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Köry J, Stewart PS, Hill NA, Luo XY, Pandolfi A. A discrete-to-continuum model for the human cornea with application to keratoconus. ROYAL SOCIETY OPEN SCIENCE 2024; 11:240265. [PMID: 39050729 PMCID: PMC11265872 DOI: 10.1098/rsos.240265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 05/02/2024] [Indexed: 07/27/2024]
Abstract
We introduce a discrete mathematical model for the mechanical behaviour of a planar slice of human corneal tissue, in equilibrium under the action of physiological intraocular pressure (IOP). The model considers a regular (two-dimensional) network of structural elements mimicking a discrete number of parallel collagen lamellae connected by proteoglycan-based chemical bonds (crosslinks). Since the thickness of each collagen lamella is small compared to the overall corneal thickness, we upscale the discrete force balance into a continuum system of partial differential equations and deduce the corresponding macroscopic stress tensor and strain energy function for the micro-structured corneal tissue. We demonstrate that, for physiological values of the IOP, the predictions of the discrete model converge to those of the continuum model. We use the continuum model to simulate the progression of the degenerative disease known as keratoconus, characterized by a localized bulging of the corneal shell. We assign a spatial distribution of damage (i.e. reduction of the stiffness) to the mechanical properties of the structural elements and predict the resulting macroscopic shape of the cornea, showing that a large reduction in the element stiffness results in substantial corneal thinning and a significant increase in the curvature of both the anterior and posterior surfaces.
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Affiliation(s)
- J. Köry
- School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QQ, UK
| | - P. S. Stewart
- School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QQ, UK
| | - N. A. Hill
- School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QQ, UK
| | - X. Y. Luo
- School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QQ, UK
| | - A. Pandolfi
- Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy
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2
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Wells HC, Sizeland KH, Kirby N, Haverkamp RG. Structure and Strength of Bovine and Equine Amniotic Membrane. BIOLOGY 2022; 11:biology11081096. [PMID: 35892952 PMCID: PMC9329871 DOI: 10.3390/biology11081096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 07/20/2022] [Accepted: 07/21/2022] [Indexed: 11/16/2022]
Abstract
Simple Summary Thin, strong scaffold materials are needed for surgical applications. There is a limited selection of available materials and new materials are required. Amnionic membrane from cattle and horses were investigated for this purpose. The structure of these materials was characterized with synchrotron techniques and the strength was measured. A possible relationship between the structure and strength was identified. These amnion materials from animal sources are strong, thin, and elastic materials, although weaker than some other collagen tissues. They may be suitable for use in surgery as an alternative to material from human donors. Abstract Thin, strong scaffold materials are needed for surgical applications. New materials are required, particularly those readily available, such as from non-human sources. Bovine amniotic membrane (antepartum) and equine amniotic membrane (postpartum) were characterized with tear and tensile tests. The structural arrangement of the collagen fibrils was determined by small-angle X-ray scattering, scanning electron microscopy, and ultrasonic imaging. Bovine amnion had a thickness-normalized tear strength of 12.6 (3.8) N/mm, while equine amnion was 14.8 (5.3) N/mm. SAXS analysis of the collagen fibril arrangement yielded an orientation index of 0.587 (0.06) and 0.681 (0.05) for bovine and equine, respectively. This may indicate a relationship between more highly aligned collagen fibrils and greater strength, as seen in other materials. Amnion from bovine or equine sources are strong, thin, elastic materials, although weaker than other collagen tissue materials commonly used, that may find application in surgery as an alternative to material from human donors.
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Affiliation(s)
- Hannah C. Wells
- School of Food and Advanced Technology, Massey University, Palmerston North 4442, New Zealand;
| | - Katie H. Sizeland
- ANSTO, Lucas Heights, NSW 2234, Australia;
- ANSTO, Clayton, VIC 3168, Australia;
| | | | - Richard G. Haverkamp
- School of Food and Advanced Technology, Massey University, Palmerston North 4442, New Zealand;
- Correspondence:
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3
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An ultrastructural 3D reconstruction method for observing the arrangement of collagen fibrils and proteoglycans in the human aortic wall under mechanical load. Acta Biomater 2022; 141:300-314. [PMID: 35065266 DOI: 10.1016/j.actbio.2022.01.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 01/10/2022] [Accepted: 01/14/2022] [Indexed: 12/31/2022]
Abstract
An insight into changes of soft biological tissue ultrastructures under loading conditions is essential to understand their response to mechanical stimuli. Therefore, this study offers an approach to investigate the arrangement of collagen fibrils and proteoglycans (PGs), which are located within the mechanically loaded aortic wall. The human aortic samples were either fixed directly with glutaraldehyde in the load-free state or subjected to a planar biaxial extension test prior to fixation. The aortic ultrastructure was recorded using electron tomography. Collagen fibrils and PGs were segmented using convolutional neural networks, particularly the ESPNet model. The 3D ultrastructural reconstructions revealed a complex organization of collagen fibrils and PGs. In particular, we observed that not all PGs are attached to the collagen fibrils, but some fill the spaces between the fibrils with a clear distance to the collagen. The complex organization cannot be fully captured or can be severely misinterpreted in 2D. The approach developed opens up practical possibilities, including the quantification of the spatial relationship between collagen fibrils and PGs as a function of the mechanical load. Such quantification can also be used to compare tissues under different conditions, e.g., healthy and diseased, to improve or develop new material models. STATEMENT OF SIGNIFICANCE: The developed approach enables the 3D reconstruction of collagen fibrils and proteoglycans as they are embedded in the loaded human aortic wall. This methodological pipeline comprises the knowledge of arterial mechanics, imaging with transmission electron microscopy and electron tomography, segmentation of 3D image data sets with convolutional neural networks and finally offers a unique insight into the ultrastructural changes in the aortic tissue caused by mechanical stimuli.
