average distances between terminal carbon atoms of the chains (end-to-end distances) were calculated and compared. The trends in the end-to-end distances obtained for the unperturbed chains were found to be qualitatively similar to those obtained for the same lipid chains in the bilayers. So, for understanding of a number of processes in biological membranes (e.g., changes in fatty acid composition caused by environmental changes such as temperature and pressure), it is possible to use, at least as a first approximation, the relationships between the structure and properties for unperturbed or isolated hydrocarbon chains.
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Affiliation(s)
- Alexander L Rabinovich
- Institute of Biology, Karelian Research Center, Russian Academy of Sciences, Pushkinskaya 11, Petrozavodsk, 185910, Russian Federation
| | - Alexander P Lyubartsev
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91, Stockholm, Sweden.
| | - Dmitrii V Zhurkin
- Physics and Technology Department, Petrozavodsk State University, Universitetskaya 10, Petrozavodsk, 185910, Russian Federation
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17
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Ortiz-Suarez ML, Samsudin F, Piggot TJ, Bond PJ, Khalid S. Full-Length OmpA: Structure, Function, and Membrane Interactions Predicted by Molecular Dynamics Simulations. Biophys J 2017; 111:1692-1702. [PMID: 27760356 PMCID: PMC5071624 DOI: 10.1016/j.bpj.2016.09.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/30/2016] [Accepted: 09/06/2016] [Indexed: 12/02/2022] Open
Abstract
OmpA is a multidomain protein found in the outer membranes of most Gram-negative bacteria. Despite a wealth of reported structural and biophysical studies, the structure-function relationships of this protein remain unclear. For example, it is still debated whether it functions as a pore, and the precise molecular role it plays in attachment to the peptidoglycan of the periplasm is unknown. The absence of a consensus view is partly due to the lack of a complete structure of the full-length protein. To address this issue, we performed molecular-dynamics simulations of the full-length model of the OmpA dimer proposed by Robinson and co-workers. The N-terminal domains were embedded in an asymmetric model of the outer membrane, with lipopolysaccharide molecules in the outer leaflet and phospholipids in the inner leaflet. Our results reveal a large dimerization interface within the membrane environment, ensuring that the dimer is stable over the course of the simulations. The linker is flexible, expanding and contracting to pull the globular C-terminal domain up toward the membrane or push it down toward the periplasm, suggesting a possible mechanism for providing mechanical stability to the cell. The external loops were more stabilized than was observed in previous studies due to the extensive dimerization interface and presence of lipopolysaccharide molecules in our outer-membrane model, which may have functional consequences in terms of OmpA adhesion to host cells. In addition, the pore-gating behavior of the protein was modulated compared with previous observations, suggesting a possible role for dimerization in channel regulation.
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Affiliation(s)
- Maite L Ortiz-Suarez
- School of Chemistry, Highfield Campus, University of Southampton, Southampton, United Kingdom
| | - Firdaus Samsudin
- School of Chemistry, Highfield Campus, University of Southampton, Southampton, United Kingdom
| | - Thomas J Piggot
- School of Chemistry, Highfield Campus, University of Southampton, Southampton, United Kingdom
| | - Peter J Bond
- Bioinformatics Institute (A(∗)STAR), Singapore, Singapore; Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
| | - Syma Khalid
- School of Chemistry, Highfield Campus, University of Southampton, Southampton, United Kingdom.
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18
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Peyre J, Hamraoui A, Faustini M, Humblot V, Baccile N. Surface-induced assembly of sophorolipids. Phys Chem Chem Phys 2017; 19:15227-15238. [DOI: 10.1039/c7cp01339f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The surface self-assembly properties of acidic sophorolipids, a bolaform microbial glycolipid with pH-responsive properties, were studied based on the chemical nature of the support and pH of the solution.
