Alternative search strategies for a BSM resonance fitting the ATLAS diboson excess

We study an s-channel resonance R as a viable candidate to fit the diboson excess reported by ATLAS. We compute the contribution of the similar to 2 TeV resonance R to semileptonic and leptonic final states at the 13 TeV LHC. To explain the absence of an excess in the semileptonic channel, we explore the possibility where the particle R decays to additional light scalars X, X or X, Y. A modified analysis strategy has been proposed to study the three-particle final state of the resonance decay and to identify decay channels of X. Associated production of R with gauge bosons has been studied in detail to identify the production mechanism of R. We construct comprehensive categories for vector and scalar beyond-standard-model particles which may play the role of particles R, X, Y and find alternate channels to fix the new couplings and search for these particles.

Future collider signatures of the possible 750 GeV state

If the recent indications of a possible state I broken vertical bar with mass similar to 750 GeV decaying into two photons reported by ATLAS and CMS in LHC collisions at 13 TeV were to become confirmed, the prospects for future collider physics at the LHC and beyond would be affected radically, as we explore in this paper. Even minimal scenarios for the I broken vertical bar resonance and its gamma gamma decays require additional particles with masses . We consider here two benchmark scenarios that exemplify the range of possibilities: one in which I broken vertical bar is a singlet scalar or pseudoscalar boson whose production and gamma gamma decays are due to loops of coloured and charged fermions, and another benchmark scenario in which I broken vertical bar is a superposition of (nearly) degenerate CP-even and CP-odd Higgs bosons in a (possibly supersymmetric) two-Higgs doublet model also with additional fermions to account for the gamma gamma decay rate. We explore the implications of these benchmark scenarios for the production of I broken vertical bar and its new partners at colliders in future runs of the LHC and beyond, at higher-energy pp colliders and at e (+) e (-) and gamma gamma colliders, with emphasis on the bosonic partners expected in the doublet scenario and the fermionic partners expected in both scenarios.

Searches for new symmetries in pp collisions with the razor kinematic variables at √s = 7 TeV

The construction and LHC phenomenology of the razor variables M_R, an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the transverse momentum imbalance of events and missing transverse energy, are presented.  The variables are used  in the analysis of the first proton-proton collisions dataset at CMS  (35 pb^-1) in a search for superpartners of the quarks and gluons, targeting indirect hints of dark matter candidates in the context of supersymmetric theoretical frameworks. The analysis produced the highest sensitivity results for SUSY to date and extended the LHC reach far beyond the previous Tevatron results.  A generalized inclusive search is subsequently presented for new heavy particle pairs produced in √s = 7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb^-1 of integrated luminosity from the second LHC run of 2011.  The selected events are analyzed in the 2D razor-space of M_R and R and the analysis is performed in 12 tiers of all-hadronic, single and double leptons final states in the presence and absence of b-quarks, probing the third generation sector using the event heavy-flavor content.   The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number or shape of event yields relative to Standard Model predictions. Exclusion limits are derived in the CMSSM framework with  gluino masses up to 800 GeV and squark masses up to 1.35 TeV excluded at 95% confidence level, depending on the model parameters. The results are also interpreted for a collection of simplified models, in which gluinos are excluded with masses as large as 1.1 TeV, for small neutralino masses, and the first-two generation squarks, stops and sbottoms are excluded for masses up to about 800, 425 and 400 GeV, respectively.

With the discovery of a new boson by the CMS and ATLAS experiments in the γ-γ and 4 lepton final states, the identity of the putative Higgs candidate must be established through the measurements of its properties. The spin and quantum numbers are of particular importance, and we describe a method for measuring the J^PC of this particle using the observed signal events in the H to ZZ^* to 4 lepton channel developed before the discovery. Adaptations of the razor kinematic variables are introduced for the H to WW^* to 2 lepton/2 neutrino channel, improving the resonance mass resolution and increasing the discovery significance. The prospects for incorporating this channel in an examination of the new boson J^PC is discussed, with indications that this it could provide complementary information to the H to ZZ^* to 4 lepton final state, particularly for measuring CP-violation in these decays.

