In this paper,tannic acid(TA)and Fe~(3+)were added to form a layer of metal-polyphenol network structure on the surface of the nanoparticles which were fabricated by zein and carbon quantum dots(CQDs)encapsulating phl...In this paper,tannic acid(TA)and Fe~(3+)were added to form a layer of metal-polyphenol network structure on the surface of the nanoparticles which were fabricated by zein and carbon quantum dots(CQDs)encapsulating phlorotannins(PTN).pH-Responsive nanoparticles were prepared successfully(zein-PTN-CQDs-Fe-~Ⅲ).Further,the formation of composite nanoparticles was confirmed by a series of characterization methods.The zeta-potential and Fourier transform infrared spectroscopy data proved that electrostatic interaction and hydrogen bonding are dominant forces to form nanoparticles.The encapsulation efficiency(EE)revealed that metal-polyphenol network structure could improve the EE of PTN.Thermogravimetric analysis and differential scanning calorimetry experiment indicated the thermal stability of zein-PTN-CQDs-Fe~Ⅲnanoparticles increased because of metal-polyphenol network structure.The pH-responsive nanoparticles greatly increased the release rate of active substances and achieved targeted release.展开更多
Amine transaminases(ATAs)catalyze the asymmetric amination of prochiral ketones or aldehydes to their corresponding chiral amines.However,the trade-off between activity and stability in enzyme engineering represents a...Amine transaminases(ATAs)catalyze the asymmetric amination of prochiral ketones or aldehydes to their corresponding chiral amines.However,the trade-off between activity and stability in enzyme engineering represents a major obstacle to the practical application of ATAs.Overcoming this trade-off is important for developing robustly engineered enzymes and a universal approach for ATAs.Herein,we modified the binding pocket of co-ATA from Aspergillus terreus(AtATA)to identify the key amino acid residues controlling the activity and stability of AtATA toward 1-acetonaphthone.We discovered a structural switch comprising four key amino acid sites(R128,V149,L182,and L187),as well as the"best"mutant(AtATAD224K/V149A/L182 F/L187F;termed M4).Compared to the parent enzyme AtATAD224K(AtATAPa),M4 increased the catalytic efficiency(k_(cat)/K_(m)^(1-acetonaphthone),where kcatis the constant of catalytic activities and is 10.1 min^(-1),K_(m)^(1-acetonaphthoneis) Michaelis-Menten constant and is 1.7 mmol·L^(-1))and half-life(t1/2)by 59-fold to 5.9 L·min^(-1)·mmol-1and by 1.6-fold to 46.9 min,respectively.Moreover,using M4 as the biocatalyst,we converted a 20 mmol·L^(-1)aliquot of 1-acetonaphthone in a 50 mL scaled-up system to the desired product,(R)-(+)-1(1-naphthyl)ethylamine((R)-NEA),with 78%yield and high enantiomeric purity(R>99.5%)within 10 h.M4 also displayed significantly enhanced activity toward various 1-acetonaphthone analogs.The related structural properties derived by analyzing structure and sequence information of robust ATAs illustrated their enhanced activity and thermostability.Strengthening of intramolecular interactions and expansion of the angle between the substratebinding pocket and the pyridoxal 5’-phosphate(PLP)-binding pocket contributed to synchronous enhancement of ATA thermostability and activity.Moreover,this pocket engineering strategy successfully transferred enhanced activity and thermostability to three other ATAs,which exhibited 8%-22%sequence similarity with AtATA.This research has important implications for overcoming the trade-off between ATA activity and thermostability.展开更多
Toxicities (–lgEC50) of 16 phenolic compounds against Q67 were determined, and structural parameters as well as thermodynamic parameters of these compounds were obtained through fully optimized calculations by using ...Toxicities (–lgEC50) of 16 phenolic compounds against Q67 were determined, and structural parameters as well as thermodynamic parameters of these compounds were obtained through fully optimized calculations by using B3LYP method of density functional theory (DFT) at the 6-311G** level. Moreover, a 3-parameter (molecular average polarizability (α), heat energy corrected value (Eth) and the most positive hydrogen atomic charge (qH+)) correlation model with R2 = 0.981 and q2 = 0.967 to predict –lgEC50 was obtained from experimental data based on the above-mentioned parameters as theoretical descriptors. Therein α was the most significant on –lgEC50. Variance Inflation Factors (VIF), t-value and cross-validation were applied to verify the model, confirming that the resultant model has fairly better stability and predictive ability to predict –lgEC50 of similar compounds.展开更多
Optimized calculations of 75 PCDDs and their parent DD were carried out at the B3LYP/6-31G* level by density functional theory (DFT) method. The structural parameters were obtained and significant correlation between ...Optimized calculations of 75 PCDDs and their parent DD were carried out at the B3LYP/6-31G* level by density functional theory (DFT) method. The structural parameters were obtained and significant correlation between the Cl substitution position and some structural parameters was found. Consequently, the number of Cl substitution positions was taken as theoretical descriptors to establish two novel QSPR models for predicting lgKow and –lgSw of all PCDD congeners. The two models achieved in this work contain two variables (Nα and Nβ), of which r = 0.9312, 0.9965 and SD = 0.27, 0.12 respectively, and t values are all large. The variation inflation factors (VIF) of variables in the two models herein are both less than 5.0, suggesting high accuracy of the lgKow and –lgSw predicting models, and the results of cross-validation test also show that the two models exhibit optimum stability and good predictive power. By comparison, the correlation and predictive ability of the present work are more advantageous than those obtained using semi-empirical AM1 and GC-RI methods.展开更多
