The response of steady-state fluorescence (Fs) to irradiance in apple (Malus pumila Mill. cv. Tengmu No.1/Malus hupehensis Rehd.) leaf increased and decreased at light levels below and above 400 mumol(.)m(-2.)s(-1) ph...The response of steady-state fluorescence (Fs) to irradiance in apple (Malus pumila Mill. cv. Tengmu No.1/Malus hupehensis Rehd.) leaf increased and decreased at light levels below and above 400 mumol(.)m(-2.)s(-1) photosynthetic photon flux density (PPFD), respectively, while the light-adapted maximal fluorescence (Fm') and minimal fluorescence (Fo') decreased constantly with the increasing PPFD, and the closure of photosystem 11 reaction center (PS 11 RC) increased continuously, reflected by the chlorophyll fluorescence parameter of (Fs-Fo')/(Fm'-Fo'). These facts indicated that decrease of Fs above 400 mumol(.)m(-2.)s(-1) PPFD was not caused by closure of PS 11 RC, but was mainly resulted from the process of light transfer from light-harvesting complex II (LHC II) to PS II RC. In the presence of N- ethylmaleimide (NEM), an inhibitor of photosynthetic state transition, Fs kept on increasing in apple leaf at light levels from 400 to 700 mumol(.)m(-1.)s(-1), which was the photosynthetic saturation irradiance of apple leaves. In addition, Fs still increased at light levels over 700 mumol(.)m(-2.)s(-1) in apple leaf pre-treated with dithiothreitol (DTT), an inhibitor of xanthophyll cycle. These changes showed that state transition and xanthophyll cycle caused a decrease of Fs in apple leaf at light levels below and above the photosynthetic saturation irradiance, respectively. When apple leaf was pre-treated with NEM, the PS II apparent rate of photochemical reaction (P-rate) and photochemical quenching (qP) decreased significantly in the light range of 600-800 mumol(.)m(-2.)s(-1), but the non-photochemical quenching (qN) existed a small increase at 600-800 mumol(.)m(-2.)s(-1) and a decrease above 800 mumol(.)m(-2.)s(-1). These phenomena suggested that state transition was mainly a photochemical and a non-photochemical process in apple leaf responding to light lower and higher than photosynthetic saturation irradiance, respectively.展开更多
Identifying state transition and determining the critical value of the Duffing oscillator are crucial to indicating external signal existence and have a great influence on detection accuracy in weak signal detection. ...Identifying state transition and determining the critical value of the Duffing oscillator are crucial to indicating external signal existence and have a great influence on detection accuracy in weak signal detection. A circular zone counting （CZC） method is proposed in this paper, by combining the Duffing oscillator＇s phase trajectory feature and numerical calculation for quickly and accurately identifying state transition and determining the critical value, to realize a high- efficiency weak signal detection. Detailed model analysis and method construction of the CZC method are introduced. Numerical experiments into the reliability of the proposed CZC method compared with the maximum Lyapunov exponent （MLE） method are carried out. The CZC method is demonstrated to have better detecting ability than the MLE method, and furthermore it is simpler and clearer in calculation to extend to engineering application.展开更多
ATP-binding cassette exporters transport many substrates out of cellular membranes via alternating between inward-facing and outward-facing conformations. Despite extensive research efforts over the past decades, unde...ATP-binding cassette exporters transport many substrates out of cellular membranes via alternating between inward-facing and outward-facing conformations. Despite extensive research efforts over the past decades, understanding of the molecular mechanism remains elusive. As these large-scale conformational movements are global and collective, we have previously performed extensive coarse-grained molecular dynamics simulations of the potential of mean force along the conformational transition pathway [J. Phys. Chem. B 119, 1295(2015)]. However, the occluded conformational state, in which both the internal and external gate are closed, was not determined in the calculated free energy profile. In this work, we extend the above methods to the calculation of the free energy profile along the reaction coordinate, d1-d2, which are the COM distances between the two sides of the internal(d1)and the external gate(d2). The potential of mean force is thus obtained to identify the transition pathway, along which several outward-facing, inward-facing, and occluded state structures are predicted in good agreement with structural experiments. Our coarse-grained molecular dynamics free-energy simulations demonstrate that the internal gate is closed before the external gate is open during the inward-facing to outward-facing transition and vice versa during the inward-facing to outward-facing transition. Our results capture the unidirectional feature of substrate translocation via the exporter, which is functionally important in biology. This finding is different from the previous result, in which both the internal and external gates are open reported in an X-ray experiment [Proc. Natl. Acad. Sci. USA 104,19005(2007)]. Our study sheds light on the molecular mechanism of the state transitions in an ATP-binding cassette exporter.展开更多
State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This pr...State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II （LHCII） and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations （MDS） were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond （H-bond） interactions and extended the distances between neighboring monomers, which stemmed from the conformational ad- justment of each monomer itself. Global conformational change of LHCII monomer started from its stromal N- terminal （including the phosphorylation sites） by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer andintra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.展开更多
Textured silicon （Si） substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanize...Textured silicon （Si） substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanized by self-assembly octadecyl- trichlorosilane （OTS） film. The systematic water contact angle （CA） measurements and micro/nanoscale hierarchical rough structure models are used to analyze the wetting behaviors of original and silanized textured Si substrates each as a function of pillar interval-to-width ratio. On the original textured Si substrate with hydrophilic pillars, the water droplet possesses a larger apparent CAs （〉 90~） and contact angle hysteresis （CAH）, induced by the hierarchical roughness of microscale pil- lar arrays and nanoscale pit-like roughness. However, the silanized textured substrate shows superhydrophobicity induced by the low free energy OTS overcoat and the hierarchical roughness of microscale pillar arrays, and nanoscale island-like roughness. The largest apparent CA on the superhydrophobic surface is 169.8~. In addition, the wetting transition of a gently deposited water droplet is observed on the original textured substrate with pillar interval-to-width ratio increasing. Furthermore, the wetting state transition is analyzed by thermodynamic approach with the consideration of the CAH effect. The results indicate that the wetting state changed from a Cassie state to a pseudo-Wenzel during the transition.展开更多
INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation a...INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation and phasetransitions of polymers. A description of the conformational state transition requires questions about; 1) howmany stable conformational states for a specific σ bond; 2) the barriers between the states; 3) the mechanismof the conformational transition; 4) any cooperative behavior during the transition. Flory and his coworkers展开更多
In this study, the initial perturbations that are the easiest to trigger the Kuroshio Extension （KE） transition connecting a basic weak jet state and a strong, fairly stable meandering state, are investigated using ...In this study, the initial perturbations that are the easiest to trigger the Kuroshio Extension （KE） transition connecting a basic weak jet state and a strong, fairly stable meandering state, are investigated using a reduced-gravity shallow water ocean model and the CNOP （Conditional Nonlinear Optimal Perturbation） approach. This kind of initial perturbation is called an optimal precursor （OPR）. The spatial structures and evolutionary processes of the OPRs are analyzed in detail. The results show that most of the OPRs are in the form of negative sea surface height （SSH） anomalies mainly located in a narrow band region south of the KE jet, in basic agreement with altimetric observations. These negative SSH anomalies reduce the merid- ional SSH gradient within the KE, thus weakening the strength of the jet. The KE jet then becomes more convoluted, with a high-frequency and large-amplitude variability corresponding to a high eddy kinetic energy level; this gradually strengthens the KE jet through an inverse energy cascade. Eventually, the KE reaches a high-energy state characterized by two well defined and fairly stable anticyclonic meanders. Moreover, sensitivity experiments indicate that the spatial structures of the OPRs are not sensitive to the model parameters and to the optimization times used in the analysis.展开更多
Activities of the chloroplasts and nucleus are coordinated by retrograde signaling,which play crucial roles in plant development and environmental adaptation.However,the connection between chloroplast status and nucle...Activities of the chloroplasts and nucleus are coordinated by retrograde signaling,which play crucial roles in plant development and environmental adaptation.However,the connection between chloroplast status and nuclear genome stability is poorly understood.Chloroplast state transitions enable the plant to balance photosystem absorption capacity in an environment with changing light quality.Here,we report that abnormal chloroplast state transitions lead to instability in the nuclear genome and impaired plant growth.We observed increased DNA damage in the state transition-defective Arabidopsis thaliana mutant stn7,and demonstrated that this damage was triggered by cytokinin accumulation and activation of cytokinin signaling.We showed that cytokinin signaling promotes a competitive association between ARABIDOPSIS RESPONSE REGULATOR 10(ARR10)with PROLIFERATING CELLULAR NUCLEAR ANTIGEN 1/2(PCNA1/2),inhibiting the binding of PCNA1/2 to nuclear DNA.This affects DNA replication,leading to replicationdependent genome instability.Treatment with 2,5-dibromo-3-methyl-6-isopropylbenzoquinone that simulates the reduction of the plastoquinone pool during abnormal state transitions increased the accumulation of ARABIDOPSIS HISTIDINE-CONTAINING PHOSPHOTRANSMITTER 1,a phosphotransfer protein involved in cytokinin signaling,and promoted the interaction between ARR10 with PCNA1/2,leading to increased DNA damage.These findings highlight the function of cytokinin signaling in coordinating chloroplast function and nuclear genome integrity during plant acclimation to environmental changes.展开更多
Configuration stability is essential for a space-based Gravitational-Wave(GW)observatory,which can be impacted by orbit insertion uncertainties.Configuration uncertainty propagation is vital for investigating the infl...Configuration stability is essential for a space-based Gravitational-Wave(GW)observatory,which can be impacted by orbit insertion uncertainties.Configuration uncertainty propagation is vital for investigating the influences of uncertainties on configuration stability and can be potentially useful in the navigation and control of GW observatories.Current methods suffer from drawbacks related to high computational burden.To this end,a Radial-Tangential-Ddirectional State Transition Tensor(RT-DSTT)-based configuration uncertainty propagation method is proposed.First,two sensitive directions are found by capturing the dominant secular terms.Considering the orbit insertion errors along the two sensitive directions only,a reduced-order RT-DSTT model is developed for orbital uncertainty propagation.Then,the relationship between the uncertainties in the orbital states and the uncertainties in the configuration stability indexes is mapped using highorder derivatives.The result is a semi-analytical solution that can predict the deviations in the configuration stability indexes given orbit insertion errors.The potential application of the proposed RT-DSTT-based method in calculating the feasible domain is presented.The performance of the proposed method is validated on the Laser Interferometer Space Antenna(LISA)project.Simulations show that the proposed method can provide similar results to the STT-based method but requires only half of the computational time.展开更多
The accurate understanding of rockburst mechanism poses a global challenge in the field of rock mechanics.Particularly for strain rockburst,achieving self-initiated static-dynamic state transition is a crucial step in...The accurate understanding of rockburst mechanism poses a global challenge in the field of rock mechanics.Particularly for strain rockburst,achieving self-initiated static-dynamic state transition is a crucial step in the formation of catastrophic events.However,the state transition behavior and its impact on rockburst have not received sufficient attention,and are still poorly understood.Therefore,this study specifically focuses on the state transition behavior,aiming to investigate its abrupt transition process and formation mechanism,and triggering effects on rockburst.To facilitate the study,a novel burst rock-surrounding rock combined laboratory test model is proposed and its effectiveness is validated through experiment verification.Subsequently,corresponding numerical models are established using the three-dimensional(3D)discrete element method(DEM),enabling successful simulation of static brittle failure and rockbursts of varying intensities under quasi-static displacement loading conditions.Moreover,through secondary development,comprehensive recording of the mechanical and energy information pertaining to the combined specimen system and its subsystems is achieved.As a result of numerical investigation studies,the elastic rebound dynamic behavior of the surrounding rock was discovered and identified as the key factor triggering rockburst and controlling its intensity.The impact loading on the burst rock,induced by elastic rebound,directly initiates the dynamic processes of rockburst,serving as the direct cause.Additionally,the transient work and energy convergence towards the burst rock resulting from elastic rebound are recognized as the inherent cause of rockburst.Moreover,it has been observed that a larger extent of surrounding rock leads to a stronger elastic rebound,thereby directly contributing to a more intense rockburst.The findings can provide novel theoretical insights for the exploring of rockburst mechanism and the development of monitoring and prevention techniques.展开更多
