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Patel MB, Spikes H, Bailey RS, Connell T, Gill H, Gokel MR, Harris R, Meisel JW, Negin S, Yin SA, Gokel GW. Antimicrobial and Adjuvant Potencies of Di- n-alkyl Substituted Diazalariat Ethers. Antibiotics (Basel) 2023; 12:1513. [PMID: 37887214 PMCID: PMC10603992 DOI: 10.3390/antibiotics12101513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 09/28/2023] [Accepted: 09/28/2023] [Indexed: 10/28/2023] Open
Abstract
Lariat ethers are macrocyclic polyethers-crown ethers-to which sidearms are appended. 4,13-Diaza-18-crown-6 having twin alkyl chains at the nitrogens show biological activity. They exhibit antibiotic activity, but when co-administered at with an FDA-approved antibiotic, the latter's potency is often strongly enhanced. Potency enhancements and resistance reversals have been documented in vitro for a range of Gram-negative and Gram-positive bacteria with a variety of antimicrobials. Strains of E. coli and Staphylococcus aureus having resistance to a range of drugs have been studied and the potency enhancements (checkerboards) are reported here. Drugs included in the present study are ampicillin, cefepime, chlortetracycline, ciprofloxacin, doxycycline, kanamycin, minocycline, norfloxacin, oxycycline, penicillin G, and tetracycline. Enhancements of norfloxacin potency against S. aureus 1199B of up to 128-fold were observed. The properties of these lariat ethers have been studied to determine solubility, their membrane penetration, cytotoxicity and mammalian cell survival, and their effect on bacterial efflux pumps. It is shown that in some cases, the lariat ethers have complex antimicrobials with considerable selectivity. Based on these observations, including 1:1 complexation between lariat ethers and antimicrobials and the cytotoxicity of the MeI salts showing a separation index of 32-fold, they hold significant potential for further development.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - George W. Gokel
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, St. Louis, MO 63121, USA
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Kumari H, Negin S, Eisenhart A, Patel MB, Beck TL, Heinrich F, Spikes HJ, Gokel GW. Assessment of a host-guest interaction in a bilayer membrane model. RSC Adv 2022; 12:32046-32055. [PMID: 36415550 PMCID: PMC9648047 DOI: 10.1039/d2ra03851j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 10/20/2022] [Indexed: 10/28/2023] Open
Abstract
Supramolecular interactions are well recognized and many of them have been extensively studied in chemistry. The formation of supramolecular complexes that rely on weak force interactions are less well studied in bilayer membranes. Herein, a supported bilayer membrane is used to probe the penetration of a complex between tetracycline and a macrocyclic polyether. In a number of bacterial systems, the presence of the macrocycle has been found to significantly enhance the potency of the antimicrobial in vitro. The crown·tetracycline complex has been characterized in solution, neutron reflectometry has probed complex penetration, and the phenomena have been modeled by computational methods.
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Affiliation(s)
- Harshita Kumari
- James L. Winkle College of Pharmacy, University of Cincinnati Cincinnati Ohio USA 45267-0514
| | - Saeedeh Negin
- Chemistry & Biochemistry, University of Missouri-St. Louis 1 University Blvd. St. Louis MO 63121 USA
| | | | - Mohit B Patel
- Chemistry & Biochemistry, University of Missouri-St. Louis 1 University Blvd. St. Louis MO 63121 USA
| | - Thomas L Beck
- Department of Chemistry, University of Cincinnati OH 45267 USA
- National Center for Computational Sciences, Oak Ridge National Laboratory Oak Ridge TN 37830 USA
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University Pittsburgh PA 15213 USA
- NIST Center for Neutron Research, National Institute of Standards and Technology Gaithersburg MD 20899 USA
| | - Helena J Spikes
- Chemistry & Biochemistry, University of Missouri-St. Louis 1 University Blvd. St. Louis MO 63121 USA
| | - George W Gokel
- Chemistry & Biochemistry, University of Missouri-St. Louis 1 University Blvd. St. Louis MO 63121 USA
- Biology, University of Missouri-St. Louis 1 University Blvd. St. Louis MO 63121 USA
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3
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Gokel MR, McKeever M, Meisel JW, Negin S, Patel MB, Yin S, Gokel GW. Crown ethers having side arms: a diverse and versatile supramolecular chemistry. J COORD CHEM 2021. [DOI: 10.1080/00958972.2021.1878352] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Michael R. Gokel
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
| | - Michael McKeever
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
| | - Joseph W. Meisel
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
| | - Saeedeh Negin
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
| | - Mohit B. Patel
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
| | - Shanheng Yin
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
| | - George W. Gokel
- Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, St. Louis, MO, USA
- Departments of Biology, University of Missouri – St. Louis, St. Louis, MO, USA
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Patel MB, Garrad E, Meisel JW, Negin S, Gokel MR, Gokel GW. Synthetic ionophores as non-resistant antibiotic adjuvants. RSC Adv 2019; 9:2217-2230. [PMID: 35516101 PMCID: PMC9059958 DOI: 10.1039/c8ra07641c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 12/31/2018] [Indexed: 12/19/2022] Open
Abstract
Antimicrobial resistance is a world-wide health care crisis. New antimicrobials must both exhibit potency and thwart the ability of bacteria to develop resistance to them. We report the use of synthetic ionophores as a new approach to developing non-resistant antimicrobials and adjuvants. Most studies involving amphiphilic antimicrobials have focused on either developing synthetic amphiphiles that show ion transport, or developing non-cytotoxic analogs of such peptidic amphiphiles as colistin. We have rationally designed, prepared, and evaluated crown ether-based synthetic ionophores (‘hydraphiles’) that show selective ion transport through bilayer membranes and are toxic to bacteria. We report here that hydraphiles exhibit a broad range of antimicrobial properties and that they function as adjuvants in concert with FDA-approved antibiotics against multi-drug resistant (MDR) bacteria. Studies described herein demonstrate that benzyl C14 hydraphile (BC14H) shows high efficacy as an antimicrobial. BC14H, at sub-MIC concentrations, forms aggregates of ∼200 nm that interact with the surface of bacteria. Surface-active BC14H then localizes in the bacterial membranes, which increases their permeability. As a result, antibiotic influx into the bacterial cytosol increases in the presence of BCnHs. Efflux pump inhibition and accumulation of substrate was also observed, likely due to disruption of the cation gradient. As a result, BC14H recovers the activity of norfloxacin by 128-fold against resistant Staphylococcus aureus. BC14H shows extremely low resistance development and is less cytotoxic than colistin. Overall, synthetic ionophores represent a new scaffold for developing efficient and non-resistant antimicrobial-adjuvants. Antimicrobial resistance is a world-wide health care crisis.![]()
