核酸探针技术

本文对核酸探针技术进行了较全面的综述，介绍了核探针的制备及非放射性标记方法，并对核酸的Ｓｏｕｔｈｅｒｎ转印杂交，Ｎｏｒｔｈｅｒｎ转印杂交，ＩｎＳｉｔｕ转印杂交及斑点杂交法的原理及应用进行了简明的评述。     

游离氨抑制协同过程控制实现渗滤液短程硝化

采用UASB-SBR生化系统处理高氮晚期渗滤液为研究对象,在获得稳定有机物和氮去除的前提下,考察了采用游离氨(FA)协同过程控制对实现渗滤液长期稳定短程硝化的可行性,建立实现与维持SBR系统内稳定短程硝化的途径及方法.试验结果表明:经过36d的运行,SBR系统的亚硝积累率始终稳定在90%以上,获得了稳定的短程硝化.游离氨和过程控制的协同作用是实现与维持SBR反应器稳定短程硝化的决定因素,以DO,ORP和pH作为渗滤液短程硝化反硝化的过程控制参数是可行的,在充分利用较高FA抑制亚硝酸盐氧化菌活性的前提下,过程控制能够准确判断硝化终点,避免过度曝气破坏短程硝化,从而为氨氧化菌(AOB)的生长创造有利条件,有效抑制亚硝酸盐氧化菌(NOB)的生长并逐渐从系统中淘洗出去,实现了硝化菌种群的优化,荧光原位杂交技术(FISH)检测也证明这一点.在此基础上,通过批次实验考察了微生物种群的反硝化动力学特性,符合Monod动力学方程,NO2--N基质最大比利用速率和半饱和常数分别为0.44gNO2--NgVSS-1d-1和15.8mgL-1.     

A G‐Quadruplex/Hemin Complex with Switchable Peroxidase Activity by DNA Hybridization

A hemin‐binding DNA G‐quadruplex (also known as a hemin aptamer or DNAzyme) has been previously reported to be able to enhance the peroxidase activity of hemin. In this work, we described a DNAzyme structure that had an effector‐recognizing part appearing as a single stranded DNA linkage flanked by two split G‐quadruplex halves. Hybridization of the single stranded part in the enzyme with a perfectly matched DNA strand (effector) formed a rigid DNA duplex between the two G‐quadruplex halves and thus efficiently suppressed the enzymatic activity of the G‐quadruplex/hemin complex, while the mismatched effector strand was not able to regulate the peroxidase activity effectively. With 2,2′‐azinobis(3‐ethylbenzthiazoline)‐6‐sulfonic acid (ABTS) as an oxidizable substrate, we were able to characterize the formation of the re‐engineered G‐quadruplex/hemin complex and verify its switchable peroxidase activity. Our results show that the split G‐quadruplex is an especially useful module to design low‐cost and label‐free sensors toward various biologically or environmentally interesting targets.     

Fast and sensitive DNA analysis using changes in the FRET signals of molecular beacons in a PDMS microfluidic channel

A new DNA hybridization analytical method using a microfluidic channel and a molecular beacon-based probe (MB-probe) is described. A stem-loop DNA oligonucleotide labeled with two fluorophores at the 5′ and 3′ termini (a donor dye, TET, and an acceptor dye, TAMRA, respectively) was used to carry out a fast and sensitive DNA analysis. The MB-probe utilized the specificity and selectivity of the DNA hairpin-type probe DNA to detect a specific target DNA of interest. The quenching of the fluorescence resonance energy transfer (FRET) signal between the two fluorophores, caused by the sequence-specific hybridization of the MB-probe and the target DNA, was used to detect a DNA hybridization reaction in a poly(dimethylsiloxane) (PDMS) microfluidic channel. The azoospermia gene, DYS 209, was used as the target DNA to demonstrate the applicability of the method. A simple syringe pumping system was used for quick and accurate analysis. The laminar flow along the channel could be easily controlled by the 3-D channel structure and flow speed. By injecting the MB-probe and target DNA solutions into a zigzag-shaped PDMS microfluidic channel, it was possible to detect their sequence-specific hybridization. Surface-enhanced Raman spectroscopy (SERS) was also used to provide complementary evidence of the DNA hybridization. Our data show that this technique is a promising real-time detection method for label-free DNA targets in the solution phase. Figure FRET-based DNA hybridization detection using a molecular beacon in a zigzag-shaped PDMS microfluidic channel     

Impedance DNA Biosensor Using Electropolymerized Polypyrrole/Multiwalled Carbon Nanotubes Modified Electrode

