The microstrueture and various hydrides precipitated in Ti-6A1-4V alloys containing hydrogen 0.16,0.58,0.87,1.49 wt-%,respectively,have been studied by means of TEM and X-ray diffraction.The Ti_3Al phase may precipita...The microstrueture and various hydrides precipitated in Ti-6A1-4V alloys containing hydrogen 0.16,0.58,0.87,1.49 wt-%,respectively,have been studied by means of TEM and X-ray diffraction.The Ti_3Al phase may precipitate when H over 0.58 wt-%.In the same time,the morphology of hydrides gradually changed from rugged sheets to narrow laths as H contents increased.The microstructure of highly H-doped alloys is obviously fine.A mas- sive hydride and the hydride with tetragonal lattice were observed in the specimen containing 1.49 wt-%H.The twin hydrides were found in the alloys with different H contents and the electron diffraction patterns of the twin hydrides can be served as a simple criterion for distin- guishing the cubic and tetragonal structures.展开更多
The methods of determination of 6-methyl coumarin in cosmetics by HPLC-DAD and GC-FID were compared. The positive samples were confirmed by GC-MS. Methanol was used to extract 6-methyl coumarin from cosmetics. The chr...The methods of determination of 6-methyl coumarin in cosmetics by HPLC-DAD and GC-FID were compared. The positive samples were confirmed by GC-MS. Methanol was used to extract 6-methyl coumarin from cosmetics. The chromatographic conditions of the two methods were optimized and the samples were determined. The recovery, precision, correlation coefficient, detection limit and quantitative limit of the two methods were compared. The results showed that the linear relationship between the two methods was good. The percentage recovery of standard addition by HPLC-DAD was 92.20%~102.80%, by RSD was 0.77%~2.00%;the detection limit was 0.05 mg/kg, the quantitative limit was 0.17 mg/kg. The percentage recovery of standard addition by GC-FID was 97.30%~103.28%, by RSD was 0.47%~4.87%;the detection limit was 1.3 mg/kg, the quantitative limit was 5.0 mg/kg. The detection limit by HPLC-DAD was lower and more sensitive than that by GC-FID , which also shows that HPLC-DAD has more advantages for the detection of low content samples.展开更多
Epigenetic marks on histones and DNA,such as DNA methylation at N6-adenine(6mA),play crucial roles in gene expression and genome maintenance,but their deposition and function in microalgae remain largely uncharacteriz...Epigenetic marks on histones and DNA,such as DNA methylation at N6-adenine(6mA),play crucial roles in gene expression and genome maintenance,but their deposition and function in microalgae remain largely uncharacterized.Here,we report a genome-wide 6mA map for the model industrial oleaginous microalga Nannochloropsis oceanica produced by single-molecule real-time sequencing.Found in 0.1%of adenines,6mA sites are mostly enriched at the AGGYV motif,more abundant in transposons and 30 untranslated re-gions,and associated with active transcription.Moreover,6mA gradually increases in abundance along the direction of gene transcription and shows special positional enrichment near splicing donor and transcrip-tion termination sites.Highly expressed genes tend to show greater 6mA abundance in the gene body than do poorly expressed genes,indicating a positive interaction between 6mA and general transcription fac-tors.Furthermore,knockout of the putative 6mA methylase NO08G00280 by genome editing leads to changes in methylation patterns that are correlated with changes in the expression of molybdenum cofactor,sulfate transporter,glycosyl transferase,and lipase genes that underlie reductions in biomass and oil productivity.By contrast,knockout of the candidate demethylase NO06G02500 results in increased 6mA levels and reduced growth.Unraveling the epigenomic players and their roles in biomass productivity and lipid metabolism lays a foundation for epigenetic engineering of industrial microalgae.展开更多
The phase constitution and variation of Nd_(14)Fe_(73)Co_6B_7 alloy after hydriding and subsequent dehydriding treatment at 770℃ have been investigated respectively by means of X-ray diffraction,SEM,TEM and magnetic ...The phase constitution and variation of Nd_(14)Fe_(73)Co_6B_7 alloy after hydriding and subsequent dehydriding treatment at 770℃ have been investigated respectively by means of X-ray diffraction,SEM,TEM and magnetic measurement techniques.The original coarse,as cast grain structure,is dissolved into α-Fe,Nd hydride and Fe_2B mixture with average dimension of 0.1 μm,during hydriding process,and subsequently the triphase mixture recombined into finely unique Nd_2Fe_(14)B phase with dimension of 0.3 μm by desorbing the hydrogen.It was found that the Nd-rich phase distributed at the boundary of as-cast grain structure diffused into matrix Nd_2Fe_(14)B grain during hydriding.It remains during dehydriding and distribute homogeneously around some colonies composed of fine grains of Nd_2Fe_(14)B.展开更多
