Adenine tautomers

Molecular Energies in Adenine Tautomers (CNDO/2 Calculation) with Respect to the Most Stable Tautomer... 

Fig. 9. Relative stabilities of the associated amine and imine forms of adenine tautomers.

Fig. 11. Net electronic charges in adenine tautomers evaluated by the CNDO/2 method. Upper numbers a charges lower numbers tt charges.

Concerning other outstanding electronic properties of the adenine tautomers, some of the theoretically evaluated ones are listed in Table X. They are self-explanatory. It may just indicate that the... 

TABLE 7.15 Relative Energies (in kcal mol of Adenine Tautomers (15a-n)... 

Mishra and coworkers have reported spectral oscillation in the absorption spectra of adenine solution in water when air was passed through the solution and exposed to UV-radiation intermittently over a long period of time. The main absorption peak near 260 nm (4.77 eV) was shifted to near 300 nm (4.13 eV) region which was explained in terms of the formation of the N3H tautomer of adenine,the process of which is closely related to the tautomerization of 7-azaindole. This assertian (the formation of the N3H tautomer in the excited state) is also supported fixim a recent theoretical study of adenine tautomers at the MCQDPT2/CASSCF levels of theory. ... 

Figure 3. Structure of adenine tautomers (a) N9H tautomer in the SsfnJi ) state, (b) N7H tautomer in the SsCnji ) state, (c) hydrated form of the N9H tautomer in the ground state (top indices) and Si(JDt ) state (bottom indices), (d) hydrated form of the N7H tautomer in the ground state (top indices) and Si(jnt ) state (bottom indices).

The hydrated structures of the N9H and N7H tautomers showing hydrogen bond lengths in the ground and lowest singlet nn excited states are presented in Figs. 3c and 3d, respectively. Hydration of adenine tautomers with three... 

Selected values of torsional angles of adenine tautomers calculated at the B3LYP/6-311G(d,p) level. 

FIGURE 16. Hydrogen-bonded network (dashed lines) around the ///-adenine tautomer. 

Based on these findings, previous studies have suggested that the 7H-adenine tautomer might be present in a relatively large eoneentration in aqueous solution ( 20%) and biological systems. Nevertheless, most of the known solid-state structures containing noncoordinated adenine molecules have a hydrogen atom at N9.35,70,72,73,85,86 proton is only transferred to... 

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