Relative energies guanine

Carbocation Reacting Nitrogen of Guanine Relative Energy (kcal/mol) Gas Aqueous Phase Phase Ereactior Gas Phaseb fkcal/molf Aqueous Phase... 

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.

In this section, we present the results of computational studies of the five nucleic acid bases cytosine 13, guanine 14, adenine 15, thymine 16, and uracil 17. The canonical structures, those that are involved in the Watson-Crick base pairing within DNA, are drawn below. Other tautomers for each base can be energetically competitive with the canonical structure, and these other tautomers are invoked in some models of DNA mutations and anomalous DNA structures. The ensuing discussion focuses on the relative energies of the tautomers, in both the gas and solution phases. Structural changes that accompany this phase change are also noted. 

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

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 ...

Table 9 Relative Energies and Dipole Moments of Guanine (G), 6-Thioguanine (6TG), and 6-Selenogua-nine (6SeG) Tautomers ...

Table 11-5. Vertical excitation energies in eV relative to the ground state minimum of the singlet electronic excited states in guanine...

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