1
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Murakami H, Kanahara Y, Sasaki K. Freezing of Water Solvation Dynamics in Nanoconfinement by Reverse Micelles at Room Temperature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:13082-13091. [PMID: 38867455 DOI: 10.1021/acs.langmuir.4c00926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2024]
Abstract
Much attention has recently been paid to anomalously low dielectric constants of nanoconfined water between two slabs at room temperature (Fumagalli et al. Science, 2018, 360, 1339). These low values imply that the dipole rotation of the interfacial water on the slab is completely suppressed. Such freezing has so far been observed for water confined between solids. In contrast, it remains unclear whether this holds for water in soft confinement, which is omnipresent naturally and artificially. Here, we address this question using encapsulated reverse micelles with a dye molecule, allowing us to study water sandwiched between the surfactant and dye molecules in solution. Moreover, we examine the solvation related to the dielectric property of water, which is reorientational motion in the hydration layer of the dye molecule, by persistent hole-burning spectroscopy. We first show that the dye molecule is surrounded by water without contact with the surfactant and that the dye molecule has two or three hydration layers on average. We next demonstrate that the solvation dynamics is frozen below the water droplet size of ∼4 nm, whereas they become liquid-like when the RM size is further increased. The average gap distance (∼1.5 nm) for freezing the solvation agrees with the gap distance with no rotational water motions between slabs. Our findings may have biological relevance, providing a new aspect for understanding biological function in cells.
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Affiliation(s)
- Hiroshi Murakami
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology (QST), Kyoto 619-0215, Japan
| | - Yuko Kanahara
- Faculty of Human Life and Environment, Nara Women's University, Nara 630-8506, Japan
| | - Kaito Sasaki
- Department of Physics, School of Science, and Micro/Nano Technology Center, Tokai University, Kanagawa 259-1292, Japan
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2
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Poghosyan AH, Abel S, Koetz J. Simulation of AOT reverse micelles with polyethylenimine in hexane. Colloid Polym Sci 2023. [DOI: 10.1007/s00396-023-05059-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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3
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Wang S, Wang M, Han L, Sun Y, Cai W, Shao X. Insight into the stability of protein in confined environment through analyzing the structure of water by temperature-dependent near-infrared spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 267:120581. [PMID: 34776375 DOI: 10.1016/j.saa.2021.120581] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/13/2021] [Accepted: 11/01/2021] [Indexed: 06/13/2023]
Abstract
To understand the stability of protein in confined environment, the near-infrared (NIR) spectra of aqueous solutions and reverse micelles (RMs) containing bovine serum albumin (BSA), human serum albumin (HSA) and ovalbumin (OVA) were measured at different temperature. With the resolution enhanced spectra calculated by continuous wavelet transform (CWT), the intensity change of the α-helix band at 4617 cm-1 with temperature shows a clear denaturation of the protein in aqueous solution but not in RMs. The effect of the confined environment on the stability of the proteins is indicated. More importantly, the intensity change of the spectral bands of water around 6956 and 6842 cm-1 provide an evidence for the denaturation, suggesting that water can be a probe exhibiting the structural change of proteins. Furthermore, comparing the spectral features of different water structures obtained by principal component analysis (PCA) from the spectra of RM with and without BSA, it is demonstrated that the bridging water connecting NH in protein and SO in the inner surface of RM may be the reason for the stabilization.
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Affiliation(s)
- Shiying Wang
- Research Center for Analytical Sciences, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Tianjin 300071, PR China
| | - Mian Wang
- Research Center for Analytical Sciences, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Tianjin 300071, PR China
| | - Li Han
- Research Center for Analytical Sciences, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Tianjin 300071, PR China
| | - Yan Sun
- Research Center for Analytical Sciences, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Tianjin 300071, PR China
| | - Wensheng Cai
- Research Center for Analytical Sciences, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Tianjin 300071, PR China
| | - Xueguang Shao
- Research Center for Analytical Sciences, Frontiers Science Center for New Organic Matter, College of Chemistry, Nankai University, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Tianjin 300071, PR China.
