1
|
Mielke S, Sorkin R, Klein J. Effect of cholesterol on the mechanical stability of gel-phase phospholipid bilayers studied by AFM force spectroscopy. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:77. [PMID: 37672138 DOI: 10.1140/epje/s10189-023-00338-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 08/24/2023] [Indexed: 09/07/2023]
Abstract
The remarkably low sliding friction of articular cartilage in the major joints such as hips and knees, which is crucial for its homeostasis and joint health, has been attributed to lipid bilayers forming lubricious boundary layers at its surface. The robustness of such layers, and thus their lubrication efficiency at joint pressures, depends on the lipids forming them, including cholesterol which is a ubiquitous component, and which may act to strengthen of weaken the bilayer. In this work, a systematic study using an atomic force microscope (AFM) was carried out to understand the effect of cholesterol on the nanomechanical stability of two saturated phospholipids, DSPC (1,2-distearoyl-sn-glycero-3-phosphatidlycholine) and DPPC (1,2-dipalmitoyl-sn-glycero- phosphatidylcholine), that differ in acyl chain lengths. Measurements were carried out both in water and in phosphate buffer solution (PBS). The nanomechanical stability of the lipid bilayers was quantitatively evaluated by measuring the breakthrough force needed to puncture the bilayer by the AFM tip. The molar fractions of cholesterol incorporated in the bilayers were 10% and 40%. We found that for both DSPC and DPPC, cholesterol significantly decreases the mechanical stability of the bilayers in solid-ordered (SO) phase. In accordance with the literature, the strengthening effect of salt on the lipid bilayers was also observed. For DPPC with 10 mol % cholesterol, the effect of tip properties and the experimental procedure parameters on the breakthrough forces were also studied. Tip radius (2-42 nm), material (Si, Si3N4, Au) and loading rate (40-1000 nm/s) were varied systematically. The values of the breakthrough forces measured were not significantly affected by any of these parameters, showing that the weakening effect of cholesterol does not result from such changes in experimental conditions. As we have previously demonstrated that mechanical robustness improves the tribological performance of lipid layers, this study helps to shed light on the mechanism of physiological lubrication. Nanoindentation of SDPC bilayers.
Collapse
Affiliation(s)
- Salomé Mielke
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, 76100, Rehovot, Israel
| | - Raya Sorkin
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Jacob Klein
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, 76100, Rehovot, Israel.
| |
Collapse
|
2
|
Laudadio E, Minnelli C, Mobbili G, Sabbatini G, Stipa P, Rusciano D, Galeazzi R. Salt effects on mixed composition membranes containing an antioxidant lipophilic edaravone derivative: a computational-experimental study. Org Biomol Chem 2022; 20:5784-5795. [PMID: 35822625 DOI: 10.1039/d2ob01143c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The protection of lipid membranes against oxidation avoids diseases associated with oxidative stress. As a strategy to contrast it, functionalized lipids with antioxidant activity are used to become part of membranes thus protecting them. For this purpose, a lipophilic edaravone derivative has been synthesized, adding a C18 saturated chain to the original structure. The antioxidant activity of C18-Edv has been demonstrated in our previous work. In this study, molecular dynamics simulations have been performed to define the effects of NaCl, MgCl2, KCl, and CaCl2 salts on a palmitoyl-oleoyl-sn-glycero-phosphocholine (POPC) lipid bilayer encapsulating C18-Edv. The results showed how different salts influence POPC lateral diffusion, and the movements of C18-Edv heads, which are antioxidant moieties, were correlated to the ability of C18-Edv molecules to protect membranes. MgCl2 showed a negative impact leading to C18-Edv clusterization and membrane stretching, while KCl and NaCl showed a moderate influence on the mixed lipid membrane structure. CaCl2 increased the exposure of the C18-Edv heads to the lipid-water interface, resulting in the salt with a higher propensity to guarantee protection against radicals in the aqueous phase. Finally, C18-Edv-POPC liposomes have been prepared following the simulation conditions, and then an experimental Oxygen Radical Absorbance Capacity (ORAC) assay has been performed to confirm the in silico predicted results.
