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中国环境科学 2021,41(3):1162~1171 China Environmental Science UiO-66/BiVO4复合光催化剂的制备及其对四环素的光解綦毓文1,魏砾宏1*,石冬妮1,蒋进元2,烟征1(1.沈阳航空航天大学能源与环境学院,辽宁沈阳 110112;2.中国环境科学研究院,北京 100012)摘要:通过两步溶剂热法成功制备了UiO-66/BiVO4复合光催化材料,考察其对四环素(TC)的光催化降解性能.在模拟可见光下,当锆(Zr):铋(Bi)物质的量投料比为2:1时,对TC的光解效果最好(85.8%).对TC的总去除率分别比纯UiO-66和纯BiVO4提高27.1%和23.5%,降解速率是纯BiVO4的47.9倍.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射(UV-vis DRS)等对所制备的纳米光催化剂进行结构、形貌、组成及光电性能表征分析.结果表明:UiO-66与BiVO4紧密结合形成II型异质结,复合材料性能的提升归因于比表面积的和光生载流子分离率的提升及孔隙结构的改善.关键词:UiO-66/BiVO4;异质结;光催化;四环素降解中图分类号:X703 文献标识码:A 文章编号:1000-6923(2021)03-1162-10Preparation of UiO-66/BiVO4 composite photocatalyst and its photodegradation of tetracycline. QI Yu-wen1, WEI Li-hong1*, SHI Dong-ni1, JIANG Jin-yuan2, YAN Zheng1 (1.College of Energy and Environment, Shenyang Aerospace University, Shenyang 110122, China;2.Chinese Research Academy of Environmental Sciences, Beijing 100012, China). China Environmental Science, 2021,41(3):1162~1171Abstract:The UiO-66/BiVO4 composite photocatalytic material was successfully preparated by a two-step solvothermal method, and its photocatalytic degradation performance for tetracycline (TC) was investigated. Under simulated visible light, when the amount of substance about zirconium(Zr): bismuth(Bi) was 2:1, the photolysis effect of TC was the best (85.8%). Its total removal rate of TC was increased by 27.1% and 23.5% compared to pure UiO-66 and pure BiVO4, respectively. The degradation rate was 47.9times that of pure BiVO4. The structure, morphology and composition of the prepared nano-photocatalyst by X-ray diffractometer (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflection (UV-vis DRS) and photoelectric performance characterization analysis. The results showed that UiO-66 and BiVO4 were tightly combined to form II heterojunction. The improvement of composite material performance was attributed to improvements in various aspects, including specific surface area, photogenerated carrier separation rate, and pore structure.Key words:UiO-66/BiVO4;heterojunction;photocatalysis;Tetracycline degradation抗生素作为重要的药物成分,已经广泛用于人类医学和兽医学[1-2].中国是世界上最大的抗生素生产国和使用国,2013年,我国抗生素使用量为16.2万吨,约占全球抗生素使用量的一半[3].抗生素的大量使用导致其通过各种途径进入到污水处理厂[4]、地表水[5]等环境介质中.据有关报道,制药和医院废水中的抗生素浓度最高可达100~ 500mg/L[6],我国海河流域沉积物中四环素类平均含量为2783.2ng/g[7].抗生素的滥用导致水体中的细菌产生抗药性.根据世界卫生组织的预测,到2050年,因“耐药性”导致细菌感染而引起的死亡人数将超过癌症的致死人数[8].因此,水环境中的抗生素因其溶解性、持久性和高毒性而成为全球性的环境问题.电化学、臭氧氧化法等高级氧化技术是现行处理难降解有机废水的主要技术,但因存在能耗高、运行费用高等缺陷而受到限制.近年来,光催化技术作为一种绿色、高效的手段被用于抗生素废水的处理,引起了广泛关注.钒酸铋(BiVO4)作为一种廉价、环境友好型催化剂,且具有适宜的禁带宽度(约2.4eV),在可见光下对难降解有机物展现出了良好的降解性能[9-10],已被证明是一种具有良好应用前景的可见光催化剂[11].由于受到反应位点少及光生载流子效率低的限制[12],BiVO4作为光催化剂尚不能达到较好的光催化效果而无法满足实际应用的需要.研究者采用了多种方法对其改性,其中构建异质结作为一种提高收稿日期:2020-07-27基金项目:沈阳市科技局“中青年科技创新人才计划”(RC190169);辽宁省教育厅“服务地方项目”(JYT19011)* 责任作者, 教授,*****************.cn3期綦毓文等:UiO-66/BiVO4复合光催化剂的制备及其对四环素的光解 1163催化剂光电转换性能的有效方法被广泛使用[13-14].半导体异质结包含TypeⅠ型(内嵌型)、TypeⅡ型(交错型)和TypeⅢ型(错开型),Ⅱ型异质结中的半导体单元因具有载流子相互传递的特性而被广泛研究.宋等[15]制备出具有II型异质结的BiOCl/ BiVO4复合纳米片,经4h光催化后对10mg/L的RhB的降解率达96%.杜等[16]研制的BiVO4/WO3异质结复合膜经3h可见光辐射后对诺氟沙星有较好的降解效果.然而传统的铋基双半导体异质结复合催化剂仍存在处理时间长、催化剂投加量大等制约工程应用的弊端,需要进一步研究提高其表面积及载流子传输能力等性能,以期加快其进一步实际应用的进程.近十几年来,金属有机框架(MOFs)作为一种新型的多孔晶体材料引起了较多关注[17-18],其中锆(Zr)基MOFs[19]不仅具有多活性位点、高比表面积等MOFs的通用特性,还兼具强可修饰性[20]、强稳定性[21]的特点,在吸附[22]、催化[23]、传感[24]等领域被广泛应用.其中UiO-66的结构以Zr6O4(OH)4原子簇作为节点[25],与12个BDC2–配位组装而成. UiO-66中含有两种笼状结构,直径约0.8nm的正四方体笼和直径约1.1nm的正八面体笼,丰富的孔道及笼状结构使其具有很高的比表面积(600~ 1600m2/g)[26].因此,UiO-66作为Zr基直接半导体[27] MOFs的典型代表,在光催化研究中数见不鲜[28].但是,纯相UiO-66光致电子-空穴对分离率低以及光利用能力差[29],从而导致其光催化性能有限.为了克服上述缺点,许多研究者通过UiO-66与其他半导体材料构建异质结来提升其光催化性能[30-31].因此,将多活性位点的UiO-66与廉价、具有可见光响应的BiVO4相结合可能是提高材料光催化性能和实际应用性的有效方法.然而,目前对UiO-66/ BiVO4复合催化剂的构建及其可见光光催化降解机制的系统研究还鲜有报道.本研究将载流子复合率高的BiVO4锚定在UiO-66周围及表面,形成能级及尺寸匹配的异质结,提升复合催化剂的活性位点数和光生载流子分离率,同时增强复合催化剂对四环素的吸附和光催化降解能力.以期为新型铋系MOFs可见光光催化剂的设计和光催化机理的深入研究提供参考. 1材料与方法1.1主要试剂与仪器1.1.1试剂本实验中使用的试剂和溶剂均为分析纯,无需进一步纯化,购自上海阿拉丁生化科技股份有限公司.五水硝酸铋[Bi(NO3)3·5H2O]、偏钒酸铵(NH4VO3)、乙二醇(C2H6O2)用于合成BiVO4;二甲基甲酰胺(C3H7NO)、氯化锆(ZrCl4)、对苯二甲酸(C8H6O4)、苯甲酸(C7H6O2)用于合成UiO-66;实验用水为娃哈哈纯净水.1.1.2仪器 AHD500W型光化学反应器,深圳中图博安光电有限公司;紫外-可见分光光度计UV2000,上海精密科学仪器有限公司;X射线衍射仪(XRD),D8-Advance,BrukerAXS,Germany;场发射扫描电镜(SEM/EDS),∑IGMA,卡尔蔡司(上海)管理有限公司,电压15KV,观察催化剂形貌;全自动比表面积分析仪(BET),Quantachrome AUTOSORB IQ,USA;紫外-可见-近红外分光光度计(DRS),Agilent Cary 5000,Australia;X射线光电子能谱仪(XPS),紫外电子能谱(UPS),KRATOS Axis Ultra, England.1.2UiO-66和UiO-66/BiVO4的制备1.2.1UiO-66的制备准确称量5mmol的ZrCl4及30当量(相对于ZrCl4)的C7H6O2分别超声完全溶解于40mL和25mL二甲基甲酰胺(DMF)中,分别记为溶液A和B.随后将5mmol C8H6O4加入A溶液中超声至完全溶解,记为溶液C.待溶液C磁力搅拌20min后将溶液B逐滴加入搅拌40min后转移至100mL衬底为聚四氟乙烯的水热反应釜中,120℃恒温24h.待反应溶液冷却后,离心分离并用DMF和无水甲醇清洗多次去除杂质,干燥研磨制得白色固体粉末.1.2.2 UiO-66/BiVO4的制备称取2mmol Bi(NO3)3·5H2O完全溶解于10mL乙二醇中,记为溶液D.称取2.4mmol的NH4VO3溶解于15mL纯净水中,记为溶液E.为了研究不同复合比例对产物光催化性能的影响,在相同Bi3+(2mmol)投加量下,分别称取1.1094g、0.5547g、0.2774g的UiO-66超声分散于50mL乙二醇中,即溶液中的Zr含量分别为4mmol、2mmol和1mmol,记为溶液F.将溶液D加入F中充分混合,随后将溶液E逐滴加入搅拌1h后移入100mL衬底为聚四氟乙烯的水热反应釜中,1801164 中国环境科学 41卷℃恒温12h,待反应溶液冷却后,离心分离并用无水乙醇和纯净水清洗多次去除杂质,干燥研磨制得黄色固体粉末.最后将制得的Zr:Bi物质的量投料比分别为1:0.5、1:1、1:2的复合催化剂分别编号为UB-0.5、UB-1、UB-2.1.3UiO-66/BiVO4的光催化性能测试将90mg所制备的光催化剂加入到300mL浓度为10mg/L的四环素(TC)溶液中.为了保证在光催化降解实验之前保持吸附-解吸平衡,将溶液在黑暗条件下搅拌90min.随后将样品放置于500W的氙灯下(滤光片滤除λ<420nm紫外光)进行光催化降解,光强(50±5)mW/cm2.在光催化过程中,间隔抽取5mL样品,通过三次离心去除催化剂.采用紫外可见分光光度计测量357nm处的吸光度值,通过标准曲线确定TC浓度.2结果与讨论2.1XRD分析XRD分析可以提供所合成样品的组成和晶相信息.UiO-66、BiVO4及UB-X(X为Zr:Bi物质的量投料比,数值为0.5、1、2)的XRD图谱如图1所示.纯UiO-66在7.34°和8.46°出现特征衍射峰,与之前的报道相同[21-32],证明UiO-66的成功合成.纯BiVO4在18.88°、28.86°、30.56°出现特征衍射峰,对应的晶面指数分别为(011)、(121)、(040),与单斜白钨矿型BiVO4的标准卡片(JCPDS:00-14-0688)吻合.当BiVO4与UiO-66复合后,其衍射峰相对于纯BiVO4没有显著差别,UiO-66在7.34°的特征峰并没有消失,且衍射峰强度随着BiVO4复合量的增加而减少,这可能是复合材料中UiO-66含量相对少所致.UB-X中均保留了BiVO4和UiO-66的特征峰,说明UiO-66/ BiVO4复合材料成功制备.根据文献[33],Bi3+与UiO-66的官能团(-OH和-COOH)之间存在配位关系.因此,Bi3+首先通过配位键吸附在UiO-66的表面上,然后由过量VO3-转化的VO43-逐渐与UiO-66表面固定的Bi3+结合形成化学键,成键的BiVO4分子在溶剂热环境下充分结晶生长成与UiO-66尺寸匹配的BiVO4颗粒,最终形成UiO-66/BiVO4复合催化剂.此外,在27.2°出现Bi单质的衍射峰,由于在这种典型的多元醇反应过程中,乙二醇既是溶剂又是还原剂.微量乙二醇在溶剂热反应过程中首先分解生成中间体甲醛再将Bi3+还原为Bi单质,最终生成微量粒径为150nm左右的球形Bi颗粒(图2(b)),这与先前研究报道的一致,反应见式(1)和式(2)[34-35].HOCH2CH2OH→CH3CHO+H2O (1) 2Bi3++6CH3CHO→3CH3CO–OCCH3+2Bi+6H+ (2)1020304050 60 7080(4)(121)UiO-66UB-2UB-1UB-0.52θ(°)BiVO4(11)Bi图1 样品的XRD谱图Fig.1The XRD patterns of the samples(e1) (e2)(e3) (e4) (e5)图2 UiO-66(a), BiVO4(b), UB-0.5(c)的SEM图;UB-0.5(d~e)的EDS分析Fig.2 SEM images of UiO-66(a), BiVO4(b), UB-0.5(c); theEDS analysis of UB-0.5(d~e)3期綦毓文等:UiO -66/BiVO 4复合光催化剂的制备及其对四环素的光解 11652.2 形貌分析为了进一步确定复合材料中UiO -66与BiVO 4的结合方式,对样品进行表观形貌分析(SEM)和元素分析(EDS).图2为纯UiO -66、纯BiVO 4及UB -0.5的SEM 图.在30当量的苯甲酸调节下,结晶良好的纯UiO -66为尺寸800-1100nm 的正八面体(图2a).纯BiVO 4为长度在500-1000nm 的纺锤状颗粒(图2b).负载前后UiO -66与BiVO 4的形貌和颗粒尺寸相似,纺锤状BiVO 4紧密结合在UiO -66周围,另外如图2d 中的EDS 点谱图像显示,UiO -66表面能检测到BiVO 4的所有元素,即表明一些未结晶完全的BiVO 4颗粒分散在八面体UiO -66表面(图2c),说明BiVO 4与UiO -66复合后在界面处形成了异质结结构.UB -0.5的EDS 分层图像如图2(e)所示,组成UB - 0.5的Bi 、O 、V 、Zr 、C 元素分布在整个复合颗粒中,且组成BiVO 4的Bi 、O 、V 元素在外侧显示突出,组成UiO -66的Zr 、C 元素主要集中在对应的中心八面体处,与SEM 图像2c 的结果一致.进一步表明了异质结的成功构建. 2.3 XPS 及UPS 分析通过XPS 进一步分析研究了UiO -66/BiVO 4复合材料的表面元素化学态.图3(a)为BiVO 4和UB - 0.5的完整测量光谱.相较于单一BiVO 4,当UiO -66与BiVO 4复合后,出现Zr 的衍射峰,表明Bi 、Zr 、C 、V 、O 存在于UiO -66/BiVO 4异质结的表面上,这与EDS 的结果一致.如图3(b)中显示,BiVO 4主要在Bi 4f 7/2的159.2eV 和Bi 4f 5/2的164.5eV 附近处有两个对称峰,为Bi 3+在BiVO 4中的典型值[36].与原始BiVO 4相比,UB -0.5中的Bi 4f 的主要拟合峰的结合能升高,分别由BiVO 4中的159.2eV 和164.5eV 变为UB -0.5中的159.4eV 和164.7eV ,表明的Bi 3+的价态因UB - 0.5异质结中的电荷转移而变低,即电子由BiVO 4向UiO -66转移,与电荷转移机制图8一致.此外,Bi 的XPS 光谱表明UB -0.5具有更大的半峰全宽(FWHM),这是由于BiVO 4颗粒相对较小而增强的无序性和化学不均一性所致,表明大表面积的UiO -66可以有效地稳定BiVO 4颗粒并抑制聚集[37].图3(c)显示了V 元素与UiO -66结合前后的结合能同样发生了变化,且结合后的结合能移至更低的位置.UB -0.5的O1s 峰可以拟合为图3(d)中530.27eV ,531.44eV 和532.88eV 的三个峰.其中530.27eV 处的峰属于Bi -O 和Zr -O 键[38-39].531.44eV 处的峰则与表面吸附氧有关,可归因于BiVO 4表面的氧空位[40],而532.88eV 处的峰与表面羟基有关[41].对于UB -0.5的C1s 的光谱(图3(e)),约284.90eV 、286.30eV 和288.60eV 处的三个结合能峰分别属于UiO -66的C=C 、C -C 和C=O 基[36].UB - 0.5中Zr 3d 光谱(图3(f))在184.58和182.18eV 处显示典型的Zr 3d 3/2和3d 5/2峰,这些峰源自[Zr 6O 4(OH)4(CO 2)12]集群[42].综上,XPS 结果进一步提供了UiO -66/BiVO 4异质结构形成的证据,且UiO -66与BiVO 4相之间的界面结合紧密.图4显示了样品的UPS 结果.BiVO 4和UiO -66样品的VB(价带)水平为2.08eV 和3.77eV ,分别与报道的实验数据2.10eV [11]和3.50eV [43]相符.与BiVO 4相比,UiO -66/BiVO 4异质结的VB 电位为1.76eV ,负移动为0.32eV ,这证明表面部分的UiO -66/BiVO 4异质结可以向能带位置的负方向移动,增强了将氧气转化为超氧自由基的能力.1000 800 600 4002000强度(a) Survey UB-0.5BiVO 4Z r 3p B i 4fZ r 3d B i 5dC 1sB i 4dV 2p O 1sO K L LO K L LO 1s B i 4dB i 4pV 2p C 1sB i 4fB i 5d结合能(eV)170168166164162160158 156结合能(eV)1166中 国 环 境 科 学 41卷强度526 524522 520 518 516514512510(c) V2p V2p 1/2524.4 V2p 3/2517.0BiVO 4516.9524.1UB-0.5结合能(eV)538536534532530528 526结合能(eV)295 290 285 280275结合能(eV)192190188186184182180 178 176结合能(eV)图3 样品的XPS 光谱.(a)全扫描,(b)Bi 4f,(c)V 2p,(d)O 1s,(e)C 1s,(f)Zr 3dFig.3 The XPS spectrum of the sample. Typical wide survey(a), and high resolution XPS spectrum of Bi 4f(b);V 2p(c);O 1s(d);C1s(e);Zr 3d(f)图4 样品的UPS 结果 Fig.4 The UPS results of sample2.4 比表面积及孔径分析表1和图5是催化剂在77K 下的N 2吸附-脱附测试结果.对于纯UiO -66纳米颗粒,N 2吸附-脱附等温线属于无滞后环的I 型吸附-脱附等温线,这是微孔材料所具有的特定吸附-脱附等温线类型[44],且比表面积为1502.1m 2/g,其中微孔面积为1372.00m 2/g,占总比表面积的91.34%.对于复合材料UB -0.5,N 2吸附-脱附等温线由I 型转变为Ⅳ型,在较高的相对压力下出现小的回滞环(图5(a)),表明介孔的出现主要是由于BiVO 4纳米粒子在UiO -66表面堆积而引起的,如SEM 图2(c)所示.随着BiVO 4的引入,比表面积值从原始UiO -66的1502.1m 2/g 降为UB -0.5的256.3m 2/g,孔体积值从原始UiO -66的0.58cm 3/g 降为UB -0.5的0.26cm 3/g.尽管如此,其数值仍远高于纯BiVO 4纳米颗粒的17.8m 2/g 和0.05cm 3/g.相似地,在图5(b)~(c)的孔径分布曲线中,UiO -66的孔径主要分布在0.78nm 和1.10nm 附近,为八面体UiO -66的典型值,BiVO 4的孔径主要分布在5.69-14nm.在UiO -66与BiVO 4成功复合后,微孔和介孔的分布曲线分别和UiO -66与BiVO 4相似,表明UiO -66与BiVO 4分别主导了UB -0.5的微孔和介孔结构.因为在UB -0.5的复合过程中,先加入的UiO -66载体影响了的结晶过程,原先纺锤状BiVO 4的形貌发生改变(图2(b)~(c)),导致原来介孔结构发生改变而呈现出新的孔径分布,使得BiVO 4的孔径主要分布在3.81nm 附近((图5(d)).当BiVO 4复合分散在UiO -66的表面后,UiO -66的部分空隙被覆盖或堵塞((图2(c)),导致UB -0.5的微孔孔径主要分布在0.43nm.相应地,平均孔径为13.11nm 的BiVO 4负载到平均孔径为1.77nm 的UiO -66表面后,形成了平均孔径为4.36nm 的UB -0.5复合材料.