1
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Kolesnikov ES, Xiong Y, Onufriev AV. Implicit Solvent with Explicit Ions Generalized Born Model in Molecular Dynamics: Application to DNA. J Chem Theory Comput 2024. [PMID: 39283928 DOI: 10.1021/acs.jctc.4c00833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/21/2024]
Abstract
The ion atmosphere surrounding highly charged biomolecules, such as nucleic acids, is crucial for their dynamics, structure, and interactions. Here, we develop an approach for the explicit treatment of ions within an implicit solvent framework suitable for atomistic simulations of biomolecules. The proposed implicit solvent/explicit ions model, GBION, is based on a modified generalized Born (GB) model; it includes separate, modified GB terms for solute-ion and ion-ion interactions. The model is implemented in the AMBER package (version 24), and its performance is thoroughly investigated in atomistic molecular dynamics (MD) simulations of double-stranded DNA on a microsecond time scale. The aggregate characteristics of monovalent (Na+ and K+) and trivalent (Cobalt Hexammine, CoHex3+) counterion distributions around double-stranded DNA predicted by the model are in reasonable agreement with the experiment (where available), all-atom explicit water MD simulations, and the expectation from the Manning condensation theory. The radial distributions of monovalent cations around DNA are reasonably close to the ones obtained using the explicit water model: expressed in units of energy, the maximum deviations of local ion concentrations from the explicit solvent reference are within 1 kBT, comparable to the corresponding deviations expected between different established explicit water models. The proposed GBION model is able to simulate DNA fragments in a large volume of solvent with explicit ions with little additional computational overhead compared with the fully implicit GB treatment of ions. Ions simulated using the developed model explore conformational space at least 2 orders of magnitude faster than in the explicit solvent. These advantages allowed us to observe and explore an unexpected "stacking" mode of DNA condensation in the presence of trivalent counterions (CoHex3+) that was revealed by recent experiments.
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Affiliation(s)
- Egor S Kolesnikov
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Yeyue Xiong
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Alexey V Onufriev
- Departments of Computer Science and Physics, Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
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2
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Kolesnikov ES, Gushchin IY, Zhilyaev PA, Onufriev AV. Why Na+ has higher propensity than K+ to condense DNA in a crowded environment. J Chem Phys 2023; 159:145103. [PMID: 37815107 DOI: 10.1063/5.0159341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 08/22/2023] [Indexed: 10/11/2023] Open
Abstract
Experimentally, in the presence of the crowding agent polyethylene glycol (PEG), sodium ions compact double-stranded DNA more readily than potassium ions. Here, we have used molecular dynamics simulations and the "ion binding shells model" of DNA condensation to provide an explanation for the observed variations in condensation of short DNA duplexes in solutions containing different monovalent cations and PEG; several predictions are made. According to the model we use, externally bound ions contribute the most to the ion-induced aggregation of DNA duplexes. The simulations reveal that for two adjacent DNA duplexes, the number of externally bound Na+ ions is larger than the number of K+ ions over a wide range of chloride concentrations in the presence of PEG, providing a qualitative explanation for the higher propensity of sodium ions to compact DNA under crowded conditions. The qualitative picture is confirmed by an estimate of the corresponding free energy of DNA aggregation that is at least 0.2kBT per base pair more favorable in solution with NaCl than with KCl at the same ion concentration. The estimated attraction free energy of DNA duplexes in the presence of Na+ depends noticeably on the DNA sequence; we predict that AT-rich DNA duplexes are more readily condensed than GC-rich ones in the presence of Na+. Counter-intuitively, the addition of a small amount of a crowding agent with high affinity for the specific condensing ion may lead to the weakening of the ion-mediated DNA-DNA attraction, shifting the equilibrium away from the DNA condensed phase.
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Affiliation(s)
- Egor S Kolesnikov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Ivan Yu Gushchin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Petr A Zhilyaev
- The Center for Materials Technologies, Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, Moscow 121205, Russia
| | - Alexey V Onufriev
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
- Department of Computer Science, Virginia Tech, 2160C Torgersen Hall, Blacksburg, Virginia 24061, USA
- Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
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3
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Beverley KM, Shahi PK, Kabra M, Zhao Q, Heyrman J, Steffen J, Pattnaik BR. Kir7.1 disease mutant T153I within the inner pore affects K+ conduction. Am J Physiol Cell Physiol 2022; 323:C56-C68. [PMID: 35584325 DOI: 10.1152/ajpcell.00093.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Inward-rectifier potassium channel 7.1 (Kir7.1) is present in polarized epithelium, including the RPE. A single amino acid change at position 153 in the KCNJ13 gene, a substitution of threonine to isoleucine in Kir7.1 protein, causes blindness. We hypothesized that the disease caused by this single amino acid substitution within the transmembrane protein domain could alter the translation, localization, or ion transport properties. We assessed the effects of amino acid side-chain length, arrangement, and polarity on channel structure and function. We showed that the T153I mutation yielded a full-length protein localized to the cell membrane. Whole-cell patch-clamp recordings and chord conductance analyses revealed that the T153I mutant channel had negligible K+ conductance and failed to hyperpolarize the membrane potential. However, the mutant channel exhibited enhanced inward current when Rb+ was used as a charge carrier, suggesting that an inner pore had formed, and the channel was dysfunctional. Substituting with a polar, non-polar, or short side-chain amino acid did not affect the localization of the protein. Still, it had an altered channel function due to differences in pore radius. Polar side chains (cysteine and serine) with inner pore radii comparable to wildtype exhibited normal inward K+ conductance. Short side-chains (glycine and alanine) produced a channel with wider than expected inner pore size and lacked the biophysical characteristics of the wildtype channel. Leucine substitution produced results similar to the T153I mutant channel. This study provides direct electrophysiological evidence for the structure and function of the Kir7.1 channel's narrow inner pore in regulating conductance.
