基于氯化血红素对G-四链体/盐酸小檗碱复合物的竞争作用构建DNA逻辑门

利用荧光法研究了盐酸小檗碱对不同DNA构象的识别能力,研究发现盐酸小檗碱与G-四链体有较强的相互作用,形成的复合物可以在530nm处发出较强的荧光.当一定量的氯化血红素加入到G-四链体/盐酸小檗碱复合物中时,氯化血红素与G-四链体结合力更强,从而把盐酸小檗碱置换出来,荧光发生猝灭.利用这种荧光信号的开关响应,成功构建了INHIBIT逻辑门.     

钌配合物[Ru(MeIm)4(4mopip]2+急定G-四链体对抑制肺癌细胞生长机制的研究

制备一种新型钌配合物[Ru(MeI m)_4(4mopip)]~(2+)(RuM e Mo),运用元素分析(C、H、N)、电喷雾电离质谱(ESI-MS)、核磁共振谱(~1H NMR)对Ru Me Mo进行了结构表征。紫外光谱、热变性试验和圆二色光谱研究RuM e Mo与F21T的分子作用机制,发现其能诱导线性G-四链体DNA形成混合型结构并能有效稳定G-四链体。MTT法评估RuM e Mo对癌细胞的抑制作用及其对正常细胞的毒性,发现其对肺癌细胞(A549)表现出高选择的抑制作用,而对正常人类肺原胚细胞(CDDP)则表现出较低的细胞毒性。本研究结果表明,RuM e Mo因其稳定G-四链体DNA的能力,从而有被运用于肺癌治疗的潜质。     

钌配合物[Ru（MeIm）4（dpq）]2+与G-四链体DNA的相互作用及抗肿瘤活性

目的研究钌配合物[Ru(Me Im)4(dpq)]与端粒DNA:HTG21(AG3(T2AG3)3)的相互作用,并初步探讨其体外抗肿瘤活性。方法应用紫外-可见吸收光谱、圆二色谱、荧光共振能量转移和显色反应实验研究钌配合物与HTG21的相互作用;采用MTT法检测其对肿瘤细胞株A549、He La、Hep G2细胞增殖的影响,用流式细胞术、Hoechst33342荧光染色检测细胞周期及细胞凋亡的变化。结果钌配合物与G-四链体之间存在较强亲和力,可诱导人体端粒HTG21形成G-四链体并稳定该结构,阻滞A549细胞在S期并诱导肿瘤细胞凋亡。结论钌配合物可能通过稳定端粒DNA发挥抗肿瘤活性,端粒DNA可能是钌配合物抗肿瘤作用的靶点。     

环介导等温扩增技术的研究进展

环介导等温扩增(loop-mediated isothermal amplification,LAMP)技术是利用2对特殊设计的引物和一种具有链置换活性的DNA聚合酶,在恒温条件下特异、高效地扩增DNA的新技术,扩增产物为一系列反向重复的靶序列构成的茎环结构和多环花椰菜样结构的DNA片段混合物,电泳图谱呈阶梯式带状分布,反应伴有白色的副产物焦磷酸镁沉淀产生,可通过肉眼定性判断反应结果.LAMP技术已在核酸的科学研究、疾病诊断和动物胚胎性别的鉴定等领域得到了广泛的应用.从LAMP技术的原理、引物组成及反应过程、技术特点、方法延伸和应用等方面对其进行了概述,以期为同类研究提供参考.     

端粒及端粒酶活性检测方法研究进展

缩短的端粒是细胞老化的信号,检测端粒酶活性可间接测定细胞状态。端粒酶通过p66Shc信号通路对胚胎发育永久性停滞产生影响。本文对哺乳动物卵母细胞或胚胎永久性停育与端粒酶活性水平变化的关系、端粒酶活性检测方法研究进展及各种方法的优缺点进行综述,包括端粒重复扩增法(TRAP)、TRAP-酶联免疫吸附(ELISA)法、TRAP-银染法、杂交链式信号放大反应结合磁分离技术法和亚甲蓝MB作为G-四联体结合探针法、H-GNs比色法、依赖无标记分子信标的级联放大DNA机制法。     

适配体的研究进程与思考

适配体（aptamer）是指利用指数富集的配体系统进化（SELEX）技术，从人工合成的寡核苷酸文库中筛选获得的能够与靶分子特异结合的短单链DNA和RNA分子。筛选得到的适配体可以与DNA，RNA，蛋白质或其它靶分子结合，影响这些靶分子的性质，从而起到改变与靶分子相关的生物学功能的效果。而且研究发现，适配体在与靶分子相互作用时，不仅序列，它们所形成的三维结构也尤其重要。同时，适配体在生物医药研究方面显示出广阔的应用前景。介绍了适配体的发展历程，以及一些典型适配体的生物学功效。提出了RNA适配体三维结构在与靶分子进行相互作用时可能发挥重要作用，以期为RNA适配体的筛选提供理论思考。     

