变压器寄生参数和负载特性对高压脉冲波形的影响

构建了输出电压幅值为0～20 kV、脉冲重复频率为0.25～20 kHz的双极性高压脉冲电源实验平台,研究了变压器寄生参数与负载特性对输出脉冲波形的影响。采用等效电路复频域解析方法,分析了变压器寄生参数对输出脉冲波形的上升沿、平顶及下降沿的影响规律,并通过改变变压器绕线方案间接验证。发现变压器分布电容和漏感越大,输出脉冲波形上升沿与下降沿越平缓,过冲电压幅值越大,并采用脉冲变压器二次侧均匀密绕、一次侧均匀疏绕、高匝数的方案进行优化。进一步分析了纯阻性、阻容性或阻感性负载特性对输出高压脉冲波形的影响规律,发现电阻值增大（5～50 kΩ）,过冲电压幅值增大,脉冲上升沿和下降沿变陡;当负载电阻回路串联小电容时,过冲电压幅值显著增大,而电容值高于一定值时输出脉冲波形恢复至与纯电阻波形一样;当负载电阻回路串联电感时,输出脉冲波形下降沿变平缓。     

基于JMCT-JBURN的燃料棒径向功率分布计算

研究给出基于蒙特卡罗粒子输运软件JMCT耦合燃耗分析软件JBURN计算燃料棒径向功率分布的方法。介绍了计算模型的建立、输运及燃耗计算的相关设置以及裂变功率、俘获功率的统计方法。UO₂燃料棒径向功率分布的计算结果表明,采用JMCT-JBURN软件的结果与工程常用软件符合较好,最大偏差不超过3%,证明了计算方法和计算软件的适用性。该方法可用于工程设计。     

Narrowband Deep-Blue Multi-Resonance Induced Thermally Activated Delayed Fluorescence: Insights from the Theoretical Molecular Design

Multi-resonance thermal activated delayed fluorescence (MR-TADF) has been promising with large oscillator strength and narrow full width at half maxima of luminescence, overcoming the compromise of emission intensity and energy criteria of traditional charge transfer TADF frameworks. However, there are still limited theoretical investigations on the excitation mechanism and systematic molecular manipulation of MR-TADF structures. We systematically study the highly localized excitation (LE) characteristics based on typical blue boron-nitrogen (BN) MR-TADF emitters and prove the potential triangular core with theoretical approaches. A design strategy by extending the planar π-conjugate core structure is proposed to enhance the multiple resonance effects. Moreover, several substituted groups are introduced to the designed core, achieving color-tunable functions with relatively small energy split and strong oscillator strength simultaneously. This work provides a theoretical direction for molecular design strategy and a series of potential candidates for highly efficient BN MR-TADF emitters.     

超高效液相色谱-串联质谱法同时测定土壤中239种农药的残留量

建立了超高效液相色谱-串联质谱法(UPLC-MS/MS),可于10 min内快速测定土壤中的239种农药残留。土壤样品经AOAC (Association of Official Analytical Chemists) QuEChERS方法处理,用乙腈萃取;无水硫酸镁、乙酸钠固液分离后,过0.2 μm滤膜;在UPLC-MS/MS正、负离子同步扫描多反应监测模式下进行分析。239种农药中,线性相关系数(r²)大于0.99的有236个,占总数的99%。在40 μg/kg添加水平下所有被检测农药的回收率均在50%~150%之间,且相对标准偏差(RSD)均小于20%;其中有209种农药的回收率达到70%~120%,有161种的RSD小于10%。方法的检出限(LOD)范围为0.69~29.04 μg/kg。土壤中多种农药残留的同时检测要求时间短、准确度和精密度高,本方法符合这些检测要求,适用于土壤中农药残留的检测。     

Visually precise,low-damage,single-cell spatial manipulation with single-pixel resolution

The analysis of single living cells, including intracellular delivery and extraction, is essential for monitoring their dynamic biochemical processes and exploring intracellular heterogeneity. However, owing to the 2D view in bright-field microscopy and optical distortions caused by the cell shape and the variation in the refractive index both inside and around the cells, achieving spatially undistorted imaging for high-precision manipulation within a cell is challenging. Here, an accurate and visual system is developed for single-cell spatial manipulation by correcting the aberration for simultaneous bright-field triple-view imaging. Stereo information from the triple view enables higher spatial resolution that facilitates the precise manipulation of single cells. In the bright field, we resolved the spatial locations of subcellular structures of a single cell suspended in a medium and measured the random spatial rotation angle of the cell with a precision of ±5°. Furthermore, we demonstrated the visual manipulation of a probe to an arbitrary spatial point of a cell with an accuracy of <1 pixel. This novel system is more accurate and less destructive for subcellular content extraction and drug delivery.

We achieved the low-damage spatial puncture of single cells at specific visual points with an accuracy of <65 nm.     

