Green and red upconversion luminescence in ytterbium-sensitized erbrium-doped novel lead-free germanium bismuth lanthanum glass

Structural and infrared-to-visible upconversion fluorescence properties in ytterbium-sensitized erbrium-doped novel lead-free germanium bismuth-lanthanum glass have been studied. The structure of lead-free germanium-bismuth-lanthanum glass was investigated by peak-deconvolution of Raman spectrum, and the structural information was obtained from the peak wavenumbers. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. This novel lead-free germanium-bismuth-lanthanum glass with low maximum phonon energy (similar to 751 cm(-1)) can be used as potential host material for upconversion lasers. (c) 2005 Published by Elsevier B.V.

Fluorescence lifetime increase by introduction of F- ions in ytterbium-doped TeO2-based glasses

this paper was retracted

Effect of F- ions on spectroscopic properties of Yb3+-doped zinc-tellurite glasses

this paper is retracted

Effect of Al(PO3)(3) content on physical, chemical and optical properties of fluorophosphate glasses for 2 mu m application

The effect of Al(PO3)(3) content on physical, chemical and optical properties of fluorophosphate glasses for 2 mu m application, such as thermal stability, chemical durability, surface hardness, absorption spectra and emission spectra, is investigated. With the increment of Al(PO3)(3) content, the thermal stability characterized by the gap of T-g and T,, increases first and then decreases, and reaches the maximum level containing 5 mol% Al(PO3)(3) content. The density and chemical durability decrease monotonously with the introduction of Al(PO3)(3) content increasing, while the refractive index and surface hardness increase. Above properties of fluorophosphate glasses are also compared with fluoride glasses and phosphate glasses. The Judd-Ofelt parameters, absorption and emission cross sections are discussed based on the absorption spectra of Tm-doped glasses. The emission spectra are also measured and the 1.8 mu m fluorescence of the sample is obvious indicating that it is suitable to 2 mu m application. (c) 2008 Elsevier B.V. All rights reserved.

碱金属和碱土金属氟化物对掺Er^3＋氟磷酸盐玻璃光谱性质的影响

研究了碱金属和碱土金属离子修饰的掺Er^3＋氟磷酸盐玻璃的光谱性质，讨论了碱金属和碱土金属对铒氟磷玻璃的吸收和发射截面、荧光半高宽，Judd-Ofelt强度参数和上转换发光强度等光谱性质的影响，并与一些传统氧化物玻璃系统进行了比较．研究表明碱金属K^＋和碱土金属Sr^2＋掺杂高的玻璃更适宜用作光放大器基质．含12mol％K^＋的氟磷玻璃展现出7．83×10^-21cm^2的高发射截面和最小的荧光上转换强度；含23mol％Sr^2＋的氟磷玻璃则有7．58×10^-21cm^2的高发射截面、65nm的荧光半高

Crystal growth and spectroscopic characterization of Yb-doped and Yb, Na-codoped CaF2 laser crystals by TGT

High-quality 2at%-doped Yb:CaF2 and Yb,Na:CaF2 single crystals with diameter of 76mm were grown by the temperature gradient technique. For the first time, distribution coefficients (KO) of Yb in the two crystals were determined to be 1.07 and 0.91, respectively, by measuring the Yb concentrations at the growth starting position in the as-grown boules. Absorption and emission spectra of the two different crystals were measured at room temperature. Experimental results show that Na+ ions codoping with Yb3+ as charge compensators make Yb3+ ions in CaF2 lattice to be a quasi-single-center system, and greatly suppress the deoxidization of Yb3+ to Yb2+ (c) 2005 Elsevier B.V. All rights reserved.

