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Sahu AK, Reddy UC, Kannoth Manheri M, Mishra AK. Exploring the Physical Properties of Lipid Membranes with Polyhydroxy Oxanorbornane Head Group Using NBD-Conjugated and DPH Fluorescent Probes. Langmuir 2024; 40:5106-5120. [PMID: 38427698 DOI: 10.1021/acs.langmuir.3c02941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/03/2024]
Abstract
The present study focuses on exploring the physical properties of lipid membranes based on the polyhydroxy oxanorbornane (PH-ONB) headgroup, designed as synthetic analogues of naturally occurring archaeal lipid membranes. Specifically, we study two variants of PH-ONB headgroup-based lipids differing in the number of hydroxy groups present in the headgroup, with one having two hydroxy groups (ONB-2OH) and the other having three (ONB-3OH). These lipids form stable bilayer membranes. The study begins with a comprehensive analysis of the fluorescence characteristics of nitrobenzoxadiazole (NBD)-tagged ONB-based lipids in different solvent environments and within a model lipid membrane 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Subsequently, the physical properties of the ONB-based membranes were examined by using an NBD-tagged ONB-based probe and a commonly used extrinsic 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescent probe. The steady-state and time-resolved fluorescence properties of the NBD-tagged ONB-based probe and DPH were used to compare the physical properties of the ONB-based membranes, including polarity, fluidity, phase transition, order, hydration, location, heterogeneity, and rotational diffusion. The solid gel to liquid crystalline phase transition temperatures of ONB-2OH and ONB-3OH lipid membranes are found to be (68 ± 1) °C and (74 ± 1) °C, respectively. The variation in organization (size), fluidity, and phase transition temperature of ONB-based lipid membranes is explained by the extent of hydrogen bonding interactions between lipid head groups. ONB-based membranes exhibit characteristics similar to those of phospholipid membranes and possess a notably high phase transition temperature. These properties make them a promising and cost-effective synthetic alternative to archaeal lipid membranes with a wide range of potential applications.
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Affiliation(s)
- Anand Kumar Sahu
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
| | - U Chandrasekhar Reddy
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
| | | | - Ashok Kumar Mishra
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
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Kurakin S, Badreeva D, Dushanov E, Shutikov A, Efimov S, Timerova A, Mukhametzyanov T, Murugova T, Ivankov O, Mamatkulov K, Arzumanyan G, Klochkov V, Kučerka N. Arrangement of lipid vesicles and bicelle-like structures formed in the presence of Aβ(25-35) peptide. Biochim Biophys Acta Biomembr 2024; 1866:184237. [PMID: 37820938 DOI: 10.1016/j.bbamem.2023.184237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/31/2023] [Accepted: 10/03/2023] [Indexed: 10/13/2023]
Abstract
Our complementary experimental data and molecular dynamics (MD) simulations results reveal the structure of previously observed lipid bicelle-like structures (BLSs) formed in the presence of amyloid-beta peptide Aβ(25-35) below the main phase transition temperature (Tm) of saturated phosphatidylcholine lipids and small unilamellar vesicles (SUVs) above this temperature. First, we show by using solid-state 31P nuclear magnetic resonance (NMR) spectroscopy that our BLSs being in the lipid gel phase demonstrate magnetic alignment along the magnetic field of NMR spectrometer and undergo a transition to SUVs in the lipid fluid phase when heated through the Tm. Secondly, thanks to the BLS alignment we present their lipid structure. Lipids are found located not only in the flat bilayered part but also around its perimeter, which is corroborated by the results of coarse-grained (CG) MD simulations. Finally, peptides appear to mix randomly with lipids in SUVs while assuming predominantly unordered secondary structures revealed by circular dichroism (CD), Raman spectroscopy, and all-atom MD simulations. Importantly, the former is changing little when the system undergoes morphological transitions between BLSs and SUVs. Our structural results then offer a platform for studying and understanding mechanisms of morphological transformations caused by the disruptive effect of amyloid-beta peptides on the lipid bilayer.
