动态损伤演化的空间不连续性实验研究

对冲击加载下高纯铝的损伤演化进行了实验研究. 利用基于白光轴向色差的表面轮廓测试技术测试冲击加载“软回收”的样品截面, 对测试结果进行三维重构和损伤量化计算. 结果表明: 受到孔洞形核效应、尺寸效应和应力松弛作用, 在损伤演化早期, 损伤度随着空间的分布是不连续的, 除最大损伤度以外还存在一个次高峰. 在损伤演化后期, 受到贯穿作用的影响, 损伤度增量随空间的分布也是不连续的, 贯穿区域损伤度迅速增加, 损伤度曲线的次高峰特征消失. 关键词： 高纯铝 冲击波 损伤演化 空间不连续性     

快速简便的杂交检测DNA

Southern杂交作为黄金标准,已广泛运用于DNA的检测上。但是,经典的southern杂交和近年来一些DNA检测方法存在放射性污染,操作繁琐,耗时,对实验仪器设备要求高等问题。本文利用异硫氰酸荧光素(FITC)标记的dUTP合成DNA探针建立了快速检测DNA的液相杂交方法。该方法包括探针制备、液相杂交、电泳分离和信号检测四个步骤,并在此基础上对FITC-双链和FITC-单链探针的杂交效果作了比较。结果显示,使用FITC标记的两种探针都能取得良好的实验结果,但单链探针较双链的检测灵敏度高;双链DNA探针可以检测出0.8 μg(3.64×10-13 mol)的质粒,而单链DNA探针可以检测出0.38 μg(1.82×10-13 mol)的质粒DNA,在检出效率上是前者的2.1倍。整个检测过程操作简便,可在3 h内完成,可较好地解决了其他DNA检测方法存在的费时费力的问题。     

滑移爆轰作用下内爆柱形钢壳层裂的数值模拟

 Иванов等发表了滑移爆轰作用下内爆柱形钢壳层裂实验的回收试件测量结果，也给出了相应的数值模拟结果，但两者的差别较大。本文利用损伤度函数方法，对上述实验做了数值研究，所得到的回收试件尺寸数值结果与Иванов实验结果十分相符。这说明，损伤度函数方法对研究动态断裂问题有一定的普适性。本文还对Иванов实验的柱形钢壳内爆运动过程进行了数值模拟，讨论了临界损伤度α_c取值对断裂面位置、钢层运动轨迹及钢壳运动速度历史的影响，指出了在分析界面不稳定性问题时要注意α_c取值的影响。     

材料层裂研究的主要进展

层裂是一种重要的动态损伤破坏现象,由物质界面的反射稀疏波相互作用引起,其细观尺度上的物理机制是微损伤(即微孔洞和微裂纹)的成核、生长和汇合。围绕美国物理学会George E. Duvall冲击压缩科学奖的3位获奖者Grady、Curran和Johnson的相关工作,概述层裂现象的一些主要研究进展,简要介绍层裂现象的研究历史,以期更深刻地理解那些著名的层裂物理模型和实验技术。此外,报道了最近取得的最新研究成果,阐述了冻结不同损伤水平状态的双层靶层裂实验技术与Hopkinson压杆共通的工作原理。针对微损伤成核和生长断裂破碎模型NAG/FRAG在数学上的不一致性和在物理上的不完备性,指出对于延性材料的层裂过程,只要微孔洞成核的累积数目密度满足尺寸的指数分布、微孔洞半径的生长速度与半径呈线性关系,就能够得到解析形式的损伤度演化方程,该修正模型MNAG在数学上是一致的,在物理上是完备的;对于白以龙等建立的欧拉形式的微损伤数目守恒方程,指出计算损伤度不必显式求解该方程,损伤度的表达式一般通过拉格朗日形式的微损伤数目守恒方程获得;针对损伤度函数模型或封加坡模型,以更加简洁的方法进行了推导。     