Defects in U3+: CaF2 single crystals grown under different conditions by the temperature gradient technique

Defects in as-grown U3+ : CaF2 crystals grown with or without PbF2 as an oxygen scavenger were studied using Raman spectra, thermoluminescence glow curves, and additional absorption (AA) spectra induced by heating and gamma-irradiation. The effects of heating and irradiation on as-grown U3+: CaF2 crystals are similar, accompanied by the elimination of H-type centers and production of F-type centers. U3+ is demonstrated to act as an electron donor in the CaF2 lattice, which is oxidized to the tetravalent form by thermal activation or gamma-irradiation. In the absence of PbF(2)as an oxygen scavenger, the as-grown U3+:CaF2 crystals contain many more lattice defects in terms of both quantity and type, due to the presence of O2- impurities. Some of these defects can recombine with each other in the process of heating and gamma-irradiation. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High quantum fluorescence yield of Er3+ at 1.5 mu m in an Yb3+, Ce3+-codoped CaF2 crystal

For the first time, a quaternary doping system of Er3+, Yb3+, Ce3+, Na+:CaF2 single crystal was demonstrated to have high fluorescence yield in the eye-safe 1.5 mu m region under 980 nm laser diode pumping, with relatively broad and flat gain curves. A simplified model was established to illustrate the effect of Ce3+ on the branching ratio for the Er3+4I11/2 -> I-4(13/2) transition. With 0.2-at.% Er3+ and 2.0-at.% Ce3+ in the quaternary-doped CaF2 crystal, the branching ratio was estimated to be improved more than 40 times by the deactivating effect of Ce3+ on the Er3+ 4I11/2 level. The quaternary-doped CaF2, system shows great potential to achieve high laser performance in the 1.5 mu m region. (c) 2006 Elsevier B.V. All rights reserved.

ScAlMgO_4晶体的生长缺陷

采用提拉法生长出φ30 mm×55 mm的ScAlMgO4晶体。在晶体生长过程中有轻微的挥发,粉末X射线衍射分析表明:挥发物质为MgO单相。运用扫描电镜、光学显微镜以及高分辨X射线衍射仪对晶体中的包裹物、开裂、生长条纹和小角晶界缺陷进行了研究。结果表明:温度梯度和热应力是形成晶体中缺陷的主要原因。通过合理设计温场,控制固-液界面的形状及冷却过程的降温速率,可以提高晶体的完整性。

点源污染对三峡库区陆生植物群落的影响

三峡库区一些污染严重的工业企业是当地主要的点源污染源，对周围植物群落产生了巨大危害，而植物是生态系统赖以存在的基础，它的生长发育直接影响到生态系统的结构及其正常功能的实现。本研究按照与点源污染源的距离为梯度，通过在三峡库区兴山县白沙河磷化工厂周围布设了32个植物群落固定样地，并以点源污染无法影响到的植物群落为对照，进行样地的野外群落学调查;在每个样地取不同种植物叶片100克左右和样地0~20cm土壤500克，以石灰滤纸法同步进行大气氟化物的取样。样品带回室内应用氟离子选择电极法，测定大气氟化物含量、植物叶片氟的累积量和土壤水溶性氟的含量。同时在野外调查时使用PAM2100叶绿素荧光仪测定植物最大光化学效率即Fv/Fm的值。通过野外调查试验和相关的室内分析，研究了（1）：点源污染对三峡库区陆生植物群落组成和物种多样性的影响;（2）：点源污染中的主要污染物对植物及土壤环境的影响;（3）：不同物种叶片最大光化学效率Fv/Fm对污染胁迫响应的差异。结果如下： 点源污染对植物群落物种丰富度以及Pielou均匀度指数均有不同程度的影响，对于群落结构相对简单的马尾松林和柏木林的不利影响更为显著。相对于污染区来说，对照区中物种重要值的集中程度有所下降。许多物种的重要值在污染区与对照区有明显的变化。马尾松（Pinus massoniana）、檵木（Loropetalum chinense ）、铁仔（Myrsine africana）、卷柏（Selaginella tamariscina ）等对照区重要值较污染区为高，黄檀（Dalbergia hupeana ）、菱叶海桐（Pittosporum truncatum）、君迁子（Diospyros lotus）等污染区的重要值较对照区为高。群落中有些物种比如柏木（Cupressus funebris）的天然更新也受到污染的影响。 污染区土壤pH值大多低于对照区，但是与离污染源距离的相关性不强。污染区有些物种比如马尾松、柏木等叶片中的全氟含量与大气中氟化物的含量和土壤水溶性氟含量明显正相关。但是另外有些物种氟的累积量受点源污染的影响不显著，比如菱叶海桐、翅柃（Eurya alata）等在污染严重的样地内生存状况仍然很好。 在距离点源污染近的样地内，大多数物种的最大光化学效率Fv/Fm的值显著下降。栓皮栎（Quercus variabilis）、马尾松和柏木等的Fv/Fm值与距污染源的距离呈明显的正相关，都是随着离污染源越来越近而逐渐降低。根据污染区相对对照区Fv/Fm值下降幅度的不同，把植物划分为三种类型：对污染敏感型如柏木、铁仔、檵木等，中等敏感型如油桐（Vernicia fordii）、香叶树（Lindera communis）和不敏感型如山胡椒（Lindera glauca）和 蝴蝶花（Iris japonica）等。

