1
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Chandra A, Kayal A, Das B, Chandra A. Dynamical Crossover of Interfacial Water upon Melting of a Lipid Bilayer: Influence of Different Parts of the Headgroups. J Phys Chem B 2023. [PMID: 38032152 DOI: 10.1021/acs.jpcb.3c04792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
All-atom molecular dynamics simulations of a 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer in contact with liquid water were performed at different temperatures ranging from 285 to 320 K. We have investigated the heterogeneity and dynamical transitions in interfacial water as the lipid bilayer undergoes a melting transition. Results are obtained for water at the outer surface of the bilayer and for those buried more deeply in the lipid chains of the bilayer. It is found that lipid bilayer melting influences both the structure and dynamics of interfacial water. The number of interfacial water molecules shows a jump in the melting of the bilayer. The temperature dependence of the diffusivity and orientational relaxation of interfacial water molecules exhibits a dynamical crossover upon melting of the bilayer. The extent of dynamical crossover is found to be rather strong with significant changes in activation barriers for interfacial water around the carbonyl groups, which are deeply buried toward the lipid chains of the bilayer. The dynamical crossover gradually decreases as one moves further away from the outer surface, and it essentially vanishes for water in the region of 5-10 Å from the outer surface. It is found that the lipid melting-induced dynamical crossover of interfacial water is significant only for water that is in close proximity to the bilayer surface or deeply buried into it. The current results reveal that water molecules in different parts of the interface respond differently on melting of the bilayer. The current study also shows that the carbonyl-bound water molecules can play an important role in the phase transition of the bilayer as the temperature is raised through its melting point.
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Affiliation(s)
- Abhilash Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India
| | - Abhijit Kayal
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India
| | - Banshi Das
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India
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2
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Miyajima A, Nakao H, Ikeda K, Nakano M. The Nanometer-Scale Proximity of Bilayers Facilitates Intermembrane Lipid Transfer. J Phys Chem Lett 2023; 14:4172-4178. [PMID: 37114850 DOI: 10.1021/acs.jpclett.3c00154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Biological membranes approach one another in various biological phenomena, such as lipid transport at membrane contact sites and membrane fusion. The proximity of two bilayers may cause environmental changes in the interbilayer space and alter the dynamics of lipid molecules. Here, we investigate the structure and dynamics of vesicles aggregated due to the depletion attraction caused by polyethylene glycol (PEG) through static and dynamic small-angle neutron scattering. Manipulation of the interbilayer distance using PEG-conjugated lipids reveals that lipid molecules rapidly transfer between vesicles when the opposing bilayers are within ∼2 nm of each other. This distance corresponds to a region in which water molecules are more structured than in bulk water. Kinetic analysis suggests that the decrease in water entropy is responsible for the progression of lipid transfer. These results provide a basis for understanding the dynamic function of biomembranes in confined regions.
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Affiliation(s)
- Ayari Miyajima
- Department of Biointerface Chemistry, Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Hiroyuki Nakao
- Department of Biointerface Chemistry, Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Keisuke Ikeda
- Department of Biointerface Chemistry, Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Minoru Nakano
- Department of Biointerface Chemistry, Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
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3
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Hande VR, Chakrabarty S. How Far Is "Bulk Water" from Interfaces? Depends on the Nature of the Surface and What We Measure. J Phys Chem B 2022; 126:1125-1135. [PMID: 35104127 DOI: 10.1021/acs.jpcb.1c08603] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using systematic molecular dynamics (MD) simulations, we revisit the question: At what distance from an interface do the properties of "bulk water" get recovered? We have considered three different kinds of interfaces: nonpolar (hydrophobic; isooctane-water interface), charged (negative; AOT bilayer), and polar (zwitterionic; POPC bilayer). In order to interrogate the extent of perturbation of the interfacial water molecules as a function of the distance from the interface, we utilize a diverse range of structural and dynamical parameters. To capture the structural perturbations, we look into local density (translational order), local tetrahedral order parameter, and dipolar orientation of the water molecules. We also explore the anisotropic diffusion of the water molecules in the direction perpendicular to the interface as well as the planar diffusion parallel to the interface in a distance dependent manner. In addition, the orientational time correlation functions have been computed to understand the extent of slowdown in the rotational dynamics. As expected, the electrostatic field emanating from the charged AOT interface seems to have the highest long-range effect on the orientational order and dynamics of the water molecules, whereas specific interactions like hydrogen bonding and electrostatic interaction lead to significant trapping and kinetic slowdown for both AOT and POPC (zwitterionic) very close to the interface. Our analysis highlights that not only the length-scale of perturbation depends on the nature of the interfaces and specific interactions but also the type of water property that we measure/calculate. Different water properties seem to have widely different length-scale of perturbation. Orientational order parameters seem to be perturbed to a much longer length-scale as compared to translational order parameters. The global orientational order of water can be perturbed even up to ∼4-5 nm near the negatively charged AOT surface in the absence of any extra electrolyte. This observation has significant implication toward the interpretation of experimental measurements as well since different spectroscopic techniques would probe different parameters or water properties with possible mutual disagreement and inconsistency between different types of measurements. Thus, our study provides a broader and unifying perspective toward the aspect of "context dependent" structural and dynamical perturbation of "interfacial water".
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Affiliation(s)
- Vrushali R Hande
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, Maharashtra, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Suman Chakrabarty
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata 700106, India
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4
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Malik S, Debnath A. Dehydration induced dynamical heterogeneity and ordering mechanism of lipid bilayers. J Chem Phys 2021; 154:174904. [PMID: 34241050 DOI: 10.1063/5.0044614] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Understanding the influence of dehydration on the membrane structure is crucial to control membrane functionality related to domain formation and cell fusion under anhydrobiosis conditions. To this end, we perform all-atom molecular dynamic simulations of 1,2-dimyristoyl-sn-glycero-3-phosphocholine dimyristoylphosphatidylcholine lipid membranes at different hydration levels at 308 K. As dehydration increases, the lipid area per head group decreases with an increase in bilayer thickness and lipid order parameters indicating bilayer ordering. Concurrently, translational and rotational dynamics of interfacial water (IW) molecules near membranes slow down. On the onset of bilayer ordering, the IW molecules exhibit prominent features of dynamical heterogeneity evident from non-Gaussian parameters and one-dimensional van Hove correlation functions. At a fully hydrated state, diffusion constants (D) of the IW follow a scaling relation, D∼τα -1, where the α relaxation time (τα) is obtained from self-intermediate scattering functions. However, upon dehydration, the relation breaks and the D of the IW follows a power law behavior as D∼τα -0.57, showing the signature of glass dynamics. τα and hydrogen bond lifetime calculated from intermittent hydrogen bond auto-correlation functions undergo a similar crossover in association with bilayer ordering on dehydration. The bilayer ordering is accompanied with an increase in fraction of caged lipids spanned over the bilayer surface and a decrease in fraction of mobile lipids due to the non-diffusive dynamics. Our analyses reveal that the microscopic mechanism of lipid ordering by dehydration is governed by dynamical heterogeneity. The fundamental understanding from this study can be applied to complex bio-membranes to trap functionally relevant gel-like domains at room temperature.