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Affiliation(s)
- Jessie Peyre
- Sorbonne Universités
- UPMC Univ Paris 06
- CNRS
- Collège de France UMR 7574
- Chimie de la Matière Condensée de Paris
| | - Ahmed Hamraoui
- Sorbonne Universités
- UPMC Univ Paris 06
- CNRS
- Collège de France UMR 7574
- Chimie de la Matière Condensée de Paris
| | - Marco Faustini
- Sorbonne Universités
- UPMC Univ Paris 06
- CNRS
- Collège de France UMR 7574
- Chimie de la Matière Condensée de Paris
| | - Vincent Humblot
- Sorbonne Universités
- UPMC Univ Paris 06
- CNRS
- Laboratoire de Réactivité de Surface
- UMR 7197
| | - Niki Baccile
- Sorbonne Universités
- UPMC Univ Paris 06
- CNRS
- Collège de France UMR 7574
- Chimie de la Matière Condensée de Paris
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19
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Baccile N, Cuvier AS, Prévost S, Stevens CV, Delbeke E, Berton J, Soetaert W, Van Bogaert INA, Roelants S. Self-Assembly Mechanism of pH-Responsive Glycolipids: Micelles, Fibers, Vesicles, and Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10881-10894. [PMID: 27730816 DOI: 10.1021/acs.langmuir.6b02337] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A set of four structurally related glycolipids are described: two of them have one glucose unit connected to either stearic or oleic acid, and two other ones have a diglucose headgroup (sophorose) similarly connected to either stearic or oleic acid. The self-assembly properties of these compounds, poorly known, are important to know due to their use in various fields of application from cleaning to cosmetics to medical. At basic pH, they all form mainly small micellar aggregates. At acidic pH, the oleic and stearic derivatives of the monoglucose form, respectively, vesicles and bilayer, while the same derivatives of the sophorose headgroup form micelles and twisted ribbons. We use pH-resolved in situ small angle X-ray scattering (SAXS) under synchrotron radiation to characterize the pH-dependent mechanism of evolution from micelles to the more complex aggregates at acidic pH. By pointing out the importance of the COO-/COOH ratio, the melting temperature, Tm, of the lipid moieties, hydration of the glycosidic headgroup, the packing parameter, membrane rigidity, and edge stabilization, we are now able to draw a precise picture of the full self-assembly mechanism. This work is a didactical illustration of the complexity of the self-assembly process of a stimuli-responsive amphiphile during which many concomitant parameters play a key role at different stages of the process.
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Affiliation(s)
- Niki Baccile
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France UMR 7574, Chimie de la Matière Condensée de Paris, UMR 7574, F-75005 Paris, France
| | - Anne-Sophie Cuvier
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France UMR 7574, Chimie de la Matière Condensée de Paris, UMR 7574, F-75005 Paris, France
| | - Sylvain Prévost
- ESRF - The European Synchrotron , High Brilliance Beamline ID02, 38043 Grenoble, France
| | - Christian V Stevens
- SynBioC, Department of Sustainable Organic Chemistry and Technology, Ghent University , Ghent, Belgium
| | - Elisabeth Delbeke
- SynBioC, Department of Sustainable Organic Chemistry and Technology, Ghent University , Ghent, Belgium
| | - Jan Berton
- SynBioC, Department of Sustainable Organic Chemistry and Technology, Ghent University , Ghent, Belgium
| | - Wim Soetaert
- InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, 9000 Ghent, Belgium
| | - Inge N A Van Bogaert
- InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, 9000 Ghent, Belgium
| | - Sophie Roelants
- InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, 9000 Ghent, Belgium
- Bio Base Europe Pilot Plant , Rodenhuizekaai 1, 9042 Ghent, Belgium
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20
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Duan Y, Liu Y, Zhang C, Chen Z, Wen S. Insight into the Tribological Behavior of Liposomes in Artificial Joints. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10957-10966. [PMID: 27687876 DOI: 10.1021/acs.langmuir.6b02822] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Liposomes are widely used in drug delivery and gene therapy, and their new role as boundary lubricant in natural/artificial joints has been found in recent years. In this study, the tribological properties of liposomes on titanium alloy (Ti6Al4 V)/UHMWPE interface were studied by a ball-on-disc tribometer. The efficient reduction of friction coefficient and wear on both surfaces under various velocities and loads is found. A multilayer structure of physically adsorbed liposomes on Ti6Al4 V surface was also observed by atomic force microscope (AFM). Except for the hydration mechanism by phosphatidylcholine (PC) groups, the well-performed tribological properties by liposomes is also attributed to the existence of adsorbed liposome layers on both surfaces, which could reduce asperities contact and show great bearing capacity. This work enriches the research on liposomes for lubrication improvement on artificial surface and shows their value in clinical application.
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Affiliation(s)
- Yiqin Duan
- State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China
| | - Yuhong Liu
- State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China
| | - Caixia Zhang
- Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology , Beijing 100124, China
| | - Zhe Chen
- State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China
| | - Shizhu Wen
- State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China
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21
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Kettiger H, Québatte G, Perrone B, Huwyler J. Interactions between silica nanoparticles and phospholipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2163-2170. [DOI: 10.1016/j.bbamem.2016.06.023] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 06/17/2016] [Accepted: 06/23/2016] [Indexed: 12/11/2022]
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22
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Lyubartsev AP, Rabinovich AL. Force Field Development for Lipid Membrane Simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2483-2497. [PMID: 26766518 DOI: 10.1016/j.bbamem.2015.12.033] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 12/21/2015] [Accepted: 12/23/2015] [Indexed: 02/04/2023]
Abstract
With the rapid development of computer power and wide availability of modelling software computer simulations of realistic models of lipid membranes, including their interactions with various molecular species, polypeptides and membrane proteins have become feasible for many research groups. The crucial issue of the reliability of such simulations is the quality of the force field, and many efforts, especially in the latest several years, have been devoted to parametrization and optimization of the force fields for biomembrane modelling. In this review, we give account of the recent development in this area, covering different classes of force fields, principles of the force field parametrization, comparison of the force fields, and their experimental validation. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Alexander P Lyubartsev
- Department of Materials and Environmental Chemistry, Stockholm University, SE 106 91, Stockholm, Sweden.
| | - Alexander L Rabinovich
- Institute of Biology, Karelian Research Center, Russian Academy of Sciences, Pushkinskaya 11, Petrozavodsk, 185910, Russian Federation.
