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Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM

We estimate the elasticity of single polymer chains using atomic force microscope (AFM)-based oscillatory experiments. An accurate estimate of elasticity using AFM is limited by assumptions in describing the dynamics of an oscillating cantilever. Here, we use a home-built fiber-interferometry-based...

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Autores principales: Ahlawat, Vikhyaat, Deopa, Surya Pratap S., Patil, Shivprasad
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8839736/
https://www.ncbi.nlm.nih.gov/pubmed/35159871
http://dx.doi.org/10.3390/nano12030526
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author Ahlawat, Vikhyaat
Deopa, Surya Pratap S.
Patil, Shivprasad
author_facet Ahlawat, Vikhyaat
Deopa, Surya Pratap S.
Patil, Shivprasad
author_sort Ahlawat, Vikhyaat
collection PubMed
description We estimate the elasticity of single polymer chains using atomic force microscope (AFM)-based oscillatory experiments. An accurate estimate of elasticity using AFM is limited by assumptions in describing the dynamics of an oscillating cantilever. Here, we use a home-built fiber-interferometry-based detection system that allows a simple and universal point-mass description of cantilever oscillations. By oscillating the cantilever base and detecting changes in cantilever oscillations with an interferometer, we extracted stiffness versus extension profiles for polymers. For polyethylene glycol (PEG) in a good solvent, stiffness–extension data showed significant deviation from conventional force–extension curves (FECs) measured in constant velocity pulling experiments. Furthermore, modeling stiffness data with an entropic worm-like chain (WLC) model yielded a persistence length of (0.5 ± 0.2 nm) compared to anomaly low value (0.12 nm ± 0.01) in conventional pulling experiments. This value also matched well with equilibrium measurements performed using magnetic tweezers. In contrast, polystyrene (PS) in a poor solvent, like water, showed no deviation between the two experiments. However, the stiffness profile for PS in good solvent (8M Urea) showed significant deviation from conventional force–extension curves. We obtained a persistence length of (0.8 ± 0.2 nm) compared to (0.22 nm ± 0.01) in pulling experiments. Our unambiguous measurements using interferometer yield physically acceptable values of persistence length. It validates the WLC model in good solvents but suggests caution for its use in poor solvents.
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spelling pubmed-88397362022-02-13 Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM Ahlawat, Vikhyaat Deopa, Surya Pratap S. Patil, Shivprasad Nanomaterials (Basel) Article We estimate the elasticity of single polymer chains using atomic force microscope (AFM)-based oscillatory experiments. An accurate estimate of elasticity using AFM is limited by assumptions in describing the dynamics of an oscillating cantilever. Here, we use a home-built fiber-interferometry-based detection system that allows a simple and universal point-mass description of cantilever oscillations. By oscillating the cantilever base and detecting changes in cantilever oscillations with an interferometer, we extracted stiffness versus extension profiles for polymers. For polyethylene glycol (PEG) in a good solvent, stiffness–extension data showed significant deviation from conventional force–extension curves (FECs) measured in constant velocity pulling experiments. Furthermore, modeling stiffness data with an entropic worm-like chain (WLC) model yielded a persistence length of (0.5 ± 0.2 nm) compared to anomaly low value (0.12 nm ± 0.01) in conventional pulling experiments. This value also matched well with equilibrium measurements performed using magnetic tweezers. In contrast, polystyrene (PS) in a poor solvent, like water, showed no deviation between the two experiments. However, the stiffness profile for PS in good solvent (8M Urea) showed significant deviation from conventional force–extension curves. We obtained a persistence length of (0.8 ± 0.2 nm) compared to (0.22 nm ± 0.01) in pulling experiments. Our unambiguous measurements using interferometer yield physically acceptable values of persistence length. It validates the WLC model in good solvents but suggests caution for its use in poor solvents. MDPI 2022-02-03 /pmc/articles/PMC8839736/ /pubmed/35159871 http://dx.doi.org/10.3390/nano12030526 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Ahlawat, Vikhyaat
Deopa, Surya Pratap S.
Patil, Shivprasad
Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM
title Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM
title_full Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM
title_fullStr Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM
title_full_unstemmed Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM
title_short Quantitative Elasticity of Flexible Polymer Chains Using Interferometer-Based AFM
title_sort quantitative elasticity of flexible polymer chains using interferometer-based afm
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8839736/
https://www.ncbi.nlm.nih.gov/pubmed/35159871
http://dx.doi.org/10.3390/nano12030526
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