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Affiliation(s)
- Sheeba Malik
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwad, Rajasthan, India
| | - Ananya Debnath
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwad, Rajasthan, India
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5
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Borocci S, Bozzuto G, Bombelli C, Ceccacci F, Formisano G, Stringaro A, Molinari A, Mancini G. How stereochemistry of lipid components can affect lipid organization and the route of liposome internalization into cells. NANOSCALE 2021; 13:11976-11993. [PMID: 34212969 DOI: 10.1039/d1nr02175c] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Though liposome-based drugs are in clinical use, the mechanism of cell internalization of liposomes is yet an object of controversy. The present experimental investigation, carried out on human glioblastoma cells, indicated different internalization routes for two diastereomeric liposomes. Molecular dynamics simulations of the lipid bilayers of the two formulations indicated that the different stereochemistry of a lipid component controls some parameters such as area per lipid molecule and fluidity of lipid membranes, surface potential and water organization at the lipid/water interface, all of which affect the interaction with biomolecules and cell components.
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Affiliation(s)
- Stefano Borocci
- Dipartimento per la Innovazione nei sistemi Biologici, Agroalimentari e Forestali (DIBAF), Università degli Studi della Tuscia, L.go dell'Università, s.n.c., 01100 Viterbo, Italy.
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6
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Abstract
Water determines the properties of biological systems. Therefore, understanding the nature of the mutual interaction between water and biosystems is of primary importance for a proper assessment of any biological activity, e.g., the efficacy of new drugs or vaccines. A convenient way to characterize the interactions between biosystems and water is to analyze their impact on water density and dynamics in the proximity of the interfaces. It is commonly accepted that water bulk density and dynamical properties are recovered at distances of the order of 1 nm away from the surface of biological systems. This notion leads to the definition of hydration or biological water as the nanoscopic layer of water covering the surface of biosystems and to the expectation that all the effects of the water-interface interaction are limited to this thin region. Here, we review some of our latest contributions, showing that phospholipid membranes affect the water dynamics, structural properties, and hydrogen bond network at a distance that is more than twice as large as the commonly evoked ∼1nm thick layer and of the order of 2.4 nm. Furthermore, we unveil that at a shorter distance ∼0.5nm from the membrane, instead, there is an additional interface between lipid-bound and unbound water. Bound water has a structural role in the stability of the membrane. Our results imply that the concept of hydration water should be revised or extended and pave the way to a deeper understanding of the mutual interactions between water and biological systems.
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7
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Martelli F, Crain J, Franzese G. Network Topology in Water Nanoconfined between Phospholipid Membranes. ACS NANO 2020; 14:8616-8623. [PMID: 32578978 DOI: 10.1021/acsnano.0c02984] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Water provides the driving force for the assembly and stability of many cellular components. Despite its impact on biological functions, a nanoscale understanding of the relationship between its structure and dynamics under soft confinement has remained elusive. As expected, water in contact with biological membranes recovers its bulk density and dynamics at ∼1 nm from phospholipid headgroups but surprisingly enhances its intermediate range order (IRO) over a distance, at least, twice as large. Here, we explore how the IRO is related to the water's hydrogen-bond network (HBN) and its coordination defects. We characterize the increased IRO by an alteration of the HBN up to more than eight coordination shells of hydration water. The HBN analysis emphasizes the existence of a bound-unbound water interface at ∼0.8 nm from the membrane. The unbound water has a distribution of defects intermediate between bound and bulk water, but with density and dynamics similar to bulk, while bound water has reduced thermal energy and many more HBN defects than low-temperature water. This observation could be fundamental for developing nanoscale models of biological interactions and for understanding how alteration of the water structure and topology, for example, due to changes in extracellular ions concentration, could affect diseases and signaling. More generally, it gives us a different perspective to study nanoconfined water.
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Affiliation(s)
- Fausto Martelli
- Hartree Centre, IBM Research Europe, Daresbury WA4 4AD, United Kingdom
| | - Jason Crain
- Hartree Centre, IBM Research Europe, Daresbury WA4 4AD, United Kingdom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Giancarlo Franzese
- Secció de Física Estadística i Interdisciplinària, Departament de Física de la Matèria Condensada, and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, C. Martí i Franquès 1, 08028 Barcelona, Spain
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8
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Deplazes E, Sarrami F, Poger D. Effect of H3O+ on the Structure and Dynamics of Water at the Interface with Phospholipid Bilayers. J Phys Chem B 2020; 124:1361-1373. [DOI: 10.1021/acs.jpcb.9b10169] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Evelyne Deplazes
- School of Life Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
- School of Pharmacy and Biomedical Sciences, Curtin Institute for Computation, Curtin University, Perth, Western Australia 6845, Australia
| | - Farzaneh Sarrami
- School of Chemistry and Biochemistry, The University of Western Australia, Perth, Western Australia 6009, Australia
| | - David Poger
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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9
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Lee E, Kundu A, Jeon J, Cho M. Water hydrogen-bonding structure and dynamics near lipid multibilayer surface: Molecular dynamics simulation study with direct experimental comparison. J Chem Phys 2019; 151:114705. [DOI: 10.1063/1.5120456] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Euihyun Lee
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Achintya Kundu
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Str. 2a, 12489 Berlin, Germany
| | - Jonggu Jeon
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
| | - Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
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10
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Calero C, Franzese G. Membranes with different hydration levels: The interface between bound and unbound hydration water. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2018.10.074] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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11
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Yan C, Kramer PL, Yuan R, Fayer MD. Water Dynamics in Polyacrylamide Hydrogels. J Am Chem Soc 2018; 140:9466-9477. [DOI: 10.1021/jacs.8b03547] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Chang Yan
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Patrick L. Kramer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Rongfeng Yuan
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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12
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Hartkamp R, Moore TC, Iacovella CR, Thompson MA, Bulsara PA, Moore DJ, McCabe C. Composition Dependence of Water Permeation Across Multicomponent Gel-Phase Bilayers. J Phys Chem B 2018; 122:3113-3123. [PMID: 29504755 PMCID: PMC6028149 DOI: 10.1021/acs.jpcb.8b00747] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
![]()
The permeability
of multicomponent phospholipid bilayers in the
gel phase is investigated via molecular dynamics simulation. The physical
role of the different molecules is probed by comparing multiple mixed-component
bilayers containing distearylphosphatidylcholine (DSPC) with varying
amounts of either the emollient isostearyl isostearate or long-chain
alcohol (dodecanol, octadecanol, or tetracosanol) molecules. Permeability
is found to depend on both the tail packing density and hydrogen bonding
between lipid headgroups and water. Whereas the addition of emollient
or alcohol molecules to a gel-phase DSPC bilayer can increase the
tail packing density, it also disturbed the hydrogen-bonding network,
which in turn can increase interfacial water dynamics. These phenomena
have opposing effects on bilayer permeability, which is found to depend
on the balance between enhanced tail packing and decreased hydrogen
bonding.