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23
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Antonova K, Vitkova V, Meyer C. Membrane tubulation from giant lipid vesicles in alternating electric fields. Phys Rev E 2016; 93:012413. [PMID: 26871107 DOI: 10.1103/physreve.93.012413] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Indexed: 06/05/2023]
Abstract
We report on the formation of tubular membrane protrusions from giant unilamellar vesicles in alternating electric fields. The construction of the experimental chamber permitted the application of external AC fields with strength of dozens of V/mm and kHz frequency during relatively long time periods (several minutes). Besides the vesicle electrodeformation from quasispherical to prolate ellipsoidal shape, the formation of long tubular membrane protrusions with length of up to several vesicle diameters, arising from the vesicular surface in the field direction, was registered and analyzed. The threshold electric field at which the electro-induced protrusions appeared was lower than the field strengths inducing membrane electroporation.
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Affiliation(s)
- K Antonova
- Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee, Sofia 1784, Bulgaria
| | - V Vitkova
- Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee, Sofia 1784, Bulgaria
| | - C Meyer
- Laboratoire de Physique des Systèmes Complexes, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens, France
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24
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Paran CW, Zou K, Ferrara PJ, Song H, Turk J, Funai K. Lipogenesis mitigates dysregulated sarcoplasmic reticulum calcium uptake in muscular dystrophy. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1530-8. [PMID: 26361872 DOI: 10.1016/j.bbalip.2015.09.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/27/2015] [Accepted: 09/06/2015] [Indexed: 01/07/2023]
Abstract
Muscular dystrophy is accompanied by a reduction in activity of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) that contributes to abnormal Ca(2+) homeostasis in sarco/endoplasmic reticulum (SR/ER). Recent findings suggest that skeletal muscle fatty acid synthase (FAS) modulates SERCA activity and muscle function via its effects on SR membrane phospholipids. In this study, we examined muscle's lipid metabolism in mdx mice, a mouse model for Duchenne muscular dystrophy (DMD). De novo lipogenesis was ~50% reduced in mdx muscles compared to wildtype (WT) muscles. Gene expressions of lipogenic and other ER lipid-modifying enzymes were found to be differentially expressed between wildtype (WT) and mdx muscles. A comprehensive examination of muscles' SR phospholipidome revealed elevated phosphatidylcholine (PC) and PC/phosphatidylethanolamine (PE) ratio in mdx compared to WT mice. Studies in primary myocytes suggested that defects in key lipogenic enzymes including FAS, stearoyl-CoA desaturase-1 (SCD1), and Lipin1 are likely contributing to reduced SERCA activity in mdx mice. Triple transgenic expression of FAS, SCD1, and Lipin1 (3TG) in mdx myocytes partly rescued SERCA activity, which coincided with an increase in SR PE that normalized PC/PE ratio. These findings implicate a defect in lipogenesis to be a contributing factor for SERCA dysfunction in muscular dystrophy. Restoration of muscle's lipogenic pathway appears to mitigate SERCA function through its effects on SR membrane composition.
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Affiliation(s)
- Christopher W Paran
- Department of Kinesiology, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA; Department of Physiology, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA
| | - Kai Zou
- Department of Kinesiology, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA
| | - Patrick J Ferrara
- Department of Kinesiology, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA
| | - Haowei Song
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - John Turk
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - Katsuhiko Funai
- Department of Kinesiology, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA; Department of Physiology, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, 115 Heart Drive, Greenville, North Carolina 27834, USA.
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25
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Donaldson SH, Røyne A, Kristiansen K, Rapp MV, Das S, Gebbie MA, Lee DW, Stock P, Valtiner M, Israelachvili J. Developing a general interaction potential for hydrophobic and hydrophilic interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2051-64. [PMID: 25072835 DOI: 10.1021/la502115g] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We review direct force measurements on a broad class of hydrophobic and hydrophilic surfaces. These measurements have enabled the development of a general interaction potential per unit area, W(D) = -2γ(i)Hy exp(-D/D(H)) in terms of a nondimensional Hydra parameter, Hy, that applies to both hydrophobic and hydrophilic interactions between extended surfaces. This potential allows one to quantitatively account for additional attractions and repulsions not included in the well-known combination of electrostatic double layer and van der Waals theories, the so-called Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The interaction energy is exponentially decaying with decay length D(H) ≈ 0.3-2 nm for both hydrophobic and hydrophilic interactions, with the exact value of D(H) depending on the precise system and conditions. The pre-exponential factor depends on the interfacial tension, γ(i), of the interacting surfaces and Hy. For Hy > 0, the interaction potential describes interactions between partially hydrophobic surfaces, with the maximum hydrophobic interaction (i.e., two fully hydrophobic surfaces) corresponding to Hy = 1. Hydrophobic interactions between hydrophobic monolayer surfaces measured with the surface forces apparatus (SFA) are shown to be well described by the proposed interaction potential. The potential becomes repulsive for Hy < 0, corresponding to partially hydrophilic (hydrated) interfaces. Hydrated surfaces such as mica, silica, and lipid bilayers are discussed and reviewed in the context of the values of Hy appropriate for each system.
