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Wurl A, Saalwächter K, Mendes Ferreira T. Time-domain proton-detected local-field NMR for molecular structure determination in complex lipid membranes. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2023; 4:115-127. [PMID: 37904803 PMCID: PMC10583295 DOI: 10.5194/mr-4-115-2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 04/03/2023] [Indexed: 11/01/2023]
Abstract
Proton-detected local-field (PDLF) NMR spectroscopy, using magic-angle spinning and dipolar recoupling, is presently the most powerful experimental technique for obtaining atomistic structural information from small molecules undergoing anisotropic motion. Common examples include peptides, drugs, or lipids in model membranes and molecules that form liquid crystals. The measurements on complex systems are however compromised by the larger number of transients required. Retaining sufficient spectral quality in the direct dimension requires that the indirect time-domain modulation becomes too short for yielding dipolar splittings in the frequency domain. In such cases, the dipolar couplings can be obtained by fitting the experimental data; however ideal models often fail to fit PDLF data properly due to effects of radiofrequency field (RF) spatial inhomogeneity. Here, we demonstrate that by accounting for RF spatial inhomogeneity in the modeling of R-symmetry-based PDLF NMR experiments, the fitting accuracy is improved, facilitating the analysis of the experimental data. In comparison to the analysis of dipolar splittings without any fitting procedure, the accurate modeling of PDLF measurements makes possible three important improvements: the use of shorter experiments that enable the investigation of samples with a higher level of complexity, the measurement of C-H bond order parameters with smaller magnitudes | S CH | and of smaller variations of | S CH | caused by perturbations of the system, and the determination of | S CH | values with small differences from distinct sites having the same chemical shift. The increase in fitting accuracy is demonstrated by comparison with 2 H NMR quadrupolar echo experiments on mixtures of deuterated and non-deuterated dimyristoylphosphatidylcholine (DMPC) and with 1-palmitoyl-2-oleoyl-s n -glycero-3-phosphoethanolamine (POPE) membranes. Accurate modeling of PDLF NMR experiments is highly useful for investigating complex membrane systems. This is exemplified by application of the proposed fitting procedure for the characterization of membranes composed of a brain lipid extract with many distinct lipid types.
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Affiliation(s)
- Anika Wurl
- NMR group, Institute for Physics, Martin Luther University Halle–Wittenberg, Halle (Saale), Germany
| | - Kay Saalwächter
- NMR group, Institute for Physics, Martin Luther University Halle–Wittenberg, Halle (Saale), Germany
| | - Tiago Mendes Ferreira
- NMR group, Institute for Physics, Martin Luther University Halle–Wittenberg, Halle (Saale), Germany
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2
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Kinnun JJ, Scott HL, Bolmatov D, Collier CP, Charlton TR, Katsaras J. Biophysical studies of lipid nanodomains using different physical characterization techniques. Biophys J 2023; 122:931-949. [PMID: 36698312 PMCID: PMC10111277 DOI: 10.1016/j.bpj.2023.01.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/12/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023] Open
Abstract
For the past 50 years, evidence for the existence of functional lipid domains has been steadily accumulating. Although the notion of functional lipid domains, also known as "lipid rafts," is now widely accepted, this was not always the case. This ambiguity surrounding lipid domains could be partly attributed to the fact that they are highly dynamic, nanoscopic structures. Since most commonly used techniques are sensitive to microscale structural features, it is therefore, not surprising that it took some time to reach a consensus regarding their existence. In this review article, we will discuss studies that have used techniques that are inherently sensitive to nanoscopic structural features (i.e., neutron scatting, nuclear magnetic resonance, and Förster resonance energy transfer). We will also mention techniques that may be of use in the future (i.e., cryoelectron microscopy, droplet interface bilayers, inelastic x-ray scattering, and neutron reflectometry), which can further our understanding of the different and unique physicochemical properties of nanoscopic lipid domains.
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Affiliation(s)
- Jacob J Kinnun
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
| | - Haden L Scott
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Dima Bolmatov
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee
| | - C Patrick Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Timothy R Charlton
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - John Katsaras
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee; Labs and Soft Matter Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
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3
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Schachter I, Paananen RO, Fábián B, Jurkiewicz P, Javanainen M. The Two Faces of the Liquid Ordered Phase. J Phys Chem Lett 2022; 13:1307-1313. [PMID: 35104407 PMCID: PMC8842317 DOI: 10.1021/acs.jpclett.1c03712] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Coexisting liquid ordered (Lo) and liquid disordered (Ld) lipid phases in synthetic and plasma membrane-derived vesicles are commonly used to model the heterogeneity of biological membranes, including their putative ordered rafts. However, raft-associated proteins exclusively partition to the Ld and not the Lo phase in these model systems. We believe that the difference stems from the different microscopic structures of the lipid rafts at physiological temperature and the Lo phase studied at room temperature. To probe this structural diversity across temperatures, we performed atomistic molecular dynamics simulations, differential scanning calorimetry, and fluorescence spectroscopy on Lo phase membranes. Our results suggest that raft-associated proteins are excluded from the Lo phase at room temperature due to the presence of a stiff, hexagonally packed lipid structure. This structure melts upon heating, which could lead to the preferential solvation of proteins by order-preferring lipids. This structural transition is manifested as a subtle crossover in membrane properties; yet, both temperature regimes still fulfill the definition of the Lo phase. We postulate that in the compositionally complex plasma membrane and in vesicles derived therefrom, both molecular structures can be present depending on the local lipid composition. These structural differences must be taken into account when using synthetic or plasma membrane-derived vesicles as a model for cellular membrane heterogeneity below the physiological temperature.
