Redesigning trypsin: alteration of substrate specificity

A general method for modifying eukaryotic genes by site-specific mutagenesis and subsequent expression in mammalian cells was developed to study the relation between structure and function of the proteolytic enzyme trypsin. Glycine residues at positions 216 and 226 in the binding cavity of trypsin were replaced by alanine residues, resulting in three trypsin mutants. Computer graphic analysis suggested that these substitutions would differentially affect arginine and lysine substrate binding of the enzyme. Although the mutant enzymes were reduced in catalytic rate, they showed enhanced substrate specificity relative to the native enzyme. This increased specificity was achieved by the unexpected differential effects on the catalytic activity toward arginine and lysine substrates. Mutants containing alanine at position 226 exhibited an altered conformation that may be converted to a trypsin-like structure upon binding of a substrate analog.     

基于KEGG千针万线草光合代谢通路分析

千针万线草是一种药用植物,光合作用是植物最基本的代谢途径。本研究通过千针万线草种子转录组测序及功能注释,分析KEGG数据库注释功能并挖掘光合代谢通路基因。结果表明：比对到KEGG中的6 262条Unigenes被归类为6个类别,其中注释到代谢相关通路的Unigene数量最多,有3 051条,占比48.72%;同时,在代谢通路中千针万线草光合代谢通路涉及光合作用、光合作用-天线蛋白和碳同化3个代谢途径,其中光合作用途径涉及光系统Ⅰ反应中心亚基1个、5种光系统Ⅱ蛋白、1种细胞色素b6复合物、2种细胞色素b6-f亚基、1种铁氧化还原蛋白、1种铁氧还蛋白-NADP⁺还原酶、5种F-型H⁺-ATP酶亚基,光合作用-天线蛋白途径包括2种光系统Ⅱ结合蛋白,碳同化途径包括卡尔文循环、C4、景天酸代谢3个途径,分别涉及12种、12种、5种酶。本研究为开展光合作用分子机制研究奠定了基础。     

A functional protein chip for pathway optimization and in vitro metabolic engineering

Pathway optimization is difficult to achieve owing to complex, nonlinear, and largely unknown interactions of enzymes, regulators, and metabolites. We report a pathway reconstruction using RNA display-derived messenger RNA-enzyme fusion molecules. These chimeras are immobilized by hybridization of their messenger RNA end with homologous capture DNA spotted on a substrate surface. Enzymes thus immobilized retain activity proportional to the amount of capture DNA, allowing modulation of the relative activity of pathway enzymes. Entire pathways can thus be reconstructed and optimized in vitro from genomic information. We provide concept validation with the sequential reactions catalyzed by luciferase and nucleoside diphosphate kinase and further illustrate this method with the optimization of the five-step pathway for trehalose synthesis.     

Microrobots for micrometer-size objects in aqueous media: potential tools for single-cell manipulation

Conducting polymers are excellent materials for actuators that are operated in aqueous media. Microactuators based on polypyrrole-gold bilayers enable large movement of structures attached to these actuators and are of particular interest for the manipulation of biological objects, such as single cells. A fabrication method for creating individually addressable and controllable polypyrrole-gold microactuators was developed. With these individually controlled microactuators, a micrometer-size manipulator, or microrobotic arm, was fabricated. This microrobotic arm can pick up, lift, move, and place micrometer-size objects within an area of about 250 micrometers by 100 micrometers, making the microrobot an excellent tool for single-cell manipulation.     

Geometric manipulation of trapped ions for quantum computation

We propose an experimentally feasible scheme to achieve quantum computation based solely on geometric manipulations of a quantum system. The desired geometric operations are obtained by driving the quantum system to undergo appropriate adiabatic cyclic evolutions. Our implementation of the all-geometric quantum computation is based on laser manipulation of a set of trapped ions. An all-geometric approach, apart from its fundamental interest, offers a possible method for robust quantum computation.     

