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Nucleobases purine

Pliitzer C, Hiinig I, Kleinermanns K, Nir E, de Vries MS (2003) On the photochemistry of purine nucleobases. Chem Phys Chem 4 838-842... [Pg.337]

Figure 6. Schematic structures of common purine nucleobases with the numbering scheme. Figure 6. Schematic structures of common purine nucleobases with the numbering scheme.
Figure 9 Structures of the purine nucleobases used in elaborating metallacalixarenes. Figure 9 Structures of the purine nucleobases used in elaborating metallacalixarenes.
Each WCP dimer model consists of two purine bases (G and A) and two pyrimidine bases (C and T). According to the calculations, the two highest-lying orbitals HOMO and HOMO-1 of each duplex are mainly locahzed on the purine nucleobases, whereas the two occupied MOs following at lower energies, HOMO-2 and HOMO-3, are locahzed on pyrimidine nucleobases. Therefore, the purine-purine electronic coupling provides the dominant contribution to the hole transfer matrix elements, irrespective whether the bases belong to the same or to opposite strands. [Pg.56]

Comparing matrix elements of simple models of two purine nucleobases with those calculated for WCP dimers (Table 3), one wonders about the effect of pyrimidine nucleobases on the electronic coupling matrix elements of hole transfer in DNA [14, 73]. [Pg.56]

Ammonium formate was also used in the synthesis of adenine 1 from DAMN [76]. Irrespective of the experimental conditions used for the synthesis of purine nucleobases, only a few procedures for the preparation of guanine have been reported. [Pg.37]

Fig. 1. Structural formulas and numbering system for the purine nucleobases and nucleosides... Fig. 1. Structural formulas and numbering system for the purine nucleobases and nucleosides...
Key words purines, nucleobases, boronic acids, cross-coupling, palladium... [Pg.1]

The pyrimidine nucleobases have the highest quantum yields for photoreactivity, with thymine uracil > cytosine. The purine nucleobases have much lower quantum yields for photochemistry, but can be quite reactive in the presence of oxygen. As can be seen from Figure 9-3, thymine forms primarily cyclobutyl photodimers (ToT) via a [2ir + 2tt cycloaddition, with the cis-syn photodimer most prevalent in DNA. This is the lesion which is found most often in DNA and has been directly-linked to the suntan response in humans [65]. A [2Tr + 2Tr] cycloaddition reaction between the double bond in thymine and the carbonyl or the imino of an adjacent pyrimidine nucleobase can eventually yield the pyrimidine pyrimidinone [6 1]-photoproduct via spontaneous rearrangement of the initially formed oxetane or azetidine. This photoproduct has a much lower quantum yield than the photodimer in both dinucleoside monophosphates and in DNA. Finally, thymine can also form the photohydrate via photocatalytic addition of water across the C5 = C6 bond. [Pg.241]

Very few reports of the excited-state structural dynamics of the purine nucleobases have appeared in the literature. This lack of research effort is probably due to a number of factors. The primary factor is the lack of photochemistry seen in the purines. Although adenine can form photoadducts with thymine, and this accounts for 0.2% of the photolesions found upon UVC irradiation of DNA [67], the purines appear to be relatively robust to UV irradiation. This lack of photoreactivity is probably due to the aromatic nature of the purine nucleobases. A practical issue with the purine nucleobases is their insolubility in water. While adenine enjoys reasonable solubility, it is almost an order of magnitude lower than that of thymine and uracil, the two most soluble nucleobases [143], Guanine is almost completely insoluble in water at room temperature [143],... [Pg.255]

Nevertheless, a few reports of UV resonance Raman spectra of the purine nucleobases and their derivatives have appeared. Peticolas s group has reported the identification of resonance Raman marker bands of guanine, 9-methylguanine and 9-ethylguanine for DNA conformation [118, 144], In the process of doing that work, very rudimentary excitation profiles were measured, which yielded preliminary structures for two of the ultraviolet excited electronic states. Tsuboi has also performed UV resonance Raman on purine nucleobases in an effort to determine the resonance enhanced vibrational structure [94], Thus far, no excited-state structural dynamics for any of the purine nucleobases have been determined. [Pg.255]

Mazurkiewicz K, Rak J (2007). Purine nucleobases as possible electron traps in DNA-protein complexes. To be submitted. [Pg.666]

Fig. 1 Model of the adenine molecule (77/-purin-6-amine), one of the two purine nucleobases forming the nucleotides of the nucleic acids. The molecule has the formula C5H5N5 making it a 70-electron system. Today, systems of this size are amenable to high quality ab initio quantum chemical studies. Fig. 1 Model of the adenine molecule (77/-purin-6-amine), one of the two purine nucleobases forming the nucleotides of the nucleic acids. The molecule has the formula C5H5N5 making it a 70-electron system. Today, systems of this size are amenable to high quality ab initio quantum chemical studies.
Figure 5.4 Optimized geometries of the purine nucleobases adenine (a) and guanine (b). The molecules lie in thexy-plane as indicated. Figure 5.4 Optimized geometries of the purine nucleobases adenine (a) and guanine (b). The molecules lie in thexy-plane as indicated.
The anisotropy of fhe purine nucleobases is larger than that of fhe pyrimidines, which is attributable to the larger physical extension in the direction of the molecular plane. The mean excitation energy of fhe nucleobases is also more anisotropic than in the case of fhe amino acids, which is caused by the fact that the nucleobases include planar heterocycles with conjugated 7T-bonds. [Pg.235]

The location of cations between phospho-diesteric groups (type II) is carried out by chelation of the phosphorous group with N7 of the purine nucleobase from GMP (Figure 7.5). Such a structure characterizes the DNA complexes with Mn " " and Zn " " -cations which present a strong tendency of binding to the phosphodiesteric groups and a low affinity for coordination with purine nucleobases. [Pg.409]

Binding of the to a purine nucleobase (type V) occurs at N and O from C6 of adenine or N and O from Cg of guanine (Figure 7.8). In these cases, water molecules can bind at the chelate. This type of chelation is usually met at transition metals, and affects the conformation of helix causing local denaturations in the macromolec-ular structure. [Pg.410]

The major purine nucleobases that exist in DNA and RNA are derivatives of adenine and guanine (Fig. 3-31). [Pg.81]


See other pages where Nucleobases purine is mentioned: [Pg.331]    [Pg.337]    [Pg.123]    [Pg.131]    [Pg.131]    [Pg.918]    [Pg.48]    [Pg.55]    [Pg.62]    [Pg.918]    [Pg.42]    [Pg.208]    [Pg.253]    [Pg.439]    [Pg.441]    [Pg.442]    [Pg.444]    [Pg.448]    [Pg.450]    [Pg.377]    [Pg.278]    [Pg.394]    [Pg.1795]    [Pg.1802]    [Pg.749]    [Pg.377]    [Pg.34]    [Pg.340]    [Pg.340]    [Pg.259]    [Pg.408]   
See also in sourсe #XX -- [ Pg.32 ]




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