Collapse
Affiliation(s)
- Emiliano Laudadio
- Department SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - Cristina Minnelli
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| | - Giovanna Mobbili
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| | - Giulia Sabbatini
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| | - Pierluigi Stipa
- Department SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - Dario Rusciano
- Research Center, Sooft Italia SpA, 95100, Catania, Italy
| | - Roberta Galeazzi
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| |
Collapse
|
3
|
The lung surfactant activity probed with molecular dynamics simulations. Adv Colloid Interface Sci 2022; 304:102659. [PMID: 35421637 DOI: 10.1016/j.cis.2022.102659] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 03/18/2022] [Accepted: 03/31/2022] [Indexed: 01/17/2023]
Abstract
The surface of pulmonary alveolar subphase is covered with a mixture of lipids and proteins. This lung surfactant plays a crucial role in lung functioning. It shows a complex phase behavior which can be altered by the interaction with third molecules such as drugs or pollutants. For studying multicomponent biological systems, it is of interest to couple experimental approach with computational modelling yielding atomic-scale information. Simple two, three, or four-component model systems showed to be useful for getting more insight in the interaction between lipids, lipids and proteins or lipids and proteins with drugs and impurities. These systems were studied theoretically using molecular dynamic simulations and experimentally by means of the Langmuir technique. A better understanding of the structure and behavior of lung surfactants obtained from this research is relevant for developing new synthetic surfactants for efficient therapies, and may contribute to public health protection.
Collapse
|
4
|
Galván-Hernández A, Kobayashi N, Hernández-Cobos J, Antillón A, Nakabayashi S, Ortega-Blake I. Morphology and dynamics of domains in ergosterol or cholesterol containing membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183101. [DOI: 10.1016/j.bbamem.2019.183101] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/02/2019] [Accepted: 10/24/2019] [Indexed: 12/19/2022]
|
5
|
Favela-Rosales F, Galván-Hernández A, Hernández-Cobos J, Kobayashi N, Carbajal-Tinoco MD, Nakabayashi S, Ortega-Blake I. A molecular dynamics study proposing the existence of statistical structural heterogeneity due to chain orientation in the POPC-cholesterol bilayer. Biophys Chem 2019; 257:106275. [PMID: 31790909 DOI: 10.1016/j.bpc.2019.106275] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 10/02/2019] [Accepted: 10/21/2019] [Indexed: 01/08/2023]
Abstract
We performed molecular dynamics simulations of a lipid bilayer consisting of POPC and cholesterol at temperatures from 283 to 308K and cholesterol concentrations from 0 to 50% mol/mol. The purpose of this study was to look for the existence of structural differences in the region delimited by these parameters and, in particular, in a region where coexistence of liquid disordered and liquid ordered phases has been proposed. Our interest in this range of concentration and temperature responds to the fact that polyene ionophore activity varies considerably along it. Two force fields, CHARMM36 and Slipids, were compared in order to determine the most suitable. Both force fields predict non-monotonic behaviors consistent with the existence of phase transitions. We found the presence of lateral structural heterogeneity, statistical in nature, in some of the bilayers occurring in this range of temperatures and sterol concentrations. This heterogeneity was produced by correlated ordering of the POPC tails and not due to cholesterol enrichment, and lasts for tens of nanoseconds. We relate these observations to the action of polyenes in these membranes.
Collapse
Affiliation(s)
- Fernando Favela-Rosales
- Departamento de Física, Centro de Investigación y de Estudios Avanzados, Av. IPN No. 2508, México, DF, 07360, Mexico; Tecnológico Nacional de México, Campus Zacatecas Occidente, Ave. Tecnológico No. 2000, Col. Loma la Perla, Sombrerete, Zacatecas, 99102, Mexico
| | - Arturo Galván-Hernández
- Departamento de Física, Centro de Investigación y de Estudios Avanzados, Av. IPN No. 2508, México, DF, 07360, Mexico
| | - Jorge Hernández-Cobos
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México Av. Universidad s/n Cuernavaca, Morelos, 62251, Mexico
| | - Naritaka Kobayashi
- Department of Chemistry, Faculty of Science, Saitama University, Shimo-Ohkubo 255, Sakura-Ku, Saitama City, 338-8570, Japan
| | - Mauricio D Carbajal-Tinoco
- Departamento de Física, Centro de Investigación y de Estudios Avanzados, Av. IPN No. 2508, México, DF, 07360, Mexico
| | - Seiichiro Nakabayashi
- Department of Chemistry, Faculty of Science, Saitama University, Shimo-Ohkubo 255, Sakura-Ku, Saitama City, 338-8570, Japan
| | - Iván Ortega-Blake
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México Av. Universidad s/n Cuernavaca, Morelos, 62251, Mexico.
