Cytochrome P450 enzymes catalyze diverse oxidative transformations at the expense of reduced nicotinamide adenine dinucleotide phosphate(NADPH),however,their applications remain limited largely because NADPH is cost-p...Cytochrome P450 enzymes catalyze diverse oxidative transformations at the expense of reduced nicotinamide adenine dinucleotide phosphate(NADPH),however,their applications remain limited largely because NADPH is cost-prohibitive for biocatalysis at scale yet tightly regulated in host cells.A highly challenging task for P450 catalysis has been to develop an alternative and biocompatible electrondonating system.Here we engineered P450 BM3 to favor reduced nicotinamide cytosine dinucleotide(NCDH)and created non-natural cofactor-dependent P450 catalysis.Two outstanding mutants were identified with over 640-fold NCDH preference improvement and good catalytic efficiencies of over15,000 M^(-1)s^(-1)for the oxidation of the fatty acid probe 12-(para-nitrophenoxy)-dodecanoate.Molecular docking analysis indicated that these mutants bear a compacted cofactor entrance.Upon fusing with an NCD-dependent formate dehydrogenase,fused proteins functioned as NCDH-specific P450catalysts by using formate as the electron donor.Importantly,these mutants and fusions catalyzed NCDH-dependent hydroxylation of fatty acids with similar chain length preference to those by natural P450 BM3 in the presence of NADPH and also similar regioselectivity for subterminal hydroxylation of lauric acid.As P450 BM3 and its variants are catalytically powerful to take diverse substrates and convey different reaction paths,our results offer an exciting opportunity to devise advanced cell factories that convey oxidative biocatalysis with an orthogonal reducing power supply system.展开更多
The potential energy difference of trivalent Pr/Nd complex ions with various α hydroxyl carboxylic acids were computed by molecular mechanics plus(MM +) model. Its relationships with the steric hindrance of the...The potential energy difference of trivalent Pr/Nd complex ions with various α hydroxyl carboxylic acids were computed by molecular mechanics plus(MM +) model. Its relationships with the steric hindrance of the coordinating lignads and with the separation factor of Pr/Nd were discussed. It is found that the MM + model can be used for selecting and designing ligand as effective eluant, with which Pr 3+ and Nd 3+ can be separated by ion exchange chromatography.展开更多
The compound 15α-hydroxyl-oleanolic acid was biotransformed from oleanolic acid with Colletotrichum lini AS3.4486,and its structure was characterized by 1H NMR,13C NMR,HR-ESI-MS and single-crystal X-ray diffraction.T...The compound 15α-hydroxyl-oleanolic acid was biotransformed from oleanolic acid with Colletotrichum lini AS3.4486,and its structure was characterized by 1H NMR,13C NMR,HR-ESI-MS and single-crystal X-ray diffraction.The crystal of the title compound belongs to monoclinic,space group R3 with a=34.255（5）,b=34.255（5）,c=6.8671（14）,β=90°,Z=9,V=6978（2）3,Mr=490.70,Dc=1.051 mg/m3,μ=0.069 mm-1,F（000）=2430,R=0.0375 and wR=0.0808.The title compound is stacked into a three-dimensional network through hydrogen bonds.展开更多
The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicyl...The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicylic acid was employed as an innovative molecular probe of hydroxyl radical(OH) generated in aqueous nitrate and nitrite solutions through photochemical reactions. Kinetic studies showed that the steady-state concentrations of OH in aqueous NO- 3(10 mmol/L, pH=5) and NO- 2(10 mmol/L, pH=5) solutions under ultraviolet irradiation were at a same magnitude, 10 -15 mol/L. Apparent quantum yields of OH at 313 nm were measured as 0.011 and 0.07 for NO- 3 and NO- 2 respectively, all comparable to the results of previous studies.展开更多