表明UiO -66与BiVO 4复合之后,使孔径结构向更有利于提高吸附速率和3期綦毓文等:UiO -66/BiVO 4复合光催化剂的制备及其对四环素的光解 1167容量的方向发展,具有显著改善单一材料的表面吸附性能的潜力.0 0.2 0.4 0.6 0.81.01234567891000.20.40.60.81.01.2 1.100.78(b)孔体积变化率(d V /d r )孔径(nm)UiO-66吸附量(c m 3/g )相对压力(P/P 0)12345678910-0.020.020.040.060.080.100.120.14UB-0.53.810.43孔体积变化率(d V /d r )孔径(nm)(d)0 510 15 20 2530350.002 0.004 0.006 0.008 0.010 (c)BiVO 4孔体积变化率(d V /d r )孔径(nm)7.45图5 合成样品的BET 曲线(a)及孔径分布图UiO -66(b); BiVO4(c); UB -0.5(d)Fig.5 BET curve(a) and pore size distribution of synthetic samples. UiO -66(b); BiVO4(c); UB -0.5(d) 表1 样品的比表面积、孔径和孔体积Table 1 S BET , average pore size and pore volume of samples样品 比表面积 (m 2/g)微孔面积 (m 2/g)平均孔径 (nm)孔体积 (cm 3/g) UiO -661502.1 1372.00 1.770.58BiVO 417.8 0.18 13.11 0.05UB -0.5 256.3 107.73 4.36 0.262.5 UV -vis DRS 漫反射分析光催化剂对可见光的吸收能力是决定着其光催化性能的重要因素,因此对纯UiO -66、纯BiVO 4及复合材料UB -0.5进行UV -vis DRS 漫反射表征.如图6(a)所示,纯UiO -66在380~780nm 可见光区吸收能力微弱,纯BiVO 4具有较强的吸收能力,复合材料UB -0.5的吸收能力相较于纯UiO -66明显提升,特别是在380~500nm 尤为明显.另外,根据Kubelka -Munk 方法,利用式(3)可计算得到BiVO 4、UiO -66和UB -0.5的带隙能[36].2()n/g Ahv A hv E =− (3)式中:α,h ,ν,E g 和A 分别为吸收系数、以eV 为单位的普朗克(Planck)常数、光频率、带隙宽度和样品在吸收边处的吸光系数.同时,由于UiO -66和BiVO 4属于直接带隙半导体,因此n 取值为l.将各参数代入式(3),计算得到纯BiVO 4、UiO -66和UB -0.5的带隙能分别为2.34eV 、2.38eV 和4.00eV,如图6(b)所示.UB -0.5的带隙宽度相较于UiO -66明显减小,略高于纯BiVO 4,与图6(a)中光吸收曲线一致.说明UB -0.5复合光催化剂易于被可见光激发产生光生载流子,提高量子效率.通过图4中的UPS 分析可知,BiVO 4与UiO -66的VB 位置分别为2.08eV 、3.77eV.从图6的Tauc 图可知BiVO 4与UiO -66的Eg 分别为2.34eV 和4.00eV.CB(导带)位置可以由式(4)计算得出:E CB = E g - E VB(4)式中:E VB 代表半导体价带电位,eV;E CB 代表半导体导带电位,eV;E g 代表半导体带隙能,eV.计算出知BiVO 4与UiO -66的E g 分别为2.34eV 和4.00eV.1168 中 国 环 境 科 学 41卷BiVO 4与UiO -66的CB 位置分别为-0.26eV 和-0.23eV.300 400 500 600 700 800UiO-66UB-0.5 BiVO 4 强度波长(nm) (a)1.52.0 2.53.0 3.54.04.5带隙宽度(e V )结合能(eV)图6 样品的DRS 光谱图(a)及相应的Tauc 图(b) Fig.6 The DRS spectrum (a) and (b)corresponding Taucdiagram of Sample2.6 光催化性能通过在模拟可见光照射下抗生素TC 的降解来评判催化剂的光催化性能,结果如图7所示.如图7(a)所示,纯UiO -66在暗吸附90min 后对TC 的吸附率为51.1%,明显低于其他样品.但由于曲线斜率较大,可能尚未达到吸附平衡.为此,开展了更长时间的暗吸附实验,发现12h 后UiO -66对TC 达到吸附平衡,总吸附去除率为88.14%.纯UiO -66对TC 的吸附效率低主要因为理论分子动力学直径为1.26nm 的TC 分子[45]难以进入UiO -66中1.1nm 左右八面体笼孔道[46],并造成部分堵塞.纯BiVO 4及复合材料UB - X (X =0.5、1、2)在暗吸附第90min 达到吸附平衡,对TC 的吸附去除率分别为59.6%、68.7%、61.5%、61.6%.其中复合材料UB -0.5的吸附能力明显高于纯UiO -66,主要由于亲水性良好的BiVO 4[47]的引入极大的改善了孔径结构并提高了单一UiO -66的表面亲水性能,在比表面积减少的情况下反而加速了对液相中TC 的吸附.UB -0.5对TC 的吸附能力皆高于纯BiVO 4、UB -1和UB -2,主要由于高比表面积和孔隙率的UiO -66提供了大量的吸附位点.因此,材料对目标污染物的吸附,不仅仅依赖于高比表面积提供的多活性位点,材料的相对孔径结构和亲水性质也是非常关键的因素.UB -0.5对TC 的强吸附能力主要归因于复合材料UB -0.5良好的亲水性、较大的比表面积和适当的孔径.-90-60-300 30 60 900.10.20.30.40.50.60.70.80.91.0C /C 0时间(min)2040 60 8000.20.40.60.81.0l n (C 0/C )时间(min)图7 模拟可见光下催化剂对TC 的去除曲线(a)及降解速率曲线(b)Fig.7 The removal curve and degradation rate curve ofcatalyst for TC under visible light经90min 可见光照射后,空白实验表明TC 的直接光解可以忽略不计.纯UiO -66对TC 的总去除率为58.7%,主要因为90min 的吸附时间,尚未达到吸附平衡.相同条件下,纯BiVO 4及复合材料UB -X(X= 0.5、1、2)对TC 的总去除率分别为62.3%、85.8%、72.6%、73.2%.其中,纯BiVO 4在开灯后去除率变化微小,说明纯的BiVO 4对TC 光降解作用微弱.结果3期綦毓文等:UiO-66/BiVO4复合光催化剂的制备及其对四环素的光解 1169表明,复合材料对TC的总去除率均高于单一催化剂,其中UB-0.5异质结光催化剂最高为85.8%,比纯UiO-66和纯BiVO4分别提升27.1%和23.5%.结合BET、DRS等表征结果,显然UB-0.5对TC降解效率的提升归因于复合材料催化活性位点的增多、可见光吸收能力的增强和形成异质结复合材料后光生载流子效率的提高.研究TC的光催化降解动力学,其结果如图7(b)所示.拟一阶动力学模型很好地拟合了所有光催化剂对TC降解的动力学曲线,空白、纯UiO-66、纯BiVO4和UB-X(X=0.5、1、2)的速率常数为分别为1.19×10−4min-1、2.32×10−3min-1、1.59×10−4min-1、7.61×10−3min-1、3.74×10−3min-1和3.53×10−3min-1.毫无疑问,UB-0.5异质结的速率常数最高,分别是UB-1和UB-2速率常数的2.03和2.16倍,是纯BiVO4的47.9倍.显然,异质结复合催化剂的成功制备,极大的升高了对TC的可见光光降解速率.2.7光催化机理探讨为了探究异质结体系提高光催化活性的机制,根据我们的实验结果,提出了UiO-66/BiVO4复合材料在可见光下的光催化反应机理.当UiO-66与BiVO4复合时,复合材料的能带结构发生变化,在两个半导体之间的界面处形成稳定的异质结构.通过考虑样品的带隙和VB水平,可以绘制UiO-66/ BiVO4异质结的能带排列图.如图8所示,当复合材料暴露于可见光时,BiVO4产生电子-空穴对,由于II型异质结的形成且BiVO4的CB电势比UiO-66更负,光生电子易于从BiVO4层的CB移动到高比面积的UiO-66的CB.同时,受到VB电势的限制,两者VB层不容易发生空穴转移,从而抑制了光生电子-空穴对的复合.理论上,只有CB电势低于氧气(O2)转变为超氧自由基(·O2-)的电势(+0.13eV),溶解氧才能与CB上的电子结合生成·O2-[48],故迁移到BiVO4表面的电子和迁移到UiO-66表面的电子都能与吸附氧和溶解氧结合产生·O2-对四环素进行降解.同样,只有当电势大于·OH/H2O的转化电势(+2.68eV),光致空穴才能氧化吸附的水分子产生羟基自由基[49],故BiVO4的CB边的空穴直接对四环素氧化降解,而没有将吸附的H2O分子转化为·OH后再降解的转化过程.综上,超氧自由基和空穴是对四环素进行降解的主要活性物种,催化降解性能的提高主要归因于UiO-66/BiVO4异质结的成功构建.一方面,被激发的载流子得以有效分离,从而减少了电子-空穴对的重组并延长了载流子的寿命;另一方面,UiO-66的引入大大的增加了吸附位点和催化位点数量,进而提高了光催化降解性能.图8 UiO-66/BiVO4异质结的光催化机理示意Fig.8 Schematic diagram of the photocatalytic mechanism ofUiO-66/BiVO4 heterojunction3结论3.1采用两步溶剂热法成功制备了UiO-66/BiVO4异质结光催化剂.研究表明UiO-66的加入量对该复合材料的光学性能、吸附及光催化降解TC的性能有显著的影响.其中复合材料UB-0.5的可见光光催化活性最高,对TC的光解率达85.8%,比纯UiO-66和纯BiVO4分别提高27.1%和23.5%,降解速率是纯BiVO4的47.9倍.3.2能级匹配异质结复合材料的成功构建使光生载流子在界面电场的作用下迅速迁移,抑制了光生电子-空穴对的复合,延长了载流子寿命;其次,相较于单一材料,UB-0.5具有更高的比表面积和光吸收能力,提升了处理效率和光利用率.从而二者共同增强了复合催化剂的光催化活性.3.3根据能带隙、UPS表征结果,向负方向移动的异质结导带加强了氧气向超氧自由基的转化,进而有利于四环素的催化降解,且超氧自由基和空穴是降解TC的主要活性物种.参考文献:[1] Tang L, Zeng G M, Shen G L, et al. 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嗜热酯酶EstTs1的远源三维结构模建及分子对接詹冬玲;邵鸿泽;韩葳葳;刘景圣【摘要】利用Phyre网络服务器,构建嗜热酯酶EstTs1的三维结构,并通过分子动力学优化构型,得到了可靠的构型.分子对接研究表明,p-硝基苯基丁酸酯是EstTs1的最适底物,其大小正适合EstTs1的活性口袋.Thr111是底物与酶结合的重要残基,与底物形成了氢键; Ser85是重要的催化残基.%A 3D structure of thermostable esterase ( EstTsl ) was built by means of the protein homology/ analogy recognition engine ( Phyre ) program and further refined via unrestrained dynamics simulation. The docking results reveal that j?-nitrophenyl butyrate ( C4 ) is the best substrate of EstTsl , which has the adaptive size to the EstTsl. In addition, the key binding-site residue of Thrl 11 plays an important role in the catalysis of EstTsl for it made a hydrogen bond with j?-nitrophenyl butyrate. One important finding was that the identification of the key binding site: residue of Ser85 which plays an important role in the catalysis of EstTsl.【期刊名称】《吉林大学学报(理学版)》【年(卷),期】2011(049)006【总页数】5页(P1131-1135)【关键词】远源三维结构模建;分子对接;嗜热酯酶EstTs1【作者】詹冬玲;邵鸿泽;韩葳葳;刘景圣【作者单位】吉林农业大学,食品科学与工程学院,长春,130118;吉林农业大学,食品科学与工程学院,长春,130118;吉林大学,分子酶学工程教育部重点实验室,长春,130012;吉林农业大学,食品科学与工程学院,长春,130118【正文语种】中文【中图分类】O623脂肪水解酶广泛存在于动物、植物及微生物中, 它可以催化水解反应和合成反应, 且反应具有很高的区域选择性、立体选择性和商业价值[1-4]. 细菌产生的脂肪水解酶根据水解底物的不同划分为: 1) 水解短链羧酸酯(小于12个C) 的酯酶[EC 3.1.1.1]; 2) 可以在油水界面上水解长链甘油酯(大于12个C)的脂肪酶[EC 3.1.1.3];3) 可以水解极性磷脂的磷脂酶[EC 3.1.4.3]. 而普通脂肪水解酶作为具有生物活性的大分子, 在高温、强酸、强碱等条件下易失活, 因此在应用上受到较大限制. 而嗜热酶具有耐高温、抗酸碱、热稳定性好等优点[3-4], 应用广泛.Plessis等[1]从嗜热菌Thermus scotoductus中发现一种含量丰富的嗜热酯酶: EstTs1, 序列分析表明, 它是一种新的脂肪水解酶家族成员. 近年来, 通过质谱、定点突变等实验方法推测出了脂肪水解酶的反应机理[5]及其在催化过程中所涉及的其他重要残基, 但由于EstTs1与同家族的酶同源性较低(与EstTs1同源性最高的是来源于结核分枝杆菌中的Rv0554(PDB code 2E3A ), 同源性为27%), 使得人们无法通过比较模建法构建模型, 研究其反应机理, 在一定程度上影响了对EstTs1酶的更深入研究. 本文利用远源三维结构模建(remote homology modeling)技术, 先将EstTs1的序列提交到Phyre(protein homology/analogy recognition engine)的模建服务器上[6-7], 然后通过分子动力学模拟方法建立了可靠的EstTs1三维结构, 分析其活性位点的组成和结构, 并在此基础上进行了EstTs1与其最适底物p-硝基苯基丁酸酯的对接研究, 确定了复合物形成具有重要作用的残基, 对进一步揭示EstTs1的催化机理及嗜热酯酶的开发利用提供了理论依据.1 理论方法同源模建技术是目前应用最广的蛋白质三维结构预测方法[8-9], 但EstTs1与同家族酶的同源性低于30%, 所以不能搭建可靠的嗜热酯酶模型. Phyre网络服务器基于折叠模式识别搭建模型, 适合于构建折叠结构相似但远源的蛋白质模型[6-7].在初始的三维结构基础上, 利用AMBFR 9程序[9]对其进行分子动力学(MD)模拟, 模拟过程中使用周期性边界条件和FF03力场, 并用PME(particle mesh ewald)计算体系的静电相互作用. 考虑到溶剂化效应, 初始结构外加入了0.8 nm的TIP3P 水分子层, 并将其置于八面体的周期性盒子中, 采用Na+平衡蛋白质中的负电荷. 能量最小化后, 在最初0.05 ns的MD模拟中升温0~353 K, 然后进行2.5 ns的MD 模拟使体系达到平衡. 最终得到EstTs1的三维结构, 使用ProStat和PROFILE-3D 程序进行评估与比较. 利用得到的稳定构象, 使用Binding-Site模型[10]进行活性部位搜索, 并结合已知的实验数据, 预测EstTs1的活性位点. 通过AutoDock4.2[11]与多种底物进行对接, 验证底物的选择性. 并用Afinity模块[12]将最适底物p-硝基苯基丁酸酯(C4), 与EstTs1对接, 得到稳定的复合物结构, 确定与底物作用时的重要残基.2 结果与讨论2.1 EstTs1的远源模建图1 EstTs1 2.5 ns动力学的RMSDFig.1 Root-mean square deviation obtained from the 2.5 ns molecular dynamics trajectory for EstTs1在2.5 ns的MD模拟过程中均方根偏差(root-mean square deviations, RMSD)随时间变化曲线如图1所示. 由图1可见, 体系的RMSD在最初的1 ns内变化剧烈, 2 ns后体系的RMSD趋于不变, 表明体系已经稳定. 图2(A)为采用Profile-3D程序对EstTs1最初搭建构型的评估结果; 图2(B)为经过分子动力学优化后各残基的Profile-3D得分. 由图2可见, 所有残基的Profile-3D得分均大于0, 表明所有残基都处于合理位置. Profile-3D的评分为121.64(程序得出的最优评分为116.34), ProStat的二面角检查结果为81.9%, 均在合理范围内. 因此, 本文所模建的EstTs1三维结构是可靠的, 如图3所示.2.2 活性位点的预测关于EstTs1的活性位点, 目前尚未见文献报道活性口袋所处的位置及组成. Plessis 等[1]只提出了EstTs1包含Gly-Leu-Ser-Asn-Gly这样的活性位点模块. 通过同一家族的同源序列对比分析, 发现这一区域为Gly83-Leu84-Ser85-Asn86-Gly87, 其中Ser85为亲核进攻试剂. 通过Binding-site模块搜寻活性口袋, 搜寻到一处包含Ser85位点, 可以确定为活性部位. 活性位点的组成为:Leu146,Trp145,Gly20,Leu21,Asn19,Asn86,Trp125,Pro237,Leu84,Arg149,Ala2 36,Phe22和Leu179.图2 EstTs1初始结构的PROFILE-3D打分值(A)与经过2.5 ns动力学优化 EstTs1结构的PROFILE-3D打分值(B)Fig.2 PROFILE-3D scores for the structures of initial EstTs1 (A) and final EstTs1 (B)2.3 分子对接使用AutoDock 4.2软件将p-硝基苯基乙酸酯(C2)、 p-硝基苯基丁酸酯(C4)、 p-硝基苯基辛酸酯(C8)和p-棕榈酸对硝基苯酯(C16)分别与EstTs1对接, 结果列于表1. 由表1可见, C4与EstTs1的结合自由能最低(为-5.05 kJ/mol), C2~C4酶与底物的结合自由能降低; C4~C16酶与底物的结合自由能升高. 通常复合物的结合自由能越低, 表明体系越稳定, 稳定的体系有利于反应发生. 上述结果与Plessis等[1]给出的4种底物的相对活力实验相符.表1 用AutoDock4.2计算的酶与不同底物和EstTs1的结合自由能Table 1Calculated binding free energies with AutoDock 4.2 program底物Δ Gbinding/(kJ·mol-1)相对活性/%p-硝基苯基乙酸酯-3.5859p-硝基苯基丁酸酯-5.05100p-硝基苯基辛酸酯-2.342p-棕榈酸对硝基苯酯-1.030为解释底物选择性的原因, 将这4种底物采用Gaussian 03软件[12]对其结构进行优化, 使用B3LYP方法6-31G*基组. 表2列出了4种底物羟基上连接的C和O的Mulliken电荷分布情况. 由于烷基是斥电子基, 中心带正电荷的碳连接的烷基越多, 整个系统的电荷可以得到越有效的分散, 因而越稳定. 随着碳链的增加(C2~C16), 烷基的供电效应增强, 体系稳定, 即C4比C2稳定. EstTs1的催化机制为典型的α/β水解酶家族两步反应:丝氨酸作为亲核试剂进攻底物的羟基氧, 生成中间产物. 体系越稳定, 亲核反应越容易发生,因此EstTs1对它的催化活力更高. 但EstTs1的活性口袋较小, 图4为C4和C16的活性口袋示意图. 由图4可见, C4的大小正好适合活性口袋. 之后随碳链的增加, 空间位阻加大, 反应较不易发生. 这与C4~C16随着碳链的增加, EstTs1对底物的催化活力降低实验结果一致.表2 底物的Mulliken电荷分布Table 2 Mulliken atomic charges with substrates底物COO1p-硝基苯基乙酸酯0.595-0.438-0.511p-硝基苯基丁酸酯0.596-0.441-0.519p-硝基苯基辛酸酯0.620-0.448-0.524p-棕榈酸对硝基苯酯0.629-0.457-0.527为确定与最适底物C4结合时起重要作用的残基, 使用Affinity软件, 将C4与EstTs1进行对接研究. 氢键对分子的结构和功能, 尤其是酶的催化作用具有重要作用. C4与EstTs1的活性口袋中形成的氢键如图5所示. C4中的羟基氧与Thr111形成氢键, 因此Thr111是与底物结合过程中起重要作用的残基.图3 EstTs1的三维结构(A)与p-硝基苯基丁酸酯的结构(B)Fig.3 3D structures of EstTs1 (A) and p-nitrophenyl butyrate (B)图4 C4在活性口袋中(A)与C16在活性口袋中(B)示意图Fig.4 C4 in the activepocket (A) and C16 in the active pocket (B)图5 底物C4与EstTs1活性位点部分残基的氢键示意图Fig.5 Hydrogen bond between C4 and EstTs1C4与EstTs1相互作用主要体现为非键相互作用. 