1
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Lucker J, Kio M, Klauda JB. Expanding the CHARMM36 United Atom Chain Model for the Inclusion of Sphingolipids. J Phys Chem B 2024. [PMID: 38688001 DOI: 10.1021/acs.jpcb.4c01404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
The inclusion of accurate yet computationally inexpensive lipid force fields (FF) is pertinent for the study of lipids and lipid-containing systems using molecular dynamics (MD). Within the past decade, the implementation and further expansion of a united atom (UA) FF for lipids have been developed in the CHARMM family of FFs. The most recent version of the UA presented more accurate descriptions of lipid properties for several phospholipids with saturated and monounsaturated chains, termed C36UAr. However, the original C36UAr model lacks parameters for an important class of lipids, such as sphingolipids. The focus of this article is to broaden the scope of the C36UAr chain model to incorporate these lipids. In this study, two common sphingolipids, N-palmitoyl sphingomyelin and N-stearoyl sphingomyelin are converted to a UA-chain representation and simulated to investigate the accuracy and speed over the all-atom FF model for sphingolipids. Improvements were found among multiple parameters, for example, in the surface area per lipid (SA/lip) and hydrogen order parameters, over the all-atom simulations of these sphingomyelins in C36, while as much as halving the simulation time for simulations of the same setup otherwise. Thus, the accuracy and efficiency found in this study are consistent with those found in the C36UAr model for phospholipids and expand the application of C36UAr to a wider array of membrane models to better match that in vivo.
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Affiliation(s)
- Joshua Lucker
- Institute for Physical Science and Technology, Biophysics Program, University of Maryland, College Park, Maryland 20742, United States
| | - Michael Kio
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Jeffery B Klauda
- Institute for Physical Science and Technology, Biophysics Program, University of Maryland, College Park, Maryland 20742, United States
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States
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2
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Paraskevopoulos G, Fandrei F, Kumar Pratihast A, Paraskevopoulou A, Panoutsopoulou E, Opálka L, Singh Mithu V, Huster D, Vávrová K. Effects of imidazolium ionic liquids on skin barrier lipids - Perspectives for drug delivery. J Colloid Interface Sci 2024; 659:449-462. [PMID: 38183811 DOI: 10.1016/j.jcis.2023.12.139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 11/27/2023] [Accepted: 12/20/2023] [Indexed: 01/08/2024]
Abstract
Ionic liquids (ILs) have great potential to facilitate transdermal and topical drug delivery. Here, we investigated the mechanism of action of amphiphilic ILs 1-methyl-3-octylimidazolium bromide (C8MIM) and 3-dodecyl-1-methylimidazolium bromide (C12MIM) in skin barrier lipid models in comparison to their complex effects in human skin. C8MIM incorporated in a skin lipid model was a better permeation enhancer than C12MIM for water and model drugs, theophylline and diclofenac. Solid state 2H NMR and X-ray diffraction indicated that both ILs prefer the cholesterol-rich regions in skin lipids without significantly perturbing their lamellar arrangement and that C8MIM induces the formation of an isotropic lipid phase to a greater extent compared to C12MIM. C12MIM applied topically to the lipid model or human skin as a pretreatment was more potent than C8MIM. When co-applied with the drugs to human skin, aqueous C12MIM was more potent than C8MIM in enhancing theophylline permeation, but neither IL affected (even decreased) diclofenac permeation. Thus, the IL's ability to permeabilize skin lipid barrier is strongly modulated by its ability to reach the site of action and its interactions with drug and solvent. Such an interplay is far from trivial and requires detailed investigation to realize the full potential of ILs.
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Affiliation(s)
- Georgios Paraskevopoulos
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Ferdinand Fandrei
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany
| | - Ajit Kumar Pratihast
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Anna Paraskevopoulou
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Eleni Panoutsopoulou
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Lukáš Opálka
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Venus Singh Mithu
- Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany
| | - Kateřina Vávrová
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic.
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3
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Akkerman V, Scheidt HA, Reinholdt P, Bashawat M, Szomek M, Lehmann M, Wessig P, Covey DF, Kongsted J, Müller P, Wüstner D. Natamycin interferes with ergosterol-dependent lipid phases in model membranes. BBA ADVANCES 2023; 4:100102. [PMID: 37691996 PMCID: PMC10482743 DOI: 10.1016/j.bbadva.2023.100102] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023] Open
Abstract
Natamycin is an antifungal polyene macrolide that is used as a food preservative but also to treat fungal keratitis and other yeast infections. In contrast to other polyene antimycotics, natamycin does not form ion pores in the plasma membrane, but its mode of action is poorly understood. Using nuclear magnetic resonance (NMR) spectroscopy of deuterated sterols, we find that natamycin slows the mobility of ergosterol and cholesterol in liquid-ordered (Lo) membranes to a similar extent. This is supported by molecular dynamics (MD) simulations, which additionally reveal a strong impact of natamycin dimers on sterol dynamics and water permeability. Interference with sterol-dependent lipid packing is also reflected in a natamycin-mediated increase in membrane accessibility for dithionite, particularly in bilayers containing ergosterol. NMR experiments with deuterated sphingomyelin (SM) in sterol-containing membranes reveal that natamycin reduces phase separation and increases lipid exchange in bilayers with ergosterol. In ternary lipid mixtures containing monounsaturated phosphatidylcholine, saturated SM, and either ergosterol or cholesterol, natamycin interferes with phase separation into Lo and liquid-disordered (Ld) domains, as shown by NMR spectroscopy. Employing the intrinsic fluorescence of natamycin in ultraviolet-sensitive microscopy, we can visualize the binding of natamycin to giant unilamellar vesicles (GUVs) and find that it has the highest affinity for the Lo phase in GUVs containing ergosterol. Our results suggest that natamycin specifically interacts with the sterol-induced ordered phase, in which it disrupts lipid packing and increases solvent accessibility. This property is particularly pronounced in ergosterol containing membranes, which could underlie the selective antifungal activity of natamycin.
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Affiliation(s)
- Vibeke Akkerman
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Holger A. Scheidt
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107, Leipzig, Germany
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Mohammad Bashawat
- Department of Biology, Humboldt University Berlin, Invalidenstr. 43, D-10115, Berlin, Germany
| | - Maria Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Max Lehmann
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam, Germany
| | - Pablo Wessig
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam, Germany
| | - Douglas F. Covey
- Department of Developmental Biology, Washington University, St. Louis, MO, 63110, USA
- Taylor Family Institute for Innovative Psychiatric Research, St. Louis, Missouri, USA
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Peter Müller
- Department of Biology, Humboldt University Berlin, Invalidenstr. 43, D-10115, Berlin, Germany
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
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4
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Fandrei F, Havrišák T, Opálka L, Engberg O, Smith A, Pullmannová P, Kučerka N, Ondrejčeková V, Demé B, Nováková L, Steinhart M, Vávrová K, Huster D. The Intriguing Molecular Dynamics of Cer[EOS] in Rigid Skin Barrier Lipid Layers Requires Improvement of the Model. J Lipid Res 2023; 64:100356. [PMID: 36948272 PMCID: PMC10154977 DOI: 10.1016/j.jlr.2023.100356] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/07/2023] [Accepted: 03/08/2023] [Indexed: 03/24/2023] Open
Abstract
Omega-O-acyl ceramides such as 32-linoleoyloxydotriacontanoyl sphingosine (Cer[EOS]) are essential components of the lipid skin barrier, which protects our body from excessive water loss and the penetration of unwanted substances. These ceramides drive the lipid assembly to epidermal-specific long periodicity phase (LPP), structurally much different than conventional lipid bilayers. Here, we synthesized Cer[EOS] with selectively deuterated segments of the ultralong N-acyl chain or deuterated or 13C-labeled linoleic acid and studied their molecular behavior in a skin lipid model. Solid-state 2H NMR data revealed surprising molecular dynamics for the ultralong N-acyl chain of Cer[EOS] with increased isotropic motion towards the isotropic ester-bound linoleate. The sphingosine moiety of Cer[EOS] is also highly mobile at skin temperature, in stark contrast to the other LPP components, N-lignoceroyl sphingosine acyl, lignoceric acid and cholesterol, which are predominantly rigid. The dynamics of the linoleic chain is quantitatively described by distributions of correlation times and using dynamic detector analysis. These NMR results along with neutron diffraction data suggest an LPP structure with alternating fluid (sphingosine chain-rich), rigid (acyl chain-rich), isotropic (linoleate-rich), rigid (acyl-chain rich), and fluid layers (sphingosine chain-rich). Such an arrangement of the skin barrier lipids with rigid layers separated with two different dynamic "fillings" i) agrees well with ultrastructural data, ii) satisfies the need for simultaneous rigidity (to ensure low permeability) and fluidity (to ensure elasticity, accommodate enzymes or antimicrobial peptides), and iii) offers a straightforward way to remodel the lamellar body lipids into the final lipid barrier.
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Affiliation(s)
- Ferdinand Fandrei
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany
| | - Tomáš Havrišák
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Lukáš Opálka
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Oskar Engberg
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany
| | - AlbertA Smith
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany
| | - Petra Pullmannová
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Norbert Kučerka
- Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, 832 32 Bratislava, Slovakia
| | - Veronika Ondrejčeková
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Bruno Demé
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble, CEDEX 9, France
| | - Lucie Nováková
- Department of Analytical Chemistry, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Miloš Steinhart
- Institute of Macromolecular Chemistry, Czech Academy of Science in Prague, Heyrovského nám. 2, 162 06 Prague, Czech Republic
| | - Kateřina Vávrová
- Skin Barrier Research Group, Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany
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5
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Doole FT, Gupta S, Kumarage T, Ashkar R, Brown MF. Biophysics of Membrane Stiffening by Cholesterol and Phosphatidylinositol 4,5-bisphosphate (PIP2). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:61-85. [PMID: 36988877 DOI: 10.1007/978-3-031-21547-6_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Cell membranes regulate a wide range of phenomena that are implicated in key cellular functions. Cholesterol, a critical component of eukaryotic cell membranes, is responsible for cellular organization, membrane elasticity, and other critical physicochemical parameters. Besides cholesterol, other lipid components such as phosphatidylinositol 4,5-bisphosphate (PIP2) are found in minor concentrations in cell membranes yet can also play a major regulatory role in various cell functions. In this chapter, we describe how solid-state deuterium nuclear magnetic resonance (2H NMR) spectroscopy together with neutron spin-echo (NSE) spectroscopy can inform synergetic changes to lipid molecular packing due to cholesterol and PIP2 that modulate the bending rigidity of lipid membranes. Fundamental structure-property relations of molecular self-assembly are illuminated and point toward a length and time-scale dependence of cell membrane mechanics, with significant implications for biological activity and membrane lipid-protein interactions.
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Affiliation(s)
- Fathima T Doole
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Sudipta Gupta
- Department of Physics and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, USA
| | - Teshani Kumarage
- Department of Physics and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, USA
| | - Rana Ashkar
- Department of Physics and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, USA.
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA.
- Department of Physics, University of Arizona, Tucson, AZ, USA.
