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Neal J Zondlo - One of the best experts on this subject based on the ideXlab platform.
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Effects of i and i+3 residue identity on Cis–Trans Isomerism of the aromatici+1–prolyli+2 amide bond: Implications for type VI β‐turn formation
Biopolymers, 2020Co-Authors: Hai Yun Meng, Krista M Thomas, Neal J ZondloAbstract:Cis-Trans isomerization of amide bonds plays critical roles in protein molecular recognition, protein folding, protein misfolding, and disease. Aromatic-proline sequences are particularly prone to exhibit Cis amide bonds. The roles of residues adjacent to a tyrosine-proline residue pair on Cis-Trans Isomerism were examined. A short series of peptides XYPZ was synthesized and Cis-Trans Isomerism was analyzed. Based on these initial studies, a series of peptides XYPN, X = all 20 canonical amino acids, was synthesized and analyzed by NMR for i residue effects on Cis-Trans isomerization. The following effects were observed: (a) aromatic residues immediately preceding Tyr-Pro disfavor Cis amide bonds, with K(Trans/Cis)= 5.7-8.0, W > Y > F; (b) proline residues preceding Tyr-Pro lead to multiple species, exhibiting Cis-Trans isomerization of either or both X-Pro amide bonds; and (c) other residues exhibit similar values of K(Trans/Cis) (= 2.9-4.2), with Thr and protonated His exhibiting the highest fraction Cis. beta-Branched and short polar residues were somewhat more favorable in stabilizing the Cis conformation. Phosphorylation of serine at the i position modestly increases the stability of the Cis conformer. In addition, the effect of the i+3 residue was examined in a limited series of peptides TYPZ. NMR data indicated that aromatic residues, Pro, Asn, Ala, and Val at the i+3 residue all favor Cis amide bonds, with aromatic residues and Asn favoring more compact phi at Tyr(Cis) and Ala and Pro favoring more extended phi at Tyr(Cis). D-Alanine at the i+3 position particularly disfavors Cis amide bonds.
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electronic control of amide Cis Trans Isomerism via the aromatic prolyl interaction
Journal of the American Chemical Society, 2006Co-Authors: Krista M Thomas, Devan Naduthambi, Neal J ZondloAbstract:The Cis−Trans isomerization of prolyl amide bonds results in large structural and functional changes in proteins and is a rate-determining step in protein folding. We describe a novel electronic strategy to control Cis−Trans isomerization, based on the demonstration that interactions between aromatic residues and proline are tunable by aromatic electronics. A series of peptides of sequence TXPN, X = Trp, pyridylalanine, pentafluorophenylalanine, or 4-Z-phenylalanine derivatives (Z = electron-donating, electron-withdrawing, or electron-neutral substituents), was synthesized and KTrans/Cis analyzed by NMR. Electron-rich aromatic residues stabilized Cis amide bond formation, while electron-poor aromatics relatively favored Trans amide bond formation. A Hammett correlation between aromatic electronics and Cis−Trans isomerization was observed. These results indicate that the interaction between aromatic residues and proline, which is observed to stabilize Cis amide bonds and is also a general stabilizing inter...
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effects of i and i 3 residue identity on Cis Trans Isomerism of the aromatici 1 prolyli 2 amide bond implications for type vi β turn formation
Biopolymers, 2006Co-Authors: Hai Yun Meng, Krista M Thomas, Neal J ZondloAbstract:: Cis-Trans isomerization of amide bonds plays critical roles in protein molecular recognition, protein folding, protein misfolding, and disease. Aromatic-proline sequences are particularly prone to exhibit Cis amide bonds. The roles of residues adjacent to a tyrosine-proline residue pair on Cis-Trans Isomerism were examined. A short series of peptides XYPZ was synthesized and Cis-Trans Isomerism was analyzed. Based on these initial studies, a series of peptides XYPN, X = all 20 canonical amino acids, was synthesized and analyzed by NMR for i residue effects on Cis-Trans isomerization. The following effects were observed: (a) aromatic residues immediately preceding Tyr-Pro disfavor Cis amide bonds, with K(Trans/Cis)= 5.7-8.0, W > Y > F; (b) proline residues preceding Tyr-Pro lead to multiple species, exhibiting Cis-Trans isomerization of either or both X-Pro amide bonds; and (c) other residues exhibit similar values of K(Trans/Cis) (= 2.9-4.2), with Thr and protonated His exhibiting the highest fraction Cis. beta-Branched and short polar residues were somewhat more favorable in stabilizing the Cis conformation. Phosphorylation of serine at the i position modestly increases the stability of the Cis conformer. In addition, the effect of the i+3 residue was examined in a limited series of peptides TYPZ. NMR data indicated that aromatic residues, Pro, Asn, Ala, and Val at the i+3 residue all favor Cis amide bonds, with aromatic residues and Asn favoring more compact phi at Tyr(Cis) and Ala and Pro favoring more extended phi at Tyr(Cis). D-Alanine at the i+3 position particularly disfavors Cis amide bonds.
