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Wang J, Liu X, Li R, Fan Y. Biomimetic strategies and technologies for artificial tactile sensory systems. Trends Biotechnol 2023; 41:951-964. [PMID: 36658007 DOI: 10.1016/j.tibtech.2022.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 12/12/2022] [Accepted: 12/21/2022] [Indexed: 01/19/2023]
Abstract
The sense of touch events, achieved by artificial tactile sensory systems (ATSSs), is a milestone in the progress of human-machine interactions. However, it has been a challenge for ATSSs to serve functions comparable with the human tactile perception system (HTPS). The biomimetic strategies and technologies inspired by HTPS are considered an optimal solution to this challenge. Recent studies have reported bioinspired strategies for improving specific aspects of ATSS performance, such as feature collection, signal conversion, and information computation. Here, we present a systematic interpretation of biomechanisms for HTPSs, and correspondingly, address biomimetic strategies and technologies contributing to ATSSs as an integral system. This review will benefit the development and application of ATSSs in the future.
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Affiliation(s)
- Jinghui Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing 100083, China
| | - Xiaoyu Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing 100083, China; State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing 100083, China.
| | - Ruya Li
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing 100083, China
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing 100083, China; State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing 100083, China; School of Medical Science and Engineering Medicine, Beihang University, Beijing 100083, China.
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2
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Effects of Ionophores on Ruminal Function of Beef Cattle. Animals (Basel) 2021; 11:ani11102871. [PMID: 34679890 PMCID: PMC8532634 DOI: 10.3390/ani11102871] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 09/14/2021] [Accepted: 09/29/2021] [Indexed: 01/19/2023] Open
Abstract
Ionophores have been widely used in the beef and dairy industry for decades to improve feed efficiency and performance by altering ruminal fermentation dynamics, increasing the level of propionate. Ionophores can also reduce ruminal proteolysis and ammonia synthesis, thus increasing the influx of protein into the small intestine in cattle, leading to improvements in performance and efficiency responses. Ionophores indirectly impact ruminal methanogenesis by decreasing the substrate used to produce methane. Despite the consistent benefits of using ionophores in cattle nutrition, their utilization is under public scrutiny due to concerns related to microbial adaptation. However, there is inconsistent evidence supporting these concerns, whereas ionophores are still an important dietary tool to enhance productivity and profitability in beef production systems.
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Epsztein R, DuChanois RM, Ritt CL, Noy A, Elimelech M. Towards single-species selectivity of membranes with subnanometre pores. NATURE NANOTECHNOLOGY 2020; 15:426-436. [PMID: 32533116 DOI: 10.1038/s41565-020-0713-6] [Citation(s) in RCA: 238] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 05/12/2020] [Indexed: 05/12/2023]
Abstract
Synthetic membranes with pores at the subnanometre scale are at the core of processes for separating solutes from water, such as water purification and desalination. While these membrane processes have achieved substantial industrial success, the capability of state-of-the-art membranes to selectively separate a single solute from a mixture of solutes is limited. Such high-precision separation would enable fit-for-purpose treatment, improving the sustainability of current water-treatment processes and opening doors for new applications of membrane technologies. Herein, we introduce the challenges of state-of-the-art membranes with subnanometre pores to achieve high selectivity between solutes. We then analyse experimental and theoretical literature to discuss the molecular-level mechanisms that contribute to energy barriers for solute transport through subnanometre pores. We conclude by providing principles and guidelines for designing next-generation single-species selective membranes that are inspired by ion-selective biological channels.
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Affiliation(s)
- Razi Epsztein
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA
- Faculty of Civil and Environmental Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Ryan M DuChanois
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA
| | - Cody L Ritt
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA
| | - Aleksandr Noy
- Materials Science Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
- School of Natural Sciences, University of California Merced, Merced, CA, USA
| | - Menachem Elimelech
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA.
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Luesch H, Paavilainen VO. Natural products as modulators of eukaryotic protein secretion. Nat Prod Rep 2020; 37:717-736. [PMID: 32067014 DOI: 10.1039/c9np00066f] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Covering: up to the end of 2019Diverse natural product small molecules have allowed critical insights into processes that govern eukaryotic cells' ability to secrete cytosolically synthesized secretory proteins into their surroundings or to insert newly synthesized integral membrane proteins into the lipid bilayer of the endoplasmic reticulum. In addition, many components of the endoplasmic reticulum, required for protein homeostasis or other processes such as lipid metabolism or maintenance of calcium homeostasis, are being investigated for their potential in modulating human disease conditions such as cancer, neurodegenerative conditions and diabetes. In this review, we cover recent findings up to the end of 2019 on natural products that influence protein secretion or impact ER protein homeostasis, and serve as powerful chemical tools to understand protein flux through the mammalian secretory pathway and as leads for the discovery of new therapeutics.