A study of protein targeting reveals insights into mitigating protein aggregation

A unique chloroplast Signal Recognition Particle (SRP) in green plants is primarily dedicated to the post-translational targeting of light harvesting chlorophyll-a/b binding (LHC) proteins. Our study of the thermodynamics and kinetics of the GTPases of the system demonstrates that GTPase complex assembly and activation are highly coupled in the chloroplast GTPases, suggesting they may forego the GTPase activation step as a key regulatory point. This reflects adaptations of the chloroplast SRP to the delivery of their unique substrate protein. Devotion to one highly hydrophobic family of proteins also may have allowed the chloroplast SRP system to evolve an efficient chaperone in the cpSRP43 subunit. To understand the mechanism of disaggregation, we showed that LHC proteins form micellar, disc-shaped aggregates that present a recognition motif (L18) on the aggregate surface. Further molecular genetic and structure-activity analyses reveal that the action of cpSRP43 can be dissected into two steps: (i) initial recognition of L18 on the aggregate surface; and (ii) aggregate remodeling, during which highly adaptable binding interactions of cpSRP43 with hydrophobic transmembrane domains of the substrate protein compete with the packing interactions within the aggregate. We also tested the adaptability of cpSRP43 for alternative substrates, specifically in attempts to improve membrane protein expression and inhibition of amyloid beta fibrillization. These preliminary results attest to cpSRP43’s potential as a molecular chaperone and provides the impetus for further engineering endeavors to address problems that stem from protein aggregation.

Multi-model inference ranking and applications to physics at the Large Hadron Collider

In the measurement of the Higgs Boson decaying into two photons the parametrization of an appropriate background model is essential for fitting the Higgs signal mass peak over a continuous background. This diphoton background modeling is crucial in the statistical process of calculating exclusion limits and the significance of observations in comparison to a background-only hypothesis. It is therefore ideal to obtain knowledge of the physical shape for the background mass distribution as the use of an improper function can lead to biases in the observed limits. Using an Information-Theoretic (I-T) approach for valid inference we apply Akaike Information Criterion (AIC) as a measure of the separation for a fitting model from the data. We then implement a multi-model inference ranking method to build a fit-model that closest represents the Standard Model background in 2013 diphoton data recorded by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). Potential applications and extensions of this model-selection technique are discussed with reference to CMS detector performance measurements as well as in potential physics analyses at future detectors.

New Physics Models in the Diphoton Final State at CMS

Since the discovery of the Higgs boson at the LHC, its use as a probe to search for beyond the standard model physics, such as supersymmetry, has become important, as seen in a recent search by the CMS experiment using razor variables in the diphoton final state. Motivated by this search, this thesis examines the LHC discovery potential of a SUSY scenario involving bottom squark pair production with a Higgs boson in the final state. We design and implement a software-based trigger using the razor variables for the CMS experiment to record events with a bottom quark-antiquark pair from a Higgs boson. We characterize the full range of signatures at the LHC from this Higgs-aware SUSY scenario and demonstrate the sensitivity of the CMS data to this model.

Estudo do comportamento de variáveis cinemáticas na produção difrativa de mésons D-+* em colisões próton-próton √s = 7TeV

Apresentamos um estudo preliminar da produção difrativa de mésons utilizando dados obtidos da colisão próton-próton, a energias de centro de massa de 7 TeV, com o experimento CMS-LHC. O trabalho inclui o desenvolvimento do algoritmo de reconstrução dos mésons D* através do canal de decaimento D*->D0 + pion (lento) ->K+pion, a medida da eficiência de detecção e reconstrução, e uma análise do comportamento de variáveis cinemáticas na produção difrativa dessas partículas, particularmente, das lacunas de rapidez. Para isso, foi utilizada uma luminosidade integrada de 3,171pb^(-1) de dados coletados no ano de 2010. As análises com os dados experimentais foram comparadas com os resultados obtidos com geradores de Monte Carlo PYTHIA6, PYTHIA8 e POMPYT.

