Ab initio studies of γ-aminobutyric acid (GABA), γ-aminobutyric acid imine (GABA imine) and aminooxyacetic acid (AOAA)

Ab initio studies onl-2,4-diaminobutyric acid (l-DABA)

“…In the case of GABA, a structure similar to 3d was shown to be very stable also, more stable by 7.3 kcal tool-1 than the reported cation of the partially folded GABA [18]. The L-DABA cations that have H + positioned on N2 are found to be more stable than the cations that have H + positioned on N 1 for the partially folded, extended, and cyclic conformations.…”

“…The increased positive charge on H1 in structure 3a is typical for a hydrogen bond. It is interesting to notice that the charge separation between C1, O1, and H1 is higher in the cyclic conformation of L-DABA than in the cyclic conformation of GABA [18]. This factor may contribute to its stability.…”

“…This may contribute to the flexibility of the molecule by sub- stantially decreasing the C l-C2 bond dipole and thus preventing preferential interactions. The proton affinities of the amino groups and the carboxyl group may be important factors bearing on lipophilicity and perhaps on the ability of L-DABA to cross the BBB [18]. A higher proton affinity at NH2 facilitates the formation of the NH; ~ group, while a low proton affinity for the carboxylate leads to the formation of the anion.…”

“…Sapse and co-workers have performed ab initio calculations on GABA, determining energies, bond angles, bond lengths, and dihedral angles for various molecular conformations [18]. It appeared to be of interest to perform similar calculations on DABA to see whether the information obtained could provide insights into the similarities and differences in the transport behaviors of GABA and DABA.…”

“…Ab initio calculations can provide useful information on bond lengths, bond angles, dihedral angles, energies, and molecular conformations that may exist in a particular model system. The structural characteristics of L-DABA are compared to GABA [18], taurine, and hypotaurine [19] in order to identify the similarities and differences between their lowest energy conformations. The ability of L-DABA to inhibit GABA, taurine, and hypotaurine in high-affinity transport in synaptosomal tissue [16] is correlated with the conformational structures of the compounds.…”