分子间的非键相互作用, 对于确定底物与蛋白的相对位置及关键残基非常重要. 底物在EstTs1活性口袋中的取向如图4所示, p-硝基苯基丁酸酯与EstTs1活性部位的残基间的相互作用能列于表3. 为验证Ser85的作用, 将Ser85突变成Ala, 然后将p-硝基苯基丁酸酯与突变后的酶进行对接. 由表3可见, S85A突变使酶和底物的相互作用能升高, 体系不稳定, 不易于化学反应的发生, 表明Ser85是重要的催化残基. 表4列出了与底物结合时起重要作用的残基. 在所有活性部位的残基中, Ile146和Trp145与底物的相互作用最强(与底物的相互作用能最低), 是在催化过程中稳定底物的重要氨基酸. 此外, Gly20,Leu21,Asn19,Asn86,Trp125,Pro237,Leu84,Arg149,Ala236,Phe22和Leu179与底物的相互作用以范德华力为主.表3 EstTs1和S85A突变体与底物的结合自由能Table 3 Calculated binding energies of ligand tested with EstTs1 and S85A mutant酶Evdw/(kJ·mol-1)Eele/(kJ·mol-1)Etotal/(kJ·mol-1)WT-51.73-15.77-67.54S85A突变体-33.93-2.59-26.52综上可见, 底物p-硝基苯基丁酸酯在EstTs1的稳定性主要依靠范德华力, 而在催化过程中, Ser85担当亲核试剂. 活性部位残基Ile146与Trp145底物的相互作用最强, Thr111与底物形成了氢键, 因此, Ile146,Trp145,Thr111是在催化过程中稳定底物的重要氨基酸.表4 底物p-硝基苯基丁酸酯和EstTs1活性位点部分残基的总能量(Etotal)、范德华相互作用能(Evdw)及静电相互作用能(Eele)Table 4 Total energy Etotal, van-der-Waal energy Evdw and electrostatic Eele between p-nitrophenylbutyrate and individual residue残基Evdw/(kJ·mol-1)Eele/(kJ·mol-1)Etotal/(kJ·mol-1)Ile146-8.080.12-7.97Ser85-0.98-6.81-7.79Trp145-6.11-0.12-6.23Gly20-3.59-2.14-5.73Leu21-3.54-1.70-5.24Asn19-3.08-0.76-3.84Asn86-1.68-1.77-3.46Trp125-2.980.23-2.75Pro237-1.53-1.19-2.73Leu84-2.820.14-2.69Arg149-1.94-0.57-2.51Ala236-1.02-0.93-1.95Phe22-1.20-0.26-1.47Leu179-1.330.05-1.28参考文献【相关文献】[1] Plessis E M, Berger E, Stark T, et al. 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原子与分子物理学报JOURNAL OF ATOMIC AND MOLECULAR PHYSICS Vol.38No.3 Jun.2021第3"卷第3期2021年6月5,15-二"二茂铁基)-口卜咻献菁钇结构和振动光谱的密度泛函理论研究姜力,周启,陈玉锋,蔡雪(牡丹江师范学院化学化工学院,牡丹江市157000)摘要:本文选用混杂的B3LYP密度泛函理论方法,在Lanl2dz水平上,对5,15-二"二茂铁基)-”卜啉酞菁钇[Por(Fc)2]Y(Pc)的结构进行了优化,结果表明,5,15-二"二茂铁基)-”卜啉駄菁钇呈现出三明治型构型,”卜啉环与与菁环呈穹型围绕在金属铉原子周围.对分子內主要的键长与键角进行了理论计算,通过频率计算,得到了5,15-二"二茂铁基)-”卜啉駄菁原[Por(Fc)2] Y(Pc)的红外光谱图,与实验所得的红外光谱图进行比对,将理论计算和实验所得的光谱主要振动峰进行了线性回归拟合,相关系数为0.992,标准偏差为16.96.理论计算与实验所获得的红外光谱图基本一致,说明本文文选用的DFT理论计算方方是可行行.通过GaussView软件对5,15-二"二茂铁基)-”卜啉駄菁原红外谱带简正振动模式进行了指认.此卜,分析讨论了5,15-二"二茂铁基)-”卜啉駄菁原Por(Fc)2] Y(Pc)的分子静电势,确定了极大值与极小值的位置.对于研究5,15-二"二茂铁基)-”卜啉駄菁原分子周性质,提供了相应的理论基础.关键词:"卜啉駄菁;密度泛泛理论;振动光谱;分子静电势中图分类号:O641.4文献标识码:A DOI:10.19855/j.l000-0364.2021.031007Theoretical study on the structure and vibrational spectroscopy of5,15-bis(伽,。
中国肝癌病人p53突变体R248W的细胞功能研究赵晶;郭泽坤【期刊名称】《西北农林科技大学学报(自然科学版)》【年(卷),期】2008(036)010【摘要】[目的]探索p53基因突变对细胞正常功能的影响,阐明肝癌的发病机制.[方法]利用PCR产物直接测序的方法,对202例中国肝癌患者p53基因的11个外显子进行突变筛查;利用定点突变的方法构建真核表达载体pCMV-R248W,Western blot检测突变体蛋白R248W在p53缺失型H1299细胞中的表达情况;采用双荧光素酶报告基因检测系统和流式细胞仪,研究R248W突变对转录活性及促凋亡能力的影响.[结果]在其中1例样本的7号外显子处筛查到突变形式为CGG→TGG的点突变,使p53蛋白248位的精氨酸(Arg)突变为色氨酸(Trp),即R248W,突变率为0.495%;在H1299细胞中转染等量的pCMV-p53和pOMV-R248W时.野生型p53与突变体R248W的蛋白表达量相当,但R248W的转录活性及促凋亡能力显著低于野生型p53.[结论]R248W突变可能引起p53蛋白构象的改变,从而影响p53的转录活性及促凋亡能力,使细胞的正常生理功能紊乱,导致肿瘤发生.【总页数】7页(P186-192)【作者】赵晶;郭泽坤【作者单位】西北农林科技大学,生命科学学院,农业分子生物学重点实验室,陕西,杨凌,712100;西北农林科技大学,生命科学学院,农业分子生物学重点实验室,陕西,杨凌,712100【正文语种】中文【中图分类】Q279【相关文献】1.中国兰春剑隆昌素叶色突变体光合特性的初步研究 [J], 熊剑锐;何俊蓉;蒋彧;李萍2.恶性肿瘤复发与p53热点突变体的相关性研究 [J], 王焕彬;许杰3.中国汉族人群24种CYP2C19新突变体的体外活性研究 [J], 李传保;戴大鹏;蔡杰;耿培武;王双虎;王豪;胡国新;蔡剑平4.突变体p53研究进展 [J], 李大虎;张令强;贺福初5.四引物扩增受阻突变体系PCR技术在中国明对虾SNP基因分型中的研究 [J], 张建勇;王清印;王伟继;孟宪红;孔杰;张全启因版权原因,仅展示原文概要,查看原文内容请购买。
LncRNA H19在肿瘤发病中的作用机制研究进展①朱敏郗雪艳杜伯雨(湖北医药学院基础医学院,十堰442000)中图分类号R735.3文献标志码A文章编号1000-484X(2021)07-0883-05[摘要]随着研究的深入和研究技术的提高,研究者在人类基因组中发现了大量非编码RNA(NcRNA),这类RNA一直受到人们的广泛关注。
越来越多的研究显示,NcRNA可能参与各种基因表达的调控。
目前的研究已证实,长链非编码RNA (LncRNA)在生长调控及生理代谢中发挥重要作用,并且参与肿瘤调控。
LncRNA H19是最早发现的印迹LncRNA,虽然在大多数组织中LncRNA H19的表达在出生后被关闭,但很多研究提示其可在肿瘤发生期间被重新激活或抑制,从而影响肿瘤进展。
本文主要综述近期LncRNA H19在肿瘤发病中作用机制的研究进展,为今后的研究提供参考。
[关键词]LncRNA;H19;肿瘤;作用机制Research progress of mechanism of LncRNA H19in cancer disease development ZHU Min,XI Xue-Yan,DU Bo-Yu.School of Basic Medical Sciences,Hubei University of Medicine,Shiyan 442000,China[Abstract]With the deepening of study and the improvement of research techniques,researchers have found a large number of noncoding RNA(NcRNAs)in human genome,which has been receiving attention.Increasing evidence indicated that NcRNA is likely to involve in the regulation of various gene expression.Recent studies have confirmed that long noncoding RNA(LncRNA)plays im‐portant regulator roles in various biological processes,including cancer development.LncRNA H19is the first imprinted gene. Although H19expression is turned off after birth in most tissues,there are many studies demonstrate that it can be reactivated or inhib‐ited during tumorigenesis.This article mainly reviews the recent research progress of the pathogenic mechanism of LncRNA H19in cancer disease development,aimed to provide a reference for future research.[Key words]LncRNA;H19;Cancer;Mechanism1概述由美国国立人类基因组研究院启动的多国联合研究项目计划——DNA元件百科全书(EN‐CODE)项目已证实,基因组中有80%的基因可被转录,然而最终可表达为蛋白质的基因只有不到2%[1]。
双去甲氧基姜黄素对四氯化碳致小鼠急性肝损伤的保护作用及机制矫春丽; 宋艳芹; 杜源; 卢永颖; 张雷明【期刊名称】《《药学研究》》【年(卷),期】2019(038)005【总页数】5页(P253-256)【关键词】双去甲氧基姜黄素; 肝损伤; 抗炎; 抗凋亡【作者】矫春丽; 宋艳芹; 杜源; 卢永颖; 张雷明【作者单位】[1]烟台大学药学院山东烟台264005; [2]烟台市食品药品检验检测中心山东烟台264000【正文语种】中文【中图分类】R967肝损伤是临床上的常见病,各种物理和化学因素均可导致急慢性肝损伤,严重或持续的肝损伤最终可导致急性肝功能衰竭,危及患者生命[1-2]。
实验性肝损伤包括化学性肝损伤、免疫性肝损伤、酒精性肝损伤及药物性肝损伤等多种类型,其中四氯化碳(CCl4)是经典的诱导肝损伤动物模型的化学物质,当肝脏持续受到CCl4作用时,肝细胞内的多种酶大量释放入血,包括谷丙转氨酶(alanine transferase,ALT)、谷草转氨酶(aspartate transferase,AST)及环氧化物酶-2等,其能促进炎症反应的发生,最终导致肝纤维化[3-4]。
细胞色素P450酶系(CYP450)将CCl4转化为有毒的代谢产物,损伤细胞DNA和生物膜 [5]。
另外,肝细胞还能分泌大量的炎症因子,其中肿瘤坏死因子α(tumor necrosis factor α,TNF-α)能刺激免疫相关细胞产生大量细胞因子,引起局部或全身炎症反应,还可激活细胞内相关死亡区域的蛋白,激活半胱氨酸蛋白酶(caspase)家族,最终诱导细胞凋亡[6]。
双去甲氧基姜黄素(Bisdemethoxycurcumin,BDMC)、去甲氧基姜黄素和姜黄素统属姜黄素类化合物,是从植物姜黄根茎中提取的一种植物色素,这3种成分结构简单且相近,易于合成,具有多种相似的药理活性,如抗炎、抗氧化、抗肿瘤等,无明显的毒副作用[7]。
未培养微生物的研究与微生物分子生态学的发展*叶姜瑜1,2罗固源1,2(重庆大学三峡库区生态环境教育部重点实验室重庆400045)1(重庆大学城市建设与环境工程学院重庆400045)2摘要:近年来现代分子技术和基因组学逐渐渗透到有关生命科学的整个领域,也为微生物生态学提供了新的研究方法和机遇。
16S rRNA基因序列分析、DNA-DNA杂交、核酸指纹图谱以及宏基因组学等分子技术检查自然环境中的微生物,可以克服传统纯培养技术的不足,是一条探知未培养微生物、寻找新基因及其产物的新途径,开启了我们认识微生物多样性和获得新资源的大门。
关键词:未培养微生物,微生物分子生态学,分子技术中图分类号:Q93文献标识码:A文章编号:0253-2654(2004)05-0111-05Progress in the Biodiversity of Nonculturab le Microorganisms andM icrobial Molecular EcologyYE Jiang-Yu1,2LUO Gu-Yuan1,2(Chon gqin g U ni versit y Ke y L a bora tory o f Eco-en vironmen ts o f Three Gorges Reservoir Re gion,Min ist ry o f Edu cation Ch ongqin g400045)1(Cit y Construction an d En viron men ta l En gin eerin g Aca de my,Chon gqin g Un ive rsity,Chon gqing400045)2 Abs tract:Recent progress in molecu lar microbial ecology has revealed that traditi on al cultu rin g method s fail to rep resen tthe scope of microb ial di versity i n n ature,only a small proportion of viab le microorgani sms i n a samp le are recove red bycu lturing techni ques1Molecular techni ques,16S rRNA seq uencin g,DNA-DNA h yb rid ization,genetic fin gerp rin ti ngtech niqu e and metagenomics etc,have become rou ti ne methods in microbial ecol ogy,which are u sed to expl ore the d-ive rsi ty of uncul tured microb ial commu nities an d ob tain novel environmental D NA w i thou t an y cultivation1K ey words:Noncu lturable microorgan ism,Mic robial molecular ecology,Molecular techniq ue1原核微生物是地球上最早的生命形式,在数十亿年的进化过程中,形成了适应各种环境的生理和分子机制,占据了地球几乎所有环境,包括没有其它生命形式能够共存的极端环境。
Release of Intracellular Metabolites From Cyanobacteria During Oxidation Processes [Project #4406]ORDER NUMBER: 4406DATE AVAILABLE: April 2014PRINCIPAL INVESTIGATORS:Eric C. Wert, Mei Mei Dong, Fernando L. Rosario-Ortiz, and Julie KorakOBJECTIVESThe objective of this project was to determine the effect of common preoxidants used during drinking water treatment on the integrity of cyanobacteria cells, and to evaluate the subsequent release of toxic metabolites, odorous metabolites, and disinfection byproduct (DBP) precursors.BACKGROUNDDrinking water utilities often begin the treatment process by using an oxidation process to meet different water quality objectives (e.g., disinfection, control of invasive species, oxidation of organic/inorganic contaminants). If cyanobacteria cells are not physically removed prior to oxidation, cell damage or lysis may result in the release of intracellular (or cell bound) organic matter (IOM) into the water supply. The IOM may contain algal toxins (e.g., microcystin, cylindrospermospin, anatoxin), taste and odor compounds (e.g., 2-methylisoborneol [MIB], geosmin), or disinfection byproduct precursors. Few studies have investigated the risk of releasing cell-bound IOM during oxidation processes including ozone, chlorine, chlorine dioxide, and chloramines.APPROACHThree cyanobacteria (i.e., Microcystis aeruginosa[MA], Oscillatoria sp.[OSC], and Lyngbya sp.