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Affiliation(s)
- Remco Hartkamp
- Process & Energy Department , Delft University of Technology , Leeghwaterstraat 39 , 2628 CB Delft , The Netherlands
| | | | | | - Michael A Thompson
- GlaxoSmithKline Consumer Healthcare , 184 Liberty Corner Road , Suite 200, Warren , New Jersey 07059 , United States
| | - Pallav A Bulsara
- GlaxoSmithKline Consumer Healthcare , 184 Liberty Corner Road , Suite 200, Warren , New Jersey 07059 , United States
| | - David J Moore
- GlaxoSmithKline Consumer Healthcare , 184 Liberty Corner Road , Suite 200, Warren , New Jersey 07059 , United States
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13
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Affiliation(s)
- Jesse G. McDaniel
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Arun Yethiraj
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
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14
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Abstract
The structure and function of biomolecules are strongly influenced by their hydration shells. Structural fluctuations and molecular excitations of hydrating water molecules cover a broad range in space and time, from individual water molecules to larger pools and from femtosecond to microsecond time scales. Recent progress in theory and molecular dynamics simulations as well as in ultrafast vibrational spectroscopy has led to new and detailed insight into fluctuations of water structure, elementary water motions, electric fields at hydrated biointerfaces, and processes of vibrational relaxation and energy dissipation. Here, we review recent advances in both theory and experiment, focusing on hydrated DNA, proteins, and phospholipids, and compare dynamics in the hydration shells to bulk water.
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Affiliation(s)
- Damien Laage
- École
Normale Supérieure, PSL Research University, UPMC Univ Paris
06, CNRS, Département de Chimie,
PASTEUR, 24 rue Lhomond, 75005 Paris, France
- Sorbonne
Universités, UPMC Univ Paris 06, ENS, CNRS, PASTEUR, 75005 Paris, France
| | - Thomas Elsaesser
- Max-Born-Institut
für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany
| | - James T. Hynes
- École
Normale Supérieure, PSL Research University, UPMC Univ Paris
06, CNRS, Département de Chimie,
PASTEUR, 24 rue Lhomond, 75005 Paris, France
- Sorbonne
Universités, UPMC Univ Paris 06, ENS, CNRS, PASTEUR, 75005 Paris, France
- Department
of Chemistry and Biochemistry, University
of Colorado, Boulder, Colorado 80309, United
States
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15
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Laage D, Elsaesser T, Hynes JT. Perspective: Structure and ultrafast dynamics of biomolecular hydration shells. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:044018. [PMID: 28470026 PMCID: PMC5398927 DOI: 10.1063/1.4981019] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 03/31/2017] [Indexed: 05/25/2023]
Abstract
The structure and function of biomolecules can be strongly influenced by their hydration shells. A key challenge is thus to determine the extent to which these shells differ from bulk water, since the structural fluctuations and molecular excitations of hydrating water molecules within these shells can cover a broad range in both space and time. Recent progress in theory, molecular dynamics simulations, and ultrafast vibrational spectroscopy has led to new and detailed insight into the fluctuations of water structure, elementary water motions, and electric fields at hydrated biointerfaces. Here, we discuss some central aspects of these advances, focusing on elementary molecular mechanisms and processes of hydration on a femto- to picosecond time scale, with some special attention given to several issues subject to debate.
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Affiliation(s)
- Damien Laage
- Ecole Normale Supérieure, PSL Research University, UPMC Univ Paris 06, CNRS, Départment de Chimie, PASTEUR, 24 rue Lhomond, 75005 Paris, France
| | - Thomas Elsaesser
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
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16
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Biswas S, Mukherjee SK, Chowdhury PK. Crowder-Induced Rigidity in a Multidomain Protein: Insights from Solvation. J Phys Chem B 2016; 120:12501-12510. [DOI: 10.1021/acs.jpcb.6b10478] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Saikat Biswas
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Sanjib Kumar Mukherjee
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Pramit Kumar Chowdhury
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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17
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McDaniel JG, Mantha S, Yethiraj A. Dynamics of Water in Gemini Surfactant-Based Lyotropic Liquid Crystals. J Phys Chem B 2016; 120:10860-10868. [PMID: 27671427 DOI: 10.1021/acs.jpcb.6b08087] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dynamics of water confined to nanometer-sized domains is important in a variety of applications ranging from proton exchange membranes to crowding effects in biophysics. In this work, we study the dynamics of water in gemini surfactant-based lyotropic liquid crystals (LLCs) using molecular dynamics simulations. These systems have well characterized morphologies, for example, hexagonal, gyroid, and lamellar, and the surfaces of the confining regions can be controlled by modifying the headgroup of the surfactants. This allows one to study the effect of topology, functionalization, and interfacial curvature on the dynamics of confined water. Through analysis of the translational diffusion and rotational relaxation, we conclude that the hydration level and resulting confinement length scale is the predominate determiner of the rates of water dynamics, and other effects, namely, surface functionality and curvature, are largely secondary. This novel analysis of the water dynamics in these LLC systems provides an important comparison for previous studies of water dynamics in lipid bilayers and reverse micelles.
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Affiliation(s)
- Jesse G McDaniel
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
| | - Sriteja Mantha
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
| | - Arun Yethiraj
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
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18
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Huang Y, Zhou G, Li Y, Yang Z, Shi M, Wang X, Chen X, Zhang F, Li W. Molecular dynamics simulations of temperature-dependent structures and dynamics of ethylammonium nitrate protic ionic liquid: The role of hydrogen bond. Chem Phys 2016. [DOI: 10.1016/j.chemphys.2016.03.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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19
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Structural Interpretation of the Large Slowdown of Water Dynamics at Stacked Phospholipid Membranes for Decreasing Hydration Level: All-Atom Molecular Dynamics. MATERIALS 2016; 9:ma9050319. [PMID: 28773441 PMCID: PMC5503093 DOI: 10.3390/ma9050319] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/18/2016] [Accepted: 04/21/2016] [Indexed: 11/27/2022]
Abstract
Hydration water determines the stability and function of phospholipid membranes as well as the interaction of membranes with other molecules. Experiments and simulations have shown that water dynamics slows down dramatically as the hydration decreases, suggesting that the interfacial water that dominates the average dynamics at low hydration is slower than water away from the membrane. Here, based on all-atom molecular dynamics simulations, we provide an interpretation of the slowdown of interfacial water in terms of the structure and dynamics of water–water and water–lipid hydrogen bonds (HBs). We calculate the rotational and translational slowdown of the dynamics of water confined in stacked phospholipid membranes at different levels of hydration, from completely hydrated to poorly hydrated membranes. For all hydrations, we analyze the distribution of HBs and find that water–lipids HBs last longer than water–water HBs and that at low hydration most of the water is in the interior of the membrane. We also show that water–water HBs become more persistent as the hydration is lowered. We attribute this effect (i) to HBs between water molecules that form, in turn, persistent HBs with lipids; (ii) to the hindering of the H-bonding switching between water molecules due to the lower water density at the interface; and (iii) to the higher probability of water–lipid HBs as the hydration decreases. Our interpretation of the large dynamic slowdown in water under dehydration is potentially relevant in understanding membrane biophysics at different hydration levels.