共振瑞利散射法测定核酸的研究进展

DNA在许多生命现象和生命过程中起着决定性的作用,因此寻求快速检测DNA的方法具有重要的社会意义。本文对共振瑞利散射法分析检测DNA的研究进展进行了综述。     

基于InP@ZnS QDs/Dured纳米荧光探针的DNA检测

利用巯基丙酸包覆的In P@Zn S量子点(QDs)与Dured构建了一种检测DNA的荧光探针。在该探针中,以环境友好型带负电的In P@Zn S量子点为荧光团,与带正电的Dured通过静电结合,构建了In P@Zn S QDs/Dured纳米荧光探针。通过荧光共振能量转移(FRET)机理,量子点荧光被猝灭;当DNA存在时,Dured与DNA的特异性结合使Dured从In P@Zn S QDs表面脱附,FRET过程被打断,In P@Zn S QDs荧光恢复,以荧光"关-开"方式检测DNA。该探针检测DNA的线性范围为2.0~275.0 ng·L-1,检测限为1.0 ng·L-1,并可用于模拟生物生理条件下的DNA检测。     

强激光辐照下纳米铜动态拉伸型断裂的数值模拟

 基于强激光辐照加载下纳米铜的层裂实验,采用含逾渗软化函数的损伤度函数模型对实验结果进行了数值模拟研究。强激光加载条件被简化为高斯分布脉冲压力施加在镍合金基体的前表面上。数值计算结果显示：损伤演化明显地改变了试样中波传播特性,无论是对微损伤还是完全层裂的试样,计算都较好地再现了实测自由面速度剖面,表明了含逾渗软化函数的损伤度函数模型在强激光加载条件下纳米铜层裂问题分析中具有较好适用性。     

科技动态

量子点DNA传感器快速、准确地检测DNA在疾病诊断中是至关重要的,传统方法非常繁琐、耗时.美国科学家基于荧光共振低能传输发明了超敏传感器,能检测低浓度、无须分离的DNA.他们用量子点接到DNA探针上捕捉目标,通过比较荧光共振低能传输信号来确定DNA,量子点还起着检测浓度的作用.此方法已经在临床应用中成功测出了一些卵巢肿瘤点突变的类型.(Nature Materials2005.10)金属软化的机制通常在金属中添加杂质使其硬化和增加强度,比如在铁中加碳使钢变硬.但对有些金属来说,杂质却会使其软化,钼就是这样的金属,这种金属材料有可能是高温应用…     

Goldview标记的DNA荧光毛细生物传感器的研究

对Goldview(GV)作为荧光标记物的DNA荧光毛细生物传感器进行了研究。以荧光毛细分析法(fluorescence capillary analysis, FCA)为基础, 在毛细管内壁通过Poly-l-lysine将20-mer-ssDNA探针固定, 制成DNA荧光毛细生物传感器(DNA fluorescence capillary biosensor, DNA-FCB),DNA-FCB与互补靶DNA杂交,通过GV染色后,检测杂交产物的荧光强度,实现对靶DNA的定性和定量分析。样品用量12 μL, 靶DNA的浓度在0.4～4 μmol·L-1(2.4～24 mg·L-1)范围内和荧光强度有良好的线性关系(y=65.911x+3.994 4,r=0.998 9);RSD<3.5%,检出限0.39 μmol·L-1(2.2 mg·L-1),能达到定量检测靶DNA的目的。用DNA-FCB测定靶DNA操作简便, 试样、试剂用量少,测定成本极低, 能大大减少环境污染。     

快中子辐照对枯草芽孢杆菌DNA损伤研究

采用脉冲场凝胶电泳技术检测并定量分析了CFBR-Ⅱ快中子脉冲堆产生的快中子在不同剂量和剂量率条件下, 对枯草芽孢杆菌黑色变种(ATCC 9372)DNA双链断裂的诱导. 通过DNA释放百分比PR值、DNA断裂水平L值、断裂DNA平均分子量和DNA片段分布等指标的分析, 结果表明：在不同的辐射条件下, DNA片段均明显分布于两个区域, 表明枯草芽孢杆菌黑色变种DNA分子上可能存在对中子辐射较为敏感的位点; 并且随着中子辐射剂量和剂量率的变化, DNA~释放百分比PR值、DNA断裂水平L值和各片段区双链断裂的含量也会发生一定规律性的变化.     