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4
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Mayoral E, Arcos-Casarrubias J, Gama Goicochea A. Self – assembly of model surfactants as reverse micelles in nonpolar solvents and their role as interfacial tension modifiers. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126244] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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5
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Roberts P, Perry JK, Gupta RK, Karna SP, Frechette J. Confinement-Enhanced Luminescence in Protein-Gold Nanoclusters. J Phys Chem Lett 2020; 11:10278-10282. [PMID: 33216558 DOI: 10.1021/acs.jpclett.0c03054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Confinement has profound effects on protein functions. Nanoscale probes for confinement or excluded volume interactions could help us understand how these interactions influence protein functions. This work reports on the increased luminescence of BSA-gold nanoclusters when confined. Confinement of the BSA-gold nanoclusters occurred within reverse micelles (RMs), where the size of the RMs determined the degree of confinement. The confinement-enhanced luminescence is reversible, i.e., the emission returns to its original value following cyclic changes in RM size. Circular dichroism measurements show an increase in alpha-helical character of the BSA-stabilized nanoclusters with confinement, which could provide a mechanism for the increase in luminescence. The alpha-helical character of the native proteins also increases with confinement, suggesting that the protein-nanocluster might sense confinement in an analogous fashion as the proteins. When the RMs approach the size of the protein, the intensity becomes independent of alpha-helical character, suggesting a different mechanism for the luminescence increase.
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Affiliation(s)
| | - Jeneh Karima Perry
- CCDC Army Research Laboratory, Weapons and Material Research Directorate, 6300 Rodman Road, Aberdeen, Proving Ground, Maryland 21005, United States
| | - Raj K Gupta
- DoD Blast Injury Research Coordinating Office, U.S. Army Medical Research and Development Command, 504 Scott Street, Fort Detrick, Maryland 21702, United States
| | - Shashi P Karna
- CCDC Army Research Laboratory, Weapons and Material Research Directorate, 6300 Rodman Road, Aberdeen, Proving Ground, Maryland 21005, United States
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6
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de Souza RM, Ratochinski RH, Karttunen M, Dias LG. Self-Assembly of Phosphocholine Derivatives Using the ELBA Coarse-Grained Model: Micelles, Bicelles, and Reverse Micelles. J Chem Inf Model 2020; 60:522-536. [PMID: 31714768 DOI: 10.1021/acs.jcim.9b00790] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The ELBA coarse-grained force field was originally developed for lipids, and its water model is described as a single-site Lennard-Jones particle with electrostatics modeled by an embedded point-dipole, while other molecules in this force field have a three (or four)-to-one mapping scheme. Here, ELBA was applied to investigate the self-assembly processes of dodecyl-phosphocholine (DPC) micelle, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dihexaoyl-sn-glycero-3-phosphocholine (DPPC/DHPC) bicelles, and DPPC/cyclohexane/water reverse micelles through coarse-grained molecular dynamics (MD) simulations. New parameters were obtained using a simplex algorithm-based calibration procedure to determine the Lennard-Jones parameters for cyclohexane, dodecane, and cyclohexane-dodecane cross-interactions. Density, self-diffusion coefficient, surface tension, and mixture excess volume were found to be in fair agreement with experimental data. These new parameters were used in the simulations, and the obtained structures were analyzed for shape, size, volume, and surface area. Except for the shape of DPC micelles, all other properties match well with available experimental data and all-atom simulations. Remarkably, in agreement with experiments the rodlike shape of the DPPC reverse micelle is well described by ELBA, while all-atom data in the literature predicts a disclike shape. To further check the consistency of the force field in reproducing the correct shapes of reverse micelles, additional simulations were performed doubling the system size. Two distinct reverse micelles were obtained both presenting the rodlike shape and correct aggregation number.
