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Wu HC, Yoshioka T, Nakagawa K, Shintani T, Matsuyama H. Water Transport and Ion Diffusion Investigation of an Amphotericin B-Based Channel Applied to Forward Osmosis: A Simulation Study. MEMBRANES 2021; 11:membranes11090646. [PMID: 34564464 PMCID: PMC8467697 DOI: 10.3390/membranes11090646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 08/13/2021] [Accepted: 08/18/2021] [Indexed: 11/17/2022]
Abstract
The use of an Amphotericin B_Ergosterol (AmBEr) channel as an artificial water channel in forward osmosis filtration (FO) was studied via molecular dynamics (MD) simulation. Three channel models were constructed: a common AmBEr channel and two modified C3deOAmB_Ergosterol (C3deOAmBEr) channels with different diameters (12 Å and 18 Å). During FO filtration simulation, the osmotic pressure of salt-water was a driving force for water permeation. We examined the effect of the modified C3deOAmBEr channel on the water transport performance. By tracing the change of the number of water molecules along with simulation time in the saltwater region, the water permeability of the channel models could be calculated. A higher water permeability was observed for a modified C3deOAmBEr channel, and there was no ion permeation during the entire simulation period. The hydrated ions and water molecules were placed into the channel to explore the ion leakage behavior of the channels. The mean squared displacement (MSD) of ions and water molecules was obtained to study the ion leakage performance. The Amphotericin B-based channels showed excellent selectivity of water molecules against ions. The results obtained on an atomistic scale could assist in determining the properties and the optimal filtration applications for Amphotericin B-based channels.
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Affiliation(s)
- Hao-Chen Wu
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Tomohisa Yoshioka
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
- Correspondence: ; Tel.: +81-78-803-6299
| | - Keizo Nakagawa
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Takuji Shintani
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Hideto Matsuyama
- Research Center for Membrane and Film Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan; (H.-C.W.); (K.N.); (T.S.); (H.M.)
- Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
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Wu HC, Yoshioka T, Nakagawa K, Shintani T, Saeki D, Matsuyama H. Molecular simulation of a modified amphotericin B-Ergosterol artificial water channel to evaluate structure and water molecule transport performance. J Memb Sci 2019. [DOI: 10.1016/j.memsci.2019.04.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Wu HC, Yoshioka T, Nakagawa K, Shintani T, Tsuru T, Saeki D, Shaikh AR, Matsuyama H. Preparation of Amphotericin B-Ergosterol structures and molecular simulation of water adsorption and diffusion. J Memb Sci 2018. [DOI: 10.1016/j.memsci.2017.09.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Wu HC, Yoshioka T, Nagasawa H, Kanezashi M, Tsuru T, Saeki D, Matsuyama H. Preparation of cyclic peptide nanotube structures and molecular simulation of water adsorption and diffusion. J Memb Sci 2017. [DOI: 10.1016/j.memsci.2017.04.060] [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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Abstract
Metal ions play significant roles in numerous fields including chemistry, geochemistry, biochemistry, and materials science. With computational tools increasingly becoming important in chemical research, methods have emerged to effectively face the challenge of modeling metal ions in the gas, aqueous, and solid phases. Herein, we review both quantum and classical modeling strategies for metal ion-containing systems that have been developed over the past few decades. This Review focuses on classical metal ion modeling based on unpolarized models (including the nonbonded, bonded, cationic dummy atom, and combined models), polarizable models (e.g., the fluctuating charge, Drude oscillator, and the induced dipole models), the angular overlap model, and valence bond-based models. Quantum mechanical studies of metal ion-containing systems at the semiempirical, ab initio, and density functional levels of theory are reviewed as well with a particular focus on how these methods inform classical modeling efforts. Finally, conclusions and future prospects and directions are offered that will further enhance the classical modeling of metal ion-containing systems.
