The hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by seryl-histidine or histidine has been monitored by electrospray ionization mass spectrometry in the presence of the internal calibration, 8-anilino-1-naphth...The hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by seryl-histidine or histidine has been monitored by electrospray ionization mass spectrometry in the presence of the internal calibration, 8-anilino-1-naphthalenesulfonic acid ammonium salt (ANS). The half-life of p-NPA in the presence of 10 mmol·L -1 seryl-histidine or histidine at 25 ℃ was 370 min and 70 min respectively. With the occurrence of acetyl seryl-histidine and acetyl histidine in the reaction, and the fact that p-NPA was stable in the presence of 10 mmol·L -1 serine, an imidazolysis mechanism has been proposed, which is in accordance with the reported work.展开更多
Polymeric β-cyclodextrin (β-CD) supported by crosslinked poly(acrylamide-co-vinylamine) was synthesized as anartificial analog of hydrolytic enzyme and its catalysis of the hydrolysis of p-nitrophenyl acetate (p-NPA...Polymeric β-cyclodextrin (β-CD) supported by crosslinked poly(acrylamide-co-vinylamine) was synthesized as anartificial analog of hydrolytic enzyme and its catalysis of the hydrolysis of p-nitrophenyl acetate (p-NPA) was theninvestigated. The result showed that the polymer-supported β-CD could accelerate the hydrolytic reaction of p-NPA morequickly than β-CD itself and crosslinked poly(acrylamide-co-vinylamine) alone. The acceleration rate of the polymer-supported β-CD was about 10 times as fast as that of free β-CD in 0.01 mol/L phosphate buffer (pH 7.4) containing 32%DMSO at 37±0.1℃ when the molar amount of β-CD units in the polymer was equal to that of free β-CD in the experiments.The enhanced acceleration of thc polymer-supported β-CD should be ascribed to the cooperative contribution of theinclusion effect of β-CD ring and the nucleophilic effect of amino groups on the polymeric support.展开更多
文摘The hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by seryl-histidine or histidine has been monitored by electrospray ionization mass spectrometry in the presence of the internal calibration, 8-anilino-1-naphthalenesulfonic acid ammonium salt (ANS). The half-life of p-NPA in the presence of 10 mmol·L -1 seryl-histidine or histidine at 25 ℃ was 370 min and 70 min respectively. With the occurrence of acetyl seryl-histidine and acetyl histidine in the reaction, and the fact that p-NPA was stable in the presence of 10 mmol·L -1 serine, an imidazolysis mechanism has been proposed, which is in accordance with the reported work.
文摘Polymeric β-cyclodextrin (β-CD) supported by crosslinked poly(acrylamide-co-vinylamine) was synthesized as anartificial analog of hydrolytic enzyme and its catalysis of the hydrolysis of p-nitrophenyl acetate (p-NPA) was theninvestigated. The result showed that the polymer-supported β-CD could accelerate the hydrolytic reaction of p-NPA morequickly than β-CD itself and crosslinked poly(acrylamide-co-vinylamine) alone. The acceleration rate of the polymer-supported β-CD was about 10 times as fast as that of free β-CD in 0.01 mol/L phosphate buffer (pH 7.4) containing 32%DMSO at 37±0.1℃ when the molar amount of β-CD units in the polymer was equal to that of free β-CD in the experiments.The enhanced acceleration of thc polymer-supported β-CD should be ascribed to the cooperative contribution of theinclusion effect of β-CD ring and the nucleophilic effect of amino groups on the polymeric support.
