In order to better understand the mechanism of NO_(x)and N_(2)Oprecursors(NH_(3)and HCN)from aspartic acid(Asp)pyrolysis,decomposition reaction networks resulting in the generation of NH_(3)and HCN were investigated by employing density function theory methods.After several pathways were analyzed in detail,two series of pyrolytic reactions containing three possible pathways were proposed.All the reactants,transition states,intermediates and products were optimized,also the electronic properties on these crucial points were discussed,which shows that Cαacts as the most active site to initiate the pyrolysis reaction,where the direct Cα-Cβbond breakage,due to the atomic charge population of repulsion,led to one key route for the generation of HCN,and the transfer of Hαfrom Cαto Cβresulting in another key route for the generation of HCN,while the transfer of Hαfrom Cαto N atom of Asp resulting in the key route for the generation of HN3.Further,the kinetic analysis based on speed control method in each key reaction pathway was conducted to further compare the generation of HCN and NH_(3)under various temperatures.The above results are in accordance with the related experimental results.
Kang PengQin WuFu ZongqiangWang TipengJu LiweiTan Zhongfu
The nature of DNA-graphene interaction system was investigated by using molecular dynamic simulations and density functional theory calculations. The detailed adsorption behaviors of single-stranded DNA( ssDNA) and double-stranded DNA( dsDNA) on the surface of graphene were discussed. The π-π stacking would contribute to the maximum average loading of ssDNA( 167 segments) with the adsorption potential distribution at the range of-6. 0 eV to-2. 1 eV,higher than that of dsDNA( 30 segments) with the adsorption energy distribution ranging from-3. 0 eV to- 0. 2 eV. Gradually shielding the base of ssDNA using hydrogen atom and gradually changing ssDNA into dsDNA through base-pairing were performed to further detect the detailed interaction between DNA and graphene. E B for * CGC,G* GC,GC* C,and GCG* is-15. 130,-15. 276,-15. 137,and- 15. 271 eV,respectively. E B for GCGC-CGCG / graphene,GCGC-CGC / graphene,GCGC-CG / graphene,GCGC-C / graphene,and GCGC / graphene is-14. 941,-14. 700,-14. 204,-15. 561,and- 15. 810 eV,respectively. DOS of the adsorbed ssDNA down shifted 1. 885 eV,which becomes more stable and less reactive than the other cases. Further,oxidation reaction shows that graphene protects ssDNA from breaking by active oxide. And stable adsorption,protection from destroying,and undamaged desorption insure the possibility of graphene to deliver or hybrid DNA for novel and creative use.
