作者:hacker发布时间:2022-07-11分类:网站入侵浏览:137评论:4
A.快速动作的基本级
B.带延时的附加级
C.延时级
三部分
AFL指按频率自动减负荷装置。为了提高电能质量,保证重要用户供电的可*性,当系统中出现有功功率缺额引起频率下降时,根据频率下降的程度,自动断开一部分不重要的用户,阻止频率下降,以便使频率迅速恢复到正常值,这种装置叫按频率自动减负荷装置,简称AFL装置。它不仅可以保证重要用户的供电,而且可以避免频率下降引起的系统瓦解事故。继电保护测试仪中AFL装置基本工作原理 自动按频率负荷装置的工作原理,可用下图说明,假定变电所馈电母线上有多条供配电线路,俺店里用户的重要性分为n个级别
SIGNIFICANCE
Drought is a major cause of lost agricultural productivity. Even moderate water limitation can lead to down-regulation of plant growth; however, the underlying mechanisms of stress sensing and growth regulation are little understood. We identified At14a-Like1 (AFL1) and its interacting proteins protein disulfide isomerase 5 (PDI5) and NAI2 as positive and negative regulators, respectively, of growth and proline accumulation. Despite numerous ideas that membrane-based mechanisms are important for drought sensing and initial signaling, AFL1 is one of only a few membrane proteins with a demonstrated effect on drought resistance. AFL1 structure, localization, and interaction with endomembrane proteins indicate novel functions in drought signaling. Increased growth of AFL1 overexpression in plants under stress without negative effects on unstressed plants make AFL1 an attractive target for biotechnology.
Keywords: drought, At14a, vesicle endocytosis, protein disulfide isomerase, clathrin adaptor AP2-2a
意义
干旱是农业生产力下降的主要原因。即使是适度的水分限制也会导致植物生长下调;然而,压力感知和生长调节的潜在机制很少被理解。我们鉴定了At14a-Like1(AFL1)及其相互作用蛋白质蛋白质二硫键异构酶5(PDI5)和NAI2分别作为生长和脯氨酸积累的正调节剂和负调节剂。尽管有许多观点认为基于膜的机制对干旱传感和初始信号传导很重要,但AFL1是少数几种对抗旱性有显着作用的膜蛋白之一。 AFL1结构,定位和与内膜蛋白的相互作用表明干旱信号传导中的新功能。在压力下植物中AFL1过表达的增加,对无应激植物没有负面影响,使AFL1成为生物技术的一个有吸引力的目标。
关键词:干旱,At14a,囊泡内吞作用,蛋白质二硫键异构酶,网格蛋白衔接子AP2-2a
ABSTRACT
Limited knowledge of how plants regulate their growth and metabolism in response to drought and reduced soil water potential has impeded efforts to improve stress tolerance. Increased expression of the membrane-associated protein At14a-like1 (AFL1) led to increased growth and accumulation of the osmoprotective solute proline without negative effects on unstressed plants. Conversely, inducible RNA-interference suppression of AFL1 decreased growth and proline accumulation during low water potential while having no effect on unstressed plants. AFL1 overexpression lines had reduced expression of many stress-responsive genes, suggesting AFL1 may promote growth in part by suppression of negative regulatory genes. AFL1 interacted with the endomembrane proteins protein disulfide isomerase 5 (PDI5) and NAI2, with the PDI5 interaction being particularly increased by stress. PDI5 and NAI2 are negative regulatory factors, as pdi5, nai2, and pdi5-2nai2-3 mutants had increased growth and proline accumulation at low water potential. AFL1 also interacted with Adaptor protein2-2A (AP2-2A), which is part of a complex that recruits cargo proteins and promotes assembly of clathrin-coated vesicles. AFL1 colocalization with clathrin light chain along the plasma membrane, together with predictions of AFL1 structure, were consistent with a role in vesicle formation or trafficking. Fractionation experiments indicated that AFL1 is a peripheral membrane protein associated with both plasma membrane and endomembranes. These data identify classes of proteins (AFL1, PDI5, and NAI2) not previously known to be involved in drought signaling. AFL1-predicted structure, protein interactions, and localization all indicate its involvement in previously uncharacterized membrane-associated drought sensing or signaling mechanisms.
Even relatively mild drought that causes reduced soil water potential (ψw) can result in dramatically reduced plant growth and agricultural productivity. Physiological analyses have shown that plant growth is actively down-regulated during drought and is not limited by carbon supply (1–3). Reductions of growth help ensure survival by conserving water but can be undesirable for agriculture, as plant productivity is reduced more than need be if growth were less sensitive to changes in water status (3). Also, specific metabolic pathways, such as proline metabolism, are stress regulated and contribute to drought tolerance.