The traditional energy hub based model has difficulties in clearly describing the state transition and transition conditions of the energy unit in the integrated energy system(IES).Therefore,this study proposes a stat...The traditional energy hub based model has difficulties in clearly describing the state transition and transition conditions of the energy unit in the integrated energy system(IES).Therefore,this study proposes a state transition modeling method for an IES based on a cyber-physical system(CPS)to optimize the state transition of energy unit in the IES.This method uses the physical,integration,and optimization layers as a three-layer modeling framework.The physical layer is used to describe the physical models of energy units in the IES.In the integration layer,the information flow is integrated into the physical model of energy unit in the IES to establish the state transition model,and the transition conditions between different states of the energy unit are given.The optimization layer aims to minimize the operating cost of the IES and enables the operating state of energy units to be transferred to the target state.Numerical simulations show that,compared with the traditional modeling method,the state transition modeling method based on CPS achieves the observability of the operating state of the energy unit and its state transition in the dispatching cycle,which obtains an optimal state of the energy unit and further reduces the system operating costs.展开更多
Battery lifetime prediction at early cycles is crucial for researchers and manufacturers to examine product quality and promote technology development.Machine learning has been widely utilized to construct data-driven...Battery lifetime prediction at early cycles is crucial for researchers and manufacturers to examine product quality and promote technology development.Machine learning has been widely utilized to construct data-driven solutions for high-accuracy predictions.However,the internal mechanisms of batteries are sensitive to many factors,such as charging/discharging protocols,manufacturing/storage conditions,and usage patterns.These factors will induce state transitions,thereby decreasing the prediction accuracy of data-driven approaches.Transfer learning is a promising technique that overcomes this difficulty and achieves accurate predictions by jointly utilizing information from various sources.Hence,we develop two transfer learning methods,Bayesian Model Fusion and Weighted Orthogonal Matching Pursuit,to strategically combine prior knowledge with limited information from the target dataset to achieve superior prediction performance.From our results,our transfer learning methods reduce root-mean-squared error by 41%through adapting to the target domain.Furthermore,the transfer learning strategies identify the variations of impactful features across different sets of batteries and therefore disentangle the battery degradation mechanisms and the root cause of state transitions from the perspective of data mining.These findings suggest that the transfer learning strategies proposed in our work are capable of acquiring knowledge across multiple data sources for solving specialized issues.展开更多
Dynamic Reactive Power Optimization(DRPO) is a large-scale, multi-period, and strongly coupled nonlinear mixed-integer programming problem that is difficult to solve directly. First, to handle discrete variables and s...Dynamic Reactive Power Optimization(DRPO) is a large-scale, multi-period, and strongly coupled nonlinear mixed-integer programming problem that is difficult to solve directly. First, to handle discrete variables and switching operation constraints, DRPO is formulated as a nonlinear constrained two-objective optimization problem in this paper. The first objective is to minimize the real power loss and the Total Voltage Deviations(TVDs), and the second objective is to minimize incremental system loss. Then a Filter Collaborative State Transition Algorithm(FCSTA) is presented for solving DRPO problems. Two populations corresponding to two different objectives are employed. Moreover, the filter technique is utilized to deal with constraints. Finally, the effectiveness of the proposed method is demonstrated through the results obtained for a 24-hour test on Ward & Hale 6 bus, IEEE 14 bus, and IEEE 30 bus test power systems. To substantiate the effectiveness of the proposed algorithms, the obtained results are compared with different approaches in the literature.展开更多
Postnatal heart maturation Is the basis of normal cardiac function and provides critical insights into heart repair and regenerative medicine.While static snapshots of the maturing heart have provided much Insight int...Postnatal heart maturation Is the basis of normal cardiac function and provides critical insights into heart repair and regenerative medicine.While static snapshots of the maturing heart have provided much Insight into its molecular signatures,few key events during postnatal cardiomyocyte maturation have been uncovered.Here,we report that cardiomyocytes(CMs)experience epige-netic and transcriptional decline of cardiac gene expression immediately after birth,leading to a transi-tion state of CMs at postnatal day 7(P7)that was essential for CM subtype specification during heart maturation.Large-scale single-cell analysis and genetic lineage tracing confirm the presence of transition state CMs at P7 bridging immature state and mature states.Silencing of key transcription factor JUN In P1-hearts significantly repressed CM transition,resulting in per-turbed CM subtype proportions and reduced cardiac function in mature hearts.In addition,transplantation of P7-CMs into infarcted hearts exhibited cardiac repair potential superior to P1-CMs.Collectively,our data uncover CM state transition as a key event in postnatal heart maturation,which not only provides insights into molecular foundations of heart maturation,but also opens an avenue for manipulation of cardiomyocyte fate in disease and regenerative medicine.展开更多
Midcourse correction design is key to space transfers in the cislunar space.Autonomous guidance has garnered significant attention for its promise to decrease the dependence on ground control systems.This study addres...Midcourse correction design is key to space transfers in the cislunar space.Autonomous guidance has garnered significant attention for its promise to decrease the dependence on ground control systems.This study addresses the problem of midcourse corrections for Earth-Moon transfer orbits based on high-order state transition tensors(STTs).The scenarios considered are direct Earth-Moon transfers and low-energy transfers to lunar distant retrograde orbits(DROs),where the latter involve weak stability boundary(WSB)and lunar gravity assist(LGA)techniques.Semi-analytical formulas are provided for computing the trajectory correction maneuvers(TCMs)using high-order STTs derived using the differential algebraic method.Monte Carlo simulations are performed to evaluate the effectiveness of the proposed approach.Compared with existing explicit guidance algorithms,the STT-based approach is much cheaper computationally and features fewer final position errors.These results are promising for fast and efficient orbital autonomous correction guidance approaches in the cislunar space.展开更多
