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Rauscher PM, de Pablo JJ. Random Knotting in Fractal Ring Polymers. Macromolecules 2022; 55:8409-8417. [PMID: 36186575 PMCID: PMC9520986 DOI: 10.1021/acs.macromol.2c01676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 08/23/2022] [Indexed: 11/28/2022]
Abstract
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Many ring polymer
systems of physical and biological
interest exhibit
both pronounced topological effects and nontrivial self-similarity,
but the relationship between these two phenomena has not yet been
clearly established. Here, we use theory and simulation to formulate
such a connection by studying a fundamental topological property—the
random knotting probability—for ring polymers with varying
fractal dimension, df. Using straightforward scaling arguments, we generalize a classic
mathematical result, showing that the probability of a trivial knot
decays exponentially with chain size, N, for all
fractal dimensions: P0(N) ∝ exp(−N/N0). However, no such simple considerations can account for
the dependence of the knotting length, N0, on df, necessitating
a more involved analytical calculation. This analysis reveals a complicated
double-exponential dependence, which is well supported by numerical
data. By contrast, functional forms typical of simple scaling theories
fail to adequately describe the observations. These findings are equally
valid for two-dimensional ring polymer systems, where “knotting”
is defined as the intersection of any two segments.
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Affiliation(s)
- Phillip M. Rauscher
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Juan J. de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
- Materials Science Division (MSD) and Center for Molecular Engineering (CME), Argonne National Laboratory, Lemont, Illinois 60439, United States
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Hebbeker P, Steinschulte AA, Schneider S, Plamper FA. Balancing Segregation and Complexation in Amphiphilic Copolymers by Architecture and Confinement. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4091-4106. [PMID: 28221801 DOI: 10.1021/acs.langmuir.6b04602] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Segregation is a well-known principle for micellization, as solvophobic components try to minimize interactions with other entities (such as solvent) by self-assembly. An opposite principle is based on complexation (or coacervation), leading to the coassembly/association of different components. Most cases in the literature rely on only one of these modes, though the classical micellization scheme (such as spherical micelles, wormlike micelles, and vesicles) can be enriched by a subtle balance of segregation and complexation. Because of their counteraction, micellar constructs with unprecedented structure and behavior could be obtained. In this feature, systems are highlighted, which are between both mechanisms, and we study concentration, architecture, and confinement effects. Systems with inter- and intramolecular interactions are presented, and the effects of polymer topology and monomer sequence on the resulting structures are discussed. It is shown that complexation can lead to altered micellization behavior as the complex of one hydrophobic and one hydrophilic component can have a very low surface tension toward the solvent. Then, the more soluble component is enriched at the surface of the complex and acts as a microsurfactant. Although segregation dominates for amphiphilic copolymers in solution, the effect of the complexation can be enhanced by branching (change of architecture). Another possibility to enhance the complexation is by confining copolymers in a (pseudo-) 2D environment (like the one available at liquid-liquid interfaces). These observations show how new structural features can be achieved by tuning the subtle balance between segregation and complexation/solubilization.
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Affiliation(s)
- Pascal Hebbeker
- Institute of Physical Chemistry II, RWTH Aachen University , Landoltweg 2, 52056 Aachen, Germany
| | - Alexander A Steinschulte
- Institute of Physical Chemistry II, RWTH Aachen University , Landoltweg 2, 52056 Aachen, Germany
| | - Stefanie Schneider
- Institute of Physical Chemistry II, RWTH Aachen University , Landoltweg 2, 52056 Aachen, Germany
| | - Felix A Plamper
- Institute of Physical Chemistry II, RWTH Aachen University , Landoltweg 2, 52056 Aachen, Germany
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3
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Katashima T, Asai M, Urayama K, Chung UI, Sakai T. Mechanical properties of tetra-PEG gels with supercoiled network structure. J Chem Phys 2014; 140:074902. [DOI: 10.1063/1.4863917] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
Most proteins, in order to perform their biological function, have to fold to a compact native state. The increasing number of knotted and slipknotted proteins identified suggests that proteins are able to manoeuvre around topological barriers during folding. In the present article, we review the current progress in elucidating the knotting process in proteins. Although we concentrate on theoretical approaches, where a knotted topology can be unambiguously detected, comparison with experiments is also reviewed. Numerical simulations suggest that the folding process for small knotted proteins is composed of twisted loop formation and then threading by either slipknot geometries or flipping. As the size of the knotted proteins increases, particularly for more deeply threaded termini, the prevalence of traps in the free energy landscape also increases. Thus, in the case of longer knotted and slipknotted proteins, the folding mechanism is probably supported by chaperones. Overall, results imply that knotted proteins can be folded efficiently and survive evolutionary pressure in order to perform their biological functions.
