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Garrett P, Baiz CR. Hidden Beneath the Layers: Extending the Core/Shell Model of Reverse Micelles. J Phys Chem B 2023; 127:9399-9404. [PMID: 37870992 DOI: 10.1021/acs.jpcb.3c04978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Reverse micelles (RMs) provide a unique and highly tunable model system to study water in confined environments. The complex properties of water within RMs arise from the disruption of extended hydrogen bond (H-bond) networks that mediate local and long-range dynamics in bulk aqueous systems. Modulating the water pool size influences its H-bond dynamics, with smaller RMs increasingly restricting the H-bond network rearrangements leading to slower dynamics; however, within small confined systems, the dynamics of the surfactants also influence the water dynamics. Using ultrafast two-dimensional infrared spectroscopy, we investigate the effects of RM size on the surfactant headgroup rotamer populations and picosecond interfacial H-bond dynamics of aerosol-OT surfactants. We find that the increased water penetration accelerates H-bond dynamics, with larger RMs showing faster dynamics. These results imply that the changes in the RM structure alter the physical structure of the RM interface and thus alter the solvation dynamics. The findings in this study can be used for developing models for structure-specific solvation dynamics that account for the surfactant packing and hydration at the interface.
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Affiliation(s)
- Paul Garrett
- Department of Chemistry, the University of Texas at Austin, Austin, Texas 78712, United States
| | - Carlos R Baiz
- Department of Chemistry, the University of Texas at Austin, Austin, Texas 78712, United States
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Bandyopadhyay D, Bhanja K, Choudhury N. On the Propensity of Excess Hydroxide Ions at the Alcohol Monolayer-Water Interface. J Phys Chem B 2023; 127:783-793. [PMID: 36639623 DOI: 10.1021/acs.jpcb.2c05719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Atomistic molecular dynamics simulations have been employed to study the self-ion (H+ and OH-) distribution at the interface between long-chain C16-OH alcohol (cetyl alcohol) monolayer and water. It is well known that the free air-water interface is acidic due to accumulation of the hydronium (H3O+) ions at the interface. In the present study, we have observed that contrary to the air-water interface, at the long-chain alcohol monolayer-water interface, it is the hydroxide (OH-) ion, not the hydronium ion (H3O+) that gets accumulated. By calculating the potential of mean forces, it is confirmed that there is extra stabilization for the OH- ions at the interface relative to the bulk, but no such stabilization is observed for the H3O+ ions. By analyzing the interaction of the self-ions with other constituents in the medium, it is clearly shown that the favorable interaction of the OH- ions with the alcoholic -OH groups stabilizes this ion at the interface. By calculating coordination numbers of the self-ions it is observed that around 50% water neighbors are substituted by alcoholic -OH in case of the hydroxide ion at the interface, whereas in the case of hydronium ions, only 15% water neighbors are substituted by the alcoholic -OH. The most interesting observation about the local structure and H-bonding pattern is that the hydroxide ion acts solely as the H-bond acceptor, but the hydronium ion acts only as the H-bond donor.
