HOMO guanine

CT-induced damage, consistent with theoretical predictions that the HOMO of guanine doublets is localized on the 5 -G [90]. Conversely, non-specific oxidation of both guanines is indicative of an alternative chemistry, for instance reaction with singlet oxygen. 

Mattera, R., Pitts, B. J., Entman, M. L., and Bimbaumer, L. (1985) Guanine nucleotide regulation of a mammalian myocardial muscarinic receptor system. Evidence for homo-and heterotropic cooperativity in ligand binding analyzed by computer-assisted curve fitting. J. Biol. Chem. 260,7410-7421. 

Fig. 18 Contour (left) and isosurface (right) plots of the HOMO-band convolution of electron states for the G4-DNA base-core structure [93], The delocalized character along the guanines is evident, as highlighted by the arrow parallel to the axis of the stack (adapted from [93], with permission Copyright 2002 by the American Institute of Physics)...

The Energies of Highest Occupied (HOMO) and Lowest Empty (LEMO) Molecular Orbitals of Guanine, Cytosine, and their Pair Calculated by w-SCF MO (Closed-Shell)0... 

Eisenhaure, T. M., Francis, S. A., Willison, L. D., Coughlin, S. R., and Lerner, D. J. (2003). The Rho guanine nucleotide exchange factor Lsc homo-oligomerizes and is negatively regulated through domains in its carboxyl terminus that are absent in novel splenic isoforms. / Biol. Chem. 278, 30975-30984. 

Table 24. Orbital energies for the highest occupied molecular orbital (HOMO) and the lowest unoccupied moler cular orbital (LUMO) for the hydrogen-bonded pai-guanine-cytosine a...

As in the homo-base pair series, most hetero-base pair associations involve two hydrogen bonds. Only the Watson-Crick G-C base pair and two guanine-uracil pairs of no biological importance form three hydrogen bonds. In the following, we summarize the possible base-base combinations in matrix notation, with those possible with nucleic acids [where pyrimidine N(l) and purine N(9) are substituted] indicated in italic letters, as before. 

Groebke, K. et al. (1998). Why pentose- and not hexose-nucleic acids V. Purine-purine pairing in homo-DNA guanine, isoguanine, 2,6-diaminopurine, and xanthine. Helvetica Chimica Acta, 81, 375—474 (footnote 64 on p. 444). 

In Homo-DNA adenine and guanine pair strongly with themselves the base pairing selectivities in Homo-DNA are different from those operating in DNA. 

Figure 62. In p-RNA, thoe is guanine-isoguanine (Watson-CMck) pairing as in homo-DNA (see fig. 22 in lecture 1) but no reverse-Hoogsteen self-pairing of isoguanine.

---