放疗污染电子对皮肤细胞损伤的蒙特卡罗模拟研究

采用Geant4-DNA低能物理模型研究了污染电子在细胞DNA水平上的物理作用和能量沉积。利用密度聚类算法分析了损伤产额分布;并结合皮肤细胞辐射敏感性参数和临床表征剂量,探讨了低能电子对皮肤细胞的损伤特征。模拟发现,产生的DSB中约20%是cDSB;DSB产额是SSB的约4%;损伤聚类包含的SSB一般3个,20 keV和100 keV电子也可造成5个SSB的聚类损伤;晚反应、高α值的组织更应注意防护低能电子辐射;由于LQ模型中剂量平方项的影响,cDSB损伤致死系数ε随入射电子数目的增加而增大。当105个电子入射时,ε的数值可较单个电子增大3%～15%。可通过调节直接电离损伤概率弥补间接损伤产额,研究细胞辐照损伤的内在机理。本工作建立的低能电子对细胞DNA的损伤模型及结果,可用于评价放疗中低能污染电子对皮肤细胞的损伤效应。     

Mdm2生成速率调控的p53-Mdm2振子的全局动力学和稳定性

肿瘤抑制蛋白p53的动力学在一定程度上可以决定DNA损伤后的细胞命运.p53的动力学行为与p53信号通路中p53-Mdm2振子模块密切相关.然而,p53的负调控子Mdm2的生成速率的增加使其在一些癌细胞中过表达.因此探讨Mdm2生成速率对p53动力学的影响有重要意义.同时,PDCD5作为p53的激活子也调控p53的表达.因此,本文针对PDCD5调控的p53-Mdm2振子模型,通过分岔分析获得了Mdm2生成速率所调控的p53的单稳态、振荡以及单稳态与振荡共存的动力学行为,且稳定性通过能量面进行了分析.此外,噪声强度对p53动力学的稳定性有重要的影响.因此,针对p53的振荡行为,探讨了噪声强度对势垒高度和周期的影响.本文所获得的结果对理解DNA损伤后的p53信号通路调控起到一定的指导作用.     

Evaluation of DNA damage and cytotoxicity of polyurethane-based nano- and microparticles as promising biomaterials for drug delivery systems

The in vitro cytotoxicity and DNA damage evaluation of biodegradable polyurethane-based micro- and nanoparticles were carried out on animal fibroblasts. For cytotoxicity measurement and primary DNA damage evaluation, MTT and Comet assays were used, respectively. Different formulations were tested to evaluate the influence of chemical composition and physicochemical characteristics of particles on cell toxicity. No inhibition of cells growth surrounding the polyurethane particles was observed. On the other hand, a decrease of cell viability was verified when the anionic surfactant sodium dodecyl sulfate (SDS) was used as droplets stabilizer of monomeric phase. Polyurethane nanoparticles stabilized with Tween 80 and Pluronic F68 caused minor cytotoxic effects. These results indicated that the surface charge plays an important role on cytotoxicity. Particles synthesized from MDI displayed a higher cytotoxicity than those synthesized from IPDI. Size and physicochemical properties of the particles may explain the higher degree of DNA damage produced by two tested formulations. In this way, a rational choice of particles’ constituents based on their cytotoxicity and genotoxicity could be very useful for conceiving biomaterials to be used as drug delivering systems.     

