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Croquette V, Orero JV, Rieu M, Allemand JF. Magnetic tweezers principles and promises. Methods Enzymol 2024; 694:1-49. [PMID: 38492947 DOI: 10.1016/bs.mie.2024.01.026] [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] [Indexed: 03/18/2024]
Abstract
Magnetic tweezers have become popular with the outbreak of single molecule micromanipulation: catching a single molecule of DNA, RNA or a single protein and applying mechanical constrains using micron-size magnetic beads and magnets turn out to be easy. Various factors have made this possible: the fact that manufacturers have been preparing these beads to catch various biological entities-the ease of use provided by magnets which apply a force or a torque at a distance thus inside a flow cell-some chance: since the forces so generated are in the right range to stretch a single molecule. This is a little less true for torque. Finally, one feature which also appears very important is the simplicity of their calibration using Brownian motion. Here we start by describing magnetic tweezers used routinely in our laboratory where we have tried to develop a device as simple as possible so that the experimentalist can really focus on the biological aspect of the biomolecules that he/she is interested in. We discuss the implications of the various components and their important features. Next, we summarize what is easy to achieve and what is less easy. Then we refer to contributions by other groups who have brought valuable insights to improve magnetic tweezers.
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Affiliation(s)
- Vincent Croquette
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France; ESPCI Paris, Université PSL, Paris, France.
| | - Jessica Valle Orero
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France; The American University of Paris, Paris, France
| | - Martin Rieu
- Department of Physics, New Biochemistry Building, University of Oxford, South Parks Road, Oxford, United Kingdom
| | - Jean-François Allemand
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
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Truong HP, Saleh OA. Magnetic tweezers characterization of the entropic elasticity of intrinsically disordered proteins and peptoids. Methods Enzymol 2024; 694:209-236. [PMID: 38492952 DOI: 10.1016/bs.mie.2023.12.011] [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] [Indexed: 03/18/2024]
Abstract
Understanding the conformational behavior of biopolymers is essential to unlocking knowledge of their biophysical mechanisms and functional roles. Single-molecule force spectroscopy can provide a unique perspective on this by exploiting entropic elasticity to uncover key biopolymer structural parameters. A particularly powerful approach involves the use of magnetic tweezers, which can easily generate lower stretching forces (0.1-20 pN). For forces at the low end of this range, the elastic response of biopolymers is sensitive to excluded volume effects, and they can be described by Pincus blob elasticity model that allow robust extraction of the Flory polymer scaling exponent. Here, we detail protocols for the use of magnetic tweezers for force-extension measurements of intrinsically disordered proteins and peptoids. We also discuss procedures for fitting low-force elastic curves to the predictions of polymer physics models to extract key conformational parameters.
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Affiliation(s)
- Hoang P Truong
- Materials Department, University of California, Santa Barbara, CA, United States
| | - Omar A Saleh
- Materials Department, University of California, Santa Barbara, CA, United States; Biomolecular Sciences and Engineering Program, University of California, Santa Barbara, CA, United States; Physics Department, University of California, Santa Barbara, CA, United States.