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Affiliation(s)
- Sergei Kurakin
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia; Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia.
| | - Dina Badreeva
- Meshcheryakov Laboratory of Information Technologies, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Ermuhammad Dushanov
- Laboratory of Radiation Biology, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Artyom Shutikov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Sergey Efimov
- Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Ayzira Timerova
- Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Timur Mukhametzyanov
- Butlerov Chemistry Institute, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Tatiana Murugova
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Oleksandr Ivankov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Kahramon Mamatkulov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Grigory Arzumanyan
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia
| | - Vladimir Klochkov
- Institute of Physics, Kazan Federal University, Kremlevskaya 18, Kazan 420008, Russia
| | - Norbert Kučerka
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980, Russia; Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, Odbojárov 10, Bratislava 832 32, Slovakia.
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McCalpin SD, Fu R, Ravula T, Wu G, Ramamoorthy A. Magnetically aligned nanodiscs enable direct measurement of 17O residual quadrupolar coupling for small molecules. J Magn Reson 2023; 346:107341. [PMID: 36473327 DOI: 10.1016/j.jmr.2022.107341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 06/17/2023]
Abstract
The use of 17O in NMR spectroscopy for structural studies has been limited due to its low natural abundance, low gyromagnetic ratio, and quadrupolar relaxation. Previous solution 17O work has primarily focused on studies of liquids where the 17O quadrupolar coupling is averaged to zero by isotropic molecular tumbling, and therefore has ignored the structural information contained in this parameter. Here, we use magnetically aligned polymer nanodiscs as an alignment medium to measure residual quadrupolar couplings (RQCs) for 17O-labelled benzoic acid in the aqueous phase. We show that increasing the magnetic field strength improves spectral sensitivity and resolution and that each satellite peak of the expected pentet pattern resolves clearly at 18.8 T. We observed no significant dependence of the RQC magnitudes on the magnetic field strength. However, changing the orientation of the alignment medium alters the RQC by a consistent factor, suggesting that 17O RQCs measured in this way can provide reliable orientational information for elucidations of molecular structures.
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Affiliation(s)
- Samuel D McCalpin
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Riqiang Fu
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Thirupathi Ravula
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Gang Wu
- Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
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Krishnarjuna B, Ravula T, Faison EM, Tonelli M, Zhang Q, Ramamoorthy A. Polymer-Nanodiscs as a Novel Alignment Medium for High-Resolution NMR-Based Structural Studies of Nucleic Acids. Biomolecules 2022; 12:1628. [PMID: 36358983 PMCID: PMC9687133 DOI: 10.3390/biom12111628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022] Open
Abstract
Residual dipolar couplings (RDCs) are increasingly used for high-throughput NMR-based structural studies and to provide long-range angular constraints to validate and refine structures of various molecules determined by X-ray crystallography and NMR spectroscopy. RDCs of a given molecule can be measured in an anisotropic environment that aligns in an external magnetic field. Here, we demonstrate the first application of polymer-based nanodiscs for the measurement of RDCs from nucleic acids. Polymer-based nanodiscs prepared using negatively charged SMA-EA polymer and zwitterionic DMPC lipids were characterized by size-exclusion chromatography, 1H NMR, dynamic light-scattering, and 2H NMR. The magnetically aligned polymer-nanodiscs were used as an alignment medium to measure RDCs from a 13C/15N-labeled fluoride riboswitch aptamer using 2D ARTSY-HSQC NMR experiments. The results showed that the alignment of nanodiscs is stable for nucleic acids and nanodisc-induced RDCs fit well with the previously determined solution structure of the riboswitch. These results demonstrate that SMA-EA-based lipid-nanodiscs can be used as a stable alignment medium for high-resolution structural and dynamical studies of nucleic acids, and they can also be applicable to study various other biomolecules and small molecules in general.
