101
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Habartová A, Roeselová M, Cwiklik L. Investigation of Mixed Surfactant Films at Water Surface Using Molecular Dynamics Simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:11508-11515. [PMID: 26439598 DOI: 10.1021/acs.langmuir.5b02854] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Multicomponent Langmuir monolayers are important models of organic coatings of naturally occurring water-vapor interfaces such as the surfaces of oceans or aerosol particles. We investigated mixed monolayers comprised of palmitic acid, C15H31COOH (PA) and 1-bromoalkanes of different chain length (C5, C10, and C16) at the air-water interface employing classical molecular dynamics simulations. Different composition ratios and lateral compression of the monolayers were considered. The structural parameters, such as density profiles, and deuterium order parameter, evaluated as functions of composition and the lateral film packing, provide microscopic information about organization and dynamics of the mixed monolayers. Simulations demonstrate that stable and well mixed monolayers are formed by the mixtures of PA and BrC16H33 (BrCl6), whereas the two considered shorter bromoalkanes, BrC5H11 (BrC5) and BrC10H21 (BrC10), do not form stable films. This is in accord with earlier experimental studies. Under high lateral pressures, in PA/BrC10 mixed systems molecules of the bromoalkane readily flip in the monolayer and subsequently leave the film, while the molecules of the longer BrC16 are expelled from the PA film but no flipping occurs. These results suggest that the film collapse under pressure is preceded by squeezing-out of bromoalkanes from the PA monolayer.
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Affiliation(s)
- Alena Habartová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nám. 2, 16610, Prague 6, Czech Republic
| | - Martina Roeselová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nám. 2, 16610, Prague 6, Czech Republic
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic , v.v.i., Dolejškova 3, 18223 Prague 8, Czech Republic
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102
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Barnoud J, Urbini L, Monticelli L. C₆₀ fullerene promotes lung monolayer collapse. J R Soc Interface 2015; 12:20140931. [PMID: 25589571 DOI: 10.1098/rsif.2014.0931] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C₆₀ fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m(-1)). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m(-1)). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo, which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant.
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Affiliation(s)
- Jonathan Barnoud
- INSERM, UMR-S665, Paris 75015, France Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris 75013, France
| | - Laura Urbini
- INSERM, UMR-S665, Paris 75015, France Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris 75013, France
| | - Luca Monticelli
- BMSSI, CNRS UMR 5086, IBCP, Lyon, France Université Claude Bernard Lyon I, Lyon, France
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103
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Telesford DM, Verreault D, Reick-Mitrisin V, Allen HC. Reduced Condensing and Ordering Effects by 7-Ketocholesterol and 5β,6β-Epoxycholesterol on DPPC Monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:9859-9869. [PMID: 26322794 DOI: 10.1021/acs.langmuir.5b02539] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The exposure of organic-coated marine aerosols containing cholesterol (Chol) to radiation and/or an oxidizing atmosphere results in the formation of oxidized derivatives or oxysterols and will likely change aerosol surface properties. However, the intermolecular interactions between oxysterols and other lipid components and their influence on the surface properties of marine aerosols are not well-known. To address this question, the interfacial behavior and domain morphology of model Langmuir monolayers of two ring-substituted oxysterols, 7-ketocholesterol (7-KChol) and 5β,6β-epoxycholesterol (5,6β-EChol), mixed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were investigated by means of compression isotherms and Brewster angle microscopy (BAM) over a broad range of surface pressures and sterol molar ratios. Mixed DPPC/cholesterol (Chol) monolayers were also measured for comparison. The results of compression experiments showed that the condensing effect induced on mixed DPPC/sterol monolayers at low surface pressures and for intermediate molar ratios (0.3 ≤ X(sterol) ≤ 0.7) was weaker for oxysterols than for Chol. Additionally, mixed DPPC/oxysterol monolayers exhibited markedly smaller (∼2-3-fold) interfacial rigidity. Examination of the excess free energy of mixing further revealed that DPPC monolayers containing 7-KChol and Chol were thermodynamically more stable at high surface pressures than those with 5,6β-EChol, indicating that the strength of interactions between DPPC and 5,6β-EChol was the smallest. Finally, BAM images in the LE-LC phase of DPPC revealed that in comparison to Chol the addition of small amounts of oxysterols results in larger and less numerous domains, showing that oxysterols are not as effective in fluidizing the condensed phase of DPPC. Taken together, these results suggest that the strength of van der Waals interactions of DPPC alkyl chains with sterols follows the sterol hydrophobicity, with Chol being the most hydrophobic and oxysterols more hydrophilic due to their ketone and epoxy moieties. The difference in the condensing ability and stability of 7-KChol and 5,6β-EChol on DPPC likely originates from the distinct molecular structure and position of oxidation on the steroid nucleus. As suggested by recent MD simulations, depending on the oxidation position, ring-substituted oxysterols have a broader angular distribution of orientation than Chol in bilayers, which could be responsible for the observed reduction in condensing ability.
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Affiliation(s)
- Dana-Marie Telesford
- Department of Chemistry & Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Dominique Verreault
- Department of Chemistry & Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Victoria Reick-Mitrisin
- Department of Chemistry & Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Heather C Allen
- Department of Chemistry & Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States
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104
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Mohammad-Aghaie D, Bresme F. Force-field dependence on the liquid-expanded to liquid-condensed transition in DPPC monolayers. MOLECULAR SIMULATION 2015. [DOI: 10.1080/08927022.2015.1059428] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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105
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Nishizawa K, Nishizawa M, Gnanasambandam R, Sachs F, Sukharev SI, Suchyna TM. Effects of Lys to Glu mutations in GsMTx4 on membrane binding, peptide orientation, and self-association propensity, as analyzed by molecular dynamics simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2767-78. [PMID: 26342676 DOI: 10.1016/j.bbamem.2015.09.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 08/27/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
Abstract
GsMTx4, a gating modifier peptide acting on cationic mechanosensitive channels, has a positive charge (+5e) due to six Lys residues. The peptide does not have a stereospecific binding site on the channel but acts from the boundary lipids within a Debye length of the pore probably by changing local stress. To gain insight into how these Lys residues interact with membranes, we performed molecular dynamics simulations of Lys to Glu mutants in parallel with our experimental work. In silico, K15E had higher affinity for 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine bilayers than wild-type (WT) peptide or any other mutant tested, and showed deeper penetration than WT, a finding consistent with the experimental data. Experimentally, the inhibitory activities of K15E and K25E were most compromised, whereas K8E and K28E inhibitory activities remained similar to WT peptide. Binding of WT in an interfacial mode did not influence membrane thickness. With interfacial binding, the direction of the dipole moments of K15E and K25E was predicted to differ from WT, whereas those of K8E and K28E oriented similarly to that of WT. These results support a model in which binding of GsMTx4 to the membrane acts like an immersible wedge that serves as a membrane expansion buffer reducing local stress and thus inhibiting channel activity. In simulations, membrane-bound WT attracted other WT peptides to form aggregates. This may account for the positive cooperativity observed in the ion channel experiments. The Lys residues seem to fine-tune the depth of membrane binding, the tilt angle, and the dipole moments.
