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Knyazev DG, Winter L, Vogt A, Posch S, Öztürk Y, Siligan C, Goessweiner-Mohr N, Hagleitner-Ertugrul N, Koch HG, Pohl P. YidC from Escherichia coli Forms an Ion-Conducting Pore upon Activation by Ribosomes. Biomolecules 2023; 13:1774. [PMID: 38136645 PMCID: PMC10741985 DOI: 10.3390/biom13121774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 12/01/2023] [Accepted: 12/06/2023] [Indexed: 12/24/2023] Open
Abstract
The universally conserved protein YidC aids in the insertion and folding of transmembrane polypeptides. Supposedly, a charged arginine faces its hydrophobic lipid core, facilitating polypeptide sliding along YidC's surface. How the membrane barrier to other molecules may be maintained is unclear. Here, we show that the purified and reconstituted E. coli YidC forms an ion-conducting transmembrane pore upon ribosome or ribosome-nascent chain complex (RNC) binding. In contrast to monomeric YidC structures, an AlphaFold parallel YidC dimer model harbors a pore. Experimental evidence for a dimeric assembly comes from our BN-PAGE analysis of native vesicles, fluorescence correlation spectroscopy studies, single-molecule fluorescence photobleaching observations, and crosslinking experiments. In the dimeric model, the conserved arginine and other residues interacting with nascent chains point into the putative pore. This result suggests the possibility of a YidC-assisted insertion mode alternative to the insertase mechanism.
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Affiliation(s)
- Denis G. Knyazev
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
| | - Lukas Winter
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
| | - Andreas Vogt
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, Albert Ludwig University of Freiburg, 79104 Freiburg, Germany (Y.Ö.); (H.-G.K.)
- Spemann-Graduate School of Biology and Medicine (SGBM), Albert Ludwig University of Freiburg, 79104 Freiburg, Germany
- Faculty of Biology, Albert Ludwig University of Freiburg, 79104 Freiburg, Germany
| | - Sandra Posch
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
| | - Yavuz Öztürk
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, Albert Ludwig University of Freiburg, 79104 Freiburg, Germany (Y.Ö.); (H.-G.K.)
| | - Christine Siligan
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
| | - Nikolaus Goessweiner-Mohr
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
| | - Nora Hagleitner-Ertugrul
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
| | - Hans-Georg Koch
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, Albert Ludwig University of Freiburg, 79104 Freiburg, Germany (Y.Ö.); (H.-G.K.)
- Spemann-Graduate School of Biology and Medicine (SGBM), Albert Ludwig University of Freiburg, 79104 Freiburg, Germany
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; (D.G.K.); (L.W.); (S.P.); (C.S.); (N.G.-M.); (N.H.-E.)
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2
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Wachlmayr J, Fläschner G, Pluhackova K, Sandtner W, Siligan C, Horner A. Entropic barrier of water permeation through single-file channels. Commun Chem 2023; 6:135. [PMID: 37386127 DOI: 10.1038/s42004-023-00919-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 06/02/2023] [Indexed: 07/01/2023] Open
Abstract
Facilitated water permeation through narrow biological channels is fundamental for all forms of life. Despite its significance in health and disease as well as for biotechnological applications, the energetics of water permeation are still elusive. Gibbs free energy of activation is composed of an enthalpic and an entropic component. Whereas the enthalpic contribution is readily accessible via temperature dependent water permeability measurements, estimation of the entropic contribution requires information on the temperature dependence of the rate of water permeation. Here, we estimate, by means of accurate activation energy measurements of water permeation through Aquaporin-1 and by determining the accurate single channel permeability, the entropic barrier of water permeation through a narrow biological channel. Thereby the calculated value for [Formula: see text] = 2.01 ± 0.82 J/(mol·K) links the activation energy of 3.75 ± 0.16 kcal/mol with its efficient water conduction rate of ~1010 water molecules/second. This is a first step in understanding the energetic contributions in various biological and artificial channels exhibiting vastly different pore geometries.
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Affiliation(s)
- Johann Wachlmayr
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Gotthold Fläschner
- Department of Biosystems Science and Engineering, Eidgenössiche Technische Hochschule (ETH) Zürich, Basel, Switzerland
| | - Kristyna Pluhackova
- Stuttgart Center for Simulation Science, Cluster of Excellence EXC 2075, University of Stuttgart, Universitätsstr. 32, 70569, Stuttgart, Germany
| | - Walter Sandtner
- Center of Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Schwarzspanierstr. 17A, 1090, Vienna, Austria
| | - Christine Siligan
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Andreas Horner
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria.
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3
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Yılmaz H, Erdoğan EM, Ergenekon P, Özkan M. Comparison of ion selectivities of nitrite channel NirC and water channel aquaporin. World J Microbiol Biotechnol 2023; 39:120. [PMID: 36918441 DOI: 10.1007/s11274-023-03553-z] [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] [Received: 09/21/2022] [Accepted: 02/20/2023] [Indexed: 03/16/2023]
Abstract
nirC gene coding for the nitrite channel of E. coli K12 was cloned into the pET28a vector and expressed in E. coli BL21 cells. 28.5 kDa NirC monomer was purified from membrane components of E. coli. Selectivity of NirC for different ions including nitrite, nitrate, sulfate, formate, and acetate anions, and a divalent cation, magnesium, was compared with that of bacterial aquaporin from Halomonas elongata. Water and ion permeability values were determined by measuring the light scattering rates of proteoliposomes containing NirC and aquaporins during their water loss and gain. NirC shows a selective permeability to nitrite and is more resistant to the entry of other anions as compared to aquaporin. The single channel permeability of NirC for nitrite is about 10-fold that of a single aquaporin channel. Both aquaporin and NirC channel proteins were impermeable to MgCl2 and (NH4)2SO4 and their permeability to other tested ions was remarkably lower as compared to nitrite ions. The study also presents the 3D model and channel characteristics of NirC. The translocation channel of E. coli NirC is determined to be larger, and its length is shorter than aquaporin channels. Although the NirC channel throat is more hydrophobic than aquaporin, its water permeability is almost equal to that of aquaporin. The hydrophobic nature of the NirC channel might play an important role in the selective permeability of the channel for nitrite ions.
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Affiliation(s)
- Hilal Yılmaz
- Environmental Engineering Department, Gebze Technical University, 41400, Kocaeli, Turkey
| | - Esra Meşe Erdoğan
- Environmental Engineering Department, Gebze Technical University, 41400, Kocaeli, Turkey
| | - Pınar Ergenekon
- Environmental Engineering Department, Gebze Technical University, 41400, Kocaeli, Turkey
| | - Melek Özkan
- Environmental Engineering Department, Gebze Technical University, 41400, Kocaeli, Turkey.
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Danaeifar M, Ocheje OM, Mazlomi MA. Exploitation of renewable energy sources for water desalination using biological tools. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:32193-32213. [PMID: 36725802 DOI: 10.1007/s11356-023-25642-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 01/26/2023] [Indexed: 06/18/2023]
Abstract
The emerging impacts of climate change and the growing world population are driving the demand for more food resources and creating an urgent need for new water resources. About 93% of Earth's surface is made up of water bodies, mainly oceans. Seawater attracted a lot of attention in order to be used as a sustainable source of usable water. However, an essential step in harnessing this source of water is desalination. Utilizing renewable sources of energy, biology offers several tools for removal of salts. This article for the first time reviews all currently available biological water desalination tools and compares their efficiency with industrial systems. Bacteria are employed as electrical power generators to provide the energy needed for desalination in microbial desalination cells. Its salt removal efficiency varied from 0.8 to 30 g/L/d. Many strains of algal cells can grow in high concentrations of salts, adsorb and accumulate it inside the cell, and therefore could be used without prior treatment for seawater desalination. This biological tool can yield salt removal efficiency of 0.4-5 g/L/d. Biopolymers are also used for treatment of seawater through enhancing water evaporation as a component of solar steam generators. Despite significant advances in biological water desalination, further modifications and improvements are still needed to make its use sustainable and cost-effective.
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Affiliation(s)
- Mohsen Danaeifar
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Onuche Musa Ocheje
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Ali Mazlomi
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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Pfeffermann J, Pohl P. Tutorial for Stopped-Flow Water Flux Measurements: Why a Report about “Ultrafast Water Permeation through Nanochannels with a Densely Fluorous Interior Surface” Is Flawed. Biomolecules 2023; 13:biom13030431. [PMID: 36979366 PMCID: PMC10046062 DOI: 10.3390/biom13030431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/02/2023] [Accepted: 02/20/2023] [Indexed: 03/03/2023] Open
Abstract
Millions of years of evolution have produced proteinaceous water channels (aquaporins) that combine perfect selectivity with a transport rate at the edge of the diffusion limit. However, Itoh et al. recently claimed in Science that artificial channels are 100 times faster and almost as selective. The published deflation kinetics of vesicles containing channels or channel elements indicate otherwise, since they do not demonstrate the facilitation of water transport. In an illustrated tutorial on the experimental basis of stopped-flow measurements, we point out flaws in data processing. In contrast to the assumption voiced in Science, individual vesicles cannot simultaneously shrink with two different kinetics. Moreover, vesicle deflation within the dead time of the instrument cannot be detected. Since flawed reports of ultrafast water channels in Science are not a one-hit-wonder as evidenced by a 2018 commentary by Horner and Pohl in Science, we further discuss the achievable limits of single-channel water permeability. After analyzing (i) diffusion limits for permeation through narrow channels and (ii) hydrodynamics in the surrounding reservoirs, we conclude that it is unlikely to fundamentally exceed the evolutionarily optimized water-channeling performance of the fastest aquaporins while maintaining near-perfect selectivity.
