The main constituents of a typical medicinal herb, Polygonum multiflorum （Heshouwu in Chinese）, that induces idiosyncratic liver injury remain unclear. Our previous work has shown that cotreatment with a nontoxic do...The main constituents of a typical medicinal herb, Polygonum multiflorum （Heshouwu in Chinese）, that induces idiosyncratic liver injury remain unclear. Our previous work has shown that cotreatment with a nontoxic dose of lipopolysaccharide （LPS） and therapeutic dose of Heshouwu can induce liver injury in rats, whereas the solo treatment cannot induce observable injury. In the present work, using the constituent ＂knock-out＂ and ＂knock-in＂ strategy, we found that the ethyl acetate （EA） extract of Heshouwu displayed comparable idiosyncratic hepatotoxicity to the whole extract in LPS-treated rats. Results indicated a significant elevation of plasma alanine aminotransferase, aspartate aminotransferase, and liver histologic changes, whereas other separated fractions failed to induce liver injury. The mixture of EA extract with other separated fractions induced comparable idiosyncratic hepatotoxicity to the whole extract in LPS-treated rats. Chemical analysis further revealed that 2,3,5,4＇-tetrahydroxy trans-stilbene-2-O-p-glucoside （trans-SG） and its cis-isomer were the two major compounds in EA extract. Furthermore, the isolated cis-, and not its trans-isomer, displayed comparable idiosyncratic hepatotoxicity to EA extract in LPS-treated rats. Higher contents of cis-SG were detected in Heshouwu liquor or preparations from actual liver intoxication patients associated with Heshouwu compared with general collected samples. In addition, plasma metabolomics analysis showed that cis-SG-disturbing enriched pathways remarkably differed from trans-SG ones in LPS-treated rats. All these results suggested that cis-SG was closely associated with the idiosyncratic hepatotoxicity of Heshouwu. Considering that the cis-trans isomerization oftrans- SG was mediated by ultraviolet light or sunlight, our findings serve as reference for controlling photoisomerization in drug discovery and for the clinical use of Heshouwu and stilbene-related medications.展开更多
In plant chloroplasts,photosystem II(PSII)complexes,together with light-harvesting complex II(LHCII),form various PSII-LHCII supercomplexes(SCs).This process likely involves immunophilins,but the underlying regulatory...In plant chloroplasts,photosystem II(PSII)complexes,together with light-harvesting complex II(LHCII),form various PSII-LHCII supercomplexes(SCs).This process likely involves immunophilins,but the underlying regulatory mechanisms are unclear.Here,by comparing Arabidopsis thaliana mutants lacking the chloroplast lumen-localized immunophilin CYCLOPHILIN28(CYP28)to wildtype and transgenic complemented lines,we determined that CYP28 regulates the assembly and accumulation of PSII-LHCII SCs.Compared to the wild type,cyp28 plants showed accelerated leaf growth,earlier flowering time,and enhanced accumulation of high molecular weight PSII-LHCII SCs under normal light conditions.The lack of CYP28 also significantly affected the electron transport rate.Blue native-polyacrylamide gel electrophoresis analysis revealed more Lhcb6 and less Lhcb4 in M-LHCII-Lhcb4-Lhcb6 complexes in cyp28 versus wild-type plants.Peptidyl-prolyl cis/trans isomerase(PPIase)activity assays revealed that CYP28 exhibits weak PPIase activity and that its K113 and E187 residues are critical for this activity.Mutant analysis suggested that CYP28 may regulate PSIILHCII SC accumulation by altering the configuration of Lhcb6 via its PPIase activity.Furthermore,the Lhcb6-P139 residue is critical for PSII-LHCII SC assembly and accumulation.Therefore,our findings suggest that CYP28 likely regulates PSII-LHCII SC assembly and accumulation by altering the configuration of P139 of Lhcb6 via its PPIase activity.展开更多
The Irvingia gabonensis kernels, which have been extensively studied for their numerous virtues, including the ability to act against the accumulation of fats in the body[1], contain an oil. The aging of this oil unde...The Irvingia gabonensis kernels, which have been extensively studied for their numerous virtues, including the ability to act against the accumulation of fats in the body[1], contain an oil. The aging of this oil under two different conditions of conservation was the subject of our work. One of the results was an increase in the content of long-chain carbonaceous fatty acids during aging for 11 months of storage at low temperature (6℃) and at 30℃. This behavior does not find a concordant explanation by the comparative analysis of the chemical indices. Hence, there is