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4
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Chen Y, Guan Q, Han X, Bai D, Li D, Tian Y. Proteoglycans in the periodontium: A review with emphasis on specific distributions, functions, and potential applications. J Periodontal Res 2021; 56:617-632. [PMID: 33458817 DOI: 10.1111/jre.12847] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 02/05/2023]
Abstract
Proteoglycans (PGs) are largely glycosylated proteins, consisting of a linkage sugar, core proteins, and glycosaminoglycans (GAGs). To date, more than 40 kinds of PGs have been identified, and they can be classified as intracellular, cell surface, pericellular, and extracellular PGs according to cellular locations. To illustrate, extracellular PGs are known for regulating the homeostasis of the extracellular matrix; cell-surface PGs play a role in mediating cell adhesion and binding various growth factors. In the field of periodontology, PGs are implicated in cellular proliferation, migration, adhesion, contractility, and anoikis, thereby exerting a profound influence on periodontal tissue development, wound repair, the immune response, biomechanics, and pathological process. Additionally, the expression patterns of some PGs are dynamic and cell-specific. Therefore, determining the roles and spatial-temporal expression patterns of PGs in the periodontium could shed light on treatments for wound healing, tissue regeneration, periodontitis, and gingival overgrowth. In this review, close attention is paid to the distributions, functions, and potential applications of periodontal PGs. Related genetically modified animal experiments and involved signal transduction cascades are summarized for improved understanding of periodontal PGs. To date, however, there is a large amount of speculation on this topic that requires rigorous experiments for validation.
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Affiliation(s)
- Yilin Chen
- State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.,Department of Orthodontics and Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Qiuyue Guan
- Department of Geriatrics, People's Hospital of Sichuan Province, Chengdu, China
| | - Xianglong Han
- State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.,Department of Orthodontics and Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Ding Bai
- State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Defu Li
- Department of Pharmaceutics and Bioengineering, School of Chemical Engineering, Sichuan University, Chengdu, China
| | - Ye Tian
- State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.,Department of Orthodontics and Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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5
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Sizeland KH, Wells HC, Kirby NM, Hawley A, Mudie ST, Ryan TM, Haverkamp RG. Bovine Meniscus Middle Zone Tissue: Measurement of Collagen Fibril Behavior During Compression. Int J Nanomedicine 2020; 15:5289-5298. [PMID: 32821095 PMCID: PMC7419642 DOI: 10.2147/ijn.s261298] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 07/09/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Type I collagen is the major component of the extracellular matrix of the knee's meniscus and plays a central role in that joint's biomechanical properties. Repair and reconstruction of tissue damage often requires a scaffold to assist the body to rebuild. The middle zone of bovine meniscus is a material that may be useful for the preparation of extracellular matrix scaffolds. METHODS Here, synchrotron-based small-angle X-ray scattering (SAXS) patterns of bovine meniscus were collected during unconfined compression. Collagen fibril orientation, D-spacing, compression distance and force were measured. RESULTS The collagen fibrils in middle zone meniscal fibrocartilage become more highly oriented perpendicular to the direction of compression. The D-spacing also increases, from 65.0 to 66.3 nm with compression up to 0.43 MPa, representing a 1.8% elongation of collagen fibrils perpendicular to the compression. CONCLUSION The elasticity of the collagen fibrils under tension along their length when the meniscus is compressed, therefore, contributes to the overall elastic response of the meniscus only under loads that exceed those likely to be experienced physiologically.
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Affiliation(s)
| | - Hannah C Wells
- School of Food and Advanced Technology, Massey University, Palmerston North4472, New Zealand
| | - Nigel M Kirby
- SAXS/WAXS Beamline, Australian Synchrotron, ANSTO, Clayton, Melbourne, VIC3168, Australia
| | - Adrian Hawley
- SAXS/WAXS Beamline, Australian Synchrotron, ANSTO, Clayton, Melbourne, VIC3168, Australia
| | - Stephen T Mudie
- SAXS/WAXS Beamline, Australian Synchrotron, ANSTO, Clayton, Melbourne, VIC3168, Australia
| | - Tim M Ryan
- SAXS/WAXS Beamline, Australian Synchrotron, ANSTO, Clayton, Melbourne, VIC3168, Australia
| | - Richard G Haverkamp
- School of Food and Advanced Technology, Massey University, Palmerston North4472, New Zealand
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6
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Holzapfel GA, Ogden RW. A damage model for collagen fibres with an application to collagenous soft tissues. Proc Math Phys Eng Sci 2020; 476:20190821. [PMID: 32398939 DOI: 10.1098/rspa.2019.0821] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 03/19/2020] [Indexed: 11/12/2022] Open
Abstract
We propose a mechanical model to account for progressive damage in collagen fibres within fibrous soft tissues. The model has a similar basis to the pseudoelastic model that describes the Mullins effect in rubber but it also accounts for the effect of cross-links between collagen fibres. We show that the model is able to capture experimental data obtained from rat tail tendon fibres, and the combined effect of damage and collagen cross-links is illustrated for a simple shear test. The proposed three-dimensional framework allows a straightforward implementation in finite-element codes, which are needed to analyse more complex boundary-value problems for soft tissues under supra-physiological loading or tissues weakened by disease.
