Zhendong Ding

Theoretical and experimental investigation on dissolution and regeneration of cellulose in ionic liquid

Density functional theory calculations and atoms in molecules theory were performed to investigate the mechanism of cellulose dissolution and regeneration in 1-ethyl-3-methylimidazolium acetate ([emim]Ac), and (1,4)-dimethoxy-β-D-glucose (Glc) was chosen as the model for cellulose. The theoretical results show that the interaction of [emim]Ac with Glc is stronger than that of Glc with Glc. Further studies indicate that the anion acetate of [emim]Ac forms strong H-bonds with hydroxyl groups of Glc. It is also observed that the H-bonds between [emim]Ac and Glc are weakened or even destroyed by the addition of water. In addition, both the original and regenerated cellulose samples were characterized with FT-IR, XRD, TGA and SEM. The experimental results prove that cellulose can be readily reconstituted from the [emim]Ac-based cellulose solution by the addition of water and the crystalline structure of cellulose is converted to cellulose II from cellulose I in the original cellulose.

Catalytic conversion of cellulose to 5-hydroxymethyl furfural using acidic ionic liquids and co-catalyst.

Efficient catalytic conversion of microcrystalline cellulose (MCC) to 5-hydroxymethyl furfural (HMF), is achieved using acidic ionic liquids (ILs) as the catalysts and metal salts as co-catalysts in the solvent of 1-ethyl-3-methylimidazo-lium acetate ([emim][Ac]). A series of acidic ILs has been synthesized and tested in conversion of MCC to HMF. The effect of reaction conditions, such as reaction time, temperature, catalyst dosage, metal salts, water dosage, Cu(2+) concentration and various acidic ILs are investigated in detail. The results show that CuCl(2) in 1-(4-sulfonic acid) butyl-3-methylimidazolium methyl sulfate ([C(4)SO(3)Hmim][CH(3)SO(3)]), is found to be an efficient catalyst for catalytic conversion of MCC to HMF, and 69.7% yield of HMF is obtained. A mechanism to explain the high activity of CuCl(2) in [C(4)SO(3)Hmim][CH(3)SO(3)] is proposed. To the best of our knowledge, this report first proposes that the Cu(2+) and [C(4)SO(3)Hmim][CH(3)SO(3)] show better catalytic performance in catalytic conversion of MCC to HMF.

Theoretical study on the binding mechanism between N6-methyladenine and natural DNA bases

AbstractN6-methyladenine (m6A) is a rare base naturally occurring in DNA. It is different from the base adenine due to its N-CH3. Therefore, the base not only pairs with thymine, but also with other DNA bases (cytosine, adenine and guanine). In this work, Møller-Plesset second-order (MP2) method has been used to investigate the binding mechanism between m6A and natural DNA bases in gas phase and in aqueous solution. The results show that N-CH3 changed the way of N6-methyladenine binding to natural DNA bases. The binding style significantly influences the stability of base pairs. The trans-m6A:G and trans-m6A:C conformers are the most stable among all the base pairs. The existence of solvent can remarkably reduce the stability of the base pairs, and the DNA bases prefer pairing with trans-m6A to cis-m6A. Besides, the properties of these hydrogen bonds have been analyzed by atom in molecules (AIM) theory, natural bond orbital (NBO) analysis and Wiberg bond indexes (WBI). In addition, pairing with m6A decreases the binding energies compared to the normal Watson-Crick base pairs, it may explain the instability of the N6 site methylated DNA in theory. FigureFigure The most stable configurations of the base pairs