In this paper,we develop the deep learning-based Fourier neural operator(FNO)approach to find parametric mappings,which are used to approximately display abundant wave structures in the nonlinear Schr?dinger(NLS)equat...In this paper,we develop the deep learning-based Fourier neural operator(FNO)approach to find parametric mappings,which are used to approximately display abundant wave structures in the nonlinear Schr?dinger(NLS)equation,Hirota equation,and NLS equation with the generalized PT-symmetric Scarf-II potentials.Specifically,we analyze the state transitions of different types of solitons(e.g.bright solitons,breathers,peakons,rogons,and periodic waves)appearing in these complex nonlinear wave equations.By checking the absolute errors between the predicted solutions and exact solutions,we can find that the FNO with the Ge Lu activation function can perform well in all cases even though these solution parameters have strong influences on the wave structures.Moreover,we find that the approximation errors via the physics-informed neural networks(PINNs)are similar in magnitude to those of the FNO.However,the FNO can learn the entire family of solutions under a given distribution every time,while the PINNs can only learn some specific solution each time.The results obtained in this paper will be useful for exploring physical mechanisms of soliton excitations in nonlinear wave equations and applying the FNO in other nonlinear wave equations.展开更多
State transition is a fundamental light acclimation mechanism of photosynthetic organisms in response to the environmental light conditions.This process rebalances the excitation energy between photosystemI(PSl)and ph...State transition is a fundamental light acclimation mechanism of photosynthetic organisms in response to the environmental light conditions.This process rebalances the excitation energy between photosystemI(PSl)and photosystem Il through regulated reversible binding of the light-harvesting complex Il(LHCll)to PSl.However,the structural reorganization of PSI-LHCI,the dynamic binding of LHCll,and the regulatory mechanisms underlying state transitions are less understood in higher plants.In this study,using cryoelectron microscopy we resolved the structures of PSI-LHCI in both state 1(PSI-LHCI-ST1)and state 2(PSILHCI-LHCll-ST2)from Arabidopsis thaliana.Combined genetic and functional analyses revealed novel contacts between Lhcb1 and PsaK that further enhanced the binding of the LHCll trimer to the PSI core with the known interactions between phosphorylated Lhcb2 and the PsaL/PsaH/PsaO subunits.Specifically,PsaO was absent in the PSI-LHCI-ST1 supercomplex but present in the PSI-LHCI-LHCIl-ST2 supercomplex,in which the PsaL/PsaK/PsaA subunits undergo several conformational changes to strengthen the binding of PsaO in ST2.Furthermore,the PSI-LHCI module adopts a more compact configuration with shorter Mg-to-Mg distances between the chlorophylls,which may enhance the energy transfer efficiency from the peripheral antenna to the PSl core in ST2.Collectively,our work provides novel structural and functional insights into the mechanisms of light acclimation during state transitions in higher plants.展开更多
In the IEEE 802.16e/m standard, three power saving classes （PSCs） are defined to save the energy of a mobile sub- scriber station （MSS）. However, how to set the parameters of PSCs to maximize the power saving and ...In the IEEE 802.16e/m standard, three power saving classes （PSCs） are defined to save the energy of a mobile sub- scriber station （MSS）. However, how to set the parameters of PSCs to maximize the power saving and guarantee the quality of service is not specified in the standard. Thus, many algorithms were proposed to set the PSCs in IEEE 802.16 networks. However, most of the proposed algorithms consider only the power saving for a single MSS. In the algorithms designed for multiple MSSs, the sleep state, which is set for activation of state transition overhead power, is not considered. The PSC setting for real-time connections in multiple MSSs with consideration of the state transition overhead is studied. The problem is non-deterministic polynomial time hard （NP-hard）, and a suboptimal algorithm for the problem is proposed. Simulation results demonstrate that the energy saving of the proposed algorithm is higher than that of state-of-the-art algorithms and approaches the optimum limit.展开更多
The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G″ were investigated. The results show that the suspension transfo...The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G″ were investigated. The results show that the suspension transforms from a liquid-like state to a solid-like state with increasing the volume fraction of silica. Such a solid-like state can be transformed back into a liquid-like state under the application of a larger stress. At the higher volume fraction, the larger critical stress is required to induce the transition from solid-like to liquid-like state. As the electrolyte concentration decreases or pH value increases, the inter-particle force increases, which causes the state transition to occur at a higher stress.展开更多
Under natural environments,plants and algae have evolved various photosynthetic acclimation mechanisms in response to the constantly changing light conditions.The state transition and long-term response processes in p...Under natural environments,plants and algae have evolved various photosynthetic acclimation mechanisms in response to the constantly changing light conditions.The state transition and long-term response processes in photosynthetic acclimation involve remodeling and composition alteration of thylakoid membrane.A chloroplast protein kinase named Stt7/STN7 has been found to have pivotal roles in both state transition and longterm response.Here we report the crystal structures of the kinase domain of a putative Stt7/STN7 homolog from Micromonas sp.RCC299(MsStt7d)in the apo form and in complex with various nucleotide substrates.MsStt7d adopts a canonical protein kinase fold and contains all the essential residues at the active site.A novel hairpin motif,found to be a conserved feature of the Stt7/STN7 family and indispensable for the kinase stability,interacts with the activation loop and fi xes it in an active conformation.We have also demonstrated that MsStt7d is a dualspecifi city kinase that phosphorylates both Thr and Tyr residues.Moreover,preliminary in vitro data suggest that it might be capable of phosphorylating a consensus N-terminal pentapeptide of light-harvesting proteins Micromonas Lhcp4 and Arabidopsis Lhcb1 directly.The potential peptide/protein substrate binding site is predicted based on the location of a pseudo-substrate contributed by the adjacent molecule within the crystallographic dimer.The structural and biochemical data presented here provide a framework for an improved understanding on the role of Stt7/STN7 in photosynthetic acclimation.展开更多