A facile and efficient approach was developed to access 5, 7-disubstitued thiazolo[5,4-d]pyrimidine-4, 6（5H, 7H）-diones through condensation of N-substituted 5-amino-4-carbethoxythiazole with structurally diverse is...A facile and efficient approach was developed to access 5, 7-disubstitued thiazolo[5,4-d]pyrimidine-4, 6（5H, 7H）-diones through condensation of N-substituted 5-amino-4-carbethoxythiazole with structurally diverse isocyanates in the presence of sodium hydride. The easy availability of substrates and tolerance of structural diversity in this reaction make it attractive to be used for construction of libraries in drug discovery process.展开更多
The TEM and HRTEM were utilized to investigate the phase transformation of hydrogenated Ti-6Al-4V alloys （0 wt pct–0.9 wt pct H） treated by annealing and quenching from β field. The results indicate that the ortho...The TEM and HRTEM were utilized to investigate the phase transformation of hydrogenated Ti-6Al-4V alloys （0 wt pct–0.9 wt pct H） treated by annealing and quenching from β field. The results indicate that the orthorhombic α martensite and β phase appear progressively with the increase of hydrogen concentration. On the other hand, hydrides with sizes of 2–5 nm are observed in the specimens containing more than 0.6 wt pct hydrogen. The formation of α and twins can be attributed to the internal stress caused by solid solution of hydrogen and hydrides precipitation.展开更多
Nineteen diterpenoids, including saldigitin A(1) bearing an unprecedented 10-methylated 6/7/6 carbon ring system, two new icetexanes(2, 3), and two new nor-abietanes(5, 6) were characterized from the roots of Salvia d...Nineteen diterpenoids, including saldigitin A(1) bearing an unprecedented 10-methylated 6/7/6 carbon ring system, two new icetexanes(2, 3), and two new nor-abietanes(5, 6) were characterized from the roots of Salvia digitaloides. Their structures were elucidated by the analysis of the spectroscopic data,X-ray crystallography, and TDDFT calculations of ECD spectra. The novel architecture of 1 should be biogenetically derived through the cleavage and re-cyclization of the B/C rings from the normal abietane skeleton. Biologically, 1–5 exhibited noticeable inhibitions on Ca_(v)3.1 low voltage-gated Ca2+channel(LVGCC), with IC50values in the range of 3.43–11.70 μmol/L. They are the first example of diterpenoids with 6/7/6 carbon rings system as Ca_(v)3.1 antagonists.展开更多
The recently proposed global and local calibrations for the mean annual air temperature(MAT) reconstruction on the basis of 5-and 6-methyl brGDGTs have rarely been applied to the Chinese LPS yet, leaving the applicabi...The recently proposed global and local calibrations for the mean annual air temperature(MAT) reconstruction on the basis of 5-and 6-methyl brGDGTs have rarely been applied to the Chinese LPS yet, leaving the applicability of these calibrations unclear. Here, we used the improved chromatography method to analyze 198 loess-paleosol samples from the Weinan section in the southern CLP for the past 350 kyr. The 6-methyl brGDGTs comprise a major proportion of total brGDGTs, pointing to alkaline conditions for most soil samples from the Weinan LPS. The decoupled profile variation of MBT′6ME and MBT′_(5ME) suggests their response to different enviromental factors, possibly soil pH(or soil moisture) and temperature, respectively. This discrimination further corraborates that temperature and monsoonal precipitation were not in phase during the last four deglaciations on the CLP. Temperature estimates for the six calibrations tested show similar trends but remarkably differ in amplitudes. The soil moisture appears to affect the global MBT′/CBT calibration, the global MATmr calibration(a calibration based on the multiple linear regression) and the Chinese local SSM(Stepwise Selection Method) calibration, resulting in a significant underestimation of late Holocene temperature. In contrast, the dry climate has no effect on the global MBT′5ME calibration. Of the six calibrations,only the Chinese local SSM calibration and global MATmr calibration produce temperature variation amplitude over the past 350 ka that is consistent with other independent proxy data. The recently proposed local calibrations based on 5-and 6-methyl brGDGTs for North China yield the amplitude of temperature changes that is much larger than the results determined by other approaches.All the six calibrations have their own weakness in the MAT reconstruction, due partly to the inconsistency between the brGDGT distribution in the Weinan LPS and the modern soils used to establish these calibrations.展开更多
Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in par...Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in particular the 6-methyl isomers of bacterial branched GDGTs(bGDGTs), in the lakes with contrasting pH, are still unknown, hindering their application for paleo-reconstructions. Here, we investigated the environmental impacts on the distribution of GDGTs in 17 alkaline lakes and 1 acid lake in China. It was found that the dissolved oxygen content in water column may have an impact on the distribution of archaeal isoprenoid GDGTs(iGDGTs) by causing the change in archaeal communities. The ratio of GDGT-0/crenarchaeol increases with decreasing oxygen content, indicating that the relative abundance of anaerobic methanogenic archaea or Miscellaneous Crenarchaeotic Group(MCG) vs. aerobic Thaumarchaeota is controlled by the oxygen content dissolved in water of these lakes. Thaumarchaeota are likely to contribute only a small proportion of iGDGTs in the relatively oxygen-depleted lakes, and thus TEX_(86) is not suitable for the reconstruction of the surface temperature of these lakes. The abundance ratio of iGDGTs to bGDGTs(R_(i/b)) appears to show no relationship with water pH in all the lakes, but exhibits a significant positive correlation with the water depth of the acid Lake Qinghai in Tengchong. As expected, the methylation degree of bGDGTs(MBT′) was found to correlate with both mean annual air temperature(MAT) and water pH, and the cyclization degree of bGDGTs(CBT) correlates only with water pH in these lakes. However, the MBT′_(5ME), an index to measure the methylation degree of 5-methyl bGDGTs, exhibits no relationship with MAT, whereas MBT′_(6ME), the methylation degree of 6-methyl bGDGTs, was found to correlate significantly with MAT. This is opposite to the situation observed in the global soils, pointing to a different adaptation of b GDGT-producing bacteria to environmental variables or different microbial sources of bGDGTs in these lakes. The relative abundance of 6- vs. 5-methyl bGDGTs is controlled by pH in these lakes, similar to that observed in worldwide soils. Hence, the isomer ratio(IR) of 6-methyl bGDGTs or CBT′ can be used as a proxy for water pH, although they might be influenced by other environmental factors including temperature in the lakes with a narrow range of pH.展开更多
文摘The microstrueture and various hydrides precipitated in Ti-6A1-4V alloys containing hydrogen 0.16,0.58,0.87,1.49 wt-%,respectively,have been studied by means of TEM and X-ray diffraction.The Ti_3Al phase may precipitate when H over 0.58 wt-%.In the same time,the morphology of hydrides gradually changed from rugged sheets to narrow laths as H contents increased.The microstructure of highly H-doped alloys is obviously fine.A mas- sive hydride and the hydride with tetragonal lattice were observed in the specimen containing 1.49 wt-%H.The twin hydrides were found in the alloys with different H contents and the electron diffraction patterns of the twin hydrides can be served as a simple criterion for distin- guishing the cubic and tetragonal structures.
文摘The methods of determination of 6-methyl coumarin in cosmetics by HPLC-DAD and GC-FID were compared. The positive samples were confirmed by GC-MS. Methanol was used to extract 6-methyl coumarin from cosmetics. The chromatographic conditions of the two methods were optimized and the samples were determined. The recovery, precision, correlation coefficient, detection limit and quantitative limit of the two methods were compared. The results showed that the linear relationship between the two methods was good. The percentage recovery of standard addition by HPLC-DAD was 92.20%~102.80%, by RSD was 0.77%~2.00%;the detection limit was 0.05 mg/kg, the quantitative limit was 0.17 mg/kg. The percentage recovery of standard addition by GC-FID was 97.30%~103.28%, by RSD was 0.47%~4.87%;the detection limit was 1.3 mg/kg, the quantitative limit was 5.0 mg/kg. The detection limit by HPLC-DAD was lower and more sensitive than that by GC-FID , which also shows that HPLC-DAD has more advantages for the detection of low content samples.
基金supported by the Synthetic Biology Program of the Ministry of Science and Technology of the People’s Republic of China (2021YFA0909700)I201908 and E1551402 from the Qingdao Institute of Bioenergy and Bioprocess Technology,Chinese Academy of Sciences,31900071 from the Natural Science Foundation of ChinaZR2019QC012 from the Natural Science Foundation of Shandong Province.
