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Teruo Miyata - One of the best experts on this subject based on the ideXlab platform.
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wet spun chitosan collagen fibers their chemical n modifications and blood compatibility
Biomaterials, 2000Co-Authors: Shigehiro Hirano, Min Zhang, Masuo Nakagawa, Teruo MiyataAbstract:Abstract Based on an in vitro test for an improvement of the blood compatibility of chitin by blending with Tropocollagen, we prepared a novel biocompatible blended fiber and its chemically N -modified fibers. Each (1 g/30 ml) of a clear mixed solution of chitosan with Tropocollagen or collagen and a clear solution of chitosan itself in aqueous 2% acetic acid–methanol (2 : 1 , v/v) was spun through a viscose-type spinneret into an aqueous 5% ammonia solution containing 40–43% ammonium sulfate at room temperature to afford a white fiber of chitosan–Tropocollagen blends (1.08–1.65 g/denier for the tenacity and 10.9–43.2% for the elongation). The Tropocollagen content up to 50% by weight) in the blended fiber affected little their tenacity and elongation values. The blended fiber was chemically N -modified at the fiber state by treatment with a series of carboxylic anhydrides and aldehydes to afford the corresponding N -modified fiber (0.86–1.31 g/denier for the tenacity and 8.0–12.1% for the elongation). A transparent blended hydrogel of N -acetylchitosan (chitin) with Tropocollagen was produced from the above mixed solution by treatment with acetic anhydride, and its membrane and sponge sheet were also prepared from the hydrogel.
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Wet spun chitosan-collagen fibers, their chemical N-modifications, and blood compatibility.
Biomaterials, 2000Co-Authors: Shigehiro Hirano, Min Zhang, Masuo Nakagawa, Teruo MiyataAbstract:Abstract Based on an in vitro test for an improvement of the blood compatibility of chitin by blending with Tropocollagen, we prepared a novel biocompatible blended fiber and its chemically N -modified fibers. Each (1 g/30 ml) of a clear mixed solution of chitosan with Tropocollagen or collagen and a clear solution of chitosan itself in aqueous 2% acetic acid–methanol (2 : 1 , v/v) was spun through a viscose-type spinneret into an aqueous 5% ammonia solution containing 40–43% ammonium sulfate at room temperature to afford a white fiber of chitosan–Tropocollagen blends (1.08–1.65 g/denier for the tenacity and 10.9–43.2% for the elongation). The Tropocollagen content up to 50% by weight) in the blended fiber affected little their tenacity and elongation values. The blended fiber was chemically N -modified at the fiber state by treatment with a series of carboxylic anhydrides and aldehydes to afford the corresponding N -modified fiber (0.86–1.31 g/denier for the tenacity and 8.0–12.1% for the elongation). A transparent blended hydrogel of N -acetylchitosan (chitin) with Tropocollagen was produced from the above mixed solution by treatment with acetic anhydride, and its membrane and sponge sheet were also prepared from the hydrogel.
Markus J Buehler - One of the best experts on this subject based on the ideXlab platform.
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nanomechanics of collagen fibrils under varying cross link densities atomistic and continuum studies
Journal of The Mechanical Behavior of Biomedical Materials, 2008Co-Authors: Markus J BuehlerAbstract:Abstract Collagen is a protein material with intriguing mechanical properties — it is highly elastic, shows large fracture strength and plays a crucial role in making Nature’s structural materials tough. Collagen based tissues consist of collagen fibrils, each of which is composed out of a staggered array of ultra-long Tropocollagen molecules extending to several hundred nanometers. Albeit the macroscopic properties of collagen based tissues have been studied extensively, less is known about the nanomechanical properties of Tropocollagen molecules and collagen fibrils, their elementary building blocks. In particular, the relationship between molecular properties and tissue properties remains a scarcely explored aspect of the science of collagen materials. Results of molecular multi-scale modeling of the nanomechanical properties of the large-strain deformation regime of collagen fibrils under varying cross-link densities are reported in this paper. The results confirm the significance of cross-links in collagen fibrils in improving its mechanical strength. Further, it is found that cross-links influence the nature of its large-deformation and fracture behavior. Cross-link deficient collagen fibrils show a highly dissipative deformation behavior with large yield regimes. Increasing cross-link densities lead to stronger fibrils that display an increasingly brittle deformation character. The simulation results are compared with recent nanomechanical experiments at the scale of Tropocollagen molecules and collagen fibrils.
