101
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Adžić N, Podgornik R. Charge regulation in ionic solutions: thermal fluctuations and Kirkwood-Schumaker interactions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:022715. [PMID: 25768539 DOI: 10.1103/physreve.91.022715] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2014] [Indexed: 06/04/2023]
Abstract
We study the behavior of two macroions with dissociable charge groups, regulated by local variables such as pH and electrostatic potential, immersed in a monovalent salt solution, considering cases where the net charge can either change sign or remain of the same sign depending on these local parameters. The charge regulation in both cases is described by the proper free-energy function for each of the macroions, while the coupling between the charges is evaluated on the approximate Debye-Hückel level. The charge correlation functions and the ensuing charge fluctuation forces are calculated analytically and numerically. Strong attraction between like-charged macroions is found close to the point of zero charge, specifically due to asymmetric, anticorrelated charge fluctuations of the macroion charges. The general theory is then implemented for a system of two proteinlike macroions, generalizing the form and magnitude of the Kirkwood-Schumaker interaction.
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Affiliation(s)
- Nataša Adžić
- Department of Theoretical Physics, J. Stefan Institute, 1000 Ljubljana, Slovenia
| | - Rudolf Podgornik
- Department of Theoretical Physics, J. Stefan Institute, 1000 Ljubljana, Slovenia
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia
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102
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Markovich T, Andelman D, Podgornik R. Surface tension of electrolyte interfaces: Ionic specificity within a field-theory approach. J Chem Phys 2015; 142:044702. [DOI: 10.1063/1.4905954] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Tomer Markovich
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - David Andelman
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Rudi Podgornik
- Department of Theoretical Physics, J. Stefan Institute and Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia
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103
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Alcaraz O, Demmel F, Trullas J. Single ion dynamics in molten sodium bromide. J Chem Phys 2014; 141:244508. [DOI: 10.1063/1.4904821] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- O. Alcaraz
- Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain
| | - F. Demmel
- ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - J. Trullas
- Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain
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104
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Naji A, Ghodrat M, Komaie-Moghaddam H, Podgornik R. Asymmetric Coulomb fluids at randomly charged dielectric interfaces: Anti-fragility, overcharging and charge inversion. J Chem Phys 2014; 141:174704. [DOI: 10.1063/1.4898663] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ali Naji
- School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran
| | - Malihe Ghodrat
- School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran
| | - Haniyeh Komaie-Moghaddam
- School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran
| | - Rudolf Podgornik
- Department of Theoretical Physics, J. Stefan Institute, SI-1000 Ljubljana, Slovenia
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
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105
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Yasar S, Podgornik R, Valle-Orero J, Johnson MR, Parsegian VA. Continuity of states between the cholesteric → line hexatic transition and the condensation transition in DNA solutions. Sci Rep 2014; 4:6877. [PMID: 25371012 PMCID: PMC4220286 DOI: 10.1038/srep06877] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 09/12/2014] [Indexed: 11/25/2022] Open
Abstract
A new method of finely temperature-tuning osmotic pressure allows one to identify the cholesteric → line hexatic transition of oriented or unoriented long-fragment DNA bundles in monovalent salt solutions as first order, with a small but finite volume discontinuity. This transition is similar to the osmotic pressure-induced expanded → condensed DNA transition in polyvalent salt solutions at small enough polyvalent salt concentrations. Therefore there exists a continuity of states between the two. This finding, together with the corresponding empirical equation of state, effectively relates the phase diagram of DNA solutions for monovalent salts to that for polyvalent salts and sheds some light on the complicated interactions between DNA molecules at high densities.
