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Ahmad K, Yang Q, Martini A. Simulations of Friction Anisotropy on Self-Assembled Monolayers in Water. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6273-6280. [PMID: 35549237 DOI: 10.1021/acs.langmuir.1c03234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Molecular dynamics simulations were performed to study nanoscale friction on hydrophilic and hydrophobic self-assembled monolayers (SAMs) immersed in water. Sliding was simulated in two different directions to capture anisotropy due to the direction of motion relative to the inherent tilted orientation of the molecules. It was shown that friction depends on both hydrophobicity and sliding direction, with the highest friction observed for sliding on hydrophobic SAM in the direction against the initial orientation of the molecules. The origins of the friction trends were analyzed by differentiating the tip-SAM and tip-water force contributions to friction. The tip-water force was higher on the hydrophilic SAM, and this was shown to be due to the presence of a dense layer of water adjacent to the surface and hydrogen bonding. In contrast, the tip-SAM force was higher on the hydrophobic SAM due to a water depletion layer, which enabled the tip to be closer to the SAM terminal group. The higher-friction cases all exhibited greater penetration of the tip below the surface of the SAM, accommodated by further tilting and reorientation of the SAM molecules.
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Affiliation(s)
- Khurshid Ahmad
- US-Pakistan Center for Advanced Studies in Energy, University of Engineering and Technology, Peshawar 25000, Pakistan
| | - Quanpeng Yang
- Department of Mechanical Engineering, University of California-Merced, 5200 N. Lake Road, Merced, California 95343, United States
| | - Ashlie Martini
- Department of Mechanical Engineering, University of California-Merced, 5200 N. Lake Road, Merced, California 95343, United States
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Herman K, Zemła J, Ptak A, Lekka M. Single-molecule force spectroscopy reveals structural differences of heparan sulfate chains during binding to vitronectin. Phys Rev E 2021; 104:024409. [PMID: 34525582 DOI: 10.1103/physreve.104.024409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 07/22/2021] [Indexed: 12/18/2022]
Abstract
The syndecans represent an ongoing research field focused on their regulatory roles in normal and pathological conditions. The role of syndecans in cancer progression is well documented, implicating their importance in diagnosis and even proposing various potential cancer treatments. Thus, the characterization of the unbinding properties at the single-molecule level will appeal to their use as targets for therapeutics. In our study, syndecan-1 and syndecan-4 were measured during the interaction with the vitronectin HEP II binding site. Our findings show that syndecans are calcium ion dependent molecules that reveal distinct, unbinding properties indicating the alterations in the structure of heparan sulfate (HS) chains, possibly in the chain sequence or sulfation pattern. In this way, we suppose that HS chain affinity to extracellular matrix proteins may govern cancer invasion by altering the syndecans' ability to interact with cancer-related receptors present in the tumor microenvironment, thereby promoting the activation of various signaling cascades regulating tumor cell behavior.
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Affiliation(s)
- Katarzyna Herman
- Institute of Physics, Faculty of Materials Engineering and Technical Physics, Poznan University of Technology, Piotrowo 3, PL-60965 Poznań, Poland
| | - Joanna Zemła
- Department of Biophysical Microstructures, Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland
| | - Arkadiusz Ptak
- Institute of Physics, Faculty of Materials Engineering and Technical Physics, Poznan University of Technology, Piotrowo 3, PL-60965 Poznań, Poland
| | - Małgorzata Lekka
- Department of Biophysical Microstructures, Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland
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Li D, Wang Q, Xu C, Cheng Y, Zhang YW, Ji B. How Does Nature Evade the "Larger is Weaker" Fate of Ultralong Silk β-Sheet Nanocrystallites. NANO LETTERS 2020; 20:8516-8523. [PMID: 33054228 DOI: 10.1021/acs.nanolett.0c02968] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Silk protein builds up one of the strongest fibers superior to most synthetic and natural polymers. However, the strengthening mechanisms of the silk proteins remain largely elusive because of their complex nanocomposite structures. Here, we report an unusual behavior of this kind of material that is distinctively different from those of metals and other polymers. We find that there are multiple interface microcracks nucleating and stacking under the shear loading, dividing the interchain interface into small segments, by which the silk protein can achieve a high strength even with the ultralong chains. This is a new strategy of microstructure design of soft matter that could avoid the "larger is weaker" fate due to the increase of the chain length. This novel mechanism is crucial for building strong polymer materials with long chain molecules and at the same time retaining their complex functional and structural properties.
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Affiliation(s)
- Dechang Li
- Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, China
- Department of Applied Mechanics, Beijing Institute of Technology, Beijing 100081, China
| | - Qianchun Wang
- Department of Applied Mechanics, Beijing Institute of Technology, Beijing 100081, China
| | - Changjian Xu
- Department of Applied Mechanics, Beijing Institute of Technology, Beijing 100081, China
| | - Yuan Cheng
- Institute of High Performance Computing, Agency for Science Technology and Research (A*STAR), 1 Fusionopolis Way, Singapore 138632, Singapore
| | - Yong-Wei Zhang
- Institute of High Performance Computing, Agency for Science Technology and Research (A*STAR), 1 Fusionopolis Way, Singapore 138632, Singapore
| | - Baohua Ji
- Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, China
- Department of Applied Mechanics, Beijing Institute of Technology, Beijing 100081, China
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Dąbrowski J, Nowak W, Ptak A. How strong are hydrogen bonds in the peptide model? Phys Chem Chem Phys 2020; 22:1392-1399. [DOI: 10.1039/c9cp05564a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We provide a methodology based on the steered molecular dynamics simulations and dynamic force spectroscopy calculations to determine the kinetic and energetic characteristics of hydrogen bonds.
