[Objective] This study was conducted to evaluate the effect of 1-methylcy- clopropene （1-MCP） on fruit firmness, and the activity of the enzymes involved in ethylene metabolism and membrane lipid peroxidation. [Meth...[Objective] This study was conducted to evaluate the effect of 1-methylcy- clopropene （1-MCP） on fruit firmness, and the activity of the enzymes involved in ethylene metabolism and membrane lipid peroxidation. [Method] The nearly ripe fruits of the papaya cultivar Risheng were randomly assigned to one of four groups. Two groups were treated under hypobaric and hypoxic （HH） atmosphere condition for six hours, and immediately soaked in deionized water （HH alone）, or fumigated with 2.0 mg/L 1-MCP （HH＋I-MCP） for 24 h. The other two groups untreated under HH condition were also soaked in deionized water （negative control）, or fumigated with 2.0 mg/L 1-MCP （1-MCP alone） for 24 h. After that, the fruits of all the four treatments were stored at room temperature （23＋1） ℃. Cell membrane permeability, fruit firmness, respiration rate, ethylene release rate, SOD activity, POD activity, CAT activity, MAD content and LOX activity were measured once every three days during storage. [Result] Treatment with 1-MCP delayed the occurrence of the peaks of respiration rate and ethylene release rate, significantly reduced the accumulation of malondialdehyde （MDA）, and inhibited the decrease in papaya fruit firmness. Compared with the control, 1-MCP treatment significantly increased the SOD （su- peroxide dismutase）, POD （peroxidase） and CAT （catalase） activity, reduced the ac- tivity of lipoxygenase （LOX）, a product of lipid peroxidatlon in membranes, and in- hibited ethylene biosynthesis, thus delaying the aging process and prolonging the storage life of papaya fruits. [Conclusion] The results will provide a theoretical basis for analvzina the key factors controllinq postharvest maturity and aging of papaya fruits.展开更多
We report a hydrogen-evolution dimerization of styrenes via the synergistic merger of Acr＋-Mes photocatalyst and cobaloxime proton reduction catalysts. By utilizing this dual catalyst system, 1,2-dihydro-1-arylnaphth...We report a hydrogen-evolution dimerization of styrenes via the synergistic merger of Acr＋-Mes photocatalyst and cobaloxime proton reduction catalysts. By utilizing this dual catalyst system, 1,2-dihydro-1-arylnaphthalene derivatives can be directly constructed from commercially available styrenes. Our reaction proceeds smoothly under mild conditions without the need for oxidants or hydrogen atom transfer reagents, and the sole byproduct is hydrogen gas. Mechanistic investigation suggests that the reaction is initiated by photoinduced electron transfer under visible-light irradiation.展开更多
The title compound (C28H27NO5S3, Mr= 553. 69) was prepared bythe reaction of a-thiobenzoylthioformmorholine with diethyl acetylene dicarboxylate.The crystal is monoclinic, space group P21/n with a= 9. 160(3), b= 17. 7...The title compound (C28H27NO5S3, Mr= 553. 69) was prepared bythe reaction of a-thiobenzoylthioformmorholine with diethyl acetylene dicarboxylate.The crystal is monoclinic, space group P21/n with a= 9. 160(3), b= 17. 726(3), c=16. 602(3) A ; β= 100. 375(13)°; V=2651. 4(10) A3, Z=4, Dc= 1. 387 g/cm3, μ(MoKa) =0. 319 mm-1, F(000) =1160, R=0. 0428, wR(F2) =0. 0910 for 2438 observed reflections (I>2(I)). X-ray analysis reveals that interatomic distances for C(5)-C(6), C(13)-C(14) and C(21)-C(22) are 1. 331(4), 1. 351(4), 1. 344(4)A respectively, which show that they are normal C=C double bonds. All S-C bondlengths are similar to typical S-C single bonds (1. 75 - 1. 78 A ). The five-membered ring A (C(5) -C(6) -S(2)-C(13) -S(1) ) (Fig. 1) and six-membered ringB (C(14) -C(15) -C(20) -C(21)-C(22)-S(3) ) (Fig. 1) adopt the flat twist conformation. Furthermore, the morpholine ring adopts chair conformtion.展开更多