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6
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Biophysical quantification of unitary solute and solvent permeabilities to enable translation to membrane science. J Memb Sci 2022. [DOI: 10.1016/j.memsci.2022.121308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Liu K, Guo J, Li Y, Chen J, Li P. High-Flux Ultrafiltration Membranes Combining Artificial Water Channels and Covalent Organic Frameworks. MEMBRANES 2022; 12:membranes12090824. [PMID: 36135843 PMCID: PMC9503389 DOI: 10.3390/membranes12090824] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/18/2022] [Accepted: 08/18/2022] [Indexed: 05/26/2023]
Abstract
Artificial water channels (AWCs) have been well investigated, and the imidazole-quartet water channel is one of the representative channels. In this work, covalent organic frameworks (COFs) composite membranes were fabricated through assembling COF layers and imidazole-quartet water channel. The membranes were synthesized by interfacial polymerization and self-assembly process, using polyacrylonitrile (PAN) ultrafiltration substrates with artificial water channels (HC6H) as modifiers. Effective combination of COF layers and imidazole-quartet water channels provide the membrane with excellent performance. The as-prepared membrane exhibits a water permeance above 271.7 L·m−2·h−1·bar−1, and high rejection rate (>99.5%) for CR. The results indicated that the composite structure based on AWCs and COFs may provide a new idea for the development of high-performance membranes for dye separation.
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Affiliation(s)
- Kai Liu
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Tianjin Key Laboratory of Membrane Science and Desalination Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, China
| | - Jinwen Guo
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Tianjin Key Laboratory of Membrane Science and Desalination Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, China
| | - Yingdong Li
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Tianjin Key Laboratory of Membrane Science and Desalination Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, China
| | - Jinguang Chen
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Tianjin Key Laboratory of Membrane Science and Desalination Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, China
| | - Pingli Li
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Tianjin Key Laboratory of Membrane Science and Desalination Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, China
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Shen J, Roy A, Joshi H, Samineni L, Ye R, Tu YM, Song W, Skiles M, Kumar M, Aksimentiev A, Zeng H. Fluorofoldamer-Based Salt- and Proton-Rejecting Artificial Water Channels for Ultrafast Water Transport. NANO LETTERS 2022; 22:4831-4838. [PMID: 35674810 DOI: 10.1021/acs.nanolett.2c01137] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Here, we report on a novel class of fluorofoldamer-based artificial water channels (AWCs) that combines excellent water transport rate and selectivity with structural simplicity and robustness. Produced by a facile one-pot copolymerization reaction under mild conditions, the best-performing channel (AWC 1) is an n-C8H17-decorated foldamer nanotube with an average channel length of 2.8 nm and a pore diameter of 5.2 Å. AWC 1 demonstrates an ultrafast water conduction rate of 1.4 × 1010 H2O/s per channel, outperforming the archetypal biological water channel, aquaporin 1, while excluding salts (i.e., NaCl and KCl) and protons. Unique to this class of channels, the inwardly facing C(sp2)-F atoms being the most electronegative in the periodic table are proposed as being critical to enabling the ultrafast and superselective water transport properties by decreasing the channel's cavity and enhancing the channel wall smoothness via reducing intermolecular forces with water molecules or hydrated ions.
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Affiliation(s)
- Jie Shen
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, China
| | - Arundhati Roy
- Department of Pharmacy, Ludwig Maximilian University Munich Butenandtstraße 5-13, Munich 81377, Germany
| | - Himanshu Joshi
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Laxmicharan Samineni
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Ruijuan Ye
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, China
| | - Yu-Ming Tu
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Woochul Song
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Matthew Skiles
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Manish Kumar
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Aleksei Aksimentiev
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Huaqiang Zeng
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, China
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Barta T, Sandtner W, Wachlmayr J, Hannesschlaeger C, Ebert A, Speletz A, Horner A. Modeling of SGLT1 in Reconstituted Systems Reveals Apparent Ion-Dependencies of Glucose Uptake and Strengthens the Notion of Water-Permeable Apo States. Front Physiol 2022; 13:874472. [PMID: 35784872 PMCID: PMC9242095 DOI: 10.3389/fphys.2022.874472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
The reconstitution of secondary active transporters into liposomes shed light on their molecular transport mechanism. The latter are either symporters, antiporters or exchangers, which use the energy contained in the electrochemical gradient of ions to fuel concentrative uptake of their cognate substrate. In liposomal preparations, these gradients can be set by the experimenter. However, due to passive diffusion of the ions and solutes through the membrane, the gradients are not stable and little is known on the time course by which they dissipate and how the presence of a transporter affects this process. Gradient dissipation can also generate a transmembrane potential (VM). Because it is the effective ion gradient, which together with VM fuels concentrative uptake, knowledge on how these parameters change within the time frame of the conducted experiment is key to understanding experimental outcomes. Here, we addressed this problem by resorting to a modelling approach. To this end, we mathematically modeled the liposome in the assumed presence and absence of the sodium glucose transporter 1 (SGLT1). We show that 1) the model can prevent us from reaching erroneous conclusions on the driving forces of substrate uptake and we 2) demonstrate utility of the model in the assignment of the states of SGLT1, which harbor a water channel.
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Affiliation(s)
- Thomas Barta
- Department of Molecular Biophysics and Membrane Biophysics, Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Walter Sandtner
- Center of Physiology and Pharmacology, Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Medical University of Vienna, Vienna, Austria
| | - Johann Wachlmayr
- Department of Molecular Biophysics and Membrane Biophysics, Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Christof Hannesschlaeger
- Department of Molecular Biophysics and Membrane Biophysics, Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Andrea Ebert
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research—UFZ, Leipzig, Germany
| | - Armin Speletz
- Department of Molecular Biophysics and Membrane Biophysics, Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Andreas Horner
- Department of Molecular Biophysics and Membrane Biophysics, Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
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The energetic barrier to single-file water flow through narrow channels. Biophys Rev 2022; 13:913-923. [PMID: 35035593 PMCID: PMC8724168 DOI: 10.1007/s12551-021-00875-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 10/26/2021] [Indexed: 10/30/2022] Open
Abstract
Various nanoscopic channels of roughly equal diameter and length facilitate single-file diffusion at vastly different rates. The underlying variance of the energetic barriers to transport is poorly understood. First, water partitioning into channels so narrow that individual molecules cannot overtake each other incurs an energetic penalty. Corresponding estimates vary widely depending on how the sacrifice of two out of four hydrogen bonds is accounted for. Second, entropy differences between luminal and bulk water may arise: additional degrees of freedom caused by dangling OH-bonds increase entropy. At the same time, long-range dipolar water interactions decrease entropy. Here, we dissect different contributions to Gibbs free energy of activation, ΔG ‡, for single-file water transport through narrow channels by analyzing experimental results from water permeability measurements on both bare lipid bilayers and biological water channels that (i) consider unstirred layer effects and (ii) adequately count the channels in reconstitution experiments. First, the functional relationship between water permeabilities and Arrhenius activation energies indicates negligible differences between the entropies of intraluminal water and bulk water. Second, we calculate ΔG ‡ from unitary water channel permeabilities using transition state theory. Plotting ΔG ‡ as a function of the number of H-bond donating or accepting pore-lining residues results in a 0.1 kcal/mol contribution per residue. The resulting upper limit for partial water dehydration amounts to 2 kcal/mol. In the framework of biomimicry, our analysis provides valuable insights for the design of synthetic water channels. It thus may aid in the urgent endeavor towards combating global water scarcity.
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Pohl P. Biophysical Reviews' "Meet the Councilor Series"-a profile of Peter Pohl. Biophys Rev 2021; 13:839-844. [PMID: 35035592 PMCID: PMC8724173 DOI: 10.1007/s12551-021-00897-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 11/01/2021] [Indexed: 10/30/2022] Open
Abstract
It is my pleasure to write a few words to introduce myself to the readers of Biophysical Reviews as part of the "Meet the Councilor Series." Currently, I am serving the second period as IUPAB councilor after having been elected first in 2017. Initially, I studied Biophysics in Moscow (Russia) and later Medicine in Halle (Germany). My scientific carrier took me from the Medical School of the Martin Luther University of Halle-Wittenberg, via the Leibniz Institute for Molecular Pharmacology (Berlin) and the Institute for Biology at the Humboldt University (Berlin) to the Physics Department of the Johannes Kepler University in Linz (Austria). My key research interests lie in the molecular mechanisms of transport phenomena occurring at the lipid membrane, including (i) spontaneous and facilitated transport of water and other small molecules across membranes in reconstituted systems, (ii) proton migration along the membrane surface, (iii) protein translocation, and (iv) bilayer mechanics. Training of undergraduate, graduate, and postdoctoral researchers from diverse academic disciplines has been-and shall remain-a consistent part of my work.