文摘The response of steady-state fluorescence (Fs) to irradiance in apple (Malus pumila Mill. cv. Tengmu No.1/Malus hupehensis Rehd.) leaf increased and decreased at light levels below and above 400 mumol(.)m(-2.)s(-1) photosynthetic photon flux density (PPFD), respectively, while the light-adapted maximal fluorescence (Fm') and minimal fluorescence (Fo') decreased constantly with the increasing PPFD, and the closure of photosystem 11 reaction center (PS 11 RC) increased continuously, reflected by the chlorophyll fluorescence parameter of (Fs-Fo')/(Fm'-Fo'). These facts indicated that decrease of Fs above 400 mumol(.)m(-2.)s(-1) PPFD was not caused by closure of PS 11 RC, but was mainly resulted from the process of light transfer from light-harvesting complex II (LHC II) to PS II RC. In the presence of N- ethylmaleimide (NEM), an inhibitor of photosynthetic state transition, Fs kept on increasing in apple leaf at light levels from 400 to 700 mumol(.)m(-1.)s(-1), which was the photosynthetic saturation irradiance of apple leaves. In addition, Fs still increased at light levels over 700 mumol(.)m(-2.)s(-1) in apple leaf pre-treated with dithiothreitol (DTT), an inhibitor of xanthophyll cycle. These changes showed that state transition and xanthophyll cycle caused a decrease of Fs in apple leaf at light levels below and above the photosynthetic saturation irradiance, respectively. When apple leaf was pre-treated with NEM, the PS II apparent rate of photochemical reaction (P-rate) and photochemical quenching (qP) decreased significantly in the light range of 600-800 mumol(.)m(-2.)s(-1), but the non-photochemical quenching (qN) existed a small increase at 600-800 mumol(.)m(-2.)s(-1) and a decrease above 800 mumol(.)m(-2.)s(-1). These phenomena suggested that state transition was mainly a photochemical and a non-photochemical process in apple leaf responding to light lower and higher than photosynthetic saturation irradiance, respectively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61172047 and 61071025)
文摘Identifying state transition and determining the critical value of the Duffing oscillator are crucial to indicating external signal existence and have a great influence on detection accuracy in weak signal detection. A circular zone counting （CZC） method is proposed in this paper, by combining the Duffing oscillator＇s phase trajectory feature and numerical calculation for quickly and accurately identifying state transition and determining the critical value, to realize a high- efficiency weak signal detection. Detailed model analysis and method construction of the CZC method are introduced. Numerical experiments into the reliability of the proposed CZC method compared with the maximum Lyapunov exponent （MLE） method are carried out. The CZC method is demonstrated to have better detecting ability than the MLE method, and furthermore it is simpler and clearer in calculation to extend to engineering application.
基金supported by the National Natu-ral Science Foundation of China(No.21073170 and No.21273209).
文摘ATP-binding cassette exporters transport many substrates out of cellular membranes via alternating between inward-facing and outward-facing conformations. Despite extensive research efforts over the past decades, understanding of the molecular mechanism remains elusive. As these large-scale conformational movements are global and collective, we have previously performed extensive coarse-grained molecular dynamics simulations of the potential of mean force along the conformational transition pathway [J. Phys. Chem. B 119, 1295(2015)]. However, the occluded conformational state, in which both the internal and external gate are closed, was not determined in the calculated free energy profile. In this work, we extend the above methods to the calculation of the free energy profile along the reaction coordinate, d1-d2, which are the COM distances between the two sides of the internal(d1)and the external gate(d2). The potential of mean force is thus obtained to identify the transition pathway, along which several outward-facing, inward-facing, and occluded state structures are predicted in good agreement with structural experiments. Our coarse-grained molecular dynamics free-energy simulations demonstrate that the internal gate is closed before the external gate is open during the inward-facing to outward-facing transition and vice versa during the inward-facing to outward-facing transition. Our results capture the unidirectional feature of substrate translocation via the exporter, which is functionally important in biology. This finding is different from the previous result, in which both the internal and external gates are open reported in an X-ray experiment [Proc. Natl. Acad. Sci. USA 104,19005(2007)]. Our study sheds light on the molecular mechanism of the state transitions in an ATP-binding cassette exporter.
基金supported by the National Key Basic Research Foundation of China(2006CB910303 and 2011CB710904)the National Natural Science Foundation of China(11072251 and31230027)+1 种基金the CAS Knowledge Innovation Program(KJCX2YW-L08)the Scientific Research Equipment Project(Y2010030)
文摘State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II （LHCII） and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations （MDS） were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond （H-bond） interactions and extended the distances between neighboring monomers, which stemmed from the conformational ad- justment of each monomer itself. Global conformational change of LHCII monomer started from its stromal N- terminal （including the phosphorylation sites） by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer andintra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.
基金Project supported by the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No.NCET-09-0211)the Fundamental Research Funds for the Central Universities (Grant Nos.2012YJS105 and M13JB00240)
文摘Textured silicon （Si） substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanized by self-assembly octadecyl- trichlorosilane （OTS） film. The systematic water contact angle （CA） measurements and micro/nanoscale hierarchical rough structure models are used to analyze the wetting behaviors of original and silanized textured Si substrates each as a function of pillar interval-to-width ratio. On the original textured Si substrate with hydrophilic pillars, the water droplet possesses a larger apparent CAs （〉 90~） and contact angle hysteresis （CAH）, induced by the hierarchical roughness of microscale pil- lar arrays and nanoscale pit-like roughness. However, the silanized textured substrate shows superhydrophobicity induced by the low free energy OTS overcoat and the hierarchical roughness of microscale pillar arrays, and nanoscale island-like roughness. The largest apparent CA on the superhydrophobic surface is 169.8~. In addition, the wetting transition of a gently deposited water droplet is observed on the original textured substrate with pillar interval-to-width ratio increasing. Furthermore, the wetting state transition is analyzed by thermodynamic approach with the consideration of the CAH effect. The results indicate that the wetting state changed from a Cassie state to a pseudo-Wenzel during the transition.
