Theoretical study of vitamin properties from combined QM-MM methods: Comparison of chemical shifts and energy |
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Authors: | M Monajjemi M Heshmat H H Haeri F Kaveh |
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Institution: | (1) Science and Research Branch, Islamic Azad University, P.O. Box 14515-775, Tehran, Iran;(2) Islamshahr Branch, Islamic Azad University, Tehran, Iran;(3) Gorgan Branch, Islamic Azad University, Gorgan, Iran |
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Abstract: | The combination of quantum mechanics (QM) and molecular mechanics (MM) methods has become an alternative tool for many applications
for which pure QM and MM are not suitable. The QM-MM method has been used for different types of problems, for example, structural
biology, surface phenomena, and the liquid phase. In this paper, we have implemented these methods for vitamins, an important
kind of biological molecule, and then compared results. The calculations were done by the full ab initio method (HF/3–21 g
and HF/6–31 g) and QM-MM (ONIOM) method with HF(3–21 g)/AM1/UFF; then, we found that the geometry obtained by the QM-MM method
is very accurate and this rapid method can be used in place of time consuming ab initio methods for large molecules. A comparison
of energy values in the QM-MM and QM methods is given. We compare chemical shifts and conclude that the QM-MM method is a
perturbed full QM method.
The text was submitted by the authors in English. |
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