With light and electron microscopy the substructural change and the ATPase activity of corn (Zea mays L.) root cap cells after short-term osmotic stress were studied. Some spoke-like fine strands originating from the ...With light and electron microscopy the substructural change and the ATPase activity of corn (Zea mays L.) root cap cells after short-term osmotic stress were studied. Some spoke-like fine strands originating from the departed periplasm and stretching towards cell wall could be observed even after plasmolysis. By observing the precipitation of ATPase activity product (lead phosphate) at plasma membrane and plasmodesmata, it was found that the fine strands were plasma membrane-lined channels surrounding the cytoplasm and that they still firmly connected to the plasmodesmata during plasmolysis. Compared with the control (unstressed), a sharp decrease of ATPase activity in the plasmodesmata of the stressed cells was observed. Inhibition of energy metabolism in these limited locales would affect the physiological activity, maybe including the regulation of permeability and the change of size exclusion limit (SEL) of plasmodesmata.展开更多
Vanadium pentoxide（V2O5）/molybdenum trioxide（MoO 3） composites with different molar ratios of vanadium（V） to molybdenum（Mo） were synthesized via a simple electrospinning technique. The photocatalytic activity ...Vanadium pentoxide（V2O5）/molybdenum trioxide（MoO 3） composites with different molar ratios of vanadium（V） to molybdenum（Mo） were synthesized via a simple electrospinning technique. The photocatalytic activity of the composites were evaluated by their ability to photodegrade methylene blue and dimethyl phthalate（DMP） under visible-light irradiation. Compared with pure V2O5 and MoO 3,the V2O5/MoO 3 composites showed enhanced visible-light photocatalytic activity because of a V 3d impurity energy level and the formation of heterostructures at the interface between V2O5 and MoO 3. The optimal molar ratio of V to Mo in the V2O5/MoO 3 composites was found to be around 1/2. Furthermore,high-performance liquid chromatographic monitoring revealed that phthalic acid was the main intermediate in the photocatalytic degradation process of DMP.展开更多
In order to investigate the origin of catalytic power for serine proteases,the role of the hydrogen bond in the catalytic triad was studied in the proteolysis process of the peptides chymotrypsin inhibitor 2(CI2),MCTI...In order to investigate the origin of catalytic power for serine proteases,the role of the hydrogen bond in the catalytic triad was studied in the proteolysis process of the peptides chymotrypsin inhibitor 2(CI2),MCTI-A,and a hexapeptide(SUB),respectively.We first calculated the free energy profile of the proton transfer between His and Asp residues of the catalytic triad in the enzyme-substrate state and transition state by employing QM/MM molecular dynamics simulations.The results show that a low-barrier hydrogen bond(LBHB)only forms in the transition state of the acylation of CI2,while it is a normal hydrogen bond in the acylation of MCTI-A or SUB.In addition,the change of the hydrogen bond strength is much larger in CI2 and SUB systems than in MCTI-A system,which decreases the acylation energy barrier significantly for CI2 and SUB.Clearly,a LBHB formed in the transition state region helps accelerate the acylation reaction.But to our surprise,a normal hydrogen bond can also help to decrease the energy barrier.The key to reducing the reaction barrier is the increment of hydrogen bond strength in the transition state state,whether it is a LBHB or not.Our studies cast new light on the role of the hydrogen bond in the catalytic triad,and help to understand the catalytic triad of serine proteases.展开更多
Investigations on the chemical constituents from the ethanol extract of the agarwood originating from Aquilaria filaria led to the isolation of 26 compounds by column chromatography,including silica gel,Sephadex LH-20...Investigations on the chemical constituents from the ethanol extract of the agarwood originating from Aquilaria filaria led to the isolation of 26 compounds by column chromatography,including silica gel,Sephadex LH-20,and semi-preparative high-performance liquid chromatography.Their structures were determined to beβ-sitostenone(1),24α-ethyl-cholestan-3α-ol(2),ergosta-4,6,8(14),22-tetraene-3-one(3),gypsogenin(4),hederagenin(5),17αH-trisnorhopanone(6),lupeol(7),friedelin(8),(-)-episyringaresinol(9),(-)-syringaresinol(10),5-hydroxy-7,4′-dimethoxyflavone(11),5,4’-dihydroxy-7,3′-dimethoxyflavone(12),2′-hydroxy-4,3′,6′,4′′-tetramethoxy-p-terphenyl(13),scopularide A(14),4-(4-hydroxyphenyl)butan-2-one(15),zingerone(16),coniferaldehyde(17),scopoletin(18),acetovanillon(19),isovanillin(20),vanillin(21),p-hydroxybenzaldehyde(22),p-hydroxybenzoic acid(23),protocatechuic acid(24),vanillic acid(25)and 4,5-dihydroxy-3-methoxybenzoic acid(26)by using spectroscopic techniques.All compounds were isolated from agarwood of A.filaria for the first time,and this was also the first report about the isolation of compounds 2,4,6,7,9,10,13-15,17-20,22,24 and 26 from agarwood and Aquilaria plants.展开更多