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6
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Serotonergic drugs modulate the phase behavior of complex lipid bilayers. Biochimie 2022; 203:40-50. [PMID: 35447219 DOI: 10.1016/j.biochi.2022.04.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/21/2022] [Accepted: 04/13/2022] [Indexed: 12/16/2022]
Abstract
Serotonin is an endogenous neurotransmitter involved in both physiological and pathophysiological processes. Traditionally, serotonin acts as a ligand for G protein-coupled receptors (GPCRs) leading to subsequent cell signaling. However, serotonin can also bind to lipid membranes with high affinity and modulate the phase behavior in 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC)/N-palmitoyl-D-erythro-sphingosylphosphorylcholine (PSM)/cholesterol model membranes mimicking the outer leaflet of the plasma membrane. Here, we investigated if serotonergic drugs containing the pharmacophore from serotonin would also modulate phase behavior in lipid membranes in a similar fashion. We used 2H NMR spectroscopy to explore the phase behavior of POPC/PSM/cholesterol (4/4/2 molar ratio) mixtures in the presence of the serotonergic drugs aripiprazole, BRL-54443, BW-723C86, and CP-135807 at a lipid to drug molar ratio of 10:1. POPC and PSM were perdeuterated in the palmitoyl chain, respectively, and prepared in individual samples. Numerical lineshape simulations of the 2H NMR spectra were used to calculate the order parameter profiles and projected lengths of the saturated acyl chains. All serotonergic drugs induce two components in 2H NMR spectra, indicating that they increased the hydrophobic mismatch between the thickness of the coexisting lipid phases leading to larger domain sizes, relatively similarly to serotonin. AFM force indentation and Raman spectral studies, which interrogate membrane mechanical properties, also indicate changes in membrane order in the presence of these drugs. These findings highlight how serotonergic drugs alter membrane phase behavior and could modulate both target and other membrane proteins, possibly explaining the side effects observed for serotonergic and other clinically relevant drugs.
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7
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Doole FT, Kumarage T, Ashkar R, Brown MF. Cholesterol Stiffening of Lipid Membranes. J Membr Biol 2022; 255:385-405. [PMID: 36219221 PMCID: PMC9552730 DOI: 10.1007/s00232-022-00263-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 08/05/2022] [Indexed: 11/30/2022]
Abstract
Biomembrane order, dynamics, and other essential physicochemical parameters are controlled by cholesterol, a major component of mammalian cell membranes. Although cholesterol is well known to exhibit a condensing effect on fluid lipid membranes, the extent of stiffening that occurs with different degrees of lipid acyl chain unsaturation remains an enigma. In this review, we show that cholesterol locally increases the bending rigidity of both unsaturated and saturated lipid membranes, suggesting there may be a length-scale dependence of the bending modulus. We review our published data that address the origin of the mechanical effects of cholesterol on unsaturated and polyunsaturated lipid membranes and their role in biomembrane functions. Through a combination of solid-state deuterium NMR spectroscopy and neutron spin-echo spectroscopy, we show that changes in molecular packing cause the universal effects of cholesterol on the membrane bending rigidity. Our findings have broad implications for the role of cholesterol in lipid–protein interactions as well as raft-like mixtures, drug delivery applications, and the effects of antimicrobial peptides on lipid membranes.
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Affiliation(s)
- Fathima T Doole
- Deaprtment of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85712, USA
| | - Teshani Kumarage
- Department of Physics, Virginia Tech, Blacksburg, VA, 24061, USA.,Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Rana Ashkar
- Department of Physics, Virginia Tech, Blacksburg, VA, 24061, USA. .,Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, 24061, USA.
| | - Michael F Brown
- Deaprtment of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85712, USA. .,Department of Physics, University of Arizona, Tucson, AZ, 85712, USA.
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8
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Murata M, Matsumori N, Kinoshita M, London E. Molecular substructure of the liquid-ordered phase formed by sphingomyelin and cholesterol: sphingomyelin clusters forming nano-subdomains are a characteristic feature. Biophys Rev 2022; 14:655-678. [PMID: 35791389 DOI: 10.1007/s12551-022-00967-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 05/26/2022] [Indexed: 11/29/2022] Open
Abstract
As a model of lipid rafts, the liquid-ordered (Lo) phase formed by sphingomyelin (SM) and cholesterol (Cho) in bilayer membranes has long attracted the attention of biophysics researchers. New approaches and methodologies have led to a better understanding of the molecular basis of the Lo domain structure. This review summarizes studies on model membrane systems consisting of SM/unsaturated phospholipid/Cho implying that the Lo phase contains SM-based nanodomains (or nano-subdomains). Some of the Lo phase properties may be attributed to these nanodomains. Several studies suggest that the nanodomains contain clustered SM molecules packed densely to form gel-phase-like subdomains of single-digit nanometer size at physiological temperatures. Cho and unsaturated lipids located in the Lo phase are likely to be concentrated at the boundaries between the subdomains. These subdomains are not readily detected in the Lo phase formed by saturated phosphatidylcholine (PC) molecules, suggesting that they are strongly stabilized by homophilic interactions specific to SM, e.g., between SM amide groups. This model for the Lo phase is supported by experiments using dihydro-SM, which is thought to have stronger homophilic interactions than SM, as well as by studies using the enantiomer of SM having opposite stereochemistry to SM at the 2 and 3 positions and by some molecular dynamics (MD) simulations of lipid bilayers containing Lo-lipids. Nanosized gel subdomains seem to play an important role in controlling membrane organization and function in biological membranes.
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Affiliation(s)
- Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan.,ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
| | - Nobuaki Matsumori
- Department of Chemistry, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 Japan
| | - Masanao Kinoshita
- ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan.,Department of Chemistry, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 Japan
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215 USA
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9
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Borcik C, Eason IR, Vanderloop B, Wylie BJ. 2H, 13C-Cholesterol for Dynamics and Structural Studies of Biological Membranes. ACS OMEGA 2022; 7:17151-17160. [PMID: 35647452 PMCID: PMC9134247 DOI: 10.1021/acsomega.2c00796] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 04/08/2022] [Indexed: 05/19/2023]
Abstract
We present a cost-effective means of 2H and 13C enrichment of cholesterol. This method exploits the metabolism of 2H,13C-acetate into acetyl-CoA, the first substrate in the mevalonate pathway. We show that growing the cholesterol producing strain RH6827 of Saccharomyces cerevisiae in 2H,13C-acetate-enriched minimal media produces a skip-labeled pattern of deuteration. We characterize this cholesterol labeling pattern by mass spectrometry and solid-state nuclear magnetic resonance spectroscopy. It is confirmed that most 2H nuclei retain their original 2H-13C bonds from acetate throughout the biosynthetic pathway. We then quantify the changes in 13C chemical shifts brought by deuteration and the impact upon 13C-13C spin diffusion. Finally, using adiabatic rotor echo short pulse irradiation cross-polarization (RESPIRATIONCP), we acquire the 2H-13C correlation spectra to site specifically quantify cholesterol dynamics in two model membranes as a function of temperature. These measurements show that cholesterol acyl chains at physiological temperatures in mixtures of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), sphingomyelin, and cholesterol are more dynamic than cholesterol in POPC. However, this overall change in motion is not uniform across the cholesterol molecule. This result establishes that this cholesterol labeling pattern will have great utility in reporting on cholesterol dynamics and orientation in a variety of environments and with different membrane bilayer components, as well as monitoring the mevalonate pathway product interactions within the bilayer. Finally, the flexibility and universality of acetate labeling will allow this technique to be widely applied to a large range of lipids and other natural products.
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10
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Tsuchikawa H, Monji M, Umegawa Y, Yasuda T, Slotte JP, Murata M. Depth-Dependent Segmental Melting of the Sphingomyelin Alkyl Chain in Lipid Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5515-5524. [PMID: 35477243 DOI: 10.1021/acs.langmuir.2c00092] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The chain melting of lipid bilayers has often been investigated in detail using calorimetric methods, such as differential scanning calorimetry (DSC), and the resultant main transition temperature is regarded as one of the most important parameters in model membrane experiments. However, it is not always clear whether the hydrocarbon chains of lipids are gradually melting along the depth of the lipid bilayer or whether they all melt concurrently in a very narrow temperature range, as implied by DSC. In this study, we focused on stearoyl-d-sphingomyelin (SSM) as an example of raft-forming lipids. We synthesized deuterium-labeled SSMs at the 4', 10', and 16' positions, and their depth-dependent melting was measured using solid-state deuterium NMR by changing the temperature by 1.0 °C, and comparing with that observed from a saturated lipid, palmitoylstearoylphosphatidylcholine (PSPC). The results showed that SSM exhibited a characteristic depth-dependent melting, which was not observed for PSPC. The strong intermolecular hydrogen bonds between the sphingomyelin amide moiety probably caused the chain melting to start from the chain terminus through the middle part and end in the upper part. This depth-dependent melting implies that the small gel-like domains of SSM remain at temperatures slightly above the main transition temperature. These sphingomyelin features may be responsible for the biological properties of SM-based lipid rafts.
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Affiliation(s)
- Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
- Faculty of Medicine, Oita University, Oita, Oita 879-5593, Japan
| | - Mami Monji
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
| | - Yuichi Umegawa
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
- Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Tomokazu Yasuda
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6A, Turku FIN-20520, Finland
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
- Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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11
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Cholesterol Sulfate Fluidizes the Sterol Fraction of the Stratum Corneum Lipid Phase and Increases its Permeability. J Lipid Res 2022; 63:100177. [PMID: 35143845 PMCID: PMC8953687 DOI: 10.1016/j.jlr.2022.100177] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/02/2022] [Accepted: 02/03/2022] [Indexed: 12/02/2022] Open
Abstract
Desulfation of cholesterol sulfate (CholS) to cholesterol (Chol) is an important event in epidermal homeostasis and necessary for stratum corneum (SC) barrier function. The CholS/Chol ratio decreases during SC maturation but remains high in pathological conditions, such as X-linked ichthyosis, characterized by dry and scaly skin. The aim of this study was to characterize the influence of the CholS/Chol molar ratio on the structure, dynamics, and permeability of SC lipid model mixtures. We synthesized deuterated CholS and investigated lipid models with specifically deuterated components using 2H solid-state NMR spectroscopy at temperatures from 25°C to 80°C. Although the rigid acyl chains in ceramides and fatty acids remained essentially rigid upon variation of the CholS/Chol ratio, both sterols were increasingly fluidized in lipid models containing higher CholS concentrations. We also show the X-ray repeat distance of the lipid lamellar phase (105 Å) and the orthorhombic chain packing of the ceramide’s acyl chains and long free fatty acids did not change upon the variation of the CholS content. However, the Chol phase separation visible in models with high Chol concentration disappeared at the 50:50 CholS/Chol ratio. This increased fluidity resulted in higher permeabilities to model markers of these SC models. These results reveal that a high CholS/Chol ratio fluidizes the sterol fraction and increases the permeability of the SC lipid phase while maintaining the lamellar lipid arrangement with an asymmetric sterol distribution.
