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Huang C, Podgornik R, Man X. Selective Adsorption of Confined Polymers: Self-Consistent Field Theory Studies. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Changhang Huang
- Center of Soft Matter Physics and its Applications, Beihang University, Beijing 100191, China
- School of Physics, Beihang University, Beijing 100191, China
| | - Rudolf Podgornik
- School of Physical Sciences and Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China
- Wenzhou Institute of the University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Xingkun Man
- Center of Soft Matter Physics and its Applications, Beihang University, Beijing 100191, China
- School of Physics, Beihang University, Beijing 100191, China
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Matsuda A, Mofrad MRK. Free energy calculations shed light on the nuclear pore complex's selective barrier nature. Biophys J 2021; 120:3628-3640. [PMID: 34339633 PMCID: PMC8456294 DOI: 10.1016/j.bpj.2021.07.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/27/2021] [Accepted: 07/27/2021] [Indexed: 12/27/2022] Open
Abstract
The nuclear pore complex (NPC) is the exclusive gateway for traffic control across the nuclear envelope. Although smaller cargoes (less than 5-9 nm in size) can freely diffuse through the NPC, the passage of larger cargoes is restricted to those accompanied by nuclear transport receptors (NTRs). This selective barrier nature of the NPC is putatively associated with the intrinsically disordered, phenylalanine-glycine repeat-domains containing nucleoporins, termed FG-Nups. The precise mechanism underlying how FG-Nups carry out such an exquisite task at high throughputs has, however, remained elusive and the subject of various hypotheses. From the thermodynamics perspective, free energy analysis can be a way to determine cargo's transportability because the traffic through the NPC must be in the direction of reducing the free energy. In this study, we developed a computational model to evaluate the free energy composed of the conformational entropy of FG-Nups and the energetic gain associated with binding interactions between FG-Nups and NTRs and investigated whether these physical features can be the basis of NPC's selectivity. Our results showed that the reduction in conformational entropy by inserting a cargo into the NPC increased the free energy by an amount substantially greater than the thermal energy (≫kBT), whereas the free energy change was negligible (
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Affiliation(s)
- Atsushi Matsuda
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, Berkeley, California
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, Berkeley, California; Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California.
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Koumarianos S, Kaiyum R, Barrett CJ, Madras N, Mermut O. Theory and experiment of chain length effects on the adsorption of polyelectrolytes onto spherical particles: the long and the short of it. Phys Chem Chem Phys 2021; 23:300-310. [PMID: 33346762 DOI: 10.1039/d0cp04359a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We study here the role of polyelectrolyte chain length, that is number of repeat units (mers), in the competitive adsorption of a simple model polyanion, poly(acrylic acid), onto 85 nm spherical silica particles capped with a model polycation, poly(allylamine hydrochloride). Performing fluorescence spectroscopy experiments, we measured chain-length dependence of dilute aqueous polyelectrolyte adsorption, at full surface coverage, onto an oppositely charged polyelectrolyte overtop spherical silica nanoparticles (10-3 g L-1). Preferential adsorption was determined by comparing the characteristic fluorescence intensities of the two fluorophore-labeled and narrowly disperse polyacrylic acid samples (NMA-PAA450k and Dan-PAA2k) of 450k- and 2k-molecular weight (6250- and 28-mers), respectively. To compare and validate experimental results, a lattice model was developed for computing the probabilities of the different arrangements of two polymer chain lengths of polyacrylic acid on the surface of the silica nanosphere. We then determined which numbers of long and short adsorbed chains corresponded to the most configurations in our model. Both spectroscopic experiment results and the combinatorial model demonstrated that there is an entropic preference for complete adsorption of the longer 450k polyacrylic acid chain vs. 2k. This study provides insights on entropy driven chain-length dependence of polyelectrolyte adsorption onto spherical nanoparticle surfaces for directing and optimizing their layer-by-layer self-assembly in organic films.
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Affiliation(s)
- Sperydon Koumarianos
- Department of Physics and Astronomy, York University, Toronto, ON M3J 1P3, Canada.
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Gupta S, Biswas P. Conformational properties of complexes of poly(propylene imine) dendrimers with linear polyelectrolytes in dilute solutions. J Chem Phys 2020; 153:194902. [PMID: 33218232 DOI: 10.1063/5.0030270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This study investigates the conformational properties of complexes of poly(propylene imine) dendrimers with a linear polyelectrolyte (LPE) at neutral pH in an aqueous solution via molecular dynamics simulations. Various conformational properties, such as the atomic density profile, counterion density distribution, charge distribution, cavity volume, and the static structure factor are studied as a function of the charge and chain length of the LPE. The lower generation dendrimer complexes encapsulate the shorter linear PE chains, while the longer PE chains are adsorbed on the dendrimer surface that screen the surface charge and prevent the penetration of the counterions and water molecules. However, the overall charge of the higher generation dendrimers is not neutralized by the charge of the PE chains, which results in chloride counterion penetration within the dendrimers. The adsorption of the PE chains on the dendrimers is also verified from the charge distribution of the dendrimer-PE complexes. The charge on the lower generation dendrimer complexes is overcompensated by the longer PE chains resulting in an overall negative charge on the complexes, while the PE chains do not completely neutralize the charge of the higher generation dendrimers and produce positively charged complexes. The results of the structure factor indicate a conformational transition of the dendrimer-PE complexes from a dense compact structure to an open one with an increase in the PE chain length. This transition is characterized by an increase in the cavity volume in dendrimers with an increase in the PE chain length.
