The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Bekington Myrboh - One of the best experts on this subject based on the ideXlab platform.
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one pot synthesis of α ketoacetals from aryl methyl ketones in the presence of Selenous Acid catalyzed by boron trifluoride etherate
ChemInform, 2015Co-Authors: Icydora Kharkongor, Bekington MyrbohAbstract:The reaction of aryl methyl ketones with triethylorthoformate proceeds under mild, solvent free conditions and tolerates a variety of functional groups.
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one pot synthesis of α ketoacetals from aryl methyl ketones in the presence of Selenous Acid catalyzed by boron trifluoride etherate
Tetrahedron Letters, 2015Co-Authors: Icydora Kharkongor, Bekington MyrbohAbstract:A simple and efficient one-pot preparation of α-ketoacetals from substituted acetophenones and triethylorthoformate in the presence of H2SeO3 and BF3·Et2O as catalyst has been developed. The desired products are obtained in good yields by a simple protocol involving neat and mild reaction conditions. The present methodology provides an attractive alternative method for the preparation of α-ketoacetal derivatives.
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one pot synthesis of unsymmetrical benzils from aryl methyl ketones and arenes in the presence of Selenous Acid catalyzed by p toluenesulfonic Acid monohydrate
ChemInform, 2012Co-Authors: Icydora Kharkongor, Md Rumum Rohman, Bekington MyrbohAbstract:A modified process is presented for the oxidative coupling of acetophenones with weakly or unactivated arenes to produce the synthetically important benzil structures.
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one pot synthesis of unsymmetrical benzils from aryl methyl ketones and arenes in the presence of Selenous Acid catalysed by p toluenesulfonic Acid monohydrate
Tetrahedron Letters, 2012Co-Authors: Icydora Kharkongor, Md Rumum Rohman, Bekington MyrbohAbstract:Abstract A modified one-pot method for the synthesis of unsymmetrical and heteroaryl benzils from substituted acetophenones and unactivated or weakly activated arenes by the use of H 2 SeO 3 and p -TsOH·H 2 O as catalysts at 35 °C is established. The present method is regioselective and avoids the use of p -TsOH·H 2 O in stoichiometric amount in the presence of H 2 SeO 3 and afforded unsymmetrical benzils in good yields.
Icydora Kharkongor - One of the best experts on this subject based on the ideXlab platform.
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one pot synthesis of α ketoacetals from aryl methyl ketones in the presence of Selenous Acid catalyzed by boron trifluoride etherate
ChemInform, 2015Co-Authors: Icydora Kharkongor, Bekington MyrbohAbstract:The reaction of aryl methyl ketones with triethylorthoformate proceeds under mild, solvent free conditions and tolerates a variety of functional groups.
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one pot synthesis of α ketoacetals from aryl methyl ketones in the presence of Selenous Acid catalyzed by boron trifluoride etherate
Tetrahedron Letters, 2015Co-Authors: Icydora Kharkongor, Bekington MyrbohAbstract:A simple and efficient one-pot preparation of α-ketoacetals from substituted acetophenones and triethylorthoformate in the presence of H2SeO3 and BF3·Et2O as catalyst has been developed. The desired products are obtained in good yields by a simple protocol involving neat and mild reaction conditions. The present methodology provides an attractive alternative method for the preparation of α-ketoacetal derivatives.
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one pot synthesis of unsymmetrical benzils from aryl methyl ketones and arenes in the presence of Selenous Acid catalyzed by p toluenesulfonic Acid monohydrate
ChemInform, 2012Co-Authors: Icydora Kharkongor, Md Rumum Rohman, Bekington MyrbohAbstract:A modified process is presented for the oxidative coupling of acetophenones with weakly or unactivated arenes to produce the synthetically important benzil structures.
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one pot synthesis of unsymmetrical benzils from aryl methyl ketones and arenes in the presence of Selenous Acid catalysed by p toluenesulfonic Acid monohydrate
Tetrahedron Letters, 2012Co-Authors: Icydora Kharkongor, Md Rumum Rohman, Bekington MyrbohAbstract:Abstract A modified one-pot method for the synthesis of unsymmetrical and heteroaryl benzils from substituted acetophenones and unactivated or weakly activated arenes by the use of H 2 SeO 3 and p -TsOH·H 2 O as catalysts at 35 °C is established. The present method is regioselective and avoids the use of p -TsOH·H 2 O in stoichiometric amount in the presence of H 2 SeO 3 and afforded unsymmetrical benzils in good yields.
Gerard A Ateshian - One of the best experts on this subject based on the ideXlab platform.
