共查询到20条相似文献，搜索用时 46 毫秒
1.
Bao-zhong Zhang Xin Zhang Xiao-ping An Duo-liang Ran Yu-sen Zhou Jun Lu Yi-gang Tong 《Journal of Zhejiang University. Science. B》2009,10(6):479-482
Site-directed mutagenesis (SDM) has been a very important method to probe the function-structure relationship of proteins. In this study, we introduced an easy-to-use, polymerase chain reaction (PCR)-based SDM method for double-stranded plasmid DNA, with a designed restriction site to ensure simple and efficient mutant screening. The DNA sequence to be mutated was first translated into amino acid sequence and then the amino acid sequence was reversely translated into DNA sequence with degenerate codons, resulting in a large number of sequences with silent mutations, which contained various restriction endonuclease (RE) sites. Certain mutated sequence with an appropriate RE site was selected as the target DNA sequence for designing a pair of mutation primers to amplify the full-length plasmid via inverse PCR. The amplified product was 5'-phosphorylated, circularized, and transformed into an Escherichia coli host. The transformants were screened by digesting with the designed RE. This protocol uses only one pair of primers and only one PCR is conducted, without the need for hybridization with hazardous isotope for mutant screening or subcloning step. 相似文献
2.
3.
本文的目的是研究半多孔内皮细胞的包膜(SPEUs)的效应 以PTMEG1000为基础的SPEU的多孔性为51.58%(±5.86%) 与天然脉管相比较,例如与一头6个月小牛胸部的上部下来的主动脉大血管相比较,SPEU的拉伸强度是足够强的 脉管的典型脉动压力服从静脉管压力(1.5～2%Δd/d),此压力小于动脉管压力(9～15%Δd/d) 在种植EC之前,观察了在SPEUs上培育的人皮的成纤维细胞(HDF) SPEU的DNA数量与HDF在一天之内种植;有71.9%(±11.01%)细胞被种植在SPEUs上 LDH试验表明:在有控制的和实验群数据之间没有显著的差别,说明没有细胞毒素 因此,EC在SPRUs上具有良好的粘附性,这是所期望的,而应用胶原实现了将EC种植在半微孔的SPEUs上的表面改善 相似文献
4.
Zhang XG Miao J Li MW Jiang SP Hu FQ Du YZ 《Journal of Zhejiang University. Science. B》2008,9(6):506-510
Herein, solid lipid nanoparticles (SLN) were proposed as a new drug delivery system for adefovir dipivoxil (ADV). The octadecylamine-fluorescein isothiocynate (ODA-FITC) was synthesized and used as a fluorescence maker to be incorporated into SLN to investigate the time-dependent cellular uptake of SLN by HepG2.2.15. The SLN of monostearin with ODA-FITC or ADV were prepared by solvent diffusion method in an aqueous system. About 15wt% drug entrapment efficiency (EE) and 3wt% drug loading (DL) could be reached in SLN loading ADV. Comparing with free ADV, the inhibitory effects of ADV loaded in SLN on hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and hepatitis B virus (HBV) DNA levels in vitro were significantly enhanced. 相似文献
5.
6.
枇杷属植物RAPD反应体系的优化与应用 总被引：2，自引：0，他引：2
采用CTAB—蛋白酶K法提取了48份枇杷种质的DNA,以西班牙枇杷品种Ullera为模板DNA,对枇杷属植物RAPD反应体系进行优化研究,结果表明:25μL反应体系中,Taq DNA聚合酶、Mg2+、引物、模板DNA和dNTPs等5种主要成分的适宜浓度或用量分别是:Mg2+为2.0 mmol/L,Taq DNA聚合酶为1.0 U,引物为0.25"mol/L,dNTPs为0.100—0.125 mmol/L,模板DNA为25—30 ng。利用该优化体系对48份枇杷种质进行RAPD随机扩增,经琼脂糖电泳获得了清晰的扩增图谱。 相似文献
7.
基于一种新的非参数方法计算了HDR (high data rate)无线网络的吞吐率容量区域. 首先把HDR吞吐率容量区域的计算问题转化为一个不带参数的数学优化问题, 然后通过贪婪算法求解得到该优化问题的解, 从而最终给出了HDR吞吐率容量区域的非参数解析刻划. 与传统的参数化方法的庞大计算量相比, 该方法的计算复杂度降低很多, 最多只需要计算N(M2-M 1)N-1个线性约束即可, 其中N为用户数, M为系统支持速率数. 数值计算例子验证了这种非参数方法的正确性. 相似文献
8.