Observação de eventos de dijatos de alto pT separados por uma lacuna de rapidez no contexto de BFKL no CMS

Apresenta-se neste trabalho um estudo da produção de eventos de dijatos com alto momentum transverso separados por uma lacuna de rapidez, na topologia de jato+lacuna+jato, nos primeiro período de coleta de dados do CMS a √s = 7 TeV, isto é, para baixa luminosidade (1034cm-2s-1). A escala dura do evento é apresentada na forma dos dois jatos e da lacuna de rapidez no estado final. No contexto de BFKL, uma escada de glúons é trocada no canal t do espalhamento partônico. O processo acima foi simulado com o gerador HARDCOL (1), onde é implementado o cálculo de BFKL até ordem dominante de logaritmo ln s. As amostras foram simuladas e reconstruídas pelo software do CMS. Como evento de fundo dominante, temos a combinação de um evento de QCD com eventos de empilhamento na mesma colisão de feixe no LHC, onde observamos o excesso de dados sobre os eventos de fundo. Através do estudo dos jatos e da baixa atividade na região da lacuna, mostra-se a possibilidade de se observar os eventos com lacuna de rapidez a √s = 7 TeV.

Procura do bóson de Higgs a partir da fusão de bósons vetoriais no Experimento CMS

O presente trabalho tem por finalidade determinar a luminosidade necessária para se impor um limite para exclusão e a signifucância para evidência e descoberta para um bóson de Higgs de mH = 200 GeV no canal qqH → ZZ → 4. Também, apresenta-se uma crítica a qualidade da relação sinal/fundo em eventos de fusão de bósons vetoriais conhecida da literatura atual.

Obtenção de um limite para a largura do bóson de Higgs no experimento CMS via H→ ZZ → (4e, 4, 2e2)

Apresenta-se neste trabalho um estudo sobre a largura de decaimento total do bóson de Higgs através do canal H→ ZZ → (4e, 4, 2e2). Segundo o Modelo Padrão da Física de Partículas Elementares, um bóson de Higgs com massa de 126 GeV deve ter uma largura de decaimento total ΓH = 4.15 MeV, muito abaixo da resoluções dos experimentos instalados no LHC. Isto impede uma medida direta sobre os eventos da ressonância. Recentemente foi proposto limitar ΓH a partir da relação entre a taxa de eventos observados na região da ressonância e na região off-shell. Utilizando o pacote de análise desenvolvido pela colaboração CMS obteve-se um limite de ΓH < 31.46(12.82) MeV em 95(68.3)% CL combinando os dados coletados pelo LHC em colisões pp em √s = 7 TeV (5.1fb-1) e em √s = 8 TeV (19.7fb -1).

