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Yong-doo Park - One of the best experts on this subject based on the ideXlab platform.
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effect of hesperetin on tyrosinase inhibition kinetics integrated Computational Simulation study
International Journal of Biological Macromolecules, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Jun-mo Yang, Guo-ying Qian, Yong-doo Park, Sufang WangAbstract:Abstract Tyrosinase inhibitors have potential applications in medicine, cosmetics and agriculture to prevent hyperpigmentation or browning effects. Some of the flavonoids mostly found in herbal plants and fruits are revealed as tyrosinase inhibitors. We studied the inhibitory effects of one such flavonoid, hesperetin, on mushroom tyrosinase using inhibition kinetics and Computational Simulation. Hesperetin reversibly inhibited tyrosinase in a competitive manner with K i = 4.03 ± 0.26 mM. Measurements of ANS-binding fluorescence showed that hesperetin induced the hydrophobic disruption of tyrosinase. For further insight, we used the docking algorithms to simulate binding between tyrosinase and hesperetin. Simulation was successful (binding energies for Dock6.3: −34.41 kcal/mol and for AutoDock4.2: −5.67 kcal/mol) and showed that a copper ion coordinating with 3 histidine residues (HIS61, HIS85, and HIS259) within the active site pocket was chelated via hesperetin binding. Our study provides insight into the inhibition of tyrosinase in response to flavonoids. A combination of inhibition kinetics and Computational prediction may facilitate the identification of potential natural tyrosinase inhibitors such as flavonoids and the prediction of their inhibitory mechanisms.
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Tyrosinase inhibition by isophthalic acid: Kinetics and Computational Simulation
International journal of biological macromolecules, 2011Co-Authors: Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Hai-meng Zhou, Jun-mo Yang, Guo-ying Qian, Yong-doo ParkAbstract:Using inhibition kinetics and Computational Simulation, we studied the reversible inhibition of tyrosinase by isophthalic acid (IPA). IPA inhibited tyrosinase in a complex manner with K(i)=17.8 ± 1.8mM. Measurements of intrinsic and ANS-binding fluorescence showed that IPA induced no changes in tertiary protein structure. For further insight, we predicted the 3D structure of tyrosinase and used a docking algorithm to simulate binding between tyrosinase and IPA. Simulation was successful (binding energies for Dock6.3: -25.19 kcal/mol and for AutoDock4.2: -4.28 kcal/mol), suggesting that IPA interacts with PRO175 or VAL190. This strategy of predicting tyrosinase inhibition based on hydroxyl group number and orientation may prove useful for the screening of potential tyrosinase inhibitors.
Shang-jun Yin - One of the best experts on this subject based on the ideXlab platform.
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Effects of isorhamnetin on tyrosinase: inhibition kinetics and Computational Simulation.
Bioscience biotechnology and biochemistry, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Jun-mo Yang, Hyoung Oh Jeong, Guo-ying QianAbstract:We studied the inhibitory effects of isorhamnetin on mushroom tyrosinase by inhibition kinetics and Computational Simulation. Isorhamnetin reversibly inhibited tyrosinase in a mixed-type manner at K i=0.235 ± 0.013 mM. Measurements of intrinsic and 1-anilinonaphthalene-8-sulfonate(ANS)-binding fluorescence showed that isorhamnetin did not induce significant changes in the tertiary structure of tyrosinase. To gain insight into the inactivation process, the kinetics were computed via time-interval measurements and continuous substrate reactions. The results indicated that inactivation induced by isorhamnetin was a first-order reaction with biphasic processes. To gain further insight, we simulated docking between tyrosinase and isorhamnetin. Simulation was successful (binding energies for Dock6.3: −32.58 kcal/mol, for AutoDock4.2: −5.66 kcal/mol, and for Fred2.2: −48.86 kcal/mol), suggesting that isorhamnetin interacts with several residues, such as HIS244 and MET280. This strategy of predicting tyrosinase i...