Simultaneous in situ profiling of DNA lesion endpoints based on image cytometry and a single cell database approach

Analyzing the integrity of DNA is one of the most frequent used endpoints for risk assessment of chemical and physical agents. In the framework of a radiobiological space experiment, this work aimed at having (1) a histochemical tool for the in situ assessment of DNA damage in as long as 20 days old fixed cell cultures, (2) a comprehensive tool for the quantification of different types of DNA lesions, and (3) a methodology of sampling thousands of nuclei based on confocal microscopy, automated stage scanning and digital image processing. For this purpose several fixatives and permeabilization techniques were tested together with the combinatorial use of terminal dUTP transferase-mediated nick end-labeling (TUNEL) and the DNA polymerase I mediated in situ nick translation. These biochemical tools are useful for scoring DNA single and double breaks, and oxidative lesions. Ltk(-) cells were exposed either to hydrogen peroxide or heavy ion beam irradiation. Combination of paraformaldehyde fixation, sodium citrate permeabilization and heat gave the best staining results. A three-channel fluorescence methodology was established including a DNA counter stain for nucleus identification and normalization of DNA content. Communication between confocal imaging software, image analysis software and a relational database proved to be pivotal for a semi-automated high-end single cell analysis and storage of images. In this way, DNA damage data per nucleus can be traced back to the original image. As much as 2500 cells could be analyzed in situ within a day and correlations drawn between different DNA lesion endpoints.     

VPRBP 蛋白与Abl 激酶诱发、抑制前列腺癌的 一种物理机制

在本文基于Hill动力学与Michaelis-Menten方程,建立理论模型研究VPRBP蛋白与Abl激酶诱发、抑制前列腺癌的一种物理机制.研究发现,DNA损伤使得ATM(共济失调毛细血管扩张症突变)很快激活,并激活上调p53蛋白表达,DNA损伤的后续破坏会在很大程度上通过p53表达上调而被抑制. VPRBP通过上调MDM2蛋白的激活水平,使得p53表达水平异常,进而无法正常抑制前列腺癌的发生发展.通过考察Abl在前列腺癌进程中的作用发现,Abl使得AKT的表达水平下调,由于Abl对AKT的抑制作用,致使在AKT信号通路中MDM2表达水平受到抑制,进而稳定p53表达.由此表明了,过少的Abl对AKT的抑制程度减弱,不仅使得细胞代谢出现紊乱,而且还会促使p53正常的周期表达水平异常,对DNA损伤诱发的肿瘤抑制性减弱,进而促进前列腺癌的发生发展.基于本文模型,可以预测VPRBP与Abl作为诱发、抑制前列腺癌的调节剂对现有和潜在的抗癌治疗较为敏感. VPRBP与Abl在诱发、抑制前列腺癌过程中的时滞效应,导致信号通路中p53与PTEN蓄积量增多、AKT蓄积量减少,以及Plk1周期振荡相位转移...     

Effects of therapeutic ultrasound on the nucleus and genomic DNA

In recent years, data have been accumulating on the ability of ultrasound to affect at a distance inside the cell. Previous conceptions about therapeutic ultrasound were mainly based on compromising membrane permeability and triggering some biochemical reactions. However, it was shown that ultrasound can access deep to the nuclear territory resulting in enhanced macromolecular localization as well as alterations in gene and protein expression. Recently, we have reported on the occurrence of DNA double-strand breaks in different human cell lines exposed to ultrasound in vitro with some insight into the subsequent DNA damage response and repair pathways. The impact of these observed effects again sways between extremes. It could be advantageous if employed in gene therapy, wound and bone fracture-accelerated healing to promote cellular proliferation, or in cancer eradication if the DNA lesions would culminate in cell death. However, it could be a worrying sign if they were penultimate to further cellular adaptations to stresses and thus shaking the safety of ultrasound application in diagnosis and therapy. In this review, an overview of the rationale of therapeutic ultrasound and the salient knowledge on ultrasound-induced effects on the nucleus and genomic DNA will be presented. The implications of the findings will be discussed hopefully to provide guidance to future ultrasound research.     

