PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octa...PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.展开更多
2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(HNIW), commonly called as CL-20, is a high energy and high density material of keen interest to both commercial and scientific worlds due to its greater insen...2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(HNIW), commonly called as CL-20, is a high energy and high density material of keen interest to both commercial and scientific worlds due to its greater insensitivity(reduced sensitivity) along with a positive high heat of formation, which is due to the azanitro groups attached to the skeleton of HNIW and its highly strained cage structure. It plays a remarkable role in modification and replacement of most of the propellant(gun and rocket) preparations. In this report we present the comparative strategies involved in the syntheses of HNIW with respect to economical and environmental aspects. Various methods reported in the literature on the purification of the crude HNIW(α-HNIW) to obtain ε-form of HNIW(high dense/more potential) are consolidated. Understanding of the structure, morphology, energetics, thermal behavior and their modification to meet the applicability(decreased impact sensitivity) determines the industrial application of HNIW. A compilation of the available literature on the aforementioned characteristic properties for obtaining a value added ε-HNIW is discussed here. This overview also reports the literature available on newer forms of HNIW including derivatives and cocrystals,which increase the performance of HNIW.展开更多
A new caged polyprenylated xanthone, gambogic aldehyde （1）, was isolated from the resin of Garcinia hanburyi. Its structure was elucidated on the basis of spectral data including 1D and 2D NMR data. In addition, the...A new caged polyprenylated xanthone, gambogic aldehyde （1）, was isolated from the resin of Garcinia hanburyi. Its structure was elucidated on the basis of spectral data including 1D and 2D NMR data. In addition, the antiproliferative ability of compound 1 was determined in mouse leukemia P388 and P388/ADR cells.展开更多
AIM:To investigate the growth inhibitory mechanism of four caged xanthones from Garcinia hanburyi in cholangiocarcinoma(CCA) KKU-100 and KKU-M156 cells.METHODS:Four caged xanthones,selected on the basis of their antic...AIM:To investigate the growth inhibitory mechanism of four caged xanthones from Garcinia hanburyi in cholangiocarcinoma(CCA) KKU-100 and KKU-M156 cells.METHODS:Four caged xanthones,selected on the basis of their anticancer potency and chemical structure diversities(i.e.isomorellin,isomorellinol,forbesione and gambogic acid) were used in this study.Growth inhibition of these caged xanthones was determined using the sulforhodamine B assay.Induction of apoptosis was assessed by observing cell morphology,ethidium bromide and acridine orange staining and DNA fragmentation assay.Levels of apoptotic-related gene and protein expressions were determined by a real-time reverse transcriptase polymerase chain reaction and Western blotting analysis,respectively.RESULTS:The compounds were found to inhibit growth of both cell lines in a dose-dependent manner and also showed selective cytotoxicity against the cancer cells when compared with normal peripheral blood mononuclear cells.Growth suppression by these compounds was due to apoptosis,as evidenced by the cell morphological changes,chromatin condensation,nuclear fragmentation,and DNA ladder formation.At the molecular level,these compounds induced down-regulation of Bcl-2 and survivin proteins with up-regulation of Bax and apoptosisinducing factor proteins,leading to the activation of caspase-9 and-3 and DNA fragmentation.The functional group variations did not appear to affect the anticancer activity with regard to the two CCA cell lines;however,at a mechanistic level,isomorellinol exhibited the highest potency in increasing the Bax/Bcl-2 protein expression ratio(120 and 41.4 for KKU-100 and KKU-M156,respectively) and in decreasing survivin protein expression(0.01 fold as compared to control cells in both cell lines).Other activities at the molecular level indicate that functional groups on the prenyl side chain may be important.CONCLUSION:Our findings for the first time demonstrate that four caged xanthones induce apoptosis in CCA cells which is mediated through a mitochond展开更多