[LYN]) were selected for the study based upon (1) occurrence in source water supplies, (2) availability of an axenic culture, (3) ability to produce odorous or toxic metabolites, and (4) cell morphology. These cyanobacteria were placed into a growth chamber under controlled light and temperature conditions. Cells were harvested around the late exponential or early stationary growth phase (28 days).A purified cell suspension was used to evaluate cyanobacteria cell integrity and metabolite release in Colorado River water. In order to evaluate cell degradation, digital flow cytometry (FlowCAM) in combination with chlorophyll-a measurements provide an assessmentof cyanobacteria cell damage and lysis after exposure to ozone, chlorine, chlorine dioxide, or chloramine. Digital and binary images were collected by the FlowCAM to provided qualitative information regarding cyanobacteria cell damage. The release of toxic (i.e., microcystin-LR [MC-LR]) or odorous metabolites (i.e., MIB, geosmin) was investigated after filtration of the damaged cyanobacteria cells.DBP formation was evaluated using a standard of IOM extracted from each of the cyanobacteria species. IOM was extracted using a freeze-thaw/sonication/filtration process. Formation potential (FP) testing was conducting using chlorine and chloramines. FP testing with chlorine focused on the formation of total organic halogen (TOX), trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and trichloronitromethane (or chloropicrin). FP testing with chloramines focused on the formation of nitrosamines (including N-nitrosodimethylamine [NDMA]).RESULTS/CONCLUSIONSThe digital flow cytometer provided a rapid method to obtain quantitative and qualitative information regarding cyanobacteria cell damage and lysis compared to conventional light microscopy. Cell damage was defined by the loss of chlorophyll-a or a decrease in the fluorescent particle concentration measured using the FlowCAM. Cell lysis was defined by the fragmentation of the unicellular or filamentous structure. Results showed that cyanobacteria cell damage occurred without complete lysis or fragmentation of the cell membrane under the conditions tested. During ozone and chlorine experiments, the unicellular MA was more susceptible to oxidation than the filamentous OSC and LYN. Digital and binary images provided some perspective regarding how the oxidants may be damaging the cell structure. In most cases, the oxidant appeared to penetrate the cell wall and oxidize or release chlorophyll-a and other metabolites without completely fragmenting the cell membrane.The release of metabolites was measured after filtration of the damaged cyanobacteria cells: MA (200,000 cells/mL), OSC (2,800 cells/mL), and LYN (1,600 cells/mL). The DOC release after oxidation was less than 0.3 mg/L under the conditions tested. During the oxidation of 200,000 cells/mL of MA, release of intracellular MC-LR exceeded 1 µg/L during the lowest oxidant exposures (CT) tested: ozone (0 mg-min/L, dose below the ozone demand), chlorine (<40 mg-min/L), chlorine dioxide (<558 mg-min/L), and chloramine (<636 mg-min/L). As the CT increased, ozone, chlorine, and chlorine dioxide were able to oxidize the released MC-LR, which was expected based upon published kinetic information.MIB and geosmin release were investigated after oxidation of OSC and LYN cells. Releases of MIB and geosmin exceeded their respective threshold odor values after oxidation by chlorine, chlorine dioxide, and chloramine. These oxidants have low reactivity with MIB and geosmin. When insufficient ozone residual was established (below or near demand), there was a measured increase in MIB and geosmin concentration. As ozone CT increased, hydroxyl radicals were able to oxidize the release MIB and geosmin, which was expected based upon published kinetic information.DBP yields from IOM were identified for carbonaceous and nitrogenous species. FP testing showed that IOM has the potential to provide another source of DBP precursors. During FP testing with chlorine, most of the TOX was identified (62‒78%) among THMs, HAAs, TCNM, and HANs. TOX is a surrogate for the overall formation of halogenated DBPs in a sample. During FP testing with 100 µg/L of bromide, the formation of different brominatedDBPs was observed, although overall mass yields of specific classes of DBPs were unchanged. During FP testing with chloramines, NDMA yields were identified between 10‒52 ng/mg C depending on the source of the IOM (MA, OSC, or LYN). Other nitrosamines were also formed including N-nitrosodimethylamine, N-nitrosopyrrolidine, and N-nitrosopiperidine. The IOM was also analyzed for assimilable organic carbon (AOC). Results showed that >99% of the IOM extracted from OSC and LYN was present as AOC. Therefore, IOM may be removed during a biological treatment process.APPLICATIONS/RECOMMENDATIONSUtilities can use this research to better understand the impact of their pretreatment strategy on the risk of releasing toxic metabolites, odorous metabolites, and/or DBP precursors. Results from this study showed that low oxidant exposures can result in the release of cyanobacteria metabolites. Depending on the cell concentration, oxidant exposure, and the magnitude of DOC release, sufficient IOM concentrations may be released resulting in impacts on regulatory compliance (THMs and HAAs) or consumer confidence (MIB and geosmin). With respect to MC-LR, utilities using chloramines ahead of any physical treatment barrier are at the greatest risk for releasing and accumulating MC-LR within the treatment process. With respect to MIB and geosmin, utilities using chlorine, chlorine dioxide, or chloramines are at the greatest risk for releasing and accumulating MIB and geosmin within the treatment process. Ozonation has shown the ability to release metabolites. However, ozone reacts rapidly with MC-LR and hydroxyl radicals react with MIB and geosmin, which can minimize the effect of the metabolite release via cell damage. Overall, physical removal of cells is recommended before the primary disinfection step in a water treatment process to avoid the release of these metabolites.FP testing identified the potential to form DBPs from IOM sources. During cyanobacteria cell testing, DOC releases did not exceed 0.3 mg/L based on the cell concentrations used in this study. Therefore, the magnitude of DOC release and subsequent chlorine or chloramine exposure must be taken into consideration when evaluating DBP risk. Furthermore, AOC results showed IOM from OSC and LYN to be largely biodegradable. This finding could indicate that cyanobacteria-derived organic matter released into the environment (perhaps during cell decay) may be biodegraded before entering the water treatment facility. It also implies that any released IOM may be removed (along with corresponding DBP precursors) through a biological treatment process. Therefore, the significance of IOM as a DBP precursor source may be very site specific depending on cyanobacteria specie, cell concentration, oxidation conditions, magnitude of DOC release, and subsequent chlorine or chloramine exposure. RESEARCH PARTNERSouthern Nevada Water Authority。
第44卷第7期2024年4月生态学报ACTAECOLOGICASINICAVol.44,No.7Apr.,2024基金项目:国家自然科学基金项目(32071845);甘肃省科技计划资助(23JRRA572);内蒙古自治区科技重大专项(2021ZD0015);甘肃省科技计划资助(23JRRA671)收稿日期:2023⁃05⁃20;㊀㊀网络出版日期:2024⁃01⁃12∗通讯作者Correspondingauthor.E⁃mail:liyl@lzb.ac.cnDOI:10.20103/j.stxb.202305201065程莉,李玉霖,宁志英,杨红玲,詹瑾,姚博.木本植物应对干旱胁迫的响应机制:基于水力学性状视角.生态学报,2024,44(7):2688⁃2705.ChengL,LiYL,NingZY,YangHL,ZhanJ,YaoB.Responsemechanismsofwoodyplantstodroughtstress:areviewbasedonplanthydraulictraits.ActaEcologicaSinica,2024,44(7):2688⁃2705.木本植物应对干旱胁迫的响应机制:基于水力学性状视角程㊀莉1,2,李玉霖1,2,3,∗,宁志英1,2,杨红玲1,2,詹㊀瑾1,2,姚㊀博1,21中国科学院西北生态环境资源研究院,兰州㊀7300002中国科学院大学,北京㊀1000493中国科学院西北生态环境资源研究院奈曼沙漠化研究站,通辽㊀028300摘要:干旱最显著的影响表现在区域尺度的森林死亡事件中,可以在短时间内杀死数百万棵树木㊂鉴于未来极端干旱事件的频率和强度可能随温度的升高而增加,迫切需要明确树木对干旱胁迫的响应对策以及衰退死亡机理,揭示木本植物在干旱环境中存活和死亡的生理机制,了解树木在未来气候下的适应机制,提高预测树木对干旱反应的准确性㊂在常用植物功能性状的基础上,重点纳入与植物水分运输能力及耐旱性相关的水力学性状,系统总结了:1)植物木质部水分运输的物理机制;2)植物应对干旱胁迫的水力响应过程:3)干旱胁迫下木本植物水分利用对策;以及4)干旱胁迫下木本植物衰退/死亡机理㊂最后,提出3个尚待解决的主要问题:1)加强纳入水力性状阐明植物对干旱胁迫的响应和调节机制;2)加强从全株植物的角度考虑植物不同组织性状间的关系;3)深入探究树木干旱致死机理㊂关键词:木本植物;干旱胁迫;水力性状;水分运输策略;干旱致死机理Responsemechanismsofwoodyplantstodroughtstress:areviewbasedonplanthydraulictraitsCHENGLi1,2,LIYulin1,2,3,∗,NINGZhiying1,2,YANGHongling1,2,ZHANJin1,2,YAOBo1,21NorthwestInstituteofEco⁃EnvironmentandResources,ChineseAcademyofSciences,Lanzhou730000,China2UniversityofChineseAcademyofSciences,Beijing100049,China3NaimanDesertificationResearchStation,NorthwestInstituteofEco⁃EnvironmentandResources,ChineseAcademyofSciences,Tongliao028300,ChinaAbstract:Themostnotableeffectsofdroughtaremanifestedinregional⁃scaleforestmortalityevents,whichcankillmillionsoftreesinashorttime,furtheraffectingregionalclimateandecosystemstructureandfunction.Giventhatthefrequencyandintensityofextremedroughteventsinthefuturemayincreasewithincreasingtemperature,itisurgenttoclarifytheresponsestrategiesoftreestodroughtstressandthemechanismsoftheirsurvivalanddeath,revealthephysiologicalmechanismofwoodyplantsinaridenvironment,understandtheadaptationmechanismoftreesinfutureclimates,andimprovetheaccuracyofpredictingtheresponseoftreestodroughtstress.Plantfunctionaltraitsrefertothemorphological,physiological,orphenologicalcharacteristicsofplantsattheindividuallevel,whichindirectlyaffecttheperformanceofplantsbydirectlyaffectingthegrowth,survivalorreproductionofplants,andatthesametimereflectthelong⁃termadaptationofplantstothegrowthenvironment.Plantfunctionaltraitsandtheirvariationregulationscanbeusedtoexplaintheadaptivemechanismandfunctionaloptimizationmechanismofplantstotheenvironment,andhelptopredicttheresponseoftreestodrought.Comparedwithcommonlyusedplantfunctionaltraits,hydraulictraitsmaybetterdescribetheresponseoftreestodroughtstress.Onthebasisofcommonplantfunctionaltraits,weincreasedthehydraulictraitswhicharerelatedtowatertransportcapacityanddroughttoleranceandsystematicallysummarized:1)thephysicalmechanismoflong⁃distancewatertransportinxylem;2)phasesofdroughtstressandtheresponseofplants;3)plasticityinplantfunctionaltraitsandwaterregulationstrategies:Isohydricregulationstrategyandanisohydricregulationstrategy,xylemefficiency⁃safetytrade⁃offstrategy,conservativewaterusestrategyandrisk⁃takingwaterusestrategy;and4)mechanismsofdrought⁃relatedmortality:hydraulicfailurehypothesis,carbonstarvationhypothesisandbioticagentshypothesis.Finally,threemainproblemswereputforwardtobesolved:1)strengtheningtheinclusionofhydraulictraitstoclarifytheresponseandregulationmechanismofplantstodroughtstress,understandingandpredictingplantsurvival,growth,distributionanddeathinthecontextofglobalchange.2)strengtheningtheconsiderationoftherelationshipbetweendifferentplanttissuetraitsfromtheperspectiveofthewholeplant,revealingthedistributioncharacteristicsofplantsintheecosystem,andpredictingcommunitycomposition;3)theprecisephysiologicalmechanismbehindtreedeathisstillunclear,futurestudiesneedtofurtherexplorethemechanismsofdrought⁃relatedmortality.KeyWords:woodyplants;droughtstress;hydraulictraits;waterregulationstrategies;drought⁃relatedmortalitymechanisms㊀自工业革命以来,不断增强的人类活动导致了全球变暖[1 