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Affiliation(s)
- Gerhard A Holzapfel
- Institute of Biomechanics, Graz University of Technology, Stremayrgasse 16-II, 8010 Graz, Austria.,Norwegian University of Science and Technology (NTNU), Faculty of Engineering Science and Technology, 7491 Trondheim, Norway
| | - Ray W Ogden
- School of Mathematics and Statistics, University of Glasgow, University Place, Glasgow G12 8SQ, UK
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7
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Wells HC, Sizeland KH, Kelly SJ, Kirby N, Hawley A, Mudie S, Haverkamp RG. Collagen Fibril Intermolecular Spacing Changes with 2-Propanol: A Mechanism for Tissue Stiffness. ACS Biomater Sci Eng 2017; 3:2524-2532. [DOI: 10.1021/acsbiomaterials.7b00418] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hannah C. Wells
- School
of Engineering and Advanced Technology, Massey University, Private Bag
11222, Palmerston North 4442, New Zealand
| | - Katie H. Sizeland
- School
of Engineering and Advanced Technology, Massey University, Private Bag
11222, Palmerston North 4442, New Zealand
- Australian Synchrotron, 800 Blackburn
Road, Clayton, Melbourne, Victoria 3168, Australia
| | - Susyn J.R. Kelly
- School
of Engineering and Advanced Technology, Massey University, Private Bag
11222, Palmerston North 4442, New Zealand
| | - Nigel Kirby
- Australian Synchrotron, 800 Blackburn
Road, Clayton, Melbourne, Victoria 3168, Australia
| | - Adrian Hawley
- Australian Synchrotron, 800 Blackburn
Road, Clayton, Melbourne, Victoria 3168, Australia
| | - Stephen Mudie
- Australian Synchrotron, 800 Blackburn
Road, Clayton, Melbourne, Victoria 3168, Australia
| | - Richard G. Haverkamp
- School
of Engineering and Advanced Technology, Massey University, Private Bag
11222, Palmerston North 4442, New Zealand
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8
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de Mattos Pimenta Vidal C, Leme-Kraus AA, Rahman M, Farina AP, Bedran-Russo AK. Role of proteoglycans on the biochemical and biomechanical properties of dentin organic matrix. Arch Oral Biol 2017. [PMID: 28651092 DOI: 10.1016/j.archoralbio.2017.06.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
OBJECTIVE Proteoglycans (PGs) are multifunctional biomacromolecules of the extracellular matrix of collagen-based tissues. In teeth, besides a pivotal regulatory role on dentin biomineralization, PGs provide mechanical support to the mineralized tissue and compressive strength to the biosystem. This study assessed enzymatic protocols for selective PGs removal from demineralized dentin to determine the roles of these biomacromolecules in the bulk mechanical properties and biostability of type I collagen. METHODS Selective removal of glycosaminoglycans chains (GAGs) and PGs from demineralized dentin was carried out by enzymatic digestion protocols using chondroitinase ABC (c-ABC) and trypsin (Try). A comprehensive study design included assessment of dentin matrix mass loss, biodegradability of the PGs/GAGs-depleted dentin matrix, ultimate tensile strength (UTS) and energy to fracture tests. Quantitative data was statistically analyzed by two-way and one-way ANOVA followed by the appropriate post hoc tests (α=0.05). RESULTS Transmission electron microscopy images show effective GAGs removal by c-ABC and Try and both enzymatic methods released statistically similar amounts of GAGs from the demineralized dentin. Try digestion resulted in about 25% dentin matrix mass loss and increased susceptibility to collagenolytic digestion when compared to c-ABC (p=0.0224) and control (p=0.0901). Moreover, PGs digestion by Try decreased the tensile strengths of dentin. Statistically lower energy to fracture was observed in c-ABC-treated dentin matrix. CONCLUSIONS GAGs plays a pivotal role on tissue mechanics and anisotropy, while the core protein of PGs have a protective role on matrix biostability.
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Affiliation(s)
- Cristina de Mattos Pimenta Vidal
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, 801 South Paulina St, Chicago, IL, 60612, USA; Department of Operative Dentistry, College of Dentistry, University of Iowa, 801 Newton Rd, Iowa City, IA, 52242, USA
| | - Ariene Arcas Leme-Kraus
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, 801 South Paulina St, Chicago, IL, 60612, USA
| | - Momina Rahman
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, 801 South Paulina St, Chicago, IL, 60612, USA
| | - Ana Paula Farina
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, 801 South Paulina St, Chicago, IL, 60612, USA; School of Dentistry, University of Passo Fundo, BR 285, São José,Building A7, Passo Fundo, RS, 99052-900, Brazil
| | - Ana K Bedran-Russo
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, 801 South Paulina St, Chicago, IL, 60612, USA.
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9
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Bertassoni LE. Dentin on the nanoscale: Hierarchical organization, mechanical behavior and bioinspired engineering. Dent Mater 2017; 33:637-649. [PMID: 28416222 PMCID: PMC5481168 DOI: 10.1016/j.dental.2017.03.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/09/2017] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Knowledge of the structural organization and mechanical properties of dentin has expanded considerably during the past two decades, especially on a nanometer scale. In this paper, we review the recent literature on the nanostructural and nanomechanical properties of dentin, with special emphasis in its hierarchical organization. METHODS We give particular attention to the recent literature concerning the structural and mechanical influence of collagen intrafibrillar and extrafibrillar mineral in healthy and remineralized tissues. The multilevel hierarchical structure of collagen, and the participation of non-collagenous proteins and proteoglycans in healthy and diseased dentin are also discussed. Furthermore, we provide a forward-looking perspective of emerging topics in biomaterials sciences, such as bioinspired materials design and fabrication, 3D bioprinting and microfabrication, and briefly discuss recent developments on the emerging field of organs-on-a-chip. RESULTS The existing literature suggests that both the inorganic and organic nanostructural components of the dentin matrix play a critical role in various mechanisms that influence tissue properties. SIGNIFICANCE An in-depth understanding of such nanostructural and nanomechanical mechanisms can have a direct impact in our ability to evaluate and predict the efficacy of dental materials. This knowledge will pave the way for the development of improved dental materials and treatment strategies. CONCLUSIONS Development of future dental materials should take into consideration the intricate hierarchical organization of dentin, and pay particular attention to their complex interaction with the dentin matrix on a nanometer scale.