盐角草（Salicornia europaea L.）SePSY和SeLCY基因克隆及功能分析

盐角草（Salicornia europaea L.）是一种叶片退化而茎肉质化，不具有盐腺和盐囊泡的真盐生植物，可以在1020 mM NaCl下生存。其特殊的形态适应特点使其成为研究植物抗盐性的良好实验材料。但目前与盐角草抗盐机理相关的生理和分子方面的研究还非常有限。本文以盐角草为材料，首先探讨了盐分和渗透胁迫对其光合作用和渗透平衡的影响，在此基础上进一步克隆了盐角草类胡萝卜素合成途径中的两个关键酶，八氢番茄红素合成酶（SePSY）和番茄红素β-环化酶（SeLCY）基因，并进行了功能分析。该研究对于了解类胡萝卜素在植物抗盐性中所起的作用具有重要意义。 盐分和渗透胁迫对其光合作用和渗透平衡影响的实验结果表明：200 mM NaCl是盐生植物盐角草生长的最适盐浓度，在该盐度下盐角草中叶绿素a/b的比值和光饱和点升高，植株的光合作用表现出增强的效应，植株生长最佳。而27％ PEG-6000所模拟的渗透胁迫显著降低了盐角草中叶绿色a/b的比值，抑制其光合作用和生长。200 mM NaCl下，Na+的含量显著增加，但脯氨酸含量保持不变，说明Na+对盐角草渗透平衡的作用要强于脯氨酸。同时盐角草中液泡H+-ATPase（V-H+-ATPase）活性增强，而盐角草Na+/H+逆向转运蛋白基因（SeNHX1）在盐分和渗透胁迫下却表现为组成型表达;我们因此推断在盐分胁迫下，Na+的吸收是由于液泡H+-ATPase活性的增强，而不是诱导SeNHX1基因的表达。同时Na+的吸收可能进一步诱导了与光合作用相关基因的表达。 盐分对植物的影响涉及植物体内包括光合作用和活性氧代谢在内的多个代谢过程。在植物中，类胡萝卜素是植物捕光天线复合体（LHC）和光系统反应中心叶绿素结合蛋白的重要组成部分。植物体内类胡萝卜素能够清除植物叶绿体，线粒体和过氧化物体在电子传递过程中产生的活性氧。同时类胡萝卜素是植物激素ABA的前体。200 mM NaCl虽然增加了盐角草细胞的渗透势，但并没有对其造成氧化胁迫和离子毒害，相反提高了其光合能力。类胡萝卜素作为植物活性氧的淬灭剂和光系统的组成成分，可能在盐角草抗盐机理中发挥着比较重要的作用。在过去的十年中，类胡萝卜素研究大多集中在其生物合成和提高作物中类胡萝卜素含量方面，可是，在植物对非生物逆境（如氧化和盐分胁迫）的适应机制中，类胡萝卜素合成途径究竟发挥什么作用目前还不是很清楚。为了了解盐角草中类胡萝卜素合成途径在植物逆境的适应机制中所发挥的作用，本文采用RACE的方法克隆了盐角草类胡萝卜素合成途径中的两个关键酶基因 SePSY和SeLCY，将它们构建到植物表达载体SN1301中，转化拟南芥，并对它们进行了初步的功能分析。 研究发现盐角草SePSY基因全长1655 bp，编码419个氨基酸，推测分子量为47.2 kDa，等电点为8.92。其蛋白在1-65个氨基酸处有一个信号肽。在1-19和242-264氨基酸处有2个跨膜区。盐角草SeLCY基因全长1937 bp，编码498个氨基酸，推测分子量为56.1 kDa，等电点为8.41。其蛋白在1-37个氨基酸处有一个信号肽。在79-96，367-385和454-474氨基酸处有3个跨膜区。SePSY和SeLCY基因过量表达均促进转基因拟南芥的生长，转SePSY基因拟南芥次生根数目比野生型拟南芥明显增多。SePSY和SeLCY基因的过量表达还使转基因拟南芥对百草枯的抗性得到提高;SePSY基 因的过量表达增强了植株体内抗氧化保护酶过氧化物酶（POD），超氧化物歧化酶（SOD）活性，但过氧化氢酶 （CAT）的变化不显著;转SeLCY基因株系POD，SOD，CAT的活性都有所增强，但转SePSY基因株系中POD活性明显高于 转SeLCY基因株系。转SePSY和SeLCY基因拟南芥叶片中丙二醛（MDA）和H2O2含量均降低，但转SePSY基因株系中MDA和H2O2含量明显低于转SeLCY基因株系。说明转基因拟南芥对氧化胁迫的抗性得到了提高，同时使得光系统II（PSII）和细胞膜的结构和功能不被破坏。而转SePSY基因株系对盐分和氧化胁迫的抗性明显高于转SeLCY基因株系。SePSY和SeLCY基因的过量表达还提高了转基因拟南芥的光合效率，气孔导度和Fv/Fm比值。 SePSY和SeLCY基因转化拟南芥及其功能分析的初步结果表明，SePSY和SeLCY基因的过量表达提高了转基因拟南芥对体内活性氧（ROS）的清除能力，增强了拟南芥的光合能力，进而提高了拟南芥的抗盐性。

