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Yuan X, Shen J, Zeng H. Artificial transmembrane potassium transporters: designs, functions, mechanisms and applications. Chem Commun (Camb) 2024; 60:482-500. [PMID: 38111319 DOI: 10.1039/d3cc04488b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
Potassium channels represent the most prevalent class of ion channels, exerting regulatory control over numerous vital biological processes, including muscle contraction, neurotransmitter release, cell proliferation, and apoptosis. The seamless integration of astonishing functions into a sophisticated structure, as seen in these protein channels, inspires the chemical community to develop artificial versions, gearing toward simplifying their structure while replicating their key functions. In particular, over the past ten years or so, a number of elegant artificial potassium transporters have emerged, demonstrating high selectivity, high transport efficiency or unprecedented transport mechanisms. In this review, we will provide a detailed exposition of these artificial potassium transporters that are derived from a single molecular backbone or self-assembled from multiple components, with their respective structural designs, channel functions, transport mechanisms and biomedical applications thoroughly reviewed.
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Affiliation(s)
- Xiyu Yuan
- College of Chemistry Fuzhou University Fuzhou, Fujian 350116, China.
| | - Jie Shen
- College of Chemistry Fuzhou University Fuzhou, Fujian 350116, China.
| | - Huaqiang Zeng
- College of Chemistry Fuzhou University Fuzhou, Fujian 350116, China.
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Johnson TG, Langton MJ. Molecular Machines For The Control Of Transmembrane Transport. J Am Chem Soc 2023; 145:27167-27184. [PMID: 38062763 PMCID: PMC10740008 DOI: 10.1021/jacs.3c08877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 11/21/2023] [Accepted: 11/22/2023] [Indexed: 12/21/2023]
Abstract
Nature embeds some of its molecular machinery, including ion pumps, within lipid bilayer membranes. This has inspired chemists to attempt to develop synthetic analogues to exploit membrane confinement and transmembrane potential gradients, much like their biological cousins. In this perspective, we outline the various strategies by which molecular machines─molecular systems in which a nanomechanical motion is exploited for function─have been designed to be incorporated within lipid membranes and utilized to mediate transmembrane ion transport. We survey molecular machines spanning both switches and motors, those that act as mobile carriers or that are anchored within the membrane, mechanically interlocked molecules, and examples that are activated in response to external stimuli.
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Affiliation(s)
- Toby G. Johnson
- Department of Chemistry, Chemistry
Research Laboratory, University of Oxford Mansfield Road, Oxford OX1 3TA United Kingdom
| | - Matthew J. Langton
- Department of Chemistry, Chemistry
Research Laboratory, University of Oxford Mansfield Road, Oxford OX1 3TA United Kingdom
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Johnson TG, Docker A, Sadeghi-Kelishadi A, Langton MJ. Halogen bonding relay and mobile anion transporters with kinetically controlled chloride selectivity. Chem Sci 2023; 14:5006-5013. [PMID: 37206385 PMCID: PMC10189858 DOI: 10.1039/d3sc01170d] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/03/2023] [Indexed: 05/21/2023] Open
Abstract
Selective transmembrane transport of chloride over competing proton or hydroxide transport is key for the therapeutic application of anionophores, but remains a significant challenge. Current approaches rely on enhancing chloride anion encapsulation within synthetic anionophores. Here we report the first example of a halogen bonding ion relay in which transport is facilitated by the exchange of ions between lipid-anchored receptors on opposite sides of the membrane. The system exhibits non-protonophoric chloride selectivity, uniquely arising from the lower kinetic barrier to chloride exchange between transporters within the membrane, compared to hydroxide, with selectivity maintained across membranes with different hydrophobic thicknesses. In contrast, we demonstrate that for a range of mobile carriers with known high chloride over hydroxide/proton selectivity, the discrimination is strongly dependent on membrane thickness. These results demonstrate that the selectivity of non-protonophoric mobile carriers does not arise from ion binding discrimination at the interface, but rather through a kinetic bias in transport rates, arising from differing membrane translocation rates of the anion-transporter complexes.
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Affiliation(s)
- Toby G Johnson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford 12 Mansfield Road Oxford OX1 3TA UK
| | - Andrew Docker
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford 12 Mansfield Road Oxford OX1 3TA UK
| | - Amir Sadeghi-Kelishadi
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford 12 Mansfield Road Oxford OX1 3TA UK
| | - Matthew J Langton
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford 12 Mansfield Road Oxford OX1 3TA UK
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Jin L, Sun C, Li Z, Shen J, Zeng H. A K +-selective channel with a record-high K +/Na + selectivity of 20.1. Chem Commun (Camb) 2023; 59:3610-3613. [PMID: 36891811 DOI: 10.1039/d2cc04396c] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
For compounds each containing a phenylalanine moiety with its two ends amidated to have a 15-crown-5 unit and an alkyl chain, a simple tuning of the alkyl chain length delivered a K+-selective channel with a record-high K+/Na+ selectivity of 20.1.
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Affiliation(s)
- Lei Jin
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shannxi 710072, China
| | - Chang Sun
- College of Textile Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Zhongyan Li
- College of Chemistry, Fuzhou University, Fuzhou, Fujian 350116, China.
| | - Jie Shen
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shannxi 710072, China
- College of Chemistry, Fuzhou University, Fuzhou, Fujian 350116, China.
| | - Huaqiang Zeng
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, Shannxi 710072, China
- College of Chemistry, Fuzhou University, Fuzhou, Fujian 350116, China.
