膜脂组成与植物抗冷性的关系及其分子生物学研究进展

植物的抗冷性与膜脂的组分和结构密切相关,与质膜中脂肪酸的不饱和度关系更为密切。膜脂不饱和脂肪酸含量越高,膜脂相变温度越低,植物的抗冷性提高。植物体内存在一些降低膜脂脂肪酸饱和程度的酶,如甘油3磷酸酰基转移酶,ω3脂肪酸去饱和酶等,它们能够催化膜中脂肪酸的去饱和反应,生成不饱和脂肪酸,从而提高植物的抗冷性。本文就低温对膜脂的影响、膜脂组成与植物抗寒性的关系及其分子生物学研究进展作一简单综述。     

以单细胞免疫荧光技术观察烟草细胞融合过程中微管骨架的变化

本文建立了单细胞免疫荧光标记技术并以此结合单对细胞融合技术对细胞融合过程中微管骨架组织形式的动态变化进行了追踪观察。发现在聚乙二醇(PEG)诱导条件下,一旦细胞开始粘连,细胞内微管骨架便开始解聚。在细胞融合的整个过程中一直维持着这种解聚的状态,直到融合完成,在后续的培养中微管骨架才重新出现。在微管骨架呈解聚状态时融合产物不能完成与另外的细胞融合。实验揭示了细胞的再融合能力可能受细胞本身微管骨架状态的影响。该结果为解释高等植物如何避免多精入卵提供了新的可能性。     

木聚糖酶分子结构与重要酶学性质关系的研究进展

木聚糖是一种多聚五碳糖 ,是植物细胞中主要的半纤维素成分。木聚糖酶是可将木聚糖降解成低聚木糖和木糖的水解酶 ,它在饲料、造纸、食品、能源工业和环境科学上有着广阔的应用前景。随着分子生物学、结构生物学的发展及蛋白质工程的应用 ,对木聚糖酶结构和功能的研究不断深入。这里重点阐述与酶的活性、热稳定性、作用pH、等电点、底物亲和性及催化效率等重要性质相关的分子结构研究进展 ,讨论了其进一步的研究发展方向。研究木聚糖酶结构与功能的关系 ,对进一步加深木聚糖酶作用机制的了解、指导木聚糖酶的分子改良有重要意义。     

药用前胡研究进展

介绍了中药前胡近10年来的植物资源、化学成分和药理作用的研究成果,详细阐述了其主要药用部位药理作用研究的最新进展.     

Strategies and Decision-Support Tools for Optimizing Long-Term Groundwater Monitoring Plans—MAROS 2.0

Existing long-term groundwater monitoring programs can be optimized to increase their effectiveness/efficiency with the potential to generate considerable cost savings. The optimization can be achieved through an overall evaluation of conditions of the contaminant plume and the monitoring network, focused spatial and temporal sampling analyses, and automated and efficient management of data, analyses, and reporting. Version 2.0 of the Monitoring and Remediation Optimization System (MAROS) software, by integrating long-term monitoring analysis strategies and innovative optimization methods with a data management, processing, and reporting system, allows site managers to quickly and readily develop cost-effective long-term groundwater monitoring plans. The MAROS optimization strategy consists of a hierarchical combination of analysis methods essential to the decision-making process. Analyses are performed in three phases: 1) evaluating site information and historical monitoring data to obtain local concentration trends and an overview of the plume status; 2) developing optimal sampling plans for future monitoring at the site with innovative optimization methods; and 3) assessing the statistical sufficiency of the sampling plans to provide insights into the future performance of the monitoring program. Two case studies are presented to demonstrate the usefulness of the developed techniques and the rigor of the software.     

山东早始新世五图组的一种古有蹄类Olbitherium millenariusum gen.et sp.nov.(哺乳动物纲,"伪齿兽集目")

记述了在山东省五图盆地下始新统发现的一种“伪齿兽集目”化石 :千禧福兽 (Olbither iummillenariusumgen.etsp .nov.)。千禧福兽其颊齿形态基本上与原始奇蹄类相似 ,同时也具有伪齿兽类的一些特征 ,如m1～ 2下次尖没有与下内尖直接连接的下次脊。千禧福兽的M3次尖具前、后棱 ,这一点似与原始的蹄兔Seggeurius相似。因此 ,新种在目一级的归类有困难 ,暂置于McKenna ( 1 975 )创立的“伪齿兽集目”(“MirorderPhenacodonta”)。千禧福兽的发现进一步证明了奇蹄类可能起源于亚洲和北非类似伪齿兽类 (phenacodontids)的古有蹄类 ,福兽仅是类似伪齿兽类的古新世古有蹄类向奇蹄类进化过程中的一叉支的代表。     