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Affiliation(s)
- Mohit B. Patel
- Department of Biology
- University of Missouri – St. Louis
- St. Louis
- USA
| | - Evan Garrad
- Department of Biology
- University of Missouri – St. Louis
- St. Louis
- USA
| | - Joseph W. Meisel
- Department of Chemistry
- Biochemistry University of Missouri – St. Louis
- St. Louis
- USA
| | - Saeedeh Negin
- Department of Chemistry
- Biochemistry University of Missouri – St. Louis
- St. Louis
- USA
| | - Michael R. Gokel
- Department of Chemistry
- Biochemistry University of Missouri – St. Louis
- St. Louis
- USA
| | - George W. Gokel
- Department of Biology
- University of Missouri – St. Louis
- St. Louis
- USA
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Negin S, Patel MB, Gokel MR, Meisel JW, Gokel GW. Inside Cover: Antibiotic Potency against E. coli
Is Enhanced by Channel-Forming Alkyl Lariat Ethers (ChemBioChem 22/2016). Chembiochem 2016. [DOI: 10.1002/cbic.201600569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Saeedeh Negin
- Department of Chemistry and Biochemistry; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
| | - Mohit B. Patel
- Department of Biology; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
| | - Michael R. Gokel
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
| | - Joseph W. Meisel
- Center for Nanoscience; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Department of Chemistry and Biochemistry; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
| | - George W. Gokel
- Center for Nanoscience; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Department of Chemistry and Biochemistry; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Department of Biology; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
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Negin S, Patel MB, Gokel MR, Meisel JW, Gokel GW. Antibiotic Potency againstE. coliIs Enhanced by Channel-Forming Alkyl Lariat Ethers. Chembiochem 2016; 17:2153-2161. [DOI: 10.1002/cbic.201600428] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Saeedeh Negin
- Department of Chemistry and Biochemistry; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
| | - Mohit B. Patel
- Department of Biology; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
| | - Michael R. Gokel
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
| | - Joseph W. Meisel
- Center for Nanoscience; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Department of Chemistry and Biochemistry; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
| | - George W. Gokel
- Center for Nanoscience; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Department of Chemistry and Biochemistry; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Department of Biology; University of Missouri; 1 University Blvd. St. Louis MO 63121 USA
- Upaya Pharmaceuticals, LLC; 4633 World Parkway Berkeley MO 63134 USA
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Meisel JW, Patel MB, Garrad E, Stanton RA, Gokel GW. Reversal of Tetracycline Resistance in Escherichia coli by Noncytotoxic bis(Tryptophan)s. J Am Chem Soc 2016; 138:10571-7. [DOI: 10.1021/jacs.6b05578] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joseph W. Meisel
- Center for Nanoscience, Departments of ‡Chemistry & Biochemistry and §Biology, University of Missouri − St. Louis, 1 University Blvd., St. Louis, Missouri 63121, United States
| | - Mohit B. Patel
- Center for Nanoscience, Departments of ‡Chemistry & Biochemistry and §Biology, University of Missouri − St. Louis, 1 University Blvd., St. Louis, Missouri 63121, United States
| | - Evan Garrad
- Center for Nanoscience, Departments of ‡Chemistry & Biochemistry and §Biology, University of Missouri − St. Louis, 1 University Blvd., St. Louis, Missouri 63121, United States
| | - Ryan A. Stanton
- Center for Nanoscience, Departments of ‡Chemistry & Biochemistry and §Biology, University of Missouri − St. Louis, 1 University Blvd., St. Louis, Missouri 63121, United States
| | - George W. Gokel
- Center for Nanoscience, Departments of ‡Chemistry & Biochemistry and §Biology, University of Missouri − St. Louis, 1 University Blvd., St. Louis, Missouri 63121, United States
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Meisel JW, Patel MB, Gokel GW. Condensation of plasmid DNA by benzyl hydraphiles and lariat ethers: dependence on pH and chain length. Supramol Chem 2016. [DOI: 10.1080/10610278.2016.1192170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Joseph W. Meisel
- Center for Nanoscience, University of Missouri–St. Louis, St. Louis, MO, USA
- Department of Chemistry & Biochemistry, University of Missouri–St. Louis, St. Louis, MO, USA
| | - Mohit B. Patel
- Center for Nanoscience, University of Missouri–St. Louis, St. Louis, MO, USA
- Department of Biology, University of Missouri–St. Louis, St. Louis, MO, USA
| | - George W. Gokel
- Center for Nanoscience, University of Missouri–St. Louis, St. Louis, MO, USA
- Department of Chemistry & Biochemistry, University of Missouri–St. Louis, St. Louis, MO, USA
- Department of Biology, University of Missouri–St. Louis, St. Louis, MO, USA
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Meisel JW, Gokel GW. A Simplified Direct Lipid Mixing Lipoplex Preparation: Comparison of Liposomal-, Dimethylsulfoxide-, and Ethanol-Based Methods. Sci Rep 2016; 6:27662. [PMID: 27323668 PMCID: PMC4914933 DOI: 10.1038/srep27662] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/18/2016] [Indexed: 11/09/2022] Open
Abstract
Established transfection methodology often uses commercial reagents, which must be formed into liposomes in a sequence of about half a dozen steps. The simplified method reported here is a direct lipid mixing approach that requires fewer steps, less manipulation, and is less time-consuming. Results are comparable to those obtained with more commonly used methods, as judged by a variety of analytical techniques and by comparisons of transfection results. The method reported here may be applied to non-liposome-forming compounds, thereby greatly expanding the range of structures that can be tested for transfection ability.