In this paper, we present an electrochemical impedance‐based DNA biosensor by using a composite material of polypyrrole (PPy) and multiwalled carbon nanotubes (MWNTs) to modify glassy carbon electrode (GCE). The polymer film was electropolymerized onto GCE by cyclic voltammetry (CV) in the presence of carboxylic groups ended MWNTs (MWNTs‐COOH). Such electrode modification method is new for DNA hybridization sensor. Amino group ended single‐stranded DNA (NH₂‐ssDNA) probe was linked onto the PPy/MWNTs‐COOH/GCE by using EDAC, a widely used water‐soluble carbodiimide for crosslinking amine and carboxylic acid group. The hybridization reaction of this ssDNA/PPy/MWNTs‐COOH/GCE resulted in a decreased impedance, which was attributed to the lower electronic transfer resistance of double‐stranded DNA than single‐stranded DNA. As the result of the PPy/MWNTs modification, the electrode obtained a good electronic transfer property and a large specific surface area. Consequently, the sensitivity and selectivity of this sensor for biosensing DNA hybridization were improved. Complementary DNA sequence as low as 5.0×10^?12 mol L^?1 can be detected without using hybridization marker or intercalator. Additionally, it was found that the electropolymerization scan rate was an important factor for DNA biosensor fabrication. It has been optimized at 20 mV s^?1.     

Covalent DNA–Streptavidin Conjugates as Building Blocks for Novel Biometallic Nanostructures

Supramolecular aggregates of DNA, RNA, streptavidin, immunoglobulin, and nanocrystalline metal clusters can be generated by self-assembly on the basis of oligonucleotide hybridization (shown schematically). Following selective immunosorption on surface-immobilized antigen, the biometallic hybrid is detectable by electron microscopy.     

Chromosomal instability is more frequent in metastasized than in non-metastasized pulmonary carcinoids but is not a reliable predictor of metastatic potential

Pulmonary carcinoids are infrequent neoplasms of the lung that normally display a less aggressive biological behavior compared to small cell and non-small cell lung cancers. Approximately 15-25% of carcinoids, in particular atypical carcinoids, show lymph node metastasis and have a worse prognosis than their non-metastasized counterparts. To date, there is no morphological or molecular marker that may help to differentiate between carcinoids that metastasize and carcinoids of identical differentiation that show only local tumor growth. In this study, we analyzed 7 metastasized and 10 non-metastasized pulmonary carcinoids for chromosomal and microsatellite instability in order to determine whether microsatellite instability or chromosomal imbalances are associated with metastasis. Due to the rare occurrence of metastasized carcinoids we compared our results of chromosomal instability with the hitherto published comparative genomic hybridization (CGH) profiles of pulmonary carcinoids, for which information about the absence or presence of metastasis was available. While microsatellite instability was not detected we found chromosomal instability as a common event in pulmonary carcinoids with an increase of frequency and extent of chromosomal alterations in atypical and metastasized carcinoids. These findings are in accordance with the collected and herein compiled data of previous studies and indicate increasing numbers of chromosomal imbalances to play a role in the sequential process of tumor development and metastasis.     

超薄类金刚石膜生长和结构特性的分子动力学模拟

利用分子动力学模拟方法研究了2—3nm厚的类金刚石(DLC)薄膜在金刚石基体(100)表面上的生长过程. 分析了用来表征沉积后无定型碳膜质量的重要结构特性，如sp³杂化比例、薄膜密度、径向分布函数等，计算结果和现有的实验结果基本一致. 不同入射原子能量对结构特性进而对薄膜性能有重要影响，入射原子能量在20—60eV时，薄膜可以获得最优性能. 载能原子入射是生长均匀、连续、致密固体薄膜的前提，稳定的中间区域对于保证薄膜优良的力学性质是必需的. 关键词： DLC膜 分子动力学模拟 3杂化比例')" href="#">sp³杂化比例     

A New Fluorescence Resonance Energy Transfer Pair and Its Application to Oligonucleotide Labeling and Fluorescence Resonance Energy Transfer Hybridization Studies

We describe two new fluorescence resonance energy transfer (FRET) compatible labels, their covalent linkage to oligonucleotides, and their use as donor and acceptor, respectively, in FRET hybridization studies. The dyes belong to the cyanine dyes, and water solubility is imparted by a phosphonate which represents a new solubilizing group in DNA labels. They were linked to amino-modified synthetic oligonucleotides via oxysuccinimide (OSI) esters. The studies performed include binding assays, determinations of molecular distances, homogeneous competitive assays, and limits of detection, which are in the order of 5 pmol/L for a 15-mer.     

最近邻格点间直接杂化机制引起的超导电性

给出了高 T_c 超导电性的直接杂化机制,并运用平均场近似做了研究.由最近邻格点间杂化作用为媒介形成局域空穴对.对转变温度、零温能隙和比热跃变作为掺杂参数的函数做了估算,并且给出了能隙、比热和热力学临界场对温度的依赖关系.