Combining with the diatom-based conductivity transfer function from Qing-hai-Xizang (Tibetan) Plateau lakes, the lake salinity for the past 300 years was quantitatively reconstructed based on the analysis of diatom as...Combining with the diatom-based conductivity transfer function from Qing-hai-Xizang (Tibetan) Plateau lakes, the lake salinity for the past 300 years was quantitatively reconstructed based on the analysis of diatom assemblages from a sediment core in Chencuo Lake, southern Tibet. The distinct negative relationship between inferred conductivity and recorded lakelevels in recent years suggests that the lake salinity can reflect the fluctuations of effective moisture of climate in lake area. The salinity inferred from diatoms reveals several major hydrological episodes. An obvious desalination of lake water occurred during the last cold interval of the Little Ice Age (about 1845–1885 AD), indicating a cold and moist climate. The lake salinity presented a rapid increase trend since the middle 1960s, with a peak value and high amplitude of salinity variability in the whole past 300 years. The low effective moisture inferred from the lake salinity may have contributed to the enhanced evaporation by the continuous increase of temperature in recent years. Keywords diatoms - conductivity or salinity - quantitative reconstruction - Chencuo Lake展开更多
Lipoteichoic acids(LTAs)are macroamphiphiles composed of alditol,lipid,phosphate,and carbohydrate units.Due to their inherent complexity,it is a severe challenge to access LTAs with structural integrity from natural s...Lipoteichoic acids(LTAs)are macroamphiphiles composed of alditol,lipid,phosphate,and carbohydrate units.Due to their inherent complexity,it is a severe challenge to access LTAs with structural integrity from natural sources for biological or immunological evaluation.Here,we describe the first total synthesis of Lactococcus garvieae LTA(type II LTA),containing five distinct 1,2-cis gluco/galactopyranosidic linkages,via a novel additive-modulated O-glycosyl trichloroacetimidate preactivation glycosidation strategy.This strategy features(1)high glycosidation yields and excellent 1,2-cis stereoselectivities independent of the donor anomeric configuration,(2)common and inexpensive reagents as promoters and additives,(3)application to standard glycosyl imidate donors without resorting to participating protection,and(4)general application to reactive and less reactive glycosyl acceptors.Thus,via the precise stereocontrolled construction of three galactopyranosidic and two glucopyranosidic bonds on a multigram scale,a series of structurally well-defined LTA molecules were successfully assembled.Immunological evaluation of these type II synthetic LTAs showed a structure–activity relationship in the stimulation of a proinflammatory response.展开更多
Based on careful sampling and accurate analysis of recent sediments in Lake Chenghai, this paper discusses the staggered positive/negative correlation between organic carbon (OC) concentration and inorganic carbon (IC...Based on careful sampling and accurate analysis of recent sediments in Lake Chenghai, this paper discusses the staggered positive/negative correlation between organic carbon (OC) concentration and inorganic carbon (IC) concentration. The result indicates that temperature change, and its induced relative changes are the main factors affecting the relationship between IC concentration, δ13C of carbonate and OC concentration. When temperature and its induced photosynthesis strength change control autochthonous calcite precipitation, OC concentration is positively correlated with IC concentration and δ13C of carbonate. When temperature and its induced physical/chemical changes dominate, OC concentration displays negative correlation with IC concentration and δ13C of carbonate. IC concentration and δ13C of carbonate in sediments of Lake Chenghai are good proxies for climatic warm/cold changes.展开更多
O-Mannosylation plays a vital role in the regulation of a variety range of biological processes,for instance,brain and muscle development.However,the precise function remains largely unknown due to its innate heteroge...O-Mannosylation plays a vital role in the regulation of a variety range of biological processes,for instance,brain and muscle development.However,the precise function remains largely unknown due to its innate heterogeneity.In this regard,it is still welcome to develop efficient methods to access diverse structurally-defined glycopeptides.In this study,a diversity-oriented assembly of O-mannosylα-dystroglycan(α-DG)glycopeptides has been achieved via a chemoenzymatic strategy.This strategy features(i)gram scale divergent synthesis of core m1,core m2 and core m3 mannosylated amino acids from judiciously designed protecting group strategies and chemical glycosidation;(i)efficient glycopeptide assembly via the optimized microwave-assisted solid phase peptide synthesis(SPpS);and(ii)enzymatic elaboration of the core glycan structures to install galactosyl and sialyl-galactosyl moieties.The efficiency and flexibility of this chemoenzymatic approach was demonstrated with the construction of 12 glycopeptides with different core m1,core m2 and core m3 mannosyl glycans,including a core m2 glycopeptide bearing a heptasaccharide for the first time.展开更多