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Affiliation(s)
- Luiz E Bertassoni
- Division of Biomaterials and Biomechanics, Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, USA; Center for Regenerative Medicine, Oregon Health and Science University, School of Medicine, Portland, OR, USA; Department of Biomedical Engineering, Oregon Health and Science University, School of Medicine, Portland, OR, USA.
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10
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Irani AH, Owen JL, Mercadante D, Williams MAK. Molecular Dynamics Simulations Illuminate the Role of Counterion Condensation in the Electrophoretic Transport of Homogalacturonans. Biomacromolecules 2017; 18:505-516. [DOI: 10.1021/acs.biomac.6b01599] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Amir H. Irani
- Institute
of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Jessie L. Owen
- Institute
of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | | | - Martin A. K. Williams
- Institute
of Fundamental Sciences, Massey University, Palmerston North, New Zealand
- The MacDiarmid Institute
of Advanced Materials and Nanotechnology, Wellington, New Zealand
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11
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Hecht H, Srebnik S. Structural Characterization of Sodium Alginate and Calcium Alginate. Biomacromolecules 2016; 17:2160-7. [PMID: 27177209 DOI: 10.1021/acs.biomac.6b00378] [Citation(s) in RCA: 266] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Alginate readily aggregates and forms a physical gel in the presence of cations. The association of the chains, and ultimately gel structure and mechanics, depends not only on ion type, but also on the sequence and composition of the alginate chain that ultimately determines its stiffness. Chain flexibility is generally believed to decrease with guluronic residue content, but it is also known that both polymannuronate and polyguluronate blocks are stiffer than heteropolymeric blocks. In this work, we use atomistic molecular dynamics simulation to primarily explore the association and aggregate structure of different alginate chains under various Ca(2+) concentrations and for different alginate chain composition. We show that Ca(2+) ions in general facilitate chain aggregation and gelation. However, aggregation is predominantly affected by alginate monomer composition, which is found to correlate with chain stiffness under certain solution conditions. In general, greater fractions of mannuronic monomers are found to increase chain flexibility of heteropolymer chains. Furthermore, differences in chain guluronic acid content are shown to lead to different interchain association mechanisms, such as lateral association, zipper mechanism, and entanglement, where the mannuronic residues are shown to operate as an elasticity moderator and therefore promote chain association.
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Affiliation(s)
- Hadas Hecht
- The Interdisciplinary Program in Polymer Engineering and ‡Department of Chemical Engineering, Technion - Israel Institute of Technology , Haifa, Israel 32000
| | - Simcha Srebnik
- The Interdisciplinary Program in Polymer Engineering and ‡Department of Chemical Engineering, Technion - Israel Institute of Technology , Haifa, Israel 32000
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12
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Kayed HR, Sizeland KH, Kirby N, Hawley A, Mudie ST, Haverkamp RG. Collagen cross linking and fibril alignment in pericardium. RSC Adv 2015. [DOI: 10.1039/c4ra10658j] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cross linking was found to be a factor in collagen fibril alignment in pericardium tissue.
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Affiliation(s)
- Hanan R. Kayed
- School of Engineering and Advanced Technology
- Massey University
- New Zealand
| | - Katie H. Sizeland
- School of Engineering and Advanced Technology
- Massey University
- New Zealand
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13
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Kayed HR, Kirby N, Hawley A, Mudie ST, Haverkamp RG. Collagen fibril strain, recruitment and orientation for pericardium under tension and the effect of cross links. RSC Adv 2015. [DOI: 10.1039/c5ra21870e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The response to stress of collagen fibrils in bovine pericardium depends on the nature of the cross links.
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Affiliation(s)
- Hanan R. Kayed
- School of Engineering and Advanced Technology
- Massey University
- Palmerston North, New Zealand
| | | | | | | | - Richard G. Haverkamp
- School of Engineering and Advanced Technology
- Massey University
- Palmerston North, New Zealand
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14
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Bertassoni LE, Swain MV. The contribution of proteoglycans to the mechanical behavior of mineralized tissues. J Mech Behav Biomed Mater 2014; 38:91-104. [DOI: 10.1016/j.jmbbm.2014.06.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 06/12/2014] [Accepted: 06/14/2014] [Indexed: 10/25/2022]
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15
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Wells HC, Edmonds RL, Kirby N, Hawley A, Mudie ST, Haverkamp RG. Collagen fibril diameter and leather strength. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:11524-11531. [PMID: 24199635 DOI: 10.1021/jf4041854] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The main structural component of leather and skin is type I collagen in the form of strong fibrils. Strength is an important property of leather, and the way in which collagen contributes to the strength is not fully understood. Synchrotron-based small angle X-ray scattering (SAXS) is used to measure the collagen fibril diameter of leather from a range of animals, including sheep and cattle, that had a range of tear strengths. SAXS data were fit to a cylinder model. The collagen fibril diameter and tear strength were found to be correlated in bovine leather (r(2) = 0.59; P = 0.009), with stronger leather having thicker fibrils. There was no correlation between orientation index, i.e., fibril alignment, and fibril diameter for this data set. Ovine leather showed no correlation between tear strength and fibril diameter, nor was there a correlation across a selection of other animal leathers. The findings presented here suggest that there may be a different structural motif in skin compared with tendon, particularly ovine skin or leather, in which the diameter of the individual fibrils contributes less to strength than fibril alignment does.