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Affiliation(s)
- Peter Pohl
- Institute of Biophysics, Johannes Kepler University, Linz, Austria
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Wu HC, Yoshioka T, Nakagawa K, Shintani T, Matsuyama H. Water Transport and Ion Diffusion Investigation of an Amphotericin B-Based Channel Applied to Forward Osmosis: A Simulation Study. MEMBRANES 2021; 11:membranes11090646. [PMID: 34564464 PMCID: PMC8467697 DOI: 10.3390/membranes11090646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 08/13/2021] [Accepted: 08/18/2021] [Indexed: 11/17/2022]
Abstract
The use of an Amphotericin B_Ergosterol (AmBEr) channel as an artificial water channel in forward osmosis filtration (FO) was studied via molecular dynamics (MD) simulation. Three channel models were constructed: a common AmBEr channel and two modified C3deOAmB_Ergosterol (C3deOAmBEr) channels with different diameters (12 Å and 18 Å). During FO filtration simulation, the osmotic pressure of salt-water was a driving force for water permeation. We examined the effect of the modified C3deOAmBEr channel on the water transport performance. By tracing the change of the number of water molecules along with simulation time in the saltwater region, the water permeability of the channel models could be calculated. A higher water permeability was observed for a modified C3deOAmBEr channel, and there was no ion permeation during the entire simulation period. The hydrated ions and water molecules were placed into the channel to explore the ion leakage behavior of the channels. The mean squared displacement (MSD) of ions and water molecules was obtained to study the ion leakage performance. The Amphotericin B-based channels showed excellent selectivity of water molecules against ions. The results obtained on an atomistic scale could assist in determining the properties and the optimal filtration applications for Amphotericin B-based channels.
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Affiliation(s)
- Hao-Chen Wu
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Tomohisa Yoshioka
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
- Correspondence: ; Tel.: +81-78-803-6299
| | - Keizo Nakagawa
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Takuji Shintani
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Hideto Matsuyama
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
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Roy A, Shen J, Joshi H, Song W, Tu YM, Chowdhury R, Ye R, Li N, Ren C, Kumar M, Aksimentiev A, Zeng H. Foldamer-based ultrapermeable and highly selective artificial water channels that exclude protons. NATURE NANOTECHNOLOGY 2021; 16:911-917. [PMID: 34017100 DOI: 10.1038/s41565-021-00915-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 04/06/2021] [Indexed: 06/12/2023]
Abstract
The outstanding capacity of aquaporins (AQPs) for mediating highly selective superfast water transport1-7 has inspired recent development of supramolecular monovalent ion-excluding artificial water channels (AWCs). AWC-based bioinspired membranes are proposed for desalination, water purification and other separation applications8-18. While some recent progress has been made in synthesizing AWCs that approach the water permeability and ion selectivity of AQPs, a hallmark feature of AQPs-high water transport while excluding protons-has not been reproduced. We report a class of biomimetic, helically folded pore-forming polymeric foldamers that can serve as long-sought-after highly selective ultrafast water-conducting channels with performance exceeding those of AQPs (1.1 × 1010 water molecules per second for AQP1), with high water-over-monovalent-ion transport selectivity (~108 water molecules over Cl- ion) conferred by the modularly tunable hydrophobicity of the interior pore surface. The best-performing AWC reported here delivers water transport at an exceptionally high rate, namely, 2.5 times that of AQP1, while concurrently rejecting salts (NaCl and KCl) and even protons.
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Affiliation(s)
- Arundhati Roy
- Department of Chemistry, College of Science, Hainan University, Haikou, Hainan, China
- NanoBio Lab, 31 Biopolis Way, The Nanos, Singapore
| | - Jie Shen
- Department of Chemistry, College of Science, Hainan University, Haikou, Hainan, China
| | - Himanshu Joshi
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Woochul Song
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Yu-Ming Tu
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Ratul Chowdhury
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Ruijuan Ye
- Department of Chemistry, College of Science, Hainan University, Haikou, Hainan, China
| | - Ning Li
- NanoBio Lab, 31 Biopolis Way, The Nanos, Singapore
| | | | - Manish Kumar
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Aleksei Aksimentiev
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Huaqiang Zeng
- Department of Chemistry, College of Science, Hainan University, Haikou, Hainan, China.
- Institute of Advanced Synthesis, Northwestern Polytechnical University, Xi'an, Shaanxi, China.
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14
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Pluhackova K, Horner A. Native-like membrane models of E. coli polar lipid extract shed light on the importance of lipid composition complexity. BMC Biol 2021; 19:4. [PMID: 33441107 PMCID: PMC7807449 DOI: 10.1186/s12915-020-00936-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 11/27/2020] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Lipid-protein interactions stabilize protein oligomers, shape their structure, and modulate their function. Whereas in vitro experiments already account for the functional importance of lipids by using natural lipid extracts, in silico methods lack behind by embedding proteins in single component lipid bilayers. However, to accurately complement in vitro experiments with molecular details at very high spatio-temporal resolution, molecular dynamics simulations have to be performed in natural(-like) lipid environments. RESULTS To enable more accurate MD simulations, we have prepared four membrane models of E. coli polar lipid extract, a typical model organism, each at all-atom (CHARMM36) and coarse-grained (Martini3) representations. These models contain all main lipid headgroup types of the E. coli inner membrane, i.e., phosphatidylethanolamines, phosphatidylglycerols, and cardiolipins, symmetrically distributed between the membrane leaflets. The lipid tail (un)saturation and propanylation stereochemistry represent the bacterial lipid tail composition of E. coli grown at 37∘C until 3/4 of the log growth phase. The comparison of the Simple three lipid component models to the complex 14-lipid component model Avanti over a broad range of physiologically relevant temperatures revealed that the balance of lipid tail unsaturation and propanylation in different positions and inclusion of lipid tails of various length maintain realistic values for lipid mobility, membrane area compressibility, lipid ordering, lipid volume and area, and the bilayer thickness. The only Simple model that was able to satisfactory reproduce most of the structural properties of the complex Avanti model showed worse agreement of the activation energy of basal water permeation with the here performed measurements. The Martini3 models reflect extremely well both experimental and atomistic behavior of the E. coli polar lipid extract membranes. Aquaporin-1 embedded in our native(-like) membranes causes partial lipid ordering and membrane thinning in its vicinity. Moreover, aquaporin-1 attracts and temporarily binds negatively charged lipids, mainly cardiolipins, with a distinct cardiolipin binding site in the crevice at the contact site between two monomers, most probably stabilizing the tetrameric protein assembly. CONCLUSIONS The here prepared and validated membrane models of E. coli polar lipids extract revealed that lipid tail complexity, in terms of double bond and cyclopropane location and varying lipid tail length, is key to stabilize membrane properties over a broad temperature range. In addition, they build a solid basis for manifold future simulation studies on more realistic lipid membranes bridging the gap between simulations and experiments.
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Affiliation(s)
- Kristyna Pluhackova
- Department of Biosystems Science and Engineering, Eidgenössiche Technische Hochschule (ETH) Zürich, Mattenstr. 26, Basel, 4058, Switzerland.
| | - Andreas Horner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, Linz, 4020, Austria
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15
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Huang L, Di Vincenzo M, Li Y, Barboiu M. Artificial Water Channels: Towards Biomimetic Membranes for Desalination. Chemistry 2020; 27:2224-2239. [DOI: 10.1002/chem.202003470] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/03/2020] [Indexed: 01/05/2023]
Affiliation(s)
- Li‐Bo Huang
- Lehn Institute of Functional Materials, School of Chemistry Sun Yat-Sen University Guangzhou 510275 P. R. China
| | - Maria Di Vincenzo
- Institut Européen des Membranes Adaptive Supramolecular Nanosystems Group University of Montpellier, ENSCM-CNRS Place E. Bataillon CC047 34095 Montpellier France
| | - Yuhao Li
- Lehn Institute of Functional Materials, School of Chemistry Sun Yat-Sen University Guangzhou 510275 P. R. China
| | - Mihail Barboiu
- Lehn Institute of Functional Materials, School of Chemistry Sun Yat-Sen University Guangzhou 510275 P. R. China
- Institut Européen des Membranes Adaptive Supramolecular Nanosystems Group University of Montpellier, ENSCM-CNRS Place E. Bataillon CC047 34095 Montpellier France
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16
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Zhao DL, Japip S, Zhang Y, Weber M, Maletzko C, Chung TS. Emerging thin-film nanocomposite (TFN) membranes for reverse osmosis: A review. WATER RESEARCH 2020; 173:115557. [PMID: 32028249 DOI: 10.1016/j.watres.2020.115557] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 01/22/2020] [Accepted: 01/26/2020] [Indexed: 06/10/2023]
Abstract
Thin-film composite (TFC) membranes are the heart of reverse osmosis (RO) processes for desalination and water reuse. In recent years, nanomaterials with high permeability, selectivity and chemical resistance, and low fouling tendency have begun to emerge and be applied in many other fields. This has stimulated the research on novel RO membranes consisting of nanomaterials (non-porous and porous) in their selective layers. Encouraging results have been demonstrated. Herein, the state-of-the-art developments of polyamide thin-film nanocomposite (TFN) membranes for RO processes are summarized since the concept of TFN was introduced in 2007. While it is obvious that nanomaterials could impart exclusive properties, it should also be noted that significant challenges still exist for research and commercialization of TFN membranes, such as selection of proper nanomaterials, prevention of leaching of nanoparticles, and performance and cost analysis before large-scale RO membrane manufacturing. Future research directions are outlined to offer insights for the fabrication of much advanced TFN membranes with optimal interface morphology and separation performance.
