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Chu B, Marchioro A, Roke S. Size dependence of second-harmonic scattering from nanoparticles: Disentangling surface and electrostatic contributions. J Chem Phys 2023; 158:094711. [PMID: 36889968 DOI: 10.1063/5.0135157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
Polarimetric angle-resolved second-harmonic scattering (AR-SHS) is an all-optical tool enabling the study of unlabeled interfaces of nano-sized particles in an aqueous solution. As the second harmonic signal is modulated by interference between nonlinear contributions originating at the particle's surface and those originating in the bulk electrolyte solution due to the presence of a surface electrostatic field, the AR-SHS patterns give insight into the structure of the electrical double layer. The mathematical framework of AR-SHS has been previously established, in particular regarding changes in probing depth with ionic strength. However, other experimental factors may influence the AR-SHS patterns. Here, we calculate the size dependence of the surface and electrostatic geometric form factors for nonlinear scattering, together with their relative contribution to the AR-SHS patterns. We show that the electrostatic term is stronger in the forward scattering direction for smaller particle sizes, while the ratio of the electrostatic to surface terms decreases with increasing size. Besides this competing effect, the total AR-SHS signal intensity is also weighted by the particle's surface characteristics, given by the surface potential Φ0 and the second-order surface susceptibility χs,2 2. The weighting effect is experimentally demonstrated by comparing SiO2 particles of different sizes in NaCl and NaOH solutions of varying ionic strengths. For NaOH, the larger χs,2 2 values generated by deprotonation of surface silanol groups prevail over the electrostatic screening occurring at high ionic strengths; however, only for larger particle sizes. This study establishes a better connection between the AR-SHS patterns and surface properties and predicts trends for arbitrarily-sized particles.
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Affiliation(s)
- Bingxin Chu
- Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), École polytechnique fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Arianna Marchioro
- Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), 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), and Institute of Materials Science (IMX), School of Engineering (STI), École polytechnique fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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2
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Zheng R, Tian J, Binks BP, Cui Z, Xia W, Jiang J. Oil-in-Water emulsions stabilized by alumina nanoparticles with organic electrolytes: Fate of particles. J Colloid Interface Sci 2022; 627:749-760. [PMID: 35878465 DOI: 10.1016/j.jcis.2022.07.085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 07/12/2022] [Accepted: 07/13/2022] [Indexed: 11/17/2022]
Abstract
HYPOTHESIS Oil-in-dispersion emulsions can be stabilized by like charged particles and surfactant. Surfactant adsorbs at the oil-water interface to reduce the interfacial tension and endow the interface with charge, while particles remain dispersed in the aqueous phase to provide electrostatic repulsion between droplets and particles. Can weakly surface-active organic electrolytes adsorb at the oil-water interface and behave like surfactants in stabilizing oil-in-dispersion emulsions with like charged particles? EXPERIMENTS Symmetrical organic electrolytes, tetraalkylammonium bromides (R4NBr), with either no or very low interfacial activity endowing oil droplets with charge were combined with alumina nanoparticles to stabilize emulsions. The effect of R chain length (varying from methyl to butyl) on the type and stability of emulsions was investigated. FINDINGS Mixtures of high concentrations of short chain R4NBr salts (R = methyl or ethyl) and alumina particles stabilise oil-in-water Pickering emulsions, whereas longer chain (R = propyl or butyl) analogues stabilize oil-in-dispersion emulsions assisted by alumina particles. Tetrapropylammonium and tetrabutylammonium cations adsorb at the oil-water interface reducing the interfacial tension and endowing the interface with charge. The stability of the oil-in-dispersion emulsions is dominated by the electrostatic repulsion between the droplets and between droplets and particles in the continuous aqueous phase.