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Affiliation(s)
- Stephen H Donaldson
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106-5080, United States
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pH Alters PEG-mediated fusion of phosphatidylethanolamine-containing vesicles. Biophys J 2015; 107:1327-38. [PMID: 25229141 DOI: 10.1016/j.bpj.2014.07.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 07/18/2014] [Accepted: 07/25/2014] [Indexed: 11/22/2022] Open
Abstract
Here, we examine the different mechanisms of poly(ethylene glycol)-mediated fusion of small unilamellar vesicles composed of dioleoylphosphatidylcholine/dioleoylphosphatidylethanolamine (DOPE)/sphingomyelin/cholesterol in a molar ratio of 35:30:15:20 at pH 7.4 versus pH 5. In doing so, we test the hypothesis that fusion of this lipid mixture should be influenced by differences in hydration of DOPE at these two pH values. An examination of the literature reveals that DOPE should be less hydrated at pH 5 (where influenza virus particles fuse with endosome membranes) than at pH 7.4 (where synaptic vesicles or HIV virus particles fuse with plasma membrane). Ensemble kinetic experiments revealed substantial differences in fusion of this plasma membrane mimetic system at these two pH values. The most dramatic difference was the observation of two intermediates at pH 5 but loss of one of these fusion intermediates at pH 7.4. Analysis of data collected at several temperatures also revealed that formation of the initial fusion intermediate (stalk) was favored at pH 7.4 due to increased activation entropy. Our observations support the hypothesis that the different negative intrinsic curvature of DOPE can account for different fusion paths and activation thermodynamics in steps of the fusion process at these two pH values. Finally, the effects of 2 mol % hexadecane on fusion at both pH values seemed to have similar origins for step 1 (promotion of acyl chain or hydrocarbon excursion into interbilayer space) and step 3 (reduction of interstice energy leading to expansion to a critical stalk radius). Different hexadecane effects on activation thermodynamics at these two pH values can also be related to altered DOPE hydration. The results support our kinetic model for fusion and offer insight into the critical role of phosphatidylethanolamine in fusion.
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Abstract
It is commonly assumed that the structure of water at a lipid-water interface is influenced mostly in the first hydration layer. However, recent results from different experimental methods show that perturbation extends through several hydration layers. Due to its low light penetration depth, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is specifically suited to study interlamellar water structure in multibilayers. Results obtained by this technique confirm the long-range water structure disturbance. Consequently, in confined membrane environments nearly all water molecules can be perturbed. It is important to note that the behavior of confined water molecules differs significantly in samples prepared in excess water and in partially hydrated samples. We show in what manner the interlamellar water perturbation is influenced by the hydration level and how it is sequentially modified with a step-by-step dehydration of samples either by water evaporation or by osmotic pressure. Our results also indicate that besides different levels of hydration the lipid-water interaction is modulated by different lipid headgroups and different lipid phases as well. Therefore, modification of interlamellar water properties may clarify the role of water-mediated effects in biological processes.
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Affiliation(s)
- Zoran Arsov
- Laboratory of Biophysics, Department of Solid State Physics, "Jozef Stefan" Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
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Pott T, Gerbeaud C, Barbier N, Méléard P. Melittin modifies bending elasticity in an unexpected way. Chem Phys Lipids 2015; 185:99-108. [DOI: 10.1016/j.chemphyslip.2014.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/28/2014] [Accepted: 05/18/2014] [Indexed: 12/22/2022]
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Khattari Z, Köhler S, Xu Y, Aeffner S, Salditt T. Stalk formation as a function of lipid composition studied by X-ray reflectivity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:41-50. [PMID: 25261611 DOI: 10.1016/j.bbamem.2014.08.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 07/24/2014] [Accepted: 08/08/2014] [Indexed: 10/24/2022]
Abstract
We have investigated the structure and interaction of solid-supported multilamellar phospholipid bilayers in view of stalk formation as model systems for membrane fusion. The multi-component bilayers were composed of ternary and quaternary mixtures, containing phosphatidylcholines, phosphatidylethanolamines, sphingomyelin, cholesterol, diacylglycerol, and phosphatidylinositol. Analysis of the obtained electron density profiles and the pressure-distance curves reveals systematic changes in structure and hydration repulsion. The osmotic pressure needed to induce stalk formation at the transition from the fluid lamellar to the rhombohedral phase indicates how membrane fusion properties are modified by bilayer composition.