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Affiliation(s)
| | - Kalyan Bhanja
- Heavy Water Division, Bhabha Atomic Research Centre, Mumbai400 085, India
| | - Niharendu Choudhury
- Theoretical Chemistry Section, Chemistry Division, Bhabha Atomic Research Centre, Mumbai400 085, India.,Homi Bhabha National Institute, Anushaktinagar, Mumbai400 094, India
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Kaur H, Verma M, Kaur S, Rana B, Singh N, Jena KC. Elucidating the Molecular Structure of Hydrophobically Modified Polyethylenimine Nanoparticles and Its Potential Implications for DNA Binding. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13456-13468. [PMID: 36279506 DOI: 10.1021/acs.langmuir.2c01912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The structural properties of the polyethylenimine (PEI) polymer are generally tuned and selectively modified to reinforce its potential in a broad spectrum of applied domains of medicine, healthcare, material design, sensing, and electronic optimization. The selective modification of the polymer brings about changes in its interfacial characteristics and behavior. The current work involves the synthesis of naphthalimide conjugated polyethylenimine organic nanoparticles (NPEI-ONPs). The interfacial molecular structure of NPEI-ONPs is explored in an aqueous medium at pH 7.4 using surface tensiometry and sum-frequency generation vibrational spectroscopy (SFG-VS). The hydrophobic functionalization rendered a concentration-dependent surface coverage of NPEI-ONPs, where the SFG-VS analysis exhibited the molecular rearrangement of its hydrophobic groups at the interface. The interaction of NPEI-ONPs with double-stranded DNA (dsDNA) is carried out to observe the relevance of the synthesized nanocomposites in the biomedical domain. The bulk-specific studies (i.e., thermal denaturation, viscometry, zeta (ζ) potential, and ATR-FTIR) reveal the condensation of dsDNA in the presence of NPEI-ONPs, making its structure more compact. The interface-sensitive SFG-VS showcased the impact of the dsDNA and NPEI-ONP interaction on the interfacial molecular behavior of NPEI-ONPs at the air-aqueous interface. Our results exhibit the potential of such hydrophobically functionalized ONPs as promising candidates for developing biomedical sealants, substrate coatings, and other biomedical domains.
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Hosseinpour S, Götz V, Peukert W. Einfluss von Tensiden auf die molekulare Struktur der Öl/Wasser‐Grenzfläche. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202110091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Saman Hosseinpour
- Lehrstuhl für Feststoff- und Grenzflächenverfahrenstechnik (LFG) Interdisziplinäres Zentrum für Funktionale Partikelsysteme (FPS) Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Cauerstraße 4 91058 Erlangen Deutschland
| | - Vanessa Götz
- Lehrstuhl für Feststoff- und Grenzflächenverfahrenstechnik (LFG) Interdisziplinäres Zentrum für Funktionale Partikelsysteme (FPS) Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Cauerstraße 4 91058 Erlangen Deutschland
| | - Wolfgang Peukert
- Lehrstuhl für Feststoff- und Grenzflächenverfahrenstechnik (LFG) Interdisziplinäres Zentrum für Funktionale Partikelsysteme (FPS) Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Cauerstraße 4 91058 Erlangen Deutschland
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Hosseinpour S, Götz V, Peukert W. Effect of Surfactants on the Molecular Structure of the Buried Oil/Water Interface. Angew Chem Int Ed Engl 2021; 60:25143-25150. [PMID: 34478223 PMCID: PMC9293143 DOI: 10.1002/anie.202110091] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Indexed: 12/30/2022]
Abstract
The oil/water interface, for instance in emulsions, is often stabilized by surfactants. Hence, the co-existence of oil, water, and surfactant molecules at the buried oil/water interface determines macroscopic properties such as surface tension or emulsion stability. Utilizing an inherently surface sensitive spectroscopic method, sum frequency generation (SFG) spectroscopy, we show that adsorption of an anionic surfactant to the buried oil/water interface increases the magnitude of the interfacial electric field. Meanwhile, the degree of ordering of the interfacial oil molecules increases with the surfactant concentration owing to the intercalation of aliphatic chains of interfacial oil and surfactant molecules. At sufficiently high surfactant concentrations, the interfacial charge reaches a maximum value and the interfacial oil molecules arrange in a fully ordered conformation, a state which coincides with the significant decrease in interfacial tension and increased emulsion stability.
