Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In...Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In order to well understand their MS fragmentation behaviors,they were investigated by electrospray ionization ion-trap time-of-flight multistage product ion mass spectrometry(ESI-IT-TOF-MSn)for the first time.The protonated molecules([M?H]?)of swerilactones J and K,and deprotonated molecules([M-H]-)of swerilactones H,J and K were readily observed in the conventional single-stage mass spectra(MS);however only the[M?Cl]-ion for swerilactone I was obtained in negative mode.Based on the MSn study,the fragmentation pathways of swerilactones H and I in negative mode,and swerilactones J and K in both positive and negative modes were proposed.The neutral losses of H_(2)O,CO,CO_(2)and C_(2)H_(4)O moieties are the particular elimination from the precursor ions due to the presence of hydroxyl,d-lactone and 1-O-ethyl moieties in their structures,of which the retro-Diels–Alder cleavage was the most particular dissociation.The fragment ions at m/z 341 and 291 in negative mode can be considered as the diagnostic ions for secoiridoid trimers.This investigation will provide valuable information for their fast characterization from complicated natural mixtures and extensive understanding their structural architectures.展开更多
We collected waveforms of a teleseismic event which occurred from January 2007 to October 2011 from 174 broadband seismic stations deployed in Hebei and its adjacent areas. Using the H-k stacking method,the average th...We collected waveforms of a teleseismic event which occurred from January 2007 to October 2011 from 174 broadband seismic stations deployed in Hebei and its adjacent areas. Using the H-k stacking method,the average thickness and Poisson's ratio of the crust are acquired. In order to obtain reliable receiver functions, the broadband seismograms of 488 teleseismic earthquakes occurring in the epicentral distance range from 30° to 90° with magnitudes larger than Mb6. 0 are collected. The results show that crustal thickness have conspicuous lateral heterogeneity and have good correlation to the regional geological tectonic features. Poisson ratio's value is equated with the global models estimates which fluctuate at about 0. 25. Crustal thickness has positive correlation to the topography and the Taihang Mountains form the transition zone of thick and thin crustal thickness. There is an obvious difference in crustal thickness beneath the north and south of the Shanxi earthquake zone and the Poisson ratio of Datong,Ningwu and Anze basins is greater than 0. 3. The crustal thickness beneath the Zhang-Bo( Zhangjiakou-Bohai Sea)earthquake zone decreases from west to north and its Poisson ratio shows conspicuous lateral heterogeneity. The thin crust and low Poisson ratio in the Huabei( North China)basin may correlate with the delamination of the North China craton.展开更多
Hongkong’s smooth return creates vast prospect and numerous opportunities for Guangdong-Hongkong economic cooperation. Over the past decade the cooperation has gone a long way, from non-governmental to governmental, ...Hongkong’s smooth return creates vast prospect and numerous opportunities for Guangdong-Hongkong economic cooperation. Over the past decade the cooperation has gone a long way, from non-governmental to governmental, from processing trade to high technology. Presently, it has become a highprofile activity which covers various areas.More than 20,000 representatives from 5,063 corporations participated the symposium. And 1,559 agreements, involving $ 13.159 billion, were signed. Of the investment, $8.7851 billion, or 66.8 per cent is from overseas investors. Of the agreements, 810 or 65 per cent, are high new展开更多
Histone methylation is an important epigenetic phenomenon that participates in a diverse array of cellular processes and has been found to be associated with cancer. Recent identification of several histone demethylas...Histone methylation is an important epigenetic phenomenon that participates in a diverse array of cellular processes and has been found to be associated with cancer. Recent identification of several histone demethylases has proved that histone methylation is a reversible process. Through a candidate approach, we have biochemically identified JMJD3 as an H3K27 demethylase. Transfection of JMJD3 into HeLa cells caused a specific reduction oftrimethyl H3K27, but had no effect on di-and monomethyl H3K27, or histone lysine methylations on H3K4 and H3K9. The enzymatic activity requires the JmjC domain and the conserved histidine that has been suggested to be important for a cofactor binding. In vitro biochemical experiments demonstrated that JMJD3 directly catalyzes the demethylation. In addition, we found that JMJD3 is upregulated in prostate cancer, and its expression is higher in metastatic prostate cancer. Thus, we identified JMJD3 as a demethylase capable of removing the trimethyl group from histone H3 lysine 27 and upregulated in prostate cancer.展开更多
