Optimization of culture media for large‐scale lutein production by heterotrophic Chlorella vulgaris

Lutein is a carotenoid with a purported role in protecting eyes from oxidative stress, particularly the high‐energy photons of blue light. Statistical optimization was performed to growth media that supports a higher production of lutein by heterotrophically cultivated Chlorella vulgaris. The effect of media composition of C. vulgaris on lutein was examined using fractional factorial design (FFD) and central composite design (CCD). The results indicated that the presence of magnesium sulfate, EDTA‐2Na, and trace metal solution significantly affected lutein production. The optimum concentrations for lutein production were found to be 0.34 g/L, 0.06 g/L, and 0.4 mL/L for MgSO₄·7H₂O, EDTA‐2Na, and trace metal solution, respectively. These values were validated using a 5‐L jar fermenter. Lutein concentration was increased by almost 80% (139.64 ± 12.88 mg/L to 252.75 ± 12.92 mg/L) after 4 days. Moreover, the lutein concentration was not reduced as the cultivation was scaled up to 25,000 L (260.55 ± 3.23 mg/L) and 240,000 L (263.13 ± 2.72 mg/L). These observations suggest C. vulgaris as a potential lutein source. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:736–743, 2014     

重组人骨保护素片段OPG179与人血清白蛋白在毕赤酵母中的融合表达

目的:在毕赤酵母中融合表达人骨保护素(OPG)片段OPG179与人血清白蛋白(HSA).方法:通过RT-PCR扩增获得OPG179基因,构建表达质粒pHILD2-rhOPG179-HSA,转化至毕赤酵母菌中进行表达、纯化,对分泌表达产物进行SDS-PAGE及Western印迹检测.结果:酶切鉴定与测序结果显示重组表达质...     

长白山垂直带森林叶片-凋落物-土壤连续体有机碳动态——基于稳定性碳同位素分析

稳定性碳同位素自然丰度(δ~(13)C)记录着生态系统碳循环过程的关键信息,常被用于评价全球变化情景下陆地生态系统碳的动态。以长白山北坡垂直带4种典型森林生态系统为研究对象,测定乔木建群种叶片、凋落物以及不同深度土壤有机碳(SOC)含量和δ~(13)C值,探讨植物叶片-凋落物-土壤连续体碳含量、δ~(13)C丰度的分布格局及其生态学暗示。研究结果表明:植物叶片碳含量随海拔高度的增加呈现抛物线型变化,且阔叶树叶片碳含量显著低于针叶树,体现气候要素和植被功能型的支配作用,并且暗示针叶树种潜在的碳蓄积能力更强。此外,植物叶片δ~(13)C随海拔高度升高而降低,表明高海拔植物叶片水分利用效率较低,即固碳耗水成本更高。凋落物碳含量随海拔增加逐渐下降,而矿质表层土壤则表现为阔叶红松林、岳桦林显著高于暗针叶林,体现了植被类型和土壤质地的共同支配作用。总体上,岳桦林SOC周转最快,其次是暗针叶林,位于基带的阔叶红松林最慢。可见,小尺度上气候因子并不是温带森林地下碳循环的主导因素,植被功能型和土壤属性对SOC周转与稳定的影响更大。在探讨环境因子对陆地生态系统碳循环和碳平衡的影响时需要考虑研究尺度,不同的研究尺度影响SOC周转的驱动因子并不相同。研究方法方面,基于log SOC和δ~(13)C的SOM周转模型能够很好地概括不同生态系统类型下SOM周转的相对快慢,可用来评价SOC动态对全球变化的响应。     

流式细胞术在哺乳动物精液质量检测中的应用

精液检测的首要目标就是快速准确地确定精子的生育力。同时具备多种特性和功能完整的精子才能受精,因而只有同时客观地检测多个指标,才能更好地反映精子的生育力。精子检测的传统方法费时费力,检测精子数量少,指标单一,而且易受操作者的主观影响,不能准确地反映精子功能。流式细胞术(FCM)为精子功能研究提供了一种快速、客观、多指标、大通量的检测手段;利用FCM检测精子的质膜完整性、顶体状态、染色质结构、线粒体功能以及细胞凋亡等,可以得知精子功能的相关情况。随着新的荧光探针、染色方法的不断开发和改进,FCM为精液质量检测提供了一种新的检测平台,应用前景极其广阔。     

Enhanced immobilization of hexa-arginine-tagged esterase on gold nanoparticles using mixed self-assembled monolayers

Mixed self-assembled monolayers (MSAMs) composed of diverse ligands offer a mechanism for the specific binding of biomolecules onto solid surfaces. In this study, we examined the formation of MSAMs on gold nanoparticles (AuNPs) and the immobilization of hexa-arginine-tagged esterase (Arg₆-esterase) on the surfaces of the resulting particles. The functionalization of AuNPs with MSAMs was achieved by introducing a mixture of tethering and shielding ligands into an AuNP solution. The formation of self-assembled monolayers (SAMs) on the AuNP surface was characterized by UV/visible spectroscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy. Arg₆-esterase was immobilized in a highly specific manner onto AuNPs treated with mixed SAMs (MSAM–AuNPs) by providing a shielding ligand which reduce the non-specific adsorption of enzymes caused by hydrophobic interaction compared to AuNPs treated with single-component SAMs (SSAM–AuNPs). Moreover, Arg₆-esterase immobilized on MSAM–AuNPs showed substantially enhanced catalytic activity up to an original activity compared to that on SSAM–AuNPs (58%).     

