In the continuation of our study on the Serratta marcescens O-antigen, two disaccharides8 and 13, corresponding to the key intermediates of oligosaccharides related to the S. marcescensO10 antigen, were srythesized by...In the continuation of our study on the Serratta marcescens O-antigen, two disaccharides8 and 13, corresponding to the key intermediates of oligosaccharides related to the S. marcescensO10 antigen, were srythesized by the trichloroacetate method. Their structures and compositionswere characterized by H NMR, C NMR, 2D NMR and IR, FAB-MS spectra.展开更多
Tl2Ba2Ca2Cu3O10 was reported to be a superconductor with a highest transition temperature of 125 K among the homologous series of Tl2Ba2Can-1CunO2n＋4. The direct information on the Cu ion site at the atomic level is ...Tl2Ba2Ca2Cu3O10 was reported to be a superconductor with a highest transition temperature of 125 K among the homologous series of Tl2Ba2Can-1CunO2n＋4. The direct information on the Cu ion site at the atomic level is important for elucidating the superconductivity mechanism. The local bond properties of Tl2Ba2Ca2Cu3O10 were studied using the average band-gap model. The calculated results show that the covalency of Cu（1）-O bond is 0.561, and the average covalency of Cu（2）-O is 0.296. Mossbauer isomer shifts of 57Fe in Tl2Ba2Ca2Cu3O10 were calculated using the chemical surrounding factor, defined by covalency and electronic polarizability. It is verified that for lower doping, Fe substitute the Cu at the Cu （1） site in forms of Fe^3＋ and Fe^4＋; for higher doping, Fe^3＋ and Fe^4＋ ion occupies Cu（1） and Cu（2） site respectively. The studies show that the determination of the correspondence between spectrum components and actual copper sites occupied by MSssbauer nucleus was made easier with the aid of the calculation results of the chemical bond parameters.展开更多
During a 2018 antimicrobial resistance surveillance of Escherichia coli isolates from diarrheal calves in Xinjiang Province,China,an unexpectedly high prevalence(48.5%)of fosfomycin resistance was observed.This study ...During a 2018 antimicrobial resistance surveillance of Escherichia coli isolates from diarrheal calves in Xinjiang Province,China,an unexpectedly high prevalence(48.5%)of fosfomycin resistance was observed.This study aimed to reveal the determinants of fosfomycin resistance and the underlying transmission mechanism.Polymerase chain reaction(PCR)screening showed that all fosfomycin-resistant E.coli carried the fosA3 gene.Pulsed-field gel electrophoresis(PFGE)and southern blot hybridization revealed that the 16 fosA3-positive isolates belonged to four different PFGE patterns(i.e.,A,B,C,D).The fosA3 genes of 11 clonally related strains(pattern D)were located on the chromosome,while others were carried by plasmids.Whole-genome and long-read sequencing indicated that the pattern D strains were E.coli O101:H9-ST10,and the pattern C,B,and A strains were O101:H9-ST167,O8:H30-ST1431,and O101:H9 with unknown ST,respectively.Among the pattern C strains,the blaCTX-M-14 gene was co-localized with the fosA3 gene on the F18:A-:B1 plasmids.Interestingly,phylogenetic analysis based on core genome single nucleotide polymorphisms(cgSNPs)showed that the O101:H9-ST10 strains were closely related to a Australian-isolated Chroicocephalus-origin E.coli O101:H9-ST10 strain producing CTX-M-14 and FosA3,with a difference of only 11 SNPs.These results indicate possible international dissemination of the high-risk E.coli clone O101:H9-ST10 by migratory birds.展开更多
A new pentaborate, KNa2CdB5O（10）, has been synthesized and its crystal structure was determined by single-crystal XRD method with the following crystal data： KNa2CdB5O（10）, Pccn, a = 18.4555（13）, b = 8.3040（10...A new pentaborate, KNa2CdB5O（10）, has been synthesized and its crystal structure was determined by single-crystal XRD method with the following crystal data： KNa2CdB5O（10）, Pccn, a = 18.4555（13）, b = 8.3040（10）, c = 12.8772（9） A, V = 1973.5（3） A3, Z = 8, Mr = 411.53, Dc= 2.770 g/cm3, μ = 2.765 mm（-1）, F（000） = 1552, R = 0.0648 and w R = 0.1756 for 1684 observed reflections and 175 variables. It contains the double ring [B5O（10）]（5-） groups composed of one BO4 tetrahedron and four BO3 triangles that are bridged by tetrahedral Cd（2＋） centers via common O atoms to form 2D [CdB5O（10）]n（3n-） layers, with A＋（A = K/Na, Na） cations situated between and within the layers. IR spectrum confirms the existence of BO3 and BO4 groups. UV-VIS diffuse reflectance spectrum shows a band gap of about 3.44 eV and solid-state fluorescence spectrum exhibits a broad emission band at around 386 nm. Band structure calculations indicate that KNa2CdB5O（10） is an indirect band-gap insulator, with the calculated energy gap（3.68 eV） close to the experimental one.展开更多
文摘In the continuation of our study on the Serratta marcescens O-antigen, two disaccharides8 and 13, corresponding to the key intermediates of oligosaccharides related to the S. marcescensO10 antigen, were srythesized by the trichloroacetate method. Their structures and compositionswere characterized by H NMR, C NMR, 2D NMR and IR, FAB-MS spectra.
