Facial selectivities in the nucleophilic additions of 2,3-unsaturated 3-arylsulfinyl pyranosides

2,3-Unsaturated 3-arylsulfinyl pyranosides undergo nucleophilic additions at C-2, with facial selectivities depending on the nucleophile and the substituent on sulfinyl sulfur. The reactions of such sugar vinyl sulfoxides lead to the addition of nucleophile preferring an axial orientation at C-2, with concomitant formation of an allylic bond at C-3 to C-4. This trend in the addition pattern is observed for primary amine, carbon and sulfur nucleophiles, whereas secondary amines prefer an equatorial addition at C-2. The effect of p-tolylthio-versus (p-isopropylphenyl)thio vinyl sulfoxide is that the equatorial nucleophilic addition is preferred even more with the latter vinyl sulfoxide. (C) 2013 Published by Elsevier Ltd.

The exploration of Kemp's triacid (KTA) as the core for the synthesis of 3-fold symmetric 2(3)-cyclophane, 2(2)-cyclophane and novel linker directed designs

For the first time, two units of KTA have been linked to three units of cyst-di-OMe. The reaction is noteworthy since it involves the formation of six amide bonds leading to a three-fold symmetric 23-cyclophane (3) harboring a cluster of three S-S bridges. The major product is a di-imide (4), arising from the interaction of a cystine NH with a neighbouring activated ester. A third reaction of tethering KTA with a single cyst-di-OMe unit afforded the flexible compound 6 and, with benzidine, the novel linker directed 7 with orthogonally disposed anchor modules.

Endoplasmic Reticulum Stress-Mediated Activation of p38 MAPK, Caspase-2 and Caspase-8 Leads to Abrin-Induced Apoptosis

Abrin from Abrus precatorius plant is a potent protein synthesis inhibitor and induces apoptosis in cells. However, the relationship between inhibition of protein synthesis and apoptosis is not well understood. Inhibition of protein synthesis by abrin can lead to accumulation of unfolded protein in the endoplasmic reticulum causing ER stress. The observation of phosphorylation of eukaryotic initiation factor 2 alpha and upregulation of CHOP (CAAT/enhancer binding protein (C/EBP) homologous protein), important players involved in ER stress signaling by abrin, suggested activation of ER stress in the cells. ER stress is also known to induce apoptosis via stress kinases such as p38 MAPK and JNK. Activation of both the pathways was observed upon abrin treatment and found to be upstream of the activation of caspases. Moreover, abrin-induced apoptosis was found to be dependent on p38 MAPK but not JNK. We also observed that abrin induced the activation of caspase-2 and caspase-8 and triggered Bid cleavage leading to mitochondrial membrane potential loss and thus connecting the signaling events from ER stress to mitochondrial death machinery.

Descripção dos emblemas allegoricos, e seus epigramas, com que se adornou a illuminação que na fachada das cazas de sua residencia apresentou ao publico o coronel Antonio José da Silva Braga, na noute de 6 de fevereiro de 1818, em que se celebrou com pompa verdadeiramente real a feliz, e gloriosa acclamação do muito alto, e poderoso Rei Nosso Senhor D. João Sexto, e nas tres noites seguintes dos dias 7, 8, e 9 em memoria do seu reconhecimento, amor, e lealdade, que professa ao mesmo Augusto senhor, cuja preciosa vida os ceos dilatem por longos annos para gloria e delicia de toda a naçam portugueza

Coleção Marcio Moreira Alves.

Synthesis and matrix isolated photolysis of 2,3-dimethylbicyclo [2.2.0]hexa-2,5-diene-1,4-dicarboxylic acid anhydride: a potential percursor to 2,3-dimethyl-1,4-dehydrobenzene

The synthesis of the first member of a new class of Dewar benzenes has been achieved. The synthesis of 2,3- dimethylbicyclo[2.2.0]hexa-2,5-diene-1, 4-dicarboxylic acid and its anhydride are described. Dibromomaleic anhydride and dichloroethylene were found to add efficiently in a photochemical [2+2] cycloaddition to produce 1,2-dibromo- 3,4-dichlorocyclobutane-1,2-dicarboxylic acid. Removal of the bromines with tin/copper couple yielded dichloro- cyclobutenes which added to 2-butyne under photochemical conditions to yield 5,6-dichloro-2,3-dimethylbicyclo [2.2.0] hex-2-ene dicarboxylic acids. One of the three possible isomers yielded a stable anhydride which could be dechlorinated using triphenyltin radicals generated by the photolysis of hexaphenylditin.

