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Liu Z, Lin L, Li T, Premadasa UI, Hong K, Ma YZ, Sacci RL, Katsaras J, Carrillo JM, Doughty B, Collier CP. Physicochemical control of solvation and molecular assembly of charged amphiphilic oligomers at air-aqueous interfaces. J Colloid Interface Sci 2024; 669:552-560. [PMID: 38729003 DOI: 10.1016/j.jcis.2024.05.008] [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: 11/16/2023] [Revised: 03/07/2024] [Accepted: 05/02/2024] [Indexed: 05/12/2024]
Abstract
HYPOTHESIS Understanding the rules that control the assembly of nanostructured soft materials at interfaces is central to many applications. We hypothesize that electrolytes can be used to alter the hydration shell of amphiphilic oligomers at the air-aqueous interface of Langmuir films, thereby providing a means to control the formation of emergent nanostructures. EXPERIMENTS Three representative salts - (NaF, NaCl, NaSCN) were studied for mediating the self-assembly of oligodimethylsiloxane methylimidazolium (ODMS-MIM+) amphiphiles in Langmuir films. The effects of the different salts on the nanostructure assembly of these films were probed using vibrational sum frequency generation (SFG) spectroscopy and Langmuir trough techniques. Experimental data were supported by atomistic molecular dynamic simulations. FINDINGS Langmuir trough surface pressure - area isotherms suggested a surprising effect on oligomer assembly, whereby the presence of anions affects the stability of the interfacial layer irrespective of their surface propensities. In contrast, SFG results implied a strong anion effect that parallels the surface activity of anions. These seemingly contradictory trends are explained by anion driven tail dehydration resulting in increasingly heterogeneous systems with entangled ODMS tails and appreciable anion penetration into the complex interfacial layer comprised of headgroups, tails, and interfacial water molecules. These findings provide physical and chemical insight for tuning a wide range of interfacial assemblies.
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Affiliation(s)
- Zening Liu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Lu Lin
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Tianyu Li
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, United States
| | - Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Kunlun Hong
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - John Katsaras
- Neutron Scattering Division and Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Jan-Michael Carrillo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
| | - C Patrick Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
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Scott HL, Bolmatov D, Premadasa UI, Doughty B, Carrillo JMY, Sacci RL, Lavrentovich M, Katsaras J, Collier CP. Cations Control Lipid Bilayer Memcapacitance Associated with Long-Term Potentiation. ACS APPLIED MATERIALS & INTERFACES 2023; 15:44533-44540. [PMID: 37696028 DOI: 10.1021/acsami.3c09056] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
Phospholipid bilayers can be described as capacitors whose capacitance per unit area (specific capacitance, Cm) is determined by their thickness and dielectric constant─independent of applied voltage. It is also widely assumed that the Cm of membranes can be treated as a "biological constant". Recently, using droplet interface bilayers (DIBs), it was shown that zwitterionic phosphatidylcholine (PC) lipid bilayers can act as voltage-dependent, nonlinear memory capacitors, or memcapacitors. When exposed to an electrical "training" stimulation protocol, capacitive energy storage in lipid membranes was enhanced in the form of long-term potentiation (LTP), which enables biological learning and long-term memory. LTP was the result of membrane restructuring and the progressive asymmetric distribution of ions across the lipid bilayer during training, which is analogous, for example, to exponential capacitive energy harvesting from self-powered nanogenerators. Here, we describe how LTP could be produced from a membrane that is continuously pumped into a nonequilibrium steady state, altering its dielectric properties. During this time, the membrane undergoes static and dynamic changes that are fed back to the system's potential energy, ultimately resulting in a membrane whose modified molecular structure supports long-term memory storage and LTP. We also show that LTP is very sensitive to different salts (KCl, NaCl, LiCl, and TmCl3), with LiCl and TmCl3 having the most profound effect in depressing LTP, relative to KCl. This effect is related to how the different cations interact with the bilayer zwitterionic PC lipid headgroups primarily through electric-field-induced changes to the statistically averaged orientations of water dipoles at the bilayer headgroup interface.
