捕光叶绿素a/b蛋白复合体LHCP-II和LHCP-I在类囊体膜中的模向迁移及其对激发能在两个光系统间分配的影响

本文主要研究了Mg2+对LHCP－II和LHCP－I在基粒膜与基质膜之间横向迁移的作用及其对激发能在两个光系统间分配的影响，进一步证实和发展了Kyle等提出的移动天线色素假说（mobile antenna hypothesis）。揭示了二价金属阳离子使激发能有利于向光系统II（PSII）分配，而不利于向光系统I（PSI）分配的生化基础。 用毛地黄皂（Digitonin）方法分离了悬浮在低渗、低浓度一价金属阳离子介质中的小麦类囊体的基粒膜与基质膜，结果发现，事先用5m MMgol2预处理过的类囊体，其基质膜比未处理的有较高的叶绿素a/b比值，基粒膜的叶绿素a/b比值变化不大。 低温荧光（77K）发射光谱表明，mg2+处理能增强类囊体膜和基粒膜的687nm荧光发射峰，降低F741/F687比值。除此以外，在对照的基质膜里还发现F687-向F688以及F741向F738的位移。 解垛叠及Mg~(2+)诱导的重垛叠实验表明，低温荧光F741/F687比值在解垛叠进程中上升，而在重垛叠过程中，F741／F687比值下降。 湿和的SDS－聚丙烯酰胺凝胶电泳分析表明，Mg2+处理使LHCP寡聚体解聚成单体，类囊体膜凝胶柱上LHCP寡聚体的含量减少，单体的含量增加。基质膜的电泳分析发现，Mg2+处理促时了LHCP从富含PSI的基质区向富含PSII的基粒膜区的迁移。同时还证明，不仅LHCP－II，LHCP－I也能向基粒膜区迁移。 进一步用梯度胶分析基粒膜与基质膜的多肽组成，发现经Mg2+处理的基质膜中相应于LHCP－II的两条多肽，25KD和27KD的量明显减少，尤其是27KD多肽变化更为显著。 此外，我们还研究了介质中pH值（H+浓度）对两个光系统间能量分配与传递的影响，发现H+的作用机理与Mg2+的不同。H+能引起膜垛叠，改变类囊体膜的低温荧光发射光谱，使F741／F687比值降低。而对基粒膜和基质膜的作用却与Mg2+作用相反。温和的SDS－聚丙烯酰胺凝胶电泳分析结果表明，pH的变化不改变类囊体膜上色素蛋白复合体的种类、组成和比例。 据此，我们比较并讨论了金属阳离子与H对光系统间能量分配与传递的影响的不同作用，认为二价金属阳离子除能引起类囊体膜垛叠、改变色素蛋白复合体的空间构象和排列，从而影响激发能在两个光系统间的分配外，还能调节和促进LHCP－II及LHCP－I从富含PSI的基质膜向富含PSII的基粒迁移，使PSII的光捕获截面增加，调节激发能有利于向PSII分配。而介质中的质子（H+）浓度的改变只能引起类囊体膜片层垛叠，可能改变光合膜中色素蛋白复合体的构象和排列，最终影响激发能在光系统间的分配。