To date,there is still a lack of a comprehensive explanation for caged dynamics which is regarded as one of the intricate dynamic behaviors in amorphous alloys.This study focuses on Pd_(82)Si_(18)as the research objec...To date,there is still a lack of a comprehensive explanation for caged dynamics which is regarded as one of the intricate dynamic behaviors in amorphous alloys.This study focuses on Pd_(82)Si_(18)as the research object to further elucidate the underlying mechanism of caged dynamics from multiple perspectives,including the cage's lifetime,atomic local environment,and atomic potential energy.The results reveal that Si atoms exhibit a pronounced cage effect due to the hindrance of Pd atoms,resulting in an anomalous peak in the non-Gaussian parameters.An in-depth investigation was conducted on the caged dynamics differences between fast and slow Si atoms.In comparison to fast Si atoms,slow Si atoms were surrounded by more Pd atoms and occupied lower potential energy states,resulting in smaller diffusion displacements for the slow Si atoms.Concurrently,slow Si atoms tend to be in the centers of smaller clusters with coordination numbers of 9 and 10.During the isothermal relaxation process,clusters with coordination numbers 9 and 10 have longer lifetimes,suggesting that the escape of slow Si atoms from their cages is more challenging.The findings mentioned above hold significant implications for understanding the caged dynamics.展开更多
E.coli AlkB is a direct DNA/RNA repair protein that oxidatively reverses N1 alkylated purines and N3 alkylated pyrimidines to regular bases.Previous crystal structures have revealed N1-methyl adenine(1-meA) recognitio...E.coli AlkB is a direct DNA/RNA repair protein that oxidatively reverses N1 alkylated purines and N3 alkylated pyrimidines to regular bases.Previous crystal structures have revealed N1-methyl adenine(1-meA) recognition by AlkB and a unique base flipping mechanism,but how the AlkB active site can accommodate bulky base adducts is largely unknown.Employing a previously developed chemical cross-linking technique,we crystallized AlkB with a duplex DNA containing a caged thymine base(cagedT).The structure revealed a flexible hairpin lid and a reorganized substrate recognition loop used by AlkB to accommodate cagedT.These observations demonstrate,at the molecular level,how bulky DNA adducts may be recognized and processed by AlkB.展开更多
Photouncaging of second messengers has been successfully employed to gain mechanistic insight of cellular signaling path- ways. One of the most enigmatic processes of ion channel regulation is lipid recognition and li...Photouncaging of second messengers has been successfully employed to gain mechanistic insight of cellular signaling path- ways. One of the most enigmatic processes of ion channel regulation is lipid recognition and lipid-gating of TRPC channels, which represents pivotal mechanisms of cellular Ca2＋ homeostasis. Recently, optopharmacological tools including caged lipid mediators became available, enabling an unprecedented level of temporal and spatial control of the activating lipid species within a cellular environment. Here we tested a commonly used caged ligand approach for suitability to investigate TRPC sig- naling at the level of membrane conductance and cellular Ca2＋ handling. We report a specific photouncaging artifact that is triggered by the cage structure coumarin at UV illumination. Electrophysiological characterization identified a light-dependent membrane effect of coumarin. UV light （340 nm） as used for photouncaging, initiated a membrane conductance specifically in the presence of coumarin as low as 30 pmol L-1 concentrations. This conductance masked the TRPC3 conductance evoked by photouncaging, while TRPC-mediated cellular Ca2＋ responses were largely preserved. The observed light-induced membrane effects of the released caging moiety may well interfere with certain cellular functions, and prompt caution in using couma- fin-caged second messengers in cellular studies.展开更多
Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives contain...Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives containing single caged bicyclic phosphate structure（ 1a, 2a, 3a）, another three PEPA deviratives containing two caged bicyclic phosphate structures（1b, 2b, 3b） and one devirative（1c） containing three caged bicyclic phosphate structures. Structures of the products were characterized by FTIR, ^1H NMR, elemental analysis and TG analysis. The reaction conditions were also discussed. Thermal analysis showed they had high thermal stability and excellent char-forming ability. Besides, these compounds had pentaerythritol bone and flame retardant dements of phosphorus, bromine or nitrogen simultaneously in their molecules, endowed them with good fire retardancy, and made them can be used as intumescent flame retardant.展开更多
Maya Angelou(1928-2014)is a celebrated African American woman writer.She's not only an autobiographer,a poet,an educator,but also a politician,an actress and a director.Her first autobiographical novel I Know Why ...Maya Angelou(1928-2014)is a celebrated African American woman writer.She's not only an autobiographer,a poet,an educator,but also a politician,an actress and a director.Her first autobiographical novel I Know Why the Caged Bird Sings is a significant milestone of the African American literature of woman.The novel depicts Marguerite life experience from the age of 3 to the age of17,recording how she breaks through the bondage of racial discrimination and sex prejudice,and realizes self-consciousness.From the perspective of post-colonist criticism and feminism,this thesis analyses how the protagonist suffered from the"othering"under the colonial discourse and patriarchal ideology and how she got out of the bondage and reconstruct her identity.Finally,it is concluded that only if the black women break through the cage of race and gender,accept and reconstruct their identities,can they gain the real emancipation and respect.展开更多