A novel ternary complex of [NiL1L2·2H2O]·NO3·H2O （L1 = 2-hydroxyl-1,10-phenanthroline （HOphen）, L2 = 2-hydroxynicotinic acid （H2nicO）） was synthesized, and its crystal structure was determined by ...A novel ternary complex of [NiL1L2·2H2O]·NO3·H2O （L1 = 2-hydroxyl-1,10-phenanthroline （HOphen）, L2 = 2-hydroxynicotinic acid （H2nicO）） was synthesized, and its crystal structure was determined by X-ray diffraction and further characterized by infrared and elementary analysis. The title complex （C18H18NiN4O10, Mr = 509.07） belongs to the triclinic system, space group P1^- with a = 712490（7）, b = 11.0164（10）, c = 13.3864（13）A, α = 91.6040（10）,β= 98.8620（10）, γ= 107.1140（10）°, V= 1006.43（17）A^3, Z = 2, Dc = 1.680 g/cm^3,μ= 1.032 mm^-1, F（000） = 524, the final R = 0.0461 and wR= 0.1238. In the complex, the Ni（H） ion is six-coordinated to assume a distorted octahedral geometry, and a 3D supramolecular network comes into being via weak intermolecular interactions of X-O--.H （X = N, O）.展开更多
Many primary,secondary,tertiary alcohols,and phenolic hydroxyl groups were effectively converted to their corresponding trimethylsilyl ethers using hexamethyldisilazane in the presence of catalytic amounts of tribromo...Many primary,secondary,tertiary alcohols,and phenolic hydroxyl groups were effectively converted to their corresponding trimethylsilyl ethers using hexamethyldisilazane in the presence of catalytic amounts of tribromoisocyanuric acid and DABCO-bromine under mild conditions at room temperature with short reaction times in good to excellent yields.Excellent chemoselective silylation of hydroxyl groups in the presence of other functional groups were also observed.展开更多
Direct hydroxylation of benzene catalyzed by vanadium-con- taining heteropoly compounds with Keggin or Dawson structure has been investigated.The effects of several factors upon the hydroxylation reaction have also be...Direct hydroxylation of benzene catalyzed by vanadium-con- taining heteropoly compounds with Keggin or Dawson structure has been investigated.The effects of several factors upon the hydroxylation reaction have also been examined.It is indicated that the highest yield of phenol reached 76%(based on H_2O_(?))with 99.4～100% selectivity.展开更多
Objective： We have continued previous work in which we demonstrated that #117 and #372 amino acids contributed to the high activities of human CYP2A13 in catalyzing 4-methylnitrosamino-1-（3-pyridyl）-1-butanone（NNK...Objective： We have continued previous work in which we demonstrated that #117 and #372 amino acids contributed to the high activities of human CYP2A13 in catalyzing 4-methylnitrosamino-1-（3-pyridyl）-1-butanone（NNK） and aflatoxin BI（AFB1） carcinogenic activation. The present study was designed to identify other potential amino acid residues that contribute to the different catalytic characteristics of two CYP2A enzymes, CYP2A6 and CYP2A13, in nicotine metabolism and provide insights of the substrate and related amino acid residues interactions. Methods： A series of reciprocally substituted mutants of CYP2A6lle^300→ Phe, CYP2A6Gly^301aAla, CYP2A6Ser^369 → Gly, CYP2A13Phe^300→ Ile, CYP2A13Ala^301 → Gly and CYP2A13Gly^369 → Set were generated by site-directed mutagenesis/baculovirus-Sf9 insect cells expression. Comparative kinetic analysis of nicotine 5＇hydroxylatin by wild type and mutant CYP2A proteins was performed. Results：All amino acid residue substitutions at 300, 301 and 369 caused significant kinetic property changes in nicotine metabolism. While CYP2A6Ile^300→ Phe and CYP2A6Gly^301→Ala mutations had notable catalytic efficiency increases compared to that for the wild type CYP2A6, CYP2A13Phe^300→Ile and CYP2A13Ala^301→Gly replacement introduced remarkable catalytic efficiency decreases. In addition, all these catalytic efficiency alterations were caused by Vmax variations rather than Km changes. Substitution of #369 residue significantly affected both Km and Vmax values. CYP2A6Ser^369 → Gly increase the catalytic efficiency via a significant Km decrease versus Vmax enhancement, while the opposite effects were seen with CYP2A13Gly^369 → Ser. Conclusion：#300, #301 and #369 residues in human CYP2A6/13 play important roles in nicotine 5＇ -oxidation. Switching #300 or #301 residues did not affect the CYP2A protein affinities toward nicotine, although these amino acids are located in the active center. Set369 to Gly substitution indirectly affected nicotine binding by creating more space and conformational flexibility for the nearby residues, such as Leu^370 which is crucial for many hydroxylations.展开更多
