广西外来入侵植物

通过调查和文献整理,初步确认广西有外来入侵植物114种,隶属于36科80属,其中以菊科的种类最多,有26种。外来入侵植物来源于世界各地,以来源于美洲居多,有87种,占76.3%。入侵植物以草本植物为主,有90种,占78.9%。外来入侵植物主要通过有意引入和无意传入等方式入侵广西。它们的入侵,特别是一些恶性杂草的入侵,给广西农业、林业、人类健康以及生态环境带来巨大的负面影响。加强对外来入侵植物的调查和评估,恢复当地植被和物种的多样性,开展有害生物风险分析是防范外来入侵植物的有效途径。     

Improving simvastatin bioconversion in Escherichia coli by deletion of bioH

Simvastatin is an important cholesterol lowering compound and is currently synthesized from the natural product lovastatin via multistep chemical synthesis. We have previously reported the use of an Escherichia coli strain BL21(DE3)/pAW31 as the host for whole-cell biocatalytic conversion of monacolin J acid to simvastatin acid. During fermentation and bioconversion, unknown E. coli enzyme(s) hydrolyzed the membrane permeable thioester substrate dimethylbutyryl-S-methyl mercaptopropionate (DMB-S-MMP) to the free acid, significantly decreased the efficiencies of the whole-cell bioconversion and the downstream purification steps. Using the Keio K-12 Singe-Gene Knockout collection, we identified BioH as the sole enzyme responsible for the observed substrate hydrolysis. Purification and reconstitution of E. coli BioH activity in vitro confirmed its function. BioH catalyzed the rapid hydrolysis of DMB-S-MMP with kcat and Km values of 260+/-45 s(-1) and 229+/-26 microM, respectively. This is in agreement with previous reports that BioH can function as a carboxylesterase towards fatty acid esters. YT2, which is a delta bioH mutant of BL21(DE3), did not hydrolyze DMB-S-MMP during prolonged fermentation and was used as an alternative host for whole-cell biocatalysis. The rate of simvastatin acid synthesis in YT2 was significantly faster than in BL21(DE3) and 99% conversion of 15 mM simvastatin acid in less than 12 h was achieved. Furthermore, the engineered host required significantly less DMB-S-MMP to be added to accomplish complete conversion. Finally, simvastatin acid synthesized using YT2 can be readily purified from fermentation broth and no additional steps to remove the hydrolyzed dimethylbutyryl-S-mercaptopropionic acid is required. Together, the proteomic and metabolic engineering approaches render the whole-cell biocatalytic process more robust and economically attractive.     

Tumor angiogenic endothelial cell targeting by a novel integrin-targeted nanoparticle

Angiogenesis is an important process in cancer growth and metastasis. During the tumor angiogenic process, endothelial cells express various cell surface receptors which can be utilized for molecular imaging and targeted drug delivery. One such protein receptor of interest is the integrin alphav beta3. Our group is involved in the development of molecular imaging probes and drug delivery systems targeting alphav beta3. Based on extensive lead optimization study with the integrin antagonist compounds, we have developed a new generation of integrin alphav beta3 compound (IA) which has superior binding affinity to alphav beta3. Utilizing this IA as a targeting agent, we have developed a novel integrin-targeted nanoparticle (ITNP) system for targ alphav beta3 was observed. These ITNPs also were rapidly taken up by cells that express alphav beta3. The ITNPs accumulated in the angiogenic vessels, after systemic administration in a murine squamous cell carcinoma model. This novel intergrin targeted ITNP platform will likely have an application in targeted delivery of drugs and genes in vivo and can also be used for molecular imaging.     

Three-dimensional reconstruction of bovine brain V-ATPase by cryo-electron microscopy and single particle analysis

Bovine V-ATPase from brain clathrin-coated vesicles was investigated by cryo-electron microscopy and single particle analysis. Our studies revealed great flexibility of the central linker region connecting V₁ and V₀. As a consequence, the two sub-complexes were processed separately and the resulting volumes were merged computationally. We present the first three-dimensional (3D) map of a V-ATPase obtained from cryo-electron micrographs. The overall resolution was estimated 34 Å by Fourier shell correlation (0.5 cutoff). Our 3D reconstruction shows a large peripheral stalk and a smaller, isolated peripheral density, suggesting a second, less well-resolved peripheral connection. The 3D map reveals new features of the large peripheral stator and of the collar-like density attached to the membrane domain. Our analyses of the membrane domain indicate the presence of six proteolipid subunits. In addition, we could localize the V₀ subunit a flanking the large peripheral stalk.     

A reduction-based exact algorithm for the contact map overlap problem.

Aligning proteins based on their structural similarity is a fundamental problem in molecular biology with applications in many settings, including structure classification, database search, function prediction, and assessment of folding prediction methods. Structural alignment can be done via several methods, including contact map overlap (CMO) maximization that aligns proteins in a way that maximizes the number of common residue contacts. In this paper, we develop a reduction-based exact algorithm for the CMO problem. Our approach solves CMO directly rather than after transformation to other combinatorial optimization problems. We exploit the mathematical structure of the problem in order to develop a number of efficient lower bounding, upper bounding, and reduction schemes. Computational experiments demonstrate that our algorithm runs significantly faster than existing exact algorithms and solves some hard CMO instances that were not solved in the past. In addition, the algorithm produces protein clusters that are in excellent agreement with the SCOP classification. An implementation of our algorithm is accessible as an on-line server at http://eudoxus.scs.uiuc.edu/cmos/cmos.html.     

