Guanine Tautomer energy

TABLE 7.14 Relative Energies (in kcal moi of Guanine Tautomers (14a-j)... 

Figure 5. Energy level diagrams of guanine tautomers, (A) isolated form (B) hydrated form. In the ease of isolated tautom s, (a),... 

The rotational constants and dipole moments of the normal tautomer of adenine and four lower-energy tautomeric forms of guanine are presented in Tables 6 and 7. While the calculated data are in good agreement with available experimental parameters for adenine, the experimental data for guanine tautomers are not accessible. On the basis of a comparison of the DFT, MP2, and experimental rotational constants for all other NABs, similar accuracy is expected for the predicted parameters of the guanine tautomers. 

Figure 8 Relative energies of guanine tautomers estimated at the MP4 level with different basis sets A. 6-3 IG(d,p) B, 6-3 l-l-l-G(d,p) C, 6-31 IG(d,p)...

Table 8 Relative Energies of the Three Guanine Tautomers Calculated at Different Levels of Theory and Basis Set with Different Optimized Geometries ...

Figure 7.2 Fifteen of the lowest energy tautomers of guanine. Relative energies are in wavenumbers. From Ref (27). Solidly shaded structures are observed In gas-phase nanosecond R2PI experiments. Hashed structures have subpicosecond excited-state lifetimes. The rectangle marks the structures observed in helium droplets. Keto-N9H is the Watson-Crick structure.

Chen H, Li SH (2006) Theoretical study on the excitation energies of six tautomers of guanine evidence for the assignment of the rare tautomers. J Phys Chem A 110 12360-12362... 

Figure 13-2. Energetic ordering of the tautomers of isolated guanine as obtained by quantum chemistry. The five level of theory presented refer to a, b) [25] c) [8] and d, e) [30]. For the four lowest tautomers (lower panel) the energies are corrected for zero-point vibrational energy...

Figure 13-7. Adiabatic energies of the lowest tttt transitions calculated of the most stable tautomers of guanine at several levels of theory (a-d) compared to experimental origin transitions [18]. Lower panel absolute values for the 7AHi species Upper panel relative values. Labels a-d refer to the following references a, b) [38] c) [30] and d) [24]. In this latter case, frequency values corrected for zero-point vibrational energies are also given when available...

Figure 13-8. Relevant schematic potential energy curves for the near UV photophysics of the most stable tautomers of guanine. The region of the first singlet tht excited state surface accessible by Franck-Condon excitation is indicated in bold. Excited state internal conversion through a conical intersection (Cl) with S0 is illustrated by curved arrows. Vertical arrows indicate fluorescence emission. The eventual role of excited nir singlet states cannot be ruled out, especially at high energy excess in the excited state (see text)...

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