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Structures of pyrimidine dimers

When DNA is exposed to radiation at wavelengths of about 260 nm, adjacent pyrimidines become covalently linked by the formation of a four-member ring structure resulting from the saturation of their respective C5, C6 double bonds. The structure formed by this photochemical cycloaddition is referred to as a pyrimidine dimer. The pyrimidine bases in DNA are thymine and cytosine. [Pg.214]

The total energies of ToT and ToT( +) are shown in Table 1. The value of S of ToT( +) is 0.782 it is surprisingly close to the ideal value (0.75) for a doublet, as we could have expected a larger spin contamination due to the 7C orbitals of the moities. The orbital energy of the highest occupied molecular orbital (HOMO) of the neutral ToT is -0.407 au, while the vertical ionization potential of ToT is 11.1 eV according to Koopmans theorem. The adiabatic ionization potential after taking account of orbital relaxation (ASCF method) is [Pg.216]

which is the difference between the total energies of the optimized T T and the optimized ToT( -F). The adiabatic ionization potential calculated with the ASCF method is usually underestimated by around 10 %. Therefore, the adiabatic ionization potential is predicted to be around 9.3 eV. There are no experimental data directly comparable. Table 1 Total Energies (in au) and bond lengths (in A) around the four-member ring of thymine dimer (RHF/6-31G) and its radical cation (UHF/6-31G)  [Pg.217]

Selected bond angles of thymine dimer (RHF/6-31G) and its radical cation (UHF/6-31G)  [Pg.217]


Scheme 1. Structures of pyrimidine dimers (I) electrochemically generated hydrodimer of pyri-midone-2 (II) photochemically generated pyrimidine adducts (III) photochemically generated cyclobutane dimers... Scheme 1. Structures of pyrimidine dimers (I) electrochemically generated hydrodimer of pyri-midone-2 (II) photochemically generated pyrimidine adducts (III) photochemically generated cyclobutane dimers...

See other pages where Structures of pyrimidine dimers is mentioned: [Pg.1166]    [Pg.214]   


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Dimeric structures

Of pyrimidine

Pyrimidine structure

Structural and electronical characteristics of pyrimidine dimers

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