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insulin ascorbate and glucose have a much greater influence than transferrin and Selenous Acid on the in vitro growth of engineered cartilage in chondrogenic media
Tissue Engineering Part A, 2013Co-Authors: Alexander D Cigan, Robert J Nims, Michael B Albro, John D Esau, Marissa P Dreyer, Gordana Vunjaknovakovic, Clark T Hung, Gerard A AteshianAbstract:The primary goal of this study was to characterize the response of chondrocyte-seeded agarose constructs to varying concentrations of several key nutrients in a chondrogenic medium, within the overall context of optimizing the key nutrients and the placement of nutrient channels for successful growth of cartilage tissue constructs large enough to be clinically relevant in the treatment of osteoarthritis (OA). To this end, chondrocyte-agarose constructs (o4×2.34 mm, 30×10(6) cells/mL) were subjected to varying supplementation levels of insulin (0× to 30× relative to standard supplementation), transferrin (0× to 30×), Selenous Acid (0× to 10×), ascorbate (0× to 30×), and glucose (0× to 3×). The quality of resulting engineered tissue constructs was evaluated by their compressive modulus (E(-Y)), tensile modulus (E(+Y)), hydraulic permeability (k), and content of sulfated glycosaminoglycans (sGAG) and collagen (COL); DNA content was also quantified. Three control groups from two separate castings of constructs (1× concentrations of all medium constituents) were used. After 42 days of culture, values in each of these controls were, respectively, E(-Y)=518±78, 401±113, 236±67 kPa; E(+Y)=1420±430, 1140±490, 1240±280 kPa; k=2.3±0.8×10(-3), 5.4±7.0×10(-3), 3.3±1.3×10(-3) mm(4)/N·s; sGAG=7.8±0.3, 6.3±0.4, 4.1±0.5%/ww; COL=1.3±0.2, 1.1±0.3, 1.4±0.4%/ww; and DNA=11.5±2.2, 12.1±0.6, 5.2±2.8 μg/disk. The presence of insulin and ascorbate was essential, but their concentrations may drop as low as 0.3× without detrimental effects on any of the measured properties; excessive supplementation of ascorbate (up to 30×) was detrimental to E(-Y), and 30× insulin was detrimental to both E(+Y) and E(-Y). The presence of glucose was similarly essential, and matrix elaboration was significantly dependent on its concentration (p<10(-6)), with loss of functional properties, composition, and cellularity observed at ≤0.3×; excessive glucose supplementation (up to 3×) showed no detrimental effects. In contrast, transferrin and Selenous Acid had no influence on matrix elaboration. These findings suggest that adequate distributions of insulin, ascorbate, and glucose, but not necessarily of transferrin and Selenous Acid, must be ensured within large engineered cartilage constructs to produce a viable substitute for joint tissue lost due to OA.
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insulin and ascorbate have a much greater influence than transferrin and Selenous Acid on the growth of engineered cartilage in chondrogenic media
ASME 2012 Summer Bioengineering Conference Parts A and B, 2012Co-Authors: Alexander D Cigan, Robert J Nims, Michael B Albro, Clark T Hung, Sarah L Breves, Gerard A AteshianAbstract:Tissue engineering of cartilage, which is a much sought-after approach for treatment of osteoarthritis and cartilage defects, requires appreciable culture time. Chemically defined chondrogenic media (CM) are commonly employed as they offer a promising alternative to serum-based media, and often include insulin, transferrin, and Selenous Acid (ITS) as well as ascorbate [1]. Concentrations of ITS constituents have been optimized based upon their ability to stimulate proliferation of a variety of cell types [2]. However, little is reflected in the literature as to the influences of various ITS constituent concentrations upon cartilage matrix deposition by chondrocytes. In engineered cartilage constructs that seek to match compositional and mechanical properties of native cartilage, knowledge of such influences would be highly desirable, especially when optimizing nutrient, hormone and vitamin supply for large constructs wherein rates of transport and consumption become more critical. Furthermore, this information would prove useful in modeling growth and remodeling of engineered tissues. Therefore, this study seeks to elucidate mechanical and biochemical properties as a direct result of modulating ITS and ascorbate concentrations within chondrocyte-agarose constructs.Copyright © 2012 by ASME
Kurt J. Irgolic - One of the best experts on this subject based on the ideXlab platform.
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Retention behavior of inorganic and organic selenium compounds on a silica-based strong-cation-exchange column with an inductively coupled plasma mass spectrometer as selenium-specific detector
Journal of Chromatography A, 1997Co-Authors: Walter Goessler, Mulat Abegaz, Claudia Schlagenhaufen, Kurt Kalcher, Doris Kuehnelt, Kurt J. IrgolicAbstract:Abstract The retention behavior of eight selenium compounds (Selenous Acid, selenic Acid, selenocystine, selenohomocystine, selenomethionine, selenoethionine, trimethylselenonium iodide, and dimethyl(3-amino-3-carboxy-1-propyl)selenonium iodide) with aqueous solutions of pyridine (20 mmol/l) in the pH range 2.0–5.7 on a Supelcosil LC-SCX cation-exchange column was investigated. An inductively coupled plasma mass spectrometer was employed as the selenium-specific detector. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by a hydraulic high-pressure nebulizer. At pH 5.0, seven selenium compounds could be separated within 400 s, but selenohomocystine and selenomethionine had the same retention time. Selenomethionine can be separated from selenohomocystine with an aqueous solution of pyridine (20 mmol/l) adjusted with formic Acid to pH 2.0. At 1 ng Se ml−1, the relative standard deviations (n=5) of the signal area for the eight selenium compounds ranged from 7 to 11%, and at 50 ng Se ml−1 from 0.6 to 2.6%.