细胞色素b6f蛋白复合体中叶绿素 a的性质和功能研究

细胞色素b6f蛋白复合体（Cytochrome b6f complex, Cyt b6f）是光合膜上参与光合作用原初反应过程的主要膜蛋白超分子复合体之一。莱茵衣藻和嗜热蓝细菌的Cyt b6f三维晶体结构均显示，每Cyt b6f单体分子含有1分子Chlorophyll a (Chl a )，充分肯定了Chl a 是Cyt b6f天然成分的观点(Kurisu et al，2003;Stroebel et al，2003)。研究表明不同来源的Cyt b6f中Chla单线激发态寿命(或荧光寿命)并不一样，多数的研究结果认为Cyt b6f中Chla单线激发态寿命只有200ps左右，但是也有Cyt b6f中Chla单线激发态寿命为～600ps的报道;而甲醇中游离Chl a 的单线激发态寿命为4ns左右。针对Cyt b6f中Chla单线激发态寿命快速淬灭的现象，Dashdorj 等(2005)根据晶体结构推测Cyt b6f中Chla单线激发态和邻近的Cyt b6亚基上Tyr105残基发生电子交换传递，从而快速淬灭Chla单线激发态，减少了三线态Chl a和单线态氧的产生，并且认为这是Cyt b6f保护自身不受单线态氧破坏的一种机制，但是这一推测缺乏有力的证据。另外，Cyt b6f中Chla的功能仍然未知。本文以菠菜Cyt b6f为对象，结合多种实验手段，测定了菠菜Cyt b6f中Chl a单线激发态寿命，并对复合体中Chl a 单线激发态淬灭的机理进行了深入研究。此外，我们还对复合体中Chl a 可能的功能进行了初步地探讨。获得了如下的结果： 1．针对不同来源的Cyt b6f中Chla单线激发态寿命（或荧光寿命）测定结果不同的报道，仔细分析了其中的原因，发现除了样品来源的差异外，使用不同的去垢剂可能是一个不可忽视的因素。在实验中，不同的研究者分别采用了十二烷基麦芽糖苷（n-Dodecyl β-D-maltoside，DDM，）和八烷基葡萄糖苷（n-Octyl β-D-glucopyranoside，β－OG)作为溶解样品的去垢剂。因此，本文借助稳态吸收和稳态荧光光谱、瞬态光散射技术，CD光谱和亚皮秒时间分辨吸收光谱等技术，分别研究了这两种去垢剂对Cyt b6f结构和功能的不同影响。结果表明，DDM去垢剂能使Cyt b6f处于较好的分散体系中，其中血红素和Chl a分子处于特定的蛋白环境中，不会导致Cyt b6f变性;而β－OG去垢剂会使Cyt b6f产生聚合现象，其中的血红素和Chl a与蛋白环境的相互作用减弱，和DDM相比其电子传递活性显著降低，Chl a单线激发态寿命延长，Chl a更容易被光破坏。通过这一工作，我们优化和确定了Cyt b6f的溶解条件，为下面的研究工作打下了良好的基础。 2．利用Tyr的特异性修饰剂p-Nitrobenzenesulfonyl Fluoride（NBSF）对Cyt b6f样品进行特性修饰，经原子吸收谱、荧光谱、CD谱、质谱等方法对修饰后的样品进行鉴定，并结合时间分辨飞秒吸收光谱技术，测得修饰后的样品在660nm激发下Chl a 单线激发态寿命延长，从而在实验上提供了Tyr与淬灭Chla单线激发态有关的证据。但是对Cyt b6f 中Chl a瞬态吸收图谱仔细研究表明，菠菜Cyt b6f 中Chl a单线激发态快速淬灭过程中并没有发现Tyr与Chl a 之间发生电子传递时所形成的Chla•¯。以上结果表明，Cyt b6f 中Chl a单线激发态快速的淬灭确实和邻近的Tyr105有关，但是与Dashdorj 等提出的Chla单线激发态和Tyr105残基发生了电子交换传递从而淬灭Chla单线激发态这一想法不符，关于这一问题值得进一步深入研究。 3．红光和绿光对Cyt b6f 照射，Cyt f可以被还原，并且红光比绿光更容易使Cyt f 还原，暗示Cyt f 的还原与Chl a 的关系密切，有可能是Chl a 被激发后，其被激发的电子传给Cyt f。对这一现象的进一步研究表明，Cyt b6f在光照条件下，Cyt f 的还原与体系内C10－PQ库的氧化还原状况相关，氧化型的C10－PQ可能介导电子从Chla传向Cyt f。由于在体内质体醌库的氧化还原状态往往决定Cyt b6f 的氧化还原状态，而通过对Cyt b6f不同氧化和还原状态的吸收谱和荧光谱的研究表明，氧化态和还原态的Cyt b6f 中，Chl a 与蛋白的结合状态是有差异的。这些差异可能暗示着Chl a 分子在行使其功能时与复合体的氧化还原状态是有关系的。通过以上的结果，对Cyt b6f中Chl a 可能的功能进行了假设。 4．此外，我们还发现Cyt b6f具有明显的过氧化物酶活性。在0.1 mmol/L乙酸钠缓冲液，pH3.6，25℃，[H2O2] <40mmol/L的条件下，其催化反应的速度常数为kobs＝26±1.2M•s-1;对H2O2的Km 值为50mmol/L，对guaiacol的Km 值为2mmol/L;反应的最适pH为3.6，最适离子强度为0.1，最适温度为35℃。推测Cyt b6f的这种过氧化物酶活性可能是在胁迫环境下使Cyt b6f中的血红素和Chl a 分子免受H2O2的破坏。