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Affiliation(s)
| | - Kenneth M. Merz
- Department of Chemistry, Department of Biochemistry and Molecular Biology, and Institute of Cyber-Enabled Research, Michigan State University, East Lansing, Michigan 48824, United States
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Karthikeyan S, Singh NJ, Kim KS. Undissociated versus Dissociated Structures for Water Clusters and Ammonia−Water Clusters: (H2O)n and NH3(H2O)n−1 (n = 5, 8, 9, 21). Theoretical Study. J Phys Chem A 2008; 112:6527-32. [DOI: 10.1021/jp801678r] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S. Karthikeyan
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea
| | - N. Jiten Singh
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea
| | - Kwang S. Kim
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea
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7
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Min SK, Lee EC, Lee HM, Kim DY, Kim D, Kim KS. Complete basis set limit ofAb initio binding energies and geometrical parameters for various typical types of complexes. J Comput Chem 2008; 29:1208-21. [DOI: 10.1002/jcc.20880] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Theoretical Approaches to the Design of Functional Nanomaterials. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s1380-7323(04)80019-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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10
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Cole CD, Frost AS, Thompson N, Cotten M, Cross TA, Busath DD. Noncontact dipole effects on channel permeation. VI. 5F- and 6F-Trp gramicidin channel currents. Biophys J 2002; 83:1974-86. [PMID: 12324416 PMCID: PMC1302287 DOI: 10.1016/s0006-3495(02)73959-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Fluorination of peptide side chains has been shown to perturb gramicidin channel conductance without significantly changing the average side chain structure, which, it is hoped, will allow detailed analysis of electrostatic modulation of current flow. Here we report a 1312-point potassium current-voltage-concentration data set for homodimeric channels formed from gramicidin A (gA) or any of eight fluorinated Trp analogs in both lecithin and monoglyceride bilayers. We fit the data with a three-barrier, two-site, two-ion (3B2S) kinetic model. The fluorination-induced changes in the rate constants were constrained by the same factor in both lipids. The rate constant changes were converted to transition-state free-energy differences for comparison with previous electrostatic potential energy differences based on an ab initio force field. The model allowed a reasonably good fit (chi = 8.29 with 1271 degrees of freedom). The measured changes were subtle. Nevertheless, the fitted energy perturbations agree well with electrostatic predictions for five of the eight peptides. For the other three analogs, the fitted changes suggested a reduced translocation barrier rather than the reduced exit barrier as predicted by electrostatics.
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Affiliation(s)
- Chad D Cole
- Center for Neuroscience and Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah 84062, USA
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12
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Suh SB, Cui C, Son HS, U JS, Won Y, Kim KS. Novel Amphi-ionophore in Aqueous Solution: Cyclohexaalanyl. J Phys Chem B 2002. [DOI: 10.1021/jp011809g] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Seung Bum Suh
- National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Korea, and Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, Korea
| | - Chunzhi Cui
- National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Korea, and Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, Korea
| | - Hyeon S. Son
- National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Korea, and Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, Korea
| | - Jong Sun U
- National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Korea, and Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, Korea
| | - Youngdo Won
- National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Korea, and Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, Korea
| | - Kwang S. Kim
- National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Korea, and Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, Korea
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Anderson DG, Shirts RB, Cross TA, Busath DD. Noncontact dipole effects on channel permeation. V. Computed potentials for fluorinated gramicidin. Biophys J 2001; 81:1255-64. [PMID: 11509342 PMCID: PMC1301607 DOI: 10.1016/s0006-3495(01)75783-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Experimental and theoretical calculations indicate that the dipole moment of the four Trp side chains in gramicidin A (gA) channels modify channel conductance through long-range electrostatic interactions. Electrostatic ion/side-chain interaction energies along the channel were computed with CHARMM using ab initio atom charges for native and 4-, 5-, or 6-fluorinated Trp side chains. The bulk water reaction to the polar side chains was included using the method of images as implemented by, and channel waters in idealized structures were included. Ion/Trp interaction energies were approximately -0.6 kcal/mol throughout the channel for all four of the native Trp pairs. Channel waters produced a modest reduction in the magnitude of interactions, essentially offsetting images representing the bulk water outside the channel. The effects of side-chain fluorination depended on ring position and, to a lesser extent, residue number. Compared with native Trp, 5-fluorination reduces the translocation barrier with minor effects on the exit barrier. In contrast, 6-fluorination primarily reduces exit barrier. 4-Fluorination produces a more complex double-well energy profile. Effects of measured side-chain movements resulting from fluorination or change in lipid bilayer were negligible whereas thermal side chain librations cause large effects, especially in the region of the ion-binding sites.