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effect of hesperetin on tyrosinase inhibition kinetics integrated Computational Simulation study
International Journal of Biological Macromolecules, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Jun-mo Yang, Guo-ying Qian, Yong-doo Park, Sufang WangAbstract:Abstract Tyrosinase inhibitors have potential applications in medicine, cosmetics and agriculture to prevent hyperpigmentation or browning effects. Some of the flavonoids mostly found in herbal plants and fruits are revealed as tyrosinase inhibitors. We studied the inhibitory effects of one such flavonoid, hesperetin, on mushroom tyrosinase using inhibition kinetics and Computational Simulation. Hesperetin reversibly inhibited tyrosinase in a competitive manner with K i = 4.03 ± 0.26 mM. Measurements of ANS-binding fluorescence showed that hesperetin induced the hydrophobic disruption of tyrosinase. For further insight, we used the docking algorithms to simulate binding between tyrosinase and hesperetin. Simulation was successful (binding energies for Dock6.3: −34.41 kcal/mol and for AutoDock4.2: −5.67 kcal/mol) and showed that a copper ion coordinating with 3 histidine residues (HIS61, HIS85, and HIS259) within the active site pocket was chelated via hesperetin binding. Our study provides insight into the inhibition of tyrosinase in response to flavonoids. A combination of inhibition kinetics and Computational prediction may facilitate the identification of potential natural tyrosinase inhibitors such as flavonoids and the prediction of their inhibitory mechanisms.
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Tyrosinase inhibition by isophthalic acid: Kinetics and Computational Simulation
International journal of biological macromolecules, 2011Co-Authors: Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Hai-meng Zhou, Jun-mo Yang, Guo-ying Qian, Yong-doo ParkAbstract:Using inhibition kinetics and Computational Simulation, we studied the reversible inhibition of tyrosinase by isophthalic acid (IPA). IPA inhibited tyrosinase in a complex manner with K(i)=17.8 ± 1.8mM. Measurements of intrinsic and ANS-binding fluorescence showed that IPA induced no changes in tertiary protein structure. For further insight, we predicted the 3D structure of tyrosinase and used a docking algorithm to simulate binding between tyrosinase and IPA. Simulation was successful (binding energies for Dock6.3: -25.19 kcal/mol and for AutoDock4.2: -4.28 kcal/mol), suggesting that IPA interacts with PRO175 or VAL190. This strategy of predicting tyrosinase inhibition based on hydroxyl group number and orientation may prove useful for the screening of potential tyrosinase inhibitors.
Guo-ying Qian - One of the best experts on this subject based on the ideXlab platform.
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Effects of isorhamnetin on tyrosinase: inhibition kinetics and Computational Simulation.
Bioscience biotechnology and biochemistry, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Jun-mo Yang, Hyoung Oh Jeong, Guo-ying QianAbstract:We studied the inhibitory effects of isorhamnetin on mushroom tyrosinase by inhibition kinetics and Computational Simulation. Isorhamnetin reversibly inhibited tyrosinase in a mixed-type manner at K i=0.235 ± 0.013 mM. Measurements of intrinsic and 1-anilinonaphthalene-8-sulfonate(ANS)-binding fluorescence showed that isorhamnetin did not induce significant changes in the tertiary structure of tyrosinase. To gain insight into the inactivation process, the kinetics were computed via time-interval measurements and continuous substrate reactions. The results indicated that inactivation induced by isorhamnetin was a first-order reaction with biphasic processes. To gain further insight, we simulated docking between tyrosinase and isorhamnetin. Simulation was successful (binding energies for Dock6.3: −32.58 kcal/mol, for AutoDock4.2: −5.66 kcal/mol, and for Fred2.2: −48.86 kcal/mol), suggesting that isorhamnetin interacts with several residues, such as HIS244 and MET280. This strategy of predicting tyrosinase i...