新型DNA分子标记技术及在遗传与育种研究中的应用

对近年来发展的几种新型DNA分子标记技术RMAPD、SRAP、TRAP、CAPS、SCAR与RSAP的原理、特点及其应用进行了综述.这些新型DNA分子标记技术与传统的RAPD、AFLP标记相比,具有重复性高、操作简便等特点,应用前景广泛.     

用生物合成的长链开环探针进行SNP分型

由于化学合成长链开环探针面临许多困难,因此需要开发一种长链开环探针的生物合成方法.该研究利用生物合成的146 bp长链开环探针进行单核苷酸多态性(SNP)分型,以验证长链开环探针生物合成的可行性.结果表明:长链开环探针能够特异地与目的DNA结合,完美配对的长链开环探针能够被DNA连接酶连接,形成环状单链DNA分子,不能...     

1G-175A侧边齿轮箱体的有限元静动态分析及其模态试验

运用有限元方法对1G-175A旋耕机的主要部件之一的侧边齿轮箱体进行了静态和动态的强度与刚度计算,并对其动特性用结构模态试验方法进行了分析,验证了所建立的有限元模型的合理性。     

组蛋白八聚体的装配及荧光标记检测体外组装核小体的效率

基于影响核小体定位的DNA序列TA 10-bp周期性和R5Y5序列模体,设计6条对组蛋白亲和性不同的DNA序列,将其克隆到重组质粒中,分别命名为CS1~CS6。通过PCR扩增的方法,在引物上标记Cy3荧光信号分子,获得大量标有Cy3的目的序列;同时,从大肠杆菌中表达纯化了H2A、H2B、H3、H4共4种组蛋白,经复性装配成组蛋白八聚体,利用盐透析法将目的 DNA序列与组蛋白八聚体组装成核小体结构;经荧光信号检测,分析6条目的序列形成核小体的能力。结果发现,CS2、CS3形成核小体的能力较强,该结果与Trifonov EN提出的核小体在该模体上的精确定位基本吻合,该试验方法的建立对核小体结构及相关表观遗传学领域的研究具有一定的意义。     

The leucine zipper: a hypothetical structure common to a new class of DNA binding proteins

A 30-amino-acid segment of C/EBP, a newly discovered enhancer binding protein, shares notable sequence similarity with a segment of the cellular Myc transforming protein. Display of these respective amino acid sequences on an idealized alpha helix revealed a periodic repetition of leucine residues at every seventh position over a distance covering eight helical turns. The periodic array of at least four leucines was also noted in the sequences of the Fos and Jun transforming proteins, as well as that of the yeast gene regulatory protein, GCN4. The polypeptide segments containing these periodic arrays of leucine residues are proposed to exist in an alpha-helical conformation, and the leucine side chains extending from one alpha helix interdigitate with those displayed from a similar alpha helix of a second polypeptide, facilitating dimerization. This hypothetical structure is referred to as the "leucine zipper," and it may represent a characteristic property of a new category of DNA binding proteins.     

苏云金芽孢杆菌杀虫晶体蛋白结构和功能研究进展

对目前解析的苏云金芽孢杆菌杀虫晶体蛋白的三维结构进行了比较分析。它们都有类似的结构,有三个结构域,结构域Ⅰ是由7个α螺旋以α5螺旋为中心形成的α螺旋束;结构域Ⅱ是由三个反平行β折叠形成的β棱柱;结构域Ⅲ是一个β"三明治"结构。对这三个结构域的Loop及氨基酸残基与杀虫活性的关系、与通道形成相关的杀虫作用机制的研究进展进行了综述。     

Helix signals in proteins

The alpha helix, first proposed by Pauling and co-workers, is a hallmark of protein structure, and much effort has been directed toward understanding which sequences can form helices. The helix hypothesis, introduced here, provides a tentative answer to this question. The hypothesis states that a necessary condition for helix formation is the presence of residues flanking the helix termini whose side chains can form hydrogen bonds with the initial four-helix greater than N-H groups and final four-helix greater than C-O groups; these eight groups would otherwise lack intrahelical partners. This simple hypothesis implies the existence of a stereochemical code in which certain sequences have the hydrogen-bonding capacity to function as helix boundaries and thereby enable the helix to form autonomously. The three-dimensional structure of a protein is a consequence of the genetic code, but the rules relating sequence to structure are still unknown. The ensuing analysis supports the idea that a stereochemical code for the alpha helix resides in its boundary residues.     

