1
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Chen L, Wang Y, Yang G. Locally Denatured DNA Compaction by Divalent Cations. J Phys Chem B 2023. [PMID: 37205854 DOI: 10.1021/acs.jpcb.3c01858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The denaturation of DNA is a critical process in biology and has many biotechnological applications. We investigated the compaction of locally denatured DNA by a chemical denaturation agent, dimethyl sulfoxide (DMSO), using magnetic tweezers (MTs), atomic force microscopy (AFM), and dynamic light scattering (DLS). Our results show that DMSO not only is capable of denaturing DNA but also able to compact DNA directly. When the DMSO concentration is above 10%, DNA condensation occurs due to the reduction in the persistence length of DNA and excluded volume interactions. Meanwhile, locally denatured DNA is easily condensed by divalent cations, such as magnesium ions (Mg2+), contrasting with no native DNA condensation by the classical divalent cations. Specifically, the addition of more than 3 mM Mg2+ to a 5% DMSO solution leads to DNA condensation. The critical condensing force (FC) increases from 6.4 to 9.5 pN when the Mg2+ concentration grows from 3 to 10 mM. However, FC decreases gradually with a further increase in Mg2+ concentration. For 3% DMSO solution, above 30 mM Mg2+ is needed to compact DNA and a weaker condensing force was measured. With increasing Mg2+ concentration, the morphology of the DMSO partially denatured DNA complex changes from loosely random coils to a dense network structure, even forming a spherical condensation nucleus, and finally to a partially disintegrated network. These findings show that the elasticity of DNA plays an important role in its denaturation and condensation behavior.
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Affiliation(s)
- Ling Chen
- Department of Physics, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Yanwei Wang
- Department of Physics, Wenzhou University, Wenzhou, Zhejiang 325035, China
| | - Guangcan Yang
- Department of Physics, Wenzhou University, Wenzhou, Zhejiang 325035, China
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2
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Vanderlinden W, Skoruppa E, Kolbeck PJ, Carlon E, Lipfert J. DNA fluctuations reveal the size and dynamics of topological domains. PNAS NEXUS 2022; 1:pgac268. [PMID: 36712371 PMCID: PMC9802373 DOI: 10.1093/pnasnexus/pgac268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/18/2022] [Indexed: 11/23/2022]
Abstract
DNA supercoiling is a key regulatory mechanism that orchestrates DNA readout, recombination, and genome maintenance. DNA-binding proteins often mediate these processes by bringing two distant DNA sites together, thereby inducing (transient) topological domains. In order to understand the dynamics and molecular architecture of protein-induced topological domains in DNA, quantitative and time-resolved approaches are required. Here, we present a methodology to determine the size and dynamics of topological domains in supercoiled DNA in real time and at the single-molecule level. Our approach is based on quantifying the extension fluctuations-in addition to the mean extension-of supercoiled DNA in magnetic tweezers (MT). Using a combination of high-speed MT experiments, Monte Carlo simulations, and analytical theory, we map out the dependence of DNA extension fluctuations as a function of supercoiling density and external force. We find that in the plectonemic regime, the extension variance increases linearly with increasing supercoiling density and show how this enables us to determine the formation and size of topological domains. In addition, we demonstrate how the transient (partial) dissociation of DNA-bridging proteins results in the dynamic sampling of different topological states, which allows us to deduce the torsional stiffness of the plectonemic state and the kinetics of protein-plectoneme interactions. We expect our results to further the understanding and optimization of magnetic tweezer measurements and to enable quantification of the dynamics and reaction pathways of DNA processing enzymes in the context of physiologically relevant forces and supercoiling densities.
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Affiliation(s)
| | | | - Pauline J Kolbeck
- Department of Physics and Center for NanoScience (CeNS), LMU Munich, Amalienstrasse 54, 80799 Munich, Germany,Department of Physics and Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
| | - Enrico Carlon
- Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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3
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Xu M, Dai T, Wang Y, Yang G. The incipient denaturation mechanism of DNA. RSC Adv 2022; 12:23356-23365. [PMID: 36090395 PMCID: PMC9383117 DOI: 10.1039/d2ra02480b] [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: 04/20/2022] [Accepted: 07/19/2022] [Indexed: 11/21/2022] Open
Abstract
DNA denaturation is related to many important biological phenomena, such as its replication, transcription and the interaction with some specific proteins for single-stranded DNA. Dimethyl sulfoxide (DMSO) is a common chemical agent for DNA denaturation. In the present study, we investigate quantitatively the effects of different concentrations of DMSO on plasmid and linear DNA denaturation by atomic force microscopy (AFM) and UV spectrophotometry. We found that persistent length of DNA decreases significantly by adding a small amount of DMSO before ensemble DNA denaturation occurs; the persistence length of DNA in 3% DMSO solution decreases to 12 nm from about 50 nm without DMSO in solution. And local DNA denaturation occurs even at very low DMSO concentration (such as 0.1%), which can be directly observed in AFM imaging. Meanwhile, we observed the forming process of DNA contacts between different parts for plasmid DNA with increasing DMSO concentration. We suggest the initial mechanism of DNA denaturation as follows: DNA becomes more flexible due to the partial hydrogen bond braking in the presence of DMSO before local separation of the two complementary nucleotide chains. The persistent length of DNA decreases significantly by adding small amount of DMSO. Local DNA denaturation occurs even at very low DMSO concentration, which can be observed by atomic force microscopy directly.![]()
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Affiliation(s)
- Min Xu
- Department of Physics, Wenzhou University, Wenzhou 325035, China
| | - Tinghui Dai
- Department of Physics, Wenzhou University, Wenzhou 325035, China
| | - Yanwei Wang
- Department of Physics, Wenzhou University, Wenzhou 325035, China
| | - Guangcan Yang
- Department of Physics, Wenzhou University, Wenzhou 325035, China
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4
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Salerno D, Marrano CA, Cassina V, Cristofalo M, Shao Q, Finzi L, Mantegazza F, Dunlap D. Nanomechanics of negatively supercoiled diaminopurine-substituted DNA. Nucleic Acids Res 2021; 49:11778-11786. [PMID: 34718727 PMCID: PMC8599871 DOI: 10.1093/nar/gkab982] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 10/05/2021] [Accepted: 10/13/2021] [Indexed: 11/25/2022] Open
Abstract
Single molecule experiments have demonstrated a progressive transition from a B- to an L-form helix as DNA is gently stretched and progressively unwound. The particular sequence of a DNA segment defines both base stacking and hydrogen bonding that affect the partitioning and conformations of the two phases. Naturally or artificially modified bases alter H-bonds and base stacking and DNA with diaminopurine (DAP) replacing adenine was synthesized to produce linear fragments with triply hydrogen-bonded DAP:T base pairs. Both unmodified and DAP-substituted DNA transitioned from a B- to an L-helix under physiological conditions of mild tension and unwinding. This transition avoids writhing and the ease of this transition may prevent cumbersome topological rearrangements in genomic DNA that would require topoisomerase activity to resolve. L-DNA displayed about tenfold lower persistence length than B-DNA. However, left-handed DAP-substituted DNA was twice as stiff as unmodified L-DNA. Unmodified DNA and DAP-substituted DNA have very distinct mechanical characteristics at physiological levels of negative supercoiling and tension.
