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Naumowicz M, Kruszewski MA, Gál M. Electrical properties of phosphatidylcholine bilayers containing canthaxanthin or β -carotene, investigated by electrochemical impedance spectroscopy. J Electroanal Chem (Lausanne) 2017. [DOI: 10.1016/j.jelechem.2017.07.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Janovjáková A, Gál M, Krahulec J, Sokolová R, Naumowicz M, Híveš J. Native and denatured enzyme enterokinase determined by electrochemical methods. MONATSHEFTE FUR CHEMIE 2017. [DOI: 10.1007/s00706-016-1915-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Petelska AD, Kotyńska J, Naumowicz M, Figaszewski ZA. Equilibria Between Cell Membranes and Electrolyte Solution: Effect of Fatal Accidental Hypothermia. J Membr Biol 2016; 249:375-80. [PMID: 26843064 PMCID: PMC4875062 DOI: 10.1007/s00232-016-9875-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 01/22/2016] [Indexed: 12/01/2022]
Abstract
Equilibria between the membranes of erythrocytes as well as thrombocytes and solution ions in fatal accidental hypothermia were analyzed using a theoretical four-equilibria model. The model was developed to determinate parameters characterizing cell membrane—surrounding ion interactions: the total surface concentrations of both acidic and basic groups CA, CB, and association constants KAH, KBOH. Knowledge of these parameters was necessary to calculate the theoretical values of surface charge density. The model was validated by curve-fitting the experimental data points to simulated data generated by the model. The experimental and theoretical surface charge density values agree at pH 2–8, at higher pH the deviation was observed.
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Naumowicz M, Figaszewski ZA. Pore formation in lipid bilayer membranes made of phosphatidylcholine and cholesterol followed by means of constant current. Cell Biochem Biophys 2013; 66:109-19. [PMID: 23104105 PMCID: PMC3627032 DOI: 10.1007/s12013-012-9459-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
This paper describes the application of chronopotentiometry to lipid bilayer research. The experiments were performed on bilayer lipid membranes composed of phosphatidylcholine and cholesterol and formed using the painting technique. Chronopotentiometric (U = f(t)) measurements were used to determine the membrane capacitance, resistance, and breakdown voltage as well as pore conductance and diameter.
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Naumowicz M, Petelska AD, Figaszewski ZA. Electrochemical impedance spectroscopy as a method for electrical characterization of the bilayers formed from lipid-amino acid systems. Chem Phys Lipids 2013; 175-176:116-22. [PMID: 24055996 DOI: 10.1016/j.chemphyslip.2013.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 07/29/2013] [Accepted: 09/04/2013] [Indexed: 10/26/2022]
Abstract
Bilayer lipid membranes composed of phosphatidylcholine and isoleucine or phosphatidylcholine and tyrosine were investigated using electrochemical impedance spectroscopy. Interaction between membrane components causes significant deviations from the additivity rule which can be explained by formation of the domain structures. The surface area of domains was calculated based on derived equations. We suggest that the stoichiometry of phosphatidylcholine-isoleucine domain is equal 3:1. In the case of tyrosine-modified phosphatidylcholine membranes, domain with stoichiometry 7:1 should be taken into consideration.
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Naumowicz M, Figaszewski ZA, Poltorak L. Electrochemical impedance spectroscopy as a useful method for examination of the acid–base equilibria at interface separating electrolyte solution and phosphatidylcholine bilayer. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2012.12.093] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Petelska AD, Naumowicz M, Figaszewski ZA. Influence of pH on sphingomyelin monolayer at air/aqueous solution interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:13331-13335. [PMID: 22924621 DOI: 10.1021/la3028594] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The pH dependence of the interfacial tension is an important factor in the behavior of sphingomyelin (SM) monolayers. We developed a theoretical model to describe this dependence in which the interfacial tension and molecular area contributions of each sphingomyelin form were additive and dependent on pH. The interfacial tension values and the molecular areas values for the SMH(+) and SMOH(-) forms of sphingomyelin were calculated and the proposed model was experimentally verified. The theoretical predictions agreed with the experimental results for pH values ranging from 2 to 12.