the need to use the Medium Infra-Red spectroscopy (MIR) which allowed to clarify the information of the saponification index, to justify the weakness of the formation of peroxides in the case of the conservation at 30℃ and to confirm the information given by the peroxide index. It also allowed to understand the formation of the long carbon chains by the “cis-trans” isomerization and the homolytic cuts which intervene within the matrix of the fat by the analysis of the number of -CH<sub>2</sub> and -CH<sub>3</sub> groups in the two conditions of conservation. This study reveals that the rapid solidification of Irvingia gabonensis oil at room temperature[2] is an advantage for its preservation at room temperature but a great weakness when the fat is stored at low temperature.展开更多
FKBP23 was found in mouse endoplasmic reticulum (ER) in 1998. It consists of an N-terminal peptidyl-prolyl cis-trans isomerase (PPlase) domain and a C-terminal domain with Ca2+ binding sites. The fusion protein of mou...FKBP23 was found in mouse endoplasmic reticulum (ER) in 1998. It consists of an N-terminal peptidyl-prolyl cis-trans isomerase (PPlase) domain and a C-terminal domain with Ca2+ binding sites. The fusion protein of mouse FKBP23 and glutathione S-transferase (GST), GST-FKBP23, and the fusion protein of BiP, a member of heat shock protein 70 (Hsp 70) in ER, and GST, GST-BiP, were subcloned in E. coli, expressed and purified. The fusion proteins were restrictively digested by Factor Xa (FaXa) to obtain the free cloned proteins FKBP23 and BiP. With the assay of adsorption of free FKBP23 or BiP with GST-BiP or GST-FKBP23 attached to the Glutathione-Sepharose 4B, the adsorbed FKBP23 or BiP could be detected by Immunoblot. It means that FKBP23 binds to BiP. Furthermore, BiP in leukocyte ER-extract can be adsorbed with GST-FKBP23 attached to the glutathione-Sepharose 4B. It shows that FKBP23 binds to natural BiP in ER, too. These experiments show that a PPIase binds to a molecular chaperone of the Hsp70 family.展开更多
In order to investigate the expression levels of Pinl mRNA and protein in cervical cancer and its association with Ki67 and their clinical significance, amplification of Pinl gene was examined by RT-PCR, and the expre...In order to investigate the expression levels of Pinl mRNA and protein in cervical cancer and its association with Ki67 and their clinical significance, amplification of Pinl gene was examined by RT-PCR, and the expression of both Pinl and Ki67 protein was detected by immunohistochemistry in cervical cancer tissues. It was shown that the expression levels of Pinl were higher in cervical cancer than in normal cervical tissues （P〈0.05）. The expression of Pinl protein was increased progressively along with the disease process from normal cervix to CIN and to cervical cancer （P〈0.05）. No significant difference in the Pinl expression was found between disease stages （FIGO）, pathological grades or pelvic lymph node metastasis status （P〉0. 05）. The expression of Pin1 was significantly higher in adenocarcinoma than in squamous carcinoma of the uterine cervix （P〈0.05）. In cervical cancer, the overexpression of Pinl was positively correlated with that of Ki67 （P〈 0. 05）. These results suggested that the overexpression of Pinl was closely related with cancer cell proliferation or progression of cervical cancer and contributed to oncogenesis. Pinl may serve as a potential marker for cervical cancer diagnosis.展开更多
The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method. The energy values obtained from two meth...The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method. The energy values obtained from two methods are close to each other with a correlation coefficient of 0.96. Furthermore, the hydrogen-bonding energies based on the substitution method are consistent with the geometrical features of intramolecular hydrogen bonds. Both of them demonstrate that the substitution method is capable of providing a good estimation of intramolecular hydrogen-bonding energy.展开更多
The empirical valence bond model, solved by the DMRG technique, is applied to the systematical study of the photochemical processes of carotenoids. The polyenes with five up to one hundred of C== C bonds are investiga...The empirical valence bond model, solved by the DMRG technique, is applied to the systematical study of the photochemical processes of carotenoids. The polyenes with five up to one hundred of C== C bonds are investigated. The probability of the state arrangement for the conjugated bond, Pij, is evaluated. It is a parameter to correlate the bond lengths, and could also be applied to rationalizing the quantum yields of the photo-isomerization and the reaction constant of the quenching of singlet-oxygen happened to the external C== C bond of the carotenoids. The maximum reaction constant in long chain limit is determined as about 2.92×1010 L·mol-1·s-1.展开更多