AN ACTIVATOR OF BLOOD-COAGULATION FACTOR-X FROM THE VENOM OF BUNGARUS-FASCIATUS

A specific activator of blood coagulation factor X was purified from the venom of Bungarus fasciatus by gel filtration and by ion-exchange chromatography on a Mono-Q column (FPLC). It consisted of a single polypeptide chain, with a mel. wt of 70,000 in reducing and non-reducing conditions. The enzyme had an amidolytic activity towards the chromogenic substrates S-2266 and S-2302 but it did not hydrolyse S-2238, S2251 or S-2222, which are specific substrates for thrombin, plasmin and factor Xa, respectively. The enzyme activated factor X in vitro and the effect was Ca2+ dependent with a Hill coefficient of 7.9. As with physiological activators, the venom activator cleaves the heavy chain of factor X, producing the activated factor Xa alpha. The purified factor X activator from B. fasciatus venom did not activate prothrombin, nor did it cleave or clot purified fibrinogen. The amidolytic activity and the factor X activation activity of the factor X activator from B. fasciatus venom were readily inhibited by serine protease inhibitors such as diisopropyl fluorophosphate (DFP), phenylmethanesulfonyl fluoride (PMSF), benzamidine and by soybean trypsin inhibitor but not by EDTA. These observations suggest that the factor X activator from B. fasciatus venom is a serine protease. It therefore differs from those of activators obtained from Vipera russelli and Bothrops atrox venoms, which are metalloproteinases.