The states of small molecule H2 and N2 in the Coo cage have been studied. It is shown that the molecular stable configUrations of the caged states exhibits little change compared with the free states, but the bond int...The states of small molecule H2 and N2 in the Coo cage have been studied. It is shown that the molecular stable configUrations of the caged states exhibits little change compared with the free states, but the bond intensities of the caged states have become much stronger.展开更多
The potential energy curves of some small molecules, H2, N2, O2, F2, HF, CO and NO, in the caged state within C60 cage and in the free state have been calculated by the quantum-chemical method AM1. In this study, the ...The potential energy curves of some small molecules, H2, N2, O2, F2, HF, CO and NO, in the caged state within C60 cage and in the free state have been calculated by the quantum-chemical method AM1. In this study, the focus is on the cage effect of C60, and the concept of caged state is put forward. The results show that the bond lengths in the caged states are not much different from those in their corresponding free states, but the bond intensities in the caged states are much greater than those in their corresponding free states.展开更多
Caged bicyclic phosphate （CBP） and its dimelamine salt （PDS） were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by ...Caged bicyclic phosphate （CBP） and its dimelamine salt （PDS） were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index （LOI） and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS, although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER 〈 PDS30/ER 〈 PDS15/ER 〈 CBPI5/ER, whereas that of specific extinction area is CBP15/ER 〉 CBP30/ER 〉 PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses （TG） and Fourier transform infrared spectroscopy （FT-IR）, it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy （SEM）, a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species. Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.展开更多
The flame-retarded polycarbonate（PC） has been made with octaphenyl polyhedral silsesquioxane（OPS） and/or caged bicyclic phosphate（Trimer）.Thermal gravimetric analysis（TGA）,Fourier-transform infrared（FTIR）,TG...The flame-retarded polycarbonate（PC） has been made with octaphenyl polyhedral silsesquioxane（OPS） and/or caged bicyclic phosphate（Trimer）.Thermal gravimetric analysis（TGA）,Fourier-transform infrared（FTIR）,TGA-FTIR,limiting oxygen index（LOI）,and mechanical tests have been employed to characterize the modified PC.The additives of OPS and Trimer in PC have been proved to be effective flame-retardants because of the synergistic interaction between the elements of P and Si.The role of OPS and Trimer in PC degradation are different：OPS participates in the charring of PC,while Trimer makes PC degrade in advance.In addition,OPS and Trimer induced obvious differences in the mechanical properties of PC.展开更多
The photocaging strategy has been widely used for activating biomolecules and hence regulating the underlying biological processes with high temporal and spatial resolution.Herein,we integrate this strategy into metab...The photocaging strategy has been widely used for activating biomolecules and hence regulating the underlying biological processes with high temporal and spatial resolution.Herein,we integrate this strategy into metabolic glycan labeling,which enables optical-ly-controlled metabolic labeling of cell-surface sialoglycans with azides.N-Azidoacetylmannosamine(ManNAz)is caged with a 4,5-dimethoxy-2-nitrobenzyl(DMNB)group at the anomeric hydroxyl group to block its cellular metabolism.After feeding to the cells,irradiation with 365 nm UV light or 405 nm visible light cleaves the photocage and generates ManNAz within the cells.ManNAz is metabolically converted to azido sialic acid,which is then incorporated into cell-surface sialoglycans.We demonstrated spatial and temporal control of this strategy by specifically labeling sialoglycans on a single cell and tracking the metabolism of ManNAz based on light-triggered pulse-chase labeling,respectively.The light-controlled metabolic glycan labeling strategy should facilitate probing of glycosylation in complex biological systems with high spatiotemporal precision.展开更多