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Affiliation(s)
- Bankala Krishnarjuna
- Biophysics Program, Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Thirupathi Ravula
- Biophysics Program, Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
- National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Edgar M. Faison
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Qi Zhang
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program, Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
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Umegawa Y, Shimonishi T, Tsuchikawa H, Murata M. LnDOTA-d 8 , a versatile chemical-shift thermometer for 2 H solid-state NMR. Magn Reson Chem 2022; 60:1005-1013. [PMID: 35938541 DOI: 10.1002/mrc.5303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/03/2022] [Accepted: 08/05/2022] [Indexed: 06/15/2023]
Abstract
2 H solid-state nuclear magnetic resonance (NMR) is a method for examining the mobility and orientation of molecules in the field of biophysics. In studies on lipid bilayer membranes, 2 H NMR is often adopted to detect a phase transition from the gel to the liquid-crystal phase, which is observed as a change in spectral shape, and to evaluate the ordering of lipid alkyl chains using quadrupole coupling values. Because the mobility of membrane lipids is highly temperature dependent, precise temperature control is a prerequisite for evaluating the physical properties of membranes. Generally, NMR instruments monitor the temperature of the variable temperature (VT) gas. The temperature inside the sample tube and the VT gas match only when the heat generated by the radio frequency (rf) pulse emitted from the coil or magic angle spinning is significantly lower than the cooling capacity of the VT gas. In other words, the sample temperature inside the tube depends on the measurement method. Therefore, in this study, we took advantage of temperature-dependent changes in the chemical shift of a paramagnetic metal-ligand complex. We designed and synthesized a deuterated ligand complex and evaluated its temperature dependence as a thermometer for 2 H solid-state NMR spectroscopy. We chose Tb, Dy, Ho, and Er as the paramagnetic central metals. We then measured the 2 H NMR spectrum of each metal complex and confirmed the 2 H chemical shift to be temperature dependent. Furthermore, with the use of the thermometer molecule with Er, we succeeded in accurately evaluating the segmental melting of an alkyl chain in lipid bilayers with 0.1°C accuracy.
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Affiliation(s)
- Yuichi Umegawa
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, Osaka, Japan
| | - Takeshi Shimonishi
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- Faculty of Medicine, Oita University, Yufu, Oita, Japan
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, Osaka, Japan
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Salnikov E, Bechinger B. Effect of lipid saturation on the topology and oligomeric state of helical membrane polypeptides. Biochim Biophys Acta Biomembr 2022; 1864:184001. [PMID: 35817122 DOI: 10.1016/j.bbamem.2022.184001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/27/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
Natural liquid crystalline membranes are made up of many different lipids carrying a mixture of saturated and unsaturated fatty acyl chains. Whereas in the past considerable attention has been paid to cholesterol content, the phospholipid head groups and the membrane surface charge the detailed fatty acyl composition was often considered less important. However, recent investigations indicate that the detailed fatty acyl chain composition has pronounced effects on the oligomerization of the transmembrane helical anchoring domains of the MHC II receptor or the membrane alignment of the cationic antimicrobial peptide PGLa. In contrast the antimicrobial peptides magainin 2 and alamethicin are less susceptible to lipid saturation. Using histidine-rich LAH4 designer peptides the high energetic contributions of lipid saturation in stabilizing transmembrane helical alignments are quantitatively evaluated. These observations can have important implications for the biological regulation of membrane proteins and should be taken into considerations during biophysical or structural experiments.
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Affiliation(s)
- Evgeniy Salnikov
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France
| | - Burkhard Bechinger
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France; Institut Universitaire de France, France.
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Abstract
Structural studies of membrane proteins in native-like environments require the development of diverse membrane mimetics. Currently there is a need for nanodiscs formed with nonionic belt molecules to avoid nonphysiological electrostatic interactions between the membrane system and protein of interest. Here, we describe the formation of lipid nanodiscs from the phospholipid DMPC and a class of nonionic glycoside natural products called saponins. The morphology, surface characteristics, and magnetic alignment properties of the saponin nanodiscs were characterized by light scattering and solid-state NMR experiments. We determined that preparing nanodiscs with high saponin/lipid ratios reduced their size, diminished their ability to spontaneously align in a magnetic field, and favored insertion of individual saponin molecules in the lipid bilayer surface. Further, purification of saponin nanodiscs allowed flipping of the orientation of aligned nanodiscs by 90°. Finally, we found that aligned saponin nanodiscs provide a sufficient alignment medium to allow the measurement of residual dipolar couplings (RDCs) in aqueous cytochrome c.
