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Qian S, Nagy G, Zolnierczuk P, Mamontov E, Standaert R. Nonstereotypical Distribution and Effect of Ergosterol in Lipid Membranes. J Phys Chem Lett 2024; 15:4745-4752. [PMID: 38661394 DOI: 10.1021/acs.jpclett.4c00385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Ergosterol, found in fungi and some protist membranes, is understudied compared with cholesterol from animal membranes. Generally, ergosterol is assumed to modulate membranes in the same manner as cholesterol, based on their similar chemical structures. Here we reveal some fundamental structural and dynamical differences between them. Neutron diffraction shows that ergosterol is embedded in the lipid bilayer much shallower than cholesterol. Ergosterol does not change the membrane thickness as much as cholesterol does, indicating little condensation effect. Neutron spin echo shows that ergosterol can rigidify and soften membranes at different concentrations. The lateral lipid diffusion measured by quasielastic neutron scattering indicates that ergosterol promotes a jump diffusion of the lipid, whereas cholesterol keeps the same continuous lateral diffusion as the pure lipid membrane. Our results point to quite distinct interactions of ergosterol with membranes compared with cholesterol. These insights provide a basic understanding of membranes containing ergosterol with implications for phenomena such as lipid rafts and drug interactions.
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Affiliation(s)
- Shuo Qian
- Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, United States
| | - Gergely Nagy
- Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, United States
| | - Piotr Zolnierczuk
- Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, United States
| | - Eugene Mamontov
- Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, United States
| | - Robert Standaert
- Oak Ridge National Laboratory, PO BOX 2008, Oak Ridge, Tennessee 37831, United States
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2
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Bryant SJ, Garvey CJ, Darwish TA, Georgii R, Bryant G. Molecular interactions with bilayer membrane stacks using neutron and X-ray diffraction. Adv Colloid Interface Sci 2024; 326:103134. [PMID: 38518550 DOI: 10.1016/j.cis.2024.103134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/14/2024] [Accepted: 03/14/2024] [Indexed: 03/24/2024]
Abstract
Lamellar unit cell reconstruction from neutron and X-ray diffraction data provides information about the disposition and position of molecules and molecular segments with respect to the bilayer. When supplemented with the judicious use of molecular deuteration, the technique probes the molecular interactions and conformations within the bilayer membrane and the water layer which constitute the crystallographic unit cell. The perspective is model independent, and potentially, with a higher degree of resolution than is available with other techniques. In the case of neutron diffraction the measurement consists of carefully normalised diffracted intensity under conditions of contrast variation of the water layer. The subsequent Fourier reconstruction of the unit cell is made using the phase information from variation of peak intensities with contrast. Although the phase problem is not as easily solved for the corresponding X-ray measurements, an intuitive approach can often suffice. Here we discuss the two complimentary techniques as probes of scattering length density profiles of a bilayer, and how such a perspective provides information about the location and orientation of molecules within or between lipid bilayers. Within the basic paradigm of lamellar phases this method has provided, for example, detailed insights into the location and interaction of cryoprotectants and stress proteins, of the mechanisms of actions of viral proteins, antimicrobial compounds and drugs, and the underlying structure of the stratum corneum. In this paper we review these techniques and provide examples of the systems that have been examined. We finish with a future outlook on the use of these techniques to improve our understanding of the interactions of membranes with biomolecules.
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Affiliation(s)
- Saffron J Bryant
- School of Science, College of STEM, RMIT University, Melbourne, Australia
| | - Christopher J Garvey
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany
| | - Tamim A Darwish
- National Deuteration Facility, Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia; Faculty of Science and Technology, University of Canberra, ACT 2617, Australia
| | - Robert Georgii
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany
| | - Gary Bryant
- School of Science, College of STEM, RMIT University, Melbourne, Australia.