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Affiliation(s)
- Die Ling Zhao
- Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore
| | - Susilo Japip
- Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore
| | - Yu Zhang
- Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore
| | - Martin Weber
- Advanced Materials and Systems Research, BASF SE, RAP/OUB - B1, 67056, Ludwigshafen, Germany
| | - Christian Maletzko
- Performance Materials, BASF SE, G-PMFSU-F206, 67056, Ludwigshafen, Germany
| | - Tai-Shung Chung
- Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore.
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17
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Song W, Joshi H, Chowdhury R, Najem JS, Shen YX, Lang C, Henderson CB, Tu YM, Farell M, Pitz ME, Maranas CD, Cremer PS, Hickey RJ, Sarles SA, Hou JL, Aksimentiev A, Kumar M. Artificial water channels enable fast and selective water permeation through water-wire networks. NATURE NANOTECHNOLOGY 2020; 15:73-79. [PMID: 31844288 PMCID: PMC7008941 DOI: 10.1038/s41565-019-0586-8] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Accepted: 11/04/2019] [Indexed: 05/09/2023]
Abstract
Artificial water channels are synthetic molecules that aim to mimic the structural and functional features of biological water channels (aquaporins). Here we report on a cluster-forming organic nanoarchitecture, peptide-appended hybrid[4]arene (PAH[4]), as a new class of artificial water channels. Fluorescence experiments and simulations demonstrated that PAH[4]s can form, through lateral diffusion, clusters in lipid membranes that provide synergistic membrane-spanning paths for a rapid and selective water permeation through water-wire networks. Quantitative transport studies revealed that PAH[4]s can transport >109 water molecules per second per molecule, which is comparable to aquaporin water channels. The performance of these channels exceeds the upper bound limit of current desalination membranes by a factor of ~104, as illustrated by the water/NaCl permeability-selectivity trade-off curve. PAH[4]'s unique properties of a high water/solute permselectivity via cooperative water-wire formation could usher in an alternative design paradigm for permeable membrane materials in separations, energy production and barrier applications.
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Affiliation(s)
- Woochul Song
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Himanshu Joshi
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Ratul Chowdhury
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Joseph S Najem
- Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, TN, USA
- Department of Mechanical Engineering, The Pennsylvania State University, UniversityPark, PA, USA
| | - Yue-Xiao Shen
- Department of Civil, Environmental, & Construction Engineering, Texas Tech University, Lubbock, TX, USA
| | - Chao Lang
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Codey B Henderson
- Department of Chemistry, The Pennsylvania State University, University Park, PA, USA
| | - Yu-Ming Tu
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Megan Farell
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Megan E Pitz
- Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, TN, USA
| | - Costas D Maranas
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Paul S Cremer
- Department of Chemistry, The Pennsylvania State University, University Park, PA, USA
| | - Robert J Hickey
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Stephen A Sarles
- Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, TN, USA
| | - Jun-Li Hou
- Department of Chemistry, Fudan University, Shanghai, China
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Manish Kumar
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA.
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA.
- Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA, USA.
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA.
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18
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19
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Wu HC, Yoshioka T, Nakagawa K, Shintani T, Saeki D, Matsuyama H. Molecular simulation of a modified amphotericin B-Ergosterol artificial water channel to evaluate structure and water molecule transport performance. J Memb Sci 2019. [DOI: 10.1016/j.memsci.2019.04.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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20
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The Effect of Buffers on Weak Acid Uptake by Vesicles. Biomolecules 2019; 9:biom9020063. [PMID: 30781892 PMCID: PMC6406578 DOI: 10.3390/biom9020063] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/07/2019] [Accepted: 02/08/2019] [Indexed: 11/16/2022] Open
Abstract
The assessment of weak acid membrane permeability (Pm) frequently involves large unilamellar vesicles. It relies on measurements of the intravesicular pH drop, ΔpHin, in response to a sudden augmentation of external acid concentration. However, ΔpHin may be primarily governed by non-instantaneous protonation and deprotonation reactions of (i) the acid itself, (ii) the buffer molecules, and (iii) the fluorescent pH reporter dye. Moreover, buffer concentration and acid gradient also serve as determinants of ΔpHin, as we show here. The uniexponential time constant (τ) of ΔpHin(t) is an invalid measure of Pm as Arrhenius plots of Pm and τ reveal different activation energies for acid influx. We calculate Pm by fitting a mathematical model to experimental stopped-flow traces. The model takes into account not only the time course of total internal buffer capacity but also (i) water self-dissociation, (ii) volume changes due to acid induced osmotic water flow, and (iii) the spontaneous membrane proton leak. It allows extracting a Pm of 30.8 ± 3.5 μm/s for formic acid for 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) vesicles.
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21
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Li Q, Li X, Ning L, Tan CH, Mu Y, Wang R. Hyperfast Water Transport through Biomimetic Nanochannels from Peptide-Attached (pR)-pillar[5]arene. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1804678. [PMID: 30637936 DOI: 10.1002/smll.201804678] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 12/13/2018] [Indexed: 06/09/2023]
Abstract
Synthetic water channels offer great promise to replace natural aquaporins (AQPs) for making new-generation biomimetic membranes for water treatment. However, the water permeability of the current synthetic water channels is still far below that of AQPs. Here, peptide-attached (pR)-pillar[5]arene (pR-PH) channels are reported to mimic the high permeability of AQPs. It is demonstrated that the pR-PH channels with an open pore can transport water smoothly and efficiently. The pR-PH channels are competitive with AQPs in terms of water permeability and are much superior to diastereomer peptide-attached (pS)-pillar[5]arene (pS-PH) and other reported synthetic water channels. The exceptional water-transport properties of the pR-PH channels are further demonstrated in a composite polymeric membrane that incorporates the nanochannels into the top selective layer. This membrane gives a significantly improved water flux while retaining high salt rejection. The results establish a tangible foundation for developing highly efficient artificial water channel-based biomimetic membrane for water purification applications.
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Affiliation(s)
- Qing Li
- Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore, 637141, Singapore
| | - Xuesong Li
- Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore, 637141, Singapore
| | - Lulu Ning
- Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore, 637141, Singapore
| | - Choon-Hong Tan
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - Rong Wang
- Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore, 637141, Singapore
- School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, 639798, Singapore
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22
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Song W, Tu YM, Oh H, Samineni L, Kumar M. Hierarchical Optimization of High-Performance Biomimetic and Bioinspired Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:589-607. [PMID: 30577695 DOI: 10.1021/acs.langmuir.8b03655] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Biomimetic and bioinspired membranes have emerged as an innovative platform for water purification and aqueous separations. They are inspired by the exceptional water permeability (∼109 water molecules per second per channel) and perfect selectivity of biological water channels, aquaporins. However, only few successes have been reported for channel-based membrane fabrication due to inherent challenges of realizing coherence between channel design at the angstrom level and development of scalable membranes that maintain these molecular properties at practice-relevant scales. In this article, we feature recent progress toward practical biomimetic membranes, with the review organized along a hierarchical structural perspective that biomimetic membranes commonly share. These structures range from unitary pore shapes and tubular hydrophobic channel geometries to self-assembled bilayer structures and finally to macroscale membranes covering a size range from the angstrom, to the micrometer scale, and finally to the centimeter and larger scales. To maximize the advantage of water channel implementation into membranes, each feature needs to be optimized in an appropriate manner that provides a path to successful scale-up to achieve high performance in practical biomimetic and bioinspired membranes.