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Affiliation(s)
- Samuel D. McCalpin
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Thirupathi Ravula
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
- Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
- Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Corresponding Author:
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8
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Abstract
Recent developments in lipid nanodisc technology have successfully overcome the major challenges in the structural and functional studies of membrane proteins and drug delivery. Among the different types of nanodiscs, the use of synthetic amphiphilic polymers created new directions including the applications of solution and solid-state NMR spectroscopy. The ability to magnetically align large-size (>20 nm diameter) polymer nanodiscs and flip them using paramagnetic lanthanide ions has enabled high-resolution studies on membrane proteins using solid-state NMR techniques. The use of polymer-based macro-nanodiscs (>20 nm diameter) as an alignment medium to measure residual dipolar couplings (RDCs) and residual quadrupole couplings by NMR experiments has also been demonstrated. In this study, we demonstrate the use of magnetically aligned and 90°-flipped polymer nanodiscs as alignment media for structural studies on proteins by solution NMR spectroscopy. These macro-nanodiscs, composed of negatively charged SMA-EA polymers and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipids, were used to measure residual 1H-15N dipolar couplings (RDCs) from the water-soluble ∼21 kDa uniformly 15N-labeled flavin mononucleotide binding domain (FBD) of cytochrome-P450 reductase. The experimentally measured 1H-15N RDC values are compared with the values calculated from the crystal structures of cytochrome-P450 reductase that lacks the transmembrane domain. The N-H RDCs measured using aligned and 90°-flipped nanodiscs show a modulation by the function (3 cos2 θ - 1), where θ is the angle between the N-H bond vector and the applied magnetic field direction. This successful demonstration of the use of two orthogonally oriented alignment media should enable structural studies on a variety of systems including small molecules, DNA, and RNA.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA
- National Magnetic Resonance Facility at Madison, Department of Biochemistry, University of Wisconsin, Madison, WI 53706-1544, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA
- Corresponding author’s
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Abstract
Membrane proteins (MPs) play a pivotal role in cellular function and are therefore predominant pharmaceutical targets. Although detailed understanding of MP structure and mechanistic activity is invaluable for rational drug design, challenges are associated with the purification and study of MPs. This review delves into the historical developments that became the prelude to currently available membrane mimetic technologies before shining a spotlight on polymer nanodiscs. These are soluble nanosized particles capable of encompassing MPs embedded in a phospholipid ring. The expanding range of reported amphipathic polymer nanodisc materials is presented and discussed in terms of their tolerance to different solution conditions and their nanodisc properties. Finally, the analytical scope of polymer nanodiscs is considered in both the demonstration of basic nanodisc parameters as well as in the elucidation of structures, lipid-protein interactions, and the functional mechanisms of reconstituted membrane proteins. The final emphasis is given to the unique benefits and applications demonstrated for native nanodiscs accessed through a detergent free process.
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Affiliation(s)
| | - Lisandra L Martin
- School of Chemistry, Monash University, Clayton, 3800, Vic, Australia
| | - San H Thang
- School of Chemistry, Monash University, Clayton, 3800, Vic, Australia
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Affiliation(s)
- Thirupathi Ravula
- Biophysics and Department of Chemistry Biomedical Engineering, Macromolecular Science and Engineering The University of Michigan Ann Arbor MI 48109-1055 USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry Biomedical Engineering, Macromolecular Science and Engineering The University of Michigan Ann Arbor MI 48109-1055 USA