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Affiliation(s)
- Raojun Zheng
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical & Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jingjing Tian
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical & Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Bernard P Binks
- Department of Chemistry, University of Hull, Hull HU6 7RX. UK
| | - Zhenggang Cui
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical & Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Wenshui Xia
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jianzhong Jiang
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical & Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
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3
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Liu Y, Xia XH. Thermally Driven Transformation of Water Clustering Structures at Self-Assembled Monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:11493-11498. [PMID: 34549963 DOI: 10.1021/acs.langmuir.1c01724] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Water clustering structures are considered to play key roles in various temperature-dependent life activities. However, our fundamental understanding of the temperature-dependent water structures remains murky because of the limits of the real-time and real-condition monitoring techniques at the molecular level. We propose an in situ ATR-IR approach combining Gaussian fitting to qualitatively and quantitatively explore the temperature-dependent structural stability and transformation of the three water components, multimer water (MW), intermediate water (IW), and network water (NW), on interfaces with different wettabilities. Our results show that the transformation between NW and IW/MW will occur with a change in temperature. This conversion process shows reversibility on hydrophilic Au NPs film/ZnSe, while it is irreversible on a hydrophobic mercaptohexane self-assembled monolayer due to the irreversibility of the monolayer structure and the hydrophobic confinement effect. The established approach enables us to explore the change in the water properties at any interfaces upon external stimuli.
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Affiliation(s)
- Yang Liu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu 210023, China
- School of Environment, Nanjing Normal University, Nanjing, Jiangsu 210023, China
| | - Xing-Hua Xia
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu 210023, China
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4
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Foster MJ, Carpenter AP, Richmond GL. Dynamic Duo: Vibrational Sum Frequency Scattering Investigation of pH-Switchable Carboxylic Acid/Carboxylate Surfactants on Nanodroplet Surfaces. J Phys Chem B 2021; 125:9629-9640. [PMID: 34402616 DOI: 10.1021/acs.jpcb.1c05508] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Surfactants containing pH-switchable, carboxylic acid moieties are utilized in a variety of environmental, industrial, and biological applications that require controlled stability of hydrophobic droplets in water. For nanoemulsions, kinetically stable oil droplets in water, surface adsorption of the anionic form of the carboxylic acid surfactant stabilizes the droplet, whereas a dominant surface presence of the neutral form leads to destabilization. Through the use of dynamic light scattering, ζ-potential, and vibrational sum frequency scattering spectroscopy (VSFSS), we investigate this mechanism and the relative surface population of the neutral and charged species as pH is adjusted. We find that the relative population of the two surfactant species at the droplet surface is distinctly different than their bulk equilibrium concentrations. The ζ-potential measurements show that the surface concentration of the charged surfactant stays nearly constant throughout the stabilizing pH range. In contrast, VSFSS shows that the neutral carboxylic acid form increasingly adsorbs to the surface with increased acidity. The spectral features of the headgroup vibrational modes confirm this behavior and go further to reveal additional molecular details of their adsorption. A significant hydrogen-bonding interaction occurs between the headgroups that, along with hydrophobic chain-chain interactions, assists in drawing more carboxylic acid surfactant to the interface. The charged surfactant provides the stabilizing force for these droplets, while the neutral surfactant introduces complexity to the interfacial structure as the pH is lowered. The results are significantly different than what has been found for the planar oil/water studies where stabilization of the interface is not a factor.
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Affiliation(s)
- Marc J Foster
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
| | - Andrew P Carpenter
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
| | - Geraldine L Richmond
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
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5
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Carpenter AP, Christoffersen EL, Mapile AN, Richmond GL. Assessing the Impact of Solvent Selection on Vibrational Sum-Frequency Scattering Spectroscopy Experiments. J Phys Chem B 2021; 125:3216-3229. [PMID: 33739105 DOI: 10.1021/acs.jpcb.1c00188] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The development of vibrational sum-frequency scattering (S-VSF) spectroscopy has opened the door to directly probing nanoparticle surfaces with an interfacial and chemical specificity that was previously reserved for planar interfacial systems. Despite its potential, challenges remain in the application of S-VSF spectroscopy beyond simplified chemical systems. One such challenge includes infrared absorption by an absorptive continuous phase, which will alter the spectral lineshapes within S-VSF spectra. In this study, we investigate how solvent vibrational modes manifest in S-VSF spectra of surfactant stabilized nanoemulsions and demonstrate how corrections for infrared absorption can recover the spectral features of interfacial solvent molecules. We also investigate infrared absorption for systems with the absorptive phase dispersed in a nonabsorptive continuous phase to show that infrared absorption, while reduced, will still impact the S-VSF spectra. These studies are then used to provide practical recommendations for anyone wishing to use S-VSF to study nanoparticle surfaces where absorptive solvents are present.
