Bound phenolic compounds from the residue of Apocynum venetum(A.venetum)tea were released by alkaline digestion with sonication,followed by extraction using ethyl acetate(EtOAc).The fragment ions of compounds in free ...Bound phenolic compounds from the residue of Apocynum venetum(A.venetum)tea were released by alkaline digestion with sonication,followed by extraction using ethyl acetate(EtOAc).The fragment ions of compounds in free and bound forms were identified by liquid chromatography electrospray ionization tandem mass spectrometry(LC-ESI-MS/MS)in both positive and negative modes.Further investigation of chemical constituents in the EtOAc extract led to the isolation of eleven individual compounds,and their chemical structures were identified as(−)-epicatechin(1),(−)-loliolide(2),(−)-syringaresinol-4-O-β-D-glucopyranoside(3),alloside of benzyl alcohol(4),3-[(6-O-hexopyranosylhexopyranosyl)oxy]-2-(palmitoyloxy)propyl(9Z,12Z,15Z)-9,12,15-octadecatrienoate(5),apocynoside I(6),quercetin-3-O-β-D-glucopyranoside(7),kaempferol-3-O-β-D-glucopyranoside(8),[1-acetyloxy-3-[3,4,5-trihydroxy-6-[[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxymethyl]oxan-2-yl]oxypropan-2-yl]hexadecanoate(9),1-stearoyl-2-palmitoyl-sn-glycerol(10),and 3-hexene-l-O-β-D-glucoside(11)using a series of spectroscopic methods.Compounds 2–5 and 9–11 were isolated for the first time from A.venetum,while antioxidant experiments showed that compounds 1,7,and 8 displayed strong DPPH and ABTS+radical scavenging activities.This study represents the first investigation of bound phenolic compounds with potential health benefits in the residue of A.venetum tea.展开更多
We report the direct observation of coupling between a single self-assembled InAs quantum dot and a wetting layer, based on strong diamagnetic shifts of many-body exciton states using magneto-photoluminescence spectro...We report the direct observation of coupling between a single self-assembled InAs quantum dot and a wetting layer, based on strong diamagnetic shifts of many-body exciton states using magneto-photoluminescence spectroscopy. An extremely large positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in the quantum dot; the coefficient is nearly one order of magnitude larger than that of the exciton states confined in the quantum dots. Recombination of electrons with holes in a quantum dot of the coupled system leads to an unusual negative diamagnetic effect, which is five times stronger than that in a pure quantum dot system. This effect can be attributed to the expansion of the wavefunction of remaining electrons in the wetting layer or the spread of electrons in the excited states of the quantum dot to the wetting layer after recombination. In this case, the wavefunction extent of the final states in the quantum dot plane is much larger than that of the initial states because of the absence of holes in the quantum dot to attract electrons. The properties of emitted photons that depend on the large electron wavefunction extents in the wetting layer indicate that the coupling occurs between systems of different dimensionality, which is also verified from the results obtained by applying a magnetic field in different configurations. This study paves a new way to observe hybrid states with zero- and two-dimensional structures, which could be useful for investigating the Kondo physics and implementing spin-based solid-state quantum information processing.展开更多
Bacillus amyloliquefaciens generally secretes a mixture of multiple cyclic lipopeptides,including iturin,surfactin,and plipastatin,and it is challenging to discriminate each cyclic lipopeptide’s antimicrobial activit...Bacillus amyloliquefaciens generally secretes a mixture of multiple cyclic lipopeptides,including iturin,surfactin,and plipastatin,and it is challenging to discriminate each cyclic lipopeptide’s antimicrobial activity directly.In this study,a chassis strain Bacillus subtilis 1A751 WR without cyclic lipopeptides operons was constructed by CRISPR/Cas9.The iturin gene cluster of B.amyloliquefaciens HYM-12 was captured and assembled with sfp and degQ genes using transformation-associated recombination(TAR).It was then integrated into the chassis strain to obtain an iturin mono-producing strain that could synthesize six iturin isoforms.The frameshift sfp gene of strain 1A751Δpps was repaired by a scarless gene knock-in method to generate a surfactin mono-producing strain.Antimicrobial activity experiments indicated that the extracts of iturin,surfactin,and our previously constructed plipastatin mono-producing strains exhibited powerful inhibitory effects toward pathogenic bacteria.Interest-ingly,iturin showed significant antifungal activity,but surfactin and plipastatin exhibited weak antifungal ac-tivity.Compared with amphotericin B,iturin has a solid and durable antifungal activity.This study demonstrates that TAR cloning is efficient for cloning large gene clusters,proves the differences in the antimicrobial activity of three cyclic lipopeptides,and lays a theoretical basis for further elucidating their antimicrobial mechanism.展开更多