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Affiliation(s)
- Hendrik Luesch
- Department of Medicinal Chemistry, Center for Natural Products, Drug Discovery and Development (CNPD3), University of Florida, P.O. Box 100485, Gainesville, Florida 32610, USA.
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Thompson B, Burt K, Lee A, Lingard K, Maurer SE. Partitioning of amino acids and proteins into decanol using phase transfer agents towards understanding life in non-polar liquids. Sci Rep 2019; 9:17750. [PMID: 31780746 PMCID: PMC6882823 DOI: 10.1038/s41598-019-54322-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 10/17/2019] [Indexed: 11/21/2022] Open
Abstract
Water has many roles in the context of life on Earth, however throughout the universe, other liquids may be able to support the emergence of life. We looked at the ability of amino acids, peptides, a depsipeptide, and proteins to partition into a non-polar decanol phase, with and without the addition of a phase transfer agent. Partitioning evaluated using UV detection, or with HPLC coupled to either charged aerosol detection or ESI-MS. For amino acids and short peptides, phase transfer agents were used to move the biomolecules to the decanol phase, and this transfer was pH dependent. For larger molecules, phase transfer agents did not seem to affect the transfer. Both the depsipetide, valinomycin, and the protein Taq DNA polymerase had solubility in the decanol phase. Additionally, valinomycin appeared to retain its biological ability to bind to potassium ions. These results show that most terrestrial biological molecules are not compatible with non-polar solvents, but it is possible to find and perhaps evolve polymers that are functional in such phases.
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Affiliation(s)
- Brooke Thompson
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Kayla Burt
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Andrew Lee
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Kyle Lingard
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Sarah E Maurer
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA.
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Ross EE, Hoag B, Joslin I, Johnston T. Measurements of Ion Binding to Lipid-Hosted Ionophores by Affinity Chromatography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:9410-9421. [PMID: 31282163 DOI: 10.1021/acs.langmuir.9b01301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The binding affinity between antibiotic ionophores and alkali ions within supported lipid bilayers was evaluated using affinity chromatography. We used zonal elution and frontal analysis methods in nanovolume liquid chromatography to characterize the binding selectivity of the carrier and channel ionophores valinomycin and gramicidin A within different phosphatidylcholine bilayers. Distinct binding sensitivity to the lipid phase, both in affinity and selectivity, is observed for valinomycin, whereas gramicidin is less sensitive to changes in a membrane environment, behavior that is consistent with ion binding occurring within the interior of an established channel. There is good agreement between the chromatographic retention and the reported binding selectivity measured by other techniques. Surface potential near the binding site affects ion retention and the apparent association binding constants, but not the binding selectivity or enthalpy measurements. A model accounting for the surface potential contributions of retained ions during frontal analyses yields values close to intrinsic binding constants for gramicidin A (KA for K+ between 70 and 120 M-1) using reasonable estimates of the initial potential that is postulated to arise from the underlying silica.
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Affiliation(s)
- Eric E Ross
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
| | - Bridget Hoag
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
| | - Ian Joslin
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
| | - Taylor Johnston
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
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Hartinger T, Gresner N, Südekum KH. Does intra-ruminal nitrogen recycling waste valuable resources? A review of major players and their manipulation. J Anim Sci Biotechnol 2018; 9:33. [PMID: 29721317 PMCID: PMC5911377 DOI: 10.1186/s40104-018-0249-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Accepted: 03/06/2018] [Indexed: 12/15/2022] Open
Abstract
Nitrogenous emissions from ruminant livestock production are of increasing public concern and, together with methane, contribute to environmental pollution. The main cause of nitrogen-(N)-containing emissions is the inadequate provision of N to ruminants, leading to an excess of ammonia in the rumen, which is subsequently excreted. Depending on the size and molecular structure, various bacterial, protozoal and fungal species are involved in the ruminal breakdown of nitrogenous compounds (NC). Decelerating ruminal NC degradation by controlling the abundance and activity of proteolytic and deaminating microorganisms, but without reducing cellulolytic processes, is a promising strategy to decrease N emissions along with increasing N utilization by ruminants. Different dietary options, including among others the treatment of feedstuffs with heat or the application of diverse feed additives, as well as vaccination against rumen microorganisms or their enzymes have been evaluated. Thereby, reduced productions of microbial metabolites, e.g. ammonia, and increased microbial N flows give evidence for an improved N retention. However, linkage between these findings and alterations in the rumen microbiota composition, particularly NC-degrading microbes, remains sparse and contradictory findings confound the exact evaluation of these manipulating strategies, thus emphasizing the need for comprehensive research. The demand for increased sustainability in ruminant livestock production requests to apply attention to microbial N utilization efficiency and this will require a better understanding of underlying metabolic processes as well as composition and interactions of ruminal NC-degrading microorganisms.