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Affiliation(s)
- Andrew P Carpenter
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
| | - Evan L Christoffersen
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
| | - Ashley N Mapile
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
| | - Geraldine L Richmond
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97405, United States
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6
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Suárez-Herrera MF, Scanlon MD. Quantitative Analysis of Redox-Inactive Ions by AC Voltammetry at a Polarized Interface between Two Immiscible Electrolyte Solutions. Anal Chem 2020; 92:10521-10530. [PMID: 32608226 DOI: 10.1021/acs.analchem.0c01340] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The interface between two immiscible electrolyte solutions (ITIES) is ideally suited to detect redox-inactive ions by their ion transfer. Such electroanalysis, based on the Nernst-Donnan equation, has been predominantly performed using amperometry, cyclic voltammetry, or differential pulse voltammetry. Here, we introduce a new electroanalytical method based on alternating-current (AC) voltammetry with inherent advantages over traditional approaches such as avoidance of positive feedback iR compensation, a major issue for liquid|liquid electrochemical cells containing resistive organic media and interfacial areas in the cm2 and mm2 range. A theoretical background outlining the generation of the analytical signal is provided and based on extracting the component that depends on the Warburg impedance from the total impedance. The quantitative detection of a series of model redox-inactive tetraalkylammonium cations is demonstrated, with evidence provided of the transient adsorption of these cations at the interface during the course of ion transfer. Since ion transfer is diffusion-limited, by changing the voltage excitation frequency during AC voltammetry, the intensity of the Faradaic response can be enhanced at low frequencies (1 Hz) or made to disappear completely at higher frequencies (99 Hz). The latter produces an AC voltammogram equivalent to a "blank" measurement in the absence of analyte and is ideal for background subtraction. Therefore, major opportunities exist for the sensitive detection of ionic analyte when a "blank" measurement in the absence of analyte is impossible. This approach is particularly useful to deconvolute signals related to reversible electrochemical reactions from those due to irreversible processes, which do not give AC signals.
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Affiliation(s)
- Marco F Suárez-Herrera
- Departamento De Química, Facultad De Ciencias, Universidad Nacional De Colombia, Cra 30 # 45-03, Edificio 451, Bogotá, Colombia
| | - Micheál D Scanlon
- The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick (UL), Limerick V94 T9PX, Ireland
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7
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Shimizu M, Hirahara K, Arai S. Morphology control of zinc electrodeposition by surfactant addition for alkaline-based rechargeable batteries. Phys Chem Chem Phys 2019; 21:7045-7052. [PMID: 30874263 DOI: 10.1039/c9cp00223e] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The development of Zn-air batteries with a high energy density of 1350 W h kg-1 is one of the breakthroughs required to achieve a low carbon society. However, morphology control of the Zn negative electrode during charge/discharge (Zn-deposition/stripping) is essential for practical application. Considering the manufacturing process, a simple strategy is preferable. Herein, we employed surfactants as an inhibitor of the formation of mossy and dendrite Zn structures, and studied electrochemical Zn growth from the perspective of the electric charge of the surfactant. Even by using an additive free electrolyte of 0.25 M ZnO + 4 M KOH and with 1 mM sodium dodecyl sulfate (SDS: anionic surfactant) or polyacrylic acid (PAA: non-ionic surfactant), mossy and dendrite formations were unavoidable irrespective of the current density. On the other hand, a cationic surfactant, trimethyloctadecylammonium chloride (STAC), suppressed the shape change and resulted in a smooth and dense morphology. Zeta potential measurements, kinetic current densities observed from Tafel plots, and constant potential electrolysis indicate that quaternary ammonium cations (STAC) with bulky size adsorb onto protrusions which are the cause of shape change and suppress Zn deposition in the region to promote lateral growth. Although the adsorption of STAC increased the average overvoltage for Zn-deposition/stripping in a symmetric Zn|Zn cell under a current density of 10 mA cm-2, significantly stable behavior continued for 200 h. In contrast, the overvoltage of the additive free system suddenly increased after 156 h, associated with the accumulation of insulating ZnO and Zn(OH)2 formed on the Zn surface. In charge-discharge tests using an asymmetric Cu|Zn cell, the coulombic efficiency in the additive free electrolyte was less than 95%, whereas the addition of STAC at 1 mM achieved superior cycling performance without any capacity loss originating from the generation of dead Zn (electrical isolation). These results demonstrate that the addition of STAC is a promising method of controlling the Zn morphology.