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Affiliation(s)
- D G Anderson
- Zoology Department and Center for Neuroscience, Brigham Young University, Provo, Utah 84602, USA
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14
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Hao Y, Pear MR, Busath DD. Molecular dynamics study of free energy profiles for organic cations in gramicidin A channels. Biophys J 1997; 73:1699-716. [PMID: 9336167 PMCID: PMC1181072 DOI: 10.1016/s0006-3495(97)78202-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The free energy profiles for four organic cations in right-handed single-helix gramicidin A dimers were computed by using umbrella sampling molecular dynamics with CHARMM. Ion-water column translocations were facilitated by using a novel "water-tunnel" approach. The overlapping pieces of free energy profile for adjacent windows were selected from three trajectories that differed in initial ion rotation and were aligned by the method of umbrella potential differences. Neglected long-range electrostatic energies from the bulk water and the bilayer were computed with DelPhi and added to the profile. The approach was corroborated for the formamidinium-guanidinium pair by using perturbation dynamics at axial positions 0, 6, 12, and 15 A from the channel center. The barrier to ethylammonium entry was prohibitive at 21 kcal/mol, whereas for methylammonium it was 5.5 kcal/mol, and the profile was quite flat through the channel, roughly consistent with conductance measurements. The profile for formamidinium was very similar to that of methylammonium. Guanidinium had a high entry barrier (deltaF = +8.6 kcal/mol) and a narrow deep central well (deltaF = -2.6 kcal/mol), qualitatively consistent with predictions from voltage-dependent potassium current block measurements. Its deep central well, contrasting with the flat profile for formamidinium, was verified with perturbation dynamics and was correlated with its high propensity to form hydrogen bonds with the channel at the dimer junction (not shared by the other three cations). Analysis of the ensemble average radial forces on the ions demonstrates that all four ions undergo compressive forces in the channel that are at maximum at the center of the monomer and relieved at the dimer junction, illustrating increased flexibility of the channel walls in the center of the channel.
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Affiliation(s)
- Y Hao
- Brown University, Department of Physiology, Providence, Rhode Island 02912, USA
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15
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Duca KA, Jordan PC. Ion-water and water-water interactions in a gramicidinlike channel: effects due to group polarizability and backbone flexibility. Biophys Chem 1997; 65:123-41. [PMID: 9175269 DOI: 10.1016/s0301-4622(96)02233-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In the gramicidin channel, ionic transport and water transport occur simultaneously. Gramicidin's transport properties are influenced by ionic interactions with both the polypeptide and the channel waters. We present results of molecular dynamics studies on a series of alkali metal ions interacting with a water-filled gramicidinlike channel (a configurationally constrained polyglycine analog) at the dimer junction, in mid-monomer, and near the channel entrance. We investigate details of both short and long range ion-water and water-water correlation; these are notably dependent on the explicit consideration of polarizability and the degree of backbone flexibility. The nature of ion-water and water-water correlations changes as ionic size decreases and these changes may be augmented or attenuated by manipulation of the two parameters under study. Incorporating polarizability generally shortens ion-water distances and enhances ion-induced electrostriction (decreased water-water separations), while simultaneously reducing the long range orientational correlation of the single filing waters within the channel. Increasing flexibility predictably results in a broadening of the distribution of water-water and ion-water separations and contributes to the loss of long range orientational correlations. Both effects are ion specific; Cs+ and Na+ interact with the channel in distinctly different ways, while K+ represents an intermediate case more closely resembling Cs+. Our results demonstrate that incorporation of polarizability in the potential function has significant effects on the properties of channel water and, consequently, on the ionic transport process. While ion-water and water-water distances are decreased due to this feature, thereby fostering longer ranged correlations within the channel, enhanced interactions between water molecules and peptide groups tend to mitigate this effect. Possible implications for the multiple occupancy states of gramicidin and long range information transfer via a single file water chain are considered.
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Affiliation(s)
- K A Duca
- Program in Biophysics, Brandeis University, South Street, Waltham, MA 02254, USA
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16
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Arteca GA, Van Allen DR. Three-dimensional lipophilicity characterization of molecular pores and channel-like cavities. JOURNAL OF MOLECULAR GRAPHICS 1996; 14:235-42. [PMID: 9076638 DOI: 10.1016/s0263-7855(96)00076-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Molecular lipophilicity is a useful property for assessing molecular similarity or complementarity within the context of computer-aided drug design. As well, local contributions to solvent affinity help us to understand both dynamics and conformational stability in biomolecules. In this work, we discuss an approach to characterize the local contributions to hydrophobicity by using one- and two-dimensional representations of molecular channel-like cavities. The method monitors how a phenomenological lipophilicity potential (based on fragmental atom contributions) changes over a continuum of "molecular tubes" used for modeling channels and pores. Our results convey a relatively detailed picture of the spatial distribution of water affinity. The procedure can then be used as a complement to the hydrophobicity scales based on averaging contributions from single amino acids. In addition, we can study how the water affinity changes for inner and outer regions of the pores. As an application, we compute the 3D distribution of lipophilicity in the "pore conformation" of gramicidin A. The qualitative trends indicated by our results are broadly consistent with computer simulations of the gramicidin channel in the presence of hydrated ions. The behavior revealed by the simulations can then be incorporated to produce an improved, simple 2D model for water-channel interactions.