| |
Collapse
|
6
|
Interactions of a short hyaluronan chain with a phospholipid membrane. Colloids Surf B Biointerfaces 2019; 184:110539. [PMID: 31629183 DOI: 10.1016/j.colsurfb.2019.110539] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 09/09/2019] [Accepted: 09/29/2019] [Indexed: 01/06/2023]
Abstract
Hyaluronic acid and phospholipids are two components that are present in the synovial fluid, and both are implicated as important facilitators of joint lubrication. In this work we aim to clarify how hyaluronic acid interacts with a phospholipid bilayer through their molecular interactions at the bilayer surface. To this end we performed molecular dynamics simulations of one hyaluronic acid molecule at a phospholipid bilayer in aqueous solution. The simulations were carried out for two aqueous solutions of equal concentrations, containing either NaCl or CaCl2. We analyzed hydrogen bonds, hydrophobic contacts and cation mediated bridges to clarify how hyaluoronic acid binds to a phospholipid bilayer. The analysis shows that calcium ions promote longer lasting bonds between the species as they create calcium ion bridges between the carboxylate group of hyaluronic acid and the phosphate group of the phospholipid. This type of additional bonding does not significantly influence the total number of contact created, but rather stabilizes the contact. The presented results can facilitate understanding of the role of hyaluronic acid and phospholipid interactions in terms of lubrication of articular cartilage.
Collapse
|
7
|
Prislan I, Lokar M, Zirdum M, Valant J, Poklar Ulrih N. Contribution of headgroup and chain length of glycerophospholipids to thermal stability and permeability of liposomes loaded with calcein. Chem Phys Lipids 2019; 225:104807. [PMID: 31390525 DOI: 10.1016/j.chemphyslip.2019.104807] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/31/2019] [Accepted: 07/31/2019] [Indexed: 10/26/2022]
Abstract
Biological membranes are complex systems that are composed of lipids, proteins and carbohydrates. They are difficult to study, so it is established practice to use lipid vesicles that consist of closed 'shells' of phospholipid bilayers as model systems to study various functional and structural aspects of lipid organisation. To define the effects of the structural properties of lipid vesicles on their phase behaviour, we investigated their headgroup and chain length, and the chemical bonds by which their acyl chains are attached to the glycerol moiety of glycerophospholipid species, in terms of phase transition temperature, enthalpy change and calcein permeability. We used differential scanning calorimetry to measure the temperature and enthalpy changes of phase transition, and fluorescence to follow calcein release through the bilayer structure. Our data show that longer acyl chains increase the stability of the lipid bilayers, whereas higher salt concentrations decrease the thermal stability and widen the phase transitions of these lipid bilayers. We discuss the possible reasons for the observed phase transition behaviour.
Collapse
Affiliation(s)
- Iztok Prislan
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000, Ljubljana, Slovenia
| | - Maruša Lokar
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000, Ljubljana, Slovenia
| | - Martina Zirdum
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000, Ljubljana, Slovenia
| | - Janez Valant
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000, Ljubljana, Slovenia
| | - Nataša Poklar Ulrih
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000, Ljubljana, Slovenia.