文摘[Objective] This study was conducted to evaluate the effect of 1-methylcy- clopropene （1-MCP） on fruit firmness, and the activity of the enzymes involved in ethylene metabolism and membrane lipid peroxidation. [Method] The nearly ripe fruits of the papaya cultivar Risheng were randomly assigned to one of four groups. Two groups were treated under hypobaric and hypoxic （HH） atmosphere condition for six hours, and immediately soaked in deionized water （HH alone）, or fumigated with 2.0 mg/L 1-MCP （HH＋I-MCP） for 24 h. The other two groups untreated under HH condition were also soaked in deionized water （negative control）, or fumigated with 2.0 mg/L 1-MCP （1-MCP alone） for 24 h. After that, the fruits of all the four treatments were stored at room temperature （23＋1） ℃. Cell membrane permeability, fruit firmness, respiration rate, ethylene release rate, SOD activity, POD activity, CAT activity, MAD content and LOX activity were measured once every three days during storage. [Result] Treatment with 1-MCP delayed the occurrence of the peaks of respiration rate and ethylene release rate, significantly reduced the accumulation of malondialdehyde （MDA）, and inhibited the decrease in papaya fruit firmness. Compared with the control, 1-MCP treatment significantly increased the SOD （su- peroxide dismutase）, POD （peroxidase） and CAT （catalase） activity, reduced the ac- tivity of lipoxygenase （LOX）, a product of lipid peroxidatlon in membranes, and in- hibited ethylene biosynthesis, thus delaying the aging process and prolonging the storage life of papaya fruits. [Conclusion] The results will provide a theoretical basis for analvzina the key factors controllinq postharvest maturity and aging of papaya fruits.
基金supported by the Ministry of Science and Technology of China (2014CB239402, 2017YFA0206903)the National Natural Science foundation of China (21390404)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Science (XDB17000000)the Key Research Pro-gram of Frontier Sciences, the Chinese Academy of Sciences (QYZDY-SSW-JSC029)~~
文摘We report a hydrogen-evolution dimerization of styrenes via the synergistic merger of Acr＋-Mes photocatalyst and cobaloxime proton reduction catalysts. By utilizing this dual catalyst system, 1,2-dihydro-1-arylnaphthalene derivatives can be directly constructed from commercially available styrenes. Our reaction proceeds smoothly under mild conditions without the need for oxidants or hydrogen atom transfer reagents, and the sole byproduct is hydrogen gas. Mechanistic investigation suggests that the reaction is initiated by photoinduced electron transfer under visible-light irradiation.
文摘The title compound (C28H27NO5S3, Mr= 553. 69) was prepared bythe reaction of a-thiobenzoylthioformmorholine with diethyl acetylene dicarboxylate.The crystal is monoclinic, space group P21/n with a= 9. 160(3), b= 17. 726(3), c=16. 602(3) A ; β= 100. 375(13)°; V=2651. 4(10) A3, Z=4, Dc= 1. 387 g/cm3, μ(MoKa) =0. 319 mm-1, F(000) =1160, R=0. 0428, wR(F2) =0. 0910 for 2438 observed reflections (I>2(I)). X-ray analysis reveals that interatomic distances for C(5)-C(6), C(13)-C(14) and C(21)-C(22) are 1. 331(4), 1. 351(4), 1. 344(4)A respectively, which show that they are normal C=C double bonds. All S-C bondlengths are similar to typical S-C single bonds (1. 75 - 1. 78 A ). The five-membered ring A (C(5) -C(6) -S(2)-C(13) -S(1) ) (Fig. 1) and six-membered ringB (C(14) -C(15) -C(20) -C(21)-C(22)-S(3) ) (Fig. 1) adopt the flat twist conformation. Furthermore, the morpholine ring adopts chair conformtion.