A significant promotion effect of low-molecular hydroxyl compounds(LMHCs) was found in the nano-photoelectrocatalytic(NPEC) degradation of fulvic acid(FA),which is a typical kind of humic acid existing widely in natur...A significant promotion effect of low-molecular hydroxyl compounds(LMHCs) was found in the nano-photoelectrocatalytic(NPEC) degradation of fulvic acid(FA),which is a typical kind of humic acid existing widely in natural water bodies,and its influence mechanism was proposed.A TiO_2 nanotube arrays(TNAs) material is served as the photoanode.Methanol,ethanediol,and glycerol were chosen as the representative of LMHCs in this study.The adsorption performance of organics on the surface of TNAs was investigated by using the instantaneous photocurrent value.The adsorption constants of FA,methanol,ethanediol,and glycerol were 43.44,19.32,7.00,and 1.30,respectively,which indicates that FA has the strongest adsorption property.The degradation performance of these organics and their mixture were observed in a thin-layer reactor.It shows that FA could hardly achieve exhausted mineralization alone,while LMHCs could be easily oxidized completely in the same condition.The degradation degree of FA,which is added LMHCs,improves significantly and the best promotion effect is achieved by glycerol.The promotion effect of LMHCs in the degradation of FA could be contributed to the formation of a tremendous amount of hydroxyl radicals in the NPEC process.The hydroxyl radicals could facilitate the complete degradation of both FA and its intermediate products.Among the chosen LMHCs,glycerol molecule which has three hydroxyls could generate the most hydroxyl radicals and contribute the best effective promotion.This work provides a new way to promote the NPEC degradation of FA and a direction to remove humus from polluted water.展开更多
In the studying of the stereospecific hydroxylation of different Δ5-steroids with performic acid, followed by hydrolysis with CH3OH/KOH, we found 19-substituting groups considerably affected the reaction and we put f...In the studying of the stereospecific hydroxylation of different Δ5-steroids with performic acid, followed by hydrolysis with CH3OH/KOH, we found 19-substituting groups considerably affected the reaction and we put forward the mechanism.展开更多
基金supported by the National Key R&D Program of China(2019YFA0904900)the National Natural Science Foundation of China(21877112,21837002,21721004)。
文摘Cytochrome P450 enzymes catalyze diverse oxidative transformations at the expense of reduced nicotinamide adenine dinucleotide phosphate(NADPH),however,their applications remain limited largely because NADPH is cost-prohibitive for biocatalysis at scale yet tightly regulated in host cells.A highly challenging task for P450 catalysis has been to develop an alternative and biocompatible electrondonating system.Here we engineered P450 BM3 to favor reduced nicotinamide cytosine dinucleotide(NCDH)and created non-natural cofactor-dependent P450 catalysis.Two outstanding mutants were identified with over 640-fold NCDH preference improvement and good catalytic efficiencies of over15,000 M^(-1)s^(-1)for the oxidation of the fatty acid probe 12-(para-nitrophenoxy)-dodecanoate.Molecular docking analysis indicated that these mutants bear a compacted cofactor entrance.Upon fusing with an NCD-dependent formate dehydrogenase,fused proteins functioned as NCDH-specific P450catalysts by using formate as the electron donor.Importantly,these mutants and fusions catalyzed NCDH-dependent hydroxylation of fatty acids with similar chain length preference to those by natural P450 BM3 in the presence of NADPH and also similar regioselectivity for subterminal hydroxylation of lauric acid.As P450 BM3 and its variants are catalytically powerful to take diverse substrates and convey different reaction paths,our results offer an exciting opportunity to devise advanced cell factories that convey oxidative biocatalysis with an orthogonal reducing power supply system.