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Affiliation(s)
- G A Arteca
- Département de Chimie et Biochimie, Laurentian University, Sudbury, Ontario, Canada
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Abstract
The reaction path and free energy profile of Na+ were computed in the interior of the channel protein gramicidin, with the program MOIL. Gramicidin was represented in atomic detail, but surrounding water and lipid molecules were not included. Thus, only short range interactions were investigated. The permeation path of the ion was an irregular spiral, far from a straight line. Permeation cannot be described by motions of a single Na+ ion. The minimal energy path includes significant motion of water and channel atoms as well as motion of the permeating ion. We think of permeation as motion of a permion, a quasi-particle that includes the many body character of the permeation process, comparable with quasi-particles like holes, phonons, and electrons of solid-state physics. Na+ is accompanied by a plug of water molecules, and motions of water, Na+, and the atoms of gramicidin are highly correlated. The permion moves like a linear polymer made of waters and ion linked and moving coherently along a zigzag line, following the reptation mechanism of polymer transport. The effective mass, free energy, and memory kernel (of the integral describing time-dependent friction) of short range interactions were calculated. The effective mass of the permion (properly normalized) is much less than Na+. Friction varies substantially along the path. The free energy profile has two deep minima and several maxima. In certain regions, the dominant motions along the reaction path are those of the channel protein, not the permeating ion: there, ion waits while the other atoms move. At these waiting sites, the permion's motion along the reaction path is a displacement of the atoms of gramicidin that prepare the way for the Na+ ion.
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Affiliation(s)
- R Elber
- Department of Chemistry, University of Illinois at Chicago 60680, USA
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Abstract
Ionic permeation in the selectivity filter of ion channels is analyzed by a microscopic model based on molecular kinetic theory. The energy and flux equations are derived by assuming that: (a) the selectivity filter is formed by a symmetrical array of carbonyl groups; (b) ion movement is near the axis of the channel; (c) a fraction of water molecules is separated from the ion while it moves across the selectivity filter; (d) the applied voltage drops linearly across the selectivity filter; (e) ions move independently. Energy profiles, single channel conductances, and the degree of hydration of K+ in a hypothetical K+ channel are examined by varying the following microscopic parameters: ion radius and mass, channel radius, number of effective water dipoles, and number of carbonyl groups. The i-V curve is linear up to +/- 170 mV. If the positions of energy maxima and minima are fixed, this linear range is reduced to +/- 50 mV. Channel radius and ion-water interactions are found to be two major channel structural determinants for selectivity sequences. Both radius and mass of an ion are important in selectivity mediated by these interactions. The theory predicts a total of 15 possible kinetic selectivity sequences for alkali cations in ion channels with a single selectivity filter.