All-trans spheroidene was extracted from the cells of Rhodobacer sphaeroides 2.4.1 and a set of cis-trans isomers were isolated from an isomeric mixture obtained by iodine-sensitized photo-isomerization of the all-tra...All-trans spheroidene was extracted from the cells of Rhodobacer sphaeroides 2.4.1 and a set of cis-trans isomers were isolated from an isomeric mixture obtained by iodine-sensitized photo-isomerization of the all-trans isomer by high-pressure liquid chromatography (HPLC). On the basis of assignment of the 1H-NMR spectra (COSY, long-range COSY, rekyed COSY, ROESY and NOESY) of the all-trans isomer, the configurations of cis isomers were determined by the isomerization shifts of the olefinic 1H signals. The peaks of HPLC could be assigned as follows: A: 9,13’-cis, B1: 5,13-cis, B2: 13,9’-cis, C: 13-cis, E: 9-cis, F: 13’-cis, G: 5,9’-cis, H: 9’-cis, I: all-trans.展开更多
Manufacturing machines converting energy to mechanical work at the molecular level is a vital pathway to ex- plore the microscopic world. A kind of operable molecular engines, composed offl-cyclodextrin （fl-CD）, ary...Manufacturing machines converting energy to mechanical work at the molecular level is a vital pathway to ex- plore the microscopic world. A kind of operable molecular engines, composed offl-cyclodextrin （fl-CD）, aryl, al- kene and amide moiety was investigated using molecular dynamics simulations combined with free-energy calcula- tions. To understand how the integrated alkene double bond controls the work performed on the engines, two alkene isomers of the prototype were considered as two molecular engines. The free-energy profiles delineating the binding process of the amide （Z）- and （E）-isomers for each alkene isomer with 1-adamantanol indicate that for the alkene （E）-isomer, the apparent work performed on the amide bond is 1.6 kcal/mol, while the alkene （Z）-isomer is incapa- ble to perform work. Direct switch on/off of engines caused by the isomerization of the alkene bond was, therefore, witnessed, in line with experimental measurements. Decomposition of the free-energy profile into different compo- nents and structural analyses suggest that the isomerization of the alkene bond controls the position of the aryl unit relative to the cavity of the CD, resulting in the difference among the free-energy profiles and the stark contrast of the work performed on engines.展开更多
Two novel biscrown ethers with rigid cis/trans ethylene linker were synthesized via Wittig reaction in high yield （about 80%）. Their pure cisltrans-isomers were obtained by column chromatography separation. And thei...Two novel biscrown ethers with rigid cis/trans ethylene linker were synthesized via Wittig reaction in high yield （about 80%）. Their pure cisltrans-isomers were obtained by column chromatography separation. And their structure/configuration was confirmed by ^1H NMR,^ 13C NMR, ESI mass spectrum, elemental analysis and UV-vis speca＇a.展开更多
PBOND is a web server that predicts the conformation of the peptide bond between any two amino acids. PBOND classifies the peptide bonds into one out of four classes, namely cis imide （cis-Pro）, cis amide （cis-non...PBOND is a web server that predicts the conformation of the peptide bond between any two amino acids. PBOND classifies the peptide bonds into one out of four classes, namely cis imide （cis-Pro）, cis amide （cis-nonPro）, trans imide （trans-Pro） and trans amide （trans-nonPro）. Moreover, for every prediction a reliability index is computed. The underlying structure of the server consists of three stages： （1） feature extraction, （2） feature selection and （3） peptide bond classification. PBOND can handle both single sequences as well as multiple sequences for batch processing. The predictions can either be directly downloaded from the web site or returned via e-mail. The PBOND web server is freely available at http：//195.251.198.21/pbond.html.展开更多