复苏植物牛耳草Boea hygrometrica耐旱复苏过程中LEA基因表达调控及功能研究

本实验室以复苏被子植物旋蒴苣苔（Boea hygrometrica (Bunge) R Br，牛耳草）为实验材料，利用cDNA微阵列技术，筛选到2个LEA蛋白的cDNA片段。它们在干旱条件下表达水平增加一倍以上。在上述基础上，通过5’-RACE的方法扩增得到这两个LEA基因的全长cDNA，BhLEA1和BhLEA2，发现二者编码蛋白均与玄参科复苏植物Craterostigma plantagineum中的第4组LEA蛋白pcCC2具有最高的同源性。PCR扩增得到的基因组序列中发现BhLEA1和BhLEA2在靠近5’端处各有一内含子，分别为97和171bp。利用tail-PCR和inverse-PCR扩增得到BhLEA2的1215bp的启动子序列，其中含ABRE、W-box、HDEs、MYB、MYC、和生长素响应元件等。两个基因在不同胁迫、激素等处理下都有诱导表达。构建过量表达载体, 转化烟草。筛选T2代的纯合体植株进行抗旱试验，测定了干旱过程中的土壤和叶片含水量，PSⅡ最大光化学效率Fv/Fm、SOD和POD酶的活性及蛋白质降解程度，发现BhLEA1和BhLEA2过量表达的烟草抗旱性有明显提高，与野生型相比，叶片含水量和光系统Ⅱ活性下降慢、SOD和POD活性增高、蛋白质降解减少。Western blot检测发现在干旱时，野生型烟草的RbcL、LHCⅡ和PsBO蛋白明显降解，而转基因植物的几乎没有降解，或者降解较少，说明BhLEA的过量表达可以在一定程度上抑制干旱诱导的蛋白质降解。这些结果表明，BhLEA基因可能直接或间接地在牛耳草干旱过程中参与了保护蛋白质的作用，为牛耳草叶片的复苏提供了基础。