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Jahn R, Cafiso DC, Tamm LK. Mechanisms of SNARE proteins in membrane fusion. Nat Rev Mol Cell Biol 2024; 25:101-118. [PMID: 37848589 DOI: 10.1038/s41580-023-00668-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2023] [Indexed: 10/19/2023]
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are a family of small conserved eukaryotic proteins that mediate membrane fusion between organelles and with the plasma membrane. SNAREs are directly or indirectly anchored to membranes. Prior to fusion, complementary SNAREs assemble between membranes with the aid of accessory proteins that provide a scaffold to initiate SNARE zippering, pulling the membranes together and mediating fusion. Recent advances have enabled the construction of detailed models describing bilayer transitions and energy barriers along the fusion pathway and have elucidated the structures of SNAREs complexed in various states with regulatory proteins. In this Review, we discuss how these advances are yielding an increasingly detailed picture of the SNARE-mediated fusion pathway, leading from first contact between the membranes via metastable non-bilayer intermediates towards the opening and expansion of a fusion pore. We describe how SNARE proteins assemble into complexes, how this assembly is regulated by accessory proteins and how SNARE complexes overcome the free energy barriers that prevent spontaneous membrane fusion.
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Affiliation(s)
- Reinhard Jahn
- Laboratory of Neurobiology, Max-Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
| | - David C Cafiso
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Lukas K Tamm
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
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Qian S, Heller W, Chen WR, Christianson A, Do C, Wang Y, Lin JYY, Huegle T, Jiang C, Boone C, Hart C, Graves V. CENTAUR-The small- and wide-angle neutron scattering diffractometer/spectrometer for the Second Target Station of the Spallation Neutron Source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:075104. [PMID: 35922314 DOI: 10.1063/5.0090527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 06/11/2022] [Indexed: 06/15/2023]
Abstract
CENTAUR has been selected as one of the eight initial instruments to be built at the Second Target Station (STS) of the Spallation Neutron Source at Oak Ridge National Laboratory. It is a small-angle neutron scattering (SANS) and wide-angle neutron scattering (WANS) instrument with diffraction and spectroscopic capabilities. This instrument will maximally leverage the high brightness of the STS source, the state-of-the-art neutron optics, and a suite of detectors to deliver unprecedented capabilities that enable measurements over a wide range of length scales with excellent resolution, measurements on smaller samples, and time-resolved investigations of evolving structures. Notably, the simultaneous WANS and diffraction capability will be unique among neutron scattering instruments in the United States. This instrument will provide much needed capabilities for soft matter and polymer sciences, geology, biology, quantum condensed matter, and other materials sciences that need in situ and operando experiments for kinetic and/or out-of-equilibrium studies. Beam polarization and a high-resolution chopper will enable detailed structural and dynamical investigations of magnetic and quantum materials. CENTAUR's excellent resolution makes it ideal for low-angle diffraction studies of highly ordered large-scale structures, such as skyrmions, shear-induced ordering in colloids, and biomembranes. Additionally, the spectroscopic mode of this instrument extends to lower momentum transfers than are currently possible with existing spectrometers, thereby providing a unique capability for inelastic SANS studies.