The sensing and signaling mechanisms controlling growth and metabolic responses to drought remain unclear. Many hypotheses of how plants sense water loss center on detection of mechanical stimuli generated by loss of turgor and cell shrinkage. This includes changes in membrane shape or disruption of cell wall–cell membrane connections possibly detected by proteins, such as mechanosensitive channels or receptor-like kinases that bind cell wall components (4–9). Proteins that induce or detect membrane curvature are known in mammalian cells (10) but have been little considered in plants. Also, in analogy to mammalian cells, integrin-related proteins have been hypothesized to play stress-sensing roles in plant cells. Plants lack clear orthologs to integrins. Nonetheless, modeling has identified at least one Arabidopsis protein with integrin-like structure and possible stress-related function (11), and other proteins with small integrin similarity domains also have been identified (12). Endomembrane compartments, particularly the endoplasmic reticulum (ER), are involved in responding to cytotoxic stresses such as the accumulation of unfolded proteins (13). How endomembrane proteins may be involved in responding to water limitation, and whether this may occur via mechanisms other than the unfolded protein response, is less understood. Trafficking of membrane proteins between cellular compartments is also emerging as an important aspect of plant signaling, with plasma membrane (PM) aquaporins being one example of intracellular trafficking affecting drought resistance (14). Sites of ER–PM contact have also been proposed to be critical for mechanosensing and stress tolerance (15).
With the motivation of testing a different class of protein that could have roles in sensing or signaling abiotic stress, we investigated the function of At14a-Like1 (AFL1, At3g28270). At14a (At3g28300) was first identified by immunoscreening an Arabidopsis expression library with antisera recognizing mammalian β1-integrin and was reported to be a PM-associated protein (12). A cluster of At14a-related genes, including AFL1, is present in Arabidopsis. AFL1 contains a small domain with similarity to integrins (domain of unknown function 677), but there is little other information that could reveal its cellular function. Our investigation found that AFL1 has a dramatic effect on plant growth during drought and identified AFL1 association with endomembrane proteins and clathrin-coated vesicle formation at the PM as key aspects of AFL1 cellular function.