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Affiliation(s)
- Domenico Salerno
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, Università di Milano-Bicocca, via R. Follereau 3, Vedano al Lambro (MB), Italy
| | - Claudia Adriana Marrano
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, Università di Milano-Bicocca, via R. Follereau 3, Vedano al Lambro (MB), Italy
| | - Valeria Cassina
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, Università di Milano-Bicocca, via R. Follereau 3, Vedano al Lambro (MB), Italy
| | - Matteo Cristofalo
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, Università di Milano-Bicocca, via R. Follereau 3, Vedano al Lambro (MB), Italy
| | - Qing Shao
- Department of Physics, Emory University, Atlanta, GA USA
| | - Laura Finzi
- Department of Physics, Emory University, Atlanta, GA USA
| | - Francesco Mantegazza
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, Università di Milano-Bicocca, via R. Follereau 3, Vedano al Lambro (MB), Italy
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, GA USA
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5
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Sengar A, Ouldridge TE, Henrich O, Rovigatti L, Šulc P. A Primer on the oxDNA Model of DNA: When to Use it, How to Simulate it and How to Interpret the Results. Front Mol Biosci 2021; 8:693710. [PMID: 34235181 PMCID: PMC8256390 DOI: 10.3389/fmolb.2021.693710] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 05/27/2021] [Indexed: 11/13/2022] Open
Abstract
The oxDNA model of Deoxyribonucleic acid has been applied widely to systems in biology, biophysics and nanotechnology. It is currently available via two independent open source packages. Here we present a set of clearly documented exemplar simulations that simultaneously provide both an introduction to simulating the model, and a review of the model's fundamental properties. We outline how simulation results can be interpreted in terms of-and feed into our understanding of-less detailed models that operate at larger length scales, and provide guidance on whether simulating a system with oxDNA is worthwhile.
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Affiliation(s)
- A. Sengar
- Centre for Synthetic Biology, Department of Bioengineering, Imperial College London, London, United Kingdom
| | - T. E. Ouldridge
- Centre for Synthetic Biology, Department of Bioengineering, Imperial College London, London, United Kingdom
| | - O. Henrich
- Department of Physics, SUPA, University of Strathclyde, Glasgow, United Kingdom
| | - L. Rovigatti
- Department of Physics, Sapienza University of Rome, Rome, Italy
- CNR Institute of Complex Systems, Sapienza University of Rome, Rome, Italy
| | - P. Šulc
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ, United States
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States
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6
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Buglione E, Salerno D, Marrano CA, Cassina V, Vesco G, Nardo L, Dacasto M, Rigo R, Sissi C, Mantegazza F. Nanomechanics of G-quadruplexes within the promoter of the KIT oncogene. Nucleic Acids Res 2021; 49:4564-4573. [PMID: 33849064 PMCID: PMC8096272 DOI: 10.1093/nar/gkab079] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 01/07/2021] [Accepted: 04/09/2021] [Indexed: 12/31/2022] Open
Abstract
G-quadruplexes (G4s) are tetrahelical DNA structures stabilized by four guanines paired via Hoogsteen hydrogen bonds into quartets. While their presence within eukaryotic DNA is known to play a key role in regulatory processes, their functional mechanisms are still under investigation. In the present work, we analysed the nanomechanical properties of three G4s present within the promoter of the KIT proto-oncogene from a single-molecule point of view through the use of magnetic tweezers (MTs). The study of DNA extension fluctuations under negative supercoiling allowed us to identify a characteristic fingerprint of G4 folding. We further analysed the energetic contribution of G4 to the double-strand denaturation process in the presence of negative supercoiling, and we observed a reduction in the energy required for strands separation.
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Affiliation(s)
- Enrico Buglione
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Domenico Salerno
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Claudia Adriana Marrano
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Valeria Cassina
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Guglielmo Vesco
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Luca Nardo
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Mauro Dacasto
- Department of Comparative Biomedicine and Food Science, University of Padova, 35020 Legnaro (PD), Italy
| | - Riccardo Rigo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova (PD), Italy
| | - Claudia Sissi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova (PD), Italy.,Interdepartmental Research Center for Innovative Biotechnologies (CRIBI), University of Padova, 35121 Padova (PD), Italy
| | - Francesco Mantegazza
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
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7
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Souza JCP, Macedo LJA, Hassan A, Sedenho GC, Modenez IA, Crespilho FN. In Situ
and
Operando
Techniques for Investigating Electron Transfer in Biological Systems. ChemElectroChem 2020. [DOI: 10.1002/celc.202001327] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- João C. P. Souza
- São Carlos Institute of Chemistry University of São Paulo 13560-970 São Carlos São Paulo Brazil
- Campus Rio Verde Goiano Federal Institute of Education, Science and Technology 75901-970 Rio Verde Goiás Brazil
| | - Lucyano J. A. Macedo
- São Carlos Institute of Chemistry University of São Paulo 13560-970 São Carlos São Paulo Brazil
| | - Ayaz Hassan
- São Carlos Institute of Chemistry University of São Paulo 13560-970 São Carlos São Paulo Brazil
| | - Graziela C. Sedenho
- São Carlos Institute of Chemistry University of São Paulo 13560-970 São Carlos São Paulo Brazil
| | - Iago A. Modenez
- São Carlos Institute of Chemistry University of São Paulo 13560-970 São Carlos São Paulo Brazil
| | - Frank N. Crespilho
- São Carlos Institute of Chemistry University of São Paulo 13560-970 São Carlos São Paulo Brazil
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8
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Cristofalo M, Marrano CA, Salerno D, Corti R, Cassina V, Mammola A, Gherardi M, Sclavi B, Cosentino Lagomarsino M, Mantegazza F. Cooperative effects on the compaction of DNA fragments by the nucleoid protein H-NS and the crowding agent PEG probed by Magnetic Tweezers. Biochim Biophys Acta Gen Subj 2020; 1864:129725. [PMID: 32891648 DOI: 10.1016/j.bbagen.2020.129725] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 07/22/2020] [Accepted: 08/30/2020] [Indexed: 11/30/2022]
Abstract
BACKGROUND DNA bridging promoted by the H-NS protein, combined with the compaction induced by cellular crowding, plays a major role in the structuring of the E. coli genome. However, only few studies consider the effects of the physical interplay of these two factors in a controlled environment. METHODS We apply a single molecule technique (Magnetic Tweezers) to study the nanomechanics of compaction and folding kinetics of a 6 kb DNA fragment, induced by H-NS bridging and/or PEG crowding. RESULTS In the presence of H-NS alone, the DNA shows a step-wise collapse driven by the formation of multiple bridges, and little variations in the H-NS concentration-dependent unfolding force. Conversely, the DNA collapse force observed with PEG was highly dependent on the volume fraction of the crowding agent. The two limit cases were interpreted considering the models of loop formation in a pulled chain and pulling of an equilibrium globule respectively. CONCLUSIONS We observed an evident cooperative effect between H-NS activity and the depletion of forces induced by PEG. GENERAL SIGNIFICANCE Our data suggest a double role for H-NS in enhancing compaction while forming specific loops, which could be crucial in vivo for defining specific mesoscale domains in chromosomal regions in response to environmental changes.
