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Rao YF, Sun LZ, Luo MB. Na +-Mg 2+ ion effects on conformation and translocation dynamics of single-stranded RNA: Cooperation and competition. Int J Biol Macromol 2024; 267:131273. [PMID: 38569994 DOI: 10.1016/j.ijbiomac.2024.131273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Revised: 03/20/2024] [Accepted: 03/28/2024] [Indexed: 04/05/2024]
Abstract
The nanopore-based translocation of a single-stranded RNA (ssRNA) in mixed salt solution has garnered increasing interest for its biological and technological significance. However, it is challenging to comprehensively understand the effects of the mixed ion species on the translocation dynamics due to their cooperation and competition, which can be directly reflected by the ion screening and neutralizing effects, respectively. In this study, Langevin dynamics simulation is employed to investigate the properties of ssRNA conformation and translocation in mixed Na+-Mg2+ ion environments. Simulation results reveal that the ion screening effect dominates the change in the ssRNA conformational size, the ion neutralizing effect controls the capture rate of the ssRNA by the nanopore, and both of them take charge of the different changes in translocation time of the ssRNA under various mixed ion environments. Under high Na+ ion concentration, as Mg2+ concentration increases, the ion neutralizing effect strengthens, weakening the driving force inside the nanopore, leading to longer translocation time. Conversely, at low Na+ concentration, an increase in Mg2+ concentration enhances the ion screening effect, aiding in faster translocation. Furthermore, these simulation results will be explained by quantitative analysis, advancing a deeper understanding of the complicated effects of the mixed Na+-Mg2+ ions.
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Affiliation(s)
- Yi-Fan Rao
- School of Physics, Zhejiang University, Hangzhou 310027, China; Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China
| | - Li-Zhen Sun
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Meng-Bo Luo
- School of Physics, Zhejiang University, Hangzhou 310027, China.
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Kravikass M, Koren G, Saleh OA, Beck R. From isolated polyelectrolytes to star-like assemblies: the role of sequence heterogeneity on the statistical structure of the intrinsically disordered neurofilament-low tail domain. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2024; 47:13. [PMID: 38358563 PMCID: PMC10869404 DOI: 10.1140/epje/s10189-024-00409-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Accepted: 02/02/2024] [Indexed: 02/16/2024]
Abstract
Intrinsically disordered proteins (IDPs) are a subset of proteins that lack stable secondary structure. Given their polymeric nature, previous mean-field approximations have been used to describe the statistical structure of IDPs. However, the amino-acid sequence heterogeneity and complex intermolecular interaction network have significantly impeded the ability to get proper approximations. One such case is the intrinsically disordered tail domain of neurofilament low (NFLt), which comprises a 50 residue-long uncharged domain followed by a 96 residue-long negatively charged domain. Here, we measure two NFLt variants to identify the impact of the NFLt two main subdomains on its complex interactions and statistical structure. Using synchrotron small-angle x-ray scattering, we find that the uncharged domain of the NFLt induces attractive interactions that cause it to self-assemble into star-like polymer brushes. On the other hand, when the uncharged domain is truncated, the remaining charged N-terminal domains remain isolated in solution with typical polyelectrolyte characteristics. We further discuss how competing long- and short-ranged interactions within the polymer brushes dominate their ensemble structure and, in turn, their implications on previously observed phenomena in NFL native and diseased states.
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Affiliation(s)
- Mathar Kravikass
- School of Physics and Astronomy, The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv, Israel
- The Center of Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel
| | - Gil Koren
- School of Physics and Astronomy, The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv, Israel
- The Center of Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel
| | - Omar A Saleh
- Materials Department, Biomolecular Sciences and Engineering Program, University of California, Santa Barbara, USA
- Physics Department, University of California, Santa Barbara, USA
| | - Roy Beck
- School of Physics and Astronomy, The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv, Israel.
- The Center of Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel.
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Dabhade A, Chauhan A, Chaudhury S. Coupling Effects of Electrostatic Interactions and Salt Concentration Gradient in Polymer Translocation through a Nanopore: A Coarse-Grained Molecular Dynamics Simulations Study. Chemphyschem 2023; 24:e202200666. [PMID: 36314101 DOI: 10.1002/cphc.202200666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/29/2022] [Indexed: 11/09/2022]
Abstract
We study the influence of polymer pore interactions and focus on the role played by the concentration gradient of salt in the translocation of polyelectrolytes (PE) through nanopores explicitly using coarse-grained Langevin dynamics simulations. The mean translocation time is calculated by varying the applied voltage, the pH, and the salt concentration gradient. Changing the pH can alter the electrostatic interaction between the protein pore and the polyelectrolyte chain. The polymer pore interaction is weakened by the increase in the strength of the externally applied electric field that drives translocation. Additionally, the screening effect of the salt can reduce the strong charge-charge repulsion between the PE beads which can make translocation faster. The simulation results show there can be antagonistic or synergistic coupling between the salt concentration-induced screening effect and the drift force originating from the salt concentration gradient thereby affecting the translocation time. Our simulation results are explained qualitatively with free energy calculations.
