早春短命植物鸢尾蒜和准噶尔鸢尾蒜的光合途径

该研究以鸢尾蒜属两种早春短命植物准噶尔鸢尾蒜(Ixiolirion songaricum)和鸢尾蒜(Ixiolirion tataricum)为对象,通过解剖结构、光合参数、稳定碳同位素比值(δ¹³C)和光合关键酶活性分析二者的光合途径。结果发现：(1)显微结构和超微结构显示,两种短命植物的叶脉维管束鞘细胞1层、排列较紧密,鞘细胞内含有较多叶绿体且多离心分布,类似C₄花环结构。(2)准噶尔鸢尾蒜和鸢尾蒜最大净光合速率分别为14.81和15.04 μmol·m^-2·s^-1;两者的CO₂补偿点较低,分别为3.57和2.54 μmol·mol^-1,δ¹³C分别为-25.36±0.55‰和-25.76±1.38‰,光合酶PEPC/Rubisco比值分为别0.244和0.322。(3)最大净光合速率、δ¹³C和PEPC/Rubisco比值均说明两种植物为C₃光合途径,但二者均具有类似C₄的维管束鞘结构、较低的CO₂补偿点和暗呼吸速率,并具有高于部分C₃和C₃ C₄中间型植物的PEPC/Rubisco比值,表明两种短命植物的光合途径并非典型的C₃途径,而是C₃ C₄中间型。     

NH4+对L-色氨酸发酵的影响

目的:探究NH₄⁺浓度对大肠杆菌E.coli TRTH发酵生产L-色氨酸的影响。方法:通过外源添加试验,利用30 L发酵罐进行分批补料发酵试验,考察E. coli TRTH发酵生产L-色氨酸过程中生物量、L-色氨酸产量、有机酸含量、耗糖速率、发酵液中NH₄⁺浓度及质粒稳定性变化。建立了大肠杆菌合成L-色氨酸的代谢流平衡模型,应用 MATLAB 软件计算出E. coli TRTH发酵中后期代谢网络的代谢流分布。结果:发酵结果显示,利用NaOH和氨水混合补料,控制NH₄⁺浓度在120 mmol/L以下,菌体能够以较长时间和较高比生长速率保持对数生长,最终菌体生物量和L-色氨酸产量分别提高了12.16%和19.80%。随着NH₄⁺浓度的增加,发酵液中丙酮酸、乳酸及乙酸浓度均略有增加,细胞质粒稳定性下降。控制NH₄⁺浓度在120 mmol/L以下,E. coli TRTH发酵生产L-色氨酸的代谢流量分析结果表明,EMP途径的代谢流量降低7.31%,PP途径的代谢流量增加7.14%,TCA循环的代谢流量降低22.04%。结论:高浓度的NH₄⁺导致菌体生长提前结束,耗糖速率降低,产酸受阻,控制NH₄⁺浓度在120 mmol/L以下,解除了NH₄⁺对菌体生长和产物生成的抑制,使得菌体生物量和L-色氨酸产量大幅提高,实现了高密度发酵培养的目的。     

铕标记抗癌胚抗原单克隆抗体C17的研究和应用

用合成的N′-(对-异硫氰基苄基)-二乙三胺-N¹,N²,N³,N³-四乙酸铕钠为螫合剂.用Sephadex G-50凝胶柱层析分离标记C₁₇和过量试剂.分部收集的层析物的光密度图和荧光强度图完全一致.蛋白峰处两管标记C₁₇的比活性分别为5.2和8.9Eu³⁺离子每C₁₇分子,而且C₁₇的标记回收率为64%.标记C₁₇至少在6个月内是稳定的.用铕标记物得到的时间分辨免疫荧光分析的标准曲线具有良好线性和斜率,表明标记物免疫活性良好,而且已用于血清CEA分析.     

内蒙古草原常见植物叶片δ13C和δ15N对环境因子的响应

在中国东北样带沿线的内蒙古草原地区采集了一些常见植物的叶片样品,并测定其δ¹³C和δ¹⁵N值,分析了其统计学特征以及对环境因子(年平均降雨量和温度)的响应模式。发现东北样带草原区同时存在C₃和C₄两种不同光合途径的植物,但是C₃植物占主导地位,C₄植物数量有限。C₃植物叶片δ¹³C随着年平均降雨量和年平均温度的升高而显著降低,反映了此区域C₃植物δ¹³C受控于降水量和温度。C₄植物的叶片δ¹³C值随着降雨量的增多而有轻微升高的趋势,但是C₄植物的叶片δ¹³C值对年平均温度的响应不敏感。不论对C₃植物还是C₄植物而言,叶片δ¹⁵N都随降雨量增加而显著降低,即干旱区的植物叶片δ¹⁵N大于湿润地区,这说明降水是影响植物叶片δ¹⁵N的一个重要因素。然而两者叶片δ¹⁵N对温度的响应不敏感。     

What is the usual internal carbon dioxide concentration in C<Subscript>4</Subscript> species under midday field conditions?