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Affiliation(s)
- Hannah C Wells
- School of Engineering and Advanced Technology, Massey University , Private Bag 11222, Palmerston North, New Zealand 4442
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16
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Miserez A, Guerette PA. Phase transition-induced elasticity of α-helical bioelastomeric fibres and networks. Chem Soc Rev 2013; 42:1973-95. [DOI: 10.1039/c2cs35294j] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Facilitating high-force single-polysaccharide stretching using covalent attachment of one end of the chain. Carbohydr Polym 2012; 87:806-815. [PMID: 34663040 DOI: 10.1016/j.carbpol.2011.08.073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 08/23/2011] [Indexed: 11/24/2022]
Abstract
Single polysaccharide force spectroscopy has yielded particularly interesting data, the interpretation of which requires the marriage of statistical-mechanical theories of polymer physics to the complexities afforded by possible force-induced conformational transitions of the constituent sugar rings. However, the difficulty of designing handles for the specific attachment of the different ends of polysaccharide chains to substrates, such as piezoelectric scanners, cantilevers or microbeads has meant that the majority of studies to date have been carried out with the polymer physisorbed to the substrates between which it is stretched, or at best chemically attached via bonds formed at uncontrolled locations along the length of the molecule. This means that the lengths of obtained polysaccharide stretches, as well as the forces that can be placed on the molecule without generating detachment, are generally smaller than those obtainable for polymers that offer the ability to be covalently attached to substrates specifically at their ends. As a consequence it is troublesome and tedious to record a statistically significant number of force curves that extend chains to high enough forces to investigate certain conformational transitions, such as the boat-to-inverted chair, exhibited by polysaccharides such as pectin. Herein, single molecule force-extension curves have been measured for the several pectin samples using AFM. The results are compared when either (1) the polymers have been physisorbed between the cantilever and the surface of the piezo-electric scanner, under several different solvent conditions of pH and ionic strength, or (2) the polymer molecule has been chemically attached at one end to the piezo surface using a recently reported coupling procedure. In fact, using such a chemical attachment to tether the end of the polysaccharide, reduced the frequency of successful stretching events obtained in a particular location, confirming the role of surface diffusion in the physisorbed experiments. Nevertheless, when polymer stretches were successfully recorded, the force that could be applied before detachment was significantly increased, indicating that this methodology has great potential for improving the acquisition of data reporting on force-induced conformational transitions of the sugar ring that require the application of significant stresses.
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Fellah A, Anjukandi P, Hemar Y, Otter D, Williams MA. Towards polysaccharide handles for single molecule experiments: Spectroscopic evidence for the selective covalent coupling of terminal sugar residues to desired substrates. Carbohydr Polym 2011. [DOI: 10.1016/j.carbpol.2011.04.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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19
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Han L, Frank EH, Greene JJ, Lee HY, Hung HHK, Grodzinsky AJ, Ortiz C. Time-dependent nanomechanics of cartilage. Biophys J 2011; 100:1846-54. [PMID: 21463599 DOI: 10.1016/j.bpj.2011.02.031] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 01/27/2011] [Accepted: 02/22/2011] [Indexed: 10/18/2022] Open
Abstract
In this study, atomic force microscopy-based dynamic oscillatory and force-relaxation indentation was employed to quantify the time-dependent nanomechanics of native (untreated) and proteoglycan (PG)-depleted cartilage disks, including indentation modulus E(ind), force-relaxation time constant τ, magnitude of dynamic complex modulus |E(∗)|, phase angle δ between force and indentation depth, storage modulus E', and loss modulus E″. At ∼2 nm dynamic deformation amplitude, |E(∗)| increased significantly with frequency from 0.22 ± 0.02 MPa (1 Hz) to 0.77 ± 0.10 MPa (316 Hz), accompanied by an increase in δ (energy dissipation). At this length scale, the energy dissipation mechanisms were deconvoluted: the dynamic frequency dependence was primarily governed by the fluid-flow-induced poroelasticity, whereas the long-time force relaxation reflected flow-independent viscoelasticity. After PG depletion, the change in the frequency response of |E(∗)| and δ was consistent with an increase in cartilage local hydraulic permeability. Although untreated disks showed only slight dynamic amplitude-dependent behavior, PG-depleted disks showed great amplitude-enhanced energy dissipation, possibly due to additional viscoelastic mechanisms. Hence, in addition to functioning as a primary determinant of cartilage compressive stiffness and hydraulic permeability, the presence of aggrecan minimized the amplitude dependence of |E(∗)| at nanometer-scale deformation.
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Affiliation(s)
- Lin Han
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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Han L, Grodzinsky AJ, Ortiz C. Nanomechanics of the Cartilage Extracellular Matrix. ANNUAL REVIEW OF MATERIALS RESEARCH 2011; 41:133-168. [PMID: 22792042 PMCID: PMC3392687 DOI: 10.1146/annurev-matsci-062910-100431] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Cartilage is a hydrated biomacromolecular fiber composite located at the ends of long bones that enables proper joint lubrication, articulation, loading, and energy dissipation. Degradation of extracellular matrix molecular components and changes in their nanoscale structure greatly influence the macroscale behavior of the tissue and result in dysfunction with age, injury, and diseases such as osteoarthritis. Here, the application of the field of nanomechanics to cartilage is reviewed. Nanomechanics involves the measurement and prediction of nanoscale forces and displacements, intra- and intermolecular interactions, spatially varying mechanical properties, and other mechanical phenomena existing at small length scales. Experimental nanomechanics and theoretical nanomechanics have been applied to cartilage at varying levels of material complexity, e.g., nanoscale properties of intact tissue, the matrix associated with single cells, biomimetic molecular assemblies, and individual extracellular matrix biomolecules (such as aggrecan, collagen, and hyaluronan). These studies have contributed to establishing a fundamental mechanism-based understanding of native and engineered cartilage tissue function, quality, and pathology.