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Affiliation(s)
- M Cristofalo
- School of Medicine and Surgery, Nanomedicine Center NANOMIB, University of Milano-Bicocca, via Raoul Follereau 3, 20854, Vedano al Lambro (MB), Italy
| | - C A Marrano
- School of Medicine and Surgery, Nanomedicine Center NANOMIB, University of Milano-Bicocca, via Raoul Follereau 3, 20854, Vedano al Lambro (MB), Italy
| | - D Salerno
- School of Medicine and Surgery, Nanomedicine Center NANOMIB, University of Milano-Bicocca, via Raoul Follereau 3, 20854, Vedano al Lambro (MB), Italy
| | - R Corti
- School of Medicine and Surgery, Nanomedicine Center NANOMIB, University of Milano-Bicocca, via Raoul Follereau 3, 20854, Vedano al Lambro (MB), Italy
| | - V Cassina
- School of Medicine and Surgery, Nanomedicine Center NANOMIB, University of Milano-Bicocca, via Raoul Follereau 3, 20854, Vedano al Lambro (MB), Italy
| | - A Mammola
- Università degli Studi di Milano, Via Celoria 16, 20133 Milano (MI), Italy
| | - M Gherardi
- Università degli Studi di Milano, Via Celoria 16, 20133 Milano (MI), Italy; IFOM, FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milano (MI), Italy; I.N.F.N. Sezione di Milano, Via Celoria 16, 20133 Milano (MI), Italy
| | - B Sclavi
- Université Pierre et Marie Curie, Institut de Biologie Paris Seine, 7-9 Quai Saint Bernard, 75005 Paris, France
| | - M Cosentino Lagomarsino
- Università degli Studi di Milano, Via Celoria 16, 20133 Milano (MI), Italy; IFOM, FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milano (MI), Italy; I.N.F.N. Sezione di Milano, Via Celoria 16, 20133 Milano (MI), Italy
| | - F Mantegazza
- School of Medicine and Surgery, Nanomedicine Center NANOMIB, University of Milano-Bicocca, via Raoul Follereau 3, 20854, Vedano al Lambro (MB), Italy.
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9
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Bao Y, Luo Z, Cui S. Environment-dependent single-chain mechanics of synthetic polymers and biomacromolecules by atomic force microscopy-based single-molecule force spectroscopy and the implications for advanced polymer materials. Chem Soc Rev 2020; 49:2799-2827. [PMID: 32236171 DOI: 10.1039/c9cs00855a] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
"The Tao begets the One. One begets all things of the world." This quote from Tao Te Ching is still inspiring for scientists in chemistry and materials science: The "One" can refer to a single molecule. A macroscopic material is composed of numerous molecules. Although the relationship between the properties of the single molecule and macroscopic material is not well understood yet, it is expected that a deeper understanding of the single-chain mechanics of macromolecules will certainly facilitate the development of materials science. Atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS) has been exploited extensively as a powerful tool to study the single-chain behaviors of macromolecules. In this review, we summarize the recent advances in the emerging field of environment-dependent single-chain mechanics of synthetic polymers and biomacromolecules by means of AFM-SMFS. First, the single-chain inherent elasticities of several typical linear macromolecules are introduced, which are also confirmed by one of three polymer models with theoretical elasticities of the corresponding macromolecules obtained from quantum mechanical (QM) calculations. Then, the effects of the external environments on the single-chain mechanics of synthetic polymers and biomacromolecules are reviewed. Finally, the impacts of single-chain mechanics of macromolecules on the development of polymer science especially polymer materials are illustrated.
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Affiliation(s)
- Yu Bao
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China.
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10
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Pinnapireddy SR, Giselbrecht J, Strehlow B, Janich C, Husteden C, Meister A, Loppnow H, Sedding D, Erdmann F, Hause G, Brezesinski G, Groth T, Langner A, Bakowsky U, Wölk C. A triple chain polycationic peptide-mimicking amphiphile - efficient DNA-transfer without co-lipids. Biomater Sci 2019; 8:232-249. [PMID: 31681923 DOI: 10.1039/c9bm01093a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Non-viral gene delivery in its current form is largely dependent upon the ability of a delivery vehicle to protect its cargo in the extracellular environment and release it efficiently inside the target cell. Also a simple delivery system is required to simplify a GMP conform production if a marketing authorization is striven for. This work addresses these problems. We have developed a synthetic polycationic peptide-mimicking amphiphile, namely DiTT4, which shows efficient transfection rates and good biocompatibility without the use of a co-lipid in the formulation. The lipid-nucleic acid complex (lipoplex) was characterized at the structural (electron microscopy), physical (laser Doppler velocimetry and atomic force microscopy) and molecular levels (X-ray scattering). Stability studies of the lipoplexes in the presence of serum and heparin indicated a stable formation capable of protecting the cargo against the extracellular milieu. Hemocompatibility studies (hemolysis, complement activation and erythrocyte aggregation) demonstrated the biocompatibility of the formulation for systemic administration. The transfection efficiency was assessed in vitro using the GFP assay and confocal laser scanning microscopy studies. With the chorioallantoic membrane model, an animal replacement model according to the 3R strategy (replacement, refinement, and reduction), initial in vivo experiments were performed which demonstrate fast and efficient transfection in complex tissues and excellent biocompatibility.
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Affiliation(s)
- Shashank Reddy Pinnapireddy
- Department of Pharmaceutics and Biopharmaceutics, University of Marburg, Robert-Koch-Str. 4, 35037, Marburg, Germany.
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11
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Borberg E, Zverzhinetsky M, Krivitsky A, Kosloff A, Heifler O, Degabli G, Soroka HP, Fainaro RS, Burstein L, Reuveni S, Diamant H, Krivitsky V, Patolsky F. Light-Controlled Selective Collection-and-Release of Biomolecules by an On-Chip Nanostructured Device. NANO LETTERS 2019; 19:5868-5878. [PMID: 31381354 DOI: 10.1021/acs.nanolett.9b01323] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The analysis of biosamples, e.g., blood, is a ubiquitous task of proteomics, genomics, and biosensing fields; yet, it still faces multiple challenges, one of the greatest being the selective separation and detection of target proteins from these complex biosamples. Here, we demonstrate the development of an on-chip light-triggered reusable nanostructured selective and quantitative protein separation and preconcentration platform for the direct analysis of complex biosamples. The on-chip selective separation of required protein analytes from raw biosamples is performed using antibody-photoacid-modified Si nanopillars vertical arrays (SiNPs) of ultralarge binding surface area and enormously high binding affinity, followed by the light-controlled rapid release of the tightly bound target proteins in a controlled liquid media. Two important experimental observations are presented: (1) the first demonstration on the control of biological reaction binding affinity by the nanostructuring of the capturing surface, leading to highly efficient protein collection capabilities, and (2) the light-triggered switching of the highly sticky binding surfaces into highly reflective nonbinding surfaces, leading to the rapid and quantitative release of the originally tightly bound protein species. Both of these two novel behaviors were theoretically and experimentally investigated. Importantly, this is the first demonstration of a three-dimensional (3D) SiNPs on-chip filter with ultralarge binding surface area and reversible light-controlled quantitative release of adsorbed biomolecules for direct purification of blood samples, able to selectively collect and separate specific low abundant proteins, while easily removing unwanted blood components (proteins, cells) and achieving desalting results, without the requirement of time-consuming centrifugation steps, the use of desalting membranes, or affinity columns.
