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Li Z, Misra RP, Li Y, Yao YC, Zhao S, Zhang Y, Chen Y, Blankschtein D, Noy A. Breakdown of the Nernst-Einstein relation in carbon nanotube porins. NATURE NANOTECHNOLOGY 2023; 18:177-183. [PMID: 36585518 DOI: 10.1038/s41565-022-01276-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 10/17/2022] [Indexed: 06/17/2023]
Abstract
For over 100 years, the Nernst-Einstein relation has linked a charged particle's electrophoretic mobility and diffusion coefficient. Here we report experimental measurements of diffusion and electromigration of K+ ions in narrow 0.8-nm-diameter single-walled carbon nanotube porins (CNTPs) and demonstrate that the Nernst-Einstein relation in these channels breaks down by more than three orders of magnitude. Molecular dynamics simulations using polarizable force fields show that K+ ion diffusion in CNTPs in the presence of a single-file water chain is three orders of magnitude slower than bulk diffusion. Intriguingly, the simulations also reveal a disintegration of the water chain upon application of electric fields, resulting in the formation of distinct K+-water clusters, which then traverse the CNTP at high velocity. Finally, we show that although individual ion-water clusters still obey the Nernst-Einstein relation, the overall relation breaks down because of two distinct mechanisms for ion diffusion and electromigration.
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Affiliation(s)
- Zhongwu Li
- Materials Science Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, China
- School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, China
| | - Rahul Prasanna Misra
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Yuhao Li
- Materials Science Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Yun-Chiao Yao
- 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
| | - Sidi Zhao
- Materials Science Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
- School of Engineering, University of California Merced, Merced, CA, USA
| | - Yuliang Zhang
- Materials Science Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Yunfei Chen
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, China
| | - Daniel Blankschtein
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 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.
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Broniec A, Żądło A, Pawlak A, Fuchs B, Kłosiński R, Thompson D, Sarna T. Interaction of plasmenylcholine with free radicals in selected model systems. Free Radic Biol Med 2017; 106:368-378. [PMID: 28232206 DOI: 10.1016/j.freeradbiomed.2017.02.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 01/10/2017] [Accepted: 02/13/2017] [Indexed: 12/13/2022]
Abstract
Plasmalogens (Plg) - naturally occurring glycerophospholipids with the vinyl-ether group in the sn-1 position are generally viewed as physiological antioxidants. Although there are numerous examples of antioxidant action of plasmalogen in cell cultures and in experimental animals, this hypothesis is far from being satisfactorily proven due to substantial limitations of such studies. Thus, plasmalogen reactivity in cells results in the accumulation of toxic byproducts and the experimental design is usually too complicated to evaluate the protective function of solely one type of lipid molecular species. In this study, experiments were performed in homogenous and heterogeneous model systems consisting of solutions in organic solvents as well as micelles and liposomes containing pure synthetic plasmenylcholines. Under the experimental conditions used, chemical reactivity of plasmalogens could be attributed to specific fatty acid esterification pattern. This is important because the chemical reactivity cannot be separated from physico-chemical properties of the lipids. Time-dependent formation of phospholipid and cholesterol hydroperoxides were determined by iodometric assay and HPLC-EC. EPR oximetry and Clark electrode were employed to detect the accompanying changes in oxygen concentration. Oxidation of the studied lipids was monitored by standard colorimetric TBARS method as well as MALDI-TOF mass spectrometry. Our data indicate that the reactivity of sn-2 monounsaturated vinyl ether lipids in peroxyl radical-induced or iron-catalyzed peroxidation reactions is comparable with that of their diacyl analogs. In samples containing cholesterol and plasmalogens, oxidative processes lead to accumulation of the radical oxidation product of cholesterol. It can be concluded that the antioxidant action of plasmalogens takes place intramolecularly rather than intermolecularly and depends on the degree of unsaturation of esterified fatty acids. Thus, it is questionable if plasmalogens can really be viewed as "endogenous antioxidant", even though they may exhibit, under special conditions, protective effect.