文摘The potential energy difference of trivalent Pr/Nd complex ions with various α hydroxyl carboxylic acids were computed by molecular mechanics plus(MM +) model. Its relationships with the steric hindrance of the coordinating lignads and with the separation factor of Pr/Nd were discussed. It is found that the MM + model can be used for selecting and designing ligand as effective eluant, with which Pr 3+ and Nd 3+ can be separated by ion exchange chromatography.
基金supported by the starting Foundation of Tianjin University of Science and Technology (No. 20070449)the Natural Science Foundation of Tianjin (Nos. 08JCZDJC15200 and 08JCZDJC15300)
文摘The compound 15α-hydroxyl-oleanolic acid was biotransformed from oleanolic acid with Colletotrichum lini AS3.4486,and its structure was characterized by 1H NMR,13C NMR,HR-ESI-MS and single-crystal X-ray diffraction.The crystal of the title compound belongs to monoclinic,space group R3 with a=34.255（5）,b=34.255（5）,c=6.8671（14）,β=90°,Z=9,V=6978（2）3,Mr=490.70,Dc=1.051 mg/m3,μ=0.069 mm-1,F（000）=2430,R=0.0375 and wR=0.0808.The title compound is stacked into a three-dimensional network through hydrogen bonds.
文摘The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicylic acid was employed as an innovative molecular probe of hydroxyl radical(OH) generated in aqueous nitrate and nitrite solutions through photochemical reactions. Kinetic studies showed that the steady-state concentrations of OH in aqueous NO- 3(10 mmol/L, pH=5) and NO- 2(10 mmol/L, pH=5) solutions under ultraviolet irradiation were at a same magnitude, 10 -15 mol/L. Apparent quantum yields of OH at 313 nm were measured as 0.011 and 0.07 for NO- 3 and NO- 2 respectively, all comparable to the results of previous studies.
文摘A novel ternary complex of [NiL1L2·2H2O]·NO3·H2O （L1 = 2-hydroxyl-1,10-phenanthroline （HOphen）, L2 = 2-hydroxynicotinic acid （H2nicO）） was synthesized, and its crystal structure was determined by X-ray diffraction and further characterized by infrared and elementary analysis. The title complex （C18H18NiN4O10, Mr = 509.07） belongs to the triclinic system, space group P1^- with a = 712490（7）, b = 11.0164（10）, c = 13.3864（13）A, α = 91.6040（10）,β= 98.8620（10）, γ= 107.1140（10）°, V= 1006.43（17）A^3, Z = 2, Dc = 1.680 g/cm^3,μ= 1.032 mm^-1, F（000） = 524, the final R = 0.0461 and wR= 0.1238. In the complex, the Ni（H） ion is six-coordinated to assume a distorted octahedral geometry, and a 3D supramolecular network comes into being via weak intermolecular interactions of X-O--.H （X = N, O）.
基金Supported by Bu-Ali Sina University Research Council.
文摘Many primary,secondary,tertiary alcohols,and phenolic hydroxyl groups were effectively converted to their corresponding trimethylsilyl ethers using hexamethyldisilazane in the presence of catalytic amounts of tribromoisocyanuric acid and DABCO-bromine under mild conditions at room temperature with short reaction times in good to excellent yields.Excellent chemoselective silylation of hydroxyl groups in the presence of other functional groups were also observed.
文摘Direct hydroxylation of benzene catalyzed by vanadium-con- taining heteropoly compounds with Keggin or Dawson structure has been investigated.The effects of several factors upon the hydroxylation reaction have also been examined.It is indicated that the highest yield of phenol reached 76%(based on H_2O_(?))with 99.4～100% selectivity.