Optimization calculations of 209 polychlorinated biphenyls (PCBs) were carried out at the B3LYP/6-31G* level. It was found that there is significant correlation between the Cl substitution position and some structural...Optimization calculations of 209 polychlorinated biphenyls (PCBs) were carried out at the B3LYP/6-31G* level. It was found that there is significant correlation between the Cl substitution position and some structural parameters. Consequently, Cl substitution positions were taken as theoretical descriptors to establish a novel QSPR model for predicting –lgS_w of all PCB congeners. The model achieved in this work contains four variables, of which r2 = 0.9527, q2 = 0.9490 and SD = 0.25 with large t values. In addition, the variation inflation factors (VIFs) of variables in this model are all less than 5.0, suggesting high accuracy of the –lgS_w predicting model. And the results of cross-validation test and method validation also show that the model exhibits optimum stability and better predictive capability than that from the AM1 method.展开更多
Toxicities (–lgEC50) of 16 halogeno-benzenes against vibrio qinghaiensis (Q67) were measured systematically, and their 2D-QSAR model (R2=0.875, q2=0.821) was established, which included two parameters: averaged polar...Toxicities (–lgEC50) of 16 halogeno-benzenes against vibrio qinghaiensis (Q67) were measured systematically, and their 2D-QSAR model (R2=0.875, q2=0.821) was established, which included two parameters: averaged polarizability (α) and total energy (TE). The proposed model indicated that the toxicities of this kind of compounds were proportionate to α, i.e., their toxicities were relative to the molecular volume. Furthermore, 3D-QSAR model (R2=0.929, q2=0.712) of –lgEC50 was proposed by using comparative molecular force field (CoMFA) based on the molecular simulation. To our interest, 3D-QSAR model suggested that the hydrophobicity of substituents was the dominating factor for the toxicities, the electrostatic effect was the secondly important, and the steric field gave the least contribution. Comparably, the prediction ability of the 3D-QSAR model is slightly more advantageous than that of 2D-QSAR, and they can be used complementally in the toxicity description of this kind of compounds.展开更多
The thermodynamic properties and molecular volumes (Vm) of 76 polychlorophe- nazines (PCPZs) have been calculated at the B3LYP/6-31G* level by using density functional theory. The isodesmic reactions were designed to ...The thermodynamic properties and molecular volumes (Vm) of 76 polychlorophe- nazines (PCPZs) have been calculated at the B3LYP/6-31G* level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation (△fHθ) and standard free energy of formation (△fGθ) of PCPZ congeners. According to the relative magnitude of their △fGθ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin (PCDD) isomers, it was found that Sθ, △fHθ, △fGθ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.展开更多
In this paper, n-octanol/water partition coefficients (lgKow) of 15 fluorobenzene derivatives at 25 ℃ were determined with shake-flask method. Molecular structures of 19 fluorobenzene derivatives were fully optimized...In this paper, n-octanol/water partition coefficients (lgKow) of 15 fluorobenzene derivatives at 25 ℃ were determined with shake-flask method. Molecular structures of 19 fluorobenzene derivatives were fully optimized with B3LYP method of density functional theory (DFT) on the 6-311G** basis set. The obtained structural parameters and thermodynamic parameters were taken as theoretical descriptors with SPSS 12.0 for windows program so as to obtain the predicted correlation model of lgKow. Its correlation coefficient R2 is 0.966, and the model was verified with variance inflation factor (VIF) and t value so that the cross-validation coefficient (q2) was obtained as 0.931. In addition, the four homogeneous compounds were predicted.展开更多
The structural and thermodynamic properties of 75 polychlorinated thianthrenes(PCTAs) in the ideal gas state at 298.15 K and 1.013 ×105 Pa have been calculated at the B3LYP/6-31G level using Gaussian 98 program.B...The structural and thermodynamic properties of 75 polychlorinated thianthrenes(PCTAs) in the ideal gas state at 298.15 K and 1.013 ×105 Pa have been calculated at the B3LYP/6-31G level using Gaussian 98 program.Based on the output data of Gaussian=the isodesmic reactions were designed to calculate standard enthalpy of formation(△fHθ) and standard free energy of formation(△fGθ) of PCTAs congeners.The relations of these thermodynamic parameters with the number and position of Cl atom substitution(NPCS) were discussed=and it was found that there exists high correlation between thermodynamic parameters(total energy(TE)=zero-point vibrational energy(ZPE)=thermal correction to energy(Eth)=heat capacity at constant volume(Cvθ)=entropy(Sθ)=enthalpy(Hθ)=free energy(Gθ)=standard enthalpies of formation(△fHθ) and standard Gibbs energies of formation(△fGθ)) and NPCS.On the basis of the relative magnitude of their △fGθ=the order of relative stability of PCTA congeners was theoretically proposed.In addition=the correlations between structural parameters and NPCS were also discussed.The good correlations were found between molecular average polarizability(α)=energy of the highest occupied molecular orbital(EHOMO)=molecular volume(Vm) and NPCS=and all R2 values are larger than 0.95.Moreover=it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA .展开更多