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Affiliation(s)
- J Wu
- Department of Physiology, University of Rochester Medical Center, New York 14642
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20
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Leherte L, Andre JM, Derouane EG, Vercauteren DP. Study of the water behavior into a ferrierite zeolite by molecular dynamics simulations. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0097-8485(91)80016-f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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21
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Leherte L, André JM, Derouane EG, Vercauteren DP. Self-diffusion of water into a ferrierite-type zeolite by molecular dynamics simulations. ACTA ACUST UNITED AC 1991. [DOI: 10.1039/ft9918701959] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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22
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Jordan PC. Ion-water and ion-polypeptide correlations in a gramicidin-like channel. A molecular dynamics study. Biophys J 1990; 58:1133-56. [PMID: 1705448 PMCID: PMC1281060 DOI: 10.1016/s0006-3495(90)82456-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
This work describes a molecular dynamics study of ion-water and ion-polypeptide correlation in a model gramicidin-like channel (the polyglycine analogue) based upon interaction between polarizable, multipolar groups. The model suggests that the vicinity of the dimer junction and of the ethanolamine tail are regions of unusual flexibility. Cs+ binds weakly in the mouth of the channel: there it coordinates five water molecules and the #11CO group with which it interacts strongly and is ideally aligned. In the channel interior it is generally pentacoordinate; at the dimer junction, because of increased channel flexibility, it again becomes essentially hexacoordinate. The ion is also strongly coupled to the #13 CO but not to either #9 or #15, consistent with 13C NMR data. Water in the channel interior is strikingly different from bulk water; it has a much lower mean dipole moment. This correlates with our observation (which differs from that of previous studies) that water-water angular correlations do not persist within the channel, a result independent of ion occupancy or ionic polarity. In agreement with streaming potential measurements, there are seven single file water molecules associated with Cs+ permeation; one of these is always in direct contact with bulk water. At the mouth of an ion-free channel, there is a pattern of dipole moment alteration among the polar groups. Due to differential interaction with water, exo-carbonyls have unusually large dipole moments whereas those of the endo-carbonyls are low. The computed potential of mean force for CS+ translocation is qualitatively reasonable. However, it only exhibits a weakly articulated binding site and it does not quantitatively account for channel energetics. Correction for membrane polarization reduces, but does not eliminate, these problems.
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Affiliation(s)
- P C Jordan
- Department of Chemistry, Brandeis University, Waltham, Massachusetts 02254-9110
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Heinemann SH, Sigworth FJ. Open channel noise. V. Fluctuating barriers to ion entry in gramicidin A channels. Biophys J 1990; 57:499-514. [PMID: 1689592 PMCID: PMC1280744 DOI: 10.1016/s0006-3495(90)82566-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have measured the fluctuations in the current through gramicidin A (GA) channels in symmetrical solutions of monovalent cations of various concentrations, and compared the spectral density values with those computed using E. Frehland's theory for noise in discrete transport systems (Frehland, E. 1978. Biophys. Chem. 8:255-265). The noise for the transport of NH4+ and Na+ ions in glycerol-monooleate/squalene membranes could be accounted for entirely by "shot noise" in the process of transport through a single-filing pore with two ion binding sites. However, in confirmation of results in a previous paper (Sigworth, F. J., D. W. Urry, and K. U. Prasad. 1987. Biophys. J. 52:1055-1064) currents of Cs+ showed a substantial excess noise at low ion concentrations, as did currents of K+ and Rb+. The excess noise was increased in thicker membranes. The observations are accounted for by a theory that postulates fluctuations of the entry rates of ions into the channel on a time scale of approximately 1 microsecond. These fluctuations occur preferentially when the channel is empty; the presence of bound ions stabilizes the "high conductance" conformation of the channel. The fluctuations are sensed to different degrees by the various ion species, and their kinetics depend on membrane thickness.
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Affiliation(s)
- S H Heinemann
- Max-Planck-Institut für biophysikalische Chemie, Göttingen, Federal Republic of Germany
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Chiu SW, Subramaniam S, Jakobsson E, McCammon JA. Water and polypeptide conformations in the gramicidin channel. A molecular dynamics study. Biophys J 1989; 56:253-61. [PMID: 2476188 PMCID: PMC1280474 DOI: 10.1016/s0006-3495(89)82671-2] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Theoretical studies of ion channels address several important questions. The mechanism of ion transport, the role of water structure, the fluctuations of the protein channel itself, and the influence of structural changes are accessible from these studies. In this paper, we have carried out a 70-ps molecular dynamics simulation on a model structure of gramicidin A with channel waters. The backbone of the protein has been analyzed with respect to the orientation of the carbonyl and the amide groups. The results are in conformity with the experimental NMR data. The structure of water and the hydrogen bonding network are also investigated. It is found that the water molecules inside the channel act as a collective chain; whereas the conformation in which all the waters are oriented with the dipoles pointing along the axis of the channel is a preferred one, others are also accessed during the dynamics simulation. A collective coordinate involving the channel waters and some of the hydrogen bonding peptide partners is required to describe the transition of waters from one configuration to the other.
