Dissertation/Thesis Abstract

Ab Initio Modeling of the Electronic Absorption Spectrum of Previtamin D in Solution
by Zhu, Tianyang, M.S., California State University, Long Beach, 2017, 80; 10265071
Abstract (Summary)

To study the solvent effects of water on the previtamin D absorption spectrum, we use the quantum mechanics (QM)/molecular mechanics (MM) method combined with replica-exchange molecular dynamics (REMD). The QM method is applied for the previtamin D molecule and the MM method is used for the water molecules. To enhance conformational sampling of the flexible previtamin D molecule we apply REMD.

Based on the REMD structures, we calculate the macroscopic ensemble of the absorption spectrum in solution by time-dependent density functional theory (TDDFT). Comparison between the calculated spectrum in the gas phase and in the solution reveals minor influences of the solvent on the absorption spectrum. In the conventional molecule dynamics simulation, the previtamin D molecule can be trapped by local minimum and cannot overcome energetics barriers when it is calculated at the room temperature. In addition, the higher temperature calculation for the molecule in REMD allows to overcome energetics barriers and to change the structure to other rotational isomers, then switch to the lower temperature and gives a more complete result in the configuration space for the lower temperature.

Indexing (document details)
Advisor: Bill, Andreas
Commitee: Gu, Jiyeong, Tapavicza, Enrico
School: California State University, Long Beach
Department: Physics and Astronomy
School Location: United States -- California
Source: MAI 56/04M(E), Masters Abstracts International
Subjects: Physics
Keywords: Absorption spectrum, Previtamin D, QM/MM, REMD
Publication Number: 10265071
ISBN: 9781369829693
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