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Affiliation(s)
- R M de Souza
- Department of Chemistry , The University of Western Ontario , London , Ontario , Canada N6A 3K7.,Departamento de Química, FFCLRP , Universidade de São Paulo , Avenida Bandeirantes 3900 , 14040-901 Ribeirão Preto , SP , Brazil.,The Center for Advanced Materials and Biomaterials Research , The University of Western Ontario , London , Ontario , Canada N6K 3K7
| | - R H Ratochinski
- Departamento de Química, FFCLRP , Universidade de São Paulo , Avenida Bandeirantes 3900 , 14040-901 Ribeirão Preto , SP , Brazil
| | - Mikko Karttunen
- Department of Chemistry , The University of Western Ontario , London , Ontario , Canada N6A 3K7.,The Center for Advanced Materials and Biomaterials Research , The University of Western Ontario , London , Ontario , Canada N6K 3K7.,Department of Applied Mathematics , The University of Western Ontario , London , Ontario , Canada N6A 5B7
| | - L G Dias
- Departamento de Química, FFCLRP , Universidade de São Paulo , Avenida Bandeirantes 3900 , 14040-901 Ribeirão Preto , SP , Brazil
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7
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Honegger P, Steinhauser O. The nuclear Overhauser Effect (NOE) as a tool to study macromolecular confinement: Elucidation and disentangling of crowding and encapsulation effects. J Chem Phys 2020; 152:024120. [PMID: 31941328 DOI: 10.1063/1.5135816] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We propose a methodology to capture short-lived but biophysically important contacts of biomacromolecules using the biomolecule-water nuclear Overhauser effect as an indirect microscope. Thus, instead of probing the direct correlation with the foreign biomolecule, we detect its presence by the disturbance it causes in the surrounding water. In addition, this information obtained is spatially resolved and can thus be attributed to specific sites. We extend this approach to the influence of more than one change in chemical environment and show a methodological way of resolution. This is achieved by taking double differences of corresponding σNOE/σROE ratios of the systems studied and separating specific, unspecific, and intermediate influence. While applied to crowding and encapsulation in this study, this method is generally suitable for any combination of changes in chemical environment.
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Affiliation(s)
- Philipp Honegger
- University of Vienna, Faculty of Chemistry, Department of Computational Biological Chemistry, Währingerstraße 17, A-1090 Vienna, Austria
| | - Othmar Steinhauser
- University of Vienna, Faculty of Chemistry, Department of Computational Biological Chemistry, Währingerstraße 17, A-1090 Vienna, Austria
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8
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Honegger P, Steinhauser O. The protein-water nuclear Overhauser effect (NOE) as an indirect microscope for molecular surface mapping of interaction patterns. Phys Chem Chem Phys 2019; 22:212-222. [PMID: 31799520 DOI: 10.1039/c9cp04752b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In this computational study, the intermolecular solute-solvent Nuclear Overhauser Effect (NOE) of the model protein ubiquitin in different chemical environments (free, bound to a partner protein and encapsulated) is investigated. Short-ranged NOE observables such as the NOE/ROE ratio reveal hydration phenomena on absolute timescales such as fast hydration sites and slow water clefts. We demonstrate the ability of solute-solvent NOE differences measured of the same protein in different chemical environments to reveal hydration changes on the relative timescale. The resulting NOE/ROE-surface maps are shown to be a central key for analyzing biologically relevant chemical influences such as complexation and confinement: the presence of a complexing macromolecule or a confining surface wall modulates the water mobility in the vicinity of the probe protein, hence revealing which residues of said protein are proximate to the foreign interface and which are chemically unaffected. This way, hydration phenomena can serve to indirectly map the precise influence (position) of other molecules or interfaces onto the protein surface. This proposed one-protein many-solvents approach may offer experimental benefits over classical one-protein other-protein pseudo-intermolecular transient NOEs. Furthermore, combined influences such as complexation and confinement may exert non-additive influences on the protein compared to a reference state. We offer a mathematical method to disentangle the influence of these two different chemical environments.
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Affiliation(s)
- Philipp Honegger
- University of Vienna, Faculty of Chemistry, Department of Computational Biological Chemistry, Währingerstr. 17, A-1090 Vienna, Austria.
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9
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Sun X, Bandara N. Applications of reverse micelles technique in food science: A comprehensive review. Trends Food Sci Technol 2019. [DOI: 10.1016/j.tifs.2019.07.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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10
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Honegger P, Steinhauser O. Towards capturing cellular complexity: combining encapsulation and macromolecular crowding in a reverse micelle. Phys Chem Chem Phys 2019; 21:8108-8120. [DOI: 10.1039/c9cp00053d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This paper studies the orientational structure and dynamics of multi-protein systems under confinement and discusses the implications on biological cells.
