不同施氮水平下加工番茄植株生长和氮素积累与利用率的动态模拟

通过3年的大田试验,设置不同的氮素水平(0、75、150、300、450、600 kg·hm^-2)对不同施氮量下加工番茄地上部生物量、氮素累积及利用率的动态变化进行模拟.结果表明: 加工番茄地上部生物量、氮素累积量和氮素利用率随出苗后累积生理发育时间(PDT)的动态变化符合Logistic模型,氮素快速累积起始时间较地上部生物量快速累积起始时间早4～6 d(PDT);瞬时氮利用率随出苗后累积生理发育时间的动态变化呈先增加后降低的单峰曲线.不同施氮水平下,300 kg·hm^-2处理的氮累积量和地上部生物量最多,产量最高.根据Quadratic模型得出,北疆地区加工番茄滴灌栽培的理论适宜施氮量为349～382 kg·hm^-2.     

Recombinant protein production using the Semliki Forest Virus expression system

We report here the successful scale up of transient recombinant protein expression to litre scale using Semliki Forest Virus System. The expression of bacterial β-galactosidase was initially compared in BHK and CHO cells and the conditions for optimal infection of BHK cells were identified. 10% FCS in a medium at pH 6.9 and infection in small volumes were found to be optimal. A high MOI results in an increased recombinant protein yield. Stirring does not affect the infection process. Finally we applied these optimal conditions to the production of a microsomal enzyme, human cyclooxygenase-2 in suspension spinners. Five independant productions at the 1 litre scale yielded reproducible substantial amounts of recombinant protein (16 mg microsomal protein 10⁹ cells⁻¹) with an average specific activity of 3942 ± 765 pg PGE₂ μg⁻¹ microsomal protein 5 min⁻¹. This revised version was published online in July 2006 with corrections to the Cover Date.     

高龄隐匿性冠心病患者围术期心血管功能异常研究

目的：探讨隐匿性冠心病（或无症状心肌缺血SMI）患者围术期的心血管功能异常及与年龄的相关性,探讨围术期心律失常的临床治疗和转归。方法：180例择期手术的无症状心肌缺血患者,年龄≥51岁者130例,按年龄将其分为51～60岁组、61～70岁组和71～80岁组,其余50例年龄≤50岁者为对照组。动态心电图连续记录患术前24h、术后24h、术后48h心电图信息,专业医师分析统计s11段下移及弓背样抬高的幅度、时间,各型心律失常、各时间段心律失常发生率等,同时记录临床治疗、效果及转归。结果：随年龄增加,ST段改变幅度及持续时间增大（P〈0．05,P〈0．01）;71～80岁组ST段弓背样抬高发生率大于对照组（P〈0．05）;61～70岁组ST段下移时间、71～80岁组ST段下移时间及弓背样抬高幅度大于51～60岁组（P〈0．05）。61～70岁组的加速性室性自主心率（A巩）发生率和71。80岁组的窦性的心动过缓（SB）、室性早搏（VPB）、室性心动过速（vT）发生率大于对照组（P〈0．05,P〈0．01）;61～70岁组的房颤（AF）发生率和71～80岁组的VP、VT及AF发生率大于51-60岁组（P〈0．05,P〈0．01）。各组术后24h心律失常发生率大于术后48h及术前24h（P〈0．01）;随年龄增加,排除诱因后可逆转的心律失常明显减少,需药物逆转和电学逆转者明显增加（P〈0．05）。结论：高龄SMI患者围术期心肌缺血及心律失常高发,且随着年龄的增加而增加,术后24h是心功能异常高发时段。     

黄土高原刺槐林地土壤水分垂直分布特征及其动态模型的建立

以位于黄土高原半干旱丘陵沟壑区的陕西省安塞县和半湿润残塬沟壑区的甘肃省泾川县为代表,研究了不同水分生态区刺槐林地土壤水分垂直分布特征;并在原有林地土壤水分入渗平衡模型的基础上,建立了林地土壤水分随时间、土壤深度变化的动态模型。结果表明:(1)不同水分生态区林地土壤水分垂直变化规律具有明显区别,泾川的土壤含水量峰值出现在20~40cm土层深处,后随着土层深度的增加逐渐降低,在200cm土层深度土壤含水量趋于稳定(11%左右);安塞的土壤含水量峰值出现在约60cm左右的土层,并在220cm深度土壤含水量趋于稳定(5.5%左右);说明泾川的土壤含水量高于安塞,安塞的降雨和林木根系耗水对土壤水分的影响程度和深度均大于泾川,且两地深层土壤水分含量不受降水和林木根系耗水等的影响。(2)利用降水在土壤中的入渗平衡模型能够很好地拟合黄土高原两地(泾川、安塞)刺槐林地的土壤水分垂直分布;并通过引入参数t(月份)建立了林地土壤水分随时间和土壤深度变化的动态模型,经验证该模型能够准确地刻画黄土高原不同水分生态区刺槐林地土壤水分的动态变化。     

Modeling of Transition State by Molecular Dynamics. Prediction of Catalytic Efficiency of the Mutants of Mandelate Racemase

Abstract

Modeling of transition state by molecular dynamic method often requires modification of the force field parameters to describe energy profile accurately. In this work, we avoided the modification by modeling a series of mutants at binding-related site. In predicting the catalytic efficiency (k _cat /K _m ) of the mutants of mandelate racemase (MR), the prediction performance of three energy subsets was investigated. It was indicated that the interaction-energy subset exhibited better prediction performance than whole-system subset and binding-site subset in both quantity and trend. When prediction error (PE) criterion was equal to 5%, 10 out of 12 samples were predicted correctly within interaction-energy subset, which demonstrated a great application potential of this method in prediction of enzyme catalytic efficiency and enzyme rational design.     