| |
Collapse
|
8
|
Cationic interaction with phosphatidylcholine in a lipid cubic phase studied with electrochemical impedance spectroscopy and small angle X-ray scattering. J Colloid Interface Sci 2018; 528:321-329. [PMID: 29860201 DOI: 10.1016/j.jcis.2018.05.065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/18/2018] [Accepted: 05/21/2018] [Indexed: 12/20/2022]
Abstract
HYPOTHESIS Electrochemical Impedance Spectroscopy (EIS) can be used to investigate cationic interaction with the choline headgroup in the ternary system of monoolein/dioleoylphosphatidylcholine/water (MO/DOPC/H2O). EXPERIMENTS EIS was used to estimate the resistance and capacitance of a freestanding membrane of a lipid cubic phase (LCP). The membrane was formed in a small cylindrical aperture separating two compartments, containing one Pt electrode each. The impedance experiments were carried out in a two electrode setup with electrolyte solutions made of KCl, CsCl, MgCl2 and CaCl2 filling the compartments at two different ionic strength. Small angle X-ray diffraction (SAXRD) was used to establish the structure and cell unit parameters of the LCP. FINDINGS The interpretation of ionic interaction with phosphatidylcholine was based on estimated membrane resistances and capacitances from EIS measurements. The magnitude of cationic interaction with the lipid headgroup in the water channels is correlated to the membrane resistance that increases in the order Cs+ < K+ < Mg2+ < Ca2+ following the Hofmeister direct series and also reflecting the order of intrinsic binding constants. The membrane capacitance and SAXRD results are discussed as an effect of cationic interaction and it was possible to observe both swelling and condensing effects. The stability of the cubic phase throughout the experiments was confirmed by SAXRD.
Collapse
|
9
|
Anomalous behavior of membrane fluidity caused by copper-copper bond coupled phospholipids. Sci Rep 2018; 8:14093. [PMID: 30237448 PMCID: PMC6148289 DOI: 10.1038/s41598-018-32322-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 08/17/2018] [Indexed: 11/09/2022] Open
Abstract
Membrane fluidity, essential for cell functions, is obviously affected by copper, but the molecular mechanism is poorly understood. Here, we unexpectedly observed that a decrease in phospholipid (PL) bilayer fluidity caused by Cu2+ was more significant than those by Zn2+ and Ca2+, while a comparable reduction occurred in the last two ions. This finding disagrees with the placement in the periodic table of Cu just next to Zn and far from Ca. The physical nature was revealed to be an anomalous attraction between Cu+ cations, as well as the induced motif of two phospholipids coupled by Cu-Cu bond (PL-diCu-PL). Namely, upon Cu2+ ion binding to a negatively charged phosphate group of lipid, Cu2+ was reduced to Cu+. The attraction of the cations then caused one Cu+ ion simultaneously binding to two lipids and another Cu+, resulting in the formation of PL-diCu-PL structure. In contrast, this attraction cannot occur in the cases of Zn and Ca ions. Remarkably, besides lipids, the phosphate group also widely exists in other biological molecules, including DNA, RNA, ADP and ATP. Our findings thus provide a new view for understanding the biological functions of copper and the mechanism underlying copper-related diseases, as well as lipid assembly.
Collapse
|
10
|
Link KA, Hsieh CY, Tuladhar A, Chase Z, Wang Z, Wang H, Walker RA. Vibrational studies of saccharide-induced lipid film reorganization at aqueous/air interfaces. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.02.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
|
11
|
Controlling the mechanoelasticity of model biomembranes with room-temperature ionic liquids. Biophys Rev 2018; 10:751-756. [PMID: 29754282 DOI: 10.1007/s12551-018-0424-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 04/16/2018] [Indexed: 10/16/2022] Open
Abstract
Room-temperature ionic liquids (RTILs) are a vast class of organic non-aqueous electrolytes whose interaction with biomolecules is receiving great attention for potential applications in bio-nano-technology. Recently, it has been shown that RTILs dispersed at low concentrations at the water-biomembrane interface diffuse into the lipid region of the biomembrane, without disrupting the integrity of the bilayer structure. In this letter, we present the first exploratory study on the effect of absorbed RTILs on the mechanoelasticity of a model biomembrane. Using atomic force microscopy, we found that both the rupture force and the elastic modulus increase upon the insertion of RTILs into the biomembrane. This preliminary result points to the potential use of RTILs to control the mechanoelasticity of cell membranes, opening new avenues for applications in bio-medicine and, more generally, bio-nano-technology. The variety of RTILs offers a vast playground for future studies and potential applications.
