Many cells have the ability to recognize and eliminate damage to their DNA, particularly thymine dimers formed by UV light. The elimination of this damage may be achieved by enzymatic, light-dependent cleavage of the dimers into the monomers (photoreactivation) or more frequently by dark repair, in which the damaged part is completely removed from the, DNA. In this repair process, the DNA is incised by an endonuclease in the immediate vicinity of the thymine dimers. Oligonucleotides containing the thymine dimer are removed hydrolytically from the DNA by the 5→3′ exonuclease activity of DNA polymerase I (Kornberg enzyme). The resulting gaps are immediately closed by a de novo synthesis with the aid of the same DNA polymerase I, the complementary strand serving as a template (excision repair). The final step is the formation of the phosphodiester bond between the newly synthesized DNA fragment and the old DNA strand by a DNA ligase. Xeroderma pigmentosum patients lack the endonuclease as a result of a genetic defect; they therefore cannot eliminate thymine dimers from their DNA, and are extremely sensitive to sunlight. All information so far suggests that genetic recombination and DNA repair are performed by the same enzyme system. 相似文献
The oxidative DNA lesion, FaPydG rapidly anomerizes to form a mixture of the alpha and beta anomer. To investigate the mutagenic potential of both forms, we prepared stabilized bioisosteric analogues of both configurational isomers and incorporated them into oligonucleotides. These were subsequently used for thermodynamic melting-point studies and for primer-extension experiments. While the beta compound, in agreement with earlier data, prefers cytidine as the pairing partner, the alpha compound is not able form a stable base pair with any natural base. In primer-extension studies with the high-fidelity polymerase Bst Pol I, the polymerase was able to read through the lesion. The beta compound showed no strong mutagenic potential. The alpha compound, in contrast, strongly destabilized DNA duplexes and also blocked all of the tested DNA polymerases, including two low-fidelity polymerases of the Y-family. 相似文献
Biaryl derivatives that consist of one DNA‐intercalating unit and a sterically demanding component exhibit a specific behavior towards abasic site‐containing DNA (AP‐DNA) as determined by thermal DNA denaturation experiments, spectrometric titrations and CD spectroscopic analysis. Specifically, these ligands strongly stabilize AP‐DNA towards dissociation, whereas they do not or only marginally affect the melting temperature of regular duplex DNA. 相似文献
We describe the synthesis of the phosphoramidite building blocks of alpha-tricyclo-DNA (alpha-tc-DNA) covering all four natural bases, starting from the already known corresponding alpha-tc-nucleosides. These building blocks were used for the preparation of three alpha-tc-oligonucleotide 10-mers representing a homopurine, a homopyrimidine, and a mixed purine/pyrimidine base sequence. The base-pairing properties with complementary parallel and antiparallel oriented DNA and RNA were studied by UV-melting analysis and CD spectroscopy. We found that alpha-tc-DNA binds preferentially to parallel nucleic acid complements through Watson-Crick duplex formation, with a preference for RNA over DNA. In comparison with natural DNA, alpha-tc-DNA shows equal to enhanced affinity to RNA and also pairs to antiparallel DNA or RNA complements, although with much lower affinity. In the mixed-base sequence these antiparallel duplexes are of the reversed Watson-Crick type, while in the homopurine/homopyrimidine sequences Hoogsteen and/or reversed Hoogsteen pairing is observed. Antiparallel duplex formation of two alpha-tc-oligonucleotides was also observed, although the thermal stability of this duplex was surprisingly low. The base-pairing properties of alpha-tc-DNA are discussed in the context of alpha-DNA, alpha-RNA, and alpha-LNA. 相似文献
With silicon-based microelectronic technology pushed to its limit,scientists hunt to exploit biomolecules to power the bio-computer as substitutes.As a typical biomolecule,DNA now has been employed as a tool to create computing systems because of its superior parallel computing ability and outstanding data storage capability.However,the key challenges in this area lie in the human intervention during the computation process and the lack of platforms for central processor.DNA nanotechnology has created hundreds of complex and hierarchical DNA nanostructures with highly controllable motions by exploiting the unparalleled self-recognition properties of DNA molecule.These DNA nanostructures can provide platforms for central processor and reduce the human intervention during the computation process,which can offer unprecedented opportunities for biocomputing.In this review,recent advances in DNA nanotechnology are briefly summarized and the newly emerging concept of biocomputing with DNA nanostructures is introduced. 相似文献