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Affiliation(s)
- Joseph W Meisel
- Center for Nanoscience, University of Missouri - St. Louis, 1 University Blvd., St. Louis, MO 63121, USA.,Department of Chemistry &Biochemistry, University of Missouri - St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - George W Gokel
- Center for Nanoscience, University of Missouri - St. Louis, 1 University Blvd., St. Louis, MO 63121, USA.,Department of Chemistry &Biochemistry, University of Missouri - St. Louis, 1 University Blvd., St. Louis, MO 63121, USA.,Department of Biology, University of Missouri - St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
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Patel MB, Garrad EC, Stavri A, Gokel MR, Negin S, Meisel JW, Cusumano Z, Gokel GW. Hydraphiles enhance antimicrobial potency against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis. Bioorg Med Chem 2016; 24:2864-70. [PMID: 27166575 DOI: 10.1016/j.bmc.2016.04.058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 04/19/2016] [Accepted: 04/27/2016] [Indexed: 10/21/2022]
Abstract
Hydraphiles are synthetic amphiphiles that form ion-conducting pores in liposomal membranes. These pores exhibit open-close behavior when studied by planar bilayer conductance techniques. In previous work, we showed that when co-administered with various antibiotics to the DH5α strain of Escherichia coli, they enhanced the drug's potency. We report here potency enhancements at low concentrations of hydraphiles for the structurally and mechanistically unrelated antibiotics erythromycin, kanamycin, rifampicin, and tetracycline against Gram negative E. coli (DH5α and K-12) and Pseudomonas aeruginosa, as well as Gram positive Bacillus subtilis. Earlier work suggested that potency increases correlated to ion transport function. The data presented here comport with the function of hydraphiles to enhance membrane permeability in addition to, or instead of, their known function as ion conductors.
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Affiliation(s)
- Mohit B Patel
- Center for Nanoscience, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA; Department of Biology, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - Evan C Garrad
- Department of Biology, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - Ariel Stavri
- Department of Biology, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - Michael R Gokel
- Upaya Pharmaceuticals, LLC, 4633 World Pkwy. Cir., Berkeley, MO 63134, USA; Center for Nanoscience, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - Saeedeh Negin
- Center for Nanoscience, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA; Department of Chemistry & Biochemistry, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - Joseph W Meisel
- Center for Nanoscience, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA; Department of Chemistry & Biochemistry, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA
| | - Zachary Cusumano
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - George W Gokel
- Center for Nanoscience, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA; Department of Chemistry & Biochemistry, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA; Department of Biology, University of Missouri-St. Louis, 1 University Blvd., St. Louis, MO 63121, USA; Upaya Pharmaceuticals, LLC, 4633 World Pkwy. Cir., Berkeley, MO 63134, USA.
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Cantwell R, C. Garrad E, R. Gokel M, J. Hayes M, W. Meisel J, Negin S, B. Patel M, W. Gokel G. Biological Activity of Macrocyclic Cation Transporters. CURR ORG CHEM 2015. [DOI: 10.2174/1385272819666150618195919] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
A series of straight and branched chain pyrogallol[4]arenes was studied and found to be essentially nontoxic to two strains of E. coli.
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Affiliation(s)
- Saeedeh Negin
- Center for Nanoscience
- University of Missouri-St. Louis
- St. Louis
- USA
- Dept. of Chemistry
| | - Michael R. Gokel
- Center for Nanoscience
- University of Missouri-St. Louis
- St. Louis
- USA
| | - Mohit B. Patel
- Dept. of Chemistry
- University of Missouri-St. Louis
- St. Louis
- USA
- Department of Biology
| | - Sergey L. Sedinkin
- Center for Nanoscience
- University of Missouri-St. Louis
- St. Louis
- USA
- Dept. of Chemistry
| | - David C. Osborn
- Center for Nanoscience
- University of Missouri-St. Louis
- St. Louis
- USA
| | - George W. Gokel
- Center for Nanoscience
- University of Missouri-St. Louis
- St. Louis
- USA
- Dept. of Chemistry
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Patel MB, Stavri A, Curvey NS, Gokel GW. Hydraphile synthetic ion channels alter root architecture in Arabidopsis thaliana. Chem Commun (Camb) 2014; 50:11562-4. [DOI: 10.1039/c4cc04769a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Negin S, Li R, Kulikov OV, Daschbach MM, Gokel GW. Ion transport through bilayer membranes mediated by pyrogallol[4]arenes. Inorganica Chim Acta 2014. [DOI: 10.1016/j.ica.2013.11.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Affiliation(s)
- Oleg V. Kulikov
- Center for Nanoscience, University of Missouri – St Louis, One University Boulevard, , St Louis, MO 63121, USA
| | - Saeedeh Negin
- Center for Nanoscience, University of Missouri – St Louis, One University Boulevard, , St Louis, MO 63121, USA
- Department of Chemistry & Biochemistry, University of Missouri – St Louis, One University Boulevard, St Louis, MO 63121, USA
| | - Nigam P. Rath
- Center for Nanoscience, University of Missouri – St Louis, One University Boulevard, , St Louis, MO 63121, USA
- Department of Chemistry & Biochemistry, University of Missouri – St Louis, One University Boulevard, St Louis, MO 63121, USA
| | - George W. Gokel
- Center for Nanoscience, University of Missouri – St Louis, One University Boulevard, , St Louis, MO 63121, USA
- Department of Chemistry & Biochemistry, University of Missouri – St Louis, One University Boulevard, St Louis, MO 63121, USA
- Department of Biology, University of Missouri – St Louis, One University Boulevard, , St Louis, MO 63121, USA
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Abstract
In this Account, we describe the development of several diverse families of synthetic, membrane-active amphiphiles that form pores and facilitate transport within membrane bilayers. For the most part, the compounds are amphiphiles that insert into the bilayer and form pores either on their own or by self-assembly. The first family of synthetic ion channels prepared in our lab, the hydraphiles, used crown ethers as head groups and as a polar central element. In a range of biophysical studies, we showed that the hydraphiles formed unimolecular pores that spanned the bilayer. They mediated the transport of Na(+) and K(+) but were blocked by Ag(+). The hydraphiles are nonrectifying and disrupt ion homeostasis. As a result, these synthetic ion channels are toxic to various bacteria and yeast, a feature that has been used therapeutically in direct injection chemotherapy. We also developed a family of amphiphilic heptapeptide ion transporters that selected Cl(-) >10-fold over K(+) and showed voltage dependent gating. The formed pores were approximately dimeric, and variations in the N- and C-terminal anchor chains and the acids affected transport rates. Surprisingly, the longer N-terminal anchor chains led to less transport but greater Cl(-) selectivity. A proline residue, which is present in the ClC protein channel's conductance pore, proved to be critical for Cl(-) transport selectivity. Pyrogallol[4]arenes are macrocycles formed by acid-catalyzed condensation of four 1,2,3- trihydroxybenzenes with four aldehydes. The combination of 12 hydroxyl groups on one face of the macrocycle and four pendant alkyl chains conferred considerable amphiphilicity to these compounds. The pyrogallol[4]arenes inserted into bilayer membranes and conducted ions. Based on our experimental evidence, the ions passed through a self-assembled pore comprising four or five amphiphiles rather than passing through the central opening of a single macrocycle. Pyrogallol[4]arenes constructed with branched chains are also amphiphilic and active in membranes. The pyrogallol[4]arene with 3-pentyl sidechains formed a unique nanotube assembly and functioned as an ion channel in bilayer membranes. Finally, we showed that dianilides of either isophthalic or dipicolinic acids, compounds which have been extensively studied as anion binders, can self-assemble to form pores within bilayers. We called these dianilides tris-arenes and have shown that they readily bind to phosphate anions. These structures also mediated the transport of DNA plasmids through vital bilayer membranes in the bacterium Escherichia coli and in the yeast Saccharomyces cerevisiae . This transformation or transfection process occurred readily and without any apparent toxicity or mutagenicity.
