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Figure37.Fateofdeoxyguanosineradicalcation.AdditionofH2OispreferredinduplexDNA,butdep...
Figure 37.
Fate of deoxyguanosine radical cation.Addition of H2O is preferred in duplex DNA,but deprotonation and reaction with O2 are observed in nucleosides.
Figure 38 Guanine reactions leading to 8-oxoG
8-Oxoguanine,kr its minior tautomer 7,8-dihydro-8-hydroxyguanine,can be formed by at least 4 different pathways (Figure 38).C8 appears to be especially susceptible to radical addition, and this is a major route proposed in HO. oxidation(path a).The majority of oxidants react via the one-electron abstraction pathway(b)to provide G.+ which is then hydrated and further oxidixed to form 22(see Tables 2 to 3).Singlet oxygen might react by a one-electron but an alternative pathway (c) has also been proposed.In this mechanism,the imidazole ring of guanineundergoes a [2 +4] cycloaddition to producean endoperoxide that can ri observed in ng open to 8-hydroperoxyguanine,113,which should undergo facile reduction to 22.Finally ,two-electron oxidation of guanine should be possible for metal-oxo species capable of oxygen atom transfer reactions(d).Evidence for intermediate 114 generated from oxo transfer from a ruthenium(Ⅳ)complex has been reported.
Bromination of uracil is facilitated by some-what acidic conditions. For NBS brominations,Cis most reactive at pH while G is more reactive at pH9
Iodination can be effected by use of N-iodosuccinimide KI/TlCl3,or I2.Cytosine is the used with DNA or RNA in aqueous solutions, although ICl in DNF will more readily iodinate uracil .Very little, if any iodination if guanine has been observed. As with bromination, the C residues that are iodinated in folded RNA structures are those that are in single-stranded, exposed regions. Similarly, denatured calf thymus DNA is more than 20-lode more reactive than the native structure.
B. Guanine Reactions
Electrophiles find several possible reaction sited in guanine, depending upon the nature of the electrophile. Carbon electrophiles generally choose N7, the N2-amino group,N3 or O6, in roughly that order of reactivity. On the other hand, the known chemistry of halogens is restricted entirely to C8 attack, a position that also appears in oxidation chemistry and reactions with various radical species. In contrast, nitrogen electrophiles such as HONO react at the exocyclic amino group, N2 展开
Fate of deoxyguanosine radical cation.Addition of H2O is preferred in duplex DNA,but deprotonation and reaction with O2 are observed in nucleosides.
Figure 38 Guanine reactions leading to 8-oxoG
8-Oxoguanine,kr its minior tautomer 7,8-dihydro-8-hydroxyguanine,can be formed by at least 4 different pathways (Figure 38).C8 appears to be especially susceptible to radical addition, and this is a major route proposed in HO. oxidation(path a).The majority of oxidants react via the one-electron abstraction pathway(b)to provide G.+ which is then hydrated and further oxidixed to form 22(see Tables 2 to 3).Singlet oxygen might react by a one-electron but an alternative pathway (c) has also been proposed.In this mechanism,the imidazole ring of guanineundergoes a [2 +4] cycloaddition to producean endoperoxide that can ri observed in ng open to 8-hydroperoxyguanine,113,which should undergo facile reduction to 22.Finally ,two-electron oxidation of guanine should be possible for metal-oxo species capable of oxygen atom transfer reactions(d).Evidence for intermediate 114 generated from oxo transfer from a ruthenium(Ⅳ)complex has been reported.
Bromination of uracil is facilitated by some-what acidic conditions. For NBS brominations,Cis most reactive at pH while G is more reactive at pH9
Iodination can be effected by use of N-iodosuccinimide KI/TlCl3,or I2.Cytosine is the used with DNA or RNA in aqueous solutions, although ICl in DNF will more readily iodinate uracil .Very little, if any iodination if guanine has been observed. As with bromination, the C residues that are iodinated in folded RNA structures are those that are in single-stranded, exposed regions. Similarly, denatured calf thymus DNA is more than 20-lode more reactive than the native structure.