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Affiliation(s)
- Thomas Hartinger
- Institute of Animal Science, University of Bonn, 53115 Bonn, Germany
| | - Nina Gresner
- Institute of Animal Science, University of Bonn, 53115 Bonn, Germany
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Patel R, Parray MUD, Singh UK, Islam A, Venkatesu P, Singh S, Bohidar HB. Effect of 1,4-bis(3-dodecylimidazolium-1-yl) butane bromide on channel form of gramicidin vesicles. Colloids Surf A Physicochem Eng Asp 2016. [DOI: 10.1016/j.colsurfa.2016.08.058] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Štěpánová S, Kašička V. Affinity Capillary Electrophoresis Applied to Investigation of Valinomycin Complexes with Ammonium and Alkali Metal Ions. Methods Mol Biol 2016; 1466:219-232. [PMID: 27473493 DOI: 10.1007/978-1-4939-4014-1_17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This chapter deals with the application of affinity capillary electrophoresis (ACE) to investigation of noncovalent interactions (complexes) of valinomycin, a macrocyclic dodecadepsipeptide antibiotic ionophore, with ammonium and alkali metal ions (lithium, sodium, potassium, rubidium, and cesium). The strength of these interactions was characterized by the apparent binding (stability, association) constants (K b) of the above valinomycin complexes using the mobility shift assay mode of ACE. The study involved measurements of effective electrophoretic mobility of valinomycin at variable concentrations of ammonium or alkali metal ions in the background electrolyte (BGE). The effective electrophoretic mobilities of valinomycin measured at ambient temperature and variable ionic strength were first corrected to the reference temperature 25 °C and constant ionic strength (10 or 25 mM). Then, from the dependence of the corrected valinomycin effective mobility on the ammonium or alkali metal ion concentration in the BGE, the apparent binding constants of the valinomycin-ammonium or valinomycin-alkali metal ion complexes were determined using a nonlinear regression analysis. Logarithmic form of the binding constants (log K b) were found to be in the range of 1.50-4.63, decreasing in the order Rb(+) > K(+) > Cs(+) > > Na(+) > NH4 (+) ~ Li(+).
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Affiliation(s)
- Sille Štěpánová
- Academy of Sciences of the Czech Republic, Institute of Organic Chemistry and Biochemistry, Flemingovo 2, Prague 6, 166 10, Czech Republic
| | - Václav Kašička
- Academy of Sciences of the Czech Republic, Institute of Organic Chemistry and Biochemistry, Flemingovo 2, Prague 6, 166 10, Czech Republic.
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10
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Rodríguez-Vázquez N, Fuertes A, Amorín M, Granja JR. Bioinspired Artificial Sodium and Potassium Ion Channels. Met Ions Life Sci 2016; 16:485-556. [DOI: 10.1007/978-3-319-21756-7_14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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11
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Structural characterization of a complex derived from lead(II) perchlorate and acridono-18-crown-6 ether. Struct Chem 2015. [DOI: 10.1007/s11224-015-0657-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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12
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Singh UK, Dohare N, Mishra P, Singh P, Bohidar HB, Patel R. Effect of pyrrolidinium based ionic liquid on the channel form of gramicidin in lipid vesicles. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2015; 149:1-8. [DOI: 10.1016/j.jphotobiol.2015.04.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/22/2015] [Accepted: 04/22/2015] [Indexed: 10/23/2022]
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Németh T, Kormos A, Tóth T, Balogh GT, Huszthy P. Synthesis and cation binding of acridono-18-crown-6 ether type ligands. MONATSHEFTE FUR CHEMIE 2015. [DOI: 10.1007/s00706-015-1454-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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14
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Avan I, Hall CD, Katritzky AR. Peptidomimetics via modifications of amino acids and peptide bonds. Chem Soc Rev 2014; 43:3575-94. [DOI: 10.1039/c3cs60384a] [Citation(s) in RCA: 183] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Avan I, Tala SR, Steel PJ, Katritzky AR. Benzotriazole-Mediated Syntheses of Depsipeptides and Oligoesters. J Org Chem 2011; 76:4884-93. [DOI: 10.1021/jo200174j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ilker Avan
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
- Department of Chemistry, Anadolu University, 26470, Eskişehir, Turkey
| | - Srinivasa R. Tala
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Peter J. Steel
- Department of Chemistry, University of Canterbury, Christchurch, New Zealand
| | - Alan R. Katritzky
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
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Halide‐Guided Oligo(aryl‐triazole‐amide)s Foldamers: Receptors for Multiple Halide Ions. Chemistry 2010; 17:613-9. [DOI: 10.1002/chem.201001560] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Indexed: 02/05/2023]
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A combined experimental and theoretical study on the complexation of the ammonium cation with valinomycin. MONATSHEFTE FUR CHEMIE 2010. [DOI: 10.1007/s00706-010-0395-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Späth A, König B. Molecular recognition of organic ammonium ions in solution using synthetic receptors. Beilstein J Org Chem 2010; 6:32. [PMID: 20502608 PMCID: PMC2874414 DOI: 10.3762/bjoc.6.32] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2010] [Accepted: 03/09/2010] [Indexed: 01/12/2023] Open
Abstract
Ammonium ions are ubiquitous in chemistry and molecular biology. Considerable efforts have been undertaken to develop synthetic receptors for their selective molecular recognition. The type of host compounds for organic ammonium ion binding span a wide range from crown ethers to calixarenes to metal complexes. Typical intermolecular interactions are hydrogen bonds, electrostatic and cation-π interactions, hydrophobic interactions or reversible covalent bond formation. In this review we discuss the different classes of synthetic receptors for organic ammonium ion recognition and illustrate the scope and limitations of each class with selected examples from the recent literature. The molecular recognition of ammonium ions in amino acids is included and the enantioselective binding of chiral ammonium ions by synthetic receptors is also covered. In our conclusion we compare the strengths and weaknesses of the different types of ammonium ion receptors which may help to select the best approach for specific applications.