Collapse
|
12
|
Ricci M, Trewby W, Cafolla C, Voïtchovsky K. Direct observation of the dynamics of single metal ions at the interface with solids in aqueous solutions. Sci Rep 2017; 7:43234. [PMID: 28230209 PMCID: PMC5322364 DOI: 10.1038/srep43234] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 01/23/2017] [Indexed: 01/14/2023] Open
Abstract
The dynamics of ions adsorbed at the surface of immersed charged solids plays a central role in countless natural and industrial processes such as crystal growth, heterogeneous catalysis, electrochemistry, or biological function. Electrokinetic measurements typically distinguish between a so-called Stern layer of ions and water molecules directly adsorbed on to the solid’s surface, and a diffuse layer of ions further away from the surface. Dynamics within the Stern layer remain poorly understood, largely owing to a lack of in-situ atomic-level insights. Here we follow the dynamics of single Rb+ and H3O+ ions at the surface of mica in water using high-resolution atomic force microscopy with 25 ms resolution. Our results suggest that single hydrated Rb+ions reside τ1 = 104 ± 5 ms at a given location, but this is dependent on the hydration state of the surface which evolves on a slower timescale of τ2 = 610 ± 30 ms depending on H3O+ adsorption. Increasing the liquid’s temperature from 5 °C to 65 °C predictably decreases the apparent glassiness of the interfacial water, but no clear effect on the ions’ dynamics was observed, indicating a diffusion-dominated process. These timescales are remarkably slow for individual monovalent ions and could have important implications for interfacial processes in electrolytes.
Collapse
Affiliation(s)
- Maria Ricci
- University of Cambridge, Cavendish Laboratory, Cambridge CB3 0HE, UK
| | - William Trewby
- Department of Physics, Durham University, Durham DH1 3LE, UK
| | | | | |
Collapse
|
13
|
|
14
|
Effect of Sodium and Chloride Binding on a Lecithin Bilayer. A Molecular Dynamics Study. MEMBRANES 2017; 7:membranes7010005. [PMID: 28125062 PMCID: PMC5371966 DOI: 10.3390/membranes7010005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/12/2017] [Accepted: 01/14/2017] [Indexed: 01/17/2023]
Abstract
The effect of ion binding on the structural, mechanical, dynamic and electrostatic properties of a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer in a 0.5 M aqueous NaCl solution is investigated using classical atomistic molecular dynamics simulation with different force-field descriptions for ion-ion and ion-lipid interactions. Most importantly, the repulsive Lennard-Jones parameters for the latter were modified, such that approximately similar binding of cations and anions to the lipid membrane is achieved. This was done to qualitatively improve the apparent ion-lipid binding constants obtained from simulations with the original force field (Berger lipids and GROMOS87 ions in combination with the SPC water model) in comparison to experimental data. Furthermore, various parameters characterizing membrane structure, elasticity, order and dynamics are analyzed. It is found that ion binding as observed in simulations involving the modified in comparison to the original force-field description leads to: (i) a smaller salt-induced change in the area per lipid, which is in closer agreement with the experiment; (ii) a decrease in the area compressibility and bilayer thickness to values comparable to a bilayer in pure water; (iii) lipid deuterium order parameters and lipid diffusion coefficients on nanosecond timescales that are very similar to the values for a membrane in pure water. In general, salt effects on the structural properties of a POPC bilayer in an aqueous sodium-chloride solution appear to be reproduced reasonably well by the new force-field description. An analysis of membrane-membrane disjoining pressure suggests that the smaller salt-induced change in area per lipid induced by the new force-field description is not due to the alteration of membrane-associated net charge, but must rather be understood as a consequence of ion-specific effects on the arrangement of lipid molecules.