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Petelska AD, Naumowicz M, Figaszewski ZA. The interfacial tension of the lipid membrane formed from lipid-amino acid systems. Cell Biochem Biophys 2012; 61:289-96. [PMID: 21567131 PMCID: PMC3210364 DOI: 10.1007/s12013-011-9207-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The interfacial tension of lipid membranes composed of phosphatidylcholine (lecithin, PC)-valine (Val), phosphatidylcholine-isoleucine (Ile), phosphatidylcholine-tyrosine (Tyr), and phosphatidylcholine-phenylalanine (Phe) has been studied. The membrane components formed 1:1 complexes. The interfacial tension measurements were used to determine the membrane surface concentration A (3)(-1), the membrane interfacial tension γ(3), and the stability constant K.
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Naumowicz M, Petelska AD, Figaszewski ZA. Chronopotentiometric studies of phosphatidylcholine bilayers modified by ergosterol. Steroids 2011; 76:967-73. [PMID: 21641920 DOI: 10.1016/j.steroids.2011.05.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/19/2011] [Accepted: 05/19/2011] [Indexed: 10/18/2022]
Abstract
We have monitored the effect of ergosterol on electrical capacitance and electrical resistance of the phosphatidylcholine bilayer membranes using chronopotentiometry method. The chronopotentiometric characteristic of the bilayers depends on constant-current flow through the membranes. For low current values, no electroporation takes place and the membrane voltage rises exponentially to a constant value described by the Ohm's law. Based on these kinds of chronopotentiometric curves, a method of the membrane capacitance and the membrane resistance calculations is presented.
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Petelska AD, Naumowicz M, Figaszewski ZA. The Equilibrium of Phosphatidylcholine–Amino Acid System in Monolayer at the Air/water Interface. Cell Biochem Biophys 2010; 60:155-60. [DOI: 10.1007/s12013-010-9133-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Petelska AD, Naumowicz M, Figaszewski ZA. Complex Formation Equilibria in Two-Component Bilayer Lipid Membrane: Interfacial Tension Method. J Membr Biol 2009; 228:71-7. [DOI: 10.1007/s00232-009-9160-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Accepted: 02/02/2009] [Indexed: 11/28/2022]
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Naumowicz M, Figaszewski ZA. Impedance spectroscopic investigation of the bilayer lipid membranes formed from the phosphatidylserine-ceramide mixture. J Membr Biol 2009; 227:67-75. [PMID: 19122973 DOI: 10.1007/s00232-008-9144-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 11/22/2008] [Indexed: 10/21/2022]
Abstract
Electrochemical impedance spectroscopy was used for the study of two-component lipid membranes. Phosphatidylserine and ceramide were to be investigated because they play an important biochemical role in cell membranes. The research on biolipid interaction was focused on a quantitative description of processes that take part in a bilayer. Assumed models of interaction between amphiphilic molecules and the equilibria that take place there were described by mathematical equations for the studied system. The possibility of complex formation for a two-component system forming bilayers was assumed, which could explain the deviation from the additivity rule. The molecular area and the equilibrium constant of the complex were determined.
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Naumowicz M, Petelska AD, Figaszewski ZA. Physicochemical analysis of phosphatidylcholine-ceramide system in bilayer lipid membranes. Acta Biochim Pol 2008; 55:721-730. [PMID: 19081852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 11/02/2008] [Accepted: 12/03/2008] [Indexed: 05/27/2023]
Abstract
Electrochemical impedance spectroscopy was used for the study of two-component lipid membranes. Phosphatidylcholine and ceramide were to be investigated, since they play an important biochemical role in cell membranes. The research on biolipid interaction was focused on quantitative description of processes that take part in a bilayer. Assumed models of interaction between amphiphilic molecules and the equilibria that take place there were described by mathematical equations for the studied system. The possibility of complex formation for two-component system forming bilayers was assumed that could explain the deviation from additivity rule. Equilibria were described by mathematical equations that were further verified experimentally. The determined values of parameters (stability constant, molecular area of complex, capacitance and conductance of the lipid membranes formed from molecules and complexes) were used for calculation of model curves. The comparison of model curves and experimental points verified the assumed model.