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Affiliation(s)
- George W. Gokel
- Departments of †Chemistry & Biochemistry and ‡Biology, §Center for Nanoscience, University of Missouri—St. Louis, St. Louis, Missouri 63121, United States
| | - Saeedeh Negin
- Departments of †Chemistry & Biochemistry and ‡Biology, §Center for Nanoscience, University of Missouri—St. Louis, St. Louis, Missouri 63121, United States
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Gokel GW, Lu T, Rudnick DA, Jackson-Machelski E, Gordon JI. MyristoylCoA:proteinN-Myristoyltransferase: Probing Host-Guest Interactions Using Synthetic Substrates. Isr J Chem 2013. [DOI: 10.1002/ijch.199200017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ogirala P, Negin S, Agena C, Schäfer C, Geisler T, Mattay J, Gokel GW. Properties of long alkyl-chained resorcin[4]arenes in bilayers and on the Langmuir trough. NEW J CHEM 2013. [DOI: 10.1039/c2nj40337d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Atkins JL, Patel MB, Daschbach MM, Meisel JW, Gokel GW. Anion complexation and transport by isophthalamide and dipicolinamide derivatives: DNA plasmid transformation in E. coli. J Am Chem Soc 2012; 134:13546-9. [PMID: 22862681 DOI: 10.1021/ja304816e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tris-arenes based on either isophthalic acid or 2,6-dipicolinic acid have been known for more than a decade to bind anions. Recent studies have also demonstrated their ability to transport various ions through membranes. In this report, we demonstrate two important properties of these simple diamides. First, they transport plasmid DNA into Escherichia coli about 2-fold over controls, where the ampicillin resistance gene is expressed in the bacteria. These studies were done with plasmid DNA (~2.6 kilobase (kb)) in JM109 E. coli cells. Second, known methods do not typically transport large plasmids (>15 kb). We demonstrate here that transformation of large pVIB plasmids (i.e., >20 kb) were enhanced over water controls by ~10-fold. These results are in striking contrast to the normal decrease in transformation with increasing plasmid size.
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Affiliation(s)
- Jason L Atkins
- Department of Chemistry & Biochemistry, and Center for Nanoscience, University of Missouri-St. Louis, St. Louis, Missouri 63121, USA
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20
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Abstract
During the past several decades, various synthetic organic compounds that form pores in bilayer membranes have been prepared and studied. These membrane active amphiphiles have also proved to be useful in affecting the transport of molecules into or through the bilayer. This article discusses the evolution of these compounds and exemplifies recent applications such as enhancement of antimicrobial activity.
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Affiliation(s)
- George W Gokel
- Center for Nanoscience, Department of Chemistry & Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
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21
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Daschbach MM, Negin S, You L, Walsh M, Gokel GW. Aggregation and Supramolecular Membrane Interactions that Influence Anion Transport in Tryptophan-Containing Synthetic Peptides. Chemistry 2012; 18:7608-23. [DOI: 10.1002/chem.201103203] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 01/16/2012] [Indexed: 11/05/2022]
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22
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Shan Y, Liu J(J, Rath NP, Gokel GW. Rapid Acyl Migration between Pyrogallyl 1,2- and 1,3-Dipivaloates. Nat Prod Commun 2012. [DOI: 10.1177/1934578x1200700313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Pyrogallol and its derivatives are biologically active compounds, and pyrogallol also forms the basis of an increasingly important tetrameric supramolecular scaffold. Pyrogallol[4]arenes are tetrameric macrocycles that form from 1,2,3-trihydroxybenzene and aldehydes under acidic conditions. Pyrogallol was treated with two equivalents of pivaloyl chloride to form pyrogallyl dipivaloate. A mixture of regioisomers was invariably obtained and a rapid equilibrium was observed between the 1,2- and 1,3-diesters in polar solvents. A pure sample of solid pyrogallyl 1,2-dipivaloate was isolated and its crystal structure was obtained. The pure compound was shown to rearrange to mixtures similar to those isolated initially.
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Affiliation(s)
- Yaming Shan
- Center for Nanoscience, University of Missouri, Saint Louis, MO 63121, USA
| | - Jimmy (Jingyue) Liu
- Center for Nanoscience, University of Missouri, Saint Louis, MO 63121, USA
- Department of Chemistry & Biochemistry, University of Missouri, Saint Louis, MO 63121, USA
| | - Nigam P. Rath
- Center for Nanoscience, University of Missouri, Saint Louis, MO 63121, USA
- Department of Chemistry & Biochemistry, University of Missouri, Saint Louis, MO 63121, USA
| | - George W. Gokel
- Center for Nanoscience, University of Missouri, Saint Louis, MO 63121, USA
- Department of Chemistry & Biochemistry, University of Missouri, Saint Louis, MO 63121, USA
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23
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Shan Y, Liu J, Rath NP, Gokel GW. Rapid acyl migration between pyrogallyl 1,2- and 1,3-dipivaloates. Nat Prod Commun 2012; 7:333-336. [PMID: 22545406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
Pyrogallol and its derivatives are biologically active compounds, and pyrogallol also forms the basis of an increasingly important tetrameric supramolecular scaffold. Pyrogallol[4]arenes are tetrameric macrocycles that form from 1,2,3-trihydroxybenzene and aldehydes under acidic conditions. Pyrogallol was treated with two equivalents of pivaloyl chloride to form pyrogallyl dipivaloate. A mixture of regioisomers was invariably obtained and a rapid equilibrium was observed between the 1,2- and 1,3-diesters in polar solvents. A pure sample of solid pyrogallyl 1,2-dipivaloate was isolated and its crystal structure was obtained. The pure compound was shown to rearrange to mixtures similar to those isolated initially.