2]㊂联合国政府间气候变化专门委员会(IPCC)评估报告表明,2011 2020年全球地表温度比1850 1900年高出1.1ħ,预计在2021 2040年全球升温或将达到1.5ħ㊂随着气温上升,未来干旱肯定会恶化(当自然干旱发生时,它们会来的更快,强度更大)[3]㊂较高的温度通常会导致更大的蒸散,与温度较低时相比,土壤和植物会更快的干燥[4]㊂这种 全球变化型干旱 已经对生态系统产生了严重影响,比如大量树木死亡[5 6]㊂区域尺度上的树木死亡事件改变了地表反照率以及地表⁃大气能量和潜热交换,对区域气候产生反馈[7];广泛的树木死亡事件有能力在十年以下的时间尺度内从根本上改变区域尺度的景观,对生态系统结构和功能产生重大影响[8]㊂在此背景下,我们必须提高预测树木对干旱反应的准确性,以了解树木在未来气候制度下的适应能力[9]㊂植物功能性状是指植物在个体水平上的形态㊁生理或物候特征,它们通过直接影响植物的生长㊁存活或繁殖,从而间接影响植物的性能[10 11],同时反映植物对生长环境的长期适应[12]㊂植物功能性状有助于预测树木对干旱的响应[12 13]㊂近30多年来,科研人员常使用植物功能性状及其变异规律来解释植物对环境的适应机制和功能优化机制㊂然而,随着研究的深入,人们逐步发现自然界生长的植物均是通过多个功能性状共同来完成其适应或功能优化,或者说任何一种功能均是通过多种功能性状来协同实现㊂准确量化这些多性状间的权衡和依赖关系,有助于我们更好地揭示植物的生境适应策略㊂然而,研究发现:1)常用植物功能性状的变异性与降水梯度并不一致,例如平均年降水量(Meanannualprecipitation,MAP)对全球尺度上自然生物群系比叶面积(Specificleafarea,SLA)变异的解释率不到1%;2)常用植物功能性状与干旱引起的树木死亡率的跨物种模式仅存在微弱的相关性,例如纳入SLA和木材密度(Wooddensity,WD)时,模型对物种死亡率的解释率从只考虑干旱的30%增加到37%[14]㊂相比之下,水力性状可能更好地描述树木对干旱胁迫的响应㊂近年来发现反映植物水分运输能力或植物耐旱性的水力性状如叶片的最大导水率(Kmax)㊁膨压消失点叶水势(Ψtlp)㊁水力安全边际(Hydraulicsafetymargin,HSM)等与降水梯度高度吻合[15 17]㊂因此纳入水力性状阐明植物对干旱的响应和调节机制,对于理解和预测全球变化背景下植物生存㊁生长㊁分布以及死亡有着重要意义㊂鉴于未来极端干旱事件的频率和强度可能随温度的升高而增加,迫切需要更好地了解植物对干旱胁迫的应对和调节机制以及不同植物的干旱致死机制,本文重点阐述了:1)植物木质部水分运输的物理机制;2)干旱胁迫下植物的水力响应过程;3)植物水分利用策略的多样性;以及4)植物干旱致死机理㊂9862㊀7期㊀㊀㊀程莉㊀等:木本植物应对干旱胁迫的响应机制:基于水力学性状视角㊀1㊀植物体内的水分传输与所有维管植物一样,木本植物通过一个复杂的中空死亡细胞(导管或管胞)管道系统,即木质部,将水分从土壤输送到叶片来防止干燥损伤[9]㊂植物木质部长距离水分运输是保证植物体内水分平衡㊁叶片气孔运动㊁光合作用以及其它各种代谢活动的主要纽带,被称为 植物生理学的支柱 [18]㊂综述植物体内木质部长距离水分运输过程,特别是了解防止植物蒸腾速率(E)超过临界速率(Ecrit)的结构和生理机制,有助于理解植物发生水力失败和碳饥饿的风险:1)临界蒸腾速率会导致与水力失败和共质体失败相关的木质部水势阈值(Ψcrit)的发生;2)此外,避免Ecrit(关闭气孔)对光合作用的影响以及随后对碳水化合物储备的影响对理解碳饥饿至关重要[19 20]㊂为了维持组织的水合和光合作用,植物必须补充蒸腾作用损失的水分[8]㊂内聚力⁃张力假说(C⁃T理论)认为,蒸腾拉力是水分沿木质部上升的主要驱动力,叶面的蒸腾拉力将土壤中的水分通过植物木质部长距离运输提升到冠层并扩散到大气中[8,21 22],这样从根系到叶片的水就能补充蒸腾作用损失的水分[23]㊂其中,蒸腾拉力(E)可以通过土壤⁃植物⁃大气水力连续体的稳态公式明确描述[8]:E=K1(Ψs-Ψleaf-hρwg)式中,E为叶片蒸腾拉力,K1为叶片水力导度,Ψs是土壤水势,Ψleaf是叶水势,hρwg是高度为h,密度为ρw的水柱的重力拉力㊂当E为0时,Ψleaf=Ψs(图1A,a点)㊂随着E的增加,当K1保持不变时,导管并未发生空穴化,植物体内的张力差(Ψs-Ψleaf)与E成正比,Ψleaf逐渐下降(图1左,虚线a b)㊂然而气种假说表明:木质部导管中的水柱在张力作用下处于亚稳定状态,导管中的亚稳态液流所承受的张力随E的增加而增加,此时空气经由木质部导管壁上的纹孔膜进入导管,导管开始发生空穴化,空穴化的发展逐渐加重木质部导管栓塞程度,K1逐渐下降㊂当E每增加一个单位时,由于K1的下降,会导致Ψleaf的下降逐渐增大(图1左,实线a c)㊂当E超过Ecrit时,木质部水势(Ψ)超过Ψcrit,则会发生水力失败㊂在干旱胁迫发生时,干旱降低了根区的Ψs,植物在E较低时便会发生水力失败(图1右,将实线a c和实线d e进行比较)㊂在昼夜尺度上,植物通过关闭气孔保持E低于Ecrit(植物通过降低气孔导度(Gs)来响应增加的E[24],气孔闭合程度与导致栓塞的Ψcrit有关[25])㊂减少Gs的好处是减少水分损失,但他的代价是减少二氧化碳(CO2)从大气扩散到羧基化位点,从而限制光合作用对CO2的吸收[20],这种水分流失和CO2吸收之间的平衡可能会在干旱期间导致植物出现生存㊁水力衰竭和碳饥饿三种结果㊂图1㊀基于达西定律模型求解的蒸腾拉力(E)与叶水势(Ψleaf)的变化Fig.1㊀Thetranspirationrate(E)versusleafwaterpotential(Ψleaf)isbasedonthemodelsolutionofDarcyᶄslawΨs是土壤水势;Ecrit是最大蒸腾速率,取决于Ψs;Ψcrit是Ecrit处的Ψleaf,也是允许水分吸收的最低Ψs2㊀植物应对干旱胁迫的水力响应过程植物应对干旱胁迫的响应过程主要分为两个阶段:1)干旱胁迫开始到气孔闭合期间;2)气孔闭合到木质0962㊀生㊀态㊀学㊀报㊀㊀㊀44卷㊀部完全栓塞期间[26]㊂在干旱期间,降水减少导致土壤湿度下降,这往往伴随着更高的温度和增加的大气蒸发需求,这些因素结合在一起引起植物的水分胁迫,导致植物Ψx下降(木质部水柱所受张力增加),因此植物关闭气孔以限制水分流失和延缓Ψx的下降㊂最近研究表明,尽管气孔关闭会造成一系列负面影响,但气孔仍旧会在木质部水势达到明显的气穴化形成阈值(气孔导度损失88%对应的水势值,thewaterpotentialat88%lossofstomatalconductance,Pgs88)之前关闭[26 28]㊂气孔关闭后,Ψx随着水分通过气孔渗漏[29]以及表皮和树皮等其他组织损失而继续缓慢下降,植物通过释放内部储存水来缓冲Ψx的下降[30]㊂与此同时,植物整个水力途径的水力导度通过一系列生物物理和生理机制而下降,比如叶脉的可逆塌缩[31]㊁细胞膜水通道蛋白调节[32]和细根皮层腔隙的形成[33]等㊂这一阶段的失水速率通常比气孔完全打开时低100 1000倍[29]㊂如果持续干旱,水势持续下降最终达到一个临界阈值(水力导度损失50%对应的水势值,thewaterpotentialat50%lossofhydraulicconductance,P50)时,栓塞开始在木质部中扩散[34 35],这一过程发生在包括植物根茎叶在内的整个水力系统中[36 37]㊂由于栓塞大大减少了向冠层的水分输送,这种水力功能障碍导致了分支斑块性死亡和冠层叶面积显著减少[38]㊂随着栓塞逐渐遍布整个输水网络,造成植物水力系统不可逆的损伤(水力导度损失80%对应的水势值,thewaterpotentialat88%lossofhydraulicconductance,P88),最终导致整株植株死亡㊂图2㊀植物对干旱胁迫的水力响应过程Fig.2㊀Phaseofdroughtresponsetodroughtstressinplants随干旱胁迫增加,虚线代表气孔和表皮导度变化趋势,实线代表木质部水力导度损失率;Pgs88代表气孔关闭时的水势;P50和P88分别代表水力导度下降50%和88%的水势3㊀植物水分运输策略的多样性植物功能性状对植物的建立㊁存活㊁生长和繁殖有很大影响,可以很好地表征植物的生长策略[39]㊂然而,在哪些性状可以用来评估生态耐旱性方面,我们的知识仍然有限㊂3.1㊀衡量植物抗旱性的性状3.1.1㊀压力⁃容积曲线(Pressure⁃volumecurve,简称P⁃V曲线)基于P⁃V曲线计算得到的参数(如膨压消失点叶水势(Ψtlp)㊁质壁分离时的相对含水量(RWCtlp)㊁饱和含水时的叶渗透势(π0)和细胞体积弹性模量(ε))在机制上均与耐旱性有关[40 41]㊂其中,Ψtlp代表了引起萎蔫的叶片和土壤的干燥程度[40],被认为是最直接量化植物耐旱性的 更高级别 的性状[42 43]㊂植物会改变其他P⁃V参数:1)渗透调节:积累溶质(减少π0);2)质外体调节:通过将更多的水重新分配到细胞壁外部来减少共质体水分(增加af);3)弹性调节:增加细胞壁的弹性(减少ε)以达到足够负的Ψtlp值[41 43],提高他们的耐1962㊀7期㊀㊀㊀程莉㊀等:木本植物应对干旱胁迫的响应机制:基于水力学性状视角㊀2962㊀生㊀态㊀学㊀报㊀㊀㊀44卷㊀旱性㊂然而,由于这些参数通常是同时调整的,因此他们在影响Ψtlp方面的相对重要性仍然存在争议㊂前人的研究表明,Ψtlp与干旱指数呈显著正相关,湿润地区的生物群系比干旱区的生物群系具有更小的负值,这支持了膨压消失点叶水势在木本生物群系尺度上反映耐旱性的观点㊂尽管大多数人认为负值较大的Ψtlp有利于耐旱性,但也有人提出了相反的观点,认为负值较小的Ψtlp是有益的㊂当Ψleaf下降时,负值较小的Ψtlp使叶片迅速失去膨压并关闭气孔,从而保持较高的RWCtlp㊂RWCtlp,也被认为是植物耐旱性的重要衡量标准㊂尽管大多数研究认为更负的Ψtlp有利于耐旱,一些研究则认为维持细胞水合比维持膨压更重要,因为脱水会导致细胞收缩,细胞壁结构损伤以及由于高离子浓度而产生的潜在渗透压,最终破坏代谢过程㊂除此之外,细胞总相对含水量低于75%时会严重抑制ATP,RUBP和蛋白质的产生[44]㊂Ψtlp和RWCtlp作为耐旱性预测因子的重要性经常受到争议,但没有得到解决㊂一个最近的meta分析表明Ψtlp而不是RWCtlp驱动物种与栖息地水分供应的关系[41]㊂3.1.2㊀木质部栓塞脆弱性曲线(Vulnerabilitycurves,简称VCs)木质部栓塞抗性是决定植物抗旱性的最重要性状之一,也是解释近年来干旱导致植物死亡的重要性状之一[45]㊂木质部栓塞抗性通常由VCs决定,该曲线描述了当Ψx降低时,水力导度丧失百分比(Precentlossofconductivity,PLC)如何增加㊂VCs可以提供有关特定植物干旱响应的有价值的信息,并已被用于量化植物抗旱性和生态适应性㊂例如,P50或P88以及水力安全范围被广泛用于量化抗旱性和水力失败的风险[46]㊂大量研究表明,当Ψx降到P50或P88以下后,Ψx很小的变化将引起水分传导速率大幅下降,树木也因此面临严重栓塞及死亡风险㊂P50是最常用的栓塞抗性指标㊂Lamy等对地中海松树的513种基因型的研究发现,气候差异明显的不同种群其P50的遗传和表型变异均有限,P50可能是松树固有特征[45]㊂但是关于栓塞脆弱性的遗传变异和表型可塑性的研究仅限于少数物种,仍需进一步的研究来确定这一结论是否在所有树种中适用㊂物种水平上,对栓塞抗性在木本种中种间变异的meta分析表明,不同树种木质部栓塞脆弱性存在巨大差异,植物木质部栓塞脆弱性与其生长环境的年平均降水量和干旱程度相关,来自干燥气候的物种比来自湿润气候的物种具有更大的P50值,对干旱的忍耐力越强[47 48]㊂然而在群落水平上,在较干燥的栖息地,植物脆弱性的变化往往很大,这表明脆弱性和干旱在某些情况下是解耦的[49]㊂这种解耦是因为一些物种所使用的水分胁迫规避策略,如深根系植物或干旱落叶,这些策略使得它们在干旱时期保持较高的Ψx[9]㊂具有系统发生学差异的植物,其致死的水势临界点(即木质部导水性不能再恢复)与P50或P88的关系有所差异㊂裸子植物中的水势临界点与P50具有很大正相关性,但被子植物的水势临界点却与P88有更高的相关度[9]㊂水力安全范围有2种计算方式:1)HSM:树种木质部最低水势(Ψmin)与栓塞抗性(P50或P88)的差值(即Ψmin-P50或Ψmin-P88),是预测树木干旱死亡率的关键指标[50]㊂HSM值越小,说明树种面临水力失败的风险越大,反之树种面临水力失败的风险越小[51]㊂然而,Choat等针对全球81个地点226种森林的研究结果发现,70%的森林在应对干旱胁迫时的HSM很窄(约<1MPa),安全边际在很大程度上与年降水量无关,森林对干旱的脆弱性存在全球趋同:所有森林生物群落无论当前的降雨环境如何,都同样容易遭受水力失败[48]㊂因为Ψmin集成了与环境相关的植物结构(例如,生根深度)和生理(例如,气孔行为)性状的许多重要方面,在不同森林类型中发现的狭窄水力安全边际为植物生态学提供了一个重要视角,这表明植物的水力策略是根据其环境进行微调的,允许最大限度的碳获得,但在干旱期间将植物暴露在水力失败的风险中[9]㊂这也表明了一种普遍存在的 有风险 的策略,即植物对环境的快速变化做出反应的生理潜力有限[9]㊂这加剧了气候变化下极端干旱事件增加所构成的威胁[9]㊂2)气孔安全边际(Stomatalsafemargin,SSM):气孔闭合时的水势(Pgs88)与抗栓塞能力(P50或P88)的差值(即Pgs88-P50或Pgs88-P88),用来反映树种的气孔调控策略[52],更直接地将气孔对水势的响应和木质部栓塞抗性结合起来㊂正的SSM表明气孔关闭发生在茎严重栓塞之前,而负的SSM表明气孔关闭发生在栓塞之后;SSM宽的物种的耐旱时间更长㊂有明确证据表明,等水和非等水植物的部分死亡和完全死亡与水力失败有关,这进一步凸显了气孔调节和木质部栓塞抗性之间协调的重要性㊂总的来说,气孔安全边际随着栓塞抗性的增加而持续增加,并且气孔安全边际与水力安全边际相关[53]㊂最重要的是,将气孔调节策略与木质部水力策略相结合有助于更全面地表达植物对干旱的适应[54]㊂3.1.3㊀非结构性碳水化合物(NSC)NSC包括淀粉和可溶性糖[55 56],在树木的抗旱性中发挥重要作用[57]㊂淀粉是一种长期的碳储存分子,它以一种紧凑的㊁不溶性的形式存在,允许植物在高光合速率的情况下储存碳水化合物㊂可溶性糖为植物提供能量和底物,同时也可充当中间代谢产物㊁信号分子或渗透物㊂植物通过光合作用将CO2固定为碳水化合物,然后用于呼吸㊁防御㊁生长㊁繁殖或在光合作用无法发生时(如夜间㊁休眠季节或环境压力时期)为植物提供能量储备[58]㊂在干旱胁迫下,NSC扮演着两种角色[59],缓冲了植物的碳供应不足[60 61]:1)作为 碳饥饿 的缓冲㊂在 碳饥饿 过程中,光合作用受到干旱胁迫,植物缓慢地消耗他们储存的碳水化合物直到死亡[8]㊂因此,生活在炎热和干燥气候中的植物比生活在潮湿气候中的植物分配更多的碳储存,作为应对干旱胁迫的保守缓冲[62]㊂2)作为渗透缓冲剂㊂当水分胁迫激活淀粉降解酶时,植物可以将不溶性淀粉转化回可溶性糖[63]㊂这种从淀粉到糖的转化可以降低植物的渗透势,从而在干旱期间维持细胞膨压[64 65]㊂因此,有人认为在干燥环境中进化或生长的植物将保持较高的NSC储存量,并保持更大比例的可溶性糖储存,以防止细胞失水,保持细胞稳定,在干旱条件下生存更长时间[41,66 68]㊂3.1.4㊀结构性状结构性状可以很好地反映不同树种面对干旱胁迫时的适应能力㊂比如,叶片厚度(Leafthickness,LT)与植物获取㊁利用资源的策略紧密相关㊂具有较高LT的植物可以增强蓄水能力,避免环境胁迫造成伤害㊂叶干物质含量(Leafdrymattercontent,LDMC)常用干重和鲜重的比值来表示,干旱地区的植物LDMC也较高,对环境胁迫有较强的抗性[69]㊂比叶重(Leafmassperunitarea,LMA)和叶密度(Leafdensity,LD)是表示干旱容忍能力的重要叶片功能性状,因为LMA较高和LD较高表明细胞壁较厚或者较密,从而能够较大程度地防止由于叶水势下降引起的变型诱导的损坏㊂LMA常用叶片单位面积的干物质量来表示[70]㊂LMA高的植物因其较强的碳同化能力能够更好地生长㊂干旱地区的植物通过提高比叶重来提高植物固持资源(碳㊁氮)的效率,从而提高竞争力㊂LD反映叶片的紧实程度及植物对外界干旱环境的忍耐能力㊂具有较高LD的植物通常适应于干旱的生境㊂通常LD高,则叶片细胞小且细胞壁较厚,能够高效积累渗透物质同时减少水分损失,从而减弱水分可利用性低对叶片造成的破坏㊂胡伯尔值(AL:AS)与WD都是物种对不同水分可利用环境进行水力调节的重要性状㊂AL:AS表征枝条对叶片的供水能力,反映蒸腾叶面积与茎输导供水之间的权衡[71 72]㊂低AL:AS可以避免蒸腾过程过度失水,促进叶片水平供水以适应干旱条件,降低水力紊乱的风险㊂WD常用植物对单位体积木材投资的生物量来表示,反应植物机械支撑㊁水分运输和生长速率[73]㊂低WD意味着储水能力较高,有利于木质部再充水而修复栓塞;高WD意味着较厚的导管壁或较丰富的机械组织,结构紧密,相应的导管面积较小㊂在干旱胁迫的环境中,植物通常具有较高的WD,保护木质部避免空穴化[72]㊂根系与土壤环境直接接触,负责吸收养分和水分,但由于其藏匿于地下,根系性状成为了植物对干旱响应的一个重要但被忽视的预测因子[74]㊂有关根系性状对干旱反应的数据仅限于少数几种植物[74]㊂因此,关于植物根性状响应策略的结论似乎很特殊,或者年代太久远[74]㊂例如,有研究报告称,一些植物种因干旱而产生更细的根,具有高比根长(Specificrootlength,SRL)和比根表面积(Specificrootsurfacearea,SRSA),这一策略被解释为以低投资改善水资源获取[75]㊂相比之下,其他研究报告称,植物种产生的根更粗,SRL和SRSA较低,这已被证明可以降低水力失败的风险[76]㊂更粗的根与通过真菌营养获得高养分和高水分有关[77 78],并与由于储存非结构性碳水化合物而产生的渗透调节有关[79]㊂植物性状有助于预测树木对干旱的响应[73]㊂相比于常用功能性状,现在已经出现了一套经过充分研究的与耐旱性机制相关的水力性状(表1),被寄予厚望用于预测植物对干旱胁迫的响应,这代表了未来研究的方向[9]㊂3962㊀7期㊀㊀㊀程莉㊀等:木本植物应对干旱胁迫的响应机制:基于水力学性状视角㊀表1㊀与树木耐旱性相关的植物水力性状列表Table1㊀Listofhydraulictraits(physiological,morphological,andanatomical)associatedwithdroughttoleranceintrees性状Trait性状描述Traitdescription参考文献References叶片Leaves气孔响应Stomatalresponse气孔闭合速率和敏感性对VPD和叶片水势变化[80 87]膨压消失点和渗透调节Turgorlosspoint&osmoticregulation叶片叶肉细胞失去膨压和叶片枯萎的水势,以及叶片叶肉细胞渗透含量的适应性调节[41,43,88 98]最小气孔导度Minimumstomatalconductance当气孔处于最小孔径时,叶片角质层的水分损失率[99 101]木质部外通路Extraxylarypathways液体和蒸汽通过叶肉和支持组织的阻力变化[102 104]叶脱落Leafshedding在干旱期间通过叶片脱落减少叶面积可以减缓干燥速度,减轻水分对剩余叶片的压力[87,105 106]气孔解剖结构Stomatalanatomy气孔的形状㊁大小和分布,影响失水相关的叶片生理性状[42,107]根系Roots皮层空腔形成Corticallacunaeformation根皮层细胞解体,使维管组织从表皮及周围干燥土壤分离[33,108 109]细根损失Finerootloss细根脱落,减少根系与土壤接触的总表面积,重新平衡根枝比[33,108 111]根系深度Rootingdepth深层根系生长,获得更稳定的水源[112 118]组织性状Traitsamongtissues栓塞脆弱性Vulnerabilitytocavitation木质部汁液的负压导致木质部最大水力导度损失50%或88%㊂如,裸子植物的生理临界点(P50);被子植物的生理临界点(P88)[47 48,100,119 138]水容Capacitance在木质部周围组织中储存的水分,可以缓冲导致空穴化事件的木质部汁液负液压[30,113,139 141]细胞膜通透性Cellmembranepermeability水通道蛋白的活性可以改变细胞膜的通透性,导致跨膜通路的水力导度降低[32,103,142 143]木质部解剖性状Xylemanatomicaltraits木质部导管尺寸㊁数量和连通性Xylemconduit木质部导管(管胞和导管)的直径㊁长度和连通性影响最大水力导度和空穴化脆弱性㊂[132,144 145]纹孔膜孔隙度/厚度Pitmembraneporosity/thickness纹孔膜解剖结构决定了木质部导管之间的空气传播阈值,并影响水力导度和空穴化脆弱性㊂[121 122,131,146 147]木材密度Wooddensity木材密度由木质部解剖性状决定,并与许多生理性状相关㊂[28,127,148]连接性Sectoriality维管组织的空间分离,防止栓塞在分支间扩散[149 154]㊀㊀VPD:饱和水汽压差Vaporpressuredeficit3.2㊀植物水分利用策略鉴于植物在异质环境中争夺空间㊁阳光㊁水和养分的策略多种多样,任何单一植物功能性状均不足以表征植物在干旱胁迫下的生存力,常需结合一系列形态功能性状㊁生理功能性状㊁生物化学功能性状来阐明植物的水分调节对策及机制,进一步揭示植物对气候变化的响应和适应[155]㊂3.2.1㊀等水和非等水调节策略1936年,Berger提出等水/非等水概念,基于叶片水势或者蒸腾来描述植物昼夜水分调节关系㊂在昼夜转换间,等水植物会在正午来临时,及时关闭气孔,维持较高的正午叶片水势㊂而非等水植物气孔则持续张开,保持水碳交换,故而正午叶片水势较低㊂近期,研究者将等水/非等水概念用于长期干旱条件下的水分管理[86]㊂即随着土壤水势的持续降低,等水植物的叶片水势会保持较高水平,然后缓慢降低,而非等水植物的叶片水势会持续降低㊂等水植物的叶片蒸腾随着土壤变干而迅速降低,而非等水植物则先缓慢降低而后加快4962㊀生㊀态㊀学㊀报㊀㊀㊀44卷㊀。
