用单分子磁镊研究顺铂导致的DNA凝聚

本文报道了用单分子磁镊研究抗癌药顺铂导致的DNA凝聚过程.结果表明,当拉力比较小时,DNA凝聚的长度-时间曲线是连续缩短和阶跃缩短并存的复杂曲线.而当拉力较大但又不足以阻止DNA的凝聚时,凝聚曲线为连续缩短的双曲线.增加顺铂浓度只会增大凝聚速度而不会改变反应曲线的形状.实验结果与下列成环凝聚模型一致：在水溶液中顺铂能够与DNA形成双臂加合物,也能形成单臂加合物.当顺铂使DNA长链上相距较远的碱基间发生远程交联时,形成小环,导致DNA凝聚.小环间的进一步交联会引起DNA的完全凝聚.DNA凝聚产物十分稳定. 关键词： 顺铂 DNA凝聚 单分子操纵 抗癌药     

抗生物素蛋白与DNA相互作用的单分子研究

抗生物素蛋白(avidin)在生物单分子实验中被广泛用于DNA与修饰表面的连接,同时avidin也可作为一种DNA载体用于基因治疗中.本文利用原子力显微镜(AFM)、动态光散射(DLS)、单分子磁镊(MT)技术系统地研究了avidin与DNA之间的相互作用,以及avidin引起DNA凝聚的机理.首先通过AFM对avidin-DNA复合体形貌进行观察,发现不但有avidin导致DNA凝聚的环状形貌,同时也存在avidin自身聚集引起的DNA凝聚现象,通过定量分析,发现其凝聚尺寸越来越小,而当avidin浓度大于2 ng·μL~(-1)时,其凝聚尺寸又突然变大.DLS实验结果也显示了同样的规律,伴随着avidin浓度的升高,DNA的粒径大小从大约170 nm减小到125 nm左右,其电泳迁移率由-2.76(10~(-4)cm~2·V~(-1)·s~(-1))变化到-0.1(10~(-4)cm~2·V~(-1)·~(-1)).此外,通过MT技术的力谱曲线变化,发现avidin导致的DNA凝聚与其他多价离子相比,长度的变化曲线几乎呈线性变化,偶尔存在少而小的阶跃,这种变化趋势与组蛋白的变化曲线更相似.因此可以判断,avidin导致DNA凝聚是由avidin与DNA的静电吸引和avidin自身聚集两种相互作用引起的.     

观察三氯六氨络合钴对DNA凝聚的影响

通过动态光散射技术与原子力显微镜观察了Co(NH3)63+导致的λ-DNA凝聚.用动态光散射测量溶液中Co(NH3)63+作用后的DNA粒径大小,结果表明凝聚后的粒径与样品培育时间和Co(NH3)63+的浓度有关,随着培育时间或者Co(NH3)36+浓度的增加,凝聚后的粒径都会慢慢变小,最后趋于稳定.粒径的分析采用单峰的分布模式处理,表明所有DNA由松散构象向凝聚构象转化的过程基本趋于一致.用原子力显微镜观察Co(NH3)63+导致DNA凝聚的形态变化,并进一步证明了凝聚粒径的单峰分布模式.     

DNA平衡离子凝聚的动态光散射分析

利用动态光散射技术系统地研究了不同化合价的平衡离子氯化钠 (Na⁺)、氯化镁 (Mg²⁺)、三氯六氨络合钴 ([Co(NH₃)₆]³⁺) 和精胺 ([C₁₀N₄H₃₀]⁴⁺) 与DNA之间的相互作用. 实验结果显示, 当缓冲液中只包含Na⁺ 或Mg²⁺, 且浓度c≥ 5 mM时, DNA电泳迁移率之比约为2:1; 当缓冲液单独包含Na⁺或[Co(NH₃)₆]³⁺, 且浓度c≥ 5 mM时, DNA 的电泳迁移率之比约为4.5:1. 而当平衡离子的化合价为4时, 观察到DNA的电泳迁移率由负变正, 意味着发生了电荷反转. 在平衡离子浓度c<5 mM时, 随着离子浓度的增大, 迁移率之比逐渐增大. 对于一价或二价平衡离子情形, 实验结果与Manning的平衡离子凝聚理论的预言相符. 对于三价平衡离子, 实验结果与理论值有明显偏离. 而对于四价离子, 由于发生了DNA电荷逆转, 基于平均场的平衡离子凝聚理论失效. 另外, 通过原子力显微镜观察到当平衡离子的化合价大于等于3 时, DNA分子的构型发生变化. 因此, 自由溶液中的聚电解质的构型和离子关联效应在聚电解质迁移过程中起重要作用. 关键词： 电泳迁移率 平衡离子 动态光散射 DNA     