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Naumowicz M, Petelska AD, Figaszewski ZA. Physicochemical analysis of phosphatidylcholine-ceramide system in bilayer lipid membranes. Acta Biochim Pol 2008. [DOI: 10.18388/abp.2008_3033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Electrochemical impedance spectroscopy was used for the study of two-component lipid membranes. Phosphatidylcholine and ceramide were to be investigated, since they play an important biochemical role in cell membranes. The research on biolipid interaction was focused on quantitative description of processes that take part in a bilayer. Assumed models of interaction between amphiphilic molecules and the equilibria that take place there were described by mathematical equations for the studied system. The possibility of complex formation for two-component system forming bilayers was assumed that could explain the deviation from additivity rule. Equilibria were described by mathematical equations that were further verified experimentally. The determined values of parameters (stability constant, molecular area of complex, capacitance and conductance of the lipid membranes formed from molecules and complexes) were used for calculation of model curves. The comparison of model curves and experimental points verified the assumed model.
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Petelska AD, Naumowicz M, Figaszewski ZA. Interfacial tension of the lipid membrane formed from lipid-fatty acid and lipid-amine systems. Bioelectrochemistry 2007; 70:28-32. [PMID: 16713376 DOI: 10.1016/j.bioelechem.2006.03.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Indexed: 11/19/2022]
Abstract
Interfacial tension has been determined for phosphatidylcholine-stearic acid and phosphatidylcholine-stearylamine membranes. Phosphatidylcholine, stearic acid and stearylamine were used in the experimental. The interfacial tension values of the pure components are 1.62x10(-3) N/m, - 1.54x10(-2) N/m and 4.40x10(-3) N/m (hypothetical values), respectively. The 1:1 complexes were formed during formation of phosphatidylcholine-stearic acid and phosphatidylcholine-stearylamine membranes. The following parameters describing the complexes were determined: the surface concentrations of the lipid membranes formed from these complexes, A(3)(-1), the interfacial tensions of such membranes, gamma(3) and the stability constants of these complexes, K.
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Petelska AD, Naumowicz M, Figaszewski ZA. The interfacial tension of the lipid membrane formed from lipid-cholesterol and lipid-lipid systems. Cell Biochem Biophys 2006; 44:205-11. [PMID: 16456222 DOI: 10.1385/cbb:44:2:205] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Interfacial tension has been determined for phosphatidylcholine-cholesterol, phosphatidylcholine-phosphatidylethanolamine, and phosphatidylethanolamine-cholesterol membranes. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol (Ch) were to be investigated, because of their presence in biological membranes. Interfacial tension values of pure components are 0.81 x 10(-3) N/m, 1.67 x 10(-3) N/m, and 2.36 x 10(-3) N/m, respectively. The 1:1 complexes were formed during formation of the PC-Ch, PC-PE, and PE-Ch lipid membranes. The following parameters describing the complexes were determined: A3(-1), the surface concentrations of the lipid membranes formed from these complexes; gamma3, the interfacial tensions of such membranes and K, the stability constants of these complexes.