Photolysis of argon matrix isolated 2,3-dimethylbicyclo [2.2.0]hexa-2, 5-diene-1,4-dicarboxylic acid anhydride produced traces whose strongest bands in the infrared were at 3350 and 600 cm^(-1). This suggested the formation of terminal acetylenes. The spectra of argon matrix isolated E- and Z- 3,4-dimethylhexa-1,5-diyne-3-ene and cis-and trans-octa- 2,6-diyne-4-ene were compared with the spectrum of the photolysis products. Possibly all four diethynylethylenes were present in the anhydride photolysis products. Gas chromatograph-mass spectral analysis of the volatiles from the anhydride photolysis again suggested, but did not confirm, the presence of the diethynylethylenes.

Photosensitized CIS-TRANS isomerization of 2,3-diphenylbutene-2 investigation of anomalous sensitizers for substituted Stilbene isometrization

The behavior of the photosensitized cis-trans isomerization of 2,3-diphenylbutene-2 was studied as a function of sensitizer energy by previously established methods. In addition, certain sensitizers for which parameters other than energy transfer are operative in inducting isomerizations, were studied in more detail. Sensitization of various stilbenes and substituted stilbenes by triphenylene is discussed in terms of excited state complex formation with stilbene. Sensitization by quinones, halogen-containing aromatics and 1,2-diketones is discussed in terms of attack by photolytically produced free radicals, either by addition to and elimination from the double bond, or in the cases of 1,2-diphenylpropene and 2,3-diphenylbutene-2, by hydrogen abstraction from one of the methyl groups and reversible abstraction by the allylic radical to produce cis-trans isomerized substrate and the structurally isomerized products, 2,3-diphenylpropene and 2,3-diphenylbutene-1.

I. The 3.7 Å crystal structure of horse heart ferricytochrome C. II. The application of the Karle-Hauptman tangent formula to protein phasing

I. The 3.7 Å Crystal Structure of Horse Heart Ferricytochrome C.

The crystal structure of horse heart ferricytochrome c has been determined to a resolution of 3.7 Å using the multiple isomorphous replacement technique. Two isomorphous derivatives were used in the analysis, leading to a map with a mean figure of merit of 0.458. The quality of the resulting map was extremely high, even though the derivative data did not appear to be of high quality.

Although it was impossible to fit the known amino acid sequence to the calculated structure in an unambiguous way, many important features of the molecule could still be determined from the 3.7 Å electron density map. Among these was the fact that cytochrome c contains little or no α-helix. The polypeptide chain appears to be wound about the heme group in such a way as to form a loosely packed hydrophobic core in the molecule.

The heme group is located in a cleft on the molecule with one edge exposed to the solvent. The fifth coordinating ligand is His 18 and the sixth coordinating ligand is probably neither His 26 nor His 33.

The high resolution analysis of cytochrome c is now in progress and should be completed within the next year.

II. The Application of the Karle-Hauptman Tangent Formula to Protein Phasing.

The Karle-Hauptman tangent formula has been shown to be applicable to the refinement of previously determined protein phases. Tests were made with both the cytochrome c data from Part I and a theoretical structure based on the myoglobin molecule. The refinement process was found to be highly dependent upon the manner in which the tangent formula was applied. Iterative procedures did not work well, at least at low resolution.

The tangent formula worked very well in selecting the true phase from the two possible phase choices resulting from a single isomorphous replacement phase analysis. The only restriction on this application is that the heavy atoms form a non-centric cluster in the unit cell.

Pages 156 through 284 in this Thesis consist of previously published papers relating to the above two sections. References to these papers can be found on page 155.

Synthesis, applications and reactivity of 1,2,3-triazolium salts

276 p.