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Affiliation(s)
- Yaming Shan
- Center for Nanoscience, University of Missouri, Saint Louis, MO 63121, USA
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24
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Daschbach MM, Kulikov OV, Long EF, Gokel GW. Pyrogallol[4]arenes Show Highly Variable Amphiphilic Behavior at the Air-Water Interface Dependent Upon Side Chain Length and Branching. Chemistry 2011; 17:8913-21. [DOI: 10.1002/chem.201100221] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Indexed: 11/11/2022]
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25
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Smith BA, Daschbach MM, Gammon ST, Xiao S, Chapman SE, Hudson C, Suckow M, Piwnica-Worms D, Gokel GW, Leevy WM. In vivo cell death mediated by synthetic ion channels. Chem Commun (Camb) 2011; 47:7977-9. [PMID: 21681307 DOI: 10.1039/c1cc12933c] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthetic ion channel hydraphiles, which are known to infiltrate membranes and disrupt ion homeostasis, were tested as direct injection toxins in live mice as potential schlerotic agents. The study uses a near-IR dye to image and evaluate the success of the approach.
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Affiliation(s)
- Bryan A Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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26
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Schlamadinger DE, Daschbach MM, Gokel GW, Kim JE. UV resonance Raman study of cation-π interactions in an indole crown ether. J Raman Spectrosc 2011; 42:633-638. [PMID: 25635155 PMCID: PMC4307609 DOI: 10.1002/jrs.2781] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
UV resonance Raman (UVRR) spectroscopy is used to probe changes in vibrational structure associated with cation-π interactions for the most prevalent amino acid π -donor, tryptophan. The model compound studied here is a diaza crown ether with two indole substituents. In the presence of sodium or potassium sequestered in the crown ether, or a protonated diaza group on the compound, the indole moieties participate in a cation-π interaction in which the pyrrolo group acts as the primary π-donor. Systematic shifts in relative intensity in the 760-780 cm-1 region are observed upon formation of this cation-π interaction; we propose that these modifications reflect shifts of the delocalized, ring-breathing W18 and hydrogen-out-of-plane (HOOP) vibrational modes in this spectral region. The observed changes are attributed to perturbations of the π-electron density as well as of normal modes that involve large displacement of the hydrogen atom on the C2 position of the pyrrole ring. Modest variations in the UVRR spectra for the three complexes studied here are correlated to differences in cation-π strength. Specifically, the UVRR spectrum of the sodium-bound complex differs from those of the potassium-bound or protonated-diaza complexes, and may reflect the observation that the C2 hydrogen atom in the sodium-bound complex exhibits the greatest perturbation relative to the other species. Normal modes sensitive to hydrogen-bonding, such as the tryptophan W10, W9, and W8 modes, also undergo shifts in the presence of the salts. These shifts reflect the strength of interaction of the indole N-H group with the iodide or hexafluorophosphate counteranion. The current observation that the W18 and HOOP normal mode regions of the indole crown ether compound are sensitive to cation-pyrrolo π interactions suggests that this region may provide reliable spectroscopic evidence of these important interactions in proteins.
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Affiliation(s)
- Diana E. Schlamadinger
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093 USA
| | | | - George W. Gokel
- Department of Chemistry, Washington University, St. Louis, MO 63110 USA
- Departments of Chemistry and Biochemistry, and Biology, Center for Nanoscience, University of Missouri – St. Louis, St. Louis, MO 63121 USA
- Department of Developmental Biology, Washington University, St. Louis, MO 63110 USA
| | - Judy E. Kim
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093 USA
- Correspondence to: Judy E. Kim, Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093 USA.
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27
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Smith BA, Gammon ST, Xiao S, Wang W, Chapman S, McDermott R, Suckow MA, Johnson JR, Piwnica-Worms D, Gokel GW, Smith BD, Leevy WM. In vivo optical imaging of acute cell death using a near-infrared fluorescent zinc-dipicolylamine probe. Mol Pharm 2011; 8:583-90. [PMID: 21323375 DOI: 10.1021/mp100395u] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cell death is a fundamental biological process that is present in numerous disease pathologies. Fluorescent probes that detect cell death have been developed for a myriad of research applications ranging from microscopy to in vivo imaging. Here we describe a synthetic near-infrared (NIR) conjugate of zinc(II)-dipicolylamine (Zn²+-DPA) for in vivo imaging of cell death. Chemically induced in vivo models of myopathy were established using an ionphore, ethanol, or ketamine as cytotoxins. The Zn²+-DPA fluorescent probe or corresponding control was subsequently injected, and whole animal fluorescence imaging demonstrated probe uptake at the site of muscle damage, which was confirmed by ex vivo and histological analyses. Further, a comparative study with a NIR fluorescent conjugate Annexin V showed less intense uptake at the site of muscle damage and high accumulation in the bladder. The results indicate that the fluorescent Zn²+-DPA conjugate is an effective probe for in vivo cell death detection and in some cases may be an appropriate alternative to fluorescent Annexin V conjugates.