文摘INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation and phasetransitions of polymers. A description of the conformational state transition requires questions about; 1) howmany stable conformational states for a specific σ bond; 2) the barriers between the states; 3) the mechanismof the conformational transition; 4) any cooperative behavior during the transition. Flory and his coworkers
基金supported by the National Natural Science Foundation of China (Grant Nos. 41576015, 41306023, 41490644 and 41490640)the Natural Science Foundation Of China (NSFC) Innovative Group (Grant No. 41421005)+1 种基金the NSFC–Shandong Joint Fund for Marine Science Research Centers (Grant No. U1406401)support from the University of Naples Parthenope (Grant No. DSTE315)
文摘In this study, the initial perturbations that are the easiest to trigger the Kuroshio Extension （KE） transition connecting a basic weak jet state and a strong, fairly stable meandering state, are investigated using a reduced-gravity shallow water ocean model and the CNOP （Conditional Nonlinear Optimal Perturbation） approach. This kind of initial perturbation is called an optimal precursor （OPR）. The spatial structures and evolutionary processes of the OPRs are analyzed in detail. The results show that most of the OPRs are in the form of negative sea surface height （SSH） anomalies mainly located in a narrow band region south of the KE jet, in basic agreement with altimetric observations. These negative SSH anomalies reduce the merid- ional SSH gradient within the KE, thus weakening the strength of the jet. The KE jet then becomes more convoluted, with a high-frequency and large-amplitude variability corresponding to a high eddy kinetic energy level; this gradually strengthens the KE jet through an inverse energy cascade. Eventually, the KE reaches a high-energy state characterized by two well defined and fairly stable anticyclonic meanders. Moreover, sensitivity experiments indicate that the spatial structures of the OPRs are not sensitive to the model parameters and to the optimization times used in the analysis.
基金supported by the National Natural Science Foundation of China(grant no.32322007,32100192,and U22A20446).
文摘Activities of the chloroplasts and nucleus are coordinated by retrograde signaling,which play crucial roles in plant development and environmental adaptation.However,the connection between chloroplast status and nuclear genome stability is poorly understood.Chloroplast state transitions enable the plant to balance photosystem absorption capacity in an environment with changing light quality.Here,we report that abnormal chloroplast state transitions lead to instability in the nuclear genome and impaired plant growth.We observed increased DNA damage in the state transition-defective Arabidopsis thaliana mutant stn7,and demonstrated that this damage was triggered by cytokinin accumulation and activation of cytokinin signaling.We showed that cytokinin signaling promotes a competitive association between ARABIDOPSIS RESPONSE REGULATOR 10(ARR10)with PROLIFERATING CELLULAR NUCLEAR ANTIGEN 1/2(PCNA1/2),inhibiting the binding of PCNA1/2 to nuclear DNA.This affects DNA replication,leading to replicationdependent genome instability.Treatment with 2,5-dibromo-3-methyl-6-isopropylbenzoquinone that simulates the reduction of the plastoquinone pool during abnormal state transitions increased the accumulation of ARABIDOPSIS HISTIDINE-CONTAINING PHOSPHOTRANSMITTER 1,a phosphotransfer protein involved in cytokinin signaling,and promoted the interaction between ARR10 with PCNA1/2,leading to increased DNA damage.These findings highlight the function of cytokinin signaling in coordinating chloroplast function and nuclear genome integrity during plant acclimation to environmental changes.
基金supported by the National Key R&D Program of China(No.2020YFC2201200).
文摘Configuration stability is essential for a space-based Gravitational-Wave(GW)observatory,which can be impacted by orbit insertion uncertainties.Configuration uncertainty propagation is vital for investigating the influences of uncertainties on configuration stability and can be potentially useful in the navigation and control of GW observatories.Current methods suffer from drawbacks related to high computational burden.To this end,a Radial-Tangential-Ddirectional State Transition Tensor(RT-DSTT)-based configuration uncertainty propagation method is proposed.First,two sensitive directions are found by capturing the dominant secular terms.Considering the orbit insertion errors along the two sensitive directions only,a reduced-order RT-DSTT model is developed for orbital uncertainty propagation.Then,the relationship between the uncertainties in the orbital states and the uncertainties in the configuration stability indexes is mapped using highorder derivatives.The result is a semi-analytical solution that can predict the deviations in the configuration stability indexes given orbit insertion errors.The potential application of the proposed RT-DSTT-based method in calculating the feasible domain is presented.The performance of the proposed method is validated on the Laser Interferometer Space Antenna(LISA)project.Simulations show that the proposed method can provide similar results to the STT-based method but requires only half of the computational time.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22A20597,and 42142019)the“Unveiling and Commanding”Project of Science and Technology Program of Tibet(Grant No.XZ202303ZY0006G)the Shanghai Peak Plateau Discipline(Class I).
文摘The accurate understanding of rockburst mechanism poses a global challenge in the field of rock mechanics.Particularly for strain rockburst,achieving self-initiated static-dynamic state transition is a crucial step in the formation of catastrophic events.However,the state transition behavior and its impact on rockburst have not received sufficient attention,and are still poorly understood.Therefore,this study specifically focuses on the state transition behavior,aiming to investigate its abrupt transition process and formation mechanism,and triggering effects on rockburst.To facilitate the study,a novel burst rock-surrounding rock combined laboratory test model is proposed and its effectiveness is validated through experiment verification.Subsequently,corresponding numerical models are established using the three-dimensional(3D)discrete element method(DEM),enabling successful simulation of static brittle failure and rockbursts of varying intensities under quasi-static displacement loading conditions.Moreover,through secondary development,comprehensive recording of the mechanical and energy information pertaining to the combined specimen system and its subsystems is achieved.As a result of numerical investigation studies,the elastic rebound dynamic behavior of the surrounding rock was discovered and identified as the key factor triggering rockburst and controlling its intensity.The impact loading on the burst rock,induced by elastic rebound,directly initiates the dynamic processes of rockburst,serving as the direct cause.Additionally,the transient work and energy convergence towards the burst rock resulting from elastic rebound are recognized as the inherent cause of rockburst.Moreover,it has been observed that a larger extent of surrounding rock leads to a stronger elastic rebound,thereby directly contributing to a more intense rockburst.The findings can provide novel theoretical insights for the exploring of rockburst mechanism and the development of monitoring and prevention techniques.