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Affiliation(s)
- S W Chiu
- Department of Physiology and Biophysics, University of Illinois, Urbana 61801
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Abstract
The crystal structure of the uncomplexed orthorhombic form of gramicidin A has been determined at 0.86 A resolution. The polypeptide crystallizes from ethanol as a left-handed, double-stranded, antiparallel beta 5.6-helical dimer that is 31 A long and an average of 4.8 A in diameter. The uncomplexed channel does not contain ions or solvent molecules, and its diameter is not uniform but varies from a minimum of 3.85 A to a maximum of 5.47 A. There are three empty cavities in the channel that have a diameter exceeding 5.25 A and appear to be large enough to accommodate water molecules or potassium ions in a chemically reasonable coordination environment. The observed crystal structure does not offer any obvious clues as to why an antiparallel beta 5.6-helix cannot function as an ion channel in lipid bilayers.
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26
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Leherte L, Vercauteren D, Derouane E, Lie G, Clementi E, Andre JM. Effects of Long-Range Interactions in Zeolites-Like Systems: Dynamical Behavior of Water in Ferrierite From Molecular Dynamics Simulation. ACTA ACUST UNITED AC 1989. [DOI: 10.1016/s0167-2991(08)61964-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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27
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Kim DH, Sreter FA, Ikemoto N. Involvement of the 60 kDa phosphoprotein in the regulation of Ca2+ release from sarcoplasmic reticulum of normal and malignant hyperthermia susceptible pig muscles. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 945:246-52. [PMID: 3191123 DOI: 10.1016/0005-2736(88)90486-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Junctional sarcoplasmic reticulum (SR) vesicles isolated from back muscles of normal and malignant hyperthermia susceptible (MHS) pigs were phosphorylated by addition of MgATP in the presence of 5 mM Ca2+ and 1 microM calmodulin (CaM). The major site of phosphorylation was a 60 kDa protein both in normal and MHS SR. The maximal amount of phosphorylation in MHS SR (5 pmol P/mg SR) was significantly lower than that in the normal SR (12 pmol P/mg SR). The phosphorylated 60 kDa protein was spontaneously dephosphorylated both in normal and MHS SR. Ca2+ release from the passively loaded SR was induced by a Ca2+-jump, and monitored by stopped-flow fluorometry using chlorotetracycline. In the absence of preincubation with MgATP, no significant difference was found in any of the kinetic parameters of Ca2+ release between normal and MHS SR. Upon addition of 20 microM MgATP to the passively loaded SR to phosphorylate the 60 kDa protein, the initial rate of Ca2+ release in normal SR significantly decreased from 659 +/- 102 to 361 +/- 105 nmol Ca2+/mg SR per s, whereas in MHS SR the rate decreased from 749 +/- 124 to 652 +/- 179 nmol Ca2+/mg SR per s. Addition of 20 microM adenosine 5'-[beta, gamma-imido]triphosphate (p[NH]ppA) did not significantly alter the initial rate of Ca2+ release both in normal and MHS SR. These results suggest that the previously reported higher Ca2+ release rate in MHS SR (Kim et al. (1984) Biochim. Biophys. Acta 775, 320-327) is at least partly due to the reduced extent of the Ca2+/CaM-dependent phosphorylation of the 60 kDa protein. Two-dimensional gel electrophoresis study showed that amount of a protein with Mr = 55,000 was significantly lower in MHS SR than in normal SR suggesting that the abnormally lower amount of 55 kDa protein would cause the lower amount of phosphorylation of the 60 kDa protein in MHS SR.
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Affiliation(s)
- D H Kim
- Department of Muscle Research, Boston Biomedical Research Institute, MA
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28
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Leherte L, Lie G, Swamy K, Clementi E, Derouane E, André J. Determination of the self-diffusion coefficient of water in ferrierite by molecular dynamics. Chem Phys Lett 1988. [DOI: 10.1016/0009-2614(88)80186-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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29
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Abstract
The dynamics of the gramicidin-A dimer channel is studied in the harmonic approximation by a vibrational analysis of the atomic motions relative to their equilibrium positions. The system is represented by an empirical potential energy function, and all degrees of freedom (bonds lengths, bond angles, and torsional angles) are allowed to vary. The thermal fluctuations in the backbone dihedral angles phi and psi, atomic root mean square displacements, and the correlations between the different amide planes are computed. It is found that only adjacent dihedral psi i and phi i+1 are strongly correlated, while different hydrogen-bonded amide planes are only weakly correlated. Modes with relatively low vibrational frequencies (75-175 cm-1) make the dominant contributions to the carbonyl librations. The general flexibility of the structure and the role of carbonyl librations in the ion transport mechanism are discussed.