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Affiliation(s)
- Bryan A Smith
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Negin S, Daschbach MM, Kulikov OV, Rath N, Gokel GW. Pore Formation in Phospholipid Bilayers by Branched-Chain Pyrogallol[4]arenes. J Am Chem Soc 2011; 133:3234-7. [DOI: 10.1021/ja1085645] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Saeedeh Negin
- Center for Nanoscience, Departments of Chemistry & Biochemistry and ‡Biology, University of Missouri - Saint Louis, Saint Louis, Missouri 63121, United States
| | - Megan M. Daschbach
- Center for Nanoscience, Departments of Chemistry & Biochemistry and ‡Biology, University of Missouri - Saint Louis, Saint Louis, Missouri 63121, United States
| | - Oleg V. Kulikov
- Center for Nanoscience, Departments of Chemistry & Biochemistry and ‡Biology, University of Missouri - Saint Louis, Saint Louis, Missouri 63121, United States
| | - Nigam Rath
- Center for Nanoscience, Departments of Chemistry & Biochemistry and ‡Biology, University of Missouri - Saint Louis, Saint Louis, Missouri 63121, United States
| | - George W. Gokel
- Center for Nanoscience, Departments of Chemistry & Biochemistry and ‡Biology, University of Missouri - Saint Louis, Saint Louis, Missouri 63121, United States
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29
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Elidrisi I, Negin S, Bhatt PV, Govender T, Kruger HG, Gokel GW, Maguire GEM. Pore formation in phospholipid bilayers by amphiphilic cavitands. Org Biomol Chem 2011; 9:4498-506. [DOI: 10.1039/c0ob01236j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Carasel IA, Yamnitz CR, Winter RK, Gokel GW. Halide Ions Complex and Deprotonate Dipicolinamides and Isophthalamides: Assessment by Mass Spectrometry and UV−Visible Spectroscopy. J Org Chem 2010; 75:8112-6. [DOI: 10.1021/jo101749a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- I. Alexandru Carasel
- Departments of Chemistry and Developmental Biology, Washington University, St. Louis, Missouri 63130, United States
| | - Carl R. Yamnitz
- Departments of Chemistry and Developmental Biology, Washington University, St. Louis, Missouri 63130, United States
| | | | - George W. Gokel
- Center for Nanoscience,
- Departments of Chemistry & Biochemistry
- Biology
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31
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Abstract
Hydraphile synthetic ion channels were found to enhance the cytotoxicity to E. coli and B. subtilis of erythromycin, kanamycin, rifampicin, and tetracycline when co-administered with the antibiotic at sublethal concentrations of channel.
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Affiliation(s)
- Jason L Atkins
- Department of Chemistry & Biochemistry, Center for Nanoscience, University of Missouri-Saint Louis, Saint Louis, MO 63121, USA
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32
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Yamnitz CR, Negin S, Carasel IA, Winter RK, Gokel GW. Dianilides of dipicolinic acid function as synthetic chloride channels. Chem Commun (Camb) 2010; 46:2838-40. [DOI: 10.1039/b924812a] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Affiliation(s)
- Ruiqiong Li
- a Department of Chemistry , Washington University , 1 Brookings Drive, Saint Louis, MO, 63130, USA
| | - Rudolph E.K. Winter
- b Departments of Chemistry & Biochemistry and Biology , Center for Nanoscience, University of Missouri – Saint Louis , One University Boulevard, Saint Louis, MO, 63121, USA
| | - Joseph Kramer
- b Departments of Chemistry & Biochemistry and Biology , Center for Nanoscience, University of Missouri – Saint Louis , One University Boulevard, Saint Louis, MO, 63121, USA
| | - George W. Gokel
- b Departments of Chemistry & Biochemistry and Biology , Center for Nanoscience, University of Missouri – Saint Louis , One University Boulevard, Saint Louis, MO, 63121, USA
- c Washington University School of Medicine , Saint Louis, MO, 63110, USA
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Kulikov OV, Li R, Gokel GW. A synthetic ion channel derived from a metallogallarene capsule that functions in phospholipid bilayers. Angew Chem Int Ed Engl 2009; 48:375-7. [PMID: 19053120 DOI: 10.1002/anie.200804099] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Oleg V Kulikov
- Department of Chemistry, Center for Nanoscience, University of Missouri-Saint Louis, One University Boulevard, Saint Louis, MO 63121, USA
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35
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Li R, Kulikov OV, Gokel GW. Pyrogallarene-based ion-conducting pores that show reversible conductance properties. Chem Commun (Camb) 2009:6092-4. [DOI: 10.1039/b907750b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Kulikov OV, Daschbach MM, Yamnitz CR, Rath N, Gokel GW. Self-assembled, cogged hexameric nanotubes formed from pyrogallol[4]arenes with a unique branched side chain. Chem Commun (Camb) 2009:7497-9. [DOI: 10.1039/b917431a] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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37
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38
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Kulikov OV, Rath NP, Zhou D, Carasel IA, Gokel GW. Guest molecule entrapment by both capsule and hydrocarbon sidechains in self-assembled pyrogallol[4]arenes. NEW J CHEM 2009. [DOI: 10.1039/b823160e] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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39
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Wang W, Li R, Gokel GW. “Aplosspan:” a bilayer-length, ion-selective ionophore that functions in phospholipid bilayers. Chem Commun (Camb) 2009:911-3. [DOI: 10.1039/b816819a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Abstract
The amphiphilic heptapeptides-referred to as synthetic anion transporters (SATs)-mediate chloride transport in planar lipid bilayer membranes, synthetic liposomes, and mammalian cells. The SATs described have the general formula R1(2)NCOCH2OCH2CO-(Gly)3-Pro-(Gly)3-OR2. Substitution at R1 and R2 with various aliphatic or aromatic groups alters the ability of SATs to transport chloride through a phospholipid bilayer membrane. Despite extensive structure-activity relationship studies concerning Cl(-)-mediated transport by SATs, relatively little was known about the mechanism of insertion and pore-formation in the membrane. In the current study, the mechanistic behavior of SATs was investigated in aqueous solution and at the air-water interface. In the latter case, Langmuir trough studies and Brewster angle microscopy (BAM) revealed the extent of monolayer stability and organization for SATs. Dynamic light scattering and transmission electron microscopy (TEM) confirmed these results and defined the aggregation behavior of SATs in solution. SAT derivatives that showed low chloride transport activity organized into stable monolayers at the air-water interface, while more active SATs formed less stable monolayers. The relationship between intermolecular organization of SATs and pore-formation in the membrane is discussed along with its implications for chloride transport.