Main observation and conclusion Nineteen unprecedented 7-methoxylated caged xanthones(1—19)were isolated from the twigs of Garcinia oligantha under the guidance of NMR spectroscopy.Their structures and absolute confi...Main observation and conclusion Nineteen unprecedented 7-methoxylated caged xanthones(1—19)were isolated from the twigs of Garcinia oligantha under the guidance of NMR spectroscopy.Their structures and absolute configurations were demonstrated by extensive spectroscopic data,single-crystal X-ray diffraction,electronic circular dichroism(ECD)calculations,and the modified Mosher's method.Compound 1 is a rare scalemic 7-methoxylated neo-caged xanthone,which was resolved using HPLC with CD detection on a chiral-phase AD column,and compounds 2—3 are rare 7-methoxylated caged xanthones with the hydrogenatedΔ^(8(8a))double bond.Fourteen compounds exhibited promising inhibitory activities against four human cancer cell lines with IC50 values ranging from 1.9 to 14.3μmol/L.A cell apoptosis analysis using flow cytometry showed that compound 11 could induce apoptosis in a dose dependent manner.Moreover,PARP,caspase-9,and Bcl-2 western blotting suggested that compound 11-induced apoptosis may be involved in caspase-dependent pathway.展开更多
As one of Mark Twain＇ s most classic short story, ＂ Is He Living or Is He Dead＂ does not reflect the major problems and the serious drawbacks of society fi＇om the surface significance of novel, however, the events...As one of Mark Twain＇ s most classic short story, ＂ Is He Living or Is He Dead＂ does not reflect the major problems and the serious drawbacks of society fi＇om the surface significance of novel, however, the events described in the novel can actually touch sensitive topic as well as the shortcomings of the era where, pointedly disclose the nature of society at that time. Mark Twain＇s short story tries to use this caged bird imagery to criticize the camouflage events occur and makes irony of this tragic story behind the social problems. Little caged bird in the novel contains profound social implications and is worthy of scrutiny and research.展开更多
The benzoin group caged compound has received strong interests due to its excellent photo- deprotection properties and wide use in chemical and biological studies. We used timeresolved infrared spectroscopy to investi...The benzoin group caged compound has received strong interests due to its excellent photo- deprotection properties and wide use in chemical and biological studies. We used timeresolved infrared spectroscopy to investigate the photochemical reaction of the benzoin caged compound, o-（2-methylbenzoyl）-DL-benzoin under 266 nm laser irradiation. Taking advantage of the specific vibrational marker bands and the IR discerning capability, we have detected and identified the uncaging product 2-methylbenzoic acid, and two intermediate radicals of benzoyl and 2-methylbenzoate benzyl in the transient infrared spectra. Our results provide spectral evidence to support the homolytic cleavage reaction of C-C=O bond in competition with the deprotection reaction. Moreover, the product yields of 2-methylbenzoic acid and benzoyl radical were observed to be affected by solvents and a largely water contalning solvent can be in favor of the deprotection reaction.展开更多
文摘PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.
基金financial assistance under the sponsored project "Novel materials for high energy reactions" (H/A: 4254) to Gulbarga University, Kalaburagi, India
文摘2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(HNIW), commonly called as CL-20, is a high energy and high density material of keen interest to both commercial and scientific worlds due to its greater insensitivity(reduced sensitivity) along with a positive high heat of formation, which is due to the azanitro groups attached to the skeleton of HNIW and its highly strained cage structure. It plays a remarkable role in modification and replacement of most of the propellant(gun and rocket) preparations. In this report we present the comparative strategies involved in the syntheses of HNIW with respect to economical and environmental aspects. Various methods reported in the literature on the purification of the crude HNIW(α-HNIW) to obtain ε-form of HNIW(high dense/more potential) are consolidated. Understanding of the structure, morphology, energetics, thermal behavior and their modification to meet the applicability(decreased impact sensitivity) determines the industrial application of HNIW. A compilation of the available literature on the aforementioned characteristic properties for obtaining a value added ε-HNIW is discussed here. This overview also reports the literature available on newer forms of HNIW including derivatives and cocrystals,which increase the performance of HNIW.
文摘A new caged polyprenylated xanthone, gambogic aldehyde （1）, was isolated from the resin of Garcinia hanburyi. Its structure was elucidated on the basis of spectral data including 1D and 2D NMR data. In addition, the antiproliferative ability of compound 1 was determined in mouse leukemia P388 and P388/ADR cells.