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Affiliation(s)
- Ella Borberg
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Marina Zverzhinetsky
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Adva Krivitsky
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine , Tel Aviv University , Tel Aviv 69978 , Israel
| | - Alon Kosloff
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Omri Heifler
- Department of Materials Science and Engineering, The Iby and Aladar Fleischman Faculty of Engineering , Tel Aviv University , Tel Aviv 69978 , Israel
| | - Gal Degabli
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Hagit Peretz Soroka
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Ronit Satchi Fainaro
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine , Tel Aviv University , Tel Aviv 69978 , Israel
| | - Larisa Burstein
- The Wolfson Applied Materials Research Centre , Tel-Aviv University , Tel-Aviv 69978 , Israel
| | - Shlomi Reuveni
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Haim Diamant
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Vadim Krivitsky
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
| | - Fernando Patolsky
- School of Chemistry, Faculty of Exact Sciences , Tel Aviv University , Tel Aviv , 69978 , Israel
- Department of Materials Science and Engineering, The Iby and Aladar Fleischman Faculty of Engineering , Tel Aviv University , Tel Aviv 69978 , Israel
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12
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Cristofalo M, Kovari D, Corti R, Salerno D, Cassina V, Dunlap D, Mantegazza F. Nanomechanics of Diaminopurine-Substituted DNA. Biophys J 2019; 116:760-771. [PMID: 30795872 DOI: 10.1016/j.bpj.2019.01.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 01/23/2019] [Accepted: 01/24/2019] [Indexed: 10/27/2022] Open
Abstract
2,6-diaminopurine (DAP) is a nucleobase analog of adenine. When incorporated into double-stranded DNA (dsDNA), it forms three hydrogen bonds with thymine. Rare in nature, DAP substitution alters the physical characteristics of a DNA molecule without sacrificing sequence specificity. Here, we show that in addition to stabilizing double-strand hybridization, DAP substitution also changes the mechanical and conformational properties of dsDNA. Thermal melting experiments reveal that DAP substitution raises melting temperatures without diminishing sequence-dependent effects. Using a combination of atomic force microscopy (AFM), magnetic tweezer (MT) nanomechanical assays, and circular dichroism spectroscopy, we demonstrate that DAP substitution increases the flexural rigidity of dsDNA yet also facilitates conformational shifts, which manifest as changes in molecule length. DAP substitution increases both the static and dynamic persistence length of DNA (measured by AFM and MT, respectively). In the static case (AFM), in which tension is not applied to the molecule, the contour length of DAP-DNA appears shorter than wild-type (WT)-DNA; under tension (MT), they have similar dynamic contour lengths. At tensions above 60 pN, WT-DNA undergoes characteristic overstretching because of strand separation (tension-induced melting) and spontaneous adoption of a conformation termed S-DNA. Cyclic overstretching and relaxation of WT-DNA at near-zero loading rates typically yields hysteresis, indicative of tension-induced melting; conversely, cyclic stretching of DAP-DNA showed little or no hysteresis, consistent with the adoption of the S-form, similar to what has been reported for GC-rich sequences. However, DAP-DNA overstretching is distinct from GC-rich overstretching in that it happens at a significantly lower tension. In physiological salt conditions, evenly mixed AT/GC DNA typically overstretches around 60 pN. GC-rich sequences overstretch at similar if not slightly higher tensions. Here, we show that DAP-DNA overstretches at 52 pN. In summary, DAP substitution decreases the overall stability of the B-form double helix, biasing toward non-B-form DNA helix conformations at zero tension and facilitating the B-to-S transition at high tension.
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Affiliation(s)
- Matteo Cristofalo
- School of Medicine and Surgery, Università di Milano-Bicocca, Monza (MB), Italy
| | - Daniel Kovari
- Department of Physics, Emory University, Atlanta, Georgia
| | - Roberta Corti
- School of Medicine and Surgery, Università di Milano-Bicocca, Monza (MB), Italy
| | - Domenico Salerno
- School of Medicine and Surgery, Università di Milano-Bicocca, Monza (MB), Italy.
| | - Valeria Cassina
- School of Medicine and Surgery, Università di Milano-Bicocca, Monza (MB), Italy
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, Georgia.
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13
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Kriegel F, Matek C, Dršata T, Kulenkampff K, Tschirpke S, Zacharias M, Lankaš F, Lipfert J. The temperature dependence of the helical twist of DNA. Nucleic Acids Res 2018; 46:7998-8009. [PMID: 30053087 PMCID: PMC6125625 DOI: 10.1093/nar/gky599] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 06/08/2018] [Accepted: 07/20/2018] [Indexed: 01/11/2023] Open
Abstract
DNA is the carrier of all cellular genetic information and increasingly used in nanotechnology. Quantitative understanding and optimization of its functions requires precise experimental characterization and accurate modeling of DNA properties. A defining feature of DNA is its helicity. DNA unwinds with increasing temperature, even for temperatures well below the melting temperature. However, accurate quantitation of DNA unwinding under external forces and a microscopic understanding of the corresponding structural changes are currently lacking. Here we combine single-molecule magnetic tweezers measurements with atomistic molecular dynamics and coarse-grained simulations to obtain a comprehensive view of the temperature dependence of DNA twist. Experimentally, we find that DNA twist changes by ΔTw(T) = (-11.0 ± 1.2)°/(°C·kbp), independent of applied force, in the range of forces where torque-induced melting is negligible. Our atomistic simulations predict ΔTw(T) = (-11.1 ± 0.3)°/(°C·kbp), in quantitative agreement with experiments, and suggest that the untwisting of DNA with temperature is predominantly due to changes in DNA structure for defined backbone substates, while the effects of changes in substate populations are minor. Coarse-grained simulations using the oxDNA framework yield a value of ΔTw(T) = (-6.4 ± 0.2)°/(°C·kbp) in semi-quantitative agreement with experiments.