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effect of hesperetin on tyrosinase inhibition kinetics integrated Computational Simulation study
International Journal of Biological Macromolecules, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Jun-mo Yang, Guo-ying Qian, Yong-doo Park, Sufang WangAbstract:Abstract Tyrosinase inhibitors have potential applications in medicine, cosmetics and agriculture to prevent hyperpigmentation or browning effects. Some of the flavonoids mostly found in herbal plants and fruits are revealed as tyrosinase inhibitors. We studied the inhibitory effects of one such flavonoid, hesperetin, on mushroom tyrosinase using inhibition kinetics and Computational Simulation. Hesperetin reversibly inhibited tyrosinase in a competitive manner with K i = 4.03 ± 0.26 mM. Measurements of ANS-binding fluorescence showed that hesperetin induced the hydrophobic disruption of tyrosinase. For further insight, we used the docking algorithms to simulate binding between tyrosinase and hesperetin. Simulation was successful (binding energies for Dock6.3: −34.41 kcal/mol and for AutoDock4.2: −5.67 kcal/mol) and showed that a copper ion coordinating with 3 histidine residues (HIS61, HIS85, and HIS259) within the active site pocket was chelated via hesperetin binding. Our study provides insight into the inhibition of tyrosinase in response to flavonoids. A combination of inhibition kinetics and Computational prediction may facilitate the identification of potential natural tyrosinase inhibitors such as flavonoids and the prediction of their inhibitory mechanisms.
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Tyrosinase inhibition by isophthalic acid: Kinetics and Computational Simulation
International journal of biological macromolecules, 2011Co-Authors: Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Hai-meng Zhou, Jun-mo Yang, Guo-ying Qian, Yong-doo ParkAbstract:Using inhibition kinetics and Computational Simulation, we studied the reversible inhibition of tyrosinase by isophthalic acid (IPA). IPA inhibited tyrosinase in a complex manner with K(i)=17.8 ± 1.8mM. Measurements of intrinsic and ANS-binding fluorescence showed that IPA induced no changes in tertiary protein structure. For further insight, we predicted the 3D structure of tyrosinase and used a docking algorithm to simulate binding between tyrosinase and IPA. Simulation was successful (binding energies for Dock6.3: -25.19 kcal/mol and for AutoDock4.2: -4.28 kcal/mol), suggesting that IPA interacts with PRO175 or VAL190. This strategy of predicting tyrosinase inhibition based on hydroxyl group number and orientation may prove useful for the screening of potential tyrosinase inhibitors.
Christos C. Chamis - One of the best experts on this subject based on the ideXlab platform.
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Composite Erosion by Computational Simulation
2013Co-Authors: Christos C. ChamisAbstract:Abstract Composite degradation is evaluated by Computational Simulation when the erosion degradation occurs on a ply-by-ply basis and the degrading medium (device) is normal to the ply. The Computational Simulation is performed by a multi factor interaction model and by a multi scale and multi physics available computer code. The erosion process degrades both the fiber and the matrix simultaneously in the same slice (ply). Both the fiber volume ratio and the matrix volume ratio approach zero while the void volume ratio increases as the ply degrades. The multi factor interaction model simulates the erosion degradation, provided that the exponents and factor ratios are selected judiciously. Results obtained by the Computational composite mechanics show that most composite characterization properties degrade monotonically and approach “zero” as the ply degrades completely. 1. Introduction Composites erosion is an important design requirement when composite structures are subjected to erosion environments. A significant amount of research has been and continues to be conducted on that subject. Some of that research is summarized in references 1 and 2. Reference 1 covers research up to 1986. This is a multi author publication by specialists in all aspects of erosion. Reference 2 is another multi author publication that covers tribology research up to 1993. This publication also covers various aspects of tribology research that has been performed through August of 1992. These two publications provide a very good orientation for beginners in composites erosion and some of the concepts described in the present article. Specific aspects of erosion in injection moulded thermoplastic composites are described in reference 3. The main feature in this reference is that erosion occurs on a composite slice (ply) at the time. Friction and wear of several polymer composites are investigated experimentally in reference 4. The main finding in that investigation is that the friction coefficient remains constant and does depend on which surface the eroding device is acting. They found that for the various laminates that they tested the coefficient of friction was about the same. They also found that the prodding mass depends on the pressure exerted by the eroding device on the eroding surface. Barkoula and Karger-Kocsis performed solid particle tests (ref. 5) on composites with different fiber/matrix adhesion. They found that improvements in the interface bond reduce substantially the eroded mass for the same testing conditions. The only Simulation that was found is that for thermal analysis by finite element for the heat transfer in sliding friction (ref. 6). They found that the finite element can be used in that sliding situation. An ASME publication (ref. 7) describes micro and nano tribology. This publication deals mainly with chemistry at the nano scale. The articles that were reviewed do not deal with the composite mechanics Simulation of the composite erosion and the composite properties as the erosion proceeds. It became obvious to the author that an investigation that utilizes Simulation of the composite erosion was needed. Therefore, the objective of the present investigation is to use Computational composite mechanics in order to evaluate composite erosion and the respective composite degradation in terms of its degraded properties. Specifically, the application of available Computational methods ICAN (ref. 8) to evaluate composite degradation due to erosion. The other Computational Simulation method used was the Multi Factor Interaction Model (MFIM) which can be used to simulate composite erosion when the exponents of each factor and their respective ratios are chosen judiciously. The erosion considered is that as the erosion progresses as the fiber volume ratio the matrix volume ratio and the fiber diameter decrease simultaneously. The properties predicted then will be as each slice in a ply degrades due to the changes in those variables.
