This grant, in the Analytical and Surface Chemistry program of the Chemistry Division, supports the work of Professor Fred Lytle on the development of two-photon fluorescence spectroscopy for analytical microbiological applications. Several avenues of research are being pursued, including instrumentation developments to enhance two photon fluorescence detection limits, characterization of two-photon fluorophors, microbiological applications involving the identification of bacteria, and the characterization of enzyme release from cells. Two photon fluorescence methods allow essentially background-free measurements to be made on complex biological samples. This work involves the use of laser induced fluorescence to detect small concentrations of chemically tagged molecules in biological samples. The two photon spectroscopic technique developed in this work will allow the targeted molecules to be detected without interference from the myriad of other species present in biological specimens. This work has implications for a broad range of biotechnology research and applications.