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Affiliation(s)
- Katie M Beverley
- Endocrinology and Reproductive Physiology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Pawan K Shahi
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Meha Kabra
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Qianqian Zhao
- Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Joseph Heyrman
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Jack Steffen
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Bikash R Pattnaik
- Endocrinology and Reproductive Physiology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States.,Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
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4
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Zhang C, Tian F, Lu Y, Yuan B, Tan ZJ, Zhang XH, Dai L. Twist-diameter coupling drives DNA twist changes with salt and temperature. SCIENCE ADVANCES 2022; 8:eabn1384. [PMID: 35319990 PMCID: PMC8942373 DOI: 10.1126/sciadv.abn1384] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
DNA deformations upon environmental changes, e.g., salt and temperature, play crucial roles in many biological processes and material applications. Here, our magnetic tweezers experiments observed that the increase in NaCl, KCl, or RbCl concentration leads to substantial DNA overwinding. Our simulations and theoretical calculation quantitatively explain the salt-induced twist change through the mechanism: More salt enhances the screening of interstrand electrostatic repulsion and hence reduces DNA diameter, which is transduced to twist increase through twist-diameter coupling. We determined that the coupling constant is 4.5 ± 0.8 kBT/(degrees∙nm) for one base pair. The coupling comes from the restraint of the contour length of DNA backbone. On the basis of this coupling constant and diameter-dependent DNA conformational entropy, we predict the temperature dependence of DNA twist Δωbp/ΔT ≈ -0.01 degree/°C, which agrees with our and previous experimental results. Our analysis suggests that twist-diameter coupling is a common driving force for salt- and temperature-induced DNA twist changes.
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Affiliation(s)
- Chen Zhang
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China
| | - Fujia Tian
- Department of Physics, City University of Hong Kong, Hong Kong 999077, China
| | - Ying Lu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Bing Yuan
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Zhi-Jie Tan
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Xing-Hua Zhang
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China
| | - Liang Dai
- Department of Physics, City University of Hong Kong, Hong Kong 999077, China
- Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, China
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5
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Hamilton I, Gebala M, Herschlag D, Russell R. Direct Measurement of Interhelical DNA Repulsion and Attraction by Quantitative Cross-Linking. J Am Chem Soc 2022; 144:1718-1728. [PMID: 35073489 PMCID: PMC8815069 DOI: 10.1021/jacs.1c11122] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Indexed: 12/30/2022]
Abstract
To better understand the forces that mediate nucleic acid compaction in biology, we developed the disulfide cross-linking approach xHEED (X-linking of Helices to measure Electrostatic Effects at Distance) to measure the distance-dependent encounter frequency of two DNA helices in solution. Using xHEED, we determined the distance that the electrostatic potential extends from DNA helices, the dependence of this distance on ionic conditions, and the magnitude of repulsion when two helices approach one another. Across all conditions tested, the potential falls to that of the bulk solution within 15 Å of the major groove surface. For separations of ∼30 Å, we measured a repulsion of 1.8 kcal/mol in low monovalent ion concentration (30 mM Na+), with higher Na+ concentrations ameliorating this repulsion, and 2 M Na+ or 100 mM Mg2+ eliminating it. Strikingly, we found full screening at very low Co3+ concentrations and net attraction at higher concentrations, without the higher-order DNA condensation that typically complicates studies of helical attraction. Our measurements define the relevant distances for electrostatic interactions of nucleic-acid helices in biology and introduce a new method to propel further understanding of how these forces impact biological processes.
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Affiliation(s)
- Ian Hamilton
- Department
of Molecular Biosciences, University of
Texas at Austin, Austin, Texas 78712, United States
| | - Magdalena Gebala
- Department
of Biochemistry, Stanford University, Stanford California 94305, United States
| | - Daniel Herschlag
- Department
of Biochemistry, Stanford University, Stanford California 94305, United States
| | - Rick Russell
- Department
of Molecular Biosciences, University of
Texas at Austin, Austin, Texas 78712, United States
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6
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7
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Kolesnikov ES, Gushchin IY, Zhilyaev PA, Onufriev AV. Similarities and Differences between Na + and K + Distributions around DNA Obtained with Three Popular Water Models. J Chem Theory Comput 2021; 17:7246-7259. [PMID: 34633813 DOI: 10.1021/acs.jctc.1c00332] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have compared distributions of sodium and potassium ions around double-stranded DNA, simulated using fixed charge SPC/E, TIP3P, and OPC water models and the Joung/Cheatham (J/C) ion parameter set, as well as the Li/Merz HFE 6-12 (L/M HFE) ion parameters for OPC water. In all the simulations, the ion distributions are in qualitative agreement with Manning's condensation theory and the Debye-Hückel theory, where expected. In agreement with experiment, binding affinity of monovalent ions to DNA does not depend on ion type in every solvent model. However, behavior of deeply bound ions, including ions bound to specific sites, depends strongly on the solvent model. In particular, the number of potassium ions in the minor groove of AT-tracts differs at least 3-fold between the solvent models tested. The number of sodium ions associated with the DNA agrees quantitatively with the experiment for the OPC water model, followed closely by TIP3P+J/C; the largest deviation from the experiment, ∼10%, is seen for SPC/E+J/C. On the other hand, SPC/E+J/C model is most consistent (67%) with the experimental potassium binding sites, followed by OPC+J/C (60%), TIP3P+J/C (53%), and OPC+L/M HFE (27%). The use of NBFIX correction with TIP3P+J/C improves its consistency with the experiment. In summary, the choice of the solvent model matters little for simulating the diffuse atmosphere of sodium and potassium ions around DNA, but ion distributions become increasingly sensitive to the solvent model near the helical axis. We offer an explanation for these trends. There is no single gold standard solvent model, although OPC water with J/C ions or TIP3P with J/C + NBFIX may offer an imperfect compromise for practical simulations of ionic atmospheres around DNA.