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12
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Kumar N, Sastry GN. Study of lipid heterogeneity on bilayer membranes using molecular dynamics simulations. J Mol Graph Model 2021; 108:108000. [PMID: 34365255 DOI: 10.1016/j.jmgm.2021.108000] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 07/17/2021] [Accepted: 07/29/2021] [Indexed: 11/26/2022]
Abstract
Human cell membranes consist of various lipids that are essential for their structure and function. It typically comprises phosphatidylcholine (POPC), phosphatidylethanolamine (POPE), phosphatidylserine (POPS), sphingomyelin (PSM), and cholesterol (CHL). Several experimental and computational techniques have been employed to characterize the composition of human cell membranes, however, CHL enriched membrane is still not clearly understood through these techniques. Molecular dynamics simulation results illustrated the biophysical properties of heterogeneous membranes based on the lipid composition as well as the concentration of lipids, exclusively for CHL and PSM. Herein, we have investigated the structure-function relationships of lipids comparatively to delineate the effect of heterogeneity on the biophysical properties of different membranes. It has been observed that the significant fraction of CHL (i.e., ~33% in ternary, ~25% in quaternary, and ~16% in senary type bilayers) in combination with other lipids introduced compactness, and increased the thickness of the membrane. The analysis of lipid mass density stated that the density of lipid head group, phosphate, and glycerol-ester in presence of CHL with or without PSM is an underlying reason for membrane ordering. Results also revealed that the presence of POPI and POPS are the reasons for an adequate drop in the ordering of lipid chain, particularly on POPE chain. The self-interaction of CHL, PSM, POPE and the interaction of CHL and POPC with POPE seem to determine the structure and function of the heterogeneous membrane. Our findings provide a qualitative understanding of the effect of membrane heterogeneity on the physiological properties of membranes. The structures inspected in this study would help to select the heterogeneous bilayer model to mimic the human cell membranes to analyse or characterize the membrane-associated phenomena.
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Affiliation(s)
- Nandan Kumar
- Centre for Molecular Modelling, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad, 500007, Telangana State, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, U. P., India
| | - G Narahari Sastry
- Centre for Molecular Modelling, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad, 500007, Telangana State, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, U. P., India; Advanced Computation and Data Sciences Division, CSIR-North East Institute of Science and Technology, Jorhat, 785006, Assam, India.
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13
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Elkins MR, Bandara A, Pantelopulos GA, Straub JE, Hong M. Direct Observation of Cholesterol Dimers and Tetramers in Lipid Bilayers. J Phys Chem B 2021; 125:1825-1837. [DOI: 10.1021/acs.jpcb.0c10631] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Matthew R. Elkins
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Asanga Bandara
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - George A. Pantelopulos
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - John E. Straub
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
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14
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Schmidt TF, Riske KA, Caseli L, Salesse C. Dengue fusion peptide in Langmuir monolayers: A binding parameter study. Biophys Chem 2021; 271:106553. [PMID: 33626461 DOI: 10.1016/j.bpc.2021.106553] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/08/2021] [Accepted: 01/27/2021] [Indexed: 10/22/2022]
Abstract
Membrane fusion is known to be the primary mechanism of entry of flaviviruses into host cells. Several studies reported the investigation of the membrane fusion mechanism mediated by the fusion peptide, a component of the membrane protein surrounding the flaviviruses. In this study, we investigated the interaction of Dengue fusion peptide (FLAg) with Langmuir monolayers to uncover the role of membrane charges and organization in its membrane binding. Binding parameters of FLAg were obtained by measuring its adsorption onto Langmuir monolayers of different types of individual lipids, as well as their mixtures. Specific peptide binding was observed in the presence of charged lipid monolayers at different pHs, revealing that the lipid composition of the membrane modulates peptide interaction, and the preference of the peptide for negatively charged lipids.
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Affiliation(s)
- Thaís F Schmidt
- Universidade Federal de São Paulo, Biophysics Department, São Paulo, SP, Brazil; Universidade Federal de São Paulo, Chemistry Department, Diadema, SP, Brazil; CUO-Recherche, Centre de recherche du CHU de Québec-Université Laval and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada.
| | - Karin A Riske
- Universidade Federal de São Paulo, Biophysics Department, São Paulo, SP, Brazil
| | - Luciano Caseli
- Universidade Federal de São Paulo, Chemistry Department, Diadema, SP, Brazil
| | - Christian Salesse
- CUO-Recherche, Centre de recherche du CHU de Québec-Université Laval and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
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15
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Bochicchio A, Brandner AF, Engberg O, Huster D, Böckmann RA. Spontaneous Membrane Nanodomain Formation in the Absence or Presence of the Neurotransmitter Serotonin. Front Cell Dev Biol 2020; 8:601145. [PMID: 33330494 PMCID: PMC7734319 DOI: 10.3389/fcell.2020.601145] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/06/2020] [Indexed: 11/23/2022] Open
Abstract
Detailed knowledge on the formation of biomembrane domains, their structure, composition, and physical characteristics is scarce. Despite its frequently discussed importance in signaling, e.g., in obtaining localized non-homogeneous receptor compositions in the plasma membrane, the nanometer size as well as the dynamic and transient nature of domains impede their experimental characterization. In turn, atomistic molecular dynamics (MD) simulations combine both, high spatial and high temporal resolution. Here, using microsecond atomistic MD simulations, we characterize the spontaneous and unbiased formation of nano-domains in a plasma membrane model containing phosphatidylcholine (POPC), palmitoyl-sphingomyelin (PSM), and cholesterol (Chol) in the presence or absence of the neurotransmitter serotonin at different temperatures. In the ternary mixture, highly ordered and highly disordered domains of similar composition coexist at 303 K. The distinction of domains by lipid acyl chain order gets lost at lower temperatures of 298 and 294 K, suggesting a phase transition at ambient temperature. By comparison of domain ordering and composition, we demonstrate how the domain-specific binding of the neurotransmitter serotonin results in a modified domain lipid composition and a substantial downward shift of the phase transition temperature. Our simulations thus suggest a novel mode of action of neurotransmitters possibly of importance in neuronal signal transmission.
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Affiliation(s)
- Anna Bochicchio
- Computational Biology, Department Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Astrid F Brandner
- Computational Biology, Department Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Oskar Engberg
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany.,Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Rainer A Böckmann
- Computational Biology, Department Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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16
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Engberg O, Bochicchio A, Brandner AF, Gupta A, Dey S, Böckmann RA, Maiti S, Huster D. Serotonin Alters the Phase Equilibrium of a Ternary Mixture of Phospholipids and Cholesterol. Front Physiol 2020; 11:578868. [PMID: 33192582 PMCID: PMC7645218 DOI: 10.3389/fphys.2020.578868] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 10/06/2020] [Indexed: 12/20/2022] Open
Abstract
Unsaturated and saturated phospholipids tend to laterally segregate, especially in the presence of cholesterol. Small molecules such as neurotransmitters, toxins, drugs etc. possibly modulate this lateral segregation. The small aromatic neurotransmitter serotonin (5-HT) has been found to bind to membranes. We studied the lipid structure and packing of a ternary membrane mixture consisting of palmitoyl-oleoyl-phosphatidylcholine, palmitoyl-sphingomyelin, and cholesterol at a molar ratio of 4/4/2 in the absence and in the presence of 5-HT, using a combination of solid-state 2H NMR, atomic force microscopy, and atomistic molecular dynamics (MD) simulations. Both NMR and MD report formation of a liquid ordered (L o ) and a liquid disordered (L d ) phase coexistence with small domains. Lipid exchange between the domains was fast such that single component 2H NMR spectra are detected over a wide temperature range. A drastic restructuring of the domains was induced when 5-HT is added to the membranes at a 9 mol% concentration relative to the lipids. 2H NMR spectra of all components of the mixture showed two prominent contributions indicative of molecules of the same kind residing both in the disordered and the ordered phase. Compared to the data in the absence of 5-HT, the lipid chain order in the disordered phase was further decreased in the presence of 5-HT. Likewise, addition of serotonin increased lipid chain order within the ordered phase. These characteristic lipid chain order changes were confirmed by MD simulations. The 5-HT-induced larger difference in lipid chain order results in more pronounced differences in the hydrophobic thickness of the individual membrane domains. The correspondingly enlarged hydrophobic mismatch between ordered and disordered phases is assumed to increase the line tension at the domain boundary, which drives the system into formation of larger size domains. These results not only demonstrate that small membrane binding molecules such as neurotransmitters have a profound impact on essential membrane properties. It also suggests a mechanism by which the interaction of small molecules with membranes can influence the function of membrane proteins and non-cognate receptors. Altered membrane properties may modify lateral sorting of membrane protein, membrane protein conformation, and thus influence their function as suspected for neurotransmitters, local anesthetics, and other small drug molecules.
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Affiliation(s)
- Oskar Engberg
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
| | - Anna Bochicchio
- Computational Biology, Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Astrid F. Brandner
- Computational Biology, Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Ankur Gupta
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Simli Dey
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Rainer A. Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Sudipta Maiti
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
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17
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Tsuchikawa H, Ono T, Yamagami M, Umegawa Y, Shinoda W, Murata M. Conformation and Orientation of Branched Acyl Chains Responsible for the Physical Stability of Diphytanoylphosphatidylcholine. Biochemistry 2020; 59:3929-3938. [PMID: 32945657 DOI: 10.1021/acs.biochem.0c00589] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Diphytanoylphosphatidylcholine (DPhPC) is a synthetic phospholipid in which two methyl-branched acyl chains are introduced into the glycerol moiety, mimicking phospholipids of eukaryotic and eubacterial origins. The lipid bilayers of DPhPC reproduce the outstanding physical properties of methyl-branched lipids that occur in archaeal membranes. DPhPC is commonly used as the base lipid in biophysical experiments, particularly for recording ion-channel currents. However, the dynamics of lipid molecules that induces their useful physical properties is still unclear. In this study, we examined the conformation and orientation of the methyl-branched acyl chain of DPhPC in a membrane using 2H nuclear magnetic resonance (NMR) measurements of the synthetic lipid with a high stereochemical purity and molecular dynamics (MD) simulations. Deuterium-labeled 3',3'-CD3,D-DPhPC (2) and 7',7'-CD3,D-DPhPC (3) showed the characteristic quadrupole splitting width in the 2H NMR spectra, which corresponded to the bent orientation reported for the archaeal lipid PGP-Me [Yamagami, M., et al. (2019) Biochemistry 58, 3869-3879]. However, MD simulations, which reproduced the 2H NMR results well, unveiled the unknown features of DPhPC in the membrane; DPhPC has a chain-specific average orientation, where two bent orientations with upward and downward methyl groups occur at positions C3 and C7 of the sn-1 and sn-2 chains of DPhPC, respectively. These MD and NMR results reveal that these two bent orientations define the average orientation of DPhPC for the shallow part of the acyl chains, which is considered to be an important factor in the stability of DPhPC membranes.