高等植物PSI ,PSII反应中心及天线系统色素蛋白复合体结构与功能的研究

一、实验证明了Cd H、Mg“在小麦类囊体膜上色素蛋白复合体的解聚和再聚合过程中，具有不同的作用。因此，二阶阳离子对激发能在光系统间的分配调节作用，可能不能仅仅用“静电现象”(Barber(1980))去解释。分析表明，在Ca2+作用下与PSII内周天线CP-47，GP-43多肽结合的L H C II和LHClb是来自间质膜区的PS I系统的。从PSI迁移到P S II的捕光色素蛋白，增加了PSII的捕光截面，从而促进了激发能有利于PsII分配。 二、Ca2*、Mg2+对小麦和菠菜类囊体膜光谱性质的影响有所差异。Ca2+对小麦类囊体膜光谱性质的影响还可以随着介质中Ca2+的消除而消除。同小麦类囊体膜相比，菠菜PSII以及LHCII更为集中在基粒区域，这可能是菠菜类囊体膜强Fv以及高F888／F735，F89H／F735比值的原因。因此，Ca2+，HgH对激发能在光系统间分配的调节作用是依赖于光系统间激发能及天线色素蛋白的分配状况的。 三、对菠菜叶中分离的PSII-RC: D1-D2-cyt b55g复合物进行的低温荧光发射光谱的研究表明，这一复合物可能具有F681和F684两种波长的低温荧光发射，但它们通常并不是同时存在，而是取决于Ca-670与Ca-680 Chla分子的相对含量的。PSII-RC内周无线GP-47，GP-43多肽的存在是D1-D2-cyt b559复合物低温荧光发射红移的原因;而D1一D2cyt b559复合物的不稳定性则与其低温荧光发射的蓝移现象有关。 从蕹菜叶中分离的Dl—D2-cyt b559复合物的F 381低温荧光发射也是由其相对含量较高的C．i-6 7 0 Chla分子的存在决定的。对蕹菜D 1一D 2-cyt b559复合物中的分析还表明，F 681的低温荧光发射直接来源于Di／D2复合物，而415nm处相对较强的吸收，则可能主要是与Pheo的存在有关的。 四、多肽分析与光谱分析的对照表明，CP-26内周天线多肽可能是PSII中F695低温荧光发射的真正来源。 五、实验分析了蔗糖密度离心分离的LHClI和PSI颗粒。结果排除了CP-27多肽（以及CP，一2 5，GP-47，CP -4 3多肽）具有F695低温荧光发射的可能，因此支持了CP-26多肽是PSII中F695低荧光发射来源的看法。对PsI颗粒的分析表明，P700的存在可能是与PSI-RC中较大的Sub-I亚基相联系的。 六、根据以上的研究结果，提出了PSI，PSII在类囊体膜上的结构模式，并对其内容进行了分析和讨论。

光系统Ⅱ核心天线复合物CP43和CP47的分离纯化及其光谱学特性的研究

应用改进DEAE-Toyopearl 650S阴离子交换柱层析从高等植物菠菜(Spinacia oleracea)中分离纯化了核心天线复合物CP43和CP47。并对它们的纯度和完整性色素种类和含量，以及色素分子的结合状态进行了研究并对色素分子间的能量传递机制进行了讨论。结果如下： 1、HPLC检测结果表明：纯化的CP43和CP47均只含Chla和β-Car两种色素分子，并且，平均每分子CP43多肽含19-20分子Chla和4-5分子β-Car;而平均每分CP47则含20-21分子Chla和3-4分子β-Car。 2、以436nm和480nm激发光激发样品得到的CP43和CP47的低温荧光发射光谱的最大荧光发射峰分别位于683nm和693nm。进一步发现，CP43和CP47，在相同条件下分别以436nm和480nm激发光激发样品得到的低温荧光发射光谱经归一化后几乎完全重叠，而且400-500nm波长范围内的激发光扫描得到的三维低温荧光发射光谱沿激发轴具有较好的对应关系，表明纯化的CP43和CP47都具有较高的完整性。 3、纯化的CP43和CP47的吸收光谱的红区最大吸收峰分别位于671nm和674nm。该光区的导数光谱均分辨出偏蓝区和偏红区两个子峰，CP43的这两个子峰分别位于669nm和682nm;而CP47的两个子峰则分别位于669nm和680nm。进一步用包含这两个子峰的高斯解析参数对红区最大吸收峰进行拟合，结果证明，拟合的曲线与实测曲线几乎完全吻合，这表明，CP43和CP47均至少包含两种不同状态的Chla分子。 