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Affiliation(s)
- Andreas Späth
- Institut für Organische Chemie, Universität Regensburg, D-93040 Regensburg, Germany, Phone: +49-943-941-4576, Fax: +49-943-941-1717
| | - Burkhard König
- Institut für Organische Chemie, Universität Regensburg, D-93040 Regensburg, Germany, Phone: +49-943-941-4576, Fax: +49-943-941-1717
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Dybal J, Makrlík E, Vaňura P. Extraction and DFT study on the complexation of Mg2+ with valinomycin. MONATSHEFTE FUR CHEMIE 2009. [DOI: 10.1007/s00706-009-0217-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Dybal J, Makrlík E, Vanura P. Experimental and DFT Study on the Complexation of Zn2+with Valinomycin. Z PHYS CHEM 2009. [DOI: 10.1524/zpch.2009.5465] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractFrom extraction experiments andγ-activity measurements, the exchange extraction constant corresponding to the equilibrium Zn2+(aq) +1 ·Sr2+(nb) ⇌1 ·Zn2+(nb) + Sr2+(aq) taking place in the two–phase water–nitrobenzene system (1= valinomycin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as logKex(Zn2+,1 ·Sr2+) = −0.2±0.1. Further, the stability constant of the valinomycin–zinc complex (abbrev.1 ·Zn2+) in nitrobenzene saturated with water was calculated for a temperature of 25oC: logβnb(1 ·Zn2+) = 6.1±0.1. By using quantum mechanical DFT calculations, the most probable structure of the1 ·Zn2+complex species was predicted. In this complex, the Zn2+cation sits in the center of the coordination cavity formed by six ester carbonyls, which are oriented almost exactly in the “radial directions”. Finally, the calculated binding energy of the resulting complex1 ·Zn2+is −359.5 kcal/mol confirming relatively high stability of the considered cationic complex species.
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A combined extraction and DFT study on the complexation of K+ with valinomycin. MONATSHEFTE FUR CHEMIE 2009. [DOI: 10.1007/s00706-009-0178-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Application of capillary affinity electrophoresis and density functional theory to the investigation of valinomycin–lithium complex. J Chromatogr A 2009; 1216:3660-5. [DOI: 10.1016/j.chroma.2009.02.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2008] [Revised: 01/29/2009] [Accepted: 02/02/2009] [Indexed: 11/20/2022]
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Ehala S, Dybal J, Makrlík E, Kašička V. Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation. Electrophoresis 2009; 30:883-9. [DOI: 10.1002/elps.200800610] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Ehala S, Dybal J, Makrlík E, Kašička V. Capillary affinity electrophoresis andab initiocalculation studies of valinomycin complexation with Na+ion. J Sep Sci 2009; 32:597-604. [DOI: 10.1002/jssc.200800555] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Devarajan S, Vijayan M, Easwaran K. Conformation of valinomycin in its barium perchlorate complex from X-ray crystallography and n.m.r. ACTA ACUST UNITED AC 2009. [DOI: 10.1111/j.1399-3011.1984.tb02727.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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27
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A combined experimental and theoretical study on the complexation of Li+ with valinomycin. MONATSHEFTE FUR CHEMIE 2008. [DOI: 10.1007/s00706-008-0003-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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28
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Dybal J, Makrlík E, Vaňura P. Extraction and ab initio calculation studies on the complexation of Ca2+ with valinomycin. J Radioanal Nucl Chem 2008. [DOI: 10.1007/s10967-008-7344-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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29
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Dybal J, Ehala S, Kašička V, Makrlík E. Theoretical and experimental study of the complexation of valinomycin with ammonium cation. Biopolymers 2008; 89:1055-60. [DOI: 10.1002/bip.21034] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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30
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Makrlík E, Vaňura P, Selucký P. Experimental evidences for some unusual divalent cation complexes of valinomycin. MONATSHEFTE FUR CHEMIE 2008. [DOI: 10.1007/s00706-007-0816-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Ehala S, Kašička V, Makrlík E. Determination of stability constants of valinomycin complexes with ammonium and alkali metal ions by capillary affinity electrophoresis. Electrophoresis 2008; 29:652-7. [DOI: 10.1002/elps.200700583] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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Solvent extraction of magnesium, zinc and manganese into nitrobenzene by using strontium dicarbollylcobaltate in the presence of valinomycin. J Radioanal Nucl Chem 2008. [DOI: 10.1007/s10967-007-7022-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