We studied the responses of the activities of adenosine-triphosphate (ATP) sulfurylase (ATPS) and serine acetyltransferase (SAT) to cadmium (Cd) levels and treatment time in hyperaccumulating ecotype (HE) Sedum alfred...We studied the responses of the activities of adenosine-triphosphate (ATP) sulfurylase (ATPS) and serine acetyltransferase (SAT) to cadmium (Cd) levels and treatment time in hyperaccumulating ecotype (HE) Sedum alfredii Hance, as compared with its non-hyperaccumulating ecotype (NHE). The results show that plant growth was inhibited in NHE but promoted in HE when exposed to high Cd level. Cd concentrations in leaves and shoots rapidly increased in HE rather than in NHE, and they became much higher in HE than in NHE along with increasing treatment time and Cd supply levels. ATPS activity was higher in HE than in NHE in all Cd treatments, and increased with increasing Cd supply levels in both HE and NHE when exposed to Cd treatment within 8 h. However, a marked difference of ATPS activity between HE and NHE was found with Cd treatment for 168 h, where ATPS activity increased in HE but decreased in NHE. Similarly, SAT activity was higher in HE than in NHE at all Cd treatments, but was more sensitive in NHE than in HE. Both ATPS and SAT activities in NHE leaves tended to decrease with increasing treatment time after 8 h at all Cd levels. The results reveal the different responses in sulfur assimilation enzymes and Cd accumulation between HE and NHE. With increasing Cd stress, the activities of sulfur assimilation enzymes (ATPS and SAT) were induced in HE, which may contribute to Cd accumulation in the hyperaccumulator Sedum alfredii Hance.展开更多
基金Supported by the grants from the National Natural Science Foundation of China.
文摘With light and electron microscopy the substructural change and the ATPase activity of corn (Zea mays L.) root cap cells after short-term osmotic stress were studied. Some spoke-like fine strands originating from the departed periplasm and stretching towards cell wall could be observed even after plasmolysis. By observing the precipitation of ATPase activity product (lead phosphate) at plasma membrane and plasmodesmata, it was found that the fine strands were plasma membrane-lined channels surrounding the cytoplasm and that they still firmly connected to the plasmodesmata during plasmolysis. Compared with the control (unstressed), a sharp decrease of ATPase activity in the plasmodesmata of the stressed cells was observed. Inhibition of energy metabolism in these limited locales would affect the physiological activity, maybe including the regulation of permeability and the change of size exclusion limit (SEL) of plasmodesmata.
基金supported by the National Natural Science Foundation of China(2137312021471022)+5 种基金the Development of Science and Technology Plan of Jilin ProvinceChina(2010154920130102001JC)Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT13022)of Chinathe Program of Jilin Provincial Education Department(20131302013146)~~
文摘Vanadium pentoxide（V2O5）/molybdenum trioxide（MoO 3） composites with different molar ratios of vanadium（V） to molybdenum（Mo） were synthesized via a simple electrospinning technique. The photocatalytic activity of the composites were evaluated by their ability to photodegrade methylene blue and dimethyl phthalate（DMP） under visible-light irradiation. Compared with pure V2O5 and MoO 3,the V2O5/MoO 3 composites showed enhanced visible-light photocatalytic activity because of a V 3d impurity energy level and the formation of heterostructures at the interface between V2O5 and MoO 3. The optimal molar ratio of V to Mo in the V2O5/MoO 3 composites was found to be around 1/2. Furthermore,high-performance liquid chromatographic monitoring revealed that phthalic acid was the main intermediate in the photocatalytic degradation process of DMP.