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Affiliation(s)
- B Roux
- Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138
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30
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Monte Carlo Simulations of Water Interaction with a Ferrlerite Type Zeolite Structure. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/s0167-2991(09)60606-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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31
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32
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Imagawa T, Smith JS, Coronado R, Campbell KP. Purified ryanodine receptor from skeletal muscle sarcoplasmic reticulum is the Ca2+-permeable pore of the calcium release channel. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)49303-9] [Citation(s) in RCA: 349] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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33
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Portmann P, Maruizumi T, Welti M, Badertscher M, Neszmelyi A, Simon W, Pretsch E. Pair potentials for the interaction energy of Li+, Na+, K+, and NH+4with organic molecules. J Chem Phys 1987. [DOI: 10.1063/1.453595] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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34
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Abstract
Molecular dynamics simulations have been used to study the interaction of Cl- with a gramicidin-like channel. The results suggest that there is a high-energy barrier at the entrance of the channel, which would correspond to a permeability 10(-9)-times that of a cation of the same size. This could account for the cationic selectivity of the gramicidin channel and indicates that valence selectivity is kinetically controlled.
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35
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Skerra A, Brickmann J. Simulation of voltage-driven hydrated cation transport through narrow transmembrane channels. Biophys J 1987; 51:977-83. [PMID: 2440486 PMCID: PMC1330031 DOI: 10.1016/s0006-3495(87)83425-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Molecular dynamics studies for the voltage-driven transport of the alkali metal ions lithium, sodium, and potassium through gramicidin A-type channels filled with water molecules are presented. The number of water molecules in the channel is obtained from a previous study (Skerra, A., and J. Brickmann, 1987, Biophys. J., 51:969-976). It is shown that the selectivity of the intrachannel ion diffusion through our model pore conforms to the experimentally observed selectivity of the gramicidin A channel. It is demonstrated that the number of water molecules in the channel plays a key role for the selectivity.
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36
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Okabe E, Kato Y, Sasaki H, Saito G, Hess ML, Ito H. Calmodulin participation in oxygen radical-induced cardiac sarcoplasmic reticulum calcium uptake reduction. Arch Biochem Biophys 1987; 255:464-8. [PMID: 3036009 DOI: 10.1016/0003-9861(87)90416-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of scavengers of oxygen radicals on canine cardiac sarcoplasmic reticulum (SR) Ca2+ uptake velocity was investigated at pH 6.4, the intracellular pH of the ischemic myocardium. With the generation of oxygen radicals from a xanthine-xanthine oxidase reaction, there was a significant depression of SR Ca2+ uptake velocity. Xanthine alone or xanthine plus denatured xanthine oxidase had no effect on this system. Superoxide dismutase (SOD), a scavenger of .O2-, or denatured SOD had no effect on the depression of Ca2+ uptake velocity induced by the xanthine-xanthine oxidase reaction. However, catalase, which can impair hydroxyl radical (.OH) formation by destroying the precursor H2O2, significantly inhibited the effect of the xanthine-xanthine oxidase reaction. This effect of catalase was enhanced by SOD, but not by denatured SOD. Dimethyl sulfoxide (Me2SO), a known .OH scavenger, completely inhibited the effect of the xanthine-xanthine oxidase reaction. The observed effect of oxygen radicals and radical scavengers was not seen in the calmodulin-depleted SR vesicles. Addition of exogenous calmodulin, however, reproduced the effect of oxygen radicals and the scavengers. The effect of oxygen radicals was enhanced by the calmodulin antagonists (compounds 48/80 and W-7) at concentrations which showed no effect alone on Ca2+ uptake velocity. Taken together, these findings strongly suggest that .OH, but not .O2-, is involved in a mechanism that may cause SR dysfunction, and that the effect of oxygen radicals is calmodulin dependent.
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37
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Abstract
Calculations contrasting the channel solvation energy for cesium ions and chloride ions associated with water in gramicidin-like channels are presented. The energy profile for the cation exhibits a deep well at the channel entrance; within the single file region the solvation energy is roughly constant. The anion exhibits a totally different energy profile. There is an energy barrier at the channel entrance; if the ion could surmount this barrier, it would be quite stable within the channel. At the channel entrance, the calculated solvation energy difference between anion and cation is approximately 15 kcal mol-1. This is completely consistent with the observation that chloride neither permeates nor blocks the channel since the estimated rate of ion entry would be approximately 0.01-10(-5) s-1, far slower than the rate at which the channel dimer dissociates into monomers.
