Mechanism of oxidative damage to DNA by Fe-loaded MCM-41 irradiated with visible light

The mechanism of oxidative damage to deoxyribonucleic acid (DNA) by iron-containing mesoporous molecular sieves (MCM-41) irradiated with visible light was elucidated. Fe-loaded MCM-41 (Fe/MCM-41) was used as a photocatalyst and the damage to calf thymus DNA caused by hydrogen peroxide (H2O2) was studied. The damage and extent of oxidation of DNA were measured by high-performance liquid chromatography (HPLC) and intermediate products were detected by HPLC/electrospray ionization tandem mass spectrometry. Electron spin resonance was used to detect changes in reactive oxygen species and peroxidase catalytic spectrophotometry was used to determine the concentration of H2O2. The results indicated that Fe/MCM-41 efficiently activated H2O2 in solution at pH 4.0-8.0 under irradiation with visible light. The photocatalytic system degraded DNA most effectively at pH 5.0-6.0 but also operated at pH 8.0. At pH 4.2, the degree of DNA damage reached 25.65% after 5 h and the kinetic constant was 5.89×10 2 min 1. Damage to DNA was predominantly caused by hydroxyl radicals generated in the system. The mechanism of DNA damage is of potential concern to human health because it can occur in neutral solutions irradiated by visible light.     

Advances in the study of helminth mitochondrial genomes and their associated applications

Helminths, including flatworms and roundworms, are abundant organisms that have a variety of life histories. Of these, the genera Schistosoma, Echinococcus, Trichinella are notable parasites of veterinary and medical importance, and cause substantial socio- economic losses throughout China and the rest of the world. Genetic markers in the mitochondrial (mt) genome have proven use- ful for systematic, ecological, evolutionary and population studies, and the growth of mt genomic research has increased in the last two decades. Technological improvements, such as the long-polymerase chain reaction method and high-throughput se- quencing have allowed minute amounts of DNA from single worms, biopsy samples or microscopic organisms to be used for whole mt genome characterization. To facilitate the retrieval, annotation and analyses of mitochondrial features, multiple data- bases and specific software have also been designed and established. This review focuses on current progress, applications and perspectives regarding helminth mt genomics. To date, the complete mt genomes for 93 species of helminths have been sequenced and analyzed. Analyses of the mt genes, including gene content, arrangement, composition and variation have revealed unique features among the helminths when compared with other metazoans. This provides important data concerning their functional and comparative mitochondrial genomics, molecular taxonomy and characterization, population genetics and systematics, and evolu- tionary history. Moreover, mt genome data for parasitic helminths are important for diagnosis, epidemiology and ecology of in- fections. Mitochondrial genome data offer a rich source of markers for the systematics and population genetics of socioeconomi- cally important parasitic helminths of humans and other animals.     

新型咪唑并邻菲罗啉衍生物对人端粒G-四链体相对于双螺旋DNA的选择性识别

G-四链体DNA是抗肿瘤药物研究开发的重要靶点,选择性识别并稳定G-四链体DNA的化合物是潜在的抗肿瘤药物.文章利用紫外可见吸收滴定,荧光滴定,CD光谱以及荧光共振能量转移熔点实验(FRET-melring)研究了三个基于邻菲罗啉的新型衍生物(A,B和C)与人端粒G-四链体DNA的相互作用.结果表明三个化合物通过末端堆积方式与G四链体DNA相互作用,结合常数(K)约为106 mol-1·L.当浓度为3 μmol·L-1时,化合物A,B和C分别使G四链体DNA熔点温度增加(△Tm)16.2,10.5和10.9℃.而且在10倍过量双螺旋DNA存在下均能选择性识别并稳定G-四链体结构.     