The carbon dioxide concentrating system in C₄ photosynthesis allows high net photosynthetic rates (P _N) at low internal carbon dioxide concentrations (C _i), permitting higher P _N relative to stomatal conductance (g _s) than in C₃ plants. This relation would be reflected in the ratio of C _i to external ambient (C _a) carbon dioxide concentration, which is often given as 0.3 or 0.4 for C₄ plants. For a C _a of 360 μmol mol⁻¹ that would mean a C _i about 110–140 μmol mol⁻¹. Our field observations made near midday on three weedy C₄ species, Amaranthus retroflexus, Echinochloa crus-galli, and Setaria faberi, and the C₄ crop Sorghum bicolor indicated mean values of C _i of 183–212 μ mol mol⁻¹ at C _a = 360 μmol mol⁻¹. Measurements in two other C₄ crop species grown with three levels of N fertilizer indicated that while midday values of C _i at high photon flux were higher at limiting N, even at high nitrogen C _i averaged 212 and 196 μmol mol⁻¹ for Amaranthus hypochondriacus and Zea mays, respectively. In these two crops midday C _i decreased with increasing leaf to air water vapor pressure difference. Averaged over all measurement days, the mean C _i across all C₄ species was 198 μmol mol⁻¹, for a C _i/C _a ratio of 0.55. Prior measurements on four herbaceous C₃ species using the same instrument indicated an average C _i/C _a ratio of 0.69. Hence midday C _i values in C ₄ species under field conditions may often be considerably higher and more similar to those of C₃ species than expected from measurements made on plants in controlled environments. Reducing g _s in C₄ crops at low water vapor pressure differences could potentially improve their water use efficiency without decreasing P _N.     

Preparation of recombinant six-histidine-tagged human LECT2, a chemotactic protein to neutrophils, in Escherichia coli

LECT2 is a chemotactic protein to neutrophils. A recombinant six-histidine-tagged human LECT2, (His)₆-LECT2, was expressed in E. coli using a pET21a(+) vector. The (His)₆-LECT2 was purified from the soluble fraction in E. coli as a single band in sodium dodesyl sulfate/polyacrylamide gel electrophoresis using three steps of column chromatography with Ni²⁺-charged nitrilo-triacetic acid (Ni-NTA) agarose, DEAE-Sepharose, and CM-Sepharose. The purified (His)₆-LECT2 was yielded with 96 μg from the soluble fraction of 1,500 ml culture of E. coli. The circular dichroism spectrum of (His)₆-LECT2 showed the folded structure, which is rich in β-sheet structure and rare in α-helix. This revised version was published online in June 2006 with corrections to the Cover Date.     

Differences in Field Gas Exchange and Water Relations Between a C3 Dicot (Plantago Asiatica) and a C4 Monocot (Eleusine Indica)

Field gas exchange and water potential in the leaves of a C₃ dicot, Plantago asiatica L., and a C₄ monocot, Eleusine indica Gaertn., which dominate in trampled vegetation in eastern Japan were surveyed during the growing periods for two consecutive years. Net photosynthetic rate (P _N) of E. indica increased with photosynthetic photon flux density (PPFD) and leaf temperature (T_L). P _N was not saturated at PPFDs above 1500 μmol m⁻² s⁻¹ and at T_L above 30 °C. On a sunny day in mid summer, maximum P _N was two times higher in E. indica than in P. asiatica [42 vs. 20 μmol(CO₂) m⁻² s⁻¹], but their transpiration rate (E) and the leaf water potential (Ψ_L) were similar. Soil-to-leaf hydraulic conductance, which probably plays a role in water absorption from the trampled compact soil, was higher in E. indica than in P. asiatica. The differences in photosynthetic traits between E. indica explain why E. indica communities more commonly develop at heavily trampled sites in summer than the P. asiatica communities. This revised version was published online in June 2006 with corrections to the Cover Date.     