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Affiliation(s)
- Franziska Kriegel
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstr. 54, 80799 Munich, Germany
| | - Christian Matek
- Technical University of Munich and Institute of Computational Biology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
| | - Tomáš Dršata
- Department of Informatics and Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Klara Kulenkampff
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstr. 54, 80799 Munich, Germany
| | - Sophie Tschirpke
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstr. 54, 80799 Munich, Germany
| | - Martin Zacharias
- Physics-Department T38, Technical University of Munich, James-Franck-Strasse 1, 85748 Garching, Germany
| | - Filip Lankaš
- Department of Informatics and Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Jan Lipfert
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstr. 54, 80799 Munich, Germany
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14
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Cai G, Yu Z, Ren R, Tang D. Exciton-Plasmon Interaction between AuNPs/Graphene Nanohybrids and CdS Quantum Dots/TiO 2 for Photoelectrochemical Aptasensing of Prostate-Specific Antigen. ACS Sens 2018; 3:632-639. [PMID: 29465232 DOI: 10.1021/acssensors.7b00899] [Citation(s) in RCA: 198] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A competitive-displacement reaction strategy based on target-induced dissociation of gold nanoparticle coated graphene nanosheet (AuNPs/GN) from CdS quantum dot functionalized mesoporous titanium dioxide (CdS QDs/TiO2) was designed for the sensitive photoelectrochemical (PEC) aptasensing of prostate-specific antigen (PSA) through the exciton-plasmon interaction (EPI) between CdS QDs and AuNPs. To construct such an aptasensing system, capture DNA was initially conjugated covalently onto CdS QDs/TiO2-modified electrode, and then AuNPs/GN-labeled PSA aptamer was bound onto biofunctionalized CdS QDs/TiO2 via hybridization chain reaction of partial bases with capture DNA. Introduction of AuNPs/GN efficiently quenched the photocurrent of CdS QDs/TiO2 thanks to energy transfer. Upon addition of target PSA, the sandwiched aptamer between CdS QDs/TiO2 and AuNPs/GN reacted with the analyte analyte, thus resulting in the dissociation of AuNPs/GN from the CdS QDs/TiO2 to increase the photocurrent. Under optimum conditions, the aptasensing platform exhibited a high sensitivity for PSA detection within a dynamic linear range of 1.0 pg/mL to 8.0 ng/mL at a low limitat of detection of 0.52 pg/mL. The interparticle distance of exciton-plasmon interaction and contents of AuNPs corresponding to EPI effect in this system were also studied. Good selectivity and high reproducibility were obtained for the analysis of target PSA. Importantly, the accuracy and matrix effect of PEC aptasensor was evaluated for the determination of human serum specimens and newborn calf serum-diluted PSA standards, giving a well-matched result with the referenced PSA ELISA kit.
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Affiliation(s)
- Guoneng Cai
- Key Laboratory for Analytical Science of Food Safety and Biology (MOE & Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 35011168, People’s Republic of China
| | - Zhengzhong Yu
- Key Laboratory for Analytical Science of Food Safety and Biology (MOE & Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 35011168, People’s Republic of China
| | - Rongrong Ren
- Key Laboratory for Analytical Science of Food Safety and Biology (MOE & Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 35011168, People’s Republic of China
| | - Dianping Tang
- Key Laboratory for Analytical Science of Food Safety and Biology (MOE & Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 35011168, People’s Republic of China
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15
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Martínez-Santiago CJ, Quiñones E. Magnetic modulation of the unbraiding dynamics of pairs of DNA molecules to model the system as an intermittent oscillator. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2017.12.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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16
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Racko D, Benedetti F, Dorier J, Stasiak A. Transcription-induced supercoiling as the driving force of chromatin loop extrusion during formation of TADs in interphase chromosomes. Nucleic Acids Res 2018; 46:1648-1660. [PMID: 29140466 PMCID: PMC5829651 DOI: 10.1093/nar/gkx1123] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 10/03/2017] [Accepted: 10/30/2017] [Indexed: 12/16/2022] Open
Abstract
Using molecular dynamics simulations, we show here that growing plectonemes resulting from transcription-induced supercoiling have the ability to actively push cohesin rings along chromatin fibres. The pushing direction is such that within each topologically associating domain (TAD) cohesin rings forming handcuffs move from the source of supercoiling, constituted by RNA polymerase with associated DNA topoisomerase TOP1, towards borders of TADs, where supercoiling is released by topoisomerase TOPIIB. Cohesin handcuffs are pushed by continuous flux of supercoiling that is generated by transcription and is then progressively released by action of TOPIIB located at TADs borders. Our model explains what can be the driving force of chromatin loop extrusion and how it can be ensured that loops grow quickly and in a good direction. In addition, the supercoiling-driven loop extrusion mechanism is consistent with earlier explanations proposing why TADs flanked by convergent CTCF binding sites form more stable chromatin loops than TADs flanked by divergent CTCF binding sites. We discuss the role of supercoiling in stimulating enhancer promoter contacts and propose that transcription of eRNA sends the first wave of supercoiling that can activate mRNA transcription in a given TAD.
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Affiliation(s)
- Dusan Racko
- Center for Integrative Genomics, University of Lausanne, 1015-Lausanne, Switzerland
- SIB Swiss Institute of Bioinformatics, 1015-Lausanne, Switzerland
- Polymer Institute of the Slovak Academy of Sciences, 842 36 Bratislava, Slovakia
| | - Fabrizio Benedetti
- Center for Integrative Genomics, University of Lausanne, 1015-Lausanne, Switzerland
- Vital-IT, SIB Swiss Institute of Bioinformatics, 1015-Lausanne, Switzerland
| | - Julien Dorier
- Center for Integrative Genomics, University of Lausanne, 1015-Lausanne, Switzerland
- Vital-IT, SIB Swiss Institute of Bioinformatics, 1015-Lausanne, Switzerland
| | - Andrzej Stasiak
- Center for Integrative Genomics, University of Lausanne, 1015-Lausanne, Switzerland
- SIB Swiss Institute of Bioinformatics, 1015-Lausanne, Switzerland
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17
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Benedetti F, Racko D, Dorier J, Burnier Y, Stasiak A. Transcription-induced supercoiling explains formation of self-interacting chromatin domains in S. pombe. Nucleic Acids Res 2017; 45:9850-9859. [PMID: 28973473 PMCID: PMC5622301 DOI: 10.1093/nar/gkx716] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 08/04/2017] [Indexed: 12/12/2022] Open
Abstract
The question of how self-interacting chromatin domains in interphase chromosomes are structured and generated dominates current discussions on eukaryotic chromosomes. Numerical simulations using standard polymer models have been helpful in testing the validity of various models of chromosome organization. Experimental contact maps can be compared with simulated contact maps and thus verify how good is the model. With increasing resolution of experimental contact maps, it became apparent though that active processes need to be introduced into models to recapitulate the experimental data. Since transcribing RNA polymerases are very strong molecular motors that induce axial rotation of transcribed DNA, we present here models that include such rotational motors. We also include into our models swivels and sites for intersegmental passages that account for action of DNA topoisomerases releasing torsional stress. Using these elements in our models, we show that transcription-induced supercoiling generated in the regions with divergent-transcription and supercoiling relaxation occurring between these regions are sufficient to explain formation of self-interacting chromatin domains in chromosomes of fission yeast (S. pombe).
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Affiliation(s)
- Fabrizio Benedetti
- Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.,Vital-IT, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Dusan Racko
- Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.,SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland.,Polymer Institute of the Slovak Academy of Sciences, 842 36 Bratislava, Slovakia
| | - Julien Dorier
- Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.,Vital-IT, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Yannis Burnier
- Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.,Institute of Theoretical Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Andrzej Stasiak
- Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.,SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
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18
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Kriegel F, Ermann N, Forbes R, Dulin D, Dekker NH, Lipfert J. Probing the salt dependence of the torsional stiffness of DNA by multiplexed magnetic torque tweezers. Nucleic Acids Res 2017; 45:5920-5929. [PMID: 28460037 PMCID: PMC5449586 DOI: 10.1093/nar/gkx280] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 04/28/2017] [Indexed: 12/14/2022] Open
Abstract
The mechanical properties of DNA fundamentally constrain and enable the storage and transmission of genetic information and its use in DNA nanotechnology. Many properties of DNA depend on the ionic environment due to its highly charged backbone. In particular, both theoretical analyses and direct single-molecule experiments have shown its bending stiffness to depend on salt concentration. In contrast, the salt-dependence of the twist stiffness of DNA is much less explored. Here, we employ optimized multiplexed magnetic torque tweezers to study the torsional stiffness of DNA under varying salt conditions as a function of stretching force. At low forces (<3 pN), the effective torsional stiffness is ∼10% smaller for high salt conditions (500 mM NaCl or 10 mM MgCl2) compared to lower salt concentrations (20 mM NaCl and 100 mM NaCl). These differences, however, can be accounted for by taking into account the known salt dependence of the bending stiffness. In addition, the measured high-force (6.5 pN) torsional stiffness values of C = 103 ± 4 nm are identical, within experimental errors, for all tested salt concentration, suggesting that the intrinsic torsional stiffness of DNA does not depend on salt.