核磁共振技术及其在生命科学中的应用

核磁共振(NMR)是一种不破坏样品的无损伤分析技术,是分子结构分析不可或缺的手段。随着新技术、新方法的不断发展,其研究领域和应用范围已扩展到了几乎所有的自然科学领域。本文简要介绍了核磁共振波谱技术的基本原理、多维NMR以及在结构鉴定、构象分析、医学临床检测、蛋白质组学、代谢组学等方面的应用。同时,本文还就NMR技术的发展前景提出了一些看法。     

Relationship between the virtual dynamic thinning line and the self-thinning boundary line in simulated plant populations

The self-thinning rule defines a straight upper boundary line on log-log scales for all possible combinations of mean individual biomass and density in plant populations. Recently, the traditional slope of the upper boundary line, -3/2, has been challenged by -4/3 which is deduced from some new mechanical theories, like the metabolic theory. More experimental or field studies should be carried out to identify the more accurate self-thinning exponent. But it＇s hard to obtain the accurate self-thinning exponent by fitting to data points directly because of the intrinsic problem of subjectivity in data selection. The virtual dynamic thinning line is derived from the competition-density （C-D） effect as the initial density tends to be positive infinity, avoiding the data selection process. The purpose of this study was to study the relationship between the virtual dynamic thinning line and the upper boundary line in simulated plant stands. Our research showed that the upper boundary line and the virtual dynamic thinning line were both straight lines on log-log scales. The slopes were almost the same value with only a very little difference of 0.059, and the intercept of the upper boundary line was a little larger than that of the virtual dynamic thinning line. As initial size and spatial distribution patterns became more uniform, the virtual dynamic thinning line was more similar to the upper boundary line. This implies that, given appropriate parameters, the virtual dynamic thinning line may be used as the upper boundary line in simulated plant stands.     

退化典型草原狼毒种群结构与数量动态

狼毒(Stellera chamaejasme)是我国退化草原上常见的一种毒害草,在一些退化严重的草原上可能形成以狼毒为优势种的群落,严重影响我国天然草原畜牧业的可持续发展。本文根据狼毒的枝条数将狼毒种群划分成10个龄级(Ⅰ～Ⅹ),研究了坝上地区退化典型草原狼毒种群的年龄结构、种群结构动态指数、种群静态生命表、存活曲线及生存分析,量化狼毒种群的生存状况。结果表明: 研究区内狼毒种群年龄结构呈增长型,狼毒幼苗充足但存活率不高;狼毒种群结构呈增长型,但种群发展过程存在波动性,特别是在第Ⅱ、Ⅷ龄级时个体数量会发生骤降,是狼毒种群自身发展的瓶颈时期;狼毒种群的存活曲线为Deevey-Ⅱ型,但生存分析表明狼毒种群具有前期锐减、后期稳定的特点,主要因为Ⅰ或Ⅱ龄级狼毒的死亡密度函数(f_x)和危险率(λ_x)最大。Ⅰ龄级个体充足是狼毒种群在退化典型草原扩张的基础,但幼龄个体的转化率低可能是狼毒种群在草原退化早期无法快速扩张的原因之一。建议在草原退化早期狼毒数量有限时及早介入进行防除。     

AB-8型树脂对无患子皂苷的动态吸附与解吸性能

采用单因素实验法,以树脂的饱和吸附量、产品的得率及纯度为指标,考察各因素对动态吸附与解吸的影响,优化大孔树脂动态吸附分离无患子皂苷的工艺条件。结果表明,当pH为4.5的无患子皂苷水提液以流速1 mL/min通过高径比为5.4∶1的吸附柱时,AB-8树脂对无患子皂苷的饱和吸附量达568 mg/g;采用1.5 BV的95%乙醇以1 mL/min的流速洗脱吸附后的树脂,产品得率为83.48%、纯度达93.00%;树脂重复使用8次后其吸附解吸性能基本不变。该方法可以用于无患子皂苷的工业化分离提纯。     

基于结构信息的RNA多序列比对

多序列比对是生物信息学中重要的基础研究内容,对各种RNA序列分析方法而言,这也是非常重要的一步。不像DNA和蛋白质,许多功能RNA分子的序列保守性要远差于其结构的保守性,因此,对RNA的分析研究要求其多序列比对不仅要考虑序列信息,而且要充分考虑到其结构信息。本文提出了一种考虑了结构信息的同源RNA多序列比对算法,它先利用热力学方法计算出每条序列的配对概率矩阵,得到结构信息,由此构造各条序列的结构信息矢量,结合传统序列比对方法,提出优化目标函数,采用动态规划算法和渐进比对得到最后的多序列比对。试验证实该方法的有效性。