基金supported by the National Natural Science Foundation of China(No.52107108)。
文摘The traditional energy hub based model has difficulties in clearly describing the state transition and transition conditions of the energy unit in the integrated energy system(IES).Therefore,this study proposes a state transition modeling method for an IES based on a cyber-physical system(CPS)to optimize the state transition of energy unit in the IES.This method uses the physical,integration,and optimization layers as a three-layer modeling framework.The physical layer is used to describe the physical models of energy units in the IES.In the integration layer,the information flow is integrated into the physical model of energy unit in the IES to establish the state transition model,and the transition conditions between different states of the energy unit are given.The optimization layer aims to minimize the operating cost of the IES and enables the operating state of energy units to be transferred to the target state.Numerical simulations show that,compared with the traditional modeling method,the state transition modeling method based on CPS achieves the observability of the operating state of the energy unit and its state transition in the dispatching cycle,which obtains an optimal state of the energy unit and further reduces the system operating costs.
基金This work is supported by the startup fund of Shanghai Jiao Tong UniversitySouthern University of Science and TechnologyS.J.H is supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S.Department of Energy contract no.DE-AC02-05CH11231.
文摘Battery lifetime prediction at early cycles is crucial for researchers and manufacturers to examine product quality and promote technology development.Machine learning has been widely utilized to construct data-driven solutions for high-accuracy predictions.However,the internal mechanisms of batteries are sensitive to many factors,such as charging/discharging protocols,manufacturing/storage conditions,and usage patterns.These factors will induce state transitions,thereby decreasing the prediction accuracy of data-driven approaches.Transfer learning is a promising technique that overcomes this difficulty and achieves accurate predictions by jointly utilizing information from various sources.Hence,we develop two transfer learning methods,Bayesian Model Fusion and Weighted Orthogonal Matching Pursuit,to strategically combine prior knowledge with limited information from the target dataset to achieve superior prediction performance.From our results,our transfer learning methods reduce root-mean-squared error by 41%through adapting to the target domain.Furthermore,the transfer learning strategies identify the variations of impactful features across different sets of batteries and therefore disentangle the battery degradation mechanisms and the root cause of state transitions from the perspective of data mining.These findings suggest that the transfer learning strategies proposed in our work are capable of acquiring knowledge across multiple data sources for solving specialized issues.
基金supported by the National Natural Science Foundation of China(Nos.51767022 and 51575469)
文摘Dynamic Reactive Power Optimization(DRPO) is a large-scale, multi-period, and strongly coupled nonlinear mixed-integer programming problem that is difficult to solve directly. First, to handle discrete variables and switching operation constraints, DRPO is formulated as a nonlinear constrained two-objective optimization problem in this paper. The first objective is to minimize the real power loss and the Total Voltage Deviations(TVDs), and the second objective is to minimize incremental system loss. Then a Filter Collaborative State Transition Algorithm(FCSTA) is presented for solving DRPO problems. Two populations corresponding to two different objectives are employed. Moreover, the filter technique is utilized to deal with constraints. Finally, the effectiveness of the proposed method is demonstrated through the results obtained for a 24-hour test on Ward & Hale 6 bus, IEEE 14 bus, and IEEE 30 bus test power systems. To substantiate the effectiveness of the proposed algorithms, the obtained results are compared with different approaches in the literature.
基金supported by CAMS Innovation Fund for Medical Sciences(2021-I2M-1-019)National Natural Science Foundation of China(Grants 82088101 and 82025004 to L.W.,grant 82070287 to B.Z.)+2 种基金Beijing Natural Science Foundation(Grant Z200026 to L.W.)Shenzhen Fundamental Research Program(Grant ZDSYS20200923172000001 to L.W.)Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences(grant 2019PT320026 to L.W.).
文摘Postnatal heart maturation Is the basis of normal cardiac function and provides critical insights into heart repair and regenerative medicine.While static snapshots of the maturing heart have provided much Insight into its molecular signatures,few key events during postnatal cardiomyocyte maturation have been uncovered.Here,we report that cardiomyocytes(CMs)experience epige-netic and transcriptional decline of cardiac gene expression immediately after birth,leading to a transi-tion state of CMs at postnatal day 7(P7)that was essential for CM subtype specification during heart maturation.Large-scale single-cell analysis and genetic lineage tracing confirm the presence of transition state CMs at P7 bridging immature state and mature states.Silencing of key transcription factor JUN In P1-hearts significantly repressed CM transition,resulting in per-turbed CM subtype proportions and reduced cardiac function in mature hearts.In addition,transplantation of P7-CMs into infarcted hearts exhibited cardiac repair potential superior to P1-CMs.Collectively,our data uncover CM state transition as a key event in postnatal heart maturation,which not only provides insights into molecular foundations of heart maturation,but also opens an avenue for manipulation of cardiomyocyte fate in disease and regenerative medicine.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12003054)National Key R&D Program of China(Grant No.2022YFC2204700)Strategic Priority Program on Space Science of the Chinese Academy of Sciences(Grant No.XDA30010200).
文摘Midcourse correction design is key to space transfers in the cislunar space.Autonomous guidance has garnered significant attention for its promise to decrease the dependence on ground control systems.This study addresses the problem of midcourse corrections for Earth-Moon transfer orbits based on high-order state transition tensors(STTs).The scenarios considered are direct Earth-Moon transfers and low-energy transfers to lunar distant retrograde orbits(DROs),where the latter involve weak stability boundary(WSB)and lunar gravity assist(LGA)techniques.Semi-analytical formulas are provided for computing the trajectory correction maneuvers(TCMs)using high-order STTs derived using the differential algebraic method.Monte Carlo simulations are performed to evaluate the effectiveness of the proposed approach.Compared with existing explicit guidance algorithms,the STT-based approach is much cheaper computationally and features fewer final position errors.These results are promising for fast and efficient orbital autonomous correction guidance approaches in the cislunar space.
