Search

Effects of the anisotropic DNA environment on nitrosative guanine deamination based on results of an ab initio study of the aggregate formed by guaninediazonium ion and cytosine are discussed. An electronic structure analysis of (2-diazonium-9H-purin-6-olate) shows that this betaine is not mesoionic and only the negative charge is delocalised in the pi-system while the positive charge resides in the sigma-system.

The gas-phase electron diffraction (GED) was used to understand the molecular structure and dynamics of thymine, cytosine, adenine, and guanine nucleobases that form the nucleic acid and gain insight into some of the biological processes. The findings from the study would be significant for designing pharmacological substances and methods for therapy against cancer, virus infections, and malformation.

High-level ab initio studies are used for studying the tautomerization equilibrium and rate constants of water-assisted proton transfer of 1-methyl-cytosine (MeC) to its MeC* imino tautomeric form in the presence of up to two water molecules (W) and the [Na.sup.+] cation. The interactions with [Na.sup.+] have led to a decrease of both the rate and the equilibrium constants of the tautomerization reactions in hydrated MeC.

A comprehensive ab initio study is used to observe and analyze the structure, stability and electronic properties of guanine-zinc-cytosine (G-Zn-C) base pair, which when combined with metals like Zn and Co lead to the formation of M-DNA at high values of pH. The analysis suggest that a lot of things should be taken care of while studying the electronic properties of such base-pairs, as M-DNAs with functionals do not account for strong electronic correlations.

Predictions on the photoelectron spectra of deprotonated cytosine anions were made with ab initio electron propagator methods. A group of six most stable isomers with energies within 10 kcal/mol of each other was found after a thorough exploration of the potential energy surfaces corresponding to 95 [Cye.sup.-] species.

A three-state conical intersection between the ground state and the (pi,pi*) and (n0,pi*) singlet excited states of cytosine is the topological feature that dominates the ultrafast decay of singlet excited cytosine. The results suggest that the experimental excited-state lifetime is the effect of two factors, namely, an energetically accessible region of S(sub 1)/S(sub 0) degeneracy and a region where the decay can be slowed by recrossing to S(sub 2)