常绿灌木沙地柏对变化环境的反应

毛乌素沙地位于内蒙古鄂尔多斯高原东南部，是一个多层次生态过渡带。沙地柏系柏科(Cupressaceae)圆柏属(Sabina)常绿灌木，是毛乌素沙地中唯一的天然常绿灌木，也是一种具代表性的木本克隆植物。由于沙地柏起源古老、对半干旱沙地的适应性较强，因而吸引了许多中外研究者。本文的目的是初步探讨沙地柏对变化环境的反应。 第2章探讨沙地柏的叶结构与功能随性别、叶型、生长型和生境的变化。（1）沙地柏雌性植株的叶片厚度、失水系数、净光合速率和表观光能利用效率均显著大于雄性植株，而前者的微管束宽度显著小于后者。（2）鳞叶的表皮厚度和水分利用效率显著大于针叶，而针叶的组织密度、失水系数、光合速率、蒸腾速率和Ci/Ca显著大于鳞叶。（3）匍匐茎的最大光合速率、最大表观光能利用效率、光补偿点、暗呼吸速率、表皮细胞长度和微管束大小都显著大于起立茎，而光饱和点、水分利用效率恰好相反。水分饱和亏缺不受生长型的影响。（4）叶片的比叶面积、结构特征、失水系数、气体交换和资源利用效率均受生境类型的显著影响。（5）沙地柏叶结构与功能具有许多普遍性特征，例如，光合曲线为双峰型、具有午休现象，最大光合速率和暗呼吸速率随叶片厚度的增加而降低。 第3章探讨沙地柏根系的分布特征及其对水分资源的共享。（1）地下部分生物量投资、根密度、根面积指数随土壤水分可利用性降低而减小，这种格局有利于减缓沙地柏植株地下部分对水分资源的竞争，从而经济、长时间地利用有限水分资源。（2）根系深度系数、最大根系深度、含50％或90％根系生物量或表面积的根系深度随土壤水分可利用性降低而增大。这些结果指示，沙地柏根系通过增加深度以补偿土壤水分可利用性的降低。（3）根系生物量和表面积分布与土壤现有水分含量的有关性随生境发生变化。（4）根系分布特征既可能记载了植物生境中水分状况的变化，又可在一定程度上为群落动态提供证据。（5）沙地柏根系具有共享水分资源的潜力。 第4章分析沙地柏对养分贫瘠的沙地环境的适应策略。（1）土壤养分并不随土壤水分不可利用性的梯度变化而成梯度变化。（2）叶重比随土壤干旱度增加而增大，地下部分投资比例却相反。（3）N、P、K在叶中分配比随土壤养分含量降低而增大，而在根中的分配恰好相反。（4）N、P利用效率随土壤养分含量减少降低，重吸收效率却相反;K利用效率和重吸收效率、Ca、Mg利用效率均随土壤养分含量降低而增大。（5）沙地柏植株地上部分与地下部分对养分内循环的贡献恰好相反，这指示沙地柏植株对养分内循环的贡献可能存在一种权衡。（6）根系分布对不同养分异质性的影响存在差异，而且对水平和垂直剖面上异质性的影响也不相同。 第5章研究沙地柏种群的繁殖和更新特征。（1）根原基是沙地柏进行营养繁殖的结构基础，它反映营养繁殖能力的潜在大小，受性别、生长型、生境和植株大小级的显著影响;由根原基转化而来的不定根可吸收充足的土壤资源供给萌生分株代谢需要，因此定居分株能够独立维持。（2）雌株的繁殖分配显著大于雄株，但繁殖效率恰好相反;生长型、生境和植株大小级对繁殖分配、繁殖效率和种子产生有明显影响。（3）沙地柏同时具有营养繁殖和有性繁殖，这为种群更新提供了两种方式。由于可供分配的资源有限，两种繁殖方式各有利弊，因此两者间可能存在权衡。（4）根原基数量、繁殖分配、繁殖效率和种子产生随生境变化。这表明未来气候变化对沙地柏种群繁殖特征具有潜在影响。（5）种子质量差、种子萌发率低和幼苗存活率低是制约沙地柏种群有性更新的三个“瓶颈”。（6）沙地柏营养繁殖力强、萌生苗存活率高，这使自然条件下沙地柏种群以无性更新为主。 第6章探讨沙地柏群落的发生和演替。（1）沙地柏系古北极成分，起源古老，天然分布在大陆性干旱、半干旱草原气候带。（2）沙地柏群落的发生方式有两种，即滩地发生和固定沙地发生，但以前者为主。（3）由于毛乌素沙地的干扰频繁，因而沙地柏群落的发展具有多种途径。 第7章探讨切断匍匐茎和除叶干扰对沙地柏生理和生长特征的影响。（1）切断匍匐茎对沙地柏子株存活率的影响不显著，这批示天然压条形成的定居子株能够独立维持。（2）切断匍匐茎对子株气体交换和资源利用效率的影响都不显著，而显著影响其生长和生物量分配特征。（3）除叶干扰通过改变生理指标峰值出现时间从而影响沙地柏生理动态。（4）除叶干扰（尤其是除部分老叶）具有补偿效应，可以促进当年生枝生长和生物量积累。（5）干扰效应受干扰方式、干扰强度和环境因子的共同影响，因此干扰效应多种多样。（6）不同生理、生长指标对模拟干扰的敏感性存在差异。 第8章探讨模拟降雨变化对沙地柏实生苗生理和生长特征的影响。（1）水分变化显著影响沙地柏实生苗的气体交换特征，对所测荧光特征的影响均不显著。这种影响差异指示水分变化主要影响样片的表观性生理特征，而对光系统II的内在本质基本无影响。（2）水分变化显著影响实生苗的水分特征和水分构筑特征。两类特征的变化趋势表明，随施水量增加，沙地柏实生苗的抗旱性和水分利用效率逐渐降低。（3）水分变化显著影响生物量分配，而对形态和生产力指标均无显著影响;根系对水分变化的敏感性高于叶和茎，地下部分生物量投资随水分可利用性提高而增大。