基金the NSFC under Grant Nos.11925108 and 11731014the NSFC under Grant No.11975306
文摘In this paper,we develop the deep learning-based Fourier neural operator(FNO)approach to find parametric mappings,which are used to approximately display abundant wave structures in the nonlinear Schr?dinger(NLS)equation,Hirota equation,and NLS equation with the generalized PT-symmetric Scarf-II potentials.Specifically,we analyze the state transitions of different types of solitons(e.g.bright solitons,breathers,peakons,rogons,and periodic waves)appearing in these complex nonlinear wave equations.By checking the absolute errors between the predicted solutions and exact solutions,we can find that the FNO with the Ge Lu activation function can perform well in all cases even though these solution parameters have strong influences on the wave structures.Moreover,we find that the approximation errors via the physics-informed neural networks(PINNs)are similar in magnitude to those of the FNO.However,the FNO can learn the entire family of solutions under a given distribution every time,while the PINNs can only learn some specific solution each time.The results obtained in this paper will be useful for exploring physical mechanisms of soliton excitations in nonlinear wave equations and applying the FNO in other nonlinear wave equations.
基金the National Key Research and Development Program of China(2020YFA0907600 to L.Z.)the National Natural Science Foundation of China(National Science Foundation of China)(32241030 to S.S.).
文摘State transition is a fundamental light acclimation mechanism of photosynthetic organisms in response to the environmental light conditions.This process rebalances the excitation energy between photosystemI(PSl)and photosystem Il through regulated reversible binding of the light-harvesting complex Il(LHCll)to PSl.However,the structural reorganization of PSI-LHCI,the dynamic binding of LHCll,and the regulatory mechanisms underlying state transitions are less understood in higher plants.In this study,using cryoelectron microscopy we resolved the structures of PSI-LHCI in both state 1(PSI-LHCI-ST1)and state 2(PSILHCI-LHCll-ST2)from Arabidopsis thaliana.Combined genetic and functional analyses revealed novel contacts between Lhcb1 and PsaK that further enhanced the binding of the LHCll trimer to the PSI core with the known interactions between phosphorylated Lhcb2 and the PsaL/PsaH/PsaO subunits.Specifically,PsaO was absent in the PSI-LHCI-ST1 supercomplex but present in the PSI-LHCI-LHCIl-ST2 supercomplex,in which the PsaL/PsaK/PsaA subunits undergo several conformational changes to strengthen the binding of PsaO in ST2.Furthermore,the PSI-LHCI module adopts a more compact configuration with shorter Mg-to-Mg distances between the chlorophylls,which may enhance the energy transfer efficiency from the peripheral antenna to the PSl core in ST2.Collectively,our work provides novel structural and functional insights into the mechanisms of light acclimation during state transitions in higher plants.
基金supported by the Ministry of Science, ICT and Future Planning (Korea), the Information Technology Research Center Support Program (No. IITP-2016-H860116-1005)the Research Fund of Hanyang University, Korea (No. HY-2016), and supervised by the Institute for Information & Communications Technology Promotion
文摘In the IEEE 802.16e/m standard, three power saving classes （PSCs） are defined to save the energy of a mobile sub- scriber station （MSS）. However, how to set the parameters of PSCs to maximize the power saving and guarantee the quality of service is not specified in the standard. Thus, many algorithms were proposed to set the PSCs in IEEE 802.16 networks. However, most of the proposed algorithms consider only the power saving for a single MSS. In the algorithms designed for multiple MSSs, the sleep state, which is set for activation of state transition overhead power, is not considered. The PSC setting for real-time connections in multiple MSSs with consideration of the state transition overhead is studied. The problem is non-deterministic polynomial time hard （NP-hard）, and a suboptimal algorithm for the problem is proposed. Simulation results demonstrate that the energy saving of the proposed algorithm is higher than that of state-of-the-art algorithms and approaches the optimum limit.
基金the National Natural Science Foundation of China(No.2 0 2 4 30 0 2 )
文摘The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G″ were investigated. The results show that the suspension transforms from a liquid-like state to a solid-like state with increasing the volume fraction of silica. Such a solid-like state can be transformed back into a liquid-like state under the application of a larger stress. At the higher volume fraction, the larger critical stress is required to induce the transition from solid-like to liquid-like state. As the electrolyte concentration decreases or pH value increases, the inter-particle force increases, which causes the state transition to occur at a higher stress.
基金We thank the staffs at Shanghai Synchrotron Radiation Facility(SSRF)as well as Yi Han and Shengquan Liu at the X-ray core facility at the Institute of Biophysics(IBP),Chinese Academy of Sciences(CAS)for their technical support during crystal screening and data collection.We also thank Hongmei Zhang for the as sistance with molecular biology and biochemistry,Zhensheng Xie and Fuquan Yang at the Proteomic Core Facility Center of IBP,CAS and Jieyuan Liu at the Center of Biomedical Analysis of Tsinghua University for their technical assistance at the Mass Spectrometry analysis.This work was supported by the National Basic Research Program(973 Program)(Nos.2011CBA00902 and 2011CBA00903)awarded to W.R.C.and Z.F.L.,respectivelythe National Natural Science Foundation(Grant No.31021062).
文摘Under natural environments,plants and algae have evolved various photosynthetic acclimation mechanisms in response to the constantly changing light conditions.The state transition and long-term response processes in photosynthetic acclimation involve remodeling and composition alteration of thylakoid membrane.A chloroplast protein kinase named Stt7/STN7 has been found to have pivotal roles in both state transition and longterm response.Here we report the crystal structures of the kinase domain of a putative Stt7/STN7 homolog from Micromonas sp.RCC299(MsStt7d)in the apo form and in complex with various nucleotide substrates.MsStt7d adopts a canonical protein kinase fold and contains all the essential residues at the active site.A novel hairpin motif,found to be a conserved feature of the Stt7/STN7 family and indispensable for the kinase stability,interacts with the activation loop and fi xes it in an active conformation.We have also demonstrated that MsStt7d is a dualspecifi city kinase that phosphorylates both Thr and Tyr residues.Moreover,preliminary in vitro data suggest that it might be capable of phosphorylating a consensus N-terminal pentapeptide of light-harvesting proteins Micromonas Lhcp4 and Arabidopsis Lhcb1 directly.The potential peptide/protein substrate binding site is predicted based on the location of a pseudo-substrate contributed by the adjacent molecule within the crystallographic dimer.The structural and biochemical data presented here provide a framework for an improved understanding on the role of Stt7/STN7 in photosynthetic acclimation.