转几丁质酶基因黑杨的获得

以G1黑杨幼叶为外植体建立了组织培养高频再生体系 ,对传统的农杆菌介导法进行了改进 ,用来自于菜豆的几丁质酶基因 (CH5B)进行转化 ,经PCR和PCR Southern杂交鉴定 ,证实CH5B基因已整合入G1黑杨核基因组中。     

植物提取物微生物限量标准及检测技术进展

植物提取物的微生物检测是保证植物产品安全性的重要手段, 制定严格的植物提取物质量控制标准体系, 特别是功能性食品、食品添加剂和植物源日用化学品等产品中微生物的检测和控制, 对产品的质量及安全保证具有重要作用, 是影响植物提取业实现全面发展的关键问题。本文主要介绍了部分国家植物提取物的微生物限量标准和植物提取物微生物检测的国内外现状与发展趋势, 并就如何建立植物提取物微生物检测行业标准体系提出了若干建议。希望对我国植物提取业实现新时期跨越式发展提供参考。     

Identification and Characterization of Shiga Toxin Type 2 Variants in Escherichia coli Isolates from Animals, Food, and Humans

There is considerable heterogeneity among the Shiga toxin type 2 (Stx2) toxins elaborated by Shiga toxin-producing Escherichia coli (STEC). One such Stx2 variant, the Stx2d mucus-activatable toxin (Stx2dact), is rendered more toxic by the action of elastase present in intestinal mucus, which cleaves the last two amino acids of the A2 portion of the toxin A subunit. We screened 153 STEC isolates from food, animals, and humans for the gene encoding Stx2dact by using a novel one-step PCR procedure. This method targeted the region of stx_2dact that encodes the elastase recognition site. The presence of stx_2dact was confirmed by DNA sequencing of the complete toxin genes. Seven STEC isolates from cows (four isolates), meat (two isolates), and a human (one isolate) that carried the putative stx_2dact gene were identified; all were eae negative, and none was the O157:H7 serotype. Three of the isolates (CVM9322, CVM9557, and CVM9584) also carried stx₁, two (P1332 and P1334) carried stx₁ and stx_2c, and one (CL-15) carried stx_2c. One isolate, P1130, harbored only stx_2dact. The Vero cell cytotoxicities of supernatants from P1130 and stx₁ deletion mutants of CVM9322, CVM9557, and CVM9584 were increased 13- to 30-fold after treatment with porcine elastase. Thus, Stx2dact-producing strains, as detected by our one-step PCR method, can be isolated not only from humans, as previously documented, but also from food and animals. The latter finding has important public health implications based on a recent report from Europe of a link between disease severity and infection with STEC isolates that produce Stx2dact.     

A Novel Gene, Encoding 6-Hydroxy-3-Succinoylpyridine Hydroxylase, Involved in Nicotine Degradation by Pseudomonas putida Strain S16

Previous research suggested that Pseudomonas spp. may attack the pyrrolidine ring of nicotine in a way similar to mammalian metabolism, resulting in the formation of pseudooxynicotine, the direct precursor of a potent tobacco-specific lung carcinogen. In addition, the subsequent intermediates, 6-hydroxy-3-succinoylpyridine (HSP) and 2,5-dihydroxypyridine (DHP) in the Pseudomonas nicotine degradation pathway are two important precursors for drug syntheses. However, there is little information on the molecular mechanism for nicotine degradation via the pyrrolidine pathway until now. In this study we cloned and sequenced a 4,879-bp gene cluster involved in nicotine degradation. Intermediates N-methylmyosmine, pseudooxynicotine, 3-succinoylpyridine, HSP, and DHP were identified from resting cell reactions of the transformant containing the gene cluster and shown to be identical to those of the pyrrolidine pathway reported in wild-type strain Pseudomonas putida S16. The gene for 6-hydroxy-3-succinoylpyridine hydroxylase (HSP hydroxylase) catalyzing HSP directly to DHP was cloned, sequenced, and expressed in Escherichia coli, and the purified HSP hydroxylase (38 kDa) is NADH dependent. DNA sequence analysis of this 936-bp fragment reveals that the deduced amino acid shows no similarity with any protein of known function.