Resin protects wounded trees from microbial infection,but also provides a suitable substrate for the growth of highly specialized fungi.Chaenothecopsis proliferatus is described growing on resin of Cunninghamia lanceo...Resin protects wounded trees from microbial infection,but also provides a suitable substrate for the growth of highly specialized fungi.Chaenothecopsis proliferatus is described growing on resin of Cunninghamia lanceolata from Hunan Province,China.The new fungus is compared with extant species and two new fossil specimens from Eocene Baltic and Oligocene Bitterfeld ambers.The Oligocene fossil had produced proliferating ascomata identical to those of the newly described species and to other extant species of the same lineage.This morphology may represent an adaptation to growing near active resin flows:the proliferating ascomata can effectively rejuvenate if partially overrun by fresh,sticky exudate.Inward growth of fungal hyphae into resin has only been documented from Cenozoic amber fossils suggesting comparatively late occupation of resin as substrate by fungi.Still,resinicolous Chaenothecopsis species were already well adapted to their special ecological niche by the Eocene,and the morphology of these fungi has since remained remarkably constant.展开更多
文摘Combining with the diatom-based conductivity transfer function from Qing-hai-Xizang (Tibetan) Plateau lakes, the lake salinity for the past 300 years was quantitatively reconstructed based on the analysis of diatom assemblages from a sediment core in Chencuo Lake, southern Tibet. The distinct negative relationship between inferred conductivity and recorded lakelevels in recent years suggests that the lake salinity can reflect the fluctuations of effective moisture of climate in lake area. The salinity inferred from diatoms reveals several major hydrological episodes. An obvious desalination of lake water occurred during the last cold interval of the Little Ice Age (about 1845–1885 AD), indicating a cold and moist climate. The lake salinity presented a rapid increase trend since the middle 1960s, with a peak value and high amplitude of salinity variability in the whole past 300 years. The low effective moisture inferred from the lake salinity may have contributed to the enhanced evaporation by the continuous increase of temperature in recent years. Keywords diatoms - conductivity or salinity - quantitative reconstruction - Chencuo Lake
基金supported by the National Natural Science Foundation of China(grant nos.21977063,92053110,and 22177061)the National Key Research and Development Program of China(grant no.2018YFA0902000)+3 种基金the China Postdoctoral Science Foundation(grant no.2020M680090)the Qilu Youth Scholar Program of Shandong University,the Central Government Guide Local Science and Technology Development Funds(grant no.YDZX20203700002579)the Nonprofit Central Research Institute Fund of Chinese Academy of Medical Sciences(grant no.2021-RC350-002)the CAMS Innovation Fund for Medical Sciences(CIFMS)(grant no.2021-1-I2M-026).
文摘Lipoteichoic acids(LTAs)are macroamphiphiles composed of alditol,lipid,phosphate,and carbohydrate units.Due to their inherent complexity,it is a severe challenge to access LTAs with structural integrity from natural sources for biological or immunological evaluation.Here,we describe the first total synthesis of Lactococcus garvieae LTA(type II LTA),containing five distinct 1,2-cis gluco/galactopyranosidic linkages,via a novel additive-modulated O-glycosyl trichloroacetimidate preactivation glycosidation strategy.This strategy features(1)high glycosidation yields and excellent 1,2-cis stereoselectivities independent of the donor anomeric configuration,(2)common and inexpensive reagents as promoters and additives,(3)application to standard glycosyl imidate donors without resorting to participating protection,and(4)general application to reactive and less reactive glycosyl acceptors.Thus,via the precise stereocontrolled construction of three galactopyranosidic and two glucopyranosidic bonds on a multigram scale,a series of structurally well-defined LTA molecules were successfully assembled.Immunological evaluation of these type II synthetic LTAs showed a structure–activity relationship in the stimulation of a proinflammatory response.