Alexander D Cigan - One of the best experts on this subject based on the ideXlab platform.
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insulin ascorbate and glucose have a much greater influence than transferrin and Selenous Acid on the in vitro growth of engineered cartilage in chondrogenic media
Tissue Engineering Part A, 2013Co-Authors: Alexander D Cigan, Robert J Nims, Michael B Albro, John D Esau, Marissa P Dreyer, Gordana Vunjaknovakovic, Clark T Hung, Gerard A AteshianAbstract:The primary goal of this study was to characterize the response of chondrocyte-seeded agarose constructs to varying concentrations of several key nutrients in a chondrogenic medium, within the overall context of optimizing the key nutrients and the placement of nutrient channels for successful growth of cartilage tissue constructs large enough to be clinically relevant in the treatment of osteoarthritis (OA). To this end, chondrocyte-agarose constructs (o4×2.34 mm, 30×10(6) cells/mL) were subjected to varying supplementation levels of insulin (0× to 30× relative to standard supplementation), transferrin (0× to 30×), Selenous Acid (0× to 10×), ascorbate (0× to 30×), and glucose (0× to 3×). The quality of resulting engineered tissue constructs was evaluated by their compressive modulus (E(-Y)), tensile modulus (E(+Y)), hydraulic permeability (k), and content of sulfated glycosaminoglycans (sGAG) and collagen (COL); DNA content was also quantified. Three control groups from two separate castings of constructs (1× concentrations of all medium constituents) were used. After 42 days of culture, values in each of these controls were, respectively, E(-Y)=518±78, 401±113, 236±67 kPa; E(+Y)=1420±430, 1140±490, 1240±280 kPa; k=2.3±0.8×10(-3), 5.4±7.0×10(-3), 3.3±1.3×10(-3) mm(4)/N·s; sGAG=7.8±0.3, 6.3±0.4, 4.1±0.5%/ww; COL=1.3±0.2, 1.1±0.3, 1.4±0.4%/ww; and DNA=11.5±2.2, 12.1±0.6, 5.2±2.8 μg/disk. The presence of insulin and ascorbate was essential, but their concentrations may drop as low as 0.3× without detrimental effects on any of the measured properties; excessive supplementation of ascorbate (up to 30×) was detrimental to E(-Y), and 30× insulin was detrimental to both E(+Y) and E(-Y). The presence of glucose was similarly essential, and matrix elaboration was significantly dependent on its concentration (p<10(-6)), with loss of functional properties, composition, and cellularity observed at ≤0.3×; excessive glucose supplementation (up to 3×) showed no detrimental effects. In contrast, transferrin and Selenous Acid had no influence on matrix elaboration. These findings suggest that adequate distributions of insulin, ascorbate, and glucose, but not necessarily of transferrin and Selenous Acid, must be ensured within large engineered cartilage constructs to produce a viable substitute for joint tissue lost due to OA.
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insulin and ascorbate have a much greater influence than transferrin and Selenous Acid on the growth of engineered cartilage in chondrogenic media
ASME 2012 Summer Bioengineering Conference Parts A and B, 2012Co-Authors: Alexander D Cigan, Robert J Nims, Michael B Albro, Clark T Hung, Sarah L Breves, Gerard A AteshianAbstract:Tissue engineering of cartilage, which is a much sought-after approach for treatment of osteoarthritis and cartilage defects, requires appreciable culture time. Chemically defined chondrogenic media (CM) are commonly employed as they offer a promising alternative to serum-based media, and often include insulin, transferrin, and Selenous Acid (ITS) as well as ascorbate [1]. Concentrations of ITS constituents have been optimized based upon their ability to stimulate proliferation of a variety of cell types [2]. However, little is reflected in the literature as to the influences of various ITS constituent concentrations upon cartilage matrix deposition by chondrocytes. In engineered cartilage constructs that seek to match compositional and mechanical properties of native cartilage, knowledge of such influences would be highly desirable, especially when optimizing nutrient, hormone and vitamin supply for large constructs wherein rates of transport and consumption become more critical. Furthermore, this information would prove useful in modeling growth and remodeling of engineered tissues. Therefore, this study seeks to elucidate mechanical and biochemical properties as a direct result of modulating ITS and ascorbate concentrations within chondrocyte-agarose constructs.Copyright © 2012 by ASME