圆度误差的快速傅立叶变换分析 总被引：1，自引：0，他引：1
回转零件正截面轮廓的圆度误差可以视为周期函数。对正截面轮廓等角度间隔采样获得的数据点,可进行离散傅立叶变换(DFT)。通过对数据点序列的快速傅立叶变换(FFT)结果加以分析,可以发现隐藏在圆度误差信号中的各种频率成分。文章首先简要介绍了圆度误差的数学模型,然后分析了各种频率成分对圆度误差的影响。最后提出了圆度误差计算的新方法。 相似文献
9.
Muhammad Abubakkar Azmat Iqrar Ahmad Khan Hafiza Masooma Naseer Cheema Ishtiaq Ahmad Rajwana Ahmad Sattar Khan Asif Ali Khan 《Journal of Zhejiang University. Science. B》2012,13(4):239-243
Good quality deoxyribonucleic acid (DNA) is the pre-requisite for its downstream applications. The presence of high concentrations of polysaccharides, polyphenols, proteins, and other secondary me- tabolites in mango leaves poses problem in getting good quality DNA fit for polymerase chain reaction (PCR) applications. The problem is exacerbated when DNA is extracted from mature mango leaves. A reliable and modified protocol based on the cetyl- trimethylammonium bromide (CTAB) method for DNA extraction from mature mango leaves is described here. High concentrations of inert salt were used to remove polysaccharides; Polyvinylpyrrolidone (PVP) and β-mercaptoethanol were employed to manage phenolic compounds. Extended chloroform-isoamyl alcohol treatment followed by RNase treatment yielded 950?1050 μg of good quality DNA, free of protein and RNA. The problems of DNA degradation,contamination, and low yield due to irreversible binding of phenolic compounds and coprecipitation of polysaccharides with DNA were avoided by this method. The DNA isolated by the modified method showed good PCR amplification using simple se- quence repeat (SSR) primers. This modified protocol can also be used to extract DNA from other woody plants having similar problems. 相似文献
10.
Polyethylenimine-cyclodextrin-tegafur (PEI-CyD-tegafur) conjugate was synthesized as a novel multifunctional prodrug of tegafur
for co-delivery of chemotherapeutic agent tegafur and enhanced green fluorescent protein (EGFP) reporter plasmid DNA. Conjugation
of tegafur to PEI-CyD via chemical linkage was characterized by 1H NMR spectrometry and ultraviolet (UV) spectrometry. PEI-CyD-tegafur was able to condense plasmid DNA into complexes of around
150 nm with positive charge at the N/P ratio of 25, in accordance with electron microscopy observation of compact and monodisperse
nanoparticles. The results of in vitro experiments showed enhanced cytotoxicity and considerable transfection efficiency in
B16F10 cell line. Therefore, PEI-CyD-tegafur may have great potential as a co-delivery system with anti-cancer activity and
potential for gene delivery. 相似文献
11.
采用密度泛函(DFT)计算方法,在UB3LYP/6-311 G(3d,2p)水平上优化了过渡金属正离子乙炔络合物M(C2H2) (M=Sc,Ti,V)不同自旋态的稳定几何构型,并对此络合物体系的全部振动频率进行了计算和全面分析。结果表明,能量较低的高自旋态M 与C2H2在形成络合物时,M 的价电子要发生翻转,形成稳定的低自旋态络合物。根据频率分析,所计算的振动频率值反映出低自旋态络合物比高自旋态络合物有较强的M-C键,在形成低自旋态络合物的同时,过渡金属正离子M 已活化了乙炔的C-C三键和C-H键。 相似文献
12.
A pilot-scale ultrafiltration membrane plant was set up for treating Luanhe River water with flocculating and precipitation process of waterworks.The aim is to investigate the variation and characteristics of natural organic matter and disinfection byproducts formation potential in the whole process in winter.The results show that dissolved organic matter(DOM),UV254,trihalomethanes formation potential(THMsFP) and haloacetic acids formation potential(HAAsFP) of Luanhe River water were mainly distributed in t... 相似文献
13.