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Affiliation(s)
- Itay Schachter
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 542/2, CZ-16000 Prague 6, Czech Republic
- Institute
of Chemistry, the Fritz Haber Research Center, and the Harvey M. Kruger
Center for Nanoscience & Nanotechnology, The Hebrew University, Jerusalem 9190401, Israel
| | - Riku O. Paananen
- Department
of Chemistry, FI-00014 University of Helsinki, Helsinki, Finland
- Department
of Ophthalmology, FI-00014 University of
Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Balázs Fábián
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 542/2, CZ-16000 Prague 6, Czech Republic
| | - Piotr Jurkiewicz
- J.
Heyrovský Institute of Physical Chemistry of the Czech Academy
of Sciences, Dolejškova
2155/3, CZ-18223 Prague 8, Czech Republic
- E-mail:
| | - Matti Javanainen
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 542/2, CZ-16000 Prague 6, Czech Republic
- Institute
of Biotechnology, FI-00014 University of
Helsinki, Helsinki, Finland
- E-mail:
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4
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Antila HS, Wurl A, Ollila OS, Miettinen MS, Ferreira TM. Rotational decoupling between the hydrophilic and hydrophobic regions in lipid membranes. Biophys J 2022; 121:68-78. [PMID: 34902330 PMCID: PMC8758420 DOI: 10.1016/j.bpj.2021.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/17/2021] [Accepted: 12/02/2021] [Indexed: 01/07/2023] Open
Abstract
Cells use homeostatic mechanisms to ensure an optimal composition of distinct types of lipids in cellular membranes. The hydrophilic region of biological lipid membranes is mainly composed of several types of phospholipid headgroups that interact with incoming molecules, nanoparticles, and viruses, whereas the hydrophobic region consists of a distribution of acyl chains and sterols affecting membrane fluidity/rigidity related properties and forming an environment for membrane-bound molecules such as transmembrane proteins. A fundamental open question is to what extent the motions of these regions are coupled and, consequently, how strongly the interactions of phospholipid headgroups with other molecules depend on the properties and composition of the membrane hydrophobic core. We combine advanced solid-state nuclear magnetic resonance spectroscopy with high-fidelity molecular dynamics simulations to demonstrate how the rotational dynamics of choline headgroups remain nearly unchanged (slightly faster) with incorporation of cholesterol into a phospholipid membrane, contrasting the well-known extreme slowdown of the other phospholipid segments. Notably, our results suggest a new paradigm in which phospholipid dipole headgroups interact as quasi-freely rotating flexible dipoles at the interface, independent of the properties in the hydrophobic region.
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Affiliation(s)
- Hanne S. Antila
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany,Corresponding author
| | - Anika Wurl
- NMR Group, Institute for Physics, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany
| | | | - Markus S. Miettinen
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Tiago M. Ferreira
- NMR Group, Institute for Physics, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany,Corresponding author
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Mann SK, Devgan MK, Franks WT, Huband S, Chan CL, Griffith J, Pugh D, Brooks NJ, Welton T, Pham TN, McQueen LL, Lewandowski JR, Brown SP. MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal. J Phys Chem B 2020; 124:4975-4988. [PMID: 32412761 PMCID: PMC7341529 DOI: 10.1021/acs.jpcb.0c02328] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structure and molecular order in the thermotropic ionic liquid crystal (ILC), [choline][geranate(H)octanoate], an analogue of Choline And GEranate (CAGE), which has potential for use as a broad-spectrum antimicrobial and transdermal and oral delivery agent, were investigated by magic-angle spinning (MAS) nuclear magnetic resonance (NMR), polarizing optical microscopy, small-angle X-ray scattering (SAXS), and mass spectrometry. Mass spectrometry and the 1H NMR chemical shift reveal that CAGE-oct is a dynamic system, with metathesis (the exchange of interacting ions) and hydrogen exchange occurring between hydrogen-bonded/ionic complexes such as [(choline)(geranate)(H)(octanoate)], [(choline)(octanoate)2(H)], and [(choline)(geranate)2(H)]. These clusters, which are shown by mass spectrometry to be significantly more stable than expected for typical electrostatic ion clusters, involve hydrogen bonding between the carboxylic acid, carboxylate, and hydroxyl groups, with rapid hydrogen bond breaking and re-formation observed to average the 1H chemical shifts. The formation of a partial bilayer liquid crystal (LC) phase was identified by SAXS and polarizing optical microscopy at temperatures below ∼293 K. The occurrence of this transition close to room temperature could be utilized as a potential temperature-induced "switch" of the anisotropic properties for particular applications. The presence of an isotropic component of approximately 23% was observed to coexist with the LC phase, as detected by polarizing optical microscopy and quantified by both 1H-13C dipolar-chemical shift correlation (DIPSHIFT) and 1H double-quantum (DQ) MAS NMR experiments. At temperatures above the LC-to-isotropic transition, intermediate-range order (clustering of polar and nonpolar domains), a feature of many ILs, persists. Site-specific order parameters for the LC phase of CAGE-oct were obtained from the MAS NMR measurement of the partially averaged 13C-1H dipolar couplings (DCH) by cross-polarization (CP) build-up curves and DIPSHIFT experiments, and 1H-1H dipolar couplings (DHH) by double-quantum (DQ) build-up curves. The corresponding order parameters, SCH and SHH, are in the range 0-0.2 and are lower compared to those for smectic (i.e., layered) phases of conventional nonionic liquid crystals, resembling those of lamellar phases formed by lyotropic surfactant-solvent systems.