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41
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Abstract
A family of heptapeptide-based chloride transporters (called synthetic anion transporters, SATs) were designed to insert into phospholipid membrane bilayers and form pores. Many of these compounds have proved to be chloride selective transporters. The transporters were designed to incorporate hydrophilic heptapeptides that could serves as headgroups and hydrocarbon tails that could serve as hydrophobic membrane anchors. Insertion of the SAT molecules into a bilayer requires approach to and insertion at the aqueous-membrane surface. The studies reported here were conducted to model and understand this process by studying SAT behavior at the air-water interface. A Langmuir trough was used to obtain surface pressure-area isotherm data. These data for amphiphilic SATs were augmented by Brewster angle microscopy (BAM), molecular modeling, and calculations of the hydrophobicity parameter log P. The analyses showed that the heptapeptide (hydrophilic) module of the SAT molecule rested on the water surface while the dialkyl (hydrophobic) tails oriented themselves in the air, perpendicular to the water surface. Brewster angle microscopy visually confirmed a high order of molecular organization. Results from these studies are consistent with the previously proposed mechanism of SAT membrane insertion and pore formation.
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Affiliation(s)
- Elizabeth K Elliott
- Department of Chemistry, Washington University, St. Louis, MO 63130, United States
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42
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You L, Li R, Gokel GW. Anion transport properties of amine and amide-sidechained peptides are affected by charge and phospholipid composition. Org Biomol Chem 2008; 6:2914-23. [PMID: 18688484 DOI: 10.1039/b800530c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four synthetic anion transporters (SATs) having the general formula (n-C(18)H(37))(2)N-COCH(2)OCH(2)CO-(Gly)(3)Pro-Lys(epsilon-N-R)-(Gly)(2)-O-n-C(7)H(15) were prepared and studied. The group R was Cbz, H (TFA salt), t-Boc, and dansyl in peptides 1, 2, 3, and 4 respectively. The glutamine analog (GGGPQAG sequence) was also included. A dansyl-substituted fluorescent SAT was used to probe peptide insertion; the dansyl sidechain resides in an environment near the bilayer's midpolar regime. When the lysine sidechain was free or protected amine, little effect was noted on final Cl(-) transport rate in DOPC : DOPA (7 : 3) liposomes. This stands in contrast to the significant retardation of transport previously observed when a negative glutamate residue was present in the peptide sequence. It was also found that Cl(-) release from liposomes depended on the phospholipid composition of the vesicles. Chloride transport diminished significantly for the free lysine containing SAT, 2, when the lipid was altered from DOPC : DOPA to pure DOPC. Amide-sidechained SATs 1 and 5 showed a relatively small decrease in Cl(-) transport. The effect of lipid composition on Cl(-) transport was explained by differences in electrostatic interaction between amino acid sidechain and lipid headgroup, which was modeled by computation.
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Affiliation(s)
- Lei You
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
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43
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Abstract
Hydraphiles are synthetic ionophores that were designed to mimic some properties of protein channels that conduct such cations as sodium. They use macrocyclic (crown) polyethers as amphiphilic headgroups and as entry and exit portals. Their overall length is controlled by covalent links between the two headgroups (distal macrocycles) and the "central relay" unit, typically also an azacrown. The hydraphiles insert in the bilayer membranes of synthetic phospholipid vesicles or vital cells and mediate the transport of cations. The hydraphiles were intended to be models but they are functional channels. Because they are symmetric, they are non-rectifying but they show open-close behavior characteristic of natural channels. Because they are non-rectifying, when they insert into a microbial membrane, they lead to a rapid change in osmotic balance that proves fatal to bacteria.
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Affiliation(s)
- George W Gokel
- Department of Chemistry & Biochemistry and Center for Nanoscience, University of Missouri-St. Louis, One University Blvd., St. Louis, MO 63121, USA
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44
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Meadows ES, De Wall SL, Salama PW, Abel E, Gokel GW. N,N-Didansyl-4,13-diaza-18-Crown-6: A Fluorescence-sensitive, Weakly Complexing Macrocycle Used to Probe the Phospholipid Vesicle Environment. Supramol Chem 2008. [DOI: 10.1080/10610279908559282] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Eric S. Meadows
- a Bioorganic Chemistry Program and Dept. of Molecular Biology and Pharmacology , Washington University School of Medicine , 660 South Euclid Ave., Campus Box 8103, St. Louis, MO, 63110, USA
| | - Stephen L. De Wall
- a Bioorganic Chemistry Program and Dept. of Molecular Biology and Pharmacology , Washington University School of Medicine , 660 South Euclid Ave., Campus Box 8103, St. Louis, MO, 63110, USA
| | - Paul W. Salama
- a Bioorganic Chemistry Program and Dept. of Molecular Biology and Pharmacology , Washington University School of Medicine , 660 South Euclid Ave., Campus Box 8103, St. Louis, MO, 63110, USA
| | - Ernesto Abel
- a Bioorganic Chemistry Program and Dept. of Molecular Biology and Pharmacology , Washington University School of Medicine , 660 South Euclid Ave., Campus Box 8103, St. Louis, MO, 63110, USA
| | - George W. Gokel
- a Bioorganic Chemistry Program and Dept. of Molecular Biology and Pharmacology , Washington University School of Medicine , 660 South Euclid Ave., Campus Box 8103, St. Louis, MO, 63110, USA
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45
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You L, Ferdani R, Li R, Kramer JP, Winter REK, Gokel GW. Carboxylate anion diminishes chloride transport through a synthetic, self-assembled transmembrane pore. Chemistry 2008; 14:382-96. [PMID: 17924596 DOI: 10.1002/chem.200701071] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Six amphiphilic heptapeptides with the structure (C18H37)2NCOCH2OCH2CO-(Gly)3-Pro-(Gly)n-(Glx)-(Gly)m-O(CH2)6CH3, in which Glx represents glutamic acid or its benzyl ester and n+m=2, have been studied. In addition, the glutamate residue in the GGGPGGE sequence was esterified by fluorescent 1-pyrenemethanol. These compounds insert into phospholipid bilayers and form anion-conducting pores. Hill plots based on carboxyfluorescein release indicate that the pores are at least dimeric. Studies that involved ion-selective electrode techniques showed that transport of chloride varied with the position of glutamate within the peptide chain and whether glutamic acid was present as the free acid or its benzyl ester. Chloride transport activity was significantly higher for the glutamate esters than for free carboxylates irrespective of the glutamate position. Activity was highest when the glutamate residue in approximately (Gly)3-Pro-(Xxx)3 approximately was closest to the C terminus of the peptide. A fluorescent pyrene residue was introduced to probe the aggregation state of the amphiphile. The selectivity of the pore for Cl(-) over K+ was maintained even when the carboxylate anion was present within it. Complexation of Cl(-) by the ionophoric peptides was confirmed by negative ion mass spectrometry. Planar bilayer voltage clamp experiments confirmed that pores with more than one conductance state may form in these dynamic, self-assembled pores.
