杂交水稻结实率稳定性的遗传分析

本文采用三套同核异质不育系与５个恢复力不同的恢复系按Ｐ×Ｑ模式配组、分５期播种的试验设计,在ＡＭＭＩ模型分析结实率稳定性的基础上,进一步剖析了不育胞质、保持系、恢复系及其工作的各种遗传效应。     

Molecular Dynamics Simulations of Carbon Nanotube Rolling and Sliding on Graphite

Abstract

Molecular dynamics simulations were carried out to investigate the origin of friction for carbon nanotubes on graphite substrates. In an initial simulation, a (10,10) nanotube was placed in an ‘in-registry’ starting position where the hexagonal lattice of the substrate matched that of the nanotube. In a second simulation, the substrate was oriented 90 degrees to the nanotube. A uniform force was applied to the nanotubes for 500 fs to set them into motion. The simulation was then run until the nanotubes stopped moving relative to the substrate. Only sliding was observed in the out-of-registry simulation, while periodic sliding and rolling was observed in the in-registry simulation. The latter is a result of the relatively larger surface corrugation for the in-registry case and occurs to avoid direct atomic collisions between nanotube and substrate atoms as the nanotube is moved along the substrate. Analysis of the kinetic energy suggests that the transition between sliding and rolling contributes to enhanced energy dissipation and higher net friction. These results are consistent with preliminary experimental observations by Superfine and coworkers.     

A Mathematical Model of the Stability Control of Human Thorax and Pelvis Movements During Walking

A mathematical model is developed to study the human thorax and pelvis movements in the frontal plane during normal walking. The model comprises of two-link base-excited inverted pendulums with one-degree of rotational freedom for each link. Since the linear motion of the pelvis has a significant effect on the upper body stability, this effect is included in the model by having a base point moving in the frontal plane in a general way. Furthermore, because the postural stability is the primary requirement of normal human walking, the control law is developed based on Lyapunov's stability theory, which guarantees the stability of the pendulum system around the up-right position. To evaluate the model, the simulation results, including the angular displacement of each link and the torque applied on each link, are compared with those from gait measurements. It is shown that the simulation results match those from gait measurements closely. These results suggest that the proposed model can provide a useful framework for analysis of postural control mechanisms.     

昆虫抗冻蛋白的结构与生物学特性研究

抗冻蛋白(antifreeze proteins AFPs)是一类抑制冰晶生长的蛋白质,它能以非依数性形式降低溶液的冰点而对其熔点影响甚微,因而也被称作热滞蛋白。近几年来对于昆虫抗冻蛋白的研究取得了较快的发展,已有20多种昆虫抗冻蛋白被分离纯化。就昆虫抗冻蛋白的结构特征、生物学特性以及在农业、医学和食品工业等方面的应用进行介绍。     

镉在南美蟛蜞菊、蟛蜞菊及其杂交种中的迁移和分布特征

为了解植物对镉的吸收和迁移特性,用200μmol/L镉处理蟛蜞菊(Sphagneticola calendulacea)、南美蟛蜞菊(S.trilobata)及其杂交种,研究了其对镉的吸收、迁移与分布的差异.结果表明,随着镉处理时间的延长,3种植物茎和叶中的镉含量逐渐上升,叶片的镉含量逐渐与茎相当,而根部的镉含量一直是...     

水稻杂种与亲本间差异表达cDNA片段S600的分离克隆

采用cDNA-AFLP技术分离克隆了水稻杂种与亲本间差异表达基因片段S600。Northern杂交结果表明:在分蘖期和始穗期,S600在杂种和父本中表达丰度均较高,而在母本中表达丰度相对较低。S600在分蘖期和始穗期表达量不同,暗示了该基因的表达还受到发育时期的调节。同源搜索结果表明S600片段是水稻SBPase的部分编码序列。为了获得完整编码序列,以S600序列检索粳稻日本晴cDNA数据库,获得了两个高度同源(99%)且功能未知的全长cDNA克隆(AK062089和AK065773)。序列分析表明它们均包含一个相同的1179bp的开放阅读框,编码392个氨基酸组成的水稻SBPase前体,其中包含有与底物结合、氧化还原调节有关的保守氨基酸残基。检索发现该基因在水稻日本晴基因组中只有单个座位。     