The ability to precisely measure and monitor temperature at high resolution at the nanoscale is an important task for better understanding the thermodynamic properties of functional entities at the nanoscale in complex systems, or at the level of a single cell. However, the development of high‐resolution and robust thermal nanosensors is challenging. The design, assembly, and characterization of a group of thermal‐responsive deoxyribonucleic acid (DNA) joints, consisting of two interlocked double‐stranded DNA (dsDNA) rings, is described. The DNA nanojoints reversibly switch between the static and mobile state at different temperatures without a special annealing process. The temperature response range of the DNA nanojoint can be easily tuned by changing the length or the sequence of the hybridized region in its structure, and because of its interlocked structure the temperature response range of the DNA nanojoint is largely unaffected by its own concentration; this contrasts with systems that consist of separated components. 相似文献
Efficient DNA nick sealing catalyzed by T4 DNA ligase was carried out on a modified DNA template in which an intercalator such as azobenzene had been introduced. The intercalator was attached to a D-threoninol linker inserted into the DNA backbone. Although the structure of the template at the point of ligation was completely different from that of native DNA, two ODNs could be connected with yields higher than 90% in most cases. A systematic study of sequence dependence demonstrated that the ligation efficiency varied greatly with the base pairs adjacent to the azobenzene moiety. Interestingly, when the introduced azobenzene was photoisomerized to the cis form on subjection to UV light (320-380 nm), the rates of ligation were greatly accelerated for all sequences investigated. These unexpected ligations might provide a new approach for the introduction of functional molecules into long DNA strands in cases in which direct PCR cannot be used because of blockage of DNA synthesis by the introduced functional molecule. The biological significance of this unexpected enzymatic action is also discussed on the basis of kinetic analysis. 相似文献
Monodentate DNA binding of [PtCl(dien)]+ (dien=diethylenetriamine) complexes may considerably affect the biophysical properties of DNA and consequently downstream cellular processes as a result of a large increase in the bulkiness of the nonleaving ligand by multiple methylation (see illustration).
In this study, we have developed a PCR multiplex that can be used to assess DNA degradation and at the same time monitor for inhibition: primers have been designed to amplify human, pig, and rabbit DNA, allowing pig and rabbit to be used as experimental models for taphonomic research, but also enabling studies on human DNA persistence in forensic evidence. Internal amplified controls have been added to monitor for inhibition, allowing the effects of degradation and inhibition to be differentiated. Sequence data for single‐copy nuclear recombination activation gene (RAG‐1) from human, pig, and rabbit were aligned to identify conserved regions and primers were designed that targeted amplicons of 70, 194, 305, and 384 bp. Robust amplification in all three species was possible using as little as 0.3 ng of template DNA. These have been combined with primers that will amplify a bacterial DNA template within the PCR. The multiplex has been evaluated in a series of experiments to gain more knowledge of DNA persistence in soft tissues, which can be important when assessing what material to collect following events such as mass disasters or conflict, when muscle or bone material can be used to aid with the identification of human remains. The experiments used pigs as a model species. When whole pig bodies were exposed to the environment in Northwest England, DNA in muscle tissue persisted for over 24 days in the summer and over 77 days in the winter, with full profiles generated from these samples. In addition to time, accumulated degree days (ADD) were also used as a measure that combines both time and temperature—24 days was in summer equivalent to 295 ADD whereas 77 days in winter was equivalent to 494 ADD. 相似文献
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