In the present study, a photoresponsive chromophoric system such as 4-[(E)-2-(3-hydro xynaphthalen-2-yl)diazen-1-yl] benzoic acid was incorporated on to lignin core by functional transformation reactions and the photo...In the present study, a photoresponsive chromophoric system such as 4-[(E)-2-(3-hydro xynaphthalen-2-yl)diazen-1-yl] benzoic acid was incorporated on to lignin core by functional transformation reactions and the photoresponsive beha-vior of the green, environment friendly product was investigated. The end hydroxyl group of lignin was modified with the chromophoric systems by DCC coupling. The chromophoric systems as well as the chromophore-bound biopolymer core systems were purified by column chromatography. The products were characterized by UV-visible, fluorescence, FT-IR and NMR spectroscopic methods. The results of the studies show that incorporation of the chromophoric system on to the lignin core enhanced the light absorption, emission and light stabilization properties of the chromophoric system. The light fastening properties of chromophoric system and the modified product were compared. It shows that stability of the chromophoric system greatly enhanced on attaching to the polymeric system. The trans-cis photoisomerisation and the reverse cis-trans thermal conversions were also assisted by the lignin core. The remarkable stability on irradiation shows that this is a novel photoresponsive system with excellent light fastening properties which would find application in coating materials, dyes, paints, inks, therapeutic agents and many more.展开更多
Photochromism of two bispyrryl-substituted ethenes, 2, 3-bis-(1-p-methoxyphenyl-5-phenyl-2-methyl-3-pyrryl)-2-butene (BPE1) and 2,3-bis(1-p-bromophenyl-4-phenyl-2-methyl-3-pyrryl)-2-butene (BPE2), was studied by laser...Photochromism of two bispyrryl-substituted ethenes, 2, 3-bis-(1-p-methoxyphenyl-5-phenyl-2-methyl-3-pyrryl)-2-butene (BPE1) and 2,3-bis(1-p-bromophenyl-4-phenyl-2-methyl-3-pyrryl)-2-butene (BPE2), was studied by laser flash photolysis technique. The results indicate that photocyclization of these compounds proceeds mainly via the excited triplet state, and the cis-trans isomerization proceeds mainly via the excited singlet state. After UV laser pulse irradiation, both photocylization and cis-trans isomerization of BPEl occur, but photocydization is the main reaction. On the other hand, laser photolysis of BPE2 leads mainly to photocydization. The effects of the substituents on the photochromic mechanism are also discussed.展开更多
The thermal decomposition reactions of the complexes cis/trans-[Cu(gly)_(2)]·H_(2)Owere studied by TG-DSC methods.The results showed that they have similar decomposition process,which occur in two steps.The first...The thermal decomposition reactions of the complexes cis/trans-[Cu(gly)_(2)]·H_(2)Owere studied by TG-DSC methods.The results showed that they have similar decomposition process,which occur in two steps.The first step is the loss of water and the second step is the decomposition of anhydrous complexes.But for cis-[Cu(gly)_(2)]·H_(2)O,the tempoerature of losing water is higher than that of trans-isomer.Their reaction mechanisms of the two-step decomposition were also proposed.展开更多
文摘The main constituents of a typical medicinal herb, Polygonum multiflorum （Heshouwu in Chinese）, that induces idiosyncratic liver injury remain unclear. Our previous work has shown that cotreatment with a nontoxic dose of lipopolysaccharide （LPS） and therapeutic dose of Heshouwu can induce liver injury in rats, whereas the solo treatment cannot induce observable injury. In the present work, using the constituent ＂knock-out＂ and ＂knock-in＂ strategy, we found that the ethyl acetate （EA） extract of Heshouwu displayed comparable idiosyncratic hepatotoxicity to the whole extract in LPS-treated rats. Results indicated a significant elevation of plasma alanine aminotransferase, aspartate aminotransferase, and liver histologic changes, whereas other separated fractions failed to induce liver injury. The mixture of EA extract with other separated fractions induced comparable idiosyncratic hepatotoxicity to the whole extract in LPS-treated rats. Chemical analysis further revealed that 2,3,5,4＇-tetrahydroxy trans-stilbene-2-O-p-glucoside （trans-SG） and its cis-isomer were the two major compounds in EA extract. Furthermore, the isolated cis-, and not its trans-isomer, displayed comparable idiosyncratic hepatotoxicity to EA extract in LPS-treated rats. Higher contents of cis-SG were detected in Heshouwu liquor or preparations from actual liver intoxication patients associated with Heshouwu compared with general collected samples. In addition, plasma metabolomics analysis showed that cis-SG-disturbing enriched pathways remarkably differed from trans-SG ones in LPS-treated rats. All these results suggested that cis-SG was closely associated with the idiosyncratic hepatotoxicity of Heshouwu. Considering that the cis-trans isomerization oftrans- SG was mediated by ultraviolet light or sunlight, our findings serve as reference for controlling photoisomerization in drug discovery and for the clinical use of Heshouwu and stilbene-related medications.