Raman Spectroscopy–Based Multivariate Statistical Analysis Reveals the Molecular Mechanism of K562 Cell Apoptosis Induced by Adriamycin

Based on the combination of Raman spectroscopy with principal component analysis and hierarchical cluster analysis, the molecular mechanism of K562 cell apoptosis induced by Adriamycin in physiological conditions is presented. The obtained results reveal that DNA of K562 cells treated with Adriamycin is lowered greatly, indicating that the damage of the DNA of K562 cells is indeed the main molecular mechanism of K562 cell apoptosis induced by Adriamycin. Specially, by combining principal component analysis and hierarchical cluster analysis, the statistical difference between Raman spectra of different cell types can be revealed effectively. Importantly, this kind of Raman spectroscopy–based multivariate statistical analysis will supply a useful tool for the molecular mechanism detection of cell behavior in physiological conditions.     

Radiation damage to DNA: the importance of track structure

A wide variety of biological effects are induced by ionizing radiation, from cell death to mutations and carcinogenesis. The biological effectiveness is found to vary not only with the absorbed dose but also with the type of radiation and its energy, i.e., with the nature of radiation tracks. An overview is presented of some of the biological experiments using different qualities of radiation, which when compared with Monte Carlo track structure studies, have highlighted the importance of the localized spatial properties of stochastic energy deposition on the nanometer scale at or near DNA. The track structure leads to clustering of damage which may include DNA breaks, base damage etc., the complexity of the cluster and therefore its biological repairability varying with radiation type.

The ability of individual tracks to produce clustered damage, and the subsequent biological response are important in the assessment of the risk associated with low-level human exposure. Recent experiments have also shown that biological response to radiation is not always restricted to the ‘hit’ cell but can sometimes be induced in ‘un-hit’ cells near by.     

模拟微重力效应对辐射致细胞DNA损伤修复效应的影响

在地面模拟微重力的情况下, 应用碱性单细胞凝胶电泳（SCGE）技术对80 MeV/u Ne离子辐射诱发人血淋巴细胞DNA损伤修复效应进行了研究。 在不同时刻对相同剂量辐照后的淋巴细胞经单细胞电泳处理后显示, 在模拟微重力下孵育的彗星尾更长, 彗星头面积更小。 这表明, 相对地面环境而言, 模拟微重力环境对淋巴细胞的DNA损伤修复有一定的抑制作用。 Effect of the modeled microgravity (MMG) on heavy ion induced lymphocytes DNA repair by using single cell gel electrophoresis (SCGE) has been studied. The results showed that residual DNA damage induced by Ne ions irradiation increased more in cultures incubated in MMG than in 1 g, which indicated that MMG incubation after Ne ions irradiation reduce the DNA damage repair capacity.     

基于DNA损伤的蛋白调控网络研究

细胞生长的每个阶段都离不开蛋白质相互作用.研究细胞周期的功能、调控机理及参与调控的蛋白质之间的关系对生物工程等领域有重大的应用价值.本文通过研究电离辐射下生物体细胞的DNA损伤后,细胞内以p53为核心的扩展蛋白调控网络的功能、原理及其自修复机理,在现有蛋白网络基础上引入更多蛋白网络调控因子来建立蛋白调控网络,仿真模拟更为全面的细胞周期进程;并且从复杂网络图论和细胞周期调控两个方面分析扩展PMP调控网络的抗扰能力及自修复机理,结果表明:1)蛋白网络在对抗环境中出现的小扰动时具有较强的稳定性.但在面对蓄意攻击时网络的稳定性较差.2)受损的DNA能否被修复取决于p53蛋白的动力学行为,即低损伤与中损伤情况下,p53可诱导细胞周期进程阻滞来完成细胞的自修复;而当高损伤或过损伤时,p53蛋白浓度表现为周期振荡行为并诱导细胞凋亡.