基因工程菌高密度培养补料调控策略的研究进展

补料调控策略是基因工程菌实现高密度培养的关键技术之一。本文结合大量实例,着重介绍了基因工程菌高密度培养补料控制策略在国内外的发展现状及发展趋势。并探讨了模式识别技术、人工神经网络、PSO优化算法等在补料策略及其控制系统中的应用情况及发展趋势。     

潘氏细胞研究进展

潘氏细胞是位于小肠腺底部的浆液性腺上皮细胞,其主要特征是细胞顶部有大量粗大的嗜酸性分泌颗粒,内含防御素、溶菌酶、sIgA等多种抗菌物质。表达于潘氏细胞的NOD2、Toll样受体9、肝癌-肠-胰腺／胰腺炎相关蛋白、RegⅢγ、肿瘤坏死因子仅、粒细胞-巨噬细胞集落刺激因子、白介素-17等也是免疫与炎症反应的重要成分。金属硫蛋白、富半胱氨酸肠蛋白、潘氏细胞锌结合蛋白等金属结合蛋白均分布于潘氏细胞,提示潘氏细胞参与金属代谢。潘氏细胞是构成肠黏膜屏障的重要细胞成分。NOD2单核苷酸多态性与克罗恩病有关。潘氏细胞化生常发生于胃、大肠的炎症与肿瘤病变,其病理意义有待于进一步研究。     

DNA end recognition by the Mre11 nuclease dimer: insights into resection and repair of damaged DNA

The Mre11–Rad50–Nbs1 (MRN) complex plays important roles in sensing DNA damage, as well as in resecting and tethering DNA ends, and thus participates in double-strand break repair. An earlier structure of Mre11 bound to a short duplex DNA molecule suggested that each Mre11 in a dimer recognizes one DNA duplex to bridge two DNA ends at a short distance. Here, we provide an alternative DNA recognition model based on the structures of Methanococcus jannaschii Mre11 (MjMre11) bound to longer DNA molecules, which may more accurately reflect a broken chromosome. An extended stretch of B-form DNA asymmetrically runs across the whole dimer, with each end of this DNA molecule being recognized by an individual Mre11 monomer. DNA binding induces rigid-body rotation of the Mre11 dimer, which could facilitate melting of the DNA end and its juxtaposition to an active site of Mre11. The identified Mre11 interface binding DNA duplex ends is structurally conserved and shown to functionally contribute to efficient resection, non-homologous end joining, and tolerance to DNA-damaging agents when other resection enzymes are absent. Together, the structural, biochemical, and genetic findings presented here offer new insights into how Mre11 recognizes damaged DNA and facilitates DNA repair.     

长三角地区植被覆盖演变城乡差异及其原因

城市生态环境和城市化之间的关系是城市可持续发展的关键。研究不同城市化水平下植被覆盖的长时间演变趋势,对理解城市化过程对植被生长动态的影响,城市更新以及推进城市绿化的科学管理具有重要意义。然而,目前对城市内部沿城乡梯度植被生长趋势差异的认识还比较有限。以我国城市化发展最为强烈的长三角地区为研究对象,基于2000-2020年长三角归一化植被指数数据,采用趋势分析和地理探测器方法,探究了长三角地区城市内部植被覆盖演变城乡差异,并从土地利用/覆被变化和城市化发展的角度解析其成因。研究结果表明：（1）2000-2020年长三角地区植被总体呈绿化趋势,植被明显绿化占最大比例（52.06%）,轻微绿化与稳定不变地区占31.68%,零星分布的褐化区占6.82%。（2）城市老城区植被覆盖变化总体呈现返绿趋势（0.016/10 a）,新城区褐化明显（-0.019/10 a）,农郊区绿化突出（0.023/10 a）。在上海、南京和杭州等人口城市化水平较高的城市中,老城区土地利用变化强度最高,其绿化趋势也最高,体现了城市更新过程对绿地空间的促进作用;而在人口城市化水平相对较低的宣城、蚌埠和阜阳等城市,土地利用变化强度相对较低的农郊区也呈现明显的绿化趋势,更多的是受到区域生态保护的影响。（3）土地城市化是长三角地区老城区和新城区植被覆盖变化的主导因子,而城市化因子对农郊区解释程度总体不显著。从长三角总体区域看,城镇人口比重、不透水面积/总面积以及地区生产总值三者对植被覆盖演变存在显著影响,其中城镇人口比重影响最大。     

Preparation and Enantioselectivity Binding Studies of a New Chiral Cobalt(II)porphyrin‐Tröger's Base Conjugate

A new bis[cobalt(II)porphyrin]‐Tröger's base conjugate was studied as a potential receptor for methyl esters of several amino acids. The conjugate was prepared as racemate, and then resolved via preparative high‐performance liquid chromatography (HPLC) on a chiral column. The high affinity to lysine, histidine, and proline methyl esters was found by complexation studies followed by UV‐Vis spectroscopy. The studies of pure enantiomers, followed by UV‐Vis and electronic circular dichroism spectroscopy, revealed the highest enantioselectivity for lysine methyl ester. Chirality 26:361–367, 2014. © 2014 Wiley Periodicals, Inc.     

How to escape from the host nest: Imperfect chemical mimicry in eucharitid parasitoids and exploitation of the ants’ hygienic behavior

Communication in ants is based to a great extent on chemical compounds. Recognition of intruders is primarily based on cuticular hydrocarbon (CHC) profile matching but is prone to being cheated. Eucharitid wasps are specific parasitoids of the brood of ants; the immature stages are either well integrated within the colony or are protected within the host cocoons, whereas adult wasps at emergence must leave their host nest to reproduce and need to circumvent the ant recognition system to escape unscathed. The behavioral interactions between eucharitid wasps and workers of their host, the Neotropical ant Ectatomma tuberculatum, are characterized. In experimental bioassays, newly emerged parasitoids were not violently aggressed. They remained still and were grabbed by ants upon contact and transported outside the nest; host workers were even observed struggling to reject them. Parasitoids were removed from the nest within five minutes, and most were unharmed, although two wasps (out of 30) were killed during the interaction with the ants. We analyzed the CHCs of the ant and its two parasitoids, Dilocantha lachaudii and Isomerala coronata, and found that although wasps shared all of their compounds with the ants, each wasp species had typical blends and hydrocarbon abundance was also species specific. Furthermore, the wasps had relatively few CHCs compared to E. tuberculatum (22–44% of the host components), and these were present in low amounts. Wasps, only partially mimicking the host CHC profile, were immediately recognized as alien and actively removed from the nest by the ants. Hexane-washed wasps were also transported to the refuse piles, but only after being thoroughly inspected and after most of the workers had initially ignored them. Being recognized as intruder may be to the parasitoids’ advantage, allowing them to quickly leave the natal nest, and therefore enhancing the fitness of these very short lived parasitoids. We suggest that eucharitids take advantage of the hygienic behavior of ants to quickly escape from their host nests.