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Affiliation(s)
- A Broniec
- Biophysics Department, Biochemistry, Biophysics and Biotechnology Faculty, Jagiellonian University, Krakow, Poland.
| | - A Żądło
- Biophysics Department, Biochemistry, Biophysics and Biotechnology Faculty, Jagiellonian University, Krakow, Poland
| | - A Pawlak
- Biophysics Department, Biochemistry, Biophysics and Biotechnology Faculty, Jagiellonian University, Krakow, Poland
| | - B Fuchs
- Institute of Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Germany
| | - R Kłosiński
- Biophysics Department, Biochemistry, Biophysics and Biotechnology Faculty, Jagiellonian University, Krakow, Poland
| | - D Thompson
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
| | - T Sarna
- Biophysics Department, Biochemistry, Biophysics and Biotechnology Faculty, Jagiellonian University, Krakow, Poland
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Clinical concentrations of chemically diverse general anesthetics minimally affect lipid bilayer properties. Proc Natl Acad Sci U S A 2017; 114:3109-3114. [PMID: 28265069 DOI: 10.1073/pnas.1611717114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
General anesthetics have revolutionized medicine by facilitating invasive procedures, and have thus become essential drugs. However, detailed understanding of their molecular mechanisms remains elusive. A mechanism proposed over a century ago involving unspecified interactions with the lipid bilayer known as the unitary lipid-based hypothesis of anesthetic action, has been challenged by evidence for direct anesthetic interactions with a range of proteins, including transmembrane ion channels. Anesthetic concentrations in the membrane are high (10-100 mM), however, and there is no experimental evidence ruling out a role for the lipid bilayer in their ion channel effects. A recent hypothesis proposes that anesthetic-induced changes in ion channel function result from changes in bilayer lateral pressure that arise from partitioning of anesthetics into the bilayer. We examined the effects of a broad range of chemically diverse general anesthetics and related nonanesthetics on lipid bilayer properties using an established fluorescence assay that senses drug-induced changes in lipid bilayer properties. None of the compounds tested altered bilayer properties sufficiently to produce meaningful changes in ion channel function at clinically relevant concentrations. Even supra-anesthetic concentrations caused minimal bilayer effects, although much higher (toxic) concentrations of certain anesthetic agents did alter lipid bilayer properties. We conclude that general anesthetics have minimal effects on bilayer properties at clinically relevant concentrations, indicating that anesthetic effects on ion channel function are not bilayer-mediated but rather involve direct protein interactions.
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Nishimukai M, Maeba R, Ikuta A, Asakawa N, Kamiya K, Yamada S, Yokota T, Sakakibara M, Tsutsui H, Sakurai T, Takahashi Y, Hui SP, Chiba H, Okazaki T, Hara H. Serum choline plasmalogens—those with oleic acid in sn− 2—are biomarkers for coronary artery disease. Clin Chim Acta 2014; 437:147-54. [DOI: 10.1016/j.cca.2014.07.024] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 07/07/2014] [Accepted: 07/17/2014] [Indexed: 10/25/2022]
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Zha HY, Shen B, Yau KH, Li ST, Yao XQ, Yang D. A small synthetic molecule forms selective potassium channels to regulate cell membrane potential and blood vessel tone. Org Biomol Chem 2014; 12:8174-9. [PMID: 25183342 DOI: 10.1039/c4ob01420k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In living cell membranes, K(+) permeability is higher than that of other ions such as Na(+) and Cl(-) owing to abundantly expressed K(+) channels. Polarized membrane potential is mainly established by K(+) outward flow because the K(+) concentration in the intracellular side is much higher than that in the extracellular side. We have found that the small synthetic molecule 1 is capable of self-assembling into selective K(+) channels, enhancing K(+) permeability and hyperpolarizing liposome membrane potential. Interestingly, molecule 1 also functions as K(+) channel hyperpolarizing living cell membrane potential and relaxing agonist-induced blood vessel contraction. Therefore, it may have the potential to become a lead compound for the treatment of human diseases associated with K(+) channel dysfunction.
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Affiliation(s)
- Hui-Yan Zha
- Morningside Laboratory for Chemical Biology, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China.
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Broniec A, Goto M, Matsuki H. A peculiar phase transition of plasmalogen bilayer membrane under high pressure. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:11265-11268. [PMID: 19697955 DOI: 10.1021/la902503n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The bilayer phase transition of plasmalogen, monounsaturated plasmenylcholine 1-O-1'-(Z)-octadecenyl-2-oleoyl-sn-glycero-3-phosphocholine (Plg-SOPC), was examined by differential scanning calorimetry, high-pressure transmittance, and fluorescence techniques. The bilayer properties of Plg-SOPC such as the temperature-pressure phase diagram, the thermodynamic quantities of the transition, and the location of a fluorescent membrane probe in the bilayer, were compared with those of a similar phospholipid 1-stearoyl-2-oleoyl-phosphatidylcholine (SOPC). It turned out that a vinyl-ether bond in the sn-1 position of the glycerol backbone in the Plg-SOPC molecule produces a peculiar phase transition under high pressure and significantly affects the membrane properties.