抽象
关于植物如何响应干旱和降低土壤水势来调节其生长和代谢的知识有限,阻碍了改善胁迫耐受性的努力。膜相关蛋白At14a-like1(AFL1)的表达增加导致渗透保护性溶质脯氨酸的生长和积累增加而对无应激植物没有负面影响。相反,AFL1的诱导型RNA干扰抑制在低水势期间降低了生长和脯氨酸积累,而对无应激植物没有影响。 AFL1过表达株系降低了许多应激反应基因的表达,表明AFL1可能通过抑制负调控基因促进生长。 AFL1与内膜蛋白蛋白质二硫键异构酶5(PDI5)和NAI2相互作用,PDI5相互作用通过应激特别增加。 PDI5和NAI2是负调节因子,因为pdi5,nai2和pdi5-2nai2-3突变体在低水势下具有增加的生长和脯氨酸积累。 AFL1还与衔接蛋白2-2A(AP2-2A)相互作用,后者是招募货物蛋白并促进网格蛋白包被囊泡组装的复合物的一部分。 AFL1与质膜上的网格蛋白轻链共定位,以及AFL1结构的预测,与囊泡形成或运输中的作用一致。分级实验表明AFL1是与质膜和内膜相关的外周膜蛋白。这些数据识别以前未知参与干旱信号传导的蛋白质类别(AFL1,PDI5和NAI2)。 AFL1预测的结构,蛋白质相互作用和定位均表明其参与了之前未表征的膜相关干旱传感或信号传导机制。
即使相对温和的干旱导致土壤水势降低(ψw)也会导致植物生长和农业生产力大幅下降。生理分析表明,在干旱期间植物生长受到积极的下调,并且不受碳供应的限制(1-3)。减少生长有助于通过节约水来确保生存,但对农业来说可能是不合需要的,因为如果生长对水的状况变化不太敏感,植物生产力会降低(3)。此外,特定的代谢途径,例如脯氨酸代谢,受到压力调节并有助于耐旱性。
控制生长和对干旱的代谢反应的传感和信号传导机制仍不清楚。关于植物如何感知水分流失的许多假设都集中在检测由于膨胀和细胞萎缩造成的机械刺激。这包括膜形状的变化或可能由蛋白质检测到的细胞壁 - 细胞膜连接的破坏,例如机械敏感性通道或结合细胞壁组分的受体样激酶(4-9)。诱导或检测膜弯曲的蛋白质在哺乳动物细胞中是已知的(10),但在植物中很少考虑。此外,与哺乳动物细胞类似,假设整联蛋白相关蛋白在植物细胞中发挥应激感应作用。植物缺乏整合素的明确直向同源物。尽管如此,建模已经鉴定出至少一种具有整合素样结构和可能的应激相关功能的拟南芥蛋白(11),并且已经鉴定了具有小整联蛋白相似结构域的其他蛋白(12)。内膜隔室,特别是内质网(ER),参与细胞毒性应激的响应,例如未折叠蛋白的积累(13)。内膜蛋白如何参与响应水限制,以及这是否可能通过除了未折叠的蛋白质反应之外的机制发生,还不太了解。在细胞区室之间运输膜蛋白也是植物信号传导的一个重要方面,质膜(PM)水通道蛋白是影响抗旱性的细胞内运输的一个例子(14)。 ER-PM接触点也被认为对机械传感和应力耐受至关重要(15)。
为了测试可能在感知或发出非生物应激信号中起作用的不同类别蛋白质的动机,我们研究了At14a-Like1(AFL1,At3g28270)的功能。 At14a(At3g28300)首先通过用识别哺乳动物β1整联蛋白的抗血清免疫筛选拟南芥表达文库来鉴定,并且据报道是PM相关蛋白(12)。拟南芥中存在At14a相关基因簇,包括AFL1。 AFL1包含一个与整合素相似的小域(未知功能域677),但几乎没有其他信息可以揭示其细胞功能。我们的研究发现,AFL1对干旱期间的植物生长具有显着影响,并确定AFL1与内膜蛋白的结合以及PM处的网格蛋白包被的囊泡形成是A的关键方面。
在紫外线下,黄曲霉毒素b1,b2发蓝色荧光,黄曲霉毒素g1,g2发绿色荧光.黄曲霉毒素的相对分子量为312-346.难溶于水,易溶于油,甲醇,丙酮和氯仿等有机溶剂,但不溶于石油醚,己烷和乙醚中.一般在中性溶液中较稳定,但在强酸性溶液中稍有分解,在ph9-10的强碱溶液中分解迅速.其纯品为无色结晶,耐高温,黄曲霉毒素b1的分解温度为268℃紫外线对低浓度黄曲霉毒素有一定的破坏性.
液相色谱法
液相色谱(liquid chromatography,lc)与薄层层析在许多方面具有相似性,二者互相补充.通常用tlc进行前期的条件设定,选择适宜的分离条件后,再用lc进行黄曲霉毒素的定量测定.
免疫化学分析方法
利用具有高度专一性的单克隆抗体或多克隆抗体设计的黄曲霉毒素的免疫分析方法,也是最常用的黄曲霉毒素检测方法.这类方法通常包括放射免疫分析方法(radioimmunoassay,ria),酶联免疫法(enzyme-linked of immunosorbent assay,elisa)和免疫层析法(immunoaflinity column assay,ica).它们均可以对黄曲霉毒素进行定量测定.
(1) 免疫亲和柱-荧光分光光度法和免疫亲和术-hplc法
免疫亲和柱法和酶联免疫吸附法虽然都可达到速简便效果,但酶联免疫吸附法仅能检测单一毒素(如黄曲霉毒素b1)含量,而且易出现假阳性结果,难以控制.免疫亲和柱法(包括荧光光度法和hplc法)却能达到既定量准确又快速简便的要求.
免疫亲和柱的使用可以避免传统tlc和hplc的缺点,同时免疫亲和柱与tlc和hplc法结合可以大大提高工作效率,提高灵敏度和准确度.
黄曲霉毒素免疫亲和柱-荧光光度计法是以单克隆免疫亲和柱为分离手段,用荧光计,紫外灯作为检测工具的快速分析方法.它克服了tlc和hplc法在操作过程中使用剧毒的真菌毒素作为标定标准物和在样品预处理过程中使用多种有毒,异味的有机溶剂,毒害操作人员和污染环境的缺点.同时黄曲霉毒素免疫亲和柱-荧光光度计法分析速度快,一个样品只需10-15min,比传统方法快几个小时甚至几天时间;仪器设备轻便容易携带,自动化程度高,操作简单,直接读出测试结果,可以在小型实验或现场使用.可以进行黄曲霉毒素总量 (b1b2g1g2) 的测定,检测限可达到1ug/kg,达到黄曲霉毒素标准限量值以下测定范围为1-300ug/kg.
