Computer Modeling of Optical Activity of AN Amino Acid in Liquids.
After a general review on optical activity phenomena, the molecular theory of optical activity is derived in detail by a linear response theory. The correction due to the liquid state is also incorporated. An ab initio computational model is then developed for the numerical calculation. The validity of the program is checked by performing a calculation on twisted ethylene which has been studied thoroughly by many authors. The program works quite satisfactorily from a computational point of view for twisted ethylene. The model is then applied to alanine. First, the rotational strength of the alanine molecule is calculated, and curves of rotational strength vs. chromophore orientation are obtained. We find that they exhibit the same features as those produced from a semi-empirical model, though with different amplitudes, and are shifted horizontally about 10 degrees. The molecular and liquid circular dichroism (CD) for alanine are then calculated respectively. Curves of circular dichroism vs. wavelength are plotted for two different excitation lifetimes. We find that the major effects in the liquid state are a suppression of the structures of CD curve that exist in the free molecular state and a broadening of the CD bands. A conclusion with suggestions of future studies is offered at the end of the dissertation.
- Pub Date:
- December 1988
- Physics: Molecular