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Affiliation(s)
- Agnieszka Broniec
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
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Abstract
Myocardial phospholipids serve as primary reservoirs of arachidonic acid (AA), which is liberated through the rate-determining hydrolytic action of cardiac phospholipases A2 (PLA2s). A predominant PLA2 in myocardium is calcium-independent phospholipase A2beta (iPLA2beta), which, through its calmodulin (CaM) and ATP-binding domains, is regulated by alterations in local cellular Ca2+ concentrations and cardiac bioenergetic status, respectively. Importantly, iPLA2beta has been demonstrated to be activated by ischaemia through elevation of the concentration of myocardial fatty acyl-CoA, which abrogates Ca2+/CaM-mediated inhibition of iPLA2beta. AA released by PLA2-catalysed hydrolysis of phospholipids serves as a precursor for eicosanoids generated by pathways dependent on cyclooxygenases (COX), lipoxygenases (LOX), and cytochromes P450 (CYP). Eicosanoids initiate and propagate diverse signalling cascades, primarily through their interaction with cellular receptors and ion channels. However, during pathologic states such as ischaemia or congestive heart failure, eicosanoids contribute to multiple maladaptive changes including inflammation, alterations of cellular growth programmes, and activation of multiple transcriptional events leading to the deleterious sequelae of these pathologic states. This review summarizes the central roles of myocardial PLA(2)s in eicosanoid signalling in the heart, the major COX, LOX, and CYP pathways of eicosanoid generation in the myocardium, and the effects of important eicosanoids on receptor-, ion channel-, and transcription-mediated processes that facilitate cardiac hypertrophy, mediate ischaemic preconditioning, and precipitate arrhythmogenesis in response to pathologic stimuli.
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Affiliation(s)
- Christopher M Jenkins
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8020, St Louis, MO 63110, USA
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Pytel M, Mercik K, Mozrzymas JW. Interaction between cyclodextrin and neuronal membrane results in modulation of GABA(A) receptor conformational transitions. Br J Pharmacol 2006; 148:413-22. [PMID: 16702996 PMCID: PMC1751786 DOI: 10.1038/sj.bjp.0706747] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cyclodextrins (CDs) are nanostructures widely applied in biotechnology and chemistry. Owing to partially hydrophobic character, CDs interact with biological membranes. While the mechanisms of CDs interactions with lipids were widely studied, their effects on proteins are less understood. In the present study we investigated the effects of beta cyclodextrin (betaCD) on GABA(A) receptor (GABA(A)R) gating. To reliably resolve the kinetics of conformational transitions, currents were elicited by ultrafast gamma-aminobutyric acid (GABA) applications to outside-out patches from rat cultured hippocampal neurons. betaCD increased the amplitude of responses to saturating GABA concentration ([GABA]) in a dose-dependent manner and this effect was accompanied by profound alterations in the current kinetics. Current deactivation was slowed down by betaCD but this effect was biphasic with a maximum at around 0.5 mM betaCD. While the fast deactivation time constant was monotonically slowed down within considered betaCD concentration range, the slow component first increased and then, at millimolar betaCD concentration, decreased. The rate and extent of desensitization was decreased by betaCD in a dose-dependent manner. The analysis of current responses to nonsaturating [GABA] indicated that betaCD affected the GABA(A)R agonist binding site by slowing down the unbinding rate. Modulation of GABA(A)R desensitization and binding showed different concentration-dependence suggesting different modualtory sites with higher affinity of the latter one. All the betaCD effects were fully reversible indicating that cholesterol uptake into betaCD was not the primary mechanism. We conclude that betaCD is a strong modulator of GABA(A)R conformational transitions.
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Affiliation(s)
- Maria Pytel
- Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Poland.
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Lee TC. Biosynthesis and possible biological functions of plasmalogens. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1394:129-45. [PMID: 9795186 DOI: 10.1016/s0005-2760(98)00107-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- T C Lee
- Basic and Applied Research, Oak Ridge Institute for Science and Education/Oak Ridge Associated Universities, Oak Ridge, TN 37831-0117, USA
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