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Affiliation(s)
- Philipp Honegger
- University of Vienna
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- A-1090 Vienna
- Austria
| | - Othmar Steinhauser
- University of Vienna
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- A-1090 Vienna
- Austria
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11
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Kundu K, Singh AP, Panda S, Singh V, Gardas RL, Senapati S. Study on the Conformation of Entrapped Protein inside the Reverse Micellar Confinement Based on the Amino Acid Derived Ionic Liquid. ChemistrySelect 2018. [DOI: 10.1002/slct.201800918] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Kaushik Kundu
- Department of Biotechnology; Bhupat and Jyoti Mehta School of Biosciences; Indian Institute of Technology Madras; Chennai 600036 India
| | - Akhil Pratap Singh
- Department of Biotechnology; Bhupat and Jyoti Mehta School of Biosciences; Indian Institute of Technology Madras; Chennai 600036 India
- Department of Chemistry; Indian Institute of Technology Madras; Chennai 600036 India
| | - Somenath Panda
- Department of Chemistry; Indian Institute of Technology Madras; Chennai 600036 India
| | - Vikram Singh
- Department of Chemistry; Indian Institute of Technology Madras; Chennai 600036 India
| | - Ramesh L. Gardas
- Department of Chemistry; Indian Institute of Technology Madras; Chennai 600036 India
| | - Sanjib Senapati
- Department of Biotechnology; Bhupat and Jyoti Mehta School of Biosciences; Indian Institute of Technology Madras; Chennai 600036 India
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12
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Sett R, Sen S, Paul BK, Guchhait N. How Does Nanoconfinement within a Reverse Micelle Influence the Interaction of Phenazinium-Based Photosensitizers with DNA? ACS OMEGA 2018; 3:1374-1385. [PMID: 31458466 PMCID: PMC6641382 DOI: 10.1021/acsomega.7b01820] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 01/17/2018] [Indexed: 06/10/2023]
Abstract
The major focus of the present work lies in exploring the influence of nanoconfinement within aerosol-OT (AOT) reverse micelles on the binding interaction of two phenazinium-based photosensitizers, namely, phenosafranin (PSF) and safranin-O (SO), with the DNA duplex. Circular dichroism and dynamic light-scattering studies reveal the condensation of DNA within the reverse micellar interior (transformation of the B-form of native DNA to ψ-form). Our results unveil a remarkable effect of the degree of hydration of the reverse micellar core on the stability of the stacking interaction (intercalation) of the drugs (PSF and SO) into DNA; increasing size of the water nanopool (that is, w 0) accompanies decreasing curvature of the DNA duplex structure with the consequent effect of increasing stabilization of the drug:DNA intercalation. The marked differences in the dynamical aspects of the interaction scenario following encapsulation within the reverse micellar core and the subsequent dependence on the size of the water nanopool are also meticulously explored. The differential degrees of steric interactions offered by the drug molecules (presence of methyl substitutions on the planar phenazinium ring in SO) are also found to affect the extent of intercalation of the drugs to DNA. In this context, it is imperative to state that the water pool of the reverse micellar core is often argued to approach bulk-like properties of water with increasing micellar size (typically w 0 ≥ 10), so that deviation from the bulk water properties is likely to be minimized in large reverse micelles (w 0 ≥ 10). On the contrary, our results (particularly quantitative elucidation of micropolarity and dynamical aspects of the interaction) explicitly demonstrate that the bulk-like behavior of the nanoconfined water is not truly achieved even in large reverse micelles.
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Affiliation(s)
- Riya Sett
- Department
of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700009, India
| | - Swagata Sen
- Department
of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700009, India
| | - Bijan K. Paul
- Department
of Chemistry, Mahadevananda Mahavidyalaya, Barrackpore, Kolkata 700120, India
| | - Nikhil Guchhait
- Department
of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700009, India
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13
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Honegger P, Steinhauser O. Revival of collective water structure and dynamics in reverse micelles brought about by protein encapsulation. Phys Chem Chem Phys 2018; 20:22932-22945. [DOI: 10.1039/c8cp03422b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel mechanism of depolarization in reverse micelles with zwitterionic surfactants and containing polar species but lacking ions is reported.
