Salmonella enterica serovar Typhimurium,the causative agent of gastroenteritis,is one of the most successful intracellular pathogens.Although certain host factors for Salmonella infection have been unveiled,the factor...Salmonella enterica serovar Typhimurium,the causative agent of gastroenteritis,is one of the most successful intracellular pathogens.Although certain host factors for Salmonella infection have been unveiled,the factors mediating Salmonella entry,particularly the invasion process,remain obscure.Here,we have unearthed β2 integrin,a crucial member of the integrin family,as an important host factor facilitating Salmonella invasion.It is demonstrated that overexpression of β2 integrin promotes Salmonella invasion,while the knockdown of β2 integrin significantly diminishes the extent of invasion.Moreover,Salmonella exhibits specific binding affinity towards β2 integrin,and the block of β2 integrin on cell surface substantially reduces the infection of cells in vitro.The ectodomain soluble protein of β2 integrin neutralized Salmonella infection both in cells(in vitro)and in mice(in vivo).Additionally,Salmonella protein YrbD directly interacts with β2 integrin to facilitate its invasion.To our knowledge,this study showed for the first time that the protein YrbD mediates Salmonella adhesion and internalization into host cells by interacting with β2 integrin.These findings not only broaden our understanding of the mechanisms underlying Salmonella entry,but also identify a prospective target for therapeutic control.展开更多
Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters,and therefore it is a highly challenging target for...Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters,and therefore it is a highly challenging target for synthetic chemists.We herein reported a modular synthetic strategy toward this alkaloid,featuring a formal [5+2] annulation and an asymmetric Michael addition.The efficient synthesis of the long-chain aliphatic aldehyde and chiral amino acetal fragments have been achieved.A simplified tetracyclic intermediate bearing the core structure of atkamine has been successfully constructed through the formal [5+2] annulation.展开更多
Iron-based oxides are promising bifunctional electrocatalysts. The energy conversion efficiency of water splitting is limited by the scarcity of active sites and sluggish surface reactions in Fe_(2)O_(3). Therefore, w...Iron-based oxides are promising bifunctional electrocatalysts. The energy conversion efficiency of water splitting is limited by the scarcity of active sites and sluggish surface reactions in Fe_(2)O_(3). Therefore, we prepared one-dimensional Fe_(2)O_(3) nanobelt arrays (HNBs-V_(O)(LRO)-S) with ordered oxygen vacancy (V_(O)) structures via Pd-catalyzed oxygen reduction and sulfide thermal treatment. While preserving the ordered oxygen vacancy structure, sulfur (S) atoms selectively fill the trap-state oxygen vacancies to improve the bifunctional electrocatalytic activity and stability of Fe_(2)O_(3). Fe_(2)O_(3) nanobelt arrays with synergistic interactions between S atoms and ordered oxygen vacancies have low overpotentials for the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER). Under 1 M potassium hydroxide (KOH), HNBs-V_(O)(LRO)-S exhibited excellent electrocatalytic performance for both the HER (226 mV@100 mA·cm^(-2)) and the OER (262 and 306 mV@100 mA·cm^(-2)). In addition, the HNBs-V_(O)(LRO)-S bifunctional catalyst only requires a low cell voltage of 1.92 V to deliver a current density of 100 mA·cm^(-2) and exhibits excellent long-term durability for over 100 h. The long-range ordered oxygen vacancies serve as fast channels for electron transfer and as active sites for the catalytic reaction. The S atoms only fill the trap-state oxygen vacancies (TS-V_(O)) in the Fe_(2)O_(3) nanobelts, which eliminates the negative effect of TS-V_(O) in the reaction. Moreover, the formed Fe-S coordination structure both stabilizes the ordered oxygen vacancy structure of HNBs-V_(O)(LRO)-S and provides more reactive active sites for the electrocatalytic reaction. Theoretical calculations show that the filling of S atoms lowers the free energy barrier such that the formation of OOH^(*) from O^(*) optimizes the free energy of uptake of the hydrogen intermediate H^(*) (∆G_(H^(*))) of the Fe_(2)O_(3) surface. This ingenious synergistic mechanism of vacancy filling provides new insights into the defective design of catalysts.展开更多
