The long term goal of this project has been to utilize the surface-enhanced Raman effect for both fundamental studies and bioanalytical applications. The current project extends this goal to include the study of other effects that are influenced by plasmon resonance and surface-molecule interactions. Fundamental issues relating to electron transfer reactions at the metal/protein interface are addressed. Surface sensitive spectroscopies, including surface-enhanced Raman, FT-IR, FT-Raman and electroreflectance, together with electrochemistry will be used to characterize the protein at the metal surface and to quantitate the influence of various factors on the electron transfer process. These will include the distance between the protein and the metal surface, its orientation at the surface and the chemical nature of the intervening medium. Cytochromes c and b5 and their mutants are used as model systems. The results of this study will reveal fundamental information with practical implications for the development of different types of biosensors. A series of new immunoassay protocols based on surface-enhanced phenomena are proposed for study. The overall goal is to develop a format of practical importance which will provide significantly lower detection limits with reduced background interference. Suspensions of nanosized silver and gold particles will be used for a homogeneous assay. Three main phenomena will be targeted in this research: enhanced Raman (surface-enhanced Raman scattering, SERS); enhanced fluorescence; and plasmon-enhanced elastic light scattering. The first of these three is a continuation of our current project, whereas the latter two represent new approaches. Results obtained from this study will provide the fundamental background required for the design of improved immunoassay procedures as applied to clinical and environmental analysis.
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