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Affiliation(s)
| | | | | | - Frederick Sachs
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA
| | - Sergei I Sukharev
- Department of Biology, University of Maryland, College Park, MD, USA
| | - Thomas M Suchyna
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA
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106
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Ortiz A, Domènech O, Muñoz-Juncosa M, Prat J, Haro I, Girona V, Alsina MA, Pujol M. A study of HIV-1 FP inhibition by GBV-C peptides using lipid nano-assemblies. Colloids Surf A Physicochem Eng Asp 2015. [DOI: 10.1016/j.colsurfa.2014.12.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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107
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Miyoshi T, Kato S. Detailed Analysis of the Surface Area and Elasticity in the Saturated 1,2-Diacylphosphatidylcholine/Cholesterol Binary Monolayer System. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:9086-9096. [PMID: 26255826 DOI: 10.1021/acs.langmuir.5b01775] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The surface pressure-area (π-A) isotherms of DMPC, DPPC, and DSPC/cholesterol binary monolayers were systematically measured with great care to gain insight into the lateral molecular packing in these binary monolayer systems. The average molecular area A and the area elastic modulus C(s)⁻¹ at a given surface pressure were calculated as a function of cholesterol mole fraction x(chol). As a result, data reliable enough for the analysis of detailed phase behavior were obtained. We identified several characteristic phase regions and assigned the phase state in each region on the basis of the deviation of A(x(chol)) and C(s)⁻¹(x(chol)) from ideal additivity. We also estimated the partial molecular areas of DMPC, DPPC, DSPC, and cholesterol in the single-phase regions, where C(s)⁻¹(x(chol)) values fell on an ideal additivity curve. We found that the addition of cholesterol induces the formation of a highly condensed phase where the diacylphosphatidylcholine (diacyl PC) molecule has a surface area even smaller than that in the solid phase, irrespective of the surface pressure and the chain length of diacyl PC. Here, we call the cholesterol-induced condensed phase the CC phase. Furthermore, we demonstrated that the basic features of A(x(chol)) and C(s)⁻¹(x(chol)) profiles can be explained semiquantitatively by assuming the state of vicinity lipids surrounding sparsely distributed cholesterol molecules in the low x(chol) region as a third state of the diacyl PC molecule in addition to the states in the pure diacyl PC monolayer and in the CC phase.
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Affiliation(s)
- Tsubasa Miyoshi
- Department of Physics, Graduate School of Science and Technology, Kwansei Gakuin University , 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan
| | - Satoru Kato
- Department of Physics, Graduate School of Science and Technology, Kwansei Gakuin University , 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan
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108
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Chen Y, Jena KC, Lütgebaucks C, Okur HI, Roke S. Three Dimensional Nano "Langmuir Trough" for Lipid Studies. NANO LETTERS 2015; 15:5558-5563. [PMID: 26151602 DOI: 10.1021/acs.nanolett.5b02143] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A three-dimensional-phospholipid monolayer with tunable molecular structure was created on the surface of oil nanodroplets from a mixture of phospholipids, oil, and water. This simple nanoemulsion preparation technique generates an in situ prepared membrane model system with controllable molecular surface properties that resembles a lipid droplet. The molecular interfacial structure of such a nanoscopic system composed of hexadecane, 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC), and water was determined using vibrational sum frequency scattering and second harmonic scattering techniques. The droplet surface structure of DPPC can be tuned from a tightly packed liquid condensed phase like monolayer to a more dilute one that resembles the liquid condensed/liquid expanded coexistence phase by varying the DPPC/oil/water ratio. The tunability of the chemical structure, the high surface-to-volume ratio, and the small sample volume make this system an ideal model membrane for biochemical research.
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Affiliation(s)
- Yixing Chen
- †Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Kailash C Jena
- †Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
- ‡Department of Physics, Indian Institute of Technology Ropar, Rupnagar, 140001, India
| | - Cornelis Lütgebaucks
- †Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Halil I Okur
- †Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Sylvie Roke
- †Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
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109
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Huston KJ, Larson RG. Reversible and Irreversible Adsorption Energetics of Poly(ethylene glycol) and Sorbitan Poly(ethoxylate) at a Water/Alkane Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:7503-7511. [PMID: 26079039 DOI: 10.1021/acs.langmuir.5b00398] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We simulate poly(ethylene glycol) (PEG) oligomers and model Tween 80 (polyoxyethylene sorbitan monooleate) molecules at water/alkane interfaces. Using the weighted histogram analysis method (WHAM), including an extension of WHAM to two reaction coordinates to remove hysteresis, we calculate interfacial potentials of mean force (PMFs) for PEG and Tween 80 using three force fields: the atomistic GROMOS 53a6OXY+D and two coarse-grained (CG) MARTINI force fields. Because the force fields have not yet been validated for PEO adsorption to hydrophobic interfaces, we calculate PMFs for alcohol ethoxylates C12E2 and C12E8 and find that they agree with semiempirical results of Mulqueen and Blankschtein [Langmuir 2002, 18 (2), 365-376] for the GROMOS 53a6OXY+D force field, whereas for both MARTINI force fields, PEO adsorbs too weakly to a clean hydrophobic interface. One MARTINI force field incorrectly shows depletion rather than adsorption to a clean hydrophobic interface. We find that the adsorption free energy for PEG oligomers at a clean, planar water/alkane interface is around 1.3 kBT per monomer for the atomistic force field but is less than half of this for the two CG force fields. With the newly validated GROMOS 53a6OXY+D force field, we bracket the dilute adsorption free energy for a model Tween 80 molecule at the clean water/squalane interface. We also calculate the pressure-area isotherm. We exploit these data with the Nikas-Mulqueen-Blankschtein (NMB) theory and a simple transport model to demonstrate a transition from irreversible to reversible adsorption with increasing surface coverage, consistent with experimental results of Reichert and Walker [Langmuir 2013, 29 (6), 1857-1867].
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Affiliation(s)
- Kyle J Huston
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, United States
| | - Ronald G Larson
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, United States
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110
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Vora SR, Bognet B, Patanwala HS, Chinesta F, Ma AWK. Surface pressure and microstructure of carbon nanotubes at an air-water interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4663-4672. [PMID: 25844761 DOI: 10.1021/la504934x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This article reports the surface pressure and microstructure of two different types of carbon nanotubes (CNTs) at an air-water interface; namely, as-produced CNTs (nf-CNTs) and CNTs functionalized with carboxyl groups (f-CNTs). Both types of CNTs formed 3D aggregates upon compression using a Langmuir-Pockels trough. However, f-CNTs showed a lower degree of aggregation compared with that of nf-CNTs. This is attributed to the deprotonation of the carboxyl groups within the water subphase, leading to additional electrostatic repulsion between f-CNTs. For the same initial amount of CNTs spread onto the interface, the actual coverage of f-CNTs was higher than that of nf-CNTs at a given trough area. At high compression, f-CNTs formed aligned CNT domains at the interface. These 2D domains resembled 3D liquid-crystalline structures formed by excluded volume interactions. The denser packing and orientational ordering of f-CNTs also contributed to a compressional modulus higher than that of nf-CNTs, as calculated from the surface pressure isotherms. A Volmer equation of state was applied to model the measured surface pressure containing both thermodynamic and mechanical contributions. The Volmer model, however, did not consider the loss of CNTs from the interface due to 3D aggregation and consequently overestimated the surface pressure at high compression. The actual coverage of CNT during compression was back calculated from the model and was in agreement with the value obtained independently from optical micrographs. The findings of this work may have a broader impact on understanding the assembly and collective behavior of rod-like particles with a high aspect ratio at an air-water interface.