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Naumowicz M, Kotynska J, Petelska A, Figaszewski Z. Impedance analysis of phosphatidylcholine membranes modified with valinomycin. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2005; 35:239-46. [PMID: 16283290 DOI: 10.1007/s00249-005-0030-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Revised: 10/10/2005] [Accepted: 10/18/2005] [Indexed: 10/25/2022]
Abstract
The effect of the ion carrier valinomycin on the electrochemical features of the phosphatidylcholine membrane was investigated by electrochemical impedance spectroscopy. Phosphatidylcholine and valinomycin were chosen for the study because they fulfil essential functions in lively organisms. The experimental impedance values obtained in the presence of different amounts of carrier, studied with several potassium ion concentrations, were used for the research ability of valinomycin to form a 1:1 potassium ion complex on the lipid bilayer/electrolyte solution interface. Based on derived mathematical equations, the heterogeneous equilibrium constant (K (h)), association rate constant of the complex (k (R)) and dissociation rate constant of the complex (k (D)) were calculated. The result of the investigation is the proposal of a new method for the determination of the parameters used to describe the chemical reaction at the interface between a carrier molecule from the membrane and a monovalent ion from the aqueous phase.
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Naumowicz M, Figaszewski ZA. Impedance analysis of lipid domains in phosphatidylcholine bilayer membranes containing ergosterol. Biophys J 2005; 89:3174-82. [PMID: 16126831 PMCID: PMC1366813 DOI: 10.1529/biophysj.105.063446] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Accepted: 07/07/2005] [Indexed: 11/18/2022] Open
Abstract
The effect of ergosterol on the electrochemical features of the phosphatidylcholine bilayer membrane was investigated by impedance spectroscopy. The experimental impedance values obtained in the presence of different amounts of ergosterol showed evidence of domain structures within the bilayer containing < 0.06 molar fraction of ergosterol. Based on derived mathematical equations, the surface area of phospholipid/ergosterol domain was calculated; it amounts to 262 A(2). This value is consistent, taking into consideration the presented measurements as well as ordering and condensation effects of ergosterol, with a stoichiometry of such a domain equal to 3:1. The result of the investigation is the proposal of a new and simple method for the determination of the surface area and description stoichiometry of domains formed in any two-component system.
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Petelska AD, Naumowicz M, Figaszewski ZA. The effect of the presence of valinomycin on the interfacial tension of lecithin membrane. Colloids Surf B Biointerfaces 2005; 44:158-62. [PMID: 16051474 DOI: 10.1016/j.colsurfb.2005.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Accepted: 06/20/2005] [Indexed: 11/16/2022]
Abstract
The effect of the presence of valinomycin in lecithin membrane on its interfacial tension has been studied. The experiments have been carried out at various forming solution compositions and at various potassium ion concentrations in electrolyte solution. Potassium chloride was used as the electrolyte. A complex was formed between the valinomycin molecule and K+ ion. The following parameters describing the complex were determined: K, the stability constant of the valinomycin-K+ complex and B, partition coefficient. These values are equal to 3.52 x 10(5) m3 mol(-1) and 6.0, respectively.
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Naumowicz M, Figaszewski ZA. Impedance Analysis of Phosphatidylcholine/α-Tocopherol System in Bilayer Lipid Membranes. J Membr Biol 2005; 205:29-36. [PMID: 16245040 DOI: 10.1007/s00232-005-0760-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2004] [Revised: 02/24/2005] [Indexed: 11/30/2022]
Abstract
The effect of alpha-tocopherol on the electrochemical features of the phosphatidylcholine membrane was investigated by impedance spectroscopy. Phosphatidylcholine and alpha-tocopherol were chosen for the study because they are present in biological membranes and they fulfill essential functions in living organisms. The experimental impedance values obtained in the presence of different amounts of alpha-tocopherol showed evidence of domain structures within the bilayer containing less than 0.048 molar fraction of alpha-tocopherol. Based on derived mathematical equations, the surface area of phospholipid/alpha-tocopherol domain was calculated; it amounts to 832 A(2). This value is consistent, taking into consideration ordering and condensation effects of alpha-tocopherol, with the acknowledged, well documented, stoichiometry of such a domain of 10:1. The result of the investigation is the proposal of a new method for the determination of the surface area and description of the stoichiometry of domains formed in any two-component system.