Compensatory effects of elevated CO<Subscript>2</Subscript> concentration on the inhibitory effects of high temperature and irradiance on photosynthetic gas exchange in carrots

We determined the interactive effects of irradiance, elevated CO₂ concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m⁻² s⁻¹), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO₂ concentrations (C _a), AC and EC (350 and 750 μmol mol⁻¹, respectively). Rates of net photosynthesis (P _N) and transpiration (E) and stomatal conductance (g _s ) were measured, along with water use efficiency (WUE) and ratio of internal and external CO₂ concentrations (C _i/C _a). P _N revealed an interactive effect between PAR and C _a. As PAR increased so did P _N under both C _a regimes. The g _s showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 °C and 1 200 μmol m⁻² s^{− 1} PAR under EC. The C _i /C _a was influenced independently by temperature and C _a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO₂ concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on P _N and WUE.     

中华绒螯蟹眼柄MTXO细胞GABA受体通道研究

采用全细胞膜片钳技术测定了中华绒螯蟹（Eriocheir sinensis）眼柄视神经节端髓X器官（MTXO）三种类型神经内分泌细胞对0.01～5mmol/L γ氨基丁酸（γ-aminobutyric acid,GABA）的反应,并结合选择性拮抗剂和激动剂的使用进行了GABA受体研究.在电流钳模式下,依据不同Nernst Cl^－电位,三种类型细胞均对GABA产生去极化或超级化反应.在电压钳模式下,GABA激活Cl^－通道电流（I_GABA）.I_GABA在灌流GABA后约1 200 ms内激活,800 ms内达到峰值,没有明显的脱敏反应,反转电位接近Nernst Cl^－电位.I_GABA幅值呈浓度依赖性,激活阈值为0.01 mmol/L,约在0.5 mmol/L达到饱和.药理学实验结果表明,中华绒螯蟹眼柄神经内分泌细胞GABA受体是Cl^－通道蛋白,对Cl^－离子通道阻断剂Picrotoxin和Niflumic acid敏感,但是对GABA_A受体拮抗剂Bicuculline和GABA_C受体激动剂cis-4-aminocrotonic acid (CACA)和trans-4-aminocrotonic (TACA)均不敏感.     

纤维蛋白对尿激酶原激活纤溶酶原反应动力学的影响

反应体系中存在的纤维蛋白（fibrin）对尿激酶（UK）、scu-PA以及组织型纤溶酶原激活剂（t-PA）激活纤溶酶原（plasminogen）的反应有不同的作用：UK、t-PA激活plasminogen的反应可被反应体系中存在的fibrin所加强;fibrin对scu-PA激活plasminogen反应的动力学常数无明显影响;但对小分子质量scu-PA与单链抗体的嵌合分子激活plasminogen的反应起明显的抑制作用.为确定反应体系中存在的fibrin对scu-PA的K区插入突变体-InB激活plasminogen反应的影响,测定了在反应体系中存在fibrin的情况下的InB激活plasminogen反应的K_m^fibrin以及k_cat^fibrin.K_m^fibrin＝4.2 μmol·L^-1,远远大于无fibrin时的K_m＝0.379 μmol·L^-1,说明有fibrin存在时突变体InB与天然底物plasminogen的亲和性降低了.k_cat^fibrin＝0.107 s^-1,也远远大于无fibrin时k_cat＝0.0165 s^-1,说明有fibrin存在时突变体InB对plasminogen的反应活性增强了.原因可能是：与fibrin结合的plasminogen的构象发生了有利于被纤溶酶原激活剂水解的变化.     

Photosynthetic response of <Emphasis Type="Italic">Quercus ilex</Emphasis> L. plants grown on compost and exposed to increasing photon flux densities and elevated CO<Subscript>2</Subscript>

Quercus ilex plants grown on two different substrates, sand soil (C) and compost (CG), were exposed to photosynthetic photon flux densities (PPFD) at 390 and 800 μmol(CO₂) mol⁻¹ (C₃₉₀ and C₈₀₀). At C₈₀₀ both C and CG plants showed a significant increase of net photosynthetic rate (P _N) and electron transport rate (ETR) in response to PPFD increase as compared to C₃₉₀. In addition, at C₈₀₀ lower non-photochemical quenching (NPQ) values were observed. The differences between C₃₉₀ and C₈₀₀ were related to PPFD. The higher P _N and ETR and the lower dissipative processes found in CG plants at both CO₂ concentrations as compared to C plants suggest that substrate influences significantly photosynthetic response of Q. ilex plants. Moreover, short-term exposures at elevated CO₂ decreased nitrate photo-assimilation in leaves independently from substrate of growth.     