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Entropic elasticity controls nanomechanics of single Tropocollagen molecules.
Biophysical journal, 2007Co-Authors: Markus J Buehler, Sophie Y. WongAbstract:We report molecular modeling of stretching single molecules of Tropocollagen, the building block of collagen fibrils and fibers that provide mechanical support in connective tissues. For small deformation, we observe a dominance of entropic elasticity. At larger deformation, we find a transition to energetic elasticity, which is characterized by first stretching and breaking of hydrogen bonds, followed by deformation of covalent bonds in the protein backbone, eventually leading to molecular fracture. Our force-displacement curves at small forces show excellent quantitative agreement with optical tweezer experiments. Our model predicts a persistence length ξp ≈ 16 nm, confirming experimental results suggesting that Tropocollagen molecules are very flexible elastic entities. We demonstrate that assembly of single Tropocollagen molecules into fibrils significantly decreases their bending flexibility, leading to decreased contributions of entropic effects during deformation. The molecular simulation results are used to develop a simple continuum model capable of describing an entire deformation range of Tropocollagen molecules. Our molecular model is capable of describing different regimes of elastic and permanent deformation, without relying on empirical parameters, including a transition from entropic to energetic elasticity.
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Atomistic and continuum modeling of mechanical properties of collagen: Elasticity, fracture, and self-assembly
Journal of Materials Research, 2006Co-Authors: Markus J BuehlerAbstract:We report studies of the mechanical properties of Tropocollagen molecules under different types of mechanical loading including tension, compression, shear, and bending. Our modeling yields predictions of the fracture strength of single Tropocollagen molecules and polypeptides, and also allows for quantification of the interactions between Tropocollagen molecules. Atomistic modeling predicts a persistence length of Tropocollagen molecules ξ ≈ 23.4 nm, close to experimental measurements. Our studies suggest that to describe large-strain or hyperelastic properties, it is critical to include a correct description of the bond behavior and breaking processes at large bond stretch, information that stems from the quantum chemical details of bonding. We use full atomistic calculations to derive parameters for a mesoscopic bead-spring model of Tropocollagen molecules. We demonstrate that the mesoscopic model enables one to study the finite temperature, long-time scale behavior of Tropocollagen fibers, illustrating the dynamics of solvated Tropocollagen molecules for different molecular lengths.