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Affiliation(s)
| | - Brice Bognet
- §GeM UMR CNRS-Centrale Nantes, 1 rue de la Noë, F-44300 Nantes, France
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111
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Melbourne J, Clancy A, Seiffert J, Skepper J, Tetley TD, Shaffer MSP, Porter A. An investigation of the carbon nanotube--Lipid interface and its impact upon pulmonary surfactant lipid function. Biomaterials 2015; 55:24-32. [PMID: 25934449 DOI: 10.1016/j.biomaterials.2015.03.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 03/08/2015] [Accepted: 03/15/2015] [Indexed: 11/16/2022]
Abstract
Multiwalled carbon nanotubes (MWCNTs) are now synthesized on a large scale, increasing the risk of occupational inhalation. However, little is known of the MWCNT-pulmonary surfactant (PS) interface and its effect on PS functionality. The Langmuir-Blodgett trough was used to evaluate the impact of MWCNTs on fundamental properties of PS lipids which influence PS function, i.e. compression resistance and maximum obtainable pressure. Changes were found to be MWCNT length-dependent. 'Short' MWCNTs (1.1 μm, SD = 0.61) penetrated the lipid film, reducing the maximum interfacial film pressure by 10 mN/m (14%) in dipalmitoylphosphatidylcholine (DPPC) and PS, at an interfacial MWCNT-PS lipid mass ratio range of 50:1 to 1:1. 'Long' commercial MWCNTs (2.1 μm, SD = 1.2) caused compression resistance at the same mass loadings. 'Very long' MWCNTs (35 μm, SD = 19) sequestered DPPC and were squeezed out of the DPPC film. High resolution transmission electron microscopy revealed that all MWCNT morphologies formed DPPC coronas with ordered arrangements. These results provide insight into how nanoparticle aspect ratio affects the interaction mechanisms with PS, in its near-native state at the air-water interface.
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Affiliation(s)
- Jodie Melbourne
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
| | - Adam Clancy
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
| | - Joanna Seiffert
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK
| | - Jeremy Skepper
- Multi-Imaging Centre, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Teresa D Tetley
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK
| | - Milo S P Shaffer
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
| | - Alexandra Porter
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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112
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Schulz EP, Piñeiro Á, Miñones J, Miñones Trillo J, Frechero MA, Pieroni O, Schulz PC. Effect of ionization on the behavior of n-eicosanephosphonic acid monolayers at the air/water interface. Experimental determinations and molecular dynamics simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2269-2280. [PMID: 25664607 DOI: 10.1021/la5050283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Monolayers of n-eicosanephosphonic acid, EPA, were studied using a Langmuir balance and a Brewster angle microscope at different subphase pH values to change the charge of the polar headgroups (Zav) from 0 to -2. Molecular dynamics simulations (MDS) results for |Zav| = 0, 1, and 2 were compared with the experimental ones. EPA monolayers behave as mixtures of mutually miscible species (C20H41-PO3H2, C20H41-PO3H(-), and C20H41-PO3(2-), depending on the subphase pH). The order and compactness of the monolayers decrease when increasing |Zav|, while go from strongly interconnected by phosphonic-phosphonic hydrogen bonds (|Zav| = 0-0.03) through an equilibrium between the total cohesive energy and the electrostatic repulsion between the charged polar groups (0.03 < |Zav| < 1.6) to an entirely ionic monolayer (|Zav| ≈ 2). MDS reveal for |Zav| = 0 that the chains form spiralled nearly rounded structures induced by the hydrogen-bonded network. When |Zav| ≈ 1 fingering domains were identified. When Z ≈ 2, the headgroups are more disordered and distanced, not only in the xy plane but also in the z direction, forming a rough layer and responding to compression with a large plateau in the isotherm. The monolayers collapse behavior is consistent with the structures and domains founds in the different ionization states and their consequent in-plane rigidity: there is a transition from a solid-like response at low pH subphases to a fluid-like response at high pH subphases. The film area in the close-packed state increases relatively slow when the polar headgroups are able to form hydrogen bonds but increases to near twice that this value when |Zav| ≈ 2. Other nanoscopic properties of monolayers were also determined by MDS. The computational results confirm the experimental findings and offer a nanoscopic perspective on the structure and interactions in the phosphonate monolayers.
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Affiliation(s)
- Erica P Schulz
- Departamento de Química e INQUISUR, Universidad Nacional del Sur y CONICET , Bahía Blanca, Argentina
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113
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González-Castro CA, Ramírez-Santiago G. Phase behavior of Langmuir monolayers with ionic molecular heads: Molecular simulations. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:032409. [PMID: 25871125 DOI: 10.1103/physreve.91.032409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Indexed: 06/04/2023]
Abstract
We carried out Monte Carlo simulations in the N,Π,T ensemble of a Langmuir monolayer coarse-grained molecular model. Considering that the hydrophilic groups can be ionized by modulating acid-base interactions, here we study the phase behavior of a model that incorporates the short-range steric and long-range ionic interactions. The simulations were carried out in the reduced temperature range 0.1≤T*<4.0, where there is a competition of these interactions. Different order parameters were calculated and analyzed for several values of the reduced surface pressure in the interval, 1≤Π*≤40. For most of the surface pressures two directions of molecular tilt were found: (i) towards the nearest neighbor (NN) at low temperatures, T*<0.7, and most of the values of Π* and (ii) towards next-nearest neighbors (NNN) in the temperature interval 0.7≤T*<1.1 for Π*<25. We also found the coexistence of the NN and NNN at intermediate temperatures and Π*>25. A low-temperature reentrant disorder-order-disorder transition in the positions of the molecular heads and in the collective tilt of the tails was found for all the surface pressure values. It was also found that the molecular tails arranged forming "rotating patterns" in the temperature interval, 0.5<T*<1.5, at intermediate surface pressures. We estimated the monolayer's surface pressure versus temperature and the temperature versus area per molecule phase diagrams. It was found that the LE↔LC phase transition shifts to smaller temperatures when the molecular heads carry an ion in qualitative agreement with experimental observations of fatty acid monolayers with ionic head groups. Two surface pressure versus area per molecule isotherms were also calculated. At low temperatures near the LC-NN ↔ LC-NNN transitions and at higher temperatures close to the LE ↔ LC transitions. From these isotherms the monolayer's area compression modulus was obtained and its variation ranges in the LE and LC phases were found to be consistent with the experimental values.
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Affiliation(s)
- Carlos A González-Castro
- Departamento de Física-Química, Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, México 01000, D.F., Mexico
| | - Guillermo Ramírez-Santiago
- Departamento de Física-Química, Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, México 01000, D.F., Mexico
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114
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Lin W, Clark AJ, Paesani F. Effects of surface pressure on the properties of Langmuir monolayers and interfacial water at the air-water interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2147-2156. [PMID: 25642579 DOI: 10.1021/la504603s] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effects of surface pressure on the physical properties of Langmuir monolayers of palmitic acid (PA) and dipalmitoylphosphatidic acid (DPPA) at the air/water interface are investigated through molecular dynamics simulations with atomistic force fields. The structure and dynamics of both monolayers and interfacial water are compared across the range of surface pressures at which stable monolayers can form. For PA monolayers at T = 300 K, the untilted condensed phase with a hexagonal lattice structure is found at high surface pressure, while the uniformly tilted condensed phase with a centered rectangular lattice structure is observed at low surface pressure, in agreement with the available experimental data. A state with uniform chain tilt but no periodic spatial ordering is observed for DPPA monolayers on a Na(+)/water subphase at both high and low surface pressures. The hydrophobic acyl chains of both monolayers pack efficiently at all surface pressures, resulting in a very small number of gauche defects. The analysis of the hydrogen-bonding structure/dynamics at the monolayer/water interface indicates that water molecules hydrogen-bonded to the DPPA head groups reorient more slowly than those hydrogen-bonded to the PA head groups, with the orientational dynamics becoming significantly slower at high surface pressure. Possible implications for physicochemical processes taking place on marine aerosols in the atmosphere are discussed.