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Affiliation(s)
- Masahiro Shimizu
- Department of Materials Chemistry, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano, 380-8553, Japan.
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8
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Zdrali E, Baer MD, Okur HI, Mundy CJ, Roke S. The Diverse Nature of Ion Speciation at the Nanoscale Hydrophobic/Water Interface. J Phys Chem B 2019; 123:2414-2423. [DOI: 10.1021/acs.jpcb.8b10207] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Evangelia Zdrali
- Laboratory for fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Marcel D. Baer
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Halil I. Okur
- Laboratory for fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Christopher J. Mundy
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
- Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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9
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Li J, Cheng Y, Chen X, Zheng S. Impact of electroviscous effect on viscosity in developing highly concentrated protein formulations: Lessons from non-protein charged colloids. INTERNATIONAL JOURNAL OF PHARMACEUTICS-X 2018; 1:100002. [PMID: 31545855 PMCID: PMC6733305 DOI: 10.1016/j.ijpx.2018.100002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/13/2018] [Accepted: 12/13/2018] [Indexed: 11/26/2022]
Abstract
Subcutaneous delivery of highly concentrated protein formulations is paramount for reducing healthcare cost and improving patient compliance, where reducing the solution viscosity of formulations is critical for drug delivery. The objective of this paper is to provide some mechanistic understanding about the contribution of electrostatic repulsion to the viscosity of protein solutions at high concentrations, along with the effect of excipients such as salts on relative viscosity. Proteins are treated as charged colloids in this paper. At high concentrations, the electrical double layer starts to overlap, and secondary electroviscous effect becomes significant in addition to primary electroviscous effect. In other words, the hydrodynamic volume of proteins plays a great role in influencing their solution viscosity because of the excluded volume effect. Currently, it is hypothesized that the high viscosity of concentrated protein solutions is attributed to formation of clusters due to either electrostatic attraction or hydrophobic interactions, especially for monoclonal antibodies, in which anybody molecules in high concentration formulations may form networks. Consequently, viscosity reduction in the presence of inorganic or organic salts in these formulations is due to breaking up of these networks. In this review, authors hope to provide another point of view based on the effect of the electrostatic repulsion on the excluded volume-hydrodynamic volume. Finally, authors hope the proposed theoretical framework can be used to guide excipient selection in the product development of highly concentrated proteins.
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Affiliation(s)
- Jinjiang Li
- Drug Product Science & Technology, Bristol-Myers Squibb Corporation, 1 Squibb Dr., New Brunswick, NJ 08903, United States
| | - Yuan Cheng
- Discovery Pharmaceutics and Analytical Sciences, Bristol-Myers Squibb Corporation, 3551 Lawrenceville Princeton, Lawrence Township, NJ 08648, United States.,Formulation Development, Regeneron Pharmaceuticals, 777 Old Saw Mill River Rd., Tarrytown, NY 10591, United States
| | - Xiaodong Chen
- Drug Product Science & Technology, Bristol-Myers Squibb Corporation, 1 Squibb Dr., New Brunswick, NJ 08903, United States
| | - Songyan Zheng
- Drug Product Science & Technology, Bristol-Myers Squibb Corporation, 1 Squibb Dr., New Brunswick, NJ 08903, United States
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10
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Kovacik F, Okur HI, Smolentsev N, Scheu R, Roke S. Hydration mediated interfacial transitions on mixed hydrophobic/hydrophilic nanodroplet interfaces. J Chem Phys 2018; 149:234704. [PMID: 30579299 DOI: 10.1063/1.5035161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Interfacial phase transitions are of fundamental importance for climate, industry, and biological processes. In this work, we observe a hydration mediated surface transition in supercooled oil nanodroplets in aqueous solutions using second harmonic and sum frequency scattering techniques. Hexadecane nanodroplets dispersed in water freeze at a temperature of ∼15 °C below the melting point of the bulk alkane liquid. Addition of a trimethylammonium bromide (CXTA+) type surfactant with chain length equal to or longer than that of the alkane causes the bulk oil droplet freezing transition to be preceded by a structural interfacial transition that involves water, oil, and the surfactant. Upon cooling, the water loses some of its orientational order with respect to the surface normal, presumably by reorienting more parallel to the oil interface. This is followed by the surface oil and surfactant alkyl chains losing some of their flexibility, and this chain stretching induces alkyl chain ordering in the bulk of the alkane phase, which is then followed by the bulk transition occurring at a 3 °C lower temperature. This behavior is reminiscent of surface freezing observed in planar tertiary alkane/surfactant/water systems but differs distinctively in that it appears to be induced by the interfacial water and requires only a very small amount of surfactant.