水稻2,3-氧化鲨烯环化酶基因的功能研究

植物通过异戊二烯代谢途径合成多种具有生物活性和功能的三萜及甾醇类化合物，它们在调节植物生长发育、维持膜的完整和功能、抵抗病原微生物侵染中发挥着重要的作用。2,3-氧化鲨烯为三萜和甾醇合成途径的分枝点，参与这一关键步骤的酶被通称为2,3-氧化鲨烯环化酶（OSCs）。本研究系统分了水稻基因组中全部11个OSC基因序列，发现其中四个可能为假基因。亚种间非同义替换率Ka和同义替换率Ks的比值（Ka/Ks）以及进化树的分析表明OsOSC8是单子叶植物特有的功能保守基因，而OsOSC9在水稻两个亚种间发生了功能快速进化，这种快速进化的基因往往参与植物和病原菌相互作用的代谢途径。 根据基因结构、表达谱以及与其它植物已知功能的OSC酶氨基酸序列的比对推测OsOSC3可能具有环阿屯醇合成酶的功能，参与植物甾醇的合成，而OsOSC7、OsOSC10和OsOSC11可能具有β-香树素合成酶的功能，其余OSCs可能参与合成其它三萜化合物。为了进一步分析和验证OSCs酶的功能，将水稻7个OSC基因的开放阅读框（ORF）构建到酵母表达载体并在pichia酵母中表达，发现仅有OsOSC9和OsOSC12能够将酵母内源的2,3-氧化鲨烯分别环化为四环三萜化合物Parkeol和植物中稀有的五环三萜化合物Isoarborinol，目前还未在其它植物中发现参与这两种三萜化合物的基因。另外，水稻所有的OSC基因均不能互补酵母羊毛甾醇缺陷型菌株，表明水稻OSCs不具有合成羊毛甾醇的功能。 RNAi沉默以及启动子融合GUS的表达实验发现OsOSC8可能参与花粉的发育，该基因的下调影响水稻的育性，暗示水稻中存在一个可能与雄性不育有关的三萜代谢途径。水稻其它OSC基因RNAi植株可能在逆境环境和病原菌侵染下才会显现出表型。

Discovery of a new 2.3 s isomer in neutron-rich 174Tm

A new program of K-isomer research has been initiated with the 8π spectrometer sited at the ISAC facility of TRIUMF. We discuss in this paper the identification of a new 2.3 s isomer in 174Tm and its implications. © Società Italiana di Fisica / Springer-Verlag 2005.

An internally-matched GaN HEMTs device with 45.2 W at 8 GHz for X-band application

Optimized AlGaN/AlN/GaN high electron mobility transistor (HEMT) with high mobility GaN channel layer structures were grown on 2-in. diameter semi-insulating 6H-SiC substrates by MOCVD. The 2-in. diameter GaN HEMT wafer exhibited a low average sheet resistance of 261.9 Omega/square, with the resistance un-uniformity as low as 2.23%. Atomic force microscopy measurements revealed a smooth AlGaN surface whose root-mean-square roughness is 0.281 nm for a scan area of 5 x 5 mu m. For the single-cell HEMTs device of 2.5-mm gate width fabricated using the materials, a maximum drain current density of 1.31 A/mm, an extrinsic transconductance of 450 mS/mm, a current gain cutoff frequency of 24 GHz and a maximum frequency of oscillation 54 GHz were achieved. The four-cell internally-matched GaN HEMTs device with 10-mm total gate width demonstrated a very high output power of 45.2 W at 8 GHz under the condition of continuous-wave (CW), with a power added efficiency of 32.0% and power gain of 6.2 dB. To our best knowledge, the achieved output power of internally-matched devices are the state-of-the-art result ever reported for X-band GaN-based HEMTs. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

7.8μm二级分布反馈量子级联激光器

报道了基于应变补偿的InP基In0.53+xGa0.47-xAs/In0.52-yAl0.48+yAs分布反馈量子级联激光器.采用二级光栅作为反馈,激射工作波长为7.8μm,在1%占空比,5kHz频率的工作条件下,在93～173K的温度范围内,单模发射光谱边模抑制比均超过20dB,调谐系数dλ/dT=0.5125nm/K.在93K时,峰值功率为30mW,直到153K时,峰值光功率仍达到12mW.