Stability of discrete age-structured and aggregated delay-difference population models

Sufficiency conditions for local stability are derived for a class of density dependent Leslie matrix models. Four of the recruitment functions in common use in fisheries management are then considered. In two of these oscillating instability can never occur (Beverton and Holt and Cushing forms). In the other two (Deriso-Schnute and Shepherd forms) undamped oscillations are possible within the region of parameter space described here. An algorithm is developed for calculating necessary and sufficient local stability conditions for a simplified form of the general age-structured model. The complete spectrum of stability states (monotonic stability; monotonic instability; oscillating-stable; oscillating-unstable) and the bifurcation periods are given for selected examples of this model. The examples cover a large portion of the parameter space of interest in resource management. It is shown that in perfectly deterministic systems which are observed with error, oscillating instabilities may be missed, and such systems could be erroneously assumed to be stable.     

Equilibrium, solid state behavior and reactions of four and five co-ordinate carbonyl stibine complexes of rhodium. Crystal Structures of trans-[Rh(Cl)(CO)(SbPh3)2], trans-[Rh(Cl)(CO)(SbPh3)3] and trans-[Rh(I)2(CH3)(CO)(SbPh3)2]

The crystal structures of the four-coordinate trans-[Rh(Cl)(CO)(SbPh₃)₂] (1) and the five-coordinate trans-[Rh(Cl)(CO)(SbPh₃)₃] (2) are reported, as well as the unexpected oxidative addition product, trans-[Rh(I)₂(CH₃)(CO)(SbPh₃)₂] (3), obtained from the reaction of 2 with CH₃I. The formation constants of the five-coordinate complex were determined in dichloromethane, benzene, diethyl ether, acetone and ethyl acetate as 163±8, 363±10, 744±34, 1043±95 and 1261±96 M⁻¹, respectively. While coordinating solvents facilitate the formation of the five-coordinate complex, the four-coordinate complex could be obtained from diethyl ether due to the favorable low crystallization energy. The tendency of stibine ligands to form five-coordinate rhodium(I) complexes is attributed mainly to electron deficient metal centers in these systems, with smaller contributions by the steric effects. The average effective cone angle for the SbPh₃ ligand in the three crystallographic studies was determined as 139° with individual values ranging from 133 to 145°.     

杂交油菜ISSR-PCR反应体系的建立和优化

利用正交试验设计的方法,对影响ISSR-PCR反应的Mg²⁺、dNTP、引物和Taq DNA聚合酶4个因素进行优化试验,以期建立其最佳反应条件。并在此基础上,对DNA模板浓度和ISSR PCR反应程序中的退火温度进行梯度筛选。结果表明：杂交油菜20 μL ISSR-PCR最佳反应体系包括1.50 mmol·L^-1 Mg²⁺、0.125 mmol·L^-1 dNTP、2.00 μmol·L^-1 primer、0.50 U Taq DNA聚合酶、2.5 μL 10×buffer和40 ng DNA模板;引物UBC891适宜的退火温度为54.2℃。该体系在青杂3号及其父本不同个体中能够扩增出条带清晰、稳定性好的条带。ISSR-PCR反应体系的建立为利用分子标记技术研究杂交油菜品种纯度和真实性鉴定奠定了良好基础。     

