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93.
DNA methylation at cytosine/guanine dinucleotide islands (CpGIs) is the most prominent epigenetic modification in prokaryotic and eukaryotic genomes. DNA methyltransferases (MTases) are responsible for genomic methylation, and their aberrant activities are closely associated with various diseases including cancers. However, the specific and sensitive detection of multiple DNA MTases has remained a great challenge due to the specificity of the methylase substrate and the rareness of methylation-sensitive restriction endonuclease species. Here, we demonstrate for the first time the cytosine-5 methylation-directed construction of a Au nanoparticle (AuNP)-based nanosensor for simultaneous detection of multiple DNA MTases at the single-molecule level. We used the methyl-directed endonuclease GlaI to cleave the site-specific 5-methylcytosine (5-mC). In the presence of CpG and GpC MTases (i.e., M.SssI and M.CviPI), their hairpin substrates are methylated at cytosine-5 to form the catalytic substrates for GlaI, respectively, followed by simultaneous cleavage by GlaI to yield two capture probes. These two capture probes can hybridize with the Cy5/Cy3–signal probes which are assembled on the AuNPs, respectively, to form the double-stranded DNAs (dsDNAs). Each dsDNA with a guanine ribonucleotide can act as the catalytic substrate for ribonuclease (RNase HII), inducing recycling cleavage of signal probes to liberate large numbers of Cy5 and Cy3 molecules from the AuNPs. The released Cy5 and Cy3 molecules can be simply quantified by total internal reflection fluorescence (TIRF)-based single-molecule imaging for simultaneous measurement of M.SssI and M.CviPI MTase activities. This method exhibits good specificity and high sensitivity with a detection limit of 2.01 × 10−3 U mL−1 for M.SssI MTase and 3.39 × 10−3 U mL−1 for M.CviPI MTase, and it can be further applied for discriminating different kinds of DNA MTases, screening potential inhibitors, and measuring DNA MTase activities in human serum and cell lysate samples, holding great potential in biomedical research, clinical diagnosis, drug discovery and cancer therapeutics.Cytosine-5 methylation-directed construction of Au nanoparticle-based nanosensors enables specific and sensitive detection of multiple DNA methyltransferases. 相似文献
94.
In this paper, we show that the peeling property still holds for Bondi-Sachs metrics with nonzero cosmological constants under the boundary condition given by Sommerfeld's radiation condition together with three nontrivial Λ-independent functions B, a and b. This should indicate that the new boundary condition is natural. Moreover, we construct some nonstationary vacuum Bondi-Sachs metrics without Bondi news, whose Newman-Penrose quantities fall faster than usual. This provides a new feature of gravitational waves for nonzero cosmological constants. 相似文献
95.
Bin‐Wen Liu Xiao‐Ming Jiang Bing‐Xuan Li Hui‐Yi Zeng Guo‐Cong Guo 《Angewandte Chemie (International ed. in English)》2020,59(12):4856-4859
A large nonlinear optical (NLO) coefficient and a wide band gap are two crucial but contradictory parameters that are difficult to achieve simultaneously in a single infrared (IR) NLO compound. A salt‐inclusion chalcogenide (SIC), Li[LiCs2Cl][Ga3S6] ( 1 ), was prepared that presents a nanosized tunnel framework constructed from monotype chalcogenide tetrahedra. Highly oriented covalent GaS4 tetrahedra in the host lead to a moderate second harmonic generation response (0.7 AgGaS2), and ionic guests effectively broaden the band gap to the widest value (4.18 eV) among all IR NLO chalcogenides, thereby achieving a remarkable balance between NLO efficiency and band gap. 相似文献
96.
利用密度泛函理论(DFT)研究3d过渡金属掺杂硅团簇的几何结构和稳定性,计算了绝热电子亲和能和垂直电离能,内嵌双金属间距,自旋磁矩等.结果表明内嵌的Sc、Ti、V、Mn金属二聚体和十二面体硅笼构成了稳定的富勒烯结构,随着d电子数目的增加其内嵌的富勒烯构型有部分畸变,总体而言Si_(20)团簇掺杂双金属后稳定性得到了提高. 相似文献
97.
节能减排已成为当今社会发展的主题,对节约能源、提高太阳能的高效综合利用的新型窗用透明隔热材料的理论设计和研究尤其重要.本文采用基于密度泛函理论的计算方法,研究了六方相三氧化钨Ti掺杂前、后的晶格参数、电子能带结构、形成能和光学性质.研究结果表明,Ti掺杂后晶格体积增大,系统能量降为负值,体系具有更好的稳定性;掺杂后电子能带结构发生很大的变化,但材料仍保持n型电导率;随之,其光学性质也发生改变,掺杂前h-WO3无近红外吸收性能,掺杂后的Ti0.33WO3具有很强的近红外吸收性能.在此基础上研究了Ti掺杂h-WO3前、后的太阳辐射屏蔽性能,掺杂前无太阳辐射屏蔽性能;掺杂后的Ti0.33WO3薄膜具有可见光高透明、近红外屏蔽的性能.计算结果为Ti掺杂h-WO3在窗用透明隔热材料方面的研究提供了理论依据. 相似文献
98.
Nonlinear Dynamics - A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and... 相似文献
99.
An incremental bundle method for portfolio selection problem under second-order stochastic dominance
Numerical Algorithms - We propose a preconditioner to accelerate the convergence of the GMRES iterative method for solving the system of linear equations obtained from discretize-then-optimize... 相似文献
100.
QiuHong Wang Abdusalam Abdukerim Wei Chen Xun Chen YunHua Chen XiangYi Cui YingJie Fan DeQing Fang ChangBo Fu LiSheng Geng Karl Giboni Franco Giuliani LinHui Gu XuYuan Guo Ke Han ChangDa He Di Huang Yan Huang YanLin Huang Zhou Huang Peng Ji XiangDong Ji YongLin Ju YiHui Lai Kun Liang HuaXuan Liu JiangLai Liu WenBo Ma YuGang Ma YaJun Mao Yue Meng Parinya Namwongsa KaiXiang Ni JinHua Ning XuYang Ning XiangXiang Ren ChangSong Shang Lin Si AnDi Tan AnQing Wang HongWei Wang Meng Wang SiGuang Wang XiuLi Wang Zhou Wang MengMeng Wu ShiYong Wu JingKai Xia MengJiao Xiao PengWei Xie BinBin Yan JiJun Yang Yong Yang ChunXu Yu Jumin Yuan Dan Zhang HongGuang Zhang Tao Zhang Li Zhao QiBin Zheng JiFang Zhou Ning Zhou XiaoPeng Zhou 《中国科学:物理学 力学 天文学(英文版)》2020,(3):54-63
In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively. 相似文献