Organic acids in 3 kinds of soy sauces were analyzed by HRLC.Column:C18 ()Bondapak(10μm,3.9mm i.d.* 30cm;mobile phase:0.5%(NH_4)_2HPO_4(pH=2.9);flow rate:1.0 ml/m.PT-C18 cartridge was used for the sample preparation....Organic acids in 3 kinds of soy sauces were analyzed by HRLC.Column:C18 ()Bondapak(10μm,3.9mm i.d.* 30cm;mobile phase:0.5%(NH_4)_2HPO_4(pH=2.9);flow rate:1.0 ml/m.PT-C18 cartridge was used for the sample preparation.Recoveries of organic acids are between 96-111%.展开更多
Two complexes,NdL_3·2C_2H_5OH and NdL_3·2H_2O where L=cyclohexane-carboxylate anion,were synthesized and the structure of the former was determined by the single-crystal X-ray diffration method. The crystal ...Two complexes,NdL_3·2C_2H_5OH and NdL_3·2H_2O where L=cyclohexane-carboxylate anion,were synthesized and the structure of the former was determined by the single-crystal X-ray diffration method. The crystal is triclinic,Pspace group with the cell parameters:a=1.2385(6),b=1.2385(6),c=0.9421(5) nm.α=91.69(4)°,β=98.49(4)°,γ=99.16(5)°,Z=2,V=1.436 nm^3.The structure was refined to R value of 0.0866.Each Nd atom is connected with other two Nd atoms by two bidentate and two tridentate carboxyl groups to form a linear polymer.The Nd atom is further coordinated by a chelating carboxyl and two ethanol molecules.So the central atom is nine-coordinated with a distorted monocapped square-antiprism geometry.The infrared spectra and the thermal analysis of the complexes were also studied.展开更多
A new method for the determination of components in mixed acids has been developed.The mathematical model is obtained from samples of known composition and is then used to predict the concentrations of components in u...A new method for the determination of components in mixed acids has been developed.The mathematical model is obtained from samples of known composition and is then used to predict the concentrations of components in unknown sample.The practical utility of this method is demonstrated for simultaneous determination of two systems of ternary mixed acids and the results are satisfactory.展开更多
A simple isocratic HPLC technique has been developed for the quantitative analysis of phenolic acids (PAs) in fruits and vegetables. Nine benzoic and cinnamic acid derivatives were separated in less than 30 min, and t...A simple isocratic HPLC technique has been developed for the quantitative analysis of phenolic acids (PAs) in fruits and vegetables. Nine benzoic and cinnamic acid derivatives were separated in less than 30 min, and the resolution was all more than 1.23. The ranges of linearity for PAs standards were 0.2-100 ng, even up to 600 ng (r = 0.983-1.000) and the detection limits were 0.02-0.24 mg/kg. Samples of fresh vegetables and fruits were extracted with 80% mcthanol and ethyl acetate, then purified with C18 Sep-Pak cartridge and determined by HPLC. This method was applied to the determination of PAs in 7 kinds of fruits and vegetables, i.e., apple, pear, Chinese cabbage, cauliflower, turnip, soybean sprout and white grape wine. The content of the 9 PAs varied widely in the 7 kinds ol'foods studied. The average concentrations ofchlorogenic acid in apple (100.2 mg/kg) and pear (30.8 mg/kg) were quite high, and sinapinic acid was remarkable (42.5 mg/kg) in Chinese cabbage, and protocatechuic acid had the highest concentration of all the PAs in white wine.展开更多
Nowadays, modified electrodes with metal nanoparticles have appeared as an alternative for the electroanalysis of various compounds. In this study, gold nanoparticles（GNPs） were chosen as interesting metal nanoparti...Nowadays, modified electrodes with metal nanoparticles have appeared as an alternative for the electroanalysis of various compounds. In this study, gold nanoparticles（GNPs） were chosen as interesting metal nanoparticles for modifying carbon paste electrode（CPE）. GNPs and the gold nanoparticles-modified carbon paste electrode（GNPs/CPE） were characterized by UV–Vis spectroscopy, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. GNPs/CPE as a simple and sensitive electrode was used to study three important biological molecules： folic acid（FA）, uric acid（UA） and ascorbic acid（AA）. Square wave voltammetry（SWV） was used as an accurate technique for quantitative measurements. A good linear relation was observed between anodic peak current（ipa） and FA（5.2 × 10（-6）– 2.5 × 10（-5）M）, UA（1.2 × 10（-6）– 2.1 × 10（-5）M） and AA（1.2 × 10（-6）– 2.5 × 10（-5）M） concentrations in simultaneous determination of these molecules.展开更多
To accomplish their functions, proteins have to achieve different conformations accompanied by conformational transitions. However, the relationship between the preference of amino acids and the stability of the secon...To accomplish their functions, proteins have to achieve different conformations accompanied by conformational transitions. However, the relationship between the preference of amino acids and the stability of the secondary structure is still unclear. Here we perform molecular simulations on a series of helical structures. Our data show that the dissociation energy of the helical structure is related to the preference of amino acids, and the electrostatic repulsion of the residue i and i ＋ 3/4 with the same sign of charge destabilizes the alpha helix.展开更多
The acid dissociation constants of N-carboxymethyl-N-(p-hydroxy phenyl carbamoyl- methyl)-2,3-dihydroxy-5-carbomethoxy benzylamine(CHDCB) and the stability constants of its 1:1 complexes with alkaline earth, Cd(Ⅱ), ...The acid dissociation constants of N-carboxymethyl-N-(p-hydroxy phenyl carbamoyl- methyl)-2,3-dihydroxy-5-carbomethoxy benzylamine(CHDCB) and the stability constants of its 1:1 complexes with alkaline earth, Cd(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), Fe(Ⅲ),Th(Ⅳ)and U(Ⅵ)ions have been determined at 25.0±0.1℃ and at an ionic strength of 0.1(KNO_3)by pH titration method. The probable coordination sites have also been discussed.展开更多
文摘Organic acids in 3 kinds of soy sauces were analyzed by HRLC.Column:C18 ()Bondapak(10μm,3.9mm i.d.* 30cm;mobile phase:0.5%(NH_4)_2HPO_4(pH=2.9);flow rate:1.0 ml/m.PT-C18 cartridge was used for the sample preparation.Recoveries of organic acids are between 96-111%.