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POLYMER COMPOSITES CORROSIVE DEGRADATION: A Computational Simulation
2007Co-Authors: Christos C. Chamis, Levon MinnetyanAbstract:A Computational Simulation of polymer composites corrosive durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured pH factor and is represented by voids, temperature and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The Simulation is performed by a Computational composite mechanics computer code which includes micro, macro, combined stress failure and laminate theories. This accounts for starting the Simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the Simulation is applicable to other polymer composite systems as well.
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Rotorcraft Damage Tolerance Evaluated by Computational Simulation
2000Co-Authors: Christos C. Chamis, Levon Minnetyan, Frank AbdiAbstract:Abstract : An integrally stiffened graphite/epoxy composite rotorcraft structure is evaluated via Computational Simulation. A computer code that scales up constituent micromechanics level material properties to the structure level and accounts for all possible failure modes is used for the Simulation of composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the Simulation. Design implications with regard to defect and damage tolerance of integrally stiffened composite structures are examined. A procedure is outlined regarding the use of this type of information for setting quality acceptance criteria, design allowables, damage tolerance, and retirement-for-cause criteria.
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Ceramic matrix composite behavior -- Computational Simulation
1996Co-Authors: Christos C. Chamis, Pappu L. N. Murthy, Subodh K. MitalAbstract:Development of analytical modeling and Computational capabilities for the prediction of high temperature ceramic matrix composite behavior has been an ongoing research activity at NASA-Lewis Research Center. These research activities have resulted in the development of micromechanics based methodologies to evaluate different aspects of ceramic matrix composite behavior. The basis of the approach is micromechanics together with a unique fiber substructuring concept. In this new concept the conventional unit cell (the smallest representative volume element of the composite) of micromechanics approach has been modified by substructuring the unit cell into several slices and developing the micromechanics based equations at the slice level. Main advantage of this technique is that it can provide a much greater detail in the response of composite behavior as compared to a conventional micromechanics based analysis and still maintains a very high Computational efficiency. This methodology has recently been extended to model plain weave ceramic composites. The objective of the present paper is to describe the important features of the modeling and Simulation and illustrate with select examples of laminated as well as woven composites.
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Computational Simulation of Continuous Fiber-Reinforced Ceramic Matrix Composites Behavior
Journal of Advanced Materials, 1996Co-Authors: Pappu L. N. Murthy, Christos C. Chamis, Subodh K. MitalAbstract:The purpose of the present paper is to describe a methodology for predicting the behavior of ceramic matrix composites which has been incorporated into a computer code CEMCAN (CEramic Matrix Composite ANalyzer). The basis of the approach is a combination of micromechanics together with a unique fiber substructuring concept. In this new concept, the conventional unit cell (the smallest representative volume element of the composite) of the micromechanics approach has been modified by substructuring the unit cell into several slices and developing the micromechanics based equations at the slice level. The methodology also takes into account nonlinear ceramic matrix composite (CMC) behavior due to temperature and progressive fracture/degradation of the interphase. The important features of the approach and its effectiveness are described herein with select examples. Comparisons of predictions with limited experimental data are also provided.