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Affiliation(s)
- Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,Department of Clinical Pharmacology and Therapeutics, Faculty of Medicine, Oita University, 1-1 Idaigaoka, Hasama-machi, Yufu, Oita 879-5593, Japan
| | - Takuya Ono
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Masaki Yamagami
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Yuichi Umegawa
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Wataru Shinoda
- Department of Materials Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.,JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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18
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Chemically synthesized Gb 3 glycosphingolipids: tools to access their function in lipid membranes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2020; 50:109-126. [PMID: 32948883 PMCID: PMC8071800 DOI: 10.1007/s00249-020-01461-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 08/24/2020] [Accepted: 08/26/2020] [Indexed: 12/19/2022]
Abstract
Gb3 glycosphingolipids are the specific receptors for bacterial Shiga toxin. Whereas the trisaccharidic head group of Gb3 defines the specificity of Shiga toxin binding, the lipophilic part composed of sphingosine and different fatty acids is suggested to determine its localization within membranes impacting membrane organisation and protein binding eventually leading to protein internalisation. While most studies use Gb3 extracts, chemical synthesis provides a unique tool to access different tailor-made Gb3 glycosphingolipids. In this review, strategies to synthesize these complex glycosphingolipids are presented. Special emphasis is put on the preparation of Gb3 molecules differing only in their fatty acid part (saturated, unsaturated, α-hydroxylated and both, unsaturated and α-hydroxylated). With these molecules in hand, it became possible to investigate the phase behaviour of liquid ordered/liquid disordered supported membranes doped with the Gb3 species by means of fluorescence and atomic force microscopy. The results clearly highlight the influence of the different fatty acids of the Gb3 sphingolipids on the phase behaviour and the binding properties of Shiga toxin B subunits, even though the membranes were only doped with 5 mol% of the receptor lipid. To obtain fluorescent Gb3 derivatives, either fatty acid labelled Gb3 molecules or head group labelled ones were synthesized. These molecules enabled us to address the question, where the Gb3 sphingolipids are localized prior protein binding by means of fluorescence microscopy on giant unilamellar vesicles. The results again demonstrate that the fatty acid of Gb3 plays a pivotal role for the overall membrane organisation.
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19
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Kinnun JJ, Bolmatov D, Lavrentovich MO, Katsaras J. Lateral heterogeneity and domain formation in cellular membranes. Chem Phys Lipids 2020; 232:104976. [PMID: 32946808 PMCID: PMC7491465 DOI: 10.1016/j.chemphyslip.2020.104976] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/11/2020] [Accepted: 09/12/2020] [Indexed: 12/17/2022]
Abstract
Review article describing recent experimental and theoretical membrane lateral heterogeneity research. Describes the static and dynamic physical concepts behind domain formation in model membranes. Describes coarse-grained, phenomenological approaches that result in phases associated with lipid lateral heterogeneity.
As early as the development of the fluid mosaic model for cellular membranes, researchers began observing the telltale signs of lateral heterogeneity. Over the decades this has led to the development of the lipid raft hypothesis and the ensuing controversy that has unfolded, as a result. Here, we review the physical concepts behind domain formation in lipid membranes, both of their structural and dynamic origins. This, then leads into a discussion of coarse-grained, phenomenological approaches that describe the wide range of phases associated with lipid lateral heterogeneity. We use these physical concepts to describe the interaction between raft-lipid species, such as long-chain saturated lipids, sphingomyelin, and cholesterol, and non-raft forming lipids, such as those with short acyl chains or unsaturated fatty acids. While debate has persisted on the biological relevance of lipid domains, recent research, described here, continues to identify biological roles for rafts and new experimental approaches have revealed the existence of lipid domains in living systems. Given the recent progress on both the biological and structural aspects of raft formation, the research area of membrane lateral heterogeneity will not only expand, but will continue to produce exciting results.
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Affiliation(s)
- Jacob J Kinnun
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
| | - Dima Bolmatov
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States.
| | - Maxim O Lavrentovich
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States.
| | - John Katsaras
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States; Sample Environment Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
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20
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Yano Y, Hanashima S, Tsuchikawa H, Yasuda T, Slotte JP, London E, Murata M. Sphingomyelins and ent-Sphingomyelins Form Homophilic Nano-Subdomains within Liquid Ordered Domains. Biophys J 2020; 119:539-552. [PMID: 32710823 PMCID: PMC7399500 DOI: 10.1016/j.bpj.2020.06.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/19/2020] [Accepted: 06/26/2020] [Indexed: 12/29/2022] Open
Abstract
Sphingomyelin (SM), a major component of small domains (or lipid rafts) in mammalian cell membranes, forms a liquid-ordered phase in the presence of cholesterol (Cho). However, the nature of molecular interactions within the ordered SM/Cho phase remains elusive. We previously revealed that stearoyl-SM (SSM) and its enantiomer (ent-SSM) separately form nano-subdomains within the liquid-ordered phase involving homophilic SSM-SSM and ent-SSM-ent-SSM interactions. In this study, the details of the subdomain formation by SSMs at the nanometer range were examined using Förster resonance energy transfer (FRET) measurements in lipid bilayers containing SSM and ent-SSM, dioleoyl-phosphatidylcholine and Cho. Although microscopy detected a stereochemical effect on partition coefficient favoring stereochemically homophilic interactions in the liquid-ordered state, it showed no significant difference in large-scale liquid-ordered domain formation by the two stereoisomers. In contrast to the uniform domains seen microscopy, FRET analysis using fluorescent donor- and acceptor-labeled SSM showed distinct differences in SM and ent-SM colocalization within nanoscale distances. Donor- and acceptor-labeled SSM showed significantly higher FRET efficiency than did donor-labeled SSM and acceptor-labeled ent-SSM in lipid vesicles composed of “racemic” (1:1) mixtures of SSM/ent-SSM with dioleoylphosphatidylcholine and Cho. The difference in FRET efficiency indicated that SSM and ent-SSM assemble to form separate nano-subdomains. The average size of the subdomains decreased as temperature increased, and at physiological temperatures, the subdomains were found to have a single-digit nanometer radius. These results suggest that (even in the absence of ent-SM) SM-SM interactions play a crucial role in forming nano-subdomains within liquid-ordered domains and may be a key feature of lipid microdomains (or rafts) in biological membranes.
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Affiliation(s)
- Yo Yano
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan; ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, Japan
| | - Shinya Hanashima
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - Tomokazu Yasuda
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York.
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan; ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, Japan.
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21
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Licari G, Strakova K, Matile S, Tajkhorshid E. Twisting and tilting of a mechanosensitive molecular probe detects order in membranes. Chem Sci 2020; 11:5637-5649. [PMID: 32864081 PMCID: PMC7433777 DOI: 10.1039/d0sc02175j] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 04/29/2020] [Indexed: 12/29/2022] Open
Abstract
Lateral forces in biological membranes affect a variety of dynamic cellular processes. Recent synthetic efforts have introduced fluorescent "flippers" as environment-sensitive planarizable push-pull probes that can detect lipid packing and membrane tension, and respond to lipid-induced mechanical forces by a shift in their spectroscopic properties. Herein, we investigate the molecular origin of the mechanosensitivity of the best known flipper, Flipper-TR, by an extended set of molecular dynamics (MD) simulations in membranes of increasing complexity and under different physicochemical conditions, revealing unprecedented details of the sensing process. Simulations enabled by accurate refinement of Flipper-TR force field using quantum mechanical calculations allowed us to unambiguously correlate the planarization of the two fluorescent flippers to spectroscopic response. In particular, Flipper-TR conformation exhibits bimodal distribution in disordered membranes and a unimodal distribution in highly ordered membranes. Such dramatic change was associated with a shift in Flipper-TR excitation spectra, as supported both by our simulated and experimentally-measured spectra. Flipper-TR sensitivity to phase-transition is confirmed by a temperature-jump protocol that alters the lipid phase of an ordered membrane, triggering an instantaneous mechanical twisting of the probe. Simulations show that the probe is also sensitive to surface tension, since even in a naturally disordered membrane, the unimodal distribution of coplanar flippers can be achieved if a sufficiently negative surface tension is applied to the membrane. MD simulations in ternary mixtures containing raft-like nanodomains show that the probe can discriminate lipid domains in phase-separated complex bilayers. A histogram-based approach, called DOB-phase classification, is introduced that can differentiate regions of disordered and ordered lipid phases by comparing dihedral distributions of Flipper-TR. Moreover, a new sensing mechanism involving the orientation of Flipper-TR is elucidated, corroborating experimental evidence that the probe tilt angle is strongly dependent on lipid ordering. The obtained atomic-resolution description of Flipper-TR mechanosensitivity is key to the interpretation of experimental data and to the design of novel mechanosensors with improved spectroscopic properties.
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Affiliation(s)
- Giuseppe Licari
- NIH Center for Macromolecular Modeling and Bioinformatics , Beckman Institute for Advanced Science and Technology , Department of Biochemistry , Center for Biophysics and Quantitative Biology , University of Illinois at Urbana-Champaign , Urbana , Illinois , USA . ; Tel: +1-217-244-6914
| | - Karolina Strakova
- School of Chemistry and Biochemistry , National Centre of Competence in Research (NCCR) Chemical Biology , University of Geneva , Geneva , Switzerland
| | - Stefan Matile
- School of Chemistry and Biochemistry , National Centre of Competence in Research (NCCR) Chemical Biology , University of Geneva , Geneva , Switzerland
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics , Beckman Institute for Advanced Science and Technology , Department of Biochemistry , Center for Biophysics and Quantitative Biology , University of Illinois at Urbana-Champaign , Urbana , Illinois , USA . ; Tel: +1-217-244-6914
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22
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Kumari P, Kashyap HK. DMSO induced dehydration of heterogeneous lipid bilayers and its impact on their structures. J Chem Phys 2019; 151:215103. [DOI: 10.1063/1.5127852] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Pratibha Kumari
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Hemant K. Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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23
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Roux M, Bonnet V, Djedaïni-Pilard F. Ordering of Saturated and Unsaturated Lipid Membranes near Their Phase Transitions Induced by an Amphiphilic Cyclodextrin and Cholesterol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:14376-14387. [PMID: 31564102 DOI: 10.1021/acs.langmuir.9b02082] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
When inserted in membranes of dimyristoyl phosphatidylcholine (DMPC), methylated β-cyclodextrins with one (TrimβMLC) or two (TrimβDLC) lauryl acyl chains grafted onto the hydrophilic cavity exert a "cholesterol-like ordering effect", by straightening the acyl chains in the fluid phase at temperatures near the chain melting transition. This effect may be related to pretransitional events such as the "anomalous swelling" known to occur with saturated phosphatidylcholine membranes. To investigate this model, order profiles and bilayer thicknesses of DMPC and unsaturated 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) membranes containing amphiphilic cyclodextrins or cholesterol were determined by deuterium NMR. The pure lipid membranes display both a qualitatively similar chain ordering upon cooling in the fluid phase, more important at the chain extremity, which gets more pronounced near their fluid-to-gel transitions. Both membranes show a bilayer thickness increase by ∼0.5 Å just above their transition, as observed previously with saturated phosphatidylcholines of various chain lengths. Membrane-insertion of 5% TrimβMLC or cholesterol induces an important ordering of the DMPC acyl chains just above the transition, which is also more pronounced at the chain extremity. There is an additional increase of the bilayer thickness, most probably due to a deep insertion of these amphiphilic molecules, facilitated by increased bilayer softness in the anomalous swelling regime. These effects are more important with TrimβMLC than with cholesterol. By contrast, no enhanced acyl chain ordering was observed when approaching the transition of TrimβMLC-containing POPC membranes, as a possible consequence of an eventual lack of anomalous swelling in unsaturated lipid membranes. Insertion of higher concentrations of TrimβMLC was found to induce a magnetic orientation of the DMPC membranes in the fluid phase with 10% of this derivative, coupled with the appearance of a broad isotropic component when the concentration is raised to 20%. No membrane orientation or isotropic component was detected with TrimβMLC-containing POPC membranes.