基金supported by the National Natural Science Foundation of China(31700206)the Natural Science Basic Research Program of Shaanxi(2016JM3023)the Special Scientific Research Project of Education Department of Shaanxi Province(16JK1792)。
文摘In plant chloroplasts,photosystem II(PSII)complexes,together with light-harvesting complex II(LHCII),form various PSII-LHCII supercomplexes(SCs).This process likely involves immunophilins,but the underlying regulatory mechanisms are unclear.Here,by comparing Arabidopsis thaliana mutants lacking the chloroplast lumen-localized immunophilin CYCLOPHILIN28(CYP28)to wildtype and transgenic complemented lines,we determined that CYP28 regulates the assembly and accumulation of PSII-LHCII SCs.Compared to the wild type,cyp28 plants showed accelerated leaf growth,earlier flowering time,and enhanced accumulation of high molecular weight PSII-LHCII SCs under normal light conditions.The lack of CYP28 also significantly affected the electron transport rate.Blue native-polyacrylamide gel electrophoresis analysis revealed more Lhcb6 and less Lhcb4 in M-LHCII-Lhcb4-Lhcb6 complexes in cyp28 versus wild-type plants.Peptidyl-prolyl cis/trans isomerase(PPIase)activity assays revealed that CYP28 exhibits weak PPIase activity and that its K113 and E187 residues are critical for this activity.Mutant analysis suggested that CYP28 may regulate PSIILHCII SC accumulation by altering the configuration of Lhcb6 via its PPIase activity.Furthermore,the Lhcb6-P139 residue is critical for PSII-LHCII SC assembly and accumulation.Therefore,our findings suggest that CYP28 likely regulates PSII-LHCII SC assembly and accumulation by altering the configuration of P139 of Lhcb6 via its PPIase activity.
文摘The Irvingia gabonensis kernels, which have been extensively studied for their numerous virtues, including the ability to act against the accumulation of fats in the body[1], contain an oil. The aging of this oil under two different conditions of conservation was the subject of our work. One of the results was an increase in the content of long-chain carbonaceous fatty acids during aging for 11 months of storage at low temperature (6℃) and at 30℃. This behavior does not find a concordant explanation by the comparative analysis of the chemical indices. Hence, there is the need to use the Medium Infra-Red spectroscopy (MIR) which allowed to clarify the information of the saponification index, to justify the weakness of the formation of peroxides in the case of the conservation at 30℃ and to confirm the information given by the peroxide index. It also allowed to understand the formation of the long carbon chains by the “cis-trans” isomerization and the homolytic cuts which intervene within the matrix of the fat by the analysis of the number of -CH<sub>2</sub> and -CH<sub>3</sub> groups in the two conditions of conservation. This study reveals that the rapid solidification of Irvingia gabonensis oil at room temperature[2] is an advantage for its preservation at room temperature but a great weakness when the fat is stored at low temperature.
基金This work was supported by the National Natural Science Foundation of China(Grant No.30170870)the Ministry of Education of China(Department of Foreign Affairs(99)747).