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23
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Ozu M, Galizia L, Acuña C, Amodeo G. Aquaporins: More Than Functional Monomers in a Tetrameric Arrangement. Cells 2018; 7:E209. [PMID: 30423856 PMCID: PMC6262540 DOI: 10.3390/cells7110209] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/27/2018] [Accepted: 11/07/2018] [Indexed: 12/11/2022] Open
Abstract
Aquaporins (AQPs) function as tetrameric structures in which each monomer has its own permeable pathway. The combination of structural biology, molecular dynamics simulations, and experimental approaches has contributed to improve our knowledge of how protein conformational changes can challenge its transport capacity, rapidly altering the membrane permeability. This review is focused on evidence that highlights the functional relationship between the monomers and the tetramer. In this sense, we address AQP permeation capacity as well as regulatory mechanisms that affect the monomer, the tetramer, or tetramers combined in complex structures. We therefore explore: (i) water permeation and recent evidence on ion permeation, including the permeation pathway controversy-each monomer versus the central pore of the tetramer-and (ii) regulatory mechanisms that cannot be attributed to independent monomers. In particular, we discuss channel gating and AQPs that sense membrane tension. For the latter we propose a possible mechanism that includes the monomer (slight changes of pore shape, the number of possible H-bonds between water molecules and pore-lining residues) and the tetramer (interactions among monomers and a positive cooperative effect).
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Affiliation(s)
- Marcelo Ozu
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
| | - Luciano Galizia
- Instituto de investigaciones Médicas A. Lanari, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1427ARO, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, Laboratorio de Canales Iónicos, Instituto de Investigaciones Médicas (IDIM), Universidad de Buenos Aires, Buenos Aires C1427ARO, Argentina.
| | - Cynthia Acuña
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
| | - Gabriela Amodeo
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
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Abstract
Water at interfaces governs many processes on the molecular scale from electrochemical and enzymatic reactions to protein folding. Here we focus on water transport through proteinaceous pores that are so narrow that the water molecules cannot overtake each other in the pore. After a short introduction into the single-file transport theory, we analyze experiments in which the unitary water permeability, pf, of water channel proteins (aquaporins, AQPs), potassium channels (KcsA), and antibiotics (gramicidin-A derivatives) has been obtained. A short outline of the underlying methods (scanning electrochemical microscopy, fluorescence correlation spectroscopy, measurements of vesicle light scattering) is also provided. We conclude that pf increases exponentially with a decreasing number NH of hydrogen bond donating or accepting residues in the channel wall. The variance in NH is responsible for a more than hundredfold change in pf. The dehydration penalty at the channel mouth has a smaller effect on pf. The intricate link between pf and the Gibbs activation energy barrier, ΔG‡t, for water flow suggests that conformational transitions of water channels act as a third determinant of pf.
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Affiliation(s)
- Andreas Horner
- Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.
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25
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Werber JR, Elimelech M. Permselectivity limits of biomimetic desalination membranes. SCIENCE ADVANCES 2018; 4:eaar8266. [PMID: 29963628 PMCID: PMC6025908 DOI: 10.1126/sciadv.aar8266] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 05/17/2018] [Indexed: 05/12/2023]
Abstract
Water scarcity and inadequate membrane selectivity have spurred interest in biomimetic desalination membranes, in which biological or synthetic water channels are incorporated in an amphiphilic bilayer. As low channel densities (0.1 to 10%) are required for sufficient water permeability, the amphiphilic bilayer matrix will play a critical role in separation performance. We determine selectivity limits for biomimetic membranes by studying the transport behavior of water, neutral solutes, and ions through the bilayers of lipid and block-copolymer vesicles and projecting performance for varying water channel densities. We report that defect-free biomimetic membranes would have water/salt permselectivities ~108-fold greater than current desalination membranes. In contrast, the solubility-based permeability of lipid and block-copolymer bilayers (extending Overton's rule) will result in poor rejection of hydrophobic solutes. Defect-free biomimetic membranes thus offer great potential for seawater desalination and ultrapure water production, but would perform poorly in wastewater reuse. Potential strategies to limit neutral solute permeation are discussed.
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Affiliation(s)
| | - Menachem Elimelech
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511, USA
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26
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Horner A, Pohl P. Comment on “Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins”. Science 2018; 359:359/6383/eaap9173. [DOI: 10.1126/science.aap9173] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 02/28/2018] [Indexed: 12/22/2022]
Affiliation(s)
| | - Peter Pohl
- Johannes Kepler University, 4020 Linz, Austria
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27
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Saraei N, Hietsoi O, Mullins CS, Gupta AJ, Frye BC, Mashuta MS, Buchanan RM, Grapperhaus CA. Streams, cascades, and pools: various water cluster motifs in structurally similar Ni( ii) complexes. CrystEngComm 2018. [DOI: 10.1039/c8ce01153b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Hydrogen bonding (HB) interactions are well known to impact the properties of water in the bulk and within hydrated materials.
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Affiliation(s)
- Nina Saraei
- Department of Chemistry
- University of Louisville
- Louisville
- USA
| | | | | | | | - Brian C. Frye
- Department of Chemistry
- University of Louisville
- Louisville
- USA
| | - Mark S. Mashuta
- Department of Chemistry
- University of Louisville
- Louisville
- USA
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28
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Wu HC, Yoshioka T, Nagasawa H, Kanezashi M, Tsuru T, Saeki D, Matsuyama H. Preparation of cyclic peptide nanotube structures and molecular simulation of water adsorption and diffusion. J Memb Sci 2017. [DOI: 10.1016/j.memsci.2017.04.060] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Wambo TO, Rodriguez RA, Chen LY. Computing osmotic permeabilities of aquaporins AQP4, AQP5, and GlpF from near-equilibrium simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1310-1316. [PMID: 28455098 DOI: 10.1016/j.bbamem.2017.04.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 04/23/2017] [Accepted: 04/24/2017] [Indexed: 12/01/2022]
Abstract
Measuring or computing the single-channel permeability of aquaporins/aquaglyceroporins (AQPs) has long been a challenge. The measured values scatter over an order of magnitude but the corresponding Arrhenius activation energies converge in the current literature. Osmotic flux through an AQP was simulated as water current forced through the channel by kilobar hydraulic pressure or theoretically approximated as single-file diffusion. In this paper, we report large scale simulations of osmotic current under sub M gradient through three AQPs (water channels AQP4 and AQP5 and glycerol-water channel GlpF) using the mature particle mesh Ewald technique (PME) for which the established force fields have been optimized with known accuracy. These simulations were implemented with hybrid periodic boundary conditions devised to avoid the artifactitious mixing across the membrane in a regular PME simulation. The computed single-channel permeabilities at 5°C and 25°C are in agreement with recently refined experiments on GlpF. The Arrhenius activation energies extracted from our simulations for all the three AQPs agree with the in vitro measurements. The single-file diffusion approximations from our large-scale simulations are consistent with the current literature on smaller systems. From these unambiguous agreements among the in vitro and in silico studies, we observe the quantitative accuracy of the all-atom force fields of the current literature for water-channel biology. We also observe that AQP4, that is particularly rich in the central nervous system, is more efficient in water conduction and more temperature-sensitive than other water-only channels (excluding glycerol channels that also conduct water when not inhibited by glycerol).
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Affiliation(s)
- Thierry O Wambo
- Department of Physics, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Roberto A Rodriguez
- Department of Physics, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Liao Y Chen
- Department of Physics, University of Texas at San Antonio, San Antonio, TX 78249, USA.
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Agmon N, Bakker HJ, Campen RK, Henchman RH, Pohl P, Roke S, Thämer M, Hassanali A. Protons and Hydroxide Ions in Aqueous Systems. Chem Rev 2016; 116:7642-72. [PMID: 27314430 DOI: 10.1021/acs.chemrev.5b00736] [Citation(s) in RCA: 287] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the structure and dynamics of water's constituent ions, proton and hydroxide, has been a subject of numerous experimental and theoretical studies over the last century. Besides their obvious importance in acid-base chemistry, these ions play an important role in numerous applications ranging from enzyme catalysis to environmental chemistry. Despite a long history of research, many fundamental issues regarding their properties continue to be an active area of research. Here, we provide a review of the experimental and theoretical advances made in the last several decades in understanding the structure, dynamics, and transport of the proton and hydroxide ions in different aqueous environments, ranging from water clusters to the bulk liquid and its interfaces with hydrophobic surfaces. The propensity of these ions to accumulate at hydrophobic surfaces has been a subject of intense debate, and we highlight the open issues and challenges in this area. Biological applications reviewed include proton transport along the hydration layer of various membranes and through channel proteins, problems that are at the core of cellular bioenergetics.
