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The effect of phosphatidylcholine on the molecular weight properties of hyaluronic acid (HA) was studied in batch culture of Streptococcus zooepidemicus by adding phosphatidylcholine at the early stage of exponential phase. With the addition of 80 mg/L of phosphatidylcholine, maximum HA yield (2.47 g/L) and weight-average molecular weight (902.60 KDa) were achieved, increased by 17.4% and 67.1%, respectively, as compared to the control. Metabolic flux analysis was employed to study the mechanism of phosphatidylcholine on the molecular weight of HA. The normalized flux distribution maps based on fermentation data at phosphatidylcholine addition indicated that phosphatidylcholine resulted in higher flux flowing to the HA pathway and lower flux flowing to the glycolysis and biomass synthesis pathway, coupling with higher level of UDPNAG generation and extra regeneration of ATP. The GC-MS analysis of fatty acids in the plasma membrane showed that the addition of phosphatidylcholine could promote the mobility and permeability of the cell membrane, making the HA chain pass through the membrane more easily, thus decreasing the energy consumption. All these results led to higher molecular weight of hyaluronic acid. 相似文献
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首先给出了由半环的乘法半群上的格林关系所确定的半环开同余的性质和刻画.其次,由开同余出发,得到了六个不同的半环类,并证明了这六个半环类均是半环簇.最后,对半环簇的子簇格上的开算子进行了探讨,得到了一些有趣的结果. 相似文献
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利用数值求积公式,将三维第一类Fredholm积分方程进行离散,通过引入正则化方法,将离散后的积分方程转化为一离散适定问题,通过广义极小残余算法得到了其数值解.数值模拟结果表明该方法的可行有效性. 相似文献
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In the present study, ultra-performance liquid chromatography (UPLC) coupled to electrospray ionization (ESI(+)) tandem mass spectrometry (MS) was developed to identify and characterize the diarylheptanoids in the supercritical fluid extract (SFE) of Alpinia officinarum. The method established provides good reproducibility of UPLC and shows high precision with all the mass accuracy of less than 5 ppm. The ESI-MS-MS fragmentation behavior of every group and their appropriate characteristic pathways were proposed. On the basis of analyzing the fragmentation pathways, elemental composition provided by software Masslynx, mass data of the standard compounds and the information regarding polarity obtained from retention time data, in all, 23 diarylheptanods were characterized. All of them have been reported in Alpinia officinarum. They were classified into six distinct groups (homologous series). Compared to the references, the fragmentation pathways of the first and second group were detailed much more and complementary. Further more, the fragmentation pathways of the last four groups were firstly discussed. The fragmentation rules deduced and the data provided could aid in the characterization of other diarylheptanoids of these types and would be useful for the further research of diarylheptanoids in Alpinia officinarum or the other plants. 相似文献
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Metabolic profiling of luteolin‐7‐O‐glucoside in rat urine,plasma, bile and feces after oral administration using ultra‐high‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry
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