表面活性剂增敏阻抑反应动力学光度法测定痕量铂

研究了在硫酸介质中 ,在乳化剂 OP存在下 ,痕量铂 ( )阻抑溴酸钾氧化酸性品红褪色的新指示反应 ,建立了表面活性剂增敏阻抑反应动力学光度法测定痕量铂新方法。最大吸收波长为 5 44 nm。铂浓度在 0～ 2 .2 μg· L- 1范围内与ΔA呈线性关系 ,检测限为 0 .0 6 μg· L- 1。方法灵敏度高、选择性好、操作简便 ,用于抗癌药物顺铂及患者血清中铂含量的测定 ,取得较好的结果。     

Co:BaTiO3/Si(100)纳米复合薄膜制备、微结构及其紫外光电子能谱研究

采用脉冲激光气相沉积(PLD)方法,在Si(100)晶面上制备了Co:BaTiO3纳米复合薄膜.采用X射线衍射(XRD)结合透射电镜(TEM)方法研究了两种厚度Co:BaTiO3纳米复合薄膜的晶体结构,当薄膜厚度约为30 nm时,薄膜为单一择优取向;当薄膜厚度约为100 nm时,薄膜呈多晶结构.原子力显微镜(AFM)分析表明,当膜厚为30 nm时,薄膜呈现明显的方形晶粒.采用紫外光电子能谱(UPS)研究了Co的价态和Co:BaTiO3纳米复合薄膜的价带谱.研究表明:当Co浓度很高时其态密度(DOS)与晶体BaTiO3明显不同.此外,嵌埋纳米Co颗粒的BaTiO3薄膜的能带结构可用纳米颗粒的浓度来调制,从而也可对其光学和电学性质进行改性.     

石墨炉原子吸收法测定组织及超滤液中的铂类药物

顺铂是目前临床上最常用也是最有前途的抗癌药物之一,特别是应用在睾丸癌和乳腺癌上。肿瘤组织及肾组织分别是顺铂抗癌作用及毒性作用的靶组织;血浆超滤液中铂则代表了血液中(氵申)蛋白结合的活性铂。为了提高药物治疗疗效和控制药物毒性反应,有必要了解顺铂在体内的处置及合并用药后顺铂在体内处置的变化,因此需要建立生物组织及超滤液中铂浓度的测定方法。     

用液流操纵单个DNA分子形成纳米悬链线图形

首先用液流拉伸单分子DNA,使其吸附在修饰过的云母基片上.然后让二次液流沿着垂直于已拉伸的DNA的方向流过云母片,用原子力显微镜(AFM)观测,可见DNA单分子片段在基片上形成了一些纳米尺度的悬链线.提出一种“S悬桥”模型能定量地解释这一现象.该研究工作揭示,在DNA的单分子操作中,经典的弹性力学理论足以描述和控制DNA分子二维图形的形成 关键词： DNA 单分子DNA操纵 原子力显微镜(AFM) 纳米悬链线     

原子力显微镜观察脂胞囊形貌结构及稳定性

用原子力显微镜(AFM)观察了液晶态脂胞囊形貌结构和稳定性.实验结果显示,对于1,2-二油酸甘油-3-磷脂酰乙醇胺(DOPE)超分子聚集体,在扫描区域内,可观察到一些大小不同球形颗粒;对于1,2-二油酸甘油-3-磷脂酸乙醇胺(DOPE)和1,2-二油酸甘油-3-磷脂酰胆碱(DOPC)混合的超分子聚集体,则不仅观察到类似脂胞囊的球形颗粒,而且也观察到了双层膜结构,其厚度约为5～6 nm.     

