POLYCHROMATIC ATR SPECTROSCOPY ON PLANAR WAVEGUIDES

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.