不同花色品种蝴蝶兰花色素苷含量分析及相关基因表达研究

分析红色、黄色、粉紫色和白色蝴蝶兰品种不同开放度的花和叶花色素苷生物合成途径7个结构基因PAL、4CL、CHS、DFR、F3H、F3'5H和ANS基因和3个调节基因的表达.结果显示:10个基因的表达因不同花色、不同发育阶段而异.这10个基因在叶中的表达量相对花较低.黄金甲中PAL、4CL、CHS、F3H、F3'5H基因的表达量均较高,PAL、4CL、CHS和F3'5H在开花期达到峰值,粉色花空港红鹰花DFR、CHS、F3H、F3'5H表达量较高.白色花空港枫叶和黄色花富乐夕阳花中CHS、DFR、F3H、F3'5H和ANS表达量较低.CHS在6个品种花的不同阶段皆有表达.F3H基因在6个品种中表达量较低,与花色素合成不存在直接相关.调节基因b HLH 6个品种各发育阶段的表达量均较高,MYB表达量较低,这些结果表明,蝴蝶兰花色素苷积累是CHS、F3'5H、DFR和ANS等关键结构基因共同表达的结果,编码转录因子b HLH基因的表达可能在花色形成中作用较大.     

张长小说《空谷兰》的意识形态解读

哪里有话语,哪里就有意识形态。文学作为一种特殊的艺术话语,不可避免地具有意识形态性质。鲜明的、符合时代要求的意识形态意识在白族作家张长的小说《空谷兰》中,始终是占主导地位的叙述力量,它影响了张长对叙述标记及其内涵的设计,促成了小说"架桥"意象及其内涵的设置,并决定了小说最后的结局。正是这种浓郁的意识形态决定了这篇小说的精神内涵。     

Temperature Dependent In-Plane Anisotropic Magnetoresistance in HfTe_5 Thin Layers

We report the observation of in-plane anisotropic magnetoresistance and planar Hall effect in non-magnetic HfTe₅ thin layers.The observed anisotropic magnetoresistance as well as its sign is strongly dependent on the critical resistivity anomaly temperature T_p.Below T_p,the anisotropic magnetoresistance is negative with large negative magnetoresistance.When the in-plane magnetic field is perpendicular to the current,the negative longitudinal magnetoresistance reaches its maximum.The negative longitudinal magnetoresistance effect in HfTe₅ thin layers is dramatically different from that induced by the chiral anomaly as observed in Weyl and Dirac semimetals.One potential underlying origin may be attributed to the reduced spin scattering,which arises from the in-plane magnetic field driven coupling between the top and bottom surface states.Our findings provide valuable insights for the anisotropic magnetoresistance effect in topological electronic systems and the device potential of HfTe5 in spintronics and quantum sensing.     

气体团簇离子束两步能量修形法的平坦化效应

本文提出采用气体团簇离子束的两步能量修形法来改善4H-SiC(1000)晶片表面形貌.先用15 keV的高能Ar团簇离子进行整体修形,再用5 keV的低能团簇离子优化表面.结果表明,在相同的团簇离子剂量下,与单一15 keV的高能团簇处理相比,两步法修形后的表面具有更低的均方根粗糙度,两者分别为1.05 nm和0.78 nm.本文还以原子级平坦表面为研究对象,揭示了载能团簇引起的半球形离子损伤(弧坑)与团簇能量的关系,及两步能量修形法在弧坑修复中的优势.在原子力显微镜表征的基础上,引入了二维功率谱密度函数,以直观全面地给出材料的表面形貌特征及其随波长(频率)的分布.结果表明,经任何能量的团簇离子轰击的表面,在0.05—0.20μm波长范围内,团簇轰击都能有效地降低粗糙度,而在0.02—0.05μm范围内,则出现了粗化效应,这是由于形成了半球形离子损伤,但第二步更低能量的团簇离子处理可以削弱这种粗化效应.     

基于Fluent的钻井纠斜液压系统导向套叶片形状优化选择

建立3种不同叶片截面形状导向套的SolidWorks模型,利用Fluent软件对自动垂直钻井系统导向套井下多相耦合流场进行仿真分析,得到泥浆通过不同叶片截面形状导向套时的流动特性,进而对导向套叶片截面形状进行优化选择。结果表明,旋转导向套采用三角形截面叶片为最佳选择。     

Acid/base controllable self-complexes that mimic flapping butterfly

A new type of self-complexed bis-crown ether containing two bis(p-phenylene)-34-crown-10 (BPP34C10) ether rings and two secondary ammoniums has been synthesized and characterized. The formation of these bis-self-complexes has been identified by NMR spectroscopy, mass spectrometry and X-ray analysis. The acid/base controlled movement of these bis–crown ethers can mimic a flapping butterfly.     