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Affiliation(s)
- Egor S Kolesnikov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
| | - Ivan Yu Gushchin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
| | - Petr A Zhilyaev
- Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, Moscow 121205, Russia
| | - Alexey V Onufriev
- Department of Computer Science, Virginia Tech, Blacksburg 24061-0131, United States.,Department of Physics, Virginia Tech, Blacksburg 24061-0131, United States.,Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg 24061-0131, United States
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8
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Ma CY, Pezzotti S, Schwaab G, Gebala M, Herschlag D, Havenith M. Cation enrichment in the ion atmosphere is promoted by local hydration of DNA. Phys Chem Chem Phys 2021; 23:23203-23213. [PMID: 34622888 PMCID: PMC8797164 DOI: 10.1039/d1cp01963e] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electrostatic interactions are central to the structure and function of nucleic acids, including their folding, condensation, and interaction with proteins and other charged molecules. These interactions are profoundly affected by ions surrounding nucleic acids, the constituents of the so-called ion atmosphere. Here, we report precise Fourier Transform-Terahertz/Far-Infrared (FT-THz/FIR) measurements in the frequency range 30-500 cm-1 for a 24-bp DNA solvated in a series of alkali halide (NaCl, NaF, KCl, CsCl, and CsF) electrolyte solutions which are sensitive to changes in the ion atmosphere. Cation excess in the ion atmosphere is detected experimentally by observation of cation modes of Na+, K+, and Cs+ in the frequency range between 70-90 cm-1. Based on MD simulations, we propose that the magnitude of cation excess (which is salt specific) depends on the ability of the electrolyte to perturb the water network at the DNA interface: In the NaF atmosphere, the ions reduce the strength of interactions between water and the DNA more than in case of a NaCl electrolyte. Here, we explicitly take into account the solvent contribution to the chemical potential in the ion atmosphere: A decrease in the number of bound water molecules in the hydration layer of DNA is correlated with enhanced density fluctuations, which decrease the free energy cost of ion-hydration, thus promoting further ion accumulation within the DNA atmosphere. We propose that taking into account the local solvation is crucial for understanding the ion atmosphere.
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Affiliation(s)
- Chun Yu Ma
- Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Bochum, Germany.
| | - Simone Pezzotti
- Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Bochum, Germany.
| | - Gerhard Schwaab
- Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Bochum, Germany.
| | - Magdalena Gebala
- Department of Biochemistry, Stanford University, Stanford, California 94305, USA
| | - Daniel Herschlag
- Department of Biochemistry, Stanford University, Stanford, California 94305, USA
| | - Martina Havenith
- Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Bochum, Germany.
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9
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Salsbury AM, Lemkul JA. Cation competition and recruitment around the c-kit1 G-quadruplex using polarizable simulations. Biophys J 2021; 120:2249-2261. [PMID: 33794153 PMCID: PMC8390831 DOI: 10.1016/j.bpj.2021.03.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 02/22/2021] [Accepted: 03/25/2021] [Indexed: 11/24/2022] Open
Abstract
Nucleic acid-ion interactions are fundamentally important to the physical, energetic, and conformational properties of DNA and RNA. These interactions help fold and stabilize highly ordered secondary and tertiary structures, such as G-quadruplexes (GQs), which are functionally relevant in telomeres, replication initiation sites, and promoter sequences. The c-kit proto-oncogene encodes for a receptor tyrosine kinase and is linked to gastrointestinal stromal tumors, mast cell disease, and leukemia. This gene contains three unique GQ-forming sequences that have proposed antagonistic effects on gene expression. The dominant GQ, denoted c-kit1, has been shown to decrease expression of c-kit transcripts, making the c-kit1 GQ a promising drug target. Toward disease intervention, more information is needed regarding its conformational dynamics and ion binding properties. Therefore, we performed molecular dynamics simulations of the c-kit1 GQ with K+, Na+, Li+, and mixed salt solutions using the Drude-2017 polarizable force field. We evaluated GQ structure, ion sampling, core energetics, ion dehydration and binding, and ion competition and found that each analysis supported the known GQ-ion specificity trend (K+ > Na+ > Li+). We also found that K+ ions coordinate in the tetrad core antiprismatically, whereas Na+ and Li+ align coplanar to guanine tetrads, partially because of their attraction to surrounding water. Further, we showed that K+ occupancy is higher around the c-kit1 GQ and its nucleobases than Na+ and Li+, which tend to interact with backbone and sugar moieties. Finally, we showed that K+ binding to the c-kit1 GQ is faster and more frequent than Na+ and Li+. Such descriptions of GQ-ion dynamics suggest the rate of dehydration as the dominant factor for preference of K+ by DNA GQs and provide insight into noncanonical nucleic acids for which little experimental data exist.
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Affiliation(s)
| | - Justin A Lemkul
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia; Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia.
