A new approach for assembling amperometric mushroom pulp tissue based membrane electrode for determination of L tyrosine analysis is proposed. Ferrocene is used as a mediator of electron transfer between tyrosinase ...A new approach for assembling amperometric mushroom pulp tissue based membrane electrode for determination of L tyrosine analysis is proposed. Ferrocene is used as a mediator of electron transfer between tyrosinase in mushroom tissue and a graphite electrode. The optimal operation conditions are studied. The linear response range of the biosensor is 2 0×10 -4 to 4 5×10 -3 mol·L -1 with response time of less than 5 min and lifetime of at least 30 d. The biosensor can be applied to practical sample analysis.展开更多
The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration lea...The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase展开更多
Objective： To study the genes expression profile differences in the peripheral blood between esophageal carcinoma patients and normal subjects using the gene chip technique and screen out the esophageal early concera...Objective： To study the genes expression profile differences in the peripheral blood between esophageal carcinoma patients and normal subjects using the gene chip technique and screen out the esophageal early conceration associated genes. Methods： The total RNA was extracted and purified in the peripheral blood obtained from the patients with esophageal carcinoma and normal subjects. The first strand of cDNA was synthesized through retro-transcription and labeled with Cy5 and Cy3 fluorescence as probes. The mixed probes were hybridized with a piece of 4096 double dot human whole gene chip. The acquired image was analyzed by microarrav suite software using a digital computer, and the intensity of ttuorescence signal and its ratio were calculated. Results： A total of 92 genes were screened out and its expression difference was more than 2 times in the peripheral blood between the patients with esophageal carcinoma and normal subjects. Among these, the expression difference of 36 genes was more than 3 times. Two human urokinase plasminogen activator surface receptor （UPAR） genes, 80K-L protein gene, human protein tyrosine-phosphatase gent arid proto-oncogene protein mRNA were significantly up-regulated, while the collagen V type （α-2 gene was markedly down-regulated. Conclusion： 80K-L protein gene, tyrosinephophatase gene, proto-oncogene protein arid the collagen V type α-2 gene might be associated with the ontogenesis, development and its metastasis in the esophageal carcinoma. The UPAR gene may play important roles in the diagnosing the micrometastasis in the peripheral blood of esophageal carcinoma.展开更多
The isotopomers of halogenated amino acids （2＇-F-L-phenylalanine, 3＇-F- and 3＇-Cl-L-tyrosine, as well as 5＇-F-, 5＇-Br-and 6＇-F-L-tryptophan） specifically labeled with deuterium at α- and 13-carbon atom of the...The isotopomers of halogenated amino acids （2＇-F-L-phenylalanine, 3＇-F- and 3＇-Cl-L-tyrosine, as well as 5＇-F-, 5＇-Br-and 6＇-F-L-tryptophan） specifically labeled with deuterium at α- and 13-carbon atom of the side chain were synthesized by enzymatic catalyzed H/D exchange in fully deuteriated incubation medium. The extent and site of deuterium incorporation were confirmed by ^1H NMR （proton nuclear magnetic resonance） spectra.展开更多
文摘A new approach for assembling amperometric mushroom pulp tissue based membrane electrode for determination of L tyrosine analysis is proposed. Ferrocene is used as a mediator of electron transfer between tyrosinase in mushroom tissue and a graphite electrode. The optimal operation conditions are studied. The linear response range of the biosensor is 2 0×10 -4 to 4 5×10 -3 mol·L -1 with response time of less than 5 min and lifetime of at least 30 d. The biosensor can be applied to practical sample analysis.
基金Supported by the Natural Science Foundation of Guangdong Province (No. 011563, No. 04020114).
文摘The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase
基金This project was supported by a grant from the Zhejiang Medical and Health Science Foundation (No. 2002A023).
文摘Objective： To study the genes expression profile differences in the peripheral blood between esophageal carcinoma patients and normal subjects using the gene chip technique and screen out the esophageal early conceration associated genes. Methods： The total RNA was extracted and purified in the peripheral blood obtained from the patients with esophageal carcinoma and normal subjects. The first strand of cDNA was synthesized through retro-transcription and labeled with Cy5 and Cy3 fluorescence as probes. The mixed probes were hybridized with a piece of 4096 double dot human whole gene chip. The acquired image was analyzed by microarrav suite software using a digital computer, and the intensity of ttuorescence signal and its ratio were calculated. Results： A total of 92 genes were screened out and its expression difference was more than 2 times in the peripheral blood between the patients with esophageal carcinoma and normal subjects. Among these, the expression difference of 36 genes was more than 3 times. Two human urokinase plasminogen activator surface receptor （UPAR） genes, 80K-L protein gene, human protein tyrosine-phosphatase gent arid proto-oncogene protein mRNA were significantly up-regulated, while the collagen V type （α-2 gene was markedly down-regulated. Conclusion： 80K-L protein gene, tyrosinephophatase gene, proto-oncogene protein arid the collagen V type α-2 gene might be associated with the ontogenesis, development and its metastasis in the esophageal carcinoma. The UPAR gene may play important roles in the diagnosing the micrometastasis in the peripheral blood of esophageal carcinoma.
文摘The isotopomers of halogenated amino acids （2＇-F-L-phenylalanine, 3＇-F- and 3＇-Cl-L-tyrosine, as well as 5＇-F-, 5＇-Br-and 6＇-F-L-tryptophan） specifically labeled with deuterium at α- and 13-carbon atom of the side chain were synthesized by enzymatic catalyzed H/D exchange in fully deuteriated incubation medium. The extent and site of deuterium incorporation were confirmed by ^1H NMR （proton nuclear magnetic resonance） spectra.