酵母tRNAAla中修饰核苷酸T54,Ψ55的生物功能

酵母tRNA^Ala的3′半分子与一个11聚的DNA片段(5′GGAATCGAACC3′)杂交后用RNase H酶解,该酶能在Ψ₅₅的3′侧定点剪切,这样就制备得片段C₃₆-Ψ₅₅该片段经1～2个高碘酸氧化和β-消去得片段C₃₆-T₅₄和C₃₆-G₅₃机器合成了3个酵母tRNA^Ala的片段,分别j是片段C₅₆-A₇₆,U₅₅-A₇₆(以U替代Ψ₅₅)和U₅₄-A₇₆(以UU替代T₅₄Ψ₅₅).合成和制备的片段以适当的组合用T₄RNA连接酶连接,产物是酵母tRNAtRNA^Ala的3′半分子或其类似物.3种3′半分子或其类似物分别与天然5′半分子连接得重组天然酵母tRNA^Ala(tRNAr)和2个酵母tRNA^Ala的类似物:(1)tRNAa(以U替代Ψ₅₅),(2)tRNAb(以UU替代T₅₄Ψ₅₅).体外测定了它们的丙氨酸接受活力和参入活力,发现酵母tRNA^Ala的类似物tRNAa和tRNAb与天然重组酵母tRNA^Ala相比,它们的氨基酸接受活力分别降低了25%和55%,参入活力分别降低了35%和30%.说明酵母tRNA^Ala中的修饰核苷酸T₅₄和Ψ₅₅对该tRNA的功能有重要的影响.     

人MCP cDNA的克隆、序列分析及同种型的比较

以人胚胎mRNA为模板,采用RT-PCR法得到了人补体调节蛋白膜辅蛋白(MCP)的一种cDNA全基因,序列分析结果表明,所获得的MCP cDNA为文献报道中10种同种型中的一种,属MCP-C₂型,该cDNA含一编码369个氨基酸的阅读框架,其中的STP区含14个氨基酸,由STP^C编码,胞浆尾区含23个氨基酸,为CYT₂,未发现有东西方人种之间的核苷酸的差异.     

碳酸钙促进丙酮酸发酵过程中α-酮戊二酸的形成

在多重维生素营养缺陷型菌株光滑球拟酵母CCTCC M202019发酵生产丙酮酸的摇瓶和发酵罐实验中发现,CaCO₃的添加对发酵液中α-酮戊二酸（α-KG）的积累有重要影响。在维生素浓度不变且供氧充分的前提下,延迟CaCO₃添加时间可明显抑制α-KG的产生,并提高丙酮酸与α-KG的碳摩尔比(C_PYR/C_αKG);而增加培养基中的CaCO₃浓度会导致αKG积累的增加。用不同物质调节发酵液中pH的实验证实：在丙酮酸发酵过程中, Ca²⁺对αKG的积累起主要作用,CO₃^2-起辅助作用,两者对α-KG的积累具有协同效应。维持培养基中CaCO₃浓度不变,改变培养基中硫胺素的浓度,对αKG的积累,特别是对C_PYR/C_α-KG值没有影响;而增加培养基中生物素的浓度,则导致αKG的浓度不断上升且C_PYR/C_α-KG值不断下降。当有Ca2+存在时,胞内丙酮酸羧化酶的活性最高可提高40%,而丙酮酸脱氢酶系的活性没有明显变化。结果表明,丙酮酸发酵过程中α-KG的形成是由于CaCO₃促进了丙酮酸羧化反应,其中Ca²⁺可显著提高丙酮酸羧化酶的活性,而CO₃^2-则有可能作为丙酮酸羧化反应的底物。     

钙离子通道A23187对血小板聚集和蛋白质磷酸化的影响

以 ³²P-Na₂HPO₄标记猪血小板,在阿斯匹林阻断花生四烯酸代谢,Apyrase去除分泌的ADP情况下,以A23187和PMA为血小板激动剂,staurosporine为PKC抑制剂,研究Ca²⁺和蛋白激酶C在血小板聚集中的作用.结果表明,a.A23187在1～20 μmol/L引起血小板聚集,相应地,明显地引起40 ku、20 ku蛋白质磷酸化,且存在剂量和时间效应关系.b.A23187和PMA在血小板聚集和蛋白质磷酸化上都存在着协同效应.c.1 μmol/L staurosporine可大部分抑制20 μmol/L A23187诱导的血小板聚集和20 ku、40 ku蛋白质磷酸化.结果提示,Ca²⁺激活血小板是建立在激活PKC的基础上,Ca²⁺通过激活PKC诱导血小板聚集,这是Ca²⁺激活血小板的主要途径.     