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Affiliation(s)
- Shuo Qian
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - William Heller
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Wei-Ren Chen
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | | | - Changwoo Do
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Yangyang Wang
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Jiao Y Y Lin
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Thomas Huegle
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Chenyang Jiang
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Cristina Boone
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Cameron Hart
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Van Graves
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
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Qian S, Zolnierczuk PA. Interaction of a Short Antimicrobial Peptide on Charged Lipid Bilayer: A Case Study on Aurein 1.2 Peptide. BBA ADVANCES 2022; 2:100045. [PMID: 37082600 PMCID: PMC10074906 DOI: 10.1016/j.bbadva.2022.100045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 01/21/2022] [Accepted: 02/01/2022] [Indexed: 12/27/2022] Open
Abstract
Aurein 1.2 (aurein) is a short but active α-helical antimicrobial peptide discovered in Australian tree frogs (Litoria aurea). It shows inhibition on a broad spectrum of bacteria and cancer cells. With well-defined helicity, amphipathicity, and cationic charges, it readily binds to membranes and causes membrane change and disruption. This study provides details on how aurein interacts with charged lipid membranes by using neutron membrane diffraction (NMD) and neutron spin echo (NSE) spectroscopy on complex peptide-membrane systems. NMD provides higher resolution lipid bilayer structures than solution scattering. NMD revealed the peptide is mostly associated in the lipid headgroup region. Even at moderately high concentrations (e.g., peptide:lipid ratio of 1:30), aurein is located at the acyl chain-headgroup region without deep penetration into the hydrophobic acyl chain. However, it does reduce the elasticity of the membrane at that concentration, which was corroborated by the NSE results. Furthermore, NSE shows that aurein first softens the membrane, like many other α-helical peptides at low concentration, but then makes the membrane much more rigid, even without membrane pore formation. Combining our previous studies, the evidence shows that aurein at relatively low concentrations still modifies lipid distribution significantly and can cause membrane thinning and lateral segregation of charged lipids. At the same time, the membrane's mechanical properties are modified with much slower lipid diffusion. This suggests that aurein can attack the microbial membrane without the need to form membrane pores or disintegrate membranes; instead, it promotes the formation of domains at low concentration.
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Affiliation(s)
- Shuo Qian
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, United States
- Second Target Station, Oak Ridge National Laboratory, Oak Ridge, TN 37830, United States
- Corresponding author.
| | - Piotr A. Zolnierczuk
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, United States
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Cross ER, Coulter SM, Pentlavalli S, Laverty G. Unravelling the antimicrobial activity of peptide hydrogel systems: current and future perspectives. SOFT MATTER 2021; 17:8001-8021. [PMID: 34525154 PMCID: PMC8442837 DOI: 10.1039/d1sm00839k] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/19/2021] [Indexed: 05/05/2023]
Abstract
The use of hydrogels has garnered significant interest as biomaterial and drug delivery platforms for anti-infective applications. For decades antimicrobial peptides have been heralded as a much needed new class of antimicrobial drugs. Self-assembling peptide hydrogels with inherent antimicrobial ability have recently come to the fore. However, their fundamental antimicrobial properties, selectivity and mechanism of action are relatively undefined. This review attempts to establish a link between antimicrobial efficacy; the self-assembly process; peptide-membrane interactions and mechanical properties by studying several reported peptide systems: β-hairpin/β-loop peptides; multidomain peptides; amphiphilic surfactant-like peptides and ultrashort/low molecular weight peptides. We also explore their role in the formation of amyloid plaques and the potential for an infection etiology in diseases such as Alzheimer's. We look briefly at innovative methods of gel characterization. These may provide useful tools for future studies within this increasingly important field.
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Affiliation(s)
- Emily R Cross
- Biofunctional Nanomaterials Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, N. Ireland, BT9 7BL, UK.
| | - Sophie M Coulter
- Biofunctional Nanomaterials Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, N. Ireland, BT9 7BL, UK.
| | - Sreekanth Pentlavalli
- Biofunctional Nanomaterials Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, N. Ireland, BT9 7BL, UK.
| | - Garry Laverty
- Biofunctional Nanomaterials Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, N. Ireland, BT9 7BL, UK.