The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It ...The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It is found that the chlorine substitution pattern strongly influences the thermodynamic properties of the compounds.The thermodynamic properties of congeners with the same number of chlorines also depend on the chlorine substitution pattern,especially for ortho-substituted congeners.PCXT congeners with one phenyl ring fully chlorinated are found to be the least stable among the analogues.The effect of the chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution(NPCS).The results show that the NPCS model may be used to predict the thermodynamic properties for all 135 PCXT congeners. In addition,the values of molar heat capacities at constant pressure(cp,m)from 200 to 1000 K for PCXT congeners are calculated,and the temperature dependence relation of this parameter is obtained using the least-squares method.展开更多
Sulfuric acid-phenol and sulfuric acid-anthrone methods were used to detect polysaccharide content in shoots of Aralia elata( Miq.) Seem.,and the conversion factor to glucose was measured with refined polysaccharides....Sulfuric acid-phenol and sulfuric acid-anthrone methods were used to detect polysaccharide content in shoots of Aralia elata( Miq.) Seem.,and the conversion factor to glucose was measured with refined polysaccharides. Comprehensive evaluation was carried out by linear relationship,precision,reproducibility,stability and recovery rate. The results showed that the linear relationship between glucose concentration and absorbance was good when glucose concentration was0-40 μg/ml,and the average recovery rate was equal to or higher than 97. 00% with good reproducibility( RSD < 1. 60%,n = 5). It revealed that the two methods were accurate and reliable,and suitable for the determination of polysaccharide content in the shoots of A. elata. Polysaccharide content detected by sulfuric acid-phenol and sulfuric acid-anthrone methods was 19. 31% and 20. 40% respectively.展开更多
Sixteen indole derivatives have been computed at B3LYP/6-311G** level using density functional theory (DFT). Based on linear solvation energy theory, the structural para- meters were employed to present correlation be...Sixteen indole derivatives have been computed at B3LYP/6-311G** level using density functional theory (DFT). Based on linear solvation energy theory, the structural para- meters were employed to present correlation between the parameters of chromatograph capacity factor (CCF) and molecular structural parameters. As a result, the correlation equation of the reversed phased high performance liquid chromatograph capacity factor to the intercept lgk’w and slope S of CCF were obtained, from which the correlation coefficients of lgk’w to the structural parameters are r2 = 0.9596 and q2 = 0.9262. While the correlation coefficients of the parameter S with structures are r2 = 0.9750 and q2 = 0.9252. Moreover, the effect of water as solvent on the present two models was also considered using SCRF method, and the result shows that the predicting capacity of correlation equation of lgkw’ increases, while that of the model for S decreases slightly. Both two correlation equations achieved in this work are more advantageous than those using theoretical descriptors from molecular connectivity indices.展开更多
The Co-based catalysts were prepared with different cobalt acetate solutions. Effects of p H value were studied deeply on Fischer–Tropsch synthesis(FTS) through a semi-batch reactor. Among all impregnation solutions(...The Co-based catalysts were prepared with different cobalt acetate solutions. Effects of p H value were studied deeply on Fischer–Tropsch synthesis(FTS) through a semi-batch reactor. Among all impregnation solutions(water, butanol, amyl alcohol, acetic acid, nitric acid and ammonium nitrate), the catalyst prepared by NH_4NO_3 solution showed the highest catalytic activity due to its small particle size and high reduction degree. However, the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS. According to FT-IR spectra results, the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity. Whereas, the high activity of catalysts prepared from NH_4NO_3 solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower p H conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher p H value.展开更多
Ganoderma(lingzhi)is a famous herbal medicine and edible supplement in oriental countries for a long history.In this study,a simple micellar electrokinetic chromatography(MEKC)method was established for the analysis o...Ganoderma(lingzhi)is a famous herbal medicine and edible supplement in oriental countries for a long history.In this study,a simple micellar electrokinetic chromatography(MEKC)method was established for the analysis of nucleosides and bases,the major bioactive components in Ganoderma for the first time.By optimizing the borate concentration,the sodium dodecyl sulfate(SDS)concentration and the pH value of running buffer,10 nucleosides and bases achieved an ideal separation.In real sample analysis,the developed method was successfully used to determine the 10 target analytes in 23 batches of Ganoderma samples from different regions.Results indicated that contents of 10 investigated analytes in each sample showed obvious variation.The principal components analysis(PCA)and hierarchical cluster analysis(HCA)analysis classified the samples into three groups,and the HCA tree visualized the relationships which was mainly contributed by geographical partition.The results indicated geographical origin to be an important factor that affect the accumulation of nucleosides and bases in Ganoderma.In summary,this study provides a simple and practical strategy for quality assessment and cultivation reference of Ganoderma.展开更多