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He L, Zhang T, Zhu C, Yan T, Liu J. Crown Ether-Based Ion Transporters in Bilayer Membranes. Chemistry 2023; 29:e202300044. [PMID: 36723493 DOI: 10.1002/chem.202300044] [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: 01/07/2023] [Revised: 01/28/2023] [Accepted: 01/30/2023] [Indexed: 02/02/2023]
Abstract
Bilayer membranes that enhance the stability of the cell are essential for cell survival, separating and protecting the interior of the cell from its external environment. Membrane-based channel proteins are crucial for sustaining cellular activities. However, dysfunction of these proteins would induce serial channelopathies, which could be substituted by artificial ion channel analogs. Crown ethers (CEs) are widely studied in the area of artificial ion channels owing to their intrinsic host-guest interaction with different kinds of organic and inorganic ions. Other advantages such as lower price, chemical stability, and easier modification also make CE a research hotspot in the field of synthetic transmembrane nanopores. And numerous CEs-based membrane-active synthetic ion channels were designed and fabricated in the past decades. Herein, the recent progress of CEs-based synthetic ion transporters has been comprehensively summarized in this review, including their design principles, functional mechanisms, controllable properties, and biomedical applications. Furthermore, this review has been concluded by discussing the future opportunities and challenges facing this research field. It is anticipated that this review could offer some inspiration for the future fabrication of novel CEs-derived ion transporters with more advanced structures, properties, and practical applications.
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Affiliation(s)
- Lei He
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Key Laboratory of Organosilicon Material Technology of Zhejiang Province, Hangzhou Normal University, 311121, Hangzhou, P. R. China
| | - Tianlong Zhang
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Key Laboratory of Organosilicon Material Technology of Zhejiang Province, Hangzhou Normal University, 311121, Hangzhou, P. R. China
| | - Canhong Zhu
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Key Laboratory of Organosilicon Material Technology of Zhejiang Province, Hangzhou Normal University, 311121, Hangzhou, P. R. China
| | - Tengfei Yan
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Key Laboratory of Organosilicon Material Technology of Zhejiang Province, Hangzhou Normal University, 311121, Hangzhou, P. R. China
| | - Junqiu Liu
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Key Laboratory of Organosilicon Material Technology of Zhejiang Province, Hangzhou Normal University, 311121, Hangzhou, P. R. China
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Abstract
Both biological and artificial membrane transporters mediate passive transmembrane ion flux predominantly via either channel or carrier mechanisms, tightly regulating the transport of materials entering and exiting the cell. One early elegant example unclassifiable as carriers or channels was reported by Smith who derivatized a phospholipid molecule into an anion transporter, facilitating membrane transport via a two-station relay mechanism (Smith et al. J. Am. Chem. Soc. 2008, 130, 17274-17275). Our journey toward blurring or even breaking the boundaries defined by the carrier and channel mechanisms starts in January of 2018 when seeing a child swinging on the swing at the playground park. Since then, I have been wondering whether we could build a nanoscale-sized molecular swing able to perform the swing function at the molecular level to induce transmembrane ion flux. Such research journey culminates in several membrane-active artificial molecular machines, including molecular swings, ion fishers, ion swimmers, rotors, tetrapuses and dodecapuses that permeabilize the membrane via swinging, ion-fishing, swimming, rotating, or swing-relaying actions, respectively. Except for molecular ion swimmers, these unconventional membrane transporters in their most stable states readily span across the entire membrane in a way akin to channels. With built-in flexible arms that can swing or bend in the dynamic membrane environment, they transport ions via constantly changing ion permeation pathways that are more defined than carriers but less defined than channels. Applying the same benzo-crown ether groups as the sole ion-binding and -transporting units, these transporters however differ immensely in ion transport property. While the maximal K+ transport activity is achieved by the molecular swing also termed "motional channel" that displays an EC50 value of 0.021 mol % relative to lipid and transports K+ ions at rate 27% faster than gramicidin A, the highest K+/Na+ selectivity of 18.3 is attained by the molecular ion fisher, with the highest Na+/K+ selectivity of 13.7 by the molecular dodecapus. Having EC50 values of 0.49-1.60 mol % and K+/Na+ values of 1.1-6.3, molecular rotors and tetrapuses are found to be generally active but weakly to moderately K+-selective. For molecular ion swimmers that contain 10 to 14 carbon atom alkyl linkers, they all turn out to be highly active (EC50 = 0.18-0.41 mol %) and highly selective (RK+/RNa+ = 7.0-9.5) transporters. Of special note are crown ether-appended molecular dodecapuses that establish the C60-fullerene core as an excellent platform to allow for a direct translation of solution binding affinity to transmembrane ion transport selectivity, providing a de novo basis for rationally designing artificial ion transporters with high transport selectivity. Considering remarkable cytotoxic activities displayed by molecular swings and ion swimmers, the varied types of existing and emerging unconventional membrane transporters with enhanced activities and selectivities eventually might lead to medical benefits in the future.
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Affiliation(s)
- Jie Shen
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, China
| | - Changliang Ren
- School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Huaqiang Zeng
- School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, China
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