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Affiliation(s)
- Philipp Honegger
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- University of Vienna
- A-1090 Vienna
- Austria
| | - Othmar Steinhauser
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- University of Vienna
- A-1090 Vienna
- Austria
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14
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Chatzidaki MD, Papavasileiou KD, Papadopoulos MG, Xenakis A. Reverse Micelles As Antioxidant Carriers: An Experimental and Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:5077-5085. [PMID: 28481539 DOI: 10.1021/acs.langmuir.7b00213] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Water-in-oil microemulsions with biocompatible components were formulated to be used as carriers of natural antioxidants, such as hydroxytyrosol (HT) and gallic acid (GA). The system was composed of a mixture of natural surfactants, lecithin and monoglycerides, medium chain triglycerides, and aqueous phase. A dual approach was undertaken to study the structure and dynamics of these complicated systems. First, experimental data were collected by using adequate techniques, such as dynamic light scattering (DLS) and electron paramagnetic resonance (EPR) spectroscopy. Following this, a coarse-grained molecular dynamics (CGMD) study based on the experimental composition using the MARTINI force field was conducted. The simulations revealed the spontaneous formation of reverse micelles (RMs) starting from completely random initial conformations, underlying their enhanced thermodynamic stability. The location of the bioactive molecules, as well as the structure of the RM, were in accordance with the experimental findings. Furthermore, GA molecules were found to be located inside the water core, in contrast to the HT ones, which seem to lie at the surfactant interfacial layer. The difference in the antioxidants' molecular location was only revealed in detail from the computational analysis and explains the RM's swelling observed by GA in DLS measurements.
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Affiliation(s)
- Maria D Chatzidaki
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation , 116 35 Athens, Greece
| | - Konstantinos D Papavasileiou
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation , 116 35 Athens, Greece
- National Center for Scientific Research "Demokritos", Institute of Nanoscience and Nanotechnology , Aghia Paraskevi Attikis, 153 10 Athens, Greece
| | - Manthos G Papadopoulos
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation , 116 35 Athens, Greece
| | - Aristotelis Xenakis
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation , 116 35 Athens, Greece
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15
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Glycine molecules in ionic liquid based reverse micelles: Investigation of structure and dynamics using molecular dynamics simulations. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.01.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Schmollngruber M, Braun D, Oser D, Steinhauser O. Dielectric depolarisation and concerted collective dynamics in AOT reverse micelles with and without ubiquitin. Phys Chem Chem Phys 2016; 18:3606-17. [PMID: 26751837 DOI: 10.1039/c5cp07112g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this computational study we present molecular dynamics (MD) simulations of reverse micelles, i.e. nano-scale water pools encapsulated by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and dissolved in isooctane. Although consisting of highly polar components, such micro-emulsions exhibit surprisingly low dielectric permittivity, both static and frequency-dependent. This finding is well supported by experimental dielectric measurements. Furthermore, the computational dielectric spectra of reverse micelles with and without the polar protein ubiquitin are almost identical. A detailed component analysis of our simulated systems reveals the underlying mechanism of the observed dielectric depolarisation. While each component by itself would make a remarkable contribution to the static dielectric permittivity, mutual compensation leads to the observed marginal net result. This compensatory behavior is maintained for all but the highest frequencies. Dielectric model theory adapted to the peculiarities of reverse micelles provides an explanation: embedding a system in a cavity engulfed by a low dielectric medium automatically leads to depolarization. In this sense experiment, simulation and theory are in accordance.
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Affiliation(s)
| | - Daniel Braun
- Department of Computational Biological Chemistry, University of Vienna, Austria.
| | - Daniel Oser
- Department of Computational Biological Chemistry, University of Vienna, Austria.
| | - Othmar Steinhauser
- Department of Computational Biological Chemistry, University of Vienna, Austria.