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Affiliation(s)
- Franziska Kriegel
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstrasse 54, 80799 Munich, Germany
| | - Niklas Ermann
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstrasse 54, 80799 Munich, Germany
| | - Ruaridh Forbes
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - David Dulin
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.,Junior Research Group 2, Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Hartmannstrasse 14, 91052 Erlangen, Germany
| | - Nynke H Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Jan Lipfert
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, Amalienstrasse 54, 80799 Munich, Germany
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19
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Burnham DR, Nijholt B, De Vlaminck I, Quan J, Yusufzai T, Dekker C. Annealing helicase HARP closes RPA-stabilized DNA bubbles non-processively. Nucleic Acids Res 2017; 45:4687-4695. [PMID: 28334870 PMCID: PMC5416776 DOI: 10.1093/nar/gkx147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 02/27/2017] [Indexed: 02/06/2023] Open
Abstract
We investigate the mechanistic nature of the Snf2 family protein HARP, mutations of which are responsible for Schimke immuno-osseous dysplasia. Using a single-molecule magnetic tweezers assay, we construct RPA-stabilized DNA bubbles within torsionally constrained DNA to investigate the annealing action of HARP on a physiologically relevant substrate. We find that HARP closes RPA-stabilized bubbles in a slow reaction, taking on the order of tens of minutes for ∼600 bp of DNA to be re-annealed. The data indicate that DNA re-anneals through the removal of RPA, which is observed as clear steps in the bubble-closing traces. The dependence of the closing rate on both ionic strength and HARP concentration indicates that removal of RPA occurs via an association-dissociation mechanism where HARP does not remain associated with the DNA. The enzyme exhibits classical Michaelis–Menten kinetics and acts cooperatively with a Hill coefficient of 3 ± 1. Our work also allows the determination of some important features of RPA-bubble structures at low supercoiling, including the existence of multiple bubbles and that RPA molecules are mis-registered on the two strands.
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Affiliation(s)
- Daniel R Burnham
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
| | - Bas Nijholt
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
| | - Iwijn De Vlaminck
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
| | - Jinhua Quan
- Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA
| | - Timur Yusufzai
- Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
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20
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Salerno D, Beretta GL, Zanchetta G, Brioschi S, Cristofalo M, Missana N, Nardo L, Cassina V, Tempestini A, Giovannoni R, Cerrito MG, Zaffaroni N, Bellini T, Mantegazza F. Platinum-Based Drugs and DNA Interactions Studied by Single-Molecule and Bulk Measurements. Biophys J 2017; 110:2151-61. [PMID: 27224480 DOI: 10.1016/j.bpj.2016.02.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 01/07/2016] [Accepted: 02/09/2016] [Indexed: 11/24/2022] Open
Abstract
Platinum-containing molecules are widely used as anticancer drugs. These molecules exert cytotoxic effects by binding to DNA through various mechanisms. The binding between DNA and platinum-based drugs hinders the opening of DNA, and therefore, DNA duplication and transcription are severely hampered. Overall, impeding the above-mentioned important DNA mechanisms results in irreversible DNA damage and the induction of apoptosis. Several molecules, including multinuclear platinum compounds, belong to the family of platinum drugs, and there is a body of research devoted to developing more efficient and less toxic versions of these compounds. In this study, we combined different biophysical methods, including single-molecule assays (magnetic tweezers) and bulk experiments (ultraviolet absorption for thermal denaturation) to analyze the differential stability of double-stranded DNA in complex with either cisplatin or multinuclear platinum agents. Specifically, we analyzed how the binding of BBR3005 and BBR3464, two representative multinuclear platinum-based compounds, to DNA affects its stability as compared with cisplatin binding. Our results suggest that single-molecule approaches can provide insights into the drug-DNA interactions that underlie drug potency and provide information that is complementary to that generated from bulk analysis; thus, single-molecule approaches have the potential to facilitate the selection and design of optimized drug compounds. In particular, relevant differences in DNA stability at the single-molecule level are demonstrated by analyzing nanomechanically induced DNA denaturation. On the basis of the comparison between the single-molecule and bulk analyses, we suggest that transplatinated drugs are able to locally destabilize small portions of the DNA chain, whereas other regions are stabilized.
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Affiliation(s)
| | - Giovanni L Beretta
- Dipartimento di Oncologia Sperimentale e Medicina Molecolare, Fondazione IRCCS Istituto Nazionale Tumori, Milano, Italy
| | - Giuliano Zanchetta
- Dipartimento di Biotecnologie Mediche e Medicina Translazionale, Università degli Studi di Milano, Segrate, Italy
| | - Simone Brioschi
- School of Medicine, Università di Milano-Bicocca, Monza, Italy
| | | | - Natalia Missana
- School of Medicine, Università di Milano-Bicocca, Monza, Italy
| | - Luca Nardo
- School of Medicine, Università di Milano-Bicocca, Monza, Italy
| | - Valeria Cassina
- School of Medicine, Università di Milano-Bicocca, Monza, Italy
| | | | - Roberto Giovannoni
- Dipartimento di Scienze Chirurgiche, Università di Milano-Bicocca, Monza, Italy
| | | | - Nadia Zaffaroni
- Dipartimento di Oncologia Sperimentale e Medicina Molecolare, Fondazione IRCCS Istituto Nazionale Tumori, Milano, Italy
| | - Tommaso Bellini
- Dipartimento di Biotecnologie Mediche e Medicina Translazionale, Università degli Studi di Milano, Segrate, Italy
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21
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Probing the mechanical properties, conformational changes, and interactions of nucleic acids with magnetic tweezers. J Struct Biol 2016; 197:26-36. [PMID: 27368129 DOI: 10.1016/j.jsb.2016.06.022] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 05/06/2016] [Accepted: 06/28/2016] [Indexed: 11/21/2022]
Abstract
Nucleic acids are central to the storage and transmission of genetic information. Mechanical properties, along with their sequence, both enable and fundamentally constrain the biological functions of DNA and RNA. For small deformations from the equilibrium conformations, nucleic acids are well described by an isotropic elastic rod model. However, external forces and torsional strains can induce conformational changes, giving rise to a complex force-torque phase diagram. This review focuses on magnetic tweezers as a powerful tool to precisely determine both the elastic parameters and conformational transitions of nucleic acids under external forces and torques at the single-molecule level. We review several variations of magnetic tweezers, in particular conventional magnetic tweezers, freely orbiting magnetic tweezers and magnetic torque tweezers, and discuss their characteristic capabilities. We then describe the elastic rod model for DNA and RNA and discuss conformational changes induced by mechanical stress. The focus lies on the responses to torque and twist, which are crucial in the mechanics and interactions of nucleic acids and can directly be measured using magnetic tweezers. We conclude by highlighting several recent studies of nucleic acid-protein and nucleic acid-small-molecule interactions as further applications of magnetic tweezers and give an outlook of some exciting developments to come.
