The structure and function of protein films at solid/liquid interfaces are important research topics in several biotechnological areas, such as surface biocatalysis, protein and cell separations, transduction in chemical and biochemical sensing, and materials biocompatibility (1,2). A recent Panel Report on organic thin film technology sponsored by the Materials Science Division of DOE (1) stated that """"""""Modeling, preparation, characterization, and application of protein films will lead to a variety of applications. ... Most importantly the study of protein (films) could aid and stimulate materials science to better engineer new macromolecules. (However) attempts to fabricate new and complex molecular films with novel properties cannot be done efficiently without significant advances in our present analytical capabilities. More definitive methods are required to probe and characterize packing, orientation, and structure of protein films in, situ, i.e., in water."""""""" One promising new method for in situ characterization of protein films is planar integrated optical waveguide-attenuated total reflectance (IOW-ATR) spectroscopy (3-6). Proposed here is: a) development of the technology to perform polychromatic IOW-ATR spectroscopy of weakly absorbing organic films at solid/liquid interfaces; and b) the combined application of polychromatic IOW-ATR and optical linear dichroism techniques to investigate relationships between molecular orientation, biochemical reactivity, and adsorbent physicochemical properties in adsorbed protein monolayers. Specifically, the development of a grating coupled, planar waveguide device capable of measuring broadband ATR spectra will enable the following hypothesis to be examined: Self-organization of a protein monolayer by """"""""non-specific"""""""" adsorption at a solid/liquid interface is not an isotropic process yielding a geometrically random film of protein molecules; rather, specific interactions between the adsorbent surface and the surface of a protein result in a preferred orientation of the adsorbed molecules. The physical and chemical properties of the adsorbent therefore mediate orientation in the protein monolayer; molecular orientation, in turn, affects the biochemical reactivity of the monolayer. This work will establish the feasibility of performing polychromatic IOW-ATR spectroscopy at solid/liquid interfaces. The technology developed will be used to address if self-organization by adsorption to a highly ordered interface is a viable technique for creating ordered protein film's, and if the self-organization process provides a means of controlling or altering biochemical function. In broader terms, this work will yield a more thorough understanding of molecular mechanisms in protein interfacial behavior, and should thereby enhance efforts to utilize protein films in biotechnological applications.
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