A method for 3D nano-focusing of optical energy and its application to the Surface Enhanced Raman Spectroscopic Study of protein

Abstract

Protein layers are ubiquitous in biological systems. Their functions are many and varied. Unfortunately, structural studies of protein layers adsorbed onto liquid-solid interfaces are challenging, owing to the fact that such protein systems are not amenable to X-ray crystallography as well as Nuclear Magnetic Resonance Spectroscopy. This is due partly to the inevitable background signals arising from the underlying supporting substrate and to the extremely low sample concentration (few pmol per cm2) usually employed with such a system. Yet, the increasing use of protein layers in many fields of biotechnology has rendered structural studies of such bio-systems imperative. For example, the development of a label-free biosensor requires a monolayer of target-specific antibodies: their specific adsorption conformation and orientation are thought to dictate the final binding activity and capacity to give a meaningful signal. The catalytic efficiency of a bio-fuel cell for instance depends on the conformational state of the immobilized enzymes used for this application. Aside from this, a protein monolayer can also act as a model for biophysical studies. With these in mind, the current thesis work aims to devise a surface-sensitive vibrational spectroscopic technique suitable for in-situ structural studies of protein layers. Both the theory and its implementation will be discussed in this thesis.