基金Supported by Grants from the Center of Excellence for Innovation in Chemistry,Commission on Higher Education,No 48-03-3-00-144Faculty of Medicine,No 51-03-2-00-008 and Khon Kaen University,No 50-03-1-01-005,Research Funds,Khon Kaen University,Thailand
文摘AIM:To investigate the growth inhibitory mechanism of four caged xanthones from Garcinia hanburyi in cholangiocarcinoma(CCA) KKU-100 and KKU-M156 cells.METHODS:Four caged xanthones,selected on the basis of their anticancer potency and chemical structure diversities(i.e.isomorellin,isomorellinol,forbesione and gambogic acid) were used in this study.Growth inhibition of these caged xanthones was determined using the sulforhodamine B assay.Induction of apoptosis was assessed by observing cell morphology,ethidium bromide and acridine orange staining and DNA fragmentation assay.Levels of apoptotic-related gene and protein expressions were determined by a real-time reverse transcriptase polymerase chain reaction and Western blotting analysis,respectively.RESULTS:The compounds were found to inhibit growth of both cell lines in a dose-dependent manner and also showed selective cytotoxicity against the cancer cells when compared with normal peripheral blood mononuclear cells.Growth suppression by these compounds was due to apoptosis,as evidenced by the cell morphological changes,chromatin condensation,nuclear fragmentation,and DNA ladder formation.At the molecular level,these compounds induced down-regulation of Bcl-2 and survivin proteins with up-regulation of Bax and apoptosisinducing factor proteins,leading to the activation of caspase-9 and-3 and DNA fragmentation.The functional group variations did not appear to affect the anticancer activity with regard to the two CCA cell lines;however,at a mechanistic level,isomorellinol exhibited the highest potency in increasing the Bax/Bcl-2 protein expression ratio(120 and 41.4 for KKU-100 and KKU-M156,respectively) and in decreasing survivin protein expression(0.01 fold as compared to control cells in both cell lines).Other activities at the molecular level indicate that functional groups on the prenyl side chain may be important.CONCLUSION:Our findings for the first time demonstrate that four caged xanthones induce apoptosis in CCA cells which is mediated through a mitochond
基金Project supported by the National Natural Science Foundation of China (Grant No.51701071)the Natural Science Foundation of Hunan Province,China (Grant Nos.2022JJ50115 and 2021JJ30179)the Research Foundation of the Education Bureau of Hunan Province,China (Grant No.22A0522)。
文摘To date,there is still a lack of a comprehensive explanation for caged dynamics which is regarded as one of the intricate dynamic behaviors in amorphous alloys.This study focuses on Pd_(82)Si_(18)as the research object to further elucidate the underlying mechanism of caged dynamics from multiple perspectives,including the cage's lifetime,atomic local environment,and atomic potential energy.The results reveal that Si atoms exhibit a pronounced cage effect due to the hindrance of Pd atoms,resulting in an anomalous peak in the non-Gaussian parameters.An in-depth investigation was conducted on the caged dynamics differences between fast and slow Si atoms.In comparison to fast Si atoms,slow Si atoms were surrounded by more Pd atoms and occupied lower potential energy states,resulting in smaller diffusion displacements for the slow Si atoms.Concurrently,slow Si atoms tend to be in the centers of smaller clusters with coordination numbers of 9 and 10.During the isothermal relaxation process,clusters with coordination numbers 9 and 10 have longer lifetimes,suggesting that the escape of slow Si atoms from their cages is more challenging.The findings mentioned above hold significant implications for understanding the caged dynamics.
基金supported by the National Institute of Health (GM071440 to C.H.)Data collection was performed at GM/CA-CAT Beamline 23-ID-B at the Advanced Photon Source at Argonne National Laboratorysupport for this beamline comes from the National Institute of Health and the United States Department of Energy
文摘E.coli AlkB is a direct DNA/RNA repair protein that oxidatively reverses N1 alkylated purines and N3 alkylated pyrimidines to regular bases.Previous crystal structures have revealed N1-methyl adenine(1-meA) recognition by AlkB and a unique base flipping mechanism,but how the AlkB active site can accommodate bulky base adducts is largely unknown.Employing a previously developed chemical cross-linking technique,we crystallized AlkB with a duplex DNA containing a caged thymine base(cagedT).The structure revealed a flexible hairpin lid and a reorganized substrate recognition loop used by AlkB to accommodate cagedT.These observations demonstrate,at the molecular level,how bulky DNA adducts may be recognized and processed by AlkB.
