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1.
Structure of a New Pyrimidine from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> Phage SP-15 Nucleic Acid 总被引:12,自引:0,他引:12
THE unusual modified base1 of the nucleic acid of the large, generalized transducing phage of Bacillus subtilis SP-15 was predicted from the low denaturation temperature of the native nucleic acid. The base was detected as a fifth ultraviolet-absorbing component once the nucleic acid had been hydrolysed with formic acid; it partially replaces the thymine and represents 12 mol per cent of all the bases1. It is responsible for the low Tm of the nucleic acid, since once all other unusual components have been removed, the remaining material melts at the same temperature as the native nucleic acid. We report here the isolation and characterization of this new pyrimidine. 相似文献
2.
The properties of mesomorphic dispersions of double-stranded nucleic acids were studied. A comparison of these properties indicates that their diversity cannot be explained unambiguously in terms of the conception of Van-der-Waals interactions in particles of mesomorphic dispersions without regard for the specific properties of the solvent, water, in the vicinity of adjacent nucleic acid molecules. It was assumed that, with small distances between the molecules of nucleic acids, a specific "phantom" structure of the solvent appears in their vicinity, which acts as an elastic medium that modifies the interactions between nucleic acid molecules and as a medium in which a collective tunneling of protons can occur. The combination of the two effects determines the "recognition" of nucliec acid molecules and the stabilization of the cholesteric structure of mesomorphic dispersions of nucleic acids. 相似文献
3.
Recognition of nucleic acids is important for our understanding of nucleic acid structure as well as for our understanding of nucleic acid-protein interactions. In addition to the direct readout mechanisms of nucleic acids such as H-bonding, shape recognition of nucleic acids is being increasingly recognized as playing an equally important role in DNA recognition. Competition dialysis, UV, flourescent intercalator displacement (FID), computational docking, and calorimetry studies were conducted to study the interaction of neomycin with a variety of nucleic acid conformations (shapes). At pH 5.5, the results suggest the following. (1) Neomycin binds three RNA structures [16S A site rRNA, poly(rA)·poly(rA), and poly(rA)·poly(rU)] with high affinities (K(a) ~ 10(7) M(-1)). (2) The binding of neomycin to A-form GC-rich oligomer d(A(2)G(15)C(15)T(2))(2) has an affinity comparable to those of RNA structures. (3) The binding of neomycin to DNA·RNA hybrids shows a 3-fold variance that can be attributed to their structural differences [for poly(dA)·poly(rU), K(a) = 9.4 × 10(6) M(-1), and for poly(rA)·poly(dT), K(a) = 3.1 × 10(6) M(-1)]. (4) The interaction of neomycin with DNA triplex poly(dA)·2poly(dT) yields a binding affinity (K(a)) of 2.4 × 10(5) M(-1). (5) Poly(dA-dT)(2) shows the lowest association constant for all nucleic acids studied (K(a) < 10(5)). (6) Neomycin binds to G-quadruplexes with K(a) values of ~10(4)-10(5) M(-1). (7) Computational studies show that the decrease in major groove width in the B to A transition correlates with increasing neomycin affinity. Neomycin's affinity for various nucleic acid structures can be ranked as follows: RNAs and GC-rich d(A(2)G(15)C(15)T(2))(2) structures > poly(dA)·poly(rU) > poly(rA)·poly(dT) > T·A-T triplex, G-quadruplex, B-form AT-rich, or GC-rich DNA sequences. The results illustrate the first example of a small molecule-based "shape readout" of different nucleic acid conformations. 相似文献
4.
对功能核酸概念的分析需要建立在对功能核酸研究的基础上,从内涵和外延两个方面来进行探析。从内涵来看,它是对具有特殊结构、执行特定生物功能的核酸分子的统称;从外延来看,它包括适体、核酸核酶、核糖开关、发光核酸、修饰核酸、功能核酸裁剪、核酸自组装、功能核酸纳米材料、核酸纳米酶、核酸药物、核酸补充剂以及DNA存储技术等。目前功能核酸已成功地应用于生物传感、生物成像、生物医学等诸多领域。对功能核酸这一概念进行了探讨,并尝试对其范畴、特点进行归纳总结,以期梳理和完善功能核酸的基本概念,促进该领域的进一步发展。 相似文献
5.
Model studies of interactions between nucleic acids and proteins: hydrogen bonding of amides with nucleic acid bases.
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The formation of hydrogen bonded complexes between nucleic acid bases and acetamide has been studied by nuclear magnetic resonance in CDC13 at different temperatures. Pairs of hydrogen bonds are formed when acetamide binds to nucleic acid bases. Thermodynamic parameters have been computed and compared to those obtained for the association of carboxylic acids with nucleic acid bases. The role of hydrogen bonded complexes in the association of proteins with nucleic acids is discussed. 相似文献
6.