Valinomycin is shown to form a stable complex with protons in the form of H3O+ ions. Using 1H and 13C nuclear magnetic resonance (NMR), Fourier transform (FT) infrared spectroscopy, and ab initio-density functional theory (DFT) quantum mechanical calculations, it is shown that H3O+, produced by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) in the presence of water, interacts with valinomycin in 1,1,2,2-tetrachloroethane-d2 to give a relatively stable complex. The equilibrium constant K of the complex formation was derived from chemical shifts in 1H-NMR, its value being 5.9. The proton affinity constant estimated from this value taking into account HDCC dissociation is 10(5.3), i.e., high enough to be relevant under physiological conditions. Under suitable conditions there is a fast exchange of H3O+ between valinomycin molecules, the exchange correlation time being of the order of 10(-4) s. The instantaneous structure of the complex is slightly asymmetric, the H3O+ ion being strongly hydrogen-bonded to three of the six ester carbonyl groups and weekly bound to the residual ones by electrostatic interactions. This asymmetry is averaged by fast reorientation and displacement of H3O+ so that the molecule appears to be symmetric in the time window of NMR. The results indicate that valinomycin could serve as a carrier for proton transfer across a biological membrane.
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Affiliation(s)
- Jaroslav Kríz
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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34
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Abstract
In addition to the well-known complexes of valinomycin with alkali metal cations, an equimolar complex of the same compound with proton was found to be formed in nitrobenzene. Hydrogen bis(1,2-dicarbollylide) cobaltate (HDCC) was used as a proton source. According to NMR spectra, the complex formation is quantitative at proton/valinomycin molar ratios up to 1:1 but there is fast exchange of protons between coordinated and uncoordinated valinomycin molecules at lower ratios. 1H and 13C NMR spectra show a dramatic change in the valinomycin conformation during its coordination with protons, probably from a propeller-like to a bracelet-like form. As valinomycin is one of the well-known ion-carrying ionophores facilitating especially the K+ ion transport across a biological membrane, the existence of the valinomycin-proton complex could be important in biochemistry and biology.
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Affiliation(s)
- Jaroslav Kríz
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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35
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Sternberg U, Koch FT, Möllhoff M. New approach to the semiempirical calculation of atomic charges for polypeptides and large molecular systems. J Comput Chem 2004. [DOI: 10.1002/jcc.540150505] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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36
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Wang F, Zhao C, Polavarapu PL. A study of the conformations of valinomycin in solution phase. Biopolymers 2004; 75:85-93. [PMID: 15307200 DOI: 10.1002/bip.20103] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Vibrational absorption and vibrational circular dichroism (VCD) spectra of valinomycin are measured, in different solvents, in the ester and amide carbonyl stretching regions. The influence of cations, namely Li(+), Na(+), K(+), and Cs(+), in methanol-d(4) solvent is also investigated. Ab initio quantum mechanical calculations using density functional theory and 6-31G* basis set are used to predict the absorption and VCD spectra. A bracelet-type structure for valinomycin that reproduces the experimental absorption and VCD spectra in inert solvents is identified. For the structure of valinomycin in polar solvents, a propeller-type structure was optimized, but further investigations are required to confirm this structure. A symmetric octahedral environment for the ester carbonyl groups in the valinomycin-K(+) complex is supported by the experimental VCD spectra. The results obtained in the present study demonstrate that even for large macrocyclic peptides, such as valinomycin, VCD can be used as an independent structural tool for the study of conformations in solution.