3．1应用不同的变性温度处理CP43，发现随变性温度的不断提高，其红区最大吸收峰的峰值逐渐减小，四阶导数光谱分辨出的两个子峰同时减小，但差光谱显示：随处理温度的不断提高，这两个组分峰值的变化并不同步进行，较低温度范围内(55℃以下)682nm吸收峰下降明显，而较高温度范围内(55℃以上)，669nm吸收峰下降明显。 同时，随处理温度不断提高CP43脱辅基蛋白的结构也在不断发生变化，其变化过程明显表现出两个跃变阶段。这两个跃变阶段分别出现在40～50℃范围内和55～60℃范围内，恰与吸收光谱两个组分峰变化的转变过程相一致。这证明，CP43中分别位于669nm和682nm的不同的色谱组分即代表两种不同结合态的Chla分子，分别简称为“CP43-669”和“CP43-682”。它们在色素蛋白复合物中所处的环境不同，因而对蛋白质结构的依赖性不同，前者更高地依赖于蛋白复合物的整体构象，而后者则主要依赖于蛋白质的二级结构。 3.2 经不同的变性温度处理的CP47，其红区最大吸收峰的峰位逐渐蓝移，而吸收峰值无明显的变化，只有当处理温度提高到65℃以后，蓝移后的吸收峰值(669nm)才开始明显减小;四阶导数光谱表现为680nm吸收峰的信号逐渐下降669nm的吸收信号逐渐明显;处理减对照差光谱只观察到680nm吸收值的逐渐减少，而几乎观察不到669nm吸收值的变化。同时，随变性温度的不断提高，CP47的脱辅基蛋白的结构也发生相应的变化与CP43不同，蛋白结构变化最大的温度范围为60℃～65℃之间，但同CP47的峰位蓝移、导数光谱中680nm信号的减小，以及差光谱中680nm吸收值的减小相一致。由此认为，同CP43一样，CP47的吸收光谱中分辨出的分别位于669nm和680nm处的两个不同光谱组分亦分别代表两种不同结合状态的Chla分子，分别简称为“CP47-669”和“CP47-680”，与CP43中的相应组分对应，它们处于不同的蛋白环境中，从而对蛋白质结构变化的依赖性不同。 3.3 CP43和CP47的CD光谱表现出明显的正负双峰，表明色素分子间存在较强的激子相互作用。随变性温度的不断提高，正负CD双峰的信号逐渐减弱，变化过程与脱辅基蛋白结构的变化以及CP43-682的变化相一致，表明色素分子间的激子相互作用更高依赖于CP43-682和CP47-680。并认为CP43-682和CP47-680可能以二聚体或多聚体的形式存在，并且二聚体或多聚体的形成依赖于蛋白天然构象。而CP43-669和CP47-669则以单体的形式位于蛋白结构中相对伸展的区域。并提出：在CP43-682以CP47-680分子之间，激发能主要以激子偶合机制进行而在CP43-669，CP47-669分子间及CP43-669至CP43-682间，CP47-669至CP47-680之间激发能则主要以Foster机制进行。 4、以488nm激发光得到的CP43和CP47的共振拉曼光谱都具有全反式构型类胡萝卜素分子的四个典型特征峰由此认为CP43和CP47中的β-Car分子亦具有全反式构型;与溶于丙酮抽体物中的β-Car分子相比较，CP43和CP47中的β-Car分子的共振拉曼光谱中具有较强的960cm~(-1)的拉曼峰，表明，CP43和CP47中的β-Car分子具有扭曲的构象。 应用经归一化后的吸收光谱与荧光激发光谱相比较的办法发现CP43和CP47中存在β-Car分子和Chla分子间的能量传递其能量传递效率分别为29.8～29.9%和52.3～56.9%。这表明，在正常条件下，CP47中β-Car分子和Chla分子间的能量传递效率远大于CP43。此外，当选用蛋白结构变化最明显的热变性温度处理样品后，发现，不论CP43还是CP47中β-Car与Chla分子间的能量传递效率大大降低，表明，这两种色素分子间的能量传递严格依赖于蛋白复合物的天然构象，并认为，正常条件下，CP43和CP47内β-Car与Chla分子间的空间距离较近，可能不大于10A，CP43和CP47相比较，CP47内这两种色素分子间的距离更近。并进一步提出，在CP43和CP47中，β-Car到Chla分子间的能量传递最大可能以Dexter的电子交换机制进行。