文摘FKBP23 was found in mouse endoplasmic reticulum (ER) in 1998. It consists of an N-terminal peptidyl-prolyl cis-trans isomerase (PPlase) domain and a C-terminal domain with Ca2+ binding sites. The fusion protein of mouse FKBP23 and glutathione S-transferase (GST), GST-FKBP23, and the fusion protein of BiP, a member of heat shock protein 70 (Hsp 70) in ER, and GST, GST-BiP, were subcloned in E. coli, expressed and purified. The fusion proteins were restrictively digested by Factor Xa (FaXa) to obtain the free cloned proteins FKBP23 and BiP. With the assay of adsorption of free FKBP23 or BiP with GST-BiP or GST-FKBP23 attached to the Glutathione-Sepharose 4B, the adsorbed FKBP23 or BiP could be detected by Immunoblot. It means that FKBP23 binds to BiP. Furthermore, BiP in leukocyte ER-extract can be adsorbed with GST-FKBP23 attached to the glutathione-Sepharose 4B. It shows that FKBP23 binds to natural BiP in ER, too. These experiments show that a PPIase binds to a molecular chaperone of the Hsp70 family.
基金This project was supported by grants from National Key Basic Research （973） Fund （No. 2002CB513107） and National Natural Science Foundation of China （No. 30271358）.
文摘In order to investigate the expression levels of Pinl mRNA and protein in cervical cancer and its association with Ki67 and their clinical significance, amplification of Pinl gene was examined by RT-PCR, and the expression of both Pinl and Ki67 protein was detected by immunohistochemistry in cervical cancer tissues. It was shown that the expression levels of Pinl were higher in cervical cancer than in normal cervical tissues （P〈0.05）. The expression of Pinl protein was increased progressively along with the disease process from normal cervix to CIN and to cervical cancer （P〈0.05）. No significant difference in the Pinl expression was found between disease stages （FIGO）, pathological grades or pelvic lymph node metastasis status （P〉0. 05）. The expression of Pin1 was significantly higher in adenocarcinoma than in squamous carcinoma of the uterine cervix （P〈0.05）. In cervical cancer, the overexpression of Pinl was positively correlated with that of Ki67 （P〈 0. 05）. These results suggested that the overexpression of Pinl was closely related with cancer cell proliferation or progression of cervical cancer and contributed to oncogenesis. Pinl may serve as a potential marker for cervical cancer diagnosis.
基金the National Natural Science Foundation of China (No. 20573049)
文摘The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method. The energy values obtained from two methods are close to each other with a correlation coefficient of 0.96. Furthermore, the hydrogen-bonding energies based on the substitution method are consistent with the geometrical features of intramolecular hydrogen bonds. Both of them demonstrate that the substitution method is capable of providing a good estimation of intramolecular hydrogen-bonding energy.
基金Part of the computational work was done on the SGI Origin 3800 and Dawning 3000 supercom-puters at Nanjing University. This work was supported by the National Natural Science Foundation of China (Grant Nos. 20073020 and 20273030).
文摘The empirical valence bond model, solved by the DMRG technique, is applied to the systematical study of the photochemical processes of carotenoids. The polyenes with five up to one hundred of C== C bonds are investigated. The probability of the state arrangement for the conjugated bond, Pij, is evaluated. It is a parameter to correlate the bond lengths, and could also be applied to rationalizing the quantum yields of the photo-isomerization and the reaction constant of the quenching of singlet-oxygen happened to the external C== C bond of the carotenoids. The maximum reaction constant in long chain limit is determined as about 2.92×1010 L·mol-1·s-1.
文摘All-trans spheroidene was extracted from the cells of Rhodobacer sphaeroides 2.4.1 and a set of cis-trans isomers were isolated from an isomeric mixture obtained by iodine-sensitized photo-isomerization of the all-trans isomer by high-pressure liquid chromatography (HPLC). On the basis of assignment of the 1H-NMR spectra (COSY, long-range COSY, rekyed COSY, ROESY and NOESY) of the all-trans isomer, the configurations of cis isomers were determined by the isomerization shifts of the olefinic 1H signals. The peaks of HPLC could be assigned as follows: A: 9,13’-cis, B1: 5,13-cis, B2: 13,9’-cis, C: 13-cis, E: 9-cis, F: 13’-cis, G: 5,9’-cis, H: 9’-cis, I: all-trans.