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Affiliation(s)
- Ziad Khattari
- Department of Physics, Hashemite University, 13115 Zarqa, Jordan.
| | - Sebastian Köhler
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Yihui Xu
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sebastian Aeffner
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Tim Salditt
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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Kienle DF, de Souza JV, Watkins EB, Kuhl TL. Thickness and refractive index of DPPC and DPPE monolayers by multiple-beam interferometry. Anal Bioanal Chem 2014; 406:4725-33. [DOI: 10.1007/s00216-014-7866-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/09/2014] [Accepted: 04/29/2014] [Indexed: 11/30/2022]
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31
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Do C, Jang HS, Choi SM. Hydration forces between surfaces of surfactant coated single-walled carbon nanotubes. J Chem Phys 2013; 138:114701. [DOI: 10.1063/1.4793763] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Water defects induced by expansion and electrical fields in DMPC and DMPE monolayers: Contribution of hydration and confined water. Colloids Surf B Biointerfaces 2013; 102:871-8. [DOI: 10.1016/j.colsurfb.2012.09.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 09/12/2012] [Accepted: 09/17/2012] [Indexed: 11/19/2022]
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33
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Mills M, Orr BG, Banaszak Holl MM, Andricioaei I. Attractive hydration forces in DNA-dendrimer interactions on the nanometer scale. J Phys Chem B 2013; 117:973-81. [PMID: 23234339 PMCID: PMC3633417 DOI: 10.1021/jp309616t] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The energetic contribution of attractive hydration forces arising from water ordering is an interesting but often neglected aspect of macromolecular interactions. Ordering effects of water can bring about cooperativity in many intermolecular transactions, in both the short and long range. Given its high charge density, this is of particular importance for DNA. For instance, in nanotechnology, highly charged dendrimers are used for DNA compaction and transfection. Hypothesizing that water ordering and hydration forces should be maximal for DNA complexes that show charge complementarity (positive-negative), we present here an analysis of water ordering from molecular dynamics simulations and free energy calculations of the interaction between DNA and a nanoparticle with a high positive charge density. Our results indicate not only that complexation of the dendrimer with DNA affects the local water structure but also that ordered water molecules facilitate long-range interactions between the molecules. This contributes significantly to the free energy of binding of dendrimers to DNA and extends the interaction well beyond the electrostatic range of the DNA. Such water effects are of potentially substantial importance in cases when molecules appear to recognize each other across sizable distances, or for which kinetic rates are too fast to be due to pure diffusion. Our results are in good agreement with experiments on the role of solvent in DNA condensation by multivalent cations and exemplify a microscopic realization of mean-field phenomenological theories for hydration forces between mesoscopic surfaces.
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Tsai HHG, Lai WX, Lin HD, Lee JB, Juang WF, Tseng WH. Molecular dynamics simulation of cation–phospholipid clustering in phospholipid bilayers: Possible role in stalk formation during membrane fusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2742-55. [DOI: 10.1016/j.bbamem.2012.05.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 05/11/2012] [Accepted: 05/29/2012] [Indexed: 10/28/2022]
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Leite FL, Bueno CC, Da Róz AL, Ziemath EC, Oliveira ON. Theoretical models for surface forces and adhesion and their measurement using atomic force microscopy. Int J Mol Sci 2012. [PMID: 23202925 PMCID: PMC3497299 DOI: 10.3390/ijms131012773] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of afs, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution.
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Affiliation(s)
- Fabio L. Leite
- Nanoneurobiophysics Research Group, Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), P.O. Box 3031, CEP 18052-780, Sorocaba, São Paulo, Brazil; E-Mails: (C.C.B.); (A.L.D.R.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +55-015-3229-6014; Fax: +55-015-3229-5902
| | - Carolina C. Bueno
- Nanoneurobiophysics Research Group, Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), P.O. Box 3031, CEP 18052-780, Sorocaba, São Paulo, Brazil; E-Mails: (C.C.B.); (A.L.D.R.)
| | - Alessandra L. Da Róz
- Nanoneurobiophysics Research Group, Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), P.O. Box 3031, CEP 18052-780, Sorocaba, São Paulo, Brazil; E-Mails: (C.C.B.); (A.L.D.R.)