Disease problems in shrimp sector in Khulna district of Bangladesh: a question of sustainability

Disease is the main restraining factor for the development of shrimp sector in Bangladesh. Both brackish water shrimp bagda (Penaeus monodon) and freshwater prawn golda, (Macrobrachium rosenbergii) farming in Bangladesh have been facing disease problem. A study on disease outbreak in both brackish water and freshwater small-scale shrimp farms (gher) in Khulna district was carried out through interviewing randomly selected 3-5% of shrimp farmers with a structured questionnaire during March to December, 2002. The study showed that 97% bagda farming ghers and 80% golda farming ghers were affected by disease. White spot disease was the severe disease for bagda, whereas, antenna rot was the main disease for freshwater prawn. Change of water and liming were carried out as control measures of disease for bagda shrimp farming, while it was only liming for golda farming. A small number of shrimp farmers (15%) used chemicals for treatment of shrimp diseases. Development of suitable farming technology to prevent disease contamination and innovation of proper treatments for diseases are required to overcome the disease problems for sustainable shrimp farming in Bangladesh.

Investigation on biodiversity and population structure of Penaeus sernisulcatus [sic] in northern waters of Persian Gulf

Green tiger prawn, Penaeus sentisulcatus is one of the commercial species of Persian Gulf, which is distributed from north to Strait of I Iormoze. Concerning its role in fisheries economic, various research projects on stock assessment, biology and aquaculture has been conducted. This research is targeted the identification of various populations of green tiger prawn in northern waters of Persian Gulf. The area has been divided to five regions from north to south named; Bahrakan, Boushehr, Tangestan, Motaaf and Strait of Hormoz. In each region, numbers of sampling stations trawled, and live shrimp species carried in containers equipped with air pump, to coastal laboratories in Boushehr and Bandar Abbass Fisheries Research Centers. Biometeric, morphometeric and merestic measures for 45 factars done, and peices of muscles, eye and ovary tissues dissected, and stored in liquid nitrogen. Protein extraction, and polyacrylamid gel electrophoresis by SDS-PAGE technique for tissues samples conducted. Data of 45 morphometeric and merestic characteristics analyzed by principal component analysis (PCA), and clustering analysis methods. The results of analysis showed that, the populations of Bahrakan and Mota.af regions are differentiated, while population of Boushehr and Tangestan regions were mixed, and named as a single population. The analysis of electrophoretic data also confirmed this result, and showed a distinct population in Strait of Hormoz. Therefore, this research illustrated four distinct populations for P. semisulcatus in northern area of Persian Gulf, named Bahrakan (north of Boushehr), Boushehr and Tangesta.n (adjacent), Motaaf and it's south, and Strait of Hormoz. Study of morphometeric characteristics of carapace factors, genital organs, antenna and life cycle of samples of different regions resulting identification of a subspecies, which is named Penaeus seinisuleatus persicus.

Gaussian fading is the worst fading

The capacity of peak-power limited, single-antenna, noncoherent, flat-fading channels with memory is considered. The emphasis is on the capacity pre-log, i.e., on the limiting ratio of channel capacity to the logarithm of the signal-to-noise ratio (SNR), as the SNR tends to infinity. It is shown that, among all stationary and ergodic fading processes of a given spectral distribution function and whose law has no mass point at zero, the Gaussian process gives rise to the smallest pre-log. The assumption that the law of the fading process has no mass point at zero is essential in the sense that there exist stationary and ergodic fading processes whose law has a mass point at zero and that give rise to a smaller pre-log than the Gaussian process of equal spectral distribution function. An extension of these results to multiple-input single-output (MISO) fading channels with memory is also presented. © 2006 IEEE.

Gaussian fading is the worst fading

The capacity of peak-power limited, single-antenna, non-coherent, flat-fading channels with memory is considered. The emphasis is on the capacity pre-log, i.e., on the limiting ratio of channel capacity to the logarithm of the signal-to-noise ratio (SNR), as the SNR tends to infinity. It is shown that, among all stationary & ergodic fading processes of a given spectral distribution function whose law has no mass point at zero, the Gaussian process gives rise to the smallest pre-log. © 2006 IEEE.

A MIMO-OFDM testbed for wireless local area networks

We describe the design steps and final implementation of a MIMO OFDM prototype platform developed to enhance the performance of wireless LAN standards such as HiperLAN/2 and 802.11, using multiple transmit and multiple receive antennas. We first describe the channel measurement campaign used to characterize the indoor operational propagation environment, and analyze the influence of the channel on code design through a ray-tracing channel simulator. We also comment on some antenna and RF issues which are of importance for the final realization of the testbed. Multiple coding, decoding, and channel estimation strategies are discussed and their respective performance-complexity trade-offs are evaluated over the realistic channel obtained from the propagation studies. Finally,we present the design methodology, including cross-validation of the Matlab, C++, and VHDL components, and the final demonstrator architecture. We highlight the increased measured performance of the MIMO testbed over the single-antenna system. £.

An error free passive UHF RFID system using a new form of wireless signal distribution

A wide area and error free ultra high frequency (UHF) radio frequency identification (RFID) interrogation system based on the use of multiple antennas used in cooperation to provide high quality ubiquitous coverage, is presented. The system uses an intelligent distributed antenna system (DAS) whereby two or more spatially separated transmit and receive antenna pairs are used to allow greatly improved multiple tag identification performance over wide areas. The system is shown to increase the read accuracy of 115 passive UHF RFID tags to 100% from <60% over a 10m × 8m open plan office area. The returned signal strength of the tag backscatter signals is also increased by an average of 10dB and 17dB over an area of 10m 8m and 10m × 4m respectively. Furthermore, it is shown that the DAS RFID system has improved immunity to tag orientation. Finally, the new system is also shown to increase the tag read speed/rate of a population of tags compared with a conventional RFID system. © 2012 IEEE.