文摘Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In order to well understand their MS fragmentation behaviors,they were investigated by electrospray ionization ion-trap time-of-flight multistage product ion mass spectrometry(ESI-IT-TOF-MSn)for the first time.The protonated molecules([M?H]?)of swerilactones J and K,and deprotonated molecules([M-H]-)of swerilactones H,J and K were readily observed in the conventional single-stage mass spectra(MS);however only the[M?Cl]-ion for swerilactone I was obtained in negative mode.Based on the MSn study,the fragmentation pathways of swerilactones H and I in negative mode,and swerilactones J and K in both positive and negative modes were proposed.The neutral losses of H_(2)O,CO,CO_(2)and C_(2)H_(4)O moieties are the particular elimination from the precursor ions due to the presence of hydroxyl,d-lactone and 1-O-ethyl moieties in their structures,of which the retro-Diels–Alder cleavage was the most particular dissociation.The fragment ions at m/z 341 and 291 in negative mode can be considered as the diagnostic ions for secoiridoid trimers.This investigation will provide valuable information for their fast characterization from complicated natural mixtures and extensive understanding their structural architectures.
基金funded by the Seismic Situation Tracing Orientation Task,China Earthquake Administration(2014020120)the Science and Technology Support Program of Hebei Province(2014020120)
文摘We collected waveforms of a teleseismic event which occurred from January 2007 to October 2011 from 174 broadband seismic stations deployed in Hebei and its adjacent areas. Using the H-k stacking method,the average thickness and Poisson's ratio of the crust are acquired. In order to obtain reliable receiver functions, the broadband seismograms of 488 teleseismic earthquakes occurring in the epicentral distance range from 30° to 90° with magnitudes larger than Mb6. 0 are collected. The results show that crustal thickness have conspicuous lateral heterogeneity and have good correlation to the regional geological tectonic features. Poisson ratio's value is equated with the global models estimates which fluctuate at about 0. 25. Crustal thickness has positive correlation to the topography and the Taihang Mountains form the transition zone of thick and thin crustal thickness. There is an obvious difference in crustal thickness beneath the north and south of the Shanxi earthquake zone and the Poisson ratio of Datong,Ningwu and Anze basins is greater than 0. 3. The crustal thickness beneath the Zhang-Bo( Zhangjiakou-Bohai Sea)earthquake zone decreases from west to north and its Poisson ratio shows conspicuous lateral heterogeneity. The thin crust and low Poisson ratio in the Huabei( North China)basin may correlate with the delamination of the North China craton.
文摘Hongkong’s smooth return creates vast prospect and numerous opportunities for Guangdong-Hongkong economic cooperation. Over the past decade the cooperation has gone a long way, from non-governmental to governmental, from processing trade to high technology. Presently, it has become a highprofile activity which covers various areas.More than 20,000 representatives from 5,063 corporations participated the symposium. And 1,559 agreements, involving $ 13.159 billion, were signed. Of the investment, $8.7851 billion, or 66.8 per cent is from overseas investors. Of the agreements, 810 or 65 per cent, are high new
文摘Histone methylation is an important epigenetic phenomenon that participates in a diverse array of cellular processes and has been found to be associated with cancer. Recent identification of several histone demethylases has proved that histone methylation is a reversible process. Through a candidate approach, we have biochemically identified JMJD3 as an H3K27 demethylase. Transfection of JMJD3 into HeLa cells caused a specific reduction oftrimethyl H3K27, but had no effect on di-and monomethyl H3K27, or histone lysine methylations on H3K4 and H3K9. The enzymatic activity requires the JmjC domain and the conserved histidine that has been suggested to be important for a cofactor binding. In vitro biochemical experiments demonstrated that JMJD3 directly catalyzes the demethylation. In addition, we found that JMJD3 is upregulated in prostate cancer, and its expression is higher in metastatic prostate cancer. Thus, we identified JMJD3 as a demethylase capable of removing the trimethyl group from histone H3 lysine 27 and upregulated in prostate cancer.
