Analysis of Circular Dichroism and Linear Dichroism Spectroscopy

Abstract

Circular Dichroism (CD) and Linear Dichroism (LD) spectroscopies measure the difference in absorption between left and right circularly polarized light and parallel and perpendicular linearly polarized light as a function of wavelength respectively. CD and LD are popular biomedical physics techniques used to determine structural changes in biomolecules. This dissertation addresses improvements made to the measurement of CD and LD signals by characterizing the transfer function of the spectrometer. Shot noise, stray light and dark current were characterized. A new model for the measurement of the CD signal involving the presence of static birefringence was derived and tested by implementation of novel techniques used to measure the phase-difference amplitude and static birefringence in the photoelastic modulator (PEM) crystal. The model was tested by measuring the fractional change in the signal on Camphorsulfonic Acid (for CD) and Chrysazin (for LD). It is hoped that this study will impact how CD and LD are measured and analyzed in the future.