Molecular dynamics simulations of A-DNA in bivalent metal ions salt solution

A-DNA is one of the biologically active double helical structure. The study of A-DNA structure has an extensive application for developing the field of DNA packaging in biotechnology. In aqueous solution, the A-DNA structure will have a free transformation, the A-DNA structure will be translated into B-form structure with the evolution of time, and eventually stabilized in the the B-DNA structure. To explore the stability function of the bivalent metal ions on the A-DNA structure, a series of molecular dynamics simulations have been performed on the A-DNA of sequence (CCCGGCCGGG). The results show that bivalent metal ions (Mg2+, Zn2+, Ca2+) generate a great effect on the structural stability of A-DNA in the environment of high concentration. As the interaction between metal ions and electronegative DNA chains, the stability of A-DNA in solution is gradually improved with the increasing of the solution concentration of ions. In metal salt solution with high concentration, metal ions can be easily distributed in the solvation shells around the phosphate groups and further lead to the formation of shorter and more compact DNA structure. Also, in the condition of the same concentration and valency of the metal ions, the stability of A-DNA structure is different. The calculations indicate that the structure of A-DNA in CaCl2 solution is less stable than in MgCl2 and ZnCl2 solution.

Synthesis, characterization and thermal behaviour on solid pyruvates of some bivalent metal ions.

Solid state M-L compounds, were M stands for bivalent Mn, Fe, Co, Ni, Cu, Zn and L is pyruvate, have been synthesized. Thermogravimetry and derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), X-Ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, ligand denticity, and thermal decomposition of the isolated compounds.

SYNTHESIS, CHARACTERIZATION AND THERMAL BEHAVIOUR OF SOLID 2- METHOXYCINNAMYLIDENEPYRUVATE OF SOME BIVALENT METAL IONS IN CO2 AND N2 ATMOSPHERES

Solid State M-2-MeO-CP compounds, where M stands for bivalent metals (Mn, Fe, Co, Ni, Cu and Zn) and 2-MeO-CP is 2-methoxycinnamylidenepyruvate, were synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), elemental analysis and complexometry were used to establish the stoichiometry and to study the thermal behaviour of these compounds in CO and N atmospheres. The results were consistent with the general formula: M(L) ·H O. In 2 2 2 2 both atmospheres (CO , N ) the thermal decomposition occurs in consecutive steps which are characteristic of 2 2 each compound. For CO atmosphere the final residues were: Mn O , Fe O , Co O , NiO, Cu O and ZnO, while 2 3 4 3 4 3 4 2 under N atmosphere the thermal decomposition is still observed at 1000 º C.