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Affiliation(s)
- Noam Agmon
- The Fritz Haber Research Center, Institute of Chemistry, The Hebrew University of Jerusalem , Jerusalem 91904, Israel
| | - Huib J Bakker
- FOM Institute AMOLF , Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - R Kramer Campen
- Fritz Haber Institute of the Max Planck Society , Faradayweg 4-6, 14195 Berlin, Germany
| | - Richard H Henchman
- Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Peter Pohl
- Johannes Kepler University Linz , Institute of Biophysics, Gruberstrasse 40, 4020 Linz, Austria
| | - Sylvie Roke
- Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Material Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015, Lausanne, Switzerland
| | - Martin Thämer
- Fritz Haber Institute of the Max Planck Society , Faradayweg 4-6, 14195 Berlin, Germany.,Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Ali Hassanali
- CMSP Section, The Abdus Salaam International Center for Theoretical Physics , I-34151 Trieste, Italy
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Jing P, Paraiso H, Burris B. Highly efficient integration of the viral portal proteins from different types of phages into planar bilayers for the black lipid membrane analysis. MOLECULAR BIOSYSTEMS 2015; 12:480-9. [PMID: 26661052 DOI: 10.1039/c5mb00573f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The planar lipid bilayer technology is a technique that yields incredibly useful structural function information about a single channel protein. It is also currently actively utilized as a powerful platform using biological protein nanopores for the development of single-molecule nanopore sensing technology, as well as ultrafast DNA sequencing technology. The portal protein, GP10, from the bacteriophage Φ29 was the first phage portal protein shown to be successfully inserted into planar bilayer membranes, thereby it may inspire more researchers to apply the techniques to portal proteins from the other bacteriophages. However, the technology is far from perfect since the insertion of the channel proteins into planar bilayer membranes is not only technically difficult but also time-consuming. For the fusion of phage portal proteins, vesicles are typically needed to be reconstituted with the portal proteins to form proteoliposomes. However, most of the phage portal proteins have low solubility, and may self-aggregate during the preparation of the proteoliposomes. Furthermore, the fusion of the formed proteoliposomes is sporadic, unpredictable and varied from person to person. Due to the lack of experimental consistency between labs, the results from different methodologies reported for generating fusible proteoliposomes are highly variable. In this research, we propose a new method for the preparation of the fusible proteoliposomes containing portal proteins from bacteriophages, to circumvent the problems aforementioned. Compared to the conventional methods, this method was able to avoid the protein aggregation issues during the vesicle preparation by eliminating the need for detergents and the subsequent time-consuming step for detergent removal. The proteoliposomes prepared by the method were shown to be more efficiently and rapidly inserted into planar bilayer membranes bathed in different conducting buffer solutions including those with nonelectrolytes such as glycerol and PEG. In addition, the method of forming proteoliposomes has significantly extended the shelf life of the proteoliposomes. To further explore its potentials, we have successfully applied the method to the insertion of a mutant portal protein, GP20, from T4 bacteriophage, a hydrophobic portal protein that has not been explored using the planar lipid bilayer membrane technique. The results suggest that this method could be used to prepare proteoliposomes formed by hydrophobic portal proteins from other bacteriophages.
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Affiliation(s)
- Peng Jing
- Department of Chemistry, College of Arts and Sciences, Indiana-Purdue University Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805-1499, USA.
| | - Hallel Paraiso
- Department of Biology, College of Arts and Sciences, Indiana-Purdue University Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805-1499, USA
| | - Benjamin Burris
- Department of Chemistry, College of Arts and Sciences, Indiana-Purdue University Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805-1499, USA.
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Horner A, Zocher F, Preiner J, Ollinger N, Siligan C, Akimov SA, Pohl P. The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues. SCIENCE ADVANCES 2015; 1:e1400083. [PMID: 26167541 PMCID: PMC4496530 DOI: 10.1126/sciadv.1400083] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 01/12/2015] [Indexed: 05/19/2023]
Abstract
Channel geometry governs the unitary osmotic water channel permeability, pf, according to classical hydrodynamics. Yet, pf varies by several orders of magnitude for membrane channels with a constriction zone that is one water molecule in width and four to eight molecules in length. We show that both the pf of those channels and the diffusion coefficient of the single-file waters within them are determined by the number NH of residues in the channel wall that may form a hydrogen bond with the single-file waters. The logarithmic dependence of water diffusivity on NH is in line with the multiplicity of binding options at higher NH densities. We obtained high-precision pf values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.
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Affiliation(s)
- Andreas Horner
- Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria
| | - Florian Zocher
- Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria
| | - Johannes Preiner
- Center for Advanced Bioanalysis GmbH (CBL), Gruberstr. 40, 4020 Linz, Austria
| | - Nicole Ollinger
- Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria
| | - Christine Siligan
- Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria
| | - Sergey A. Akimov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr., 31/5, 119071 Moscow, Russia
- National University of Science and Technology “MISiS,” Leninsky pr., 4, 119049 Moscow, Russia
| | - Peter Pohl
- Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria
- Corresponding author. E-mail:
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Preiner J, Horner A, Karner A, Ollinger N, Siligan C, Pohl P, Hinterdorfer P. High-speed AFM images of thermal motion provide stiffness map of interfacial membrane protein moieties. NANO LETTERS 2015; 15:759-63. [PMID: 25516527 PMCID: PMC4296598 DOI: 10.1021/nl504478f] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 12/11/2014] [Indexed: 05/20/2023]
Abstract
The flexibilities of extracellular loops determine ligand binding and activation of membrane receptors. Arising from fluctuations in inter- and intraproteinaceous interactions, flexibility manifests in thermal motion. Here we demonstrate that quantitative flexibility values can be extracted from directly imaging the thermal motion of membrane protein moieties using high-speed atomic force microscopy (HS-AFM). Stiffness maps of the main periplasmic loops of single reconstituted water channels (AqpZ, GlpF) revealed the spatial and temporal organization of loop-stabilizing intraproteinaceous H-bonds and salt bridges.
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Affiliation(s)
- Johannes Preiner
- Center
for Advanced Bioanalysis GmbH, Gruberstrasse 40, 4020 Linz, Austria
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
- E-mail:
| | - Andreas Horner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Andreas Karner
- Center
for Advanced Bioanalysis GmbH, Gruberstrasse 40, 4020 Linz, Austria
| | - Nicole Ollinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Christine Siligan
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Peter Hinterdorfer
- Center
for Advanced Bioanalysis GmbH, Gruberstrasse 40, 4020 Linz, Austria
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
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34
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Knyazev DG, Winter L, Bauer BW, Siligan C, Pohl P. Ion conductivity of the bacterial translocation channel SecYEG engaged in translocation. J Biol Chem 2014; 289:24611-6. [PMID: 25016015 PMCID: PMC4148884 DOI: 10.1074/jbc.m114.588491] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
While engaged in protein transport, the bacterial translocon SecYEG must maintain the membrane barrier to small ions. The preservation of the proton motif force was attributed to (i) cation exclusion, (ii) engulfment of the nascent chain by the hydrophobic pore ring, and (iii) a half-helix partly plugging the channel. In contrast, we show here that preservation of the proton motif force is due to a voltage-driven conformational change. Preprotein or signal peptide binding to the purified and reconstituted SecYEG results in large cation and anion conductivities only when the membrane potential is small. Physiological values of membrane potential close the activated channel. This voltage-dependent closure is not dependent on the presence of the plug domain and is not affected by mutation of 3 of the 6 constriction residues to glycines. Cellular ion homeostasis is not challenged by the small remaining leak conductance.
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Affiliation(s)
- Denis G Knyazev
- From the Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria
| | - Lukas Winter
- From the Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria
| | - Benedikt W Bauer
- From the Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria
| | - Christine Siligan
- From the Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria
| | - Peter Pohl
- From the Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria
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35
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DeCoursey TE, Hosler J. Philosophy of voltage-gated proton channels. J R Soc Interface 2014; 11:20130799. [PMID: 24352668 PMCID: PMC3899857 DOI: 10.1098/rsif.2013.0799] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 11/22/2013] [Indexed: 02/02/2023] Open
Abstract
In this review, voltage-gated proton channels are considered from a mainly teleological perspective. Why do proton channels exist? What good are they? Why did they go to such lengths to develop several unique hallmark properties such as extreme selectivity and ΔpH-dependent gating? Why is their current so minuscule? How do they manage to be so selective? What is the basis for our belief that they conduct H(+) and not OH(-)? Why do they exist in many species as dimers when the monomeric form seems to work quite well? It is hoped that pondering these questions will provide an introduction to these channels and a way to logically organize their peculiar properties as well as to understand how they are able to carry out some of their better-established biological functions.
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Affiliation(s)
- Thomas E. DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, 1750 West Harrison, Chicago, IL 60612, USA
| | - Jonathan Hosler
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, MS 39216, USA
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36
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Zhang X, Lian J, Kai L, Huang L, Cen P, Xu Z. Enhanced functional expression of aquaporin Z via fusion of in situ cleavable leader peptides in Escherichia coli cell-free system. Enzyme Microb Technol 2013; 55:26-30. [PMID: 24411442 DOI: 10.1016/j.enzmictec.2013.12.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 11/26/2013] [Accepted: 12/03/2013] [Indexed: 10/25/2022]
Abstract
Aquaporin Z (AqpZ) is a water channel protein from Escherichia coli and has attracted many attentions to develop the biomimetic water filtration technology. Cell-free protein synthesis (CFPS) system, one of the most complex multi-enzymatic systems, has the ability of producing the integral membrane protein in vitro. To enhance the synthesis of AqpZ in E. coli cell-free system, several natural leader peptides were respectively fused at the N-terminus and were verified to enhance the expression level significantly. Moreover, the supplementation of detergents or liposome could activate leader peptidase from the cell-free extract and provide hydrophobic environment for proper folding of AqpZ. Thus, the release of mature AqpZ via the in situ removal of leader peptide was achieved, with a specific water transport activity of (2.1 ± 0.1) × 10⁻¹⁴ cm³ s⁻¹ monomer⁻¹. Using this in situ removable leader peptide strategy, the transcription-translation, leader sequence cleavage and membrane protein folding were integrated into a simple process in the cell-free system, providing a convenient approach to enhance the expression of target proteins, especially those membrane proteins difficult to achieve.
