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981.
EglN2 associates with the NRF1‐PGC1α complex and controls mitochondrial function in breast cancer 下载免费PDF全文
982.
Yuanwei Jia Haitang Xie Guangji Wang Jianguo Sun Wei Wang Huang Qing Xuan Wang Hao Yang Meijuan Xu Yi Gu Chen Yao Jie Shen 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(9-10):791-797
A simple liquid chromatography electrospray ionization mass spectrometry (LC–ESI–MS) method with highly improved sensitivities for the determination of helicid in rat bile, urine, feces and most tissues was developed. The tissues and feces were firstly homogenized mechanically using deionized water as the media. Bile, urine, tissues and feces homogenates were extracted by liquid–liquid extraction with n-butyl alcohol for sample preparation. The subsequent analysis procedures were performed on a Shimadzu LCMS2010A system (electrospray ionization single quadrupole mass analyzer). A Luna C18 column (150 mm × 2.00 mm, 5 μm) was used as the analytical column, while a mixture of acetonitrile and ammonium chloride water solution was used as the mobile phase. The proportions of mobile phase were changed timely according to gradient programs. Chlorinated adducts of molecular ions [M+Cl]? at m/z 319.00 and 363.05 were used to quantify helicid and bergeninum (internal standard), respectively. The method was validated to be accurate, precise and rugged with good linearity. The proposed method was successfully applied to the preclinical tissue distribution and excretion studies of helicid in rats. 相似文献
983.
Wang Pei Wang Chun-Mei Gao Li Cui Yan-Nong Yang Hai-Li de Silva Nayana D. G. Ma Qing Bao Ai-Ke Flowers Timothy J. Rowland Owen Wang Suo-Min 《Plant and Soil》2020,448(1-2):603-620
Plant and Soil - Uncontrolled uptake of Na+ is the reason that many species are sensitive to salinity. Suberin is a protective barrier found in the walls of root endodermal cells that appears to be... 相似文献
984.
以冬凌草的分枝数、单墩叶重及叶中冬凌草甲素的含量作为冬凌草药材产量和质量的评价指标,确定了河南淇县野生冬凌草和湖北广水、武汉野转家种冬凌草的最佳采收期,并分析了气象因素对冬凌草药材质量和产量的影响。结果表明:气象因素对引种地与原产地冬凌草的质量没有明显影响,药材叶中冬凌草甲素含量均在6月份左右达到峰值且十分接近;但气象因素对冬凌草产量则有影响,气候不同导致引种地野转家种药材的分枝数比原产地野生药材多2~4倍。综合质量和产量的考察结果,冬凌草的最佳采收期应定在其开花前,引种地武汉宜定在6月份,引种地广水宜定在6~7月份,原产地河南淇县宜定在6~8月份。 相似文献
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986.
988.
Raghuvir N. Sengupta Sabine N.S. Van Schie George Giamba?u Qing Dai Joseph D. Yesselman Darrin York Joseph A. Piccirilli Daniel Herschlag 《RNA (New York, N.Y.)》2016,22(1):32-48
Biological catalysis hinges on the precise structural integrity of an active site that binds and transforms its substrates and meeting this requirement presents a unique challenge for RNA enzymes. Functional RNAs, including ribozymes, fold into their active conformations within rugged energy landscapes that often contain misfolded conformers. Here we uncover and characterize one such “off-pathway” species within an active site after overall folding of the ribozyme is complete. The Tetrahymena group I ribozyme (E) catalyzes cleavage of an oligonucleotide substrate (S) by an exogenous guanosine (G) cofactor. We tested whether specific catalytic interactions with G are present in the preceding E•S•G and E•G ground-state complexes. We monitored interactions with G via the effects of 2′- and 3′-deoxy (–H) and −amino (–NH2) substitutions on G binding. These and prior results reveal that G is bound in an inactive configuration within E•G, with the nucleophilic 3′-OH making a nonproductive interaction with an active site metal ion termed MA and with the adjacent 2′-OH making no interaction. Upon S binding, a rearrangement occurs that allows both –OH groups to contact a different active site metal ion, termed MC, to make what are likely to be their catalytic interactions. The reactive phosphoryl group on S promotes this change, presumably by repositioning the metal ions with respect to G. This conformational transition demonstrates local rearrangements within an otherwise folded RNA, underscoring RNA''s difficulty in specifying a unique conformation and highlighting Nature''s potential to use local transitions of RNA in complex function. 相似文献
989.
990.
湿地碳排放及其影响因素 总被引:4,自引:0,他引:4
湿地生态系统在全球碳循环中起着重要作用.湿地独特的土壤、水文和植被条件,使得其在低氧环境下能不断累积碳,并同时释放大量温室气体——CH4和CO2,因此湿地的碳排放近年来成为全球气候变化研究关注的重点问题.湿地的土壤状况、水文条件及植被类型的不同导致湿地CH4和CO2的排放具有极强的时空变异性.土壤温度与CH4和CO2排放呈正相关关系;水位条件对湿地温室气体的排放有一定影响,在一定范围内,土壤的厌氧环境导致CH4排放量增大,CO2排放量减小;植被影响到温室气体产生、氧化和排放各个方面,因物种而异. 相似文献