A bstract Cadmium(Cd) is one of the most common and widespread heavy metals in the environment. Cd has adverse effects on photosynthesis that are countered by photosystem I(PSI) and photosystem II(PSII); however, the ...A bstract Cadmium(Cd) is one of the most common and widespread heavy metals in the environment. Cd has adverse effects on photosynthesis that are countered by photosystem I(PSI) and photosystem II(PSII); however, the protective responses of these photosystems to heavy metal stress remain unclear. Using the model diatom P haeodactylum tricornutum, a biological indicator that is widely used to assess the impact of environmental toxins, we simultaneously measured the effects of Cd on PSI and PSII and examined the levels of pigments in response to high light treatments before and after Cd exposure. Cd significantly reduced the quantum yield and electron transport rates of PSI and PSII. The quantum yield of non-photochemical energy dissipation in PSI due to donor side limitation increased faster than the quantum yield due to acceptor side limitation. The Cd treatment activated the P. tricornutum xanthophyll cycle under artificial light conditions, as indicated by an increased diatoxanthin content. Xanthophyll is important for photoprotection; therefore, the accumulation of diatoxanthin may down-regulate PSII activities to reduce oxidative damage. Together, our results suggest that the rapid reduction in PSII activities following Cd exposure is an adaptive response to heavy metal stress that reflects the variable exposure to external stressors in the native P. tricornutum environment.展开更多
The reaction of 2-6-iPr2C6H3NHSiMe3 with Tb(CH2SiMe3)3(THF)2 in benzene at room temperature afforded a binuclear terbium complex Tb2{μ-CH2SiMe2NC6H3iPr2-2, 6}3(THF)3. X-ray diffraction revealed that Tb atoms were bri...The reaction of 2-6-iPr2C6H3NHSiMe3 with Tb(CH2SiMe3)3(THF)2 in benzene at room temperature afforded a binuclear terbium complex Tb2{μ-CH2SiMe2NC6H3iPr2-2, 6}3(THF)3. X-ray diffraction revealed that Tb atoms were bridged by three methylene units. One Tb atom was six-coordinated by two nitrogen atoms, three methylene carbons, and one THF molecule, while the other Tb atom was six-coordinated by one nitrogen atom, three methylene carbons, and two THF molecules. Both Tb atoms adopted a distorted trigonal prism geometry.展开更多
The chiral sulfide Y_4InSbS_9 has been prepared from stoichiometric elements at 1223 K in an evacuated silica tube. It crystallizes in the chiral tetragonal space group P4_32_12 with a = 9.8784(3), c = 27.3106(16) ?, ...The chiral sulfide Y_4InSbS_9 has been prepared from stoichiometric elements at 1223 K in an evacuated silica tube. It crystallizes in the chiral tetragonal space group P4_32_12 with a = 9.8784(3), c = 27.3106(16) ?, V = 2665.04(19) ?~3, Z = 8, M_r = 880.75, D_c = 4.390 g/cm^3, μ = 22.285 mm^(–1), F(000) = 3200, the final R = 0.0302 and wR = 0.0669 for 2961 observed reflections with I > 2σ(I). The structure features infinite helical chains of [In_2Sb_2S_(11)^(10–)]_∞ propagating along the c direction and they are separated by isolated Y^(3+) cations and S_(2–) anions. UV/Vis diffuse reflectance spectroscopy study shows that its optical gap is around 1.94 eV. Density functional theory(DFT) study indicates an indirect band gap with an electronic transfer excitation of S 3p to Y 5d orbital electrons.展开更多
Optimized calculation of dibenzofuran (DF) and 135 polychlorinated diben- zofurans (PCDFs ) was carried out at the B3LYP/6-31G* level in GAUSSIAN 98 program. Based on the theoretical linear solvation energy relationsh...Optimized calculation of dibenzofuran (DF) and 135 polychlorinated diben- zofurans (PCDFs ) was carried out at the B3LYP/6-31G* level in GAUSSIAN 98 program. Based on the theoretical linear solvation energy relationship (TLSER) model, the obtained structural parameters were taken as theoretical descriptors to establish the novel quantitative structure- property relationship (QSPR) model for predicting n-octanol/water partition coefficients (lgKow) of PCDFs. The new model of lgKow achieved in this work contains three variables: energy of the highest occupied molecular orbital (EHOMO), the most negative atomic partial charge (q-) and average molecular polarizability (α), of which R2 = 0.9011 and SD = 0.17 with larger t values. In addition, the variation inflation factors (VIF) of variables in the present model are all less than 5.5, suggesting high accuracy of the lgKow model. And the results of cross-validation test (q2 = 0.8688) and method validation also show this model exhibits optimum stability and better predictive power than semi-empirical method. At the same time, it is found that the aqueous solubility (-lgSw) has high relative correlation with constant volume molar heat capacity (CV0), of which R2 = 0.9777 and SD = 0.22. Moreover, lgKow and -lgSw values of all PCDF congeners were predicted respectively.展开更多
