Potassium （K＋） is one of the essential macronutrients for plant growth and development. However, K＋ content in soils is usually limited so that the crop yields are restricted. Plants may adapt to K＋-deficient env...Potassium （K＋） is one of the essential macronutrients for plant growth and development. However, K＋ content in soils is usually limited so that the crop yields are restricted. Plants may adapt to K＋-deficient environment by adjusting their physiological and morphological status, indicating that plants may have evolved their sensing and signaling mechanisms in response to K＋-deficiency. This short review particularly discusses some components as possible sensors or signal transducers involved in plant sensing and signaling in response to K＋-deficiency, such as K＋ channels and transporters, H＋-ATPase, some cytoplasmic enzymes, etc. Possible involvement of Ca2＋ and ROS signals in plant responses to K＋-deficiency is also discussed.展开更多
The family of voltage-gated （Shaker-like） potassium channels in plants includes both inward-rectifying （Kin） channels that allow plant cells to accumulate K＋ and outward-rectifying （Kout） channels that mediate ...The family of voltage-gated （Shaker-like） potassium channels in plants includes both inward-rectifying （Kin） channels that allow plant cells to accumulate K＋ and outward-rectifying （Kout） channels that mediate K＋ efflux. Despite their dose structural similarities, Kin and Kout channels differ in their gating sensitivity towards voltage and the extracellular K＋ concentration. We have carried out a systematic program of domain swapping between the Kout channel SKOR and the Kin channel KAT1 to examine the impacts on gating of the pore regions, the S4, S5, and the S6 helices. We found that, in particular, the N-terminal part of the S5 played a critical role in KAT1 and SKOR gating. Our findings were supported by molecular dynamics of KAT1 and SKOR homology models. In silico analysis revealed that during channel opening and closing, displacement of certain residues, especially in the S5 and S6 segments, is more pronounced in KAT1 than in SKOR. From our analysis of the S4-S6 region, we conclude that gating （and K＋-sensing in SKOR） depend on a number of structural elements that are dispersed over this -145-residue sequence and that these place additional constraints on configurational rearrangement of the channels during gating.展开更多
针对车-车(vehicle to rechicle,V2V)通信系统对无线电信道衰落特性和模型的需求,分别在两种隧道场景中5.9 GHz和5.2 GHz频段下进行了V2V无线电信道测量活动,并对隧道外、隧道内和两者之间的连接部分场景进行了小尺度衰落特性分析.基于...针对车-车(vehicle to rechicle,V2V)通信系统对无线电信道衰落特性和模型的需求,分别在两种隧道场景中5.9 GHz和5.2 GHz频段下进行了V2V无线电信道测量活动,并对隧道外、隧道内和两者之间的连接部分场景进行了小尺度衰落特性分析.基于近距离(close-in,CI)对数模型和ABG(α-β-γ)模型建立了基于距离的接收功率模型,对两种场景隧道内外的接收功率进行了评估和比较,路径损耗指数分别为1.83和1.9,结果表明参考距离为1 m的CI对数模型具有更高的拟合度.此外,将测量数据幅度的衰落分布与五种典型的理论衰落分布进行比较分析,发现其特征更接近于具有最小拟合优度值的莱斯分布,且隧道内的莱斯K因子小于隧道外.同时,给出了隧道内和隧道外之间连接处基于距离的莱斯K因子模型,发现连接处的K因子与距离无关,而隧道内的K因子随距离增大而减小.展开更多
Our knowledge of the physiology of ion channels has increased tremendously during the past 20 years because of the advances of the single-channel recording and molecular cloning techniques. More than 50 different iden...Our knowledge of the physiology of ion channels has increased tremendously during the past 20 years because of the advances of the single-channel recording and molecular cloning techniques. More than 50 different identified potassium channels have already been found.1,2 They are distributed ubiquitously in wide variety of cells including airway smooth muscle （ASM） cells and inflammatory cells in airway such as eosinophils, basophils, macrophages and so on.3 Several types of K+ channels have been identified in ASM cells, e.g., a large-conductance, voltgage-dependent Ca2+-activated K+ channel(BKCa), a voltage-dependent delayed-rectifier K+ channel（Kv）, and an ATP-sensitve K+ channel(KATP).1 In such excitable cells,展开更多
基于室内视距(Line-of-Sight,LOS)和非视距(Non-Line-of-Sight,NLOS)无线信道测量数据,研究了28GHz多输入多输出(Multiple-Input Multiple-Output,MIMO)信道参数和容量特性.具体地说,分析了莱斯K因子、时延扩展、出发角和到达角的角度...基于室内视距(Line-of-Sight,LOS)和非视距(Non-Line-of-Sight,NLOS)无线信道测量数据,研究了28GHz多输入多输出(Multiple-Input Multiple-Output,MIMO)信道参数和容量特性.具体地说,分析了莱斯K因子、时延扩展、出发角和到达角的角度扩展等信道参数,研究了MIMO信道容量及空间相关性对容量的影响.结果表明:莱斯K因子、时延扩展以及角度扩展值取决于测量环境及场景;LOS条件下时延扩展的累积分布函数(Cumulative Distribution Function,CDF)曲线与正态分布拟合优于NLOS条件下的数据;MIMO天线空间相关性越大信道容量越小.本文结果可为28GHz无线通信系统设计提供有用信息.展开更多
基金This work was supported by the National Science Foundation of China （grant No. 30830013 to WoH.W.） and the Programme of Introducing Talents of Discipline to Universities （B06003 to W.H.W.）. No conflict of interest declared.