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Affiliation(s)
- Lin Han
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Alan J. Grodzinsky
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Christine Ortiz
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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An irreversible constitutive model for fibrous soft biological tissue: a 3-D microfiber approach with demonstrative application to abdominal aortic aneurysms. Acta Biomater 2011; 7:2457-66. [PMID: 21338718 DOI: 10.1016/j.actbio.2011.02.015] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 01/18/2011] [Accepted: 02/09/2011] [Indexed: 11/21/2022]
Abstract
Understanding the failure and damage mechanisms of soft biological tissue is critical to a sensitive and specific characterization of tissue injury tolerance and its relation to biological responses. Despite increasing experimental and analytical efforts, failure-related irreversible effects of soft biological tissue are still poorly understood. There is still no clear definition of what "damage" of a soft biological material is, and conventional macroscopic indicators, as known from damage of engineering materials for example, may not identify the tissue's tolerance to injury appropriately. To account for the complex three-dimensional arrangement of collagen, a microfiber model approach is applied, where constitutive relations for collagen fibers are integrated over the unit sphere, which in turn defines the tissue's macroscopic properties. A collagen fiber is represented by a bundle of proteoglycan cross-linked collagen fibrils that undergoes irreversible deformations when exceeding its elastic tensile limit. The proposed constitutive model is able to predict strain stiffening at physiological strain levels and does not exhibit a clear macroscopic elastic limit, two typical features known from soft biological tissue testing. An elastic-predictor/plastic-corrector implementation of the model is followed and constitutive parameters are estimated from in vitro test data from a particular abdominal aortic aneurysm (AAA). Damage-based structural instabilities of the AAA under different inflation conditions are investigated, where the collagen orientation density has been estimated from its in vivo stress state.
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Schuster E, Lundin L, Williams MAK. Insights into the potential functionality of single-chain force-induced conformational transitions in polymer networks: implications for polysaccharide signaling in the plant cell wall. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:051927. [PMID: 21230520 DOI: 10.1103/physreve.82.051927] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Revised: 09/08/2010] [Indexed: 05/30/2023]
Abstract
The behavior of biopolymer networks comprised of clickable polysaccharide chains that can undergo force-induced conformational transitions was investigated during straining using a simulation technique. The simulation was carried out both using an affine deformation field and alternatively using Lees-Edwards boundary conditions as an example of a nonaffine case. In the affine situation the simulated stress-strain curves were found to be consistent with results obtained by evaluating the molecular force-extension curve at a single average extension and calculating the bulk modulus as an average over all possible orientations with respect to the deformation. While in all cases examined the macroscopic mechanical responses of networks of randomly oriented chains, consisting either of simple extensible wormlike chains or their clickable analogs, were found to be indistinguishable, the simulation additionally allowed the number of chains containing sugar rings in different conformational states to be monitored, and this was found to change significantly during straining. This supports the hypothesis that in networks of randomly oriented clickable polysaccharide chains, such conformational transitions could have biological significance as stress switches in signaling processes but that they are unlikely to affect the bulk rheological properties of tissue.
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Affiliation(s)
- E Schuster
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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23
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Chan Y, Haverkamp RG, Hill JM. Force-extension formula for the worm-like chain model from a variational principle. J Theor Biol 2009; 262:498-504. [PMID: 19835889 DOI: 10.1016/j.jtbi.2009.10.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 08/03/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
Abstract
Stiff polymers, such as single-stranded DNA, unstructured RNA and cellulose, are all basically extremely long rods with relatively short repeating monomers. The simplest model for describing such stiff polymers is called the freely jointed chain model, which treats a molecule as a chain of perfectly rigid subunits of orientationally independent statistical segments, joined together by perfectly flexible hinges. A more realistic model that incorporates the entropic elasticity of a molecule, called the worm-like chain model, has been proposed by assuming that each monomer resists the bending force. Some force-extension formulae for the worm-like chain model have been previously found in terms of interpolation and numerical solutions resulting from statistical mechanics. In this paper, however, we adopt a variational principle to seek the minimum energy configuration of a stretched molecule by incorporating all the possible orientations of each monomer under thermal equilibrium, i.e., constant temperature. We determine a force-extension formula for the worm-like chain model analytically. We find that our formula suggests new terms such as the free energy and the cut-off force of a molecule, which define a clear transition from the entropic regime to the enthalpic regime and the fracture of the molecule, respectively. In addition, we predict two possible phase changes for a stretched molecule, i.e., from a super-helix to a soliton and then from a soliton to a vertical twisted line. We show theoretically that a molecule must undergo at least one phase change before it is fully stretched into its total contour length. This new formula is used to fit recent experimental data and shows a good agreement with some current literature that uses a statistical approach. Finally, an instability analysis is adopted to investigate the sensitivity of the new formula subject to small changes in temperature.