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Affiliation(s)
- Wei Lin
- Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093, United States
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115
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Okuno M, Mezger M, Stangenberg R, Baumgarten M, Müllen K, Bonn M, Backus EHG. Interaction of a patterned amphiphilic polyphenylene dendrimer with a lipid monolayer: electrostatic interactions dominate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:1980-1987. [PMID: 25602738 DOI: 10.1021/la504252s] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Dendrimeric macromolecules with defined shape and size are promising candidates for delivering drug or DNA molecules into cells. In this work we study the influence of an amphiphilic polyphenylene dendrimer on a model cell membrane consisting of a condensed 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid monolayer. A small surface pressure decrease is observed when the dendrimer solution is injected into the aqueous phase below the monolayer. X-ray reflectivity measurements show that the surface monolayer remains intact. The molecular-scale picture is obtained with sum-frequency generation spectroscopy. With this technique, we observe that the tails of the surfactant molecules become less ordered upon interaction with the amphiphilic polyphenylene dendrimer. In contrast, the water molecules below the DPPC layer become more ordered. Our observations suggest that electrostatic interactions between the negative charge of the dendrimer and the positively charged part of the DPPC headgroup keep the dendrimer located below the headgroup. No evidence of dendrimer insertion into the membrane has been observed. Apparently before entering the cell membrane the dendrimer can stick at the hydrophilic part of the lipids.
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Affiliation(s)
- Masanari Okuno
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
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116
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Farnoud AM, Fiegel J. Calf Lung Surfactant Recovers Surface Functionality After Exposure to Aerosols Containing Polymeric Particles. J Aerosol Med Pulm Drug Deliv 2015; 29:10-23. [PMID: 25671772 DOI: 10.1089/jamp.2014.1165] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Recent studies have shown that colloidal particles can disrupt the interfacial properties of lung surfactant and thus key functional abilities of lung surfactant. However, the mechanisms underlying the interactions between aerosols and surfactant films remain poorly understood, as our ability to expose films to particles via the aerosol route has been limited. The aim of this study was to develop a method to reproducibly apply aerosols with a quantifiable particle dose on lung surfactant films and investigate particle-induced changes to the interfacial properties of the surfactant under conditions that more closely mimic those in vivo. METHODS Films of DPPC and Infasurf® were exposed to aerosols containing polystyrene particles generated using a Dry Powder Insufflator™. The dose of particles deposited on surfactant films was determined via light absorbance. The interfacial properties of the surfactant were studied using a Langmuir-Wilhelmy balance during surfactant compression to film collapse and cycles of surface compression and expansion at a fast cycling rate within a small surface area range. RESULTS Exposure of surfactant films to aerosols led to reproducible dosing of particles on the films. In film collapse experiments, particle deposition led to slight changes in collapse surface pressure and surface area of both surfactants. However, longer interaction times between particles and Infasurf® films resulted in time-dependent inhibition of surfactant function. When limited to lung relevant surface pressures, particles reduced the maximum surface pressure that could be achieved. This inhibitory effect persisted for all compression-expansion cycles in DPPC, but normal surfactant behavior was restored in Infasurf® films after five cycles. CONCLUSIONS The observation that Infasurf® was able to quickly restore its function after exposure to aerosols under conditions that better mimicked those in vivo suggests that particle-induced surfactant inhibition is unlikely to occur in vivo due to an aerosol exposure.
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Affiliation(s)
- Amir M Farnoud
- 1 Department of Chemical and Biochemical Engineering, The University of Iowa , Iowa City, Iowa
| | - Jennifer Fiegel
- 1 Department of Chemical and Biochemical Engineering, The University of Iowa , Iowa City, Iowa.,2 Department of Pharmaceutical Sciences and Experimental Therapeutics, The University of Iowa , Iowa City, Iowa
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117
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Huynh L, Perrot N, Beswick V, Rosilio V, Curmi PA, Sanson A, Jamin N. Reply to "Comment on 'Structural properties of POPC monolayers under lateral compression: computer simulations analysis'". LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:888-889. [PMID: 25531793 DOI: 10.1021/la504104e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Lucie Huynh
- INSERM, U829, Laboratoire Structure - Activité des Biomolécules Normales et Pathologiques, Université d'Evry-Val-d'Essonne , F-91025 Evry, France
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118
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Nisoh N, Karttunen M, Monticelli L, Wong-ekkabut J. Lipid monolayer disruption caused by aggregated carbon nanoparticles. RSC Adv 2015. [DOI: 10.1039/c4ra17006g] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Carbon nanoparticles (CNP) have significant impact on the Pulmonary Surfactant (PS), the first biological barrier in the respiratory system.
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Affiliation(s)
- Nililla Nisoh
- Department of Physics
- Faculty of Science
- Kasetsart University
- Bangkok
- Thailand
| | - Mikko Karttunen
- Department of Chemistry and Waterloo Institute for Nanotechnology
- University of Waterloo
- Waterloo
- Canada
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119
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Lippoldt J, Händel C, Dietrich U, Käs J. Dynamic membrane structure induces temporal pattern formation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2380-90. [DOI: 10.1016/j.bbamem.2014.05.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 05/05/2014] [Accepted: 05/16/2014] [Indexed: 10/25/2022]
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120
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Liu B, Hoopes MI, Karttunen M. Molecular Dynamics Simulations of DPPC/CTAB Monolayers at the Air/Water Interface. J Phys Chem B 2014; 118:11723-37. [PMID: 25222268 DOI: 10.1021/jp5050892] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Bin Liu
- Department of Chemistry and
Waterloo Institute for Nanotechnology, University of Waterloo, 200 University
Avenue West, Waterloo, Ontario, Canada N2L 3G1
| | - Matthew I. Hoopes
- Department of Chemistry and
Waterloo Institute for Nanotechnology, University of Waterloo, 200 University
Avenue West, Waterloo, Ontario, Canada N2L 3G1
| | - Mikko Karttunen
- Department of Chemistry and
Waterloo Institute for Nanotechnology, University of Waterloo, 200 University
Avenue West, Waterloo, Ontario, Canada N2L 3G1
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121
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Lamberg A, Taniguchi T. Coarse-Grained Computational Studies of Supported Bilayers: Current Problems and Their Root Causes. J Phys Chem B 2014; 118:10643-52. [DOI: 10.1021/jp5053419] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antti Lamberg
- Department of Chemical Engineering, Kyoto University, Kyoto 615−8510, Japan
| | - Takashi Taniguchi
- Department of Chemical Engineering, Kyoto University, Kyoto 615−8510, Japan
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122
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Falk K, Fillot N, Sfarghiu AM, Berthier Y, Loison C. Interleaflet sliding in lipidic bilayers under shear flow: comparison of the gel and fluid phases using reversed non-equilibrium molecular dynamics simulations. Phys Chem Chem Phys 2014; 16:2154-66. [PMID: 24346163 DOI: 10.1039/c3cp53238k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The friction between two rubbing surfaces lubricated by water can be diminished if they are coated with phospholipidic bilayers or brushes of polyelectrolytes. In the case of a coating by lipid membranes, the friction is lower when the lipids are in the gel phase rather than in the liquid phase. We investigated the response of fluid or gel bilayers to a mechanical load or under shear using non-equilibrium molecular dynamics simulations (NEMD) to understand whether this difference could come from intermonolayer sliding. The system is composed of a single fully hydrated bilayer of coarse grained phospholipids under a parallel shear with vorticity parallel to the bilayer. In both the liquid and the gel phases, an intermonolayer slip was measured in the velocity profile. In the liquid phase this slip is proportional to the shear stress. In the tilted gel phase of our model the stress is not systematically linear and relaxes differently when the shear is in the direction of the tilt or perpendicular to it. The impact of surface tension (or load) on the friction is different for the liquid and gel phases, but grossly the slip remains of the same order of magnitude.