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Affiliation(s)
- Michel Roux
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS , Université Paris-Sud, Université Paris-Saclay , F-91198 Gif-sur-Yvette cedex , France
| | - Véronique Bonnet
- LG2A, UMR7378 , Université de Picardie Jules Verne , F-80039 Amiens , France
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24
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Kumari P, Kumari M, Kashyap HK. Counter-effects of Ethanol and Cholesterol on the Heterogeneous PSM–POPC Lipid Membrane: A Molecular Dynamics Simulation Study. J Phys Chem B 2019; 123:9616-9628. [DOI: 10.1021/acs.jpcb.9b07107] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Pratibha Kumari
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Monika Kumari
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Hemant K. Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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25
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Nyholm TKM, Engberg O, Hautala V, Tsuchikawa H, Lin KL, Murata M, Slotte JP. Impact of Acyl Chain Mismatch on the Formation and Properties of Sphingomyelin-Cholesterol Domains. Biophys J 2019; 117:1577-1588. [PMID: 31610877 DOI: 10.1016/j.bpj.2019.09.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 11/30/2022] Open
Abstract
Lateral segregation and the formation of lateral domains are well-known phenomena in ternary lipid bilayers composed of an unsaturated (low gel-to-liquid phase transition temperature (Tm)) phospholipid, a saturated (high-Tm) phospholipid, and cholesterol. The formation of lateral domains has been shown to be influenced by differences in phospholipid acyl chain unsaturation and length. Recently, we also showed that differential interactions of cholesterol with low- and high-Tm phospholipids in the bilayer can facilitate phospholipid segregation. Now, we have investigated phospholipid-cholesterol interactions and their role in lateral segregation in ternary bilayers composed of different unsaturated phosphatidylcholines (PCs) with varying acyl chain lengths, N-palmitoyl-D-erythro-sphingomyelin (PSM), and cholesterol. Using deuterium NMR spectroscopy, we determined how PSM was influenced by the acyl chain composition in surrounding PC environments and correlated this with the affinity of cholestatrienol (a fluorescent cholesterol analog) for PSM in the different PC environments. Results from a combination of time-resolved fluorescence measurements of trans-parinaric acid and Förster resonance energy transfer experiments showed that the relative affinity of cholesterol for phospholipids determined the degree to which the sterol promoted domain formation. From Förster resonance energy transfer, deuterium NMR, and differential scanning calorimetry results, it was clear that cholesterol also influenced both the thermostability of the domains and the degree of order in and outside the PSM-rich domains. The results of this study have shown that the affinity of cholesterol for both low-Tm and high-Tm phospholipids and the effects of low- and high-Tm phospholipids on each other influence both lateral structure and domain properties in complex bilayers. We envision that similar effects also contribute to lateral heterogeneity in even more complex biological membranes.
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Affiliation(s)
- Thomas K M Nyholm
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland.
| | - Oskar Engberg
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
| | - Victor Hautala
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
| | - Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Kai-Lan Lin
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Abo Akademi University, Turku Finland
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26
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Engberg O, Scheidt HA, Nyholm TKM, Slotte JP, Huster D. Membrane Localization and Lipid Interactions of Common Lipid-Conjugated Fluorescence Probes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:11902-11911. [PMID: 31424941 DOI: 10.1021/acs.langmuir.9b01202] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Lateral segregation of lipids in model and biological membranes has been studied intensively in the last decades using a comprehensive set of experimental techniques. Most methods require a probe to report on the biophysical properties of a specific molecule in the lipid bilayer. Because such probes can adversely affect the results of the measurement and perturb the local membrane structure and dynamics, a detailed understanding of probe behavior and its influence on the properties of its direct environment is important. Membrane phase-selective and lipid-mimicking molecules represent common types of probes. Here, we have studied how the fluorescent probes trans-parinaric acid (tPA), diphenylhexatriene (DPH), and 1-oleoyl-2-propionyl[DPH]-sn-glycero-3-phosphocholine (O-DPH-PC) affect the membrane properties of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) bilayers using 2H and 31P NMR spectroscopy in the solid state. In addition, using 2D 1H magic-angle spinning (MAS) nuclear Overhauser enhancement spectroscopy (NOESY) NMR, we have determined the distribution of the probe moieties in the POPC membrane parallel to the membrane normal. We found that the different probes exhibit distinct membrane localizations and distributions, e.g. tPA is located parallel to the membrane normal while DPH predominantly exist in two orientations. Further, tPA was conjugated to sphingomyelin (tPA-SM) as a substitute for the acyl chain in the SM. 1H NOESY NMR was used to probe the interaction of the tPA-SM with cholesterol as dominant in liquid ordered membrane domains in comparison to POPC-cholesterol interaction in membranes composed of ternary lipid mixtures. We could show that tPA-SM exhibited a strong favorable and very temperature-dependent interaction with cholesterol in comparison to POPC. In conclusion, the NMR techniques can explain probe behavior but also be used to measure lipid-specific affinities between different lipid segments and individual molecules in complex bilayers, relevant to understanding nanodomain formation in biological membranes.
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Affiliation(s)
- Oskar Engberg
- Institute for Medical Physics and Biophysics, Medical Department , Leipzig University , Leipzig , Germany
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Turku , Finland
| | - Holger A Scheidt
- Institute for Medical Physics and Biophysics, Medical Department , Leipzig University , Leipzig , Germany
| | - Thomas K M Nyholm
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Turku , Finland
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Turku , Finland
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Medical Department , Leipzig University , Leipzig , Germany
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27
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Duarte TT, Ellis CC, Grajeda BI, De Chatterjee A, Almeida IC, Das S. A Targeted Mass Spectrometric Analysis Reveals the Presence of a Reduced but Dynamic Sphingolipid Metabolic Pathway in an Ancient Protozoan, Giardia lamblia. Front Cell Infect Microbiol 2019; 9:245. [PMID: 31396488 PMCID: PMC6668603 DOI: 10.3389/fcimb.2019.00245] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Accepted: 06/24/2019] [Indexed: 12/11/2022] Open
Abstract
Giardia lamblia, a single-celled eukaryote, colonizes and thrives in the small intestine of humans. Because of its compact and reduced genome, Giardia has adapted a “minimalistic” life style, as it becomes dependent on available resources of the small intestine. Because Giardia expresses fewer sphingolipid (SL) genes—and glycosphingolipids are critical for encystation—we investigated the SL metabolic cycle in this parasite. A tandem mass spectrometry (MS/MS) analysis reveals that major SLs in Giardia include sphingomyelins, sphingoid bases, ceramides, and glycosylceramides. Many of these lipids are obtained by Giardia from the growth medium, remodeled at their fatty acyl chains and end up in the spent medium. For instance, ceramide-1-phosphate, a proinflammatory molecule that is not present in the culture medium, is generated from sphingosine (abundant in the culture medium) possibly by remodeling reactions. It is then subsequently released into the spent medium. Thus, the secretion of ceramide-1-phospate and other SL derivatives by Giardia could be associated with inflammatory bowel disease observed in acute giardiasis. Additionally, we found that the levels of SLs increase in encysting Giardia and are differentially regulated throughout the encystation cycle. We propose that SL metabolism is important for this parasite and, could serve as potential targets for developing novel anti-giardial agents.
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Affiliation(s)
- Trevor T Duarte
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States
| | - Cameron C Ellis
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States
| | - Brian I Grajeda
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States
| | - Atasi De Chatterjee
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States
| | - Igor C Almeida
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States.,Infectious Disease and Immunology Cluster, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States
| | - Siddhartha Das
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States.,Infectious Disease and Immunology Cluster, Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, United States
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28
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Bosse M, Sibold J, Scheidt HA, Patalag LJ, Kettelhoit K, Ries A, Werz DB, Steinem C, Huster D. Shiga toxin binding alters lipid packing and the domain structure of Gb 3-containing membranes: a solid-state NMR study. Phys Chem Chem Phys 2019; 21:15630-15638. [PMID: 31268447 DOI: 10.1039/c9cp02501d] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We studied the influence of globotriaosylceramide (Gb3) lipid molecules on the properties of phospholipid membranes composed of a liquid ordered (lo)/liquid disordered (ld) phase separated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/N-palmitoyl-d-erythro-sphingosylphosphorylcholine (PSM)/cholesterol mixture (40/35/20, mol/mol/mol) supplemented with 5 mol% of either short acyl chain palmitoyl-Gb3 or long acyl chain lignoceryl-Gb3 using 2H solid-state NMR spectroscopy. To this end, both globotriaosylceramides were chemically synthesized featuring a perdeuterated lipid acyl chain. The solid-state 2H NMR spectra support the phase separation into a POPC-rich ld phase and a PSM/cholesterol-rich lo phase. The long chain lignoceryl-Gb3 showed a rather unusual order parameter profile of the acyl chain, which flattens out for the last ∼6 methylene segments. Such an odd chain conformation can be explained by partial chain interdigitation and/or a very fluid midplane region of the membrane. Possibly, the Gb3 molecules may thus preferentially be localized at the lo/ld phase boundary. In contrast, the short chain palmitoyl-Gb3 was well associated with the PSM/cholesterol-rich lo phase. Gb3 molecules act as membrane receptors for the Shiga toxin (STx) produced by Shigella dysenteriae and by enterohemorrhagic strains of Escherichia coli (EHEC). The B-subunits of STx (STxB) forming a pentameric structure were produced recombinantly and incubated with the membrane mixtures leading to alterations in the lipid packing properties and lateral organization of the membranes. Typically, STxB binding led to a decrease in lipid chain order in agreement with partial immersion of protein segments into the lipid-water interface of the membrane. In the presence of STxB, Gb3 preferentially partitioned into the lo membrane phase. In particular the short acyl chain palmitoyl-Gb3 showed very similar chain order parameters to PSM. In the presence of STxB, all lipid species showed isotropic contributions to the 2H NMR powder spectra; this was most pronounced for the Gb3 molecules. Such isotropic contributions are caused by highly curved membrane structures, which have previously been detected as membrane invaginations in fluorescence microscopy. Our analysis estimated that STxB induced highly curved membrane structures with a curvature radius of less than ∼10 nm likely related to the insertion of STxB segments into the lipid-water interface of the membrane.
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Affiliation(s)
- Mathias Bosse
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.
| | - Jeremias Sibold
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, D-37077 Göttingen, Germany
| | - Holger A Scheidt
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.
| | - Lukas J Patalag
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Katharina Kettelhoit
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Annika Ries
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Daniel B Werz
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Claudia Steinem
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, D-37077 Göttingen, Germany and Max-Planck-Institute for Dynamics and Self-Organization, Am Fassberg 11, 37077 Göttingen, Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.