一个时滞微分系统的稳定性与Hopf分支

给出了一个三维时滞微分系统的平衡点的全时滞稳定的代数判据。也讨论并给出了这个系统存在Hopf分支的条件,两个例子说明了本文定理的应用。     

大头茶种群动态模型及稳定性分析

 大头茶(Gordonia acuminata)是亚热带常绿阔叶林的优势种。根据它的生活史周期特点,建立描述种群的幼苗群、幼树群和成年个体群之间盖度数量关系的数学模型;输入各项参数值,模拟种群动态的结果表明：在局部尺度上,在参数值的一定范围内,存在着稳定的平衡;但随着时间推移,种群将处于不稳定平衡状态。     

一类时滞神经网络模型的稳定性与全局Hopf分支

研究了一类由两个神经元构成的时滞神经网络模型的稳定性和局部Hopf分支,并结合一般泛函微分方程的全局Hopf分支定理,利用度理论研究了全局Hopf分支的存在性．     

水稻杂种F1结实率与亲本程氏指数差异和同工酶遗传距离的关系及其预测研究

以4个籼粳测验种做母本按NCII(4×90)设计配置的360个杂交F1组合为材料,研究亲本的程氏指数差异(ID)、同工酶遗传距离(GD)与杂种F1结实率的关系.结果显示ID、GD与杂种F1结实率呈极显著负相关(r=-0.540,p＜0.01;r=-0.316,p＜0.01),但决定系数不高,分别是0.2916、0.0999.D、GD与F1结实率的相关性受父本和母本影响,其中对非广亲和品种测交F1结实率的预测效果较好,对广亲和品种及南京11的测交F1的预测则无效.因此,在利用ID和GD对水稻杂种F1结实率进行预测时,宜在一定的亲本类型之间进行,ID比GD的预测效果更好.     

骨水泥凝固前有无血液环境对骨水泥与骨界面稳定性的影响

目的:研究在有血和无血环境下粘合骨水泥和骨,比较两种粘合骨水泥的方式对骨与骨水泥界面稳定性影响的区别。方法:选取新鲜猪肱骨头20块,随机分成两组:实验组在有血的环境下用骨水泥将股骨头与金属粘合;对照组在无血的环境下用骨水泥将肱骨头和金属粘合,再将两组实验材料分别做拉伸试验,至骨与骨水泥界面断裂,最后再沿垂直于截骨面的方向做骨切片,在扫描电镜下观察并测量出每个实验对象中骨水泥的最大浸润深度。比较两组实验过程中拉力的最大载荷和断裂时的拉力以及骨水泥最大浸润深度。结果:实验组10个实验对象拉力最大载荷平均为738.50±262.15 N,断裂时的拉力平均为656.50±242.88N,骨水泥最大浸润深度平均为1.22±0.19 MM;对照组10个实验对象实验过程中拉力最大载平均为739.60±306.98 N,断裂时的拉力平均为658.80±264.56 N,骨水泥最大浸润深度平均为1.22±0.21 MM。20个实验对象在实验过程中均无意外断裂的情况发生,均在骨与骨水泥界面发生断裂。两组实验的拉力最大载荷与断裂拉力以及骨水泥最大浸润深度,均无统计学差异(P0.05)。结论:血液环境不能增加骨与骨水泥界面的不稳定因素。因此,与应用止血带相比,在TKA手术中不用止血带可能不会对骨与骨水泥界面稳定性和假体的寿命产生影响。     

Solution Stability and Degradation Pathway of Deoxyribonucleoside Phosphoramidites in Acetonitrile

The impuritiy profiles of acetonitrile solutions of the four standard O‐cyanoethyl‐N,N‐diisopropyl‐phosphoramidites of 5′‐O‐dimethoxytrityl (DMT) protected deoxyribonucleosides (dG^ib, dA^bz, dC^bz, T) were analyzed by HPLC‐MS. The solution stability of the phosphoramidites decreases in the order T, dC>dA>dG. After five weeks storage under inert gas atmosphere the amidite purity was reduced by 2% (T, dC), 6% (dA), and 39% (dG), respectively. The main degradation pathways involve hydrolysis, elimination of acrylonitrile and autocatalytic acrylonitrile‐induced formation of cyanoethyl phosphonoamidates. Consequently, the rate of degradation is reduced by reducing the water concentration in solution with molecular sieves and by lowering the amidite concentration. Acid‐catalyzed hydrolysis could also be reduced by addition of small amounts of base.     