反向遗传学技术在流感病毒研究中的应用

流感病毒是正粘病毒科（Orthomyxoviridae）正粘病毒属分节段单股负链RNA病毒,该病毒能感染人和多种动物给人类社会造成严重危害。据统计每年流感患者达6～12亿,造成25～30万人死亡。1997年香港爆发了禽流感,首次出现跨种属感染现象,造成18人感染,6人死亡的严重后果,随后2003年香港地区和2004上半年亚洲十几个国家及欧美等国家接连爆发高致病性的禽流感并感染人类引起死亡,因此世界各国都极度重视对该病毒的研究。随着反向遗传学技术的兴起,该技术在对流感病毒的复制及调控机制、流感病毒的致病性、制备新型疫苗等各项研究中起到了举足轻重的作用。本文作者将就反向遗传学技术建立及其在流感病毒中应用概况和前景作简要概述。     

pCEP4-PTH质粒对蛋鸡蛋壳质量、激素水平及养分代谢率的影响

选56周龄新扬州鸡产蛋鸡150只,随机分为3个处理,每处理5个重复,各重复10只。研究经腿肌注射0、200和400μg鸡甲状旁腺素基因质粒(pCEP4-PTH)对蛋鸡生产性能、蛋壳质量和血液部分激素的影响。结果表明:pCEP4-PTH基因质粒可改善蛋鸡生产性能;200μg注射量可显著改善蛋壳强度(P0.05),400μg注射量对蛋壳质量影响不显著;pCEP4-PTH基因质粒可在蛋鸡体内良好表达,甲状旁腺素水平均显著升高(P0.05),且注射400μg时达到极显著水平(P0.01),注射400μg pCEP4-PTH基因质粒具有促进内源降钙素和雌激素分泌的作用(P0.05),因而不利于其生物学效应的发挥,两试验组骨钙素与对照组差异不显著,钙、磷代谢率显著升高,表明pCEP4-PTH质粒不影响蛋鸡骨骼质量,且可促进其对钙、磷吸收代谢。pCEP4-PTH基因质粒可改善蛋鸡生产性能和蛋壳质量,促进钙、磷代谢吸收,且不影响骨骼质量。     

乙烯代谢途径中基因表达与器官脱落研究进展

器官脱落是一种由各种因素共同调节的复杂生理过程,多种激素对其都有影响,其中乙烯对脱落的影响最大.乙烯含量的上升和器官脱落正相关,但乙烯含量的上升和器官脱落之间并非相邻的两个步骤.器官脱落首先须使植物体本身乙烯合成量增加,之后通过乙烯受体基因和乙烯进行结合,再通过乙烯信号传递体把乙烯上升信号传递下去,从而引起离区细胞壁水解酶活性增强和基因表达量上升,进而导致离区细胞壁发生破碎,最终导致器官脱落.综述了乙烯代谢途径中的乙烯合成、膜上乙烯受体、乙烯膜内信号传递体与器官脱落的研究进展.     

类胡萝卜素代谢途径基因变异导致园艺植物色泽差异的研究进展

类胡萝卜素是园艺植物中广泛存在的次生代谢物和色素物质,在植物生长发育和观赏价值中发挥重要作用。同时它也是高价值的天然活性物质,对人体健康有益。因此,类胡萝卜素的代谢调控一直是园艺植物的研究热点。类胡萝卜素组分和含量的差异是造成园艺植物色泽和营养成分多样性的重要原因之一,解析优质性状形成的分子机制是进行定向改良的前提和基础。目前,植物类胡萝卜素代谢途径已明确,大量研究表明代谢通路上基因的启动子和编码区变异是造成类胡萝卜素代谢多样性的关键因素之一。本文对园艺植物类胡萝卜素变异遗传机制的研究策略、启动子和编码区的变异类型及变异对类胡萝卜素代谢的影响进行综述,为园艺植物类胡萝卜素的定向改良提供理论依据。     

Differences of aroma development and metabolic pathway gene expression between Kyoho and 87-1 grapes