B. Guanine Reactions
Electrophiles find several possible reaction sited in guanine, depending upon the nature of the electrophile. Carbon electrophiles generally choose N7, the N2-amino group,N3 or O6, in roughly that order of reactivity. On the other hand, the known chemistry of halogens is restricted entirely to C8 attack, a position that also appears in oxidation chemistry and reactions with various radical species. In contrast, nitrogen electrophiles such as HONO react at the exocyclic amino group, N2 展开
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图37岁。
脱氧胸苷的命运激进阳离子水的基础上再增加的首选,而双DNA,但离子反应和氧气,核苷发现。
图38鸟嘌呤反应导致8-oxoG
8-Oxoguanine,基米-雷克南其minior tautomer 7,8-dihydro-8-hydroxyguanine,可以形成了至少4个不同的路径.C8(图38)好像特别容易受到激进加上和这是一个主要途径HO.氧化提出了路径有反应大部分氧化剂,通过one-electron抽象途径(b)提供g . +然后滋润,进一步oxidixed形成22(见表2至3).Singlet氧可能会因为一个one-electron但另一种途径(c)也被提出在该机制中,guanineundergoes咪唑环的一个[2 + 4]环加成反应体系以最近producean endoperoxide,能国际扶轮中观察到的开放,今年113 8-hydroperoxyguanine吴思远,减少面部需要接受22 . 最后,two-electron氧化的鸟嘌呤应该可以metal-oxo种族能氧原子转移反应(d).Evidence为中级114来自oxo汇款的复杂的Ⅳ钌(已有报导。
溴代产物由各行业尿some-what酸性条件。国家统计局的活性最大、企业形象策划brominations在pH而G更加容易发生反应在pH9
能影响Iodination利用N-iodosuccinimide气/ TlCl3或12 . 胞核嘧啶是用DNA或RNA在水溶液中,尽管ICl DNF将更容易iodinate尿几乎没有任何.Very iodination如果鸟嘌呤被观测到。与溴代,C的残留物碘化在折叠结构RNA那些存在single-stranded、暴露地区。同样,变性小腿胸腺DNA更加容易发生反应20-lode多比本土结构。
b鸟嘌呤反应
找几个Electrophiles受话者可能做出的反应,视鸟嘌呤座落于electrophile的性质。碳electrophiles N7通常选择,N2-amino集团O6或误,在约反应,秩序。另一方面,已知的化学限制卤素完全进攻,带领业务发展的位置也出现在氧化化学和反应和各种激进的物种。相反,氮electrophiles HONO反应等exocyclic氨基团,氮气
脱氧胸苷的命运激进阳离子水的基础上再增加的首选,而双DNA,但离子反应和氧气,核苷发现。
图38鸟嘌呤反应导致8-oxoG
8-Oxoguanine,基米-雷克南其minior tautomer 7,8-dihydro-8-hydroxyguanine,可以形成了至少4个不同的路径.C8(图38)好像特别容易受到激进加上和这是一个主要途径HO.氧化提出了路径有反应大部分氧化剂,通过one-electron抽象途径(b)提供g . +然后滋润,进一步oxidixed形成22(见表2至3).Singlet氧可能会因为一个one-electron但另一种途径(c)也被提出在该机制中,guanineundergoes咪唑环的一个[2 + 4]环加成反应体系以最近producean endoperoxide,能国际扶轮中观察到的开放,今年113 8-hydroperoxyguanine吴思远,减少面部需要接受22 . 最后,two-electron氧化的鸟嘌呤应该可以metal-oxo种族能氧原子转移反应(d).Evidence为中级114来自oxo汇款的复杂的Ⅳ钌(已有报导。
溴代产物由各行业尿some-what酸性条件。国家统计局的活性最大、企业形象策划brominations在pH而G更加容易发生反应在pH9
能影响Iodination利用N-iodosuccinimide气/ TlCl3或12 . 胞核嘧啶是用DNA或RNA在水溶液中,尽管ICl DNF将更容易iodinate尿几乎没有任何.Very iodination如果鸟嘌呤被观测到。与溴代,C的残留物碘化在折叠结构RNA那些存在single-stranded、暴露地区。同样,变性小腿胸腺DNA更加容易发生反应20-lode多比本土结构。
b鸟嘌呤反应
找几个Electrophiles受话者可能做出的反应,视鸟嘌呤座落于electrophile的性质。碳electrophiles N7通常选择,N2-amino集团O6或误,在约反应,秩序。另一方面,已知的化学限制卤素完全进攻,带领业务发展的位置也出现在氧化化学和反应和各种激进的物种。相反,氮electrophiles HONO反应等exocyclic氨基团,氮气
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