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17
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Kundu N, Roy A, Banik D, Sarkar N. Unveiling the Mode of Interaction of Berberine Alkaloid in Different Supramolecular Confined Environments: Interplay of Surface Charge between Nano-Confined Charged Layer and DNA. J Phys Chem B 2016; 120:1106-20. [PMID: 26756221 DOI: 10.1021/acs.jpcb.5b10121] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In this Article, we demonstrate a detailed characterization of binding interaction of berberine chloride (BBCl) with calf-thymus DNA (CT-DNA) in buffer solution as well as in two differently charged reverse micelles (RMs). The photophyscial properties of this alkaloid have been modulated within these microheterogeneous bioassemblies. The mode of binding of this alkaloid with DNA is of debate to date. However, fluorescence spectroscopic measurements, circular dichroism (CD) measurement, and temperature-dependent study unambiguously establish that BBCl partially intercalates into the DNA base pairs. The nonplanarity imposed by partial saturation in their structure causes the nonclassical types of intercalation into DNA. Besides the intercalation, electrostatic interactions also play a significant role in the binding between BBCl and DNA. DNA structure turns into a condensed form after encapsulation into RMs, which is followed by the CD spectra and microscopy study. The probe location and dynamics in the nanopool of the RMs depended on the electrostatic interaction between the charged surfactants and cationic berberine. The structural alteration of CT-DNA from B form to condensed form and the interplay of surface charge between RMs and DNA determine the interaction between the alkaloid and DNA in RMs. Time-resolved study and fluorescence anisotropy measurements successfully provide the binding interaction of BBCl in the nanopool of the RMs in the absence and in the presence of DNA. This study motivates us to judge further the potential applicability of this alkaloid in other biological systems or other biomimicking organized assemblies.
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Affiliation(s)
- Niloy Kundu
- Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB India
| | - Arpita Roy
- Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB India
| | - Debasis Banik
- Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB India
| | - Nilmoni Sarkar
- Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB India
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18
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Stîngă G, Maxim ME, Iovescu A, Mihăiescu DE, Băran A, Leontieş AR, Balcan M, Anghel DF. NRET — A rapid method to investigate the water–oil interface in reverse micellar systems. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2015.12.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Sengupta B, Yadav R, Sen P. Startling temperature effect on proteins when confined: single molecular level behaviour of human serum albumin in a reverse micelle. Phys Chem Chem Phys 2016; 18:14350-8. [DOI: 10.1039/c6cp00452k] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The present work reports the effect of confinement, and temperature therein, on the conformational fluctuation dynamics of domain-I of human serum albumin (HSA) by fluorescence correlation spectroscopy (FCS).
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Affiliation(s)
- Bhaswati Sengupta
- Department of Chemistry, Indian Institute of Technology Kanpur
- Kanpur
- India
| | - Rajeev Yadav
- Department of Chemistry, Indian Institute of Technology Kanpur
- Kanpur
- India
| | - Pratik Sen
- Department of Chemistry, Indian Institute of Technology Kanpur
- Kanpur
- India
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Martinez AV, Małolepsza E, Rivera E, Lu Q, Straub JE. Exploring the role of hydration and confinement in the aggregation of amyloidogenic peptides Aβ(16-22) and Sup35(7-13) in AOT reverse micelles. J Chem Phys 2015; 141:22D530. [PMID: 25494801 DOI: 10.1063/1.4902550] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Knowledge of how intermolecular interactions of amyloid-forming proteins cause protein aggregation and how those interactions are affected by sequence and solution conditions is essential to our understanding of the onset of many degenerative diseases. Of particular interest is the aggregation of the amyloid-β (Aβ) peptide, linked to Alzheimer's disease, and the aggregation of the Sup35 yeast prion peptide, which resembles the mammalian prion protein linked to spongiform encephalopathies. To facilitate the study of these important peptides, experimentalists have identified small peptide congeners of the full-length proteins that exhibit amyloidogenic behavior, including the KLVFFAE sub-sequence, Aβ16-22, and the GNNQQNY subsequence, Sup357-13. In this study, molecular dynamics simulations were used to examine these peptide fragments encapsulated in reverse micelles (RMs) in order to identify the fundamental principles that govern how sequence and solution environment influence peptide aggregation. Aβ16-22 and Sup357-13 are observed to organize into anti-parallel and parallel β-sheet arrangements. Confinement in the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles is shown to stabilize extended peptide conformations and enhance peptide aggregation. Substantial fluctuations in the reverse micelle shape are observed, in agreement with earlier studies. Shape fluctuations are found to facilitate peptide solvation through interactions between the peptide and AOT surfactant, including direct interaction between non-polar peptide residues and the aliphatic surfactant tails. Computed amide I IR spectra are compared with experimental spectra and found to reflect changes in the peptide structures induced by confinement in the RM environment. Furthermore, examination of the rotational anisotropy decay of water in the RM demonstrates that the water dynamics are sensitive to the presence of peptide as well as the peptide sequence. Overall, our results demonstrate that the RM is a complex confining environment where substantial direct interaction between the surfactant and peptides plays an important role in determining the resulting ensemble of peptide conformations. By extension the results suggest that similarly complex sequence-dependent interactions may determine conformational ensembles of amyloid-forming peptides in a cellular environment.