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Affiliation(s)
- Jakub Dąbrowski
- Institute of Physics
- Faculty of Technical Physics
- Poznan University of Technology
- PL-60965 Poznan
- Poland
| | - Wiesław Nowak
- Institute of Physics
- Faculty of Physics
- Astronomy and Informatics
- Nicolaus Copernicus University
- PL-87100 Torun
| | - Arkadiusz Ptak
- Institute of Physics
- Faculty of Technical Physics
- Poznan University of Technology
- PL-60965 Poznan
- Poland
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Herman K, Weiss M, Lekka M, Ptak A. How Complex Is the Concanavalin A-Carboxypeptidase Y Interaction? ACS Chem Biol 2019; 14:1611-1618. [PMID: 31287283 DOI: 10.1021/acschembio.9b00337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lectin-carbohydrate interactions can be exploited in ultrasensitive biochemical recognition or medical diagnosis. For this purpose, besides the high specificity of the interactions, an appropriate methodology for their quantitative and detailed characterization is demanded. In this work, we determine the unbinding properties of the concanavalin A-carboxypeptidase Y complex, which is important for characterization of glycoproteins on the surface of biological cells. To achieve the goal, we have developed a methodology based on dynamic force spectroscopy measurements and two advanced theoretical models of force-induced unbinding. Our final results allowed excluding both, rebinding processes and the multibarrier character of the interaction potential, as possible explanations of the concanavalin A-carboxypeptidase Y unbinding mechanisms. Such characteristics as the position and height of the activation barrier and the force-free dissociation rate were determined. We hope our paper contributes to a better understanding of the unbinding processes in receptor-ligand complexes.
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Affiliation(s)
- Katarzyna Herman
- Institute of Physics, Faculty of Technical Physics, Poznan University of Technology, Piotrowo 3, PL-60965 Poznan, Poland
| | - Marek Weiss
- Institute of Physics, Faculty of Technical Physics, Poznan University of Technology, Piotrowo 3, PL-60965 Poznan, Poland
| | - Małgorzata Lekka
- Department of Biophysical Microstructures, Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Cracow, Poland
| | - Arkadiusz Ptak
- Institute of Physics, Faculty of Technical Physics, Poznan University of Technology, Piotrowo 3, PL-60965 Poznan, Poland
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Dallin BC, Yeon H, Ostwalt AR, Abbott NL, Van Lehn RC. Molecular Order Affects Interfacial Water Structure and Temperature-Dependent Hydrophobic Interactions between Nonpolar Self-Assembled Monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:2078-2088. [PMID: 30645942 DOI: 10.1021/acs.langmuir.8b03287] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding how material properties affect hydrophobic interactions-the water-mediated interactions that drive the association of nonpolar materials-is vital to the design of materials in contact with water. Conventionally, the magnitude of the hydrophobic interactions between extended interfaces is attributed to interfacial chemical properties, such as the amount of nonpolar solvent-exposed surface area. However, recent experiments have demonstrated that the hydrophobic interactions between uniformly nonpolar self-assembled monolayers (SAMs) also depend on molecular-level SAM order. In this work, we use atomistic molecular dynamics simulations to investigate the relationship between SAM order, water structure, and hydrophobic interactions to explain these experimental observations. The SAM-SAM hydrophobic interactions calculated from the simulations increase in magnitude as SAM order increases, matching experimental observations. We explain this trend by showing that the molecular-level order of the SAM impacts the nanoscale structure of interfacial water molecules, leading to an increase in water structure near disordered SAMs. These findings are consistent with a decrease in the solvation entropy of disordered SAMs, which is confirmed by measuring the temperature dependence of hydrophobic interactions using both simulations and experiments. This study elucidates how hydrophobic interactions can be influenced by an interfacial physical property, which may guide the design of synthetic materials with fine-tuned interfacial hydrophobicity.
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Affiliation(s)
- Bradley C Dallin
- Department of Chemical and Biological Engineering , University of Wisconsin-Madison , 1415 Engineering Drive , Madison , Wisconsin 53706 United States
| | - Hongseung Yeon
- Department of Chemical and Biological Engineering , University of Wisconsin-Madison , 1415 Engineering Drive , Madison , Wisconsin 53706 United States
| | - Alexis R Ostwalt
- Department of Chemical and Biological Engineering , Montana State University , 306 Cobleigh Hall , Bozeman , Montana 59715 United States
| | - Nicholas L Abbott
- Department of Chemical and Biological Engineering , University of Wisconsin-Madison , 1415 Engineering Drive , Madison , Wisconsin 53706 United States
- Department of Chemical and Biomolecular Engineering , Cornell University , 120 Olin Hall , Ithaca , New York 14853 , United States
| | - Reid C Van Lehn
- Department of Chemical and Biological Engineering , University of Wisconsin-Madison , 1415 Engineering Drive , Madison , Wisconsin 53706 United States
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