溶胶-凝胶软石印法制备Zn2SiO4:Mn图案化薄膜及其发光性能的研究

采用溶胶-凝胶法制备了Zn2SiO4:Mn薄膜并结合毛细管微模板技术实现了薄膜的图案化,利用X射线衍射(XRD),原子力显微镜,光学显微镜,发光光谱等手段对Zn2SiO4:Mn的结晶过程、发光性质进行了研究.XRD结果表明,溶胶-凝胶法合成的样品在800℃时已开始结晶,在1000℃时可得到纯相的Zn2SiO4:Mn,这比传统的固相法的烧结温度低150℃.Zn2SiO4:Mn薄膜的激发光谱在220nm和280nm之间有一个强的吸收峰,峰值位于248nm,发射光谱的最大值位于522nm,为绿光发射.从原子力显微镜照片可知组成薄膜的粒子比较均匀,其平均直径为220nm.我们获得了四种图案化宽度,分别是5,10,20,50μm.光学显微镜的结果表明,图案薄膜烧结后相对于烧结前有10%～20%的收缩.     

A SPECTROSCOPIC STUDY ON THE DNA BINDING BEHAVIOR OF THE ANTICANCER DRUG DACARBAZINE

ABSTRACT

The selective binding of some drug to DNA has been explored in this study to elucidate the structure-function relationship of the anticancer agent. In the case of the binding behavior of the anticancer drug dacarbazine [5-(3,3-dimethy-1-triazenyl)imidazole-4-carboxamide; DTIC], it was found that DNA causes significant decrease of the absorption intensity of DTIC without any shift of the peak position. Besides, nuclear magnetic resonance (NMR) study shows that only slight upfield shift was observed upon addition of DNA. These results as well as our nanostructural study by atomic force microscopy (AFM) illustrate the DNA recognition specificity of DTIC though this anticancer drug interacts with DNA by using non-intercalation mode.     

Synthesis and characterization of doxorubicin hydrochloride drug molecule-intercalated DNA nanostructures

In this paper, we demonstrate the feasibility of constructing DNA nanostructures (i.e. DNA rings and double-crossover (DX) DNA lattices) with appropriate doxorubicin hydrochloride (DOX) concentration and reveal significant characteristics for specific applications, especially in the fields of biophysics, biochemistry and medicine. DOX-intercalated DNA rings and DX DNA lattices are fabricated on a given substrate using the substrate-assisted growth method. For both DNA rings and DX DNA lattices, phase transitions from crystalline to amorphous, observed using atomic force microscopy (AFM) occurred above a certain concentration of DOX (at a critical concentration of DOX, 30 μM of [DOX]_C) at a fixed DNA concentration. Additionally, the coverage percentage of DNA nanostructures on a given substrate is discussed in order to understand the crystal growth mechanism during the course of annealing. Lastly, we address the significance of optical absorption and photoluminescence characteristics for determining the appropriate DOX binding to DNA molecules and the energy transfer between DOX and DNA, respectively. Both measurements provide evidence of DOX doping and [DOX]_C in DNA nanostructures.     

Processes of DNA condensation induced by multivalent cations： Approximate annealing experiments and molecular dynamics simulations

The condensation of DNA induced by spermine is studied by atomic force microscopy （AFM） and molecular dynamics （MD） simulation in this paper. In our experiments, an equivalent amount of multivalent cations is added to the DNA solutions in different numbers of steps, and we find that the process of DNA condensation strongly depends on the speed of adding cations. That is, the slower the spermine cations are added, the slower the DNA aggregates. The MD and steered molecular dynamics （SMD） simulation results agree well with the experimental results, and the simulation data also show that the more steps of adding multivalent cations there are, the more compact the condensed DNA structure will be. This investigation can help us to control DNA condensation and understand the complicated structures of DNA--cation complexes.     

