Vibrational Raman optical activity of peptides and proteins
Vibrational Raman optical activity (ROA) which is the difference in the Raman scattering of left and right circularly polarised incident light, has recently emerged as a new and incisive probe of biomolecular structure. This thesis is based on new applications of ROA to some current biochemical problems. The first chapter is a brief explanation of the origin of chirality and the development of vibrational optical activity with special emphasis on ROA. Chapter 2 is a theoretical analysis of ROA and provides a fundamental explanation of the phenomenon. This involves a description as to how the ROA effect is generated using molecular property tensors. The third chapter concentrates on the instrumentation required to measure ROA and the importance of CCD detectors and holographic notch filters in establishing the technique with respect to biopolymers. Chapter 4 is a brief introduction to protein structure and includes an analysis of the strengths and weaknesses of current biophysical techniques used for structure determination. Chapters 5 and 6 describe detailed applications of ROA to polypeptides and native proteins. The polypeptides are a suitable starting point since from other spectroscopic techniques they are known to adopt certain conformations, such as -helix, -sheet and random coil. Native proteins are examined in Chapter 6 and the ability of ROA to detect not only secondary but also tertiary structure is highlighted. Chapter 7 is concerned with the important topics of the structure and dynamics of unfolded proteins, molten globules and ligand bound proteins. Finally, in the appendix there is a summary of the assignments made to secondary structure and to loops and turns.