文摘Epigenetic marks on histones and DNA,such as DNA methylation at N6-adenine(6mA),play crucial roles in gene expression and genome maintenance,but their deposition and function in microalgae remain largely uncharacterized.Here,we report a genome-wide 6mA map for the model industrial oleaginous microalga Nannochloropsis oceanica produced by single-molecule real-time sequencing.Found in 0.1%of adenines,6mA sites are mostly enriched at the AGGYV motif,more abundant in transposons and 30 untranslated re-gions,and associated with active transcription.Moreover,6mA gradually increases in abundance along the direction of gene transcription and shows special positional enrichment near splicing donor and transcrip-tion termination sites.Highly expressed genes tend to show greater 6mA abundance in the gene body than do poorly expressed genes,indicating a positive interaction between 6mA and general transcription fac-tors.Furthermore,knockout of the putative 6mA methylase NO08G00280 by genome editing leads to changes in methylation patterns that are correlated with changes in the expression of molybdenum cofactor,sulfate transporter,glycosyl transferase,and lipase genes that underlie reductions in biomass and oil productivity.By contrast,knockout of the candidate demethylase NO06G02500 results in increased 6mA levels and reduced growth.Unraveling the epigenomic players and their roles in biomass productivity and lipid metabolism lays a foundation for epigenetic engineering of industrial microalgae.
文摘The phase constitution and variation of Nd_(14)Fe_(73)Co_6B_7 alloy after hydriding and subsequent dehydriding treatment at 770℃ have been investigated respectively by means of X-ray diffraction,SEM,TEM and magnetic measurement techniques.The original coarse,as cast grain structure,is dissolved into α-Fe,Nd hydride and Fe_2B mixture with average dimension of 0.1 μm,during hydriding process,and subsequently the triphase mixture recombined into finely unique Nd_2Fe_(14)B phase with dimension of 0.3 μm by desorbing the hydrogen.It was found that the Nd-rich phase distributed at the boundary of as-cast grain structure diffused into matrix Nd_2Fe_(14)B grain during hydriding.It remains during dehydriding and distribute homogeneously around some colonies composed of fine grains of Nd_2Fe_(14)B.
基金supported by the National Natural Science Foundation of China(No.30500634) and NSF of Beijing (No.7102112)
文摘A facile and efficient approach was developed to access 5, 7-disubstitued thiazolo[5,4-d]pyrimidine-4, 6（5H, 7H）-diones through condensation of N-substituted 5-amino-4-carbethoxythiazole with structurally diverse isocyanates in the presence of sodium hydride. The easy availability of substrates and tolerance of structural diversity in this reaction make it attractive to be used for construction of libraries in drug discovery process.
文摘The TEM and HRTEM were utilized to investigate the phase transformation of hydrogenated Ti-6Al-4V alloys （0 wt pct–0.9 wt pct H） treated by annealing and quenching from β field. The results indicate that the orthorhombic α martensite and β phase appear progressively with the increase of hydrogen concentration. On the other hand, hydrides with sizes of 2–5 nm are observed in the specimens containing more than 0.6 wt pct hydrogen. The formation of α and twins can be attributed to the internal stress caused by solid solution of hydrogen and hydrides precipitation.
基金financially supported by the National Natural Science Foundation of China (Nos. 32070392 and 32070393)the Second Tibetan Plateau Scientific Expedition and Research(STEP) Program (Nos. 2019QZKK0502-0303 and 2019QZKK0502-0304)+2 种基金Natural Science Foundation of Yunnan Province (Nos.202001AS070040 and 202101AV070010)Yunnan Young&Elite Talents Project (No. YNWR-QNBJ-2020-277)CAS “Light of West China” Program (2021)。
文摘Nineteen diterpenoids, including saldigitin A(1) bearing an unprecedented 10-methylated 6/7/6 carbon ring system, two new icetexanes(2, 3), and two new nor-abietanes(5, 6) were characterized from the roots of Salvia digitaloides. Their structures were elucidated by the analysis of the spectroscopic data,X-ray crystallography, and TDDFT calculations of ECD spectra. The novel architecture of 1 should be biogenetically derived through the cleavage and re-cyclization of the B/C rings from the normal abietane skeleton. Biologically, 1–5 exhibited noticeable inhibitions on Ca_(v)3.1 low voltage-gated Ca2+channel(LVGCC), with IC50values in the range of 3.43–11.70 μmol/L. They are the first example of diterpenoids with 6/7/6 carbon rings system as Ca_(v)3.1 antagonists.