7.
Nucleic acids are an important class of biological macromolecules that carry out a variety of cellular roles. For many functions, naturally occurring DNA and RNA molecules need to fold into precise three-dimensional structures. Due to their self-assembling characteristics, nucleic acids have also been widely studied in the field of nanotechnology, and a diverse range of intricate three-dimensional nanostructures have been designed and synthesized. Different physical terms such as base-pairing and stacking interactions, tertiary contacts, electrostatic interactions and entropy all affect nucleic acid folding and structure. Here we review general computational approaches developed to model nucleic acid systems. We focus on four key areas of nucleic acid modeling: molecular representation, potential energy function, degrees of freedom and sampling algorithm. Appropriate choices in each of these key areas in nucleic acid modeling can effectively combine to aid interpretation of experimental data and facilitate prediction of nucleic acid structure. 相似文献
8.
The study of mechanisms of nucleic acid transport across the cell membrane is valuable both for understanding the biological function of extracellular nucleic acids and the practical use of nucleic acids in gene therapy. It has been clearly demonstrated that cell surface proteins are necessary for transport of nucleic acids into cells. A large amount of data has now been accumulated about the proteins that participate in nucleic acid transport. The methods for revealing and identification of these proteins, possible mechanisms of protein-mediated transport of nucleic acids, and cellular functions of these proteins are described. 相似文献
9.
Principles of nucleic acid hybridization and comparison with monoclonal antibody technology for the diagnosis of infectious diseases 总被引:5,自引:0,他引:5
S C Edberg 《The Yale journal of biology and medicine》1985,58(5):425-442
Until the 1980s the diagnosis of specific etiologic agents of infectious diseases rested with their isolation in vitro and identification by analysis of their phenotypic characteristics. In the 1970s the concept of a microbial species evolved from phenotypic analysis to nucleic acid homology. Currently, nucleic acid sequences specific for a given species are being isolated and amplified and utilized not only to identify the pathogen after it has been grown in vitro but also elucidate it directly in biological material. The procedures for making nucleic acid hybridization probes are analogous to the generation of monoclonal antibody tests. Currently, research and development are centered in choosing the particular nucleic acid to analyze, establishing the most efficient vector system for amplifying the nucleic acid, generating an efficient means of selecting the particular nucleic acid fragment specific for the microorganism, and in measuring the hybridization reaction. While immunological techniques have been utilized in the clinical laboratory for over thirty years, the means of detecting nucleic acid hybridization reactions are just beginning to be usable in the clinical diagnostic laboratory. Much of nucleic acid hybridization research is proprietary, and a particular challenge is to develop a means whereby information can be used for the progress of science as a whole when generated by private ownership. 相似文献
10.
From the analysis of CD-spectra of liquid crystalline microphases formed from DNA molecules in complexes with "external chromophores" requirements are formulated for the compounds to be used in revealing peculiarities of spatial structure of nucleic acids liquid crystalline microphases. These requirements satisfied it is possible to record the CD-spectra having intensive bands in the regions of chromophores absorption. These bands prove the helical pattern of the spatial structure of nucleic acid liquid crystalline microphase. 相似文献
11.
近年来,因兼具基因修饰和传统药物的双重特点,核酸药物已逐渐成为精准生物医学和疾病治疗的热点。为进一步推动我国核酸药物行业创新发展,采用定量分析和定性分析相结合的方法,对国内外核酸药物获批/授权、市场和研发情况进行分析,揭示全球ASO、siRNA、RNA aptamer及mRNA等四大类核酸药物的产业发展态势,系统梳理我国支持核酸药物创新发展的政策与措施,明确未来的技术主攻方向和应用潜力。面对国内基因治疗的迫切需求及核酸药物创制的严峻形势,研究提出推动源头创新、完善成果转移转化机制和营造良好竞争环境等对策建议。 相似文献
12.
Three variants of the model for the formation of "bridges" between the nucleic acid molecules fixed in the structure of particles of liquid-crystalline dispersions were considered. What the three variants have in common is that the bridges represent polymeric chelate cross-links consisting of alternating molecules of daunomycin and copper ions. The differences between the three variants are that in the first variant, the bridges begin and end with daunomycin molecules that form a complex by the mechanism of external binding with nucleic acids; in the second variant, the bridges begin and end with copper ions coupled with the pairs of bases of nucleic acids; and in the third variant, the bridges begin with the daunomycin molecule and end with the copper ion. For each variant, a mathematical model was constructed, which describes the formation of bridges, and equations of binding were derived. The results of calculations were compared with the experimental data. Within the framework of each variant, the values of the energy of interaction between the daunomycin molecule and the copper ion in the bridge, the energy of interaction of the daunomycin molecule with the nucleic acid, and the length of the bridge were varied. For all variants, those values of the parameters were chosen that fit best the experimental data. The theoretical curves obtained using the three variants of the model agree rather well with the family of experimental curves. The best agreement between the theoretical and experimental data was obtained when the polymeric chelate bridge includes more than two daunomycin molecules. 相似文献
13.