文摘Bound phenolic compounds from the residue of Apocynum venetum(A.venetum)tea were released by alkaline digestion with sonication,followed by extraction using ethyl acetate(EtOAc).The fragment ions of compounds in free and bound forms were identified by liquid chromatography electrospray ionization tandem mass spectrometry(LC-ESI-MS/MS)in both positive and negative modes.Further investigation of chemical constituents in the EtOAc extract led to the isolation of eleven individual compounds,and their chemical structures were identified as(−)-epicatechin(1),(−)-loliolide(2),(−)-syringaresinol-4-O-β-D-glucopyranoside(3),alloside of benzyl alcohol(4),3-[(6-O-hexopyranosylhexopyranosyl)oxy]-2-(palmitoyloxy)propyl(9Z,12Z,15Z)-9,12,15-octadecatrienoate(5),apocynoside I(6),quercetin-3-O-β-D-glucopyranoside(7),kaempferol-3-O-β-D-glucopyranoside(8),[1-acetyloxy-3-[3,4,5-trihydroxy-6-[[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxymethyl]oxan-2-yl]oxypropan-2-yl]hexadecanoate(9),1-stearoyl-2-palmitoyl-sn-glycerol(10),and 3-hexene-l-O-β-D-glucoside(11)using a series of spectroscopic methods.Compounds 2–5 and 9–11 were isolated for the first time from A.venetum,while antioxidant experiments showed that compounds 1,7,and 8 displayed strong DPPH and ABTS+radical scavenging activities.This study represents the first investigation of bound phenolic compounds with potential health benefits in the residue of A.venetum tea.
基金This work was supported by the National Basic Research Program of China （Nos. 2013CB328706 and 2014CB921003）, the National Natural Science Foundation of China （Nos. 91436101, 11174356, and 61275060）, the Strategic Priority Research Program of the Chinese Academy of Sciences （No. XDB07030200）, and the 100 Talents Program of Chinese Academy of Sciences. We thank Jean-Pierre Leburton for helpful discussions.
文摘We report the direct observation of coupling between a single self-assembled InAs quantum dot and a wetting layer, based on strong diamagnetic shifts of many-body exciton states using magneto-photoluminescence spectroscopy. An extremely large positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in the quantum dot; the coefficient is nearly one order of magnitude larger than that of the exciton states confined in the quantum dots. Recombination of electrons with holes in a quantum dot of the coupled system leads to an unusual negative diamagnetic effect, which is five times stronger than that in a pure quantum dot system. This effect can be attributed to the expansion of the wavefunction of remaining electrons in the wetting layer or the spread of electrons in the excited states of the quantum dot to the wetting layer after recombination. In this case, the wavefunction extent of the final states in the quantum dot plane is much larger than that of the initial states because of the absence of holes in the quantum dot to attract electrons. The properties of emitted photons that depend on the large electron wavefunction extents in the wetting layer indicate that the coupling occurs between systems of different dimensionality, which is also verified from the results obtained by applying a magnetic field in different configurations. This study paves a new way to observe hybrid states with zero- and two-dimensional structures, which could be useful for investigating the Kondo physics and implementing spin-based solid-state quantum information processing.
基金supported by the special funds for Agro-product Quality Safety Risk Assessment of the Ministry of Agriculture of the People’s Republic of China(GJFP20191101)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Bacillus amyloliquefaciens generally secretes a mixture of multiple cyclic lipopeptides,including iturin,surfactin,and plipastatin,and it is challenging to discriminate each cyclic lipopeptide’s antimicrobial activity directly.In this study,a chassis strain Bacillus subtilis 1A751 WR without cyclic lipopeptides operons was constructed by CRISPR/Cas9.The iturin gene cluster of B.amyloliquefaciens HYM-12 was captured and assembled with sfp and degQ genes using transformation-associated recombination(TAR).It was then integrated into the chassis strain to obtain an iturin mono-producing strain that could synthesize six iturin isoforms.The frameshift sfp gene of strain 1A751Δpps was repaired by a scarless gene knock-in method to generate a surfactin mono-producing strain.Antimicrobial activity experiments indicated that the extracts of iturin,surfactin,and our previously constructed plipastatin mono-producing strains exhibited powerful inhibitory effects toward pathogenic bacteria.Interest-ingly,iturin showed significant antifungal activity,but surfactin and plipastatin exhibited weak antifungal ac-tivity.Compared with amphotericin B,iturin has a solid and durable antifungal activity.This study demonstrates that TAR cloning is efficient for cloning large gene clusters,proves the differences in the antimicrobial activity of three cyclic lipopeptides,and lays a theoretical basis for further elucidating their antimicrobial mechanism.