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20
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Rønnest AK, Peters GH, Hansen FY, Taub H, Miskowiec A. Structure and dynamics of water and lipid molecules in charged anionic DMPG lipid bilayer membranes. J Chem Phys 2016; 144:144904. [DOI: 10.1063/1.4945278] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- A. K. Rønnest
- Department of Chemistry, Technical University of Denmark, IK 207 DTU, DK-2800 Lyngby, Denmark
| | - G. H. Peters
- Department of Chemistry, Technical University of Denmark, IK 207 DTU, DK-2800 Lyngby, Denmark
| | - F. Y. Hansen
- Department of Chemistry, Technical University of Denmark, IK 207 DTU, DK-2800 Lyngby, Denmark
| | - H. Taub
- Department of Physics and Astronomy and the University of Missouri Research Reactor,University of Missouri, Columbia, Missouri 65211, USA
| | - A. Miskowiec
- Department of Physics and Astronomy and the University of Missouri Research Reactor,University of Missouri, Columbia, Missouri 65211, USA
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21
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Wolf MG, Grubmüller H, Groenhof G. Anomalous surface diffusion of protons on lipid membranes. Biophys J 2015; 107:76-87. [PMID: 24988343 DOI: 10.1016/j.bpj.2014.04.062] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 01/06/2014] [Accepted: 04/07/2014] [Indexed: 11/30/2022] Open
Abstract
The cellular energy machinery depends on the presence and properties of protons at or in the vicinity of lipid membranes. To asses the energetics and mobility of a proton near a membrane, we simulated an excess proton near a solvated DMPC bilayer at 323 K, using a recently developed method to include the Grotthuss proton shuttling mechanism in classical molecular dynamics simulations. We obtained a proton surface affinity of -13.0 ± 0.5 kJ mol(-1). The proton interacted strongly with both lipid headgroup and linker carbonyl oxygens. Furthermore, the surface diffusion of the proton was anomalous, with a subdiffusive regime over the first few nanoseconds, followed by a superdiffusive regime. The time- and distance dependence of the proton surface diffusion coefficient within these regimes may also resolve discrepancies between previously reported diffusion coefficients. Our simulations show that the proton anomalous surface diffusion originates from restricted diffusion in two different surface-bound states, interrupted by the occasional bulk-mediated long-range surface diffusion. Although only a DMPC membrane was considered in this work, we speculate that the restrictive character of the on-surface diffusion is highly sensitive to the specific membrane conditions, which can alter the relative contributions of the surface and bulk pathways to the overall diffusion process. Finally, we discuss the implications of our findings for the energy machinery.
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Affiliation(s)
- Maarten G Wolf
- Computational Biomolecular Chemistry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Helmut Grubmüller
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Gerrit Groenhof
- Computational Biomolecular Chemistry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
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22
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Lin W, Clark AJ, Paesani F. Effects of surface pressure on the properties of Langmuir monolayers and interfacial water at the air-water interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2147-2156. [PMID: 25642579 DOI: 10.1021/la504603s] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effects of surface pressure on the physical properties of Langmuir monolayers of palmitic acid (PA) and dipalmitoylphosphatidic acid (DPPA) at the air/water interface are investigated through molecular dynamics simulations with atomistic force fields. The structure and dynamics of both monolayers and interfacial water are compared across the range of surface pressures at which stable monolayers can form. For PA monolayers at T = 300 K, the untilted condensed phase with a hexagonal lattice structure is found at high surface pressure, while the uniformly tilted condensed phase with a centered rectangular lattice structure is observed at low surface pressure, in agreement with the available experimental data. A state with uniform chain tilt but no periodic spatial ordering is observed for DPPA monolayers on a Na(+)/water subphase at both high and low surface pressures. The hydrophobic acyl chains of both monolayers pack efficiently at all surface pressures, resulting in a very small number of gauche defects. The analysis of the hydrogen-bonding structure/dynamics at the monolayer/water interface indicates that water molecules hydrogen-bonded to the DPPA head groups reorient more slowly than those hydrogen-bonded to the PA head groups, with the orientational dynamics becoming significantly slower at high surface pressure. Possible implications for physicochemical processes taking place on marine aerosols in the atmosphere are discussed.
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Affiliation(s)
- Wei Lin
- Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093, United States
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23
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Pronk S, Lindahl E, Kasson PM. Coupled diffusion in lipid bilayers upon close approach. J Am Chem Soc 2015; 137:708-14. [PMID: 25535654 PMCID: PMC4308745 DOI: 10.1021/ja508803d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Indexed: 11/28/2022]
Abstract
Biomembrane interfaces create regions of slowed water dynamics in their vicinity. When two lipid bilayers come together, this effect is further accentuated, and the associated slowdown can affect the dynamics of larger-scale processes such as membrane fusion. We have used molecular dynamics simulations to examine how lipid and water dynamics are affected as two lipid bilayers approach each other. These two interacting fluid systems, lipid and water, both slow and become coupled when the lipid membranes are separated by a thin water layer. We show in particular that the water dynamics become glassy, and diffusion of lipids in the apposed leaflets becomes coupled across the water layer, while the "outer" leaflets remain unaffected. This dynamic coupling between bilayers appears mediated by lipid-water-lipid hydrogen bonding, as it occurs at bilayer separations where water-lipid hydrogen bonds become more common than water-water hydrogen bonds. We further show that such coupling occurs in simulations of vesicle-vesicle fusion prior to the fusion event itself. Such altered dynamics at membrane-membrane interfaces may both stabilize the interfacial contact and slow fusion stalk formation within the interface region.
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Affiliation(s)
- Sander Pronk
- 'Department
of Theoretical Physics, KTH Royal Institute
of Technology, AlbaNova, 106 91 Stockholm, Sweden
| | - Erik Lindahl
- 'Department
of Theoretical Physics, KTH Royal Institute
of Technology, AlbaNova, 106 91 Stockholm, Sweden
- Science
for Life Laboratory, 171
21 Stockholm, Sweden
| | - Peter M. Kasson
- Department
of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, United States
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24
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Abstract
It is commonly assumed that the structure of water at a lipid-water interface is influenced mostly in the first hydration layer. However, recent results from different experimental methods show that perturbation extends through several hydration layers. Due to its low light penetration depth, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is specifically suited to study interlamellar water structure in multibilayers. Results obtained by this technique confirm the long-range water structure disturbance. Consequently, in confined membrane environments nearly all water molecules can be perturbed. It is important to note that the behavior of confined water molecules differs significantly in samples prepared in excess water and in partially hydrated samples. We show in what manner the interlamellar water perturbation is influenced by the hydration level and how it is sequentially modified with a step-by-step dehydration of samples either by water evaporation or by osmotic pressure. Our results also indicate that besides different levels of hydration the lipid-water interaction is modulated by different lipid headgroups and different lipid phases as well. Therefore, modification of interlamellar water properties may clarify the role of water-mediated effects in biological processes.