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Affiliation(s)
- Yue Chan
- Nanomechanics Group, School of Mathematics and Applied Statistics, University of Wollongong, Wollongong, NSW 2522, Australia
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24
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Orgel JPRO, Eid A, Antipova O, Bella J, Scott JE. Decorin core protein (decoron) shape complements collagen fibril surface structure and mediates its binding. PLoS One 2009; 4:e7028. [PMID: 19753304 PMCID: PMC2737631 DOI: 10.1371/journal.pone.0007028] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Accepted: 08/19/2009] [Indexed: 11/18/2022] Open
Abstract
Decorin is the archetypal small leucine rich repeat proteoglycan of the vertebrate extracellular matrix (ECM). With its glycosaminoglycuronan chain, it is responsible for stabilizing inter-fibrillar organization. Type I collagen is the predominant member of the fibrillar collagen family, fulfilling both organizational and structural roles in animal ECMs. In this study, interactions between decoron (the decorin core protein) and binding sites in the d and e1 bands of the type I collagen fibril were investigated through molecular modeling of their respective X-ray diffraction structures. Previously, it was proposed that a model-based, highly curved concave decoron interacts with a single collagen molecule, which would form extensive van der Waals contacts and give rise to strong non-specific binding. However, the large well-ordered aggregate that is the collagen fibril places significant restraints on modes of ligand binding and necessitates multi-collagen molecular contacts. We present here a relatively high-resolution model of the decoron-fibril collagen complex. We find that the respective crystal structures complement each other well, although it is the monomeric form of decoron that shows the most appropriate shape complementarity with the fibril surface and favorable calculated energies of interaction. One molecule of decoron interacts with four to six collagen molecules, and the binding specificity relies on a large number of hydrogen bonds and electrostatic interactions, primarily with the collagen motifs KXGDRGE and AKGDRGE (d and e1 bands). This work helps us to understand collagen-decorin interactions and the molecular architecture of the fibrillar ECM in health and disease.
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Affiliation(s)
- Joseph P R O Orgel
- BioCAT and microCoSM Centres: Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois, USA.
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25
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Chan Y, Cox GM, Haverkamp RG, Hill JM. Mechanical model for a collagen fibril pair in extracellular matrix. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:487-93. [DOI: 10.1007/s00249-008-0399-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 10/24/2008] [Accepted: 12/14/2008] [Indexed: 10/21/2022]
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26
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Williams MA, Marshall A, Haverkamp RG, Draget KI. Stretching single polysaccharide molecules using AFM: A potential method for the investigation of the intermolecular uronate distribution of alginate? Food Hydrocoll 2008. [DOI: 10.1016/j.foodhyd.2007.01.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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27
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Giannotti MI, Vancso GJ. Interrogation of Single Synthetic Polymer Chains and Polysaccharides by AFM-Based Force Spectroscopy. Chemphyschem 2007; 8:2290-307. [PMID: 17847140 DOI: 10.1002/cphc.200700175] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This contribution reviews selected mechanical experiments on individual flexible macromolecules using single-molecule force spectroscopy (SMFS) based on atomic force microscopy. Focus is placed on the analysis of elasticity and conformational changes in single polymer chains upon variation of the external environment, as well as on conformational changes induced by the mechanical stress applied to individual macromolecular chains. Various experimental strategies regarding single-molecule manipulation and SMFS testing are discussed, as is theoretical analysis through single-chain elasticity models derived from statistical mechanics. Moreover, a complete record, reported to date, of the parameters obtained when applying the models to fit experimental results on synthetic polymers and polysaccharides is presented.
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Affiliation(s)
- Marina I Giannotti
- Department of Materials Science and Technology of Polymers, MESA+Research Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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28
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Haverkamp RG, Marshall AT, Williams MAK. Entropic and Enthalpic Contributions to the Chair−Boat Conformational Transformation in Dextran under Single Molecule Stretching. J Phys Chem B 2007; 111:13653-7. [DOI: 10.1021/jp076052t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Richard G. Haverkamp
- Institute of Technology and Engineering, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Aaron T. Marshall
- Institute of Technology and Engineering, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Martin A. K. Williams
- Institute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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29
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Williams MAK, Marshall AT, Anjukandi P, Haverkamp RG. Investigation of the effects of fine structure on the nanomechanical properties of pectin. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:021927. [PMID: 17930085 DOI: 10.1103/physreve.76.021927] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Indexed: 05/25/2023]
Abstract
Pectin is an important structural polysaccharide found in the cell walls of all land plants. While in detail its composition and its organization in muro are complex, it is predominantly a copolymer of galacturonic acid and its methylesterified counterpart. Previous single-molecule stretching studies carried out on a sparsely methylesterified pectin sample indicated the importance of force-induced conformational transitions of the pyranose ring during extension, and the possible biological role of such transitions was discussed. More heavily methylesterified samples are better biomimetic models of the polymeric components as found in the plant cell wall, in particular being less restricted by the shackles of the significant intermolecular interactions expected to constrain the behavior of bare galacturonic acid sequences. Density functional theory calculations revealed that upon extending galacturonic acid monomers, whether methylesterified or not, the initial ((4)C1) chair structure is transformed to a ((3)S5) skew boat and that subsequently upon further elongation, via an intermediate inverted skew boat ((5)S3), the inverted chair ((1)C4) is reached. Experimentally, the force-extension curve of highly methylesterified pectin was found to be solvent dependent in the same manner as the un-esterified sample, indicating that minimal changes in the strength of interring hydrogen bonding result from such a substitution, and finally, as only subtle changes in the force-extension behavior of pectin resulted from changes in the degree of methylesterification, previous speculations about the role of force-induced transformations in vivo are supported.
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Affiliation(s)
- M A K Williams
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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30
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Bourge JL, Robert AM, Robert L, Renard G. Zonular fibers, multimolecular composition as related to function (elasticity) and pathology. ACTA ACUST UNITED AC 2007; 55:347-59. [PMID: 17350767 DOI: 10.1016/j.patbio.2007.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 01/20/2007] [Indexed: 11/24/2022]
Abstract
Zonular fibers (ZF) play an important role in accommodation. With the rapid increase over the last decade of the oldest part of the population in industrialized countries, age-dependent loss of accommodation became an increasingly important problem. It appeared therefore interesting to review old and recent literature on ZF, their composition, structure and pathological alterations. By comparing former and recent reports it appeared to us, that several previous reports were not sufficiently taken in consideration for the understanding of the rheological properties of ZF. Elastin and proteoglycans-glycosaminoglycans were reported previously as constituents of ZF. Their presence besides fibrillin, the major constituent, helps to explain the rheological properties of these fibers, and especially their elasticity and its age- and pathology-dependent decline. Our review points also to some of the major problems, which remain to be addressed by future experiments.