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Naumowicz M, Petelska AD, Figaszewski ZA. Impedance analysis of phosphatidylcholine–cholesterol system in bilayer lipid membranes. Electrochim Acta 2005. [DOI: 10.1016/j.electacta.2004.09.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Petelska AD, Naumowicz M, Figaszewski ZA. The effect of interaction between K+ ions and gramicidin D on the lecithin membrane interfacial tension. Bioelectrochemistry 2005; 65:143-8. [PMID: 15713565 DOI: 10.1016/j.bioelechem.2004.10.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2004] [Revised: 08/12/2004] [Accepted: 10/04/2004] [Indexed: 11/17/2022]
Abstract
The effect of the presence of gramicidin D in a lecithin membrane on its interfacial tension has been studied. The studies have been carried out at various forming solution compositions and at various potassium ion concentrations in the electrolyte solution. Potassium chloride was used as the electrolyte. The complex was formed between the gramicidin molecule and K(+) ion. The following parameters describing the complex were determined: the surface area occupied by GK(+) complex (A(GK(+))), the interfacial tension of the GK(+) membrane complex (gamma(GK+)), and the stability constant of the gramicidin-K(+) complex (K). These values are 156 A(2), 1.89 mN m(-1) and 0.033 m(3) mol(-1), respectively.
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Naumowicz M, Petelska AD, Figaszewski ZA. The effect of the presence of crown ether on ion transport across the lipid bilayer. Cell Mol Biol Lett 2004; 8:383-9. [PMID: 12813573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
We studied the electric properties of phosphatidylcholine bilayers modified with crown ether (dibenzo[18] crown-6). The studies were carried out for various crown ether concentrations in forming solutions and various potassium ion concentrations in electrolyte solutions. The presence of crown ether in the membrane influences the membrane's impedance; there is a reduction in its resistivity, a decrease in its resistance of phase transfer and an increase in its capacity of phase transfer with an increase in crown ether concentration in the bilayer and in K(+) ion concentration in the electrolyte solution.
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Naumowicz M, Petelska AD, Figaszewski ZA. Capacitance and resistance of the bilayer lipid membrane formed of phosphatidylcholine and cholesterol. Cell Mol Biol Lett 2004; 8:5-18. [PMID: 12655351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
Capacity and electric resistance of lipid membranes composed of lecithin and cholesterol were determined. The components were chosen for the study because they were present in biological membranes. Capacitance of the lecithin and cholesterol membranes amounts to 0.38 and 0.61 microF/cm(2), and resistance to 1.44(10(4)and 2.12(10(6)Omega cm(2), respectively. A 1:1 complex appears as a result of lecithin-cholesterol membrane formation. Parameters of the membrane formed of the lecithin-cholesterol complex were determined: surface concentration (Gamma(3)), capacitance (C(3)), and conductance (R;(3)(-1), as well as the stability constant (K) of the complex. The mean values of those magnitudes are as follows: 4.265(10(-6)mol/m(2), 0.54 microF/cm(2), 1.381(10(-6)Omega(-1)cm(-2)and 3.748(10(7), respectively.
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Naumowicz M, Figaszewski Z. Impedance analysis of phosphatidylcholine membranes modified with gramicidin D. Bioelectrochemistry 2003; 61:21-7. [PMID: 14642906 DOI: 10.1016/s1567-5394(03)00056-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Electrochemical impedance spectroscopy (EIS) was used to the study of gramicidin D (GD) dimerization and to transport of monovalent cations across lipid bilayers by the dimers. Phosphatidylcholine (PC) membranes were studied, unmodified and modified with very low GD concentrations in the presence of various potassium ion concentrations. A new method was proposed to determine the parameters used to describe the gramicidin dimer: gramicidin surface concentration (c(GG)), area occupied by individual channel (A(G)) and gramicidin dimerization equilibrium constant (K(GG)). It was shown that electrochemical impedance spectroscopy measurements of lipid bilayer membranes yielded the K(GG) and A(G) values of the same order of magnitude as other measurement techniques.
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