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Affiliation(s)
- Zoran Arsov
- Laboratory of Biophysics, Department of Solid State Physics, "Jozef Stefan" Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
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25
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Re S, Nishima W, Tahara T, Sugita Y. Mosaic of Water Orientation Structures at a Neutral Zwitterionic Lipid/Water Interface Revealed by Molecular Dynamics Simulations. J Phys Chem Lett 2014; 5:4343-4348. [PMID: 26273985 DOI: 10.1021/jz502299m] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ordering of water structures near the surface of biological membranes has been recently extensively studied using interface-selective techniques like vibrational sum frequency generation (VSFG) spectroscopy. The detailed structures of interface water have emerged for charged lipids, but those for neutral zwitterionic lipids remain obscure. We analyze an all-atom molecular dynamics (MD) trajectory of a hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer to characterize the orientation of interface waters in different chemical environments. The structure and dynamics of interfacial waters strongly depend on both their vertical position along the bilayer normal as well as vicinal lipid charged groups. Water orientation in the vicinity of phosphate groups is opposite to that around choline groups. The results are consistent with observed VSFG spectra and demonstrate that a mosaic of water orientation structures exists on the surface of a neutral zwitterionic phospholipid bilayer, reflecting rapid water exchange and the influence of local chemical environments.
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Affiliation(s)
- Suyong Re
- †RIKEN Theoretical Molecular Science Laboratory, ‡Molecular Spectroscopy Laboratory, §Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), and ¶RIKEN iTHES, RIKEN , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- #RIKEN Advanced Institute for Computational Science and ⊥RIKEN Quantitative Biology Center, International Medical Device Alliance (IMDA) 6F, RIKEN, 1-6-5 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Wataru Nishima
- †RIKEN Theoretical Molecular Science Laboratory, ‡Molecular Spectroscopy Laboratory, §Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), and ¶RIKEN iTHES, RIKEN , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- #RIKEN Advanced Institute for Computational Science and ⊥RIKEN Quantitative Biology Center, International Medical Device Alliance (IMDA) 6F, RIKEN, 1-6-5 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Tahei Tahara
- †RIKEN Theoretical Molecular Science Laboratory, ‡Molecular Spectroscopy Laboratory, §Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), and ¶RIKEN iTHES, RIKEN , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- #RIKEN Advanced Institute for Computational Science and ⊥RIKEN Quantitative Biology Center, International Medical Device Alliance (IMDA) 6F, RIKEN, 1-6-5 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Yuji Sugita
- †RIKEN Theoretical Molecular Science Laboratory, ‡Molecular Spectroscopy Laboratory, §Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), and ¶RIKEN iTHES, RIKEN , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- #RIKEN Advanced Institute for Computational Science and ⊥RIKEN Quantitative Biology Center, International Medical Device Alliance (IMDA) 6F, RIKEN, 1-6-5 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
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26
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Milischuk AA, Ladanyi BM. Polarizability anisotropy relaxation in nanoconfinement: Molecular simulation study of water in cylindrical silica pores. J Chem Phys 2014; 141:18C513. [DOI: 10.1063/1.4896218] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Anatoli A. Milischuk
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
| | - Branka M. Ladanyi
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
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27
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Romanenko S, Siegel PH, Wagenaar DA, Pikov V. Effects of millimeter wave irradiation and equivalent thermal heating on the activity of individual neurons in the leech ganglion. J Neurophysiol 2014; 112:2423-31. [PMID: 25122711 PMCID: PMC4233276 DOI: 10.1152/jn.00357.2014] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Many of today's radiofrequency-emitting devices in telecommunication, telemedicine, transportation safety, and security/military applications use the millimeter wave (MMW) band (30–300 GHz). To evaluate the biological safety and possible applications of this radiofrequency band for neuroscience and neurology, we have investigated the physiological effects of low-intensity 60-GHz electromagnetic irradiation on individual neurons in the leech midbody ganglia. We applied incident power densities of 1, 2, and 4 mW/cm2 to the whole ganglion for a period of 1 min while recording the action potential with a standard sharp electrode electrophysiology setup. For comparison, the recognized U.S. safe exposure limit is 1 mW/cm2 for 6 min. During the exposure to MMWs and gradual bath heating at a rate of 0.04°C/s (2.4°C/min), the ganglionic neurons exhibited similar dose-dependent hyperpolarization of the plasma membrane and decrease in the action potential amplitude. However, narrowing of the action potential half-width during MMW irradiation at 4 mW/cm2 was 5 times more pronounced compared with that during equivalent bath heating of 0.6°C. Even more dramatic difference in the effects of MMW irradiation and bath heating was noted in the firing rate, which was suppressed at all applied MMW power densities and increased in a dose-dependent manner during gradual bath heating. The mechanism of enhanced narrowing of action potentials and suppressed firing by MMW irradiation, compared with that by gradual bath heating, is hypothesized to involve specific coupling of MMW energy with the neuronal plasma membrane.
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Affiliation(s)
- Sergii Romanenko
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California; Neural Engineering Program, Huntington Medical Research Institutes, Pasadena, California; and
| | - Peter H Siegel
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California
| | - Daniel A Wagenaar
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California; Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio
| | - Victor Pikov
- Neural Engineering Program, Huntington Medical Research Institutes, Pasadena, California; and
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28
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Gruenbaum SM, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. III. Water clustering and vibrational energy transfer. J Chem Phys 2014; 139:175103. [PMID: 24206336 DOI: 10.1063/1.4827018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Water clustering and connectivity around lipid bilayers strongly influences the properties of membranes and is important for functions such as proton and ion transport. Vibrational anisotropic pump-probe spectroscopy is a powerful tool for understanding such clustering, as the measured anisotropy depends upon the time-scale and degree of intra- and intermolecular vibrational energy transfer. In this article, we use molecular dynamics simulations and theoretical vibrational spectroscopy to help interpret recent experimental measurements of the anisotropy of water in lipid multi-bilayers as a function of both lipid hydration level and isotopic substitution. Our calculations are in satisfactory agreement with the experiments of Piatkowski, Heij, and Bakker, and from our simulations we can directly probe water clustering and connectivity. We find that at low hydration levels, many water molecules are in fact isolated, although up to 70% of hydration water forms small water clusters or chains. At intermediate hydration levels, water forms a wide range of cluster sizes, while at higher hydration levels, the majority of water molecules are part of a large, percolating water cluster. Therefore, the size, number, and nature of water clusters are strongly dependent on lipid hydration level, and the measured anisotropy reflects this through its dependence on intermolecular energy transfer.