Collapse
|
15
|
Trewby W, Livesey D, Voïtchovsky K. Buffering agents modify the hydration landscape at charged interfaces. SOFT MATTER 2016; 12:2642-51. [PMID: 26837938 DOI: 10.1039/c5sm02445e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Buffering agents are widely used to stabilise the pH of solutions in soft matter and biological sciences. They are typically composed of weak acids and bases mixed in an aqueous solution, and can interact electrostatically with charged surfaces such as biomembranes. Buffers can induce protein aggregation and structural modification of soft interfaces, but a molecular-level picture is still lacking. Here we use high-resolution atomic force microscopy to investigate the effect of five commonly used buffers, namely 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 2-(N-morpholino)ethanesulfonic acid (MES), monosodium phosphate, saline sodium citrate (SSC) and tris(hydroxymethyl)aminomethane (Tris) on the hydration landscape of Muscovite mica in solution. Mica is an ideal model substrate due to its negative surface charge and identical lattice parameter when compared with gel-phase lipid bilayers. We show that buffer molecules can produce cohesive aggregates spanning over tens of nanometres of the interface. SSC, Tris and monosodium phosphate tend to create an amorphous mesh layer several molecules thick and with no preferential ordering. In contrast, MES and HEPES adopt epitaxial arrangements commensurate with the underlying mica lattice, suggesting that they offer the most suitable solution for high-resolution studies. To confirm that this effect persisted in biologically-relevant interfaces, the experiments were repeated on a silica-supported lipid bilayer. Similar trends were observed for this system using atomic force microscopy as well as ellipsometry. The effect of the buffering agents can be mitigated by the inclusion of salt which helps displace them from the interface.
Collapse
|
16
|
Catte A, Girych M, Javanainen M, Loison C, Melcr J, Miettinen MS, Monticelli L, Määttä J, Oganesyan VS, Ollila OHS, Tynkkynen J, Vilov S. Molecular electrometer and binding of cations to phospholipid bilayers. Phys Chem Chem Phys 2016; 18:32560-32569. [DOI: 10.1039/c6cp04883h] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The molecular electrometer – reorientation of lipid head due to bound charge – allows direct quantitative vetting of simulations against noninvasive NMR experiments; most simulation models overestimated lipid–cation affinities.
Collapse
|
17
|
Clark GA, Henderson JM, Heffern C, Akgün B, Majewski J, Lee KYC. Synergistic Interactions of Sugars/Polyols and Monovalent Salts with Phospholipids Depend upon Sugar/Polyol Complexity and Anion Identity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12688-12698. [PMID: 26496486 DOI: 10.1021/acs.langmuir.5b02815] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We found that interactions of dipalmitoylphosphatidylcholine (DPPC) lipid monolayers with sugars are influenced by addition of NaCl. This work is of general importance in understanding how sugar-lipid-salt interactions impact biological systems. Using Langmuir isothermal compressions, fluorescence microscopy, atomic force microscopy, and neutron reflectometry, we examined DPPC monolayers upon addition of sugars/polyols and/or monovalent salts. Sugar-lipid interactions in the presence of NaCl increased with increasing complexity of the sugar/polyol in the order glycerol ≪ glucose < trehalose. When the anion was altered in the series NaF, NaCl, and NaBr, only minor differences were observed. When comparing LiCl, NaCl, and KCl, sodium chloride had the greatest influence on glucose and trehalose interactions with DPPC. We propose that heterogeneity created by cation binding allows for sugars to bind the lipid headgroups. While cation binding increases in the order K(+) < Na(+) < Li(+), lithium ions may also compete with glucose for binding sites. Thus, both cooperative and competitive factors contribute to the overall influence of salts on sugar-lipid interactions.