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Valle-Orero J, Rieu M, Allemand JF, Bujaa D, Joubert A, Tran PLT, Croquette V, Boulé JB. Observing G4 formation and its resolution by Pif1 in real time by manipulation under magnetic tweezers. Methods Enzymol 2024; 695:119-158. [PMID: 38521583 DOI: 10.1016/bs.mie.2023.12.012] [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] [Indexed: 03/25/2024]
Abstract
G-quadruplexes (G4s) are nucleic acids secondary structures that may form in guanine-rich sequences, either intra or inter-molecularly. Ability of a primary sequence to form a G4 can be predicted computationally with an improving accuracy as well as tested in bulk using biophysical measurements. As a result, G4 density maps have been devised for a large number of genomes from all life kingdoms. Experimental validation of the formation of G4s in vivo however remains indirect and relies on their stabilization with small molecules, antibodies or proteins, or mutational studies, in order to measure downstream effects on gene expression or genome stability for example. Although numerous techniques exist to observe spontaneous formation of G4s in single-stranded DNA, observing G4 formation in double-stranded DNA (dsDNA) is more challenging. However, it is particularly relevant to understand if a given G4 sequence forms stably in a dsDNA context, if it is stable enough to dock proteins or pose a challenge to molecular motors such as helicases or polymerases. In essence, G4s can be a threat to genomic stability but carry as well as the potential to be elements of a structural language in the non-replicating genome. To study quantitatively the formation dynamics and stability of single intramolecular G4s embedded in dsDNA, we have adapted techniques of DNA manipulation under magnetic tweezers. This technique also allows to study encounters of molecular motors with G4 at a single molecule resolution, in order to gain insight into the specificity of G4 resolution by molecular motors, and its efficiency. The procedures described here include the design of the G4 substrate, the study of G4 formation probability and lifetime in dsDNA, as well as procedures to characterize the encounter between the Pif1 helicase and a G4 until G4 resolution. The procedures that we described here can easily be extended to the study of other G4s or molecular motors.
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Affiliation(s)
- Jessica Valle-Orero
- Physics Laboratory of the École Normale Supérieure, CNRS, ENS, PSL University, Sorbonne University, Paris-Cité University, Paris, France; Biology Institute of the École Normale Supérieure (IBENS), ENS, CNRS, INSERM, PSL University, Paris, France; Department of Computer Science, Mathematics and Environmental Sciences, The American University of Paris, Paris, France.
| | - Martin Rieu
- Physics Laboratory of the École Normale Supérieure, CNRS, ENS, PSL University, Sorbonne University, Paris-Cité University, Paris, France; Biology Institute of the École Normale Supérieure (IBENS), ENS, CNRS, INSERM, PSL University, Paris, France; Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Jean-François Allemand
- Physics Laboratory of the École Normale Supérieure, CNRS, ENS, PSL University, Sorbonne University, Paris-Cité University, Paris, France; Biology Institute of the École Normale Supérieure (IBENS), ENS, CNRS, INSERM, PSL University, Paris, France
| | - Dulamkhuu Bujaa
- Physics Laboratory of the École Normale Supérieure, CNRS, ENS, PSL University, Sorbonne University, Paris-Cité University, Paris, France; Biology Institute of the École Normale Supérieure (IBENS), ENS, CNRS, INSERM, PSL University, Paris, France
| | - Alexandra Joubert
- Genome Structure and Instability Laboratory, National Museum of Natural History, CNRS, INSERM, Sorbonne University Alliance, Paris, France
| | - Phong Lan Thao Tran
- Genome Structure and Instability Laboratory, National Museum of Natural History, CNRS, INSERM, Sorbonne University Alliance, Paris, France; Depixus SAS, 3-5 impasse Reille, Paris, France
| | - Vincent Croquette
- Physics Laboratory of the École Normale Supérieure, CNRS, ENS, PSL University, Sorbonne University, Paris-Cité University, Paris, France; Biology Institute of the École Normale Supérieure (IBENS), ENS, CNRS, INSERM, PSL University, Paris, France; ESPCI Paris, PSL University, Paris, France.
| | - Jean-Baptiste Boulé
- Genome Structure and Instability Laboratory, National Museum of Natural History, CNRS, INSERM, Sorbonne University Alliance, Paris, France.
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Garehbaghi S, Ashrafi AM, Adam V, Richtera L. Surface modification strategies and the functional mechanisms of gold nanozyme in biosensing and bioassay. Mater Today Bio 2023; 20:100656. [PMID: 37214551 PMCID: PMC10199192 DOI: 10.1016/j.mtbio.2023.100656] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 04/19/2023] [Accepted: 05/03/2023] [Indexed: 05/24/2023] Open
Abstract
Gold nanozymes (GNZs) have been widely used in biosensing and bioassay due to their interesting catalytic activities that enable the substitution of natural enzyme. This review explains different catalytic activities of GNZs that can be achieved by applying different modifications to their surface. The role of Gold nanoparticles (GNPs) in mimicking oxidoreductase, helicase, phosphatase were introduced. Moreover, the effect of surface properties and modifications on each catalytic activity was thoroughly discussed. The application of GNZs in biosensing and bioassay was classified in five categories based on the combination of the enzyme like activities and enhancing/inhibition of the catalytic activities in presence of the target analyte/s that is realized by proper surface modification engineering. These categories include catalytic activity enhancer, reversible catalytic activity inhibitor, binding selectivity enhancer, agglomeration base, and multienzyme like activity, which are explained and exemplified in this review. It also gives examples of those modifications that enable the application of GNZs for in vivo biosensing and bioassays.