Aroma is an important quality trait of grapes and often the focus of consumers, viticulturists and grapevine breeders. Kyoho is a hybrid between Vitis vinifera and Vitis labrusca with a strawberry-like scent, while 87-1 is an early-ripening mutant of Muscat hamburg, belonging to Vitis vinifera, with a rose scent. In this study, we compared their aroma compositions and concentrations during berry development by headspace-SPME combined with gas chromatography-mass spectrometry(GC-MS), and analyzed the expression differences of enzyme-encoding genes in the LOX-HPL, MEP and MVA metabolic pathways by qRT-PCR. Twelve esters were detected in Kyoho during the whole berry development and they were abundant after veraison, but no esters were detected in 87-1 berries. Linalool was the dominant terpene among the 14 terpenes detected in 87-1 berries, while limited amounts of terpenes were detected in Kyoho berries. qRT-PCR analysis indicated that the low expression of VvAAT might explain the low content of ester volatiles in 87-1 berries, and the low expression of coding genes in the MEP pathway, especially VvPNLin Ner1, might be the reason for the low content of volatile terpenes in Kyoho berries. The results from this work will promote our understanding of aroma metabolic mechanisms of grapes, and offer some suggestions for grape aromatic quality improvement.     

Crown gall disease and prospects for genetic manipulation of plants

Agrobacterium tumefaciens incites crown gall tumors when bacterial DNA integrates into plant nuclear DNA. Plant cells can express these integrated bacterial genes. Following insertion of desired genes into bacterial DNA using recombinant DNA techniques, this system permits introduction of these new genes into plant DNA. We discuss the potential for genetic manipulation of plants using Agrobacterium tumefaciens and the related organism Agrobacterium rhizogenes.     

Femtosecond pulse sequences used for optical manipulation of molecular motion

Optical control over elementary molecular motion is enhanced with timed sequences of femtosecond (10(-15) second) pulses produced by pulse-shaping techniques. Appropriately timed pulse sequences are used to repetitively drive selected vibrations of a crystal lattice, in a manner analogous to repetitively pushing a child on a swing with appropriate timing to build up a large oscillation amplitude. This process corresponds to repetitively "pushing" molecules along selected paths in the lattice. Amplification of selected vibrational modes and discrimination against other modes are demonstrated. Prospects for more extensive manipulation of molecular and collective behavior and structure are clearly indicated.     

GABA catabolism: localization of succinic semialdehyde dehydrogenase in brain motor and sensory nuclei

The localization of brain succinic semialdehyde dehydrogenase, a specific gamma-aminobutyric acid degradative enzyme, could potentially yield valuable information concerning the function of the enzyme. Application of a new histochemical technique for this enzyme has revealed characteristic patterns of neuronal staining that are contsistent within embryologically and functionally similar nuclei of the brainstem of the rat.     

Genome-wide association study and metabolic pathway prediction of barrenness in maize as a response to high planting density

Increasing the planting density is one way to enhance grain production in maize.However,high planting density brings about growth and developmental defects such as barrenness,which is the major factor limiting grain yield.In this study,the barrenness was characterized in an association panel comprising 280 inbred lines under normal (67 500 plants ha^–1,ND) and high (120 000 plants ha^–1,HD) planting densities in 2017 and 2018.The population was genotyped using 776 254single n...     

Photoperiod manipulation of insect diapause: a method of pest control?

Extension of day length by artificial light in selected field plots in the fall prevented 76 percent of European corn borer [Ostrinia nubilalis (Hübner)] larvae and 70 percent of codling moth [Laspeyresia pomonella (L.)] larvae from entering diapause. Nondiapausing insects cannot survive rigorous winter conditions.     

Dehalogenation: a novel pathway for the anaerobic biodegradation of haloaromatic compounds

Microorganisms of lake sediment and sewage sludge anaerobically metabolized halobenzoates by a novel pathway. The primary degradative event was loss of the aryl halide without the alteration of the aromatic ring. Dehalogenation required strict anaerobic conditions and depended on the halogen and position, but not the number of halogen substituents. A stable methanogenic bacterial consortium was enriched from sludge and found capable of dehalogenating and often mineralizing a variety of halobenzoates to CH(4) and CO(2). The results suggest that reductive dehalogenation of aromatics could be important in removal of some chlorinated xenobiotics from the environment.     

Technique for the study of alternate metabolic pathways: epinephrine metabolism in man

A general method of determining the relative magnitudes of different pathways of formation of a urinary metabolite from a single precursor substance is described. The method requires the administration of the precursor and an intermediate labeled with different isotopes, and the determination of the ratio of the isotopes in the metabolites. A preliminary application to epinephrine metabolism in man is presented.