Theoretical study of the influence of ribose on the proton transfer phenomenon of nucleic acid bases

Evolution of microstructures and hydrogen bond interactions within choline amino acid ionic liquid and water mixtures

The microstructures and interactions of choline amino acid ([Cho][AA]) ionic liquid (IL) and water molecules were investigated. When water was added to [Cho][AA], the asymmetric and symmetric vibration peaks of the -COO^- group shifted to lower and higher wavenumbers, respectively. The increase of water addition also resulted in increased conductivity values and decreased viscosity values of [Cho][AA]-water mixtures. These features are consistent with the physical picture that [Cho][AA] could gradually dissociate into hydrated tight ion pairs and water-separated ion pairs and then into free and solvated ions. When it comes to different anions (choline lysine, [Cho][Lys], and choline aspartic acid, [Cho][Asp]), the anion structure has a significant regulation on [Cho][AA]-water interactions. The shorter side chain length and strong polar -COOH group of Asp^- endow [Cho][Asp] with stronger cation-anion interactions and less dissociation by water molecules. As a result, the frequency shift degrees and conductivity values of [Cho][Asp]-water mixtures were lower, and the viscosity values were higher than those of [Cho][Lys]-water mixtures. And, [Cho][Lys] could completely dissociate as free hydrated ions at w : IL ≥ 7 : 3, while the free hydrated ions of [Cho][Asp] only occurred when the w : IL ratio reached 8 : 2. These results can ease the experimental effort and improve the application efficiency of [Cho][AA] ILs.

Regulation nature of water-choline amino acid ionic liquid mixtures on the disaggregation behavior of starch

Fully green and renewable choline amino acid (choline glycine, [Cho][Gly]) ionic liquid (IL) was firstly explored and evaluated as a solvent for starch. By a thorough investigation of microstructure evolution of water-[Cho][Gly] (w:IL) mixtures, its regulation mechanism on disaggregation behaviors of starch was revealed and illuminated. Compared with pure water, existed hydrated free ions in w:IL-9:1 and w:IL-7:3 restrict starch-water interactions to disaggregate of starch, thus hampering gelatinization of starch. While the gelatinization temperatures decreased at w:IL-5:5 and w:IL-4:6 mixtures with a result of homogeneous starch solutions. The tight and water-separated ion pairs existed at w:IL-5:5 and w:IL-4:6 mixtures allow adequate ions to interact with starch to facilitate the disaggregation of starch. At w:IL-2:8 and w:IL-0:10 mixtures, an exothermic dissolution of starch was observed at high temperatures as a result of predominant starch-ion interactions. These results provide the possibility of using [Cho][Gly] solvent to meet various application requirements of starch.

The nucleoside uridine isolated in the gas phase

Herein we present the first experimental observation of the isolated nucleoside uridine, placed in the gas phase by laser ablation and characterized by Fourier transform (FT) microwave techniques. Free from the bulk effects of their native environments, anti/C2'-endo-g+ conformation has been revealed as the most stable form of uridine. Intramolecular hydrogen bonds involving uracil and ribose moieties have been found to play an important role in the stabilization of the nucleoside.

Theoretical study of the reaction of hydroxyl radicals with uridine: the influence of ribose and solvent

The reaction of ˙OH with uridine has been investigated. The influence of ribose and the solvent effect are presented.

Stability, polarity, intramolecular interactions and π-electron delocalization for all eighteen tautomers rotamers of uracil. DFT studies in the gas phase

Complete tautomeric equilibria were investigated for uracil at the DFT(B3LYP)/6-311+G(d,p) level to establish the stability order of all possible 18 tautomers-rotamers in the gas phase and to characterize their internal effects, polarity and aromatic character. Although the di-NH form strongly predominates (100%) in the mixture, the NH–OH, di-OH and CH–NH forms can be also considered. The favored tautomer is moderately stabilized by intramolecular interactions (attractions of the NH and C=O groups); it is also moderately polar and moderately delocalized. Stability of the functional groups (both amide functions) seems to be more important than intramolecular interactions, polarity and aromaticity. This is probably the main factor that dictates the tautomeric preferences in the uracil molecule.