基金This work was supported by the Knowledge Innovation Project of Chinese Academy of Sciences (KZCX2-105) the Innovation Realm Project of the State Key Laboratory of Environmental Geochemistry and the National Natural Science Foundation of China (Gran
文摘Based on careful sampling and accurate analysis of recent sediments in Lake Chenghai, this paper discusses the staggered positive/negative correlation between organic carbon (OC) concentration and inorganic carbon (IC) concentration. The result indicates that temperature change, and its induced relative changes are the main factors affecting the relationship between IC concentration, δ13C of carbonate and OC concentration. When temperature and its induced photosynthesis strength change control autochthonous calcite precipitation, OC concentration is positively correlated with IC concentration and δ13C of carbonate. When temperature and its induced physical/chemical changes dominate, OC concentration displays negative correlation with IC concentration and δ13C of carbonate. IC concentration and δ13C of carbonate in sediments of Lake Chenghai are good proxies for climatic warm/cold changes.
基金This work is financially supported by the National Natural Science Foundation of China(Grant Nos.22177061,92053110,21977063,21907056)the China Postdoctoral Science Foundation(2020M680090)+2 种基金the Shenzhen Science and Technology Program(RCBS20200714114957255)the Open Projects Fund of Shandong Key Laboratory of Carbohydrate Chemistry and Glycobiology(2021CCG01&02)the Central Government Guide Local Science and Technology Development Funds(YDZX20203700002579).
文摘O-Mannosylation plays a vital role in the regulation of a variety range of biological processes,for instance,brain and muscle development.However,the precise function remains largely unknown due to its innate heterogeneity.In this regard,it is still welcome to develop efficient methods to access diverse structurally-defined glycopeptides.In this study,a diversity-oriented assembly of O-mannosylα-dystroglycan(α-DG)glycopeptides has been achieved via a chemoenzymatic strategy.This strategy features(i)gram scale divergent synthesis of core m1,core m2 and core m3 mannosylated amino acids from judiciously designed protecting group strategies and chemical glycosidation;(i)efficient glycopeptide assembly via the optimized microwave-assisted solid phase peptide synthesis(SPpS);and(ii)enzymatic elaboration of the core glycan structures to install galactosyl and sialyl-galactosyl moieties.The efficiency and flexibility of this chemoenzymatic approach was demonstrated with the construction of 12 glycopeptides with different core m1,core m2 and core m3 mannosyl glycans,including a core m2 glycopeptide bearing a heptasaccharide for the first time.
基金supported by research grants from the Jenny and Antti Wihuri Foundation and Ella and Georg Ehrnrooth Foundation.
文摘Resin protects wounded trees from microbial infection,but also provides a suitable substrate for the growth of highly specialized fungi.Chaenothecopsis proliferatus is described growing on resin of Cunninghamia lanceolata from Hunan Province,China.The new fungus is compared with extant species and two new fossil specimens from Eocene Baltic and Oligocene Bitterfeld ambers.The Oligocene fossil had produced proliferating ascomata identical to those of the newly described species and to other extant species of the same lineage.This morphology may represent an adaptation to growing near active resin flows:the proliferating ascomata can effectively rejuvenate if partially overrun by fresh,sticky exudate.Inward growth of fungal hyphae into resin has only been documented from Cenozoic amber fossils suggesting comparatively late occupation of resin as substrate by fungi.Still,resinicolous Chaenothecopsis species were already well adapted to their special ecological niche by the Eocene,and the morphology of these fungi has since remained remarkably constant.