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10
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Paston SV, Polyanichko AM, Shulenina OV, Osinnikova DN. A Study of the DNA Structure in Films Using FTIR Spectroscopy. Biophysics (Nagoya-shi) 2020. [DOI: 10.1134/s0006350920060159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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11
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Patra P, Banerjee R, Chakrabarti J. Control of solvent exposure of cationic polypeptides in anionic environment. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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12
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Liu L, Nakouzi E, Sushko ML, Schenter GK, Mundy CJ, Chun J, De Yoreo JJ. Connecting energetics to dynamics in particle growth by oriented attachment using real-time observations. Nat Commun 2020; 11:1045. [PMID: 32098968 PMCID: PMC7042275 DOI: 10.1038/s41467-020-14719-w] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 01/08/2020] [Indexed: 11/10/2022] Open
Abstract
The interplay between crystal and solvent structure, interparticle forces and ensemble particle response dynamics governs the process of crystallization by oriented attachment (OA), yet a quantitative understanding is lacking. Using ZnO as a model system, we combine in situ TEM observations of single particle and ensemble assembly dynamics with simulations of interparticle forces and responses to relate experimentally derived interparticle potentials to the underlying interactions. We show that OA is driven by forces and torques due to a combination of electrostatic ion-solvent correlations and dipolar interactions that act at separations well beyond 5 nm. Importantly, coalignment is achieved before particles reach separations at which strong attractions drive the final jump to contact. The observed barrier to attachment is negligible, while dissipative factors in the quasi-2D confinement of the TEM fluid cell lead to abnormal diffusivities with timescales for rotation much less than for translation, thus enabling OA to dominate.
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Affiliation(s)
- Lili Liu
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Elias Nakouzi
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Maria L Sushko
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Gregory K Schenter
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Christopher J Mundy
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.,Department of Chemical Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Jaehun Chun
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA. .,Benjamin Levich Institute, CUNY City College of New York, New York, NY, 10031, USA.
| | - James J De Yoreo
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA. .,Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA.
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13
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Roodhuizen JA, Hendrikx PJTM, Hilbers PAJ, de Greef TFA, Markvoort AJ. Counterion-Dependent Mechanisms of DNA Origami Nanostructure Stabilization Revealed by Atomistic Molecular Simulation. ACS NANO 2019; 13:10798-10809. [PMID: 31502824 PMCID: PMC6764110 DOI: 10.1021/acsnano.9b05650] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 09/09/2019] [Indexed: 05/18/2023]
Abstract
The DNA origami technique has proven to have tremendous potential for therapeutic and diagnostic applications like drug delivery, but the relatively low concentrations of cations in physiological fluids cause destabilization and degradation of DNA origami constructs preventing in vivo applications. To reveal the mechanisms behind DNA origami stabilization by cations, we performed atomistic molecular dynamics simulations of a DNA origami rectangle in aqueous solvent with varying concentrations of magnesium and sodium as well as polyamines like oligolysine and spermine. We explored the binding of these ions to DNA origami in detail and found that the mechanism of stabilization differs between ion types considerably. While sodium binds weakly and quickly exchanges with the solvent, magnesium and spermine bind close to the origami with spermine also located in between helices, stabilizing the crossovers characteristic for DNA origami and reducing repulsion of parallel helices. In contrast, oligolysine of length ten prevents helix repulsion by binding to adjacent helices with its flexible side chains, spanning the gap between the helices. Shorter oligolysine molecules with four subunits are weak stabilizers as they lack both the ability to connect helices and to prevent helix repulsion. This work thus shows how the binding modes of ions influence the stabilization of DNA origami nanostructures on a molecular level.
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Affiliation(s)
- Job A.
L. Roodhuizen
- Computational Biology Group, Department of Biomedical Engineering and Institute for Complex
Molecular Systems, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Philip J. T. M. Hendrikx
- Computational Biology Group, Department of Biomedical Engineering and Institute for Complex
Molecular Systems, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Peter A. J. Hilbers
- Computational Biology Group, Department of Biomedical Engineering and Institute for Complex
Molecular Systems, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Tom F. A. de Greef
- Computational Biology Group, Department of Biomedical Engineering and Institute for Complex
Molecular Systems, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
- E-mail:
| | - Albert J. Markvoort
- Computational Biology Group, Department of Biomedical Engineering and Institute for Complex
Molecular Systems, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- E-mail:
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14
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Marucho M. A Java Application to Characterize Biomolecules and Nanomaterials in Electrolyte Aqueous Solutions. COMPUTER PHYSICS COMMUNICATIONS 2019; 242:104-119. [PMID: 31827306 PMCID: PMC6905646 DOI: 10.1016/j.cpc.2019.03.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The electrostatic, entropic and surface interactions between a macroion (nanoparticle or biomolecule), surrounding ions and water molecules play a fundamental role in the behavior and function of colloidal systems. However, the molecular mechanisms governing these phenomena are still poorly understood. One of the major limitations in procuring this understanding is the lack of appropriate computational tools. Additionally, only experts in the field with an extensive background in programming, who are trained in statistical mechanics, and have access to supercomputers are able to study these systems. To overcome these limitations, in this article, we present a free, multiplatform, portable Java software, which provides experts and non-experts in the field an easy and efficient way to obtain an accurate molecular characterization of electrical and structural properties of aqueous electrolyte mixture solutions around both cylindrical- and spherical-like rigid macroions under multiple conditions. These properties include the normalized ions and water density profile distributions, the mean electrostatic potential, the integrated charge, the zeta potential, the electrostatic potential energy, the particle crowding entropy energy, the ion-ion electrostatic direct correlation energy, and the ionic potential of mean force. The Java software does not require outstanding skills and comes with detailed user-guide documentation. The application is based on the so-called Classical Density Functional Theory Solver (CSDFTS), which was successfully applied to a variety of rod-like biopolymers, rigid-like globular proteins, nanoparticles, and nano-rods. CSDFTS implements several electrolyte and macroion models, uses different levels of approximation and takes advantage of high performance Fortran90 routines and optimized libraries. These features enable the software to run on single processor computers at low-to-moderate computational cost depending on the computer performance, the grid resolution, and the characterization of the macroion and the electrolyte solution, among other factors. As a unique feature, the software comes with a graphical user interface (GUI) that allows users to take advantage of the visually guided setup of the required input data to properly characterize the system and configure the solver. Several examples on nanomaterials and biomolecules are provided to illustrate the use of the GUI and the solver performance.