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Affiliation(s)
- Xu Zhang
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
| | - Jiazhang Lian
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
| | - Lei Kai
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China; Centre for Biomolecular Magnetic Resonance, Institute for Biophysical Chemistry, Goethe-University of Frankfurt/Main, Max-von-Laue-Str. 9, D-60438 Frankfurt/Main, Germany
| | - Lei Huang
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Peilin Cen
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
| | - Zhinan Xu
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China.
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de Almeida A, Oliveira BL, Correia JD, Soveral G, Casini A. Emerging protein targets for metal-based pharmaceutical agents: An update. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2013.01.031] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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38
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Wang H, Chung TS, Tong YW. Study on water transport through a mechanically robust Aquaporin Z biomimetic membrane. J Memb Sci 2013. [DOI: 10.1016/j.memsci.2013.05.057] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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39
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Knyazev DG, Lents A, Krause E, Ollinger N, Siligan C, Papinski D, Winter L, Horner A, Pohl P. The bacterial translocon SecYEG opens upon ribosome binding. J Biol Chem 2013; 288:17941-6. [PMID: 23645666 PMCID: PMC3689939 DOI: 10.1074/jbc.m113.477893] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In co-translational translocation, the ribosome funnel and the channel of the protein translocation complex SecYEG are aligned. For the nascent chain to enter the channel immediately after synthesis, a yet unidentified signal triggers displacement of the SecYEG sealing plug from the pore. Here, we show that ribosome binding to the resting SecYEG channel triggers this conformational transition. The purified and reconstituted SecYEG channel opens to form a large ion-conducting channel, which has the conductivity of the plug deletion mutant. The number of ion-conducting channels inserted into the planar bilayer per fusion event roughly equals the number of SecYEG channels counted by fluorescence correlation spectroscopy in a single proteoliposome. Thus, the open probability of the channel must be close to unity. To prevent the otherwise lethal proton leak, a closed post-translational conformation of the SecYEG complex bound to a ribosome must exist.
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Affiliation(s)
- Denis G Knyazev
- Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria
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40
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Wang HL, Chung TS, Tong YW, Jeyaseelan K, Armugam A, Duong HHP, Fu F, Seah H, Yang J, Hong M. Mechanically robust and highly permeable AquaporinZ biomimetic membranes. J Memb Sci 2013. [DOI: 10.1016/j.memsci.2013.01.031] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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41
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Chen LY. Glycerol modulates water permeation through Escherichia coli aquaglyceroporin GlpF. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1786-93. [PMID: 23506682 DOI: 10.1016/j.bbamem.2013.03.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 03/05/2013] [Accepted: 03/08/2013] [Indexed: 11/17/2022]
Abstract
Among aquaglyceroporins that transport both water and glycerol across the cell membrane, Escherichia coli glycerol uptake facilitator (GlpF) is the most thoroughly studied. However, one question remains: Does glycerol modulate water permeation? This study answers this fundamental question by determining the three-dimensional potential of mean force of glycerol along the permeation path through GlpF's conducting pore. There is a deep well near the Asn-Pro-Ala (NPA) motifs (6.5kcal/mol below the bulk level) and a barrier near the selectivity filter (10.1kcal/mol above the well bottom). This profile owes its existence to GlpF's perfect steric arrangement: The glycerol-protein van der Waals interactions are attractive near the NPA but repulsive elsewhere in the conducting pore. In light of the single-file nature of waters and glycerols lining up in GlpF's amphipathic pore, it leads to the following conclusion: Glycerol modulates water permeation in the μM range. At mM concentrations, GlpF is glycerol-saturated and a glycerol residing in the well occludes the conducting pore. Therefore, water permeation is fully correlated to glycerol dissociation that has an Arrhenius activation barrier of 6.5kcal/mol. Validation of this theory is based on the existent in vitro data, some of which have not been given the proper attention they deserved: The Arrhenius activation barriers were found to be 7kcal/mol for water permeation and 9.6kcal/mol for glycerol permeation; The presence of up to 100mM glycerol did not affect the kinetics of water transport with very low permeability, in apparent contradiction with the existent theories that predicted high permeability (0M glycerol).
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Affiliation(s)
- Liao Y Chen
- Department of Physics, University of Texas at San Antonio, San Antonio, TX 78249, USA.
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42
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Zhao Y, Vararattanavech A, Li X, Hélixnielsen C, Vissing T, Torres J, Wang R, Fane AG, Tang CY. Effects of proteoliposome composition and draw solution types on separation performance of aquaporin-based proteoliposomes: implications for seawater desalination using aquaporin-based biomimetic membranes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:1496-1503. [PMID: 23311686 DOI: 10.1021/es304306t] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Aquaporins are a large family of water transport proteins in cell membranes. Their high water permeability and solute rejection make them potential building blocks for high-performance biomimetic membranes for desalination. In the current study, proteoliposomes were prepared using AquaporinZ from Escherichia coli cells, and their separation properties were characterized by stopped-flow measurements. The current study systematically investigated the effect of proteoliposome composition (lipid type, protein-to-lipid ratio (PLR), and the addition of cholesterol) on water permeability and NaCl retention. Among the various lipids investigated, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)-based proteoliposomes were found to have excellent osmotic water permeability and NaCl reflection coefficient values. Increasing the PLR of DOPC proteoliposomes up to 1:200 increased their osmotic water permeability. However, further increase in the PLR reduced the osmotic water permeability probably due to the occurrence of defects in the proteoliposomes, whereas the addition of cholesterol improved their osmotic water permeation likely due to defects sealing. The current study also investigated the effect of major dissolved ions in seawater (e.g., Mg(2+) and SO(4)(2-)) on the stability of proteoliposomes, and design criteria for aquaporin-based biomimetic membranes are proposed in the context of desalination.
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Affiliation(s)
- Yang Zhao
- Singapore Membrane Technology Centre, Nanyang Technological University, Singapore 639798
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43
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Chen LY. Glycerol inhibits water permeation through Plasmodium falciparum aquaglyceroporin. J Struct Biol 2013; 181:71-6. [PMID: 23108237 PMCID: PMC3525719 DOI: 10.1016/j.jsb.2012.10.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 10/15/2012] [Accepted: 10/16/2012] [Indexed: 11/20/2022]
Abstract
Plasmodium falciparum aquaglyceroporin (PfAQP) is a multifunctional membrane protein in the plasma membrane of P. falciparum, the parasite that causes the most severe form of malaria. The current literature has established the science of PfAQP's structure, functions, and hydrogen-bonding interactions but left unanswered the following fundamental question: does glycerol modulate water permeation through aquaglyceroporin that conducts both glycerol and water? This paper provides an affirmative answer to this question of essential importance to the protein's functions. On the basis of the chemical-potential profile of glycerol from the extracellular bulk region, throughout PfAQP's conducting channel, to the cytoplasmic bulk region, this study shows the existence of a bound state of glycerol inside aquaglyceroporin's permeation pore, from which the dissociation constant is approximately 14μM. A glycerol molecule occupying the bound state occludes the conducting pore through which permeating molecules line up in single file by hydrogen-bonding with one another and with the luminal residues of aquaglyceroporin. In this way, glycerol inhibits permeation of water and other permeants through aquaglyceroporin. The biological implications of this theory are discussed and shown to agree with the existent in vitro data. It turns out that the structure of aquaglyceroporin is perfect for the van der Waals interactions between the protein and glycerol to cause the existence of the bound state deep inside the conducting pore and, thus to play an unexpected but significant role in aquaglyceroporin's functions.
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Affiliation(s)
- Liao Y Chen
- Department of Physics, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA.
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44
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Wang H, Chung TS, Tong YW, Jeyaseelan K, Armugam A, Chen Z, Hong M, Meier W. Highly permeable and selective pore-spanning biomimetic membrane embedded with aquaporin Z. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:1185-1125. [PMID: 22378644 DOI: 10.1002/smll.201102120] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 12/15/2011] [Indexed: 05/31/2023]
Abstract
A highly permeable yet highly selective pore-spanning biomimetic membrane embedded with aquaporin Z is molecularly designed and constructed via a combination of pressure-assisted vesicle adsorption and covalent-conjugation-driven vesicle fusion on a porous support. This approach represents a significant breakthrough in the architecture of biomimetic membranes embedded with aquaporin in a planar form.