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Affiliation(s)
- Kerstin Falk
- Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex, France
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123
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Homeoviscous response of Clostridium pasteurianum to butanol toxicity during glycerol fermentation. J Biotechnol 2014; 179:8-14. [DOI: 10.1016/j.jbiotec.2014.03.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 02/05/2014] [Accepted: 03/07/2014] [Indexed: 11/20/2022]
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124
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Verwijlen T, Imperiali L, Vermant J. Separating viscoelastic and compressibility contributions in pressure-area isotherm measurements. Adv Colloid Interface Sci 2014; 206:428-36. [PMID: 24103106 DOI: 10.1016/j.cis.2013.09.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 06/17/2013] [Accepted: 09/20/2013] [Indexed: 10/26/2022]
Abstract
Monolayers of surface active molecules or particles play an important role in biological systems as well as in consumer products. Their properties are controlled by thermodynamics as well as the mechanical properties of the interface itself. For insoluble species forming Langmuir monolayers, surface pressure-area isotherms are typically used to characterize the thermodynamic state. A Langmuir trough equipped with a Wilhelmy plate is often used for such measurements. However, when Langmuir interfaces are compressed and become more structured, the elastic response of these interfaces can interfere with the measurement of the surface pressure-area isotherm, even when the compression speed is slow. Recent reports of compression data for highly elastic interfaces revealed a dependence of the apparent surface pressures on the geometry of the measurement trough. In the present work, this dependence is investigated by considering adequate constitutive models. Since deformations in such compression experiments can be large, linearized versions of the Kelvin-Voigt model do not suffice. We develop a framework for quasi-linear constitutive models by choosing suitable non-linear strain tensors, adequately separating the shear and dilatational effects in a frame invariant manner. The proposed constitutive models can be used as building blocks to describe viscoelastic behavior as well. The geometry dependence in isotherm measurements is then shown to be a consequence of varying contributions of the isotropic surface pressure and extra shear and dilatational elastic stresses. Using these insights, an approach is proposed to obtain the intrinsic surface pressure-area isotherms for elastic interfaces. As a case study, experimental data on graphene oxidesheets at the air-water interface is investigated to evaluate the proposed model.
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125
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Huynh L, Perrot N, Beswick V, Rosilio V, Curmi PA, Sanson A, Jamin N. Structural properties of POPC monolayers under lateral compression: computer simulations analysis. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:564-573. [PMID: 24397263 DOI: 10.1021/la4043809] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), a lipid comprising a saturated and an unsaturated acyl chain, belongs to the class of glycerophosphatidylcholines, major lipids in eukaryotic cell membranes. To get insight into the structural properties of this lipid within monolayers as membrane models, we performed molecular dynamics (MD) simulations of POPC monolayers under compression at the air/water interface. MD simulations were carried out at 300 K and at different surface pressures using the all-atom general Amber force field (GAFF). A good agreement was found between the simulated data and experimental isotherms. At surface pressures greater than 15 mN/m, two orientations of the head groups clearly appear: one nearly parallel to the monolayer interface and another one pointing toward the water. On the basis of the analysis of headgroup dihedral angles, we propose that the conformational variations around the bonds connecting the phosphorus atom to the adjacent oxygens are involved in these two orientations of the headgroup. The glycerol group orientation is characterized by a large distribution centered around 50° with respect to the monolayer normal. The acyl chains are predominantly in trans configuration from 7.5 to 43 mN/m surface pressures. Moreover, the calculated order parameter profiles of both chains suggest an independent behavior of the saturated and unsaturated chains that could be correlated with the formation of chain-type clusters observed along the simulated trajectories.
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Affiliation(s)
- Lucie Huynh
- INSERM, U829, Laboratoire Structure - Activité des Biomolécules Normales et Pathologiques, Université d'Evry-Val-d'Essonne , F-91025 Evry, France
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126
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Hermans E, Vermant J. Interfacial shear rheology of DPPC under physiologically relevant conditions. SOFT MATTER 2014; 10:175-186. [PMID: 24651838 DOI: 10.1039/c3sm52091a] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Lipids, and phosphatidylcholines in particular, are major components in cell membranes and in human lung surfactant. Their ability to encapsulate or form stable layers suggests a significant role of the interfacial rheological properties. In the present work we focus on the surface rheological properties of dipalmitoylphosphatidylcholine (DPPC). Literature results are confusing and even contradictory; viscosity values have been reported differ by several orders of magnitude. Moreover, even both purely viscous and gel-like behaviours have been described. Assessing the literature critically, a limited experimental window has been explored correctly, which however does not yet include conditions relevant for the physiological state of DPPC in vivo. A complete temperature and surface pressure analysis of the interfacial shear rheology of DPPC is performed, showing that the monolayer behaves as a viscoelastic liquid with a domain structure. At low frequencies and for a thermally structured monolayer, the interaction of the molecules within the domains can be probed. The low frequency limit of the complex viscosity is measured over a wide range of temperatures and surface pressures. The effects of temperature and surface pressure on the low frequency viscosity can be analysed in terms of the effects of free molecular area. However, at higher frequencies or following a preshear at high shear rates, elasticity becomes important; most probably elasticity due to defects at the edge of the domains in the layer is probed. Preshearing refines the structure and induces more defects. As a result, disagreeing interfacial rheology results in various publications might be due to different pre-treatments of the interface. The obtained dataset and scaling laws enable us to describe the surface viscosity, and its dependence under physiological conditions of DPPC. The implications on functioning of lung surfactants and lung surfactant replacements will be discussed.
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Affiliation(s)
- Eline Hermans
- Department of Chemical Engineering, KU Leuven, University of Leuven, Willem de Croylaan 46, Heverlee, Belgium.
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127
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Kong CP, Peters EAJF, Zheng QC, de With G, Zhang HX. The molecular configuration of a DOPA/ST monolayer at the air–water interface: a molecular dynamics study. Phys Chem Chem Phys 2014; 16:9634-42. [DOI: 10.1039/c4cp00555d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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128
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Insights about α-tocopherol and Trolox interaction with phosphatidylcholine monolayers under peroxidation conditions through Brewster angle microscopy. Colloids Surf B Biointerfaces 2013; 111:626-35. [DOI: 10.1016/j.colsurfb.2013.06.043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/29/2013] [Accepted: 06/25/2013] [Indexed: 11/21/2022]
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129
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You SS, Rashkov R, Kanjanaboos P, Calderon I, Meron M, Jaeger HM, Lin B. Comparison of the mechanical properties of self-assembled Langmuir monolayers of nanoparticles and phospholipids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:11751-11757. [PMID: 23957531 DOI: 10.1021/la4020064] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Nanoparticles with hydrophobic capping ligands and amphiphilic phospholipids are both found to self-assemble into monolayer films when deposited on the air/water interface. By separately measuring the anisotropic stress response of these films under uniaxial compression, we obtain both the 2D compressive and shear moduli of a range of different thin nanoparticle and phospholipid films. The compressive moduli of both nanoparticle and lipid films in the solid phase are on the same order of magnitude, whereas the shear moduli of the lipid films are found to be significantly lower. Additionally, the moduli of the nanoparticle films depended substantially on the polydispersity of the constituent particles-broader size distribution lowered the stiffness of the nanoparticle film.