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Affiliation(s)
- S M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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29
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Chattoraj S, Chowdhury R, Dey SK, Jana SS, Bhattacharyya K. Role of Red-Ox Cycle in Structural Oscillations and Solvation Dynamics in the Mitochondria of a Live Cell. J Phys Chem B 2014; 119:8842-51. [DOI: 10.1021/jp503808z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Shyamtanu Chattoraj
- Department of Physical Chemistry and ‡Department of Biological Chemistry, Indian Association For The Cultivation of Science, Jadavpur, Kolkata 700
032, India
| | - Rajdeep Chowdhury
- Department of Physical Chemistry and ‡Department of Biological Chemistry, Indian Association For The Cultivation of Science, Jadavpur, Kolkata 700
032, India
| | - Sumit Kumar Dey
- Department of Physical Chemistry and ‡Department of Biological Chemistry, Indian Association For The Cultivation of Science, Jadavpur, Kolkata 700
032, India
| | - Siddhartha Sankar Jana
- Department of Physical Chemistry and ‡Department of Biological Chemistry, Indian Association For The Cultivation of Science, Jadavpur, Kolkata 700
032, India
| | - Kankan Bhattacharyya
- Department of Physical Chemistry and ‡Department of Biological Chemistry, Indian Association For The Cultivation of Science, Jadavpur, Kolkata 700
032, India
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30
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Costard R, Heisler IA, Elsaesser T. Structural Dynamics of Hydrated Phospholipid Surfaces Probed by Ultrafast 2D Spectroscopy of Phosphate Vibrations. J Phys Chem Lett 2014; 5:506-11. [PMID: 26276601 DOI: 10.1021/jz402493b] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The properties of biomembranes depend in a decisive way on interactions of phospholipids with hydrating water molecules. To map structural dynamics of a phospholipid-water interface on the length and time scale of molecular motions, we introduce the phospholipid symmetric and asymmetric phosphate stretch vibrations as probes of interfacial hydrogen bonds and electrostatic interactions. The first two-dimensional infrared spectra of such modes and a line shape analysis by density matrix theory reveal two distinct structural dynamics components; the first 300 fs contribution is related to spatial fluctuations of charged phospholipid head groups with additional water contributions at high hydration levels; the second accounts for water-phosphate hydrogen bonds persisting longer than 10 ps. Our results reveal a relatively rigid hydration shell around phosphate groups, a behavior relevant for numerous biomolecular systems.
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Affiliation(s)
- Rene Costard
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2 a, 12489 Berlin, Germany
| | - Ismael A Heisler
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2 a, 12489 Berlin, Germany
| | - Thomas Elsaesser
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2 a, 12489 Berlin, Germany
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31
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Das J, Flenner E, Kosztin I. Anomalous diffusion of water molecules in hydrated lipid bilayers. J Chem Phys 2013; 139:065102. [DOI: 10.1063/1.4817322] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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32
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Rabinovich AL, Lyubartsev AP. Computer simulation of lipid membranes: Methodology and achievements. POLYMER SCIENCE SERIES C 2013. [DOI: 10.1134/s1811238213070060] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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33
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Gruenbaum SM, Tainter CJ, Shi L, Ni Y, Skinner JL. Robustness of Frequency, Transition Dipole, and Coupling Maps for Water Vibrational Spectroscopy. J Chem Theory Comput 2013; 9:3109-17. [DOI: 10.1021/ct400292q] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- S. M. Gruenbaum
- Theoretical Chemistry Institute and
Department of Chemistry,
1101 University Ave., University of Wisconsin-Madison Madison, Wisconsin 53706, United States
| | - C. J. Tainter
- Theoretical Chemistry Institute and
Department of Chemistry,
1101 University Ave., University of Wisconsin-Madison Madison, Wisconsin 53706, United States
| | - L. Shi
- Theoretical Chemistry Institute and
Department of Chemistry,
1101 University Ave., University of Wisconsin-Madison Madison, Wisconsin 53706, United States
| | - Y. Ni
- Theoretical Chemistry Institute and
Department of Chemistry,
1101 University Ave., University of Wisconsin-Madison Madison, Wisconsin 53706, United States
| | - J. L. Skinner
- Theoretical Chemistry Institute and
Department of Chemistry,
1101 University Ave., University of Wisconsin-Madison Madison, Wisconsin 53706, United States
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34
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Hansen FY, Peters GH, Taub H, Miskowiec A. Diffusion of water and selected atoms in DMPC lipid bilayer membranes. J Chem Phys 2013. [PMID: 23206034 DOI: 10.1063/1.4767568] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular dynamics simulations have been used to determine the diffusion of water molecules as a function of their position in a fully hydrated freestanding 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) bilayer membrane at 303 K and 1 atm. The diffusion rate of water in a ∼10 Å thick layer just outside the membrane surface is reduced on average by a factor of ∼2 relative to bulk. For water molecules penetrating deeper into the membrane, there is an increasing reduction in the average diffusion rate with up to one order of magnitude decrease for those deepest in the membrane. A comparison with the diffusion rate of selected atoms in the lipid molecules shows that ∼6 water molecules per lipid molecule move on the same time scale as the lipids and may therefore be considered to be tightly bound to them. The quasielastic neutron scattering functions for water and selected atoms in the lipid molecule have been simulated and compared to observed quasielastic neutron scattering spectra from single-supported bilayer DMPC membranes.
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Affiliation(s)
- F Y Hansen
- Department of Chemistry, Technical University of Denmark, IK 207 DTU, DK-2800 Lyngby, Denmark.
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35
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Yamamoto E, Akimoto T, Hirano Y, Yasui M, Yasuoka K. Power-law trapping of water molecules on the lipid-membrane surface induces water retardation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:052715. [PMID: 23767574 DOI: 10.1103/physreve.87.052715] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 03/14/2013] [Indexed: 06/02/2023]
Abstract
Cell membranes provide unique local environments for biological reactions, where the diffusion of biomolecules as well as water molecules plays critical roles. Translational and rotational motions of water molecules near membranes are known to be slower than those in bulk. Using all-atom molecular dynamics simulations of a membrane, we show that the temperature dependence of the water molecular motions on the membrane surface is different from that in bulk. Decreasing temperature enhances the water retardation on the membrane surface, and the lateral motions of water molecules are correlated with the vertical motions. We find that trapping times of water molecules onto membrane surfaces are distributed according to a power-law distribution and that the power-law exponents depend linearly on temperature, suggesting a random energy landscape picture. Moreover, we find that water molecules on the membrane surfaces exhibit subdiffusions in translational motions.
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Affiliation(s)
- Eiji Yamamoto
- Department of Mechanical Engineering, Keio University, Yokohama-shi, Kanagawa 223-8522, Japan
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36
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Hishida M, Tanaka K. Transition of the hydration state of a surfactant accompanying structural transitions of self-assembled aggregates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:284113. [PMID: 22738938 DOI: 10.1088/0953-8984/24/28/284113] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
What role does water play in the self-assembly of soft materials? To understand the correlation between the hydration state and the various self-assembled structures of a nonionic surfactant, terahertz time-domain spectroscopy has been performed for a C(12)E(5) solution with complementary use of small-angle x-ray scattering. Precise observations of the hydration state show clearly that transitions of the hydration state are accompanied by structural phase transitions of the surfactant from hexagonal to micelle to lamellae. These transitions of hydration state suggest that water is not a homogeneous solvent, and the interaction between water and the soft material is important for self-assembly.
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Affiliation(s)
- M Hishida
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan.