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Affiliation(s)
- Shilpa Gupta
- Department of Chemistry, University of Delhi, Delhi 110007, India
| | - Parbati Biswas
- Department of Chemistry, University of Delhi, Delhi 110007, India
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Caetano DLZ, de Carvalho SJ, Metzler R, Cherstvy AG. Critical adsorption of multiple polyelectrolytes onto a nanosphere: splitting the adsorption-desorption transition boundary. J R Soc Interface 2020; 17:20200199. [PMID: 32574545 PMCID: PMC7328387 DOI: 10.1098/rsif.2020.0199] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
Employing extensive Monte Carlo computer simulations, we investigate in detail the properties of multichain adsorption of charged flexible polyelectrolytes (PEs) onto oppositely charged spherical nanoparticles (SNPs). We quantify the conditions of critical adsorption-the phase-separation curve between the adsorbed and desorbed states of the PEs-as a function of the SNP surface-charge density and the concentration of added salt. We study the degree of fluctuations of the PE-SNP electrostatic binding energy, which we use to quantify the emergence of the phase subtransitions, including a series of partially adsorbed PE configurations. We demonstrate how the phase-separation adsorption-desorption boundary shifts and splits into multiple subtransitions at low-salt conditions, thereby generalizing and extending the results for critical adsorption of a single PE onto the SNP. The current findings are relevant for finite concentrations of PEs around the attracting SNP, such as the conditions for PE adsorption onto globular proteins carrying opposite electric charges.
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Affiliation(s)
- Daniel L. Z. Caetano
- São Paulo State University (UNESP), Institute of Biosciences, Humanities and Exact Sciences, Campus São José do Rio Preto, 15054-000 Brazil
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, Brazil
- Center for Computational Engineering and Sciences, State University of Campinas (UNICAMP), 13083-970 Campinas, Brazil
| | - Sidney J. de Carvalho
- São Paulo State University (UNESP), Institute of Biosciences, Humanities and Exact Sciences, Campus São José do Rio Preto, 15054-000 Brazil
| | - Ralf Metzler
- Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany
| | - Andrey G. Cherstvy
- Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany
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Wang C, Wu F, Zhao B, Chen YC, Luo MB. Spontaneous Injection of Polymer into a Spherical Cavity from a Narrow Tube. Macromolecules 2020. [DOI: 10.1021/acs.macromol.9b02645] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Chao Wang
- Department of Physics, Taizhou University, Taizhou 318000, China
| | - Fan Wu
- Department of Physics, Taizhou University, Taizhou 318000, China
| | - Bin Zhao
- Department of Physics, Taizhou University, Taizhou 318000, China
| | - Ying-Cai Chen
- Department of Physics, Taizhou University, Taizhou 318000, China
| | - Meng-Bo Luo
- Department of Physics, Zhejiang University, Hangzhou 310027, China
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Nguyen TD, Olvera de la Cruz M. Manipulation of Confined Polyelectrolyte Conformations through Dielectric Mismatch. ACS NANO 2019; 13:9298-9305. [PMID: 31404496 DOI: 10.1021/acsnano.9b03900] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We demonstrate that a highly charged polyelectrolyte confined in a spherical cavity undergoes reversible transformations between amorphous conformations and a four-fold symmetry morphology as a function of dielectric mismatch between the media inside and outside the cavity. Surface polarization due to dielectric mismatch exhibits an extra "confinement" effect, which is most pronounced within a certain range of the cavity radius and the electrostatic strength between the monomers and counterions and multivalent counterions. For cavities with a charged surface, surface polarization leads to an increased amount of counterions adsorbed in the outer side, further compressing the confined polyelectrolyte into a four-fold symmetry morphology. The equilibrium conformation of the chain is dependent upon several key factors including the relative permittivities of the media inside and outside the cavity, multivalent counterion concentration, cavity radius relative to the chain length, and interface charge density. Our findings offer insights into the effects of dielectric mismatch in packaging and delivery of polyelectrolytes across media with different relative permittivities. Moreover, the reversible transformation of the polyelectrolyte conformations in response to environmental permittivity allows for potential applications in biosensing and medical monitoring.
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Affiliation(s)
- Trung Dac Nguyen
- Department of Chemical and Biological Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - Monica Olvera de la Cruz
- Department of Chemical and Biological Engineering , Northwestern University , Evanston , Illinois 60208 , United States
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
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Caetano DLZ, de Carvalho SJ, Metzler R, Cherstvy AG. Critical adsorption of periodic and random polyampholytes onto charged surfaces. Phys Chem Chem Phys 2017; 19:23397-23413. [PMID: 28825753 DOI: 10.1039/c7cp04040g] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
How different are the properties of critical adsorption of polyampholytes and polyelectrolytes onto charged surfaces? How important are the details of polyampholyte charge distribution on the onset of critical adsorption transition? What are the scaling relations governing the dependence of critical surface charge density on salt concentration in the surrounding solution? Here, we employ Metropolis Monte Carlo simulations and uncover the scaling relations for critical adsorption for quenched periodic and random charge distributions along the polyampholyte chains. We also evaluate and discuss the dependence of the adsorbed layer width on solution salinity and details of the charge distribution. We contrast our findings to the known results for polyelectrolyte adsorption onto oppositely charged surfaces, in particular, their dependence on electrolyte concentration.
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Affiliation(s)
- Daniel L Z Caetano
- Sao Paulo State University (UNESP), Institute of Biosciences, Humanities and Exact Sciences (Ibilce), Campus Sao Jose do Rio Preto, 15054-000, Brazil.
| | - Sidney J de Carvalho
- Sao Paulo State University (UNESP), Institute of Biosciences, Humanities and Exact Sciences (Ibilce), Campus Sao Jose do Rio Preto, 15054-000, Brazil.
| | - Ralf Metzler
- Institute for Physics & Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany.
| | - Andrey G Cherstvy
- Institute for Physics & Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany.
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