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Affiliation(s)
- Filip Kovacik
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Halil I Okur
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Nikolay Smolentsev
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Rüdiger Scheu
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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11
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Hartkamp R, Biance AL, Fu L, Dufrêche JF, Bonhomme O, Joly L. Measuring surface charge: Why experimental characterization and molecular modeling should be coupled. Curr Opin Colloid Interface Sci 2018. [DOI: 10.1016/j.cocis.2018.08.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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12
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Lütgebaucks C, Macias-Romero C, Roke S. Characterization of the interface of binary mixed DOPC:DOPS liposomes in water: The impact of charge condensation. J Chem Phys 2018; 146:044701. [PMID: 28147550 DOI: 10.1063/1.4974084] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Solutions of liposomes composed of binary mixtures of anionic dioleoylphosphatidylserine (DOPS) and zwitterionic dioleoylphosphatidylcholine (DOPC) are investigated with label-free angle-resolved (AR) second harmonic scattering (SHS) and electrophoretic mobility measurements. The membrane surface potential is extracted from the AR-SHS response. The surface potential changes from -10 to -145 mV with varying DOPS content ( from 0% to 100%) and levels off already at ∼ 10 % DOPS content. The ζ-potential shows the same trend but with a drastically lower saturation value (-44 mV). This difference is explained by the formation of a condensed layer of Na+ counterions around the outer leaflet of the liposome as predicted by charge condensation theories for polyelectrolyte systems.
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Affiliation(s)
- Cornelis Lütgebaucks
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Carlos Macias-Romero
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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13
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Olenick LL, Troiano JM, Smolentsev N, Ohno PE, Roke S, Geiger FM. Polycation Interactions with Zwitterionic Phospholipid Monolayers on Oil Nanodroplet Suspensions in Water (D2O) Probed by Sum Frequency Scattering. J Phys Chem B 2018; 122:5049-5056. [DOI: 10.1021/acs.jpcb.8b00309] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Laura L. Olenick
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Julianne M. Troiano
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Nikolay Smolentsev
- Laboratory for fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Paul E. Ohno
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Franz M. Geiger
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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14
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Sullivan MR, Yao W, Tang D, Ashbaugh HS, Gibb BC. The Thermodynamics of Anion Complexation to Nonpolar Pockets. J Phys Chem B 2018; 122:1702-1713. [PMID: 29373793 PMCID: PMC10668596 DOI: 10.1021/acs.jpcb.7b12259] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The interactions between nonpolar surfaces and polarizable anions lie in a gray area between the hydrophobic and Hofmeister effects. To assess the affinity of these interactions, NMR and ITC were used to probe the thermodynamics of eight anions binding to four different hosts whose pockets each consist primarily of hydrocarbon. Two classes of host were examined: cavitands and cyclodextrins. For all hosts, anion affinity was found to follow the Hofmeister series, with associations ranging from 1.6-5.7 kcal mol-1. Despite the fact that cavitand hosts 1 and 2 possess intrinsic negative electrostatic fields, it was determined that these more enveloping hosts generally bound anions more strongly. The observation that the four hosts each possess specific anion affinities that cannot be readily explained by their structures, points to the importance of counter cations and the solvation of the "empty" hosts, free guests, and host-guest complexes, in defining the affinity.
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Affiliation(s)
- Matthew R. Sullivan
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Wei Yao
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Du Tang
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bruce C. Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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Chen Y, Okur HI, Lütgebaucks C, Roke S. Zwitterionic and Charged Lipids Form Remarkably Different Structures on Nanoscale Oil Droplets in Aqueous Solution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:1042-1050. [PMID: 29019694 DOI: 10.1021/acs.langmuir.7b02896] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The molecular structure of zwitterionic and charged monolayers on small oil droplets in aqueous solutions is determined using a combined second harmonic and sum frequency study. From the interfacial vibrational signature of the acyl chains and phosphate headgroups as well as the response of the hydrating water, we find that zwitterionic and charged lipids with identical acyl chains form remarkably different monolayers. Zwitterionic phospholipids form a closely packed monolayer with highly ordered acyl tails. In contrast, the charged phospholipids form a monolayer with a low number density and disordered acyl tails. The charged headgroups are oriented perpendicular to the monolayer rather than parallel, as is the case for zwitterionic lipids. These significant differences between the two types of phospholipids indicate important roles of phospholipid headgroups in the determination of properties of cellular membranes and lipid droplets. The observed behavior of charged phospholipids is different from expectations based on studies performed on extended planar interfaces, at which condensed monolayers are readily formed. The difference can be explained by nanoscale related changes in charge condensation behavior that has its origin in a different balance of interfacial intermolecular interactions.