宁夏的䗴

宁夏的含?地层出露较好,剖面和柱状剖面有7处.含?地层自下而上为:下石炭统臭牛沟组、中卫组,上石炭统羊虎沟组,上石炭—下二叠统太原组.?动物群有15属68种及亚种,其中1新种.可建立?化石带 Eostaffella-Mediocris 带 (C₁), Profusulinella 带 (C₂¹) 及 Sphaeroschwagertna 带 (P₁¹),并与甘肃靖远及华北地台其它地区的?化石带对比.     

鱼类补体系统成分及补体特异性和功能的研究进展

补体系统由30多种可溶性蛋白和膜蛋白组成,在先天性免疫和适应性免疫中均起着重要作用。补体存在三条激活途径即经典途径、凝集素途径和替代途径,并共用一条终末（或溶解）途径（图1）。经典途径是第一个被发现的补体激活途径,由结合在细胞表面的抗体激活,其作用具特异性且同时需要Ca2＋和Mg2＋参与。替代途径不依赖于抗体,可直接由C3或微生物表面的特定结构激活,只需要Mg2＋。1995年后才明确了通过MBL识别的凝集素途径,此途径也不依赖于抗体且仅需要Ca2＋。     

Differential inhibition of photosynthesis under drought stress in <Emphasis Type="Italic">Flaveria</Emphasis> species with different degrees of development of the C<Subscript>4</Subscript> syndrome

The effect of drought stress (DS) on photosynthesis and photosynthesis-related enzyme activities was investigated in F. pringlei (C₃), F. floridana (C₃–C₄), F. brownii (C₄-like), and F. trinervia (C₄) species. Stomatal closure was observed in all species, probably being the main cause for the decline in photosynthesis in the C₃ species under ambient conditions. In vitro ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and stromal fructose 1,6-bisphosphatase (sFBP) activities were sufficient to interpret the net photosynthetic rates (P _N), but, from the decreases in P _N values under high CO₂ (C _a = 700 μmol mol^{− 1}) it is concluded that a decrease in the in vivo rate of the RuBPCO reaction may be an additional limiting factor under DS in the C₃ species. The observed decline in the photosynthesis capacity of the C₃–C₄ species is suggested to be associated both to in vivo decreases of RuBPCO activity and of the RuBP regeneration rate. The decline of the maximum P _N observed in the C₄-like species under DS was probably attributed to a decrease in maximum RuBPCO activity and/or to decrease of enzyme substrate (RuBP or PEP) regeneration rates. In the C₄ species, the decline of both in vivo photosynthesis and photosynthetic capacity could be due to in vivo inhibition of the phosphoenolpyruvate carboxylase (PEPC) by a twofold increase of the malate concentration observed in mesophyll cell extracts from DS plants.     

耐热酵母与酿酒酵母原生质体融合的研究

酿酒酵母(saccharomyces cerevisiae)396是利用甘蔗糖蜜生产酒精的生产菌株,假丝酵母(Candida sp·)C₆是我们从云南温泉底泥中筛选到的一株能在45℃生长良好的耐热酵母,我们应用原生质体融合技术进行了两菌株属间融合的研究。通过亚硝基胍(NTG)诱变得到的营养缺陷型菌株396(arg^－)和C6(lys^-),其融合频率为O．91×10^-5。从检出的融合子中挑选6株进行考核、其细胞体积平均为亲株的1．3倍,DNA含量平均为亲株的1．6倍,培养特征、形态、大小和生理生化特征表现不一,特别是糖类的同化试验。除F₂、F₁₄外,其他4株可以排除异核体形成的可能性。比较了在28℃,40℃和45℃培养条件下出发亲株396、C₆、直接亲株396(arg^-)C₆(lys^-)和融合子F₁、F₇、F₁₂,F₁₃的生长曲线、基质利用率和乙醇产率等,得到一株在40℃培养条件下糖的利用率为94．3％、乙醇产量为59．7g／L的属间融合株F₁₃。     

呼吸链电子漏在细胞凋亡中的作用

实验证明细胞色素c具有很强的抗氧化功能,在线粒体中氧化态的细胞色素c直接清除O2·-,还原态的细胞色素c清除H2O2.由于呼吸链传递电子合成ATP的同时,总有少部分电子从呼吸链底物端的复合物Ⅰ和Ⅲ漏出,而且漏出的电子首先使氧分子还原成O2·- ,然后O2·-歧化成H2O2,所以细胞色素c清除O2·-和H2O2的功能使呼吸链出现了两条电子漏旁路.细胞色素c通过这两条电子漏路径实现其控制线粒体中O2·-和H2O2水平的功能.根据两条电子漏旁路都是O2·-代谢路径的事实,引进了线粒体自由基代谢的概念,并从自由基代谢失调的角度探讨了呼吸链电子漏在细胞凋亡中的作用.