Optical frequency combs(OFCs)are highly promising candidates as multichannel light sources for photonic integrated circuits(PICs).We present a tunable on-chip OFC source based on quantum dot collidingpulse mode-locked...Optical frequency combs(OFCs)are highly promising candidates as multichannel light sources for photonic integrated circuits(PICs).We present a tunable on-chip OFC source based on quantum dot collidingpulse mode-locked lasers(QD-CPMLs),capable of generating both amplitude-modulated(AM)and frequencymodulated(FM)combs through external-cavity locking.A free-running fourth-order QD-CPML with a 100 GHz repetition rate is demonstrated to produce FM and AM combs under different bias conditions,achieving an ultra-wide comb with a 3-dB bandwidth of 1.8 THz and a 10-dB bandwidth of 2.5 THz.By leveraging externalcavity locking,the modulation dynamics of the comb are finely tuned,significantly expanding the AM comb range while reducing pulse width and chirp.The shortest pulse width achieved is 0.6 ps,with a minimum time-bandwidth product of 0.33,approaching the transform limit for hyperbolic secant pulses.The near-zero linewidth enhancement factor of the QD-CPML effectively suppresses coherence collapse under optical feedback,whereas its low group velocity dispersion facilitates the generation of narrow pulses and broad bandwidths.The ability to dynamically control AM and FM comb regions through external-cavity locking represents an innovative strategy for tunable OFC generation,offering potential for applications in sensing,spectroscopy,and optical communications within PICs.展开更多
This work experimentally and theoretically demonstrates the effect of excited state lasing on the reflection sensitivity of dual-state quantum dot lasers,showing that the laser exhibits higher sensitivity to external ...This work experimentally and theoretically demonstrates the effect of excited state lasing on the reflection sensitivity of dual-state quantum dot lasers,showing that the laser exhibits higher sensitivity to external optical feedback when reaching the excited state lasing threshold.This sensitivity can be degraded by increasing the excited-to-ground-state energy separation,which results in a high excited-to-ground-state threshold ratio.In addition,the occurrence of excited state lasing decreases the damping factor and increases the linewidth enhancement factor,which leads to a low critical feedback level.These findings illuminate a path to fabricate reflectioninsensitive quantum dot lasers for isolator-free photonic integrated circuits.展开更多
This work compares the four-wave mixing(FWM)effect in epitaxial quantum dot(QD)lasers grown on silicon with quantum well(QW)lasers.A comparison of theory and experiment results shows that the measured FWM coefficient ...This work compares the four-wave mixing(FWM)effect in epitaxial quantum dot(QD)lasers grown on silicon with quantum well(QW)lasers.A comparison of theory and experiment results shows that the measured FWM coefficient is in good agreement with theoretical predictions.The gain in signal power is higher for p-doped QD lasers than for undoped lasers,despite the same FWM coefficient.Owing to the near-zero linewidth enhancement factor,QD lasers exhibit FWM coefficients and conversion efficiency that are more than one order of magnitude higher than those of QW lasers.Thus,this leads to self-mode locking in QD lasers.These findings are useful for developing on-chip sources for photonic integrated circuits on silicon.展开更多
A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synt...A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synthesis.Starting from a common intermediate,two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy.Late-stage C–H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio-and diastereoselective fashion within a complex hydrocarbon system.The stereochemical puzzles in(–)-2-acetoxybetaer13(17)-ene and(+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory(DFT)-nuclear magnetic resonance(NMR)data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers.展开更多
基金supported by the National Key R&D Program of China(2022YFF0710500)the the National Natural Science Foundation,China(31802192,32172853 and 32373013)+2 种基金the Natural Science Foundation of Heilongjiang Province of China(C2018070)China Postdoctoral Science Foundation(2017M620076)the Central Public-interest Scientific Institution Basal Research Fund,China(1610302022001)。
文摘Salmonella enterica serovar Typhimurium,the causative agent of gastroenteritis,is one of the most successful intracellular pathogens.Although certain host factors for Salmonella infection have been unveiled,the factors mediating Salmonella entry,particularly the invasion process,remain obscure.Here,we have unearthed β2 integrin,a crucial member of the integrin family,as an important host factor facilitating Salmonella invasion.It is demonstrated that overexpression of β2 integrin promotes Salmonella invasion,while the knockdown of β2 integrin significantly diminishes the extent of invasion.Moreover,Salmonella exhibits specific binding affinity towards β2 integrin,and the block of β2 integrin on cell surface substantially reduces the infection of cells in vitro.The ectodomain soluble protein of β2 integrin neutralized Salmonella infection both in cells(in vitro)and in mice(in vivo).Additionally,Salmonella protein YrbD directly interacts with β2 integrin to facilitate its invasion.To our knowledge,this study showed for the first time that the protein YrbD mediates Salmonella adhesion and internalization into host cells by interacting with β2 integrin.These findings not only broaden our understanding of the mechanisms underlying Salmonella entry,but also identify a prospective target for therapeutic control.