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Affiliation(s)
- Yixing Chen
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Halil I Okur
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Cornelis Lütgebaucks
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
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16
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Zdrali E, Chen Y, Okur HI, Wilkins DM, Roke S. The Molecular Mechanism of Nanodroplet Stability. ACS NANO 2017; 11:12111-12120. [PMID: 29224343 DOI: 10.1021/acsnano.7b05100] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Mixtures of nano- and microscopic oil droplets in water have recently been rediscovered as miniature reaction vessels in microfluidic environments and are important constituents of many environmental systems, food, personal care, and medical products. The oil nanodroplet/water interface stabilized by surfactants determines the physicochemical properties of the droplets. Surfactants are thought to stabilize nanodroplets by forming densely packed monolayers that shield the oil phase from the water. This idea has been inferred from droplet stability measurements in combination with molecular structural data obtained from extended planar interfaces. Here, we present a molecular level investigation of the surface structure and stability of nanodroplets and show that the surface structure of nanodroplets is significantly different from that of extended planar interfaces. Charged surfactants form monolayers that are more than 1 order of magnitude more dilute than geometrically packed ones, and there is no experimental correlation between stability and surfactant surface density. Moreover, dilute negatively charged surfactant monolayers produce more stable nanodroplets than dilute positively charged and dense geometrically packed neutral surfactant monolayers. Droplet stability is found to depend on the relative cooperativity between charge-charge, charge-dipole, and hydrogen-bonding interactions. The difference between extended planar interfaces and nanoscale interfaces stems from a difference in the thermally averaged total charge-charge interactions in the two systems. Low dielectric oil droplets with a size smaller than the Debye length in oil permit repulsive interactions between like charges from opposing interfaces in small droplets. This behavior is generic and extends up to the micrometer length scale.
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Affiliation(s)
- Evangelia Zdrali
- Laboratory for Fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Yixing Chen
- Laboratory for Fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Halil I Okur
- Laboratory for Fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - David M Wilkins
- Laboratory of Computational Science and Modeling, Institute of Materials, École Polytechnique Fédérale de Lausanne , 1015 Lausanne, Switzerland
| | - Sylvie Roke
- Laboratory for Fundamental BioPhotonics, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
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17
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Okur H, Chen Y, Wilkins D, Roke S. The Jones-Ray effect reinterpreted: Surface tension minima of low ionic strength electrolyte solutions are caused by electric field induced water-water correlations. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.06.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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18
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Smolentsev N, Smit WJ, Bakker HJ, Roke S. The interfacial structure of water droplets in a hydrophobic liquid. Nat Commun 2017; 8:15548. [PMID: 28537259 PMCID: PMC5458086 DOI: 10.1038/ncomms15548] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 04/05/2017] [Indexed: 12/21/2022] Open
Abstract
Nanoscopic and microscopic water droplets and ice crystals embedded in liquid hydrophobic surroundings are key components of aerosols, rocks, oil fields and the human body. The chemical properties of such droplets critically depend on the interfacial structure of the water droplet. Here we report the surface structure of 200 nm-sized water droplets in mixtures of hydrophobic oils and surfactants as obtained from vibrational sum frequency scattering measurements. The interface of a water droplet shows significantly stronger hydrogen bonds than the air/water or hexane/water interface and previously reported planar liquid hydrophobic/water interfaces at room temperature. The observed spectral difference is similar to that of a planar air/water surface at a temperature that is ∼50 K lower. Supercooling the droplets to 263 K does not change the surface structure. Below the homogeneous ice nucleation temperature, a single vibrational mode is present with a similar mean hydrogen-bond strength as for a planar ice/air interface.