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atomistic and continuum modeling of mechanical properties of collagen elasticity fracture and self assembly
Journal of Materials Research, 2006Co-Authors: Markus J BuehlerAbstract:We report studies of the mechanical properties of Tropocollagen molecules under different types of mechanical loading including tension, compression, shear, and bending. Our modeling yields predictions of the fracture strength of single Tropocollagen molecules and polypeptides, and also allows for quantification of the interactions between Tropocollagen molecules. Atomistic modeling predicts a persistence length of Tropocollagen molecules ≈ 23.4 nm, close to experimental measurements. Our studies suggest that to describe large-strain or hyperelastic properties, it is critical to include a correct description of the bond behavior and breaking processes at large bond stretch, information that stems from the quantum chemical details of bonding. We use full atomistic calculations to derive parameters for a mesoscopic bead-spring model of Tropocollagen molecules. We demonstrate that the mesoscopic model enables one to study the finite temperature, long-time scale behavior of Tropocollagen fibers, illustrating the dynamics of solvated Tropocollagen molecules for different molecular lengths. I. INTRODUCTION Biological materials may be essential for facing critical challenges related to increased energy needs, needs for new medical applications, novel concepts in sensor and actuator design, reliability and robustness of devices, conservation of resources, and development of new structural materials. The combination of (i) high-level structural control of matter as achieved in nanoscience and nanotechnology, and (ii) integration of living and nonliving systems into technologies and their interfaces may play a critical role in the coming decades. With increasing complexity, materials start to resemble systems or machines, so that the borderlines between concepts such as “machine” and “material” start to disappear. These concepts have been used systematically by nature for millions of years, and their exploitation for technological applications holds great promise. In particular, the structure and behavior of proteins and materials based on proteins plays an overarching role in determining the function and properties of biological systems. In recent years, proteins have indeed been proposed as the basis for new materials for technological applications. 1–6 Materials based on proteins hold particular
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entropic elasticity controls nanomechanics of single Tropocollagen molecules
MRS Proceedings, 2006Co-Authors: Markus J Buehler, Sophie Y. WongAbstract:We report molecular modeling of stretching single molecules of Tropocollagen, the building block of collagen fibrils and fibers that provide mechanical support in connective tissues. For small deformation, we observe a dominance of entropic elasticity. At larger deformation, we find a transition to energetic elasticity, which is characterized by first stretching and breaking of hydrogen bonds, followed by deformation of covalent bonds in the protein backbone, eventually leading to molecular fracture. Our force-displacement curves show excellent quantitative agreement with optical tweezer experiments, suggesting a persistence length of approximately 16 nm. We demonstrate that assembly of single TC molecules into fibrils significantly decreases their flexibility, leading to decreased contributions of entropic effects during deformation. We develop a simple continuum model capable of describing entire deformation range of TC molecules.
Vikas Tomar - One of the best experts on this subject based on the ideXlab platform.
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Effect of osteogenesis imperfecta mutations in Tropocollagen molecule on strength of biomimetic Tropocollagen-hydroxyapatite nanocomposites
Applied Physics Letters, 2010Co-Authors: Devendra K. Dubey, Vikas TomarAbstract:Osteogenesis Imperfecta (OI) is a genetic disorder that affects cellular synthesis of Type-I collagen fibrils and causes extreme bone fragility. This study reports the effects of OI mutations in Tropocollagen (TC) molecules on strength of model Tropocollagen-Hydroxyapatite biomaterials with two different mineral [hydroxyapatite (HAP)] distributions using three dimensional atomistic simulations. Results show that the effect of TC mutations on the strength of TC-HAP biomaterials is insignificant. Instead, change in mineral distribution showed significant impact on the overall strength of TC-HAP biomaterials. Study suggests that TC mutations manifest themselves by changing the mineral distribution during hydroxyapatite growth and nucleation period.
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Effect of Changes in Tropocollagen Residue Sequence and Hydroxyapatite Mineral Texture on the Strength of Ideal Nanoscale Tropocollagen-Hydroxyapatite Biomaterials
Journal of materials science. Materials in medicine, 2009Co-Authors: Devendra K. Dubey, Vikas TomarAbstract:Changes in mineral texture (e.g. hydroxyapatite (HAP) or aragonite) and polypeptide (e.g. Tropocollagen (TC)) residue sequence are characteristic features of a disease known as osteogenesis imperfecta (OI). In OI, different possibilities of changes in polypeptide residue sequence as well as changes in polypeptide helix replacement (e.g. 3 α1 chains instead of 2 α1 and 1 α2 chain in OI murine) exist. The cross section of the HAP crystals could be needle like or plate like. Such texture and residue sequence related changes can significantly affect the material strength at the nanoscale. In this work, a mechanistic understanding of such factors in determining strength of nanoscale TC–HAP biomaterials is presented using three dimensional molecular dynamics (MD) simulations. Analyses point out that the peak interfacial strength for failure is the highest for supercells with plate shaped HAP crystals. TC molecules with higher number of side chain functional groups impart higher strength to the TC–HAP biomaterials at the nanoscale. Overall, HAP crystal shape variation, the direction of applied loading with respect to the relative TC–HAP orientation, and the number of side chain functional groups in TC molecules are the factor that affect TC–HAP biomaterial strength in a significant manner.