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Affiliation(s)
- Siheng Sean You
- James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
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130
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Wang Z, Li Y, Guo Y, Zhang H. Investigations of Interfacial Properties of Surfactants with Different Structures at the Oil/Water Interface Using Dissipative Particle Dynamics. J DISPER SCI TECHNOL 2013. [DOI: 10.1080/01932691.2012.731637] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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131
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Hamed R, Fiegel J. Synthetic tracheal mucus with native rheological and surface tension properties. J Biomed Mater Res A 2013; 102:1788-98. [PMID: 23813841 DOI: 10.1002/jbm.a.34851] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 05/31/2013] [Accepted: 06/11/2013] [Indexed: 11/07/2022]
Abstract
In this study, the development of a model tracheal mucus with chemical composition and physical properties (bulk viscoelasticity and surface tension) matched to that of native tracheal mucus is described. The mucus mimetics (MMs) were formulated using components that are abundant in tracheal mucus (glycoproteins, proteins, lipids, ions, and water) at concentrations similar to those found natively. Pure solutions were unable to achieve the gel behavior observed with native mucus. The addition of a bifunctional cross-linking agent enabled control over the viscoelastic properties of the MMs by tailoring the concentration of the cross-linking agent and the duration of cross-linking. Three MM formulations with different bulk viscoelastic properties, all within the normal range for nondiseased tracheal mucus, were chosen for investigation of surfactant spreading at the air-mimetic interface. Surfactant spread quickly and completely on the least viscoelastic mimetic surface, enabling the surface tension of the mimetic to be lowered to match native tracheal mucus. However, surfactant spreading on the more viscoelastic mimetics was hindered, suggesting that the bulk properties of the mimetics dictate the range of surface properties that can be achieved.
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Affiliation(s)
- R Hamed
- Department of Pharmaceutical Sciences and Experimental Therapeutics, The University of Iowa, Iowa City, Iowa, 52242; Faculty of Pharmacy, Al-Zaytoonah University of Jordan, Amman, 11733, Jordan
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132
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Wnętrzak A, Lątka K, Dynarowicz-Łątka P. Interactions of alkylphosphocholines with model membranes-the Langmuir monolayer study. J Membr Biol 2013; 246:453-66. [PMID: 23673723 PMCID: PMC3682106 DOI: 10.1007/s00232-013-9557-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Accepted: 04/23/2013] [Indexed: 12/01/2022]
Abstract
Alkylphosphocholines (APCs) belong to a class of synthetic antitumor lipids, which are new-generation anticancer agents. In contrast to traditional antitumor drugs, they do not attack the cell nucleus but, rather, the cellular membrane; however, their mechanism of action is not fully understood. This work compared the interactions of selected APCs [namely, hexadecylphosphocholine (miltefosine), octadecylphosphocholine and erucylphosphocholine] with the most important membrane lipids [cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)] and examined their influence on a model membrane of tumor and normal cells. As a simple model of membranes, Langmuir monolayers prepared by mixing cholesterol either with a saturated phosphatidylcholine (DPPC), for a normal cell membrane, or with an unsaturated one (POPC), for a tumor cell membrane, have been applied. The APC–lipid interactions, based on experimental surface pressure (π) versus mean molecular area (A) isotherms, were analyzed qualitatively (with mean molecular area values) as well as quantitatively (with the ΔGexc function). Strong attractive interactions were observed for mixtures of APCs with cholesterol, contrary to the investigated phosphatidylcholines, for which the interactions were found to be weak with a tendency to separation of film components. In ternary monolayers it has been found that the investigated model systems (cholesterol/DPPC/APC vs cholesterol/POPC/APC) differ significantly as regards the interactions between film-forming molecules. The results demonstrate stronger interactions between the components of cholesterol/POPC/APC monolayers compared to cholesterol/POPC film, mimicking tumor cell membranes. In contrast, the interactions in cholesterol/DPPC/APC films were found to be weaker than those in the cholesterol/DPPC system, serving as a model of healthy cell membranes, thus proving that the incorporation of APCs is, from a thermodynamic point of view, unfavorable for binary cholesterol/DPPC monolayers. It can be concluded that the composition of healthy cell membranes is a natural barrier preventing the incorporation of APCs into normal cells.
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Affiliation(s)
- Anita Wnętrzak
- Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
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133
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Čoga L, Ilc T, Devetak M, Masiero S, Gramigna L, Spada GP, Drevenšek-Olenik I. Liponucleoside thin films: The special behaviour of guanosine. Colloids Surf B Biointerfaces 2013. [DOI: 10.1016/j.colsurfb.2012.10.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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134
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Ollila OHS, Lamberg A, Lehtivaara M, Koivuniemi A, Vattulainen I. Interfacial tension and surface pressure of high density lipoprotein, low density lipoprotein, and related lipid droplets. Biophys J 2013; 103:1236-44. [PMID: 22995496 DOI: 10.1016/j.bpj.2012.08.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 07/02/2012] [Accepted: 08/06/2012] [Indexed: 10/27/2022] Open
Abstract
Lipid droplets play a central role in energy storage and metabolism on a cellular scale. Their core is comprised of hydrophobic lipids covered by a surface region consisting of amphiphilic lipids and proteins. For example, high and low density lipoproteins (HDL and LDL, respectively) are essentially lipid droplets surrounded by specific proteins, their main function being to transport cholesterol. Interfacial tension and surface pressure of these particles are of great interest because they are related to the shape and the stability of the droplets and to protein adsorption at the interface. Here we use coarse-grained molecular-dynamics simulations to consider a number of related issues by calculating the interfacial tension in protein-free lipid droplets, and in HDL and LDL particles mimicking physiological conditions. First, our results suggest that the curvature dependence of interfacial tension becomes significant for particles with a radius of ∼5 nm, when the area per molecule in the surface region is <1.4 nm(2). Further, interfacial tensions in the used HDL and LDL models are essentially unaffected by single apo-proteins at the surface. Finally, interfacial tensions of lipoproteins are higher than in thermodynamically stable droplets, suggesting that HDL and LDL are kinetically trapped into a metastable state.
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135
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Orozco-Alcaraz R, Kuhl TL. Interaction forces between DPPC bilayers on glass. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:337-43. [PMID: 23199333 PMCID: PMC3576029 DOI: 10.1021/la3039329] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The surface force apparatus (SFA) was utilized to obtain force-distance profiles between silica-supported membranes formed by Langmuir-Blodgett deposition of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). In the absence of a membrane, a long-range electrostatic repulsion and short-range steric repulsion are measured as a result of the deprotonation of silica in water and the roughness of the silica film. The electrostatic repulsion is partially screened by the lipid membrane, and a van der Waals adhesion comparable to that measured with well-packed DPPC membranes on mica is measured. This finding suggest that electrostatic interactions due to the underlying negatively charged silica are likely present in other systems of glass-supported membranes. In contrast, the charge of an underlying mica substrate is almost completely screened when a lipid membrane is deposited on the mica. The difference in the two systems is attributed to the stronger physisorption of zwitterionic lipids to molecularly smooth mica compared to physisorption to rougher silica.