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Affiliation(s)
- Nikolay Smolentsev
- Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | | - Huib J. Bakker
- AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Sylvie Roke
- Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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19
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Stock P, Monroe JI, Utzig T, Smith DJ, Shell MS, Valtiner M. Unraveling Hydrophobic Interactions at the Molecular Scale Using Force Spectroscopy and Molecular Dynamics Simulations. ACS NANO 2017; 11:2586-2597. [PMID: 28267918 DOI: 10.1021/acsnano.6b06360] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Interactions between hydrophobic moieties steer ubiquitous processes in aqueous media, including the self-organization of biologic matter. Recent decades have seen tremendous progress in understanding these for macroscopic hydrophobic interfaces. Yet, it is still a challenge to experimentally measure hydrophobic interactions (HIs) at the single-molecule scale and thus to compare with theory. Here, we present a combined experimental-simulation approach to directly measure and quantify the sequence dependence and additivity of HIs in peptide systems at the single-molecule scale. We combine dynamic single-molecule force spectroscopy on model peptides with fully atomistic, both equilibrium and nonequilibrium, molecular dynamics (MD) simulations of the same systems. Specifically, we mutate a flexible (GS)5 peptide scaffold with increasing numbers of hydrophobic leucine monomers and measure the peptides' desorption from hydrophobic self-assembled monolayer surfaces. Based on the analysis of nonequilibrium work-trajectories, we measure an interaction free energy that scales linearly with 3.0-3.4 kBT per leucine. In good agreement, simulations indicate a similar trend with 2.1 kBT per leucine, while also providing a detailed molecular view into HIs. This approach potentially provides a roadmap for directly extracting qualitative and quantitative single-molecule interactions at solid/liquid interfaces in a wide range of fields, including interactions at biointerfaces and adhesive interactions in industrial applications.
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Affiliation(s)
- Philipp Stock
- Department for Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH , D-40237 Düsseldorf, Germany
| | - Jacob I Monroe
- Department of Chemical Engineering, University of California Santa Barbara , Santa Barbara, California 93106-5080, United States
| | - Thomas Utzig
- Department for Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH , D-40237 Düsseldorf, Germany
| | - David J Smith
- Department of Chemical Engineering, University of California Santa Barbara , Santa Barbara, California 93106-5080, United States
| | - M Scott Shell
- Department of Chemical Engineering, University of California Santa Barbara , Santa Barbara, California 93106-5080, United States
| | - Markus Valtiner
- Department for Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH , D-40237 Düsseldorf, Germany
- Department for Physical Chemistry, Technische Universität Bergakademie Freiberg , D-09599 Freiberg, Germany
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20
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Okur HI, Hladílková J, Rembert KB, Cho Y, Heyda J, Dzubiella J, Cremer PS, Jungwirth P. Beyond the Hofmeister Series: Ion-Specific Effects on Proteins and Their Biological Functions. J Phys Chem B 2017; 121:1997-2014. [PMID: 28094985 DOI: 10.1021/acs.jpcb.6b10797] [Citation(s) in RCA: 411] [Impact Index Per Article: 58.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ions differ in their ability to salt out proteins from solution as expressed in the lyotropic or Hofmeister series of cations and anions. Since its first formulation in 1888, this series has been invoked in a plethora of effects, going beyond the original salting out/salting in idea to include enzyme activities and the crystallization of proteins, as well as to processes not involving proteins like ion exchange, the surface tension of electrolytes, or bubble coalescence. Although it has been clear that the Hofmeister series is intimately connected to ion hydration in homogeneous and heterogeneous environments and to ion pairing, its molecular origin has not been fully understood. This situation could have been summarized as follows: Many chemists used the Hofmeister series as a mantra to put a label on ion-specific behavior in various environments, rather than to reach a molecular level understanding and, consequently, an ability to predict a particular effect of a given salt ion on proteins in solutions. In this Feature Article we show that the cationic and anionic Hofmeister series can now be rationalized primarily in terms of specific interactions of salt ions with the backbone and charged side chain groups at the protein surface in solution. At the same time, we demonstrate the limitations of separating Hofmeister effects into independent cationic and anionic contributions due to the electroneutrality condition, as well as specific ion pairing, leading to interactions of ions of opposite polarity. Finally, we outline the route beyond Hofmeister chemistry in the direction of understanding specific roles of ions in various biological functionalities, where generic Hofmeister-type interactions can be complemented or even overruled by particular steric arrangements in various ion binding sites.