Maintenance of cellular homeostasis and genome integrity is a critical responsibility of DNA double-strand break(DSB)signaling.P53-binding protein 1(53BP1)plays a critical role in coordinating the DSB repair pathway choice and promotes the non-homologous end-joining(NHEJ)-mediated DSB repair pathway that rejoins DSB ends.New insights have been gained into a basic molecular mechanism that is involved in 53BP1 recruitment to the DNA lesion and how 53BP1 then recruits the DNA break-responsive effectors that promote NHEJ-mediated DSB repair while inhibiting homologous recombination(HR)signaling.This review focuses on the up-and downstream pathways of 53BP1 and how 53BP1 promotes NHEJ-mediated DSB repair,which in turn promotes the sensitivity of poly(ADP-ribose)polymerase inhibitor(PARPi)in BRCA1-deficient cancers and consequently provides an avenue for improving cancer therapy strategies. 相似文献
14.
You-qun HUANG Rong GOU Yong-shu DIAO Qing-hua YIN Wen-xing FAN Ya-ping LIANG Yi CHEN Min WU Li ZANG Ling LI Jing ZANG Lu CHENG Ping FU Fang LIU 《Journal of Zhejiang University. Science. B》2014,15(1):58-66
Our intent is to examine the predictive role of Charlson comorbidity index （CCI） on mortality of patients with type 2 diabetic nephropathy （DN）. Based on the CCI score, the severity of comorbidity was categorized into three grades： mild, with CCI scores of 1-2; moderate, with CCI scores of 3-4; and severe, with CCI scores 〉5. Factors influencing mortality and differences between groups stratified by CCI were determined by logistical regression analysis and one-way analysis of variance （ANOVA）. The impact of CCI on mortality was assessed by the Kaplan- Meier analysis. A total of 533 patients with type 2 DN were enrolled in this study, all of them had comorbidity （CCI score 〉1）, and 44.7% （238/533） died. The mortality increased with CCI scores： 21.0% （50/238） patients with CCI scores of 1-2, 56.7% （135/238） patients with CCI scores of 3-4, and 22.3% （53/238） patients with CCI scores 〉5. Logistical regression analysis showed that CCI scores, hemoglobin, and serum albumin were the potential predictors of mortality （P〈0.05）. One-way ANOVA analysis showed that DN patients with higher CCI scores had lower levels of hemoglobulin, higher levels of serum creatinine, and higher mortality rates than those with lower CCI scores. The Kaplan-Meier curves showed that survival time decreased when the CCI scores and mortality rates went up. In con- clusion, CCI provides a simple, readily applicable, and valid method for classifying comorbidities and predicting the mortality of type 2 DN. An increased awareness of the potential comorbidities in type 2 DN patients may provide insights into this complicated disease and improve the outcomes by identifying and treating patients earlier and more effectively. 相似文献
15.
We extracted six Hong Kong brown seaweed species with hot water for their antiviral properties. The cytotoxicity and antiviral activity of these extracts were tested by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenlytetrezolium bromide] method, cytopathic effect reduction assay, and plaque reduction assay. The antiviral effect was further determined by flow cytometric analysis. The results showed that most of these extracts inhibited the propagation of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) standard strains with very low cytotoxicity to the host cells. The extracts ofHydroclathrus clathratus and Lobophora variegata showed more potential anti-HSV activities than the extracts of the other four seaweeds. They also had moderate anti-respiratory syncytial virus (RSV) activities but could not inhibit influenza A virus. Hydroclathrus clathratus was further extracted by diluted acid and alkali and the antiviral effects of the extracts were also detected. The result showed that the hot water extract contained the main carbohydrate components that exhibited the antiviral activities against various strains of HSV, including the acyclovir-resistant strain. HI-3, a compound fractionated from this hot water extract, showed a dose-dependent anti-HSV activity in flow cytometric analysis and plaque reduction assay. 相似文献
16.
DNA is the hereditary material in humans and almost all other organisms. It is essential for maintaining accurate transmission of genetic information. In the life cycle, DNA replication, cell division, or genome damage, including that caused by endogenous and exogenous agents, may cause DNA aberrations. Of all forms of DNA damage, DNA double-strand breaks(DSBs) are the most serious. If the repair function is defective, DNA damage may cause gene mutation, genome instability, and cell chromosome loss, which in turn can even lead to tumorigenesis. DNA damage can be repaired through multiple mechanisms. Homologous recombination(HR) and non-homologous end joining(NHEJ) are the two main repair mechanisms for DNA DSBs. Increasing amounts of evidence reveal that protein modifications play an essential role in DNA damage repair.Protein deubiquitination is a vital post-translational modification which removes ubiquitin molecules or polyubiquitinated chains from substrates in order to reverse the ubiquitination reaction. This review discusses the role of deubiquitinating enzymes(DUBs) in repairing DNA DSBs. Exploring the molecular mechanisms of DUB regulation in DSB repair will provide new insights to combat human diseases and develop novel therapeutic approaches. 相似文献
17.