Hae Young Chung - One of the best experts on this subject based on the ideXlab platform.
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Effects of isorhamnetin on tyrosinase: inhibition kinetics and Computational Simulation.
Bioscience biotechnology and biochemistry, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Jun-mo Yang, Hyoung Oh Jeong, Guo-ying QianAbstract:We studied the inhibitory effects of isorhamnetin on mushroom tyrosinase by inhibition kinetics and Computational Simulation. Isorhamnetin reversibly inhibited tyrosinase in a mixed-type manner at K i=0.235 ± 0.013 mM. Measurements of intrinsic and 1-anilinonaphthalene-8-sulfonate(ANS)-binding fluorescence showed that isorhamnetin did not induce significant changes in the tertiary structure of tyrosinase. To gain insight into the inactivation process, the kinetics were computed via time-interval measurements and continuous substrate reactions. The results indicated that inactivation induced by isorhamnetin was a first-order reaction with biphasic processes. To gain further insight, we simulated docking between tyrosinase and isorhamnetin. Simulation was successful (binding energies for Dock6.3: −32.58 kcal/mol, for AutoDock4.2: −5.66 kcal/mol, and for Fred2.2: −48.86 kcal/mol), suggesting that isorhamnetin interacts with several residues, such as HIS244 and MET280. This strategy of predicting tyrosinase i...
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effect of hesperetin on tyrosinase inhibition kinetics integrated Computational Simulation study
International Journal of Biological Macromolecules, 2012Co-Authors: Zhi-jiang Wang, Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Jun-mo Yang, Guo-ying Qian, Yong-doo Park, Sufang WangAbstract:Abstract Tyrosinase inhibitors have potential applications in medicine, cosmetics and agriculture to prevent hyperpigmentation or browning effects. Some of the flavonoids mostly found in herbal plants and fruits are revealed as tyrosinase inhibitors. We studied the inhibitory effects of one such flavonoid, hesperetin, on mushroom tyrosinase using inhibition kinetics and Computational Simulation. Hesperetin reversibly inhibited tyrosinase in a competitive manner with K i = 4.03 ± 0.26 mM. Measurements of ANS-binding fluorescence showed that hesperetin induced the hydrophobic disruption of tyrosinase. For further insight, we used the docking algorithms to simulate binding between tyrosinase and hesperetin. Simulation was successful (binding energies for Dock6.3: −34.41 kcal/mol and for AutoDock4.2: −5.67 kcal/mol) and showed that a copper ion coordinating with 3 histidine residues (HIS61, HIS85, and HIS259) within the active site pocket was chelated via hesperetin binding. Our study provides insight into the inhibition of tyrosinase in response to flavonoids. A combination of inhibition kinetics and Computational prediction may facilitate the identification of potential natural tyrosinase inhibitors such as flavonoids and the prediction of their inhibitory mechanisms.
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Tyrosinase inhibition by isophthalic acid: Kinetics and Computational Simulation
International journal of biological macromolecules, 2011Co-Authors: Shang-jun Yin, Daeui Park, Hae Young Chung, Li Yan, Hai-meng Zhou, Jun-mo Yang, Guo-ying Qian, Yong-doo ParkAbstract:Using inhibition kinetics and Computational Simulation, we studied the reversible inhibition of tyrosinase by isophthalic acid (IPA). IPA inhibited tyrosinase in a complex manner with K(i)=17.8 ± 1.8mM. Measurements of intrinsic and ANS-binding fluorescence showed that IPA induced no changes in tertiary protein structure. For further insight, we predicted the 3D structure of tyrosinase and used a docking algorithm to simulate binding between tyrosinase and IPA. Simulation was successful (binding energies for Dock6.3: -25.19 kcal/mol and for AutoDock4.2: -4.28 kcal/mol), suggesting that IPA interacts with PRO175 or VAL190. This strategy of predicting tyrosinase inhibition based on hydroxyl group number and orientation may prove useful for the screening of potential tyrosinase inhibitors.