文摘Two complexes,NdL_3·2C_2H_5OH and NdL_3·2H_2O where L=cyclohexane-carboxylate anion,were synthesized and the structure of the former was determined by the single-crystal X-ray diffration method. The crystal is triclinic,Pspace group with the cell parameters:a=1.2385(6),b=1.2385(6),c=0.9421(5) nm.α=91.69(4)°,β=98.49(4)°,γ=99.16(5)°,Z=2,V=1.436 nm^3.The structure was refined to R value of 0.0866.Each Nd atom is connected with other two Nd atoms by two bidentate and two tridentate carboxyl groups to form a linear polymer.The Nd atom is further coordinated by a chelating carboxyl and two ethanol molecules.So the central atom is nine-coordinated with a distorted monocapped square-antiprism geometry.The infrared spectra and the thermal analysis of the complexes were also studied.
基金This project is supported by National Natural Science Foundation of China
文摘A new method for the determination of components in mixed acids has been developed.The mathematical model is obtained from samples of known composition and is then used to predict the concentrations of components in unknown sample.The practical utility of this method is demonstrated for simultaneous determination of two systems of ternary mixed acids and the results are satisfactory.
文摘A simple isocratic HPLC technique has been developed for the quantitative analysis of phenolic acids (PAs) in fruits and vegetables. Nine benzoic and cinnamic acid derivatives were separated in less than 30 min, and the resolution was all more than 1.23. The ranges of linearity for PAs standards were 0.2-100 ng, even up to 600 ng (r = 0.983-1.000) and the detection limits were 0.02-0.24 mg/kg. Samples of fresh vegetables and fruits were extracted with 80% mcthanol and ethyl acetate, then purified with C18 Sep-Pak cartridge and determined by HPLC. This method was applied to the determination of PAs in 7 kinds of fruits and vegetables, i.e., apple, pear, Chinese cabbage, cauliflower, turnip, soybean sprout and white grape wine. The content of the 9 PAs varied widely in the 7 kinds ol'foods studied. The average concentrations ofchlorogenic acid in apple (100.2 mg/kg) and pear (30.8 mg/kg) were quite high, and sinapinic acid was remarkable (42.5 mg/kg) in Chinese cabbage, and protocatechuic acid had the highest concentration of all the PAs in white wine.
基金the Post-graduate Office of Guilan University(A-384579)for supporting
文摘Nowadays, modified electrodes with metal nanoparticles have appeared as an alternative for the electroanalysis of various compounds. In this study, gold nanoparticles（GNPs） were chosen as interesting metal nanoparticles for modifying carbon paste electrode（CPE）. GNPs and the gold nanoparticles-modified carbon paste electrode（GNPs/CPE） were characterized by UV–Vis spectroscopy, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. GNPs/CPE as a simple and sensitive electrode was used to study three important biological molecules： folic acid（FA）, uric acid（UA） and ascorbic acid（AA）. Square wave voltammetry（SWV） was used as an accurate technique for quantitative measurements. A good linear relation was observed between anodic peak current（ipa） and FA（5.2 × 10（-6）– 2.5 × 10（-5）M）, UA（1.2 × 10（-6）– 2.1 × 10（-5）M） and AA（1.2 × 10（-6）– 2.5 × 10（-5）M） concentrations in simultaneous determination of these molecules.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11247010,11175055,11475053 and 11347017the Natural Science Foundation for Distinguished Young Scholars of Hebei Province under Grant No C2015202340+1 种基金the Natural Science Foundation of Hebei Province under Grant Nos C2012202079 and C201400305the Scientific Innovation Fund for Excellent Young Scientists of Hebei University of Technology under Grant No 2015010
文摘To accomplish their functions, proteins have to achieve different conformations accompanied by conformational transitions. However, the relationship between the preference of amino acids and the stability of the secondary structure is still unclear. Here we perform molecular simulations on a series of helical structures. Our data show that the dissociation energy of the helical structure is related to the preference of amino acids, and the electrostatic repulsion of the residue i and i ＋ 3/4 with the same sign of charge destabilizes the alpha helix.
文摘The acid dissociation constants of N-carboxymethyl-N-(p-hydroxy phenyl carbamoyl- methyl)-2,3-dihydroxy-5-carbomethoxy benzylamine(CHDCB) and the stability constants of its 1:1 complexes with alkaline earth, Cd(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), Fe(Ⅲ),Th(Ⅳ)and U(Ⅵ)ions have been determined at 25.0±0.1℃ and at an ionic strength of 0.1(KNO_3)by pH titration method. The probable coordination sites have also been discussed.