[Objectives]This study was conducted to establish the method for simultaneous determination of six active components.[Methods]Simultaneous determination of chlorogenic acid,phellodendrine,magnoflorine,jatrorrhizine,pa...[Objectives]This study was conducted to establish the method for simultaneous determination of six active components.[Methods]Simultaneous determination of chlorogenic acid,phellodendrine,magnoflorine,jatrorrhizine,palmatine and berberine in Cortex Phellodendri was carried out by HPLC with a Diamonsil C18(4.6 mm×250 mm,5μm)column was used.The mobile phase was acetonitrile-water(1‰acetic acid,2 mmol ammonium acetate)solution in gradient elution.The detection wavelength was set at 280 nm,and the column temperature was kept at 25℃and the flow rate was 1 ml/min.[Results]The linear ranges of chlorogenic acid,phellodendrine,magnoflorine,jatrorrhizine,palmatine and berberine were 20.00-320.00,18.75-130.00,25.00-200.00,5.00-100.00,20.00-200.00,and 0.09-1.80 mg/L,respectively.The average recovery was 98.1%,99.4%,97.5%,97.3%,104.0%,and 98.5%,respectively;and the RSDs were 0.5%,0.6%,0.8%,1.0%,1.4%,and 0.9%,respectively.[Conclusions]The method is convenient,stable,reliable and suitable for quality control of Cortex Phellodendri.展开更多
基金supported by the National Key R&D Program of China (2018YFD0901106)the Wenzhou Major Science and Technology Project (ZN2021002)the Ningbo“3315 series program”for high-level talents (2020B-34-G)。
文摘In this paper,tannic acid(TA)and Fe~(3+)were added to form a layer of metal-polyphenol network structure on the surface of the nanoparticles which were fabricated by zein and carbon quantum dots(CQDs)encapsulating phlorotannins(PTN).pH-Responsive nanoparticles were prepared successfully(zein-PTN-CQDs-Fe-~Ⅲ).Further,the formation of composite nanoparticles was confirmed by a series of characterization methods.The zeta-potential and Fourier transform infrared spectroscopy data proved that electrostatic interaction and hydrogen bonding are dominant forces to form nanoparticles.The encapsulation efficiency(EE)revealed that metal-polyphenol network structure could improve the EE of PTN.Thermogravimetric analysis and differential scanning calorimetry experiment indicated the thermal stability of zein-PTN-CQDs-Fe~Ⅲnanoparticles increased because of metal-polyphenol network structure.The pH-responsive nanoparticles greatly increased the release rate of active substances and achieved targeted release.
基金National Natural Science Foundation of China(32071268 and 31971372)the Ningbo"Scientific and Technological Innovation 2025"Key Project(2020Z080)for financial support。
文摘Amine transaminases(ATAs)catalyze the asymmetric amination of prochiral ketones or aldehydes to their corresponding chiral amines.However,the trade-off between activity and stability in enzyme engineering represents a major obstacle to the practical application of ATAs.Overcoming this trade-off is important for developing robustly engineered enzymes and a universal approach for ATAs.Herein,we modified the binding pocket of co-ATA from Aspergillus terreus(AtATA)to identify the key amino acid residues controlling the activity and stability of AtATA toward 1-acetonaphthone.We discovered a structural switch comprising four key amino acid sites(R128,V149,L182,and L187),as well as the"best"mutant(AtATAD224K/V149A/L182 F/L187F;termed M4).Compared to the parent enzyme AtATAD224K(AtATAPa),M4 increased the catalytic efficiency(k_(cat)/K_(m)^(1-acetonaphthone),where kcatis the constant of catalytic activities and is 10.1 min^(-1),K_(m)^(1-acetonaphthoneis) Michaelis-Menten constant and is 1.7 mmol·L^(-1))and half-life(t1/2)by 59-fold to 5.9 L·min^(-1)·mmol-1and by 1.6-fold to 46.9 min,respectively.Moreover,using M4 as the biocatalyst,we converted a 20 mmol·L^(-1)aliquot of 1-acetonaphthone in a 50 mL scaled-up system to the desired product,(R)-(+)-1(1-naphthyl)ethylamine((R)-NEA),with 78%yield and high enantiomeric purity(R>99.5%)within 10 h.M4 also displayed significantly enhanced activity toward various 1-acetonaphthone analogs.The related structural properties derived by analyzing structure and sequence information of robust ATAs illustrated their enhanced activity and thermostability.Strengthening of intramolecular interactions and expansion of the angle between the substratebinding pocket and the pyridoxal 5’-phosphate(PLP)-binding pocket contributed to synchronous enhancement of ATA thermostability and activity.Moreover,this pocket engineering strategy successfully transferred enhanced activity and thermostability to three other ATAs,which exhibited 8%-22%sequence similarity with AtATA.This research has important implications for overcoming the trade-off between ATA activity and thermostability.
基金Supported by the National＇Naturai Science Foundation of China （30970638, 21176220 and 31240054）, Zhejiang Provincial Natural Science Foundation （Z13B06008） and the National Basic Research Program of China （2007CB714305）.
基金supported by the Natural Science Foundation of Zhejiang Province (No. 2008Y507280)
文摘Toxicities (–lgEC50) of 16 phenolic compounds against Q67 were determined, and structural parameters as well as thermodynamic parameters of these compounds were obtained through fully optimized calculations by using B3LYP method of density functional theory (DFT) at the 6-311G** level. Moreover, a 3-parameter (molecular average polarizability (α), heat energy corrected value (Eth) and the most positive hydrogen atomic charge (qH+)) correlation model with R2 = 0.981 and q2 = 0.967 to predict –lgEC50 was obtained from experimental data based on the above-mentioned parameters as theoretical descriptors. Therein α was the most significant on –lgEC50. Variance Inflation Factors (VIF), t-value and cross-validation were applied to verify the model, confirming that the resultant model has fairly better stability and predictive ability to predict –lgEC50 of similar compounds.