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22
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Mosayebi M, Louis AA, Doye JPK, Ouldridge TE. Force-Induced Rupture of a DNA Duplex: From Fundamentals to Force Sensors. ACS NANO 2015; 9:11993-2003. [PMID: 26575598 DOI: 10.1021/acsnano.5b04726] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The rupture of double-stranded DNA under stress is a key process in biophysics and nanotechnology. In this article, we consider the shear-induced rupture of short DNA duplexes, a system that has been given new importance by recently designed force sensors and nanotechnological devices. We argue that rupture must be understood as an activated process, where the duplex state is metastable and the strands will separate in a finite time that depends on the duplex length and the force applied. Thus, the critical shearing force required to rupture a duplex depends strongly on the time scale of observation. We use simple models of DNA to show that this approach naturally captures the observed dependence of the force required to rupture a duplex within a given time on duplex length. In particular, this critical force is zero for the shortest duplexes, before rising sharply and then plateauing in the long length limit. The prevailing approach, based on identifying when the presence of each additional base pair within the duplex is thermodynamically unfavorable rather than allowing for metastability, does not predict a time-scale-dependent critical force and does not naturally incorporate a critical force of zero for the shortest duplexes. We demonstrate that our findings have important consequences for the behavior of a new force-sensing nanodevice, which operates in a mixed mode that interpolates between shearing and unzipping. At a fixed time scale and duplex length, the critical force exhibits a sigmoidal dependence on the fraction of the duplex that is subject to shearing.
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Affiliation(s)
- Majid Mosayebi
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom
- School of Physics, Institute for Research in Fundamental Sciences (IPM) , Tehran 19538-33511, Iran
| | - Ard A Louis
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford , 1 Keble Road, Oxford OX1 3NP, United Kingdom
| | - Jonathan P K Doye
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Thomas E Ouldridge
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford , 1 Keble Road, Oxford OX1 3NP, United Kingdom
- Department of Mathematics, Imperial College , 180 Queen's Gate, London SW7 2AZ, United Kingdom
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23
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Vlijm R, v.d. Torre J, Dekker C. Counterintuitive DNA Sequence Dependence in Supercoiling-Induced DNA Melting. PLoS One 2015; 10:e0141576. [PMID: 26513573 PMCID: PMC4625975 DOI: 10.1371/journal.pone.0141576] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/09/2015] [Indexed: 11/19/2022] Open
Abstract
The metabolism of DNA in cells relies on the balance between hybridized double-stranded DNA (dsDNA) and local de-hybridized regions of ssDNA that provide access to binding proteins. Traditional melting experiments, in which short pieces of dsDNA are heated up until the point of melting into ssDNA, have determined that AT-rich sequences have a lower binding energy than GC-rich sequences. In cells, however, the double-stranded backbone of DNA is destabilized by negative supercoiling, and not by temperature. To investigate what the effect of GC content is on DNA melting induced by negative supercoiling, we studied DNA molecules with a GC content ranging from 38% to 77%, using single-molecule magnetic tweezer measurements in which the length of a single DNA molecule is measured as a function of applied stretching force and supercoiling density. At low force (<0.5pN), supercoiling results into twisting of the dsDNA backbone and loop formation (plectonemes), without inducing any DNA melting. This process was not influenced by the DNA sequence. When negative supercoiling is introduced at increasing force, local melting of DNA is introduced. We measured for the different DNA molecules a characteristic force Fchar, at which negative supercoiling induces local melting of the dsDNA. Surprisingly, GC-rich sequences melt at lower forces than AT-rich sequences: Fchar = 0.56pN for 77% GC but 0.73pN for 38% GC. An explanation for this counterintuitive effect is provided by the realization that supercoiling densities of a few percent only induce melting of a few percent of the base pairs. As a consequence, denaturation bubbles occur in local AT-rich regions and the sequence-dependent effect arises from an increased DNA bending/torsional energy associated with the plectonemes. This new insight indicates that an increased GC-content adjacent to AT-rich DNA regions will enhance local opening of the double-stranded DNA helix.
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Affiliation(s)
- Rifka Vlijm
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jaco v.d. Torre
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
- * E-mail:
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24
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Peretz-Soroka H, Pevzner A, Davidi G, Naddaka V, Kwiat M, Huppert D, Patolsky F. Manipulating and Monitoring On-Surface Biological Reactions by Light-Triggered Local pH Alterations. NANO LETTERS 2015; 15:4758-4768. [PMID: 26086686 DOI: 10.1021/acs.nanolett.5b01578] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Significant research efforts have been dedicated to the integration of biological species with electronic elements to yield smart bioelectronic devices. The integration of DNA, proteins, and whole living cells and tissues with electronic devices has been developed into numerous intriguing applications. In particular, the quantitative detection of biological species and monitoring of biological processes are both critical to numerous areas of medical and life sciences. Nevertheless, most current approaches merely focus on the "monitoring" of chemical processes taking place on the sensing surfaces, and little efforts have been invested in the conception of sensitive devices that can simultaneously "control" and "monitor" chemical and biological reactions by the application of on-surface reversible stimuli. Here, we demonstrate the light-controlled fine modulation of surface pH by the use of photoactive molecularly modified nanomaterials. Through the use of nanowire-based FET devices, we showed the capability of modulating the on-surface pH, by intensity-controlled light stimulus. This allowed us simultaneously and locally to control and monitor pH-sensitive biological reactions on the nanodevices surfaces, such as the local activation and inhibition of proteolytic enzymatic processes, as well as dissociation of antigen-antibody binding interactions. The demonstrated capability of locally modulating the on-surface effective pH, by a light stimuli, may be further applied in the local control of on-surface DNA hybridization/dehybridization processes, activation or inhibition of living cells processes, local switching of cellular function, local photoactivation of neuronal networks with single cell resolution and so forth.
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Affiliation(s)
- Hagit Peretz-Soroka
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Alexander Pevzner
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Guy Davidi
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Vladimir Naddaka
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Moria Kwiat
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Fernando Patolsky
- †School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
- ‡The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel
- §Department of Materials Science and Engineering, the Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
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25
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Plectoneme tip bubbles: coupled denaturation and writhing in supercoiled DNA. Sci Rep 2015; 5:7655. [PMID: 25563652 PMCID: PMC5224516 DOI: 10.1038/srep07655] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 12/02/2014] [Indexed: 02/07/2023] Open
Abstract
We predict a novel conformational regime for DNA, where denaturation bubbles form at the tips of plectonemes, and study its properties using coarse-grained simulations. For negative supercoiling, this regime lies between bubble-dominated and plectoneme-dominated phases, and explains the broad transition between the two observed in experiment. Tip bubbles cause localisation of plectonemes within thermodynamically weaker AT-rich sequences, and can greatly suppress plectoneme diffusion by a pinning mechanism. They occur for supercoiling densities and forces that are typically encountered for DNA in vivo, and may be exploited for biological control of genomic processes.