基金supported by the National Key Research and Development Program of China(2017YFA0206500)the National Natural Science Foundation of China(No.22073040)。
文摘In order to investigate the origin of catalytic power for serine proteases,the role of the hydrogen bond in the catalytic triad was studied in the proteolysis process of the peptides chymotrypsin inhibitor 2(CI2),MCTI-A,and a hexapeptide(SUB),respectively.We first calculated the free energy profile of the proton transfer between His and Asp residues of the catalytic triad in the enzyme-substrate state and transition state by employing QM/MM molecular dynamics simulations.The results show that a low-barrier hydrogen bond(LBHB)only forms in the transition state of the acylation of CI2,while it is a normal hydrogen bond in the acylation of MCTI-A or SUB.In addition,the change of the hydrogen bond strength is much larger in CI2 and SUB systems than in MCTI-A system,which decreases the acylation energy barrier significantly for CI2 and SUB.Clearly,a LBHB formed in the transition state region helps accelerate the acylation reaction.But to our surprise,a normal hydrogen bond can also help to decrease the energy barrier.The key to reducing the reaction barrier is the increment of hydrogen bond strength in the transition state state,whether it is a LBHB or not.Our studies cast new light on the role of the hydrogen bond in the catalytic triad,and help to understand the catalytic triad of serine proteases.
基金National Key Research & Development Program of China (Grant No. 2018YFC1706400)National Natural Science Foundation of China (Grant No. 31870668)China Agriculture Research System (Grant No. CARS-21)。
文摘Investigations on the chemical constituents from the ethanol extract of the agarwood originating from Aquilaria filaria led to the isolation of 26 compounds by column chromatography,including silica gel,Sephadex LH-20,and semi-preparative high-performance liquid chromatography.Their structures were determined to beβ-sitostenone(1),24α-ethyl-cholestan-3α-ol(2),ergosta-4,6,8(14),22-tetraene-3-one(3),gypsogenin(4),hederagenin(5),17αH-trisnorhopanone(6),lupeol(7),friedelin(8),(-)-episyringaresinol(9),(-)-syringaresinol(10),5-hydroxy-7,4′-dimethoxyflavone(11),5,4’-dihydroxy-7,3′-dimethoxyflavone(12),2′-hydroxy-4,3′,6′,4′′-tetramethoxy-p-terphenyl(13),scopularide A(14),4-(4-hydroxyphenyl)butan-2-one(15),zingerone(16),coniferaldehyde(17),scopoletin(18),acetovanillon(19),isovanillin(20),vanillin(21),p-hydroxybenzaldehyde(22),p-hydroxybenzoic acid(23),protocatechuic acid(24),vanillic acid(25)and 4,5-dihydroxy-3-methoxybenzoic acid(26)by using spectroscopic techniques.All compounds were isolated from agarwood of A.filaria for the first time,and this was also the first report about the isolation of compounds 2,4,6,7,9,10,13-15,17-20,22,24 and 26 from agarwood and Aquilaria plants.
基金supported by the National Natural Science Foundation of China (No. 30630046)the Hi-Tech Research and Development Program (863) of China (No. 2006AA06Z386)the Program for Changjiang Scholars and Innovative Research Team in University, China (No. IRT0536)
文摘We studied the responses of the activities of adenosine-triphosphate (ATP) sulfurylase (ATPS) and serine acetyltransferase (SAT) to cadmium (Cd) levels and treatment time in hyperaccumulating ecotype (HE) Sedum alfredii Hance, as compared with its non-hyperaccumulating ecotype (NHE). The results show that plant growth was inhibited in NHE but promoted in HE when exposed to high Cd level. Cd concentrations in leaves and shoots rapidly increased in HE rather than in NHE, and they became much higher in HE than in NHE along with increasing treatment time and Cd supply levels. ATPS activity was higher in HE than in NHE in all Cd treatments, and increased with increasing Cd supply levels in both HE and NHE when exposed to Cd treatment within 8 h. However, a marked difference of ATPS activity between HE and NHE was found with Cd treatment for 168 h, where ATPS activity increased in HE but decreased in NHE. Similarly, SAT activity was higher in HE than in NHE at all Cd treatments, but was more sensitive in NHE than in HE. Both ATPS and SAT activities in NHE leaves tended to decrease with increasing treatment time after 8 h at all Cd levels. The results reveal the different responses in sulfur assimilation enzymes and Cd accumulation between HE and NHE. With increasing Cd stress, the activities of sulfur assimilation enzymes (ATPS and SAT) were induced in HE, which may contribute to Cd accumulation in the hyperaccumulator Sedum alfredii Hance.