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Affiliation(s)
- Lei You
- Department of Chemistry, Washington University, 1 Brookings Drive, St. Louis, MO 63130, USA
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46
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Iglesias-Sánchez JC, Wang W, Ferdani R, Prados P, de Mendoza J, Gokel GW. Synthetic cation transporters incorporating crown ethers and calixarenes as headgroups and central relays: a comparison of sodium and chloride selectivity. NEW J CHEM 2008; 32:878-890. [PMID: 21720497 PMCID: PMC3124113 DOI: 10.1039/b719235p] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/06/2023]
Abstract
An earlier study showed that a calix[4]arene could function as a central relay unit to form an ion conductance pathway through a phospholipid bilayer membrane. The present study expands the range of compounds from calix[4]arene to calix[6]arene and incorporates them either as central units or as headgroups, substituting one or more diaza-18-crown-6 residues in functioning hydraphiles. Ion release was assayed by detecting either Na(+) or Cl(-) release from phospholipid vesicles. The ion transport activity for calix[4]arenes in either position is modest, but is almost non-existent when calix[6] residues were incorporated either as head groups or central relay units. The poor activity of the calix[6]arenes may result from an inability to penetrate to the midplane of the bilayer or pass entirely through it to form a conductance pathway. The transmembrane "flip-flop" may result from high polarity or steric bulk, or both. A hydraphile incorporating a single -NHCOC(6)H(4)OCH(2)CONH- as a central relay proved to be an excellent Na(+) conductor, but less selective for Cl(-). The fact that this new hydraphile molecule shows selectivity for Na (+) over Cl(-) transport and possesses two secondary amide residues in the central relay suggests a means to control ion selectivity in synthetic ion transporters.
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Affiliation(s)
- José Carlos Iglesias-Sánchez
- Facultad de Ciencias, Departamento de Química Orgánica (C-I), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Wei Wang
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
| | - Riccardo Ferdani
- Department of Molecular Biology & Pharmacology, Washington University, St. Louis, MO 63130, USA. E-mail: ; Fax: 314/516-5342; Tel: 314/516-5321
| | - Pilar Prados
- Facultad de Ciencias, Departamento de Química Orgánica (C-I), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Javier de Mendoza
- Facultad de Ciencias, Departamento de Química Orgánica (C-I), Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Institute of Chemical Research of Catalonia (ICIQ), 43007 Tarragona, Spain
| | - George W. Gokel
- Departments of Chemistry & Biochemistry and Biology, Center for Nanoscience, University of Missouri – St. Louis, St. Louis, MO 63121, USA
- Department of Molecular Biology & Pharmacology, Washington University, St. Louis, MO 63130, USA. E-mail: ; Fax: 314/516-5342; Tel: 314/516-5321
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Abstract
Synthetic anion transporters (SATs) of the general type (n-C18H37)2N-COCH2OCH2CO-(Gly)3-Pro-(Gly)3-O-n-C7H15, 1, are amphiphilic peptides that form anion-conducting pores in bilayer membranes. To better understand membrane insertion, assembly and aggregation dynamics, and membrane penetration, four novel fluorescent structures were prepared for use in both aqueous buffer and phospholipid bilayers. The fluorescent residues pyrene, indole, dansyl, and NBD were incorporated into 1 to give 2, 3, 4, and 5, respectively. Assembly of peptide amphiphiles in buffer was confirmed by monitoring changes in the pyrene monomer/excimer peaks observed for 2. Solvent-dependent fluorescence changes that were observed for indole (3) and dansyl (4) side-chained SATs in bilayers showed that these residues experienced an environment between epsilon=9 (CH2Cl2) and epsilon=24 (EtOH) in polarity. Fluorescence resonance energy transfer (FRET) between 2 and 3 demonstrated aggregation of SAT monomers within the bilayer. This self-assembly led to pore formation, which was detected as Cl(-) release from the liposomes. The results of acrylamide quenching of fluorescent SATs supported membrane insertion. Studies with NBD-labeled SAT 5 showed that peptide partition into the bilayer is relatively slow. Dithionite quenching of NBD-SATs suggests that the amphiphilic peptides are primarily in the bilayer's outer leaflet. Images obtained by using a fluorescence microscope revealed membrane localization of a fluorescent SAT. Taken together, this study helps define the insertion, membrane localization, and aggregation behavior of this family of synthetic anion transporters in liposomal bilayers.
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Affiliation(s)
- Lei You
- Department of Chemistry, Washington University, One Brookings Drive, Saint Louis, MO 63130, USA
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Lee PK, Chapman RP, Zhang L, Hu J, Barbour LJ, Elliott EK, Gokel GW, Bryce DL. K-39 Quadrupolar and Chemical Shift Tensors for Organic Potassium Complexes and Diatomic Molecules. J Phys Chem A 2007; 111:12859-63. [DOI: 10.1021/jp0774239] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Philip K. Lee
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - Rebecca P. Chapman
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - Lei Zhang
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - Jiaxin Hu
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - Leonard J. Barbour
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - Elizabeth K. Elliott
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - George W. Gokel
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
| | - David L. Bryce
- Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada, Departments of Chemistry and Biology, Center for Nanoscience, University of Missouri, St. Louis, Missouri 63121, and Washington University, St. Louis, Missouri 63110
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Gokel GW. Self-assembly in supramolecular systems. Ciba Found Symp 2007; 158:23-31; discussion 31-8, 39-41. [PMID: 1718669 DOI: 10.1002/9780470514085.ch3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The complex structural and functional properties of many natural molecules have spawned innumerable attempts to understand and mimic biological activity. This has often involved preparing extremely complex structures of carefully designed geometries. In natural systems the primary structure of a protein (the amino acid sequence) establishes all of the structural relationships within the molecule, although many of these are not apparent until the molecule folds, coils, or otherwise adopts the appropriate conformation. Nature has selected suitable amino acid sequences for various applications during eons of evolution. In this paper, we report our efforts to achieve similar results by providing all of the required structural elements on a flexible framework. This concept is illustrated in three ways: the design and preparation of a redox-switched vesicle and a small-molecule molecular receptor (both based on the ferrocene system) and of a functional cation channel.
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Affiliation(s)
- G W Gokel
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124
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