基金supported by the Austrian Science Fund(FWFW 1226-B18)
文摘Photouncaging of second messengers has been successfully employed to gain mechanistic insight of cellular signaling path- ways. One of the most enigmatic processes of ion channel regulation is lipid recognition and lipid-gating of TRPC channels, which represents pivotal mechanisms of cellular Ca2＋ homeostasis. Recently, optopharmacological tools including caged lipid mediators became available, enabling an unprecedented level of temporal and spatial control of the activating lipid species within a cellular environment. Here we tested a commonly used caged ligand approach for suitability to investigate TRPC sig- naling at the level of membrane conductance and cellular Ca2＋ handling. We report a specific photouncaging artifact that is triggered by the cage structure coumarin at UV illumination. Electrophysiological characterization identified a light-dependent membrane effect of coumarin. UV light （340 nm） as used for photouncaging, initiated a membrane conductance specifically in the presence of coumarin as low as 30 pmol L-1 concentrations. This conductance masked the TRPC3 conductance evoked by photouncaging, while TRPC-mediated cellular Ca2＋ responses were largely preserved. The observed light-induced membrane effects of the released caging moiety may well interfere with certain cellular functions, and prompt caution in using couma- fin-caged second messengers in cellular studies.
文摘Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives containing single caged bicyclic phosphate structure（ 1a, 2a, 3a）, another three PEPA deviratives containing two caged bicyclic phosphate structures（1b, 2b, 3b） and one devirative（1c） containing three caged bicyclic phosphate structures. Structures of the products were characterized by FTIR, ^1H NMR, elemental analysis and TG analysis. The reaction conditions were also discussed. Thermal analysis showed they had high thermal stability and excellent char-forming ability. Besides, these compounds had pentaerythritol bone and flame retardant dements of phosphorus, bromine or nitrogen simultaneously in their molecules, endowed them with good fire retardancy, and made them can be used as intumescent flame retardant.
文摘Maya Angelou(1928-2014)is a celebrated African American woman writer.She's not only an autobiographer,a poet,an educator,but also a politician,an actress and a director.Her first autobiographical novel I Know Why the Caged Bird Sings is a significant milestone of the African American literature of woman.The novel depicts Marguerite life experience from the age of 3 to the age of17,recording how she breaks through the bondage of racial discrimination and sex prejudice,and realizes self-consciousness.From the perspective of post-colonist criticism and feminism,this thesis analyses how the protagonist suffered from the"othering"under the colonial discourse and patriarchal ideology and how she got out of the bondage and reconstruct her identity.Finally,it is concluded that only if the black women break through the cage of race and gender,accept and reconstruct their identities,can they gain the real emancipation and respect.
文摘The states of small molecule H2 and N2 in the Coo cage have been studied. It is shown that the molecular stable configUrations of the caged states exhibits little change compared with the free states, but the bond intensities of the caged states have become much stronger.
文摘The potential energy curves of some small molecules, H2, N2, O2, F2, HF, CO and NO, in the caged state within C60 cage and in the free state have been calculated by the quantum-chemical method AM1. In this study, the focus is on the cage effect of C60, and the concept of caged state is put forward. The results show that the bond lengths in the caged states are not much different from those in their corresponding free states, but the bond intensities in the caged states are much greater than those in their corresponding free states.
基金This work was supported by the financial support of the Commission of Science and Technology of Shanghai Municipality(No.05nm05039 and No.05QMX1413).
文摘Caged bicyclic phosphate （CBP） and its dimelamine salt （PDS） were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index （LOI） and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS, although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER 〈 PDS30/ER 〈 PDS15/ER 〈 CBPI5/ER, whereas that of specific extinction area is CBP15/ER 〉 CBP30/ER 〉 PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses （TG） and Fourier transform infrared spectroscopy （FT-IR）, it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy （SEM）, a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species. Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.
基金Sponsored by the National High Technology Research and Development Program of China("863"Program)(2007AA03Z538)
文摘The flame-retarded polycarbonate（PC） has been made with octaphenyl polyhedral silsesquioxane（OPS） and/or caged bicyclic phosphate（Trimer）.Thermal gravimetric analysis（TGA）,Fourier-transform infrared（FTIR）,TGA-FTIR,limiting oxygen index（LOI）,and mechanical tests have been employed to characterize the modified PC.The additives of OPS and Trimer in PC have been proved to be effective flame-retardants because of the synergistic interaction between the elements of P and Si.The role of OPS and Trimer in PC degradation are different：OPS participates in the charring of PC,while Trimer makes PC degrade in advance.In addition,OPS and Trimer induced obvious differences in the mechanical properties of PC.