黄曲霉毒素免疫亲和柱-高效液相色谱法比传统的hplc法更加安全,可靠,灵敏度和准确度高.它采用单克隆抗体免疫技术,可以特效性地将黄曲霉毒素或其他真菌毒素分离出来,分离效率和回收率高.
分析原理试样中的黄曲霉毒素用一定比例的甲醇/水提取液经过过滤,稀释后,用免疫亲和柱净化,以甲醇将亲和柱上的黄曲霉毒素淋洗下来,在淋洗液中加入溴溶液衍生,以提高测定灵敏度,然后用荧光分光光度计进行定量.也可以将甲醇-黄曲霉毒素淋洗液的一部分注入hplc中,对黄曲霉毒素b1,b2,g1,b2分别进行定量分析.免疫亲和柱是用大剂量的黄曲霉毒素单克隆抗体固化在水不溶性的载体上,然后装柱而成.该方法的测定范围0-300ug/kg.
(2) 酶联免疫吸附法:
1996年,nakane 建立了辣根过氧化物酶标记抗体的测定技术.由于该方法简便,敏感,特异,可作为多种抗原或抗体的测定,20世纪70年代后期,该方法引入真菌毒素的检测中,下面介绍的是竞争性酶联免疫吸附间接法检测黄曲霉毒素b1.
原理:将已知抗原吸附在固态载体表面,洗除末吸附抗原,加入一定量抗体与待测样品(含有抗原)提取液的混合液,竞争培养后,在固相载体表面形成抗原抗体复合物.洗除多余抗体成分,然后加入酶标记的抗球蛋白的第二抗体结合物,与吸附在固体表面的抗原抗体结合物相结合,再加入酶底物.在酶的催化作用下,底物发生降解反应,产生有色物质,通过酶标检测仪测出酶底物的降解量,从而推知被测样品中的抗原量.
(3) 微柱筛选法 可以用来半定量测定各种食品中黄曲霉毒素b1,b2,g1,g2的总量.
原理 样品提取液中的黄曲霉毒素被微柱管风硅镁型吸附层吸附后,在波长365nm紫外光灯下显示蓝紫色荧光环,其荧光强度与黄曲霉毒素在一定的光密度范围内成正比例关系.若硅镁型吸附剂层未出现蓝紫色荧光,则样品为阴性(方法灵敏度为5-10ug/kg).由于在微柱上不能分离黄曲霉毒素b1,b2,g1,g2,所以测得结果为总的黄曲霉毒素含量.
(4) 一步式黄曲霉毒素检测金标试纸法
一步式黄曲霉毒素检测金标试纸法是利用单克隆抗体而设计的固相免疫分析法.由此产生的一步式黄曲霉毒素快速检测试纸可在5—10分钟完成对样品中黄曲霉毒素的定性测定.借助黄曲霉毒素标准样品,这种方法能估算黄曲霉毒素的含量,非常适用于现场测试和进行大量样品的初选.
不要因追求完美而为自己设置可望而不可及的目标,其实幸福很简单,就像有一所大房子,里面想要的东西一样都不缺,多余的东西一样也没有。敲响的是钟声,走过的是岁月,种下的是希望,留下的是故事,盼望的是美好,送来的...
后雾灯标志不亮可能是以下几种原因:
1、如果两个后雾灯不亮,灯泡一起坏的可能性比较小,可以稍后检查一下;
2、检查雾灯保险丝,在保险丝盒内有提示,找到相同的安培保险丝更换测试;
3、如果保险丝没有损坏,确保灯泡没有损坏,检查线路、雾灯开关。
标签:渗透测试afl工具
已有4位网友发表了看法:
访客 评论于 2022-07-11 18:46:23 回复
r mechanosensing and stress tolerance (15).With the motivation of testing a different class of protein that coul
访客 评论于 2022-07-11 13:35:34 回复
g a different class of protein that could have roles in sensing or signaling abiotic stress, we investigated the function of At14a-Lik
访客 评论于 2022-07-11 17:13:45 回复
) aquaporins being one example of intracellular trafficking affecting drought resistance (14). Sites of
访客 评论于 2022-07-11 21:08:57 回复
e channels or receptor-like kinases that bind cell wall components (4–9). Proteins tha