古尔班通古特沙漠西部地下水位和水质变化对植被的影响

通过对比分析古尔班通古特沙漠西部3a地下水位和水质的变化特点,研究了地下水位和水质变化对地表土壤理化性质、植物多样性、及建群种梭梭种群生长与更新的影响。发现地下水位和土壤理化性质空间变异较大,最浅地下水位为3.3 m,最深可达24.2 m,主要集中在6-8 m;土壤电导率、pH值、Cl^-和SO₄^2-均在表层0-40 cm含量较高,变异系数随土层深度的增加而减小。在时间上地下水位受准噶尔盆地上游农田用水的影响,水位呈季节性波动。一年中最高水位出现在4月,最低水位在7月。玛纳斯河向下游输水对提高盆地地下水位具有明显作用,地下水位平均可升高4.3 cm,地下水矿化度平均增幅1 g/L。地下水位对退化区物种多样性影响不大,但对梭梭生长产生显著影响。梭梭生长的适宜地下水位为5-8 m,且地下水矿化度小于4 g/L。地下水位大于8 m导致梭梭种群衰退,而地下水位小于4 m时,地下水矿化度影响土壤表层积盐,进而显著地降低物种多样性,阻碍梭梭幼苗更新,导致梭梭种群衰败。总结认为准噶尔盆地上游的玛纳斯河断流和农业灌溉对古尔班通古特沙漠西部平原地区的地下水位和水质产生显著影响,梭梭退化与地下水位变化显著相关,必须引起高度重视。     

Antioxidant activities of enzymatic extracts from brown seaweeds

Potential antioxidative activities of enzymatic extracts from seven species of brown seaweeds were evaluated using four different reactive oxygen species (ROS) scavenging assays containing DPPH (1,1-diphenyl-2-pricrylhydrazyl) free radical, superoxide anion, hydroxyl radical and hydrogen peroxide scavenging assay. The brown seaweeds were enzymatically hydrolyzed to prepare water-soluble extracts by using five carbohydrate degrading enzymes (Viscozyme, Celluclast, AMG, Termamyl and Ultraflo) and five proteases (Protamex, Kojizyme, Neutrase, Flavourzyme and Alcalase) of commercial and inexpensive enzymes obtained from Novozyme Co. (Novozyme Nordisk, Bagsvaerd, Denmark). The enzymatic extracts exhibited more prominent effects in hydrogen peroxide scavenging activity (approximately 90%) compared to the other scavenging activities and the activity of enzymatic extracts was even higher than that of the commercial antioxidants. In particular, Ultraflo and Alcalase extracts of S. horneri were dose-dependent and thermally stable. Moreover the two enzymatic extracts strongly inhibited DNA damage (approximately 50%). Those extracts showed significantly (p<0.05) remarkable scavenging effects in DPPH free radical scavenging assay and the activity indicated a marked correlation with phenolic contents. From the results, enzymatic extracts of the brown seaweeds might be valuable antioxidative sources.     

失巢凋亡及其在肿瘤侵袭、转移中的调控

作为肿瘤转移的屏障, 细胞与邻近细胞或者细胞外基质(Extracellular matrix, ECM)失去联系后将遭受凋亡, 这种细胞死亡方式称为“失巢凋亡”。正常上皮细胞或不具备转移性质的实体瘤细胞从原位脱落进入血液循环后就会引发失巢凋亡, 失巢凋亡的意义在于防止这些脱落的细胞种植并生长于其他不适宜的地方。而肿瘤细胞, 尤其是一些容易发生远距离转移的恶性肿瘤细胞, 具有极强的抗失巢凋亡特性, 便于转移侵袭。研究发现肿瘤细胞能通过多种方式抵抗失巢凋亡, 比如细胞自分泌生长因子或者由邻近细胞旁分泌, 激活促存活信号通路; 细胞改变整合蛋白的表达模式, 使之能够接收新环境的生存信号; 活性氧(Reactive oxygen species, ROS)通过不依赖配体的方式激活生长因子受体, 从而逃逸凋亡; 上皮间质转化(Epithelial-mesenchymal transition, EMT)激活等。这些方式导致细胞存活信号激活和凋亡途径抑制, 最终使肿瘤细胞抗失巢凋亡, 促进转移。文章综述了当前研究的肿瘤转移的关键机制, 这些策略也将成为肿瘤治疗的重要靶点。