基金the National Natural Science Foundation of China for financial support of this work by grants (Nos.21772164 and 21572187)the National Found for Fostering Talents of Basic Science (NFFTBS,No.J1310024)+1 种基金New Century Excellent Talents in University of Fujian Province (NECTFJ)Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) for support。
文摘Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters,and therefore it is a highly challenging target for synthetic chemists.We herein reported a modular synthetic strategy toward this alkaloid,featuring a formal [5+2] annulation and an asymmetric Michael addition.The efficient synthesis of the long-chain aliphatic aldehyde and chiral amino acetal fragments have been achieved.A simplified tetracyclic intermediate bearing the core structure of atkamine has been successfully constructed through the formal [5+2] annulation.
基金financial support from the National Natural Science Foundation of China(NSFC)(Nos.52472300 and 62004137)the Central Leading Science and Technology Development Foundation of Shanxi Province(No.YDZJSX20231A020)+3 种基金the Special Project for Science and Technology Cooperation and Exchange in Shanxi Province(No.202404041101025)the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2022SX-TD002)the Shanxi Scholarship Council of China(No.2020-050)the Science and Technology Program of Yuncheng City(No.YCKJ-2023056)。
文摘Iron-based oxides are promising bifunctional electrocatalysts. The energy conversion efficiency of water splitting is limited by the scarcity of active sites and sluggish surface reactions in Fe_(2)O_(3). Therefore, we prepared one-dimensional Fe_(2)O_(3) nanobelt arrays (HNBs-V_(O)(LRO)-S) with ordered oxygen vacancy (V_(O)) structures via Pd-catalyzed oxygen reduction and sulfide thermal treatment. While preserving the ordered oxygen vacancy structure, sulfur (S) atoms selectively fill the trap-state oxygen vacancies to improve the bifunctional electrocatalytic activity and stability of Fe_(2)O_(3). Fe_(2)O_(3) nanobelt arrays with synergistic interactions between S atoms and ordered oxygen vacancies have low overpotentials for the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER). Under 1 M potassium hydroxide (KOH), HNBs-V_(O)(LRO)-S exhibited excellent electrocatalytic performance for both the HER (226 mV@100 mA·cm^(-2)) and the OER (262 and 306 mV@100 mA·cm^(-2)). In addition, the HNBs-V_(O)(LRO)-S bifunctional catalyst only requires a low cell voltage of 1.92 V to deliver a current density of 100 mA·cm^(-2) and exhibits excellent long-term durability for over 100 h. The long-range ordered oxygen vacancies serve as fast channels for electron transfer and as active sites for the catalytic reaction. The S atoms only fill the trap-state oxygen vacancies (TS-V_(O)) in the Fe_(2)O_(3) nanobelts, which eliminates the negative effect of TS-V_(O) in the reaction. Moreover, the formed Fe-S coordination structure both stabilizes the ordered oxygen vacancy structure of HNBs-V_(O)(LRO)-S and provides more reactive active sites for the electrocatalytic reaction. Theoretical calculations show that the filling of S atoms lowers the free energy barrier such that the formation of OOH^(*) from O^(*) optimizes the free energy of uptake of the hydrogen intermediate H^(*) (∆G_(H^(*))) of the Fe_(2)O_(3) surface. This ingenious synergistic mechanism of vacancy filling provides new insights into the defective design of catalysts.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB2803600)the National Natural Science Foundation of China(Grant Nos.62204072,62334013,and U22A2093)+3 种基金the Basic and Applied Basic Research Foundation of Guangdong Province(Grant Nos.2021A1515110076 and 2023A1515012304)the Shenzhen Science and Technology Innovation Program(Grant Nos.GXWD20220811163623002,RCBS20210609103824050,JCYJ20240813104819027,and KJZD20240903101100002)the Research Fund of the National Key Laboratory of Laser Spatial Information(Grant No.LSI2025WDZC03)the Open Research Program of the State Key Laboratory of Radio Frequency Heterogeneous Integration(Grant No.KF2025010).