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38
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Crespo LM, Novak TS, Freedman JC. Calcium, cell shrinkage, and prolytic state of human red blood cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1987; 252:C138-52. [PMID: 3103462 DOI: 10.1152/ajpcell.1987.252.2.c138] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The effects of intracellular calcium, or Cac, on the Na permeability of human red blood cells were examined during 3-h incubations with the Ca ionophore A23187 and varied external Ca, Cao. Above 3 microM Cao, Nac increased significantly as ATP decreased. Maintenance of normal ATP with vanadate did not prevent the gain of Nac. Similar amounts of Nac were gained in 3 h by ouabain-treated cells exposed to the K ionophore valinomycin or by cells osmotically shrunken. Cells shrunken with sucrose also exhibited partial loss of Kc. When the cells with increased Nac were subsequently transferred to Na-free, high-K medium, the Nac and Kc that had changed slowly over 3 h returned toward normal within 10 min. The development of irreversible high cation permeability in shrunken cells was not prevented by a variety of transport inhibitors. These observations and cell volume distributions suggest that prolonged shrinkage induces a subpopulation of cells to become highly cation permeable, or "prolytic". The major effect of Cac on Na permeability appears to be an indirect consequence of cell shrinkage due to KCl loss.
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39
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Etchebest C, Pullman A. The gramicidin A channel: energetics and structural characteristics of the progression of a sodium ion in the presence of water. J Biomol Struct Dyn 1986; 3:805-25. [PMID: 2482047 DOI: 10.1080/07391102.1986.10508463] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The distribution of water molecules in the Gramicidin A (GA) channel is determined by theoretical computations, and the role of this water on the energetics of the system upon progression of a sodium cation through the channel is investigated. In the absence of the ion, water molecules form a chain along the channel, hydrogen bonded to one another and to the L carbonyl oxygens, while others stay at the entrances of the channel, hydrogen-bonded to the free carbonyl oxygens of the L-Tryptophan residues. According to the definition adopted for the "inside" and the "outside" of the channel, it is found to contain at most 7 or 9 water molecules. When a hydrated sodium cation approaches and enters the channel, the structural properties corresponding to the minimized total energy of the system GA-water-Na+ indicate a reorganization, but not a destruction, of the chain of water molecules. The "energy profile" for the system GA-Na+-(22 waters) is analyzed in terms of its components and in comparison to the corresponding intrinsic profile computed earlier in vacuo. It appears that the presence of water does not unduely modify the pathway or the qualitative features of the energetics of the cation passage, except at the entrance, where the partial and progressive dehydration of the cation plays an important role. The presence and characteristics of the minimum found earlier at 10.5 A from the center are conserved.
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Affiliation(s)
- C Etchebest
- Institut de Biologie Physico-Chimique, C.N.R.S., Paris, France
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40
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Tryptophan photolysis is responsible for gramicidin-channel inactivation by ultraviolet light. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 1986. [DOI: 10.1016/0005-2736(86)90403-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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41
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Prouty MS, Schechter AN, Parsegian VA. Chemical potential measurements of deoxyhemoglobin S polymerization. Determination of the phase diagram of an assembling protein. J Mol Biol 1985; 184:517-28. [PMID: 4046025 DOI: 10.1016/0022-2836(85)90298-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We have used the "osmotic stress" method to determine the phase diagram of deoxyhemoglobin S polymerization. This method involves equilibration, through a semipermeable membrane, of the protein with solutions of inert polymers of known osmotic pressure. With deoxyhemoglobin A and S solutions, in which we have demonstrated achievement of equilibrium, plots of osmotic pressure versus concentration initially agree closely with the results of other methods of measurement of colligative properties. However, once the known solubility value is exceeded for the deoxyhemoglobin S solutions at various temperatures, there is a rapid rise in hemoglobin concentration over a narrow osmotic pressure range and then a more gradual increase in concentration. We believe that these two regions correspond, respectively, to the onset of the polymerization process, and of subsequent continuing growth and compression or alignment of polymer. We derive the thermodynamic values for these processes and show that the behavior of the deoxyhemoglobin S system is analogous to the phase transition for a simple chemical system. These results are relevant to understanding the intracellular polymerization of deoxyhemoglobin S in sickle cell disease, and these concepts are applicable to other protein assembly systems.
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