Study on the interactions between anti-cancer drug oxaliplatin and DNA by atomic force microscopy

Oxaliplatin is one of the most important anticancer drugs at present. However, the mechanism of action of oxaliplatin is still controversial. In this study, the interactions between oxaliplatin and a plasmid DNA have been studied so as to reveal the structural basis of its activity. The structural characteristic of pUC19 DNA (2 ng/μL) incubated with 100 μmol/L and 1000 μmol/L of oxaliplatin for the different time on a freshly cleaved highly ordered pyrolytic graphite (HOPG) surface was investigated by atomic force microscopy (AFM). High resolution AFM observation indicated that oxaliplatin can induce pUC19 DNA molecules change from the extended conformation to the entangled structures with many nodes, and finally to the compact particles. The present AFM results provide structural evidence about the interactions between oxaliplatin and circular duplex DNA containing multiple targets.     

熔石英紫外激光初始损伤形态分析

 采取355 nm激光脉冲辐照熔石英样品,利用Nomarski微分干涉差显微镜、原子力显微镜和扫描电子显微镜观测手段对前后表面产生的损伤点进行了观察分析。对前后表面损伤形态做出详细的描述和分类,从理论上对每种损伤类型产生的条件与机理做出推测。实验结果表明：熔石英前表面存在小麻点群损伤和星状裂纹损伤两种损伤形态,横向尺寸分别为0.8～2.5和1.0～5.5 μm;后表面存在小麻点群损伤、壳状剥离损伤和火山口3种损伤形态,损伤横向尺寸分别为0.48～1.33,4～20和12～30 μm。实验证明了1 μm尺度损伤点的产生与再沉积层密切相关。     

小牛胸腺DNA分子Langmuir-Blodgett复合膜的表面增强拉曼光谱研究

本文利用Langmuir-Blodgett(LB)技术将小牛胸腺DNA分子沉积在银基底上,测试并讨论了它的π-A等温曲线,原子力图及表面增强拉曼光谱(SERS)。通过利用LB技术,获得了DNA分子的LB复合膜的高质量的SERS。在DNA分子LB膜的表面增强拉曼光谱中,DNA的核糖和碱基腺嘌呤是吸附活性部位,它们的振动光谱得到增强。DNA的其它碱基和磷酸基团的拉曼光谱强度也明显的得到增强。分析认为DNA分子增强的拉曼光谱主要是由于LB膜的有序结构的贡献,使得SERS效应得到进一步的增强。因此利用LB技术是得到DNA的高质量SERS很好的方法。     

Single Molecule Fluorescence Imaging and Its Application to the Study of DNA Condensation

Single molecule fluorescence imaging incorporated with optical tweezers and a laminar flow cell has been used to monitor the kinetic process of DNA condensation induced by spermidine. It was found that at least two steps were involved in the condensation process of the hydrodynamically-stretched linear DNA; a lag period followed by a rapid collapse of DNA. The lag time increased with the flow speed and the collapse time remained short within the range of the flow speed studied. The effect of salt concentration on the condensation process was examined, and the results suggest that the longer lag time observed in the higher salt buffer probably results from the displacement of bound cations and rearrangement of spermidine on the DNA. The flow-speed dependence of the lag time suggests that a nucleation event at the free end of the DNA, i.e. formation of a loop, may play a vital role in the kinetic process of condensation.     

应用分子梳技术对DNA与组蛋白相互作用的研究

利用分子梳技术对λ DNA和组蛋白的相互作用进行了研究. 通过这种简单有效的方法，我们将λ DNA分子拉伸到26—28 μm，相当于其原长（约162 μm）的16—17倍. 当组蛋白与DNA结合后，DNA分子发生凝聚现象，复合体的拉伸长度明显变短，其峰值分布在10—14 μm之间. DNA 组蛋白复合体的拉伸长度与组蛋白的浓度、与碱基对和荧光染料的比例有显著的关系. 关键词： 分子梳 组蛋白 DNA 荧光显微     

Effect of Torsion on Cisplatin-Induced DNA Condensation

We investigate the effect of torsion on DNA condensation with the covalently closed circular DNA as the torsionconstrained system, using an atomic force microscope. It is found that there are two stages in the DNA condensation process under torsional constraint. At the early stage, the low torsion will accelerate DNA condensation by promoting the formation of micro-loops or intersection structures; while at the later stage, the increasing torsion will slow it down by preventing the crosslinking of cisplatin and DNA since the DNA molecule becomes more rigid. Our results show the important role of torsion in DNA condensation and sheds new light on the mechanism for DNA condensation.