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Ravula T, Dai X, Ramamoorthy A. Solid-State NMR Study to Probe the Effects of Divalent Metal Ions (Ca 2+ and Mg 2+) on the Magnetic Alignment of Polymer-Based Lipid Nanodiscs. Langmuir 2021; 37:7780-7788. [PMID: 34129342 PMCID: PMC8587631 DOI: 10.1021/acs.langmuir.1c01018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Divalent cations, especially Ca2+ and Mg2+, play a vital role in the function of biomolecules and making them important to be constituents in samples for in vitro biophysical and biochemical characterizations. Although lipid nanodiscs are becoming valuable tools for structural biology studies on membrane proteins and for drug delivery, most types of nanodiscs used in these studies are unstable in the presence of divalent metal ions. To avoid the interaction of divalent metal ions with the belt of the nanodiscs, synthetic polymers have been designed and demonstrated to form stable lipid nanodiscs under such unstable conditions. Such polymer-based nanodiscs have been shown to provide an ideal platform for structural studies using both solid-state and solution NMR spectroscopies because of the near-native cell-membrane environment they provide and the unique magnetic-alignment behavior of large-size nanodiscs. In this study, we report an investigation probing the effects of Ca2+ and Mg2+ ions on the formation of polymer-based lipid nanodiscs and the magnetic-alignment properties using a synthetic polymer, styrene maleimide quaternary ammonium (SMA-QA), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipids. Phosphorus-31 NMR experiments were used to evaluate the stability of the magnetic-alignment behavior of the nanodiscs for varying concentrations of Ca2+ or Mg2+ at different temperatures. It is remarkable that the interaction of divalent cations with lipid headgroups promotes the stacking up of nanodiscs that results in the enhanced magnetic alignment of nanodiscs. Interestingly, the reported results show that both the temperature and the concentration of divalent metal ions can be optimized to achieve the optimal alignment of nanodiscs in the presence of an applied magnetic field. We expect the reported results to be useful in the design of nanodisc-based nanoparticles for various applications in addition to atomic-resolution structural and dynamics studies using NMR and other biophysical techniques.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Xiaofeng Dai
- Biophysics Program and Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA
- Xiaofeng Dai was a visiting student from the College of Chemistry, Nankai University, Tianjin 300071, China
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA
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Ravula T, Ramamoorthy A. Synthesis, Characterization, and Nanodisc Formation of Non-ionic Polymers*. Angew Chem Int Ed Engl 2021; 60:16885-16888. [PMID: 33998111 DOI: 10.1002/anie.202101950] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 05/05/2021] [Indexed: 12/31/2022]
Abstract
Although lipid nanodiscs are increasingly used in the structural studies of membrane proteins, drug delivery and other applications, the interaction between the nanodisc belt and the protein to be reconstituted is a major limitation. To overcome this limitation and to further broaden the scope of nanodiscs, a family of non-ionic amphiphilic polymers synthesized by hydrophobic functionalization of fructo-oligosaccharides/inulin is reported. We show the stability of lipid nanodiscs formed by these polymers against pH and divalent metal ions, and their magnetic-alignment properties. The reported results also demonstrate that the non-ionic polymers extract membrane proteins with unprecedented efficiency.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI, 48109-1055, USA
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13
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Pan G, Hu L, Zhang F, Chen Q. Out-of-Plane Alignment of Conjugated Semiconducting Polymers by Horizontal Rotation in a High Magnetic Field. J Phys Chem Lett 2021; 12:3476-3484. [PMID: 33792335 DOI: 10.1021/acs.jpclett.1c00385] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The effective control of film morphology and molecular packing in the out-of-plane direction of semiconductor polymers plays a critical role in governing charge carrier transport in the direction perpendicular to the substrate. In this study, a highly out-of-plane alignment of the n-type polymer P(NDI2OD-T2) film has been successfully achieved by horizontal rotation in a high magnetic field (HR-HMF). The out-of-plane alignment of the P(NDI2OD-T2) film has showed a change from 72% face-on to 98.2% face-on lamellar texture as well as a 1.6-fold increase of the π-π stacking crystalline correlation length compared with that of as-cast polymer films without HR-HMF-induced alignment. Meanwhile, the film with near-perfect face-on molecular packing exhibited more than 18-fold enhancement of electron mobility compared to the unaligned film. The excellent electrical performance achieved with the HR-HMF process indicates its application potential for fabricating high-performance sandwich-type organic electronic devices, such as solar cells and light-emitting diodes.