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Affiliation(s)
- Selcuk Yasar
- Department of Physics, University of Massachusetts, Amherst, MA 01003, United States
| | - Rudolf Podgornik
- 1] Department of Physics, University of Massachusetts, Amherst, MA 01003, United States [2] Department of Theoretical Physics, J. Stefan Institute, SI-1000 Ljubljana, Slovenia [3] Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Jessica Valle-Orero
- 1] Institut Laue Langevin, BP 156, 6, rue Jules Horowitz 38042 Grenoble Cedex 9, France [2] Laboratoire de Physique, Ecole Normale Superiéure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France
| | - Mark R Johnson
- Institut Laue-Langevin, 6 rue Jules Horowitz, BP156 38042, Grenoble, France
| | - V Adrian Parsegian
- Department of Physics, University of Massachusetts, Amherst, MA 01003, United States
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106
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Tan Q, Zhao G, Qiu Y, Kan Y, Ni Z, Chen Y. Experimental observation of the ion-ion correlation effects on charge inversion and strong adhesion between mica surfaces in aqueous electrolyte solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:10845-10854. [PMID: 25144521 DOI: 10.1021/la5024357] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Direct force measurements between two mica surfaces in aqueous electrolyte solutions over broad ranges of LaCl3 concentrations and pH values were carried out with a surface forces apparatus. Charge inversion on mica surfaces is detected once the LaCl3 concentration reaches a critical value. With the continual increase of LaCl3 concentrations, the mica surface will be overscreened by the counterions. It is demonstrated that the two mica surfaces may experience the jump-in contact even at high LaCl3 concentrations, which is seldom seen in monovalent salt solutions. The strong adhesion cannot be attributed to the van der Waals force alone, but should include the ion-ion correlation forces. Through adjusting the pH values in LaCl3 solutions, the ion-ion correlation force can be evaluated quantitatively. These results provide important insight into the fundamental understanding in the role of ion-ion correlations in ion screening mechanism and interactions between charged objects.
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Affiliation(s)
- Qiyan Tan
- School of Mechanical Engineering and Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University , Nanjing 211189, People's Republic of China
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107
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Kumar R, Sumpter BG, Muthukumar M. Enhanced Phase Segregation Induced by Dipolar Interactions in Polymer Blends. Macromolecules 2014. [DOI: 10.1021/ma501067r] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
| | | | - M. Muthukumar
- Polymer
Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01002, United States
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108
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Lee AA, Vella D, Perkin S, Goriely A. Unravelling nanoconfined films of ionic liquids. J Chem Phys 2014; 141:094904. [DOI: 10.1063/1.4893714] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alpha A. Lee
- Mathematical Institute, Andrew Wiles Building, University of Oxford, Woodstock Road, Oxford OX2 6GG, United Kingdom
| | - Dominic Vella
- Mathematical Institute, Andrew Wiles Building, University of Oxford, Woodstock Road, Oxford OX2 6GG, United Kingdom
| | - Susan Perkin
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom
| | - Alain Goriely
- Mathematical Institute, Andrew Wiles Building, University of Oxford, Woodstock Road, Oxford OX2 6GG, United Kingdom
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109
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Zhou S, Lamperski S, Zydorczak M. Properties of a planar electric double layer under extreme conditions investigated by classical density functional theory and Monte Carlo simulations. J Chem Phys 2014; 141:064701. [DOI: 10.1063/1.4892415] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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110
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Kuzovkov VN, Zvejnieks G, Kotomin EA. Theory of non-equilibrium critical phenomena in three-dimensional condensed systems of charged mobile nanoparticles. Phys Chem Chem Phys 2014; 16:13974-83. [PMID: 24898383 DOI: 10.1039/c3cp55181d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A study of 3d electrostatic self-assembly (SA) in systems of charged nanoparticles (NPs) is one of the most difficult theoretical problems. In particular, the limiting case of negligible or very low polar media (e.g. salt) concentration, where the long-range NP interactions cannot be reduced to commonly used effective short-range (Yukawa) potentials, remains unstudied. Moreover, the present study has demonstrated that unlike the Debye-Hückel theory, a complete screening of the charges in SA kinetics (dynamic SA) is not always possible. Generally speaking, one has to take into account implicitly how each NP interacts with all other NPs (the true long-range interactions). Traditional theoretical methods allow us to monitor such electrostatic 3d system kinetics only for very short times, which is far from sufficient for understanding the dynamic SA. In this paper, combining an integrated analytical approach (the non-linear integro-differential kinetic equation for correlation functions) and reverse Monte Carlo in the 3d case, we have obtained a self-consistent solution of this challenging problem. We demonstrate, in particular, the existence of critical points and critical phenomena in the non-equilibrium kinetics in a 3d system of oppositely charged mobile NPs.
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Affiliation(s)
- V N Kuzovkov
- Institute for Solid State Physics, University of Latvia, Riga, Latvia.
