In this study,protein from Porphyra haitanensis was used as raw material to prepare an antioxidant peptide,and its antioxidant activity was evaluated in vitro.A model of H_2O_2-induced oxidative damage in Hep G2 cells...In this study,protein from Porphyra haitanensis was used as raw material to prepare an antioxidant peptide,and its antioxidant activity was evaluated in vitro.A model of H_2O_2-induced oxidative damage in Hep G2 cells was established,and the effects of Porphyra haitanensis hydrolysates (PHHs) on superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were detected.Finally,the structure of PHHs was identified by ESI-MS/MS.The results showed that the 1,1-diphenyl-2-pyridylhydrazine(DPPH)-free radical-scavenging ability of PHHs was the strongest (59.28%at 1.0 mg m L~(-1)) when hydrolyzed with an acidic protease for 4 h.PHHs with different concentrations had protective effects on H_2O_2-induced damage to Hep G2 cells,and the protective effect was enhanced with increasing concentrations.When the level was 400μg m L~(-1),the cell survival rate was as high as 88.62%.Moreover,PHHs can significantly reduce oxidative damage to Hep G2 cells by H_2O_2,improve SOD activity,and reduce MDA content.The tetrapeptide Asp-Lys-Ser-Thr,with a molecular weight of 448 Da,was identified as an important fraction of PHHs by high-resolution mass spectrometry.展开更多
Based on the transmitting power of a mobile station and the maximum cell capacity,the analysis of a wide-band code-division multiple access(WCDMA)standard and the comparison of the corresponding parameters with CDMA20...Based on the transmitting power of a mobile station and the maximum cell capacity,the analysis of a wide-band code-division multiple access(WCDMA)standard and the comparison of the corresponding parameters with CDMA2000 or evolution-data only(EV-DO)are given in this paper.The result proves that the mobile station of WCDMA cannot provide the required transmitting power on the specified frequency band and data rate,and the symmetrical capacity in an up-downlink cannot meet the requirement of a mobile Internet.It is questionable for the International Telecommunication Union(ITU)to select the frequency band of 2 GHz for vehicular mobile telecommunication and unreasonable to distribute it over the downlink and uplink channels symmetrically.Only CDMA20001X EV-DO or enhanced data rate for GSM evolution(EDGE),which adopts the Time Division Multiple Access(TDMA)mode,can provide the high-speed data rate for a wireless access.展开更多
基金supported by the National Key R&D Pro-gram of China (No. 2018YFD0901102)the Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams (No. 2020KJ151)+1 种基金the Special Scientific Research Funds for Central Non-profit Institutes,Chinese Academy of Fishery Sciences (No. 2020 TD69)the China Agriculture Research System (No. CARS-50)。
文摘In this study,protein from Porphyra haitanensis was used as raw material to prepare an antioxidant peptide,and its antioxidant activity was evaluated in vitro.A model of H_2O_2-induced oxidative damage in Hep G2 cells was established,and the effects of Porphyra haitanensis hydrolysates (PHHs) on superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were detected.Finally,the structure of PHHs was identified by ESI-MS/MS.The results showed that the 1,1-diphenyl-2-pyridylhydrazine(DPPH)-free radical-scavenging ability of PHHs was the strongest (59.28%at 1.0 mg m L~(-1)) when hydrolyzed with an acidic protease for 4 h.PHHs with different concentrations had protective effects on H_2O_2-induced damage to Hep G2 cells,and the protective effect was enhanced with increasing concentrations.When the level was 400μg m L~(-1),the cell survival rate was as high as 88.62%.Moreover,PHHs can significantly reduce oxidative damage to Hep G2 cells by H_2O_2,improve SOD activity,and reduce MDA content.The tetrapeptide Asp-Lys-Ser-Thr,with a molecular weight of 448 Da,was identified as an important fraction of PHHs by high-resolution mass spectrometry.
文摘Based on the transmitting power of a mobile station and the maximum cell capacity,the analysis of a wide-band code-division multiple access(WCDMA)standard and the comparison of the corresponding parameters with CDMA2000 or evolution-data only(EV-DO)are given in this paper.The result proves that the mobile station of WCDMA cannot provide the required transmitting power on the specified frequency band and data rate,and the symmetrical capacity in an up-downlink cannot meet the requirement of a mobile Internet.It is questionable for the International Telecommunication Union(ITU)to select the frequency band of 2 GHz for vehicular mobile telecommunication and unreasonable to distribute it over the downlink and uplink channels symmetrically.Only CDMA20001X EV-DO or enhanced data rate for GSM evolution(EDGE),which adopts the Time Division Multiple Access(TDMA)mode,can provide the high-speed data rate for a wireless access.