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Affiliation(s)
- Guoxing Pan
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory (HMFL), Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Lin Hu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory (HMFL), Chinese Academy of Sciences, Hefei 230031, P. R. China
- CAS Key Lab of Photovoltaic and Energy Conservation Materials, Hefei Institutes of Physical Sciences, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Fapei Zhang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory (HMFL), Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Qianwang Chen
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory (HMFL), Chinese Academy of Sciences, Hefei 230031, P. R. China
- University of Science and Technology of China, Hefei 230026, P. R. China
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Yeh V, Goode A, Bonev BB. Membrane Protein Structure Determination and Characterisation by Solution and Solid-State NMR. Biology (Basel) 2020; 9:E396. [PMID: 33198410 PMCID: PMC7697852 DOI: 10.3390/biology9110396] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/08/2020] [Accepted: 11/11/2020] [Indexed: 12/25/2022]
Abstract
Biological membranes define the interface of life and its basic unit, the cell. Membrane proteins play key roles in membrane functions, yet their structure and mechanisms remain poorly understood. Breakthroughs in crystallography and electron microscopy have invigorated structural analysis while failing to characterise key functional interactions with lipids, small molecules and membrane modulators, as well as their conformational polymorphism and dynamics. NMR is uniquely suited to resolving atomic environments within complex molecular assemblies and reporting on membrane organisation, protein structure, lipid and polysaccharide composition, conformational variations and molecular interactions. The main challenge in membrane protein studies at the atomic level remains the need for a membrane environment to support their fold. NMR studies in membrane mimetics and membranes of increasing complexity offer close to native environments for structural and molecular studies of membrane proteins. Solution NMR inherits high resolution from small molecule analysis, providing insights from detergent solubilised proteins and small molecular assemblies. Solid-state NMR achieves high resolution in membrane samples through fast sample spinning or sample alignment. Recent developments in dynamic nuclear polarisation NMR allow signal enhancement by orders of magnitude opening new opportunities for expanding the applications of NMR to studies of native membranes and whole cells.
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Affiliation(s)
| | | | - Boyan B. Bonev
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK; (V.Y.); (A.G.)
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15
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Gravel AE, Arnold AA, Fillion M, Auger M, Warschawski DE, Marcotte I. Magnetically-orientable Tween-based model membranes for NMR studies of proteins. Biochimica et Biophysica Acta (BBA) - Biomembranes 2020; 1862:183379. [DOI: 10.1016/j.bbamem.2020.183379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 05/15/2020] [Accepted: 05/18/2020] [Indexed: 11/16/2022]
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Dufourc EJ. Bicelles and nanodiscs for biophysical chemistry. Biochim Biophys Acta Biomembr 2020; 1863:183478. [PMID: 32971065 DOI: 10.1016/j.bbamem.2020.183478] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 01/14/2023]
Abstract
Membrane nanoobjects are very important tools to study biomembrane properties. Two types are described herein: Bicelles and Nanodiscs. Bicelles are obtained by thorough water mixing of long chain and short chain lipids and may take the form of membranous discs of 10-50 nm. Temperature-composition-hydration diagrams have been established for Phosphatidylcholines and show limited domains of existence. Bicelles can be doped with charged lipids, surfactants or with cholesterol and offer a wide variety of membranous platforms for structural biology. Internal dynamics as measured by solid-state NMR is very similar to that of liposomes in their fluid phase. Because of the magnetic susceptibility anisotropy of the lipid chains, discs may be aligned along or perpendicular to the magnetic field. They may serve as weak orienting media to provide distance information in determining the 3D structure of soluble proteins. In different conditions they show strong orienting properties which may be used to study the 3D structure, topology and dynamics of membrane proteins. Lipid Bicelles with biphenyl chains or doped with lanthanides show long lasting remnant orientation after removing the magnetic field due to smectic-like properties. An alternative to pure lipid Bicelles is provided by nanodiscs where the half torus composed by short chain lipids is replaced by proteins. This renders the nano-objects less fragile as they can be used to stabilize membrane protein assemblies to be studied by electron microscopy. Internal dynamics is again similar to liposomes except that the phase transition is abolished, possibly due to lateral constrain imposed by the toroidal proteins limiting the disc size. Advantages and drawbacks of both nanoplatforms are discussed.
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Affiliation(s)
- Erick J Dufourc
- Institute of Chemistry and Biology of membranes and Nanoobjects, UMR5248, CNRS, University of Bordeaux, Bordeaux Polytechnic Institute, Allée Geoffroy Saint Hilaire, 33600 Pessac, France.
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Abstract
Natural-abundance 17O NMR experiments are used to investigate the hydrated water in magnetically aligned synthetic polymer based lipid-nanodiscs. Residual quadrupole couplings (RQCs) measured from the observed five 17O (central and satellite) transitions, and molecular dynamics simulations, are used to probe the ordering of water molecules across the lipid bilayer.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
| | - Bikash R Sahoo
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
| | - Xiaofeng Dai
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
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