文摘Manufacturing machines converting energy to mechanical work at the molecular level is a vital pathway to ex- plore the microscopic world. A kind of operable molecular engines, composed offl-cyclodextrin （fl-CD）, aryl, al- kene and amide moiety was investigated using molecular dynamics simulations combined with free-energy calcula- tions. To understand how the integrated alkene double bond controls the work performed on the engines, two alkene isomers of the prototype were considered as two molecular engines. The free-energy profiles delineating the binding process of the amide （Z）- and （E）-isomers for each alkene isomer with 1-adamantanol indicate that for the alkene （E）-isomer, the apparent work performed on the amide bond is 1.6 kcal/mol, while the alkene （Z）-isomer is incapa- ble to perform work. Direct switch on/off of engines caused by the isomerization of the alkene bond was, therefore, witnessed, in line with experimental measurements. Decomposition of the free-energy profile into different compo- nents and structural analyses suggest that the isomerization of the alkene bond controls the position of the aryl unit relative to the cavity of the CD, resulting in the difference among the free-energy profiles and the stark contrast of the work performed on engines.
基金National Natural Science Foundation of China （No. 20672038） Natural Science Foundation of Guangdong Province （No. 5005934）.
文摘Two novel biscrown ethers with rigid cis/trans ethylene linker were synthesized via Wittig reaction in high yield （about 80%）. Their pure cisltrans-isomers were obtained by column chromatography separation. And their structure/configuration was confirmed by ^1H NMR,^ 13C NMR, ESI mass spectrum, elemental analysis and UV-vis speca＇a.
文摘PBOND is a web server that predicts the conformation of the peptide bond between any two amino acids. PBOND classifies the peptide bonds into one out of four classes, namely cis imide （cis-Pro）, cis amide （cis-nonPro）, trans imide （trans-Pro） and trans amide （trans-nonPro）. Moreover, for every prediction a reliability index is computed. The underlying structure of the server consists of three stages： （1） feature extraction, （2） feature selection and （3） peptide bond classification. PBOND can handle both single sequences as well as multiple sequences for batch processing. The predictions can either be directly downloaded from the web site or returned via e-mail. The PBOND web server is freely available at http：//195.251.198.21/pbond.html.
文摘In the present study, a photoresponsive chromophoric system such as 4-[(E)-2-(3-hydro xynaphthalen-2-yl)diazen-1-yl] benzoic acid was incorporated on to lignin core by functional transformation reactions and the photoresponsive beha-vior of the green, environment friendly product was investigated. The end hydroxyl group of lignin was modified with the chromophoric systems by DCC coupling. The chromophoric systems as well as the chromophore-bound biopolymer core systems were purified by column chromatography. The products were characterized by UV-visible, fluorescence, FT-IR and NMR spectroscopic methods. The results of the studies show that incorporation of the chromophoric system on to the lignin core enhanced the light absorption, emission and light stabilization properties of the chromophoric system. The light fastening properties of chromophoric system and the modified product were compared. It shows that stability of the chromophoric system greatly enhanced on attaching to the polymeric system. The trans-cis photoisomerisation and the reverse cis-trans thermal conversions were also assisted by the lignin core. The remarkable stability on irradiation shows that this is a novel photoresponsive system with excellent light fastening properties which would find application in coating materials, dyes, paints, inks, therapeutic agents and many more.
基金Project supported by the Chinese Academy of Sciencesthe National Natural Science Foundation of China
文摘Photochromism of two bispyrryl-substituted ethenes, 2, 3-bis-(1-p-methoxyphenyl-5-phenyl-2-methyl-3-pyrryl)-2-butene (BPE1) and 2,3-bis(1-p-bromophenyl-4-phenyl-2-methyl-3-pyrryl)-2-butene (BPE2), was studied by laser flash photolysis technique. The results indicate that photocyclization of these compounds proceeds mainly via the excited triplet state, and the cis-trans isomerization proceeds mainly via the excited singlet state. After UV laser pulse irradiation, both photocylization and cis-trans isomerization of BPEl occur, but photocydization is the main reaction. On the other hand, laser photolysis of BPE2 leads mainly to photocydization. The effects of the substituents on the photochromic mechanism are also discussed.
文摘The thermal decomposition reactions of the complexes cis/trans-[Cu(gly)_(2)]·H_(2)Owere studied by TG-DSC methods.The results showed that they have similar decomposition process,which occur in two steps.The first step is the loss of water and the second step is the decomposition of anhydrous complexes.But for cis-[Cu(gly)_(2)]·H_(2)O,the tempoerature of losing water is higher than that of trans-isomer.Their reaction mechanisms of the two-step decomposition were also proposed.