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Affiliation(s)
- Haden L Scott
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Dima Bolmatov
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, United States
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jan-Michael Y Carrillo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Maxim Lavrentovich
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, United States
| | - John Katsaras
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, United States
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Charles P Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Yang P, Guo W, Ramamoorthy A, Chen Z. Conformation and Orientation of Antimicrobial Peptides MSI-594 and MSI-594A in a Lipid Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5352-5363. [PMID: 37017985 DOI: 10.1021/acs.langmuir.2c03430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
There is significant interest in the development of antimicrobial compounds to overcome the increasing bacterial resistance to conventional antibiotics. Studies have shown that naturally occurring and de novo-designed antimicrobial peptides could be promising candidates. MSI-594 is a synthetic linear, cationic peptide that has been reported to exhibit a broad spectrum of antimicrobial activities. Investigation into how MSI-594 disrupts the cell membrane is important for better understanding the details of this antimicrobial peptide (AMP)'s action against bacterial cells. In this study, we used two different synthetic lipid bilayers: zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and anionic 7:3 POPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho(1'-rac-glycerol) (POPG). Sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) were used to determine the orientations of MSI-594 and its analogue MSI-594A associated with zwitterionic POPC and anionic 7:3 POPC/POPG lipid bilayers. The simulated ATR-FTIR and SFG spectra using nuclear magnetic resonance (NMR)-determined structures were compared with experimental spectra to optimize the bent angle between the N- (1-11) and C- (12-24) termini helices and the membrane orientations of the helices; since the NMR structure of the peptide was determined from lipopolysaccharide (LPS) micelles, the optimization was needed to find the most suitable conformation and orientation in lipid bilayers. The reported experimental results indicate that the optimized MSI-594 helical hairpin structure adopts a complete lipid bilayer surface-bound orientation (denoted "face-on") in both POPC and 7:3 POPC/POPG lipid bilayers. The analogue peptide, MSI-584A, on the other hand, exhibited a larger bent angle between the N- (1-11) and C- (12-24) termini helices with the hydrophobic C-terminal helix inserted into the hydrophobic region of the bilayer (denoted "membrane-inserted") when interacting with both POPC and 7:3 POPC/POPG lipid bilayers. These experimental findings on the membrane orientations suggest that both peptides are likely to disrupt the cell membrane through the carpet mechanism.
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Affiliation(s)
- Pei Yang
- Department of Chemistry, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Wen Guo
- Department of Chemistry, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
- Department of Biophysics, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Zhan Chen
- Department of Chemistry, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
- Department of Biophysics, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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Lin L, Liu Z, Premadasa UI, Li T, Ma YZ, Sacci RL, Katsaras J, Hong K, Collier CP, Carrillo JMY, Doughty B. The Unexpected Role of Cations in the Self-Assembly of Positively Charged Amphiphiles at Liquid/Liquid Interfaces. J Phys Chem Lett 2022; 13:10889-10896. [PMID: 36394318 DOI: 10.1021/acs.jpclett.2c02921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Conventional wisdom suggests that cations play a minimal role in the assembly of cationic amphiphiles. Here, we show that at liquid/liquid (L/L) interfaces, specific cation effects can modulate the assemblies of hydrophobic tails in an oil phase despite being attached to cationic headgroups in the aqueous phase. We used oligo-dimethylsiloxane (ODMS) methyl imidazolium amphiphiles to identify these specific interactions at hexadecane/aqueous interfaces. Small cations, such as Li+, bind to the O atoms in the ODMS tail and pin it to the interface, thereby imposing a kinked conformation─as evidenced by vibrational sum frequency generation spectroscopy and molecular dynamics simulations. While larger Cs+ ions more readily partition to the interface, they do not form analogous complexes. Our data not only point to ways for controlling amphiphile structure at L/L interfaces but also suggest a means for the separation of Li+, or related applications, in soft-matter electronics.
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Affiliation(s)
- Lu Lin
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Zening Liu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Tianyu Li
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee37996, United States
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - John Katsaras
- Laboratories and Soft Matter Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Kunlun Hong
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - C Patrick Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Jan-Michael Y Carrillo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
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Gregory KP, Elliott GR, Robertson H, Kumar A, Wanless EJ, Webber GB, Craig VSJ, Andersson GG, Page AJ. Understanding specific ion effects and the Hofmeister series. Phys Chem Chem Phys 2022; 24:12682-12718. [PMID: 35543205 DOI: 10.1039/d2cp00847e] [Citation(s) in RCA: 73] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Specific ion effects (SIE), encompassing the Hofmeister Series, have been known for more than 130 years since Hofmeister and Lewith's foundational work. SIEs are ubiquitous and are observed across the medical, biological, chemical and industrial sciences. Nevertheless, no general predictive theory has yet been able to explain ion specificity across these fields; it remains impossible to predict when, how, and to what magnitude, a SIE will be observed. In part, this is due to the complexity of real systems in which ions, counterions, solvents and cosolutes all play varying roles, which give rise to anomalies and reversals in anticipated SIEs. Herein we review the historical explanations for SIE in water and the key ion properties that have been attributed to them. Systems where the Hofmeister series is perturbed or reversed are explored, as is the behaviour of ions at the liquid-vapour interface. We discuss SIEs in mixed electrolytes, nonaqueous solvents, and in highly concentrated electrolyte solutions - exciting frontiers in this field with particular relevance to biological and electrochemical applications. We conclude the perspective by summarising the challenges and opportunities facing this SIE research that highlight potential pathways towards a general predictive theory of SIE.