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29
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Aisenbrey C, Kemayo-Koumkoua P, Salnikov ES, Glattard E, Bechinger B. Investigations of the Structure, Topology, and Interactions of the Transmembrane Domain of the Lipid-Sorting Protein p24 Being Highly Selective for Sphingomyelin-C18. Biochemistry 2019; 58:2782-2795. [PMID: 31120242 DOI: 10.1021/acs.biochem.9b00375] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The p24 proteins play an important role in the secretory pathway where they selectively connect various cargo to other proteins, thereby being involved in the controlled assembly and disassembly of the coat protein complexes and lipid sorting. Recently, a highly selective lipid interaction motif has been identified within the p24 transmembrane domain (TMD) that recognizes the combination of the sphingomyelin headgroup and the exact length of the C18 fatty acyl chain (SM-C18). Here, we present investigations of the structure, dynamics, and sphingomyelin interactions of the p24 transmembrane region using circular dichroism, tryptophan fluorescence, and solid-state nuclear magnetic resonance (NMR) spectroscopies of the polypeptides and the surrounding lipids. Membrane insertion and/or conformation of the TMD is strongly dependent on the membrane lipid composition where the transmembrane helical insertion is strongest in the presence of 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC) and SM-C18. By analyzing solid-state NMR angular restraints from a large number of labeled sites, we have found a tilt angle of 19° for the transmembrane helical domain at a peptide-to-lipid ratio of 1 mol %. Only minor changes in the solid-state NMR spectra are observed due to the presence of SM-C18; the only visible alterations are associated with the SM-C18 recognition motif close to the carboxy-terminal part of the hydrophobic transmembrane region in the proximity of the SM headgroup. Finally, the deuterium order parameters of POPC- d31 were nearly unaffected by the presence of SM-C18 or the polypeptide alone but decreased noticeably when the sphingomyelin and the polypeptide were added in combination.
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Affiliation(s)
- Christopher Aisenbrey
- Université de Strasbourg/CNRS, UMR7177 , Institut de Chimie , 4, rue Blaise Pascal , 67070 Strasbourg , France
| | - Patricia Kemayo-Koumkoua
- Université de Strasbourg/CNRS, UMR7177 , Institut de Chimie , 4, rue Blaise Pascal , 67070 Strasbourg , France
| | - Evgeniy S Salnikov
- Université de Strasbourg/CNRS, UMR7177 , Institut de Chimie , 4, rue Blaise Pascal , 67070 Strasbourg , France
| | - Elise Glattard
- Université de Strasbourg/CNRS, UMR7177 , Institut de Chimie , 4, rue Blaise Pascal , 67070 Strasbourg , France
| | - Burkhard Bechinger
- Université de Strasbourg/CNRS, UMR7177 , Institut de Chimie , 4, rue Blaise Pascal , 67070 Strasbourg , France
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30
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Keyvanloo A, Shaghaghi M, Zuckermann MJ, Thewalt JL. The Phase Behavior and Organization of Sphingomyelin/Cholesterol Membranes: A Deuterium NMR Study. Biophys J 2019; 114:1344-1356. [PMID: 29590592 DOI: 10.1016/j.bpj.2018.01.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 01/10/2018] [Accepted: 01/18/2018] [Indexed: 10/17/2022] Open
Abstract
We have studied the dependence of the phase and domain characteristics of sphingomyelin (SM)/cholesterol model membranes on sterol content and temperature using deuterium nuclear magnetic resonance. NMR spectra of N-palmitoyl(D31)-D-erythro-sphingosylphosphorylcholine (PSM-d31) were taken for temperatures from 25 to 70°C and cholesterol concentrations of 0-40%. Analogous experiments were performed using 1-palmitoyl,2-palmitoyl(D31)-sn-glycero-3-phosphocholine (DPPC-d31)/cholesterol membranes to carefully compare the data obtained using palmitoyl chains that have similar "kinked" conformations. The constructed phase diagrams exhibit both solid-ordered (so) + liquid-ordered (lo) and liquid-disordered (ld) + lo phase-coexistence regions with a clear three-phase line. Macroscopic (micron-sized) coexistence of ld and lo phases was not observed; instead, line-broadening in the ld+lo region was characterized by intermediate exchange of lipids between the two types of domains. The length scales associated with the domains were estimated to be 75-150 nm for PSM-d31/cholesterol and DPPC-d31/cholesterol model membranes.
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Affiliation(s)
- Amir Keyvanloo
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Mehran Shaghaghi
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Martin J Zuckermann
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jenifer L Thewalt
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada; Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
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31
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Borcik CG, Versteeg DB, Wylie BJ. An Inward-Rectifier Potassium Channel Coordinates the Properties of Biologically Derived Membranes. Biophys J 2019; 116:1701-1718. [PMID: 31010661 DOI: 10.1016/j.bpj.2019.03.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 03/20/2019] [Accepted: 03/25/2019] [Indexed: 12/13/2022] Open
Abstract
KirBac1.1 is a prokaryotic inward-rectifier K+ channel from Burkholderia pseudomallei. It shares the common inward-rectifier K+ channel fold with eukaryotic channels, including conserved lipid-binding pockets. Here, we show that KirBac1.1 changes the phase properties and dynamics of the surrounding bilayer. KirBac1.1 was reconstituted into vesicles composed of 13C-enriched biological lipids. Two-dimensional liquid-state and solid-state NMR experiments were used to assign lipid 1H and 13C chemical shifts as a function of lipid identity and conformational degrees of freedom. A solid-state NMR temperature series reveals that KirBac1.1 lowers the primary thermotropic phase transition of Escherichia coli lipid membranes while introducing both fluidity and internal lipid order into the fluid phases. In B. thailandensis liposomes, the bacteriohopanetetrol hopanoid, and potentially ornithine lipids, introduce a similar primary lipid-phase transition and liquid-ordered properties. Adding KirBac1.1 to B. thailandensis lipids increases B. thailandensis lipid fluidity while preserving internal lipid order. This synergistic effect of KirBac1.1 in bacteriohopanetetrol-rich membranes has implications for bilayer dynamic structure. If membrane proteins can anneal lipid translational degrees of freedom while preserving internal order, it could offer an explanation to the nature of liquid-ordered protein-lipid organization in vivo.
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Affiliation(s)
- Collin G Borcik
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas
| | - Derek B Versteeg
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas
| | - Benjamin J Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas.
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32
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Monnier N, Furlan AL, Buchoux S, Deleu M, Dauchez M, Rippa S, Sarazin C. Exploring the Dual Interaction of Natural Rhamnolipids with Plant and Fungal Biomimetic Plasma Membranes through Biophysical Studies. Int J Mol Sci 2019; 20:E1009. [PMID: 30813553 PMCID: PMC6429473 DOI: 10.3390/ijms20051009] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/20/2019] [Accepted: 02/23/2019] [Indexed: 12/12/2022] Open
Abstract
Rhamnolipids (RLs) are potential biocontrol agents for crop culture protection. Their mode of action has been proposed as dual, combining plant protection activation and antifungal activities. The present work focuses on the interaction of natural RLs with plant and fungi membrane models at the molecular scale. Representative models were constructed and the interaction with RLs was studied by Fourier transform infrared (FTIR) and deuterium nuclear magnetic resonance (²H NMR) spectroscopic measurements. Molecular dynamic (MD) simulations were performed to investigate RL insertion in lipid bilayers. Our results showed that the RLs fit into the membrane models and were located near the lipid phosphate group of the phospholipid bilayers, nearby phospholipid glycerol backbones. The results obtained with plant plasma membrane models suggest that the insertion of RLs inside the lipid bilayer did not significantly affect lipid dynamics. Oppositely, a clear fluidity increase of fungi membrane models was observed. This effect was related to the presence and the specific structure of ergosterol. The nature of the phytosterols could also influence the RL effect on plant plasma membrane destabilization. Subtle changes in lipid dynamics could then be linked with plant defense induction and the more drastic effects associated with fungal membrane destabilization.
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Affiliation(s)
- Noadya Monnier
- Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Université de Picardie Jules Verne (UPJV), 80039 Amiens, France.
- Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Sorbonne Universités, Université de Technologie de Compiègne, 60200 Compiègne, France.
| | - Aurélien L Furlan
- Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Université de Picardie Jules Verne (UPJV), 80039 Amiens, France.
| | - Sébastien Buchoux
- Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Université de Picardie Jules Verne (UPJV), 80039 Amiens, France.
| | - Magali Deleu
- Laboratoire de Biophysique Moléculaire aux Interfaces, Gembloux Agro-Bio Tech, B5030 Gembloux, Belgium.
| | - Manuel Dauchez
- Matrice Extracellulaire et Dynamique Cellulaire, UMR CNRS 7369, Chaire MAgICS, Université de Reims Champagne-Ardenne (URCA), 51687 Reims, France.
| | - Sonia Rippa
- Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Sorbonne Universités, Université de Technologie de Compiègne, 60200 Compiègne, France.
| | - Catherine Sarazin
- Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Université de Picardie Jules Verne (UPJV), 80039 Amiens, France.
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33
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Kinnun JJ, Bittman R, Shaikh SR, Wassall SR. DHA Modifies the Size and Composition of Raftlike Domains: A Solid-State 2H NMR Study. Biophys J 2019; 114:380-391. [PMID: 29401435 DOI: 10.1016/j.bpj.2017.11.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 11/14/2017] [Accepted: 11/17/2017] [Indexed: 01/22/2023] Open
Abstract
Docosahexaenoic acid is an omega-3 polyunsaturated fatty acid that relieves the symptoms of a wide variety of chronic inflammatory disorders. The structural mechanism is not yet completely understood. Our focus here is on the plasma membrane as a site of action. We examined the molecular organization of [2H31]-N-palmitoylsphingomyelin (PSM-d31) mixed with 1-palmitoyl-2-docosahexaenoylphosphatylcholine (PDPC) or 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), as a monounsaturated control, and cholesterol (chol) (1:1:1 mol) in a model membrane by solid-state 2H NMR. The spectra were analyzed in terms of segregation into ordered SM-rich/chol-rich (raftlike) and disordered PC-rich/chol-poor (nonraft) domains that are nanoscale in size. An increase in the size of domains is revealed when POPC was replaced by PDPC. Spectra that are single-component, attributed to fast exchange between domains (<45 nm), for PSM-d31 mixed with POPC and chol become two-component, attributed to slow exchange between domains (r > 30 nm), for PSM-d31 mixed with PDPC and chol. The resolution of separate signals from PSM-d31, and correspondingly from [3α-2H1]cholesterol (chol-d1) and 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylcholine (PDPC-d31), in raftlike and nonraft domains enabled us to determine the composition of the domains in the PDPC-containing membrane. Most of the lipid (28% SM, 29% chol, and 23% PDPC with respect to total lipid at 30°C) was found in the raftlike domain. Despite substantial infiltration of PDPC into raftlike domains, there appears to be minimal effect on the order of SM, implying the existence of internal structure that limits contact between SM and PDPC. Our results suggest a significant refinement to the model by which DHA regulates the architecture of ordered, sphingolipid-chol-enriched domains (rafts) in membranes.
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Affiliation(s)
- Jacob J Kinnun
- Department of Physics, Indiana University-Purdue University, Indianapolis, Indiana
| | - Robert Bittman
- Department of Chemistry and Biochemistry, Queens College of CUNY, Flushing, New York
| | - Saame Raza Shaikh
- Department of Nutrition, Gillings School of Global Public Health and School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Stephen R Wassall
- Department of Physics, Indiana University-Purdue University, Indianapolis, Indiana.