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Qian S, Sharma VK, Clifton LA. Understanding the Structure and Dynamics of Complex Biomembrane Interactions by Neutron Scattering Techniques. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:15189-15211. [PMID: 33300335 DOI: 10.1021/acs.langmuir.0c02516] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The membrane is one of the key structural materials of biology at the cellular level. Composed predominantly of a bilayer of lipids with embedded and bound proteins, it defines the boundaries of the cell and many organelles essential to life and therefore is involved in almost all biological processes. Membrane-specific interactions, such as drug binding to a membrane receptor or the interactions of an antimicrobial compound with the lipid matrix of a pathogen membrane, are of interest across the scientific disciplines. Herein we present a review, aimed at nonexperts, of the major neutron scattering techniques used in membrane studies: small-angle neutron scattering, neutron membrane diffraction, neutron reflectometry, quasielastic neutron scattering, and neutron spin echo. Neutron scattering techniques are well suited to studying biological membranes. The nondestructive nature of cold neutrons means that samples can be measured for long periods without fear of beam damage from ultraviolet, electron, or X-ray radiation, and neutron beams are highly penetrating, thus offering flexibility in samples and sample environments. Most important is the strong difference in neutron scattering lengths between the two most abundant forms of hydrogen, protium and deuterium. Changing the relative amounts of protium/deuterium in a sample allows the production of a series of neutron scattering data sets, enabling the observation of differing components within complex membrane architectures. This approach can be as simple as using the naturally occurring neutron contrast between different biomolecules to study components in a complex by changing the solution H2O/D2O ratio or as complex as selectively labeling individual components with hydrogen isotopes. This review presents an overview of each experimental technique with the neutron instrument configuration, related sample preparation and sample environment, and data analysis, highlighted by a special emphasis on using prominent neutron contrast to understand structure and dynamics. This review gives researchers a practical introduction to the often enigmatic suite of neutron beamlines, thereby lowering the barrier to taking advantage of these large-facility techniques to achieve new understandings of membranes and their interactions with other molecules.
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Affiliation(s)
- Shuo Qian
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Veerendra Kumar Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Luke A Clifton
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, U.K. OX11 0QX
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Shi W. Role of Defects in Achieving Highly Asymmetric Lamellar Self-Assembly in Block Copolymer/Homopolymer Blends. J Phys Chem Lett 2020; 11:2724-2730. [PMID: 32203668 DOI: 10.1021/acs.jpclett.0c00459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Lamellar structure is a prominent state in soft condensed matter. Swelling lamellar layers to highly asymmetric structures by a second component is a facile, cost-effective strategy to impart materials with adaptive size and tunable properties. One key question that remains unsolved is how defects form and affect the asymmetric lamellar order. This study unravels the role of defects by swelling a miktoarm block copolymer with a homopolymer. Ordered lamellae first lose translational order by a significant increase in the number of dislocations and then lose orientational order by the generation of disclinations. The homopolymers are not uniformly distributed in defective lamellae and primarily segregate in the vicinity of disclination cores. The free energy of defects is mainly contributed by molecular splay and significantly alleviated by an increased radius of local curvature. This study provides direct evidence to reveal the role of defects and lamellar order in block copolymer/homopolymer blends and also sheds light on understanding analogous structural transitions in other soft systems, including lyotropic liquid crystals, phospholipid membranes, and polymer nanocomposites.
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Affiliation(s)
- Weichao Shi
- Key Laboratory of Functional Polymer Materials (Ministry of Education) and Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
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Kim M, Porras-Gomez M, Leal C. Graphene-based sensing of oxygen transport through pulmonary membranes. Nat Commun 2020; 11:1103. [PMID: 32107376 PMCID: PMC7046670 DOI: 10.1038/s41467-020-14825-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 02/04/2020] [Indexed: 11/09/2022] Open
Abstract
Lipid-protein complexes are the basis of pulmonary surfactants covering the respiratory surface and mediating gas exchange in lungs. Cardiolipin is a mitochondrial lipid overexpressed in mammalian lungs infected by bacterial pneumonia. In addition, increased oxygen supply (hyperoxia) is a pathological factor also critical in bacterial pneumonia. In this paper we fabricate a micrometer-size graphene-based sensor to measure oxygen permeation through pulmonary membranes. Combining oxygen sensing, X-ray scattering, and Atomic Force Microscopy, we show that mammalian pulmonary membranes suffer a structural transformation induced by cardiolipin. We observe that cardiolipin promotes the formation of periodic protein-free inter-membrane contacts with rhombohedral symmetry. Membrane contacts, or stalks, promote a significant increase in oxygen gas permeation which may bear significance for alveoli gas exchange imbalance in pneumonia.
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Affiliation(s)
- Mijung Kim
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Marilyn Porras-Gomez
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Cecilia Leal
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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