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Affiliation(s)
- 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
| | - Jana Hladílková
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences , Flemingovo nam. 2, 16610 Prague 6, Czech Republic.,Division of Theoretical Chemistry, Lund University , P.O.B. 124, SE-22100 Lund, Sweden
| | | | - Younhee Cho
- Department of Chemistry, Texas A&M University , College Station 77843, Texas, United States
| | - Jan Heyda
- Institut für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin für Materialien und Energie , Hahn-Meitner Platz 1, 14109 Berlin, Germany.,Department of Physical Chemistry, University of Chemistry and Technology, Prague , Technická 5, 16628 Prague 6, Czech Republic
| | - Joachim Dzubiella
- Institut für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin für Materialien und Energie , Hahn-Meitner Platz 1, 14109 Berlin, Germany.,Institut für Physik, Humboldt-Universität zu Berlin , Newtonstrasse 15, 12489 Berlin, Germany
| | | | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences , Flemingovo nam. 2, 16610 Prague 6, Czech Republic
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21
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van der Vegt NFA, Haldrup K, Roke S, Zheng J, Lund M, Bakker HJ. Water-Mediated Ion Pairing: Occurrence and Relevance. Chem Rev 2016; 116:7626-41. [DOI: 10.1021/acs.chemrev.5b00742] [Citation(s) in RCA: 155] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nico F. A. van der Vegt
- Eduard-Zintl-Institut
für Anorganische und Physikalische Chemie and Center of Smart
Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Strasse
10, 64287 Darmstadt, Germany
| | - Kristoffer Haldrup
- Physics
Department, NEXMAP Section, Technical University of Denmark, Fysikvej
307, 2800 Kongens
Lyngby, Denmark
| | - Sylvie Roke
- Laboratory
for Fundamental BioPhotonics, Institute of Bioengineering, and Institute
of Materials Science, School of Engineering, and Lausanne Centre for
Ultrafast Science, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Junrong Zheng
- College
of Chemistry and Molecular Engineering, Beijing National Laboratory
for Molecular Sciences, Peking University, Beijing 100871, China
- Department
of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005-1892, United States
| | - Mikael Lund
- Division
of Theoretical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden
| | - Huib J. Bakker
- FOM Institute AMOLF, Science
Park 104, 1098 XG Amsterdam, The Netherlands
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22
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Mahendran V, Philip J. Macromolecular conformation changes at oil-water interface in the presence of cations. Colloids Surf A Physicochem Eng Asp 2016. [DOI: 10.1016/j.colsurfa.2016.02.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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23
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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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24
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Direct and quantitative AFM measurements of the concentration and temperature dependence of the hydrophobic force law at nanoscopic contacts. J Colloid Interface Sci 2015; 446:244-51. [DOI: 10.1016/j.jcis.2015.01.032] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/15/2015] [Accepted: 01/15/2015] [Indexed: 12/30/2022]
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25
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Smolentsev N, Chen Y, Jena KC, Brown MA, Roke S. Sum frequency and second harmonic generation from the surface of a liquid microjet. J Chem Phys 2014; 141:18C524. [DOI: 10.1063/1.4896996] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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26
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Engelhardt K, Peukert W, Braunschweig B. Vibrational sum-frequency generation at protein modified air–water interfaces: Effects of molecular structure and surface charging. Curr Opin Colloid Interface Sci 2014. [DOI: 10.1016/j.cocis.2014.03.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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27
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Scheu R, Chen Y, de Aguiar HB, Rankin BM, Ben-Amotz D, Roke S. Specific Ion Effects in Amphiphile Hydration and Interface Stabilization. J Am Chem Soc 2014; 136:2040-7. [DOI: 10.1021/ja4120117] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rüdiger Scheu
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bio-Engineering (IBI),
School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), Station 17, CH-1015 Lausanne, Switzerland
| | - Yixing Chen
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bio-Engineering (IBI),
School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), Station 17, CH-1015 Lausanne, Switzerland
| | - Hilton B. de Aguiar
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bio-Engineering (IBI),
School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), Station 17, CH-1015 Lausanne, Switzerland
| | - Blake M. Rankin
- Department
of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Dor Ben-Amotz
- Department
of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Sylvie Roke
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bio-Engineering (IBI),
School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), Station 17, CH-1015 Lausanne, Switzerland
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