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34
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Molugu TR, Brown MF. Cholesterol Effects on the Physical Properties of Lipid Membranes Viewed by Solid-state NMR Spectroscopy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:99-133. [PMID: 30649757 DOI: 10.1007/978-3-030-04278-3_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this chapter, we review the physical properties of lipid/cholesterol mixtures involving studies of model membranes using solid-state NMR spectroscopy. The approach allows one to quantify the average membrane structure, fluctuations, and elastic deformation upon cholesterol interaction. Emphasis is placed on understanding the membrane structural deformation and emergent fluctuations at an atomistic level. Lineshape measurements using solid-state NMR spectroscopy give equilibrium structural properties, while relaxation time measurements study the molecular dynamics over a wide timescale range. The equilibrium properties of glycerophospholipids, sphingolipids, and their binary and tertiary mixtures with cholesterol are accessible. Nonideal mixing of cholesterol with other lipids explains the occurrence of liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids, and may drive formation of lipid rafts. The functional dependence of 2H NMR spin-lattice relaxation (R 1Z) rates on segmental order parameters (S CD) for lipid membranes is indicative of emergent viscoelastic properties. Addition of cholesterol shows stiffening of the bilayer relative to the pure lipids and this effect is diminished for lanosterol. Opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale can potentially affect lipid raft formation in cellular membranes.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA. .,Department of Physics, University of Arizona, Tucson, AZ, USA.
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35
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Hanashima S, Ibata Y, Watanabe H, Yasuda T, Tsuchikawa H, Murata M. Side-chain deuterated cholesterol as a molecular probe to determine membrane order and cholesterol partitioning. Org Biomol Chem 2019; 17:8601-8610. [DOI: 10.1039/c9ob01342c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
24dCho, which perfectly retains the cholesterol's membrane properties, was developed to examine cholesterol's interactions and membrane partitions using solid state 2H NMR.
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Affiliation(s)
- Shinya Hanashima
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Yuki Ibata
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Hirofumi Watanabe
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Tomokazu Yasuda
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Hiroshi Tsuchikawa
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Michio Murata
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
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36
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Lipid bilayer position and orientation of novel carprofens, modulators of γ-secretase in Alzheimer's disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2224-2233. [PMID: 30409518 DOI: 10.1016/j.bbamem.2018.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 08/02/2018] [Accepted: 09/05/2018] [Indexed: 11/21/2022]
Abstract
γ-Secretase is an integral membrane protein complex and is involved in the cleavage of the amyloid precursor protein APP to produce amyloid-β peptides. Amyloid-β peptides are considered causative agents for Alzheimer's disease and drugs targeted at γ-secretase are investigated as therapeutic treatments. We synthesized new carprofen derivatives, which showed γ-secretase modulating activity and determined their precise position, orientation, and dynamics in lipid membranes by combining neutron diffraction, solid-state NMR spectroscopy, and molecular dynamics simulations. Our data indicate that the carprofen derivatives are inserted into the membrane interface, where the exact position and orientation depends on the lipid phase. This knowledge will help to understand the docking of carprofen derivatives to γ-secretase and in the design of new potent drugs. The approach presented here promises to serve as a general guideline how drug/target interactions in membranes can be analyzed in a comprehensive manner.
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37
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Yasuda T, Slotte JP, Murata M. Nanosized Phase Segregation of Sphingomyelin and Dihydrosphigomyelin in Unsaturated Phosphatidylcholine Binary Membranes without Cholesterol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:13426-13437. [PMID: 30350701 DOI: 10.1021/acs.langmuir.8b02637] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this study, we applied fluorescence spectroscopy, differential scanning calorimetry (DSC), and 2H NMR to elucidate the properties of nanoscopic segregated domains in stearoylsphingomyelin (SSM)/dioleoylphosphatidylcholine (DOPC) and dihydrostearoylsphingomyelin (dhSSM)/DOPC binary membranes. The results obtained from fluorescence measurements suggest the existence of gel-like domains with high fluidity in both SSM and dhSSM macroscopic gel phases. The DSC thermograms showed that DOPC destabilizes SM-rich gel-like domains to a much lesser extent compared to the same amount of cholesterol. It was also found that a stable lateral segregation occurs without cholesterol, indicating that SSM itself undergoes homophilic interactions to form small gel-like domains. 2H NMR experiments disclosed differences in the temperature-dependent ordering of SSM/DOPC and dhSSM/DOPC bilayers; the dhSSM membrane showed less miscibility with the DOPC fluid phase, higher thermal stability, and tighter packing. In addition, the NMR results suggest the formation of mid-sized gel-like aggregates consisting of dhSSM. These differences could be accounted for by homophilic interactions, as previously reported ( Yasuda Biophys. J. 2016 , 110 , 431 - 440 ). In the absence of cholesterol, the moderately strong sphingomyelin (SM)/SM affinity results in the formation of small gel-like domains, whereas a stronger dhSSM/dhSSM affinity leads to larger gel-like domains. Considering the similar physicochemical features of SSM and dhSSM, the present results suggest that the formation of nanosized domains of SM is better characterized by homophilic interactions than by SM-cholesterol interplay. These effects are considered important to the ordered domain formation of SMs in biological membranes.
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Affiliation(s)
- Tomokazu Yasuda
- Department of Chemistry, Graduate School of Science , Osaka University , Toyonaka , Osaka 560-0043 , Japan
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Tykistökatu 6A , Turku FIN-20520 , Finland
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering , Åbo Akademi University , Tykistökatu 6A , Turku FIN-20520 , Finland
| | - Michio Murata
- Department of Chemistry, Graduate School of Science , Osaka University , Toyonaka , Osaka 560-0043 , Japan
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38
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Podewitz M, Wang Y, Gkeka P, von Grafenstein S, Liedl KR, Cournia Z. Phase Diagram of a Stratum Corneum Lipid Mixture. J Phys Chem B 2018; 122:10505-10521. [DOI: 10.1021/acs.jpcb.8b07200] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Maren Podewitz
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Yin Wang
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Paraskevi Gkeka
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527 Athens, Greece
| | - Susanne von Grafenstein
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Klaus R. Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
| | - Zoe Cournia
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527 Athens, Greece
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39
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Kumari P, Kaur S, Sharma S, Kashyap HK. Impact of amphiphilic molecules on the structure and stability of homogeneous sphingomyelin bilayer: Insights from atomistic simulations. J Chem Phys 2018; 148:165102. [DOI: 10.1063/1.5021310] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Affiliation(s)
- Pratibha Kumari
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Supreet Kaur
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Shobha Sharma
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Hemant K. Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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40
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Oropesa-Nuñez R, Seghezza S, Dante S, Diaspro A, Cascella R, Cecchi C, Stefani M, Chiti F, Canale C. Interaction of toxic and non-toxic HypF-N oligomers with lipid bilayers investigated at high resolution with atomic force microscopy. Oncotarget 2018; 7:44991-45004. [PMID: 27391440 PMCID: PMC5216700 DOI: 10.18632/oncotarget.10449] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 06/26/2016] [Indexed: 11/25/2022] Open
Abstract
Protein misfolded oligomers are considered the most toxic species amongst those formed in the process of amyloid formation and the molecular basis of their toxicity, although not completely understood, is thought to originate from the interaction with the cellular membrane. Here, we sought to highlight the molecular determinants of oligomer-membrane interaction by atomic force microscopy. We monitored the interaction between multiphase supported lipid bilayers and two types of HypF-N oligomers displaying different structural features and cytotoxicities. By our approach we imaged with unprecedented resolution the ordered and disordered lipid phases of the bilayer and different oligomer structures interacting with either phase. We identified the oligomers and lipids responsible for toxicity and, more generally, we established the importance of the membrane lipid component in mediating oligomer toxicity. Our findings support the importance of GM1 ganglioside in mediating the oligomer-bilayer interaction and support a mechanism of oligomer cytotoxicity involving bilayer destabilization by globular oligomers within GM1-rich ordered raft regions rather than by annular oligomers in the surrounding disordered membrane domains.
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Affiliation(s)
- Reinier Oropesa-Nuñez
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy.,DIBRIS Department, University of Genova, Genova, Italy
| | - Silvia Seghezza
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy
| | - Silvia Dante
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy
| | - Alberto Diaspro
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy.,Department of Physics, University of Genova, Genova, Italy
| | - Roberta Cascella
- Section of Biochemistry, Department of Biomedical Experimental and Clinical Sciences, University of Florence, Firenze, Italy
| | - Cristina Cecchi
- Section of Biochemistry, Department of Biomedical Experimental and Clinical Sciences, University of Florence, Firenze, Italy
| | - Massimo Stefani
- Section of Biochemistry, Department of Biomedical Experimental and Clinical Sciences, University of Florence, Firenze, Italy
| | - Fabrizio Chiti
- Section of Biochemistry, Department of Biomedical Experimental and Clinical Sciences, University of Florence, Firenze, Italy
| | - Claudio Canale
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy
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41
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Molugu TR, Lee S, Brown MF. Concepts and Methods of Solid-State NMR Spectroscopy Applied to Biomembranes. Chem Rev 2017; 117:12087-12132. [PMID: 28906107 DOI: 10.1021/acs.chemrev.6b00619] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Concepts of solid-state NMR spectroscopy and applications to fluid membranes are reviewed in this paper. Membrane lipids with 2H-labeled acyl chains or polar head groups are studied using 2H NMR to yield knowledge of their atomistic structures in relation to equilibrium properties. This review demonstrates the principles and applications of solid-state NMR by unifying dipolar and quadrupolar interactions and highlights the unique features offered by solid-state 2H NMR with experimental illustrations. For randomly oriented multilamellar lipids or aligned membranes, solid-state 2H NMR enables direct measurement of residual quadrupolar couplings (RQCs) due to individual C-2H-labeled segments. The distribution of RQC values gives nearly complete profiles of the segmental order parameters SCD(i) as a function of acyl segment position (i). Alternatively, one can measure residual dipolar couplings (RDCs) for natural abundance lipid samples to obtain segmental SCH order parameters. A theoretical mean-torque model provides acyl-packing profiles representing the cumulative chain extension along the normal to the aqueous interface. Equilibrium structural properties of fluid bilayers and various thermodynamic quantities can then be calculated, which describe the interactions with cholesterol, detergents, peptides, and integral membrane proteins and formation of lipid rafts. One can also obtain direct information for membrane-bound peptides or proteins by measuring RDCs using magic-angle spinning (MAS) in combination with dipolar recoupling methods. Solid-state NMR methods have been extensively applied to characterize model membranes and membrane-bound peptides and proteins, giving unique information on their conformations, orientations, and interactions in the natural liquid-crystalline state.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry & Biochemistry and ‡Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
| | - Soohyun Lee
- Department of Chemistry & Biochemistry and ‡Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
| | - Michael F Brown
- Department of Chemistry & Biochemistry and ‡Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
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42
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The Affinity of Cholesterol for Different Phospholipids Affects Lateral Segregation in Bilayers. Biophys J 2017; 111:546-556. [PMID: 27508438 DOI: 10.1016/j.bpj.2016.06.036] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 06/21/2016] [Accepted: 06/29/2016] [Indexed: 12/20/2022] Open
Abstract
Saturated and unsaturated phospholipids (PLs) can segregate into lateral domains. The preference of cholesterol for saturated acyl chains over monounsaturated, and especially polyunsaturated ones, may also affect lateral segregation. Here we have studied how cholesterol influenced the lateral segregation of saturated and unsaturated PLs, for which cholesterol had a varying degree of affinity. The fluorescence lifetime of trans-parinaric acid reported the formation of ordered domains (gel or liquid-ordered (lo)) in bilayers composed of different unsaturated phosphatidylcholines, and dipalmitoyl-phosphatidylcholine or n-palmitoyl-sphingomyelin, in the presence or absence of cholesterol. We observed that cholesterol facilitated lateral segregations and the degree of facilitation correlated with the relative affinity of cholesterol for the different PLs in the bilayers. Differential scanning calorimetry and (2)H nuclear magnetic resonance showed that cholesterol increased the thermostability of both the gel and lo-domains. Increased number of double bonds in the unsaturated PL increased the order in the lo-domains, likely by enriching the ordered domains in saturated lipids and cholesterol. This supported the conclusions from the trans-parinaric acid experiments, and offers insight into how cholesterol facilitated lateral segregation. In conclusion, the relative affinity of cholesterol for different PLs appears to be an important determinant for the formation of ordered domains. Our data suggests that knowledge of the affinity of cholesterol for the different PLs in a bilayer allows prediction of the degree to which the sterol promotes lo-domain formation.