金属调控蛋白的结构、性质及应用

金属调控蛋白是微生物体内通过转录抑制或激活机制严格控制金属离子摄入、外排和储存的特异性金属离子结合蛋白,对维持体内适宜的金属离子浓度和平衡起着举足轻重的作用。本文综述了目前主要的七大家族金属调控蛋白的调控机制和拓扑结构,详细介绍了金属离子结合区域的结构特征和金属-配体的配位构型。基于金属-配体的配位构型,重点讨论了每类金属调控蛋白对目标金属离子特异性选择的机理。此外,本文还介绍了金属调控蛋白在重金属离子检测和吸附方面的应用,拓展了金属调控蛋白的研究和应用领域,同时为生物无机化学的研究方向开辟了新的思路。     

Stabilization of G‐Quadruplex DNA,Inhibition of Telomerase Activity and Live Cell Imaging Studies of Chiral Ruthenium(II) Complexes

Telomerase inhibition is an attractive strategy for cancer chemotherapy. In the current study, we have synthesized and characterized two chiral ruthenium(II) complexes, namely, Λ‐[Ru(phen)₂(p‐MOPIP)]²⁺ and Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺, where phen is 1,10‐phenanthroline and p‐MOPIP is 2‐(4‐methoxyphenyl)‐imidazo[4,5f][1,10]phenanthroline. The chiral selectivity of the compounds and their ability to discriminate quadruplex DNA were investigated by using UV/Vis, fluorescence spectroscopy, circular dichroism spectroscopy, fluorescence resonance energy transfer melting assay, polymerase chain reaction stop assay and telomerase repeat amplification protocol. The results indicate that the two chiral compounds could induce and stabilize the formation of antiparallel G‐quadruplexes of telomeric DNA in the presence or absence of metal cations. We report the remarkable ability of the two complexes Λ‐[Ru(phen)₂(p‐MOPIP)]²⁺ and Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺ to stabilize selectively G‐quadruplex DNA; the former is a better G‐quadruplex binder than the latter. The anticancer activities of these complexes were evaluated by using the MTT assay. Interestingly, the antiproliferative activity of Λ‐[Ru(phen)₂(p‐MOPIP)]²⁺ was higher than that of Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺, and Λ‐[Ru(phen)₂(p‐MOPIP)]²⁺ showed a significant antitumor activity in HepG2 cells. The status of the nuclei in Λ/Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺‐treated HepG2 cells was investigated by using real‐time living cell microscopy to determine the effects of Λ/Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺ on intracellular accumulation. The results show that Λ/Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺ can be taken up by HepG2 cells and can enter into the cytoplasm as well as accumulate in the nuclei; this suggests that the nuclei were the cellular targets of Λ/Δ‐[Ru(phen)₂(p‐MOPIP)]²⁺.     

3‐O‐Sulfation of Heparan Sulfate Enhances Tau Interaction and Cellular Uptake

Prion‐like transcellular spreading of tau in Alzheimer's Disease (AD) is mediated by tau binding to cell surface heparan sulfate (HS). However, the structural determinants for tau–HS interaction are not well understood. Microarray and SPR assays of structurally defined HS oligosaccharides show that a rare 3‐O‐sulfation (3‐O‐S) of HS significantly enhances tau binding. In Hs3st1^?/? (HS 3‐O‐sulfotransferase‐1 knockout) cells, reduced 3‐O‐S levels of HS diminished both cell surface binding and internalization of tau. In a cell culture, the addition of a 3‐O‐S HS 12‐mer reduced both tau cell surface binding and cellular uptake. NMR titrations mapped 3‐O‐S binding sites to the microtubule binding repeat 2 (R2) and proline‐rich region 2 (PRR2) of tau. Tau is only the seventh protein currently known to recognize HS 3‐O‐sulfation. Our work demonstrates that this rare 3‐O‐sulfation enhances tau–HS binding and likely the transcellular spread of tau, providing a novel target for disease‐modifying treatment of AD and other tauopathies.     

平行四面体纳米孔道中DNA超结构的组装和离子输运特性

<正>受生物膜离子通道结构和功能的启发,人工制备固体纳米孔道门控开关器件一直备受关注[1,2].基于仿生纳米孔道的非对称离子传输性质制备的离子二极管和场效应管装置对于构建离子电路和能量转换的纳米器件至关重要[3,4].然而,仿生制备的固体纳米孔道在离子传输过程中有漏电流的存在,严重影响了固体纳米孔道应用的灵敏度和信噪比[5].针对这一问题,研究者利用DNA分子的特殊识别和自组装的功能特性,相继构筑了基于DNA和纳米孔道的智能响应体系[6,7].但在之前的研究工作中,分[8]     

FRET-based ratiometric fluorescent detection of arginine in mitochondrion with a hybrid nanoprobe

A ratiometric fluorescent hybrid nanoprobe CDs-1 for arginine(Arg),exhibiting high sensitivity(the limit of detection,LOD,being 6.5×10^-8 mol/L) and excellent selectivity and anti-interference ability,was fabricated through fluorescence resonance energy transfer(FRET) and the electrostatic attraction between positively-charged hemicyanine molecules and negatively-charged carbon dots(CDs).Arg can be quantitatively detected in the concentration range from 6.0×10^-5 mol/L to 2.7×10^-4 mol/L.Further,due to its ability to target mitochondrion and low cytotoxicity,intracellular Arg was succes s fully tracked through ratiometric fluorescence imaging.