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IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER
2009Co-Authors: J. Phys, Devendra K. Dubey, Condens Matter, Vikas TomarAbstract:The effect of tensile and compressive loading on the hierarchical strength of idealized Tropocollagen–hydroxyapatite biomaterials as a function of the chemical environmen
Alberto Redaelli - One of the best experts on this subject based on the ideXlab platform.
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Intermolecular Slip Mechanism in Tropocollagen Nanofibrils
International Journal of Materials Research, 2009Co-Authors: Alfonso Gautieri, Simone Vesentini, Alberto RedaelliAbstract:Abstract We report a detailed study of the shear interaction between two Tropocollagen molecules, a major mechanism that contributes to the fibril mechanical behavior. Using steered molecular dynamics simulations in explicit solvent, we model the slip of two Tropocollagen molecules at varying pulling rates. We find that the adhesion strength is highly sensitive to the pulling rate, and that it converges to a value of 10.12 pN A – 1 for vanishing loading rates. We find that intermolecular H-bonds play a key role in determining the resistance against slip. Our results provide quantitative details on this mechanism of load transmission inside collagen fibrils and fibers, which is crucial for the development of constitutive models of collagenous tissues at larger hierarchical levels. Such constitutive models of collagenous tissue mechanics have many applications, ranging from development of bio-inspired materials to studies in tissue engineering. By incorporating pathological collagen mutations, our studies c...
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Single molecule effects of osteogenesis imperfecta mutations in Tropocollagen protein domains.
Protein science : a publication of the Protein Society, 2009Co-Authors: Alfonso Gautieri, Simone Vesentini, Alberto RedaelliAbstract:Osteogenesis imperfecta (OI) is a genetic disease characterized by fragile bones, skeletal deformities and, in severe cases, prenatal death that affects more than 1 in 10,000 individuals. Here we show by full atomistic simulation in explicit solvent that OI mutations have a significant influence on the mechanical properties of single Tropocollagen molecules, and that the severity of different forms of OI is directly correlated with the reduction of the mechanical stiffness of individual Tropocollagen molecules. The reduction of molecular stiffness provides insight into the molecular-scale mechanisms of the disease. The analysis of the molecular mechanisms reveals that physical parameters of side-chain volume and hydropathy index of the mutated residue control the loss of mechanical stiffness of individual Tropocollagen molecules. We propose a model that enables us to predict the loss of stiffness based on these physical characteristics of mutations. This finding provides an atomistic-level mechanistic understanding of the role of OI mutations in defining the properties of the basic protein constituents, which could eventually lead to new strategies for diagnosis and treatment the disease. The focus on material properties and their role in genetic diseases is an important, yet so far only little explored, aspect in studying the mechanisms that lead to pathological conditions. The consideration of how material properties change in diseases could lead to a new paradigm that may expand beyond the focus on biochemical readings alone and include a characterization of material properties in diagnosis and treatment, an effort referred to as materiomics.
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Deformation rate controls elasticity and unfolding pathway of single Tropocollagen molecules.