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Affiliation(s)
- Marcelo Marucho
- , website: https://www.utsa.edu/physics/faculty/MarceloMarucho.html
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15
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Xi K, Wang FH, Xiong G, Zhang ZL, Tan ZJ. Competitive Binding of Mg 2+ and Na + Ions to Nucleic Acids: From Helices to Tertiary Structures. Biophys J 2019; 114:1776-1790. [PMID: 29694858 DOI: 10.1016/j.bpj.2018.03.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 02/21/2018] [Accepted: 03/06/2018] [Indexed: 12/16/2022] Open
Abstract
Nucleic acids generally reside in cellular aqueous solutions with mixed divalent/monovalent ions, and the competitive binding of divalent and monovalent ions is critical to the structures of nucleic acids because of their polyanionic nature. In this work, we first proposed a general and effective method for simulating a nucleic acid in mixed divalent/monovalent ion solutions with desired bulk ion concentrations via molecular dynamics (MD) simulations and investigated the competitive binding of Mg2+/Na+ ions to various nucleic acids by all-atom MD simulations. The extensive MD-based examinations show that single MD simulations conducted using the proposed method can yield desired bulk divalent/monovalent ion concentrations for various nucleic acids, including RNA tertiary structures. Our comprehensive analyses show that the global binding of Mg2+/Na+ to a nucleic acid is mainly dependent on its structure compactness, as well as Mg2+/Na+ concentrations, rather than the specific structure of the nucleic acid. Specifically, the relative global binding of Mg2+ over Na+ is stronger for a nucleic acid with higher effective surface charge density and higher relative Mg2+/Na+ concentrations. Furthermore, the local binding of Mg2+/Na+ to a phosphate of a nucleic acid mainly depends on the local phosphate density in addition to Mg2+/Na+ concentrations.
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Affiliation(s)
- Kun Xi
- Center for Theoretical Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, China
| | - Feng-Hua Wang
- Engineering Training Center, Jianghan University, Wuhan, China
| | - Gui Xiong
- Center for Theoretical Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, China
| | - Zhong-Liang Zhang
- Center for Theoretical Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, China
| | - Zhi-Jie Tan
- Center for Theoretical Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, China.
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16
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Expansion and shrinkage of the electrical double layer in charge-asymmetric electrolytes: A non-linear Poisson-Boltzmann description. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2018.11.163] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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17
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Tolokh IS, Thomas DG, Onufriev AV. Explicit ions/implicit water generalized Born model for nucleic acids. J Chem Phys 2018; 148:195101. [PMID: 30307229 DOI: 10.1063/1.5027260] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ion atmosphere around highly charged nucleic acid molecules plays a significant role in their dynamics, structure, and interactions. Here we utilized the implicit solvent framework to develop a model for the explicit treatment of ions interacting with nucleic acid molecules. The proposed explicit ions/implicit water model is based on a significantly modified generalized Born (GB) model and utilizes a non-standard approach to define the solute/solvent dielectric boundary. Specifically, the model includes modifications to the GB interaction terms for the case of multiple interacting solutes-disconnected dielectric boundary around the solute-ion or ion-ion pairs. A fully analytical description of all energy components for charge-charge interactions is provided. The effectiveness of the approach is demonstrated by calculating the potential of mean force for Na+-Cl- ion pair and by carrying out a set of Monte Carlo (MC) simulations of mono- and trivalent ions interacting with DNA and RNA duplexes. The monovalent (Na+) and trivalent (CoHex3+) counterion distributions predicted by the model are in close quantitative agreement with all-atom explicit water molecular dynamics simulations used as reference. Expressed in the units of energy, the maximum deviations of local ion concentrations from the reference are within k B T. The proposed explicit ions/implicit water GB model is able to resolve subtle features and differences of CoHex distributions around DNA and RNA duplexes. These features include preferential CoHex binding inside the major groove of the RNA duplex, in contrast to CoHex biding at the "external" surface of the sugar-phosphate backbone of the DNA duplex; these differences in the counterion binding patters were earlier shown to be responsible for the observed drastic differences in condensation propensities between short DNA and RNA duplexes. MC simulations of CoHex ions interacting with the homopolymeric poly(dA·dT) DNA duplex with modified (de-methylated) and native thymine bases are used to explore the physics behind CoHex-thymine interactions. The simulations suggest that the ion desolvation penalty due to proximity to the low dielectric volume of the methyl group can contribute significantly to CoHex-thymine interactions. Compared to the steric repulsion between the ion and the methyl group, the desolvation penalty interaction has a longer range and may be important to consider in the context of methylation effects on DNA condensation.