文摘Optical frequency combs(OFCs)are highly promising candidates as multichannel light sources for photonic integrated circuits(PICs).We present a tunable on-chip OFC source based on quantum dot collidingpulse mode-locked lasers(QD-CPMLs),capable of generating both amplitude-modulated(AM)and frequencymodulated(FM)combs through external-cavity locking.A free-running fourth-order QD-CPML with a 100 GHz repetition rate is demonstrated to produce FM and AM combs under different bias conditions,achieving an ultra-wide comb with a 3-dB bandwidth of 1.8 THz and a 10-dB bandwidth of 2.5 THz.By leveraging externalcavity locking,the modulation dynamics of the comb are finely tuned,significantly expanding the AM comb range while reducing pulse width and chirp.The shortest pulse width achieved is 0.6 ps,with a minimum time-bandwidth product of 0.33,approaching the transform limit for hyperbolic secant pulses.The near-zero linewidth enhancement factor of the QD-CPML effectively suppresses coherence collapse under optical feedback,whereas its low group velocity dispersion facilitates the generation of narrow pulses and broad bandwidths.The ability to dynamically control AM and FM comb regions through external-cavity locking represents an innovative strategy for tunable OFC generation,offering potential for applications in sensing,spectroscopy,and optical communications within PICs.
基金National Key Research and Development Program of China(2022YFB2803600)National Natural Science Foundation of China(62204072,U22A2093)+1 种基金Basic and Applied Basic Research Foundation of Guangdong Province(2021A1515110076,2023A1515012304)Shenzhen Science and Technology Innovation Program(GXWD20220811163623002,RCBS20210609103824050)。
文摘This work experimentally and theoretically demonstrates the effect of excited state lasing on the reflection sensitivity of dual-state quantum dot lasers,showing that the laser exhibits higher sensitivity to external optical feedback when reaching the excited state lasing threshold.This sensitivity can be degraded by increasing the excited-to-ground-state energy separation,which results in a high excited-to-ground-state threshold ratio.In addition,the occurrence of excited state lasing decreases the damping factor and increases the linewidth enhancement factor,which leads to a low critical feedback level.These findings illuminate a path to fabricate reflectioninsensitive quantum dot lasers for isolator-free photonic integrated circuits.
基金Basic and Applied Basic Research Foundation of Guangdong Province(2021A1515110076)Center for Integrated Nanotechnologies,an Office of Science User Facility operated for the U.S.Department of Energy(DOE)Office of Science by Los Alamos National Laboratory(2021BC0057)DARPA PIPES(HR0011-19-C-0083).
文摘This work compares the four-wave mixing(FWM)effect in epitaxial quantum dot(QD)lasers grown on silicon with quantum well(QW)lasers.A comparison of theory and experiment results shows that the measured FWM coefficient is in good agreement with theoretical predictions.The gain in signal power is higher for p-doped QD lasers than for undoped lasers,despite the same FWM coefficient.Owing to the near-zero linewidth enhancement factor,QD lasers exhibit FWM coefficients and conversion efficiency that are more than one order of magnitude higher than those of QW lasers.Thus,this leads to self-mode locking in QD lasers.These findings are useful for developing on-chip sources for photonic integrated circuits on silicon.
基金Financial support from the National Natural Science Foundation of China(nos.22071205,21772164,and 21572187)NFFTBS(no.J1310024),and PCSIRT is acknowledged.
文摘A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synthesis.Starting from a common intermediate,two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy.Late-stage C–H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio-and diastereoselective fashion within a complex hydrocarbon system.The stereochemical puzzles in(–)-2-acetoxybetaer13(17)-ene and(+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory(DFT)-nuclear magnetic resonance(NMR)data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers.