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Affiliation(s)
- Kasimir P Gregory
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia. .,Department of Materials Physics, Research School of Physics, Australian National University, Canberra, ACT 0200, Australia
| | - Gareth R Elliott
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
| | - Hayden Robertson
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
| | - Anand Kumar
- Flinders Institute of Nanoscale Science and Technology, College of Science and Engineering, Flinders University, South Australia 5001, Australia
| | - Erica J Wanless
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
| | - Grant B Webber
- School of Engineering, The University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Vincent S J Craig
- Department of Materials Physics, Research School of Physics, Australian National University, Canberra, ACT 0200, Australia
| | - Gunther G Andersson
- Flinders Institute of Nanoscale Science and Technology, College of Science and Engineering, Flinders University, South Australia 5001, Australia
| | - Alister J Page
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
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Yan L, Saha A, Zhao W, Neal JF, Chen Y, Flood AH, Allen HC. Recognition competes with hydration in anion-triggered monolayer formation of cyanostar supra-amphiphiles at aqueous interfaces. Chem Sci 2022; 13:4283-4294. [PMID: 35509460 PMCID: PMC9006960 DOI: 10.1039/d2sc00986b] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 03/14/2022] [Indexed: 11/21/2022] Open
Abstract
The triggered self-assembly of surfactants into organized layers at aqueous interfaces is important for creating adaptive nanosystems and understanding selective ion extraction. While these transformations require molecular recognition, the underlying driving forces are modified by the local environment in ways that are not well understood. Herein, we investigate the role of ion binding and ion hydration using cyanosurf, which is composed of the cyanostar macrocycle, and its binding to anions that are either size-matched or mis-matched and either weakly or highly hydrated. We utilize the supra-amphiphile concept where anion binding converts cyanosurf into a charged and amphiphilic complex triggering its self-organization into monolayers at the air-water interface. Initially, cyanosurf forms aggregates at the surface of a pure water solution. When the weakly hydrated and size-matched hexafluorophosphate (PF6 -) and perchlorate (ClO4 -) anions are added, the macrocycles form distinct monolayer architectures. Surface-pressure isotherms reveal significant reorganization of the surface-active molecules upon anion binding while infrared reflection absorption spectroscopy show the ion-bound complexes are well ordered at the interface. Vibrational sum frequency generation spectroscopy shows the water molecules in the interfacial region are highly ordered in response to the charged monolayer of cyanosurf complexes. Consistent with the importance of recognition, we find the smaller mis-matched chloride does not trigger the transformation. However, the size-matched phosphate (H2PO4 -) also does not trigger monolayer formation indicating hydration inhibits its interfacial binding. These studies reveal how anion-selective recognition and hydration both control the binding and thus the switching of a responsive molecular interface.
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Affiliation(s)
- Liwei Yan
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA +1-614-292-1685 +1-614-292-4707
| | - Ankur Saha
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA +1-614-292-1685 +1-614-292-4707
| | - Wei Zhao
- Department of Chemistry, Indiana University Bloomington Indiana 47405 USA +1-812-855-8300 +1-812-856-3642
| | - Jennifer F Neal
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA +1-614-292-1685 +1-614-292-4707
| | - Yusheng Chen
- Department of Chemistry, Indiana University Bloomington Indiana 47405 USA +1-812-855-8300 +1-812-856-3642
| | - Amar H Flood
- Department of Chemistry, Indiana University Bloomington Indiana 47405 USA +1-812-855-8300 +1-812-856-3642
| | - Heather C Allen
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA +1-614-292-1685 +1-614-292-4707
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