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Affiliation(s)
- Igor S Tolokh
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Dennis G Thomas
- Computational Biology, Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Alexey V Onufriev
- Departments of Computer Science and Physics, Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
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18
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Erbaş A, de la Cruz MO, Marko JF. Effects of electrostatic interactions on ligand dissociation kinetics. Phys Rev E 2018; 97:022405. [PMID: 29548245 PMCID: PMC5863579 DOI: 10.1103/physreve.97.022405] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Indexed: 11/07/2022]
Abstract
We study unbinding of multivalent cationic ligands from oppositely charged polymeric binding sites sparsely grafted on a flat neutral substrate. Our molecular dynamics simulations are suggested by single-molecule studies of protein-DNA interactions. We consider univalent salt concentrations spanning roughly a 1000-fold range, together with various concentrations of excess ligands in solution. To reveal the ionic effects on unbinding kinetics of spontaneous and facilitated dissociation mechanisms, we treat electrostatic interactions both at a Debye-Hückel (DH) (or implicit ions, i.e., use of an electrostatic potential with a prescribed decay length) level and by the more precise approach of considering all ionic species explicitly in the simulations. We find that the DH approach systematically overestimates unbinding rates, relative to the calculations where all ion pairs are present explicitly in solution, although many aspects of the two types of calculation are qualitatively similar. For facilitated dissociation (FD) (acceleration of unbinding by free ligands in solution) explicit-ion simulations lead to unbinding at lower free-ligand concentrations. Our simulations predict a variety of FD regimes as a function of free-ligand and ion concentrations; a particularly interesting regime is at intermediate concentrations of ligands where nonelectrostatic binding strength controls FD. We conclude that explicit-ion electrostatic modeling is an essential component to quantitatively tackle problems in molecular ligand dissociation, including nucleic-acid-binding proteins.
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Affiliation(s)
- Aykut Erbaş
- Department of Materials Science and Engineering, Department of Molecular Biosciences, and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - Monica Olvera de la Cruz
- Department of Materials Science and Engineering, Department of Chemistry, Department of Chemical and Biological Engineering, and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - John F Marko
- Department of Molecular Biosciences and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
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19
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Elbahnsi A, Retureau R, Baaden M, Hartmann B, Oguey C. Holding the Nucleosome Together: A Quantitative Description of the DNA–Histone Interface in Solution. J Chem Theory Comput 2018; 14:1045-1058. [DOI: 10.1021/acs.jctc.7b00936] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Ahmad Elbahnsi
- LBPA,
UMR 8113, ENS Paris-Saclay - CNRS, 61 avenue du Président Wilson, 94235 cedex Cachan, France
- LPTM,
UMR 8089, CNRS, Université de Cergy-Pontoise, 2 avenue Adolphe Chauvin, 95302 Cergy-Pontoise, France
| | - Romain Retureau
- LBPA,
UMR 8113, ENS Paris-Saclay - CNRS, 61 avenue du Président Wilson, 94235 cedex Cachan, France
| | - Marc Baaden
- Laboratoire
de Biochimie Théorique, CNRS, UPR9080, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Brigitte Hartmann
- LBPA,
UMR 8113, ENS Paris-Saclay - CNRS, 61 avenue du Président Wilson, 94235 cedex Cachan, France
| | - Christophe Oguey
- LPTM,
UMR 8089, CNRS, Université de Cergy-Pontoise, 2 avenue Adolphe Chauvin, 95302 Cergy-Pontoise, France
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20
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Kolev SK, Petkov PS, Rangelov MA, Trifonov DV, Milenov TI, Vayssilov GN. Interaction of Na+, K+, Mg2+ and Ca2+ counter cations with RNA. Metallomics 2018; 10:659-678. [DOI: 10.1039/c8mt00043c] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Data on the location of alkaline and alkaline earth ions at RNA from crystallography, spectroscopy and computational modeling are reviewed.
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Affiliation(s)
- Stefan K. Kolev
- Acad. E. Djakov Institute of Electronics
- Bulgarian Academy of Sciences
- 1784 Sofia
- Bulgaria
| | - Petko St. Petkov
- Faculty of Chemistry and Pharmacy
- University of Sofia
- 1126 Sofia
- Bulgaria
| | - Miroslav A. Rangelov
- Laboratory of BioCatalysis
- Institute of Organic Chemistry
- Bulgarian Academy of Sciences
- 1113 Sofia
- Bulgaria
| | | | - Teodor I. Milenov
- Acad. E. Djakov Institute of Electronics
- Bulgarian Academy of Sciences
- 1784 Sofia
- Bulgaria
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21
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Guerrero-García GI, González-Tovar E, Chávez-Páez M, Kłos J, Lamperski S. Quantifying the thickness of the electrical double layer neutralizing a planar electrode: the capacitive compactness. Phys Chem Chem Phys 2017; 20:262-275. [PMID: 29204593 DOI: 10.1039/c7cp05433e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The spatial extension of the ionic cloud neutralizing a charged colloid or an electrode is usually characterized by the Debye length associated with the supporting charged fluid in the bulk. This spatial length arises naturally in the linear Poisson-Boltzmann theory of point charges, which is the cornerstone of the widely used Derjaguin-Landau-Verwey-Overbeek formalism describing the colloidal stability of electrified macroparticles. By definition, the Debye length is independent of important physical features of charged solutions such as the colloidal charge, electrostatic ion correlations, ionic excluded volume effects, or specific short-range interactions, just to mention a few. In order to include consistently these features to describe more accurately the thickness of the electrical double layer of an inhomogeneous charged fluid in planar geometry, we propose here the use of the capacitive compactness concept as a generalization of the compactness of the spherical electrical double layer around a small macroion (González-Tovar et al., J. Chem. Phys. 2004, 120, 9782). To exemplify the usefulness of the capacitive compactness to characterize strongly coupled charged fluids in external electric fields, we use integral equations theory and Monte Carlo simulations to analyze the electrical properties of a model molten salt near a planar electrode. In particular, we study the electrode's charge neutralization, and the maximum inversion of the net charge per unit area of the electrode-molten salt system as a function of the ionic concentration, and the electrode's charge. The behaviour of the associated capacitive compactness is interpreted in terms of the charge neutralization capacity of the highly correlated charged fluid, which evidences a shrinking/expansion of the electrical double layer at a microscopic level. The capacitive compactness and its first two derivatives are expressed in terms of experimentally measurable macroscopic properties such as the differential and integral capacity, the electrode's surface charge density, and the mean electrostatic potential at the electrode's surface.