| | - Ervino C. Ziemath
- Institute of Geosciences and Exact Sciences, São Paulo State University (UNESP), P.O. Box 178, CEP 13550-970, Rio Claro, São Paulo, Brazil; E-Mail:
| | - Osvaldo N. Oliveira
- Institute of Physics of São Carlos, University of São Paulo (USP), P.O. Box 369, CEP 13560-970, São Carlos, São Paulo, Brazil; E-Mail:
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37
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Methylation of ethanolamine groups in phosphoethanolamines is relevant for L-arginine insertion in lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1395-401. [DOI: 10.1016/j.bbamem.2012.02.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 01/31/2012] [Accepted: 02/08/2012] [Indexed: 11/21/2022]
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38
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Stanley C, Rau DC. Evidence for water structuring forces between surfaces. Curr Opin Colloid Interface Sci 2011; 16:551-556. [PMID: 22125414 DOI: 10.1016/j.cocis.2011.04.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Structured water on apposing surfaces can generate significant energies due to reorganization and displacement of water as the surfaces encounter each other. Force measurements on a multitude of biological structures using the osmotic stress technique have elucidated commonalities that point toward an underlying hydration force. In this review, the forces of two contrasting systems are considered in detail: highly charged DNA and nonpolar, uncharged hydroxypropyl cellulose. Conditions for both net repulsion and attraction, along with the measured exclusion of chemically different solutes from these macromolecular surfaces, are explored and demonstrate common features consistent with a hydration force origin. Specifically, the observed interaction forces can be reduced to the effects of perturbing structured surface water.
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Affiliation(s)
- Christopher Stanley
- Neutron Scattering Science Division, Oak Ridge National Laboratory, PO Box 2008 MSC 6473, Oak Ridge, TN 37831
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39
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Computer simulations of water-mediated force between phospholipid membranes. Curr Opin Colloid Interface Sci 2011. [DOI: 10.1016/j.cocis.2011.04.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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40
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Gustavsson M, Traaseth NJ, Veglia G. Activating and deactivating roles of lipid bilayers on the Ca(2+)-ATPase/phospholamban complex. Biochemistry 2011; 50:10367-74. [PMID: 21992175 DOI: 10.1021/bi200759y] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The physicochemical properties of the lipid bilayer shape the structure and topology of membrane proteins and regulate their biological function. Here, we investigated the functional effects of various lipid bilayer compositions on the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA) in the presence and absence of its endogenous regulator, phospholamban (PLN). In the cardiac muscle, SERCA hydrolyzes one ATP molecule to translocate two Ca(2+) ions into the SR membrane per enzymatic cycle. Unphosphorylated PLN reduces SERCA's affinity for Ca(2+) and affects the enzymatic turnover. We varied bilayer thickness, headgroup, and fluidity and found that both the maximal velocity (V(max)) of the enzyme and its apparent affinity for Ca(2+) (K(Ca)) are strongly affected. Our results show that (a) SERCA's V(max) has a biphasic dependence on bilayer thickness, reaching maximum activity with 22-carbon lipid chain length, (b) phosphatidylethanolamine (PE) and phosphatidylserine (PS) increase Ca(2+) affinity, and (c) monounsaturated lipids afford higher SERCA V(max) and Ca(2+) affinity than diunsaturated lipids. The presence of PLN removes the activating effect of PE and shifts SERCA's activity profile, with a maximal activity reached in bilayers with 20-carbon lipid chain length. Our results in synthetic lipid systems compare well with those carried out in native SR lipids. Importantly, we found that specific membrane compositions closely reproduce PLN effects (V(max) and K(Ca)) found in living cells, reconciling an ongoing controversy regarding the regulatory role of PLN on SERCA function. Taken with the physiological changes occurring in the SR membrane composition, these studies underscore a possible allosteric role of the lipid bilayers on the SERCA/PLN complex.
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Affiliation(s)
- Martin Gustavsson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
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41
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Goldberg R, Schroeder A, Barenholz Y, Klein J. Interactions between adsorbed hydrogenated soy phosphatidylcholine (HSPC) vesicles at physiologically high pressures and salt concentrations. Biophys J 2011; 100:2403-11. [PMID: 21575574 DOI: 10.1016/j.bpj.2011.03.061] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 03/20/2011] [Accepted: 03/25/2011] [Indexed: 10/18/2022] Open
Abstract
Using a surface force balance, we measured normal and shear interactions as a function of surface separation between layers of hydrogenated soy phosphatidylcholine (HSPC) small unilamellar vesicles (SUVs) adsorbed from dispersion at physiologically high salt concentrations (0.15 M NaNO₃). Cryo-scanning electron microscopy shows that each surface is coated by a close-packed HSPC-SUV layer with an overlayer of liposomes on top. A clear attractive interaction between the liposome layers is seen upon approach and separation, followed by a steric repulsion upon further compression. The shear forces reveal low friction coefficients (μ = 0.008-0.0006) up to contact pressures of at least 6 MPa, comparable to those observed in the major joints. The spread in μ-values may be qualitatively accounted for by different local liposome structure at different contact points, suggesting that the intrinsic friction of the HSPC-SUV layers at this salt concentration is closer to the lower limit (μ = ~0.0006). This low friction is attributed to the hydration lubrication mechanism arising from rubbing of the hydrated phosphocholine-headgroup layers exposed at the outer surface of each liposome, and provides support for the conjecture that phospholipids may play a significant role in biological lubrication.
