Parsaoran Siahaan

Silica Magnetite Adsorbent: Effect of Drying Temperature of Silica Sol Gel on Magnetite Core Structure

Recently, magnetite was investigated as water purification adsorbent because it’s unique magnetic properties that improved the adsorption efficiency through desorption process. But magnetite oxidized into maghemite/hematite with the increase of temperature. This transformation should be avoided to maintain the magnetic properties of magnetite. In this research magnetite separated from iron sand by magnetic extraction then coated with silica via sol gel method. The effect of drying temperature in sol gel had change the magnetite core structure into maghemite and found no formation of hematite at 350⁰C. Silica coating proved had protected magnetite from transformation into hematite due to drying temperature until 350⁰C .

Ab initio computational study of reaction mechanism of peptide bond formation on HF/6-31G(d,p) level

Peptide plays an important role in modulation of various cell functions. Therefore, formation reaction of the peptide is important for chemical reactions. One way to probe the reaction of peptide synthesis is a computational method. The purpose of this research is to determine the reaction mechanism for peptide bond formation on Ac-PV-NH2 and Ac-VP-NH2 synthesis from amino acid proline and valine by ab initio computational approach. The calculations were carried out by theory and basis set HF/6-31G(d,p) for four mechanisms (path 1 to 4) that proposed in this research. The results show that the highest of the rate determining step between reactant and transition state (TS) for path 1, 2, 3, and 4 are 163.06 kJ.mol-1, 1868 kJ.mol-1, 5685 kJ.mol-1, and 1837 kJ.mol-1. The calculation shows that the most preferred reaction of Ac-PV-NH2 and Ac-VP-NH2 synthesis from amino acid proline and valine are on the path 1 (initiated with the termination of H+ in proline amino acid) that produce Ac-PV-NH2.