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Affiliation(s)
| | - Enrique González-Tovar
- Instituto de Física de la Universidad Autónoma de San Luis Potosí
- 78000 San Luis Potosí
- Mexico
| | - Martín Chávez-Páez
- Instituto de Física de la Universidad Autónoma de San Luis Potosí
- 78000 San Luis Potosí
- Mexico
| | - Jacek Kłos
- Faculty of Chemistry
- Adam Mickiewicz University in Poznań
- 61-614 Poznań
- Poland
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22
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Abdalla S, Obaid A, Al-Marzouki FM. Effects of Environmental Factors and Metallic Electrodes on AC Electrical Conduction Through DNA Molecule. NANOSCALE RESEARCH LETTERS 2017; 12:316. [PMID: 28454482 PMCID: PMC5407417 DOI: 10.1186/s11671-017-2076-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 04/13/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Deoxyribonucleic acid (DNA) is one of the best candidate materials for various device applications such as in electrodes for rechargeable batteries, biosensors, molecular electronics, medical- and biomedical-applications etc. Hence, it is worthwhile to examine the mechanism of charge transport in the DNA molecule, however, still a question without a clear answer is DNA a molecular conducting material (wire), semiconductor, or insulator? The answer, after the published data, is still ambiguous without any confirmed and clear scientific answer. DNA is found to be always surrounded with different electric charges, ions, and dipoles. These surrounding charges and electric barrier(s) due to metallic electrodes (as environmental factors (EFs)) play a substantial role when measuring the electrical conductivity through λ-double helix (DNA) molecule suspended between metallic electrodes. We found that strong frequency dependence of AC-complex conductivity comes from the electrical conduction of EFs. This leads to superimposing serious incorrect experimental data to measured ones. METHODS At 1 MHz, we carried out a first control experiment on electrical conductivity with and without the presence of DNA molecule. If there are possible electrical conduction due to stray ions and contribution of substrate, we will detected them. This control experiment revealed that there is an important role played by the environmental-charges around DNA molecule and any experiment should consider this role. RESULTS AND DISCUSSION We have succeeded to measure both electrical conductivity due to EFs (σ ENV) and electrical conductivity due to DNA molecule (σ DNA) independently by carrying the measurements at different DNA-lengths and subtracting the data. We carried out measurements as a function of frequency (f) and temperature (T) in the ranges 0.1 Hz < f < 1 MHz and 288 K < T < 343 K. The measured conductivity (σ MES) portrays a metal-like behavior at high frequencies near 1 MHz. However, we found that σ DNA was far from this behavior because the conduction due to EFs superimposes σ DNA, in particular at low frequencies. By measuring the electrical conductivity at different lengths: 40, 60, 80, and 100 nm, we have succeeded not only to separate the electrical conduction of the DNA molecule from all EFs effects that surround the molecule, but also to present accurate values of σ DNA and the dielectric constant of the molecule ε'DNA as a function of temperature and frequency. Furthermore, in order to explain these data, we present a model describing the electrical conduction through DNA molecule: DNA is a classical semiconductor with charges, dipoles and ions that result in creation of localized energy-states (LESs) in the extended bands and in the energy gap of the DNA molecule. CONCLUSIONS This model explains clearly the mechanism of charge transfer mechanism in the DNA, and it sheds light on why the charge transfer through the DNA can lead to insulating, semiconducting, or metallic behavior on the same time. The model considers charges on DNA, in the extended bands, either could be free to move under electric field or localized in potential wells/hills. Localization of charges in DNA is an intrinsic structural-property of this solitaire molecule. At all temperatures, the expected increase in thermal-induced charge is attributed to the delocalization of holes (or/and electrons) in potential hills (or/and potential wells) which accurately accounts for the total electric and dielectric behavior through DNA molecule. We succeeded to fit the experimental data to the proposed model with reasonable magnitudes of potential hills/wells that are in the energy range from 0.068 eV.