基金supported by the Key Research and Development Program of China (Grant No. 2016YFA0601100)the National Natural Science Foundation of China (Grant Nos. 41602189 & 41330103)the National Bureau for Foreign Experts and Ministry of Education of China (111 Project) (Grant No. B08030)
文摘The recently proposed global and local calibrations for the mean annual air temperature(MAT) reconstruction on the basis of 5-and 6-methyl brGDGTs have rarely been applied to the Chinese LPS yet, leaving the applicability of these calibrations unclear. Here, we used the improved chromatography method to analyze 198 loess-paleosol samples from the Weinan section in the southern CLP for the past 350 kyr. The 6-methyl brGDGTs comprise a major proportion of total brGDGTs, pointing to alkaline conditions for most soil samples from the Weinan LPS. The decoupled profile variation of MBT′6ME and MBT′_(5ME) suggests their response to different enviromental factors, possibly soil pH(or soil moisture) and temperature, respectively. This discrimination further corraborates that temperature and monsoonal precipitation were not in phase during the last four deglaciations on the CLP. Temperature estimates for the six calibrations tested show similar trends but remarkably differ in amplitudes. The soil moisture appears to affect the global MBT′/CBT calibration, the global MATmr calibration(a calibration based on the multiple linear regression) and the Chinese local SSM(Stepwise Selection Method) calibration, resulting in a significant underestimation of late Holocene temperature. In contrast, the dry climate has no effect on the global MBT′5ME calibration. Of the six calibrations,only the Chinese local SSM calibration and global MATmr calibration produce temperature variation amplitude over the past 350 ka that is consistent with other independent proxy data. The recently proposed local calibrations based on 5-and 6-methyl brGDGTs for North China yield the amplitude of temperature changes that is much larger than the results determined by other approaches.All the six calibrations have their own weakness in the MAT reconstruction, due partly to the inconsistency between the brGDGT distribution in the Weinan LPS and the modern soils used to establish these calibrations.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. CUGL150812)the National Natural Science Foundation of China (Grant No. 41330103)the Programme of Introducing Talents of Discipline to Universities Project (Grant No. B08030)
文摘Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in particular the 6-methyl isomers of bacterial branched GDGTs(bGDGTs), in the lakes with contrasting pH, are still unknown, hindering their application for paleo-reconstructions. Here, we investigated the environmental impacts on the distribution of GDGTs in 17 alkaline lakes and 1 acid lake in China. It was found that the dissolved oxygen content in water column may have an impact on the distribution of archaeal isoprenoid GDGTs(iGDGTs) by causing the change in archaeal communities. The ratio of GDGT-0/crenarchaeol increases with decreasing oxygen content, indicating that the relative abundance of anaerobic methanogenic archaea or Miscellaneous Crenarchaeotic Group(MCG) vs. aerobic Thaumarchaeota is controlled by the oxygen content dissolved in water of these lakes. Thaumarchaeota are likely to contribute only a small proportion of iGDGTs in the relatively oxygen-depleted lakes, and thus TEX_(86) is not suitable for the reconstruction of the surface temperature of these lakes. The abundance ratio of iGDGTs to bGDGTs(R_(i/b)) appears to show no relationship with water pH in all the lakes, but exhibits a significant positive correlation with the water depth of the acid Lake Qinghai in Tengchong. As expected, the methylation degree of bGDGTs(MBT′) was found to correlate with both mean annual air temperature(MAT) and water pH, and the cyclization degree of bGDGTs(CBT) correlates only with water pH in these lakes. However, the MBT′_(5ME), an index to measure the methylation degree of 5-methyl bGDGTs, exhibits no relationship with MAT, whereas MBT′_(6ME), the methylation degree of 6-methyl bGDGTs, was found to correlate significantly with MAT. This is opposite to the situation observed in the global soils, pointing to a different adaptation of b GDGT-producing bacteria to environmental variables or different microbial sources of bGDGTs in these lakes. The relative abundance of 6- vs. 5-methyl bGDGTs is controlled by pH in these lakes, similar to that observed in worldwide soils. Hence, the isomer ratio(IR) of 6-methyl bGDGTs or CBT′ can be used as a proxy for water pH, although they might be influenced by other environmental factors including temperature in the lakes with a narrow range of pH.