Joint application of feature extraction based on EMD-AR strategy and multi-class classifier based on LS-SVM in EMG motion classification 总被引：2，自引：0，他引：2
YAN Zhi-guo WANG Zhi-zhong REN Xiao-mei 《浙江大学学报(A卷英文版)》2007,8(8):1246-1255
This paper presents an effective and efficient combination of feature extraction and multi-class classifier for motion classification by analyzing the surface electromyografic(sEMG) signals. In contrast to the existing methods,considering the non-stationary and nonlinear characteristics of EMG signals,to get the more separable feature set,we introduce the empirical mode decomposition(EMD) to decompose the original EMG signals into several intrinsic mode functions(IMFs) and then compute the coefficients of autoregressive models of each IMF to form the feature set. Based on the least squares support vector machines(LS-SVMs) ,the multi-class classifier is designed and constructed to classify various motions. The results of contrastive experiments showed that the accuracy of motion recognition is improved with the described classification scheme. Furthermore,compared with other classifiers using different features,the excellent performance indicated the potential of the SVM techniques embedding the EMD-AR kernel in motion classification. 相似文献
18.
１ Ｉｎｔｒｏｄｕｃｔｉｏｎ ＴｈｅｍａｇｎｅｔｉｃｍａｔｅｒｉａｌｓｂｅｉｎｇｕｓｅｄｉｎｔｈｅｔｒｅａｔｍｅｎｔｏｆｄｉｓｅａｓｅｓａｒｅｏｎｅｏｆｔｈｏｓｅｆａｓｔｅｓｔｇｒｏｗｉｎｇｍｅａｓｕｒｅｓｉｎｍｅｄｉｃａｌｓｃｉｅｎｃｅｉｎＣｈｉｎａ．Ｔｈｅｐｕｒｓｕｉｎｇｆｏｒｔｈｅｒａｐｅｕｔｉｃａｌｍｅｃｈａｎｉｓｍｓｏｆｍａｇｎｅｔｉｃｍａｔｅｒｉａｌｓｉｓａｌｓｏａｎａｒｅａｏｆｔｒａｄｉｔｉｏｎａｌｃｈｉｎｅｓｅｍｅｄｉｃｉｎｅ．Ｉｔｉｓｎｏｗｃｏｎｓｉｄｅｒｅｄｔｏｌｅｓｓｅｎ… 相似文献
19.
基于全寿命周期理论的工程项目健康检测体系构建 总被引：1，自引：0，他引：1
为了更有效地对工程项目的健康状态做出全面准确的评估,将全寿命期下工程项目所有监测指标按质量指标、费用指标、时间指标、各方面满意度和可持续发展指标等加以划分．并且基于该指标体系定性与定量指标相结合的特征,构建了PCA—PR分析模型．该模型先对全寿命期指标体系进行主成分分析（PCA）,从之前构建的全寿命期指标中甄选出一批可以作为工程项目健康检测分析的主要特征指标体系;再针对这些主要特征指标体系进行模式识别分析（PR）,即通过将工程项目即时可能状态划分为绿灯至红灯5种状态,利用模式识别模型和项目主要特征指标识别出项目任意时点的健康状态．最后结合实例进行相关分析,得出与实际情况较为吻合的分析结果,验证了该指标体系和模型的有效性． 相似文献
20.
HU Jia-bing HE Yi-kang NIAN Heng 《浙江大学学报(A卷英文版)》2007,8(8):1330-1339
This paper presents a unified positive-and negative-sequence dual-dq dynamic model of wind-turbine driven doubly-fed induction generator(DFIG) under unbalanced grid voltage conditions. Strategies for enhanced control and operation of a DFIG-used back-to-back(BTB) PWM voltage source converter(VSC) are proposed. The modified control design for the grid-side converter in the stationary αβ frames diminishes the amplitude of DC-link voltage ripples of twice the grid frequency,and the two proposed control targets for the rotor-side converter are alternatively achieved,which,as a result,improve the fault-ride through(FRT) capability of the DFIG based wind power generation systems during unbalanced network supply. A complete unbalanced control scheme with both grid-and rotor-side converters included is designed. Finally,simulation was carried out on a 1.5 MW wind-turbine driven DFIG system and the validity of the developed unified model and the feasibility of the proposed control strategies are all confirmed by the simulated results. 相似文献