文摘Potassium （K＋） is one of the essential macronutrients for plant growth and development. However, K＋ content in soils is usually limited so that the crop yields are restricted. Plants may adapt to K＋-deficient environment by adjusting their physiological and morphological status, indicating that plants may have evolved their sensing and signaling mechanisms in response to K＋-deficiency. This short review particularly discusses some components as possible sensors or signal transducers involved in plant sensing and signaling in response to K＋-deficiency, such as K＋ channels and transporters, H＋-ATPase, some cytoplasmic enzymes, etc. Possible involvement of Ca2＋ and ROS signals in plant responses to K＋-deficiency is also discussed.
文摘The family of voltage-gated （Shaker-like） potassium channels in plants includes both inward-rectifying （Kin） channels that allow plant cells to accumulate K＋ and outward-rectifying （Kout） channels that mediate K＋ efflux. Despite their dose structural similarities, Kin and Kout channels differ in their gating sensitivity towards voltage and the extracellular K＋ concentration. We have carried out a systematic program of domain swapping between the Kout channel SKOR and the Kin channel KAT1 to examine the impacts on gating of the pore regions, the S4, S5, and the S6 helices. We found that, in particular, the N-terminal part of the S5 played a critical role in KAT1 and SKOR gating. Our findings were supported by molecular dynamics of KAT1 and SKOR homology models. In silico analysis revealed that during channel opening and closing, displacement of certain residues, especially in the S5 and S6 segments, is more pronounced in KAT1 than in SKOR. From our analysis of the S4-S6 region, we conclude that gating （and K＋-sensing in SKOR） depend on a number of structural elements that are dispersed over this -145-residue sequence and that these place additional constraints on configurational rearrangement of the channels during gating.
文摘Our knowledge of the physiology of ion channels has increased tremendously during the past 20 years because of the advances of the single-channel recording and molecular cloning techniques. More than 50 different identified potassium channels have already been found.1,2 They are distributed ubiquitously in wide variety of cells including airway smooth muscle （ASM） cells and inflammatory cells in airway such as eosinophils, basophils, macrophages and so on.3 Several types of K+ channels have been identified in ASM cells, e.g., a large-conductance, voltgage-dependent Ca2+-activated K+ channel(BKCa), a voltage-dependent delayed-rectifier K+ channel（Kv）, and an ATP-sensitve K+ channel(KATP).1 In such excitable cells,
文摘基于室内视距(Line-of-Sight,LOS)和非视距(Non-Line-of-Sight,NLOS)无线信道测量数据,研究了28GHz多输入多输出(Multiple-Input Multiple-Output,MIMO)信道参数和容量特性.具体地说,分析了莱斯K因子、时延扩展、出发角和到达角的角度扩展等信道参数,研究了MIMO信道容量及空间相关性对容量的影响.结果表明:莱斯K因子、时延扩展以及角度扩展值取决于测量环境及场景;LOS条件下时延扩展的累积分布函数(Cumulative Distribution Function,CDF)曲线与正态分布拟合优于NLOS条件下的数据;MIMO天线空间相关性越大信道容量越小.本文结果可为28GHz无线通信系统设计提供有用信息.