文摘Objective： We have continued previous work in which we demonstrated that #117 and #372 amino acids contributed to the high activities of human CYP2A13 in catalyzing 4-methylnitrosamino-1-（3-pyridyl）-1-butanone（NNK） and aflatoxin BI（AFB1） carcinogenic activation. The present study was designed to identify other potential amino acid residues that contribute to the different catalytic characteristics of two CYP2A enzymes, CYP2A6 and CYP2A13, in nicotine metabolism and provide insights of the substrate and related amino acid residues interactions. Methods： A series of reciprocally substituted mutants of CYP2A6lle^300→ Phe, CYP2A6Gly^301aAla, CYP2A6Ser^369 → Gly, CYP2A13Phe^300→ Ile, CYP2A13Ala^301 → Gly and CYP2A13Gly^369 → Set were generated by site-directed mutagenesis/baculovirus-Sf9 insect cells expression. Comparative kinetic analysis of nicotine 5＇hydroxylatin by wild type and mutant CYP2A proteins was performed. Results：All amino acid residue substitutions at 300, 301 and 369 caused significant kinetic property changes in nicotine metabolism. While CYP2A6Ile^300→ Phe and CYP2A6Gly^301→Ala mutations had notable catalytic efficiency increases compared to that for the wild type CYP2A6, CYP2A13Phe^300→Ile and CYP2A13Ala^301→Gly replacement introduced remarkable catalytic efficiency decreases. In addition, all these catalytic efficiency alterations were caused by Vmax variations rather than Km changes. Substitution of #369 residue significantly affected both Km and Vmax values. CYP2A6Ser^369 → Gly increase the catalytic efficiency via a significant Km decrease versus Vmax enhancement, while the opposite effects were seen with CYP2A13Gly^369 → Ser. Conclusion：#300, #301 and #369 residues in human CYP2A6/13 play important roles in nicotine 5＇ -oxidation. Switching #300 or #301 residues did not affect the CYP2A protein affinities toward nicotine, although these amino acids are located in the active center. Set369 to Gly substitution indirectly affected nicotine binding by creating more space and conformational flexibility for the nearby residues, such as Leu^370 which is crucial for many hydroxylations.
基金the National High Technology Research and Development Program of China(Grant No.2009AA063003)the National Nature Science Foundation of China(Grant No.20677039) for financial support
文摘A significant promotion effect of low-molecular hydroxyl compounds(LMHCs) was found in the nano-photoelectrocatalytic(NPEC) degradation of fulvic acid(FA),which is a typical kind of humic acid existing widely in natural water bodies,and its influence mechanism was proposed.A TiO_2 nanotube arrays(TNAs) material is served as the photoanode.Methanol,ethanediol,and glycerol were chosen as the representative of LMHCs in this study.The adsorption performance of organics on the surface of TNAs was investigated by using the instantaneous photocurrent value.The adsorption constants of FA,methanol,ethanediol,and glycerol were 43.44,19.32,7.00,and 1.30,respectively,which indicates that FA has the strongest adsorption property.The degradation performance of these organics and their mixture were observed in a thin-layer reactor.It shows that FA could hardly achieve exhausted mineralization alone,while LMHCs could be easily oxidized completely in the same condition.The degradation degree of FA,which is added LMHCs,improves significantly and the best promotion effect is achieved by glycerol.The promotion effect of LMHCs in the degradation of FA could be contributed to the formation of a tremendous amount of hydroxyl radicals in the NPEC process.The hydroxyl radicals could facilitate the complete degradation of both FA and its intermediate products.Among the chosen LMHCs,glycerol molecule which has three hydroxyls could generate the most hydroxyl radicals and contribute the best effective promotion.This work provides a new way to promote the NPEC degradation of FA and a direction to remove humus from polluted water.
文摘In the studying of the stereospecific hydroxylation of different Δ5-steroids with performic acid, followed by hydrolysis with CH3OH/KOH, we found 19-substituting groups considerably affected the reaction and we put forward the mechanism.