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26
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Huang H, Hong X, Liu F, Li N. A simple approach to study the conformational switching of i-motif DNA by fluorescence anisotropy. Analyst 2015; 140:5987-91. [DOI: 10.1039/c5an01011j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Fluorescence anisotropy is a simple, reliable and sensitive approach to study the conformational switching of the i-motif structure.
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Affiliation(s)
- Hongduan Huang
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education
- Institute of Analytical Chemistry
- College of Chemistry and Molecular Engineering
- Peking University
| | - Xinying Hong
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education
- Institute of Analytical Chemistry
- College of Chemistry and Molecular Engineering
- Peking University
| | - Feng Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education
- Institute of Analytical Chemistry
- College of Chemistry and Molecular Engineering
- Peking University
| | - Na Li
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education
- Institute of Analytical Chemistry
- College of Chemistry and Molecular Engineering
- Peking University
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27
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Burnham DR, De Vlaminck I, Henighan T, Dekker C. Skewed brownian fluctuations in single-molecule magnetic tweezers. PLoS One 2014; 9:e108271. [PMID: 25265383 PMCID: PMC4180755 DOI: 10.1371/journal.pone.0108271] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 08/26/2014] [Indexed: 11/18/2022] Open
Abstract
Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, here we demonstrate that nearby surfaces and the non-linear elasticity of DNA can skew the distribution. Through experiment and simulations, we show that such a skewing leads to inaccurate position measurements which significantly affect the extracted DNA extension and mechanical properties, leading to up to two-fold errors in measured DNA persistence length. We develop a simple, robust and easily implemented method to correct for such mismeasurements.
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Affiliation(s)
- Daniel R. Burnham
- Delft University of Technology, Kavli Institute of Nanoscience, Department of Bionanoscience, Delft, The Netherlands
| | - Iwijn De Vlaminck
- Delft University of Technology, Kavli Institute of Nanoscience, Department of Bionanoscience, Delft, The Netherlands
| | - Thomas Henighan
- Delft University of Technology, Kavli Institute of Nanoscience, Department of Bionanoscience, Delft, The Netherlands
| | - Cees Dekker
- Delft University of Technology, Kavli Institute of Nanoscience, Department of Bionanoscience, Delft, The Netherlands
- * E-mail:
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28
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Nisoli C, Bishop AR. Thermomechanical stability and mechanochemical response of DNA: A minimal mesoscale model. J Chem Phys 2014; 141:115101. [DOI: 10.1063/1.4895724] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Affiliation(s)
- Cristiano Nisoli
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - A. R. Bishop
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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29
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Galburt EA, Tomko EJ, Stump WT, Ruiz Manzano A. Force-dependent melting of supercoiled DNA at thermophilic temperatures. Biophys Chem 2014; 187-188:23-8. [PMID: 24486433 DOI: 10.1016/j.bpc.2014.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 01/07/2014] [Accepted: 01/07/2014] [Indexed: 11/28/2022]
Abstract
Local DNA opening plays an important role in DNA metabolism as the double-helix must be melted before the information contained within may be accessed. Cells finely tune the torsional state of their genomes to strike a balance between stability and accessibility. For example, while mesophilic life forms maintain negatively superhelical genomes, thermophilic life forms use unique mechanisms to maintain relaxed or even positively supercoiled genomes. Here, we use a single-molecule magnetic tweezers approach to quantify the force-dependent equilibrium between DNA melting and supercoiling at high temperatures populated by Thermophiles. We show that negatively supercoiled DNA denatures at 0.5 pN lower tension at thermophilic vs. mesophilic temperatures. This work demonstrates the ability to monitor DNA supercoiling at high temperature and opens the possibility to perform magnetic tweezers assays on thermophilic systems. The data allow for an estimation of the relative energies of base-pairing and DNA bending as a function of temperature and support speculation as to different general mechanisms of DNA opening in different environments. Lastly, our results imply that average in vivo DNA tensions range between 0.3 and 1.1 pN.
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Affiliation(s)
- E A Galburt
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - E J Tomko
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - W T Stump
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - A Ruiz Manzano
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
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30
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Swoboda M, Grieb MS, Hahn S, Schlierf M. Measuring two at the same time: combining magnetic tweezers with single-molecule FRET. EXPERIENTIA SUPPLEMENTUM (2012) 2014; 105:253-76. [PMID: 25095999 DOI: 10.1007/978-3-0348-0856-9_12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Molecular machines are the workhorses of the cell that efficiently convert chemical energy into mechanical motion through conformational changes. They can be considered powerful machines, exerting forces and torque on the molecular level of several piconewtons and piconewton-nanometer, respectively. For studying translocation and conformational changes of these machines, fluorescence methods, like FRET, as well as "mechanical" methods, like optical and magnetic tweezers, have proven well suited over the past decades. One of the current challenges in the field of molecular machines is gaining maximal information from single-molecule experiments by simultaneously measuring translocation, conformational changes, and forces exerted by these machines. In this chapter, we describe the combination of magnetic tweezers with single-molecule FRET for orthogonal simultaneous readout to maximize the information gained in single-molecule experiments.
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Affiliation(s)
- Marko Swoboda
- BCUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstraße 18, 01307, Dresden, Germany,
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31
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Naserian-Nik AM, Tahani M, Karttunen M. Molecular dynamics study of DNA oligomers under angled pulling. RSC Adv 2014. [DOI: 10.1039/c3ra45604h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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32
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Optical characterization of oligonucleotide DNA influenced by magnetic fields. Molecules 2013; 18:11797-808. [PMID: 24071986 PMCID: PMC6269815 DOI: 10.3390/molecules181011797] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/03/2013] [Accepted: 09/12/2013] [Indexed: 11/16/2022] Open
Abstract
UV-VIS spectroscopic analysis of oligonucleotide DNA exposed to different magnetic fields was performed in order to investigate the relationship between DNA extinction coefficients and optical parameters according to magnetic-field strength. The results with the oligonucleotides adenine-thymine 100 mer (AT-100 DNA) and cytosine-guanine 100 mer (CG-100 DNA) indicate that the magnetic field influences DNA molar extinction coefficients and refractive indexes. The imaginary parts of the refractive index and molar extinction coefficients of the AT-100 and CG-100 DNA decreased after exposure to a magnetic field of 750 mT due to cleavage of the DNA oligonucleotides into smaller segments.
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33
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Abstract
In cells, RNA polymerase (RNAP) must transcribe supercoiled DNA, whose torsional state is constantly changing, but how RNAP deals with DNA supercoiling remains elusive. We report direct measurements of individual Escherichia coli RNAPs as they transcribed supercoiled DNA. We found that a resisting torque slowed RNAP and increased its pause frequency and duration. RNAP was able to generate 11 ± 4 piconewton-nanometers (mean ± standard deviation) of torque before stalling, an amount sufficient to melt DNA of arbitrary sequence and establish RNAP as a more potent torsional motor than previously known. A stalled RNAP was able to resume transcription upon torque relaxation, and transcribing RNAP was resilient to transient torque fluctuations. These results provide a quantitative framework for understanding how dynamic modification of DNA supercoiling regulates transcription.
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Affiliation(s)
- Jie Ma
- Department of Physics-Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
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