Collapse
Affiliation(s)
- Ginevra A Clark
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - J Michael Henderson
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Charles Heffern
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Bülent Akgün
- Department of Chemistry, Bogazici University , Bebek, Istanbul 34342, Turkey
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, United States
- Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States
| | - Jaroslaw Majewski
- Los Alamos Neutron Scattering Center/MPA/CINT, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
- Department of Chemical Engineering, University of California , Davis, California 95616, United States
| | - Ka Yee C Lee
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| |
Collapse
|
18
|
Assemblies of pore-forming toxins visualized by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:500-11. [PMID: 26577274 DOI: 10.1016/j.bbamem.2015.11.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 10/23/2015] [Accepted: 11/09/2015] [Indexed: 02/05/2023]
Abstract
A number of pore-forming toxins (PFTs) can assemble on lipid membranes through their specific interactions with lipids. The oligomeric assemblies of some PFTs have been successfully revealed either by electron microscopy (EM) and/or atomic force microscopy (AFM). Unlike EM, AFM imaging can be performed under physiological conditions, enabling the real-time visualization of PFT assembly and the transition from the prepore state, in which the toxin does not span the membrane, to the pore state. In addition to characterizing PFT oligomers, AFM has also been used to examine toxin-induced alterations in membrane organization. In this review, we summarize the contributions of AFM to the understanding of both PFT assembly and PFT-induced membrane reorganization. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
Collapse
|
19
|
Arai T, Koshioka M, Abe K, Tomitori M, Kokawa R, Ohta M, Yamada H, Kobayashi K, Oyabu N. Atom-resolved analysis of an ionic KBr(001) crystal surface covered with a thin water layer by frequency modulation atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:3876-3883. [PMID: 25790119 DOI: 10.1021/acs.langmuir.5b00087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An ionic KBr(001) crystal surface covered with a thin water layer was observed with a frequency modulation atomic force microscope (FM-AFM) with atomic resolution. By immersing only the tip apex of the AFM cantilever in the thin water layer, the Q-factor of the cantilever in probing the solid-liquid interface can be maintained as high as that of FM-AFM operation in air, leading to improvement of the minimum detection of a differential force determined by the noise. Two types of images with atom-resolved contrast were observed, possibly owing to the different types of ions (K(+) or Br(-)) adsorbed on the tip apex that incorporated into the hydration layers on the tip and on the sample surface. The force-distance characteristics at the solid-water interface were analyzed by taking spatial variation maps of the resonant frequency shift of the AFM cantilever with the high Q-factor. The oscillatory frequency shift-distance curves exhibited atomic site dependence. The roles of hydration and the ions on the tip and on the sample surface in the measurements were discussed.
Collapse
Affiliation(s)
- Toyoko Arai
- †Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Masashi Koshioka
- †Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Kouhei Abe
- †Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Masahiko Tomitori
- ‡School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-1292, Japan
| | | | | | | | | | | |
Collapse
|
20
|
Przybyło M, Drabik D, Łukawski M, Langner M. Effect of Monovalent Anions on Water Transmembrane Transport. J Phys Chem B 2014; 118:11470-9. [DOI: 10.1021/jp505687d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Magda Przybyło
- Laboratory for Biophysics of Macromolecular Aggregates,
Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Pl. Grunwaldzki 13, 50-370 Wroclaw, Poland
| | - Dominik Drabik
- Laboratory for Biophysics of Macromolecular Aggregates,
Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Pl. Grunwaldzki 13, 50-370 Wroclaw, Poland
| | - Maciej Łukawski
- Laboratory for Biophysics of Macromolecular Aggregates,
Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Pl. Grunwaldzki 13, 50-370 Wroclaw, Poland
| | - Marek Langner
- Laboratory for Biophysics of Macromolecular Aggregates,
Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Pl. Grunwaldzki 13, 50-370 Wroclaw, Poland
| |
Collapse
|
21
|
Ricci M, Spijker P, Voïtchovsky K. Water-induced correlation between single ions imaged at the solid-liquid interface. Nat Commun 2014; 5:4400. [PMID: 25027990 DOI: 10.1038/ncomms5400] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 06/13/2014] [Indexed: 02/06/2023] Open
Abstract
When immersed into water, most solids develop a surface charge, which is neutralized by an accumulation of dissolved counterions at the interface. Although the density distribution of counterions perpendicular to the interface obeys well-established theories, little is known about counterions' lateral organization at the surface of the solid. Here we show, by using atomic force microscopy and computer simulations, that single hydrated metal ions can spontaneously form ordered structures at the surface of homogeneous solids in aqueous solutions. The structures are laterally stabilized only by water molecules with no need for specific interactions between the surface and the ions. The mechanism, studied here for several systems, is controlled by the hydration landscape of both the surface and the adsorbed ions. The existence of discrete ion domains could play an important role in interfacial phenomena such as charge transfer, crystal growth, nanoscale self-assembly and colloidal stability.