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Affiliation(s)
- Ronit Goldberg
- Department of Materials and Interfaces, Weizmann Institute, Rehovot, Israel
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42
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Hong H, Bowie JU. Dramatic destabilization of transmembrane helix interactions by features of natural membrane environments. J Am Chem Soc 2011; 133:11389-98. [PMID: 21682279 DOI: 10.1021/ja204524c] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Membrane proteins have evolved to fold and function in a lipid bilayer, so it is generally assumed that their stability should be optimized in a natural membrane environment. Yet optimal stability is not always in accord with optimization of function, so evolutionary pressure, occurring in a complex membrane environment, may favor marginal stability. Here, we find that the transmembrane helix dimer, glycophorin A (GpATM), is actually much less stable in the heterogeneous environment of a natural membrane than it is in model membranes and even common detergents. The primary destabilizing factors are electrostatic interactions between charged lipids and charged GpATM side chains, and nonspecific competition from other membrane proteins. These effects overwhelm stabilizing contributions from lateral packing pressure and excluded volume. Our work illustrates how evolution can employ membrane composition to modulate protein stability.
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Affiliation(s)
- Heedeok Hong
- Department of Chemistry and Biochemistry, UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095, USA
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43
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Allen WJ, Bevan DR. Steered Molecular Dynamics Simulations Reveal Important Mechanisms in Reversible Monoamine Oxidase B Inhibition. Biochemistry 2011; 50:6441-54. [DOI: 10.1021/bi200446w] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- William J. Allen
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - David R. Bevan
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
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The potassium channel KcsA: a model protein in studying membrane protein oligomerization and stability of oligomeric assembly? Arch Biochem Biophys 2011; 510:1-10. [PMID: 21458409 DOI: 10.1016/j.abb.2011.03.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Revised: 03/25/2011] [Accepted: 03/25/2011] [Indexed: 01/01/2023]
Abstract
Many membrane proteins are functional as stable oligomers. An understanding of the conditions that elicit and enhance oligomerization is important in many therapeutics. In this regard, protein-protein and protein-lipid interactions play crucial roles in the assembly and stability of oligomeric complexes. Recent years have seen a rapid increase in the mechanistic information on the importance of cytoplasmic termini in determining subunit assembly and stability of oligomeric complexes. In addition, the role of specific protein-lipid interaction between anionic phospholipids and "hot spots" on the protein surface has also become evident in stabilizing oligomeric assemblies. This review focuses on several contemporary developments of membrane proteins that stabilize oligomers by taking the potassium channel KcsA as an exemplary ion channel.
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Aw MS, Simovic S, Addai-Mensah J, Losic D. Polymeric micelles in porous and nanotubular implants as a new system for extended delivery of poorly soluble drugs. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c0jm04307a] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Soubias O, Teague WE, Hines KG, Mitchell DC, Gawrisch K. Contribution of membrane elastic energy to rhodopsin function. Biophys J 2010; 99:817-24. [PMID: 20682259 DOI: 10.1016/j.bpj.2010.04.068] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 04/16/2010] [Accepted: 04/23/2010] [Indexed: 11/16/2022] Open
Abstract
We considered the issue of whether shifts in the metarhodopsin I (MI)-metarhodopsin II (MII) equilibrium from lipid composition are fully explicable by differences in bilayer curvature elastic stress. A series of six lipids with known spontaneous radii of monolayer curvature and bending elastic moduli were added at increasing concentrations to the matrix lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and the MI-MII equilibrium measured by flash photolysis followed by recording UV-vis spectra. The average area-per-lipid molecule and the membrane hydrophobic thickness were derived from measurements of the (2)H NMR order parameter profile of the palmitic acid chain in POPC. For the series of ethanolamines with different levels of headgroup methylation, shifts in the MI-MII equilibrium correlated with changes in membrane elastic properties as expressed by the product of spontaneous radius of monolayer curvature, bending elastic modulus, and lateral area per molecule. However, for the entire series of lipids, elastic energy explained the shifts only partially. Additional contributions correlated with the capability of the ethanolamine headgroups to engage in hydrogen bonding with the protein, independent of the state of ethanolamine methylation, with introduction of polyunsaturated sn-2 hydrocarbon chains, and with replacement of the palmitic acid sn-1 chains by oleic acid. The experiments point to the importance of interactions of rhodopsin with particular lipid species in the first layer of lipids surrounding the protein as well as to membrane elastic stress in the lipid-protein domain.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, USA
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47
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48