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111
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Sahin B, Ralf B. Nonlocal and nonlinear electrostatics of a dipolar Coulomb fluid. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:285101. [PMID: 24920153 DOI: 10.1088/0953-8984/26/28/285101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study a model Coulomb fluid consisting of dipolar solvent molecules of finite extent which generalizes the point-like dipolar Poisson-Boltzmann model (DPB) previously introduced by Coalson and Duncan (1996 J. Phys. Chem. 100 2612) and Abrashkin et al (2007 Phys. Rev. Lett. 99 077801). We formulate a nonlocal Poisson-Boltzmann equation (NLPB) and study both linear and nonlinear dielectric response in this model for the case of a single plane geometry. Our results shed light on the relevance of nonlocal versus nonlinear effects in continuum models of material electrostatics.
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Affiliation(s)
- Buyukdagli Sahin
- Biological Nanosystems, Interdisciplinary Research Institute, Université des Sciences et des Technologies de Lille (USTL), USR CNRS 3078, 50 Avenue Halley, 59568 Villeneuve d'Ascq, France
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112
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Adhikari P, Wen AM, French RH, Parsegian VA, Steinmetz NF, Podgornik R, Ching WY. Electronic structure, dielectric response, and surface charge distribution of RGD (1FUV) peptide. Sci Rep 2014; 4:5605. [PMID: 25001596 PMCID: PMC4085632 DOI: 10.1038/srep05605] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/06/2014] [Indexed: 11/09/2022] Open
Abstract
Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.
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Affiliation(s)
- Puja Adhikari
- Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO, 64110, USA
| | - Amy M. Wen
- Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Roger H. French
- Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - V. Adrian Parsegian
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Nicole F. Steinmetz
- Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Macromolecular Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Rudolf Podgornik
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
- Department of Theoretical Physics, J. Stefan Institute, SI-1000 Ljubljana, Slovenia
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Wai-Yim Ching
- Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO, 64110, USA
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113
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Guerrero García GI, Olvera de la Cruz M. Polarization Effects of Dielectric Nanoparticles in Aqueous Charge-Asymmetric Electrolytes. J Phys Chem B 2014; 118:8854-62. [DOI: 10.1021/jp5045173] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guillermo Iván Guerrero García
- Department of Materials Science and Engineering, and ‡Department of
Chemical and Biological
Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Monica Olvera de la Cruz
- Department of Materials Science and Engineering, and ‡Department of
Chemical and Biological
Engineering, Northwestern University, Evanston, Illinois 60208, United States
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114
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Zhou S. Effects of discreteness of surface charges on the effective electrostatic interactions. J Chem Phys 2014; 140:234704. [PMID: 24952557 DOI: 10.1063/1.4881601] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Shiqi Zhou
- School of Physics and Electronics, Central South University, Changsha, Hunan 410083, China
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115
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Trefalt G, Ruiz-Cabello FJM, Borkovec M. Interaction Forces, Heteroaggregation, and Deposition Involving Charged Colloidal Particles. J Phys Chem B 2014; 118:6346-55. [DOI: 10.1021/jp503564p] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Gregor Trefalt
- Department
of Inorganic and
Analytical Chemistry, University of Geneva, Sciences II, 30 Quai Ernest−Ansermet, 1205 Geneva, Switzerland
| | - F. Javier Montes Ruiz-Cabello
- Department
of Inorganic and
Analytical Chemistry, University of Geneva, Sciences II, 30 Quai Ernest−Ansermet, 1205 Geneva, Switzerland
| | - Michal Borkovec
- Department
of Inorganic and
Analytical Chemistry, University of Geneva, Sciences II, 30 Quai Ernest−Ansermet, 1205 Geneva, Switzerland
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116
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Adžić N, Podgornik R. Field-theoretic description of charge regulation interaction. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2014; 37:5. [PMID: 24952506 DOI: 10.1140/epje/i2014-14049-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 05/14/2014] [Accepted: 05/15/2014] [Indexed: 05/24/2023]
Abstract
In order to find the exact form of the electrostatic interaction between two proteins with dissociable charge groups in aqueous solution, we have studied a model system composed of two macroscopic surfaces with charge dissociation sites immersed in a counterion-only ionic solution. Field-theoretic representation of the grand canonical partition function is derived and evaluated within the mean-field approximation, giving the Poisson-Boltzmann theory with the Ninham-Parsegian boundary condition. Gaussian fluctuations around the mean field are then analyzed in the lowest-order correction that we calculate analytically and exactly, using the path integral representation for the partition function of a harmonic oscillator with time-dependent frequency. The first-order (one loop) free-energy correction gives the interaction free energy that reduces to the zero-frequency van der Waals form in the appropriate limit but in general gives rise to a monopolar fluctuation term due to charge fluctuation at the dissociation sites. Our formulation opens up the possibility to investigate the Kirkwood-Shumaker interaction in more general contexts where their original derivation fails.