文摘Tl2Ba2Ca2Cu3O10 was reported to be a superconductor with a highest transition temperature of 125 K among the homologous series of Tl2Ba2Can-1CunO2n＋4. The direct information on the Cu ion site at the atomic level is important for elucidating the superconductivity mechanism. The local bond properties of Tl2Ba2Ca2Cu3O10 were studied using the average band-gap model. The calculated results show that the covalency of Cu（1）-O bond is 0.561, and the average covalency of Cu（2）-O is 0.296. Mossbauer isomer shifts of 57Fe in Tl2Ba2Ca2Cu3O10 were calculated using the chemical surrounding factor, defined by covalency and electronic polarizability. It is verified that for lower doping, Fe substitute the Cu at the Cu （1） site in forms of Fe^3＋ and Fe^4＋; for higher doping, Fe^3＋ and Fe^4＋ ion occupies Cu（1） and Cu（2） site respectively. The studies show that the determination of the correspondence between spectrum components and actual copper sites occupied by MSssbauer nucleus was made easier with the aid of the calculation results of the chemical bond parameters.
基金supported by the National Natural Science Foundation of China(31625026)International Science and Technology Cooperation Project of Xinjiang Production and Construction Corps(XPCC)(2019BC004)Innovation Team Project of Guangdong University(2019KCXTD001)。
文摘During a 2018 antimicrobial resistance surveillance of Escherichia coli isolates from diarrheal calves in Xinjiang Province,China,an unexpectedly high prevalence(48.5%)of fosfomycin resistance was observed.This study aimed to reveal the determinants of fosfomycin resistance and the underlying transmission mechanism.Polymerase chain reaction(PCR)screening showed that all fosfomycin-resistant E.coli carried the fosA3 gene.Pulsed-field gel electrophoresis(PFGE)and southern blot hybridization revealed that the 16 fosA3-positive isolates belonged to four different PFGE patterns(i.e.,A,B,C,D).The fosA3 genes of 11 clonally related strains(pattern D)were located on the chromosome,while others were carried by plasmids.Whole-genome and long-read sequencing indicated that the pattern D strains were E.coli O101:H9-ST10,and the pattern C,B,and A strains were O101:H9-ST167,O8:H30-ST1431,and O101:H9 with unknown ST,respectively.Among the pattern C strains,the blaCTX-M-14 gene was co-localized with the fosA3 gene on the F18:A-:B1 plasmids.Interestingly,phylogenetic analysis based on core genome single nucleotide polymorphisms(cgSNPs)showed that the O101:H9-ST10 strains were closely related to a Australian-isolated Chroicocephalus-origin E.coli O101:H9-ST10 strain producing CTX-M-14 and FosA3,with a difference of only 11 SNPs.These results indicate possible international dissemination of the high-risk E.coli clone O101:H9-ST10 by migratory birds.
基金Supported by the National Natural Science Foundation of China(No.20871012)
文摘A new pentaborate, KNa2CdB5O（10）, has been synthesized and its crystal structure was determined by single-crystal XRD method with the following crystal data： KNa2CdB5O（10）, Pccn, a = 18.4555（13）, b = 8.3040（10）, c = 12.8772（9） A, V = 1973.5（3） A3, Z = 8, Mr = 411.53, Dc= 2.770 g/cm3, μ = 2.765 mm（-1）, F（000） = 1552, R = 0.0648 and w R = 0.1756 for 1684 observed reflections and 175 variables. It contains the double ring [B5O（10）]（5-） groups composed of one BO4 tetrahedron and four BO3 triangles that are bridged by tetrahedral Cd（2＋） centers via common O atoms to form 2D [CdB5O（10）]n（3n-） layers, with A＋（A = K/Na, Na） cations situated between and within the layers. IR spectrum confirms the existence of BO3 and BO4 groups. UV-VIS diffuse reflectance spectrum shows a band gap of about 3.44 eV and solid-state fluorescence spectrum exhibits a broad emission band at around 386 nm. Band structure calculations indicate that KNa2CdB5O（10） is an indirect band-gap insulator, with the calculated energy gap（3.68 eV） close to the experimental one.