Journal of the mechanical behavior of biomedical materials, 2008Co-Authors: Alfonso Gautieri, Alberto RedaelliAbstract:Collagen is an important structural protein in vertebrates and is responsible for the integrity of many tissues like bone, teeth, cartilage and tendon. The mechanical properties of these tissues are primarily determined by their hierarchical arrangement and the role of the collagen matrix in their structures. Here we report a series of Steered Molecular Dynamics (SMD) simulations in explicit solvent, used to elucidate the influence of the pulling rate on the Young's modulus of individual Tropocollagen molecules. We stretch a collagen peptide model sequence [(Gly-Pro-Hyp)(10)](3) with pulling rates ranging from 0.01 to 100 m/s, reaching much smaller deformation rates than reported in earlier SMD studies. Our results clearly demonstrate a strong influence of the loading velocity on the observed mechanical properties. Most notably, we find that Young's modulus converges to a constant value of approximately 4 GPa tangent modulus at 8% tensile strain when the initially crimped molecule is straightened out, for pulling rates below 0.5 m/s. This enables us for the first time to predict the elastic properties of a single Tropocollagen molecule at physiologically and experimentally relevant pulling rates, directly from atomistic-level calculations. At deformation rates larger than 0.5 m/s, Young's modulus increases continuously and approaches values in excess of 15 GPa for deformation rates larger than 100 m/s. The analyses of the molecular deformation mechanisms show that the Tropocollagen molecule unfolds in distinctly different ways, depending on the loading rate, which explains the observation of different values of Young's modulus at different loading rates. For low pulling rates, the triple helix first uncoils completely at 10%-20% strain, then undergoes some recoiling in the opposite direction, and finally straightens for strains larger than 30%. At intermediate rates, the molecule uncoils linearly with increasing strain up to 35% strain. Finally, at higher velocities the triple helix does not uncoil during stretching.
Devendra K. Dubey - One of the best experts on this subject based on the ideXlab platform.
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Effect of osteogenesis imperfecta mutations in Tropocollagen molecule on strength of biomimetic Tropocollagen-hydroxyapatite nanocomposites
Applied Physics Letters, 2010Co-Authors: Devendra K. Dubey, Vikas TomarAbstract:Osteogenesis Imperfecta (OI) is a genetic disorder that affects cellular synthesis of Type-I collagen fibrils and causes extreme bone fragility. This study reports the effects of OI mutations in Tropocollagen (TC) molecules on strength of model Tropocollagen-Hydroxyapatite biomaterials with two different mineral [hydroxyapatite (HAP)] distributions using three dimensional atomistic simulations. Results show that the effect of TC mutations on the strength of TC-HAP biomaterials is insignificant. Instead, change in mineral distribution showed significant impact on the overall strength of TC-HAP biomaterials. Study suggests that TC mutations manifest themselves by changing the mineral distribution during hydroxyapatite growth and nucleation period.
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Effect of Changes in Tropocollagen Residue Sequence and Hydroxyapatite Mineral Texture on the Strength of Ideal Nanoscale Tropocollagen-Hydroxyapatite Biomaterials
Journal of materials science. Materials in medicine, 2009Co-Authors: Devendra K. Dubey, Vikas TomarAbstract:Changes in mineral texture (e.g. hydroxyapatite (HAP) or aragonite) and polypeptide (e.g. Tropocollagen (TC)) residue sequence are characteristic features of a disease known as osteogenesis imperfecta (OI). In OI, different possibilities of changes in polypeptide residue sequence as well as changes in polypeptide helix replacement (e.g. 3 α1 chains instead of 2 α1 and 1 α2 chain in OI murine) exist. The cross section of the HAP crystals could be needle like or plate like. Such texture and residue sequence related changes can significantly affect the material strength at the nanoscale. In this work, a mechanistic understanding of such factors in determining strength of nanoscale TC–HAP biomaterials is presented using three dimensional molecular dynamics (MD) simulations. Analyses point out that the peak interfacial strength for failure is the highest for supercells with plate shaped HAP crystals. TC molecules with higher number of side chain functional groups impart higher strength to the TC–HAP biomaterials at the nanoscale. Overall, HAP crystal shape variation, the direction of applied loading with respect to the relative TC–HAP orientation, and the number of side chain functional groups in TC molecules are the factor that affect TC–HAP biomaterial strength in a significant manner.
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IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER
2009Co-Authors: J. Phys, Devendra K. Dubey, Condens Matter, Vikas TomarAbstract:The effect of tensile and compressive loading on the hierarchical strength of idealized Tropocollagen–hydroxyapatite biomaterials as a function of the chemical environmen