Differential regulation of L-type Ca2+ channels in cerebral and mesenteric arteries after simulated microgravity in rats and its intervention by standing

This study was designed to clarify whether simulated microgravity can induce differential changes in the current and protein expression of the L-type Ca(2+) channel (Ca(L)) in cerebral and mesenteric arteries and whether these changes can be prevented by daily short-duration -G(x) exposure. Tail suspension [hindlimb unloading (HU)] for 3 and 28 days was used to simulate short- and medium-term microgravity-induced deconditioning effects. Standing (STD) for 1 h/day was used to provide -G(x) as a countermeasure. Whole cell patch-clamp experiments revealed an increase in current density of Ca(L) of vascular smooth muscle cells (VSMCs) isolated from cerebral arteries of rats subjected to HU and a decrease in VSMCs from mesenteric arteries. Western blot analysis revealed a significant increase and decrease of Ca(L) channel protein expression in cerebral and small mesenteric arterial VSMCs, respectively, only after 28 days of HU. STD for 1 h/day did not prevent the increase of Ca(L) current density in cerebral arterial VSMCs, but it prevented completely (within 3 days) and partially (28 days) the decrease of Ca(L) current density in small mesenteric arterial VSMCs. Consistent with the changes in Ca(L) current, STD for 1 h/day did not prevent the increase of Ca(L) expression in cerebrovascular myocytes but did prevent the reduction of Ca(L) expression in mesenteric arterial VSMCs subjected to 28 days of HU. These data indicate that simulated microgravity up- and downregulates the current and expression of Ca(L) in cerebral and hindquarter VSMCs, respectively. STD for 1 h/day differentially counteracted the changes of Ca(L) function and expression in cerebral and hindquarter arterial VSMCs of HU rats, suggesting the complexity of the underlying mechanisms in the effectiveness of intermittent artificial gravity for prevention of postflight cardiovascular deconditioning, which needs further clarification.     

Morphological Alteration of Golgi Apparatus and Subcellular Compartmentalization of TGF-β1 in Golgi Apparatus in Gerbils Following Transient Forebrain Ischemia

Golgi apparatus (GA) is a very important organelle involved in the metabolism of numerous proteins. TGF-β1 plays an important role in supporting neuronal survival after ischemic insults. Little is known, however, about the morphological alteration of GA and subcellular compartmentalization of TGF-β1 in brain after ischemia. Therefore, our present study was designed to check for GA morphological alterations and TGF-β1 subcellular localization. GA immunoreactivities were examined in the somatosensory cortex of gerbils after 10 min transient forebrain ischemia. Confocal Immunofluorographs of TGF-β1 and TGN38 were also taken. Results indicated that no fragmentation of GA was found in gerbils of norm, shams and 6, 24 and 72 h postocclusion, but some of the cortical cells showed fragmentation of GA in gerbils 7 days postocclusion. TGF-β1 was colocalized with TGN38, a marker molecule for the GA. We conclude that there was morphological alterations of GA and TGF-β1 was present in GA in the somatosensory cortex after 10 min ischemia.     

细胞外信号调节激酶1/2信号通路在慢性哮喘模型大鼠支气管平滑肌细胞迁移功能变化中的调控作用

本研究旨在探讨细胞外信号调节激酶1／2(extracellular signal-regulated kinase,ERK1/2)信号通路在慢性哮喘模型大鼠支气管平滑肌细胞(bronchial smooth muscle cells,BSMCs)迁移能力改变中的调控作用。应用卵清蛋白致敏和雾化方法制备大鼠慢性哮喘模型,体外培养大鼠BSMCs,采用免疫荧光细胞化学、Western blot和RT-PCR方法检测ERK1／2信号通路的表达,分别用平面迁移实验和跨膜迁移实验来评价BSMCs的活动和趋向迁移能力,并比较用和不用ERK1／2信号通路干预剂的差异。Western blot结果显示慢性哮喘模型大鼠BSMCs中总ERK1／2(9．13±0．87)较对照组(4．68±0．59)明显增加,磷酸化ERK1／2(p-ERK1/2)占总ERK1／2的比值(0．55±0．05)较对照组(0．48±0．04)显著提高(n=10,P<0．01)。慢性哮喘组ERK1和ERK2 mRNA的表达(1．83±0．24和1．07±0．11)较对照组(0．58±0．14和0．51±0．12)明显增高(n=10,P<0．01)。在平面迁移实验中,慢性哮喘大鼠BSMCs的迁移最远距离是对照组的(2．9±0．1)倍,在ERK1／2激动剂表皮生长因子(epidermal growth factor, EGF)刺激下增加到(5．0±0．2)倍,而在30μmol／L PD98059的作用后下降到(1．7±0．2)倍。正常对照大鼠BSMCs平面迁移能力对PD98059的反应较慢性哮喘组弱,仅在100μmol／L PD98059的作用下下降到(0．8±0．1)倍。跨膜迁移实验中,慢性哮喘大鼠BSMCs的跨膜迁移细胞是对照组的(1．9±0．1)倍,在EGF刺激下增加到(3．1±0．2)倍,而在30μmol/L PD98059作用后下降到(1.45±0.2)倍。这些结果表明慢性哮喘模型大鼠BSMCs的迁移能力明显增强,ERK1／2信号通路在该功能变化的调控中可能发挥了重要作用。