Jean-marc Belin - One of the best experts on this subject based on the ideXlab platform.
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Effect of Cis/Trans Isomerism of β-carotene on the ratios of volatile compounds produced during oxidative degradation
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Yves Waché, Aurélie Bosser-deratuld, J-c Lhuguenot, Jean-marc BelinAbstract:β-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are β-ionone, 5,6-epoxy-β-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of β-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9−C10 bond. This study investigated the influence of Cis/Trans Isomerism at the C9−C10 bond on the production of β-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. β-Carotene solutions containing high ratios of 9-Cis-isomers produced more DHA, suggesting a different pathway than for the Transformation of all-Trans-β-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds. Keywords: β-Carotene...
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effect of Cis Trans Isomerism of β carotene on the ratios of volatile compounds produced during oxidative degradation
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Yves Waché, J-c Lhuguenot, Aurelie Bosserderatuld, Jean-marc BelinAbstract:β-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are β-ionone, 5,6-epoxy-β-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of β-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9−C10 bond. This study investigated the influence of Cis/Trans Isomerism at the C9−C10 bond on the production of β-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. β-Carotene solutions containing high ratios of 9-Cis-isomers produced more DHA, suggesting a different pathway than for the Transformation of all-Trans-β-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds. Keywords: β-Carotene...
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Effect of Cis/Trans Isomerism of β-Carotene on the Ratios of Volatile Compounds Produced during Oxidative Degradation
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Yves Waché, Aurélie Bosser-deratuld, J-c Lhuguenot, Jean-marc BelinAbstract:beta-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are beta-ionone, 5,6-epoxy-beta-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of beta-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9-C10 bond. This study investigated the influence of Cis/Trans Isomerism at the C9-C10 bond on the production of beta-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. beta-Carotene solutions containing high ratios of 9-Cis-isomers produced more DHA, suggesting a different pathway than for the Transformation of all-Trans-beta-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds.
Yves Waché - One of the best experts on this subject based on the ideXlab platform.
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Effect of Cis/Trans Isomerism of β-carotene on the ratios of volatile compounds produced during oxidative degradation
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Yves Waché, Aurélie Bosser-deratuld, J-c Lhuguenot, Jean-marc BelinAbstract:β-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are β-ionone, 5,6-epoxy-β-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of β-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9−C10 bond. This study investigated the influence of Cis/Trans Isomerism at the C9−C10 bond on the production of β-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. β-Carotene solutions containing high ratios of 9-Cis-isomers produced more DHA, suggesting a different pathway than for the Transformation of all-Trans-β-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds. Keywords: β-Carotene...
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effect of Cis Trans Isomerism of β carotene on the ratios of volatile compounds produced during oxidative degradation
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Yves Waché, J-c Lhuguenot, Aurelie Bosserderatuld, Jean-marc BelinAbstract:β-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are β-ionone, 5,6-epoxy-β-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of β-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9−C10 bond. This study investigated the influence of Cis/Trans Isomerism at the C9−C10 bond on the production of β-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. β-Carotene solutions containing high ratios of 9-Cis-isomers produced more DHA, suggesting a different pathway than for the Transformation of all-Trans-β-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds. Keywords: β-Carotene...