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Affiliation(s)
- Feng Wang
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
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37
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Properties and possible functions of the adenylate cyclase in plasma membranes of Saccharomyces cerevisiae. Mol Cell Biol 2003. [PMID: 14582190 DOI: 10.1128/mcb.2.12.1481] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have examined the possible role of adenosine 3',5'-phosphate (cAMP) in functions associated with the plasma membranes of Saccharomyces cerevisiae. Purified membranes from this source contained an adenylate cyclase which was insensitive to activation by fluoride or guanine nucleotides, only weakly responsive to changes of carbon source in the growth medium, and strongly stimulated by vanadate. They also contained at least two classes of receptor proteins for guanine nucleotides (as measured by binding of labeled 5'-guanylyl methylene diphosphate) with apparent dissociation constants equal to 1.0 x 10(-7) and 3 x 10(-6) M, a protein kinase capable of phosphorylating added histones, the activity of which was stimulated by cAMP, and cAMP receptors that may function as regulatory subunits for this kinase. Membrane proteins were also susceptible to phosphorylation by endogenous kinase(s), with polypeptides of apparent molecular weights equal to 160 x 10(3), 135 x 10(3), 114 x 10(3), and 58 x 10(3) as the major targets. Of these, the 114,000-molecular-weight polypeptide was probably identical to the proton-translocating ATPase of the membranes. However, the cAMP-dependent protein kinase did not appear to be involved in these reactions. Intact (rho+ or rho0) cells responded to dissipation of the proton electrochemical gradient across their plasma membranes by rapid and transient changes in their intracellular level of cAMP, as suggested earlier (J. M. Trevillyan and M. L. Pall, J. Bacteriol., 138:397-403, 1979). Thus, although yeast plasma membranes contain all the essential components of a stimulus-responsive adenylate cyclase system, the precise nature of the coupling device and the targets involved remain to be established.
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38
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Jaynes PK, McDonough JP, Mahler HR. Properties and possible functions of the adenylate cyclase in plasma membranes of Saccharomyces cerevisiae. Mol Cell Biol 2003; 2:1481-91. [PMID: 14582190 PMCID: PMC369957 DOI: 10.1128/mcb.2.12.1481-1491.1982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have examined the possible role of adenosine 3',5'-phosphate (cAMP) in functions associated with the plasma membranes of Saccharomyces cerevisiae. Purified membranes from this source contained an adenylate cyclase which was insensitive to activation by fluoride or guanine nucleotides, only weakly responsive to changes of carbon source in the growth medium, and strongly stimulated by vanadate. They also contained at least two classes of receptor proteins for guanine nucleotides (as measured by binding of labeled 5'-guanylyl methylene diphosphate) with apparent dissociation constants equal to 1.0 x 10(-7) and 3 x 10(-6) M, a protein kinase capable of phosphorylating added histones, the activity of which was stimulated by cAMP, and cAMP receptors that may function as regulatory subunits for this kinase. Membrane proteins were also susceptible to phosphorylation by endogenous kinase(s), with polypeptides of apparent molecular weights equal to 160 x 10(3), 135 x 10(3), 114 x 10(3), and 58 x 10(3) as the major targets. Of these, the 114,000-molecular-weight polypeptide was probably identical to the proton-translocating ATPase of the membranes. However, the cAMP-dependent protein kinase did not appear to be involved in these reactions. Intact (rho+ or rho0) cells responded to dissipation of the proton electrochemical gradient across their plasma membranes by rapid and transient changes in their intracellular level of cAMP, as suggested earlier (J. M. Trevillyan and M. L. Pall, J. Bacteriol., 138:397-403, 1979). Thus, although yeast plasma membranes contain all the essential components of a stimulus-responsive adenylate cyclase system, the precise nature of the coupling device and the targets involved remain to be established.
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Affiliation(s)
- P K Jaynes
- Department of Chemistry and the Molecular, Cellular, and Developmental Biology Program, Indiana University, Bloomington, Indiana 47405, USA
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39
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Grinius L, Stanton DT, Morris CM, Howard JM, Curnow AW. Profiling of drugs for membrane activity using liposomes as an in vitro model system. Drug Dev Ind Pharm 2002; 28:193-202. [PMID: 11926363 DOI: 10.1081/ddc-120002452] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The increasing size of chemical libraries being analyzed by high-throughput screening results in a growing number of active compounds that need to be assessed before moving forward in the drug development process. As a consequence, more rapid and highly sensitive strategies are required to accelerate the process of drug discovery without increasing the cost. Due to the fact that significant numbers of compounds from combinatorial libraries are hydrophobic in nature, approaches are needed to evaluate the potentialfor these compounds to interfere with the functions of biological membranes. The liposome system was used to detect agents that act as follows: (i) ionophores able to induce specific ion permeability, e.g., valinomycin for K+ and protonophoric uncouplers for H+; (ii) ion antiporters which exchange H+ for other ions, e.g., nigericin; (iii) agents that form low specificity ion channels in the membrane, e.g., gramicidin; and (iv) detergents and other membrane-disrupting agents. We propose using this liposome assay during the drug development process to identify compounds that have membrane activity and, as a consequence, produce a biological effect by altering the physico-chemical properties of the cell membrane rather than interacting with a protein target. Screening of a representative set of biologically-active compounds (198) indicated that the majority of systemic antimicrobial drugs, but not topical drugs, lack membrane activity in this model system.
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Affiliation(s)
- Leo Grinius
- Procter & Gamble Pharmaceuticals, Mason, Ohio 45040, USA.
