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Waszkiewicz R, Ranasinghe M, Fogg JM, Catanese DJ, Ekiel-Jeżewska ML, Lisicki M, Demeler B, Zechiedrich L, Szymczak P. DNA supercoiling-induced shapes alter minicircle hydrodynamic properties. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.04.522747. [PMID: 36711572 PMCID: PMC9881935 DOI: 10.1101/2023.01.04.522747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
DNA in cells is organized in negatively supercoiled loops. The resulting torsional and bending strain allows DNA to adopt a surprisingly wide variety of 3-D shapes. This interplay between negative supercoiling, looping, and shape influences how DNA is stored, replicated, transcribed, repaired, and likely every other aspect of DNA activity. To understand the consequences of negative supercoiling and curvature on the hydrodynamic properties of DNA, we submitted 336 bp and 672 bp DNA minicircles to analytical ultracentrifugation (AUC). We found that the diffusion coefficient, sedimentation coefficient, and the DNA hydrodynamic radius strongly depended on circularity, loop length, and degree of negative supercoiling. Because AUC cannot ascertain shape beyond degree of non-globularity, we applied linear elasticity theory to predict DNA shapes, and combined these with hydrodynamic calculations to interpret the AUC data, with reasonable agreement between theory and experiment. These complementary approaches, together with earlier electron cryotomography data, provide a framework for understanding and predicting the effects of supercoiling on the shape and hydrodynamic properties of DNA.
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Affiliation(s)
- Radost Waszkiewicz
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Maduni Ranasinghe
- University of Lethbridge, Dept. of Chemistry and Biochemistry, Alberta, T1K3M4, Canada
| | - Jonathan M. Fogg
- Department of Molecular Virology and Microbiology, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Department of Pharmacology and Chemical Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Daniel J. Catanese
- Department of Biosciences, Rice University, 6100 Main St., Houston, TX 77005-1827, USA
| | - Maria L. Ekiel-Jeżewska
- Institute of Fundamental Technological Research, Polish Academy of Sciences, A. Pawińskiego 5B, 02-106 Warsaw, Poland,Co-contributing authors: MLE-J: , ML: , BD: , LZ: , PS:
| | - Maciej Lisicki
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland,Co-contributing authors: MLE-J: , ML: , BD: , LZ: , PS:
| | - Borries Demeler
- University of Lethbridge, Dept. of Chemistry and Biochemistry, Alberta, T1K3M4, Canada,University of Montana, Dept. of Chemistry and Biochemistry, Missoula, MT 59812, USA,Co-contributing authors: MLE-J: , ML: , BD: , LZ: , PS:
| | - Lynn Zechiedrich
- Department of Molecular Virology and Microbiology, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Department of Pharmacology and Chemical Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA,Co-contributing authors: MLE-J: , ML: , BD: , LZ: , PS:
| | - Piotr Szymczak
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland,Co-contributing authors: MLE-J: , ML: , BD: , LZ: , PS:
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Bagchi D. Macroscopic charge segregation in driven polyelectrolyte solutions. SOFT MATTER 2022; 18:5676-5686. [PMID: 35861507 DOI: 10.1039/d2sm00448h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Understanding the behavior of charged complex fluids is crucial for a plethora of important industrial, technological, and medical applications. Here, using coarse-grained molecular dynamics simulations, we investigate the properties of a polyelectrolyte solution with explicit counterions and implicit solvent that is driven by a steady electric field. By properly tuning the interplay between interparticle electrostatics and the applied electric field, we uncover two non-equilibrium continuous phase transitions as a function of the driving field. The first transition occurs from a homogeneous mixed phase to a macroscopic charge-segregated phase in which the polyelectrolyte solution self-organizes to form two lanes of like-charges, parallel to the applied field. We show that the fundamental underlying factor responsible for the emergence of this charge segregation in the presence of an electric field is the excluded volume interactions of the drifting polyelectrolyte chains. As the driving field is increased further, a re-entrant transition is observed from a charge-segregated phase to a homogeneous phase. The re-entrance is signaled by a decrease in the mobility of the monomers and counterions as the electric field is increased. Furthermore, with multivalent counterions, a counterintuitive regime of negative differential mobility is observed in which the charges move progressively more slowly as the driving field is increased. We show that all these features can be consistently explained using an intuitive trapping mechanism that operates between the oppositely moving charges, and present numerical evidence to support our claims. Parameter dependencies and phase diagrams are studied to better understand charge segregation in such driven polyelectrolyte solutions.
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Affiliation(s)
- Debarshee Bagchi
- International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru, India.
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