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43
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Bera I, Klauda JB. Molecular Simulations of Mixed Lipid Bilayers with Sphingomyelin, Glycerophospholipids, and Cholesterol. J Phys Chem B 2017; 121:5197-5208. [DOI: 10.1021/acs.jpcb.7b00359] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Indrani Bera
- Department
of Chemical and Biomolecular Engineering and ‡Biophysics Program, University of Maryland, College Park, Maryland 20742, United States
| | - Jeffery B. Klauda
- Department
of Chemical and Biomolecular Engineering and ‡Biophysics Program, University of Maryland, College Park, Maryland 20742, United States
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44
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Wang E, Klauda JB. Examination of Mixtures Containing Sphingomyelin and Cholesterol by Molecular Dynamics Simulations. J Phys Chem B 2017; 121:4833-4844. [DOI: 10.1021/acs.jpcb.7b01832] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Eric Wang
- Department
of Chemical and Biomolecular Engineering and ‡Biophysics Graduate Program, University of Maryland, College Park, Maryland 20742, United States
| | - Jeffery B. Klauda
- Department
of Chemical and Biomolecular Engineering and ‡Biophysics Graduate Program, University of Maryland, College Park, Maryland 20742, United States
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45
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Engberg O, Yasuda T, Hautala V, Matsumori N, Nyholm TKM, Murata M, Slotte JP. Lipid Interactions and Organization in Complex Bilayer Membranes. Biophys J 2016; 110:1563-1573. [PMID: 27074681 DOI: 10.1016/j.bpj.2015.12.043] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/01/2015] [Accepted: 12/21/2015] [Indexed: 11/18/2022] Open
Abstract
Bilayer lipids influence the lateral structure of the membranes, but the relationship between lipid properties and the lateral structure formed is not always understood. Model membrane studies on bilayers containing cholesterol and various phospholipids (PLs) suggest that high and low temperature melting PLs may segregate, especially in the presence of cholesterol. The effect of different PL headgroups on lateral structure of bilayers is also not clear. Here, we have examined the formation of lateral heterogeneity in increasingly complex (up to five-component) multilamellar bilayers. We have used time-resolved fluorescence spectroscopy with domain-selective fluorescent probes (PL-conjugated trans-parinaric acid), and (2)H NMR spectroscopy with site or perdeuterated PLs. We have measured changes in bilayer order using such domain-selective probes both as a function of temperature and composition. Our results from time-resolved fluorescence and (2)H NMR showed that in ternary bilayers, acyl chain order and thermostability in sphingomyelin-rich domains were not affected to any greater extent by the headgroup structure of the monounsaturated PLs (phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine) in the bilayer. In the complex five-component bilayers, we could not detect major differences between the different monounsaturated PLs regarding cholesterol-induced ordering. However, cholesterol clearly influenced deuterated N-palmitoyl sphingomyelin differently than the other deuterated PLs, suggesting that cholesterol favored N-palmitoyl sphingomyelin over the other PLs. Taken together, both the fluorescence spectroscopy and (2)H NMR data suggest that the complex five-component membranes displayed lateral heterogeneity, at least in the lower temperature regimen examined.
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Affiliation(s)
- Oskar Engberg
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Tomokazu Yasuda
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan; Lipid Active Structure Project, Japan Science and Technology Agency, ERATO, Toyonaka, Osaka, Japan
| | - Victor Hautala
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Nobuaki Matsumori
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan; Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
| | - Thomas K M Nyholm
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan; Lipid Active Structure Project, Japan Science and Technology Agency, ERATO, Toyonaka, Osaka, Japan.
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
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46
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Arnarez C, Webb A, Rouvière E, Lyman E. Hysteresis and the Cholesterol Dependent Phase Transition in Binary Lipid Mixtures with the Martini Model. J Phys Chem B 2016; 120:13086-13093. [PMID: 27976582 DOI: 10.1021/acs.jpcb.6b09728] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Extensive Martini simulation data, totaling 5 ms, is presented for binary mixtures of dipalmitoylphosphatidylcholine (DPPC) and cholesterol. Using simulation initiated from both gel (so) and liquid-disordered (Ld) phases, significant and strongly cholesterol-dependent hysteresis in the enthalpy as a function of temperature is observed for cholesterol mole fractions from 0 to 20 mol %. Although the precise phase transition temperature cannot be determined due to the hysteresis, the data are consistent with a first order gel to fluid transition, which increases in temperature with cholesterol. At 30 mol % cholesterol, no hysteresis is observed, and there is no evidence for a continuous transition, in either structural parameters like the area per lipid or in the heat capacity as a function of temperature. The results are consistent with a single uniform phase above a critical cholesterol composition between 20 and 30 mol % in Martini, while highlighting the importance and difficulty of obtaining the equilibrium averages to locate phase boundaries precisely in computational models of lipid bilayers.
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Affiliation(s)
- Clement Arnarez
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States
| | - Alexis Webb
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States
| | - Eric Rouvière
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States
| | - Edward Lyman
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States.,Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
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47
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Boughter CT, Monje-Galvan V, Im W, Klauda JB. Influence of Cholesterol on Phospholipid Bilayer Structure and Dynamics. J Phys Chem B 2016; 120:11761-11772. [DOI: 10.1021/acs.jpcb.6b08574] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Christopher T. Boughter
- Department
of Chemical and Biomolecular Engineering, University of Maryland, College
Park, Maryland 20742, United States
| | - Viviana Monje-Galvan
- Department
of Chemical and Biomolecular Engineering, University of Maryland, College
Park, Maryland 20742, United States
| | - Wonpil Im
- Department
of Biological Sciences and Bioengineering Program, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Jeffery B. Klauda
- Department
of Chemical and Biomolecular Engineering, University of Maryland, College
Park, Maryland 20742, United States
- Biophysics
Program, University of Maryland, College Park, Maryland 20742, United States
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48
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Vogel A, Scheidt HA, Baek DJ, Bittman R, Huster D. Structure and dynamics of the aliphatic cholesterol side chain in membranes as studied by (2)H NMR spectroscopy and molecular dynamics simulation. Phys Chem Chem Phys 2016; 18:3730-8. [PMID: 26762541 DOI: 10.1039/c5cp05084g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cholesterol is an evolutionarily highly optimized molecule particularly known for its ability to condense the phospholipids in cellular membranes. Until recently, the accompanying increase in the chain order of the surrounding phospholipids was attributed to the planar and rigid tetracyclic ring structure of cholesterol. However, detailed investigations of cholesterol's aliphatic side chain demonstrated that this side chain is responsible for approximately half of the condensation effect. Therefore, we investigated the structure and dynamics of the aliphatic side chain of cholesterol using (2)H solid-state nuclear magnetic resonance (NMR) spectroscopy and microsecond timescale all-atom molecular dynamics (MD) simulations in four different model membranes: POPC, DPPC, PSM, and POPC/PSM (1 : 1 mol/mol) and at three different temperatures: 5 °C, 37 °C, and 50 °C. A cholesterol variant, in which 11 hydrogens of the aliphatic side chain were exchanged for deuterium, was used and the respective (2)H NMR spectra confirmed the axially asymmetric rotational diffusion of cholesterol in DPPC and PSM. Furthermore, NMR spectra indicated that some hydrogens showed an unexpected magnetic inequivalency. This finding was confirmed by all-atom molecular dynamics simulations and detailed analysis revealed that the hydrogens of the methylene groups at C22, C23, and C24 are magnetically inequivalent. This inequivalency is caused by steric clashes of the aliphatic side chain with the ring structure of cholesterol as well as the branched C21 methyl group. These excluded volume effects result in reduced conformational flexibility of the aliphatic side chain of cholesterol and explain its high order (order parameter of 0.78 for chain motions) and large contribution to the condensation effect. Additionally, the motional pattern of the side chain becomes highly anisotropic such that it shows larger fluctuations perpendicular to the ring plane of cholesterol with a biaxiality of the distribution of 0.046. Overall, our results shed light on the mechanism how the aliphatic side chain is able to contribute about half of the condensation effect of cholesterol.
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Affiliation(s)
- Alexander Vogel
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany.
| | - Holger A Scheidt
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany.
| | - Dong Jae Baek
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Jeonnam, Republic of Korea and Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, NY 11367-1597, USA
| | - Robert Bittman
- Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, NY 11367-1597, USA
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04275 Leipzig, Germany.
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Marquardt D, Kučerka N, Wassall SR, Harroun TA, Katsaras J. Cholesterol's location in lipid bilayers. Chem Phys Lipids 2016; 199:17-25. [DOI: 10.1016/j.chemphyslip.2016.04.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Revised: 04/01/2016] [Accepted: 04/02/2016] [Indexed: 02/07/2023]
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50
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Sodt AJ, Pastor RW, Lyman E. Hexagonal Substructure and Hydrogen Bonding in Liquid-Ordered Phases Containing Palmitoyl Sphingomyelin. Biophys J 2016; 109:948-55. [PMID: 26331252 DOI: 10.1016/j.bpj.2015.07.036] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 07/11/2015] [Accepted: 07/14/2015] [Indexed: 10/23/2022] Open
Abstract
All-atom simulation data are presented for ternary mixtures of palmitoyl sphingomyelin (PSM), cholesterol, and either palmitoyl oleoyl phosphatidyl choline or dioleoyl phosphatidyl choline (DOPC). For comparison, data for a mixture of dipalmitoyl phosphatidyl choline (DPPC), cholesterol, and DOPC are also presented. Compositions corresponding to the liquid-ordered phase, the liquid-disordered phase, and coexistence of the two phases are simulated for each mixture. Within the liquid-ordered phase, cholesterol is preferentially solvated by DOPC if it is available, but if DOPC is replaced by POPC, cholesterol is preferentially solvated by PSM. In the DPPC mixtures, cholesterol interacts preferentially with the saturated chains via its smooth face, whereas in the PSM mixtures, cholesterol interacts preferentially with PSM via its rough face. Interactions between cholesterol and PSM have a very particular character: hydrogen bonding between cholesterol and the amide of PSM rotates the tilt of the amide plane, which primes it for more robust hydrogen bonding with other PSM. Cholesterol-PSM hydrogen bonding also locally modifies the hexagonal packing of hydrocarbon chains in the liquid-ordered phase of PSM mixtures.
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Affiliation(s)
- Alexander J Sodt
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Richard W Pastor
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Edward Lyman
- Department of Physics and Astronomy and Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware.
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