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Affiliation(s)
- S. Abdalla
- Department of Physics, Faculty of Science, King Abdulaziz University Jeddah, P.O. Box 80203, Jeddah, 21589 Saudi Arabia
| | - A. Obaid
- Department of Chemistry, Faculty of Science, King Abdulaziz University Jeddah, P.O. Box 80203, Jeddah, 21589 Saudi Arabia
| | - F. M. Al-Marzouki
- Department of Physics, Faculty of Science, King Abdulaziz University Jeddah, P.O. Box 80203, Jeddah, 21589 Saudi Arabia
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23
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Onufriev AV, Izadi S. Water models for biomolecular simulations. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2017. [DOI: 10.1002/wcms.1347] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Alexey V. Onufriev
- Department of Physics; Virginia Tech; Blacksburg VA USA
- Department of Computer Science; Virginia Tech; Blacksburg VA USA
- Center for Soft Matter and Biological Physics; Virginia Tech; Blacksburg VA USA
| | - Saeed Izadi
- Early Stage Pharmaceutical Development; Genentech Inc.; South San Francisco, CA USA
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24
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Jacobson DR, Saleh OA. Counting the ions surrounding nucleic acids. Nucleic Acids Res 2017; 45:1596-1605. [PMID: 28034959 PMCID: PMC5389524 DOI: 10.1093/nar/gkw1305] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 12/21/2016] [Indexed: 01/29/2023] Open
Abstract
Nucleic acids are strongly negatively charged, and thus electrostatic interactions—screened by ions in solution—play an important role in governing their ability to fold and participate in biomolecular interactions. The negative charge creates a region, known as the ion atmosphere, in which cation and anion concentrations are perturbed from their bulk values. Ion counting experiments quantify the ion atmosphere by measuring the preferential ion interaction coefficient: the net total number of excess ions above, or below, the number expected due to the bulk concentration. The results of such studies provide important constraints on theories, which typically predict the full three-dimensional distribution of the screening cloud. This article reviews the state of nucleic acid ion counting measurements and critically analyzes their ability to test both analytical and simulation-based models.
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Affiliation(s)
- David R Jacobson
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - Omar A Saleh
- Materials Department and BMSE Program, University of California, Santa Barbara, CA 93106, USA
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25
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Abstract
In addition to continuous rapid progress in RNA structure determination, probing, and biophysical studies, the past decade has seen remarkable advances in the development of a new generation of RNA folding theories and models. In this article, we review RNA structure prediction models and models for ion-RNA and ligand-RNA interactions. These new models are becoming increasingly important for a mechanistic understanding of RNA function and quantitative design of RNA nanotechnology. We focus on new methods for physics-based, knowledge-based, and experimental data-directed modeling for RNA structures and explore the new theories for the predictions of metal ion and ligand binding sites and metal ion-dependent RNA stabilities. The integration of these new methods with theories about the cellular environment effects in RNA folding, such as molecular crowding and cotranscriptional kinetic effects, may ultimately lead to an all-encompassing RNA folding model.
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Affiliation(s)
- Li-Zhen Sun
- Department of Physics, Department of Biochemistry, and MU Informatics Institute, University of Missouri, Columbia, Missouri 65211;
| | - Dong Zhang
- Department of Physics, Department of Biochemistry, and MU Informatics Institute, University of Missouri, Columbia, Missouri 65211;
| | - Shi-Jie Chen
- Department of Physics, Department of Biochemistry, and MU Informatics Institute, University of Missouri, Columbia, Missouri 65211;
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26
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Sushko ML, Rosso KM. The origin of facet selectivity and alignment in anatase TiO 2 nanoparticles in electrolyte solutions: implications for oriented attachment in metal oxides. NANOSCALE 2016; 8:19714-19725. [PMID: 27874139 DOI: 10.1039/c6nr06953c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Oriented attachment (OA) is an important nonclassical pathway for crystal growth from solution, occurring by the self-assembly of nanoparticles and often leading to highly organized three-dimensional crystal morphologies. The forces that drive nanocrystal reorientation for face-selective attachment and exclude improperly aligned particles have remained unknown. Here we report evidence at the microscopic level that ion correlation forces arising from dynamically interacting electrical double layers are responsible for face-selective attraction and particle rotation into lattice co-alignment as particles interact at long range. Atomic-to-mesoscale simulations developed and performed for the archetype OA system of anatase TiO2 nanoparticles in aqueous HCl solutions show that face-selective attraction from ion correlation forces outcompetes electrostatic repulsion at several nanometers apart, drawing particle face pairs into a metastable solvent-separated captured state. The analysis of the facet and pH dependence of interparticle interactions is in quantitative agreement with the observed decreasing frequency of attachment between the (112), (001), and (101) face pairs, revealing an adhesion barrier that is largely due to steric hydration forces from structured intervening solvents. This finding helps open new avenues for controlling crystal growth pathways leading to highly ordered three-dimensional nanomaterials.
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Affiliation(s)
- M L Sushko
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA.
| | - K M Rosso
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA.
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27
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Poitevin F, Delarue M, Orland H. Beyond Poisson-Boltzmann: Numerical Sampling of Charge Density Fluctuations. J Phys Chem B 2016; 120:6270-7. [PMID: 27075231 DOI: 10.1021/acs.jpcb.6b02650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a method aimed at sampling charge density fluctuations in Coulomb systems. The derivation follows from a functional integral representation of the partition function in terms of charge density fluctuations. Starting from the mean-field solution given by the Poisson-Boltzmann equation, an original approach is proposed to numerically sample fluctuations around it, through the propagation of a Langevin-like stochastic partial differential equation (SPDE). The diffusion tensor of the SPDE can be chosen so as to avoid the numerical complexity linked to long-range Coulomb interactions, effectively rendering the theory completely local. A finite-volume implementation of the SPDE is described, and the approach is illustrated with preliminary results on the study of a system made of two like-charge ions immersed in a bath of counterions.
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Affiliation(s)
- Frédéric Poitevin
- Institut de Physique Théorique, Université Paris Saclay, CEA, UMR3681 du CNRS, F-91191 Gif-sur-Yvette, France
| | - Marc Delarue
- Unit of Structural Dynamics of Macromolecules, UMR 3528 du CNRS, Institut Pasteur, 75015 Paris, France
| | - Henri Orland
- Institut de Physique Théorique, Université Paris Saclay, CEA, UMR3681 du CNRS, F-91191 Gif-sur-Yvette, France.,Beijing Computational Science Research Center, Haidian District, Beijing 100094, China
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