基金This work was supported by the National Natural Science Foundation of China (No. 20737001)(2003CB415002)China Postdoctoral Science Foundation (No. 2003033486)
文摘Optimized calculations of 75 PCDDs and their parent DD were carried out at the B3LYP/6-31G* level by density functional theory (DFT) method. The structural parameters were obtained and significant correlation between the Cl substitution position and some structural parameters was found. Consequently, the number of Cl substitution positions was taken as theoretical descriptors to establish two novel QSPR models for predicting lgKow and –lgSw of all PCDD congeners. The two models achieved in this work contain two variables (Nα and Nβ), of which r = 0.9312, 0.9965 and SD = 0.27, 0.12 respectively, and t values are all large. The variation inflation factors (VIF) of variables in the two models herein are both less than 5.0, suggesting high accuracy of the lgKow and –lgSw predicting models, and the results of cross-validation test also show that the two models exhibit optimum stability and good predictive power. By comparison, the correlation and predictive ability of the present work are more advantageous than those obtained using semi-empirical AM1 and GC-RI methods.
基金This work was supported by the 973 National Basic Research Program of China (2003CB415002)the China Postdoctoral Science Foundation (No. 2003033486)
文摘Optimization calculations of 209 polychlorinated biphenyls (PCBs) were carried out at the B3LYP/6-31G* level. It was found that there is significant correlation between the Cl substitution position and some structural parameters. Consequently, Cl substitution positions were taken as theoretical descriptors to establish a novel QSPR model for predicting –lgS_w of all PCB congeners. The model achieved in this work contains four variables, of which r2 = 0.9527, q2 = 0.9490 and SD = 0.25 with large t values. In addition, the variation inflation factors (VIFs) of variables in this model are all less than 5.0, suggesting high accuracy of the –lgS_w predicting model. And the results of cross-validation test and method validation also show that the model exhibits optimum stability and better predictive capability than that from the AM1 method.
基金supported by the Analysis Science and Technology Project of Zhejiang Province (2009F70007)
文摘Toxicities (–lgEC50) of 16 halogeno-benzenes against vibrio qinghaiensis (Q67) were measured systematically, and their 2D-QSAR model (R2=0.875, q2=0.821) was established, which included two parameters: averaged polarizability (α) and total energy (TE). The proposed model indicated that the toxicities of this kind of compounds were proportionate to α, i.e., their toxicities were relative to the molecular volume. Furthermore, 3D-QSAR model (R2=0.929, q2=0.712) of –lgEC50 was proposed by using comparative molecular force field (CoMFA) based on the molecular simulation. To our interest, 3D-QSAR model suggested that the hydrophobicity of substituents was the dominating factor for the toxicities, the electrostatic effect was the secondly important, and the steric field gave the least contribution. Comparably, the prediction ability of the 3D-QSAR model is slightly more advantageous than that of 2D-QSAR, and they can be used complementally in the toxicity description of this kind of compounds.
基金supported by the National Natural Science Foundation of China (No. 20737001 and No. 20477018)
文摘The thermodynamic properties and molecular volumes (Vm) of 76 polychlorophe- nazines (PCPZs) have been calculated at the B3LYP/6-31G* level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation (△fHθ) and standard free energy of formation (△fGθ) of PCPZ congeners. According to the relative magnitude of their △fGθ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin (PCDD) isomers, it was found that Sθ, △fHθ, △fGθ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.
基金supported by the Natural Science Foundation of Zhejiang Province (2008Y507280)
文摘In this paper, n-octanol/water partition coefficients (lgKow) of 15 fluorobenzene derivatives at 25 ℃ were determined with shake-flask method. Molecular structures of 19 fluorobenzene derivatives were fully optimized with B3LYP method of density functional theory (DFT) on the 6-311G** basis set. The obtained structural parameters and thermodynamic parameters were taken as theoretical descriptors with SPSS 12.0 for windows program so as to obtain the predicted correlation model of lgKow. Its correlation coefficient R2 is 0.966, and the model was verified with variance inflation factor (VIF) and t value so that the cross-validation coefficient (q2) was obtained as 0.931. In addition, the four homogeneous compounds were predicted.
基金the National Natural Science Foundation of China(No.20737001 and 20477018)
文摘The structural and thermodynamic properties of 75 polychlorinated thianthrenes(PCTAs) in the ideal gas state at 298.15 K and 1.013 ×105 Pa have been calculated at the B3LYP/6-31G level using Gaussian 98 program.Based on the output data of Gaussian=the isodesmic reactions were designed to calculate standard enthalpy of formation(△fHθ) and standard free energy of formation(△fGθ) of PCTAs congeners.The relations of these thermodynamic parameters with the number and position of Cl atom substitution(NPCS) were discussed=and it was found that there exists high correlation between thermodynamic parameters(total energy(TE)=zero-point vibrational energy(ZPE)=thermal correction to energy(Eth)=heat capacity at constant volume(Cvθ)=entropy(Sθ)=enthalpy(Hθ)=free energy(Gθ)=standard enthalpies of formation(△fHθ) and standard Gibbs energies of formation(△fGθ)) and NPCS.On the basis of the relative magnitude of their △fGθ=the order of relative stability of PCTA congeners was theoretically proposed.In addition=the correlations between structural parameters and NPCS were also discussed.The good correlations were found between molecular average polarizability(α)=energy of the highest occupied molecular orbital(EHOMO)=molecular volume(Vm) and NPCS=and all R2 values are larger than 0.95.Moreover=it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA .
基金Supported by the National Natural Science Foundation of China （20977046, 20737001）.