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Affiliation(s)
- Sarah K Mann
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Mohit K Devgan
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - W Trent Franks
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.,Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Steven Huband
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Chi Long Chan
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Jeraime Griffith
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - David Pugh
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Nicholas J Brooks
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Tom Welton
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Tran N Pham
- GSK R&D, Stevenage, Hertfordshire SG1 2NY, U.K
| | - Lisa L McQueen
- GSK R&D, Collegeville, Pennsylvania 19426, United States
| | | | - Steven P Brown
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
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Glycyrrhizin-induced changes in phospholipid dynamics studied by 1H NMR and MD simulation. Arch Biochem Biophys 2020; 686:108368. [PMID: 32315654 DOI: 10.1016/j.abb.2020.108368] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 03/24/2020] [Accepted: 04/10/2020] [Indexed: 11/20/2022]
Abstract
Phospholipid bilayer constitutes the basis of the cell membrane. Any changes in its structure and dynamics could significantly affect the properties and functions of the cell membrane and associated proteins. It could, in its turn, affect the mechanism and strength of drug-membrane interaction. Phase transitions in lipid bilayer play an important role in cell life and in transmembrane transport of ions and drug molecules. In the present study we have tried to clarify the mechanism of glycyrrhizin bioactivity by the study of its influence on the lipid dynamics and phase transition of the lipid bilayer. For this purpose, a combination of nuclear magnetic resonance (NMR) and molecular dynamic (MD) simulations was used. Glycyrrhizin is the saponin extracted from licorice root. It displays a wide spectrum of biological activity and is frequently used in traditional medicine since ancient times. Now glycyrrhizin attracts additional attention as a novel multifunctional drug delivery system. We have established that glycyrrhizin interaction with dipalmitoylphosphatidylcholine lipid bilayers leads to changes in lipid mobility and phase transition temperature. NMR and MD results demonstrated that a glycyrrhizin molecule is able to integrate into a lipid bilayer and form stable aggregates inside. We hypothesize that surface curvatures caused by local changes in the lipid composition and the presence of phase boundaries might affect the permeability of the cell membrane.
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7
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Affiliation(s)
- Xiaolin Cheng
- Division of Medicinal Chemistry and Pharmacognosy, Biophysics Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United States
| | - Jeremy C. Smith
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United States
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
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8
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Raghunathan K, Kenworthy AK. Dynamic pattern generation in cell membranes: Current insights into membrane organization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2018-2031. [PMID: 29752898 DOI: 10.1016/j.bbamem.2018.05.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/30/2018] [Accepted: 05/03/2018] [Indexed: 12/18/2022]
Abstract
It has been two decades since the lipid raft hypothesis was first presented. Even today, whether these nanoscale cholesterol-rich domains are present in cell membranes is not completely resolved. However, especially in the last few years, a rich body of literature has demonstrated both the presence and the importance of non-random distribution of biomolecules on the membrane, which is the focus of this review. These new developments have pushed the experimental limits of detection and have brought us closer to observing lipid domains in the plasma membrane of live cells. Characterization of biomolecules associated with lipid rafts has revealed a deep connection between biological regulation and function and membrane compositional heterogeneities. Finally, tantalizing new developments in the field have demonstrated that lipid domains might not just be associated with the plasma membrane of eukaryotes but could potentially be a ubiquitous membrane-organizing principle in several other biological systems. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
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Affiliation(s)
- Krishnan Raghunathan
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, PA 15224, USA.
| | - Anne K Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA.
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