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Affiliation(s)
- Raquel Orozco-Alcaraz
- University of California Davis. Department of Chemical Engineering and Materials Science, One Shields Avenue, Davis CA 95616
| | - Tonya L. Kuhl
- University of California Davis. Department of Chemical Engineering and Materials Science, One Shields Avenue, Davis CA 95616
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136
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Farnoud AM, Fiegel J. Low concentrations of negatively charged sub-micron particles alter the microstructure of DPPC at the air–water interface. Colloids Surf A Physicochem Eng Asp 2012. [DOI: 10.1016/j.colsurfa.2012.10.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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137
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Prime EL, Tran DN, Plazzer M, Sunartio D, Leung AH, Yiapanis G, Baoukina S, Yarovsky I, Qiao GG, Solomon DH. Rational design of monolayers for improved water evaporation mitigation. Colloids Surf A Physicochem Eng Asp 2012. [DOI: 10.1016/j.colsurfa.2012.09.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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138
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Baoukina S, Mendez-Villuendas E, Tieleman DP. Molecular View of Phase Coexistence in Lipid Monolayers. J Am Chem Soc 2012; 134:17543-53. [DOI: 10.1021/ja304792p] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Svetlana Baoukina
- Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
| | - Eduardo Mendez-Villuendas
- Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
| | - D. Peter Tieleman
- Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
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139
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Holme MN, Fedotenko IA, Abegg D, Althaus J, Babel L, Favarger F, Reiter R, Tanasescu R, Zaffalon PL, Ziegler A, Müller B, Saxer T, Zumbuehl A. Shear-stress sensitive lenticular vesicles for targeted drug delivery. NATURE NANOTECHNOLOGY 2012; 7:536-43. [PMID: 22683843 DOI: 10.1038/nnano.2012.84] [Citation(s) in RCA: 193] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 04/30/2012] [Indexed: 05/20/2023]
Abstract
Atherosclerosis results in the narrowing of arterial blood vessels and this causes significant changes in the endogenous shear stress between healthy and constricted arteries. Nanocontainers that can release drugs locally with such rheological changes can be very useful. Here, we show that vesicles made from an artificial 1,3-diaminophospholipid are stable under static conditions but release their contents at elevated shear stress. These vesicles have a lenticular morphology, which potentially leads to instabilities along their equator. Using a model cardiovascular system based on polymer tubes and an external pump to represent shear stress in healthy and constricted vessels of the heart, we show that drugs preferentially release from the vesicles in constricted vessels that have high shear stress.
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Affiliation(s)
- Margaret N Holme
- University of Geneva, Department of Organic Chemistry, Quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
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140
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Risović D, Frka S, Kozarac Z. The Structure of Percolating Lipid Monolayers. J Colloid Interface Sci 2012; 373:116-21. [DOI: 10.1016/j.jcis.2011.12.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 12/01/2011] [Accepted: 12/04/2011] [Indexed: 10/14/2022]
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141
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Mashaghi A, Partovi-Azar P, Jadidi T, Nafari N, Maass P, Tabar MRR, Bonn M, Bakker HJ. Hydration strongly affects the molecular and electronic structure of membrane phospholipids. J Chem Phys 2012; 136:114709. [DOI: 10.1063/1.3694280] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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142
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Lucas TR, Bauer BA, Davis JE, Patel S. Molecular dynamics simulation of hydrated DPPC monolayers using charge equilibration force fields. J Comput Chem 2012; 33:141-52. [PMID: 21997857 PMCID: PMC3488352 DOI: 10.1002/jcc.21927] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 06/24/2011] [Accepted: 07/30/2011] [Indexed: 12/21/2022]
Abstract
We present results of molecular dynamics simulations of a model DPPC-water monolayer using charge equilibration (CHEQ) force fields, which explicitly account for electronic polarization in a classical treatment of intermolecular interactions. The surface pressure, determined as the difference between the monolayer and pure water surface tensions at 323 K, is predicted to be 22.92 ±1.29 dyne/cm, just slightly below the broad range of experimental values reported for this system. The surface tension for the DPPC-water monolayer is predicted to be 42.35 ±1.16 dyne/cm, in close agreement with the experimentally determined value of 40.9 dyne/cm. This surface tension is also consistent with the value obtained from DPPC monolayer simulations using state-of-the-art nonpolarizable force fields. The current results of simulations predict a monolayer-water potential difference relative to the pure water-air interface of 0.64 ±0.02 Volts, an improved prediction compared to the fixed-charge CHARMM27 force field, yet still overestimating the experimental range of 0.3 to 0.45 Volts. As the charge equilibration model is a purely charge-based model for polarization, the current results suggest that explicitly modeled polarization effects can offer improvements in describing interfacial electrostatics in such systems.
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Affiliation(s)
- Timothy R. Lucas
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | - Brad A. Bauer
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | - Joseph E. Davis
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | - Sandeep Patel
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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143
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Khabiri M, Roeselova M, Cwiklik L. Properties of oxidized phospholipid monolayers: An atomistic molecular dynamics study. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2011.11.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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144
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Gang HZ, Liu JF, Mu BZ. Molecular Dynamics Study of Surfactin Monolayer at the Air/Water Interface. J Phys Chem B 2011; 115:12770-7. [DOI: 10.1021/jp206350j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Hong-Ze Gang
- State Key Laboratory of Bioreactor Engineering and Institute of Applied Chemistry, East China University of Science and Technology, Shanghai, People's Republic of China 200237
| | - Jin-Feng Liu
- State Key Laboratory of Bioreactor Engineering and Institute of Applied Chemistry, East China University of Science and Technology, Shanghai, People's Republic of China 200237
| | - Bo-Zhong Mu
- State Key Laboratory of Bioreactor Engineering and Institute of Applied Chemistry, East China University of Science and Technology, Shanghai, People's Republic of China 200237
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145
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Molecular dynamics simulation of phase transitions in model lung surfactant monolayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2450-65. [DOI: 10.1016/j.bbamem.2011.06.026] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 01/13/2023]
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146
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Nunes C, Brezesinski G, Pereira-Leite C, Lima JLFC, Reis S, Lúcio M. NSAIDs interactions with membranes: a biophysical approach. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10847-58. [PMID: 21790169 DOI: 10.1021/la201600y] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
This work focuses on the interaction of four representative NSAIDs (nimesulide, indomethacin, meloxicam, and piroxicam) with different membrane models (liposomes, monolayers, and supported lipid bilayers), at different pH values, that mimic the pH conditions of normal (pH 7.4) and inflamed cells (pH 5.0). All models are composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) which is a representative phospholipid of most cellular membranes. Several biophysical techniques were employed: Fluorescence steady-state anisotropy to study the effects of NSAIDs in membrane microviscosity and thus to assess the main phase transition of DPPC, surface pressure-area isotherms to evaluate the adsorption and penetration of NSAIDs into the membrane, IRRAS to acquire structural information of DPPC monolayers upon interaction with the drugs, and AFM to study the changes in surface topography of the lipid bilayers caused by the interaction with NSAIDs. The NSAIDs show pronounced interactions with the lipid membranes at both physiological and inflammatory conditions. Liposomes, monolayers, and supported lipid bilayers experiments allow the conclusion that the pH of the medium is an essential parameter when evaluating drug-membrane interactions, because it conditions the structure of the membrane and the ionization state of NSAIDs, thereby influencing the interactions between these drugs and the lipid membranes. The applied models and techniques provided detailed information about different aspects of the drug-membrane interaction offering valuable information to understand the effect of these drugs on their target membrane-associated enzymes and their side effects at the gastrointestinal level.