文摘The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It is found that the chlorine substitution pattern strongly influences the thermodynamic properties of the compounds.The thermodynamic properties of congeners with the same number of chlorines also depend on the chlorine substitution pattern,especially for ortho-substituted congeners.PCXT congeners with one phenyl ring fully chlorinated are found to be the least stable among the analogues.The effect of the chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution(NPCS).The results show that the NPCS model may be used to predict the thermodynamic properties for all 135 PCXT congeners. In addition,the values of molar heat capacities at constant pressure(cp,m)from 200 to 1000 K for PCXT congeners are calculated,and the temperature dependence relation of this parameter is obtained using the least-squares method.
基金Supported by Scientific Research Project of Education Department of Liaoning Province,China(L2017lkyfwdf-05)Public Welfare Fund Project of Department of Science and Technology of Liaoning Province,China(2016003003)
文摘Sulfuric acid-phenol and sulfuric acid-anthrone methods were used to detect polysaccharide content in shoots of Aralia elata( Miq.) Seem.,and the conversion factor to glucose was measured with refined polysaccharides. Comprehensive evaluation was carried out by linear relationship,precision,reproducibility,stability and recovery rate. The results showed that the linear relationship between glucose concentration and absorbance was good when glucose concentration was0-40 μg/ml,and the average recovery rate was equal to or higher than 97. 00% with good reproducibility( RSD < 1. 60%,n = 5). It revealed that the two methods were accurate and reliable,and suitable for the determination of polysaccharide content in the shoots of A. elata. Polysaccharide content detected by sulfuric acid-phenol and sulfuric acid-anthrone methods was 19. 31% and 20. 40% respectively.
基金This work was supported by the National Basic Research Program of China (2003CB415002) and the China Postdoctoral Science Foundation (No. 2003033486) and the Natural Science Research Fund of University in Jiangsu (04KJB150149)
文摘Sixteen indole derivatives have been computed at B3LYP/6-311G** level using density functional theory (DFT). Based on linear solvation energy theory, the structural para- meters were employed to present correlation between the parameters of chromatograph capacity factor (CCF) and molecular structural parameters. As a result, the correlation equation of the reversed phased high performance liquid chromatograph capacity factor to the intercept lgk’w and slope S of CCF were obtained, from which the correlation coefficients of lgk’w to the structural parameters are r2 = 0.9596 and q2 = 0.9262. While the correlation coefficients of the parameter S with structures are r2 = 0.9750 and q2 = 0.9252. Moreover, the effect of water as solvent on the present two models was also considered using SCRF method, and the result shows that the predicting capacity of correlation equation of lgkw’ increases, while that of the model for S decreases slightly. Both two correlation equations achieved in this work are more advantageous than those using theoretical descriptors from molecular connectivity indices.
基金financial support from the National Natural Science Foundation of China (21528302)Zhejiang Province Natural Science Foundation (LQ15B060004)
文摘The Co-based catalysts were prepared with different cobalt acetate solutions. Effects of p H value were studied deeply on Fischer–Tropsch synthesis(FTS) through a semi-batch reactor. Among all impregnation solutions(water, butanol, amyl alcohol, acetic acid, nitric acid and ammonium nitrate), the catalyst prepared by NH_4NO_3 solution showed the highest catalytic activity due to its small particle size and high reduction degree. However, the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS. According to FT-IR spectra results, the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity. Whereas, the high activity of catalysts prepared from NH_4NO_3 solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower p H conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher p H value.
基金financially supported by the Research Committee of the University of Macao(MYRG2018-00239-ICMS and MYRG2014-00089-ICMS-QRCM)the Macao Science and Technology Development Fund(162/2017/A3)Guangzhou International Science and Technology Cooperation Project(File no.201807010044)。
文摘Ganoderma(lingzhi)is a famous herbal medicine and edible supplement in oriental countries for a long history.In this study,a simple micellar electrokinetic chromatography(MEKC)method was established for the analysis of nucleosides and bases,the major bioactive components in Ganoderma for the first time.By optimizing the borate concentration,the sodium dodecyl sulfate(SDS)concentration and the pH value of running buffer,10 nucleosides and bases achieved an ideal separation.In real sample analysis,the developed method was successfully used to determine the 10 target analytes in 23 batches of Ganoderma samples from different regions.Results indicated that contents of 10 investigated analytes in each sample showed obvious variation.The principal components analysis(PCA)and hierarchical cluster analysis(HCA)analysis classified the samples into three groups,and the HCA tree visualized the relationships which was mainly contributed by geographical partition.The results indicated geographical origin to be an important factor that affect the accumulation of nucleosides and bases in Ganoderma.In summary,this study provides a simple and practical strategy for quality assessment and cultivation reference of Ganoderma.