Automated vision tracking of project related entities

Tracking of project related entities such as construction equipment, materials, and personnel is used to calculate productivity, detect travel path conflicts, enhance the safety on the site, and monitor the project. Radio frequency tracking technologies (Wi-Fi, RFID, UWB) and GPS are commonly used for this purpose. However, on large-scale sites, deploying, maintaining and removing such systems can be costly and time-consuming. In addition, privacy issues with personnel tracking often limits the usability of these technologies on construction sites. This paper presents a vision based tracking framework that holds promise to address these limitations. The framework uses videos from a set of two or more static cameras placed on construction sites. In each camera view, the framework identifies and tracks construction entities providing 2D image coordinates across frames. Combining the 2D coordinates based on the installed camera system (the distance between the cameras and the view angles of them), 3D coordinates are calculated at each frame. The results of each step are presented to illustrate the feasibility of the framework.

Graphene field-effect transistors as room-temperature terahertz detectors

The unique optoelectronic properties of graphene make it an ideal platform for a variety of photonic applications, including fast photodetectors, transparent electrodes in displays and photovoltaic modules, optical modulators, plasmonic devices, microcavities, and ultra-fast lasers. Owing to its high carrier mobility, gapless spectrum and frequency-independent absorption, graphene is a very promising material for the development of detectors and modulators operating in the terahertz region of the electromagnetic spectrum (wavelengths in the hundreds of micrometres), still severely lacking in terms of solid-state devices. Here we demonstrate terahertz detectors based on antenna-coupled graphene field-effect transistors. These exploit the nonlinear response to the oscillating radiation field at the gate electrode, with contributions of thermoelectric and photoconductive origin. We demonstrate room temperature operation at 0.3 THz, showing that our devices can already be used in realistic settings, enabling large-area, fast imaging of macroscopic samples. © 2012 Macmillan Publishers Limited. All rights reserved.

Increasing the open-circuit voltage of photoprotein-based photoelectrochemical cells by manipulation of the vacuum potential of the electrolytes.

The innately highly efficient light-powered separation of charge that underpins natural photosynthesis can be exploited for applications in photoelectrochemistry by coupling nanoscale protein photoreaction centers to man-made electrodes. Planar photoelectrochemical cells employing purple bacterial reaction centers have been constructed that produce a direct current under continuous illumination and an alternating current in response to discontinuous illumination. The present work explored the basis of the open-circuit voltage (V(OC)) produced by such cells with reaction center/antenna (RC-LH1) proteins as the photovoltaic component. It was established that an up to ~30-fold increase in V(OC) could be achieved by simple manipulation of the electrolyte connecting the protein to the counter electrode, with an approximately linear relationship being observed between the vacuum potential of the electrolyte and the resulting V(OC). We conclude that the V(OC) of such a cell is dependent on the potential difference between the electrolyte and the photo-oxidized bacteriochlorophylls in the reaction center. The steady-state short-circuit current (J(SC)) obtained under continuous illumination also varied with different electrolytes by a factor of ~6-fold. The findings demonstrate a simple way to boost the voltage output of such protein-based cells into the hundreds of millivolts range typical of dye-sensitized and polymer-blend solar cells, while maintaining or improving the J(SC). Possible strategies for further increasing the V(OC) of such protein-based photoelectrochemical cells through protein engineering are discussed.

Direction and polarisation estimation using polarised cylindrical conformal arrays

In this study, the authors describe two-dimensional direction finding and signal polarisation estimation from a cylindrical conformal array consisting of directional and polarised antenna elements. Firstly, a simple and general transformation procedure, based on the mathematical framework of geometric algebra, is presented for arbitrary conformal arrays with polarised and directional antennas. Subsequently, the authors utilise the symmetry of cylindrical arrays to estimate signal parameters via rotational invariance techniques. The authors show how to iteratively estimate the azimuth and elevation angles of the incident signal, as well as its polarisation. To illustrate the versatility of this method, the results of simulations on a 3×4 cylindrical conformal array are shown and discussed. © 2012 The Institution of Engineering and Technology.

Task-level control of the lateral leg spring model of cockroach locomotion

The Lateral Leg Spring model (LLS) was developed by Schmitt and Holmes to model the horizontal-plane dynamics of a running cockroach. The model captures several salient features of real insect locomotion, and demonstrates that horizontal plane locomotion can be passively stabilized by a well-tuned mechanical system, thus requiring minimal neural reflexes. We propose two enhancements to the LLS model. First, we derive the dynamical equations for a more flexible placement of the center of pressure (COP), which enables the model to capture the phase relationship between the body orientation and center-of-mass (COM) heading in a simpler manner than previously possible. Second, we propose a reduced LLS "plant model" and biologically inspired control law that enables the model to follow along a virtual wall, much like antenna-based wall following in cockroaches. © 2006 Springer.