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40
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Crystalline self-assembly of organic molecules with metal ions at the air–aqueous solution interface. A grazing incidence X-ray scattering study. Colloids Surf A Physicochem Eng Asp 2002. [DOI: 10.1016/s0927-7757(02)00112-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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41
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Fernandes MX, García de la Torre J, Castanho MARB. Joint determination by Brownian dynamics and fluorescence quenching of the in-depth location profile of biomolecules in membranes. Anal Biochem 2002; 307:1-12. [PMID: 12137772 DOI: 10.1016/s0003-2697(02)00024-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The in-depth molar distribution function of fluorophores is revealed by a new methodology for fluorescence quenching data analysis in membranes. Brownian dynamics simulation was used to study the in-depth location profile of quenchers. A Lorentzian profile was reached. Since the Stern-Volmer equation is valid at every depth in the membrane for low quencher concentrations, the molar distribution of the fluorophore (also regarded as a Lorentzian) can be achieved. The average location and the broadness of the fluorophore distribution can be calculated. The importance of the knowledge of the location width is demonstrated and discussed, since this parameter reveals important conclusions on structural features of the interaction of membranes with probes and biomolecules (e.g., conformational freedom in proteins), as well as photophysical properties (e.g., differential fluorophore quantum yields). Subsequent use of this methodology by the reader does not, necessarily, involve the performance of simulations and is not limited to the use of Lorentzian function distributions.
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Affiliation(s)
- M X Fernandes
- Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
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42
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Skulachev VP. The dual role of rhodopsin in vision: light-driven charge translocation and formation of long-lived photoproducts. FEBS Lett 2001. [DOI: 10.1016/0014-5793(82)80928-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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43
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Ovchinnikov Y, Abdulaev N, Kiselev A, Drachev L, Kaulen A, Skulachev V. The water-exposed C-terminal sequence of bacteriorhodopsin does not affect H+
pumping. FEBS Lett 2001. [DOI: 10.1016/0014-5793(86)80043-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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44
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Camarasa C, Prieto S, Ros R, Salmon JM, Barre P. Evidence for a selective and electroneutral K+/H+-exchange in Saccharomyces cerevisiae using plasma membrane vesicles. Yeast 1998. [DOI: 10.1002/(sici)1097-0061(199610)12:13<1301::aid-yea18>3.0.co;2-a] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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45
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Quick M, Jung H. A conserved aspartate residue, Asp187, is important for Na+-dependent proline binding and transport by the Na+/proline transporter of Escherichia coli. Biochemistry 1998; 37:13800-6. [PMID: 9753469 DOI: 10.1021/bi980562j] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Asp187 in the Na+/proline transporter of Escherichia coli (PutP) is conserved within the Na+/solute cotransporter family. Information on the role of this residue has been gained by amino acid substitution analysis. PutP with Glu, Asn, or Cys in place of Asp187 catalyzed Na+-coupled proline uptake at 75%, 25%, and 1.5%, respectively, of the Vmax of PutP-wild-type while the apparent Km for proline was only slightly altered. Importantly, acetylation or amidoacetylation of an engineered transporter containing a single Cys at position 187 stimulated proline uptake. Strikingly, PutP-D187C exhibited high-affinity proline binding even at very low Na+ concentrations (2 microM) while proline binding to PutP-wild-type, -D187E, and -D187N was strictly dependent on the Na+ concentration. The apparent independence of proline binding from the Na+ concentration can at least partially be attributed to an enhanced Na+ affinity of PutP-D187C. In addition, reaction of PutP containing a single Cys at position 187 with N-ethylmaleimide was inhibited by Na+ but not by Li+ or proline. The results indicate that electrostatic interactions of the amino acid side chain at position 187 in PutP with other parts of the transporter and/or the coupling ion are crucial for active proline transport. It is suggested that Asp187 is located close to the pathway of the coupling ion through the membrane and may be involved in the release of Na+ on the cytoplasmic side of the membrane.