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Affiliation(s)
- Honglei Wang
- Department of Chemical & Biomolecular Engineering, National University of Singapore, 117576 Singapore
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45
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Saparov SM, Tsunoda SP, Pohl P. Proton exclusion by an aquaglyceroprotein: a voltage clamp study. Biol Cell 2012; 97:545-50. [PMID: 15850456 DOI: 10.1042/bc20040136] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION In silico both orthodox aquaporins and aquaglyceroporins are shown to exclude protons. Supporting experimental evidence is available only for orthodox aquaporins. In contrast, the subset of the aquaporin water channel family that is permeable to glycerol and certain small, uncharged solutes has not yet been shown to exclude protons. Moreover, different aquaglyceroporins have been reported to conduct ions when reconstituted in planar bilayers. RESULTS To clarify these discrepancies, we have measured proton permeability through the purified Escherichia coli glycerol facilitator (GlpF). Functional reconstitution into planar lipid bilayers was demonstrated by imposing an osmotic gradient across the membrane and detecting the resulting small changes in ionic concentration close to the membrane surface. The osmotic water flow corresponds to a GlpF single channel water permeability of 0.7x10(-14) cm(3).subunit(-1).s(-1). Proton conductivity measurements carried out in the presence of a pH gradient (1 unit) revealed an upper limit of the H(+) (OH(-)) to H(2)O molecules transport stoichiometry of 2x10(-9). A significant GlpF-mediated ion conductivity was also not detectable. CONCLUSIONS The lack of a physiologically relevant GlpF-mediated proton conductivity agrees well with predictions made by molecular dynamics simulations.
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Affiliation(s)
- Sapar M Saparov
- Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125 Berlin, Germany
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Araya-Secchi R, Garate JA, Holmes DS, Perez-Acle T. Molecular dynamics study of the archaeal aquaporin AqpM. BMC Genomics 2011; 12 Suppl 4:S8. [PMID: 22369250 PMCID: PMC3287591 DOI: 10.1186/1471-2164-12-s4-s8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Aquaporins are a large family of transmembrane channel proteins that are present throughout all domains of life and are implicated in human disorders. These channels, allow the passive but selective movement of water and other small neutral solutes across cell membranes. Aquaporins have been classified into two sub-families: i) strict aquaporins that only allow the passage of water and ii) the less selective aquaglyceroporins that transport water and other neutral solutes, such as glycerol, CO2 or urea. Recently, the identification and characterization of a number of archaeal and bacterial aquaporins suggested the existence of a third sub-family; one that is neither a strict aquaporin nor an aquaglyceroporin. The function and phylogeny of this third family is still a matter of debate. Results Twenty nanosecond molecular dynamics (MD) simulation of a fully hydrated tetramer of AqpM embedded in a lipid bilayer permitted predictions to be made of key biophysical parameters including: single channel osmotic permeability constant (pf), single channel diffusive permeability constant (pd), channel radius, potential water occupancy of the channel and water orientation inside the pore. These properties were compared with those of well characterized representatives of the two main aquaporin sub-families. Results show that changes in the amino acid composition of the aromatic/arginine region affect the size and polarity of the selectivity filter (SF) and could help explain the difference in water permeability between aquaporins. In addition, MD simulation results suggest that AqpM combines characteristics of strict aquaporins, such as the narrow SF and channel radius, with those of aquaglyceroporins, such as a more hydrophobic and less polar SF. Conclusions MD simulations of AqpM extend previous evidence that this archaeal aquaporin exhibits hybrid features intermediate between the two known aquaporin sub-families, supporting the idea that it may constitute a member of a novel class of aquaporins.
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Affiliation(s)
- Raul Araya-Secchi
- Computational Biology Laboratory, Centro de Modelamiento Matematico, Facultad de Ciencias Fisicas y Matematicas, Universidad de Chile, Santiago, Chile.
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Erokhova L, Horner A, Kügler P, Pohl P. Monitoring single-channel water permeability in polarized cells. J Biol Chem 2011; 286:39926-32. [PMID: 21940624 PMCID: PMC3220579 DOI: 10.1074/jbc.m111.291864] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
So far the determination of unitary permeability (pf) of water channels that are expressed in polarized cells is subject to large errors because the opening of a single water channel does not noticeably increase the water permeability of a membrane patch above the background. That is, in contrast to the patch clamp technique, where the single ion channel conductance may be derived from a single experiment, two experiments separated in time and/or space are required to obtain the single-channel water permeability pf as a function of the incremental water permeability (Pf,c) and the number (n) of water channels that contributed to Pf,c. Although the unitary conductance of ion channels is measured in the native environment of the channel, pf is so far derived from reconstituted channels or channels expressed in oocytes. To determine the pf of channels from live epithelial monolayers, we exploit the fact that osmotic volume flow alters the concentration of aqueous reporter dyes adjacent to the epithelia. We measure these changes by fluorescence correlation spectroscopy, which allows the calculation of both Pf,c and osmolyte dilution within the unstirred layer. Shifting the focus of the laser from the aqueous solution to the apical and basolateral membranes allowed the FCS-based determination of n. Here we validate the new technique by determining the pf of aquaporin 5 in Madin-Darby canine kidney cell monolayers. Because inhibition and subsequent activity rescue are monitored on the same sample, drug effects on exocytosis or endocytosis can be dissected from those on pf.
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Boron WF, Endeward V, Gros G, Musa-Aziz R, Pohl P. Intrinsic CO2 permeability of cell membranes and potential biological relevance of CO2 channels. Chemphyschem 2011; 12:1017-9. [PMID: 21384488 DOI: 10.1002/cphc.201100034] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Nielsen CH. Major intrinsic proteins in biomimetic membranes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 679:127-42. [PMID: 20666229 DOI: 10.1007/978-1-4419-6315-4_10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Biological membranes define the structural and functional boundaries in living cells and their organelles. The integrity of the cell depends on its ability to separate inside from outside and yet at the same time allow massive transport of matter in and out the cell. Nature has elegantly met this challenge by developing membranes in the form of lipid bilayers in which specialized transport proteins are incorporated. This raises the question: is it possible to mimic biological membranes and create a membrane based sensor and/or separation device? In the development of a biomimetic sensor/separation technology, a unique class of membrane transport proteins is especially interesting-the major intrinsic proteins (MIPs). Generally, MIPs conduct water molecules and selected solutes in and out of the cell while preventing the passage of other solutes, a property critical for the conservation of the cells internal pH and salt concentration. Also known as water channels or aquaporins they are highly efficient membrane pore proteins some of which are capable of transporting water at very high rates up to 10(9) molecules per second. Some MIPs transport other small, uncharged solutes, such as glycerol and other permeants such as carbon dioxide, nitric oxide, ammonia, hydrogen peroxide and the metalloids antimonite, arsenite, silicic and boric acid depending on the effective restriction mechanism of the protein. The flux properties of MIPs thus lead to the question ifMIPs can be used in separation devices or as sensor devices based on, e.g., the selective permeation of metalloids. In principle a MIP based membrane sensor/separation device requires the supporting biomimetic matrix to be virtually impermeable to anything but water or the solute in question. In practice, however, a biomimetic support matrix will generally have finite permeabilities to both electrolytes and non-electrolytes. The feasibility of a biomimetic MIP device thus depends on the relative transport contribution from both protein and biomimetic support matrix. Also the biomimetic matrix must be encapsulated in order to protect it and make it sufficiently stable in a final application. Here, I specifically discuss the feasibility of developing osmotic biomimetic MIP membranes, but the technical issues are of general concern in the design ofbiomimetic membranes capable of supporting selective transmembrane fluxes.
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Affiliation(s)
- Claus Hélix Nielsen
- Quantrum Protein Center, Department of Physics, Technical University of Denmark, DK-2800 Lyngby.
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Krylova OO, Jahnke N, Keller S. Membrane solubilisation and reconstitution by octylglucoside: comparison of synthetic lipid and natural lipid extract by isothermal titration calorimetry. Biophys Chem 2010; 150:105-11. [PMID: 20392557 DOI: 10.1016/j.bpc.2010.03.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 03/12/2010] [Accepted: 03/13/2010] [Indexed: 11/28/2022]
Abstract
We have studied the solubilisation and reconstitution of lipid membranes composed of either synthetic phosphatidylcholine or Escherichia. coli polar lipid extract by the non-ionic detergent octylglucoside. For both lipid systems, composition-dependent transformations of unilamellar vesicles into micelles or vice versa were followed by high-sensitivity isothermal titration calorimetry. Data obtained over a range of detergent and lipid concentrations could be rationalised in terms of a three-stage phase separation model involving bilayer, bilayer/micelle coexistence, and micellar ranges, yielding the detergent/lipid phase diagrams and the bilayer-to-micelle partition coefficients of both detergent and lipid. The most notable difference between the lipids investigated was a substantial widening of the bilayer/micelle coexistence range for E. coli lipid, which was due to an increased preference of the detergent and a decreased affinity of the lipid for the micellar phase as compared with the bilayer phase. These effects on the bilayer-to-micelle partition coefficients could be explained by the high proportion in E. coli membranes of lipids possessing negative spontaneous curvature, which hampers both their transfer into strongly curved micellar structures as well as the insertion of detergent into condensed bilayers.
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Affiliation(s)
- Oxana O Krylova
- Leibniz Institute of Molecular Pharmacology (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
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