基金Supported by the National Natural Science Foundation of China(No.41506172)the International S&T Cooperation Program of China(No.2015DFG32160)
文摘A bstract Cadmium(Cd) is one of the most common and widespread heavy metals in the environment. Cd has adverse effects on photosynthesis that are countered by photosystem I(PSI) and photosystem II(PSII); however, the protective responses of these photosystems to heavy metal stress remain unclear. Using the model diatom P haeodactylum tricornutum, a biological indicator that is widely used to assess the impact of environmental toxins, we simultaneously measured the effects of Cd on PSI and PSII and examined the levels of pigments in response to high light treatments before and after Cd exposure. Cd significantly reduced the quantum yield and electron transport rates of PSI and PSII. The quantum yield of non-photochemical energy dissipation in PSI due to donor side limitation increased faster than the quantum yield due to acceptor side limitation. The Cd treatment activated the P. tricornutum xanthophyll cycle under artificial light conditions, as indicated by an increased diatoxanthin content. Xanthophyll is important for photoprotection; therefore, the accumulation of diatoxanthin may down-regulate PSII activities to reduce oxidative damage. Together, our results suggest that the rapid reduction in PSII activities following Cd exposure is an adaptive response to heavy metal stress that reflects the variable exposure to external stressors in the native P. tricornutum environment.
基金Project supported by the National Natural Science Foundation of China (20604023)Zhejiang Provincial Natural Science Foundation (Y406301)
文摘The reaction of 2-6-iPr2C6H3NHSiMe3 with Tb(CH2SiMe3)3(THF)2 in benzene at room temperature afforded a binuclear terbium complex Tb2{μ-CH2SiMe2NC6H3iPr2-2, 6}3(THF)3. X-ray diffraction revealed that Tb atoms were bridged by three methylene units. One Tb atom was six-coordinated by two nitrogen atoms, three methylene carbons, and one THF molecule, while the other Tb atom was six-coordinated by one nitrogen atom, three methylene carbons, and two THF molecules. Both Tb atoms adopted a distorted trigonal prism geometry.
基金Supported by the National Natural Science Foundation of China(Nos.21201185 and 21661037)the Natural Science Foundation of Chongqing(Nos.cstc2013jcyjA50033 and cstc2015jcyjA0317)+2 种基金the Natural Science Foundation of Guizhou Province(Nos.JLKZS[2014]13 and[2014]42)the Project Foundation of Chongqing University of Education(No.16xjpt08)the Natural Science Foundation of State Key Laboratory of Structural Chemistry(No.20140004)
文摘The chiral sulfide Y_4InSbS_9 has been prepared from stoichiometric elements at 1223 K in an evacuated silica tube. It crystallizes in the chiral tetragonal space group P4_32_12 with a = 9.8784(3), c = 27.3106(16) ?, V = 2665.04(19) ?~3, Z = 8, M_r = 880.75, D_c = 4.390 g/cm^3, μ = 22.285 mm^(–1), F(000) = 3200, the final R = 0.0302 and wR = 0.0669 for 2961 observed reflections with I > 2σ(I). The structure features infinite helical chains of [In_2Sb_2S_(11)^(10–)]_∞ propagating along the c direction and they are separated by isolated Y^(3+) cations and S_(2–) anions. UV/Vis diffuse reflectance spectroscopy study shows that its optical gap is around 1.94 eV. Density functional theory(DFT) study indicates an indirect band gap with an electronic transfer excitation of S 3p to Y 5d orbital electrons.
基金This work was supported by the China Postdoctoral Science Foundation (No. 2003033486)
文摘Optimized calculation of dibenzofuran (DF) and 135 polychlorinated diben- zofurans (PCDFs ) was carried out at the B3LYP/6-31G* level in GAUSSIAN 98 program. Based on the theoretical linear solvation energy relationship (TLSER) model, the obtained structural parameters were taken as theoretical descriptors to establish the novel quantitative structure- property relationship (QSPR) model for predicting n-octanol/water partition coefficients (lgKow) of PCDFs. The new model of lgKow achieved in this work contains three variables: energy of the highest occupied molecular orbital (EHOMO), the most negative atomic partial charge (q-) and average molecular polarizability (α), of which R2 = 0.9011 and SD = 0.17 with larger t values. In addition, the variation inflation factors (VIF) of variables in the present model are all less than 5.5, suggesting high accuracy of the lgKow model. And the results of cross-validation test (q2 = 0.8688) and method validation also show this model exhibits optimum stability and better predictive power than semi-empirical method. At the same time, it is found that the aqueous solubility (-lgSw) has high relative correlation with constant volume molar heat capacity (CV0), of which R2 = 0.9777 and SD = 0.22. Moreover, lgKow and -lgSw values of all PCDF congeners were predicted respectively.
文摘[Objectives]This study was conducted to establish the method for simultaneous determination of six active components.[Methods]Simultaneous determination of chlorogenic acid,phellodendrine,magnoflorine,jatrorrhizine,palmatine and berberine in Cortex Phellodendri was carried out by HPLC with a Diamonsil C18(4.6 mm×250 mm,5μm)column was used.The mobile phase was acetonitrile-water(1‰acetic acid,2 mmol ammonium acetate)solution in gradient elution.The detection wavelength was set at 280 nm,and the column temperature was kept at 25℃and the flow rate was 1 ml/min.[Results]The linear ranges of chlorogenic acid,phellodendrine,magnoflorine,jatrorrhizine,palmatine and berberine were 20.00-320.00,18.75-130.00,25.00-200.00,5.00-100.00,20.00-200.00,and 0.09-1.80 mg/L,respectively.The average recovery was 98.1%,99.4%,97.5%,97.3%,104.0%,and 98.5%,respectively;and the RSDs were 0.5%,0.6%,0.8%,1.0%,1.4%,and 0.9%,respectively.[Conclusions]The method is convenient,stable,reliable and suitable for quality control of Cortex Phellodendri.