Bienzyme-based visual and spectrophotometric aptamer assay for quantitation of nanomolar levels of mercury(II)

The article describes a bienzyme visual system for aptamer-based assay of Hg(II) at nanomolar levels. The detection scheme is based on the finding that Hg(II) ions captured by aptamer-functionalized magnetic beads are capable of inhibiting the enzymatic activity of uricase and thus affect the formation of H₂O₂ and the blue product, i.e., oxidized tetramethylbenzidine. This strategy allows for a visual detection of Hg(II) at nanomolar levels without additional amplification procedure. Measuring the absorbance at 650 nm, the logarithmic calibration plot is linear in the concentration range of 0.5–50 nM and the limit of detection (LOD) is 0.15 nM. This is as low as the LOD obtained by atomic fluorescence spectrometry (AFS). The ions K⁺, Mg²⁺, Na⁺, Ca²⁺, Cu²⁺, Zn²⁺, Fe³⁺, Al³⁺, Co²⁺, AsO₂ ^?, Ni²⁺, Cd²⁺ and Pb²⁺ do not have a significant effect on color formation. The method was applied to the analysis of (spiked) river water, lake water, mineral water, tap water and certified reference water samples, and the results agreed well with those obtained by AFS or certified values, with recoveries ranging from 97% to 109%. The relative standard deviation for five parallel detections at a 10 nM Hg(II) level is 5.2%.

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Graphical abstract A bienzyme-based visual aptasensor was fabricated for label-free detection of nanomolar Hg²⁺ in water samples without any amplification or enrichment procedure.

     

A fluorescence based immunoassay for galectin-4 using gold nanoclusters and a composite consisting of glucose oxidase and a metal-organic framework

The authors describe a fluorescence immunoassay for galectin-4, a candidate biomarker for various cancers. Glucose oxidase was encapsulated into a zeolitic imidazolate framework to give a composite (GOx/ZIF-8 composite) that acts as a signal-transduction tag via a biomimetic mineralization process. After modification of the composite with streptavidin, it binds biotinylated antibody against galectin-4. In the immunoassay, the response to galectin-4 results from the enzymatic oxidation of glucose. This reaction produces hydrogen peroxide (H₂O₂) that reacts with iron(II) ions to generate hydroxy radical (?OH), which leads to the quenching of the fluorescence of gold nanoclusters (AuNCs). Accordingly, the fluorescence quenching of AuNCs depends on the concentration of target galectin-4. The GOx/ZIF-8 composite has a high loading capacity for GOx at uncompromised enzymatic activity. The fluorescence of AuNCs is sensitively quenched by ?OH radicals. Galectin-4 can be detected by this method in concentrations as low as 10 pg·mL^?1. It is expected that this kind of enzyme/MOF composite-based immunoassay has a wide scope in that it may be adapted to other low-abundance proteins and biomarkers.

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Graphical abstract Schematic of a fluorescence immunoassay for galectin-4, a candidate biomarker for various cancers. It is based on a composite consisting of glucose oxidase and a metal-organic framework (GOx/ZIF-8 composite) as well as gold nanoclusters (AuNC)-iron(II) system.

     

Crystal Structures of Bacterial (6‐4) Photolyase Mutants with Impaired DNA Repair Activity

PhrB from Agrobacterium fabrum is the first prokaryotic photolyase which repairs (6‐4) UV DNA photoproducts. The protein harbors three cofactors: the enzymatically active FAD chromophore, a second chromophore, 6,7‐dimethyl‐8‐ribityllumazine (DMRL) and a cubane‐type Fe‐S cluster. Tyr424 of PhrB is part of the DNA‐binding site and could provide an electron link to the Fe‐S cluster. The PhrB_Y424F mutant showed reduced binding of lesion DNA and loss of DNA repair. The mutant PhrB_I51W is characterized by the loss of the DMRL chromophore, reduced photoreduction and reduced DNA repair capacity. We have determined the crystal structures of both mutants and found that both mutations only affect local protein environments, whereas the overall fold remained unchanged. The crystal structure of PhrB_Y424F revealed a water network extending to His366, which are part of the lesion‐binding site. The crystal structure of PhrB_I51W shows how the bulky Trp leads to structural rearrangements in the DMRL chromophore pocket. Spectral characterizations of PhrB_I51W suggest that DMRL serves as an antenna chromophore for photoreduction and DNA repair in the wild type. The energy transfer from DMRL to FAD could represent a phylogenetically ancient process.     

Selective electrochemical CO bond cleavage of β-O-4 lignin model compounds mediated by iodide ion

The electrochemically oxidative cleavage of lignin β-O-4 model compounds mediated by iodide ion has been studied. The results indicate that electrolytic conditions play a predominant role in determining the distribution of cleavage products. The preparative-scale electrolysis proceeds in a simple undivided cell, employing a catalytic amount of NaI as the redox mediator and supporting electrolyte in methanol. Under these conditions, the C_βO bond is selectively cleaved with 2,2-dimethoxy-2-arylacetaldehyde being the main product. In some cases, the reaction gives a good yield of cleavaged products. The results further demonstrate that the indirect electrolysis mediated by halide is a versatile approach for chemical transformation.