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Affiliation(s)
| | - Edyta Małolepsza
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA
| | - Eva Rivera
- Department of Chemistry and Biochemistry, Queens College, City University of New York (CUNY), Flushing, New York 11791, USA
| | - Qing Lu
- Division of Materials Science and Engineering, Boston University, Brookline, Massachusetts 02446, USA
| | - John E Straub
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA
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Martinez AV, Małolepsza E, Domínguez L, Lu Q, Straub JE. Role of Charge and Solvation in the Structure and Dynamics of Alanine-Rich Peptide AKA2 in AOT Reverse Micelles. J Phys Chem B 2015; 119:9084-90. [PMID: 25337983 PMCID: PMC4516319 DOI: 10.1021/jp508813n] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/20/2014] [Indexed: 11/28/2022]
Abstract
The propensity of peptides to form α-helices has been intensely studied using theory, computation, and experiment. Important model peptides for the study of the coil-to-helix transition have been alanine-lysine (AKA) peptides in which the lysine residues are placed on opposite sides of the helix avoiding charge repulsion while enhancing solubility. In this study, the effects of capped versus zwitterionic peptide termini on the secondary structure of alanine-rich peptides in reverse micelles are explored. The reverse micelles are found to undergo substantial shape fluctuations, a property observed in previous studies of AOT reverse micelles in the absence of solvated peptide. The peptides are observed to interact with water, as well as the AOT surfactant, including interactions between the nonpolar residues and the aliphatic surfactant tails. Computation of IR spectra for the amide I band of the peptide allows for direct comparison with experimental spectra. The results demonstrate that capped AKA2 peptides form more stable α helices than zwitterionic AKA2 peptides in reverse micelles. The rotational anisotropy decay of water is found to be distinctly different in the presence or absence of peptide within the reverse micelle, suggesting that the introduction of peptide significantly alters the number of free waters within the reverse micelle nanopool. However, neither the nature of the peptide termini (capped or charged) nor the degree of peptide helicity is found to significantly alter the balance of interactions between the peptides and the environment. Observed changes in the degree of helicity in AKA2 peptides in bulk solution and in reverse micelle environments result from changes in peptide confinement and hydration as well as direct nonpolar and polar interactions with the water-surfactant interface.
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Affiliation(s)
- Anna Victoria Martinez
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Edyta Małolepsza
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Laura Domínguez
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Qing Lu
- Division
of Materials Science and Engineering, Boston
University, 15 Saint
Mary’s Street, Brookline, Massachusetts 02446, United States
| | - John E. Straub
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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Martinez AV, Dominguez L, Małolepsza E, Moser A, Ziegler Z, Straub JE. Probing the structure and dynamics of confined water in AOT reverse micelles. J Phys Chem B 2013; 117:7345-51. [PMID: 23687916 DOI: 10.1021/jp402270e] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reverse micelles are attractive nanoscale systems used for the confinement of molecules in studies of structure and chemical reactions, including protein folding, and aggregation. The simulation of reverse micelles, in which a water "pool" is separated from a nonpolar bulk phase by a surfactant layer, poses significant challenges to empirical force fields due to the diversity of interactions between nonpolar, polar, and charged groups. We have explored the dependence of system density, reverse micelle structure, and water configurational relaxation times as a function of reverse micelle composition, including water:surfactant ratio, absolute number of water molecules, and force field using molecular dynamics simulations. The resulting structures and dynamics are found to depend more on the force field used than on varying interpretations of the water:surfactant ratio in terms of absolute size of the reverse micelle. Substantial deviations from spherical reverse micelle geometries are observed in all unrestrained simulations. Rotational anisotropy decay times and water residence times show a strong dependence on force field and water model used, but power-law relaxation in time is observed independent of the force field. Our results suggest the need for further experimental study of reverse micelles that can provide insight into the distribution and dynamics of shape fluctuations in these complex systems.