Collapse
Affiliation(s)
- Maria Ricci
- Department of Materials Science and Engineering, Ecole Polytechnique Fédérale de Lausanne, (EPFL), 1015 Lausanne, Switzerland
| | - Peter Spijker
- Department of Applied Physics, COMP Centre of Excellence, Aalto University, P.O. Box 11100, FI-00076 Helsinki, Finland
| | - Kislon Voïtchovsky
- 1] Department of Materials Science and Engineering, Ecole Polytechnique Fédérale de Lausanne, (EPFL), 1015 Lausanne, Switzerland [2] Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| |
Collapse
|
22
|
Almonte L, Lopez-Elvira E, Baró AM. Surface-charge differentiation of streptavidin and avidin by atomic force microscopy-force spectroscopy. Chemphyschem 2014; 15:2768-73. [PMID: 24990795 DOI: 10.1002/cphc.201402234] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Indexed: 01/24/2023]
Abstract
Chemical information can be obtained by using atomic force microscopy (AFM) and force spectroscopy (FS) with atomic or molecular resolution, even in liquid media. The aim of this paper is to demonstrate that single molecules of avidin and streptavidin anchored to a biotinylated bilayer can be differentiated by using AFM, even though AFM topographical images of the two proteins are remarkably alike. At physiological pH, the basic glycoprotein avidin is positively charged, whereas streptavidin is a neutral protein. This charge difference can be determined with AFM, which can probe electrostatic double-layer forces by using FS. The force curves, owing to the electrostatic interaction, show major differences when measured on top of each protein as well as on the lipid substrate. FS data show that the two proteins are negatively charged. Nevertheless, avidin and streptavidin can be clearly distinguished, thus demonstrating the sensitivity of AFM to detect small changes in the charge state of macromolecules.
Collapse
Affiliation(s)
- Lisa Almonte
- Department of Surfaces and Coatings, Instituto de Ciencia de Materiales de Madrid (CSIC), C/Sor Juana Inés de la Cruz 3, Campus de Cantoblanco (Spain), Fax: (+) 913720623
| | | | | |
Collapse
|
23
|
Magarkar A, Dhawan V, Kallinteri P, Viitala T, Elmowafy M, Róg T, Bunker A. Cholesterol level affects surface charge of lipid membranes in saline solution. Sci Rep 2014; 4:5005. [PMID: 24845659 PMCID: PMC4028897 DOI: 10.1038/srep05005] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 05/01/2014] [Indexed: 12/19/2022] Open
Abstract
Cholesterol is an important component of all biological membranes as well as drug delivery liposomes. We show here that increasing the level of cholesterol in a phospholipid membrane decreases surface charge in the physiological environment. Through molecular dynamics simulation we have shown that increasing the level of cholesterol decreases Na+ ion binding. Complementary experimental ζ--potential measurements have shown a decreased ζ--potential with increasing cholesterol content, indicative of reduced surface charge. Both experiments and simulations have been carried out on both saturated 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and monounsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. This result is particularly important because membrane surface charge plays an important role in the interactions of biomembranes with peripheral membrane proteins and drug delivery liposomes with the immune system.
Collapse
Affiliation(s)
- Aniket Magarkar
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Vivek Dhawan
- Bombay College of Pharmacy, University of Mumbai, Mumbai, India
| | - Paraskevi Kallinteri
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Tapani Viitala
- Division of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Mohammed Elmowafy
- Division of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Tomasz Róg
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Alex Bunker
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| |
Collapse
|
24
|
Jarerattanachat V, Karttunen M, Wong-ekkabut J. Molecular Dynamics Study of Oxidized Lipid Bilayers in NaCl Solution. J Phys Chem B 2013; 117:8490-501. [DOI: 10.1021/jp4040612] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Viwan Jarerattanachat
- Department of Physics, Faculty
of Science, Kasetsart University, 50 Phahon
Yothin Rd, Chatuchak, Bangkok, Thailand
| | - Mikko Karttunen
- Department of Chemistry and
Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario,
Canada
| | - Jirasak Wong-ekkabut
- Department of Physics, Faculty
of Science, Kasetsart University, 50 Phahon
Yothin Rd, Chatuchak, Bangkok, Thailand
| |
Collapse
|
25
|
Nanoscale mechanical properties of lipid bilayers and their relevance in biomembrane organization and function. Micron 2012; 43:1212-23. [DOI: 10.1016/j.micron.2012.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 03/19/2012] [Accepted: 03/20/2012] [Indexed: 12/27/2022]
|
26
|
Zhong J, He D. Recent Progress in the Application of Atomic Force Microscopy for Supported Lipid Bilayers. Chemistry 2012; 18:4148-55. [DOI: 10.1002/chem.201102831] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|