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Affiliation(s)
- Sanam Garehbaghi
- Central European Institute of Technology, Brno University of Technology, Purkynova 123, Brno, CZ-612 00, Czech Republic
| | - Amir M. Ashrafi
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, Brno, CZ-613 00, Czech Republic
| | - Vojtěch Adam
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, Brno, CZ-613 00, Czech Republic
| | - Lukáš Richtera
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, Brno, CZ-613 00, Czech Republic
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Valle-Orero J, Rieu M, Tran P, Joubert A, Raj S, Allemand JF, Croquette V, Boulé JB. Strand switching mechanism of Pif1 helicase induced by its collision with a G-quadruplex embedded in dsDNA. Nucleic Acids Res 2022; 50:8767-8778. [PMID: 35947696 PMCID: PMC9410907 DOI: 10.1093/nar/gkac667] [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: 01/27/2022] [Revised: 07/01/2022] [Accepted: 07/24/2022] [Indexed: 12/24/2022] Open
Abstract
G-rich sequences found at multiple sites throughout all genomes may form secondary structures called G-quadruplexes (G4), which act as roadblocks for molecular motors. Among the enzymes thought to process these structures, the Pif1 DNA helicase is considered as an archetypical G4-resolvase and its absence has been linked to G4-related genomic instabilities in yeast. Here we developed a single-molecule assay to observe Pif1 opening a DNA duplex and resolving the G4 in real time. In support of former enzymological studies, we show that the helicase reduces the lifetime of G4 from hours to seconds. However, we observe that in the presence of a G4, Pif1 exhibits a strong strand switching behavior, which can lead to Pif1 escaping G4 resolution, depending on the structural context surrounding the substrate. This behavior is also detected in the presence of other roadblocks (LNA or RNA). We propose that the efficiency of Pif1 to remove a roadblock (G4 or other) is affected by its strand switching behavior and depends on the context surrounding the obstacle. We discuss how this switching behavior may explain several aspects of Pif1 substrate preference and affect its activity as a G4 resolvase in vivo.
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Affiliation(s)
| | - Martin Rieu
- Laboratoire de physique de L’École Normale Supérieure de Paris, CNRS, ENS, Université PSL, Sorbonne Université, Université Paris Cité, 75005 Paris, France,Institut de Biologie de l’École Normale Supérieure de Paris (IBENS), École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Phong Lan Thao Tran
- Structure et Instabilité des Génomes, Museum National d’Histoire Naturelle, INSERM, CNRS, Alliance Sorbonne Université, 75005 Paris, France
| | - Alexandra Joubert
- Structure et Instabilité des Génomes, Museum National d’Histoire Naturelle, INSERM, CNRS, Alliance Sorbonne Université, 75005 Paris, France
| | - Saurabh Raj
- Laboratoire de physique de L’École Normale Supérieure de Paris, CNRS, ENS, Université PSL, Sorbonne Université, Université Paris Cité, 75005 Paris, France
| | - Jean-François Allemand
- Laboratoire de physique de L’École Normale Supérieure de Paris, CNRS, ENS, Université PSL, Sorbonne Université, Université Paris Cité, 75005 Paris, France,Institut de Biologie de l’École Normale Supérieure de Paris (IBENS), École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | | | - Jean-Baptiste Boulé
- To whom correspondence should be addressed. Tel: +33 140795616; Fax: +33 1407937050;
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