日专家尝试用纳米技术识别细胞培养物中的癌细胞
佚名
【期刊名称】《纳米科技》
【年(卷),期】2004(1)6
【摘要】最近,日本产业技术综合研究所四国中心的研究人员用被称为量子点的直径为数纳米的微粒,成功地识别出了细胞培养物中的癌细胞,并通过紫外线持续照射,杀死了与量子点结合的癌细胞。
据报道,研究人员用硒化铬合成了量子点,并用特殊试剂对量子点表面加以处理,使其能够与生物分子结合。
在实验中,专家用这种量子点与植物凝血素合为一体,而该凝血素能与某些癌细胞表面的特殊糖链结合。
【总页数】1页(P70-70)
【关键词】日本产业技术综合研究所四国中心;纳米技术;细胞培养物;癌细胞
【正文语种】中文
【中图分类】Q813.11;R730
【相关文献】
1.让血癌细胞"改邪归正"获进展/擅自延长试用期违法/专家开出健康食品和限食食品清单/令你自毁的十二种心理陷阱/樟脑丸可能成为"隐形杀手" [J],
2.细胞培养实验发现葡萄籽提取物对结肠癌细胞生长有抑制效果 [J], 红酒世界网
3.日研制传感器以纳米技术快速识别流感病毒 [J],
4.日本用纳米微粒识别出细胞培养物中的癌细胞 [J], 杨靖;
5.日专家尝试用纳米技术识别癌细胞 [J],
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第42卷第4期2021年4月发光学报CHINESE JOURNAL OF LUMINESCENCEVol.42No.4Apr.,2021文章编号:1000-7032(2021)04-0486-18全无机钙钛矿太阳能电池湿度稳定性和光热稳定性研究进展刘鲲鹏,刘德烨,刘凤敏*(吉林大学电子科学与工程学院集成光电子学国家重点实验室,吉林长春130012)摘要:近年来,钙钛矿太阳能电池因高效率、低成本等特点获得了持续的关注,但是有机成分在稳定性方面始终存在一些问题。
相比于有机-无机杂化钙钛矿太阳能电池,全无机钙钛矿材料可以很大程度上避免外界环境的影响,对氧环境要求低,对于湿度环境的容许度也比较大;由于自身结构,在光热稳定性方面,也要优于有机-无机杂化钙钛矿。
因此,发展全无机钙钛矿太阳能电池是有效提高钙钛矿太阳能电池稳定性的方向之一。
本文从稳定性方面入手,系统地介绍了全无机钙钛矿太阳能电池的最新研究进展。
结合全无机钙钛矿太阳能电池稳定性的影响因素,总结了当前全无机钙钛矿电池稳定性问题的主要解决方案,最后对解决全无机钙钛矿材料的稳定性进行了展望。
关键词:全无机钙钛矿;太阳能电池;稳定性中图分类号:TM914.4;TH691.9文献标识码:A DOI:10.37188/CJL.20200343Research Progress in Humidity Stability andLight-thermal Stability of All-inorganic Perovskite Solar CellsLIU Kun-peng,LIU De-ye,LIU Feng-min*(State Key Laboratory of Integrated Optoelectronics,College of Electronic Science and Engineering,Jilin University,Changchun130012,China)*Corresponding Author,E-mail:liufm@Abstract:In recent years,perovskite solar cells have received continuous attention due to their high efficiency and low cost,but there are problems in the stability of organic pared with organic-inorganic hybrid perovskite solar cells,all-inorganic perovskite materials can avoid the influence of the external environment,with low requirements for oxygen environment and relatively high tolerance for humidity environment.Due to its own structure,it is also superior to organic-inorganic hybrid perovskite in terms of photothermal stability.Therefore,the development of perovskite solar cells is one of the directions to effectively improve the stability of perovskite solar cells.In this paper,the latest progress in the study of all-inorganic perovskite solar cells is systematically introduced from the aspect of bined with the influencing factors of the stability of all-inorganic perovskite solar cells,the main solutions to the current stability problems of all-inorganic perovskite solar cells are summarized,and the prospects for the stability of all-inorganic perovskite solar cells are given.Key words:all-inorganic perovskite;solar cells;stability收稿日期:2020-11-10;修订日期:2021-01-13基金项目:吉林省省校共建项目(SXGJXX2017-3)资助Special Project of the Province-U niversity Co-constructing Program of Jilin Province(SXGJXX2017-3)第4期刘鲲鹏,等:全无机钙钛矿太阳能电池湿度稳定性和光热稳定性研究进展4871引言近年来,钙钛矿材料由于具有光吸收系数高、载流子迁移率大、发光波长可调等优点,被认为是最有应用前景的光电材料之一,通常是abx3结构[1-3]0基于钙钛矿材料的太阳能电池是一种新型高效的光电器件,与传统的第一代硅基太阳能电池和第二代砷化掾太阳能电池相比,钙钛矿太阳能电池具有高效率、低成本、柔性、易制备等优点[4-"]o2009年,日本Kojima等[12]将MAPbI3和MAPbBr3应用于染料敏化太阳能电池,其光电转化效率为3.8%,打开了钙钛矿太阳能电池研究的大门。
细胞周期关卡调控与细胞癌变
范祖森;敖世洲
【期刊名称】《自然杂志》
【年(卷),期】1999(021)001
【总页数】4页(P8-11)
【作者】范祖森;敖世洲
【作者单位】中国科学院上海生物化学研究所分子生物学国家重点实验;中国科学院上海生物化学研究所分子生物学国家重点实验
【正文语种】中文
【中图分类】R329.2
【相关文献】
1.细胞周期关卡基因与细胞癌变 [J], 洪宝;高世勇;季宇彬
2.细胞周期调控的分子机制与关卡调控 [J], 李鹂;黄衡宇
3.细胞周期素D与细胞癌变 [J], 高鹏
4.ALA-PDT对SW480结肠癌细胞周期阻滞作用及对G_1/S关卡调控因子的影响[J], 肖卫东;陈炜;葛海燕;陈祖林
5.关于“ALA-PDT对SW480结肠癌细胞周期阻滞作用及对G1/S关卡调控因子的影响.世界华人消化杂志 2004;12(5): 1048-1052”一文中作者出生年份的更正[J], 肖卫东
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芝麻种子中内源性蛋白酶的热稳定性及其运用廖小微;陈业明【期刊名称】《农业工程学报》【年(卷),期】2022(38)12【摘要】近年来,芝麻的深加工偏重于制油,而忽略了对芝麻蛋白的高值利用。
为了实现芝麻蛋白与油脂的高值综合利用,该研究将湿法脱皮芝麻进行干燥,经压榨制取芝麻油和压榨粕后,再利用内源性蛋白酶对芝麻压榨粕中的蛋白质进行水解,制取蛋白水解物。
在此过程中,考察了干燥温度对湿法脱皮芝麻压榨出油率和内源性蛋白酶活性的影响。
结果显示,在80~180℃干燥1 h时,脱皮芝麻出油率上升至88.55%~90.98%(带皮芝麻为81.76%);对于内源性蛋白酶而言,在130℃时,仍可保留约57%的活性,表明芝麻种子中内源性蛋白酶具有良好的热稳定性。
同时,通过将低变性芝麻粕(干燥条件为50℃、4 h)制浆,在pH值为4.5、50℃下孵育6 h,经3000 g离心5 min后,分离得到透明清液(蛋白水解物),其清液中蛋白质的分布率为66%,且主要由38%小肽(<1500 Da)和37%游离氨基酸组成,除此之外,还存在多种生物活性物质。
该研究为芝麻内源性蛋白酶的实际应用以及芝麻蛋白新产品的开发提供了一种新思路。
【总页数】7页(P301-307)【作者】廖小微;陈业明【作者单位】江南大学食品学院【正文语种】中文【中图分类】TS210.4;TS229【相关文献】1.内源性蛋白酶在宰后猪肉成熟过程中的作用2.基质金属蛋白酶-9及其内源性抑制因子-1在脓毒症致多器官功能障碍综合征中的意义3.利用芝麻内源性蛋白酶破乳的影响因素探究4.葵花籽粗油体中内源性蛋白酶系的性质探究以及鉴定5.芝麻素在芝麻种子亚细胞结构中的分布因版权原因,仅展示原文概要,查看原文内容请购买。
国际互联网上天然沸石信息资源
关毅;田健;等
【期刊名称】《现代技术陶瓷》
【年(卷),期】2000(021)004
【摘要】本文主要介绍了INTERNET上与天然沸石有关的化学化工信息资源,并且初步讨论国际互联网和国内互联网上天然沸石信息量。
【总页数】4页(P38-41)
【作者】关毅;田健;等
【作者单位】天津大学化工学院
【正文语种】中文
【中图分类】G354
【相关文献】
1.铷、钾在树脂及天然斜发沸石上的吸附行为研究 [J], 赵旭;郝晓翠;董泽亮;张文燕;宋达;张琦;黄西平
2.INTERNET上天然沸石信息资源述论 [J], 关毅;贺岩峰;韩森
3.天然沸石农业利用研究Ⅱ天然沸石对提高化肥利用率的影响 [J], 周宝库
4.天然沸石改良苏打盐碱土吸附机理的探讨——Ⅰ.天然沸石对苏打盐碱土中主要盐分吸附规律的研究 [J], 仲秀珍;吴江
5.国际互联网络上的信息资源和信息服务 [J], 姜爱蓉
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Management of singlet and triplet excitons for efficient white organic light-emitting devicesYiru Sun 1,Noel C.Giebink 1,Hiroshi Kanno 1,Biwu Ma 2,Mark E.Thompson 2&Stephen R.Forrest 1†Lighting accounts for approximately 22per cent of the electricity consumed in buildings in the United States,with 40per cent of that amount consumed by inefficient (,15lm W 21)incandescent lamps 1,2.This has generated increased interest in the use of white electroluminescent organic light-emitting devices,owing to their potential for significantly improved efficiency over incandescent sources combined with low-cost,high-throughput manufactur-ability.The most impressive characteristics of such devices reported to date have been achieved in all-phosphor-doped devices,which have the potential for 100per cent internal quantum efficiency 2:the phosphorescent molecules harness the triplet excitons that constitute three-quarters of the bound elec-tron–hole pairs that form during charge injection,and which (unlike the remaining singlet excitons)would otherwise recombine non-radiatively.Here we introduce a different device concept that exploits a blue fluorescent molecule in exchange for a phosphorescent dopant,in combination with green and red phosphor dopants,to yield high power efficiency and stable colour balance,while maintaining the potential for unity internal quantum efficiency.Two distinct modes of energy transfer within this device serve to channel nearly all of the triplet energy to the phosphorescent dopants,retaining the singlet energy exclusively on the blue fluorescent dopant.Additionally,eliminating the exchange energy loss to the blue fluorophore allows for roughly 20per cent increased power efficiency compared to a fully phosphorescent device.Our device challenges incandescent sources by exhibiting total external quantum and power efficien-cies that peak at 18.760.5per cent and 37.660.6lm W 21,respectively,decreasing to 18.460.5per cent and 23.860.5lm W 21at a high luminance of 500cd m 22.Electrophosphorescent organic light-emitting devices (OLEDs)have been shown to harvest 100%of the excitons generated by electrical injection,corresponding to a fourfold increase in efficiency compared to that achievable in singlet-harvesting fluorescent OLEDs 3.In this context,electrophosphorescent white OLEDs (WOLEDS)have been reported to exhibit 4–7high quantum (5–12%)and luminous power efficiencies (6–20lm W 21)at bright-nesses ,100cd m 22.To date,however,blue electrophosphorescent devices have exhibited short operational lifetimes 8that limit the colour stability of all-phosphor-doped WOLEDs.Also,compared with their fluorescent counterparts,WOLEDs employing phosphor-escent blue dopants excited via the conductive host introduce an approximately 0.8eV exchange energy loss in power efficiency.This results from the energetic relaxation following intersystem crossing into the emissive triplet state.This loss can be avoided by resonant injection from the hole transport layer (HTL)and electron transport layer (ETL)into the phosphor triplet state 6,9,but the subsequent transfer to green and red dopants required to generate white light canreintroduce these parasitic energy losses.Here we demonstrate a new WOLED architecture that uses a fluorescent emitting dopant to harness all electrically generated high energy singlet excitons for blue emission,and phosphorescent dopants to harvest the remainder of lower-energy triplet excitons for green and red emission.This structure takes advantage of the fortuitous connection between the proportion of singlets dictated by spin statistics (that is,one singlet versus three triplets are produced by electrical exci-tation 10)and the roughly 25%contribution of blue to the perceived white light spectrum.This allows for resonant energy transfer from both the host singlet and triplet energy levels that minimizes exchange energy losses,thereby maximizing device power efficiency while maintaining the potential for unity internal quantum efficiency (IQE).This approach has the further advantages of a stable white balance with current,a high efficiency at high brightness due to reduced geminate exciton recombination 11,and an enhanced lifetime due to the combined use of a stable fluorescent blue,and long lived phosphorescent green and red,dopants in a single emissive region.The WOLED consists of a blue fluorophore,4,40-bis(9-ethyl-3-carbazovinylene)-1,10-biphenyl (BCzVBi)12,doped in a region spatially separate from the highly efficient green