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Affiliation(s)
- M Quick
- Universität Osnabrück, Fachbereich Biologie/Chemie, Arbeitsgruppe Mikrobiologie, Germany
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46
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Rapaport H, Kuzmenko I, Kjaer K, Howes P, Bouwman W, Als-Nielsen J, Leiserowitz L, Lahav M. Structural Characterization of Valinomycin and Nonactin at the Air−Solution Interface by Grazing Incidence X-ray Diffraction. J Am Chem Soc 1997. [DOI: 10.1021/ja971410z] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hanna Rapaport
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Ivan Kuzmenko
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Kristian Kjaer
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Paul Howes
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Wim Bouwman
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Jens Als-Nielsen
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Leslie Leiserowitz
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Meir Lahav
- Contribution from the Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, Department of Solid State Physics, Risø National Laboratory, DK-4000 Roskilde, Denmark, and Niels Bohr Institute, H. C. Øersted Laboratory, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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47
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Vila N, Puggelli M, Gabrielli G. Langmuir-Blodgett monolayers and multilayers of gramicidin A and lipids as membrane-mimetic models. Colloids Surf A Physicochem Eng Asp 1996. [DOI: 10.1016/s0927-7757(96)03737-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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48
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Camarasa C, Prieto S, Ros R, Salmon JM, Barre P. Evidence for a selective and electroneutral K+/H(+)-exchange in Saccharomyces cerevisiae using plasma membrane vesicles. Yeast 1996; 12:1301-13. [PMID: 8923735 DOI: 10.1002/(sici)1097-0061(199610)12:13%3c1301::aid-yea18%3e3.0.co;2-a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The existence of a K+/H+ transport system in plasma membrane vesicles from Saccharomyces cerevisiae is demonstrated using fluorimetric monitoring of proton fluxes across vesicles (ACMA fluorescence quenching). Plasma membrane vesicles used for this study were obtained by a purification/reconstitution protocol based on differential and discontinuous sucrose gradient centrifugations followed by an octylglucoside dilution/gel filtration procedure. This method produces a high percentage of tightly-sealed inside-out plasma membrane vesicles. In these vesicles, the K+/H+ transport system, which is able to catalyse both K+ influx and efflux, is mainly driven by the K+ transmembrane gradient and can function even if the plasma membrane H(+)-ATPase is not active. Using the anionic oxonol VI and the cationic DISC2(5) probes, it was shown that a membrane potential is not created during K+ fluxes. Such a dye response argues for the presence of a K+/H+ exchange system in S. cerevisiae plasma membrane and established the non-electrogenic character of the transport. The maximal rate of exchange is obtained at pH 6.8. This reversible transport system presents a high selectivity for K+ among other monovalent cations and a higher affinity for the K+ influx into the vesicles (exit from cells). The possible role of this K+/H+ exchange system in regulation of internal potassium concentration in S. cerevisiae is discussed.
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Affiliation(s)
- C Camarasa
- Institut des Produits de la Vigne, Institut de la Recherche Agronomique, Montpellier, France
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49
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Gumila C, Ancelin ML, Jeminet G, Delort AM, Miquel G, Vial HJ. Differential in vitro activities of ionophore compounds against Plasmodium falciparum and mammalian cells. Antimicrob Agents Chemother 1996; 40:602-8. [PMID: 8851578 PMCID: PMC163165 DOI: 10.1128/aac.40.3.602] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Twenty-two ionophore compounds were screened for their antimalarial activities. They consisted of true ionophores (mobile carriers) and channel-forming quasi-ionophores with different ionic specificities. Eleven of the compounds were found to be extremely efficient inhibitors of Plasmodium falciparum growth in vitro, with 50% inhibitory concentrations of less than 10 ng/ml. Gramicidin D was the most active compound tested, with 50% inhibitory concentration of 0.035 ng/ml. Compounds with identical ionic specificities generally had similar levels of antimalarial activity, and ionophores specific to monovalent cations were the most active. Compounds were further tested to determine their in vitro toxicities against mammalian lymphoblast and macrophage cell lines. Nine of the 22 compounds, i.e., alborixin, lonomycin, nigericin, narasin, monensin and its methylated derivative, lasalocid and its bromo derivative, and gramicidin D, most specific to monovalent cations, were at least 35-fold more active in vitro against P. falciparum than against the two other mammalian cell lines. The enhanced ability to penetrate the erythrocyte membrane after infection could be a factor that determines ionophore selectivity for infected erythrocytes.
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Affiliation(s)
- C Gumila
- Dynamique Moléculaire des Interactions Membranaires, Université Montpellier II, France
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50
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Shobana S, Vishveshwara S. Conformational study of valinomycin: a molecular dynamics approach. Biophys Chem 1996; 57:163-75. [PMID: 17023338 DOI: 10.1016/0301-4622(95)00061-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/1994] [Revised: 12/27/1994] [Accepted: 03/27/1995] [Indexed: 11/25/2022]
Abstract
Valinomycin is a highly flexible cyclic dodecadepsipeptide that transports ions across membranes. Such a flexibility in the conformation is required for its biological function since it has to encounter a variety of environments and liganding state. Exploration of conformational space of this molecule is therefore important and is one of the objectives of the present study that has been carried out by means of high temperature Molecular Dynamics. Further, the stability of the known bracelet-like structure of the uncomplexed valinomycin and the inherent flexibility around this structure has been investigated. The uncomplexed form of valinomycin has been simulated at 75-100 K for 1 ns in order to elucidate the average conformational properties. An alanine-analog of valinomycin has been simulated under identical conditions in order to evaluate the effect of sidechain on the conformational properties, The studies confirm the effect of sidechain on conformational equilibrium.
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Affiliation(s)
- S Shobana
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
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