A NOVEL PLASMINOGEN-ACTIVATOR FROM SNAKE-VENOM - PURIFICATION, CHARACTERIZATION, AND MOLECULAR-CLONING

A novel plasminogen activator from Trimeresurus stejnegeri venom (TSV-PA) has been identified and purified to homogeneity. It is a single chain glycoprotein with an apparent molecular weight of 33,000 and an isoelectric point of pH 5.2. It specifically activates plasminogen through an enzymatic reaction. The activation of human native GIu-plasminogen by TSV-PA is due to a single cleavage of the molecule at the peptide bond Arg(561)-Val-(562). Purified TSV-PA, which catalyzes the hydrolysis of several tripeptide p-nitroanilide substrates, does not activate nor degrade prothrombin, factor X, or protein C and does not clot fibrinogen nor show fibrino(geno)lytic activity in the absence of plasminogen. The activity of TSV-PA was readily inhibited by phenylmethanesulfonyl fluoride and by p-nitrophenyl-p-guanidinobenzoate. Oligonucleotide primers designed on the basis of the N-terminal and the internal peptide sequences of TSV-PA were used for the amplification of cDNA fragments by polymerase chain reaction. This allowed the cloning of a full-length cDNA encoding TSV-PA from a cDNA library prepared from the venom glands. The deduced complete amino acid sequence of TSV-PA indicates that the mature TSV-PA protein is composed of 234 amino acids and contains a single potential N-gIycosylation site at Asn(1G1). The sequence of TSV-PA exhibits a high degree of sequence identity with other snake venom proteases: 66% with the protein C activator from Aghistrodon contortrix contortrix venom, 63% with batroxobin, and 60% with the factor V activator from Russell's viper venom. On the other hand, TSV-PA shows only 21-23% sequence similarity with the catalytic domains of u-PA and t-PA. Furthermore, TSV-PA lacks the sequence site that has been demonstrated to be responsible for the interaction of t-PA (KHRR) and u-PA (RRHR) with plasminogen activator inhibitor type 1.

Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejnegeri) venom

Rong Gao, Yun Zhang, Qing-Xiong Meng, Wen-Hui Lee, Dong-Sheng Li, Yu-liang Xiong and Wan-Yu Wang. Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejneger ) venom. Toxicon 36, 457-467, 1998.-From the venom of Chinese green tree viper (Trimeresurus stejnegeri), three distinct fibrinogenolytic enzymes: stejnefibrase-l, stejnefibrase-2 and stejnefibrase-3, were purified by gel filtration, ion-exchange chromatography and reverse-phase high-performance chromatograghy (HPLC). SDS-PAGE analysis of those three enzymes showed that they consisted of a single polypeptide chain with mel. wt of -50 000, 31 000 and 32 000, respectively. Like TSV-PA (a specific plasminogen activator) and stejnobin (a fibrinogen-clotting enzyme) purified from the same venom, stejnfibrase-1, -2 and -3 were able to hydrolyze several chromogenic substrate. On the other hand, different from TSV-PA. and stejnobin, stejnefibrase-l, -2 and -3 did not activate plasminogen and did not possess fibrinogen-clotting activity. The three purified enzymes directly degraded fibrinogen to small fragments and rendered it unclottable by thrombin. Stejnefibrase-2 degraded preferentially BE-chain while stejnefibrase-l and -3 cleaved concomitantly Ax and B beta-chains of fibrinogen. None of these proteases degraded the gamma-chain of fibrinogen. When correlated with the loss of clottability of fibrinogen, the most active enzyme was stejnefibrase-l. The activities of the three enzymes were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB), indicating that like TSV-PA and stejnobin, they are venom serine proteases. (C) 1998 Elsevier Science Ltd. All rights reserved.

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases

Trimeresurus stejnegeri venom, which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin. (C) 1998 Elsevier Science Ltd. All rights reserved.