and red phosphor-escent dopants fac-tris(2-phenylpyridine)iridium (Ir(ppy)3)and iridium(III )bis(2-phenyl quinolyl-N,C 20)acetylacetonate (PQIr),respectively.All lumophores are doped into a single,common conductive host,4,40-bis(N-carbazolyl)biphenyl (CBP),to form the extended emissive layer (EML)which is sandwiched between the electron transporting/hole blocking layer of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),and the 4,40-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (a -NPD)HTL.The principle of device operation is illustrated in Fig.1.Excitons are formed on the host with a singlet-to-triplet formation ratio ofx s /x t .Singlet excitons are transferred following a resonant Fo¨rster process onto the lightly doped (5%)blue fluorophore as opposed to direct trap formation 12.The non-radiative host triplets,however,cannot efficiently transfer to the fluorophore by the Fo¨rster mecha-nism,or by Dexter transfer owing to the low doping concentration.On the other hand,triplets typically have long diffusion lengths 10(,100nm),and hence can migrate into the centre of the EML where they transfer onto the phosphors.Resonant transfer of the host triplet onto the green phosphor avoids exchange energy losses at this stage,although there are some unavoidable losses in transferring into the lowest energy red phosphor.Finally,placing an undoped host spacerwith a thickness larger than the Fo¨rster radius (,3nm)between the blue fluorophore and the phosphors prevents direct energy transfer from the blue dopant to the green and red phosphors.This device architecture is unique in that the singlet and triplet excitons are harvested along completely independent channels,and hence the transfer from host to dopant for both species can be separatelyLETTERS1Department of Electrical Engineering,Princeton Institute for the Science and Technology of Materials (PRISM),Princeton University,Princeton,New Jersey 08544,USA.2Department of Chemistry,University of Southern California,Los Angeles,California 90089,USA.†Present address:Department of Electrical Engineering and Computer Science,Department of Physics,and Department of Materials Science and Engineering,University of Michigan,Ann Arbor,Michigan 48109,USA.optimized to be nearly resonant,thereby minimizing energy losses while maintaining a unity IQE.Figure 2provides evidence for this transfer mechanism by com-paring the un-normalized electroluminescent spectra of three devices at a current density of J ¼100mA cm 22.Device I has a 16-nm-thick CBP spacer placed between the two 5-nm-thick 5wt%BCzVBi:CBP layers at each side of the EML,whereas device II has a 25-nm-thick uniformly doped 5wt%BCzVBi:CBP EML.Both devices have nearly identical emission spectra and external quantum efficiencies (EQE)of h ext ¼(2.6^0.2)%,indicating that ostensibly 100%of the exciton formation occurs at the edges of the EML.Furthermore,lack of short wavelength CBP emission in device I suggests that the charge density in the middle region of EML available for exciton formation directly on the host is negligible.When a 20-nm-thick 3wt%Ir(ppy)3:CBP layer is inserted in the EML and separated from the two 5wt%BCzVBi:CBP regions by 4-nm-thick undoped CBP spacers (device III),the total efficiency is increased to h ext ¼(5.2^0.2)%,with the additional 2.6%emission coming from Ir(ppy)3.From this we conclude that exciton diffusion from the point of origin at the edges of the EML,rather than direct charge trapping and exciton formation on the phosphor,dominates,because carriers trapped by Ir(ppy)3would result in a noticeable decrease in the BCzVBi emission.Triplet diffusion from the edges of the EML to the phosphorescent doped region is consistent with previous observations in red fluorescent/phosphorescent OLEDs,where the fluorophore ‘filters’out the singlet excitons,leaving only triplets to diffuse to a spatially separated phosphor doped region 3.To determine whether the location of the exciton formation region is predominantly at either the HTL/EML or EML/ETL inter-face,we compared the emission from two comparable devices with opposite symmetries,where the structure consisted of either NPD (30nm)/5wt%BCzVBi:CBP (10nm)/CBP (20nm)/BCP (40nm),or NPD (30nm)/CBP (20nm)/5wt%BCzVBi:CBP:(10nm)/BCP (40nm).The corresponding maximum efficiencies of these deviceswere h ext ¼(1.4^0.1)%and (1.8^0.1)%,both smaller than h ext ¼(2.6^0.2)%for device II.Moreover,CBP emission at a peak wavelength of l ¼390nm is observed in the first device,and a -NPD emission at l ¼430nm is observed in the second structure.These observations suggest that excitons are generated at both the HTL/EML and EML/ETL interfaces,consistent with the ambipolar conductivity of CBP 13,14.Exciton formation at the edges,with correspondingly low generation in the bulk of the EML,can be understood as follows:large densities of holes (p )and electrons (n )pile up at the energy barriers at two EML interfaces.The exciton formation probability,which is ,n £p ,is thus also significantly higher at these locations as compared with the EML bulk.On the basis of these results,WOLEDs were fabricated by doping the middle region of the EML with both the green and red phos-phorescent dopants (Fig.3a,inset).As the high energy of the highest occupied molecular orbital of PQIr suggests that it can trap holes in the CBP host,a slight decrease of the blue emission intensity is observed in the WOLED.Fitting of the WOLED spectrum in Fig.3b with the individual dopant spectra suggests that the ratio of emission from fluorescent to phosphorescent dopants approaches the ratio of 1/3,consistent with the singlet-to-triplet exciton formation ratio in emissive organic materials 10,15,16.Furthermore,given the perform-ance characteristics of the purely fluorescent BCzVBi device (device II in Fig.2),we also find that the fraction of excitons trapped by,and formed directly on,the phosphorescent dopants in the EML is x trap ¼(18^5)%(see Methods).That is,approximately 20%of the excitons are formed by direct trapping on the phosphor dopants,whereas the remaining 80%are formed at the edges of the EML,at which point the triplets subsequently diffuse into the centre where they are transferred from host to phosphor dopant before emission.A maximum forward viewing EQE of h ext ¼(11.0^0.3)%is achieved at a current density J ¼(1.0^0.6)mA cm 22,and decreases only slightly to h ext ¼(10.8^0.3)%at a high forward viewing luminance of 500cd m 22(Fig.3a).This device gives a maximum forward viewing power efficiency of h p ¼ð22:1^0:3ÞlmW 21.As illumination sources are generally characterized by theirtotalFigure 1|Proposed energy transfer mechanisms in the fluorescent/phosphorescent WOLED.This illustrates the separate channels for triplet (T)and singlet (S)formation and transfer directly onto their corresponding emissive dopants.The majority of excitons are formed in the host material with a singlet-to-triplet formation ratio of x s /x t .The singlet excitons in the two formation regions at each side of the light emitting layer (EML)are rapidly,and near-resonantly,transferred to the blue fluorescent dye located in these regions.The phosphor-doped region is located in the centre of the EML and separated from the exciton formation zones by spacers of undoped host material.The triplets then diffuse efficiently to the central region,where they transfer to the lower energy green or red phosphor dopants,again by a nearly resonant process to the green dopant triplet manifold,and with some energy loss to the red triplet.Diffusion of singlet excitons to the phosphor dopants is negligible due to their intrinsically short diffusion lengths 23.Parasitic effects of charge trapping onto the phosphorescent dopants are discussed in thetext.Figure 2|Un-normalized electroluminescence spectra of three device structures shown in the inset.The spectra were measured at a current density of 100mA cm 22.Inset,schematic cross-section of the device;see text for definitions of abbreviations used.X ¼CBP (16nm)for device I;X ¼5wt%BCzVBi:CBP (15nm)for device II;X ¼CBP (4nm)/3wt%Ir(ppy)3:CBP (20nm)/CBP (4nm)for device III.Quantitative comparison of the three spectra suggests that excitons are primarily formed at the two interfaces,and that fluorescent doping across the entire emission layer does not increase the blue luminescence intensity (compare devices I and II).However,doping the middle of the EML with the phosphor Ir(ppy)3results in additional green emission without a corresponding decrease in blue,BCzVBi emission (devices I and III),indicating that triplets formed on CBP are efficiently transferred to Ir(ppy)3,whereas the BCzVBi acts to harvest,or ‘filter out’,all of the singlets.NATURE |Vol 440|13April 2006LETTERSemitted power,this device therefore has maximum total efficiencies 6of h p,t ¼(37.6^0.6)lm W 21,and h ext,t ¼(18.7^0.5)%.At a practical surface luminance of 500cd m 22,h p,t ¼(23.8^0.5)lm W 21,or approximately 50%greater than for common incandescent lighting.Although the commercially available blue fluorophore has a low h ext ¼2.7%(compared with a maximum expected 5%achieved in the literature),the WOLED performance,nevertheless,represents a considerable improvement over the best all-phosphorescent devices previously reported 6,7,17(see Supplementary Information).The intrinsic singlet-to-triplet ratio and the separation of thechannels in harvesting the two excitonic species gives a well-balanced and largely current-independent colour rendition,resulting in a colour rendering index of CRI ¼85at all current densities studied,which is the highest CRI among the reported