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Affiliation(s)
- Saman Hosseinpour
- Institute of Particle Technology (LFG), Interdisciplinary Center for Functional Particle Systems (FPS), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Cauerstrasse 4, 91058, Erlangen, Germany
| | - Vanessa Götz
- Institute of Particle Technology (LFG), Interdisciplinary Center for Functional Particle Systems (FPS), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Cauerstrasse 4, 91058, Erlangen, Germany
| | - Wolfgang Peukert
- Institute of Particle Technology (LFG), Interdisciplinary Center for Functional Particle Systems (FPS), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Cauerstrasse 4, 91058, Erlangen, Germany
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Lautenbach V, Hosseinpour S, Peukert W. Isoelectric Point of Proteins at Hydrophobic Interfaces. Front Chem 2021; 9:712978. [PMID: 34395381 PMCID: PMC8360839 DOI: 10.3389/fchem.2021.712978] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 07/19/2021] [Indexed: 12/02/2022] Open
Abstract
Structural and colloidal stability of proteins at different surfaces and interfaces is of great importance in many fields including medical, pharmaceutical, or material science. Due to their flexibility, proteins tend to respond to their environmental conditions and can undergo structural and conformational changes. For instance, alterations in physiological factors such as temperature, ions concentration, or pH as well as the adsorption to an interface can initiate protein aggregation. Therefore, at different surfaces and interfaces the characterization of the structural and colloidal stability of proteins, which is mainly influenced by their electrostatic and hydrophobic interactions, is of fundamental importance. In this study, we utilized sum frequency generation (SFG) spectroscopy to assess the role of solution pH on the polarity and magnitude of the electric field within the hydration shell of selected model proteins adsorbed to a hydrophobic surface. We used polystyrene (PS) as a model hydrophobic surface and determined the isoelectric point (IEP) of four structurally different model proteins. Comparing the measured IEP of proteins at the PS/solution or air/solution interface with that determined in the bulk solution via zeta potential measurement, we found significant similarities between the IEP of surface adsorbed proteins and those in the bulk aqueous phase. The pH dependence behavior of proteins was correlated to their amino acid composition and degree of hydrophobicity.
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Affiliation(s)
- Vanessa Lautenbach
- Institute of Particle Technology (LFG), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Saman Hosseinpour
- Institute of Particle Technology (LFG), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Wolfgang Peukert
- Institute of Particle Technology (LFG), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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Biswas B, Singh PC. Signature of the surface hydrated proton and associated restructuring of water at model membrane interfaces: a vibrational sum frequency generation study. Phys Chem Chem Phys 2021; 23:14764-14769. [PMID: 34196339 DOI: 10.1039/d1cp01486b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrated proton at membrane interfaces plays an important role in the bioenergetic process of almost all organisms. Herein, the signature of the hydrated proton at membrane interfaces has been investigated by measuring the vibrational sum frequency generated (VSFG) spectra of negatively charged and zwitterionic lipids in the presence of different concentrations of acids. The addition of acids decreases the intensity of the OH stretch of the VSFG signal of water present at the negatively charged and zwitterionic lipids along with the enhanced intensity of the broad VSFG signal in the range of 2500-2800 cm-1. The enhanced intensity of the broad continuum observed in the range of 2500-2800 cm-1 has been assigned to the signature of the hydrated proton at the lipid interfaces. The decrease in the VSFG signal of the OH stretch of water along with the appearance of the broad signal suggests that the hydrated proton exists in the vicinity of the lipid interfaces and restructures the interaction between the interfacial water molecules.
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Affiliation(s)
- Biswajit Biswas
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India.
| | - Prashant Chandra Singh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India.
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Baryiames CP, Ma E, Baiz CR. Ions Slow Water Dynamics at Nonionic Surfactant Interfaces. J Phys Chem B 2020; 124:11895-11900. [DOI: 10.1021/acs.jpcb.0c09086] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher P. Baryiames
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
| | - Emily Ma
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Carlos R. Baiz
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
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Benderskii A, Morita A. Nonlinear spectroscopy and interfacial structure and dynamics. J Chem Phys 2019; 151:150401. [PMID: 31640380 DOI: 10.1063/1.5129103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alexander Benderskii
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Akihiro Morita
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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Deiseroth M, Bonn M, Backus EHG. Electrolytes Change the Interfacial Water Structure but Not the Vibrational Dynamics. J Phys Chem B 2019; 123:8610-8616. [DOI: 10.1021/acs.jpcb.9b08131] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Malte Deiseroth
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Ellen H. G. Backus
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Department of Physical Chemisty, University of Vienna, Währinger Straße 42, 1090 Wien, Austria
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Sum-Frequency Generation Vibrational Spectroscopy: A Nonlinear Optical Tool to Probe the Polymer Interfaces. SPRINGER PROCEEDINGS IN PHYSICS 2019. [DOI: 10.1007/978-981-15-0202-6_3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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