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Effect of Cis/Trans Isomerism of β-Carotene on the Ratios of Volatile Compounds Produced during Oxidative Degradation
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Yves Waché, Aurélie Bosser-deratuld, J-c Lhuguenot, Jean-marc BelinAbstract:beta-Carotene is, when cleaved, an important source of flavor and aroma compounds in fruits and flowers. Among these aroma compounds, the main degradation products are beta-ionone, 5,6-epoxy-beta-ionone, and dihydroactinidiolide (DHA), which are associated by flavorists and perfumers with fruity, floral, and woody notes. These three species can be produced by degradation of beta-carotene through an attack by enzyme-generated free radicals and a cleavage at the C9-C10 bond. This study investigated the influence of Cis/Trans Isomerism at the C9-C10 bond on the production of beta-carotene degradation compounds, first with a predictive approach and then experimentally with different isomer mixtures. beta-Carotene solutions containing high ratios of 9-Cis-isomers produced more DHA, suggesting a different pathway than for the Transformation of all-Trans-beta-carotene to ionone and DHA. These results are important in the search for financially viable processes to produce natural carotene-derived aroma compounds.
Krista M Thomas - One of the best experts on this subject based on the ideXlab platform.
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Effects of i and i+3 residue identity on Cis–Trans Isomerism of the aromatici+1–prolyli+2 amide bond: Implications for type VI β‐turn formation
Biopolymers, 2020Co-Authors: Hai Yun Meng, Krista M Thomas, Neal J ZondloAbstract:Cis-Trans isomerization of amide bonds plays critical roles in protein molecular recognition, protein folding, protein misfolding, and disease. Aromatic-proline sequences are particularly prone to exhibit Cis amide bonds. The roles of residues adjacent to a tyrosine-proline residue pair on Cis-Trans Isomerism were examined. A short series of peptides XYPZ was synthesized and Cis-Trans Isomerism was analyzed. Based on these initial studies, a series of peptides XYPN, X = all 20 canonical amino acids, was synthesized and analyzed by NMR for i residue effects on Cis-Trans isomerization. The following effects were observed: (a) aromatic residues immediately preceding Tyr-Pro disfavor Cis amide bonds, with K(Trans/Cis)= 5.7-8.0, W > Y > F; (b) proline residues preceding Tyr-Pro lead to multiple species, exhibiting Cis-Trans isomerization of either or both X-Pro amide bonds; and (c) other residues exhibit similar values of K(Trans/Cis) (= 2.9-4.2), with Thr and protonated His exhibiting the highest fraction Cis. beta-Branched and short polar residues were somewhat more favorable in stabilizing the Cis conformation. Phosphorylation of serine at the i position modestly increases the stability of the Cis conformer. In addition, the effect of the i+3 residue was examined in a limited series of peptides TYPZ. NMR data indicated that aromatic residues, Pro, Asn, Ala, and Val at the i+3 residue all favor Cis amide bonds, with aromatic residues and Asn favoring more compact phi at Tyr(Cis) and Ala and Pro favoring more extended phi at Tyr(Cis). D-Alanine at the i+3 position particularly disfavors Cis amide bonds.
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electronic control of amide Cis Trans Isomerism via the aromatic prolyl interaction
Journal of the American Chemical Society, 2006Co-Authors: Krista M Thomas, Devan Naduthambi, Neal J ZondloAbstract:The Cis−Trans isomerization of prolyl amide bonds results in large structural and functional changes in proteins and is a rate-determining step in protein folding. We describe a novel electronic strategy to control Cis−Trans isomerization, based on the demonstration that interactions between aromatic residues and proline are tunable by aromatic electronics. A series of peptides of sequence TXPN, X = Trp, pyridylalanine, pentafluorophenylalanine, or 4-Z-phenylalanine derivatives (Z = electron-donating, electron-withdrawing, or electron-neutral substituents), was synthesized and KTrans/Cis analyzed by NMR. Electron-rich aromatic residues stabilized Cis amide bond formation, while electron-poor aromatics relatively favored Trans amide bond formation. A Hammett correlation between aromatic electronics and Cis−Trans isomerization was observed. These results indicate that the interaction between aromatic residues and proline, which is observed to stabilize Cis amide bonds and is also a general stabilizing inter...