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Affiliation(s)
- Nataša Adžić
- Department of Theoretical Physics, J. Stefan Institute, 1000, Ljubljana, Slovenia,
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117
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Luque-Caballero G, Martín-Molina A, Quesada-Pérez M. Polyelectrolyte adsorption onto like-charged surfaces mediated by trivalent counterions: A Monte Carlo simulation study. J Chem Phys 2014; 140:174701. [DOI: 10.1063/1.4872263] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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118
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Boroudjerdi H, Naji A, Naji A, Netz R. Global analysis of the ground-state wrapping conformation of a charged polymer on an oppositely charged nano-sphere. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2014; 37:21. [PMID: 24676863 DOI: 10.1140/epje/i2014-14021-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 02/28/2014] [Accepted: 03/03/2014] [Indexed: 06/03/2023]
Abstract
We investigate the wrapping conformations of a single, strongly adsorbed polymer chain on an oppositely charged nano-sphere by employing a reduced (dimensionless) representation of a primitive chain-sphere model. This enables us to determine the global behavior of the chain conformation in a wide range of values for the system parameters including the chain contour length, its linear charge density and persistence length as well as the nano-sphere charge and radius, and also the salt concentration in the bathing solution. The structural behavior of a charged chain-sphere complex can be described in terms of a few distinct conformational symmetry classes separated by continuous or discontinuous transition lines which are determined by means of appropriately defined (order) parameters. Our results can be applied to a wide class of strongly coupled polymer-sphere complexes including, for instance, complexes that comprise a mechanically flexible or semiflexible polymer chain or an extremely short or long chain and, as a special case, include the biologically relevant example of DNA-histone complexes.
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Affiliation(s)
- Hoda Boroudjerdi
- Fachbereich Physik, Freie Universität Berlin, Arnimalle 14, 14195, Berlin, Germany
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119
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Hoang TX, Giacometti A, Podgornik R, Nguyen NTT, Banavar JR, Maritan A. From toroidal to rod-like condensates of semiflexible polymers. J Chem Phys 2014; 140:064902. [DOI: 10.1063/1.4863996] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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120
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Grgičin D, Dolanski Babić S, Ivek T, Tomić S, Podgornik R. Effect of magnesium ions on dielectric relaxation in semidilute DNA aqueous solutions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:052703. [PMID: 24329292 DOI: 10.1103/physreve.88.052703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 09/08/2013] [Indexed: 06/03/2023]
Abstract
The effect of magnesium ion Mg(2+) on the dielectric relaxation of semidilute DNA aqueous solutions has been studied by means of dielectric spectroscopy in the 100 Hz-100 MHz frequency range. de Gennes-Pfeuty-Dobrynin semidilute solution correlation length is the pertinent fundamental length scale for sufficiently low concentration of added salt, describing the collective properties of Mg-DNA solutions. No relaxation fingerprint of the DNA denaturation bubbles, leading to exposed hydrophobic core scaling, was detected at low DNA concentrations, thus indicating an increased stability of the double-stranded conformation in Mg-DNA solutions as compared to the case of Na-DNA solutions. Some changes are detected in the behavior of the fundamental length scale pertaining to the single molecule DNA properties, reflecting modified electrostatic screening effects of the Odijk-Skolnick-Fixman type. All results consistently demonstrate that Mg(2+) ions interact with DNA in a similar way as Na(1+) ions do, their effect being mostly describable through an enhanced screening.
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Affiliation(s)
- D Grgičin
- Institut za fiziku, 10000 Zagreb, Croatia
| | | | - T Ivek
- Institut za fiziku, 10000 Zagreb, Croatia
| | - S Tomić
- Institut za fiziku, 10000 Zagreb, Croatia
| | - R Podgornik
- Department of Physics, University of Ljubljana and J. Stefan Institute, 1000 Ljubljana, Slovenia
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