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37
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Malani A, Ayappa KG. Relaxation and jump dynamics of water at the mica interface. J Chem Phys 2012; 136:194701. [DOI: 10.1063/1.4717710] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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38
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39
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Gruenbaum SM, Pieniazek PA, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. II. Two-dimensional infrared and peak shift observables within different theoretical approximations. J Chem Phys 2012; 135:164506. [PMID: 22047251 DOI: 10.1063/1.3655671] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In a previous report, we calculated the infrared absorption spectrum and both the isotropic and anisotropic pump-probe signals for the OD stretch of isotopically dilute water in dilauroylphosphatidylcholine (DLPC) multi-bilayers as a function of the lipid hydration level. These results were then compared to recent experimental measurements and are in generally good agreement. In this paper, we will further investigate the structure and dynamics of hydration water using molecular dynamics simulations and calculations of the two-dimensional infrared and vibrational echo peak shift observables for hydration water in DLPC membranes. These observables have not yet been measured experimentally, but future comparisons may provide insight into spectral diffusion processes and hydration water heterogeneity. We find that at low hydration levels the motion of water molecules inside the lipid membrane is significantly arrested, resulting in very slow spectral diffusion. At higher hydration levels, spectral diffusion is more rapid, but still slower than in bulk water. We also investigate the effects of several common approximations on the calculation of spectroscopic observables by computing these observables within multiple levels of theory. The impact of these approximations on the resulting spectra affects our interpretation of these measurements and reveals that, for example, the cumulant approximation, which may be valid for certain systems, is not a good approximation for a highly heterogeneous environment such as hydration water in lipid multi-bilayers.
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Affiliation(s)
- Scott M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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40
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Skinner JL, Pieniazek PA, Gruenbaum SM. Vibrational spectroscopy of water at interfaces. Acc Chem Res 2012; 45:93-100. [PMID: 22032305 DOI: 10.1021/ar200122a] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding liquid water's behavior at the molecular level is essential to progress in fields as disparate as biology and atmospheric sciences. Moreover, the properties of water in bulk and water at interfaces can be very different, making the study of the hydrogen-bonding networks therein very important. With recent experimental advances in vibrational spectroscopy, such as ultrafast pulses and heterodyne detection, it is now possible to probe the structure and dynamics of bulk and interfacial water in unprecedented detail. We consider here three aqueous interfaces: the water liquid-vapor interface, the interface between water and the surfactant headgroups of reverse micelles, and the interface between water and the lipid headgroups of aligned multi-bilayers. In the first case, sum-frequency spectroscopy is used to probe the interface. In the second and third cases, the confined water pools are sufficiently small that techniques of bulk spectroscopy (such as FTIR, pump-probe, two-dimensional IR, and the like) can be used to probe the interfacial water. In this Account, we discuss our attempts to model these three systems and interpret the existing experiments. For the water liquid-vapor interface, we find that three-body interactions are essential for reproducing the experimental sum-frequency spectrum, and presumably for the structure of the interface as well. The observed spectrum is interpreted as arising from overlapping and canceling positive and negative contributions from molecules in different hydrogen-bonding environments. For the reverse micelles, our theoretical models confirm that the experimentally observed blue shift of the water OD stretch (for dilute HOD in H(2)O) arises from weaker hydrogen bonding to sulfonate oxygens. We interpret the observed slow-down in water rotational dynamics as arising from curvature-induced frustration. For the water confined between lipid bilayers, our theoretical models confirm that the experimentally observed red shift of the water OD stretch arises from stronger hydrogen bonding to phosphate oxygens. We develop a model for heterogeneous vibrational lifetime distributions, and we implement the model to calculate isotropic and anisotropic pump-probe decays. We then compare these results with experimental data. Clearly, recent experimental advances in vibrational spectroscopy have led to beautiful new results, providing information about the structure and dynamics of water at interfaces. These experimental and concomitant theoretical advances (particularly the unified theoretical framework of non-linear response functions) have greatly contributed to our understanding of this unique and important substance.
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Affiliation(s)
- J. L. Skinner
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - P. A. Pieniazek
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - S. M. Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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Berkowitz ML, Vácha R. Aqueous solutions at the interface with phospholipid bilayers. Acc Chem Res 2012; 45:74-82. [PMID: 21770470 DOI: 10.1021/ar200079x] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In a sense, life is defined by membranes, because they delineate the barrier between the living cell and its surroundings. Membranes are also essential for regulating the machinery of life throughout many interfaces within the cell's interior. A large number of experimental, computational, and theoretical studies have demonstrated how the properties of water and ionic aqueous solutions change due to the vicinity of membranes and, in turn, how the properties of membranes depend on the presence of aqueous solutions. Consequently, understanding the character of aqueous solutions at their interface with biological membranes is critical to research progress on many fronts. The importance of incorporating a molecular-level description of water into the study of biomembrane surfaces was demonstrated by an examination of the interaction between phospholipid bilayers that can serve as model biological membranes. The results showed that, in addition to well-known forces, such as van der Waals and screened Coulomb, one has to consider a repulsion force due to the removal of water between surfaces. It was also known that physicochemical properties of biological membranes are strongly influenced by the specific character of the ions in the surrounding aqueous solutions because of the observation that different anions produce different effects on muscle twitch tension. In this Account, we describe the interaction of pure water, and also of aqueous ionic solutions, with model membranes. We show that a symbiosis of experimental and computational work over the past few years has resulted in substantial progress in the field. We now better understand the origin of the hydration force, the structural properties of water at the interface with phospholipid bilayers, and the influence of phospholipid headgroups on the dynamics of water. We also improved our knowledge of the ion-specific effect, which is observed at the interface of the phospholipid bilayer and aqueous solution, and its connection with the Hofmeister series. Nevertheless, despite substantial progress, many issues remain unresolved. Thus, for example, we still cannot satisfactorily explain the force of interaction between phospholipid bilayers immersed in aqueous solutions of NaI. Although we try to address many issues here, the scope of the discussion is limited and does not cover such important topics as the influence of ionic solutions on phases of bilayers, the influence of salts on the properties of Langmuir monolayers containing lipid molecules, or the influence of aqueous solutions on bilayers containing mixtures of lipids. We anticipate that the future application of more powerful experimental techniques, in combination with more advanced computational hardware, software, and theory, will produce molecular-level information about these important topics and, more broadly, will further illuminate our understanding of interfaces between aqueous solutions and biological membranes.