Thermal Stability of Onconase and Some Mutant Forms

Onconase is a small globular protein of the pancreatic ribonuclease superfamily. It is an important molecule because it possesses a selective antitumor activity. The interesting finding is that onconase has a high thermal stability, with a denaturation temperature close to 90d`C at p^H 6.0. A detailed comparison between the tertiary structures of onconase and bovine pancreatic ribonuclease has been accomplished in order to identify the molecular determinants of the high stability. The results of differential scanning calorimetry measurements confirm that the mutant forms of onconase, designed to be less stable than the parent enzyme, exhibit lower denaturation temperatures. In particular, the disulfide bridge at the C-terminus of onconase seems to play a pivotal role in stability.     

Hybrid necrosis in triticale and the expression of necrosis genes in allopolyploids

Summary The occurrence in triticale of four different genes causing hybrid necrosis is described: Ne1 and Ne2 in the B genome of wheat and Ner1 and Ner2 in the rye genome. Hybrid necrosis develops due to dominant complementary interaction of two genes. This interaction in triticale, however, may take place not only between genes belonging to the same genome but also between genes of different genomes. In triticale, these genes can cause hybrid necrosis in four different combinations. The inheritance of the phenomenon in triticale is, therefore, more complicated than it is in wheat or rye. To avoid hybrid necrosis in triticale, attention should be paid that no necrosis genes are introduced into the primary triticale stocks from the wheat and rye parents. The expression of necrosis genes is influenced by the level of ploidy. Any additional genome — A, B, D, or R — may exert a suppressing effect on the expression of necrosis genes. Therefore, when identifying genotypes of triticale with regard to their necrosis genes, the level of ploidy has to be accounted for. Moreover, the present results illustrate that gene expression in polyploids is not only determined by interactions with other single genes but that it may also be modified by the total genotype of the respective individual.     

PD-1/PD-L1免疫检查点抗体药物制剂稳定性开发

近年来抗体药物在生物医药领域发展迅速。随着抗体疗法种类的不断增加和PD-1/PD-L1靶点蛋白结构的确证,临床上,越来越多针对PD-1/PD-L1免疫检查点的单克隆抗体药物被不断开发并应用于治疗死亡率高、治愈率低的多种癌症中。但是抗体药物制剂开发水平还需进一步提高,一方面同一靶点的抗体产品同质化严重,另一方面抗体药物的理化性质比小分子药物复杂,因此需要针对不同单克隆抗体的药物特性,筛选出适应于临床应用的稳定蛋白制剂处方。概括了不同抗体药物制剂处方成分(缓冲液成分、药物辅料)的作用,结合PD-1/PD-L1靶点介绍了抗体药物制剂稳定性开发的一般策略以及CDE相关的审评要点。     

PD-1/PD-L1免疫检查点抗体药物制剂稳定性开发

近年来抗体药物在生物医药领域发展迅速。随着抗体疗法种类的不断增加和PD-1/PD-L1靶点蛋白结构的确证,临床上,越来越多针对PD-1/PD-L1免疫检查点的单克隆抗体药物被不断开发并应用于治疗死亡率高、治愈率低的多种癌症中。但是抗体药物制剂开发水平还需进一步提高,一方面同一靶点的抗体产品同质化严重,另一方面抗体药物的理化性质比小分子药物复杂,因此需要针对不同单克隆抗体的药物特性,筛选出适应于临床应用的稳定蛋白制剂处方。概括了不同抗体药物制剂处方成分(缓冲液成分、药物辅料)的作用,结合PD-1/PD-L1靶点介绍了抗体药物制剂稳定性开发的一般策略以及CDE相关的审评要点。