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Affiliation(s)
- J-L Bourge
- Department of ophthalmology, Hôtel-Dieu Hospital, University Paris-V, 1, place du Parvis-Notre-Dame, 75181 Paris cedex 04, France
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Haverkamp RG, Marshall AT, Williams MAK. Model for stretching elastic biopolymers which exhibit conformational transformations. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:021907. [PMID: 17358367 DOI: 10.1103/physreve.75.021907] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Revised: 12/18/2006] [Indexed: 05/14/2023]
Abstract
We derive an expression that represents the physical behavior of a polysaccharide molecule as it is stretched from the entropic region, through one or more ring conformational transformations, into the Hookean regime. The model adapts existing models in order to accommodate one or more force-induced conformational transformations of the glycan rings and is based on the concept of equilibrium between the clicked (longer conformers) and unclicked states. This equilibrium is determined by the Gibbs energy difference between these two states which is perturbed in favor of the clicked states by the force applied to the molecule. The derived expression is used to generate force-extension curves for model polymers and can illustrate the effect of the Gibbs energy for each transformation on the shape of these curves. It is also used to fit the force-extension curves of polysaccharides to obtain the Gibbs energy differences between the conformers. Good agreement was found between this model and experimental data on carboxymethylamylose, dextran, alginate, and pectin.
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Affiliation(s)
- R G Haverkamp
- Institute of Technology and Engineering, Massey University, Palmerston North 5331, New Zealand.
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33
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Abstracts of the XXVII Italian Society for the Study of Connective Tissues (SISC) Meeting, Bologna, Italy, 8-10 November 2007. Connect Tissue Res 2007; 48:338-63. [PMID: 18075821 DOI: 10.1080/03008200701726970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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34
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Abstract
To explore the role of the brush-like proteoglycan, aggrecan, in the shear behavior of cartilage tissue, we measured the lateral resistance to deformation of a monolayer of chemically end-attached cartilage aggrecan on a microcontact printed surface in aqueous NaCl solutions via lateral force microscopy. The effects of bath ionic strength (IS, 0.001-1.0 M) and lateral displacement rate (approximately 1-100 microm/s) were studied using probe tips functionalized with neutral hydroxyl-terminated self-assembled alkanethiol monolayers. Probe tips having two different end-radii (R approximately 50 nm and 2.5 microm) enabled access to different length-scales of interactions (nano and micro). The measured lateral force was observed to depend linearly on the applied normal force, and the lateral force to normal force proportionality constant, mu, was calculated. The value mu increased (from 0.03 +/- 0.01 to 0.11 +/- 0.01) with increasing bath IS (0.001-1.0 M) for experiments using the microsized tip due to the larger compressive strain of aggrecan that resulted from increased IS at constant compressive force. With the nanosized tip, mu also increased with IS but by a smaller amount due to the fewer number of aggrecan involved in shear deformation. The variations in lateral force as a function of applied compressive strain epsilon(n) and changes in bath IS suggested that both electrostatic and nonelectrostatic interactions contributed significantly to the shear deformational behavior of the aggrecan layers. While lateral force did not vary with lateral displacement rate at low IS, where elastic-like electrostatic interactions between aggrecan dominated, lateral force increased significantly with displacement rate at physiological and higher IS, suggestive of additional viscoelastic and/or poroelastic interactions within the aggrecan layer. These data provide insights into molecular-level deformation of aggrecan macromolecules that are important to the understanding of cartilage behavior.
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Affiliation(s)
- Lin Han
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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35
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Scott JE, Stockwell RA. Cartilage elasticity resides in shape module decoran and aggrecan sumps of damping fluid: implications in osteoarthrosis. J Physiol 2006; 574:643-50. [PMID: 16581860 PMCID: PMC1817741 DOI: 10.1113/jphysiol.2006.108100] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Accepted: 03/27/2006] [Indexed: 01/01/2023] Open
Abstract
Cartilage ultrastructure is based on collagen fibrils tied together by proteoglycans (PGs). Interfibrillar orthogonal PG bridges ('shape modules') were located by electron histochemistry using Cupromeronic blue methodology. Their frequency and size, similar to those in tendon, cornea, etc., were compatible with biochemical estimates of tissue decoran (formerly decorin), the PG component of shape module bridges. Digestion by hyaluronanase and chondroitinase AC helped to identify aggrecan and decoran and exemplified the destruction of shape modular organization by glycan-splitting agents. The anionic glycosaminoglycan (AGAG) of decoran, dermochondan sulphate (DS, formerly dermatan sulphate), contains L-iduronate, an elastic sugar unit. Chondroitan, keratan (present in aggrecan) and hyaluronan are not similarly elastic but can participate in sliding-filament reversible deformability. Mechanical properties predicted for the interfibrillar bridges accord with anisotropic stress/strain responses of articular cartilage to compressive or tensile stresses. We propose that fluid from pericellular aggrecan-rich domains moves under pressure into the interterritorial fibrillar arrays against the elastic resistance of the shape modules, which return the fluid, post-compression, to its original position. Cartilage is tendon-like, with the addition of expansile aggrecan-rich reservoirs of aqueous shock absorber fluid. Rupture or loss of interfibrillar ties would allow expansile PG to force the collagenous matrix apart, imbibing water, increasing swelling and fissuring--characteristic manifestations of osteoarthrosis (OA), a joint disease of major economic importance. Decoran may be a primary target of the OA disease process.
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Affiliation(s)
- John E Scott
- Chemical Morphology, Medical School, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
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