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Affiliation(s)
- Akash Dabhade
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, 411008, Maharashtra, India
| | - Akshay Chauhan
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, 411008, Maharashtra, India
| | - Srabanti Chaudhury
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, 411008, Maharashtra, India
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Sun LZ, Qian JL, Cai P, Xu X. Mutual effects between single-stranded DNA conformation and Na +-Mg 2+ ion competition in mixed salt solutions. Phys Chem Chem Phys 2022; 24:20867-20881. [PMID: 36043348 DOI: 10.1039/d2cp02737b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ion-dependence of single-stranded DNA (ssDNA) conformational changes has attracted growing attention because of its biological and technological importance. Although single-species ion effects have been extensively explored, it is challenging to study the ssDNA conformational properties under mixed monovalent/divalent ion conditions due to the complications of ssDNA flexibility and ion-ion competition. In this study, we apply Langevin dynamics simulations to investigate mixed Na+/Mg2+ ion-dependent ssDNA conformations. The ssDNA structure is described using a coarse-grained model, in which the phosphate, base, and sugar of each nucleotide are represented by three different beads. A novel improvement in our simulation model is that mixed-salt-related electrostatic interactions are computed via combining Manning counterion condensation (MCC) theory with the Monte Carlo tightly bound ion (MCTBI) model. Based on this MCC-MCTBI combination, we report new empirical functions to describe the ion-concentration-dependent and ssDNA conformation/structure-dependent electrostatic effects. The calculation results relating to the ion binding properties and the simulation results relating to the ssDNA conformational properties are validated against experimental results. In addition, our simulation results suggest a quantitative relationship between the ssDNA conformation and Na+-Mg2+ competition; this in turn reveals their mutual impact in the ion atmosphere.
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Affiliation(s)
- Li-Zhen Sun
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Jun-Lin Qian
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Pinggen Cai
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Xiaojun Xu
- Institute of Bioinformatics and Medical Engineering, Jiangsu University of Technology, Changzhou, 213001, China
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Wang X, Stevens KC, Ting JM, Marras AE, Rezvan G, Wei X, Taheri-Qazvini N, Tirrell MV, Liu C. Translocation Behaviors of Synthetic Polyelectrolytes through Alpha-Hemolysin (α-HL) and Mycobacterium smegmatis Porin A (MspA) Nanopores. JOURNAL OF THE ELECTROCHEMICAL SOCIETY 2022; 169:057510. [PMID: 35599744 PMCID: PMC9121822 DOI: 10.1149/1945-7111/ac6c55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
DNAs have been used as probes for nanopore sensing of noncharged biomacromolecules due to its negative phosphate backbone. Inspired by this, we explored the potential of diblock synthetic polyelectrolytes as more flexible and inexpensive nanopore sensing probes by investigating translocation behaviors of PEO-b-PSS and PEO-b-PVBTMA through commonly used alpha-hemolysin (α-HL) and Mycobacterium smegmatis porin A (MspA) nanopores. Translocation recordings in different configurations of pore orientation and testing voltage indicated efficient PEO-b-PSS translocations through α-HL and PEO-b-PVBTMA translocations through MspA. This work provides insight into synthetic polyelectrolyte-based probes to expand probe selection and flexibility for nanopore sensing.
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Affiliation(s)
- Xiaoqin Wang
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Kaden C. Stevens
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Jeffrey M. Ting
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Alexander E. Marras
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Gelareh Rezvan
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Xiaojun Wei
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
- Biomedical Engineering Program, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Nader Taheri-Qazvini
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
- Biomedical Engineering Program, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Matthew V. Tirrell
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Chang Liu
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
- Biomedical Engineering Program, University of South Carolina, Columbia, South Carolina 29208, USA
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Sun LZ, Qian JL, Cai P, Hu HX, Xu X, Luo MB. Mg2+ effects on the single-stranded DNA conformations and nanopore translocation dynamics. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.124895] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Sun LZ, Cao WP, Wang CH, Xu X. The translocation dynamics of the polymer through a conical pore: Non-stuck, weak-stuck, and strong-stuck modes. J Chem Phys 2021; 154:054903. [PMID: 33557527 DOI: 10.1063/5.0033689] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The external voltage-driven polymer translocation through a conical pore (with a large opening at the entry and a small tip at the exit) is studied by using the Langevin dynamics simulation in this paper. The entire translocation process is divided into an approaching stage and a threading stage. First, the approaching stage starts from the polymer entering the large opening and ends up at a terminal monomer reaching the pore tip. In this stage, the polymer will undergo the conformation adjustment to fit the narrowed cross-sectional area of the pore, leading to three approaching modes: the non-stuck mode with a terminal monomer arriving at the pore tip smoothly, the weak-stuck mode for the polymer stuck inside the pore for a short duration with minor conformational adjustments, and the strong-stuck mode with major conformational changes and a long duration. The approaching times (the duration of the approaching stage) of the three approaching modes show different behavior as a function of the pore apex angle. Second, the threading stage describes that the polymer threads through the pore tip with a linear fashion. In this stage, an increase in the apex angle causes the reduction of the threading time (the duration of the threading stage) due to the increase in the driving force with the apex angle at the tip. Moreover, we also find that with the increase in the apex angle or the polymer length, the polymer threading dynamics will change from the quasi-equilibrium state to the non-equilibrium state.
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Affiliation(s)
- Li-Zhen Sun
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China
| | - Wei-Ping Cao
- Institute of Optoelectronic Technology, Lishui University, Lishui 323000, China
| | - Chang-Hui Wang
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China
| | - Xiaojun Xu
- Institute of Bioinformatics and Medical Engineering, Jiangsu University of Technology, Changzhou 213001, China
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