Transmembrane protein structure: spin labeling of bacteriorhodopsin mutants

Transmembrane proteins serve important biological functions, yet precise information on their secondary and tertiary structure is very limited. The boundaries and structures of membrane-embedded domains in integral membrane proteins can be determined by a method based on a combination of site-specific mutagenesis and nitroxide spin labeling. The application to one polypeptide segment in bacteriorhodopsin, a transmembrane chromoprotein that functions as a light-driven proton pump is described. Single cysteine residues were introduced at 18 consecutive positions (residues 125 to 142). Each mutant was reacted with a specific spin label and reconstituted into vesicles that were shown to be functional. The relative collision frequency of each spin label with freely diffusing oxygen and membrane-impermeant chromium oxalate was estimated with power saturation EPR (electron paramagnetic resonance) spectroscopy. The results indicate that residues 129 to 131 form a short water-exposed loop, while residues 132 to 142 are membrane-embedded. The oxygen accessibility for positions 131 to 138 varies with a periodicity of 3.6 residues, thereby providing a striking demonstration of an alpha helix. The orientation of this helical segment with respect to the remainder of the protein was determined.     

Molecular characteristics and structure–activity relationships of food-derived bioactive peptides

Peptides are functional active fragments of proteins which can provide nutrients needed for human growth and development, and they also have unique physiological activity characteristics relative to proteins. Bioactive peptides contain a great deal of development potential. More specifically, food-derived bioactive peptides have the advantages of a wide variety of sources, unique structures, high efficiency and safety, so they have broad development prospects. This review provides an overview of the current advances regarding the preparation, functional characteristics, and structure–activity relationships of food-derived bioactive peptides. Moreover, the prospects for the future development and application of food-derived bioactive peptides are discussed. This review may provide a better understanding of foodderived bioactive peptides, and some constructive inspirations for further research and applications in the food industry.     

Cyclobutane-type pyrimidine dimers in polynucleotides

The formation of cyclobutane-type dimers between adjacent pyrimidine residues in model polynucleotides or DNA may be represented by the general scheme See pdf 379.pdf Whereas the formation of all other known photoproducts follows the irreversible path See pdf 379.pdf Thus dimers are distinguished from other photoproducts by the fact that they can be monomerized, as well as formed, by ultraviolet irradiation. At large incident fluxes of photons the steady-state value of dimers depends on wavelength and pH, as well as on other characteristics of the surrounding medium. The number of dimers in an irradiated polynucleotide may be decreased by purely photochemical means, whereas this is not true for most other photoproducts, for which continued irradiation, irrespective of wavelength, always results in the formation of more photoproduct (37). The wavelength dependence of the steady-state for dimers is also reflected in the biological activity of irradiated transforming DNA. This experiment and the fact that photoreactivating enzyme plus visible light monomerizes dimers (and has not been demonstrated to have any effect on other photoproducts) are the strongest lines of experimental evidence that pyrimidine dimers of the cyclobutane type are biologically important lesions and can account for a large fraction of the effects of ultraviolet light on DNA in solution. Insofar as DNA is one of the more important biological structures, such dimers, when formed, account for a large part of the effects of ultraviolet radiation on biological systems.     

核酸疫苗的研究进展及其在鱼类免疫中的应用

核酸疫苗是20世纪90年代初发展起来的一种新型疫苗,它克服了传统疫苗所存在的一些缺陷,具有许多传统疫苗不可比拟的优点。有关核酸疫苗的研究已成为国内外科技界研究的热点之一,呈现出良好的应用前景。作者综述了核酸疫苗的研究背景、构建过程、作用机理以及疫苗本身具有的优缺点等,同时,概述了近年来国内外对鱼类DNA疫苗基础研究和应用研究的新进展,探讨了鱼用DNA疫苗当前需要解决的问题及发展前景。     

分子标记在荔枝研究中的应用进展

近年来,分子标记技术发展快速,其在荔枝研究中的应用也越来越广泛.由于分子标记具有高效、可靠等诸多优点,因此它的发展和应用为荔枝研究提供了一条有效的途径.综述了RAPD、AFLP、SSR、ISSR、SRAP、EST-SSR等几种分子标记在荔枝中的遗传多样新分析、品种鉴定、分子辅助育种、遗传图谱构建等多方面的应用,同时分析了分子标记在荔枝研究中存在的问题和今后研究工作的重点.