长期驯化环境下丁香属植物的光合生理生态学研究

本研究是在丁香属植物半个世纪的丰富引种基础上，采用光合生理的实验手段探讨该属重要物种长期驯化中的环境响应机制。 在迁地条件下，与广布种华北紫丁香相比， 濒危种羽叶丁香有较低的光需求，在中等光强下净光合速率显著低于广布种;气孔限制值较大，对光合作用的调节较弱;蒸腾作用亦较弱，导致中午叶温较高造成叶片伤害。功能叶片的净光合速率在8:00光强及气温较低时已达峰值，叶片生长历时短暂并于初夏前结束，长此以往可能影响光合产物积累。可见羽叶丁香以“逃避”的方式适应迁入地生长季节环境胁迫。 为了探究羽叶丁香在引种地“逃避”策略的环境驱动因子，我们分别选取种植在园内全光照曝晒和60% 遮荫、生物量差异极为显著，而其它条件相同的羽叶丁香开展实验。尽管曝晒单株比遮荫单株有着显著低下的生物量，但最大量子效率及叶绿素a/b的结果都表明曝晒并未对其PSⅡ及LHCⅡ造成损伤。遮荫单株也已经由高叶绿素含量表现出对低光环境的适应。可见，其光适应机制已经存在，而引种地生长季节的高温可能是羽叶丁香生长中要回避的主要因子。 为了进一步证实这个推断，并希望了解羽叶丁香在原产地的环境响应状况和致濒的生理原因，我们在其原产地贺兰山对该种进行了调查和试验。调查发现在贺兰山羽叶丁香分布在海拔1700m、西北坡向、近谷底处。由于坡度较缓，晴朗天气光照时数达8h，叶片厚重，净光合速率极显著地高于引种地;最大量子效率表明中午的强光并未带来严重光抑制，且小幅度的光抑制在次日清晨可完全恢复，并且有较高的实际量子效率。故在原产地强光仍旧不是其生长的限制因子;其极高的光合速率及高效的实际量子效率是对冷凉强光条件的特殊适应，说明羽叶丁香具有喜冷凉不惧光的固有特点，而冷凉条件于高温炎热的引种地不能得到满足时，便放弃了对光的要求而在遮荫的生境中适应下来。因此引种地的高温应该是其要“逃避”的重要因子。同时表明较强的光合能力及强光的适应特征不会使羽叶丁香在原产地成为濒危物种。 为了搞清羽叶丁香的濒危原因，我们将原产地野外分布状况连同两地水分利用效率棕合分析发现：在水分保证适当的北京植物园栽培条件下，即使是曝晒的植株也有着较高的水分利用效率，而原产地的羽叶丁香低下的水分利用效率表明其生存和分布对水分条件极为敏感。因此，羽叶丁香是良好水分条件的“享受者”，而不是干旱条件的“耐受者”，而这对于生长在干旱半干旱地区的物种来说在一定程度上限制了其散布的可能性，以致数量极为有限。 “全能” 的华北紫丁香恰是丁香属系统演化中较为进化的种，而“低能” 的羽叶丁香又恰是居于顶生花序系（原始）与欧丁香系（进化）之间的重要过渡种。在对丁香属起源及散布进行推断的基础上，这些已经得到的结果促使我们从区系和演化的层面去了解演化系在长期迁地驯化的光合生理差异。结果发现演化过渡种羽叶丁香的光合指征也多处于中间位置;顶生花序系（原始）种类光合效能相对较低，较强的水分平衡的保持能力可能成为它们能在跨气候带引种中成活的解释。欧丁香系（进化）种类气孔导度对光梯度反应敏感，但较强的蒸腾降低了其水分利用效率，在引种地干旱高温的生长季会因水分不能及时供给而可能在年周期尺度上直接影响生物量。小乔木型的种类可能由于较高的水分利用效率而不畏干旱，形成了拟女真亚组从西北到东北继而向日本的广泛分布。 驯化的现实意义之一是应用。丁香的盐碱耐受性是区域栽培中面对的问题。我们模拟氯化物硫酸盐型盐碱土（NaCl - MgSO4）与光照梯度交互的试验结果表明紫丁香系品种曝晒栽植能耐受0.2% 的土壤盐度，如果在相同盐度生境中遮荫种植会有更高的盐分耐受表现。 对迁地物种环境适应性的研究论证着眼点从“种” 的水平归结到“系”的层次，从对特殊代表物种当今适应机制的量化比较联系到其起源和散布的历史发展，在一定程度上超越了常规引种驯化对现存实体“种” 的定性描述;将迁地驯化与就地适应相联系，以较为科学的思路贯穿驯化保护研究，并最终将研究结果回归于驯化保护实践。

重金属离子镉对高等植物叶绿体光系统Ⅱ的影响的研究

本文研究了重金属离子Cd++、Pb++、Cu++、Zn++对高等植物（菠菜）离体叶绿体两个光系统光合电子传递功能的影响，以Cd++为代表重点研究了它对光系统II（PSII）的影响，首重讨论了Cd++在PSII的作用部位及作用方式。 Cd++、Pb++、Cu++、Zn++对高等植物叶绿体光合电子传递具有抑制作用，其中对PSII电子传递的抑制作用更为显著。PSII制剂的放氧活性比叶绿体的放氧活性对Cd++的毒害作用更加敏感。不同浓度的Cd++处理后，叶绿体全电子链的电子传递活性比放氧活性的降低速率快。这暗示着PSII氧化侧不是Cd++唯一的作用部位，在PSII电子传递链上还存在一个对Cd~(++)敏感的部位。 Cd++使叶绿体和PSII制剂的DCIP光还原活性降低;可变光受到抑制。加入PSII人工电子供体DPC仅使被抑制的DCIP光还原活性稍有恢复;而加入NH2OH对被抑制的可变荧光无影响。因此我们认为Ca++除了作用于PSII氧化侧外，还直接作用于PSII反应中心。这与Bazzaz和Govindje等提出的Cd++仅作用于PSII氧化侧的观点不同。我们认为可能是Cd++改变了叶绿体或PSII制剂类囊体膜的构型或内环境，使较多的PSII反应中心不易被光活化或使其钝化的缘故。 低温（-196℃）荧光发射光谱表明，Cd++使叶绿体的F686/F736及 F696/F736比值降低。另外，Cd++还可使叶绿体和PSII制剂的低温（-196℃）荧光激发光谱的F480/F436比值下降，使叶绿体表观吸收光谱变平。 温和的SDS-PAGE分析表明，Cd++处理后，叶绿体类囊体膜与PSII制剂类囊体膜中色素蛋白复合物LHC-II的部分寡聚体解聚成单聚体，叶绿体中LHC-II总量减少。进一步用梯度胶分析叶绿体类囊体膜的多肽组成。发现Cd++使属于LHC-II的多肽减少。表明Cd++引起了LHC-II的重新分配或它本身的解离。通过比较Cd++与Mg++对PSII活性的不同影响，我们认为Cd++使激发能不利于向PSII分配，从而破坏了两个光系统的协调合作。这或许是导致PSII电子传递活性显著降低的因素之一。