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Virnau P, Mallam A, Jackson S. Structures and folding pathways of topologically knotted proteins. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:033101. [PMID: 21406854 DOI: 10.1088/0953-8984/23/3/033101] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In the last decade, a new class of proteins has emerged that contain a topological knot in their backbone. Although these structures are rare, they nevertheless challenge our understanding of protein folding. In this review, we provide a short overview of topologically knotted proteins with an emphasis on newly discovered structures. We discuss the current knowledge in the field, including recent developments in both experimental and computational studies that have shed light on how these intricate structures fold.
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Affiliation(s)
- Peter Virnau
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55128 Mainz, Germany.
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Nykypanchuk D, Hoagland DA, Strey HH. Diffusion of Circular DNA in Two-Dimensional Cavity Arrays. Chemphyschem 2009; 10:2847-51. [DOI: 10.1002/cphc.200900655] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mansfield ML. Development of knotting during the collapse transition of polymers. J Chem Phys 2007; 127:244902. [DOI: 10.1063/1.2806929] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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8
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King NP, Yeates EO, Yeates TO. Identification of rare slipknots in proteins and their implications for stability and folding. J Mol Biol 2007; 373:153-66. [PMID: 17764691 DOI: 10.1016/j.jmb.2007.07.042] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 07/17/2007] [Accepted: 07/19/2007] [Indexed: 11/27/2022]
Abstract
Among the thousands of known three-dimensional protein folds, only a few have been found whose backbones are in knotted configurations. The rarity of knotted proteins has important implications for how natural proteins reach their natively folded states. Proteins with such unusual features offer unique opportunities for studying the relationships between structure, folding, and stability. Here we report the identification of a unique slipknot feature in the fold of a well-known thermostable protein, alkaline phosphatase. A slipknot is created when a knot is formed by part of a protein chain, after which the backbone doubles back so that the entire structure becomes unknotted in a mathematical sense. Slipknots are therefore not detected by computational tests that look for knots in complete protein structures. A computational survey looking specifically for slipknots in the Protein Data Bank reveals a few other instances in addition to alkaline phosphatase. Unexpected similarities are noted among some of the proteins identified. In addition, two transmembrane proteins are found to contain slipknots. Finally, mutagenesis experiments on alkaline phosphatase are used to probe the contribution the slipknot feature makes to thermal stability. The trends and conserved features observed in these proteins provide new insights into mechanisms of protein folding and stability.
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Affiliation(s)
- Neil P King
- Department of Chemistry and Biochemistry, University of California-Los Angeles, 611 Charles Young Drive East, Los Angeles, CA 90095-1569, USA
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Ferrari F, Rostiashvili VG, Vilgis TA. Directed polymers with constrained winding angle. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:061802. [PMID: 16089756 DOI: 10.1103/physreve.71.061802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Indexed: 05/03/2023]
Abstract
In this paper we study from a nonperturbative point of view the entanglement of two directed polymers subjected to repulsive interactions given by a Dirac delta-function potential. An exact formula of the so-called second moment of the winding angle is derived. This result is used to provide a thorough analysis of entanglement phenomena in the classical system of two polymers subjected to repulsive interactions and related problems. No approximation is made in treating the constraint on the winding angle and the repulsive forces. In particular, we investigate how repulsive forces influence the entanglement degree of the two-polymer system. In the limit of ideal polymers, in which the interactions are switched off, we show that our results are in agreement with those of previous works.
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Affiliation(s)
- Franco Ferrari
- Institute of Physics, University of Szczecin, ul. Wielkopolska 15, 70-451 Szczecin, Poland.
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Mezzasalma SA. Scaling Laws for Ideal and Real Macromolecular Chains from Relativistic Theory of Self-Diffusion in a Liquid Medium. J Phys Chem B 2000. [DOI: 10.1021/jp992315a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stefano A. Mezzasalma
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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11
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Urayama K, Yokoyama K, Kohjiya S. Low-temperature behavior of deswollen poly(dimethylsiloxane) networks. POLYMER 2000. [DOI: 10.1016/s0032-3861(99)00511-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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12
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Kilian H, Oppermann W, Zink B, Marti O. Relaxation of polymer molecules in networks—the extended aggregate model. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1089-3156(98)00022-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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13
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Orientation relaxation of linear chains enclosed in a network studied by birefringence measurements. Colloid Polym Sci 1997. [DOI: 10.1007/s003960050073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Urayama K, Kohjiya S. Uniaxial elongation of deswollen polydimethylsiloxane networks with supercoiled structure. POLYMER 1997. [DOI: 10.1016/s0032-3861(96)00576-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Fawcett AH, Mee RAW, McBride FV. A new method for the recognition and size characterization of a knot in a ring molecule placed upon a lattice. J Chem Phys 1996. [DOI: 10.1063/1.470759] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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