The patterns of nucleic acid synthesis in insect cells infected with iridescent virus types 2 and 6 has been examined using nucleic acid hybridization techniques. Virus-specific RNA synthesis was detected 24 hr after infection. Virus-specific DNA synthesis was detected 96 hr after infection. Host-specific nucleic acid synthesis declined throughout infection, and host-specific nucleic acid synthesis was detected only in the first 48 hr of infection. The synthesis of iridescent virus progeny DNA molecules precedes the appearance of mature iridescent virus particles. 相似文献
14.
随着分子生物学发展,核酸实时定量检测已成为人们研究的热点问题。分子标灯与NASBA结合实时检测ssRNA发展成为一种新技术,称为AmpliDetRNA。就NASBA扩增原理、分子标灯的结构和AmpliDetRNA的特点及应用作一简单介绍 。 相似文献
15.
16.
LNA: a versatile tool for therapeutics and genomics 总被引:21,自引:0,他引:21
17.
Helicases use the energy from ATP hydrolysis to catalyze formation of single-stranded nucleic acids by unwinding double-stranded nucleic acids. The ATP-dependent reaction can be broken down into at least two steps: melting of the duplex and translocation of the enzyme along the nucleic acid lattice. Each step presents difficulties for study because clear end points for the reactions are not always available. For example, translocation involves the movement of the enzyme from one point along the lattice to a new position, with no net change in chemical structure of the nucleic acid. Hence, new assays have been developed in which the nucleic acid is modified to contain a "protein block" that impedes translocation of the enzyme. To prepare such protein blocks, biotin-streptavidin has been used due to the ease with which the biotin can be incorporated into nucleic acids by chemical synthesis. Several applications of oligonucleotides labeled with biotin-streptavidin for the study of helicase mechanisms are described. 相似文献
18.
A C Syv?nen 《Medical biology》1986,64(6):313-324
The nucleic acid hybridization reaction is extremely specific and thus a valuable tool for the identification of genes or organism of interest. The increasing use of nucleic acid hybridization in applied fields like diagnostic medicine has led to the development of more convenient hybridization assays than those originally used in basic research. In conventional nucleic acid hybridization methods immobilized nucleic acids are detected on a filter by a radiolabelled probe. Sandwich hybridization is a simple test format for the analysis of unpurified biological material, but has the disadvantage of a slow reaction rate. Solution hybridization methods are fast and easy to perform provided that a method to separate the formed hybrids from the reaction mixture is available. In non-isotopic detection the nucleic acid probe is modified with a chemical group, which is identified with a labelled detector molecule after hybridization. The low sensitivity of detection is the main problem in nucleic acid hybridization methods. Procedures to amplify the detectable signal or the amount of detectable nucleic acid sequences are potential solutions to this problem. The new hybridization methods have successfully been used for some applications, but still need to be combined into well performing tests to be applicable to any desired purpose. 相似文献
19.
Biosynthesis of nucleic acids in the pea buds released from apical dominance by decapitation has been studied.
The rate of biosynthesis of all nucleic acid classes separated by means of methylated albuminkieselgur (MAK) column chromatography
was found to be increased in released pea buds as judged by the extent of orotic-6-14C acid incorporation. This increase has been observed in all experimental points examined (15, 24, 36 and 48 h after decapitation),
being the most pronounced 15 h after decapitation. After that a certain decrease of the specific radioactivities of nucleic
acids has been registered, but even 48 h after decapitation specific activities of the main nucleic acid classes were higher
in comparison with those found in dominant buds.
Variations of the free pyrimidine nucleotide pools were about 14% suggesting that this parameter did not influence the extent
of the uptake of labelled orotic acid. 相似文献
20.
聚合酶链式反应(PCR)是一种高灵敏核酸扩增技术,广泛应用于核酸检测中.但在实际应用过程中,扩增产物及其他核酸片段的污染会导致假阳性的结果,制约了PCR在临床检测中的应用.为了解决这一问题,建立了许多PCR防污染的方法,除了早期建立的并已得到广泛应用的物理隔绝法、光照法及水解法外,近年来还发展了酶消化法、化学修饰法及DEAE纤维素法.本文对PCR防污染技术的原理、应用及进展进行了综述. 相似文献