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effects of i and i 3 residue identity on Cis Trans Isomerism of the aromatici 1 prolyli 2 amide bond implications for type vi β turn formation
Biopolymers, 2006Co-Authors: Hai Yun Meng, Krista M Thomas, Neal J ZondloAbstract:: Cis-Trans isomerization of amide bonds plays critical roles in protein molecular recognition, protein folding, protein misfolding, and disease. Aromatic-proline sequences are particularly prone to exhibit Cis amide bonds. The roles of residues adjacent to a tyrosine-proline residue pair on Cis-Trans Isomerism were examined. A short series of peptides XYPZ was synthesized and Cis-Trans Isomerism was analyzed. Based on these initial studies, a series of peptides XYPN, X = all 20 canonical amino acids, was synthesized and analyzed by NMR for i residue effects on Cis-Trans isomerization. The following effects were observed: (a) aromatic residues immediately preceding Tyr-Pro disfavor Cis amide bonds, with K(Trans/Cis)= 5.7-8.0, W > Y > F; (b) proline residues preceding Tyr-Pro lead to multiple species, exhibiting Cis-Trans isomerization of either or both X-Pro amide bonds; and (c) other residues exhibit similar values of K(Trans/Cis) (= 2.9-4.2), with Thr and protonated His exhibiting the highest fraction Cis. beta-Branched and short polar residues were somewhat more favorable in stabilizing the Cis conformation. Phosphorylation of serine at the i position modestly increases the stability of the Cis conformer. In addition, the effect of the i+3 residue was examined in a limited series of peptides TYPZ. NMR data indicated that aromatic residues, Pro, Asn, Ala, and Val at the i+3 residue all favor Cis amide bonds, with aromatic residues and Asn favoring more compact phi at Tyr(Cis) and Ala and Pro favoring more extended phi at Tyr(Cis). D-Alanine at the i+3 position particularly disfavors Cis amide bonds.
Corine Mathoniere - One of the best experts on this subject based on the ideXlab platform.
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solvent triggered Cis Trans Isomerism in cobalt dioxolene chemistry distinguishing effects of packing on valence tautomerism
Inorganic Chemistry, 2016Co-Authors: Anangamohan Panja, Narayan Ch Jana, Antonio Bauza, Antonio Frontera, Corine MathoniereAbstract:In this article, the synthesis and X-ray crystal structures of two Cis/Trans isomers of valence tautomeric (VT) cobalt dioxolene compounds are reported. The Cis isomer (1) was isolated from the polar protic methanol solvent as a kinetic product, whereas the less polar nonprotic solvent acetone yielded the Trans isomer (2). It should be noted that, although some coordination polymers involving cobalt bis(dioxolene) with the Cis disposition are known for bridging ancillary ligands, such an arrangement is unprecedented for mononuclear compounds. A careful study of intermocular interactions revealed that the methanol solvent does not have much influence on the crystal growth in 1, whereas acetone forms strong halogen-bonding interactions that are crucial in the solid-state architecture of 2. This behavior can likely be used in crystal engineering to design new organic–inorganic hybrid materials. The energy difference between the two isomers was examined using DFT calculations, confirming that the Trans form i...
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Solvent-Triggered Cis/Trans Isomerism in Cobalt Dioxolene Chemistry: Distinguishing Effects of Packing on Valence Tautomerism.
Inorganic Chemistry, 2016Co-Authors: Anangamohan Panja, Narayan Ch Jana, Antonio Bauza, Antonio Frontera, Corine MathoniereAbstract:In this article, the synthesis and X-ray crystal structures of two Cis/Trans isomers of valence tautomeric (VT) cobalt dioxolene compounds are reported. The Cis isomer (1) was isolated from the polar protic methanol solvent as a kinetic product, whereas the less polar nonprotic solvent acetone yielded the Trans isomer (2). It should be noted that, although some coordination polymers involving cobalt bis(dioxolene) with the Cis disposition are known for bridging ancillary ligands, such an arrangement is unprecedented for mononuclear compounds. A careful study of intermocular interactions revealed that the methanol solvent does not have much influence on the crystal growth in 1, whereas acetone forms strong halogen-bonding interactions that are crucial in the solid-state architecture of 2. This behavior can likely be used in crystal engineering to design new organic–inorganic hybrid materials. The energy difference between the two isomers was examined using DFT calculations, confirming that the Trans form i...