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Ladanyi BM. Computer simulation studies of counterion effects on the properties of surfactant systems. Curr Opin Colloid Interface Sci 2013. [DOI: 10.1016/j.cocis.2012.12.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Tofoleanu F, Buchete NV. Molecular interactions of Alzheimer's Aβ protofilaments with lipid membranes. J Mol Biol 2012; 421:572-86. [PMID: 22281438 DOI: 10.1016/j.jmb.2011.12.063] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2011] [Revised: 12/22/2011] [Accepted: 12/29/2011] [Indexed: 12/22/2022]
Abstract
Amyloid fibrils and peptide oligomers play central roles in the pathology of Alzheimer's disease, type 2 diabetes, Parkinson's disease, Huntington's disease, and prion-related disease. Here, we investigate the molecular interactions between preformed amyloid β (Aβ) molecular protofilaments and lipid bilayer membranes, in the presence of explicit water molecules, using computational models and all-atom molecular dynamics. These interactions play an important role in the stability and function of both Aβ fibrils and the adjacent cellular membrane. Taking advantage of the symmetry-related and directional properties of the protofilaments, we build models that cover several relative protofilament-membrane orientations. Our molecular dynamics simulations reveal the relative contributions of different structural elements to the dynamics and stability of Aβ protofilament segments near membranes, and the first steps in the mechanism of fibril-membrane interactions. During this process, we observe a significant alteration of the side-chain contact pattern in protofilaments, although a fraction of the characteristic β-sheet content is preserved. As a major driving force, we identify the electrostatic interactions between Aβ charged side chains, including E22, D23, and K28, and lipid headgroups. Together with hydrogen bonding with atoms from lipid headgroups, these interactions can facilitate the penetration of hydrophobic C-terminal amino acids through the lipid headgroup region, which can finally lead both to further loss of the initial fibril structure and to local membrane-thinning effects. Our results may guide new experiments that could test the extent to which the structural features of water-formed amyloid fibrils are preserved, lost, or reshaped by membrane-mediated interactions.
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Tian J, García AE. Simulations of the confinement of ubiquitin in self-assembled reverse micelles. J Chem Phys 2011; 134:225101. [PMID: 21682536 PMCID: PMC3133568 DOI: 10.1063/1.3592712] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 04/30/2011] [Indexed: 11/14/2022] Open
Abstract
We describe the effects of confinement on the structure, hydration, and the internal dynamics of ubiquitin encapsulated in reverse micelles (RM). We performed molecular dynamics simulations of the encapsulation of ubiquitin into self-assembled protein/surfactant reverse micelles to study the positioning and interactions of the protein with the RM and found that ubiquitin binds to the RM interface at low salt concentrations. The same hydrophobic patch that is recognized by ubiquitin binding domains in vivo is found to make direct contact with the surfactant head groups, hydrophobic tails, and the iso-octane solvent. The fast backbone N-H relaxation dynamics show that the fluctuations of the protein encapsulated in the RM are reduced when compared to the protein in bulk. This reduction in fluctuations can be explained by the direct interactions of ubiquitin with the surfactant and by the reduced hydration environment within the RM. At high concentrations of excess salt, the protein does not bind strongly to the RM interface and the fast backbone dynamics are similar to that of the protein in bulk. Our simulations demonstrate that the confinement of protein can result in altered protein dynamics due to the interactions between the protein and the surfactant.
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Affiliation(s)
- Jianhui Tian
- Department of Physics, Applied Physics and Astronomy and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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