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Affiliation(s)
- Cláudia Nunes
- REQUIMTE, Departamento de Química, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal Cunha, Porto, Portugal
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147
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Lung surfactant protein SP-B promotes formation of bilayer reservoirs from monolayer and lipid transfer between the interface and subphase. Biophys J 2011; 100:1678-87. [PMID: 21463581 DOI: 10.1016/j.bpj.2011.02.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 02/10/2011] [Accepted: 02/14/2011] [Indexed: 12/13/2022] Open
Abstract
We investigated the possible role of SP-B proteins in the function of lung surfactant. To this end, lipid monolayers at the air/water interface, bilayers in water, and transformations between them in the presence of SP-B were simulated. The proteins attached bilayers to monolayers, providing close proximity of the reservoirs with the interface. In the attached aggregates, SP-B mediated establishment of the lipid-lined connection similar to the hemifusion stalk. Via this connection, a lipid flow was initiated between the monolayer at the interface and the bilayer in water in a surface-tension-dependent manner. On interface expansion, the flow of lipids to the monolayer restored the surface tension to the equilibrium spreading value. SP-B induced formation of bilayer folds from the monolayer at positive surface tensions below the equilibrium. In the absence of proteins, lipid monolayers were stable at these conditions. Fold nucleation was initiated by SP-B from the liquid-expanded monolayer phase by local bending, and the proteins lined the curved perimeter of the growing fold. No effect on the liquid-condensed phase was observed. Covalently linked dimers resulted in faster kinetics for monolayer folding. The simulation results are in line with existing hypotheses on SP-B activity in lung surfactant and explain its molecular mechanism.
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148
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Wilde P, Chu B. Interfacial & colloidal aspects of lipid digestion. Adv Colloid Interface Sci 2011; 165:14-22. [PMID: 21377138 DOI: 10.1016/j.cis.2011.02.004] [Citation(s) in RCA: 223] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 02/04/2011] [Accepted: 02/05/2011] [Indexed: 01/01/2023]
Abstract
Amongst the main issues challenging the food manufacturing sector, health and nutrition are becoming increasingly important. Global concerns such as obesity, the ageing population and food security will have to be addressed. Food security is not just about assuring food supply, but is also about optimising nutritional delivery from the food that is available [1]. Therefore one challenge is to optimise the health benefits from the lipids and lipid soluble nutrients. Colloid scientists have an affinity for lipids because they are water insoluble, however this presents a challenge to the digestive system, which has to convert them to structures that are less insoluble so they are available for uptake. Despite this, the human digestive system is remarkably effective at digesting and absorbing most lipids. This is primarily driven through maximising energy intake, as lipids possess the highest calorific value, which was a survival trait to survive times of famine, but is now an underlying cause of obesity in developed countries with high food availability. The critical region here is the lipid-water interface, where the key reactions take place to solubilise lipids and lipid soluble nutrients. Digestive lipases have to adsorb to the oil water interface in order to hydrolyse triacylglycerols into fatty acids and mono glycerides, which accumulate at the interface [2], and inhibit lipase activity. Pancreatic lipase, which is responsible for the majority of lipid hydrolysis, also requires the action of bile salts and colipase to function effectively. Bile salts both aid the adsorption of co-lipase and lipase, and help solubilise the lipolysis products which have accumulated at the interface, into mixed micelles composing bile salts and a range of other lipids, to facilitate transport to the gut mucosal surface prior to uptake and absorption. The process can be affected by the lipid type, as shorter chain, fatty acids are more easily absorbed, whereas the uptake of longer chain fatty acids, particularly the very long chain n-3 fatty acids from fish oils are dependent on source and so may depend on food microstructure for optimal uptake [3]. The uptake of some poorly water soluble nutrients are enhanced by the presence of lipids, but the mechanisms are not clear. In addition, controlling the digestion of lipids can be beneficial as slower release of lipids into the bloodstream can reduce risk of cardiovascular disease, and can promote gut feedback processes that reduce appetite. This presents an opportunity to colloid and interfacial science, as there are many unanswered questions regarding the specific physicochemical mechanisms underlying the process of lipid digestion and uptake. I will review our current knowledge of lipid digestion and present examples of how fundamental research in colloidal and interface science is beginning to address these issues. These include the adsorption behaviour of physiological surfactants such as bile salts; interfacial processes by which different polar lipids can influence lipolysis; and the effect of emulsion based delivery systems on cellular uptake of lipid soluble nutrients. A fundamental understanding of these processes is required if we are to develop intelligent design strategies for foods that will deliver optimal nutrition and improved health benefits in order to address the global challenges facing the food sector in the future.
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149
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Takahama S, Russell LM. A molecular dynamics study of water mass accommodation on condensed phase water coated by fatty acid monolayers. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jd014842] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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150
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Meyer R, Sonnen AFP, Nau WM. Phase-dependent lateral diffusion of α-tocopherol in DPPC liposomes monitored by fluorescence quenching. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14723-14729. [PMID: 20722430 DOI: 10.1021/la101915x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The temperature-dependent fluorescence quenching of an amphiphilic palmitoyl derivative of 2,3-diazabicyclo[2.2.2]oct-2-ene (Fluorazophore-L) by α-tocopherol (α-Toc) has been determined in liposomes composed of a saturated lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The mutual lateral diffusion coefficients (D(L)) were extracted according to a laterally diffusion-controlled dynamic quenching model. Three distinct temperature regimes were identified: one between 65 and 39 °C, where the lateral diffusion coefficients were in the range of 10(-7) cm(2) s(-1) and the lifetime of the probe was monoexponential in the absence of α-Toc, a second one between 39 and 30 °C, where the lateral diffusion coefficients were in the range of 10(-8) cm(2) s(-1) and the lifetime of the probe was biexponential in the absence of α-Toc, and a third one below 30 °C, in which no diffusion was detectable, suggesting D(L) < 10(-9) cm(2)s (-1). These temperature domains were assigned, supported by differential scanning calorimetry (DSC) measurements, to the liquid-crystalline, ripple, and solid-gel phases of DPPC liposomes in the presence of the two additives. The absolute values of the individual lateral diffusion coefficients (taken as (1)/(2) of the D(L) values) of the Fluorazophore-L/α-Toc (ca. 2.5 × 10(-7) cm(2) s(-1) at 52 °C) couple demonstrates that α-Toc does not diffuse at an unexpectedly high rate in comparison to the self-diffusion of DPPC (1.5 × 10(-7) cm(2) s(-1) at 52 °C). However, diffusion in DPPC liposomes is distinctly slower than that in POPC ones (e.g., D(L) = 4.9 × 10(-7) cm(2) s(-1) versus 6.4 × 10(-7) cm(2) s(-1) at 50 °C), with an activation energy of 49 ± 5 kJ mol(-1) (value for POPC: 47 ± 5 kJ mol(-1)), in the temperature range of the liquid-crystalline phase. Diffusion in the ripple phase, that is, below the main phase transition temperature, was found to be non-negligible, with an apparent activation energy of 175 ± 50 kJ mol(-1).
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Affiliation(s)
- Roland Meyer
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
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