膜脂在类囊体不同功能膜区的分布及其与植物抗寒性的研究

一． 通过对黄瓜类囊体及其基粒片层、间质片层、PS II放氧颗粒和LHC II 复合体脂类成分的分析，得 到以下结果：各膜区均含有类囊体膜的五种脂类成分，在类囊体及其基粒片层、间质片层和PS II放氧颗粒中，MGDG含量最高，分别为42.5%、40.5%、46.3%、和35.7%，其次是DGDG，含量在31-35%之间。值得注意的是黄瓜类囊体间质片层MGDG含量高于基粒片层，而且DGDG/DGDG分子比也较高。这在其它植物材料中还未见报道。在黄瓜LHC II中，PG含量最高，为35.5%，约是类囊体膜PG含量的3倍。从基粒片层、PS II放氧颗粒到LHC II， PG含量呈逐渐增加的趋势，而在间质片层中，PG含量最低。SQDG除在LHC II中含量稍低外，在其它膜区中的分布没有明显的差异。脂类脂肪酸组成分析结果表明：MGDG主要含亚麻酸，含量在90%以上。DGDG也主要含亚麻酸，含量在90%左右，DGDG所含棕榈酸多于MGDG中的含量。SQDG中主要脂肪酸组分为棕榈酸和亚麻酸。不同膜区MGDG、DGDG和SQDG脂肪酸组成没有明显差异在PG中含量最高的脂肪酸是叶绿体特有的反式十六碳一烯酸（trans-16:1)。此外，PG还含有较多的棕榈酸、硬脂酸和油酸。在不同膜区PG的脂肪酸组成有较明显的差异。 根据以上结果，我们推测脂类除了形成膜的流动性基质外，还可能选择性地结合在膜蛋白周转形成特 异的脂质微区，通过膜脂膜蛋白的相互作用，以行使其特殊的生理功能。 二、通过比较两种不同抗寒性小麦品种在低温锻炼前后类囊体脂类及其脂肪酸成分、LHC II复合体及类囊体吸收光谱、低温荧光发射光谱，发现经低温锻炼后：（1）抗寒与不抗寒小麦品种类囊体PG的trans-16:1含量均明显降低，抗寒品种类囊体MGDG/DGDG比值也明显降低，而不抗寒品种这一比值变化不明显。（2）抗寒品种脂/色素比值明显增高，而不抗寒品种滑明显增加。（3）抗寒与不抗寒品种LHC II宏聚体含量均降低而单体含量增加。（4）抗寒与不抗寒品种类囊体吸收光谱四阶导数光谱A_(683)/A_(652)比值均升高。（5）不抗寒品种低温荧光发射光谱F_(685)/F_(738)比值上升，而抗寒品种这一比值没有变化。通过对上述结果的分析，我们认为低温锻炼过程中类囊体膜流动性增强是使抗寒品种抗寒力增强的主要原因之一，此外，MGDG含量降低对膜的稳定性可能起重要作用。trans-16:1含量的降低和LHC II寡聚体解聚可能是植物对于低温的一种适应性反应。