立对气候骤变，野牛有高招

加拿大西北部的育空地区（Yukon）分布着大面积的永久；东土层，其中埋藏的冰河时代动物的骨骼是研究古代生物DNA的重要材料。距今3万年前，地球正处末次冰期．育空地区气候变动频繁，     

生物电路的前景

●多年来，科学家一直在改造DNA片段。创造出了多种基因工程植物或动物．为人们提供了新的掌握生命的机会。“搭建生命积木的合成生物学”一文作者、波士顿大学生物医学专家詹姆斯·柯林斯（James Collins）。长期致力于改造生命体。并赋予其新的功能。就这一领域的未来前景，《自然》杂志专程采访了他。     

“垃圾DNA”都是宝

科学家对＂垃圾DNA＂研究得愈深入,就愈发现它们其实都是宝,生物少不了。这让我们再次领略了＂自然界没有废物＂这一颠扑不破的道理。前文已经说过,＂垃圾DNA＂是20世纪70年代根据通行的生物进化理论所做出的一个科学预测。按照这样的预测,人们相信非编码DNA序列没有任何功能,是＂自私＂的寄生物,不仅对生物体无用,而且可能有害。这样的观念统治了学界长达20年之久,直到20世纪90年代,以法尔和梅洛为代表的分子生物学家揭示了部分＂垃圾DNA＂的神奇功效后,人们才看到了这个巨大宝藏的冰山一角。     

制造个性化生物病毒人工合成“私生子”总统DNA保卫战

在不远的将来，根据总统的DNA就能创造出针对个人的生物武器，轻易除掉一个国家的领导人，而且不留任何痕迹。2015年的某日，哈佛大学政府专业大二学生萨曼莎收到了一份快递包襄，她以为这是刚从网上订购的新合成迷幻药，于是拿出一枚药片塞入了自己的鼻孔。当天晚上，萨曼莎就出现了轻微流感症状，由于感染了药片上的病毒，她的体内开始复制和释放数以亿计的病毒粒子，这些病毒粒子在大学校园中以惊人的速度迅速扩散，不过，感染病毒的人除了轻微发烧和打喷嚏这些感冒症状外，并不会有任何生命危险。     

设计及自组装六边形网格状DNA二维阵列

根据Watson-Crick DNA碱基互补配对原则,设计了不同黏性末端DNA序列,以两种三点星状为模块(three-point-star motif),运用DNA自组装技术,成功制备了六边形网格状DNA二维阵列.研究不同单链DNA的摩尔比例对三点星状模块结构组装的影响,以及不同起始退火温度对二维阵列自组装的影响,用凝胶电泳及原子力显微镜(AFM)对结构进行了表征.结果表明,当构成三点星状模块的3条单链摩尔比例为1:3:3时得到的模块结构更稳定,从50℃开始退火时得到的二维阵列更完整.自组装得到的二维阵列厚度约2nm,六边形边长约20nm.本研究为进一步探究三点星模块组装二维阵列的机理提供了新的思路.     

火球菌复制蛋白A的表达纯化和活性研究

将火球菌(Pyrococcus furiosus)的3个复制蛋白A相关基因pfuRPA41(PF2020),pfuRPA32(PF2018),pfuRPA14(PF2019)克隆到pDEST17质粒,并在E.coli Rosetta(DE3)表达菌株中成功表达,最终通过固定化镍离子亲和层析分别得到纯度较高的三个复制蛋白A相关蛋白,对它们的单链DNA结合活性进行了详细测试.其中单独的pfuRPA41能结合单链DNA,而单独的pfuRPA32以及pfuRPA14不能结合单链DNA;然而pfuRPA32能够促进pfuRPA41的单链DNA结合能力.同时单链DNA长度对pfuRPA41结合单链DNA的能力有显著影响;在一定长度范围内,pfuRPA41结合单链DNA能力与单链DNA长度成正比.     

美国推出纳米新技术

据《每日科学》近日报道，由美国华盛顿大学物理学家领导的研究小组设计了一种新技术，可在纳米孔内对DNA进行快速测序，而且价格比较便宜。新方法可为癌症、糖尿病或某些成瘾患者量身绘制个性化基因测序蓝图，提供更加高效的个体医疗。