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Affiliation(s)
- Max L. Berkowitz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Robert Vácha
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB21EW, United Kingdom
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42
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Gruenbaum SM, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. I. Infrared spectra and ultrafast pump-probe observables. J Chem Phys 2011; 135:075101. [PMID: 21861584 PMCID: PMC3172989 DOI: 10.1063/1.3615717] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 07/02/2011] [Indexed: 11/15/2022] Open
Abstract
The vibrational spectroscopy of hydration water in dilauroylphosphatidylcholine lipid multi-bilayers is investigated using molecular dynamics simulations and a mixed quantum/classical model for the OD stretch spectroscopy of dilute HDO in H(2)O. FTIR absorption spectra, and isotropic and anisotropic pump-probe decay curves have been measured experimentally as a function of the hydration level of the lipid multi-bilayer, and our goal is to make connection with these experiments. To this end, we use third-order response functions, which allow us to include non-Gaussian frequency fluctuations, non-Condon effects, molecular rotations, and a fluctuating vibrational lifetime, all of which we believe are important for this system. We calculate the response functions using existing transition frequency and dipole maps. From the experiments it appears that there are two distinct vibrational lifetimes corresponding to HDO molecules in different molecular environments. In order to obtain these lifetimes, we consider a simple two-population model for hydration water hydrogen bonds. Assuming a different lifetime for each population, we then calculate the isotropic pump-probe decay, fitting to experiment to obtain the two lifetimes for each hydration level. With these lifetimes in hand, we then calculate FTIR spectra and pump-probe anisotropy decay as a function of hydration. This approach, therefore, permits a consistent calculation of all observables within a unified computational scheme. Our theoretical results are all in qualitative agreement with experiment. The vibrational lifetime of lipid-associated OD groups is found to be systematically shorter than that of the water-associated population, and the lifetimes of each population increase with decreasing hydration, in agreement with previous analysis. Our theoretical FTIR absorption spectra successfully reproduce the experimentally observed red-shift with decreasing lipid hydration, and we confirm a previous interpretation that this shift results from the hydrogen bonding of water to the lipid phosphate group. From the pump-probe anisotropy decay, we confirm that the reorientational motions of water molecules slow significantly as hydration decreases, with water bound in the lipid carbonyl region undergoing the slowest rotations.
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Affiliation(s)
- S M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave. University of Wisconsin, Madison, Wisconsin 53706, USA
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43
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Hishida M, Tanaka K. Long-range hydration effect of lipid membrane studied by terahertz time-domain spectroscopy. PHYSICAL REVIEW LETTERS 2011; 106:158102. [PMID: 21568617 DOI: 10.1103/physrevlett.106.158102] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 03/11/2011] [Indexed: 05/30/2023]
Abstract
The hydration state of biomolecules is believed to affect their self-assembly. The hydration state of phospholipid bilayers is studied precisely by terahertz spectroscopy, by which water perturbed by a lipid membrane is detected sensitively from the observation of the relaxation dynamics of water molecules in the subpicosecond time scale. Combined with x-ray observation of the lamellar structure of the lipid, a long-range hydration effect on up to 4-5 layers of water is confirmed. Most water molecules in the lamellae fall into the hydration water, and condensation of them is also indicated.
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Affiliation(s)
- M Hishida
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8501, Japan
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44
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Heinzelmann G, Figueiredo W, Girardi M. Orientational dynamics for an amphiphilic-solvent solution. J Chem Phys 2011; 134:064901. [PMID: 21322728 DOI: 10.1063/1.3537737] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In this work, we performed Monte Carlo simulations on a lattice model for spontaneous amphiphilic aggregation, in order to study the orientational and hydrogen-bonding dynamics of water on different regions inside the micellar solution. We employed an associating lattice gas model that mimics the aqueous solvent, which presents a rich phase diagram with first- and second-order transition lines. Even though this is a simplified model, it makes possible to investigate the orientational dynamics of water in an equilibrium solution of amphiphiles, as well as the influence of the different phases of the solvent in the interfacial and bulk water dynamics. By means of extensive simulations, we showed that, at high temperatures, the behavior of the orientational relaxation and hydrogen bonding of water molecules in the bulk, first, and second hydration shells are considerable different. We observe the appearance of a very slow component for water molecules in the first hydration shell of micelles when the system reaches a high-density phase, consistent with previous theoretical and experimental studies concerning biological water. Also, at high temperatures, we find that water molecules in the second hydration shell of micelles have an orientational decay similar to that of bulk water, but with a generally slower dynamics. Otherwise, at low temperatures, we have two components for the orientational relaxation of bulk water in the low density liquid phase, and only a single component in the high density liquid (HDL) phase, which reflect the symmetry properties of the different phases of the solvent model. In the very dense region of water molecules in the first hydration shell of micelles at low temperatures, we find two components for the orientational relaxation on both liquid phases, one of them much slower than that in the single component of bulk water in the HDL phase. This happens even though our model does not present any hindrance to the water rotational freedom caused by the presence of the amphiphiles.
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Affiliation(s)
- G Heinzelmann
- School of Physics, University of Sydney, New South Wales 2006, Australia.
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45
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Debnath A, Mukherjee B, Ayappa KG, Maiti PK, Lin ST. Entropy and dynamics of water in hydration layers of a bilayer. J Chem Phys 2010; 133:174704. [DOI: 10.1063/1.3494115] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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46
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Heinzelmann G, Figueiredo W, Girardi M. Interplay between micelle formation and waterlike phase transitions. J Chem Phys 2010; 132:064905. [DOI: 10.1063/1.3316133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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47
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Sterpone F, Stirnemann G, Hynes JT, Laage D. Water Hydrogen-Bond Dynamics around Amino Acids: The Key Role of Hydrophilic Hydrogen-Bond Acceptor Groups. J Phys Chem B 2010; 114:2083-9. [DOI: 10.1021/jp9119793] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fabio Sterpone
- Department of Chemistry, Ecole Normale Supérieure, 24 rue Lhomond 75005 Paris, France, UMR ENS-CNRS-UPMC 8640, 24 rue Lhomond 75005 Paris, France, Fondation Pierre Gilles de Gennes pour la Recherche, Paris, France, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215
| | - Guillaume Stirnemann
- Department of Chemistry, Ecole Normale Supérieure, 24 rue Lhomond 75005 Paris, France, UMR ENS-CNRS-UPMC 8640, 24 rue Lhomond 75005 Paris, France, Fondation Pierre Gilles de Gennes pour la Recherche, Paris, France, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215
| | - James T. Hynes
- Department of Chemistry, Ecole Normale Supérieure, 24 rue Lhomond 75005 Paris, France, UMR ENS-CNRS-UPMC 8640, 24 rue Lhomond 75005 Paris, France, Fondation Pierre Gilles de Gennes pour la Recherche, Paris, France, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215
| | - Damien Laage
- Department of Chemistry, Ecole Normale Supérieure, 24 rue Lhomond 75005 Paris, France, UMR ENS-CNRS-UPMC 8640, 24 rue Lhomond 75005 Paris, France, Fondation Pierre Gilles de Gennes pour la Recherche, Paris, France, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215
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Pieniazek PA, Lin YS, Chowdhary J, Ladanyi BM, Skinner JL. Vibrational Spectroscopy and Dynamics of Water Confined inside Reverse Micelles. J Phys Chem B 2009; 113:15017-28. [DOI: 10.1021/jp906784t] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Piotr A. Pieniazek
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Yu-Shan Lin
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Janamejaya Chowdhary
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Branka M. Ladanyi
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - J. L. Skinner
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
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49
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Heinzelmann G, Figueiredo W, Girardi M. Monte Carlo simulations for amphiphilic aggregation near a water phase transition. J Chem Phys 2009; 131:144901. [DOI: 10.1063/1.3244676] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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50
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Materese CK, Savelyev A, Papoian GA. Counterion Atmosphere and Hydration Patterns near a Nucleosome Core Particle. J Am Chem Soc 2009; 131:15005-13. [DOI: 10.1021/ja905376q] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher K. Materese
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290
| | - Alexey Savelyev
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290
| | - Garegin A. Papoian
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290
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