values for a WOLED.The Commission Internationale d’Eclairage (CIE)coordinates have a negligible shift from (0.40,0.41)at 1mA cm 22to (0.38,0.40)at 100mA cm 22.This differs from observations of an all-phosphor-doped WOLED,where blue emission becomes stronger with increas-ing driving voltage 6owing to the requirement for high energy excitation of the blue phosphor.In the inset of Fig.3b are images of three devices,each driven at 4times higher drive current than the device above it in the array,to show the colour stability of the emission.To further understand exciton diffusion,in Fig.4a we plot (open circles)h ext due to Ir(ppy)3emission versus the position (x )of a thin (5nm)slab of 5wt%Ir(ppy)3:CBP located at various distancesfromFigure 3|Performance characteristics of the fluorescent/phosphorescent WOLED.a ,Forward viewing external quantum efficiency (filled squares)and power efficiency (open circles)versus current density of the WOLED shown in the inset.The forward viewing external quantum efficiency peaks at h ext ¼(11.0^0.3)%at J ¼(1.0^0.6)mA cm 22,and decreases slightly to h ext ¼(10.8^0.3)%at a forward viewing luminance of 500cd m 22.The maximum forward viewing power efficiency is h p ¼(22.1^0.3)lm W 21,with total peak and high luminance efficiencies of h p,t ¼(37.6^0.6)and (23.8^0.5)lm W 21at 500cd m 22,respectively.The forward viewingluminance at 1A cm 22is (83,000^7,000)cd m 22.The drive voltage for this device is (6.0^0.5)V at J ¼10mA cm 22.Inset,schematic structure of the WOLED with the following layer thicknesses:b 1¼15nm,b 2¼10nm,r ¼8nm,g ¼12nm,and with an electron transport layer (ETL)consisting of 20-nm 4,7-diphenyl-1,10-phenanthroline (BPhen)followed by 20-nm Li doped BPhen in 1:1molar ratio.Here,BPhen is used to further reduce device drive voltage.When 40-nm BCP is used as ETL and b 1¼10nm,b 2¼10nm,r ¼12nm and g ¼8nm,h ext and CRI are nearly identical to the above structure.b ,Normalized electroluminescence spectra of WOLED emission at various current densities.Note that colour dependence on current density is minimal,with CRI ¼85at all three values of current density.Inset,images of three,4.5mm 2devices,each driven at four times the drive current (from 1.7to 28mA cm 22)of the device above it in the array (equivalent to a two f-stop difference in illumination)to show the colour stability of theemission.Figure 4|Triplet diffusion profile and reduced efficiency roll-off at high currents.a ,External quantum efficiency (open circles)from Ir(ppy)3emission at 10mA cm 22versus distance between the 50-A˚slab of 5wt%Ir(ppy)3:CBP and the NPD/CBP interface in the structure shown inset.A fit following equation (2)for triplet diffusion gives the solid curve and atriplet diffusion length of L D ¼(460^30)A˚.The error bars indicate the standard deviations in measurement.Inset,schematic cross-section of the test structures:NPD (30nm)/CBP (x nm)/5wt%Ir(ppy)3:CBP (5nm)/CBP ((2002x )nm)/BCP (40nm),with x ¼0,50,100,150,200.b ,Comparison of external quantum efficiency roll-off.Open circles depict theperformance of the all-phosphor white device of ref.6,in comparison to the white device of this work (squares),and a blue fluorescent BCzVBi device (triangles).The high current roll-off of the phosphor device is described by triplet–triplet annihilation (fit shown as solid line),yielding an onset current density J 0¼(50^4)mA cm 22.The device of this work clearlydemonstrates a roll-off that appears qualitatively similar to that of the all-fluorescent device.For comparison,J 0¼(360^10)mA cm 22and J 0¼(1,440^10)mA cm 22for the WOLED of this work and the all-fluorescent device,respectively.LETTERSNATURE |Vol 440|13April 2006the HTL/EML interface within a200-nm-thick CBP EML(see Fig.4a inset).Fitting(solid curve,see Methods)of the efficiency versus x yields a triplet diffusion length of L D¼(460^30)A˚,and predicts that(75^5)%of the phosphorescent emission results from triplet exciton diffusion from the adjacent EML interfaces,in agreement with the value calculated from analysis of the spectral content of the emission.Compared with previous all-phosphor,high efficiency WOLEDs, the device also has a less pronounced efficiency roll-off at high current densities.For example,in Fig.4b we show a comparison of h ext versus J for an all-phosphor white device6,the device of this work,and afluorescent BCzVBi device II.The high-current decline in h ext of the all-phosphor white is due to triplet–triplet annihil-ation14,18.In contrast,there is a striking resemblance between the efficiency roll-off of the current device,and that of device II. Modelling of the roll-offs in these two structures is complicated by recombination processes such as exciton–polaron quenching11,sing-let–triplet annihilation,andfield-induced exciton dissociation. Nevertheless,for both of these latter devices,the current density at the point where h ext has declined by half from its peak is.7times that of the conventional phosphor device,while the peak EQE occurs at a value of J nearly1,000times larger.The apparent absence of triplet–triplet annihilation suggests that the highest density of triplet excitons is at the interfaces in thefluorescent doped regions,where they subsequently diffuse towards the centre,thereby lowering the local density(Fig.4a)in the region of the guest phosphors.The reduced sensitivity of h ext to current density is another clear difference between the WOLED of this study and previous,high efficiency all-phosphor devices.We note that the efficiency of the present device can be further improved by usingfluorescent dopants19with IQE¼25%and phosphors20,21with IQE¼100%,resulting in a total WOLED internal quantum efficiency of100%.Using such‘ideal’chromo-phores,whose spectra are the same as the current dopants used,an approximately34%total EQE and60lm W21power efficiency can in principle be achieved using this structure,corresponding to a four-fold increase over incandescent power efficiency,and even competing with high efficiency,high CRIfluorescent lighting sources.As noted above,the exchange energy difference between the host singlet and dopant triplet states can lead to a loss of luminance efficiency in all-phosphor doped WOLEDs.By applying this design concept to systems where the host singlet is resonant with the bluefluorophore singlet state,and the host triplet is resonant with the green phosphor triplet level,this structure could have a power efficiency improve-ment of,20%compared to similarly ideal all-phosphor devices.The highly efficient WOLED structure reported here,with a colour rendition that is unusually independent of current density,has potential for use in the next generation of sources for solid-state indoor lighting.METHODSDevice manufacture.Devices were grown on clean glass substrates pre-coated with a150-nm-thick layer of indium tin oxide(ITO)with a sheet resistance of 20Q per square.All organic layers were grown in succession without breaking vacuum(,1027torr).After organicfilm deposition,a shadow mask with 1-mm-diameter openings was affixed in a N2filled glove box before the cathode (consisting of8-A˚-thick LiF),followed by a500-A˚-thick Al cap,was deposited by high vacuum(1026torr)thermal evaporation.Current–voltage and EQE measurements were carried out using a semiconductor parameter analyser (HP4145)and a calibrated Si photodiode(Hamamatsu S3584-08)following standard procedures22.Data analysis.To interpret the emission spectrum,the WOLED EQE is expressed as:h ext¼ð12x trapÞh Bþ½ð12x trapÞx tþx trap h GRð1Þwhere h B and h GR are respectively the EQEs of a singly doped bluefluorescent device and the comparable singly doped green and red phosphorescent devices, and x trap is the fraction of excitons trapped and formed directly on the phosphorescent dopants in the EML.Byfitting the WOLED spectrum in Fig.3b at J¼100mA cm22with the electroluminescence spectra of the three individual dopant materials,and accounting for photon energy in these power spectra,wefind that(20^2)%of the total quantum efficiency is due to emission from the bluefluorescent dopant,and(80^2)%is from green and red phosphorescent dopants.Given the performance characteristics(h B)of the purely BCzVBi device(device II in Fig.2),we calculate x trap¼(18^5)%from thefirst term in equation(1).Modelling.Exciton diffusion through the EML is modelled as shown in Fig.4a (solid line)as follows:in steady state,and assuming that all singlet formation occurs at the HTL/EML(x¼0),and EML/ETL interfaces(x¼200nm)(in Fig.4a),a solution to the triplet diffusion equation gives:nðxÞ¼1sinh LL Dx t n R sinh xL Dþx t n L sinhL2xL Dþx s n L dðxÞþx s n R dðx2LÞð2Þwhere n is the total exciton density:n(x¼0)¼n L and n(x¼L¼200nm)¼x¼L¼200nm)¼n R,L D is the triplet diffusion length,and the delta function terms account for the presence of contributing singlets at the interfaces.As the EQE from Ir(ppy)3emission is proportional to the exciton density in the Ir(ppy)3-doped slab,Fig.4a(solid curve)shows thefit of the efficiency at J¼10mA cm22versus x using equation(2)and x t¼3x s,from which we infer L D¼(460^30)A˚(error bars account for the spread infits at additional current densities).With this calculated diffusion length,integration of the total exciton density in the phosphorescent doped region in the WOLED predicts that(75^5)%of the phosphorescent emission results from triplet exciton diffusion from the adjacent EML interfaces,in agreement with the value calculated from analysis of the spectral content of the emission(equation(1)).Received19June2005;accepted13February2006. 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