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Gutman M, Nachliel E, Kiryati S. Dynamic studies of proton diffusion in mesoscopic heterogeneous matrix: II. The interbilayer space between phospholipid membranes. Biophys J 2010; 63:281-90. [PMID: 19431841 DOI: 10.1016/s0006-3495(92)81585-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The thin water layer, as found in chloroplast or mitochondria, is confined between low dielectric amphypathic surfaces a few nm apart.The physical properties of this mesoscopic space, and how its dimensions affect the rate of chemical reactions proceeding in it, is the subject for this study.The method selected for this purpose is time resolved fluorometry which can monitor the reversible dissociation of a proton from excited molecule of pyranine (8 hydroxy pyrene 1,3,6 tri sulfonate) trapped in thin water layers of a multilamellar vesicle made of neutral or slightly charged phospholipids.The results were analyzed by a computer program of N. Agmon (Pines, E., D. Huppert, and N. Agmon. 1988. J. Am. Chem. Soc. 88:5620-5630) that simulates the diffusion of a proton, subjected to electrostatic attraction, in a thin water layer enclosed between low affinity, proton binding surfaces. The analysis determines the diffusion coefficient of the proton, the effective dielectric constant of the water and the water accessibility of the phosphomoieties of the lipids.These parameters were measured for various lipids [egg-phosphatidylcholine (egg PC), dipalmitoyl phosphatidylcholine (DPPC), cholesterol + DPPC (1:1) and egg PC plus phosphatidyl serine (9:1)] and under varying osmotic pressure which reduces the width of the water layer down to approximately 10 approximately across.WE FOUND THAT: (a) The effective dielectric constant of the aqueous layer, depending on the lipid composition, is approximately 40. (b) The diffusion coefficient of the proton in the thin layer (30-10 approximately across) is that measured in bulk water D = 9.3 10(-5) cm(2)/s, indicating that the water retains its normal liquid state even on contact with the membrane. (c) The reactivity of the phosphomoiety, quantitated by rate of its reaction with proton, diminishes under lateral pressure which reduces the surface area per lipid.We find no evidence for abnormal dynamics of proton transfer at the lipid water interface which, by any mechanism, accelerates its diffusion.
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Affiliation(s)
- M Gutman
- Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978 Israel
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49
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Abstract
Many biomaterials are designed to regulate the interactions between artificial and natural surfaces. However, when materials are inserted through the cell membrane itself the interface formed between the interior edge of the membrane and the material surface is not well understood and poorly controlled. Here we demonstrate that by replicating the nanometer-scale hydrophilic-hydrophobic-hydrophilic architecture of transmembrane proteins, artificial "stealth" probes spontaneously insert and anchor within the lipid bilayer core, forming a high-strength interface. These nanometer-scale hydrophobic bands are readily fabricated on metallic probes by functionalizing the exposed sidewall of an ultrathin evaporated Au metal layer rather than by lithography. Penetration and adhesion forces for butanethiol and dodecanethiol functionalized probes were directly measured using atomic force microscopy (AFM) on thick stacks of lipid bilayers to eliminate substrate effects. The penetration dynamics were starkly different for hydrophobic versus hydrophilic probes. Both 5- and 10 nm thick hydrophobically functionalized probes naturally resided within the lipid core, while hydrophilic probes remained in the aqueous region. Surprisingly, the barrier to probe penetration with short butanethiol chains (E(o,5 nm) = 21.8k(b)T, E(o,10 nm) = 15.3k(b)T) was dramatically higher than longer dodecanethiol chains (E(o,5 nm) = 14.0k(b)T, E(o,10 nm) = 10.9k(b)T), indicating that molecular mobility and orientation also play a role in addition to hydrophobicity in determining interface stability. These results highlight a new strategy for designing artificial cell interfaces that can nondestructively penetrate the lipid bilayer.
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50
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Xu W, Pincet F. Quantification of phase transitions of lipid mixtures from bilayer to non-bilayer structures: Model, experimental validation and implication on membrane fusion. Chem Phys Lipids 2009; 163:280-5. [PMID: 20018184 DOI: 10.1016/j.chemphyslip.2009.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 10/05/2009] [Accepted: 12/03/2009] [Indexed: 10/20/2022]
Abstract
Lipid bilayers provide a solute-proof barrier that is widely used in living systems. It has long been recognized that the structural changes of lipids during the phase transition from bilayer to non-bilayer have striking similarities with those accompanying membrane fusion processes. In spite of this resemblance, the numerous quantitative studies on pure lipid bilayers are difficult to apply to real membranes. One reason is that in living matter, instead of pure lipids, lipid mixtures are involved and there is currently no model that establishes the connection between pure lipids and lipid mixtures. Here, we make this connection by showing how to obtain (i) the short-range repulsion between bilayers made of lipid mixtures and, (ii) the pressure at which transition from bilayer phase to non-bilayer phases occur. We validated our models by fitting the experimental data of several lipid mixtures to the theoretical data calculated based on our model. These results provide a useful tool to quantitatively predict the behavior of complex membranes at low hydration.
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Affiliation(s)
- Weiming Xu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA
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