基金supported by the National Key R&D Program of China(No.2018YFA0507600)the National Natural Science Foundation of China(Nos.91753206 and 21521003)。
文摘The photocaging strategy has been widely used for activating biomolecules and hence regulating the underlying biological processes with high temporal and spatial resolution.Herein,we integrate this strategy into metabolic glycan labeling,which enables optical-ly-controlled metabolic labeling of cell-surface sialoglycans with azides.N-Azidoacetylmannosamine(ManNAz)is caged with a 4,5-dimethoxy-2-nitrobenzyl(DMNB)group at the anomeric hydroxyl group to block its cellular metabolism.After feeding to the cells,irradiation with 365 nm UV light or 405 nm visible light cleaves the photocage and generates ManNAz within the cells.ManNAz is metabolically converted to azido sialic acid,which is then incorporated into cell-surface sialoglycans.We demonstrated spatial and temporal control of this strategy by specifically labeling sialoglycans on a single cell and tracking the metabolism of ManNAz based on light-triggered pulse-chase labeling,respectively.The light-controlled metabolic glycan labeling strategy should facilitate probing of glycosylation in complex biological systems with high spatiotemporal precision.
基金sponsored partly by grants from the Three-year Development Plan Project for Traditional Chinese Medicine(No.ZY(2018-2020)-CCCX-2001-02)the Shanghai Sailing Program(No.17YF1419500)and NSFC(No.81803545)+2 种基金We are also grateful to NSFC-Joint Foundation of Yunnan Province(No.U1902213)the Key-Area ResearchDevelopment Program of Guangdong Province(No.2020B1111110003)for financial support.
文摘Main observation and conclusion Nineteen unprecedented 7-methoxylated caged xanthones(1—19)were isolated from the twigs of Garcinia oligantha under the guidance of NMR spectroscopy.Their structures and absolute configurations were demonstrated by extensive spectroscopic data,single-crystal X-ray diffraction,electronic circular dichroism(ECD)calculations,and the modified Mosher's method.Compound 1 is a rare scalemic 7-methoxylated neo-caged xanthone,which was resolved using HPLC with CD detection on a chiral-phase AD column,and compounds 2—3 are rare 7-methoxylated caged xanthones with the hydrogenatedΔ^(8(8a))double bond.Fourteen compounds exhibited promising inhibitory activities against four human cancer cell lines with IC50 values ranging from 1.9 to 14.3μmol/L.A cell apoptosis analysis using flow cytometry showed that compound 11 could induce apoptosis in a dose dependent manner.Moreover,PARP,caspase-9,and Bcl-2 western blotting suggested that compound 11-induced apoptosis may be involved in caspase-dependent pathway.
文摘As one of Mark Twain＇ s most classic short story, ＂ Is He Living or Is He Dead＂ does not reflect the major problems and the serious drawbacks of society fi＇om the surface significance of novel, however, the events described in the novel can actually touch sensitive topic as well as the shortcomings of the era where, pointedly disclose the nature of society at that time. Mark Twain＇s short story tries to use this caged bird imagery to criticize the camouflage events occur and makes irony of this tragic story behind the social problems. Little caged bird in the novel contains profound social implications and is worthy of scrutiny and research.
基金This work was supported by the National Natural Science Foundation of China （No.21333012 and No.21425313） and the National Basic Research Program of China （No.2013CB834602）.
文摘The benzoin group caged compound has received strong interests due to its excellent photo- deprotection properties and wide use in chemical and biological studies. We used timeresolved infrared spectroscopy to investigate the photochemical reaction of the benzoin caged compound, o-（2-methylbenzoyl）-DL-benzoin under 266 nm laser irradiation. Taking advantage of the specific vibrational marker bands and the IR discerning capability, we have detected and identified the uncaging product 2-methylbenzoic acid, and two intermediate radicals of benzoyl and 2-methylbenzoate benzyl in the transient infrared spectra. Our results provide spectral evidence to support the homolytic cleavage reaction of C-C=O bond in competition with the deprotection reaction. Moreover, the product yields of 2-methylbenzoic acid and benzoyl radical were observed to be affected by solvents and a largely water contalning solvent can be in favor of the deprotection reaction.
